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HomeMy WebLinkAboutSEPA EPIC-286-85 - JED CORPORATION - NENDEL'S MOTOR INNNENDELS MOTOR INN 3 -STORY 151 ROOM MOTEL SO. 158T" & WEST VALLEY HIGHWAY EPIC - 286 -85 ANDREA BEATTY RINIKER Director STATE OF WASHINGTON DEPARTMENT OF ECOLOGY Mail Stop PV -11 • Olympia, Washington 98504 -8711 • (206) 459 -6000 May 9, 1986 Mr. Brad Collins City of Tukwila Planning Director 6200 Southcenter Boulevard Tukwila, WA 98188 Dear Mr. Collins: [MIN MAY 14 1986 CITY OF TUK:WiLA PLANNING DEPT. 11 Thank you for the opportunity to comment on the determination of nonsignificance for the construction of a 3- story, 151 room motel by the J.E.D. Corporation (Nendels Motor Inn). We note that this project is in the Municipality of Metropolitan Se- attle sewer service area and we have the following comments. Please be advised that a hook -up ban may be imposed on the Mu- nicipality of Metropolitan Seattle (Metro) on August 1, 1986, if planning for secondary treatment is not completed by July 31, 1986. The hook -up ban, if imposed, would apply to the en- tire Metro service area. This means that there is a possibil- ity that sewer service may not be available for the proposed project. If you have any questions, please call Mr. Robert Sylvester of the Northwest Regional Office at (206) 885 -1900. Sincerely, Kr 1) KRS: cc: Marlene Wylie, NWRO Kari Rokstad Samuelson Environmental Review Section 3 r City of Tukwila 6200 Southcenter Boulevard Tukwila Washington 98188 (206) 433 -1800 Gary L. VanDusen, Mayor ADDENDUM Mitigated Determination of Nonsignificance Description of Proposal: Expansion and relocation of required parking area (75 stalls) for Nendels Motel, conference center, and restaurant into the northeast portion of the site, which is outside the Shoreline Environment (see attached site plan). Proponent: J. E. D. Corporation Lead Agency: City of Tukwila File No.: EPIC 286 -85 This addendum is issued under 197 -11 -625. There is no comment period for this addendum. Responsible Official Position /Title Planning Director Phone 433 -1846 Address 6200 Southcenter Blvd, Tukwila, WA 98188 Date April 21, 1986 WAC 197 -11 -970 REVISED MITIGATED DETERMINATION OF NONSIGNIFICANCE Description of Proposal 3 -story 151 room motel, 9635 square foot conference center, 8,000 square foot restaurant with parking. Proponent J.E.D. Corporation (Nendels Motor Inn) Location of Proposal, including street address, if any southwest corner of West Valley Highway and the extension of 158th Avenue South. Lead Agency: City of Tukwila File No. EPIC-286-84r The lead agency for this proposal has determined that it does not have a probable significant adverse impact on the environment. An environmental impact statement (EIS) is not required under RCW 43.21C.030(2)(c). This decision was made after review of a completed environmental checklist and other information on file with the lead agency. This information is available to the public on request. 0 There is no comment period for this DNS ESI This DNS is issued under 197 -11- 340(2). Comments must be submitted by May 10, 1986. . The lead agency will not act on this proposal for 15 days from the date below. Responsible Official Brad Collins Position /Title Planning Director Phone 433 -1845 Address 6200 Southcenter Boulevard, Tukwila, WA 98188 Date April 25, 1986 Signature 32",t You may appeal this determination to the City Clerk at City Hall, 6200 Southcenter Boulevard, Tukwila, WA 98188 no later than 10 days from the above date by written appeal stating the basis of the appeal for specific factual objections. You may be required to bear some of the expenses for an appeal. Copies of the procedures for SEPA appeals are available with the City Clerk and Planning Department. FM.DNS (Revised 4/25/86) MITIGATED DETERMINATION OF NONSIGNIFICANCE EPIC- 286 -8g' Nendels Motor Inn The following mitigating measures are attached to this determination: 1. Dedication and improvement of a right turn lane along West Valley Highway per requirements of the Public Works Department and Washington State Department of Transportation. 2. Prior to issuance of a Certificate of Occupancy, awarding of a contract for a traffic signal and crosswalk at South 158th Street across West Valley Highway. 3. Accommodation of the future potential extension of Tukwila Parkway across the northern portion of the property. 4. Maximum of two access points along West Valley Highway, exclusive of South 158th Street. (MDNS) ( #1) SITE PLAN NENDEL'S CHENEY PAGE ARCHITECTS CHECIIST: ENVIRONMENTAL REVIEW MAILGS ( ) U.S. ARMY CORPS OF ENGINEERS ( ) FEDERAL HIGHWAY ADMINISTRATION ) WA.ST. OFFICE OF ARCHAEOLOGY WA.ST. TRANSPORTATION DEPT. WA.ST. DEPT. OF FISHERIES OFFICE OF THE GOVERNOR WA.ST. PLANNING & COMMUNITY AFFAIRS AGENCY Federal Agencies ( )U.S. ENVIRONMENTAL PROTECTION AGENCY ( )U.S. DEPARTMENT OF H.U.D. (Region X) State Agencies ( ) WA.ST. DEPT. OF SOCIAL & HEALTH SERVICES ) WA.ST. DEPT. OF ECOLOGY, SHORELANDS DIVISI( ) WA.ST. DEPT. OF ECOLOGY, SEPA DIVISION ) WA.ST. DEPT. OF GAME ( )OFFICE OF ATTORNEY GENERAL County Agencies ( K.C. DEPT. OF PLANNING & COMMUNITY DEVEL. ( FIRE DISTRICT 18 ( ) BOUNDARY REVIEW BOARD ( ) K.C. HEALTH DEPARTMENT ( ) SOUTH CENTRAL SCHOOL DISTRICT ( ) TUKWILA LIBRARY ( ) RENTON LIBRARY ( ) KENT LIBRARY ( ) PACIFIC NORTHWEST BELL TELEPHONE ( ) SEATTLE CITY LIGHT ( ) WASHINGTON NATURAL GAS ( ) WATER DISTRICT 75 ( ) SEATTLE WATER DEPARTMENT ( ) GROUP W CABLE ( ) KENT PLANNING DEPARTMENT ( ) TUKWILA BOARD OF ADJUSTMENT ( ) TUKWILA MAYOR ) TUKWILA CITY DEPARTMENTS: ) Public Works Parks and Recreation Police Fire Finance Planning /Building ( )FIRE DISTRICT 1 ( )FIRE DISTRICT 24 ( )K.C. BLDG & LAND DEVEL.DIV. -SEPA INFO CNTR Schools /Libraries ( )HIGHLINE SCHOOL DISTRICT ( )KING COUNTY PUBLIC LIBRARY ( )SEATTLE MUNICIPAL REFERENCE LIBRARY Utilities ( )PUGET SOUND POWER & LIGHT ( )VAL -VUE SEWER DISTRICT ( )WATER DISTRICT 20 ( )WATER DISTRICT 25 ( )WATER DISTRICT 125 ( )UNION PACIFIC RAILROAD City Agencies ( ) RENTON PLANNING DEPARTMENT ( )TUKWILA PLANNING COMMISSION ( )TUKWILA CITY COUNCIL MEMBERS ( ) Edgar Bauch ( ) Marilyn Stoknes ( ) Joe Duffie ( ) Mabel Harris ( ) Charlie Simpson ( ) Doris Phelps ( ) Wendy Morgan Other Local Agencies ( ) PUGET SOUND COUNCIL OF GOVERNMENT (PSCOG) ( ) PUGET SOUND AIR POLLUTION CONTROL AGENCY ( ) TUKWILA /SEA TAC CHAMBER OF COMMERCE Media ( ) DAILY JOURNAL OF COMMERCE ( ) RENTON RECORD CHRONICLE ( )METRO ENVIRONMENTAL PLANNING DIVISION ( )HIGHLINE TIMES ( )SEATTLE TIMES City of Tukwila 6200 Southcenter Boulevard Tukwila Washington 98188 433 -1800 Gary L VanDusen, Mayor October 15, 1985 T. E. Dahl Nendels Tukwila Associates 2230 Rucker Avenue Everett, WA 98201 Re: Shoreline Management Permit #N- 590 -14 -1361 and 85 -35 -DR Dear Mr. Dahl: The City has extended the time period for commencing construction under the shorelines permit to January 1, 1987, pursuant to WAC 173.14.060(1). This should provide sufficient time to secure the required permit revision from the Department of Ecology, the necessary building and construction permits, and the completion of contracts. The conditions of the shorelines permit shall be: 1. Rip rap of dike along shoreline. 2. Geotechnical engineers providing inspection of site before and during construction. Please be aware that WAC 173.14.020(2) requires completion of the project by January 1, 1988 and you and your project will be subject to the con- ditions of the Shoreline Management Permit, Mitigated Determination of Significance (EPIC 286 -85) and site, elevation and landscape plans as approved by the Board of Architectural Review. With reference to Board of Architechtural approval, the Board met on September 26, 1985 to review your proposal. The plans were approved sub- ject to the following amended conditions from the staff report: 1. Loading and service areas must comply with TMC 18.51 and 18.56. 2. Luminaire designs must conform to architect's rendering as sub- mitted to the Board at its meeting. Condition #3 was dropped from the staff report. If you have any questions, please feel free to call me at 433 -1848. Sincerely, Moira Carr Bradshaw Assistant Planner /ks (NENDELS) (1B) cc: Planning Director Building Official Department of Ecology File) ANDREA BEATTY RINIKER Director STATE OF WASHINGTON DEPARTMENT OF ECOLOGY Mail Stop PV-11 • Olympia, Washington 98504 -8711 • (206) 459 -6000 September 23, 1985 Mr. Brad Collins City of Tukwila 6200 Southcenter Blvd. Tukwila, WA 98188 Dear Mr. Collins: f';" ti .. rt. . -0A !!: A Pi... r:!'JF G DEPT. Thank you for the opportunity to comment on the determination of nonsignificance f or. .the Nedels Motor Inn. We reviewed the environmental checklist and have the following comments: 1. The proposed 39 foot height will require a shoreline variance unless the extra four feet include only mechanical and accessory structures on the roof. 2. The shoreline master program policies encourage visual and pedestrian public access as an integral part of waterfront development. The shoreline permit should reflect how this project will comply with these policies. If you have any questions, please call Ms. Nora Jewett of the Shorelands Division at (206) 459 -6789. BJR:sr cc: Nora Jewett Sincerely, 73a.atia Barbara J. Ritchie Environmental Review Section 3 King County Executive Randy Revelle Department of Planning and Community Development Holly Miller, Director September 19, 1985 Mr. Brad Collins Planning Director City of Tukwila 6200 Southcenter Boulevard Tukwila, WA 98188 >i? 2 4 1985 P!_ ^ MC DEPT. RE: Mitigated Determination of Non - Significance (DNS) for Nendels Moto Inn Development Dear .' ins: The Department of Planning and Community Development has reviewed the referenced mitigated DNS and enclosed environmental checklist and has the following comments. Estimates of impervious area appear to be low. It is not apparent, from the information provided, if the area proposed for sale to Exxon for use as a service station is incuded as impervious area in calculations. Since service stations are typically all impervious area, calculations of appropriate surface water detention volumes should include this portion of the site as impervious area. Due to the frequent contamination of groundwater by underground storage tanks we recommend that any service station built on this site be equipped with double wall storage tanks and a secondary containment structure. It is not clear what special development conditions will be applied in response to the area's designation as a sensitive area (page 12). Special development conditions called for in the Shoreline Management Guidelines are also not clearly stated. The checklist should make clear what environmental conditions 811 Alaska Building 618 Second Avenue Seattle, Washington 98104 (206) 344 -7503 • • Mr. Brad Collins September 19, 1985 Pge Two necessitate special development controls and what special controls will be applied. These controls should be included as conditions of the mitigated DNS. Thank you for the opportunity to review this DNS. Since, . . ILW OLLY MILLER Director HM:DG:ds TPDG45 cc: Steve Miller, Deputy Director, Department of Planning and Community Development ATTN: Meredith Getches, SEPA Coordinator Harold Robertson, Manager, Planning Division ATTN: Bill Jolly, Chief, Resource Planning Section David Masters, Resource Planner Bill Hoffman, Chief, Transportation Planning Section Dave Gualtieri, Transportation Planner WAC 197 -11 -970 MITIGATED DETERMINATION OF NONSIGNIFICANCE Description of Proposal 3 -story 151 room motel, 9635 sq ft conference center, 8,000 sq ft restaurant with parking. Proponent J.E.D. Corporation (Nendels Motor Inn) Location of Proposal, including street address, if any southwest corner of West Valley Highway and the extension of 158th Ave. S. Lead Agency: City of Tukwila File No. EPIC - 286 -85 The lead agency for this proposal has determined that it does not have a probable significant adverse impact on the environment. An environmental impact statement (EIS) is not required under RCW 43.21C.030(2)(c). This decision was made after review of a completed environmental checklist and other information on file with the lead agency. This information is available to the public on request. Q There is no comment period for this DNS E! This DNS is issued under 197 -11- 340(2). Comments must be submitted by September 21, 1985 . The lead agency will not act on this proposal for 15 days from the date below. This determination is subject to the attached conditions. Responsible Official Brad Collins Position /Title Planning Director Phone 433 -1845 Address 6200 Southcenter Boulevard, Tukwila, WA 98188 Date September 6. 1985 Signature ll f� cam-- -Q . You may appeal this determination to the City Clerk at City Hall, 6200 Southcenter Boulevard, Tukwila, WA 98188 no later than 10 days from the above date by written appeal stating the basis of the appeal for specific factual objections. You may be required to bear some of the expenses for an appeal. Copies of the procedures for SEPA appeals are available with the City Clerk and Planning Department. FM.DNS MITIGATED DETERMINATION OF'NONSIGNIFICANCE EPIC - 257 -84 Nendels Motor Inn The following mitigating measures are attached to this determination: 1. Dedication and improvement of a right turn lane along West Valley Highway per requirements of the Public Works Department and Washington State Department of Transportation. 2. Prior to issuance of a Certificate of Occupancy, installation of a traffic signal and crosswalk at South 158th Street across West Valley Highway. 3. Accommodation of the future potential extension of Tukwila Parkway across the northern portion of the property. 4. Maximum of two access points along West Valley Highway, exclusive of South 158th Street. (MDNS) ( #1) JED Corporation 2230 RUCKER AVENUE , EVERETT, WASHINGTON 98201 206- 252 -6300 206- 252 -1593 August 29, 1985 C Mr. Rick Beeler Planning Department City of Tukwila 6200 Southcenter Boulevard Tukwila, Wa. 98118 Dear Rick, . • In response to the city.'s concern and in -order to expedite the permit process, I should like to offer, as a measure to mitigate the initial traffic on the project,the following: We will forego completion of any development except for the hotel complex as planned, until signalization is completed at 154th and West Valley road. This includes deferring open- ing of an Exxon Store or a fast food operation or anything else until the traffic controls are installed. Consider, if you will, that construction of the hotel will take at least six months. Ross Earnst told me this morning that the max- imum time required to plan, approve, bid and install a traffic signal system would be six -eight months. At worst, then, the maximum time we could be operative would be two months before signalization was complete. As a practical matter a more accurate estimate would probably be more like thirty days. To give you an indication of the impact on traffic the first thirty -sixty days would likely have (as opposed to the long term traffic studies you are familiar with), the new hotel we opened in February of this year had an opening occupancy rate of 17% for Feb- ruary and 23% in March. Normally a stabilized occupancy rate of 75% T1 • • August 29, 1985 Page - 2 - contd. in our type hotel takes from one to three years to develop. So the full impact likely will not be felt until sometime after April 1987. As a closing thought, not to be construed as a committment, we are very seriously considering changing our entire approach to the development of the balance of the property from the Exxon, fast -food type of thing, to a small office building complex. This would per- manently eliminate a great deal of the projected vehicle traffic. Please give this proposal your consideration. Very truly yours, JED CORP ION 7E. Da 1 President f%sf&\-A-R6col _ay4vv\ _ cc.z fv1KbEi. ftLP vvetT w■MI cs:NsrwVi-Va cMevaios CrkScILSIS _ UL5c_\ s_APS ctOW--%crS Wto`S OccL_cs- Pw0 . Vat.i\( (p--Is T6 - �- , 21 &5- MITIGATED DETERMINATION OF NONSIGNIFICANCE EPIC - 257 -84 Nendels Motor Inn The following mitigating measures are attached to this determination: 1. Dedication and improvement of a right turn lane along West Valley Highway per requirements of the Public Works Department and Washington State Department of Transportation . Prior to issuance of . Cert - of Occu•anc installation of a traffic signal and crosswa at South 1 : treet across West Valley Highway. 3. Accommodation of the future potential extension of Tukwila Parkway across the northern portion of the property. --- 4. Maximum of two access points along West Valley Highway, exclusive of South 158th Street. (MDNS) ( #1) JED Corporation 2230 RUCKER AVENUE EVERETT, WASHINGTON 98201 206- 252 -6300 206- 252 -1593 RECEIVED CITY OF TUKWILA AUG 29 1985 PUBLIC WORKS DEPT, August 27, 1985 Mr. Ross Earnst, City Engineer City of Tukwila 6200 Southcenter Boulevard Tudwila, Wa. 98118 Re: Traffic Signal, West Valley Highway /South 158th Street Dear Mr. Earnst; As a part of our development of Nendels Motor Inn and Restaurant at the southwest quadrant of the above intersection, the city is requir- ing various channelization, turning lanes, and traffic signalization improvements. We do not believe it equitable that the full cost of these improvements fall to our development. According to the traffic study prepared by KJS Associates, dated July 30, 1985, the impact of our development will increase traffic along SR 181 by two to four per- cent of the daily traffic and one to two percent of the afternoon peak traffic. Percentages such as these would appear to be a lower limit for our participation in the cost of channelization and signal - ization of the intersection, although the full cost of right turn lanes required, as well as sidewalk and right -of -way improvements, would nat- urally be our responsibility. At the other end of the scale, an upper limit of cost participation, based on our development of only one quadrant of the intersection, of 25 percent would appear to be a maximum. We believe that our participation at a midpoint between these two figures -- about 14 percent -- is appropriate, at this time. We respectfully request the City of Tukwila review our request through the appropriate channels. August 27, 1985 Page - 2 - Contd. We remain willing to discuss the issue in further detail and make the services of our traffic consultant, Joe Savage, available, shoulld the need arise. We are interested in proceeding with all due haste toward the development of this project, so that it may be completed prior to next year's racing season at Longacres. Therefore, we wish to reach a conclusion on this matter and initiate the steps required to achive the signalization. Very truly yours, JED CORP . E. Dahl President cc: Mabel Harris, Chairman Transportation Committee Joe Savage, Traffic Consultant KJS Associates DESCRIPTION OF ARCHITECTURAL FEATURES OF PROPOSED MOTOR INN AND RESTAURANT FOR NENDEL'S, TUKWILA, WASHINGTON Attached is a rendering of a very similar Nendel's Motor Inn constructed in 1984, in Everett, Washington. The proposed Tukwila facility will be very similar in appearance, although the location of the Entrance Canopy and Meeting Rooms has been altered to reflect differing site conditions. The buiding is constructed of wood frame slab on grade, the exterior materials are principally cedar bevel siding and some vertical grooved plywood siding, stained a soft pastel gray tint color. Small feature areas of split -faced concrete block will be utilized at retaining walls, garden walls, and other similar locations. The four stair towers visible on the skyline are capped with translucent fabric awnings containing the logo of the motel chain and internally lit for a soft glow at night. The level of this light is very low and does not illuminate brightly enough to provide light to the parking areas or any adjoining walkways. The overall building height of the three -story motel is approximately 29 feet above the finish grade at the first floor line. This grade will have been raised to elevation 28.75 for the required flood protection. The awnings at the top of the four stair towers will be aproximately 42 feet above this finished grade. There is a small basement service area under the restaurant and small basement service area under the motel; the floor of which extends to about four feet below the present grade of the site which is about 11 feet below the newly elevated dike height. Exterior lighting in the vicinity of the building will be down - lights mounted under the soffits and wall protections. Parking lot lighting will be provided through a series of low -level cut -off type light fixtures aimed to cut off light and glare from extending across the property lines to adjoining properties, rights -of -way, or river frontage. Ground level pathway lighting and walkway lighting will be provided at key points in the landscaping. lL ', 2 1985 '-- I lA :r � ,: A,h;I'. R yt • • 2. Prior to issuance of a Certificate of Occupancy: A. Awarding of a contract for construction of a traffic signal and crosswalk at S. 158th St. across West Valley Highway, B. Completion of channelization at this intersection, C. Construction of a right turn lane along West Valley Highway, D. Limiting access to right4t urnsin only at tie S. 158th St. and right turn out only at the southerly curb cut of the development until the traffic signal is installed.(io Csalet-'�2N5 development, o� 1tt -r f-c rlog rat �� TO: FROM: DATE: FILIZ E MEMO CITY 0 F. TUKWILA 81 is ig SUBJECT: 14 ta<1 Du --rb -m---rd\-sc:c)r-( ct )5"-D LT- C-CrL 01)\N.) •-7 (z) tivvot —rc 11\ CC Tss TJI C-)--rt.--Zi" T.L4 P Avr. s t T Ak,--311,C4 .0.7-3:), IT 'cz;-1 70-TT' Tc1;._ Co4 s:\ C-0 ) • 10 PI A 1 • I Tcri- (P6-Q: c3T-- LX\ LAC 1-7.) if . LOVV[1-Z . 1(,_ GgY\rk -P Y\r% ILIST TL.6. n 1-) To Speed Letter® 44 -902 Gra Line® 1/1/1/m/ // // / /a /l1 Speed Letterm Subject From ii i ill 7j / lily C( / "2-A-4 tr cr/0,5 -No 9610FOLD MESS, W /,T &J& 74 . & / / /160 276 I REPLY - No 9FOLD — NO tO FOLD Date Signed WilsonJones GRAYLINE FORM 44 -902 3 -PART c 1983 • PRINTED IN U.S.A RECIPIENT — RETAIN WHITE COPY, RETURN PINK COPY 583 Kegel & Associates Inc. August 6, 1985. Mr. Rich Beeler, Planner City of Tukwila Planning Department City Hall Tukwila, Washington 98188 Re: Nendels Motor Inn Our Job No. 9581 Dear Sir: RUH@ AUG 71985 CITY KWILA PLANNING DEPT. Mr. John Cheney, the architect for the Nendels Motor Inn project, has requested I inform your department that my office has reviewed his latest site plans. We have also completed preliminary revised designs of the utility plans for the project and have consulted with Jon Potter of R. W. Thorpe in his revisions of the Environmental Review. I can foresee no need for any major design revisions which would change the basic intent of the original plans submitted to the City in 1982 for the previous owner. As you are aware, we will be submitting a revised Utility Plan for the new project after the environmental review is completed. Respectfull R. Michael Spano, 1.E. Kegel & Associates, Inc. RMS:le CRD 29 ENGINEERS • SURVEYORS • PLANNERS. 9800 EVERGREEN WAY (U.S. 99), EVERETT, WASHINGTON 98204 • PHONE (206) 353 - 1119/ 775 -5424 A. BACKGROUND - Control No.` 65 `2_2h Epic File No. 269- 57 Fee $100.00 Receipt No. c15 2 MENTAL CHECKLIST 1. Name of proposed project, if applicable: Nendels Motor Inn 2. Name of applicant: R.W. Thorpe & Associates, Inc. 3. Address s -and phone number of applicant and contact.person: • ea e, WA 98104, Phone: 624-6239, Contact Jon Potter 1300 Alaska Building 4. Date checklist prepared: July 5. Agency 'requesting Checklist: 1985 City of Tukwila Immediate 6. Proposed timing or schedule (including phasing, if applicable): Construction will take submittal of building plans following Desian Review approximately 6 to 10 months. 7. Do you have any plans for future additions, expansion, or further activity related to or connected with this proposal? If yes, explain. A 30,807 s.f. area at the NE corner of the site is proposed to be subdivided and sold to Exxon Z- orporation as a gas station site. Depending upon market conditions following completion of the hotel and restaurant, an expansion /addition may be considered. Such a proposal would be subject to SEPA review. 8.. List any environmental information you know about that has been prepared, or will be prepared, directly related to this proposal. Tukwila Hotel EIS and Hampton Inn Supplemental information. 9. Do you know whether applications are pending for governmental approvals of other proposals directly affecting the property covered by your proposal? If yes, explain. None identified. a INNS, tar.. sl, ifir ,;-,- tswii.., kig,-,.'4. ,..-....• litrit. ..."ffliskiitt TIE M, PFi iF % =I !TACOMA ONAL AIRPOFt L. — is LI 33 - In; r • z .e • 11 o,� n 12 • • -- U.S. ©.S. BASE +1-.0:400D NORTH LOCATION MAP NENDELS MOTOR INN R.W. THORPE AND ASSOCIATES 10. List any government approvals or permits that will be needed for your proposal. Fill Permit. Shorelines Management substantial uevelopment permit Revision Board of Architectural Review Hauling Permit Sign Permit — Building Permit —State Flood Control one Permit / Short Plat 11. Give brief, complete description of your proposal, including the proposed uses and the size of the project and site. There are several questions later in this checklist that ask you to describe certain aspects of your proposal. You do not need to repeat those answers on this page. Section E requires a complete description of the objectives and alternatives of your proposal and should not be summarized here. Nendels Motor Inn proposes to develop a 3 story, 151 room motel with a 9,635 s.f. conference center, 8,000 s.f. restaurant and swimming pool. Exxon Corporation proposes to acquire 30,807 s.f. and build a gas station at the NE corner of the site. As a part • •- • - . -. Ke their previous work on the Tu.cwila Hotel relative to this project anr3 haves indicated only very slight modifications from theirprevious engineering plans. 12. Location of the proposal. Give sufficient information for a person to understand the precise location of your proposed project, including a street address, if any, and section, township, and range, if known. If a proposal would occur over a range of area, provide the range or boundaries of the site(s). Provide a legal description, site plan, vicinity map, and topographic map, if reasonably available. While you should submit any plans required by the agency, you are not required to duplicate maps or detailed plans submitted with any permit applica- tions related to this checklist. Township 23N Range 4E Section 24 _•• d The Southwest quadrant of the West Valley Highway /South 158th Street intersection. in Tukwila. 13. Does the proposal lie .within an area designated on the City's Comprehensive Land Use Policy Plan Map as environmentally sensitive? Yes. The site lies in an area designated as requiring special development considerations, specifically S6reline Management Guidelines. This designation does not preclude eve opment; rather it depicts areas where urban development must respond sensitively to certain environmental factors. TO'BE COMPLETED BY APPLICANT Evaluation for Agency Use Only B. ENVIRONMENTAL ELEMENTS 1. Earth a. General description of the site (circle one): rolling, hilly, steep slopes, mountainous, b. What is the steepest slope on the site (approximate percent slope)? The site is flat with the exception .of the 2 to 3 ft high levee.. ThQ parking lot slopes 2 -4% (Basic parking lot slop on initial. e ig w 1 be tti� same). The bank on the o th c. What general types of soils are found on the site 2 rioglop�.line will niave a (for example, clay, sand, gravel, peat, muck)? If you know the classification of agricultural soils, specify them and note any prime farmland. The soil characteristics are closely related-to that of Newberg —Mt loam (Ng). The soil is suitable for hay, pasture and vegetables. d. Are there surface indications or history of unstable soils in the immediate vicinity? If so, describe. No, however the site is underalin with normally con- solidate a uvia soi s. he thick clay silt is compressible and will require preloading. Also the near surtace silts and sands may be subject to liquefaction during an earthquake resuig in lateral earth movement. e. Describe the purpose, type, and approximate quanti- ties of any filling or grading proposed. Indicate source of fill._Approx. o ft of fill will be required within the motor inn portion of the structure and about 8 ft. of fill within the conference center and restaurant area. To prevent differential settlement, the site will be oreloaded with at least 12 ft. of fill above finished floor elevation, extending 20 ft. beyond the edge of the structure. Between 20 -30 thousand cu. yds. of fill will be imported. Granular imported sands & ravels as e fied by f. Could erosion occur as a result of clearing, �teport construction, or use? If so, generally describe. Tukwila Hotel DEIS. Some erasion of the fill material and worked natural soils is likely prior to construction of the building. g. About what percent of the site will be covered with impervious surfaces after project construction (for example, asphalt or buildings)? Approximately 57.6 % will be covered by asphalt and buildings. • Evaluation for Agency Use Only h. Proposed measures to reduce or control erosion, or other impacts to the earth, if any: Temporary erosion sedimentation control plan will be submitted and approved detining the o- on control during clearing & grading. Work will be allowed only during the dry season. the plan has siltation ponds and oil separation devices to control runoff over denuded land. 2. Air a. What types of emissions to the air would result from the proposal (i.e., dust, automobile odors, industrial wood smoke) during construction and when the project is completed? If any, generally describe and give approximate quantities if known. Dust during construction noxious odors due to diesel powered vehicles from asphalt paving operations. Incremental increase in carbon monoxide resulting from 3069 vehicle trips per day. b. Are there any off -site sources of emissions or odor that may affect your proposal? If so, generally describe. Traffic generated by the motel will add to existing carbon monoxide levels. c. Proposed measures to reduce or control emissions or other impacts to air, if any: None. 3. Water a. Surface: 1) Is there any surface water body on or in the immediate vicinity of the site (including year - round and seasonal streams, saltwater, lakes, ponds, wetlands)? If yes, describe type and provide names. If appropriate, state what stream or river it flows into. Green River, immediately south and west of -tihe' e- 2) Will the project require any work over, in, or adjacent to (within 200 feet) the described waters? If yes, please describe and attach available plans. yes. See attached plans. 3) Estimate the amount of fill and dredge material that would be placed in or removed from surface water or wetlands and indicate the area of the site that would be affected. Indicate the source of fill material. None. 4) Will the proposal require surface water - withdrawals or diversions? Give general description, purpose, and approximate quan- tities, if known. No. 5) Does the proposal lie within a 100 -year floodplain? I'f so, note location on the site plan. The site is within the floodway fringe. 6) Does the proposal involve any discharges of waste materials to surface waters? If so, describe the type of waste and anticipated volume of discharge. No_ Stormwater will empty into the RiXSr• Oilfwater separators will be utilized in the stormwater system. Evaluation.for Agency Use Only Evaluation for Agency Use Only 'b. Ground: 1) Will ground water be withdrawn, or will water be discharged to ground water? Give general description, purpose, and approximate quan- tities, if known. No. 2) Describe waste materials that will be discharged into the ground from septic tanks or other sour- ces, if any (for example: Domestic sewage; industrial, containing the following chemicals...; agricultural; etc.) Describe the general size of the system, the number of such systems, the number of houses to be served (if applicable), or the number of animals or humans N/A. the system(s) are expected to serve. c. Water Runoff (including storm water): 1) Describe the source of runoff (including storm water) and method of collection and disposal, if any (include quantities, if known). Where will this water flow? Will this water flow into other waters? If so, describe. Pg 37 of DEIS defines stormwater detention volume originally designed tor 8252 cu. ft. The design will be modified slightly to enable a slightly different collection system with the same or similar size --detention. The revised design will also require a controlled outlet at the existing rate of run- off prior to development. The revised design -7773-711 also Be- approved by City and County. The revised design will illustrate storm discharge at the exact same location as described in the •EIS. ( approx. 150' ft. south of the north line into the river.) This location was approved by Wa. State Dept. of Fish & Game, June 18, 1982 in;.their hydraulic project approval. This location was also reviewed and approved by City and King County Storm Water Management Division. Evaluation for Agency Use Only 2). Could waste materials enter ground or surface waters? If so, generally describe. No d. Proposed measures to reduce or control surface, ground, and runoff water impacts, if any: See P.g_ 37 .of to Tukwil • �' e The stormwater detention facility will be similar to the previously approved storm drainage /detention plan. The impervious surfaces will have very little •e,£fect on the groundwater .• .u• flux with the river. 4. Plants a. Check or circle types of vegetation found on the site: x deciduous tree: alder, aspen, other / (Cottonwoc _ evergreen tree: fir, cedar, pine, other shrubs grass pasture crop or grain > x wet soil plants: cattail, buttercu bullrush, •luegras ,,.fescue) skunk cabbage, other water plants: water lily, eelgrass, milfoil, other other types of vegetation b. What kind and amount of vegetation will be removed or altered? Most of the vegetation within the property lines of the subject site will be removed. Some vegetation along the river wi71 -be disturbed due to reconstruction of the dike &-construction of.gravel access road. The inf-Eit-is To retain as flush of the existing vegetation as possible. c. List threatened or endangered species known to be on or near the site. None iden ;tied_ _ • Evaluation for Agency Use Only d. Proposed landscaping, use of native. plants, or other measures to preserve or enhance vegetation on the site, if any: Please see attached landscape plan. All plantings will meet City of Tukwila landscape codes. Approx. 42..43 or 2_1.a reS of the_propnSeri site will be landscaped. 5. Animals a. Circle any birds and animals which have been observed on or near the site or are known to be on or near the site: birds: hawk, heron, eagle, (songbirds ) other: mammals: deer, bear, elk, beaver, other: fish: bass, salmo n o t) herring, shellfish, other: b. List any threatened or endangered species known to be on or near the site. None identified. c. Is the site part of a migration route? If so, explain. Migrptnry waterfowl have het -obSex�ted. in the freshwater and shore habitats provided by the Green River bordering the site and by an oxbow pond north of the site. d. Proposed measures to preserve or enhance wildlife, if any: An erosion control plan shall be followed ' during construction. Natural vegetation shall be maintained along the stream bank;- fill and grading operations will be limited to periods of normally dry weather; silt traps and oil /water separators shall be maintained and cleaned by project owner whenever necessary. The hotel and proposed landscaping will shade the parking lot, thereby possibly reducing the stormwater runoff temperature. Evaluation for Agency Use Only 6. Energy and Natural Resources a. What kinds of energy (electric, natural gas, oil, wood stove, solor) will be used to meet the completed project's energy needs? Describe whether it will be used for heating, manufacturing, etc. Combination of solar, gas and electricity will be utilized. Heat pumps will also be utilized. b. Would your project affect the potential use of solar energy by adjacent properties? If so, generally describe. No. c. What kinds of energy conservation features are included in the plans of this proposal? List other proposed measures to reduce or control energy impacts, if any: Prnpnsed energy plan consists of solar for domestic water system, gas for laundry and heating electricity, heat pumps for air conditioning. 7. Environmental Health a. Are there any environmental health hazards, including exposure to toxic chemicals, risk of fire and explosion, spill, or hazardous waste, that could occur as a result of this proposal? If so, describe. No. 1) Describe special emergency services that might be required. N /A. 2) Proposed measures to reduce or control environ- mental health hazards, if any: N /A. Evaluation for Agency Use Only b. Noise 1) What types of noise exist in the area which may affect your project (for example: traffic, equipment, operation, other)? Traffic on West Valley Highway is the predominant source of noise. It is not significant enough to affect hotel use. 2) What types and levels of noise would be created by or associated with the project on a short - term or a long -term basis (for example:. traf- fic, construction, operation, other)? Indicate what hours noise would come from the site. Short term construction noise peaks in the range of 85 to 95 dBA. 3) Proposed measures to reduce or control noise impacts, if any: None. 8. Land and Shoreline Use A. What is the current use of the site and adjacent properties? The site is undeveloped. Property to the south is single Talli ly.North and west of the site is the Green'River_ Fact is wes. Valley Highway. The general_vjcjn ty rnnsists of vacant lands, agricultural lands" single family, commercial and office uses. b. Has the site been used for agriculture? If so, describe. Grazing for sheep. c. Describe any structures on the site. None. • •■1 t ■■1 MEIN NW 111i... ■MEW mom 1� \1111 ■\ an ■■ ■■ ■I ■■■■■ ■I IEEE ■■■I IIMEMIE i ■t-�� EIMINIMEMI ■■■■ ,■MIME■ ■1 MEM ANEW MK ■ ■I ■■I WE ■ ■ ■, ■■ ■I ammo .... .... MULTI FAMILY RESIDENTIAL • .SINGLE FAMILY ......RESIDENTIAL ■ ■ ■ ■ ■■ WEER RETAIL . >`iVef i PARKS AND _ s5L`.'itc.f }4 PUBLIC SERVICES _COMMERCIAL WHOLESALE _ ._. UNDEVELOPED _ _. .SERVICES . _ DISTRIBUTION ___ PROCESS MANUFACTURING EXISTING LAND USE NENDELS MOTOR INN A.W. THORPE AND ASSOCIATES SCALE-1"=1200' NORTH AYr, JJ� ■ ■■ ■ ■ ■si.�_. 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S„ N ■■■■■ ■1 9.4.4., 0 so 11 �'41 %M■■M■■1 .� ti ■ ■ ■ ■ ■ ■1 , ; ei=:.s' pia —r. —■ ilio •••• "' ■i'' ili (ME • !1► �.►� ■r -._. 1■11■ ■■ • ■ 11001b. OW, = ti L- a(rJY■■M11■■ • ■ ��✓k ''_ ■ ■11■■ • ■ w lI ■i0■■ • �\�d 1s..0 ____�1 ■TIME • t______ M • z .� l ■FYI■ ■':1 yG la Eton ,� ■ ■■U■ ■IL F•r ti ■M■ ■■1\■■ ■! 101:://nammnro 1 li "'I= ■■ ■■■MIL ---j •. z •\ ■ ■Gi!\iC�K>__ gym. `' %ANE% t_ Atom, ■■MEM MINIM MENEM COMMERCIAL LIGHT INDUSTRIAL HEAVY INDUSTRIAL PUBLIC FACILITIES PARKS & OPEN SPACE RECREATION. SPECIAL DEVELOPMENT CONSIDERATIONS REFERS TO AREAS OF STEEP SLOPES. WATER SURFACE, AND AGRKULTURAL LANDS. THIS DESIGNATION DOES NOT PRECLUDE DEVELOPMENT: RATHER. IT DEPICTS AREAS WHERE URBAN DEVELOPMENT MUST RESPOND SENSITIVELY TO CERTAIN ENVIRONMENTAL FACTORS. COMPREHENSIVE PLAN NENDELS MOTOR INN R.W. THORPE AND ASSOCIATES Xeo4on ----I Tukwi b G C -M TUKWILA -- R-A Agricultural C -2 Regional Retail C -P Planned Business Center C -M Industrial Park M -1 Light Industry 44 SCALE: 1":1200 NORTH RENTON G B -1 B -P M -P H -1 Single Family Residential Business Park Business Parking Manufacturing Park Heavy Industry ZONING NENDELS MOTOR INN R.W. THORPE AND ASSOCIATES d. Will any structures be demolished? If so, what? No. e. What is the current zoning classification of the site? Regional Retail -C -2 f. What is the current comprehensive plan designation of the site? Commercial with Special Development considerations. g. If applicable, what is the current shoreline master program designation of the site? Urban Environment. h. Has any part of the site been classified as an "environmentally sensitive" area? If so, specify. YPs Tha antire site DUe to oroximit3 to River and alluvial soils. i. Approximately how many people would reside or work in the completed project? The hotel would employ approx. 25 full and part =time employees with varying schedules. The restaurant would employ approx. 45 full j. Approximately how many people would the completed project displace? None. k. Proposed measures to avoid or reduce displacement impacts, if any: NIA 1. Proposed measures to ensure the proposal is com- patible with existing and projected land uses and plans, if any: The proposal is consistent with the Comprehensive Plan, Zoning Ordinance and Shorelines Management Program. -12 Evaluation for Agency Use Only & p/t employees with varying schedules. Evaluation for Agency Use Only 9. Housing a. Approximately how many units would be provided, if any? Indicate whether high, middle, or low- income housing? None. The hotel will have 151 rooms. b. Approximately how many units, if any, would be eli- minated? Indicate whether high, middle, or low - income housing. Nnna c. Proposed measures to reduce or control housing impacts, if any: N /A. 10. Aesthetics a. What is the tallest height of any proposed structure(s), not including antennas; what is the principal exterior building material(s) proposed? Three stories or 39 feet tall. The building will be wood frame with stained wood siding. Bearing masonry will not be used. Roofing will be built up. b. What views in the immediate vicinity would be altered or obstructed? Potential view blockage could occur to the office buildings south of the site across the river. c. Proposed measures to reduce or control aesthetic impacts, if any: A landscape plan has been prepared to assure good design practice and consistency throughout the site. Approximately 42.4% or 2.3 acres ,.of the proposed site will be landscaped. I AL, U.S.O.S. BASE VIEW ASSESSMENT 1-=2000" NENDELS MOTOR INN NORTH R.W. THORPE AND ASSOCIATES :! ,,: �. Evaluation for . Agency Use Only 11. Light and Glare a. What type of light or glare will the proposal produce? What time of day would it mainly occur? Light would be emitted from motel rooms, parking lot lighting and automobiles. b. Could light or glare from the finished project be a safety hazard or interfere with views? No. c. What existing off -site sources of light or glare may affect your proposal? None, d. Proposed measures to reduce or control light and glare impacts, if any: Parking lot lighting could be limited so that no direct light spills off site. 12. Recreation a. What designed and informal, recreational oppor- tunities are in the immediate vicinity? Long Acres Race Track east of the site, Bicentennial Park 1/4 mile south. Tukwila Park 1/2 mile north of I =405, Fort Dent Park 2/3 miles north of the site. b. Would the proposed project displace any existing recreational uses? If so, describe. No. c. Proposed measures to reduce or control impacts on . recreation, including recreation opportunities to be provided by the project or applicant, if any: Swimming pool for motel guests only. Evaluation for Agency Use Only 13. Historic and Cultural Preservation a. Are there any places or objects listed on, or pro- posed for, national, state, or local preservation registers known to be on or next to the site? If so, generally describe. No_ b. Generally describe any landmarks or evidence of historic, archaeological, scientific, or cultural importance known to be on or next to the site. Based on an archaeological survey performed on site, there is no indication of any archaeologically significant artifacts on the site. c. Proposed measures to reduce or control impacts, if dny: Con •- - ill be _halted if any arrhaPnl ngi cal fi nric ara nnrnvered and conslrnctinn resimPd nnly aftar tha C)ffira of Archaeology and Historic PrpsPrvatinn has hart An opportunity to research the finds_ 14. Transportation Please see.attached transportation study for additional information on the proposed Motor Inn. a. Identify public streets and highways serving the site, and describe proposed accss to the existing street system. Show on site plans, if any. The site is accessed from West Valley Highway. b. Is the site currently served by public transit? If not, what is the approximate distance to the nearest transit stop? Transit stops within walking distance are located north of the site. c. How many parking spaces would the completed project have? How many would the •roject eliminate? The project will provide parking spaces, approx. 19 more than required y the Zoning Code. Evaluation for Agency Use Only d. Will the proposal require any new roads or streets, or improvements to existing roads or streets, not including driveways? If so, generally describe (indicate whether public or private). No. The City of Tukwila has programmed several short =range & long - range transportation improvements, as part of its 6 yr Transportation Improvement Program L1985- 1990), that should help alleviate peak hour congestion and improve traffic flows in the vicinity of the subject development. (Please see P1 n d Im- e. Will the project use (or occur in the immediate sProvements on rg 2tfor pecific vicinity of) water, rail, or air transportation? If so, generally describe. There are 2 rail lines which run north -south and lie east of West Valley Rd. f. How many vehicular trips per day.would be generated by the completed project? If known, indicate when peak volumes would occur. Please see Table 1 of the Traffic Study. g. Proposed measures to reduce or control transpor- tation impacts, if any: Please see Findings and Recommendations ( pg. 6) of Traffic Study. 15. Public Services a. Would the project result in an increased need for public services (for example: fire protection, police protection, health care, schools, other)? If _so, generally describe. The project would increase the workload for the Tukwila r'ire and Police uepts. b. Proposed measures to reduce or control direct impacts on public services, if any. The mgtel will be fully sprinkled. 16. Utilities a. Circle _ u_tilities crr.ently available at the site: ricity natural (fie serviced R are ewe , septic system, other. e site . . oped, no utilities are provided tor the site. However, the circled items above are available tor the motel use. b. Describe the utilities that are proposed for the project, the utility providing the service, and the general construction activities on the site or in the immediate vicinity which might be needed. Those activities common for equipment and underground utility installation. (e.q. tractors. trucks. grading & excavation equipment). Water, sewer. telephone, qas will serve the site. All utilities are under- ground. Same as the EIS. C. Signature Tne above answers are true and complete to the best of my knowledge. I understand tha the lead agency is relying on them to(inake its :eci, i0A Signature: Date Submitted: n 5vs reysc- Evaluation for Agency Use Only • Vegetation round at the Site Common Name TREES: Clack Cottonwood Big -leaf Maple Oregon Ash SHRUBS: Pacific Willow Japanese Knotweed Himalayan Plackberry Red Elderberry HEREACEOUS PLANTS: St i na i nr] Nettle Sourdock Buttercup var. Clover var. Foxelove Common Mullein English Plantain Mayweed Chamomile Hairy Cats -ear Wild Lettuce Common Tansy Common Dandelion Fescue -grass var. Foxtail Barley Bluegrass var. Source: R.W. Thorpe and Associates Scientific Marie Populus trichccarpa Acer macrophyllum Fraxinus Iatifolia I as i andra .Polygonum cuspidatu^i Rubus discolor Sambucus raceriosa Urtica lyallii Rumex crispus Ranunculus_ sp. Trifolium spp. Digitalis pur,urea Verbascum thaosus Plantaco lanceolata Anthemis cotula Hypochaeris radicata Lactuca sp. Tanecetur^ vulcare . Taraxacum officinale Festuca sp. Hordeun murinum Poa sp. Fish Species 2 the Green River Common Name Prickly Sculpin Threespine Stickleback Brown Bullhead Larne -mouth Black bass Chum Salmon Coho Salmon Chinook Salmon Yellow Perch ?Mountain whitefish Long -Nose Dace Speckled Dace Cutthroat Trout Steelhead Trout Rainbow Trout Dolly Varden.Trout Starry Flounder Scientific Name Cottus asper Gasterosteus aculeatus Ictalurus nebulosus Micropterus salnoides Oncorhynchus keta Oncorhynchus kisutch Oncorhynchus tshawtscha Pere: f l avescens Prosopium williamson1 Rhinichtays cataractac Rhinichtays oculus Salvo clarki Salvo gairdneri Salvo gairdneri Salvelinus nalma Prosopium stellatus Source: East Side Green River 14atershed DEIS, SCS, November, 1973. • • KJS ASSOCIATES, INC. Transportation Planning • Traffic Engineering July 30, 1985 1r. Ross Earnst, P.E. City Engineer City of Tukwila 6200 Southcenter Boulevard Tukwila, WA 96198 SUBJECT: Traffic Study for Nendeis Propo=sed Motor inn and Reiated Development at S 156th Street and nest Malley Road (SR 181) Dear Mr. Earnst: At the request of the JED Corporation, KJS Associates has prepare; an traffic impact study for the proposed Nendeis ;Tukwila Motor inn, restaurant and service station deveicpement. This study updates a previous study done by Centrac Associates (Traffic impact Analysis for Hampton inn Development, January 1985). Existing traffic data and the forecasts of `uture (1986) volumes without site development orepareo by Centrac were used as base data for our analysis. PROJECT DESCRIPTION The proposed development is located on SR 161 south of 1 -405, just west of the entrance to Langacres Race Track (5 156th Street). The site is bordered on the east by West Valley Road (SR. 181)- and on the west and south by the Green River. Nendels Tukwila deveiopement consists of a hotel with a total of 151 rooms, a quality restaurant (8,000 SF) and a gasoline service station with eight pumps. The proposal includes three driveways along the west side of SR 161, plus construction of the west leg of the S 158tH Street /SR 181 intersection. Although this lea will effectively serve as an entrance to the site in the near term, the City has plans to extend 159th westward across the Green River to provide a connection from SR 161 to Tukwila Parkway: when this is built, the west leg of the 158th. /SR 131 intersection will become part of the city street, and Nendeis will have to develop driveways along the south side of 156th to provide access to the site from this roadway. The three driveways on SR 181 will be limited to right in and right out only; left turn access into or out of.the site will only be allowed at the 153th Street intersection. EXISTING CONDITIONS The existing street/ highway system in the vicinity of the Nendeis Tukwila development is shown in Figure 1. Access to the site would be provided primarily by SR 161 (West Valley Road) via I -405 to the north; secondary access would be via Strander Blvd connecting with SR 181 to the south. 14230 NE 8th Street, Bellevue, Washington 98007 (206(644 -4766 KJS ASSOCIATES, INC. Transportation Planning • Traffic Engineering Mr. Ross Earnst July 30, 1985 Page 2 SR 181 is a five -lane roadway (two thru lanes in each direction plus a center two -way left turn lane), except for a 700 -foot section south of the site where only four lanes exist. Near the site a raised median and channelization prevent left turns toifrom SR 181 except at its intersection with S 158th Street. Traffic control in the site vicinity is provided by.traffic signals at major intersections, including Strander /ER 181 and I -405 N8 ramps/SR 181. There are stop signs at all other nearcy intersections. The 158th/SR 181 intersection is the main entrance into Longacres Race Track. During the racing season (April - October) the City of Renton assigns traffic control officers to manually control the traffic on the SR 181 from 2 -4 PM on ?Monday through Friday and 11 AM -12 P!9 on Saturdays, Sundays and holidays. Although the projected volumes for the SR 181/158th intersection (TRANSPO, 1982) may not meet signal volume warrants by 1986 (Hilton Hotel Draft E1E traffic study, The TRANSPO Group, i784), a new actuated traffic .signal was recommended by the•Centrac study. Centrac concluded that significant delays would occur without signalization due to high volumes of ieft turns to and from the Race Track, as well as left_ turning traffic toifrom the proposed project site. Also, the proposed hotel and restaurant development (located directly west of the rain entrance to Longarces) could generate significant pedestrian traffic between the site and Longarces; a signal would enhance pedestrian safety at this intersection. The developer has indicated his willingness to participate in funding a new fully actuated signal and channelization improvements at the 9R 181/153th Street intersection. It is expected that the adjacent property owners would also pay their proportional share of the cost of signal installation. Planned Improvements The City of Tukwila has programmed several short -range and long -range transportation improvements, as part of its Six -year. Transportation Improvement Program (1985 - 1990), that should help alleviate peak hour congestion and improve traffic flows in the vicinity of the subject development. These include:' * The north approach of SR 181 at the Strander intersection will be widened to accomcdate a right - turn -only lane, and sidewalks will be constructed the entire length of the Brock Residence Inn site (this site is south of the Nendels site and is under construction). r Widening of SR 181 from 5 to 7 lanes from 1-405 to Strander as a long range (1987 -89) transportation need to handle projected traffic volumes for this state highway. Providing an additional KJS ASSOCIATES, INC. Transportation Planning • Traffic Engineering Mr. Ross Earnst July 30, 1985 Page 3 southbound lane for the entire length Of Nendeis site would accomodate the ultimate 7 -lane roadway section for SR 181. * Extension of Tukwila Parkway to connect with S 158th Street at SR 181 with a new bridge crossing the Green River which would provide an alternative east -west route to Strander Blvd. The City Engineer has indicated that it would be 4 -5 years for the 158th extension to occur. * Widening of Strander (from Andover Park W to the existing Green River bridge) from 4 to 5 lanes as cart of connecting Strander to .SW 27th Street in Renton to provide a nee► east -west link south fo Langacres (1987 -89). WSDOT planned improvements: * Overlay, saftey and drainaoe improvements on SR .81 from 1 -405 to Strander. 4SOOTICity of Tukwila combined improvements: * Realignment of Scuthcenter Blvd. to intersect with Grady Way. * Widening of S 158th Street to 4 lanes (SR 161 to east city limits). * Improve pedestrian access and I -405 HOV lanes from Bellevue to Tukwila (1985 -87). PROJECT TRAFFIC Daily and peak hour trips generated by the hots'_, cuailty•restrauant,'and gasoline service station, were - generated using the trip generation, . statistics assembled by the Institute of TranSportation Engineers. (ITE Trip Generation, 1982). The categories specifically used for the trip • generation were hotel category 10, service station category 844 and quality restaurant category 831. Table 1 summarizes the daily and peak hour vehicle trips which would be generated by the proposed land uses at the Nendeis Motor inn site. The daily and PM peak traffic generated by the development were assigned to the proposed access driveways,,on SR 181, and then distributed to the adjacent street system as shown in Figure 2. .;approximately 20 percent of the project generated- traffic.was distributed to and from the Longacres Race Track due to the close promimity of the race track to the project site. The developer has been proposed a shuttle van that will travel between the hotel and the track entrance, to provide • • KJS ASSOCIATES, INC. Transportation Planning • Traffic Engineering Mr. Ross Earnst July 30, 1985 Page 4 a direct link for people from the hotel to visit the track; this may reduce site - generated vehicle traffic to /from the race tack. Thirty percent (30X) of the restaurant trips were assumed to come from the hotel and are not included in the traffic generation since the restaurant is within walking distance of.the hotel. The gasoline service station generated trips were estimated assuming that 407. of the PM peak hour volume involves vehicle traffic already on the adjacent street system for other purposes. This is a conservative estimate because the ITE Trip Generation report for category 844 suggests that 54 -56X of the peak hour volume already exists .on the adjacent street system. IMPACT ANALYSIS The estimated 3,069 daily and 173 PM peak hour trips for the restaurant, hotel and service station were combined with the projected i98 non-site traffic to estimate 1986 daily and PM peak volumes far the developement. The projected increase in traffic along SR 181 due to the new development is 2 -47 for the daily traffic and 1 -2 % of the FM peak traffic. These volumes are shown on Figures 3 and 4. Figure 3 shows the average weekday traffic volumes with and without the project as well as the percent increase due to the development. Figure 4 shows the estimated PM peak volumes with and without the project. In order to estimate the traffic impacts of the proposed project during average weekday peak conditions the 4:00 -5:00 PM peak period were analyzed. Level of Service calculations were done at the intersection of SR 181 and S 158th Street for 1986 volumes, with and without'the project development. The level of service analysis showed (assuming a traffic actuated signal would be installed at this location) that on a typical day with the Longarces Race track open that the intersection would operate at LOS C (v /c = 0.76) in 1986 during the PM peak hour. During the 3:00 - 4:00 PM period when inbound Longacres traffic is heaviest, the intersection would operate at LOS E (v /c = 0.95) unless dual southbound left turn lanes are installed to handle the Lengacres traffic. With the proposed Nendeis hotel deveiopement, the SR 131 and S 158th Street intersection would still operate at LOS C (vic =.79) during the PM peak hour with the Longarces Race Track open. Centrac Associates (Hampton Inn Development, 1985, p.16). analyzed several other intersections in the site vicinity.. Their results show that ail the intersections are currently operating at an acceptable LOS (LOS u or better) except the SR -181 and Strander Blvd which is operating near KJS ASSOCIATES, INC. Transportation Planning • Traffic Engineering Mr. Ross Earnst July 30, 1985 Page.5 capacity conditions (LOS D /E). LOS calculations by Centrac for the intersections of SR 181 with Strander. Boulevard and with the I -405 ramps showed that project traffic would have an insignificant effect on these intersections; thus, these LOS computations were not repeated for this study. 388 parking spaces for the proposed restaurant /hotel developesent will be provided on -site without any parking required off -site or on street on bordering arterials and roadways. No projected parking overflows are anticipated during peak periods, although the enforcement of patron - parking -only may be critical during the Longacres racing season. Driveway Analysis The proposed site development plan shows three driveways serving the site along SR 181, plus the entrance at 5 158th Street which will later become part of the city's street system when 158th is extended. In the future, additional driveways will be developed along the north boundary of the site to provide access to S 158th Street when it is constructed. The City Engineer has expressed concern about the number of driveways serving the site, and their effect on traffic flow along ER 181, especially the northern most driveway serving the proposed Exxon service station. Figure 5 shows estimated PM peak hour turning movements at the 158th Street entrance and .at the driveways on ER 181. Turning movements would be limited to right in, right out at the driveways, and left turns would only be allowed at the 158th Street intersection. As these volumes show, the traffic in and out of any one driveway would be small and would not adversely affect through traffic on SR 181. The middle driveway serves the major parking circulation aisle for the hotel and restaurant. The southern driveway, chile not critical, provides cdnvenient egress from the parking lot adjacent to the restaurant and for trucks supplying the restaurant. The Exxon driveway has been designed to exceed the recommended standards for driveways which have been adopted by the institute of Transportation Engineers. In its recent publication, Guidelines for Driveway Design and Location (1TE, 1985), the institute recommends a minimum offset of 50 feet for a driveway located near a liajor intersection (30-foot curb radius at the intersection, a 5 -foot tangent section, and a 15 -foot radius at the driveway). The proposed Exxon. driveway would have.a 65 -foot offset from 158th Street (30 -foot corner radius, 20 -=mot ' tangent, 15-feat driveway radius), or an additional 15 feet beyond the recommended minimum spacing. The Exxon driveway provides a smooth traffic flow for motorists entering and leaving the Exxon station, Figure 6 shows the path of a typical motorist southbound on SR 181 going to the service station under the KJS ASSOCIATES, INC. Transportation Planning • Traffic Engineering Mr. Ross Earnst July 30, 1985 Page 6 proposed configuration. The motorist can turn right into the site,and choose an available pump quickly and efficiently. Exiting the station can be accomplished by a simple left or right turn to get to SR 181 via the middle driveway or at 158th Street. Without this driveway, these maneuvers become more difficult as illustrated in Figure 7. In the near term, drivers could turn right at the 158th Street entrance, and wake a U-turn to the left into the site to reach one of the pumps. Drivers could then exit the site by heading south to the middle driveway, or by making a 360- degree sweep around the station to reach 158th Street. Once 158th Street is extended westward, the left turn pocket at the signailzed intersection with SR 181 will likely prevent motorists entering the Exxon site directly via 158th. (See Fioure 8.) The length of the left turn storage Docket and the required taper will probably extend beyond the Exxon site's frontage on 158th Street. Left turns would not be allowed across the eastbound left turn channelization. Motorists on SR 181 desiring to access the Exxon station would have to enter one of the Nendels driveways and use the internal circulation roads to reach the gas pumps; such inconvenience may have an adverse impact on the attractiveness of the gas station to motorists. Thus, it appears that the Exxon driveway would best serve the public need by allowing convenience ingress and egress to /from the service station site. FINDINGS AND RECOMMENDATIONS 1. The proposed Nendels hotel /restaurant /gas station development would generate up to 3,069 new daily vehicle trips on the surrounding street system. • In the PM peak hour, the project would add 173 vehicle trips. L. The increase in traffic volumes on SR 181 would be 1 to 4 percent of daily non- project traffic flows. This small increase is not significant and probably would not be noticeable to other motorists an SR 181 (West Valley Road). ,. Initially, primary access to the Nendels site would ^e via an entrance at the intersection of S 158th Street and SR 181 (West Valley Road). The City of Tukwila plans to extend 15Eth Street westward across the Green River to connect with Tukwila Parkway. When this extension is built, the interim entryway to the Nendels site will become part of the city. street, and driveways will be built along the new 158th to provide access into the site. • • KJS ASSOCIATES, INC. Transportation Planning • Traffic Engineering Mr. Ross Earnst July 30, 1985 Page 7 4. Secondary access will be provided by three driveways along SR 181, one for the proposed Exxon station and two for the hotel /restaurant. These driveways. will be limited to right - turn -in, and right -turn -out movements only. Each driveway serves separate functions: (a) the northerly driveway serves the Exxon station and creates smooth traffic flow through the site, (b) the middle driveway provides a main entryway to the hotel - restaurant complex and, after lSSth street is built west of SR -181, may become the primary entrance to the site for motorists from the north. (c) the southerly driveway enhances circulation for the restaurant parking lot and serves delivery trucks exiting the site. . 5. Each of the three driveways along SR 181 would be designed and constructed to City of Tukwila and WSDOT standards. Each serves a unique function and contributes to an efficient overall circulation system for the site. The Exxon driveway allows southbound drivers on SR 181 to enter the gas station site and drive to an .open pump with a minimum of turns; the proposed location and design of this driveway meets ITE recommended standards. However, since left turns will not be allowed into or out of this driveway; the width of the driveway could be reduced from 30 feet to 24 feet. The middle driveway provides the main access to the hotel and restaurant from West Valley Road, and also serves southbound traffic from the Exxon gas station. It can also be reduced to 24 feet wide. The south driveway serves the restaurant parking lot, and.is the least critical to the overall site circulation plan. Virtually no one will use the driveway to enter the site, and exiting traffic volumes would be minimal. 6 A previous study on the Nendels site by Centrac Associates (Traffic impact Analysis for Hamoton inn Deveiooment, January 1985) recommended construction of dual southbound left turn lanes on SR -181 at 158th street to accommodate Longarces traffic. Signalization of the intersection was recommended to handle the Longarces entering and exiting traffic volumes, pedestrian traffic between the site and Longarces, and emergency vehicle access to Longarces and the ±fendeis site. KJSA contours with these recommendations. KJS ASSOCIATES, INC. Transportation Planning '• Traffic Engineering Mr. Ross Earnst July 30, 1985 Page 8 7. Assuming the intersection of 156th and ER 181 is signalized, it would operate at LOS C during the 1586 peak hour•with or without the proposed Nendels development. During the 3 -4 PM Longacres peak period, the intersection would operate at LOS E unless southbound left turn lanes are installed to handle the Longacres traffic. 9. The developer of the Nendels site should participate in funding the installation of a traffic signal and turn channeiization at the intersection of S 158th Street and ER 181. Pedestrian crosswalks and pedestrian - actuation of the signal should also be provided. The project would increase total daily.traffic volumes at the intersection by 7.3 percent. • 9. Tukwila has proposed widening SR 181 to 7 lanes from 1 -405 to Strander Boulevard. The Nendeis development should participate in funding construction of the additional lane along the west side of SR 181 along its east property line to accommodate the. ultinate 7 -lane cross section. This extra lane will facilitate right -turn movements into and out of the Nendels driveways, as well as provide additional capacity for thru traffic. 10. The proposed hotel /restaurant development will generate upto 300 potential pedestrian trips daily between the site and the Longacres Race Track (when the track is openi. Provision of sidewalks on West Valley Road, crosswalks and pedestrian signals at the 158th6SR 181 intersection will allows these movements to be made safely. In addition, the developer has pr oposed to operate a shuttle bus service between the race track and the hotel to accommodate any of.these pedestrian trips. 11. The development will provide 388 parking spaces on -site. This should satisfy'all development- related parking demand generated by the Nendels development. I trust that this letter report provides adequate information for your review of the transportation impacts of the proposed Nendels :Motor Inn and related developments. Please tali :re if you have any questions. Yours truly, KJS Associates, Inc. h P. Savagc,,u r. rrincipal Enoineer KJS Associates TRAFFIC IMPACT STUDY LEND 15,400 Estimated Daily Traffic Volume (2 —Way AWDT 1984-85) 0 Traffic Signals Stop Signs,.: -. .:,.._.. Figure 1 EXISTING CONDITIONS SOUTHCENTER BLVD. TUKWILA PKWY. EVANS-BLACK OR. 27% 828 41 VO t11M7voNO1 BAKER BLVD. ANDOVER PARK E STRANGER BLVD. Off, Base Map from Centrac Assoc. (Hampton Inn _1985) KJS Associates TRAFFIC IMPACT STUDY LEND % of total traffic generated Figure 2 PROJECT GENERATED TRAFFFIC AND TRIP DISTRIBUTION AWDT 28000 28552 552 1986 w/o project 1986 v/ project increase % increase TRAFFIC IMPACT STUDY .Figure 3 Projected 1986 Daily Traffic Volumes With and Without The Proposed. project ELL 1588 3% L _ 9.7% KJS associates LkgEtsig 86 w o .ro ect 1986 w projec Figure 4 N Projected 1986 P14 Peak Traffic Volumes With and Without Proposed Project • 50 70 715 - 5 Exxon site t r Nendels Hotel and Restaurant 1a 25 1145 1 2388 114 18 < 123 125 Figure 5 1986 PM Peak Hour•. Turning Movement with project, with'Longacres open. ••• ••• 4P0541t5L-5- bt SSI A)3E5 - 4 - I • 5.11: A 3 PKftG °S0V:DE.0 • 9 Eie OR • • ekes .11.• !,:° ..,4 . - . • ...., pp- / -V-"arms f22 Figure 6 Circulation Plan 1. , I MITIGATED DETERMINATION OF NONSIGNIFICANCE EPIC - 286 -85 Nendels Motor Inn The following mitigating measures are attached to this determination: 1. Dedication and improvement of a right turn lane along West Valley Highway per requirements of the Public Works Department and Washington State Department of Transportation. 2. Prior to issuance of a Certificate of Occupancy: A. Awarding of a contract for construction of a traffic signal and crosswalk at S. 158th St. across West Valley Highway, B. Completion of channelization at this intersection, C. Construction of a right turn lane along West Valley Highway, D. Limiting access to right and left turns in only at S. 158th St. and right turn out only at the southerly curb cut of the development ( no left turns out of the property) until the traffic signal is installed. The Public Works Department reserves the discretion to require installation of temporary barriers in West Valley Highway per approval of the State Department of Transportation to prevent left turns from the property. 3. Accomodation of the future potential extension of Tukwila Parkway across the northern portion of the property. 4. Maximum of two access points along West Valley Highway, exclusive of S. 158th St. TO BE COMPLETED BY APPLICANT Evaluation for Agency Use Only E. SUP ?LEMENTAL SHEET FOR ALL PROJECT AND NON PROJECT PROPOSALS The objectives and the alternative means of reaching the objectives for a proposal will be helpful in reviewing the aforegoing items of the Environmental Checklist. This information provides a general overall perspective of the proposed action in the context of the environmental infor- mation provided and the submitted plans, documents, suppor- tive information, studies, etc._ 1. What are the objective(s) of the proposal? The proponent intends to fill a market demand for a motor inn which primarily caters tc the airport traveler. The motor inn would cater to industrial /commercial customers destined tor SouthCenter and Greater Tukwila from the airport. Loneequently, convenient access to Sea -Tac via I -405 and the local industrial /commercial businesses in Greater 'I'Ukwila is required. 2. What are the alternative means of accomplishing these objectives? Develop a larger hotel than presented in this proposal. For example., the previous proposal for this site consisted of an 8 story, .2/4 room hotel with dining room, cocktail lounge and banquet facilities. rurther description is provided in the Tukwila Hotel EIS 1982. Uther commercial uses could be developed than the service station such as small convenience grocery store or fast food. restaurant. 3. Please compare the alternative means and indicate the preferred course of action: The previous hotel proposal had 123 more rooms than the Nendels proposal of 151 rooms. Impacts created by this proposed project will be generally less tnan the previous proposal in respect to aesthetics, an flemaind for services. Trattic generation will be approx. 200 trips per day greater due to the proposed gas station. Ocher street oriented businesses such as grocery store or fast uuU restaurant will have similar traffic impacts as the proposed gas station. I. Figure 8 . Circulation Plan 31 . • - 404 F UT u RE LEFT T.4804— _es2c_ktfix _ • • • 1 P 1 P ■ 3Of - WALV- 1-c5SLV,,S titki3E5 PAR. v: DED ?-)F A _ 6■71177„, '7 44.\\,2C-VL DRIVEWAY CLOSE 1 • • TABLE 1 TRIP GENERATION SUMMARY Nendels Motor Hotel ITE Trip Trip Rate AWDT PM PEAK Category Generator AWDT /PM Pk in out Total 310 Hotel 10.5/.73 1568 55 56 110 (151 units) per room 831 Quality 74.9/6.14 599 30 19 49 Restaurant per 1000 SF (8000 sq. ft) less 30% from hotel -180 -9 -6 -15 Net Vehicle generation 419 21 13 34 844 6as Station 133/3.63 1064 26 22 48 (8 pumps) per pump 40X PM peak volume an road -11 -8 -19 Net traffic 15 14 29 GRAND TOTALS: 3069 91 83 173 INVIPORTANT INFORM ION MiCEVM ABOUT YOUR GEOTECHNICAL ENGINEERING REP G A 1985 CITY OF TUKWILA PLANNING DEPT. L More construction problems are caused by site subsurface conditions than any other factor. In the early 1970's., subsurface problems were frequently being resolved through lawsuits. In fact, the situation had grown to such alarming proportions that consulting geotechnical engineers had the worst professional liability record of all design professionals. By 1980, Association of Soil and Foundation Engineers - member consulting soil and foundation engineers had the best profes- sional liability record. This dramatic turn -about can be attributed directly to client acceptance of problem - solving programs and materials developed by ASFE for its members' application. This acceptance was gained because clients perceived this approach to be in their own best interests. Disputes benefit only those who earn their living from others' disagreements. The following suggestions and observa- tions are offered to help you reduce the geotechnical-related delays, cost -over- runs and other costly headaches that can occur during a construction project. A GEOTECHNICAL ENGINEERING REPORT IS BASED ON A UNIQUE SET OF PROJECT - SPECIFIC FACTORS A geotechnical engineering report is based on a subsurface exploration plan designed to incorporate a unique set of project- specific factors. These typi- cally include: the general nature of the structure involved, its size and configu- ration; the location of the structure on the site and its orientation; access roads, parking lots, and underground utilities, and the level of additional risk which the client assumed by virtue of limitations imposed upon the exploratory program. To help avoid costly problems, consult Earth Consultants, Inc. to determine how any factors which change subsequent to the date of this report may affect our recommendations. Unless we indicate otherwise, your geotechnical engineering report should not be used: When the nature of the proposed structure is changed, for example, if an office building will be erected instead of a parking garage, or if a refrigerated warehouse will be built instead of an unrefrig- erated one. When the size or configuration of the proposed structure is altered. When the location or orientation of the proposed structure is modified. For application to an adjacent site. We cannot accept responsibility for problems which may develop if we are not consulted, after factors considered in our reports development have changed. MOST GEOTECHNICAL "FINDINGS" PROFESSIONAL ESTIMATES Site exploration identifies actual subsurface conditions only at those points where samples are taken, when they are taken. Data derived through sampling and subsequent laboratory testing are extrapolated by the geotech- nical engineer who then renders an opinion about overall subsurface con- ditions, their likely reaction to proposed construction activity, and appropriate foundation design. Even under optimal circumstances, actual conditions may differ from those be- lieved to exist, because no geotechnical engineer, no matter how qualified, and no subsurface exploration program, no matter how comprehensive, can reveal what is hidden by earth, rock and time. For example, the actual interface be- tween materials may be far more gradual or abrupt than the report indicates, and actual conditions in areas not sampled may differ from predictions. Nothing can be done to prevent the unantici- pated, but steps can be taken to help minimize their impact. For this reason, 1 most experienced owners retain their geotechnical consultant through the construction stage, to identify vari- ances, conduct additional tests which may be needed, and to recommend solu- tions to problems encountered on site. SUBSURFACE CONDITIONS CAN CHANGE Subsurface conditions may be modified by constantly- changing natural forces. Because a geotechnical engineering report is based on conditions which existed at the time of subsurface explo- ration, construction decisions should not be based on a geotechnical engineer- ing report whose adequacy may have been affected by time. Please consult us to learn if additional tests are advisable before construction starts. Construction operations at or adjacent to the site and natural events such as floods, earthquakes or groundwater fluctuations may also affect subsurface conditions and thus, the continuing adequacy of a geotechnical report. The geotechnical engineer should be kept apprised of any such events, and should be consulted to determine if additional tests are necessary. A GEOTE RNICAL ENGINEERING REPORT IS SUBJECT TO MISINTERPRETATION Costly problems can occur when other design professionals develop their plans based on misinterpretations of a geotech- nical engineering report. To help avoid these problems, the geotechnical engi- neer should be retained to work with other appropriate design professionals to explain relevant geotechnical find- ings and to review the adequacy of their plans and specifications relative to geotechnical issues. BORING LOGS SHOULD NOT BE SEPARATED FROM THE ENGINEERING REPORT Final boring logs are developed by the geotechnical engineer based upon his interpretation of field logs (assembled by site personnel) and laboratory evaluation of field samples. Only final boring logs customarily are included in geotechnical engineering reports. These logs should not be redrawn for inclusion in architectural or other design draw- ing, because drafters may commit errors or omissions in the transfer process. Although photographic reproduction elimi- nates this problem, it does nothing to minimize the possibility of contractors misinterpretating the logs during bid preparation. When this occurs, delays, disputes and unanticipated costs are the all -too- frequent result. To minimize the likelihood of boring log misinterpretation, give contractors ready access to the complete geotechni- cal engineering report. Those who do not provide such access may proceed under the mistaken impression that simply disclaiming responsibility for the accuracy of subsurface information always insulates them from attendant liability. Providing the best available information to contractors helps prevent costly construction problems and the adversarial attitudes which aggravate them to disproportionate scale. READ RESPONSIBILITY CLAUSES CLOSELY Because geotechnical engineering is based extensively on judgement and opinion, it is far less exact than other design disciplines. This situation has resulted in wholly unwarranted claims being lodged against geotechnical consultants. To help prevent this problem, geotechnical engineers have developed model clauses for use in written transmittals. These are not exculpatory clauses designed to foist the geotechnical engineer's liabilities onto someone else. Rather, they are definitive clauses which identify where the geotechnical engineer's respon- sibilities begin and end. Their use helps all parties involved recognize their individual responsibilities and take appropriate action. Some of these definitive clauses are likely to appear in your geotechnical engineering report, and you are encouraged to read them closely. If you have questions, please contact us. Earth • Consultants Inc. Geotechnical Engineering and Geology J.E.D. Corporation 2230 Rucker Avenue Everett, Washington 98201 Attention: Ted Dahl Gentlemen: August 1, 1985 E -2699 We are pleased to submit herewith our report entitled "Geotech- nical Engineering Study, Nendels Motor Inn, West Valley Highway at South 158th Street, Tukwila, Washington." This report presents the results of our field exploration, laboratory tests, and engineering analysis. Previous studies were conducted on the site by Shannon and Wilson for the Christensen Group, Inc. The Christensen Group, Inc. was planning a medium -rise tower hotel on the site. This building would have had heavy foundation loads thus deep foundations or a mat foundation with a surcharge load would have been required. The Shannon -and Wilson report to Jensen, Krauss and Schoenleber was dated March 12, 1982, and their reference number was W- 3919 -02. The Nendel Motor Inn is to be a light wood framed three -story structure. Soils near the ground surface are very loose but essentially granular. A deeper clayey silt layer is present and could influence long -term settlement. However, it is our opinion that post- construction settlement will be on the order of two inches. Differential settlement between lightly loaded foundations and those with heavier loads will be on the order of one inch. It has been assumed that these settlements are acceptable and our report has been prepared accordingly. If such settlements are not acceptable, we can prepare surcharge or deep foundation design criteria recommendations, if requested. Site soils are very moisture sensitive. If earthwork is done in wet weather conditions, the contractor could expect that on -site soils would be easily disturbed and difficult to compact. 1805 - 136th Place N.E., Suite 101, Bellevue, Washington 98005 Phone: (206) 643- 3780 /Seattle (206) 464 -1584 J.E.D. Corporation August 1, 1985 E -2699 Page 2 The following sections of this report describe our study and contain recommendations regarding foundation design criteria, earthwork considerations, and site drainage. This report has been prepared for specific application to this project in accordance with generally accepted geotechnical engineering practices for the exclusive use of the J.E.D. Corporation and their representatives. No other warranty, expressed or implied, is made. We recommend that this report, in its entirety, be included in the project contract documents for the information of the contractor. PROJECT DESCRIPTION At the time our study was performed, the site and proposed building locations were as shown schematically on the Boring Location Plan, Plate 2. Based on our discussions with your architect, we understand that it is planned to construct a three -story wood framed building containing approximately one hundred fifty one (151) rooms and 73,335 square feet in the Phase I portion and one hundred seven (107) rooms and 42,912 square feet in the Phase II addition. A partial basement at Elev. 21 is planned in the building core. The finish floor of the main portion of the building will be Elev. 28.75 requiring about four feet of fill to meet final grades. We understand that maximum continuous footing loads of thirty five hundred (3500) pounds per lineal foot and maximum column loads of 40 kips are anticipated. If any of the above design criteria change, we should be consulted to review the recommendations contained in this report. In any case, it is recommended that Earth Consultants, Inc. provide a general review of the final design. SITE CONDITIONS Surface The proposed building site is located southwest of the intersection of West Valley Highway and South 158th Street in Renton, Washington. The property is rectangular in shape and essentially level except for a slight uphill grade towards the southeast. Side grades vary between Elev. 23 and 25. It is bound on the east by the West Valley Highway and on the south and west by the Green River. At the time of our exploration the site was covered by grasses and thistles with large diameter trees bordering the Green River. The pastureland was fenced and being utilized by grazing sheep. Earth Consultants, Inc. J.E.D. Corporation August 1, 1985 E -2699 Page 3 Subsurface The site was explored by Earth Consultants, Inc. by drilling one test boring at the location shown on Plate 2. Please refer to the boring log, Plate 4, for a detailed description of the conditions encountered at the boring location. A description of the field exploration methods and laboratory testing program is included in this report following the Discussion and Recommendations section. The site is in a former flood plain so the near - surface soils were placed by alluvial action. The near - surface soils consist of very loose sandy silts and silty sands. The density of the sands increase with depth due to an increase in overburden pressures. In the test boring drilled under our observation the soils consisted of about fifteen (15) feet of very loose sandy silt to silty sand overlying an approximately five feet thick layer of medium stiff clayey silt. Below the clayey silt was medium dense to dense sands. The Shannon and Wilson borings found a deeper soft clayey silt layer at a depth of on the order of sixty (60) feet below the ground surface. The groundwater at the site is expected to correspond closely with the level of the nearby Green River. We observed water levels at nineteen and one -half (19.5) feet below grade but Shannon and Wilson observed water levels on the order of ten feet . below grade in the winter of 1982. Fluctuations in groundwater levels may be expected as the groundwater level is not static. DISCUSSION AND RECOMMENDATIONS General As previously mentioned, there are very loose sandy silts and sands near the ground surface. Also there is a soft compressible clayey silt layer at depth. The loose sandy silts and sands are compressible; however, most settlement occurs within this strata as soon as loads are applied. About 70 percent of total settlement in these strata will occur within a couple of weeks after the loads are applied. The deeper clayey deposits have longer -term consolidation characteristics and thus will contribute more to long -term settlement. Column and footing loads for this structure are similar to tilt -up warehouse structures of which numerous structures have been constructed in the valley. Based on our experience with these types of structures and calculations based on subsurface data obtained by the test borings, we estimate that total post- construction settlement will be about two inches with differential settlements of about one inch. Earth Consultants, Inc. J.E.D. Corporation August 1, 1985 E -2699 Page 4 Prior to placement of the fill, we recommend installation of at least five settlement markers within the fill area. These markers should be protected from disturbance by construction equipment. The markers should be surveyed by Earth Consultants, Inc. personnel or a licensed surveyor during fill placement and at intervals of 2, 4, 8, 16 (and so forth) days after completion of the fill placement. The initial reading should show the natural ground elevation and readings taken during surcharge placement should show the surcharge fill thickness. We will evaluate the settlement readings. Once the settlement has stabilized the foundation construction may proceed. We estimate that the fill should remain in place about three to four weeks before foundation construction. Foundations The proposed structure may be supported on conventional conti- nuous and spread footings bearing on at least two feet of granular structural fill. The upper surface of the underlying soil should also be recompacted to the maximum extent possible. Overexcavation of soil below the footing may be required depending on final site grades. Fill placed under footings should extend outwards from the edge of the footings at least two feet. Exterior footings should be bottomed at a minimum depth of twelve (12) inches below the lowest adjacent outside finish grade. Interior footings may be at a depth of twelve (12) inches below the top of the slab. The footings may be designed for an allowable soil bearing capacity of two thousand (2000) pounds per square foot (psf). Continuous and individual spread footings should have minimum widths of twelve (12) and eighteen (18) inches, respectively. A one -third increase in the above bearing pressures may be used when considering short term wind or seismic loads. Lateral loads due to wind or seismic forces may be resisted by friction between the foundations and the supporting compacted fill subgrade or by passive earth pressure on the foundations. For the latter, the foundations must be poured "neat" against the existing soil or backfilled with a compact fill meeting the requirements of structural fill. A coefficient of friction of 0.35 may be used between the structural foundation concrete and the supporting subgrade. The passive resistance of undisturbed natural soils and well compacted fill may be taken as equal to the pressure of a fluid having a density of two hundred fifty (250) pounds per cubic foot (pcf). We recommend that drains be placed around all perimeter foot- ings that are placed below existing grades. Drainage around basement walls is particularly critical. The drains should be Earth Consultants, Inc. J.E.D. Corporation August 1, 1985 E -2699 Page 5 constructed with a four inch diameter perforated . pipe bedded and covered with free draining gravel. The drains should have a positive gradient towards suitable discharge facilities. The footing drainage system should not be tied into the roof drainage system until the drains are tightlined well away from the building. The footing excavation should be backfilled with granu- lar soil except for-the top foot which should be backfilled with a relatively impermeable soil such as silt, clay or topsoil. Alter- natively, the surface can be sealed with asphalt or concrete pave- ments. Slab -on -Grade Floors Slab -on -grade floors may be supported on twelve (12) inches of granular structural fill. Any disturbed native soils below the structural fill must be either recompacted or replaced with structural fill. The slab should be provided with a minimum of four inches of free draining sand or gravel. We also recommend that a vapor barrier such as a 6 mil plastic membrane be placed beneath the slab to reduce water vapor transmission through the slab and the resultant moisture accumulation. Two inches of sand may be placed over the membrane for protection during construction and to aid in curing of the concrete. Retaining and Foundation Walls Retaining and foundation walls should be designed to resist lateral earth pressures imposed by the soils retained by these structures. Walls that are designed to yield an amount equal to at least 0.002 times the wall height can be designed to resist the lateral earth pressure imposed by an equivalent fluid with a unit weight of thirty (30) pcf. If walls are to be restrained at the top from free movement, a uniform force of one hundred (100) psf should be added to the equivalent fluid pressure force. For calculating the base resistance to sliding, we recommend using a passive pressure equivalent to that exerted by a fluid having a density of two hundred fifty (250) pcf and a coefficient of friction of 0.35. The wall pressures apply only for a maximum wall height of ten feet. It is assumed that no hydrostatic pressures act behind the wall and that no surcharge slopes or loads will be placed above the walls. If surcharges are to be applied they should be added to the above lateral pressures. Retaining and foundation walls should be backfilled with compacted free - draining soils with no organics. The soil should contain no more than 5 percent silt or clay and no particles greater than four inches in diameter. The percentage of particles Earth Consultants, Inc. 1 • J.E.D. Corporation August 1, 1985 E -2699 Page 6 passing the No. 4 sieve should be between 25 and 70 percent. Alternatively, a geotextile product such as Miradrain may be used. We recommend the use of footing drains at the base of all perimeter retaining wall footings. The footing drains should be surrounded by at least six inches of one- inch -minus washed rock, and provided with a positive gradient towards suitable discharge facilities. The pipe invert should be at least as low as the bottom of the footing. For retaining walls, other than basement walls, weepholes can be used. The weepholes should be as low as possible to maintain drainage behind the walls. When weepholes are provided, all backfill within eighteen (18) inches of the weephole should "consist of one- inch -minus washed rock. Excavations and Slopes In no case should excavation slopes be greater than the limits specified in local, state and national government safety regula- tions. Temporary cuts greater than four feet in height should have an inclination no steeper than 1:1 (Horizontal:Vertical). All permanent cut and fill slopes should be inclined no steeper than 2.5:1 (H:V). These recommendations are applicable to slopes with a maximum height of ten feet. If higher slopes are anticipated, we should be contacted for the appropriate design and construction criteria. We also recommend that all excavated slopes be examined by Earth Consultants, Inc. to verify that conditions are as anticipated. Supplementary recommendations can then be developed, if needed, to improve stability,-' including flattening of slopes or installation of surface or subsurface drains. In any case, water should not be allowed to flow uncontrolled over the top of any slopes. 2 All permanently exposed slopes should be seeded with an appropriate species of vegetation to reduce erosion and improve stability of the surficial layer of soil. Site Drainage We suggest that appropriate locations of subsurface drains other than footing drains, if needed, be established during grading operations by a representative of Earth Consultants, Inc., at which time the seepage areas, if present, may be more clearly defined. The excavation and site should be graded so that surface water is directed off the site and away from the tops of slopes. Water should not be allowed to stand in any area where buildings, slabs, or pavements are to be constructed. During construction, loose surfaces should be sealed at night by compacting the surface soils Earth Consultants, Inc. J.E.D. Corporation August 1, 1985 E -2699 Page 7 to reduce the infiltration of rain into the soils. Final site grades should allow for drainage away from the building founda- tions. We suggest that the ground be sloped 3 percent for a distance of at least ten feet away from the buildings except in areas that are to be paved. Pavement Areas All parking and roadway areas may be supported on a minimum of twelve (12) inches of granular structural fill placed in accordance with the Site Preparation section of this report. A greater thickness and /or engineering fabric may be needed to stabilize soft, wet or unstable areas. If fill depths are less than eighteen (18) inches, we recommend placement of a fabric over the native soils. The upper twelve (12) inches of pavement subgrade should be compacted to at least 95 percent of the maximum density. Below this level a compactive effort of 90 percent would be adequate. The pavement section for lightly loaded traffic and parking areas should consist of two inches of asphalt concrete (AC) over four inches of crushed rock base (CRB) or three inches of asphalt treated base (ATB). Heavier loaded areas would require thicker sections. We will be pleased to assist you in developing appropriate pavement sections or specifications for heavy traffic zones, if needed. -Site Preparation and General Earthwork The building and pavement areas should be cleared of all trees, brush and tall grass. Removal of the grass root mat is not necessary where fill depths are greater than eighteen (18) inches. Stripped materials should be removed from the site or stockpiled for later use in landscaping, if desired. The stripped materials should not be mixed with any materials to be used as structural fill. Structural fill is defined as any fill placed under build- ings, roadways, slabs, pavements, or any other load bearing areas. Following the stripping and clearing operation, the ground surface where structural fill, foundations, or slabs are to be placed should be proof rolled. All proof rolling should be performed under the observation of a representative of Earth Consultants, Inc. Soil in any loose or soft areas should be removed and replaced with structural fill to a depth that will provide a stable base beneath the general structural fill. Structural fill under floor slabs and footings should be placed in horizontal lifts and compacted to a minimum 95 percent of the maximum dry density in accordance with ASTM Test Designa- tion D- 1557 -70 (Modified Proctor). The fill materials should be placed at or near the optimum moisture content. Fill under Earth Consultants, Inc. • • J.E.D. Corporation August 1, 1985 E -2699 Page 8 pavements and walks should also be placed in horizontal lifts and compacted to 90 percent of maximum density except for the top twelve (12) inches which should be compacted to 95 percent of maximum density. Ideally, structural fill to be placed in wet weather should consist of a granular material with a maximum size of three inches and no more than 5 percent fines passing the No. 200 sieve. During dry weather, any compactible non - organic soil can be used as structural fill. However, we recommend that at least the upper twelve (12) inches of fill below slabs and two feet of fill below footings meet the wet weather fill requirements. FIELD EXPLORATION AND LABORATORY TESTING Our field exploration was performed on July 25, 1985. Subsurface conditions at the site were explored by drilling one boring to a depth of forty nine (49) feet below the existing grade. The boring was drilled by Drilling Unlimited using a truck - mounted drill rig. Continuous flight, hollow stem augers were used to advance and support the borehole during sampling. The location of the boring was approximately determined by pacing from property corners. The elevation of the .boring was approximately determined by interpolation between contour lines shown on the site plan of the Shannon and Wilson report. The location and elevation of the boring should be considered accurate only to the degree implied by the method used. The location is shown on the Boring Location Plan, Plate 2. The field exploration was continuously monitored by a geotechnical engineer from our firm who classified the soils encountered and maintained a log of the boring, obtained representative samples, measured groundwater levels, and observed pertinent site features. A slotted standpipe was installed in the boring to monitor groundwater levels. All samples were visually classified in accordance with the Unified Soil Classification System which is presented on Plate 3, Legend. The log of the boring is presented on Plate 4. The final log represents our interpretations of the field log and the results of the laboratory examination and tests of field samples. The stratification lines on the log represent the approximate boundary between soil types. In actuality, the transition may be gradual. Standard Penetration Tests (SPT) were performed at selected intervals in accordance with ASTM Test Designation D -1586. A Shelby tube sampler was used to obtain less disturbed soil samples at selected depths. The Shelby tube sample was driven with a one hundred forty (140) pound hammer falling thirty (30) inches. Earth Consultants, Inc. J.E.D. Corporation August 1, 1985 E -2699 Page 9 Representative soil samples were placed in closed containers and returned to our laboratory for further examination and test- ing. Visual classifications were supplemented by index tests such as sieve analyses and Atterberg Limits on representative samples. Results of density and moisture determinations, together with clas- sifications, are shown on the boring log included in this report. The results of three sieve analyses are illustrated on Plate 5, Grain Size Analyses. LIMITATIONS Our recommendations and conclusions are based on the site materials observed, selective laboratory testing and engineering analyses. The conclusions and recommendations are professional opinions derived in accordance with current standards of practice. No warranty is expressed or implied. The recommendations submitted in this report are based upon the data obtained from the boring. Soil and groundwater conditions may vary from those encountered by the boring. The nature and extent of variations may not become evident until construction. If variations then appear, Earth Consultants, Inc. should be allowed to reevaluate the recommendations of this report prior to proceeding with the construction. Additional Services It is recommended that Earth Consultants, Inc. provide a general review of the final design and specifications to verify that the earthwork and foundation recommendations have been properly interpreted and implemented in the design and in the con- struction specifications. It is also recommended that Earth Consultants, Inc. be retained to provide geotechnical services during construction. Because of the nature of this project and soil conditions, we do not accept responsibility for the performance of the foundation or earthwork unless we are retained to review the construction drawings and specifications, and to provide construction observa- tion and testing services. This is to observe compliance with the design concepts, specifications or recommendations and to allow design changes in the event subsurface conditions differ from those anticipated prior to the start of construction. Earth Consultants, Inc. J.E.D. Corporation August 1, 1985 E -2699 Page 10 The following plates are attached and complete this report: JRF/tm Plate 1 Vicinity Map Plate 2 Plate 3 Plate 4 Plate 5,:,••••■•%4 4 s'S''4 \ ✓-P •• i IsTEw, 4k, ¼'2) j_ g Z41 . {q -`fit • EARTH CONSULTANTS, INC. Boring Location Plan Legend Boring Log Grain Size Analyses Respectfully submitted, bAlAl EM James R. Finley, Jr., P. E. cc: Structural Design Associates The Cheney Architects R.W. Thorpe Chief Engineer Earth Consultants, Inc. P�rPERENC.s : KING COUNT'( Bl MAP` DATED i9g4 Earth #4)$ Consultants Inc. GEOTECHNICAL ENGINEERING & GEOLOGY VICINITY MAP NENDEL.S MOTOR INNS TuKWL , wA. Proj. No. Z G 9 91 Date A. U G 8 51 Plate I 2a c- (V1/4 0 30 Lo IzOFT. 1 APPRoxIMATE SCALE I I LEGEND • B-I01 APPROxlMATE 6O IN5 ®B-1 `\ \ ` - - - 25 - -- - -- ` GREEN RIVER REFERS N CE5 : I- 51TE PLAN ST THE CHENEY /PAGE ARCHITECTS DATED 7- 8 - 85 2- BORING LOCATION PLAN BY SHANNON 4 WILSON DATED FEB. 1982 25 LOCATION E30QING FfCOM PREVIOUS SHANNON 4 WILSON REPORT DATED FEB. 1982 PROPOSED PjUILDING Earth ++ Consultants lnc.\\ GEOTECNNICAL ENGINEERING t GEOLOGY 'ORIN6 LOCATION PLAN NENDELS MOTOR INNS TUKWILA T WA. Proj. No!! 2 699 !Dote AU6 '135 'Plate 2. • MAJOR DIVISIONS GRAPH SYMBOL LETTER SYMBOL TYPICAL DESCRIPTION Coarse Grained Soils More Than 50% Material Larger Than No. 200 Sieve Size Gravel And Soils More Than 50 °b Coarse Fraction Retained On No. 4 Sieve Clean Gravels (little or no fines) •O °• •4°•r °•OO° ),° OQO:aQ •;c;° ..'0 GW gyy Well- Graded Gravels, Gravel -Sand Mixtures, Little Or No Fines ' '0::0::0:: .. .. ..;.. Gp gp Poorly-Graded Gravels, Gravel - Sand Mixtures, Little Or No Fines Gravels With Fines (appreciable amount of fines) GM gm Silty Gravels,Gravel-Sand- Silt Mixtures //, GC gC Clayey Gravels, Gravel Sand Clay Mixtures Sand . And Sandy Soils More Than 50% Coarse Fraction Passing ' No. 4 Sieve Clean Sand ( little or no fines) 6 3 ° o °oo e o o° • co ° ° ° o °oo ; pOO °O cut, SW Well- Graded Sands, Gravelly Sands, Little Or No Fines 9 .- i:::.•:••:. : •1�,4 SP Sp Poorly Graded Sands, Gravelly Sands, Little Or No Fines Sands With Fines (appreciable amount of fines) SM SM Silty Sands, Sand - Silt Mixtures SC SC Clayey Sands, Sand Clay Mixtures Fine Grained Soils More Than 50 % Material Smaller Than No 200 Sieve Size Silts Liquid Limit And Less Than 50 Clays ML ml Inorganic Silts & Very Fine Sands, Rock Flour,Silty- Clayey Fine Sands; Clayey Silts w/ Slight Plasticity �) CL CI Inorganic Clays Of Low To Medium Plasticity, Gravelly Clays, Sandy Clays. Silty Clays, Lean 1 1 1 1 1 I I OL OI Organic Silts And Organic Silty Clays Of Low Plasticity Silts Liquid Limit And Greater Than 50 Clays iii j'l MH mh Inorganic Silts, Micaceous Or Diatomaceous Fine Sand Or Silty Soils CH Ch Inorganic Clays Of High Plasticity, Fat Clays /// / �/ OH Oh Organic Clays Of Medium To High Plasticity, Organic Silts Highly Organic Soils — y PT pt Peat, Humus, Swamp Soils With High Organic Contents Topsoil Fill Humus And Duff Layer Highly Variable Constituents The Discussion In The Text Of This Report Is Necessary For A Proper Understanding Of The Nature Of The Material Presented In The Attached Logs Notes : Dual symbols are used to indicate borderline soil classification. Upper case letter symbols designate sample classifications based upon lab- oratory testing; lower case letter symbols designate classifications not verified by laboratory testing. I 2 "0.D. SPLIT SPOON SAMPLER TT 2.4" I.D. RING SAMPLER OR 11 SHELBY TUBE SAMPLER P SAMPLER PUSHED SAMPLE NOT RECOVERED SZ WATER LEVEL (DATE) 1 WATER OBSERVATION WELL C TORVANE READING, tsf qu PENETROMETER READING. tsf W MOISTURE, percent of dry weight pcf DRY DENSITY, pounds per cubic ft. LL LIQUID LIMIT, percent PI PLASTIC INDEX Earth i Consultants Inc. GEOTECHNICAL ENGINEERING & GEOLOGY LEGEND Proj. No. 2699 I Date Aug . ' 85 Plate, 3 • BORING NO. iat_. Logged By GLM 7 ELEV. 25± Date -25 -85 Graph CS Soil Description D ftpth Sample IN1 Blows Ft. ( %) • ....,:::a JJ JJJJJJJJ lJJJJIlJ� ►+�^�"" JJJJJJJ ML brownish gray sandy SILT, moist, very loose - _ H H H H H H H H H H 1 2 4 7 11 27 19 34 31 30 22 34 51 24 23 20 26 26 53 1 ' ...: `' ,:a brown to gray silty SAND, fine grained, mottled, moist to wet, very loose - - - _ 1 0 - 15 - - 20 ML gray clayey sandy SILT, low to moderate plasticity, moist, medium stiff SP dark gray SAND, medium grained, sub- angular, wet, loose to medium dense grades to fine grained and wet, at 23' - - 25 - _ 30 - - _ 35 - - 42 = 40 - sill gray silty SAND with some gravel, wet, medium dense SP black to gray SAND, fine to medium grained, poorly graded, subangular, dense 12" SILT lense at 38.7' sm fine silty SAND, wet, dilatent, dense at- 33.5' black to gray, fine to medium, silty SAND, subangular, wet, very dense 45 = - Boring terminated at 49' below existing grade` Groundwater seepage encountered at 19.5' during drilling. Boring backfilled with drill cuttings. �, Eal'tli Consultants Inc. GEOTECHNICAL ENGINEERING & ' • ` \ GEOLOGY , :, BORING LOG NENDELS MOTOR INN TUKWILA, WASHINGTON Prof. No. 2699 I Date Aug. '85 (Plate 4 0 O • Or mto.) • • n IX 0 r m z • H owe rim z O 0 m 0 O 0 .• • •oN en H a Koda]►riii:wm nammiiimme z z AIVNV 3ZIS NIV - SIEVE ANALYSIS SIZE OF OPENING IN INCHES NUMBER OF MESH PER INCH. U.S. STANDARD O 100 • et a el N 411'4 , u n d c9? 8 8 8 90 80 m XI 0 70 ? 1 60 m 50 co 40 m G) 30 20 10 0 O 0 O N 0 00 eD a 07 N O O O O O 0 O r• 00 03 N 00 co a C N r O O . N GRAIN SIZE IN MILLIMETERS • O m N HYDROMETER ANALYSIS GRAIN SIZE IN MM N o 0 0 q 0 o D F -1 11 1111 1 1 1 I 1 1 1. 1 1 I1 _I I 1 1 11 111 8 OD 3 M N • O O O O O 10 20 30 40 50 60 70 80 90 100 O O COBBLES I COARSE 1 FINE COARSE 1 MEDIUM 1 FINE GRAVEL KEY Boring or Test Pit No. B -1 B -1 B- 1 DEPTH (ft.) 2.5 17.0 37.0 USCS ML ML SP SAN D FINES DESCRIPTION Moisture Content (%) LL I M AS a3S1:UV03 1 . 3H PL SILT SILT poorly graded SAND JOHN W. DOBSON PAUL W. HOUSER DAVID C. DOBSON WYMAN K. DOBSON DOBSON, HOUSER & DOBSON ATTORNEYS AT LAW 2211 WILLIAM• AVE. •O. P. 0. BOX 59 RENTON, WASHINGTON 95057 July 20, 1982 Mr. Brad Collins Planning Director Planning Department City of Tukwila Tukwila, WA 98188 RE: Christensen Group, Inc. Dear Sir: Miss Helen Nelsen, owner of the property to the North of the property now sought to be developed by the Christensen Group, has an interest as an adjoining property owner and as the original vendor of the prop- erty now owned by the Christensen Group. The property was originally sold under contract recorded in the office of the King County ;Auditor recorded on August 14, 1969, under Auditor's File No. 6551402 being recorded in Volume 128 of records, page 590. Reference is made to the description contained in the contract; copy of which description is attached and marked Exhibit "A ". Under the terms of the contract there are certain obli- gations on the part of the purchaser. Paragraph 5 of the contract provides " * * ** *purchaser agrees not to use said premises for gasoline service station, automotive sales or repair business, including new and used cars, trucks or heavy equipment sales and service." Under Paragraph 7 of the contract the seller granted to the purchaser a slope easement ten feet in width along the north line of the property sold which carried the provision " * ** *that any fill within the slope's easement shall be made with topsoil borrowed from other portions of the premises conveyed to purchaser. COPY TELEPHONE (2001 2.5.5541 • • Mr. Brad Collins Page 2 July 20, 1;82 "Purchaser covenants and agrees they will not voluntarily grant any easement to the flood control division of King County, or to any other political subdivision or any in- dividual or corporation along the Green River, adjacent to the premises covered by this agreement, which easement would grant to the general public the right to use such - easement: It is understood and agreed that in the designing of the improvements to be placed upon the premises covered by this agreement the drainage plan will be so designed that -1 surface drainage is directed to the West Valley Road or the River, and not towards property of Seller on the north. _,In this regard drainage plans shall be submitted to the Seller for her inspection and approval, prior to the development." Paragraph /I of the contract provides: "It is understood and agreed that Purchaser proposes to construct an entrance driveway to the above described premises, which driveway shall be fifty (50) feet wide and shall provide access to and from the West Valley Highway. The center of said driveway will be located at a point on the .east line of the above described premises which poiri£ shaliTbe determined by an exten- sion of the center line of South 158th Street. Seller recognizes that the location of said driveway must con- form to the requirements of state law, and agrees to locate any driveway which she may construct on that portion of Seller's property lying north of the above described premises, at such .location as may be approved by the State Highway Department. In this connection. Seller agrees to use her best efforts to assist Pur- chaser in obtaining the location of a traffic light at the intersection of South 158th Street and West Valley Highway." Miss Nelsen desires that the County Commission and the City of Tukwila be advised as to these contract provisions and asks that in any granting of permits your department and the City of Tukwila take them into consideration. • Mr. Brad Collins Page 3 July 20, 1982 If you desire a complete copy of the contract we would be happy to furnish it to you. If you have any ques- tions, please contact either myself at 255 -8641 or Miss Nelsen at 255 -6535. Thanking you for your consideration I am Very truly yours, OHN W. DOBSON JWD:jh encls CC: Miss Helen Nelsen Christensen Group: Attention Kenneth W. Baines CITY OF TUKWILA CENTRAL PERMIT SYSTEM `?' g By GG Tu&- 6 ENVIRONMENTAL REVIEW ROUTING FO/RE-I9 T TO: [( BLDG n PLNG P.W. PROJECT 4) i deJ5 VrOt(W- fiL,✓1J LOCATION ,36, 15 4 01' `1,tJ A tat 101 ` ,J( ' FILE NO. DATE TRANSMITTED 4APT 5 RESPONSE REQUESTED BY STAFF COORDINATOR ei cie, RESPONSE RECEIVED fN EPIC FILE 5 -‘,22ly a �C� -15 QRE l POLICE n P & R THE ATTACHED ENVIRONMENTAL CHECKLIST WAS RECEIVED REGARDING THIS PROJECT. PLEASE REVIEW AND COMMENT BELOW TO ADVISE THE RESPONSIBLE OFFICIAL REGARDING THE THRESHOLD DETERMINATION. THE ENVIRONMENTAL REVIEW FILE IS AVAILABLE IN THE PLANNING DEPART- MENT THROUGH THE ABOVE STAFF COORDINATOR. COMMENTS REGARDING THE PROJECT YOU WISH CARRIED TO THE PLANNING COMMISSION, BOARD OF ADJUSTMENT, AND CITY COUNCIL SHOULD BE MADE ON THE ATTACHED CENTRAL PERMIT SYSTEM ROUTING FORM. ITEM COMMENT �fv t «o4/0-e147 / �n C is — 8 a7 - ieese- , Co min a 4/ C47`� / "`l" ` (.,046ekii_5 1 9� �•�� /. 020 / 6<;/ de -firteu2 . ��n o,) 1-70E4- g ProbeE t v S St 61.e, - r� k-2aLUreuh,ei ± (;'D ►� red �2 i�Ql1 �tJr a vJ i--eSka. Lt. ra. Q - e 5 DATE f COMMENTS PREPARED BY C.P.S. Form 11 CITY OF TUKWILA CENTRAL PERMIT SYSTEM CN 75-22267 EPIC : KL)- '5 FILE ENVIRONMENTAL REVIEW ROUTING FORM TO: 0 BLDG n PLNG [ P.W. 0 FIRE POLICE n P & R PROJECT ►1 U1C/0 5 Y/L~Y rli1 #t LOCATION ,30, f tig d' y,1J.�5- 2. -4 1:/ 14144)(i/ DATE TRANSMITTED M(/$5 RESPONSE REQUESTED BY 4e0/.3)5- FILE NO. STAFF COORDINATOR 6.0ed RESPONSE RECEIVED THE ATTACHED ENVIRONMENTAL CHECKLIST WAS RECEIVED REGARDING THIS PROJECT. PLEASE REVIEW AND COMMENT BELOW TO ADVISE THE RESPONSIBLE OFFICIAL REGARDING THE THRESHOLD DETERMINATION. THE ENVIRONMENTAL REVIEW FILE IS AVAILABLE IN THE PLANNING DEPART- MENT THROUGH THE ABOVE STAFF COORDINATOR. COMMENTS REGARDING THE PROJECT YOU WISH CARRIED TO THE PLANNING COMMISSION, BOARD OF ADJUSTMENT, AND CITY COUNCIL SHOULD BE MADE ON THE ATTACHED CENTRAL PERMIT SYSTEM ROUTING FORM. ITEM COMMENT ,14 ,���� ,, �,��� /e✓� Ca���i��s 4 LANDSCAPING: UTILIZING PRICKLEY TYPE HEDGING PARTICULARLY ALONG THE RIVER IS A RECOMMENDED SAFETY PROCEDURE. THE GREEN RIVER WITH ITS STEEP BANKS AND SWIFT I4OVTNC CURRENT CAN RR RSPRCTAT.T.Y DANGRROTTS Tf] T11f1SF. Wno AR.ELNWABY. .1 ,. 1 : 111, 1 1 : 1 1 u d . Lit lu _ .11 1! FOR PEDESTRIAN AND VEHICLE TRAFf!IC WITHIN THE NENDALS COMPLEX BUT WITH THE LigHTING_RESTRICTED TO PROVIDE A MINIMUM OF GLARE ANT) RTTNTINFSS FOB MOTORIST OR PEDESTRIANS UTILIZING SOUTH 158 ST AND /OR SR 181. 15 THE ADDITION OF A 151 ROOM HOTEL WITH ATTENDENT CONFERENCE CENTER, RESTTTRANT AND SERVICE STATION WILL MOST DEFINITELY HAVE A MEASUREABLE IMPACT UPON THIS DEPARTMENTS CALLS FOR SERVICE. RESPONSE :TIME, AND LEVELS OF SERVTCF PROVIDED THE REST OF THE CITY. CURRENT TRAFFIC LEVELS IN THE AREA, ALREADY DESIGNATED AT LOS C THRU E, CAN ONLY DETERIORATE FURTHER. THE INCREASE IN PEDESTRIAN TRAFFIC GENERATED BY HOTEL PATRONS CROSSING TO THE TRACK, VISITING ANDYS TUKWILA DINER, ETC. IS AN AREA OF MAJOR CONCERN. THE SAFETY OF THE HOTEL VISITOR /RESIDENT WHILE ON SITE IS A CONCERN THAT SHOULD BE ADDRESSED BY THE TUKWILA POLICE DEPARTMENT CRIME PREVENTION PRACTIONEER (CALL PAT LOWERY 433 - 1822). IT IS STRONGLY RECOMMENDED THE DEVELOPER INITIATE SUCH CONTACT EARLY ON IN THE DESIGN AND PLANNING PROCESS. OTHER CONCERNS; A. ENFORCEMENT OF RIGHT TURN IN /OUT ONLY WITH PRESENT TRAFFIC CONFIGURATIONS AT SOUTH 158 AND SR181. B. TRAFFIC MOVEMENT IN THE IMMEDIATE SITE VICINITY SHOULD CONSTRUCTION START WHILE THE =ACE SEASQX IS STILL ACTIVE. DATE COMMENTS PREPARED BY PJL 8 -9 -85 C.P.S. Form 11 CITY OF TUKWILA CENTRAL PERMIT SYSTEM )CN EPIC FILE 5%22 VI -a5 ENVIRONMENTALREVIEW ROUTING FORM TO: [ 7j BLDG [J PLNG (] P.W. 17 FIRE POLICE (j P & R PROJECT ti'1de! 5 V)7otCv-MA. LOCATION JL), )3 si . °)' ` ubt va,a.tv " JLk FILE NO. DATE TRANSMITTED Obig5- RESPONSE REQUESTED BY .g//.345- STAFF COORDINATOR 00%i RESPONSE RECEIVED THE ATTACHED ENVIRONMENTAL CHECKLIST WAS RECEIVED REGARDING THIS PROJECT. PLEASE REVIEW AND COMMENT BELOW TO ADVISE THE RESPONSIBLE OFFICIAL REGARDING THE THRESHOLD DETERMINATION. THE ENVIRONMENTAL REVIEW FILE IS AVAILABLE IN THE PLANNING DEPART- MENT THROUGH THE ABOVE STAFF COORDINATOR. COMMENTS REGARDING THE PROJECT YOU WISH CARRIED TO THE PLANNING COMMISSION, BOARD OF ADJUSTMENT, AND CITY COUNCIL SHOULD BE MADE ON THE ATTACHED CENTRAL PERMIT SYSTEM ROUTING FORM. ITEM COMMENT V10 6oero 'ttrcr DATE 8/6(g5--- COMMENTS PREPARED BY( C.P.S. Form 11 y / CITY OF TUKWILA CENTRAL PERMIT SYSTEM ENVIRONMENTAL REVIEW ROUTING FORM TO: (—( BLDG ri PLNG [ P.W. 1 ( FIRE 1 POLICE n P & R PROJECT '-fl ,yid eJ 5 010t11/ L,A4t LOCATION jo, J g ok 1/G.,f.I,Q„r/ I414✓(ij FILE NO. DATE TRANSMITTED O/ l 05' RESPONSE REQUESTED BY f1/3/ Z5- �cN 15 - ,22? EPIC 2 860 "U FILE STAFF COORDINATOR ei 04e, RESPONSE RECEIVED THE ATTACHED ENVIRONMENTAL CHECKLIST WAS RECEIVED REGARDING THIS PROJECT. PLEASE REVIEW AND COMMENT BELOW TO ADVISE THE RESPONSIBLE OFFICIAL REGARDING THE THRESHOLD DETERMINATION. THE ENVIRONMENTAL REVIEW FILE IS AVAILABLE IN THE PLANNING DEPART- MENT THROUGH THE ABOVE STAFF COORDINATOR. COMMENTS REGARDING THE PROJECT YOU WISH CARRIED TO THE PLANNING COMMISSION, BOARD OF ADJUSTMENT, AND CITY COUNCIL SHOULD BE MADE ON THE ATTACHED CENTRAL PERMIT SYSTEM ROUTING FORM. ITEM COMMENT (s •Dv,N,i u) P Nt-EN) i 1,1 122 i- " l 1TE S `C3T r v—v-)u I guru Su_itt=Qck ■vntTtmlut - C I-C�-1 OT-VLIA L N lU �w -cM Mt tJt..cc l DT- b crr4 s t 00 oN c , PClMit s nN iv7`t PA 11L_ 1...0!01 L e (NthiDJM6 -- sI & SS -/ i,.. 5 r v - t_z_.E/ /-uo / , euAl '%2.77 / • S'Cv-Dl w ti c L4 0v ILk'r) L(A (QM _97 1.1 S 51 cJ✓y1.Q ' L •__,_ DATE /13 Ej - COMMENTS PREPARED BY -. C.P.S. Form 11 �z CITY OF TUKWILA CENTRAL PERMIT SYSTEM )CN EPIC FILE 75-,22 lY XC� -F5 ENVIRONMENTAL REVIEW ROUTING FORM TO: BLDG PLNG r7 P.W. ( FIRE ( POLICE (j P & R PROJECT flt d(J 5 olotcv LtiL41i LOCATION 30, )51044-) °)' `1U.� �/ ��! 1 "149-) DATE TRANSMITTED STAFF COORDINATOR e,10e- i FILE NO. RESPONSE REQUESTED BY `01'31 5" RESPONSE RECEIVED THE ATTACHED ENVIRONMENTAL CHECKLIST WAS RECEIVED REGARDING THIS PROJECT. PLEASE REVIEW AND. COMMENT BELOW TO ADVISE THE RESPONSIBLE OFFICIAL REGARDING THE THRESHOLD DETERMINATION. THE ENVIRONMENTAL REVIEW FILE IS AVAILABLE IN THE PLANNING DEPART- MENT THROUGH THE ABOVE STAFF COORDINATOR. COMMENTS REGARDING THE PROJECT YOU WISH CARRIED TO THE PLANNING COMMISSION, BOARD OF ADJUSTMENT, AND CITY COUNCIL SHOULD BE MADE ON THE ATTACHED CENTRAL PERMIT SYSTEM ROUTING FORM. ITEM COMMENT 42_ a. DATE COMMENTS PREPARED BY/ ArlerArr C.P.S. Form 11 CITY OF TUKWILA 1CN CENTRAL PERMIT SYSTEM EPIC FILE 75-,226) ENVIRONMENTAL REVIEW ROUTING FORM TO: [j BLDG 17 PLNG {j P.W. FIRE POLICE PROJECT n1rid J 5 LOCATION 3/) , 1»-b- Vd I J'.J(' FILE NO. DATE TRANSMITTED 0/601F5 j RESPONSE REQUESTED BY STAFF COORDINATOR O Gie RESPONSE RECEIVED I PM P &R THE ATTACHED ENVIRONMENTAL CHECKLIST WAS RECEIVED REGARDING THIS PROJECT. PLEASE REVIEW AND. COMMENT BELOW TO ADVISE THE RESPONSIBLE OFFICIAL REGARDING THE THRESHOLD DETERMINATION. THE ENVIRONMENTAL REVIEW FILE IS AVAILABLE IN THE PLANNING DEPART- MENT THROUGH THE ABOVE STAFF COORDINATOR. COMMENTS REGARDING THE PROJECT YOU WISH CARRIED TO THE PLANNING COMMISSION, BOARD OF ADJUSTMENT, AND CITY COUNCIL SHOULD BE MADE ON THE ATTACHED CENTRAL PERMIT SYSTEM ROUTING FORM. ITEM COMMENT //� J.c2 �' >: c .v . /Crr L'' c► .f r`� �.- /ice" "rte d "4- srcQ ; s /e Q / d...,/ f" c, v`F c7,2 Lgt fs- Jr A •_ /(..1- r ‘/Z DATE y; y' COMMENTS PREPARED BY C.P.S. Form 11 . CITY OF TUKWILA CENTRAL PERMIT SYSTEM lc' 75-214p EPIC'nr FILE ENVIRONMENTAL REVIEW ROUTING FORM TO: BLDG E✓ PLNG ( P.W. FILFIRE POLICE i P & R PROJECT k-litY 1 eP5 t]t4r,)/ :5t4 i LOCATION ,31j,It g'rt) '' J ,11.5 VUUI.' " :4,11 FILE NO. DATE TRANSMITTED 2% RESPONSE REQUESTED BY `6,13 )g5— STAFF COORDINATOR RESPONSE RECEIVED THE ATTACHED ENVIRONMENTAL CHECKLIST WAS RECEIVED REGARDING THIS PROJECT. PLEASE REVIEW AND COMMENT BELOW TO ADVISE THE RESPONSIBLE OFFICIAL REGARDING THE THRESHOLD DETERMINATION. THE ENVIRONMENTAL REVIEW FILE IS AVAILABLE IN THE PLANNING DEPART- MENT THROUGH THE ABOVE STAFF COORDINATOR. COMMENTS REGARDING THE PROJECT YOU WISH CARRIED TO THE PLANNING COMMISSION, BOARD OF ADJUSTMENT, AND CITY COUNCIL SHOULD BE MADE ON THE ATTACHED CENTRAL PERMIT SYSTEM ROUTING FORM. ITEM COMMENT DATE COMMENTS PREPARED BY C.P.S. Form 11 City of Tukwila 6200 Southcenter Boulevard Tukwila Washington 98188 433 -1800 TO: FROM: DATE: SUBJECT: MEMORANDUM DRG 13eclui S.1i-B5 Eptc- 2864s: ncndd6 motortnn �cln gilic 614966 cautklist (Oat was j t4 ft di3-rributed 40 gam vu.potutke, tome ova Tuttoitd. 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FP,(Is7`1.4$.75'. oRa �aaY kIOM WATEp ' Y?\ LINE OF V2G6TPTION `� 1 FROM IGZG2L 4'p4 oc 5up,vHy; E GHENEY /PAGE. ARCCiIT CT S • • •••■ ›,'•••■• • 1•;77,••••••,•-rq,•-.7,F0'.... •”•••••••,.=•• • •• ••‘• e. '• i-71f--'1-1,,ri-1,1".P • W-1.P.n7P7A5-, 1109m• 11; 20,112iliSW ■iiiirettTWAT A472911. • '• • • /fT774:;•••••••• • • • / • • - • / • - • , • • s •:t='1AN-1"" _ „ F iw 114. • • • I • • , , • ' • e AlOt..Yit4P tr124PIV/IFf-6-'tik.1 1---:AR7. -;;.; E3Lir.c•, _ • cti- s;,apv. Fcar A.,.(17J/A/A-p‘, 1j---1J 4,("--ehA 1.,■s) . i••40:4- ffror • ••1 1/41A:10 M-i.. 0 (0e Ne FAL- ;NJ 11.7,74/11.T.- t.)E. 11 • . wini-h...1 far,,r •1uFt •fr•f-r--.-/Vp AL.01.4"; Fls,e•S• TV : IF*.vref 'NAM 1:1411Ve,-, 661N10 kr•040' Ots RIPP•:-.6.?C•Pi kV"' kicrrizikLA • TV • ff.) f;.(4') • virAtF.N.an& , klah rktissItie, 31S kv.,§„iA I .; 4A.Ati-VariA. Aduk teaitfo,A • • ...C•19-oir46-zi*4 minftk.' . . ,... ir e-u4 6.. 1Vft13L2) r.5pr, • ,•7; ; • • ; % ' • 00 • 1 . • •?11;* • .-• • --55 I • 5 C..e•t■fr. 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Earth • 1 Consultants Inc I GEOTECHNICAL ENGINEERING & GEOLOGY DOZING LOCATION PLAN NENDEL5 MOTOR INNS TUKWILA , WA. Proj.No. 2699 'Date AUG. '05 'Plate 2. • - • . 11 ii. 11111111H M !II 1 I 1 III II!! ppiri rill iii i IIIIir 11111 ' ' 4.. i i • l'.ii i.!, . - • • • l'll' 11!.111.1 I:1 11 ''4k li J1 Ijiliiiiiilliii■i Ili iili:iiI1III - -- "'"•-•?,- ... 41:. 11.....= • . •• ?....-1,81,-.1% ,..r.... • . .46?...... • ti \ 1::" 7'....1.,-• ' • .:...,. lim.p.s.....idiumplommail." ., ........_■■■..-1■„....--.-„,!_r___S_,_„..„_______ __ .--•"--- _ ........---,°•'''"°__-.1"•_---M:.-'---------.....-_—__ --=---_---:-....T."=--------_,----"-!-"----"'""--'"`""r"--___=---____z_-.-..._,"-17.",_-=,._"--7-.4) 11,,, .,,,.......„.....„ ..,..„....._.__._..... -......._.., _............•. ----------;-,6,----17.:-.-----------------..-.-.-..---.--....--_ ,_;_....___..- vex_ s .,...... ....... -, ---: ''';'-'-'s,'-:.:--',...:•:': ...'.--....., ...... ...,.._ _ .' -....0210...- - --- -••••togp...---",- _-"...-----.7-....---,• ---....._ -.41.----.... -......,-•-•.-_ -7--,----..,..--- en 45, MOTOR INNS [AuG 2 3 1985 at DEPT. °Ty THE CHENEY ARCHITECT Storm Drainage Control Stormwater Management Practices King County W Department of Public Works Division of Hydraulics September 1979 F O R E W O R D Portions of this manual contain material extracted from Chapter 3 and Appendices C, D and G from the Snomet Manual prepared as a result of the Snohomish County Metropolitan Municipal Corporation /King County 208 Area Wide Waste Management Planning Study and revised to reflect needs within King County. IMPORTANT NOTICE This manual is a companion volume to two other manuals: On -Site Surface Water Management and Storm Drainage Control - Requirements and Guidelines. 1. The On -Site manual introduces King County's - drainage regulations, the procedure for submitting a drainage plan, and a few sketches of possible management measures. 2. The Requirements and Guidelines manual specifies detailed instructions for engineering of conveyance systems, catch basins, detention ponds, buried detention vaults or pipes, etc. necessary in develop- ing a drainage plan. 3. The Stormwater Management Practices manual provides a broad overview of engineering practices related to design for storm water control, including alternative methods of runoff estimation, pond design, and of detention without ponds. In the event of any possible conflicts among these three manuals, however, Requirements and Guidelines shall override until such conflicts are resolved by future editions of these manuals. table of contents SECTION A - BEST MANAGEMENT PRACTICES PAGE Introduction 1 Control of Increases in Runoff Volume and Peak Flow 2 Control of Soil Erosion, Streambank Erosion, and Sedimentation 2 Control of Runoff Pollution 2 Selection of Best Management Practices 5 Identification of Site - specific Problems 8 Identification of Appropriate Best Management Practices 13 Best Management Practices Selection Procedure 13 Summary 14 SECTION B - ESTIMATION OF RUNOFF Introduction 15 Method #1, The 'Rational' method 15 Method #2, The SCS 'Curve Number' method 26 Summary 37 SECTION C - DESIGN OF DETENTION AND RETENTION FACILITIES Introduction 39 General Concepts 40 Stage- Discharge Relationships 42 Recommended Techniques For Determining Storage Needs 44 Other Considerations In Storage Facility Design 51 SECTION D - DESCRIPTION OF BEST MANAGEMENT PRACTICES Introduction 53 I.1 -11 Control of increases in runoff volume and peak flow 55 II.1 -21 Control of soil erosion, streambank erosion, and sedimentation 83 III.1 -3 Control of runoff pollution 161 • best management practices section a best management practices section a Management practices to solve the problems created by urban drainage may be put into four major categories: 1. Control of increases in runoff volume and peak flow; 2. Control of soil erosion, stream - bank erosion, and sedimentation; 3. Control of runoff pollution; 4. Control of flood damage. Each of the categories except flood control is discussed in general terms. Flood Control information may be obtained from the King County Department of Public Works. The detailed description of each BMP, its applications, capabilities and limitations, and appropriate design criteria are given in Description Of Best Management Practices, Section D. 1 Go 4TRcL OF It.lc-2lEAr5�5 RA 2UNopp VOLUME. AO OAK RANI As has been previously observed, the first and probably most notable effect of urbanization on runoff is a signifi- cant increase in both the peak rate of flow and in the total volume of runoff. Increased erosion and sedimentation result, causing the stream system to become overloaded, scoured or destroyed. Ponds and lakes fill with sediment. Flood flows increase and cause greater damage, while discharging pollutants at higher rates. Since it is generally easiest and least expensive to deal with a problem at its source before further complica- tions develop, efforts to reduce the peak and volume is required unless approved by the King County Depart- ment of Public Works. Measures for runoff rate control include such relatively simple measures as infiltration trenches, or terraces on the ground to delay runoff. Also included are such major fac- ilities as concrete detention basins. The progression in magnitude of controls corresponds to measures employed farther and farther from the source. GoI..i -rLoL OF SOIL ERo510 1`1 � c2EAM8A 1.1K E2o510 , AMID 5ED1MELL17 TtoK1 Erosion of both soils and streambanks is a natural process which is aggravated by urbanization. Increased runoff is one contributor through higher flow levels, greater velocities, etc. Removal of vegetation, alteration of soil structure, modification of to- pography, and many other factors also contribute to the problem. In addition, other pollutants are associated with sediment. Many metals and other toxic substances are adsorbed onto particles and may be removed from the water by removing the sediment. Thus, removal or prevention of sediment reaching the streams may have added benefits. )Jffoltion Pond 1.C1�ar rettrlipond Inf low Measures for erosion control on -site include minimization of disturbed areas, use of sod on slopes, and seeding of bare areas. Downstream measures may include temporary check dams, diversions, or rip -rap protection of streambanks. Sedimentation control measures include the use of grassed waterways and other erosion control measures which cause entrapment of sediment, as well as filters, screens, and sedimentation basins. Avoiding construction during periods of heavy rainfall, compaction of drainage soils, and use of fill material such as hardpan may also be beneficial. C—ONITROL. OF IZUNIOFF POLL(YT101s1 Natural ecosystems not only generate few pollutants but they also act as natural treatment processors for purification of polluted waters. Plants take up nutrients which would otherwise reach nearby lakes; plants and their root systems stabilize the soil, minimize erosion, and trap sediment and the various metals and other toxic substances which are associated with the sediment. Removal of natural vegetation during urbaniza- tion reduces the capability of the system to clean itself. Consequently, other measures to control runoff pollution may be required. �� H1 manhole aver " u LAT61 -1 1 N tort► T.WW RESTRIcToR MVIC.6 arruay+ie i me}-al pipe Jean 29 attC Met 5Ize.tj oytf ike Outlet contYol The pollutants of concern in the urban environment are many,as are their sources. The following list is a representative, but incomplete, sample of types and sources: o Sediment The largest single pollutant in terms of total load, "sediment ", includes considerable organic debris which exerts oxygen demand in the streams, lakes, and ponds. Drainage facilities such as cul- verts and ponds become filled .by deposited sediment. Many toxic substances such as heavy metals and pesticides also become attached to sediment particles. Furthermore, deposition of sediment covers once - thriving fish spawning and other habitat areas, and is an aesthetic pollutant. Sources of sediment include land and street surfaces, stream chan- nels, and streambanks. Control measures are discussed in Description Of Best Management Practices, Section D. o Oil /grease Such substances are toxic to many aquatic life - forms. In addition, films or coatings of oil and grease are unsightly and in some areas have been known to ignite, or even to explode. Sources of oil and grease include streets and parking lots, airports, commercial and industrial areas. Pollutant buildup in these areas may be gradual, as with automobile crankcase leakage onto parking lots, or spills may occur. Control measures include various means of separating oil and grease from runoff before it enters streams or lakes. In addition, reduction of spill potential would help. o Heavy metals This category includes such substances as mercury, copper, cadmium, chromium, lead, zinc, iron, and nickel, among others. Many are highly toxic to aquatic life - forms, as well as to birds which feed on plant or animal life in the stream system. Fish may be rendered unsafe or unfit for human consumption if pollutant levels become too high in the fish tissue. 3 Sources include highway and parking lot surfaces which may have accumulated pollutants from automobile exhaust or the settling of air pollutants, and spills of such substances as paint, cleaning compounds, and industrial process residues. Control measures range from on- site pollutant /runoff separation, to careful prevention of spills and collection of the polluted runoff for treatment. Reduction of air pollutants or auto exhaust emis- sions are other controls outside the scope of this manual. 0 Pesticides, etc. This category includes the many forms of pesticides, herbicides, and other compounds commonly known as "chlorinated hydrocarbons ". Many are acutely toxic to many life - forms; others have subtle, long -term effects such as the gradual accumulation to toxic levels in the tissue of fish or the weakening of bird eggs caused by the gradual accumulation of DDT in the birds through ingestion of plants which had been sprayed or smaller animals which had eaten the plants. Controls are very difficult, since reduction of application rates or elimination altogether of the use of such substances is far beyond the scope of this manual. Measures to minimize the runoff quantity and rate would be most effective in controlling pollutant washoff on -site. Sediment /erosion control measures may also be useful since many of these pollutants are associated with the sediment. o Nutrients This primarily refers to forms of nitrogen and phosphorus. Most nitrogen forms are very soluble in water and therefore very difficult to remove. Some nitrogen is asso- ciated with organic matter and debris, however, and is amenable to removal. Phosphorus is often bound up by soil particles, parti- cularly clays. Nutrients are responsible for dense growths of algae and aquatic weeds in lakes and ponds; the process is known as cultural (or accelerated) eutrophi- cation. Primary sources of nutrients are lawn and garden fertilizers in the urban environment, although septic tank leachate may be a significant source in areas which are not yet served by sewers. Lawn clippings and other debris dumped into or adjacent to streams is another significant source. Short of limiting the use of fertilizers or installing sewers, on -site control can only be accom- plished by minimizing runoff and erosion. Proper application methods may help somewhat; prohibi- tion of dumping of grass clippings could be effective if enforced. Phosphorus may be effectively removed from runoff by chemical addition and sedimentation or by removal of the sediment. Nitrogen removal is much more difficult and requires sophisticated treatment techniques. a.•- o Fecal coliform bacteria 4 Fecal coliform bacteria are considered an indicator of the possible presence of more serious pathogenic organisms such as viruses. State water quality standards refer to fecal coliform organisms because of possible threat to public health. Sources in the urban environment are primarily street and land surfaces due to accumulation of animal droppings. Septic tank leachate may also be an important source. The most appropriate control measures are those which minimize runoff on -site. In summary, on -site measures for reducing runoff and erosion will be most effective in controlling pollu- tants. In cases where treatment is necessary, the costs and sophisticated techniques required may dictate a regional approach to take advantage of economies of scale. The pollutant constituents of concern for a given development may not be accu- rately estimated from any available literature. Data from other areas of the country, as well as data gathered by the Municipality of Metropolitan Seattle (METRO), indicates an extremely wide variation in runoff characteris- tics. Climatic variation, precipitation conditions prior to the actual sampling and timing of the sample within the specific storm are just some of the variables which make data extrapolation hazardous. In cases where there is a probability of the generation of quantities of specific pollutants as, for example, at an industrial area, specific development -type (for nearby areas) or site - specific water quality samples should be gathered and analyzed. GCNTROL. OF FLOOD PANAA.4 Although flood damage may be reduced by means of many land use controls such as prohibition of all development or zoning to allow only low value uses within the floodplain, these options are part of the larger issues of land use planning and floodplain management and will not be discussed here. ■ SELECTtOtPI OF BEST MANIA6EMENT PRACTIGE5 Many factors must be considered in the selection of site- specific management practices, as should be obvious from the preceding discussion. The first requirement is to identify the problems of erosion, stability, etc. as outlined earlier. Once the problems have been identified, the decision process presented later in this section may be followed to identify the most appropri- ate management solution or combination of solutions. In addition to the problem - solving aspects of the BMP selection process, the early evaluation of the options available would enable the developer to more imaginatively and efficiently develop the site plan. Configurations of buildings, parking areas, etc., which take advantage of and complement existing conditions might well lead to less costly drainage management measures and simultaneously result in a more aesthetically pleasing design than would otherwise have resulted. 5 Several basic management practices should be implemented at all development sites as a matter of course. These measures involve basic "housekeeping" measures designed to reduce runoff volume and peak flow, sediment load, and erosion on -site, with a minimum of expense and effort. Refer to the appro- priate descriptions in Section D. These basic management practices are the following: o Minimization of Disturbed Areas, Conservation of Topsoil, and Use of Straw Bale Filters (BMP The practice of minimizing dis- turbed areas should be a require- ment placed on all developers. In particular, grading, clearing, grubbing, and filling should not be allowed on speculation, but rather should be allowed only when all applicable plans and permits for the development have been approved. It should also be a general policy to retain as much native vegetation as is practical, particularly as a buffer strip around the perimeter of the development and along existing streams. During site planning every effort should be made to incorporate the native vegetation. DAt.85 boutD WITH 5114W-541..E NYLON OR WIRE FIt, ?EiZs DUILD UP OF 5EDIMa1 / REMOVE PERIODICALLY Ind 5e.Twam S4i STRIPPED AREA ) 6 o Use of Gravel Barriers or Detention Rings on Roof Tops (BMP I.1) This practice could be applied to all new flat- roofed buildings. However, the load of water on the roof must be considered, and in some cases might cause the measure to be impractical. 101j E siNCE of RAINFALL-WA) o Temporary Mulching and Seeding of Stripped Areas (BMP II.2) This measure constitutes good practice for any development and should significantly reduce ero- sion from large construction sites, and in areas such as housing tracts which have been improved by the installation of roads and utilities but will not be fully developed for some time. o Traffic Control on Construction Sites, Stabilization of Roads, etc. (BMP II.4) Careful grading, stabilization with gravel, and use of alternate routes should all be implemented on sites large enough to have internal roads, stockpile areas, parking areas, etc. lOHC,ITuDIHAI, 5F1.77ON OF SWAL.E 3' LONGITuPIWAL, iON OF RA&PWAY o Minimization or Prevention of Runoff Pollution (BMP III.1 - III.3) Although control of runoff and erosion will automatically reduce the loads of many pollutants reaching the drainage system, consideration should always be taken for control of specific pollution problems during and after construction. o Removal of Existing and Prohibition of Future Roof Drain Connections No "design data" exist. However, this practice can significantly decrease volume and rate of flow by requiring discharge to lawns rather than streets or driveways. 7 o Prohibition of Dumping of Debris, Lawn Clippings, etc., in Streams Implementation of this basic measure would require an extensive public information program, but could significantly reduce organic and nutrient loads to streams and lakes. The remaining parts of this section discuss the identification of site - specific problems, critical areas, and appropriate management practices. Most any development site could benefit by one or more additional Best Management Practices. (9 TIFCGAT(o 4 OF SITS- 5 ?EC wv. M,IBLEM6 Information obtained from the Developer Checklist (and such other information as may be required by the Engineering and Planning Departments), along with generalized information as developed in the applicable Comprehen- sive Drainage Plan for the area in which the subject property is located, Will be used to determine site - specific problems relating to drainage. The "Crucial Areas" for concern are defined as follows: o Groundwater Recharge Areas, Marshes, Bogs, Closed Basins o Erosion Problem Areas o Instability Problem Areas o Areas Marginally - suited or Unsuited for Urban Development The information needed and the criteria for its interpretation are presented for each Crucial Area type below.. One other major reason for considerable concern regarding proper drainage manage- ment, specifically in the Central Puget Sound region, is the existence of salmonid spawning, rearing, and trans- portation areas. Such areas should be identified by the Comprehensive Plan for each watershed. For developing property immediately adjacent to a stream, the State Fisheries and Game Departments should be consulted to determine whether the stream supports or has supported salmonids, and whether the streambed adjacent to the develop- ment is a spawning area. In addition to the basic management practices described earlier, such requirements as prohibition of earthmoving near the stream during spawning periods may be placed on the development by the Fisheries Department. Throughout the following discussion, the limitations "slight ", "moderate ", and "severe" are based on Soil Conserva- tion Service soil limitation information. Detailed characteristics of each soil type are contained in SCS soil surveys and land use planning interpretations for each County. The limitations for storm drainage purposes are: "Slight" - conditions which do not require extensive investigations and precautions during planning and construction, and for which develop- ment costs should be lower than average for the area. "Moderate" - conditions which require specific investigations and precau- tions in addition to those needed for "slight" limitation areas, and for which development costs would be increased to compensate for or correct the limitation. "Severe" - conditions which require extensive investigation to determine viability as a development site and for which competent professional assistance should be obtained during planning and development to ensure adequate analysis. Alternate sites with lesser limitations may be more economical. Caution: SCS soil information may be used as a general indicator of site characteristics, but should NOT be used as a substitute for site - specific analysis. The SCS surveys should act as a guide for further investigation. Groundwater Recharge Areas, Marshes, Bogs, Closed Basins Marshes, bogs, and closed basins (depression areas having little, if any, outward drainage) may be identi- fied from topographic contour maps, aerial photographs, and field observa- tion, and should be shown on maps submitted in conjunction with their plans. Extensive areas should be identified in the appro- priate Comprehensive Plan. 8 Groundwater recharge will occur in marshes, bogs, and closed basins to a slight degree, since water will move laterally through the semi - permeable soil, but at a lesser rate than vertical movement through porous soils. These areas should be considered recharge areas regardless of soil type, since inflow is ponded for later infiltration if the infiltration rate is exceeded by the inflow rate. Categorization of King County soils as to their ground water recharge potential is shown in Table A -1. Classification of the soils has been based on their hydrological soil group, defined by SCS as follows: Group A - High - Soils having high infiltration rates even when thor- oughly wetted, consisting chiefly of deep, well to excessively drained sands and gravel. These soils have a high rate of water transmission and a low runoff potential. Group B - Moderate - Soils having moderate infiltration rates when thoroughly wetted, consisting chiefly of moderately deep to deep and moder- ately well to well drained soils with moderately fine to moderately coarse textures. These soils have a moderate rate of water transmission. Example: Everett Gravelly, Sandy Loam. Group C - Low - Soils having slow infiltration rates when thoroughly wetted, consisting chiefly of: (1) soils with a layer that impedes the downward movement of water (Example: Kitsap Silt Loam 0 -8% Slope), or (2) soils with moderately fine to fine texture and a slow infiltration rate. These soils have a slow rate of water transmission. Example: Puget Silty Clay Loam. Group D - None - Soils having very slow infiltration rates when thor- oughly wetted, consisting chiefly of: (1) soils with a high shrink /swell potential (2) soils with a high permanent water table (3) soils with a clay layer at or near the surface. These soils have a very slow rate of water transmission. A combination of water input, closed basins or flat areas, permeable surface soils, and connection to aquifers with low water levels represents the best recharge condition. Significant re- charge may still occur in the absence of one or more of these factors. In general, all areas with high potential should be used for recharge, while moderate potential indicates that site surveys should be conducted to determine the true potential. Recharge should be encouraged in any "moderate" area unless it can be demonstrated that there is a compelling reason not to employ the practice. Erosion Problem Areas Soil erosion occurs at varying rates according to different soil types, and it increases as land gradients increase. Erosion hazard refers to relative amounts of soil that may be lost from bare soil surfaces whenever precipita- tion occurs. 9 King County soils have been grouped as to erosion hazard in Table A -1, based on soil type and slope. Other factors which would require further investigation for "moderate" or "severe" hazard areas include depth of weathering, existing surface erosion, precipitation, stream flow characteristics, groundwater conditions, existing surface drainage, vegetation, soil fertility and conditions affect- ing vegetation establishment, and degree of urbanization or agricultural development. The services of qualified professional personnel should be obtained for such evaluations. Slight Hazard - These are areas where there is no history of slide activity. Conditions of topography, geology and hydrology are such that there is little likelihood that landslides will occur. Moderate Hazard - These are areas in which slides have occurred in the past, but have largely become stabilized through normal erosion and revegetation processes. This category also includes areas where marginal soil stability and poor internal drainage may combine to activate slide conditions. Severe Hazard - This includes exist - Crucial area designation obviously ing, active slide areas and non - active applies to "severe" hazard areas. Further- areas where conditions of soil insta- more, the existence of "moderate" erosion potential in conjunction with "moderate" stability hazard also constitutes a Crucial Area. Instability Problem Areas Landslides (soil slippage, soil creep) present significant problems to development in several parts of the Central Puget Sound area. Although drainage management is often not a cause, topographic and hydrologic conditions may combine to cause poten- tially severe slide hazard conditions. Geologic and hydrologic conditions may result in unstable soils becoming saturated to a point at which they can no longer support the applied weight load. In such cases, artificial groundwater recharge, particularly of water collected from a larger -than- natural area by storm drains, will not be advisable. Landslide conditions may be set in motion in slide -prone areas by excavation at any point within the slide area, or by overloading at its top. The soil categorizations in Table A -1 were based on SCS soil ratings according to the following general criteria. bility, excessive steepness and poor internal drainage could be expected to interact causing severe land slippage and resulting in a potentially serious threat to life and property. Profes- sional guidance should be obtained. As with erosion potential, the cate- gory requiring more detailed analysis is "moderate ". Similarly, "moderate" stability hazard and erosion potential combined constitutes a crucial area. Areas Marginally- suited or Unsuited for Urban Development Inclusion of an area in this category does not necessarily mean that all types of development are inadvisable. Rather, much more extensive investiga- tion such as compaction tests may be required, or it may be possible to determine a means of alleviating the condition causing the unsuitability. Inclusion does, however, indicate that very careful consideration must be given to any proposed development in such an area, and that for general . 10 planning purposes, development should be considered improbable. General locations of such areas should be identified in the Comprehensive Drainage Plan, and the recommendations of the Plan should consider the problems associated with development. Although development generally would not occur in such areas, several manage- ment practices may still be employed to mitigate potential problems. The soil ratings given in Table A -1 have been based on the SCS rating of suitability for dwellings up to three stories in height. The SCS ratings include consideration of soil density, wetness, flooding, plasticity, texture and shrink -swell behavior, slope, depth to bedrock, stoniness, and rockiness. Due to the complex nature of the limiting factors above, a professional engineer, practicing in Soils Mechanics, should always be consulted whenever developmental suitability is in question. 11 THE RELATIONSHIP BETWEEN SOIL TYPES AND CRUCIAL DRAINAGE AREAS WITHIN KING COUNTY SOIL GROUND WATER INFILTRATION POTENTIAL EROSION POTENTIAL BUILDING FOUNDATION LIMITATION* Alderwood gravelly sandy loam (AgB) Alderwood gravelly sandy loam (AgC) Alderwood gravelly sandy loam (AgD) Alderwood and Kitsap soils (AkF) Arents, Alderwood material (AmB) Arents, Alderwood Material (AmC) Arents, Everett material (An) Beausite gravelly sandy loam (BeC) Beausite gravelly sandy loam (BeD) Beausite gravelly sandy loam (BeF) Bellingham silt loam (Bh) Briscot silt loam (Br) Buckley silt loam (Bu) Coastal beaches (Cb) Earlmont silt loam (Ea) Edgewick fine sandy loam (Ed) Everett gravelly sandy loam (EvB) Everett gravelly sandy loam (EvC) Everett gravelly sandy loam (EvD) Everett - Alderwood gravelly sandy loamy (EwC) ** Indianola loamy fine sand (InA) Indianola loamy fine sand (InC) Indianola loamy fine sand (InD) Kitsap silt loam (KpB) Kitsap silt loam (KpC)' Kitsap silt loam (KpD) Klaus gravelly loamy sand (KsC) Mixed Alluvial land (Ma) Neilton very gravelly loamy sand (NeC) Newberg silt loam (Ng) Nooksack silt loam (Nk) Norma sandy loam (No) Orcas peat (Or) Oridia silt loam (Os) Ovall gravelly loam (OvC) Ovall gravelly loam (OvD) Ovall gravelly loam (OvF) Pilchuck loamy fine sand (Pc) Pilchuck fine sandy loam (Pk) Puget silty clay loam (Pu) Puyallup fine sandy loam (Py) Ragnar fine sandy loam (RaC) Ragnar fine sandy loam•(RaD) Renton silt loam (Re) Riverwash (Rh) Salad silt loam (Sa) Sammamish silt loam (Sh) Seattle muck (Sk) Shalcar muck (Sm) Si silt loam (Sn) Snohomish silt loam (Sr) Sultan silt loam (Su) Tukwila muck (Tu) Urban land (Ur) Woodinville silt loam (Wo) Ragnar - Indianola association (RdC) Ragnar - Indianola association (RdE) Snohomish silt loam (So) Low Low Low Low Low Low High Moderate Moderate Moderate Low Moderate Moderate High Low Moderate High High High High High High Low Low Low High ** High Moderate Moderate Moderate Low Low Low Low Low High High Low Moderate Moderate Moderate Low High Moderate Low Low Low Low Low Moderate Low ** Low High High High Slight Moderate Severe Very Severe Slight Moderate to Severe Slight Moderate Severe Very Severe Slight Slight Slight Slight Slight Slight Slight Moderate Severe Moderate Slight Moderate Severe Slight Moderate Severe Moderate Slight Slight Slight Slight Slight Slight Slight Moderate Severe Very Severe Slight Slight Slight Slight Moderate Severe Slight Slight Slight Slight Slight Slight Slight Slight Slight Slight Slight Slight Moderate Severe Slight Moderate Moderate Severe Severe Moderate Moderate None to Slight Moderate to Severe Severe Severe Severe Severe Severe Severe Severe Severe None to Slight Slight to Moderate Severe Slight to Moderate None to Slight Slight to Moderate Severe Moderate Severe Severe Slight to Moderate Severe Slight to Moderate Severe Severe Severe Severe Severe Moderate to Severe Severe Severe Severe Severe Severe Severe Slight to Moderate Severe Severe Severe Severe Severe Severe Severe Severe Severe Severe Severe Variable Severe Slight to Moderate Severe Severe * SCS rating of soils for single family dwelling foundations for 3 -story buildings or less. ** So widely variable that classification is not precise. table A- I 12 2 t∎IT I FI GAT1O t1 OF AP•FIZOQ21 A TE. EST MANAyEMENT PRAGT4E.S The identification of the appropriate Best Management Practices for any specific development will depend'on combinations of the following: o Slope o Soil conditions (surface and subsurface) o Water table conditions o Vegetative cover o Magnitude of flow entering the property o Magnitude of runoff from the property to drainage system o Magnitude of total discharge from property o Area of development o Size and location of roads and structures o Type of development contemplated o Phasing of construction o Costs o Aesthetics o Interaction with other developments o Rate of development in the basins o Known problems in the basins o Impact on fish and wildlife habitat The first four items in this list are among the factors which determine whether an area is "crucial" (see previous section). It should be noted that the existence of aquifer recharge areas is in most cases an asset to drainage planning, while other crucial area designations are indicative of hazard or potential problems. The number of possible combinations of site -type conditions and applicable BMP's is large. It is not possible to foresee all potential conditions nor to specify precisely which BMP should be implemented ahead of time. There must always be a discretionary option available to the developer, the planner, and the engineer. However, the following general procedures are offered as a means of selecting appropriate BMP's. SST MAKAI� MEMr fi1G r— I..I crioi� PeocEDVR . 1. Identify areas of concern from the applicable Comprehensive Drainage Plan as related to the proposed development 2. Determine whether or not any "crucial areas" exist within the subject property, or whether the property in its entirety falls within a "crucial area." 3. If no "crucial area" designation applies, several basic runoff, erosion, pollution, and flood damage control measures may be applied, depending on the items listed above. 4. If one or more "crucial area" is involved, then more elaborate measures will be needed, again depending on the specific condi- tions of each development. The detailed descriptions of the BMP's 13 in Section D should enable the developer, engineer, and planner to select the most appropriate measures. suNAKAAQV This chapter has presented a discus- sion about the types of problems which must be addressed in urban drainage system planning, followed by a general discussion of management practices for solving those problems. A method for identifying crucial drainage areas was outlined as well. Any BMP proposed by the developer for use in the non - crucial areas will be satisfactory as long as it meets the letter and intent of the ordinance. Although it would be desirable from an administrative point of view to be able to tell in advance exactly which BMP should be applied, this is not possible. The developer, planner, and engineer must use descretion and reach a consensus in cases where development is planned in a crucial area. The framework for reaching this agreement is provided in the detailed BMP de- scriptions in Section D, and in this Section. 14 estimation of runoff section b INTRODUCTION Two general methods are commonly used for runoff estimation. These are: • The "Rational" Method • The SCS "Curve Number" Method The Rational Method is quicker but less accurate, especially for large areas, than the SCS Method. Therefore, the engineer should select the method which is best for his or her development. The following sections describe the use of each method, the assumptions involved in their use, and the appli- cations and the limitations of each method. When reporting flows, the units of cubic feet per second (cfs) and cubic meters per second (cms) should be used. To convert cfs to cms, multiply the former by the factor 0.0283. A set of sample calculations illus- trating both methods is presented in conclusion. 15 r1THOO 4t 1 TI-E' I'ATI OVAL' METHOD IThe Rational Method is based on the Rational Formula: Q "Q" is defined as the maximum rate of runoff, expressed in cubic feet per second. (Actually, Q has units of acre inches per hour; however, since one ac -in/hr equals one cfs within one per- cent, the more common cfs is used.) "C" is a dimensionless runoff coeffi- cient which is the ratio of the maximum rate of runoff per unit area to the average rate of rainfall over the dura- tion of the design storm. "I" is the average intensity of rainfall in inches per hour for the duration of the design storm. "A" is the drainage area in acres. The drainage area, for analysis purposes, should include all tributary area above the point of interest, regardless of the development size. Assumptions The basic atIsumpt.1Un3 made when the Rational Method is applied are: 1. The maximum runoff rate occurs when the peak rainfall intensity lasts at least as long as the time of concentration for the property (see "Time of Concentration," below). 2. The rainfall is uniformly distributed over the area. 3. The relationship between rainfall intensity and peak runoff rate is linear. 4. The watershed runoff coefficient is constant for all storms of any dura- tion or frequency. 5. The return period of the rainfall event is the same as the return period of the resulting runoff. Limitations The Rational Method is a reasonable method of approximating the peak rate of runoff from a rainstorm in a given small basin. The greatest drawback to the Rational Method is that it provides only one _time point of the runoff hydrograph. When the basins become complex and where sub- basins come together, the Rational Method will tend to over- estimate the actual flow, which will result in oversizing of drainage facilities. The Rational Method provides no direct data by which to route hydrographs through the drainage facilities. One reason application of the Rational Method should not be used for large areas is that routing of hydrographs may provide a more economical design. However a simplified hydrograph method is presented later in this section to supplement the Rational Method. 16 Another disadvantage of the Rational Method is that with typical design procedures one normally assumes that all of the design flow is collected at the design point and that there is no "carry over water" running overland to the next design point. However, this is not the fault of the Rational Method, but of the design procedure. There must be some modification of the Rational Method, or another type of analysis used, when analyzing an existing system that is underdesigned or when analyzing the effects of a major storm on a system designed for the minor storm. Finally, when the Rational Method is used as the basis for establishing pre - development flow levels which are to define the restrictions needed for peak rate control, higher flow rates are normally obtained than with the SCS method. The implication of this is that greater flow rates will then be allowed after development, re- sulting in less on -site flow reduction being required and higher flow rates which must be accepted by downstream drainage facilities. Time of Concentration One of the basic assumptions under- lying the traditional application of. the Rational Method is that the runoff flowing past a given point is a function of the average rainfall rate during the "time of concentration" -- the time required for water to flow from the most remote part of the drainage area to the point under consideration. In the application of the method, the time of concentration must be estimated so that the average rainfall intensity for the same time period can be determined from the rainfall intensity- duration- frequency curves applicable to the design area. It should be noted that the calculated ti m e of concentration is not used to select an appropriate length of rainfall but only to select an appropriate duration of peak rainfall intensity. The local intensity - duration- frequency curves are developed from data on peak rainfall intensities of various durations. For example, an intensity of one inch per hour may occur for various durations at various frequencies, e.g., 25 minute duration for a 5 year return period or 45 minute duration for a 25 year return period. In neither case does the Rational Method deal with any part of the total storm other than the peak, i.e., the storm may be a summer thunderstorm of a winter frontal storm and still yield the same calculated peak. For urban storm sewers, the time of concentration is the sum of the inlet time (the time required for runoff to flow over the surface to the nearest inlet) plus the time for the flow in the sewer to reach the point under considera- tion. The latter time can be closely estimated from the hydraulic properties of the sewer as given by the Manning Formula for hydraulic conditions pre- vailing in the pipes. Inlet time, on the other hand, will vary with surface slope, depression storage, surface cover, antecedent rainfall, and infil- tration capacity of the soil, as well as distance of surface flow. In general, the higher the rainfall intensity, the shorter the inlet time. Common urban practice varies the inlet time from 10 to 30 minutes. However, better justification for an inlet time would be obtained through analysis of overland flow patterns. Furthermore, where existing conditions are being evaulated and storm sewers do not exist, the "standard" inlet times may be unreasonably short. 17 The .inlet time in this latter case can be estimated by calculating the various overland distances and flow velocities taken from the most remote point. A common mistake is to evaluate only the longest flow length, when the longest flow time is. the important element. Another common error is to combine areas with distinctly different flow patterns, much as open, graded land and forest areas. In such a case, the overland flow times for each dif- ferent portion of the area should be analyzed separately to determine the longest flow time. An example of this could be an area which has 75% in open pasture and 25% in forest. Overland flow velocities, as shown by Figure B -1, are greater for pasture land of comparable slope, so that the char- acteristic response time of the forest may be greater despite a lesser flow length. Similar consideration must be given to streets, parking lots, and other impervious areas which may be part of a development of single family homes, parks, etc. When studying a proposed development, do not necessarily take the overland flow path perpendicular to the original contours since the land will be graded and the contours altered. The revised flow pattern must serve as the basis for estimating the time of concentra- tion after development. 1A%ED AREA (%iEET Ft.OW6 SUALLD■/ 4U1 t t2 R.o\A/ GRASSED 4VATE1Z.WAy NEARLY 6AR . URoUND 6U0 2T Gi22,55, PAS-TURE, LAW1.)S rquirAki adz )41t.0 mum TLLW CULT1V4TtON FccE5T(aDt)rND ut1EI2 i MEADOW .I .2 .3 .5 t . 3 to 10 s. a 03 WZ V t •1•1.••....iiiii 1 ■1111/..Ur MIME DM ■ ■ ■ ■uu111111111■1/a1•1•'A I11U/11111t•/ ■ ■■■1111111111=OAMINUM1A1141111 ■ ■■11111111111I11111/41111UII•V1U'41111! III MIMIIMMMMWAS MMIIIMOMMVM - -- -.., .•... u— -- -- --. ,........i.,, •_...r /....ulw AMIr /M ,__•..I 22 1.11 1111111111111111,4111111111111/MMEAMIIEWE AMP ANEMONE! ■ ■■■',■11.u1r ∎, ∎'/I• A•'A•■■o 1uII ■t ■,,11111111,1_/_ MI wa iuu111 11111 MirinillinilliVAFAMP111011111 IMM HMI/ :N = =: ': ::: .:::: ::� �� ______ : ::• 11 ���_.....,....., u__•____.... u Asir .•••, ..1._ _, ___ •-- .- 11 _.. I...•, _.____... 22 II VeLac.tTY C -Feet' peY SeLotnd ) Figure B-1 may be used to help estimate overland flow times for surface flow. Intensity The intensity (I) is the average rainfall rate in inches per hour for the duration of the design storm. The design storm frequency (for example, a 10 -year or 25 -year storm) and duration are selected according to the design requirements set by the Comprehensive Plan or the Engineering Department. Ideally, the total quantity of rainfall, as well as its distribution during the specified duration, will be identified. In cases in which such information is not provided, two sources of intensity data are available. 18 figore, 15-1 AVERA6E. VELOCITIES FoR. EST "WAAL TIME. Foie OVEKLAND FLOW The first is the appropriate local intensity- duration - frequency (IDF) curve for the area, as developed by the Weather Service. Examples of IDF curves are presented as Figures B -2 and B -3 for Renton /Seattle and for Arlington Concrete /et al. Such curves may be developed from precipitation records if local curves are not available. It is important to note that the curves do not extend past a duration of 100 minutes, limiting their application. However, for proper use, a curve for each specific area must be developed, e.g., the Seattle /Renton curve may not be used for North Bend. The second source is the appropriate isopluvial (meaning equal precipitation) map for Washington. Maps for storms of 6 and 24 hour duration and return periods of 5, 10, 25 and 50 years are shown as Figures B -4 through B -11. On these maps each line represents the total rainfall during the given dura- tion. Thus, for example, the 25 year, 6 hour rainfall for Seattle is 1.6 inches, or an average hourly intensity of 1.6/6 = 0.27 inches per hour. 0 to 20 3o DUQ.ATION (w<thtsteS) Runoff Coefficient Note: Refer to "Storm Drainage Control - Requirements and Guidelines" for approved Intensity- Duration - Frequency Curves. The runoff coefficient (C) is the variable of the Rational Method least susceptible to precise determination and requires judgment and understanding on the part of the engineer. Its use in the formula implies a fixed ratio of runoff to rainfall for any given drain- age area and storm. In reality this is not the case, since the integrated effects of infiltration, detention storage, evaporation, retention, flow routing, and interception all affect the time distribution and peak rate of runoff, and themselves vary with time. When selecting a "C" value, the designer should refer to accept- able "C" values listed in King County's Storm Drainage Manual en- titled "Storm Drainage Control - Requirements and Guidelines." 19 (figure 15-2 CueartoNt wove. CI MWN4 - 5�Am -- figure -� INTENSrN -size QUEa'/ DutzrTtOt.L CJJeVE A2LI'WTON - LOt.1.R .T>✓ co5Mo5- DEMI NCq- EVEIZerT 41A4I EQ -4oLA SA-44 tTE FALLS- HAMILTON- L' MAki MAQBLEMo2tT MARt(SVIu E- MoR vK- MoS,s( Pte' V- NtoRn -t C3EMc) -PALKWooD-5NOt.1OM1t1 , Nd4t.LM tE -STFW Woo o loo 5OLTAN- V1DODLAt'tD It is often desirable to develop a composite runoff coefficient based on the percentage of different types of surface in the drainage area. This procedure is often applied to typical "sample" blocks as a guide to selection of reasonable values of the coefficient for an entire area. The procedure is illustrated below: To calculate average coefficient for contributary areas Acres 60 @ coeff 0.5 0.5 x 60 = 30 Acres 40 @ coeff 0.25 0.25 x 40 = 10 Combined coeff = (C1 x Al) + (C2 x A2) Al + A2 = 30+ 10 = 0.4 100 • Bothell Carnationl \v SEATTL / Seysomi.A .1 - 2T Snoqualmis Vashon Island Ole Moines 11 lift 5 -YEAR 6 -HtUR PRECIPITATION -t1- ISOPLUV4LS OF 5 -YEAR B -HOUR il PRECIPITATION IN TENTHS OF AN INCH NNUAL b-4 SCALE 0 10 MILES Sot eII —— SNOHOMISH COUNTY 5 -YEAR 24 -HOUR PRECIPITATION X71- ISOPLUVIiLS OF 5 YEAR 24 -HOUR PRECIPITATION IN TENTHS OF AN INCH ANNUAL figure . -5 SCALE 0 0 MLLES 20 Bothell SNOHOMISH COUNTY U/ 1,,. rl kykomish Carnation Snoeualmis Vashon Island Tukwila rmand Park Des Moines S 10•YEAR 6 -HOUR PRECIPITATION If— ISOPLIIYIALS OF 10-YEAR 6-HOUR PRECIPITATION IN TENTHS OF AN INCH ANNUAL f 19ure 15-6 SCAT E 0 10 mil ES o11411. SNOHOMISH COUNTY 0 Redmond SEATTL 4, Hie 10 4EAR 24 -`TOUR PRECIPITATION ISOPLUVIALS OF 10 YEAR 24 HOUR PRECIPITATION IN TENTHS OF AN INCH PNNUAL figure r7 -7 SCALP. 0 iO ru ES 21 Botkell SNONOMISH Ouvo1l ( -1_ Carnation COUNTY \.SEATTL 25 -YEAR 6 -HOUR PRECIPITATION - 34-ISOPLUV rILS OF 25 -YEAR 1A -HOUR PRECIPITATIONIIN TENTHS OF AN INCH ANNUAL figure -' SCALE 0 10 MILES J ?V I O/ \SEATTL ButnNl — —.— SNOHOMISH r Ouvail COUNTY_ _ ro Skykomie h /� /` ti 0 Redmond 15 \ r AI o Black Diamon • �.n, citic 25 -YEAR 24 JIOUR PRECIPITATION •11— ISOPLUVIrTS Of 25 -YEAR 24 -HOUR PRECIPITATIONIIN TENTHS Of AN INCH rNNUAL Figure , -q 67 I SCALE 0 10 MILES 22 C 4TY Both.0 Strtomf}h- 32 \SEA � v —, • • cilia 50 -YEAR 6 -OUR PRECIPITATION X11— ISOPLUVI LS Of 50 -YEAR 8 -HOUR PRECIPITATION J IN TENTHS OF AN INCH ANNUAL kivre e -10 SCALE 0 0 MILES SNOHOMISH COUNTY O. / i \SEATTL 7. 40 / l •e_it!! 50-YEAR 24 -HOUR PRECIPITATION - 34-- ISOPLUVIALS OF 50 -YEAR 24 -HOUR PRECIPITATIONIIN TENTHS OF AN. INCH NNUAI. fi9Ure ? -1 SCALE 0 10 MILES 23 Development of a Hydrograph This " hydrograph" synthesis method assumes that the rate of runoff from a given storm (1) grows linearly from zero to the calculated peak rate during a length of time equal to the time of concentration, (2) remains constant at this peak rate until the'design storm duration is reached, and (3) decreases linearly from the peak rate to zero in a length of time equal to the time of concentration, starting at the end of the storm. These assumptions are consistent with the assumptions of linear runoff response and uniform rain- fall intensity described previously. This is best illustrated by a series of examples. Assume that the time of concentration after development of a 5 acre parcel is 15 minutes and that the runoff coeffi- cient is 0.5. From Figure B -2, for a 10 year storm, the intensity is 1.3 inches per hour. The calulated'flow is therefore: Q = CIA = 0.5 (1.3) (5) 3.25 4 figure 15-12 40 O 10 20 V Mit rnlnuteP) DURATION = Te,= 15rn'f1 VoLuMe= 2925 fe) PEAK mow Figure B-12, above, represents the hydrograph for this storrn. If this procedure is followed for :;tor•ms of i.onf;or durati on and l.c:sser intensity, a series of trapezoidal hydrographs may be developed. (See Figures B-13 to B -15). In every case, the time from the beginning of the peak intensity to the hydrograph peak is equal to'the time of.concentration, 15 minutes. furthermore, the time from the end of the storm to the zero runoff level ( the reced i n; ; limb of the hyd ro- graph) is also equcal to the time or . concentration. Figure B -16 illustrates this for the 10 year, 6 hour storm for Seattle having an intensity of 0.23 inches per hour as shown by Figure B =6. Once again it must be stressed. that the assumption of uniform time of concentration for each storm is not • generally valid since intensity affects inlet time. However, these graphs do provide peak flow rate and volume of runoff (represented by the area under the curve) and may be•used for reten tion /detention basin design :;.. In summary,' the Rational Method is • applicable only to small areas and is most appropriate for highly impervious areas for which the assumptions are.most.,valid...:..;..In... ,.;. larger, more. _ complex. basins.,,:. the;r Rational Method will tend to over •estimate peak flows... 24 Cfigure ' -1 PU 4floN = 50 min. voLuMff- =4,500 PEAK 1P K rte 2.1$ cfs 2.5 2.o (.s l.o 00.5 25 4 Z.o 120.5 1.0 O 10 20 .Ei9ure ' -14 DUZAT I ON a Coo min. VOLUI1t= 4,tve20 f+' PeAK r OW c=1.0 cfrp to 20 3o TIME Iryt t m.ri-es \11 o5 1.2 fore e- l5 DUKATION = 90 min. VOWM 5,400 4 +' P ( FLOW = 1.00o 0 `TIME hou ✓5 figure D-16 DURATION 3 (0 min. (Co hr5,) VOLUM L = 12,5$0 ft* PEAK FLOW= O. ads I.o 2.0 3.o .4.0 5.0 6.0 M ff-THOb 44- Tlii= Sc5 `GUK/E NUM13ne METHOD The Soil Conservation Service has for many years conducted studies into the runoff characteristics of'various land types. Extensive data has been gathered and analyzed, and relationships between land use, soil type, vegetal cover, interception, infiltration, surface storage, and runoff have been developed. Detailed description of the development and use of this method is contained in the SCS National Engineering Handbook - Section 4: hydrology (NEH -4, SCS, .August 1972). The SCS Method can be summarized, however, in four steps: Step 1: Determining the Curve Number Step 2: Estimating the total runoff volume Step 3: Developing the unit hyd rotoraph Step 4: Developing the runoff hydrograph from the unit hydrograph. 26 STE° No. 1 DETtRHININC7 THE UJPVC NUh1p,eK SCS has developed tables of "curve numbers" for many soil types and .land uses. The combination of these two factors is called the "soil. -cover com- plex" and is the factor to which the curve numbers are keyed. There are four hydrologic soil groups, classified according to their runoff character- istics: A - (Low runoff potential). Soils having high infiltration rates even when thoroughly wetted and consisting chiefly of deep, well to excessively drained sands or gravels. These sails have a high rate of water transmission. B - Soils having moderate infiltration mutes when thoroughly wetted and con- sisting chiefly of moderately fine to moderately coarse textures. These soils have a moderate rate of water transmission. C - Soils having slow infiltration rates when thoroughly wetted and con- sisting chiefly of soils with a layer that impedes downward movement of water, or soils with moderately fine to fine texture. These soils have a slow rate of water transmission. D - (Iigh runoff potential) .' Soils having very slow infiltration rates when thoroughly wetted and consisting chiefly of clay soils with a high swelling potential, soils with a per- manent high water table, soils with a claypan or clay layer at or near the surface, and shallow soils over nearly impervious material. These soils have a very slow rate of water trans- mission. SCS has classified over 4,000 soil types into these for categories. Table B -1 shows the hydrologic soil group of the soils which are character- istic of King County. Similar tables may be prepared for any specific geographic location by consulting SCS literature. SOIL GROUP Alderwood Agents Beausite Bellingham Briscot Buckley Coastal Beaches Earlmont Silt Loam Edgewick Everett Indianola Kit sap Klaus Mixed Alluvial Nei1ton Newberg Nooksack Norma Sandy Loam H"DROLOGI C GROUP C B C B B/C Variable B B B A C A Land Variable A B Ii B/C SOIL GROUP Orcas Peat Oridia Ovall Pilchuck Puget Puyallup Ragnar Renton Riverwash Salal Sammamish Seattle Sha.car Si Silt Snohomish Sultan Tukwila Urban doodinville HYDROLOGIC DROLOGIC GROUP C C A B/C B B B/C Variable B C D D D D D D Variable table g -j HYPR.OLOGIC SOIL COUP KING, COUNTY tOlLf Table B -2 shows the recommended curve numbers for several soil -cover complexes applicable to developing areas. These numbers are for "average" conditions. If the Comprehensive Plan for the area under scrutiny, or the Department of Public Works at its descretion, so indicates assumption of either "dry" or "wet" antecedent moisture conditions can be analyzed. SCS defines these conditions as: "Dry" - Dormant season - less than 0.5 inches rainfall in preceed:ing 5 days. - Growing: season - less than 1.4 inches in 5 days. "Wet" - Dormant season - over l.1 inches in 5 days. - Growing season - over 2.1 inches in 5 days. Table B -3 gives the appropriate changes in curve number for either assumption. 27 Many t';rctor.; may n.f fect the local CN representative or a given land use Equipment onsite may compact the soil so that it has a lesser infiltration rate and greater runoff or the real amount of impervious surface may not precisely fit the limits imposed. In any case, when- ever a Curve Number for a specific land type and location has been determined by calibrration of calculated and observed data, the revised CN should be substi- tuted in Table B -2. To illustrate the use of Tables B -1 through B -3, assume that a small commer- cial area is to be built in a presently forested area on Everett soils with runoff before and after development to be'calculated for wet antecedent condi- tions. From Table B -1, it is found that Everett soils are in Hydrologic Soil Group B. From Table B -2, for forest land with good cover, Soil Group B, an average curve number of 55 is shown. From Table B -3 curve number 55 is changed to 74 for wet conditions. Sim- ilarly, for commercial areas on B soils, the average CN of 92 is changed to 97 for wet conditions. LAND USE DESCRIPTION HYDROLOGIC SOIL GROUP A B C D Cultivated Landl). Without conservation treatment 72 81 88 91 With conservation treatment 62 71 78 81 Pasture or Range Land: Poor condition 68 79 86 89 Good condition 39 61 74 80 Meadow: Good condition 30 58 71 78 Wood or Forest land: Thin stand, poor cover, no mulch 45 66 77 83 Good cover 25 55 70 77 Community Parks, Golf Courses, etc. 39 61 74 80 Residential :3,4,5) Low density, single family 70 78 86 90 < 1 unit /acre, < 20% impervious Medium density, single family 75 80 88 92 1 -3 units /acre, 20 -30% impervious High density, single family 82 85 91 94 > 3 units /acre, 30 -40% impervious Low density, multi - family 82 85 91 94 < 6 units /acre, 40% impervious High density, multi - family 85 87 92 95 > 6 units /acre, >40% impervious Commercial 89 92 94 95 Industrial 81 88 91 93 Paved Parking Lots, Roofs, Driveways, etc. 98 98 98 98 Streets and Roads Paved with curbs and storm sewers 98 98 98 98 Gravel 76 85 89 91 Dirt 72 82 87 89 1) For a more detailed description of agricultural land use curve numbers refer to National Engineering Handbook, Section 4, Hydrology, Chapter 9, August, 1912. 2) Good cover is protected from grazing and litter and brush cover soil. 3) Curve numbers are computed assuming the runoff from the house and driveway is directed towards the street with a minimum of roof water directed to lawns where additional infiltration could occur. 4) The remaining pervious areas (lawn) are considered to be in good pasture condition for these curve numbers. 5) CN's for low, medium, and high density residential land uses have been calibrated for the Lake Ballinger watershed. 28 table e)-2. c e. NUMBEC Curve Numbers may also be "area - weighted" similar to runoff coefficients for the Rational Method. For example, suppose that a development area is presently all woodland on C soils (CN = 70), but that future conditions are to be as follows: Roofs, CN = 98, 3.54 acres CN x area = 346.9 Paving, CN = 98, 9.57 acres CN x area = 937.9 Grass, CN = 74, 12.00 acres CN x area = 888.0 Landscaped, CN = 77, 1.10 acres CN x area = 84.7 (Similar to woodland, poor cover) Woodland, CN = 70, 9.29 acres CN x area = 650.3 CN Average. (Table C -3). Change of CN for Conditions Wet Dry 100 100 100 99 100 97 98 99 94 97 99 91 96 99 89 95 98 87 94 98 85 93 98 83 92 97 81 91 97 80 90 96 78 89 96 76 88 95 75 87 95 73 86 94 72 85 94 70 84 93 68 83 93 67 82 92 66 81 92 64 80 91 63 79 91 62 78 90 60 77 89 59 76 89 58 75 88 57 TOTAL 35.5 acres Area Weighted CN = 2907.8 = 81.9 35.5 CN Average (Table C -3) Change of CN for Conditions Wet. Dry 74 88 55 73 87 54 72 86 53 71 86 52 70 85 51 69 84 50 68 84 48 67 83 47 66 82 46 65 82 45 64 81 44 63 80 43 62 79 42 61 78 41 60 78 40 59 77 39 58 76 38 57 75 37 56 75 36 55 74 35 54 73 34 53 72 33 52 71 32 51 70 31 50 70 31 29 2907.8 CN Average (Table C -3) Change of CN for Conditions Wet Dry 49 69 30 48 68 29 47 67 28 46 66 27 45 65 26 44 64 25 43 63 25 42 62 24 41 61 23 40 60 22 39 59 21 38 58 21 37 57 20 36 56 19 35 55 18 34 54 18 33 53 17 32 52 16 31 51 16 30 50 15 25 43 12 20 37 9 15 30 6 10 22 4 5 13 2 t'abl� 13.3 CONE. NOMBER GNANCiES Roc2 Wer De DRY Ar rr 1.EPANT (DND1T1o•S AflPr p FeDM TABLE 10.1 NATIOI LAL ENG41 EEl21N! 4 FuBWD �y�•l One further point should be emphasized. That is, do NOT combine highly imper- vious (high CN) areas with low CN areas when the distribution of both is not uniform throughout the area. If high CN areas are very near the outlet, there will be a rapid response to pre- cipitation from the nearby area before the upper watershed contributes any runoff at all. Thus, the outlet- would actually see two peaks, rather than .one larger one which as would result if the CN's were area- weighted. Alternatively, if the high CN area are all upstream, then the runoff will take some time to travel to the outlet, by which time the low CN areas down- stream could also be responding. In this case a higher peak would result by adding the two separate flows together than would occur if CN's were area - weighted. 5T? HO. 2. CJfMA-T1NC1 'TH TO'TALM.. NOrr' VOLUME The rainfall- runoff relationship developed by SCS (see SCS, National Engineering Handbook, Section 4: Hydrology, Chapter 10) relates a land area's total runoff volume to the precipitation it receives and to its natural detention capacity as follows: (P- 0.25)2 P +0.8S for P > .2S and Q = 0 for P S .2S where Q = total runoff (in inches over the area), P = total precipitation (in inches over the area), and S = Potential maximum natural detention -- the maximum amount of rainfall which can be withheld from direct runoff by soil infiltration, surface storage, etc. (in inches/ unit area) The SCS method further relates an area's potential maximum detention, S, to its curve number, CN: CN: 5= 1000 -10 CN The combination of these two rela- tionships allows the estimation of total runoff volume given total precipitation. For example, if the curve number of the area under investigation is 70, then the value of S is 4.29. If total precipitation for the design event is 2.0 inches, then the total direct runoff would be found by direct substitution: = [2.0 - 0.2(4.29)]2 2.0 + 0.8(4.29) = 0.24 inches This runoff represents inches over the tributary area. Therefore, the total volume of direct runoff is found by multiplying Q by the area (with necessary conversions) as below: Total Runoff = 3,630 x Q x A Volume (ft3) (ft3 /ac. in.) (in.) (acres) 30 If the example above is 10 acres, in area, the total runoff volume is: 3,360 ft3 x 0.24 in. x 10 ac. Acre -inch = 8712 ft.3 STP NO. 5 GNCLOPIN( THe'UNIT 117DKOCIRAP11 The procedures outlined above provide the total quantity of direct runoff, but do not give the distribution of runoff over time, i.e., the hydrograph. The SCS technique for developing the runoff hydrograph utilizes a "unit hydrograph" method. A unit hydrograph is a runoff hydrograph which, for a given type of land and a given rainstorm duration, represents the characteristic distribu- tion over time of each one inch of runoff to be yielded by the site. Unit hydrographs may be developed from steamflow data, or may be synthe- sized from watershed characteristics. Since very few watersheds have flow records, the SCS method uses a synthetic unit hydrograph. The applicability of this method has been verified for watershed between 5 acres and 1,000 square miles. The assumptions and limitations of the unit hydrograph method are given in Table B -4, below. ASSUMPTIONS LIMITATIONS ' 1. Rainfall is uniform throughout area. 1. For larger watersheds, neither runoff nor pre- cipitation are uniform over time or area. 2. Rainfall intensity is constant during each interval of the storm. ' 2. Different unit hydrographs must be developed if land • use is altered. 3. Rainfall intensity can be approximated as a series of steps, i.e., constant for period at least as long as the rainfall duration used for calculation of the unit hydrograph. 3. The method is not applicable for very rapidly responding small watersheds. 4. The unit hydrograph adequately represents the area's combined effects of basin shape, slope, channel length, etc. 4. The rainfall duration used to develop the unit hydrograph must be much less than the time of concentration for the area. 5. The routing of runoff in the area of concern is linear: the runoff hydrograph can be constructed from a scaled sum of unit hydro- graphs calculated for the duration of each interval of the rainstorm. 5. For a given area, the unit hydrograph's distribution of rainfall over time (character - ized by the parameters, Tp and Tr, figure B -17), varies only with rainstorm duration, not with antecedent conditions or runoff volume. 31 table b -4 Al IT HVDIzo2API1 M EI'-4oc , ASSUMPTIONS AND MA ITATIONS The method described here will assume a triangular shape for the unit hydro - graph shown in Figure C -17, •below. The unit runoff (runoff of one inch over the area) grows linearly to a peak and then immediately begins to decrease linearly back to zero. * The SCS method will also accept a "sinusoidal hydrograph" pictured in Figure B -19. r fi (IN. /HR.) 1 OURATON • now (Qp) Wert iE-- 1-A4 () -A Tine To P.K. C (Tr) • fi orr r-17 5 Time of Concentration (Tc): The longest time taken for water to flow from any point in the drainage area to the point for which the hydrograph is to be generated. (The time of concentration may be calculated as in the Rational Method.) 6. Peak Flow Rate (Qp): The peak flow which results during the one inch of this total run- off as it is distributed by the unit hydrograph. SCS has developed from their data the UNIT NYDIZOCaKAPH following approximate relationships Gt1ARAG7�IZI5TIG5 between several of these variables: R2t EVNON THE (Tr) TIME. (n'nute, or ha") The parameters which define this triangle and its relationship to a. given interval's rainfall are: 1. Duration (D): The time interval chosen for the rainfall. (In each interval the rain intensity is modeled as constant). 2. Lag (L): The time between the occurrence of the rainfall and the peak runoff rate. 3. Time To Peak (Tp): The time from the beginning of runoff to the peak in runoff. 4. Recession Time (Tr): The time from the peak in runoff to the return to zero (or baseflow) storm runoff. • TIMES (Usually in minutes or hours) L = 0.6 (Tc) D* = 0.133 (Tc) Tp = D/2 + 0.6 (Tc) = 0.67 (Tc) Tr = 5/3 (Tp) = 1.67 (Tc) FLOW (in cfs) Qp**. = 29,040 QA,where A is in mil, Tp 0 is 1 inch, and Tp is in minutes. NOTES: ** or 45.38 2A, where A is in Tp acres, Q is 1 inch and Tp is in minutes. *Duration - The, duration of precipi- tation which contributed to the runoff unit hydrograph may vary somewhat from the given ratio to time of concentra- tion. Consistent with the theory of the method, however, D should fall in the range of 0.1 Tc to 0.3 Tc. For example, if Tc = 60 minutes, then .133 Tc = 8.0 minutes. Qp is the peak flow only for this assumed one inch of runoff in the unit hydrograph -- it is not the peak flow from this site. 32 ST`S' NO. 4 DVELOPING '(HC RUNCi'F HYDEOC3k4PH Front me UNIT HYDROCIKAPH Once the various characteristics of the unit hydrograph (D, L, Tr, Tp, (2p) have been established, the next step is to develop the actual runoff hydrograph due to a "design storm ". This rainfall event is specified by its recurrance interval (usually 2, 5, 25, 50, or 100 years) and by its duration (usually 6 or 24 hours). The total inches of rain which could be expected to fall in a storm of given frequency and duration is specified in "isopluvial" maps published by the National Oceanic and Atmospheric Administration (NOAA). Enlargements of the NOAA maps covering King County are reproduced in this manual as Figures B -4 to B -11. For a discussion of these maps, including a procedure for estimating total rainfall for storm durations other than 6 or 24 hours, refer to NOAA Atlas 2, "Precipitation -- Frequency Atlas of the Western United States, Volume IX -- Washington," pages 15 to 17. The pattern in which this total number of inches falls is called a rainfall distribution. For Western Washington, the SCS uses a "Type lA distribution." The peak 6 hours of a Type lA distri- bution when applied to a 24 hour storm are listed in Table B -5 and graphed in Figure B -18. Time from Beginning of Storm % of Total Rainfall 0 - 20 min. 3.9% 20 - 40 min. 3.9% 40 - 60 min. 3.9% 60 - 80 min. 3.9% 80 - 100 min. 3.9% 100 - 120 min. 5.2% 120 - 140 min. 6.2% 140 - 160 min. 9.1% 160 - 180 min. 18.1% -PEAK is.i% oFTOfAL f i cure -I5 SIB HoOlz MMt.JFALL pI5TRIB�ot�( (6G5•- IVFEIA) )866 ED 10.pNA; TEJIE(iM u (i'o2 .q 12eg�vin n of p j reoprtattoK') In this case, the design storm is assumed to consist of many smaller storms of duration D. Within each duration the rainfall is uniform according to the assumptions of the method. However, the amount of rain- fall for different time increments varies according to the specified design storm distribution. The next step is to convert the dis- tribution to quantities of rainfall for each time step. For example, using the 25 year, 6 hour total rainfall of 1.6 inches for Seattle (see Figure B -8), and breaking the SCS Type lA distribution into 10 minute distribu- tions, yields the quantities of rain- fall shown in column 2 of Table B -6. The cumulative total rainfall to the end of each successive time period should then be tabulated as shown in column 3 of Table B -6. Time from Beginning of Storm % of Total Rainfall 180 - 200 min. 8.1% 200 - 220 min. 5.2% 220 - 240 min. 5.2% 240 - 260 min. 3.9% 260 - 280 min. 3.9% 280 - 300 min. 3.9% 300 - 320 min. 3.9% 320 - 340 min. 3.9% 340 - 360 min. 3.9% 33 table, b-S S.6.6, PE IA D15re oi10N ADXPTED WA5 u5E IM . u mAtKO L VOLUME IC cooKtryit � 13 BFI Now by using the rainfall - runoff equation, Q P + 0.8 S (P - 0.2 S)2 for each successive rainfall total, the accumulated runoff at the end of each time step may be calculated (using the appropriate curve number to determine S) and entered in column 4 of Table B -6. The incremental runoff (Column 5 of Table B -6) is then completed by finding the difference in accumulated runoff between each set of time steps. The example shown in this table is based on the rainfall distribu- tion given earlier for D = 10 minutes and CN = 70. Note that runoff does not begin until the potential maximum natural detention for CN 70 has been fulfilled. This would follow from: 1000 S = 10 = 4.29 CN P -0.2S > 0 only when P > 0.858 inches (1) Time Period Ending, Min. (2) Incremental Rainfall, In. (3) Accumulated Rainfall, In. P (4) Accumulated Runoff, In. Q (5) Incremental Runoff, In. 10 0.0312 0.0312 0.0 20 0.0312 0.0624 0.0 0.0 30 0.0312 0.0936 0.0 0.0 40 0.0312 0.1248 0.0 0.0 50 0.0312 0.1560 0.0 0.0 60 0.0312 0.1872 0.0 0.0 70 0.0312 0.2184 0.0 0.0 80 0.0312 0.2496 0.0 0.0 90 0.0312 0.2808 0.0 0.0 100 0.0312 0.3120 0.0 0.0 110 0.0416 0.3536 0.0 0.0 120 0.0416 0.3952 0.0 0.0 130 0.0496 0.4448 0.0 0.0 140 0.0496 0.4944 0.0 0.0 150 0.0728 0.5672 0.0 0.0 160 0.0728 0.6400 0.0 0.0 170 0.1448 0.7848 0.0 0.0 180 0.1448 0.9296 0.0012 0.0012 190 0.0648 0.9944 0.0043 0.0031 200 0.0648 1.0592 0.0091 0.0048 210 0.0416 1.1008 0.0131 0.0040 220 0.0416 1.1424 0.0178 0.0047 230 0.0416 1.1840 0.0232 0.0054 240 0.0416 1.2256 0.0292 0.0060 250 0.0312 1.2568 0.0341 0.0049 260 0.0312 1.2880 0.0394 0.0053 270 0.0312 1.3192 0.0450 0.0056 280 . 0.0312 1.3504 0.0509 0.0059 290 0.0312 1.3816 0.0572 0.0063 300 0.0312 1.4128 0.0638 0.0066 310 0.0312 1.4440 0.0707 0.0069 320 0.0312 1.4752 0.0779 0.0072 330 0.0312 1.5064 0.0854 0.0075 340 0.0312 1.5376 0.0932 0.0078 350 0.0312 1.5688 0.1013 0.0081 360 0.0312 1.6000 0.1097 0.0084 table b -LA -rABUL.ATIDK1 of LTA UK11-1+gpgoc 2Api4 MEr�oD 34 D =10 VKi H Similar delay in runoff would occur for all CN's lower natural detention (and therefore more rapid response) would result with: 1) higher CN's such as for commercial areas or hydrologic group D, or 2) areas which have rela- tively impervious (higher CN) areas near the outlet and slower responding (lower CN) areas upstream. In this latter case, the two different areas should be treated separately, as previously detailed. For an example of how one line of Table B -6 is completed, take the time step ending at 280 minutes. 0.0312 inches of rainfall during the interval; added to the total of 1.312 inches which had fallen by 270 minutes, the total rainfall at the end of 280 minutes came to 1.3504 inches. An accumulated rainfall of 1.3192 inches yields an accumulated run- off of 0.0450 inches; similarly, an accumulated rainfall of 1.3504 inches yields an accumulated runoff of 0.0509 inches. The difference of these two amounts of runoff is the incremental runoff for the time step from 270 to 280 minutes: 0.0059 inches. 35 THE FINAL ITEM IN STEP 4 of this procedure is to scale and plot the unit graphs. Assume, for example, that the earlier unit hydrograph development had resulted' in a unit graph with the following characteristics: D = 10 minutes L = 41 minutes Tp = 46 minutes Tc = 68 minutes Tr = 76 minutes Qp = 35.2 cfs Tributary area = 35.5 acres Both SCS, triangular and sinusoidal unit hydrographs are illustrated in Figure B -19. For most purposes the triangular unit hydrograph, A, will be adequate. The reader is referred to SCS "National Engineering Handbook, Section 4, Hydrology," Chapter 16 for more information on hydrograph syn- thesis. The important thing is that both A and B represent equivalent volumes of runoff - one inch over 35.5 acres. Column (5) of Table B -6 represents the unit runoff per each time interval. Following for example, between time 270 and 280, runoff was .0059 inches. Following the method's assumption of basin linearity (assumption No. 4), scale the ordinate of the unit hydrograph by the factor, 0.006 inches, 1 inch yielding a scaled hydrograph with a new peak of 0.21 cfs but with the same time base as the unit hydrograph. Each scaled hydrograph is now plotted on a new graph as in Figure B -20, begin- ning each hydrograph at the beginning of the time interval whose runoff it represents. The final step is to add the or- dinates of each small hydrograph at each time to obtain the total run- off hydrograph for the complete storm. Note that the area under this curve which repre- sents the total volume of water to leave the site as runoff -- may be obtained directly from the precipitation, detention, runoff relationship: = (P - 0.2 S) 2 - 0.11 in. P + 0.8 S 14,200 ft.3 from this site of 35.5 acres. G' Et9ore 15-19 UNIT kVD2OCieAP4 s.s A(' foPE. T' L = 4lvnta - ED-) 35- �R2suP QP 35.2��s (; TRtAt 1*.LACZ uN tr aizPPA , ��- EQ0tVAL ►T StNO Sot DAL uNtr ) I � ZS- 1\7OWME k2EPIZESEt-1TS Ot tE tkICt -1 OF 'JNOFF a/ECZ -n-te FP_c tzry Cr. 128,865 {i4 40r p ops =er/ OF 35 s Ae-eeS 40 -'11.4 6A two-k- es) )-tzeM 1.1.E.A4 VAY t?12OLOA4 14.'_4A17TE:2 IL, 120 1•b lq l2 to 08 0.4 7m 24o fig3re 13-20 6ALC_UL A"TED 12.U1\10 -PP Jer5U5 i tMe- Fizo i t gNiK1 A).) 0 2 O t-O loo t50 20o 2.5o -3c-c, TMe E:Fvern tYiinninq of Preupi+utiam,vninofes) 36 5Sc L}oo 4 Go Soo SUMMARY Although the calculations for the ;ACS method are repetitious, they are also very straightforward. As in all cases, runoff calculations are required for conditions before and after development. 37 design of detention & retention facilities section C design of detention & retention facilities section C INTRODUCTION The primary reason for the use of detention or retention facilities is the desire (or requirement) to limit the increase in the peak flow rate caused by development of land. The . typical approach is to determine the pre - development peak flow rate which results from a specified "design storm ", and to use this rate as the limit which must be met in controlling post - development runoff. However, during the process of Comprehensive Drainage Planning it may be established that some other flow rate based on downstream capacity, flood damage limitation, effects on in- stream life forms, etc., should be selected as the criterion for detention or reten- tion facility design. In any case, the design should have a complete runoff hydrograph. Long -term retention may also be required as a means of runoff volume control in "critical" drainage areas. Such areas may be specified either by the Comprehensive Drainage Plan (general areas) or by the Engineering and Planning Department (general and /or specific areas). "Critical areas" are those in which existing flooding, drainage, erosion, and /or instability conditions present an imminent likelihood of harm to the integrity of the surface or groundwater system, or in which any changes in peak rate or volume of flow . would result in future occurrences of such problems. Limitations on both runoff peak and volume may be imposed in order to eliminate or mitigate existing problems, as well as to prevent future problems which would result from any increases above existing conditions. Finally, retention may be required for "closed basins ", i.e., areas which have no surface water discharge point, but rather act as surface water sumps. 39 The manual user should be cognizant of the following definitions:, "Detention" refers to the short -term storage of runoff. Release of the stored water is continuous, but at a lesser rate than inflow. The effect is that the peak flow rate is reduced. The same volume of water is discharged as flows into the facility, but the outflow occurs over a longer period of time. "Retention" refers to the long -term storage of runoff. Release may be continuous, but at lower rates than for detention, or there may be no release at all. The intent of reten- tion is to reduce the total volume of runoff by means of infiltration, evaporation from the pond surface, and evapotranspiration. Retention may also be used to provide much lower release rates, as well as augmentation of summer flows, such as in a case where protection of stream channels requires very low flow rates or where protection of a fishery .resource mandates maintaining stream flows throughout the year. In either case, the general approach is the same. The remainder of this Section is devoted to a description of the concepts involved in storage facility design, and to examples of the techniques recommended for determining storage requirements as the first step toward detailed design. GENERAL CONCEPTS The following general concepts apply to either detention or retention facil- ities. In either case, it is assumed that all appropriate upstream or on- site measures for controlling the peak rate or both peak rate and volume of runoff have been employed. Further- more, all appropriate erosion, sed- imentation, and pollutant control measures should be utilized upstream or on -site. Failure to provide such controls will result in larger storage facilities than necessary, as well as problems of sedimentation and loss of storage volume, inter- ference with outlet or overflow mechanism operation, unsightly accumulations of oil, grease, and other pollutants, etc. o The maximum allowable peak flow rate after development is estab- lished in one of three ways: 1. Pre - development peak runoff rate, from calculations in previous Section; 2. Comprehensive Drainage Plan recommendations; 3. Engineering Department require- ments. o The post - development runoff hydro - graph is known, as provided by the runoff calculations described in the preceding Section. {kgire G -1 '[" PIGAL INFLOW /OO Rb.M EWDIZOCIRAPU eE A 1ct4 4lP 'fDZ �'iD2M E RGJLl11ES JqFLOvki 1-1•IPIze42APLJ FizOM P -i DEVeIOPMErJT RUNOFF GALGULATlOr■1S 1 EQut2EP 4!,17,vAcIE VoLOME. MANX . A LLovVE O F1.D4d RATE SToeED VDLUMe (QEALe5e.P oVEP to►14Ee-flM cUTF LL 14■IDT2cYae.APJ -1 'TIME (hot*, or clays) 40 o For any outlet other than a pump, the maximum outflow rate will occur when the inflow and outflow hydrographs cross as illustrated in Figure C -1. This occurs because inflow is greater than outflow prior to that time, causing water to be stored. As in- flow becomes less than outflow, the accumulated water is discharged, but the rats of discharge decreases with time since the amount of stored water contributing to flow is also decreas- ing. o If a pump is to be used as the discharge method, the outflow may be taken as constant after the specified maximum inflow rate is reached. Outflow continues at the same rate until the required volume has been discharged. o The shape of the outflow hydrograph will be determined by: 1. The characteristics of the inflow hydrograph, i.e., timing, peak rate, and volume; 2. The stage (depth) - storage volume relationship for the specific site proposed; 3. The stage- discharge relationship for the proposed outlet type. Stage- discharge relationships for four commonly -used outlet types are given following this section. These are by no means the only available outlet types. Textbooks on hydraulics or engi- neering should be consulted for the stage- discharge relationships of other outlets. o For .any detention or retention facility, the volume of storage required is defined by the area between the inflow and outflow hydrographs from the beginning of runoff (Time = 0 in figure above) to the time at which the hydro - graphs cross (Time = Ts, above). The area enclosed by the hydro - graphs as shown,may be found by planimeter or other graphical methods and converted to storage volume by the following means (where the axes are. in cfs, and hours of time): Area - ft.3 3,600 sec. x (hr.) x sec. hr. = Volume (cu. ft.) 41 The conversion factor for cfs -days is 86,400, rather than 3,600. o The storage volume indicated by this analysis is based on analysis of one design storm (see previous Section) only, and assumes that the basin was empty to begin with. For detention basins, an additional volume must be allowed to account for antecedant conditions which may contribute to a partially -full basin at the beginning of the design storm. A rule -of -thumb allowance is 30% additional capacity or 1 ft. of freeboard. The initial • stage and discharge must be accounted for by the analysis, For retention basins which are designed to provide a year -round pond in addition to flood storage, the initial ( "dead ") storage must also be figured into the stage - storage and stage - discharge relationships. The reader should bear in mind that retention facilities may be handled in the same manner as detention. In the case where no discharge at all is to be allowed, the total runoff volume must be accommodated. If infiltration (and /or evaporation) is being relied upon for long -term disposal, then the appropriate infiltration and /or evaporation rate may be treated just as any other outflow in the analysis. It is recommended that a professional Civil Engineer practicing in Soil Mechanics be retained to assist with any work in- volving large -scale infiltration facilities in conjunction with retention basins. Two examples illustrating these concepts follow the tabulation of stage- discharge relationships. The first is a simplified technique com- patible with the "Rational" Method for runoff calculation, while the second is a more detailed and accurate storage routing technique. STAGE - DISCHARGE RELATIONSHIPS Sources for information regarding stage- discharge relationships are: 1. Streeter, Victor L., "Fluid Mechanics," Fifth Edition, 1971. Orifice ' General formula is Q = CdA 2gH where Q = flow, cfs Cd = discharge coefficient, usually 0.61 -0.65 for circular orifice A = orifice cross - sectional area, ft2 g = gravitational acceler- ation, 32.2 ft /sec H = liquid head (or stage) above center of orifice, feet 2. Chow, Ven Te, Editor, "Handbook of Applied Hydrology," 1964. 3. Merritt, Frederick S., Editor, "Standard Handbook for Civil Engineers," 1968. Wire .R. t ave.4_, - (tqure C-2 O1IFAGE- Cia, 5- SECTION, A: PLOY./ -Fable C -1 pKNoeme 6b . VAE1005 CIP.(L)LAZ Cal FACE S IZE.6 (6d= 0.103)" Orifice Diameter, in. 1 2 3 Stage 4 above Orifice, 5 6 feet 7 8 9 10 11 12 4 0.44 0.62 0.76 0.88 0.99 1.08 1.17 1.25 1.32 1.40 1.47 1.53 6 0.99 1.40 1.72 1.99 2.22 2.43 2.63 2.81 2.98 3.14 3.29 3.44 8 1.76 2.49 3.05 3.52 3.94 4.31 4.66 4.98 5.28 5.57 5.84 6.10 10 2.76 3.90 4.78 5.51 6.17 6.75 7.30 7.80 8.27 8.72 9.15 9.55 12 3.97 5.62 6.88 7.94 8.88 9.73 10.51 11.23 11.91 12.56 13.17 13.76 14 5.40 7.64 9.36 10.81 12.09 13.24 14.30 15.29 16.21 17.09 17.93 18.72 16 7.06 9.98 12.23 14.12 15.79 17.29 18.68 19.97 21.18 22.33 23.41 24.46 18 8.93 12.63 15.47 17.87' 19.98 21.88 23.64 25.27 26.80 28.25 29.63 30.95 20 11.03 15.60 19.10 22.06 24.66 27.02 29.18 31.20 33.09 34.88 36.58 38.21 22 13.35 18.87 23.12 26.69 29.84 32.69 35.31 37.75 40.04 42.20 44.26 46.23 24 15.88 22.46 27.51 31.77 35.52 38.91 42.02 44.92 47.65 50.23 52.68 55.02 * Variation for Cd = 0.61 or 0.65 is only 3%. 42 V- Shaped Weir General equation is Q = Cd(8 /15) 2g tan 8 2 H2.5 where - Q = flow, cfs Cd = discharge coeffcient must be defined by experimentation g = gravitational acceler- ation, 32.2 ft /sect 8 = notch angle, degrees H = stage height For a 90° weir, Q = 2.5H2.5 WA rz- sJeFac.E a f(gvre- C/-3 V- 51UAPEP WE . „�'�� i i= �W- -Nw,i =;l emu'!% KV'/, �'' Ftt i n E5'0r ecf Stage, ft. 1 2 3 4 5 6 7 V- 54APED wE12 Sharp- Crested Weir Discharge, cfs 2.50 14.14 38.97 80.00 139.75 220.45 324.1 General equation is Q = CdL 3/2 where - Q = flow, cfs Cd = discharge coefficient = 3.22 + 0.4 H /P, (P = height of weir, feet L = length of weir, feet H = stage above weir crest, feet, measured 4 -6 times H from weir If weir is inset (weir notch), as at right, subtract 0.1H from L for each side to account for end contractions of flow. This type of weir will not allow a basin to drain completely. This may be accomplished by use of a small orifice or channel discharge for normal flows, with the weir used only for flood overflows. table 6-2.2 Stage, feet 0.25 0.50 0.75 ow5(P Discharge, 6.4,0pt4welr cfs /ft. 0.40 1.15 2.12 3.29 4.62 6.10 7.72 9.48 11.37 13.39 ieLt4444 4v r wF t NorGt_t -6' ore l.- 4 6 412P-CeEsTED WEIR. WATEZ SuQFAC €-', WE( ‘Z -bTwtes N 1.00 1.25 1.50 1.75 2.00 2.25 2.50 43 Broad - Crested Weir General equation is Q = CdLH1.5 where - Q = flow, cfs Cd = discharge coeffcient approximately 3 L = weir length, feet H = stage above weir, feet For a well- rounded weir, Cd = 3.03 1'tiAi E �URFF�LE `m H figure G-5 eeoAr)-6R 4rED w� Et2 As with a sharp- crested weir, the basin will not drain completely. ruble G -4 Stage, feet 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 6IME!:P11661,Yr E Discharge, C151N P cfs /ft. 0.38 1.07 1.97 3.03 4.23 5.57 7.01 8.57 10.23 11.98 (per Hof RECOMMENDED TECHNIQUES FOR • DETERMINING STORAGE NEEDS Simplified "Rational" Method Technique For areas less than 5 acres, for which the Rational Method of runoff estimation has been recommended (see previous Section), the following simplified method is provided. From the runoff calculations the "hydrograph" due to the design storm has been developed as Figure C -6 below. The maximum allowable release rate, Qm, has also been specified by the pre - development runoff calcula- tions, the Comprehensive Drainage Plan, or the Engineering Department. t ns l THE Novi/6) EA ( ABCEA) _ XQ f 1 pure & -(9 'Iot?ola eAPLI -ADeA4E tbLUKAE. To determine the volume of storage required, first plot the inflow hydro - graph (ABCD) on graph paper at a suitable scale. Next, extend the maximum allowable outflow line, Qm, to the point where it intersects the decreasing portion of the hydrograph, point E. Then draw a line between the origin (A) and point E. The volume of storage required is represented by the shaded area ABCEA. The area may be planimetered or graphically calculated and converted to volume as given previously. c LlW DP,GC1 r2A4Ll kNLTgoLLEO QELEASE� VVV F 44 The following factors should be kept in mind whenever the above technique is used: o This method assumes that the relationship between stage in the basin and outflow is linear. In fact, this is almost never the case. However, for very small areas, the linearity assumptions of the Rational Method are most closely approximated. o The proposed facility must still be analyzed to ensure that the size and outlet type are in fact adequate to control flow below the prescribed level. Storage Routing Technique Many equations have been developed,. for routing a flood hydrograph through a storage facility. These equations are all based on the "Continuity Equation" from hydraulics, and differ primarily in their arrangement of the terms and the units of the various factors. The technique recommended for general use for detention basin sizing is the "Level Storage Routing" method. This method is described in the "Hand- book of Applied Hydrology ", (previously cited), pages 25 -81. The continuity equation is: Inflow - Outflow = Change in storage I1 + I2• - 01 + 02 2 2 At =S2 -S1 where - I = Inflow at time 1 and time 2 0 = Outflow at time 1 and time 2 S = Storage at time 1 and time 2 At = Time interval, 2 -1 In this method, the equation is rearranged to: I1 + I2 + 2S1 - 01 = 02 + 2S2 The appropriate units for each factor are: Time Interval Inflow Outflow Storage One hour cfs -hr cfs -hr cfs -hr* One day cfs -day cfs -day cfs -day* * See later section for conversion factor, cu. ft. to cfs -hr or day. As indicated in the "General Concepts" section earlier, the outflow character- istics are determined by the inflow hydrograph shape, stage- storage rela- tionship, and stage- discharge relation- ship. The inflow hydrograph is supplied by the runoff calculations, and the stage- discharge relationship is known once the outlet type has been chosen. The outlet type should be chosen with site characteristics in mind. That is, the maximum allowable depth of storage or head above a potential weir should be estimated. The stage- discharge table for the outlet or the appropriate equation from the literature may then be consulted to find an outlet which would maintain flow below the maximum allowable limit within the stage constraint. The remaining item is the stage - storage relationship. This may be obtained as follows: 45 o For basins with perpendicular sides, the stored volume is simply the bottom area times the height of storage; that is, the relationship is linear, as shown in Figure C-7. - E+qua. G -7 EMPLE OF 41ME-ow -mke4E JtctJ LP tst 4To2ED VOLUME (40.44) o For irregularly shaped areas with out perpendicular sides, the stage- storage curve may be developed as follows: 1. Topographic contours within the potential storage site must be obtained and the area enclosed by each contour planimetered or otherwise obtained. For example, see Figure C -8 in which each contour represents a one -foot interval. Contour 1 is the 1 lowest portion of the site and represents zero storage. Con- tour 6 represents a potential stage of 5 feet above the bottom of the basin. Area within each contour 1 - 600 ft2 2 - 4400 ft2 3 - 8700 ft2 4 - 11400 ft2 5 - 14500 ft2 6 - 19000 ft2 2. Calculate the average area between two contours. For the example given above the average area between contours 1 and 2 would be: 600 + 4400 2 = 2500 sq. ft. Similarly, Area 2 -3 = 6550 sq. ft. Area 3 -4 = 10050 sq. ft. Area 4 -5 = 12950 sq. ft. Area 5 -6 = 16750 sq. ft. 3. Calculate the volume repre- sented by the area between contours. This is derived by multiplying the area between contours by the difference in elevations. To illustrate, the volume between contours 1 and 2 would be: (2500)(1 foot) = 2500 cu. ft. Similarly, Area 2 -3 = 6550 cu. ft. Area 3 -4 = 10050 cu. ft. Area 4 -5 = 12950 cu. ft. Area 5 -6 = 16750 cu. ft. 4. Define the total storage below each contour. This is just the sum of the volumes from Step #3 below the contour in question. For example, there is no storage below Contour 1, 2500 cu. ft. below Contour 2, and (6550 + 2500) = 9050 cu. ft. below Contour 3. In summary, Volume 1 - zero Volume 2 - 0 + 2500 = 2500 cu. ft. Volume 3 - 2500 + 6550 = 9050 cu. ft. Volume 4 - 9050 + 10050 = 19100 cu. ft. Volume 5 - 19100 + 12950 = 32050 cu. ft. Volume 6 - 32050 + 16750 = 48800 cu. ft. 46 f igt)re (,-e) 5 oPT Ar 1 four IkrrEVAL R.b■ it DAM 0 l0 20 30 'ORACaE (GUSIc. cEET )( IOW 40 --iqulre G- 9 ST 6E.-SToRA E- 2E.LATlOt J U IP 5o The next step in the process is to develop a curve called the "Routing Curve ", which is simply a plot of outflow for a given stage versus a term, 0 + 2S, for the same stage. This curve may be easily plotted by setting up a table like Table C -5. The units of expression of outflow (0) are cubic feet per second for the time period of interest, hours in this case, (or there- fore cfs- hours). Storage, which was plotted in cubic feet, may be converted to cfs -hr by dividing by 3600. That is, 1 cfs for 1 hr 1 ft3 * 3,600 sec. sec. hr. = 3600 cu. ft. 1 or 1 cubic foot = 3600 cfs -hr. Similarly, if cfs -days are desired for longer duration runoff events and larger facilities, the conversion may be made by dividing the storage in cubic feet by 86400. The example below uses the stage - storage curve (Figure C -9) and the stage- discharge relationship for an 8 inch orifice outlet pipe. The pipe size was chosen because the maximum allowable flow is to be 4.0 cfs and the maximum storage depth is 5 feet for this example (see Table C -1) . Elevation feet Stage feet Outflow* 0 cfs Storage S cfs -hr ** 2S cfs -hr 0 + 2S 2 1 1.76 .694 1.388 3.15 3 2 2.49 2.514 5.028 7.52 4 3 3.05 5.306 10.612 13.66 5 4 3.52 8.903 17.806 21.33 6 5 3.94 13.556 27.112 31.05 * from 8" orifice, stage- discharge relationship table G -5 'TABULATION OF DATA FOR RooT tm4 GU&VE ** from stage- storage curve, figure C -9, volume converted to cfs -hr for one hour time intervals 47 Now plot the Routing Curve, as shown in Figure C -10. 10 Is 0(-51-FLOW Jr 2. (.s-roeACE' 20 ZS The final step is to route the inflow hydrograph through the proposed storage facility. This is done by completing successive columns of Table C -6 for each time period. The procedure is straight- 1 forward and repetitious. This example assumes that there is no storage (S1) nor outflow (01)initially. In this example the inflow hydrograph has the shape, peak, and time shown in Figure C -11, and contains a total volume of 100,000 cubic feet. The peak flow rate at time 3 hours is 6.94 cfs. If there was a known base flow which preceded the design storm, it could simply be added to the runoff hydrograph. ( Similarly, initial storage and discharge 5 4 30 6 -10 EZWrI NC4 CURIE Fora 4f- 1 14002. figure C -11 INFLOW! How.0(11ZAP-1 WAIN • VANIER ES • IIIUU may be treated in the analysis by o , 2 3 setting the appropriate values of S1 IIME (Incurs) and 01 for time period 1, in the table below. Time period, Hour Increments Row Items* 1 2 3 4 5 6 7 8 9 10 11 12 (1) (2)• I1 0 2.34 4.64 6.94 5.55 4.18 2.79 1.39 0 0 0 0 I2 2.34 4.64 6.94 5.55 4.18 2.79 1.39 0 0 0 0 0 (3) 2S1 0 0.84 3.97 10.17 16.23 18.96 18.76 15.97 10.86 5.21 1.11 0 (4) I1+ I2+ 2S1 2.34 7.82 15.55 22.66 25.96 25.93 22.94 17.36 10.86 5.21 1.11 0 (5) 01 0 1.50 2.35 3.03 3.40 3.60 3.57 3.40 3.10 2.55 1.55 0 (6). 02+ 2S2 2.34 6.32 13.20 19.63 22.56 22.33 19.37 13.96 7.76 2.66 - 0 (7) Stage]. (ft) 0 0..7 1.80 2.90 3.77 4.12 4.10 3.75 3.05 2.65 0.80 0 * Subscript 1 refers to the beginning of the time period, 2 refers to the end of the time period. 48 to + -able G- C. TABOLAR GAtLULATIo J OF OUTFLOW U61A!(1 LEVEL 6-rol2A1.4E, Roc/rimy The routing table is completed by the following steps. Keep in mind the equation used: +I2 +2S1 -01 = 02 +2S2 1. Initial inflow, I1, is the inflow at the beginning of each time period and is read from the inflow hydrograph for each time period. For period 1, I1 in this example is zero, and this is entered in Row (1) of the routing table. 2. I2, inflow at the end of the time period, is read from the inflow hydrograph, and entered in Row (2) for each time period. This same value is the initial inflow for the next time period. For our example 12 for time period 1 is 2.34 cfs; this is also entered in Row (1) of time period 2 as I 1' 3. Two times the initial storage, 2S1, is entered in Row (3). For the example, initial storage for time period 1 is zero. Subsequent values entered as 2S1 are calcu- lated after the remaining values for the preceding time period are filled in. This is explained below. 4. Enter in Row (4) the sum of Rows (1), (2), and (3), for the appro- priate time period. In this case, the sum for time period 1 is 2.34. 5. 01, outflow initially for the time period, is entered in Row (5). For time period 1, 01 is zero in this case. Subsequent values are read from the routing curve after Row (6) has been calculated. This is explained below. 6. From the routing equation, the entry in Row (6), 02 + 2S2, is the difference between Row (4), I1 + 12 + 2S1, and Row (5), 01. For time period 1, this value is. 2.34. This is entered and the process repeated. 7. The value of 0 for the next time period is read from the routing curve (Figure C -10) for the previous value of 02 + 2S2. In this case, a value of 1.50 is obtained for 0 1 for time period 2, corre- spondng to (02 + 2S = 2.34). Therefore, 1.50 is entered in Row (5) for time period 2. 8. The value of 2S2 for the next time period is the difference between the previous value of (02 + 2S2) and the corresponding value of 01 read from the routing curve as in item (7)., above. For this example, 02 + 2S2 = 2.34 (time period 1) O1 2S1 = 1.50 (time period 2) = 0.84 (time period 2) Therefore, enter 0.84 in Row (3) for time period 2. 9. Find the sum of Rows (1), (2), and (3) and enter value in Row (4). 10. Subtract value in Row (5) from Row (4) and enter result in Row (6). 11. Refer to routing curve for next value of 0 l' corresponding to result of item (10). Continue this process until the outflow hydrograph, as represented by the tabulated values of O1, returns to zero or to the baseflow value. The final row of entries in the Table C -6, Stage at the beginning of each time period, is obtained by dividing each value of 2S1 by 2, and referring to the stage- storage curve,. Figure C -9. For example, for time period 3, 2S. equals 3.97 cfs -hr. Referring to the stage- storage curve for storage of 1.98 cfs -hr. (or 1.98 x 3600 = 12,146 cu. ft.), a stage of 1.80 feet is obtained. 49 Finally, plot the values of 01 for each time period to plot the com- plete outflow hydrograph, as shown in Figure C -12. The volume which must be stored is represented by the dark shaded area, and may be obtained through graphical techniques. The volume may also be closely estimated from the largest tabulated value of 1 h 4 3 2S1, divided by 2 and converted to cubic feet. This will exactly coincide with the true peak only if the two hydrographs cross exactly at the end of a time interval. However, this overall difference in volume would be very small, and for practical purposes may be neglected. O I 3 TIME Ckou s) 4 S 2 S 10 s f or& G- t2 i LFWW AKID OUT / 1-EVD2Oc RAP14 (e)fwip(c problem) In summary, the characteristics of this sample storage site and the selected eight inch orifice outlet are such that the peak runoff rate will be reduced below the required -4.0 cfs. Furthermore, the full five feet of allowable storage is not used, pro- viding a margin of safety to account for wet antecedant conditions and a partially -full basin. In this case, the unused upper 0.88 feet of storage converts to approximately 14,800 cubic feet of storage (see Figure C -9), or approximately 43% reserve capacity. It cannot be overstressed that the outflow hydrograph, and therefore the storage volume, area requirements', and costs, depends entirely on the outlet type, basin characteristics, and inflow hydrograph. Thus, there is no short- cut method for adequate basin design for major facilities. OTHER CONSIDERATIONS IN STORAGE FACILITY DESIGN The following factors should also be incorporated into the process of deten- tion or retention facility design. 50 o A minimum of one foot of freeboard should be provided above the maxi- mum expected water level, and below the level of an emergency spillway for extreme floodflow conditions in excess of the design event. o An emergency spillway for accommo- dation of excessive flow should be provided, with discharge to the natural drainage course or to a parallel closed pipe system, at the discretion of the Engineering Department. o If the basin is to be used only intermittently for peak flow detention, consideration should be given to seeding the floor and sides with a suitable grass. In any event, the sides above the maximum water level should be seeded. o If the basin is to be a combination permanent pond /storage basin, the sides should be seeded down to the permanent pool elevation. o Consideration should be given to preventing siltation of the basin by means of upstream erosion control measures. If the basin is to be used as a sediment collection facility, adequate access must be provided for the necessary equip- ment to periodically remove accumulated sediment and debris. References for Detention /Retention Facilities 1. Chow, Ven Te, Editor, "Handbook of Applied Hydrology," 1964. 2. Linzley, Ray K. and Joseph B. Franzini, Water Resources Engineering, 1972. 3. Viessman, Warren, Jr., Terence E. Harbaugh, and John W. Knapp, Introduction to Hydrology, 1972. 4. Streeter, Victor L., Fluid Mechanics, Fifth Edition, 1971. 5. Poertner, Herbert G., "Practices in Detention of Urban Stormwater Runoff ", American Public Works Association Special Report No. 43, 1974. 6. Soil Conservation Service, U.S. Department of Agriculture, "National Engineering Handbook, Section 4, Hydrology ", August, 1972. 51 description of best management practices section d description of best management practices section d This section contains detailed information about Best Management Practices (BMP's). Included is information regarding the purpose, advantages and disadvantages, and appropriate site -types for each BMP. Design criteria and material specifi- cations are also provided. To the extent appropriate, relevant legal or implementation information and references for further information is also included. The majority of the detailed descrip- tions included here have been taken or adapted from "Water Resources Protec- tion Measures in Land Development - A Handbook." This Handbook was produced in Delaware and contained many regionally- specific references, design criteria, etc. These have been modified as much as possible within the scope of this study to reflect condi- tions in Western Washington. However, the bulk of the descriptions contained in the Handbook is of a generally - applicable nature. Some additional information not included in it has been developed for this manual. Graphic material was re -drawn for this manual. Many of the BMP descriptions refer to "site classes ". As used in the Delaware Handbook, these are: Woodland Marshland Aquifer Recharge Areas Poorly Drained Soils Erodible Soils Steep Slopes Flood Plains (w) (M) (R) (D) (E) (S) (F) Since these site -types occur in the Central Puget Sound region as well, the site class reference has been retained. 53 The descriptions of BMP's which follow are divided into three general categories according to the primary problems with which they deal: I. Control of increases in runoff volume and peak flow. II. Control of soil erosion, stream - bank erosion, and sedimentation. III. Control of runoff pollution. Measures employed closest to the source of a problem are usually the most effective and least expensive. In addition, measures which reduce the volume and rate of runoff will 54 have many other beneficial effects, such as reduced erosion, sedimenta- tion, and flood damage. The manual user should always keep this in mind when identifying appropriate BMP's for a particular application. Neither the Delaware Handbook nor this manual purports to be the last word regarding Best Management Prac- tices. As more data, particularly regionally, becomes available, infor- mation which is out of date should be replaced or supplemented. In this way, this manual may continue to be the useful planning and management tool it is intended to be. The BMP descriptions are arranged so that any one may be replaced without affecting the other BMP's. Mett‘OZE DELAY OF RUNOFF FROM ROOFS TYPE. GRAVEL BARRIERS ON FLAT ROOFS I.1 PURPose. To lower the flood peaks by delaying runoff from roofs. In some cases the measures may also impound a small quantity of runoff. srre. cAARA4T'EzsTics and APPLICA?1 O N Pertains to any site classes, but most applicable in dense developments. Applicable where the increased load of impounded water on roofs does not significantly increase building costs. ADVAtKrrAes By retarding runoff at the source it may be possible to reduce the size of storm drainage facilities all over the site. An increase in the time of con- centration (or response time) will reduce the peak runoff rate DtthDVANTJst&es 1. Retarding runoff on flat roofs will result in greatly increased loads, resulting in increased construction costs. In some cases the savings from reduced storm drainage costs may make up this difference. Un- fortunately, such practices are needed most for large acreage, single -story buildings where clear spans are also needed; so a small increase in load on the roof can result in large cost increases. 2. The storage capacity of 'findams' on sloping roofs is too small to affect hydrograph characteristics except for extremely short duration storms. DE15144t i C ATE.2IA and OuT1.NEE sFEGIRGATIONS A flat roof may be used much as a retarding pond by delaying the flow of runoff to the downpipe. This may be done through the use of a perforated strainer or gravel detention barriers. With the perforated strainer with limited capacity on the downpipe inlet, provision must be made for an emergency overflow so that water will not spill over the top of the roof parapet. It should also be designed to overflow before the maximum permissible load on the roof is reached. Gravel detention barriers were found to retard runoff effectively on a flat roof. The effect on the hydrograph of runoff from the roof is shown below. 55 6 g23 a a PIPE RIERS f5t42.1;1I 10 a) 30 ro 50 t o p gD ,]ME SINCE. Sfl f of RAINFALL MEASURE INFILTRATION OF PERCIPITATION 'AT SOURCE' PRIOR TO CONCENTRATION T/PE. POZ705E. To reduce the volume of storm runoff and to reduce flood peaks by increasing ground infiltration. Dutch drains intercept 'sheet' runoff prior to con- centration as compared to infiltration ditches. DUTCH DRAINS (GRAVEL- FILLED DITCHES WITH OPTIONAL DRAINAGE PIPE IN BASE) I.2 SITE 6_14NzPcreZtsnL -S alga AP2U ATIoN Dutch drains may be used on any site class where permeability of soil is sufficient or where seasonably high water tables are not anticipated. The minimum acceptable soil infiltration rate is 0.12 ft /day (all except D, F, M, W). These drains may either accom- modate the maximum flow for a 24 -hour flood, thus avoiding the need for a storm -drain system, or they may be designed to take less runoff, in which case they will act only as retarding devices as far as reduction of flood peaks is concerned. ADVA IQTA4ES 1. Reduces the total volume of runoff and can reduce 'peaking' effect of local floods. 2. Enhance groundwater supply. 3. Improve quality of vegetation on site by increasing available water in the ground. 4. Will result in a reduction in the size of storm drains required downslope of the facility. 5. Plant containers set on a paved Dutch drain can improve the visual attractiveness of a median area in a parking lot and allow seepage through the joints of brick pavers set into sand. Seepage can be in- creased by drop inlets underneath plant containers. ASADVAt.ITA6ES 1. Unless 'at source' seepage facil- ities are either designed for large storms or incorporate some method of controlled runoff release, they may not effectively reduce flood peaks when one storm follows an- other so closely that all facilities are full. The drains should, if possible, be designed to overflow before their capacity is reached during intensive storms. 2. Dutch drains are subject to clogging. 3. Dutch drains do not eliminate the need for a storm system downslope to take overflow from exceptional storms. They do, however, signifi- cantly decrease the necessary size of this system. Gttsi4r4 c trE2v, algd OoTL.NNE sPEG. IFI CAM ON.IS Suggested locations for the use of Dutch drains are as follows: 1. Roofs without gutters. Drains run the whole length of the eaves. Run- off falls directly onto the surface ��. o�O��3 C42� L K55Er SLA 2.' "SET►U1F$ C>N1 -4t1 of '6Ar.ic \ ( av►d Z'' oc SAN1D 57 of the Dutch drain which may be bare gravel, grass or, occasionally, porous paving. A combination Dutch and French drain could also be used to ease the problem of maintenance. Sidewalks running alongside may also discharge into Dutch drains. 2. Dividing strips between areas of impermeable paving to collect sheet runoff. These will usually be paved so as not to hinder the passage of traffic. Alternatives are shown below. NOTE: Tile drains set at the base of Dutch drains and discharging into an overflow storm system will more effectively reduce flood peaks during intensive storms. Similarly, if the sur- face of Dutch drains have a longitudinal fall allowing run- off during excessively heavy rain, peaks will be lower. CaeA55 4ntD (o - S" GoA2E. Sp�N D 5ET ON. G0)514ED 5TDtJE •BRSE. The design for overflow of Dutch drains is very important. Assuming that less than the design frequency storm can be accommodated in these drains, they will be subject to overflow. If the duration of the storm is longer than the time it takes for the overflow to concentrate O SGL1EMATIc g■jDraD- CgAPW OF 02m NI VJmlowr '4EARLy oV/EeFLoW sVstEM from all parts of the development, then there will be no reduction in the peak flow (although there may be a reduction in its duration). If overflow begins prior to capacity being reached, then there will be an improvement in hydro - graph of inflow. z •f• SmPA3F /AJ L�4M) DRAIN D P4NED TO ovaeFLoW SercizzeAPAcITY 15 2e.AreD t.(GTE: �PaceE. WILL 1.10T Be Ar5 4fLEx-r FbR. 114E. 56e-ot.1D CA5E. t3Vr- 111.ERE t5 5 C�NtFtGA1\1T LOWE2ItJ161 FLOW MEASuPt /,J rPLI9 . LhAlotl i'1EARE SIZING The sizing of facilities will depend entirely on whether the developer wishes to use Dutch drains as the only measure (in which case they should accommodate about 3" over 24 hours in the Seattle area) or as a supplementary measure. The minimum size must be to insure the infiltration of at least as much precipitation as before develop- ment. 58 MEASURE TYPE INFILTRATION OF PRECIPITATION 'AT SOURCE' PRIOR TO CONCENTRATION PRECAST CONCRETE LATTICE BLOCKS AND BRICKS I.3 RIZPoS� There are various types of paving slabs which provide surface and yet are porous degrees. precast a hard in varying SlT'E CtLARM I t R ts-r IGS APPLICATIOlJ Porous paving can only be used where soil is sufficiently porous to allow rapid drainage (all site classes except W, M, F, and D). These materials may be used in a wide variety of ways. CAC] Perforated slabs on a honeycomb base may be used to cover Dutch drains between areas of impermeable paving (making a lattice of permeable paving throughout a parking area). Brick strips incorporating tree pits may be used in similar ways. AOVANTP ES 1. In the case of lattice blocks, grass can substantially cover the site. 2. They are flexible and can withstand a certain amount'of movement. 3. When used as strips between asphalt, sections can be lifted to plant trees, place street signs, etc., or to maintain utility lines beneath. DISADVANTAc ES o Only perforated slabs honeycomb give a good surface. on a walking G�SIL -t►�l CRtT�21A ctvtci OUTLINE 5PEL! FIGATIDNS 1. Lattice concrete blocks. These are concrete pavers made in a variety of different shapes and specifications, which are available from many con- crete block suppliers. For example: Length ins. 24 Width ins. 16 59 Depth ins. Compressive Strength Units/ Lbs/ psi sq. yd. Unit 4 6,400 3.35 73 Use: For parking areas where an informal' grass surface is required but is sufficiently hard wearing to withstand regular use. For lining grass swales and grass ramps to provide protection from erosion. Where a surface of high porosity is required (parking areas, etc.), blocks should be laid on a bed of gravel or crushed aggregate to give a sufficient capacity for the design storm (see porous asphalt specification) and 2" layer of 1. AIM DRlvOn1AH SOIL 2. TRUCK DRIVEWR1 SAND 1" fines and gravel. Interstices of blocks should be filled by screen- ing with coarse sand. Where only erosion control only is desired, blocks should be filled by screen- ing with coarse sand. Where erosion control is desired, blocks may be laid directly on soil and screened with topsoil. Where used for a driveway under a lawn, blocks may be covered in an inch of topsoil. ZRED STaNE 3. RAD3 UNDER LAWS !.10, ,74!! lift. SOIL 2" • • 4 4 GRlt#ED STDIJ 2 5 2. Modular pavers. Perforated bricks or bricks with lugs to control spacing. Brick or concrete pavers made to a variety of specifications depending on use, usually with a compressive strength of between 7,500- 10,000 psi for use in areas where more wear is expected than for lattice blocks. Use: Interstices and perforations are usually kept free from vegeta- tion. This paving type is used in more formal areas than lattice blocks for paving around trees, for dividing strips between impermeable paved surfaces, etc. Generally, not a comfortable walking surface. Installation: Lay on a bed of gravel topped with coarse sand (2 "). The depth of the gravel will depend on the required storm water storage capacity. 3. Precast concrete perforated paver laid over precast concrete lattice block. Can be made to a variety of specifications, depending on use. Those tested by Franklin Institute (1) had 'web' openings 5" x 5" and 4.5" deep. The cover slab was only 2.5" thick with 0.75" diameter holes. These are laid on a base course comprised of the necessary depth of to provide storage capa- city and 2" coarse sand, 60 Use: In formal areas, especially where 'warping' or large impermeable surfaces would be unsightly. Also as a strip cover for French drains between areas of impermeable sur- face. Concrete blocks may be lifted and web and sand filter cleaned out if percolation rate falls. 4. Other porous paving types for special use: o A metal honeycomb covered by a butyl rubber mat has been used for landing strips for aircraft and may have an application for temporary porous surfaces. o Bricks with two perforations through which metal rods are passed and bricks separated by spacers. This paving can be preassembled and rolled out on sites rapidly. Could have occasional applications for providing temporary roads on construction sites. 61 MEA4 utZ.E INCREASE TIME OF CONCENTRATION BY INCREASING LENGTH OF OVER- LAND FLOW TERRACES, DIVERSIONS, RUNOFF SPREADERS, ETC. Pu2POSE By increasing the time of concentration of runoff, the hydrograph can be flat- tened and storm peaks reduced. This can be achieved by spreading runoff or by directing it into a system of terraces. SITE eD-WzNe:reAzIlar> atAd APPLICATION/ This may be used on any site class. On well- drained soils there will be an additional benefit of reducing total runoff by infiltration. This technique is only applicable to developments with a large proportion of open space available. ADVANTAC Es 1. Increased overland flow time in- creases the time of concentration and thus can reduce storm peaks. The size of storm drains can there- fore be reduced. 2. Increased overland flow time may also significantly increase the infiltration of runoff, particu- larly on well drained sites. 3. There are a number of secondary benefits which terracing may have (erosion control, slope protection, etc.). 171-sADVP,Ntrikele5 On poorly drained soils these techniques may leave ground waterlogged for several hours following a rainfall, which may make this method unacceptable for open space which is heavily used. 96SUaKi L21TeRIA Quid OOTLIICIE SPPGIFicATIO115 Sizing Terraces. When terraces are built to take large quantities of run- off, they must be carefully designed. The method is detailed in the SCS Engineering Field Manual for Conserva- tion Practices. This is based on the maximum allowable velocity depending on vegetation and soil type. A simplified version of that used by SCS is shown below and opposite (2). 63 Stand. Length Retardance of. Vegetation Good 30" 6 " -10" 2" A C E Stand. Length Retardance of . Vegetation Fair 30" 6 " -10" 2" B D E The capacity of the channel depends on whether it is designed solely to in- crease time of concentration, or also to protect downslope installations. Channel cross sections should be de- signed so that they may be basically maintained by machinery. Usually this Runoff Spreader. The function of a runoff spreader is to disperse runoff at nonerosive velocities over undis- turbed areas stabilized by existing vegetation. Concentrated runoff is changed to sheet flow, much of which will infiltrate in undisturbed areas. The spreader should be constructed on undisturbed soil which is neither poorly drained nor highly erodible. It Site Class Assumed Soil Texture means that they should be easy to mow. Steps in design are: 1. Determine maximum runoff in cfs at each design point. 2. Select permissible velocity from tables. 3. Select size of diversion channels from Exhibits 9 -1 to 9 -4 in SCS Manual. is necessary to estimate the inflow value of Q in cfs to determine the length L of the spreader. Periodic inspection and maintenance is vital. The following figures show the required length L for values of Q (1). Designed Q cfs Min. Length L /Ft. <10 11 -20 21 -30 31 -40 41 -50 Permissible Velocity Ft /Sec. 15 20 26 36 44 Bare Channel Retar Channel Vegetation Retardance Poor Fair Good E Others Sand, Silt Sand /Loam Silt /Loam Salty Clay Loam Sandy Clay Loam Clay 1.5 2.0 2.5 B C D B C D B C D 1.5 2.5 3.0 3.0 2.5 2.0 4.0 3.5 3.0 5.0 4.5 4.0 4.0 3.5 3.0 5.0 4.5 4.0 6.0 5.5 5.0 REFERENCES 1. USDA, SCS. College Park, Md. Detail of Level Spreader. L.S.I., Md. SCS Design Standard. 2. Chow, Ven Te. Handbook of Applied Hydrology. Section 9, p. 6. 1964. 64 INFILTRATION OF RUNOFF AFTER MEASUZ . PRELIMINARY CONCENTRATION SEEPAGE BASIN OR RECHARGE TiPE BASINS (SINGLE USE) 1.5 To allow a Large percentage of annual rainfall to recharge a valuable aquifer. Runoff is collected in various storm systems prior to being passed into the basin. SATE. C14A2.C.T�AZtsTIGS avid APPLE6A ?iot.1 Principally used on aquifer recharge areas (R), but may also be used on any site where water table is always over 48" below the ground surface. (All except D, M, F, W). Recharge basins are extensively used in urban areas of Long Island to recharge ground water. Generally, provided soil is reasonably porous, a recharge basin can recharge large quantities of water in a short time without the use of much land. A,DVAKITA6E6 1. Because basins are deeper than seepage areas, they operate under a greater head and, therefore, are capable of recharging a greater volume of water per unit area in a given time. 2. Seepage basins require less land area than seepage areas. G15ADVAMMTA6E6 1. The seepage basin is generally regarded as a single -use facility managed intensively for recharge. They must be fenced and regularly maintained and are often very ugly. 2. Seepage basins need constant maintenance to insure porosity is not reduced. Where this does happen, it may be necessary to bore seepage holes or pits in the base. 3. Unless fenced, seepage basins may be a safety hazard where more than 30" deep. 4. Additional measures may be needed to keep water clean if groundwater is a drinking water source. Dssi4N1 c2TEZIA avid OJI LINE SPEC.tr ATteDNs Size. The sizing of a recharge basin depends on what its intended use is. If it is to recharge as much water as possible, it should be sized to take the maximum 24 -hour rainfall from all paved areas. Almost certainly this is not economical, and it will be desirable to recharge most of the annual precipi- tation except the very large storms which can be recharged using a much smaller basin. If a basin is also designed to have benefits in control- ling flood peaks, it is desirable that during intense storms overflow of the basin starts early in the storm. As all basins require sediment traps, it is possible to provide an overflow system for the trap which would by -pass a considerable quantity of runoff. The design of the system will depend partly on whether one elects to trap the sediment from by- passed runoff. 65 E.0 / 17 Ric RE MaRGE 1 husar- , LOW INeirr oP U!l'E.PeLz L4J Because of the elaborate maintenance required, it is doubtful that it would be feasible to provide sufficient storage for the 'max' 24 -hour storm (about 3 -3.5 inches in the Seattle area) in order to eliminate the need for an overflow storm system. In practice, a major factor in sizing will be the available land. Dimensions. The dimensions of a storage basin can be varied consid- erably. The 88,000 cubic yard basin at Burlington, New Jersey is 27' deep. FEZ RE' RECHARGE 15:51A) ST sEDiHENT TRAP BP Sy PASS ibF crc E55 froloiP ED ENERldEa/CY OVERFLDh/ Construction. A considerable amount of recharge occurs through the side walls of the basin, so it is preferable that these should be constructed of pervious material. Gabions make ideal sidewalls. The base of the basin must be kept free of silt. In some circumstances it may be desirable to spread 2" of coarse sand over the base to improve infil- tration. Side Slopes. Where these are grass, there should be a shallow swale to prevent runoff from side slopes from reaching the basin. Sediment Trap. Runoff collected should pass into a sediment trap before dis- charging into the basin. Landscaping. Wherever possible, the design of the recharge basin should be carefully fitted with surrounding topography. Security and Safety. Recharge basins with a depth in excess of 30" must be fenced to prevent trespassing. Six - foot cyclone fencing is adequate in most cases. Maintenance. At least once each year the accumulated silt must be scraped off the bottom and the base cultivated. 66 Gabions - Standard Sizes - Ft. Length Width 6 3 9 3 12 3 Height 1' -1'6" or 3' INFILTRATION OF RUNOFF AFTER MEASU2E PRELIMINARY CONCENTRATION TYPE RECHARGE BASINS (MULTI -USE) I.6 PU2Po5a Wherever soils are relatively permeable and groundwater is not too close to the basin floor, recharge basins can be an effective means for aquifer recharge. They are often used primarily for dis- posal of storm drainage with recharge as a secondary benefit. SIrI =. 04AZACrf✓21ST'lcs Q1id APPLICATION Recharge basins can only be used effec- tively where the aquifer outcrops at the surface (i.e., at aquifer recharge areas) or in areas where the aquifer is so shallow that the basin extends to the aquifer, or in some cases, where strata overlying the aquifer are very permeable and allow percolation of water to aquifer. ADVA KtrA6aE.5 1. When a recharge basin has benefits in disposing of stormwater as well as recharging the aquifer, it may be an economically attractive method of conserving groundwater resources. 2. Often a recharge basin can be constructed as a borrow pit as part of a major construction project, e.g., a highway. p15ADVa.NI rAE.S 1. This method does not take advantage of the filtering effect of the soil (as in the case with recharge by irrigation), therefore, there is a risk of pollution where recharge water is of variable quality (e.g., storm runoff). 2. Basins are extremely susceptible to clogging unless recharge water is fairly free of sediment and the basin is maintained frequently. 17-GSi i C21TE.2lA aNd OU"f LINE SPEC.'cICATI,KIS Sizing of Basins. This depends princi- pally on the source of recharge water. In recharge basins on Long Island designed primarily for the disposal of highway runoff, sizing of basins is based on a minimum requirement of storage for runoff from the entire watershed resulting from a 5" instan- taneous rainfall. Infiltration rates during the accumulation period are not taken into account in designs (2). Although more sophisticated sizing techniques are possible, their appli- cability is doubtful in light of the difficulty of guaranteeing elaborate periodic maintenance upon which such techniques depend. Where a constant source of recharge water (for instance, effluent from a sewage treatment works) is available, sizing will depend on the rate of infiltration which can be achieved, and the amount of storage required during adverse weather condi- tions. 67 Basins used by the California Division of Highways in the Fresno area (also primarily used for disposal of runoff from highways) vary in size from 1 -6 acres. Storage is provided for two consecutive 24 -hour storms with a 10 year frequency, making no allowance for percolation during inflow. Percolation rates of about 0.42 feet per day are achieved (3). In the Central Puget Sound area, soil characteristics are widely variable. Specific on -site infiltration and percolation tests should be performed to establish the appropriate rates for design. Excavation. Although excavation may be carried out during general earthmoving activities (indeed, the fill may be required on site), great care should be taken to avoid letting runoff flow into the basin until construction is complete and vegetation is established. Other- wise, fine sediments may permanently reduce its infiltration capacity. If it is essential to use the excavation as a sediment pond during construction, it should be lined with a waterproof membrane (1). Inlet. Prevention of scour by the inlet is an important aspect of con- struction, as it will significantly reduce maintenance problems. The introduction of a 'hydraulic jump' before the water flows over the apron and into the basin is a relatively simple means of reducing the inflow velocity. An impact stilling basin is even more effective (1). Side -Slope Protection. Runoff from surrounding land should be intercepted by diversions. A dense turf on side slopes will prevent erosion and slough- ing, but also allow a relatively high infiltration rate through slope sur- faces. Side slopes should be cultivated and seeded with a suitable mix. Slopes should be fertilized and protected from erosion during the establishment of the sward (1). Basin Floor. Final grading of the basin floor followed by tilling with a rotary cultivator should be carried out, preferably after the site is well - established (1). In basins in California, the percolation has been improved in some basins by constructing gravel - filled trench drains in the basin floor (Figure 1) which have a slightly domed surface. In others a lower level is used as a sediment trap with an infiltration bench level flooded out during times of inundation. Experiments using seepage basins and recharge trenches and pits in Newark, Delaware, have been carried out to recharge an aquifer with storm runoff. These were unsuccessful due to an impermeable stratum between unsaturated material at a shallow depth and a deeper aquifer, which led to a 'perched' saturation zone. However, this shallow zone was sufficient to permit the dis- posal of large volumes of runoff. It is possible, that in the future the impermeable barrier could be breached. This points out the importance of con- sidering the characteristics of the entire soil profile down to the ground- water, rather than only the surface soils. 68 Disposal of Sewage Effluent and Aquifer Recharge Using Recharge Basins. A number of schemes are in operation throughout the world where sewage effluent is used to recharge ground- water. In some cases, disposal of effluent is the primary objective; in other cases, effluent may be used to create a barrier against salt water intrusion. A reclamation plant at Whittier Narrows, California, reclaims 12 mgd of sewage effluent, but has a 280 mgd potential. Spreading basins are used to percolate effluent into the ground. Operation cost can be 2.2 cents per 1,000 gallons.. Maintenance. Proper design of the inlet to prevent scour of the basin floor is important and will reduce maintenance. The establishment of a dense turf on the basin side slopes is recommended, while the basin floor should be kept clear of all vegetation. Sediments should be removed from the basin floor only when completely dry and "mudcracked." Light equipment should be used to grade silt into rows which should then be removed with a small front -end loader. This must be done before all tilling operations, which are required at least once annually. Tilling should be carried out with a rotovator. Settling basins using subsurface tile lines as a filter have been effective, but costs have been prohibitive. The growth of algae in the percolation area has been a problem in some basins where there is a continuous summer inflow from domes- tic watering. REFERENCES 1 Weaver, R.J.. Recharge Basins for Disposal of Highway Storm Drainage. New York State Department of Transportation. May, 1971. 2. New York State Department of Transportation. Letter to U.S. Department of the Interior. Re: Recharge Basins. August 24, 1971. 3. Gong -Guy, G. Disposal of Storm Water by Groundwater Recharge. California Division of Highways. Fresno, Undated. 4. Seaburn, G.E. Preliminary Results of Hydrologic Studies at Two Recharge Basins on Long Island, New York. USGS. Geological Survey Paper No. 627 -C. 5. Journal of Research of the U.S. Geological Society. Vol. 1, No. 6. November - December, 1973. 69 INFILTRATION OF RUNOFF AFTER MEASL)2E. PRELIMINARY CONCENTRATION SEEPAGE PITS OR DRY WELLS. PITS USUALLY FILLED WITH GRAVEL OR RUBBLE. SOMETIMES CASED. TVPE. I.7 R4zebt5 E Seepage pits collect runoff and store it until it percolates into the soil, but unlike Dutch drains, seepage pits do not conduct water along their length when filled. SITE GOARAcraosTic.s QIKf APPLIcATIO N May be used on all sites where perme- ability of soil is sufficient (over 0.15 ft /day) and where seasonably high water tables are not anticipated (all except D, W, F, M). Seepage pits may be designed to accommodate a maximum design frequency 24 -hour storm, or they may be designed at least to allow in- filtration of runoff at predevelopment level. In this case a supplementary system of storm drains will be neces- sary to accommodate overflows. AD\/ANTAc.ES 1. If properly designed, seepage pits may reduce local flood peaks. 2. Enhance groundwater. supply. 3. In some cases they may eliminate the need for storm drains or reduce the size of the storm drains which are necessary. Dt10.p\A N11-ikC-�ES A seepage pit will, provided the soil permeability is sufficient, accomplish the aim of increasing infiltration. However, unless it is very large (equi- valent to at least 3 inches over all of the impermeable surfaces drained), it may not result in a reduction of flood peaks (see schematic hydrographs for Dutch drains). Seepage pits are more susceptible to clogging from sediment than Dutch drains, as runoff has more chance to collect solids before reach- ing the pit. 9E ,tc t.1 6-2 tTE2f ik aInd OUTLINE 5 PE .1Fie -AT(o i Unless the seepage pit is designed to take the total amount of anticipated runoff for a design storm, some provi- sion for overflow must be made. In order to have the maximum benefit in reducing flood peaks, the pit should, in fact, overflow during intense storms before its capacity is reached. Alternatves for achieving this are: 1. Downpipes: Where down pipes discharge into seepage pits, they can incorporate a simple overflow to function during intense storms. 71 This system is likely to prolong the life of the pit as the sediment trap will not function effectively with full flow. DURING AJORHAL PP7 1.4.147ER fOLCOL✓5 007TEDROU7E. R' vb mirzAx. R4/NFACL 3V- /7415 S 57 l wag 5 te- r TRIP m r Of SEPAC fir LS4GeRZZJ 7 Lam A66Pl/A7E 2. Small seepage pits with a relatively low porosity capping in the overland drainage channel. In a paved channel, seepage pits may be surfaced with porous asphalt or modular blocks set on sand. The gradient and porosity of the sur- face of the pit will determine the point at which runoff starts to bypass the pits. 3. In areas where a gravel - filled seepage hole is a more appropriate, this may be situated in a depression, but with a porous section leading to the overflow channel. Porosity: Soil should have a minimum porosity of 0.1 ft. per day. (Note the range for septic tank is 0.134 -0.40 ft. per day. 7D �$4 L 4b • Ov£RFza) WILL. LAN 8ERAGEGAPAC.IN /5 Size: The minimum size of a pit should be sufficient to maintain infiltration at predevelopment level. This depends on the porosity of the soil and on the number of falls of rain per year. It is assumed that the seepage pit will be located close to the impermeable sur- faces which it served, and that the time of concentration will be less than five minutes. The normal precipitation per rainy day in the Seattle area is slightly less than 0.3 inches (Chow, 1964). Infiltration of this amount would certainly insure maintenance of infiltration. However, because the normal precipitation per rainy day is 0.3 ", it does not mean this will reach the seepage pit. On some days there, will be little runoff generated. Addi- tionally, extra capacity should be allowed to offset clogging and loss of permeability of the pit. The minimum size recommended is to take the equiva- lent of 1" of rainfall over the whole area of impermeable surface drained. The maximum size should be to take the maximum design storm for a 24 -hour period. Construction: No pits should be constructed where the water table is less than 48" below bottom of pit in all seasons. The ratio of sand or fine aggregate should be used at the bottom and edges while backfilling. Only paved areas should drain into these pits, and they should either incorpor- ate a sediment trap or allow replacement of a filter of sand. _5001 of r46/341 n_ ALT SuRF4 SEE rAnt4 PFNIN5 REFERENCES Chow, Ven Te. Handbook of Applied Hydrology. Section 9, p. 46, 1964. 72 INFILTRATION OF RUNOFF AFTER PRELIMINARY CONCENTRATION SEEPAGE BEDS - OR DITCHES I.8 PJ2P06E To dispose of runoff by infiltration into the soil via system of drains set in ditches of gravel. These systems only reduce volume and speed of runoff and require an overflow system. By increasing time of concentration, they may also reduce floodpeaks slightly. '11 E Gr- lA2�gGT QisT�Cr� aid APPI-lLitirloN Applies to all site classes except those with periodically high water tables (M, F, W) or where drainage of soil is poor (D) (less than 0.075 feet per day). This system may be used where percolation rate does not allow the use of seepage pits. 1. Distribution of water over a larger area than achieved with seepage pit. Less hazard of clogging. 2. May be placed under areas of paving if the bearing capacity of pavement is not affected. 3. Groundwater recharge. 4. Safer than infiltration basins. DIADVANITAUE& 1. No filtering effect of the topsoil although there will be some im- provement of water quality as infiltration takes place. An in -line filtering system is necessary. 2. Should beds or ditches eventually become clogged with sediments, re- placement of an entire system is necessary. Therefore, maintenance of sediment traps must be frequent and, consequently, expensive. DES «■ GelTligt4 aid OVTUNE. S'EGIFIGATIbNS Seepage Ditches 1. Movement of water into the soil - depth and spacing of the drains. The depth and spacing of the drains in a seepage bed depend primarily on the porosity of the soil (minimum 0.075' per day). Generally they should not be closer than 10'. The depth of the excavated trenches should be at least 48 ". These are 73 backfilled with at least 18" of washed gravel or other approved granular material (size 3/4 "- 1-1/2"). On this bed the distri- bution line is laid; this may be agricultural clay tile drain, perforated bituminized fibre or polyvinyl chloride pipe. At least 12" of granular material is laid over the distribution line, followed by a layer of paper (not waterproof) or 2" straw or hay. Then 12" of topsoil should be laid on the sur- face where area is to be grassed. Trenches should have a maximum width of 18 ". 2. Capacity of the system. The total storage volume of the system is calculated by estimating voids in granular material as 30% of the total volume. The design policy will vary, but the capacity would not be less than 1" x runoff coef- ficient over all areas drained. 3. Distribution and sediment removal. Prior to passing runoff into seep- age ditches, sediment must be settled out. This may be accom- plished by a combined sediment trap and distribution box. Seepage Beds. Infiltration from seep- age trenches tend to cause slight 'ridges' in the water table beneath the trenches. In order to increase the efficiency of the seepage area, trenches may be interconnected by a continuous 12" gravel bed. The bottoms of the trenches still extend at least 18" below the base of the gravel bed. In ^,_ rte_ 7 M/ /N this way, the soil beneath the gravel .• • bed dries out more regularly and its 1-445- i:!' %1•�: percolation properties are improved. % T# 1.•41Y•.e- Distribution and sediment removal systems should be the same as for .•� seepage ditches. Capacity and Overflow. In order to reduce flood peaking effects, the seepage system should be designed to overflow before capacity is reached. >Zv 161 HOY \J ATE2 TABLE BELr'.4j EEPAE ptTZ.4ES 74 AMC BilbMINIZEP F /5m a4 Fit F7PE WATEz 5EE OEED5 INFILTRATION OF RUNOFF AFTER N1EA602E PRELIMINARY CONCENTRATION Ti(PE SEEPAGE AREAS - (MULTI -USE) 1.9 COZPosE To allow a percentage of annual rain- fall to seep into the ground, to store excessive runoff and to provide for multi - purpose use of such a facility through careful design for recreational use, parking or open space. Slr� GWAR.AcTE2lsTICS atAd APPLICATIO►'1S Site classes; all except those with a periodically high water table (M, F, W) or where drainage does not exceed 0.25' per day (D). Such facilities are use- ful in areas where open space is not needed for use at all times and when the alternative use is not necessary during a storm and for a period after. There will be problems for instance in using overflow parking areas when there is a possibility of cars being left on the lot during a storm. ADI/At.1TA60E 1. Recharge facility is designed for multi -use. 2. Where a grass surface is used, there may be a significant improve- ment in the quality of recharged water due to the filtering effect. DIO DVANTA4 1. Because of the requirement for multi -use, the facility must have a higher rate or recharge and be shallower than single -use basins. 2. It is often difficult to maintain porosity of multi -use areas. 266161s4 GIZITER.1A avid oim M E PEL T F1GATto t4(S These areas may be grass and may have vertical retaining walls or grass banks. If the depth of water can reach more than 6 ", fencing around the facility should be provided. Examples: 1. Hard - surfaced basketball court, paved areas, etc., to which grassy areas are drained. Water collects 75 in grass swales around the edge, seeps into the gravel French drain, dropping its sediment load and discharges onto the porous asphalt. The grass swales should be graded so that during very intense storms some runoff can overflow to receiv- ing water before capacity of the seepage area is reached. In this way the effectiveness of the facility in reducing flood peaks is increased. sguo Lthni ��� oP &f &OS rfflAk Contee1E C08 i-PORW5 4517/Alf TILE O.4A! 2 fhli la41t & In cases where use of facility is less predictable, it may be desirable to incorporate a manually operated drain which may be used if the facility is required before seepage is complete. Note: A deep aggregate base will keep the facility dry except during heavy storms. Porous paving is in an early stage of its devilopment and its capacity to resist clogging by sediment is not known. It may be that, providing the facility is vacuumed after each inun- dation, sediment trapping swales and trenches could be dispensed with. Most sediments will settle at edges where the flow of water is slowed. 2. Grassed areas should also be pro- tected from sediment deposits and should be constructed with a deep porous base course to allow reasonable surface conditions following infiltration. Various methods may be used to settle out sediment prior to runoff discharg- ing onto grass, but it should be remembered that discharges from pipes directly onto grass should be avoided where possible. illeusgketr 41,6zz_zoe ewe Max gradient of grass slopes 3 horiz:l vert. 76 M>✓ UtZ.E- DELAY OF RUNOFF DETENTION BASINS 1.10 Q iJZP06a To detain runoff in order to increase the time of concentration or to reduce the maximum discharge rate of runoff from an urban area. SITE C►-E rzitc.Te2I5T(G4 and APPLILAroN A detention basin is the most effective technique for reducing the peak flow at a point immediately downstream of the impoundment, and should be used where frequent flooding in the area immedi- ately downstream is intolerable. Some detention ponds have a retention capa- city (a small permanent pool). Although retention of the design storm for periods longer than the time of concen- tration can depress the hydrograph, retention ponds should only be used where recreational or water supply advantages are required. ADVAt irelb4 S 1. A detention pond can be designed to catch a large proportion of suspended solids of more than 10,c in diameter. 2. A detention pond with a large freeboard for detention may have some recreational and aesthetic benefits if runoff is not carrying heavy sediment loads. 3. May allow significant reduction in the size of storm drainage struc- tures, etc. 21! AD/At.11- 5,5 1. A detention pond for maximum runoff control will have very little recreational or aesthetic value. 2. Detention basins which empty out completely can have an unsightly nature that can be a detriment in urban developments. Backup detention minimize this unsightly condition. DE:54 N c2r .2.1 A and euri_INE -sPE 1FV.ATIo1�5 A single- purpose runoff control pond will clearly have very different design criteria from one that is also required to have some recreational, aesthetic, or sediment control value. BMP II.7 shows that a single - purpose runoff control pond could be effective in settling out a large proportion of the sediment above 10 ti( in size, especially if the spillway design was modified during the construction period. Detention Ponds. The most effective reduction in peak discharge per unit of storage from a given drainage area is given by a detention basin. The aim may be to reduce the peak to predevel- opment levels or to reduce the peak to a level at which it will not damage or overflow a facility (bridge, culvert, etc.) immediately downstream. Two methods for preliminary sizing of basins are given in the previous section, depend- ing on the size of the tributary area. The first, based on the Rational Formula, assumes a trapezoidal inlet hydrograph, (Figure 1 ), and a constantly increasing 77 5o 40 �3c 0 2 0 0 ?o so w 11ME. Mmes FlLaugE t outlet hydrograph which peaks at the point at which it crosses the descending limb of the inlet hydrograph. (Point D, Figure 1 ) The volume of storage required is then represented by the points ABCD in Figure 1 . The second technique which uses variable hydro - graphs for inflow and outflow is more sophisticated and accurate. Variable discharge outlets may be used (for example, various weirs or orifice outlets). Relationships between stage (depth), discharge, and storage for a specific site are used to route the inflow hydrograph through the storage facility. A detention pond will also have sediment control benefits, although it will only be partially effective in larger storms (See BMP II.7). ® i0 70 110 90 Im no 17o 1,29 15b 130 IW 1 VD 117 11n 210 1221 Detention /Retention Ponds. Where a permanent pool is required for, say, recreation and aesthectics, flood control must be provided by additional storage 'on top' of the permanent pool (Figure 2). The same procedure may be used to calculate the necessary storage volume and maximum discharge capacity of the spillway as for a detention pond, ignoring the volume of storage in the permanent pool. Note that if runoff is carrying heavy sediment loads, the aesthetic and recreational value of the permanent pool and its surroundings will be severely reduced by deposited sediment and would neces- sitate clean -up operations following storms. Retention Ponds. Retention ponds can only be located on a drainage channel if the channel carries only storm run- -off. Their efficiency is not as great as detention ponds per unit of storage. This is for two principal reasons. DACE of fisamiamegr F Th. D F10017511 APC citg 5 OF E E�y Fu2. 78 Retention basins may be located off channel, in which case they operate more or less as flood- skimming devices and, provided they are emptied fairly soon after a storm, have a high effi- ciency per unit of storage (Figure 3). If, for instance, it is desired to limit the discharge in a channel to predevelopment peak (QN) for a 25- year storm, then a pipe with a maximum discharge capacity of QN would be located in the channel and any flow in excess of this would be diverted into the pond. This pond would be of suffi- cient capacity to contain all discharge in excess of QN for the design storm. There is no• outflow (or very restricted outflow) during the period of the storm and thus the storage capacity needs to be larger. Secondly, following a storm the pond will not be emptied rapidly and thus a second storm could cause a high peak discharge. However, if the aim of a pond is to reduce the frequency of fairly small floods downstream (which may be, for instance, causing bank erosion) and at the same time provide some storage for, say, irriga- tion water, such a retention pond may be useful. They will also be effective in controlling sediments for the design storm. 79 MEASuzE. RUNOFF - CONTROL DETENTION PONDS ON MINOR WATERWAYS FO .7 7OSE Detention basins can be used to delay runoff on sites where seepage at source is unfeasible. In some cases basins may double as sediment control ponds or may be used to 'feed' a seepage system. SITE GI..I.A2A\Cj' 2►STIC.S and APPS. (GAT leN J A detention pond requires some sort of collection system to feed it. Developers may find that the cost of such a collec- tion system makes the provision of 'at source' detention more economical. However, where 'at source' methods are expensive or unfeasible, detention ponds may be used. They are especially suited to cluster development where ponds can be incorporated into open - space systems. ADVANTAGES 1. Detention ponds hold runof and release it at a slower rate which normally results in a 'flattening' of the hydrograph. 2. Upstream flood damage may amount to a very significant proportion of the flood damage in the basin. 3. Ponds may in some cases be multi- purpose, usually fulfilling recreational or sediment control functions. The dam may also improve vehicular access on a residential site. PIsADVANLTAGE.s 1. It is probable that such measures will not significantly reduce the damaging effect of the very serious flood in the main stem of large drainage basins. 2. Unless carefully managed, runoff ponds may be an eyesore and a dan- ger in a residential development, rather than an asset. DESI4■ GQITEIZIA 43W4 OUTLINE SP €ctFIGA. ioNl'� The design criteria of a detention basin depend on two main factors. The first is the inflow hydrograph for critical storms, and the second is the outflow hydrograph desired. The choice of an outflow hydrograph will depend on where one wishes to prevent flood dam- age. It has been stated that upstream flood control measures may have little effect in reducing the impact of major floods in the main stem of large basins. It is, therefore, assumed that the main aim is to provide protection of facil- ities in upstream areas with a time of concentration from the watershed of no more than 2 hours. It is also assumed that individual detention basins will serve areas with a time of concentra- tion rarely exceeding 20 minutes. cfs. Gf2loR To 177/E-LOPMENT cf4 cr.5. azipeoe,ec, CUTCLOW .o42a i of cN bNip 81 T-o Eric.vowNk - .R ' •o7► W LL CASZ.5 It is important to remember in designing detention basins that once the time of concentration has been reached for a storm of given intensity, the flow will be constant. Generally, unless the basin is so large that it can retain more runoff than would accumulate during the time of concentration for the area contributing to the critical point, (2 hours maximum), it should release runoff prior to its capacity being reached. Thus, the overflow device of a basin will have a definite discharge rate prior to capacity being reached, at which point the basin would overflow via an emergency spillway. The overflow device is normally either a pipe of maximum diameter to give the rate of discharge required or a perforated riser pipe to a piped spillway. As a cheaper alter- native, pervious dams may be used (timber, rock fill, gabions, etc.). In some cases a permanent pool is required for recreational purposes. If the basin is to have flood control benefits, the water level should be kept as low as is feasible. The mini- mum depth to control weed growth is about 10'. rater of'PAH c Val CrsvuiWAw rOVECROJ t1. G(#V*'1'S F EAiP» Fist DAAI 3.1 41;"01.410 Iiinzee. 51 KEY mgr. 145(z um( vEUUV�.�rm+� AR 1bRk a. L r e.ger of DA •�. Cost of StatoEJXY 611111.101 0 82 MEksU E6 PREVENTION OF EROSION ON CONSTRUCTION SITES -TYPE MINIMIZATION OF STRIPPED AREAS, CONSERVATION OF TOPSOIL, AND STRAW BALES R?2Po e To reduce the generation of sediment by minimizing the areas stripped during construction and filtering or diverting runoff from large stripped areas. SITE Gt-I1k2AGTacatsTt�s cj APPLI C Tto1.1 These techniques should be applied to all sites undergoing construction, especially those where there are large areas stripped of vegetation at any one time. ADVANTA(IES 1. A vegetation cover will minimize erosion. Thus, minimizing the area of bare ground at any one time during construction will reduce the erosion hazard. 2. Minimizing erosion on site and limiting the amount of sediment being carried by runoff may pay the, developer by eliminating the need for regrading or importation of additional soil due to erosion and by eliminating damage claims by downstream landowners. r)t sADVANM ES 1. Economies of scale, mobilization costs for large earth - moving machines often are such that all earth - moving is done at one time. 2. Erosion control devices such as straw bale barriers or diversions may limit the maneuverability of machinery and equipment on site. 3. Unless carefully located, storage banks of topsoil may also obstruct site operations and, therefore, require double handling. 2E5 le4 CR I TER I A 'i va OuTI_1N SPe_GIFIGIcr IONIS 1. The Minimization of Stripped Areas. Careful programming of a development may enable the developer to reduce the area stripped of vegetation at any one time. A large development which is phased over a number of years is an example. However, the high mobiliza- tion costs of heavy earth - moving machinery often dictates that all earth - moving be done at one time. If this is the case, all areas of the site which will not be used for construction within 6 months should be seeded as specified in BMP II.2. 2. Conservation of Topsoil. Topsoil from all areas undergoing construction should be stripped to a depth of 9" and stockpiled. The location of these stockpiles should be carefully selected so as not to obstruct site operations and result in double handling. These mounds may sometimes be used as 'baffles' to reduce noise, dust, etc., reaching neighboring properties, thus minimizing complaints. Topsoil mounds should be not more than 8' in height with side slopes of 1:1.5 -1:2. If they are to be in position for more than 6 months, seed with a temporary seed mix as specified in BMP II.2. A 83 shallow trench around these mounds made with a bulldozer blade will prevent soil eroded from mounds from washing into adjacent property or into drainage channel. Respread topsoil as specified in BMP 1I.9. See paragraph (5) for imported topsoil. This should only be necessary when existing soil conditions are very poor. 3. Straw Bale Filters. In areas where straw bales are easily available, they may be used to filter sediment from runoff generated by large stripped areas. Where the length of slope exceeds about 100', the accumulation of runoff may cause serious erosion. Therefore, downslope of all stripped areas where the length of slope exceeds 100', a continuous line of straw bales should be staked (with wooden or metal stakes) along the contour. Where they do not obstruct construction activities, lines of bales may be staked at regular 100' intervals along the contour on very long slopes. Regular inspection and removal of sediment is necessary, particularly where only one line of bales is used on long slopes. (Straw may be used for mulching when the area is finally seeded.) Where straw is not available, a temporary diversion channel should be used. 4. Temporary Diversion Channels. BMP 1I.5 covers the construction of tempo- rary diversion channels for use on steep sites. Long shallow slopes may also generate sufficient runoff to cause serious erosion on stripped sites, and this runoff should be diverted at the bottom of such slopes and directed to a sediment basin (see BMP II.7) or to an area where runoff may be spread in a well- vegetated area where sediment deposits will not cause a nuisance. e4LE5 eoukD WItm 51RAW -9ALE NYLON OR WIRE FILTERS b\e13UILD UP OF SEDIMai1 REM' PERIODICALLY 6ETwEEN Se4L. f,TRIPPEo AREA i 5. Importing Topsoil. On sites where there is little topsoil available or where soil is too poor to achieve rapid vegetative cover, it may be desirable to import topsoil, but unless it is locally available, this is an extremely expensive operation. It may be necessary to apply lime to the subsoil prior to spreading topsoil if the former is highly acid or is a heavy clay. Ground limestone would in those cases be spread at about 100 lbs /1,000 sq. ft. The subsoil should be thoroughly culti- vated with a disc harrow prior to spreading topsoil. These cultivations should be along the contour. Topsoil should generally be a good quality loam, but depending on the conditions and availability, inferior soil may be acceptable. Soil should also generally be free from excessive clods, stones, trash, plant material, etc., especially undesirable weed species including poison ivy and coarse grasses. The pH should be between 4.5-7.5. A 3" depth is the minimum normally specified and topsoiling should not be carried out when the ground is frozen or when wet conditions will cause 'smearing'. Cultivation following spreading of topsoil will depend on further treat- ment, but if the area is to be seeded, soil should be cultivated along the contour and compacted lightly after harrowing in the seed. IMPLEMENTATION AND LEGAL IMPLICATIONS The conservation of topsoil is in the developer's interest as it results in more rapid and healthy grass growth, which not only prevents erosion but improves the appearance of the develop- ment. In some European countries the conservation of topsoil is mandatory. Where measures are mandatory in this country, they are often ineffective due to failure to inspect installations. For instance, hay bale filters that are required in some areas of the country 84 were found to be stockpiled at some developments but not used in the field. This points out the general need for follow -up inspection once the project has begun. If a developer will not employ even these basic control mea- sures, there is little likelihood he will employ more extensive ones. 85 PREVENTION OF EROSION ON MEA6O Z„E CONSTRUCTION SITES TEMPORARY MULCHING AND SEEDING OF ALL STRIPPED AREAS OF MORE THAN ONE ACRE TO REMAIN OPEN FOR MORE THAN SIX MONTHS II.2 Ft.)2POSE Erosion can be significantly reduced on sites which remain bare up to 12 months by the use of a temporary mulch and /or seeding. SITE 6.446tIZAGTE12-I6TIG6 C[lnci APPLIGATIOF46 This technique should be used on all sites where large areas are left bare up to 12 months but where final grading has not yet been carried out. It is also useful for stabilizing temporary heaps of spoil and topsoil. All areas which will remain open for more than 6 months on steeply sloping or highly erodible sites should be mulched and /or seeded. AD/ANTA6 ES 1. This is a relatively cheap form of erosion control but should only be used where final grading and seed- ing is not possible. 2. Vegetation will not only prevent erosion from occurring but will also trap sediment in runoff from other parts of the site. 3. Temporary mulching and seeding offers rapid protection to open areas. DISADVANTAtCES 1. As temporary cover crop is sown on subsoil in most cases, growth is often poor unless heavy applica- tions of fertilizer and lime are made while seeding. 2. Once seeded, areas cannot be used for heavy traffic. DEstct.J C2tTE IA a►nd OUTLINE 5PECCFtc.ATIOt\t6 Areas may be mulched and /or seeded. Areas which will be subjected to heavy wear by construction traffic should be mulched. The choice of mulch will depend primarily on availability. If scrubland has been cleared from part of the site, vegetation may be put through a chipper. This will make an excellent mulch. Straw is the most commonly used type. Spread at about 120 -150 bales per acre and disc into the surface of the soil. For approximate rates of application of other types of mulch, see BMP II.11. Areas which are sub- jected to almost continuous wear by construction traffic should be treated in a similar way as construction roads, receiving a dressing of crushed stone and incorporating. diversion 'berms' at regular intervals to intercept longi- tudinal runoff. Areas which are not sloping at more than 5% for lengths of slope of more than 100' or 10% for length of slopes of less than 100' may be seeded without mulch. An approved seed mix recom- mended by the local Soil Conservation Service for the area should be used. Where topsoil has been stripped, seed- ing should be preceded by application 87 of a dressing of lime at 2,000 lbs./ acre and of 10 -10 -10 fertilizer at 800 lbs. /acre. Material should be anchored with a mulch anchoring tool, asphalt, or other binding agents. Areas sloping in excess of 10% (or 5% for slope lengths exceeding 100') should be mulched as well as seeded. Mulch on steep slopes is an aid to establishing good stands of vegetation dm. to improvements in moisture rela- Lonship, especially in regard to summer and winter seeding. Straw gives the best results and should be spread after applying fertilizer, seed and lime. An application of 15-25 tons per acre should be made and thoroughly disced into the surface, making the final pass parallel to the contour. Straw mulch, along or together with fertilizer and seed, may also be applied with a hydroseeder as recom- mended in BMP 11.12. The local SCS office may be consulted regarding application amounts and schedules for the specific area. 88 PREVENTION OF EROSION ON Iu(ASURE CONSTRUCTION SITES CONSERVATION CULTIVATION TYPE PRACTICES ON ALL STEEP SLOPES II.3 PJRPo5E During the construction period, areas may be bare for periods too short to make use of temporary mulches or cover crops. Careful cultivation can in these cases greatly reduce the volume of sediment generated on the areas. SITE Cf-1AP GTERISTGS el vlci APPLIGATIoNS Applicable to all site classes, but generally steep slopes, highly erodible soils and other critical areas (e.g., floodplains) require more elaborate measures. ADVANTA E5 Careful attention to cultivation techniques will pay the developer. It is one of the cheapest and simplest methods of erosion control on sites with only slight erosion hazard, and is a worthwhile supplementary measure on more critical sites. DIADVPN►4TAGES The control given by cultivation techniques relies on three factors. Firstly, to increase the overland flow time of runoff by cultivating along the contours, thus effectively creating many very small diversion channels. Secondly, by increasing the capacity of the soil to absorb moisture; and, thirdly, reducing the hazard of wind erosion by leaving surface slightly rough and cloddy. Clearly all these factors are important but will not be effective during intense storms on critical sites where additional mea- sures must be used. PESI<r - GRtT'ERIA av►d OUTLINE- GI-rtGATIo►\1 1. Direction of Cultivation. Gener- ally, where it is not hazardous for the operator, cultivations should be along the contour leaving the surface as rough as possible for the purpose required. Thus, a recently graded area, which is not to be seeded for a time, should be disked. This will effectively create small diversion channels along the contour which will reduce the hazard of erosion. 2. Type of Cultivation. Never leave bare soil with a finer surface texture than is absolutely necessary. Thus, if disc harrowing provides a sufficiently fine seedbed for germination but too rough for mowing, it may be better to allow germination to take place on the rough seedbed and roll thoroughly after germination, rather than creating a very fine erosion prone seedbed with a chain harrow. This technique also applies to areas susceptible to wind erosion. Deep chiseling or ripping as a cultivation technique can improve the water intake rate of soil temporarily. 89 3. No Cultivation Technique or Minimum Cultivation Techniques. Where land forms are at the required grades but it is desired to change the vegetation cover, cultivation may be quite unnec- essary. Existing vegetation may be killed with a total contact herbicide (gramoxone - paraquat) when growing strongly (late May -early June). Theoretically, seeding may follow immediately but it is advisable to wait a Least a week when existing vegetation will have wilted. At this stage it is preferable to disc harrow at least once. This cuts existing vegetation into the soil where it acts as a mulch. Seeding can be carried out at the same time, usually with a dressing of 10-10-10 fertilizer at about 1,000 lbs. /acre. Some perennial weed species may not be killed by this technique but these can be eradicated later by spraying with a selective herbicide. This technique will mini- mize erosion on hazardous sites. In Columbia, Maryland, this technique was extensively used on cuts with slopes of up to 2 horizontal to 1 ver- tical. Total height of the slopes have ranged up to 20', with lengths up to 300'. Cultivation techniques have also been used on larger areas with gentler slopes. The technique is especially useful when weather condi- tions or construction schedules do not permit immediate reseeding. While grading a slope in Columbia a bulldozer was instructed to travel along the slope to make ridges which run hori- zontally instead of vertically. Scarification of the soil can also be accomplished by grading an area by means of a bucket equipped with teeth. The final pass by the front end loader is made across the grade with it bucket down. This technique can be readily incorpo- rated into a development. It is generally used by field supervisors on an as- needed basis. No great additional construction costs are incurred since the measure makes use of existing equipment and personnel; no maintenance costs are involved in this interim measure either. REFERENCES 1. U.S. Soil Conservation Service. Interim Standards and Specifica- tions for Topsoiling. College Park, Maryland. November, 1969. 2. Seelye, E.E. Specifications and Costs. Data book for civil engineers. 1971. 90 PREVENTION OF EROSION ON MEASURE CONSTRUCTION SITES TYoE PJRPa TRAFFIC CONTROL ON CONSTRUCTION SITES, BERMS AND CRUSHED STONE ON CONSTRUCTION ROADS II.4 Being in constant use, construction roads are a particularly important source of pollution. Where feasible, alternative routes should be made for construction traffic; one for use in dry conditions; the other incorporating measures listed below for wet condi- tions. SITS c14ARACTf ∎s-r-ics avid APPLZACNOtJ All site classes are susceptible, but steep slopes and highly erodible soils (particularly for more intensive land uses) are especially vulnerable. Road- way stabilization should be applied to all construction site roads. Where possible, the construction road should be routed along the same line as per- manent roads so that the permanent roadbed may be used for construction traffic. ADVAN -r ES 1. Efficient construction road stabil- ization not only reduces on -site erosion but can significantly speed on -site work, avoid instances of immobilized machinery and delivery vehicles, and generally improve site efficiency and working condi- tions during adverse weather. 2. Mud on vehicle tires is signifi- cantly reduced which avoids causing a hazard by depositing mud on the public roadway by dump trucks, delivery vehicles, etc.. 3. Inlets and other partially com- pleted storm drainage structures are protected during construction. D�SADVANTA6ES 1. Measures on temporary roads must be cheap not only to install but also to demolish if they interfere with the eventual surface treatment of the area. 2. Application of aggregate to con- struction roads may need to be made more than once during a construction period. 91 DE tCa1.1 c2LTE_catA alnd OLJVLIN1E SPEGIFIGArbots1S 1. Grading. Temporary roadways should be carefully graded to drain trans- versely. If drainage only occurs longitudinally, runoff will build up and gullying will occur which may make regrading of the roadway necessary. A cross fall of 1/2" per ft. should be allowed. This, of course, means that drainage swales each side of the road- way in the case of a crowned section, or one side in the case of superele- vated section, should be provided. These should also receive temporary stabilization treatment as specified above to avoid gullying. Where the vertical alignment of the road contains long slopes, it may be desirable to limit the buildup of sediment in longi- tudinal runoff by placing a gravel or crushed stone trench drain every 50 yards which can form a berm in the roadway. This trench should be 2' and 3' wide and run diagonally into road- side swales. Used in swales, these gravel barriers can, form minor check - dams to break runoff velocity and absorb energy. 2. Crushed Stone, Aggregate or Gravel. All temporary roadways, turning and parking areas used during construction should be dressed with crushed stone, aggregate or gravel at a rate of 1 ton per 3 linear yards of J22" wide roadway. (i.e., 1 ton per 12 yd ). The same treatment should preferably extend to bordering swales. All permanent road- ways, turning and parking areas to be used during construction should be graded to final elevations and then the permanent sub -base and /or base laid. Roadside swales should be treated tem- porarily with a dressing of crushed stone aggregate or gravel. at 1 ton/ 12 yd ". 3:I MAX GRADED ROAD SW LONGITUDINAL SEC71ON OF SWALE 3' LONGITUDINAL. SECTION OF ROADWAY Y. 2' f-- COURSE 41. "- 3"610 2.01 41UDINALj V ' � CR054 FALL. DRAINAGE SWALE MOST TEMP. ROADS CAN $E GRADED IN AM INVEKTEO V' SEGTIOM To AU.OW CZ/Y- PAL >: SIDE CHANNELS Simple gravel berms without a trench are recommended for less highly traveled roads. These are simply a gravel fil- ter placed in the same locations as trench drains already mentioned, as shown above. 3. Alternative Routes. Alternative routes for construction traffic can greatly reduce erosion problems. Each route can be rested alternately and critical areas stabilized. In some cases it is desirable to have a dry weather route and a wet weather route. 15'-20'HI(714 :IMAX COARSE 3/4" -3 "GAVE oR CKUSHED STONE cFINES LESS THAN 5%) • SPKJNL, -100 YDS DFFENDIAIG oN VERTICAL, ROADAUGNMEAIT • CoNSIOe.R ¶N .DEFLELTED PATH of RUNOFF WHICH OoES NOT FILTER T146 f3ERM 4 ITS EROSIVE POreNTIAL 92 4. Protection of Inlets, Etc., on Permanent Roadbeds. Where permanent roads or roadbeds are to be used during construction and inlets have already been installed, these should be protec- ted to prevent sediment laden water entering an incomplete storm sewer system. Any dry wells, seepage pits, etc., should also be protected. The straw bale arrangement for the pro- tection of drop inlets, as shown, can only be used prior to paving when bales can be staked into the ground for stability. In addition, bales should be wired together. Once pavement has been installed, a straw bale /gravel filter structure can be used to protect drop inlets, covered with a temporary grate as shown. To prevent vandalism, the installation can be covered with wire mesh. Sediment filters operate by slowing overland flow and permitting deposition within the ponding areas around inlets. This requires periodic maintenance, particularly the replacement of damaged straw bales. ZA$ AA4 E-5 PRIvai 1411 OMNI? R 4/00DTOP 6iILDIN& 560045 LAID lK1TNROaf WE6 HORIZONTAL- SECTION MOW.*H INI,Ef stKucfUKE REFERENCES 1. Environmental Protection Agency. Control of Erosion and Sediment Deposition from Construction of Highways and Land Development. 1971. 2. Environmental Protection Agency. Guidelines for Erosion and Sediment Control Planning and Implementation. 1972. 93 MI= ASOR.E PREVENTION OF EROSION ON CONSTRUCTION SITES TEMPORARY DIVERSIONS ON STEEPLY SLOPING SITES AND TEMPORARY CHUTES II.5 PURPOSE To divert runoff away from critical areas during construction, in order to minimize the erosion that would result from runoff crossing areas highly susceptible to erosion. SITE 6.14ACZAGTE.2lSTIGS avid AcPPLIC PPTIOt J All sites are vulnerable to erosion during construction but particularly steep slopes and highly erodible soils. Fill slopes are very suscep- tible and these techniques will be useful to drain terraces for residen- tial development and highway rights - of -way during construction, etc. ADVAr..LTAC�ES 1. A system of temporary channels prevents damage to areas (where final grading has been completed) and siltation of partially com- pleted storm drainage systems. 2. An efficient temporary drainage system minimizes the delays caused by severe storms during the con- struction period. 3. An efficient temporary drainage system minimizes the amount of regrading, etc., necessitated by erosion during the construction period. DS14,DVAt•1TACES 1. These techniques are temporary and the removal of measures will entail some costs. 2. Removal can cause additional disturbance and possible minor damage to permanent facilities. 3. Diversions can increase seepage which may cause soil instability. (75.54 N aZITERtA Qv►d OUr(_LNE SPEC IFIGATlONS Temporary diversions may be of several types: 1) Temporary diversion channel consisting of a channel and a ridge, usually across sloping land to convey runoff laterally at a reduced velocity to a safe discharge point; 2) A diver- sion berm is a compacted earthfill ridge, which effectively creates a channel on its upslope side. This measure is often installed temporarily at the top of slopes where grading and seeding are taking place; 3) An inter- ceptor berm intercepts concentrated runoff and diverts it to a safe dis- charge point. An example is the berm to intercept longitudinal flows on roadbed shown on page 92. The Design of Temporary Diversions. The design of temporary channels is basically similar to the design of permanent channels. (Refer to BMP I1.15 for more detail.) 95 1 Capacity. Calculate peak runoff for storms of the design frequency. This is done using Appendix C. The design frequency used for temporary diversion is normally two years for roads, playing fields, etc., and five years for building sites. No freeboard is usually required for temporary diversions. HIGHWAY RDW OR TBRRP -OFF C.E 5?D• METAL END SFLT NIF_ RGEPROR be RM cRl, FAN t71VERSIDN BERM r STD • METAL END SEct FLEXIBLE POWN-DRAIN (WAD PEE ,4 JALT CHUTE Z. Cross Section. The cross section of temporary diversions will depend, on a number of factors. One of the most important is how often it must be crossed by construction traffic. Where crossing is frequent, side slopes should not exceed 4:1. They should never be steeper than 2:1. The cross section may be parabolic, V- shaped, or trapezoidal. Gradient should generally be between 0.5 -1.0 %. FILL %oPE DlvrlsIbN 56.RM TbP of INT!RCEPtOR 56RM END MP 2:I OR FLAT`(ER 1'MIN 3:1 MIN IF IN g MW C.014.51. u5E • GROSS SECTION DETAIL- ite- ZCF.P1'oK 6F-RM 2'.1 OK PLATTER 2.'MIN./ -�� 16'' NIN Chutes, Downpipes, Etc. In order to convey runoff without causing erosion damage from one elevation to another, either a chute or a downpipe (usually flexible) may be used for temporary installations. 1 Temporary Chutes. These are nor- mally constructed of asphalt and should incorporate an asphalted apron which should extend at least 3' beyond the toe of the slope. Best used on cut slopes. Flexible downdrains on fill slopes. Outlets should be stabilized with rock or other material. 96 .emu P :cTIVE VIEW_ CF 1EMPoRARY PAYYP ASPHALT DROP CHUTE \ \\V'S 2. Flexible Downdrains. These are a flexible conduit of heavy duty fabric or other material. Use on cut or consolidated fill slopes. Calculate size from SCS Manual of Conservation Practices. TA85 ANCHOR P►N5 FoR SEr.-.DR/K16 PIPE IN Po5rfio1,1 Al2o' c NrE2s . 5rANDARO METAL END CrION peRSPEGT►VE VIEW OF FLEXIBLE DOWN - ORAN FLOWING FULL, ' o ezMPACt 5oIL CONPLEtr.Y AgDOND eNTRY ST(eAP RUN -oFF -4 /jN. PIPE eMP(Y PIPE FULL IZ'CMP err Naoc STRAP STp METAL alp Sfe1loM 5EOE OM CUTLET DETAIL- FLEXI E. PoWtWRAIN REFERENCES 1. Environmental Protection Agency. Control of Sediments Resulting from Highway Construction and Land Development. 1971. 2. Bucks County Soil and Water Conser- vation District. Standard Temporary Diversion. Bucks County, Pennsyl- vania. 1971. 3. Brandt, G.H., and others. An Economic Analysis of Erosion and Sediment Control Methods for Watersheds Undergoing Urbanization. USDI. OWRR. 1972. 97 MEsuZE- PREVENTION OF EROSION ON CONSTRUCTION SITES TEMPORARY CHECKDAMS ON ALL WATERWAYS DRAINING MORE THAN 1/2 ACRE OF LAND UNDER CONSTRUCTION II.6 Pu2PosE To prevent gully erosion from occurring (usually during the construction periods) either in temporary channels or in permanent channels which are unvegetated and, therefore, temporarily unable to handle design flows. 51T G�- LA21�CTCZISTIGS avid ArPPLIGATION These measures apply to all sites, but will be required more frequently on sites where soils are poorly drained and, therefore, where more runoff occurs; on sites where soils are very highly erodible; on steeply sloping sites where the hydraulic gradient of drainage swales is likely to be close to the maximum. ADVAKLTA�E6 1. Temporary waterway checks not only prevent gully erosion from occurring before vegetation is established, but also cause a high proportion of the sediment load in runoff to precipitate. 2. In some cases, if carefully located and designed these checks can re- main as permanent installations with very minor regrading, etc. They may be left as either spill- ways, in which case accumulated sediment would be graded and seeded, or as checkdams.to preci- pi'tate further sediment coming off that site, requiring a clean -out. DI6ADVANTA6 E5 1. Because of their temporary nature, many of these measures are visually poor, and it is essential to remove them before dwelling units are rented or sold. 2. Removal may be a significant cost in some areas. 3. Temporary checkdams are suitable for a limited drainage area only. D 5k N G21TE IA mid OUT' Li FiG (Or , 1. In permanent channels developers may wish to install checks which are more substantial and may remain after the channel has been vegetated. For 'these, refer to BMP II.16. 2. Temporary Erosion Checks in Drainage Channels. 99 Straw Bale Checks. On channels over 9' wide, straw bale chucks as shown on the left may be used. Bales are staked down with two 2'6" wooden or metal stakes and tied, preferably with nylon or wire. Rip rap is placed to form an apron downstream of the check for a minimum distance of 4', and at the edges of the check to bring its height level with the crest of the channel on both sides. On channels of less than 9' in width, the small checks shown on the right may be used without an apron. They should be spaced about 50' apart. Both these checks must be removed prior to final channel stabilization. Wire Fence Check with Straw Bales. A 3' cyclone fence is nailed on the up- stream side of 4" x 4" wooden stakes across the channel. Straw bales are placed on the upstream side as shown. These are wired together and to the fence. Rip rap is placed as in the Straw Bale Checks section. In some cases the straw bales may be covered in crushed stone. VIF4 FROM a1NN5Ti7i4M PJP -RAP APRDM 1b PREyeto foRMhtioN of Y-40 H01,6 I PLAN 14k4*gor '514/ DAL CHOCKS F:OK SMALL- C ANkiE4!, nor m F41-3 h ° 'J I 1 tIP -RAP APRON /10 YREValf This installation must be removed prior WIRE UPSTRfAl:) oFPc 1 ' FdICMATIAJ of 1SCOt)R ti to the final channel stabilization. i 1 This should be used in preference to the rip rap method under Straw Bale Checks, where protection is required for longer than 6 months as straw bales may be quickly and easily replaced. 1 oo Dumped Rock. A semi - permeable check may be constructed of dumped rock. (9" diameter is sufficient for velocities of up to 5 fps which is the maximum for grass channels.) The installation may become permanent. Sandbags. 100 pound sandbags may also be used as a temporary check in swales. An apron should extend at least 4' downstream. This type is useful in areas where rock is unavailable. `1ND 5 REFERENCES 1. North Carolina State Highway Commission. Temporary Erosion and Pollution Measures. 1972. 2. Environmental Protection Agency. Guidelines for Erosion and Sediment Control Planning and Implementation. 1972. 3. Soil Erosion and Sedimentation Control Manual. Pennsylvania Department of Environmental Resources. September, 1972. 101 \A PSoZE ENTRAPMENT OF SEDIMENT FROM RUNOFF PRIOR TO DISCHARGE FROM CONSTRUCTION SITES T(Pt✓ gRPo5E SEDIMENT BASINS, FILTER SCREENS, ETC. II.7 To cause the settlement of a large proportion of suspended solids (mostly in excess of 10.ze diameter) by using impoundments along drainage channels. Sire CN&RAGTEIZ l6TIC.S Qnd APPLIC.ArioN1 While erosion control techniques may reduce the problem of sediment in run- off from construction sites, developers should also install impoundments to precipitate suspended sediments before runoff is discharged from the site. This is particularly important on steeply sloping and highly erodible sites, and also on poorly drained sites where the runoff coefficient, and therefore the erosive potential of runoff, will be greater. AWAMTMES 1. Downstream riparian properties will not be damaged by sediment deposits originating from that development. 2. Sediment deposits downstream will not reduce the capacity of the stream channel. 3. Sediments will not cause the clogging of downstream impound- ments and other facilities. P15A2ANITA61E1.5 Streams carrying heavy sediment loads and with a high nutrient content will not support much algae growth due to the low light intensity. Reduced algae growth may somewhat reduce available oxygen in the water. 0€ ICaf`t CRITERIA civlc� C7UTLINE SPEC FIC.ATION'6- The effectiveness of a sediment pond depends upon the settling velocity of sediment particles. Calculation of settling velocity can be carried out using a formula in which the volume, size, and density of the particle and the density of the fluid are the main variables. (The rate of settling is significantly slower in colder water.) This velocity is then compared with the velocity in a sedi- ment pond. If this is smaller than the settling velocity of the particle, the particle will settle. Since increasing the area will reduce the velocity in the pond, the effectiveness of a pond will increase as its surface area increases. Assuming that construction costs increase as the volume of the 103 pond is increased, a relatively shallow pond with a large surface area appears to be the most economical design. The particle diameter, settling rate and minimum area requirements (in this case for an overflow rate of 29.5 gpm) are shown below. These are for ideal conditions and in practice the areas would have to be greater. Basins are also commonly maintained at a mini- mum depth of 5' -8' to allow sufficient space above the flood storage zone for settling to occur in a low velocity boundary zone between the surface (where flow is close to the average overflow rate) and the static bottom layer. From the table it can be seen that the economics of the use of sedi- Material TABLE 1 Settling Diameter Rate Microns,.( cm /sec. ment ponds depend primarily on the size of particles to be removed. For particle sizes of less than 10 microns, the size of the sediment basin required suddenly becomes very large. In cases where the increased area for settlement cannot be provided and yet a superior performance is required, flocculants may be added and runoff passed through specialized sedimentation devices having more effective removal rate /surface area ratios than ponds. Screens are avail- able commercially down to 25 microns in size, but this is generally within the economic range of a sediment basin. In practice, the design of a sediment pond will normally be based on strongly practical grounds. Min. Surtace Area For Settling ,, Chamber/ft' Overflow Rate gal/day/ft 2 1 Coarse Sand 2 Coarse Sand 3 Fine Sand 4 Fine Sand 5 Fine Sand 6 Silt 7 Coarse Clay 8 Fine Clay 1000 200 100 60 40 10 10.0 2.1 0.8 0.38 0.21 0.015 0.00015 0.0000015 0.20 2.50 133.56 13,356.00 1,335,600.00 212,400 17,000 318 3.18 .0318 1. The following procedure can be followed for sediment ponds for use during construction period, but not planned for retention for runoff con- trol after development is complete. o Select a suitable site for a pond and estimate its drainage area (say, in this case, it is 20 acres). o Estimate roughly the area of a pond with a capacity of 0.5" over the whole drainage area. Volume = 36,300 cu. ft.; at an average depth of 7'6" the associ- ated surface area will be 4,840 sq. ft. (1/9 acre). 104 o From Table 1 estimate the maximum overflow rate for capture of 10 micron particles for an area of 4,840 lg. ft. In this case = (318 gpd /ft )(4840 ft 2) = 1,539,120 gpd = 1,069 gpm = 2.4 cfs o Calculate total inflow hydrograph to the basin for a 2 -year to 10 -year design storm, depending on the duration of construction and the critical nature of the site (or lack thereof). o The discharge rate from the pond must be reduced to 2.4 cfs if the pond is to be effective. PLAIN SEDIMENTATION-3 ��1'UBE SETILJ✓R 10 1 & 30 20 ♦ . ..111 . . . . .. .) 10 100 WERRA.) RATE ((&4LMIN) To check if the 36,000 cubic ft. storage capacity of the pond is sufficient to provide this reduc- tion, plot the inflow and outflow hydrographs as described in BMP I.12 and estimate the volume of storage required. Assume in this case that it is 45,000 cubic feet, indicating that the pond is too small to give complete control of particles larger than 10.4(. In this case consider: (a) Whether it is necessary to have control of all particles down to 10,c,. (b) If the peak discharge rate from the pond is increased to 5 cfs or ag overflow rate of 668 gpd /ft , the bulk of the sediment will be settled out, as the discharge rate will only exceed 2.4 cfs for a relatively brief period. During this time, larger particles will also be pre- cipitated. During a far greater period, the discharge rate will be less than 2.4 cfs, giving control of most particles of greater than 10,4 f. FLda) MAX /1.70 aFs o0rPLOw MAX 2.2 cfs TIME - MulE,b • Note that the design storm used For runoff control by detention basins will normally be far greater than the neces- sary design storm for sediment control from construction activities. Minor modifications of spillway design can also increase the effectiveness of a detention basin for both uses. During construction, when sediment control is of primary impor- tance, the outlet can be modified to take a maximum discharge rate appro- priate for sediment control. Some runoff control benefits for large storms will be lost however. Cleanout of Facilities. Sediment con- trol ponds will fill up rapidly with sediment. The developer can expect between 10,000- 100,000 tons per square mile per year, but it should be remem- bered that most of the sediment will be carried by a few storms. Locally, considerably more sediment may be generated where'topographic and soil conditions favor erosion. Thus, one storm may severely reduce the capacity of a basin. Therefore, it is recom- mended that basins should have an additional 25 percent added to their design capacity for storage of sediment. 2. If runoff control basins are to be incorporated, they may serve a dual function. First, estimate the size and area of pond needed for runoff control. Then compare with the sediment control requirements determined as above. By comparing the maximum controlled dis- charge for sediment control with the discharge for runoff control, a rough indication of efficiency will be obtained. DVOFLOW COW IMJfS 105 Generally, the drawndown pipe is a perforated vertical riser, usually_ with 1 -1/2" holes at 8" centers verti- cally and 10 -12" spacing around (for the top 2/1 -2/3 of the riser only). The crest elevation of the riser should be at least 1' below the crest of the emergency spillway and should incorpo- rate an anti - vortex device and a trash rack. Other outlet types may also be used. REFERENCES 1. Mallory, C.W. The Beneficial Use of Stormwater. Office of Research and Monitoring. 1973. 2. Leopold, L.B. Hydrology for Urban Land Planning. Geological Survey Circular #554. 1968. 3. Environmental Protection Agency. Guidelines for Erosion and Sediment Control Planning and Implementation. R2 -72 -105. August, 1972. 4. USDA Soil Conservation Service. Guide Standards for Temporary Desilting Basin. College Park, Maryland. 106 FINAL GRADING AND THE ESTAB- LISHMENT OF PROTECTIVE 'Y aA: saze_ VEGETATIVE COVER -rVPE REDUCTION OF EFFECTIVE SLOPE LENGTH IN CRITICAL AREAS WITH BENCHES OR TERRACES II.8 R)2,P05E 1. To modify the form of steep slopes to minimize the erosive potential of runoff originating on the slope. 2. To control runoff from elsewhere so that it can pass down the slope in a protected channel or diverted so that it bypasses steep slopes. SITE✓ cA2AcT'tr2lsTtc.S alv4 APPLIGATIO»J This applies especially to steep slopes which are always more susceptible to erosion due to the greater velocity of runoff. This is also true for bare slopes which have no vegetative protec- tion during construction (particularly fill slopes). AD\/AI.ITAAES 1. Benches. Check the flow of runoff and collect sediment. Runoff may be diverted along the bench to increase the distance of overland flow. Benches also provide access for maintenance and hydroseeding. 2. Serrated Slopes. Lower the velocity of runoff, increase the distance of overland flow, and reduce effective hydraulic gradient. Hold moisture and minimize sediment. 3. Temporary Cover. Plastic sheeting can protect slopes temporarily and may be quickly and easily placed. DISADVANITA6E5 1. Benches and serrated slopes may significantly increase cut and fill costs and cause sloughing where excessive water infiltrates unstable soils. 2. Temporary plastic cover sheeting will result in rapid, 100°6 runoff which may cause serious erosion at the base of slopes. This is strictly a temporary measure, so permanent stabilization is still required. PESO J GRlrI5QIA avid OVTLt N . SPe -CIF ICAT(0N S Stabilization of Slopes. Generally, cut slopes are never graded steeper than 2:1 and fill slopes 2.5 -3:1; a 3:1 slope is generally considered to be the maximum slope on which maintenance equipment can operate. The erodibility of a bare soil will depend on: 1) the gradient, 2) the length of slope, 3) the volume of runoff which in turn depends on the degree of compaction, slope, and soil structure, and 4) inherent soil erodibility. Any effective reduction in gradient, length of slope or volume of runoff will significantly reduce erosion hazard. In cases where it is 107 not feasible to decressr the gradient of the slope, its effective length can be reduced by constructing terraces, or benches across the slope. These inter -' cept runoff and direct it along the contour, effectively reducing the hydraulic gradient, increasing the overland flow time and the time of concentration. Terraces are often used in agricultural land. Diversions on slopes, benches or serrated slopes are simply adaptations of this idea to other situations, although a diversion terrace may be capable of carrying quite large volumes of runoff, which is rarely the case with benches or serrated slopes. Ir , r ' err / r / it 1�11�1 r ��� _/l 1" 11 r l 1 r /I1 91VERSIdu A TEARXE I _ / 01(1 INAL 6ROUKD 4— GROSS FALL T RDADSIDE 4AL6 FILL. GUf SLOPE SHOWIN(, ARRANGEMENT OF 1E IN DRAWS TV guirce RUN -OFF, Diversion of Runoff at the Crest of the Slope. Runoff reaching a denuded slope from above should- be diverted to prevent it flowing onto and eroding the slope. Thus, a diversion terrace is often constructed for this purpose. Chute Spillways. Where a large volume of runoff has to be directed down a steep slope, a chute spillway (overland or underground) may be required. This is usually a corrugated metal pipe with an inlet structure at the top of the slope and an outfall well protected with rip rap. Trench Drains and Dry Wells. The volume of runoff generated on a slope may be reduced by installing a system of gravel- filled trench drains (and dry wells in some cases). Vegetation should be established quickly or drains will silt up. Drains may he interconnected with tile drains to reduce sloughing hazard. 14EA6UfzE ESTABLISHMENT OF PROTECTIVE VEGETATIVE COVER AFTER FINAL GRADING CRITICAL AREA SEEDING TECHNIQUES AND GROUND COVER FOR STEEP SLOPES II.9 12021206E. To provide permanent vegetative cover to control rapid runoff and erosion. SrrE. G4ARAc- TEZISTIG.S cwt APPLIGATIoN1 Slopes, cut banks and fill areas, grassed waterways and other critical areas that need ground cover and seeding other than from the commercial grass mixtures on the market. In con- trast to temporary seeding, permanent cover is needed on areas where the period of exposure would be more than 12 months. AD/ANTIk iE 1. Well- established grass and ground covers can give a finished and aesthetically pleasing look to developments. 2. Ground covers such as crownvetch, sage, etc., can form a vegetative filter strip that impedes sediment at the foot of a slope. DISAD�/l�t�ITA�ES 1. Vegetation and mulch cannot prevent soil slippage and erosion if soil is not inherently stable. 2. Coarse, high grasses that are not mowed can create a fire hazard in some locales. DE 'ICON GRIT -RiA cand QUT"LINE SPECIFIGATIOI4 Grasses, legumes, and other plants for critical area stabilization should be selected in light of adaptability, use, aesthetic requirements and degree of maintenance needed. In general, the selection of species becomes broader when a reasonable amount of mowing and periodic fertilization can be expected. Vegetation should be established as soon as possible after grading to mini- mize exposure time. Grasses can be classified according to Table 1. In general fine textured grass that canstand frequent mowing should be used in urban areas, and coarse grass that holds its own against annual weeds without mowing should be used in other areas. Soil moisture conditions are another consid- eration. Figure 1 shows the compati- 109 bi I itv of various species to different moisture regimes. A further considera- tion•is fertility. When nitrogen deficient subsoils are to be seeded, a legume should be included in the mix- ture for long term nitrogen production. (Legumes fix free nitrogen through bacteria in root nodules.) Site Preparation. Use conventional equipment for seedbed preparation after grading and after needed runoff control measures have been applied. Respread topsoil that was stockpiled according to BMP II.1. Lime and Fertilizer. Conduct soil test to determine needs, or apply lime at a rate of 2,000 lbs. /acre and 0 -20 -0 fer- tilizer or its equivalent at 500 to 1,000 lbs. /acre (lower rate needed on soil with low silt - plus -clay content), plus 10 -10 -10 or its equivalent at 1,000 lbs. /acre. Disc lime and ferti- lizer uniformly into the soil immedi- ately following spreading, loosening soil to a depth of at least 3 ". MIVENCY OF occurs Seeding. heed by ns tng ',in adapted mixture recommended by the local SCS office. Lime, .fertilizer, seed and mulch may be applied by hydroseeder (see BMP 11.12) Planting. Certain ground covers can be planted. Crownvetch and sage are suit- able for sunny locations while English Ivy, pachysandra and vinca can be used in urban settings and shaded areas. Procedure. 1) Plant preferably between March 15 and April 30, or September 1 and October 1. Set plants on a spacing of 3 x 3' (closer spacing will give earlier coverage). 2) Dig holes for plants with mattock deep enough to hold roots without folding. Set plants 1/4" deeper than they were growing in seed- bed. 3) Firm soil around plant with foot to eliminate air pockets around roots. S+ JD ,MOorH AL5IKKE REED 9.60540 DOMED bRaiEC> 5 GLOVER - +>NARY y 6m55 VEIN DRS( DRY MESIC ME51c ME MOIST Dr1041 ri,00DED figure TABLE 1 - METHODS AND EXAMPLES OF CLASSIFYING GRASSES Methods Texture Classification Examples Fine Kentucky bluegrass, bentgrass, red fescue, Smooth bromegrass, reed canarygrass, timothy Growth, Height Short Medium Tall Buffalo grass, Kentucky bluegrass, red fescue, Redtop, perennial rygrass Smooth bromegrass, timothy, switchgrass Growth, Turf Bunch Timothy, big bluestem, sand dropseed perennial ryegrass Quackgrass, smooth bromegrass, Kentucky bluegrass, switchgrass 110 REFERENCES 1. Erosion - Siltation Control Handbook. County of Fairfax, Virginia. November, 1971. 2. USDA Soil Conservation Service. College Park, Maryland. 3. Minnesota Department of Highways, Construction Division. Erosion Prevention and Turf Establishment Manual. 1970. 4. USDA Soil Conservation Standard and Specifications for Critical Area Planting on Unprepared Seedbed #342. 5. Baltimore City Sediment Control Manual. Department of Engineering. Baltimore, Maryland. May, 1971. 6. USDA Soil Conservation Service. Vegetating Banks and Gullies with Crownvetch. Lincoln, Nebraska. 1970. 7. Miles W. Fry & Sons Nurseries. Product Information. Ephrata R.D., Pennsylvania. 111 ESTABLISHMENT OF PROTECTIVE VEGE'T'ATIVE COVER AFTER FINAL 1\AEAU42e.. GRADING TVP� STABILIZATION OF CRITICAL AREAS WITH SOD II.10 To establish a protective layer of vegetation as fast as possible to prevent soil erosion by wind or water. Srre. G442ACT.etsrtC avvd APPLIGPTIoc'! Sodding gives the fastest possible protection by vegetation and, thus, this technique is used in those areas where immediate protection is essen- tial. It is an expensive operation and should be applied to critical areas only. Applicable to any site classes but most useful for those where imme- diate protection is essential. These include steep slopes, highly erodible soils and disturbed areas in the flood - plain, drainage channels and other critical areas. ADVAtNTAEs 1. Sod will give immediate protection. 2. Sod gives an immediate vegetative cover, which is both effective in checking erosion and is aestheti- cally pleasing. 3. Good sod has a high density of growth and this gives superior protection to a recently seeded sward. 4. Sod can be placed at any time of the year provided that soil mois- ture is adequate and the ground is not frozen. 2�sApVA►�tTAC�E5 1. Sod is expensive to purchase. 2. Sod is heavy and handling costs are high. 3. Good quality sod, free from weed species, may be difficult to obtain. 4. If laid in unfavorable season, by midsummer irrigation may be required. This also applies to very droughty sandy soils. 5. Grass species in the sod may not be suitable for site conditions. 6. If mowing is required, do not use grass sod on slopes steeper than 3:1 (use minimum maintenance ground covers.) Pe64 4 - rr .RIA e d cXYr..JNE sVC.IFk Arlors4 Sod Specifications (Adapted from Ref. 1) The following specifications are for Maryland, Delaware, and Pennsylvania. The local SCS office should be consulted for locally specific information and recommendations. 1. Sod should be free from weeds where this is an important factor. There may be cases where inferior sod may be acceptable where only erosion control is required. 2. Sod should be uniform thickness (approximately 1 "). 113 3. Sod should have a dense root mat to give adequate mechanical strength. 4. For critical slopes, a sod of Kentucky 31 tall fescue and blue- grass is to be preferred over straight bluegrass, especially if the site is droughty or shaded. 5. Sod should be moist and fresh and delivered to the site within 6 hours of cutting between June - August and within 24 hours during spring and fall. Site Preparation 1. Where possible, grade to allow use of conventional equipment for cul- tivation, spreading lime, fertilizer and seeding. 2. Apply lime and fertilizer according to soil tests (or 2,000 lbs. /acre lime, 1,000 lbs. /acre 10 -10 -10 fertilizer or equivalent). 3. Disc harrow to a depth of 2 -3" until a uniform, fine, firm bed is attained. Where possible, final cultivation should be along the contour. 4. Irrigate before laying sod. Sod Placement 1. Lay sod strips along contour, never up and down slope. Start at the bottom of the slope and work up. Use ladders on steep slopes to improve foothold and prevent damage to sod. Stagger joints and make sure joints are snug. 2. Roll or tamp thoroughly after placement. 3. On steep slopes secure sod with wood pegs, wire staples or split shingles (8 -10" x 3/4 "). 4. Use jute or plastic netting to secure sod in place at the crown of very steep slopes, in drainage swales and at other areas where water could undercut sod. 5. Irrigate sod thoroughly until moisture penetrates the soil layer beneath. Maintain optimum moisture for at least 2 weeks. Future Developments. Rapid progress is being made in growing very high quality sod in shallow pans on a thin bed of polystyrene granules. This product is very light and can be handled in wide rolls, unlike traditional sod. When unrolled onto bare ground which should have received a light dressing of fer- tilizer and thorough irrigation, the sod will become established very rapidly. This technique, when gener- ally available, will combine the advantages of traditional sod with the advantages of lightweight erosion control blankets. REFERENCES 1. U.S. Soil Conservation Service. Critical Area Stabilization. Job Sheet MD. 8. College Park, MD. June, 1968. 2. U.S. Soil Conservation Service. Interim Standard & Specification for Critical Area Stabilization. College Park, MD. November, 1969. 3. U.S. Soil Conservation Service. Critical Area Stabilization with Sod. Somerset, New .Jersey. February, 1970. 114 NIEA4Uze_ T '/PE PuReb E. ESTABLISHMENT OF PROTECTIVE VEGETATIVE COVER AFTER FINAL GRADING SEEDED AREAS PROTECTED WITH ORGANIC MULCH The application of plant residues or other suitable organic material can reduce impact of rainfall, check runoff, prevent onset of erosion and prevent surface compaction or crusting; also these will help conserve soil moisture, thus stimulating growth of plant cover. SITE. G PreAC-Tezi6TIGs cct d APPI -(C Ttot4 Any site condition, but especially steep slopes and highly erodible soils, and where large areas of soil are exposed at one time. This tech- nique may be used on any area subject to soil erosion, particularly those with unfavorable conditions for plant establishment. It may be used in conjunction with other techniques and critical area planting. Organic mulches may require anchoring with netting or chemical binders. Mulching may also be used prior to seeding in areas subject to heavy use. ADVA NTA[zES 1. Grass coverage was found to be twice as good in mulched areas as in unmulched areas in a given time. 2. The moisture retaining capacity of organic mulches, and particu- larly straw, was found to be superior to chemical mulches. 216A2YANTM1 E 5 1. If seeding is not.carried out at the same time as application of a thin layer of finely chopped mulch, it must be done only after partial decomposition of the mulch material. This may involve a separate work cycle after up to 1 year. 2. Straw mulch, generally cheapest and most effective, is a potential fire hazard. It is subject to wind blow, is unavailable in some areas and may result in the introduction of undesirable seed. DE.6II4■ G21TE2IA avid OOTt.IN SPelF16AT10Ki6 1. Site Preparation. 1) Grade, if possible, to allow the use of conven- tional machinery for application of mulch and anchoring. This generally means a maximum slope of 3:1. Steeper slopes require hand work or hydroseed- ing. 2) Cultivate soil to a depth of 2 -3" using a disc harrow. 2. Type of Mulch and Application Rate. Select from this table. 3. Mulch Anchoring. To minimize loss of mulch by wind or water, anchor those mulches susceptible to wind blow and those on steep slopes by selecting method from this table - more data on anchoring materials is contained in the matting and seeding specifications. 115 J W Aool'cation Rates Mulch Material Quality Standards Per 100 ft.2 Per Acre Coverage Remarks Compost or Straw Manor, Well shredded, free from .!xc.•";sive coarse material 400 -600 Ibs. 8-10 tons Excellent moisture conservation. Resistant to wind blow. c.ornsLalks, Shred:l.d or Chopped AI. •3rc.-d, shredded into 8-12" lengths 1511 -301) Ibs. 4 -6 tons Slow decomposition rate. Resistanr to wind 'blow. II,ic or Straw Air dried and free from weed, seeds and coarse material 75 -101) lbs. (2 -3 hales) 15 -25 tons (90 -100 bales) ■7 -90Z Effective for more than 3 months. Sub - jest to wind blow and needs anchoring. Peat Moss pried, compressed and free from ..parse materials 200 -400 ft.3 2 -4" Excellent moisture conservation. Subject to wind blow unless kept damp. fine Straw or Needle: Air dried and free from excessive coarse material 5i) -90 Ibs. 2 tons Resistant to windblow. Decomposses slowly. Peanut Nulls or Cocoa Beans Air dried and free from •.:ce;suve fine material 200 -400 ft. 2 -4" Decomposes in 1 year. Good moisture conservation, but subject to wind blow. Sawdust, Green or Composted Free from coarse material 83 -500 tt. 3 1 -7" Resistant to wind blow. Slow decom o- P sition. Treat with 35 /lhs /nitrogen /ton Shredded Sugar Cane-Bagasse Air dried, well- shredded 200 -400 ft.3 (14-28 bales) 2 -4" Slow decomposition. Resistant to wind blow. Tanbark Air dried. nun -toxic 300 -400 ft.3 3 -4" Excellent moisture - holding capacity. Wood Chips ou creen or air dried. free from coarse materials 5(10 -900 Ibs. 10 -20 tons 2 -7" Resistant to wind blow. Treat with 12! nitrogen /ton to prevent nutrient delic�i Wood Excelsior Green or air dried 0.024" x 0.031" : 4" ')U'-lbs. (1 hale) 2 tons Decomposes slowly and subject to some wind blow. tr;!od Fiber Cellulose (partly digested fiber) Sir dried fibers 3.7 mm or longer 25 -30 Ibs. 1000 -1500 Ibs. Should he applied with hydromulchec. Needs no anchoring. Ibs/ ency. : 4. Seeding. For seeding suggestions, see Critical. Area Planting (BMP 1I.9). Select mulch, depending upon expected length of time mulch is needed to pro- tect area and the decomposition rate of the mulch, and the season. 5. E(I.iipment. Power mulchers are using a dry process and air current to propel mulch. In cases where it is not required to apply seed and fertilizer during mulching operations, a hydro - seeder can be used to apply wood fiber cellulose. Anchoring Method Material/ Techni ue Manual Peg & Twine Manual Manual Punching or rucking Hay ur Straw, Cornstalks (illus. 2) Mulcts Nett ing ( illus. 11 Mulch T .e Maintenance. Mulched areas should be checked periodically, especially follow- ing severe storms, when damaged areas of mulch or tie-down material should be repaired. How to Apply Hay, Straw, Sugar Cane, Cornstalks, Pine Straw Hay, Straw, Sugar Cane, Cornstalks, Pine Straw, Wood Shavings, Tan Bark Mechanical Asphalt Spray Cocoa leans, Peanut Ilul ls, Compost, Wood Chips, Wood Shavings, Ilay, Straw, Cornstalks Mechanical Pick Chain Hay, Straw, Cornstalks, Manure, Compost, Pine Straw After mulching, drive 4 -6 stakes per sq. yd. to within 2" of surface. Secure criss cross of twine taking 2 turns around each peg. Drive pegs in flush with soil where mowing, is planned. Staple paper, jute, wood fiber or plastic: netting to soil surface according (.o manufacturer's instructions. Cut mulch into surface with square -edge spade in contour rows 18" apart. Apply asphalt emulsion at 0.04 gals. /yd.- with suitable spray equipment. Use on slopes ste, -psi than 1:1. Pull across slope with suitable power equipment. REFERENCES 1. Cumberland Co., Pennsylvania. Errosion and Sediment Control Handbook. 1971. 2. USDA Soil Conservation Service. Interim Studies and Specifications. College Park, Maryland. 3. Bucks Co., Soil and Water Conserva- tion District. Soil and Water Conservation District Specifica- tions. Bucks Co., Pennsylvania. 1972. 4. USDA Soil Conservation Service. Standard and Specification for Mulching. Bull. #484. 5. Brandt, G. and others. An Economic Analysis of Erosion and Sediment Control Methods for Watersheds Undergoing Urbanization. Dow Chemical Company. Midland, Michigan. 2/72. 6. USDA Agricultural Research Service. Mulches for Wind and Water Erosion Control. 1969. 7. Reinco Corp. Power Mulchers. Plainfield, New Jersey. 8. Benis Co. Benis Mulchnet. St. Louis, Missouri. 117 MIEALt2E ESTABLISHMENT OF PROTECTIVE VEGETATIVE COVER AFTER FINAL GRADING Ti�PE HYDROSEEDING AND CHEMICAL STABILIZATION OF CRITICAL AREAS II.12 exeosE Chemical stabilizers generally bind the soil and prevent erosion during the establishment period of seeded cover vegetation. Some products can form an effective chemical mulch which can help to conserve soil moisture during dry periods. SITea 6- 1A2ACTEIZI61-I6_ S cn'd APPLIGATION4 Any site condition but especially steep slopes, highly erodible soils and where large areas of soil are exposed at one time. This may be used either as a temporary or permanent measure. Chem- ical stabilizers may have a superficial surface action, or they may penetrate the surface and act as a soil binder. The latter can be applied to poor soils instead of a mulch or may be sprayed as a slurry with an organic (e.g., chopped straw) mulch, in which case it stabil- izes both the mulch and the soil. Arx4ANTA4a.s. 1. Chemical-soil binders prevent soil erosion either by forming super- ficial surface protection or by binding the top few millimeters of soil. 2. Can form an effective mulch in correct conditions. 3. In hydroseeding the water is thickened, allowing heavier loads of solids such as lime to be carried in the slurry. 4. Seeding, fertilizing, and mulching can be accomplished in one labor saving operation if applied by hydroseeder. 5. Areas inaccessible to agricultural machinery may be easily seeded by hydroseeder. SAD VA •YrAt 1. The crust formed by chemical binders will be damaged by traffic which must be kept off treated areas. 2. Many binders do not function as well on fine textured soils as they do on sand soils (2). 3. None of the chemical mulches (petroleum products, resin asphalt or latex emulsions) are superior to straw for erosion control except in exceptional circumstances. 4. Elaborate equipment is required for application (usually hydroseeder) which may be difficult to schedule for small job increments. 5. If hydroseeded, accelerated germi- nation during dry conditions may require irrigation later to sustain growth. 119 (7E K1 G12rTE2lA rind OUTLINE 5PEC l F! AT to N15 Site Preparation. After final rough grading, soil should be cultivated to a depth of 6" to give a good seedbed. Application. Method of application will vary according to season, size of site, steepness of slope and soil type. 1. Soil binders with surface penetrat- ing action used in lieu of mulching in conjunction with hydroseeding. 2. Soil binders applied in slurry by hydroseeder in combination with fiber mulch, seed and fertilizer. 3. Chemical stabilizers with surface action sprayed onto seeded areas. The selection of operation should be discussed with the local Soil Conserva- tion Service agent. 1. Soil Binders are useful where. fiber, straw, or other forms of mulches are unavailable. These are most commonly emulsions of resin or latex and check erosion during the establishment of vegetation by stabil- izing the seedbed. They also help to retain soil moisture and yet are sol- uble enough to allow rainwater to reach the soil. Penetration of soil binders is usually about l/2 ". They are most conveniently applied together with seed and fertilizer with a hydro - seeder. Soil conditions at the time should be moist. Soil binders alone, therefore, should only be used in favorable seasons. Binders remain effective on sandy soils longer than on finer textured soils. 2. Soil Binders in k,ombi.nation wish Fiber or Straw Mulches. In less favorable seasons, soil binders can he successfully used to stabilize short fiber mulches applied together in a hydroseeder. More than twice as much stabilizing agent is required. However, in combination with wood fiber, the moisture retention and insulating properties of the mulch are superior and, on decomposition, the organic mulch increases the organic matter in the soil. 3. Chemical Stabilizers with Surface Action. These do not penetrate the soil. Asphalt emulsion, cutback asphalt and fiberglass mulch fall into this category. Asphalt mulches cure slowly allowing seedings to penetrate it easily, but the rate of application should not exceed 1,200 gallons of concentrate per acre, or emergence of seedlings will be considerably re- stricted. Because asphalt films have a low porosity, seed should be well scarified into a moist soil before application. Asphalt stabilizers normally require heating to make them sprayable. Fiberglass is applied using a spray kit Compressed air is used to separate and propel strands of fiber from bundles of fiberglass. The mulch resembles 'angel's hair' used in Christmas decor- ations. The mulch does not break down but grows into the turf. Grading and seeding are carried out prior to application. 120 REFERENCES 1. Brandt, G.H., and others. An Econcomic Analysis of Erosion and Sediment Control Methods for Watersheds Undergoing Urbanization. USDI OWRR, 1972. 2. USDA Argicultural Research Service. Mulches for Wind and Water Erosion Control. July, 1963. 3. P.P.C. Indus. Fiberglass Matting and Grassroot . Pittsburgh, Pennsylvania. 4. Hydrograssing. Reinco Corp. Plain- field, New Jersey. 5. Terra Tack Grassgrowers, Inc. Plainfield, New Jersey. 6. American Hoechst Corp. Curosal Binders. Sommerville, New Jersey. 7. American Cynamid Corp. Aerospray 70. Wayne, New Jersey. 8. S.B. Phillips Petroleum Co. Peroset . Bartlesville, Oklahoma. 121 ESTABLISHMENT OF PROTECTIVE VEGETATIVE COVER AFTER I�/(EASUPF FINAL GRADING SEEDED AREAS PROTECTED BY NETTING OR MATTING WeE- cl4ZP05E The purpose of matting is to stabilize the surface of the soil and to prevent erosion during the establishment of vegetation. Most mattings do not have any soil moisture-retaining benefits as do mulches, but there are a few excep- tions. SITE 64A2AcrE.21STIGS atou4 APPLI.ATIONI Used almost exclusively on steep slopes and for the protection of swales and channels to be vegetated. Generally used where soil moisture conditions are good and where a mulch is unnecessary to retain moisture, yet some soil stabilization is required. If used in swales, where a high velocity of runoff during the period of establishment of vegetation is likely, netting or matting will cause scouring. ADVANTA44 -3 1. Less expensive than most other stabilization techniques. 2. Easily .placed by unskilled labor. 3. Any seed mix can be used without the necessity to consider the decomposition period of an organic mulch (see BMP II.11). 4. Not subject to wind blow as so many organic mulches, but must be well anchored to prevent slippage during rainstorms. DISADANITAUEs The lack of soil moisture retention benefits of netting may be a serious drawback. D7.S(4 til G21TERIA avid OtTLINIE SPE.GIFIGATloN15 Site Preparation. 1. Complete grading, including the installation of berms, terraces, swales, etc., where necessary. 2. Cultivate the soil to a depth of 6 ", incorporating fertilizer and lime where necessary, and providing a good surface free from excessive stones, clods or trash. 3. Broadcast seed according to BMP II.9 on the uncompacted seedbed. Choice of Matting. Choose either a mesh matting (e.g., jute or twisted paper mesh) where no mulching effect is required or a blanket type mat where mulching effect is required. The latter generally consist of chemical or organic fibers attached to a retaining net. Blanket mats should be used on soils with poor water - holding capacity. 123 Installation of Matting, Unreel matting parallel to the direction of runoff (slope). This is best achieved by placing a hollow shaft (e.g., a metal pipe) through the center of the roll through which is passed a rope. Using the core and a rope, the roll can be unwound slowly down the slope. Most mesh is reeled on a cardboard core and a rope may simply be passed through this. The material should not be stretched nor allowed to lie loosely, but should take up the contours of the ground. The manufactu'rer's recommenda- tions for overlapping adjacent strips should be .followed. Anchoring Matting. Unless properly anchored, mats are liable to slip. Uphill ends should be buried in a 6" deep slot and stapled as shown (Figure 1) on 12" centers across the width of the mat. At joints, the downhill end should be overlapped (shingle fashion) with the uphill end of the new roll which is inserted in a 6" slot (Figure 2) and stapled on 12" centers. On very severe slopes check slots should be used (Figure 3). These are 6" deep slots into which a tight fold of matting is inserted. The slot is filled and tamped and staples inserted on 12" centers down the slope of the check slot. Stapling. Matting should be stapled according to the manufacturer's instruc- tions, but generally staples should be inserted on 12" centers down each edge of the mat and down its center line. In addition, staples should be inserted at joints as illustrated. Following installation, mesh mattings should be rolled with a smooth roller to bring into close contact with the soil and to consolidate the seedbed. 124 ESTABLISHMENT of PROTECTIVE VEGETATIVE COVER AFTER NAEA'0i2E FINAL GRADING BIO- TECHNICAL PROTECTION OF VERY -IVPe STEEP SLOPES R2POSE To stabilize banks through a combina- tion of natural and technical means. SITS o..LA2AC E2lSTlGS and APPI- IGATIONi Slopes of steep grade, cut and fill banks and unstable soil conditions that cannot be stabilized through seeded vegetation. ADVA NTAc ES 1. Vegetation reduces sheet erosion on .slopes and impedes sediment at the toe of the slope. 2. Where soils are unstable and liable to slip due to wet conditions, utilization of soil moisture by vegetation can reduce the problem. 3. Shrubs and trees shelter slopes against the impact of rainstorms, and the humus formed by decaying leaves further helps to impede runoff. 4. Mechanical measures help to stabi- lize soil long enough to allow vegetation to become established. C)(ADVANt.-rikaee 1. There is a general reluctance to work with live material, the planting of which cannot be highly mechanized. 2. The planting of live willow brush is a specialized operation and cannot be installed by unskilled labor. 3. According to an opinion by a repre- sentative of SCS (3), the methods described are effective but require a complete knowledge of soil, hydrology and other physical data to design measures that will adequately solve the problem and stand up to the test of time. ct4IZI I cRlrT2lA a14d 00T1-1N E. SPEGI FIGATIONIS Bio- technical methods outlined here can be used after slopes have been protected by diversion of runoff (covered in BMP I1.5) or through the terracing of slopes (BMP 11.8). Sod walls or retaining banks are used • to stabilize terraces. Sod is piled by tilting it slightly toward the slope and should be backfilled with soil and compacted as they are built up. Sod walls can be as steep as 1:8 but should not he higher than 5'. Timber frame stabilization is effective on gradients up to 1:1 and involves the following steps in construction: 1) Lay soil retarding frames of 2 x 4" vertical members and 1 x 4" horizontal members on slopes. Frames on slopes over 15' in length need to be anchored to slope to prevent buckling. 2) Attach 14 gauge galvanized tie wires for anchoring wire mesh. 3) Fill frames with moist topsoil and compact the soil. 4) Spread straw 6" deep over slope. 5) Cover straw with 14 gauge 4" mesh galvanized reinforced wire. 6) Secure wire mesh at least 6' back of. 125 top 'lope.. 7) Plant ground cover plants through straw into topsoil. Woven willow whips may be used to form live barriers for immediate erosion control. Construction: 1) 3' poles are spaced at 5' distances and driven into the slope to a depth of 2'. 2) 2' willow sticks are inserted between poles at 1' distances. 3) Live willow branches of 5' length are sunk to a depth of 1" and interwoven with poles and sticks. 4) Spaces between the woven 'fences' are filled with topsoil. Fences are generally arranged parallel to the slope or in a grid pattern diagonal to the direction of the slope. _ Berm Planting. 1) Excavate ditches at 3 -5 distance along the slope and shape berm on the downslope side. Construct ditches with 5% longitudinal slope. 2) Plant rooted cuttings on 3' centers and mulch. Suitable trees are willow, alder, birch, pine and selected shrubs. In extremely dry situations, rooted cuttings can be planted in biodegrad- able plastic bags that are watered at the time of planting. Brush Layers. 1) Prepare 3' "niches" as shown. 2) Lay unrooted 5' live branches of willow or poplar at close spacing. 3) Starting at foot of slope, backfill lower ditch with excavated material from ditch above it. Opera- tion should be carried out during dormant season. WOV£A1 WILLOW WHIPS east lAYER5-.5eznou REFERENCES 1. California Division of Highways. Landscape Section of the Design Department. Slope Stabilization Design Sheet. 2. Schlueter, Uwe, and Lebenbau, Callwey, Publishers, Munich, Germany. 1971. 3. Opinion by Mr. Otis D. Fincher. Soil Conservation Service State Conservationist. -State of Delaware. 126 MEASU2E DESIGN AND STABILIZATION OF DRAINAGE CHANNELS TO PREVENT EROSION TqPe.. GRASS CHANNELS 11.15 For velocities of up to 5 fps, runoff can be handled by grass channels if correctly graded and stabilized. Srra c 2A rFrites 4vd AR'u .knot..! May be used on any site where flow velocities make the use of grass swales feasible. On steep sites the use of grass swales will be limited by the difficulty of keeping within the limits. for hydraulic gradient of swales. On highly erodible soils a lower design velocity must be used as shown in the table below. Natural channels can often be improved by regrading and grassing. ADVAKITAES 1. Grass -lined channels are cheaper than those lined with concrete or stabilized by a 'bio- technical' measure (see BMP I1.16). 2. Grass will delay runoff and consid- erably reduce the energy and consequently the erosive capacity of runoff. 3. Grass channels are visually much more acceptable than those lined with concrete. 4. The vegetated waterway maximizes the loss of surface runoff through infiltration, where the lined waterway allows no infiltration to occur. 25hDVANTA4ES 1. Very careful design and a good maintenance program are necessary if channels stabilized with grass are to be effective without gully erosion. 2. The installation of new areas of impermeable surface in the area ' drained by a grass channel may increase runoff velocities and exceed the capacity of the channel. This must be considered. 3. Vegetated channels should not be constructed for maximum flow velocities since, in practice, vegetation is rarely maintained well enough to take such flows. Pe.sviK1 G2LT2IA aid Our Li NE 6 uRica�T0NS Cross Section. Grassed waterways may be built in parabolic, trapezoidal, or V- shaped cross sections. Parabolic cross sections are most commonly found in nature and have proven the most satisfactory. Waterways constructed with trapezoidal sections tend to revert to a parabolic shape. Side slopes should not exceed 3:1 to enable channel to be mowed. 127 Location. Waterways should be located at areas of suitable grade where soil moisture conditions are favorable to vegetative growth. Natural swales should be favored, if possible. p 1ILX CLAM IY+C IN. Na1TERWA45 6055 diANNEL 5E77* Design Criteria. Size and location of grass waterways will depend on esti- mated runoff, gradient, the space allowable for the waterways and soil erodibility. Flow velocities on well - established soil of good quality generally do not exceed 5 -6 fps except for special situations. Most waterways are constructed to accommodate the peak flow expected from a storm of at least a 10 -year frequency before overbank 'flow occurs. The flow - retarding factor of different vegetation should be con- sidered in the design. Tables for calculating the cross section of a vegetated waterway are given in Appendix II.15. Construction. It is.important to avoid excessive compaction during construc- tion by earth - moving machinery which will result in an inferior grass sward. Between the time of seeding the cover and the actual establishment, the waterway will be unprotected and sub- ject to damage. Provisions should be made to divert flows during this period. Vegetated waterways should not be subject to continuous flows of water nor be kept wet, since this will destroy good turf. A tile drain can help to offset this problem. Tiles should be laid parallel to the center line of the waterway but offset from the center by at least 1/4 its top width. This will prevent washout of the backfill material for the tile system (see diagram above). GRASS VARIETIES AND PERMISSIBLE VELOCITIES FOR VARYING SITUA °.IONS Permissible Velocity fps Cover Type Slope Z Residential Soil Erodible Soil 0 -5 8 6 Bermuda Grass 5 -10 7 5 Over 10 6 4 Bahia Buffalo Kentucky blue brass 0 -5 7 5 Smooth brome 5 -10 6 4 Blue grama Over 10 5 3 Tall fescue Grass Mixtures 0 -5 5 4 Reed canarygrass 5 -10 4 3 Lespedeza sericea Weeping lovegrass Yellow bluestem 0 -5 3.5 2.5 Redtop Alfalfa Red fescue Common lespedeza 0 -5 3.5 2.5 Sudangrass 128 Sodding. This gives an immediate stabilizing effect and a finished look that is often needed in residential development. Correct sod placement becomes important in grassed waterways with steep slopes. Special placement procedures are shingling and overlap- ping. Overlapping involves the placement of sod strips parallel to the water flow and is used in relatively flat ditches that carry large volumes of water. A wooden stake driven through the overlapped portion of the sod strip can make it even more effec- tive. Shingling can be used on short grades that are steeper than 10 %. Grass strips are laid perpendicular to water flow. Staking will increase the effectivness. For more details on sodding, see BMP II.10. Maintenance. Careful maintenance can increase the capacity of grassed water- ways. A yearly dressing of J20 -10 -10 fertilizer at about $0.04 /yd should be given to all grass channels, and they should be mowed regularly to encourage a tight sward. REFERENCES 1. USDA. Soil Conservation Service, Engineering Field Manual for Conservation Practices. 1969. 2. Minnesota Department of Highways, Conservation Division. Erosion Prevention and Turf Establishment Manual. 1970. 129 A 7 NJDl . t.15 DES41.1 OF G2As5 6 ANKle. _.s Grass -Lined Channels Grass-lined channels are the cheapest and the least obtrusive method of conveying runoff. However, unless the channel is properly designed and maintained, gully erosion will result. Channels must be capable of withstand- ing the abrasive action of water without damage. Generally, grass channels have slopes of between 1 -10 %, and are rarely used to drain areas of more than 150 acres. Where the veloc- ity or the slope is found to be too great for the use of a grass lining, the slope may be reduced by the intro- duction of spillways which will effectively reduce the gradient between spillways and make grass lining in these sections feasible. This may be aesthetically more desirable than lining the channel with concrete, gabion mattress, etc. In exceptional cases the 'safe' velocity of flow in grass channels may be increased by reinforcing the sward with nylon netting or lattice concrete blocks and /or by introducing fiberglass erosion checks at regular intervals. In cases where grass channels are permanently wet,' install a tile drain beneath the channel. Design Criteria The design criteria for grass channels is less precise than for storm sewers due to the difficulty of assessing accurately 'n', the coefficient of roughness, and the retarding effect of the grass lining. It is important to remember that the continuing efficiency of a channel depends on maintaining a high quality sward and this is made easier by maximum side slopes of 3:1. It is also important to keep erosion in the drainage area to a minimum because silt deposits in grass channels will reduce their efficiency. Channel Section Channel shapes may be parabolic, triangular, or trapezoidal. Parabolic sections approximate to that of natural channels and look good but are difficult to build. Trapezoidal sections tend to take up a parabolic shape in time. Side slopes of 4:1 allow easy crossing for vehicles and mowing machines. Velocity Permissible velocities for various types of grass and soil erodibility are shown on Table 3. Note that the range is between 2 -6 with velocities of 7 or 8 only used where sward is of the highest quality. Roughness Coefficient For most methods of designing grass channels, the roughness coefficient (Manning's 'n' as used in the design of storm sewers) is converted into 'retardance' which depends also on the velocity and hydraulic radius (see Chapters 7 -12, SCS Engineering Field Manual for Conservation Practices). A guide to the retardance for various types of vegetation can be found on Table 1. It may be assumed that the 'coefficient of roughness' for grass channels is 0.03. Other values of 'n' can be found in the literature. Capacity The capacity of the channel must be sufficient to carry the peak design storm discharge from the drainage area. For very long channels it may be necessary to estimate the flow for different reaches. Location Try to locate channels in natural swales and keep to a sweeping alignment. Take particular care either to locate the outlet in an area of well- estab- lished vegetation, or protect the outlet to prevent erosion. 131 Calculation of Channel Size, Method A The discharge capacity of a channel (Q in cfs) is determined from V,' the velocity in the channel (in fps) and a, the end area of the channel (sq. ft.) by the formula Q =Va EQUO.Tio N V varies according to the 'coefficient of roughness', n, of the channel which is normally 0.03 for grass -lined chan- nels, the hydraulic radius, r, (end area, a, divided by wetted perimeter, p) and the slope or gradient of channel, s. This relationship is expressed by the formula / l•4e(" y3 V± n �� � (jL ) Equaiiorl Z Substituting V in Equation 1 0. i.4866rz4XS 14. la EQUArtotJ 3 The selection of channel size using the above equations is a trial- and -error process of selecting an ideal location and cross section for a channel, check- ing whether its velocity is within the safety limits for the type of grass lining (Table 2) and whether the cross section is sufficient for the discharge of runoff from the area drained. Example Select a channel alignment and cross section to drain an area with a peak discharge, Q, of 160 cfs. An ideal alignment for the channel has a slope, s, of 0.03 and it is decided that the side slopes should be a maximum of 4:1 to allow high speed maintenance by mowing. Soil conditions are very good and it is anticipated that the quality of turf will allow a maximum velocity, V, of 6 fps. g' -4 Step i) Select ideal channel section (for ease of calculation, this is trapezoidal). Step ii) Calculate area of section a = 21 -64-' Step iii) Calculate hydraulic radius r= a +p p -y ±zx= 8 +z e .Ss= Zo.t2 .: V=ZI: Zo.s =1.o3 Step iv) Calculate discharge capacity of channel Qs (40o (Y %)()' r% f sN s 1ablef i } Z) -` Q= coy 1.0z '40.1115Z.1(2.1 = 131.84.45 This is not sufficient to carry the peak discharge of 160 cfs. Step v) Select a larger cross section Note. that both a deeper or a wider channel will increase capacity but a deeper channel will result in a higher velocity of flow. 24' 41' (4—) (-- 12' - a s zi 4+2"' r = Z - 1 - + 2 . 1 - Q .4o X I . o1L i0.1/32 x Z1 =10645 This is sufficient with a safety margin to take 160 cfs discharge. Step vi) Check that the velocity of flow will not be too great for the grass lining. 132 \/ Q �tA _ (o.$ r 4 But this is too great (the maximum velocity decided on was 6 fps). One could argue that peak discharge is 160 cfs. Maximum design velocity = 160 - 5.9 fps 27 and is O.K. However, if not considered safe, then: Step vii) If velocity is too great, make the channel wider but shallower. 32' 24' a = 24545 r =3 � -v. e,7 1'484 09 rm ' )4 ./ .:xi& = 144,104, Q = 0.o4 Channel is sufficient to take discharge of 160 cfs. Step viii) Check that velocity of flow in channel (step vii) is not too great. 4 EQt»1iONL 1 v= = 5 1-�Ps wai 4 034. 5 z8 The same technique may be applied to a parabolic or 'V' shaped section; this just makes the calculation slightly more complex. Note: One could have done this example a different way. For instance, if space were very tight one could start by finding the minimum cross section for a velocity of 6 fps to take a discharge of 160 cfs, thus: GA z= 50110041101.1 Say, then, that only 24' is available; we know from Steps v and vi above that a 24' channel width will give too great a velocity. Therefore, the gradient must be decreased. Note that if the gradient is the same but the side slopes are increased, it effectively increases (a) but also Q, and therefore is not advisable. Note: About 10% should be added to width and 0.5' to depth for freeboard in permanent channels. 133 Calculation of Channel Size, Method B For the design of grass channels in critical situations, use this technique. Example B1. (From Engineering Field Manual for Conservation Practices, 1971). Determine the safe velocity and dimensions for a grass waterway with a parabolic cross section. Assume: Maximum discharge from drainage area = 55 cfs Gradient of channel = 5% or 0.05 Vegetable cover = Bluegrass Condition of vegetation = (Good stand, mowed 3 -4 ") Soil type = Easily erodible Step i) Determine retardance for Bluegrass (Table 1) =D. Step ii) Determine permissible velocity for soil /vegetation type (Table 2) = 4.0 fps. 134 Cover Condition Permissible Velocity!" A Reed canarygrass Yellow bluestem Ischaemum Excel. stand, tall (average 36 ") Excel. stand, tall (average 36 ") " 0 -5 B Smooth bromegrass Bermuda grass Native grass mixture (little bluestem, blue grama, and other long and short midwest grasses) Tall "fescue Lespedeza sericea Grass - Legume mixture -- Timothy, smooth bromegrass, or orchard grass Reed canarygrass Tall fescue, with bird's foot trefoil or lodino Blue grama Good stand, mowed (average 12 -15 ") Good stand, tall (average 12 ") Good stand, unmowed Good stand, unmowed (average 18 ") Good stand, not woody, tall (average Good stand, uncut (average 20 ") Good stand, mowed (average 12 -15 ") Good stand, uncut (average 18 ") Good stand, uncut (average 13 ") 19 ") C Bahia Bermuda grass Redtop Grass- Legume mixture -- summer (Orchard grass, redtop, Italian ryegrass, and common lespedeza) Centipede grass Kentucky bluegrass Good stand, uncut (6 -8 ") Good stand, mowed (average 6 ") Good stand, headed (15 -20 ") Good stand, uncut (6 -8 ") Very dense cover (average 6 ") Good stand, headed (6 -12 ") over 10 D Bermuda grass Red fescue Buffalo grass Grass - Legume mixture - -fall, spring (Orchard grass, redtop, Italian ryegrass, and common lespedeza) Lespedeza sericea Good stand, cut to 2.5" height Good stand, headed (12 " -18 ") Good stand, uncut (3 -6 ") Good stand, uncut (4 -5 ") After cutting to 2" height. Very good stand before cutting E Bermuda grass Bermuda grass Good stand, cut to 1.5" height Burned stubble 0 -5 -table 1 clAssiFJCAtioN OF v A M101•J (.0vER. A.‘'m DEGREE of RETAR.DAN Ca Cover Slope2/ range— (percent) Permissible Velocity!" Erosion resistant soils (fps) Easily Eroded Soils (fps) 0 -5 8 6 Bermuda grass 5 -10 7 5 over 10 6 4 Bahia Buffalo grass 0 -5 7 5 Kentucky bluegrass 5 -10 6 4 Smooth brome over 10 5 3 Blue grama Tall fescue Grass mixtures 2/ 0 -5 — 5 4 Reed canarygrass 5 -10 4 3 Lespedeza sericea Weeping lovegrass 3/ Yellow bluestem — 0 -5 3.5 2.5 Redtop Alfalfa Red fescue Common lespgdeza4/ 5/0 -5 Sudangrass —// 3.5 2.5 1/ Use velocities exceeding 5 fps only where good covers and proper maintenance can be obtained. 2/ Do not use on slopes steeper than 10% except for vegetated side slopes in combination with a stone, concrete, or highly resistant vegetative center section. 3/ Do not use on slopes steeper than 5% except for vegetated side slopes in combination with a stone, concrete, or highly resistant vegetative center section. 4/ Annuals - use on mild slopes or as temporary protection until permanent covers are established. 5/ Use on slopes steeper than 5% is not recommended. -fable 2 t -t4 t *(sL vce-rrlEs 6',42- cuANM.s LIMED Wr114 vE4m-not4 Nifeks02.e. DESLU;N AND STABILIZATION OF DRAINAGE CHANNELS TO PREVENT EROSION T�PI✓ RQPo a. BIO- TECHNICAL METHODS OF STABILIZING DRAINAGE CHANNELS To prevent erosion of drainage channels where flow /soil conditions exceed the stabilizing effect of vegetation. SITS C 1zfCTE215T1CS QV1a Pl...VC_ATlc .4 Applied to drainage channels where vege- tation is not sufficient to prevent water erosion; also where excessive grade or poor soil conditions occur, or where water falls from one elevation to another. ATAlANITACIES 1. The use of vegetation in combina- tion with mechanical means is preferable to purely mechanical liners since flow velocity is • reduced and infiltration is increased. 2. Mechanical measures can aid in the establishment of vegetation on sites that would normally be unsuitable. pl5A.DVANTA(E6 1. Checkdams and drop structures are prone to damage during high velocity flows. 2. Energy dissipators in drop spillways • collect silt and debris and require cleaning. pEE.s1UN C tTE2LA aw4 OLxr11 N 51 Gt Fl G6AT1 ONS Netting and Seeding. A variety of jute, paper and plastic nettings are on the market and are used to stabilize grassed waterways at the time of seed- ing. In larger channels, where several widths of netting are required, they should overlap 2 ". These overlaps should be stapled 4' to 10' apart. The ends of rolls should also be overlapped. The top ends should be buried, in trenches 4" deep and held by staples 10" apart. Hairpin- shaped wire staples are preferable to wooden pegs. After completion, waterways should be rolled to insure contact with soil. 137 Erosion checks are usually constructed of fiberglass which are installed across drainage swales and function as a spreader, avoiding the formation of gullies and aiding in the establishment of vegetation. Preferably they are installed at changes in gradient and downstream from confluence of tribu- taries. Construction: 1) excavate trench of 1' depth; 2) install vertical membrane and secure with staples, back - fill, compact, and trim flush with surface; 3) center netting or mat on top of vertical strip to form cap to extend 1/2' above design flow elevation and staple on 6" centers. Stone center drains are used in drainage channels that experience prolonged flow and wetness, preventing the growth of adequate turf. Gravel bedding and packed stone provide for drainage in the center of the grassed swale. (See BMP II.18 for calculation of size of stone.) Latticework concrete blocks can be used to stabilize the banks of waterways that experience high velocity flows. Gaps in the concrete blocks are back - filled with soil, compacted, and seeded with grass (BMP I.4). Drop structures and checkdams counteract gully erosion in waterways by reducing the gradient of the channel. These should be used rather than impermeable concrete or asphalt linings, when phys- ical conditions are too severe for the satisfactory establishment of vegetative cover. Selection of materials will depend on strength requirements, cost, permanence and aesthetic aspects (tem- porary checkdams were considered in BMP 1I.6). Structures can be divided CoNCRerr 9II..0AY W►tM EN Z'( OhSSIPA'ID45 into rigid or slightly flexible and into straight drop spillways and chute -type spillways. Materials can consist of timber, rock, gabions, concrete, and sod. To prevent undercutting at the toe, all structures should extend several feet or more below the existing ground surface. The selected design capacity should be for a storm of greater frequency than the one used for the drainage channel because of the damage that could be done to the structure if it were to overtop. (The method for calculating channel sizes and capacities is given in BMP 11.15). 138 L I6R 'C►l ii SF,GTI T( � ON) LV MIN 31bllk doDrREST QRKd1�lAt- -�' •FI��'• Y SfIF.AM 66D >s2'MIN REFERENCES 1. USDA, Soil Conservation Service. Engineering Field Manual for Conservation Practices. 1969. 2. Soil Conservation District. Erosion and Sediment Control Handbook. Montgomery County, Pennsylvania. 3. USDA. Controlling Erosion on Con- struction Sites. Soil Conservation Service Agriculture Information Bulletin #347. 1970. 4. Environmental Protection Agency. Guidelines for Erosion and Sediment Control and Planning and Implemen- tation. 1972. 5. Ludlow Corporation. Textile Divi- sion. Needham, Maine. 6. Brandt, G.H. and others. An Economic Analysis of Erosion and Sediment Control Methods for Watersheds Undergoing Urbanization. USDI. OWRR. 1972. 139 DESIGN AND STABILIZATION OF DRAINAGE CHANNELS TO PREVENT MEU2E. EROSION PERMANENT DIVERSIONS PJ2Pc5E., To direct runoff from areas where it could cause erosion to areas where it can be disposed of safely. srr� ct Ac -reR r(cs avid This measure is applicable to any site where there is erosion hazard created by a concentration of runoff flowing over an unprotected area. The situa- tion is most likely to occur on highly erodible soils and on sites with a high proportion of steep slopes. Recently constructed fill slopes are the most susceptible to damage by erosion. ADVAt. -rP4gs 1. The increase in the overland dis- tance of flow of runoff in diversion channels may significantly increase the time of concentration of runoff from a drainage area. This may reduce the 'peaking' of runoff allowing smaller culverts, etc., to be installed. 2. In many subdivisions, diversions may be incorporated into the pedestrian open -space system. Di4ADVar JTh Es 1. If water seeps into diversions, sloughing may occur on unstable soils. 2. if slope is too steep, the con- struction of a diversion may cause excessive disturbance and erosion. 3. Regular maintenance of channel vegetation is required in most cases unless designed for poor vegetative cover. 4. Where a drainage area is very steep or is undergoing construction, the channel may act as a sediment basin and, consequently, require cleanout and possibly revegetation. Destla f\l Ger EOP\ avid OJrL. �lE S GIFtcAATnoKs Permanent diversions generally are of three types. 1. Diversion Channel. This consists of a channel and a ridge across a sloping land surface which conveys water laterally at a slow velocity and discharges into a protected area or outlet channel. 2. Diversion Berm. This is a well - compacted, earthfill ridge installed at the top of steep slopes to divert storm runoff from these critical areas. In permanent installations a diversion channel is more common. 141 3. Bench Terraces. These are rela- tively flat areas on sloping land constructed along the contour. They can often be designed for widths to allow construction of rows of dwelling units following the natural contours. In practice, there will normally be a diversion channel at the lowest point of a bench terrace which may be con- structed with a natural or reverse fall. In effect, the same procedure for the design of the actual channel of all three types may be followed. Design Diversion Channels 1. Capacity. Diversions should be designed to handle peak runoff for storms of the design frequency. This may be done by referring to Chapter 2 (Estimating Runoff) in the Soil Conservation Service's "Engineering Field Manual for Conservation Practices." The design storm frequency should be chosen to provide protection com- patible with the hazard or damage which would occur if the diversion should overtop. (It must always be remembered in designing for runoff that a storm sometimes may overtop the facility and, therefore, it is probably desirable to reduce the design frequency in favor of making sure that there is an emergency path where runoff which overtops the facility will not cause too much damage.) Where overflow may cause limited erosion damage and some flooding of playing fields, etc., a 10 -year frequency would be appropriate with a freeboard of 0.5'. If overflow would cause flooding of actual buildings, frequencies of as much as 50 years may be used with a freeboard of 0.5'. 2. Cross Section, Location, Etc. The number and spacing of diversion channels is dependent on land slope, soil type and runoff char- acteristics. The cross section 5G1H� at NTH y -4- - E-4- 4 -f4-4- 8EN1 i -rr2P.A -9(2EUEiZ4 . FALL SE, LWreZg t 1 AL u.) should be designed to allow for efficient maintenance and mowing in the case of most waterways. Channels may be parabolic, V- shaped or trapezoidal, and slide slopes should not be steeper than 3:1. (4:1 is preferable for mowing at reasonable speeds.) The location will depend on outlet conditions, length and gradient of slope, and, of course, the development layout. The gradient of channels should generally be between 0.5% -1.0X, but it may be increased to 2% for soils with erosion resistant subsoils (K = 0.10 -0.32, where K is the soil erodibility factor used in the Universal Soil Loss Formula.) 3. Design Velocity. Design velocities should be determined using the tables below, based on Manning's formula, first determining the retardance of vegetation in the channel, then determining the maximum velocity based on soil texture and quality of vegetation. Design velocities and channel capacities may be determined by the method outlined in Chapter 9 (Diversions) in the SCS "Engineering Field Manual for Conser- vation Practices," or other accepted method. 142 4. Grading and Vegetation. The channel ridge should be graded to the design elevation plus 10% to allow for settlement. The channel should be protected against erosion as soon as possible after construc- tion by seeding (BMP 11.9), sodding (BMP II.10), or seeding with mulch or matting (BMP II.13). Average Length of Veg., Inches Retardance Good Stand Fair Stand 11 -24 B C 6 -10 C D 2-6 D Permissible Velocity - Ft. /Sec. Soil Texture Bare Channel Channel Vegetation Retardance Poor Fair Good Sand, silt, B 3.0 4.0 Sandy loam and 1.5 C 1.5 2.5. 3.5 Silty loam D 2.0 3.0 B 4.0 5.0 Silty clay loam 2.0 C 2.5 3.5 4.5 Sandy clay loam D 3.0 4.0 B 4.0 5.0 Clay 2.5 C 3.0 4.5 5.5 D 4.0 5.0 Tables from Reference 2. 5. Protection of Diversion from Sedimentation. Where sediments are being eroded from the drainage area, the diversion should be protected with a 15' wide strip of well - established vegetation. On newly graded sites this strip should be sodded. 6. Outlets may be natural grassed waterways, vegetated areas, dry wells, or stable watercourses. Vegetated outlets may be installed and well established before diver- sion construction. Where the D outlet is a stable area of sod or woodland, the outlet of the diversion should be flared in a manner to spread water over a wide area at a shallow depth. Note: Where there is a considerable build -up of runoff at a high level and not enough space to construct a diver- sion, it may be necessary to direct all or some runoff to a lower level by means of a pipe, chute or flume (see BMP II.18). REFERENCES 1. Bucks County Soil and Water Conser- vation District. Standard Permanent Diversion. Bucks County, Pennsyl- vania. 1971. 2. Soil Conservation Service, Northeast Regional Technical Service Center. Guidelines for the Control of Erosion and Sediment in Urban Areas of the Northeast. 1970. 3. Department of Public Works. Balti- more City Sediment Control Manual. Baltimore, Maryland. 1969. 4. USDA, Soil Conservation Service. Engineering Field Manual. 1969. 143 DESIGN AND STABILIZATION OF DRAINAGE CHANNELS TO PREVENT EROSION PROTECTION OF CULVERT MOUTHS, CHUTE OUTLETS, ETC. II18 2ePoSe The velocity of flow is nearly always speeded during passage through a cul- vert and always when passing down a chute. A scour hole or plunge pool will develop unless the end of the culvert or chute is protected. Gt.IARACTE0I471G6 avid APPLICATIoM All points where flow of runoff has been constricted in culverts, chutes, etc., and then passed into an unlined channel, are susceptible to erosion. Sites with highly erosive soils will be more susceptible than others. ADti/AtNrAL�E-s 1. If a plunge pool forms at a culvert mouth, it may severely weaken the toe of. the embankment and thus threaten its stability. 2. Scouring at a culvert mouth can start gully erosion which may gradually extend upstream. P16ADVAKTA4 Es Some types of structures may be unsightly. DIE.sl • N1 G42 ITE21A avid OUrLl NE 5PEL1 RIC.ATIbNS The velocity of water flowing through a culvert or down a chute will usually increase and, therefore, will tend to form a plunge pool where it flows into an unlined channel. 1. Plunge Pools. A plunge pool will dissipate a large amount of the excess energy if it is allowed to develop. Usually, however, a culvert or chute is passing through or down an embankment, and the formation of a plunge pool could 145 undermine the toe of the embankment. If a plunge pool is acceptable, one. of two measures may be taken: 1. Cantilever the end section of the culvert and support with wood for temporary installation or concrete for permanence. Aesthetically this is not a desirable solution. 2. A cut -off wall extending beyond the anticipated maximum depth of scour will prevent the plunge pool from undermining the embankment. Note: As a guide, extend the cut- off wall 1 -1/2 culvert diameters below culvert invert (only 1/2 culvert height if tailwater is above mid - height of the culvert). 2. Protective Aprons, Rip Rap, Gabions, Concrete. If a plunge pool is not acceptable, dumped rock, hand - placed rip rap or rock - filled gabion bas- kets or mats may be used. A guide to the size of rock required for various rates of flow can be found in the Appendix to BMP II.18. The height of the apron should extend at least to the design high water level. The lateral extent should be at least one culvert diameter each side of the apperture. The length of apron necessary to pre- vent a scour hole and to protect the culvert is shown in the Appen- dix to 11.18. Aprons may be used with a cut -off wall where additional protection of the outlet is desired. Dumped stone is the most effective of these types as its rough texture dissipates the energy in the water and minimizes scour. Gabions I 111111 1 1 ; I 1 enable much smaller stones to be utilized and may be aesthetically more pleasing. Concrete, without baffles to reduce energy, protects the area around the culvert from scour, but a plunge pool will often develop below a concrete apron. 3. Stilling Basins. Where flow is excessive for the economical use of dumped stone or other energy dissipators, a stilling basin may be used. The function of a stilling basin is similar to that of a plunge pool. The design of stilling basins is not considered in detail here (see Reference 2). The role of a stilling basin is very similar to that of a plunge pool in reducing the energy of flow. Essentially they form a small pool into which the culvert discharges, the outlet of which is shaped to conform to the cross section of the receiving channel. MfFLIF6 t0 DIS501"6 E 4eRG' ( A1" 94ssE OF COMCAelE CHUfe. 5Ptu. -1JAY L‘‘..4; '' ''' ?4'274. REFERENCES 1. State of New York, Department of Transportations. Bank and Channel Protective Lining Procedures. 2. U.S. Department of Interior, Bureau of Reclamation. Hydraulic Design of Stilling Basins and - Energy Dissi- pators. Engineering Monograph #25. 1963. 146 4PRF�WI)L ll•i& MATION1 of 5'1DtlE 5 12E AMID ptMEN (oN5 FbR c.utvEizrAPRoN5 Step i) Estimate flow velocity V at culvert or paved channel outlet. Step ii) For pipe culverts Do is diameter. For pipe arch, arch, and box culverts, and paved channel outlets, D = A , where A = cross sectional area o? flow at outlet. For multiple culverts, use D o = 1.25 x D o of single culvert. Step iii) For apron grades of 10% or steeper, use recommendations for next high zone (zones 1 through 6). Z5 zo l,' 10 5 0 5 Io 15 Do ih 41" Length of Apron 20 Zone Apron Material To Protect Culvert L1 To Prevent Scour Hole L2 1 Stone Filling (Fine) 3 x Do 4 x Do 2 Stone Filling (Light) 3 x Do 6 x Do 3 Stone Filling (Medium) 4 x Do 8 x Do 4 Stone Filling (Heavy) 4 x Do 8 x Do 5 Stone Filling (Heavy) 5 x Do 10 x Do 6 Stone Filling (Heavy) 6 x D o 0 x D 0 7 Special study required stilling basin, or larger (energy dissipators, size stone). Source: "Bank and Channel Lining Procedures ". New York Department of Transportation. Division of Design and Construction. 1971. 147 Z5 4-igvr- 1 rE tyro ES At�I D PE DIAMerreS Z A ?�oN LE.1.1 114 ei t*f i VrloN Determination of Stone Sizes for Dumped Stone Channel Linings and Revetments Step i) Use Fig. 3 to determine maximum stone size (e.g., for 12 fps = 20" or 550 lbs.). Step ii) Use Fig. 4 to determine acceptable size range for stone (for 12 fps it is 125 -500 lbs. for 57% of stone, and the maximum and minimum range in weight should be 25 -500 lbs.) Note: 60 20 c In determining channel velocities for stone linings and revetments, use the following coefficients of roughness at right. GDEFFIUEa.lt5 of e x414NLES Fine Light Medium Heavy Diameter (inches) 3 6 13 23 i(.,000 Io,000 8 5,000- -x,000 0 500 -25o -100 -50 4 8 10 IL 14 V ELoC TY 1N FEET /5EG. IC. 18 20 Manning's 'n' 0.031 0.035 0.040 0.044 Minimum Thickness of Lining (inches) 9 12 18 30 FoR IeiP� �e StLE Maximum Weight of Stone Required Minimum and Maximum Range in Weight of Stones Weight Range of 75% of Stones (lbs.) (lbs.) (lbs.) 150 25 - 150 50 - 150 200 25 - 200 50 - 200 250 25 - 250 50 - 250. 400 25 - 400 100 - 400 600 25 - 600 150 -. 600 800 25 - 800 200 - 800 1,000 50 - 1,000 250 - 1,000 1,300 50 - 1,300 325 - 1,300 1,600 50 - 1,600 400 - 1,600 2,000 75 - 2,000 600 - 2,000 2,700 100 - 2,700 800- 2,700 148 (RADATI Dl\l OF elP RAP Calculation of Stone Size for Waterway with Stone Center Drain Use the nomograph below (Figure 5) to determine the size of stone for water- ways with stone center drains (used where there is a problem with prolonged flow and wetness). Example.: Design grass waterway in the normal way, determining the top width and the depth of flow (see Appendix to BMP II.15). For a design depth of 1.0' and a longitudinal slope (gradient) of 5.0% (0.05)• 25% of the rock should be in sizes slightly larger than 7.9" and the remainder should be well - graded material of less than 7.9 ", including sufficient sands and gravels to fill the voids between larger rocks. Estimation of Depth of Scour at Channel Constrictions Note: This technique gives only a very rough indication of depth of scour and should be used only with extreme caution. In practice, scour depth depends on soil erodibility and other variables. Source: "Bank and Channel Lining Procedures," New York Department of Transportation, Division of Design and Construction, 1971. 3 FLOW --4 WI elAti -Figure to e471MA110N of pEpri of 4icaz AT u2.14 CoiSMIcroa AZOFILE- 1 1 1 6 7 8 9 S0 - z5 I.0 0A as 0.7 0.' 0. a4 0.s ?1 12E 'c'" 15 7s1ndrwtaarl ;ski mete, m.a 10.0 40.0 10.0 240 IS• 10.0 dzwit 50 a0 -6gore 5 SD 24 1.0 45 eq diJOp Eft 0.3 0.2 1E-I- ' MMN�I AL 0.1 19FA ey off :Om 3 ore'S` OF DRAW IN To 2.0.0 15.0 _t0.o Depth of Scour at Long Channel Constrictions 0.1' —05 Step i) Determine reduction in channel width at point of constriction. Determine ratio of W1 /W2. Step ii) On Figure 6 read equivalent value of D1 /D2 for width of channel ratio. Step iii) Knowing design depth of flow Dl, estimate depth of scour D2. Depth of Scour at Short Channel Constrictions Step i) Determine the extent of the construction Wo. to Step ii) Determine design depth of flow upstream of constriction DI. Determine ratio Wo /D1. 2 4 b -7t>, ID 1z.. 9 !L 'figure 1 esriMikno4 of PEPfl4 of 5C00eAr6Liver Got16112u`.ttoktS 18 Step iii) On Figure 7 read equivalent value of Do /D1. Step iv) Knowing D1, estimate depth of scour D 0 149 1..1EA,SU2a. STABILIZATION OF STREAM CHANNELS AND BANKS TAPS 476i2PosE Streambank erosion is a natural pheno- menon, but can become a problem when it is accelerated due to increased runoff, and where it can no longer be tolerated due to urban riparian uses. GENERAL MEASURES S ITTE J (ATZAGTE21 S cs avid APPL ic. rioQ The nature of stream erosion will vary considerably according to site char- acteristics. In hilly terrain, streams will generally be down- cutting, eroding their beds; while in flat terrain, streams will be cutting laterally. The seriousness of the erosion problem will depend largely on the erodibility of the soil and runoff characteristics upstream. Arx/IbtKirA4 6 1. The more stable a stream, generally the greater is its potential for fishing, wildlife and recreation. 2. Some methods of stream stabiliza- tion have considerable advantages. The most desirable solution is to limit runoff to a predevelopment level on all urbanizing areas in the drainage basin. This would minimize the inherent instability of the stream, and stabilization of critical areas will be more effec- tive. 3. There may be advantages in allowing streams considerable freedom during development and stabilizing criti- cal areas following development. This may produce sediment problems downstream. D►SA�D1�A�lr�C��S 1. After development a stream will be carrying greatly increased volumes of runoff and, therefore, the stream will tend to adjust its channel to accommodate this in- creased runoff. If it is desired to stabilize the stream to its predevelopment bed, there will be continuous maintenance required. 2. Stabilization of small sections of stream channel can result in serious erosion problems upstream and downstream. 151 DEsVIN 6Z1T LA 414d OorLlNE SPELFIc.AT(oKIS The policy for streambank stabilization will depend on stream profile. In upstream parts of a watershed the valley section will be V- shaped, resulting from down- cutting of the stream due to a steep gradient and high velocity of flow. The floodplain will be very confined. The effect of increase in runoff will generally be accelerated by down - cutting; but where the stream has reached bedrock, there may be some lateral cutting also. In downstream parts of the watershed the valley section will be a shallow U- shape, and the stream will usually be meandering in a broad floodplain largely composed of silts eroded from upstream. An increase in runoff in this area will usually result in lateral cutting to increase channel capacity, and this is often aggravated by deposits of silts eroded from upstream, which simultaneously tend to reduce channel capacity. The solution to erosion and scour problems stems from an understanding of these basic principles. In solving stream channel problems, first determine cause: a) Increased flows b) Fallen trees causing deflection of flow c) Brush, etc., on inside of curves d) Bedload drifts e) Ice drifts f) Damage to banks by excessive wear Then collect necessary data: a) Watershed and drainage area b) Peak runoff estimation c) Duration of flood and bankful flows d) Soil type e) Existing channel characteristics f) Flow characteristics - continuous or intermittent g) Critical areas Remember that the erosive and tran- sporting power of a stream increases with an increase in velocity, turbu- lence, depth of flow and gradient and the ability of a stream to erode its banks varies inversely with the amount of sediment it is already carrying, including both suspended and bedload material. The following actions may result in problems of instability of streams: 1. Realignment of Channel. Often, as part of urban development, stream channels are realigned and usually shortened. This automatically results in a steeper stream gradient which increases the velocity of flow and erosive capacity. The stream will compensate for this increase in energy by trying to meander, cutting laterally, or by eroding its bed. Measures may be one of the following:. o Construct waterfalls which effec- tively reduce the gradient between falls to approximately the prede- velopment gradient and dissipate the additional energy. 152 o Lining the straightened section to prevent erosion. However, if the lining is not very rough, it will further increase the velocity of flow and result in a very serious erosion problem downstream. 2. Increase in the Volume of Runoff. Urban development of a drainage basin will greatly increase the volumes of water which a stream course must handle. Not only will the extent of the floodplain be larger, but the stream will overflow its bankful stage more often. It is at or near the bank - ful stage that most damage is done to streambanks. Thus, the increase in runoff will worsen streambank erosion, although the duration of flow at bank - ful stage may be shorter due to more rapid runoff from urbanized areas. Measures should aim to: o Reduce runoff to near predevelop- ment level, if possible. It was suggested (BMP I.10) that flood peaks could be reduced by delaying the release of runoff. This, rather than reducing runoff by infiltration or by other disposal means, would effectively lengthen the duration of flow at or near bankful stage when most bank damage occurs. (See hydrographs - the volume of water in each case is approximately equal.) HA./ FLODD itAK .1. —15Vvi< FLV1 71tEE --i o Lining the channel is often used to conduct greater volumes of run- off down the channel at a greater velocity. This can be an effec- tive means, but it not only requires the complete lining of banks and usually bed of the stream (with consequent loss of much of its aesthetic value), but also very careful attention at the end of such sections where the increased velocity will tend to aggravate erosion. 3. Sedimentation of Streambed. Stream channels may become partially clogged with sediment which often originates from upstream development activities. This reduces'the capacity of the chan- nel and the stream tries to compensate for the loss by eroding laterally. Measures may consist of the following: o Prevention of erosion during construction will minimize the problem (BMP 1I.1- II.6). o Removal of sediment deposits will return a stream to a more natural configuration. This is especially important where a silt bar is deflecting flow against an eroding bank. 4. Construction of Channel. A bridge, a culvert, landfill, fallen trees, etc., may cause local channel constriction, and cause erosion. In the case of a bridge where the stream may be con- stricted laterally by abutments, the velocity may be increased, resulting in scouring of the streambed beneath the bridge (which could cause failure of abutments). Lining of the channel bed under bridges is common practice, but this may also increase velocity and constrict the channel vertically. This may result in a plunge pool where the lining ends and in scouring above the constriction. If scouring of the streambed is limited, it will often occur on the banks where revetments end. A culvert effectively restricts a channel, both laterally and vertically, so protection from scour at both ends is vital (see BMP II.18). Measures: Minimize restriction. In the case of a bridge, this may result in a wider span. It also involves removal of fallen trees, accumulated sediment or riparian vegetation, par- ticularly on the insides of bends where these deflect flow against an eroding bank. Where there may be a large amount of ice in the flow to get caught in snags, selective clearance of riparian vegetation which could trap 153 large quantities of ice and cause a local channel restriction, should be carried out. The approach to solving problems of instability may be: 1) To reduce velocity of flow by reducing the runoff from developing areas; 2) To regrade and stabilize the channel with vegeta- tion. This may be effective if velo- cities are less than 8 fps; 3) To install jetties and deflectors in critical areas; 4) To line the channel and /or protect banks from erosion in critical areas. The problems of reducing runoff are considered in BMP I.10 and channel linings and revetments in BMP II.20 and II.21. The costs and the benefits of stream protection or improvement must be very carefully considered. Some of the costs and benefits are difficult to estimate (e.g., the loss of riparian trees or reduction in recreational value). The capital cost of improve- ments may be very high, but high maintenance costs are also likely for such a dynamic situation. 'Improve- ments' in stream alignment, etc., may also result in serious problems down- stream which should be considered in estimating the benefits of a scheme. Estimating the feasibility of protection measures is also very complex. For instance, runoff reduction might not be justified on the basis of streambank protection alone, but if other benefits (e.g., groundwater recharge, reduction of flood damage, reduced size of storm drainage features, etc.) are estimated the cost may be justifiable. IMPLEMENTATION AND LEGAL IMPLICATIONS 1. The center line of a stream is frequently a property boundary. A shifting channel, therefore, may lead to legal disputes. 2. The need for channel protection often arises from development activity upstream. A riparian owner who is adversely affected should seek legal advice on whether or not he can claim compensation for damages. 3. The action of lining or realigning a stream channel may cause more severe instability of the stream channel for downstream and some- times upstream riparian owners. The possibility of causing damage to neighboring riparian owners should, therefore, be carefully considered before undertaking stream improvements. 154 Pu(�Pos� STABILIZATION OF STREAM CHANNELS AND BANKS STREAMBANK PROTECTION USING MATTRESSES, BLANKETS, GABIONS II.20 The use of various types of mattresses and blankets for lining stream channels can give effective control of scouring. SrrE. G1-146 2ISTICS ct i APPLIc- no(Y Any watercourse, particularly one draining an urbanizing area, may need some stabilization. Mattress -type linings are especially appropriate where the whole channel requires lining but where rock is in short supply, or for protecting banks where heavy scour- ing at the toe is anticipated. Sites with highly erodible soils will be the most vulnerable. 1. Because of their flexibility, blankets and mattresses are not as susceptible to instability or undercutting as rigid linings. 2. If carefully designed, a mattress will fall into place after scouring has taken place, providing contin- uous protection. 3. In gabion construction, stone of a considerably smaller size than dumped rock may be utilized. 76AJAMTP 1. Aesthetically, nylon /concrete mattresses are not desirable. 2. A large amount of hand labor may be required for all these tech- niques. 3. Difficulty in installing in deep water. DESI /u cerrER( P w d OC' LI tQE_ S LI �1CptTt0�1S 1. Gabion Mattresses. A Reno mattress, is a cellular wire cage mattress which may be used either as a revetment or as a channel lining. (The use of stone - filled baskets is, in fact, an extremely ancient form of ero- sion control.) The Reno mattress is manufactured in thicknesses of 7 ", 9" and 12" and can be used on slopes of 2:1 or flatter. They are usually 155 filled using a backhoe and selective hand packing where necessary. In order to lay in deep water, it is necessary to prefill the mattress on a raft and slide it into place. Plastic - coated wire is available for use in corrosive water. Aesthetically, a gabion mattress looks much like to hand - placed stone and has a similar roughness. If it is desired, li" lengths of willow shoots and some silty gravel may be included during the filling of the baskets, which under favorable conditions will give a dense growth of willow over protected banks. If this is done, use a maximum grade of 3:1 so that the willow can be cut to the ground periodically with a jungle buster. 1. EgooM6 STRENHBANK ,, t; . 2 Actri RAIMEAJrof - ___ -na acAUcta1rehro c _ - - - -- Rao HR7QESSES f6YE(trivi(['1 MALE woof Zizdb' c.01.5 2. Gabions. Gabions are manufactured in a number of sizes and may be adapted for protecting steeper streambanks or for lining more confined channels than the Reno mattress. Gabions are filled with a backhoe and by selective hand packing.; they are available in plastic covered mesh and have a life expectancy of over 25 years. However, by that time the rock -fill in the gabions will probably have stabilized itself. 3. Concrete - Filled Nylon Blankets. Fabriform blankets are 2 nylon sheets stitched together like a quilt and filled with Portland cement grout after they are fixed in place. This technique is not recommended on slopes steeper than 1:1. The upper layer of fabric deteriorates slowly in sunlight, but this does not greatly reduce its per- formance. Seams are sewn in the field with a portable air - operated or elec- tric bag closer. Ready -mix concrete is injected with a mortar pump filling the toe first. 4. Fabriform blankets are capable of withstanding small movements unlike concrete linings, so are less suscep- tible to undercutting, etc. The channel must be entirely dewatered prior to installation. Fabriform blankets have similar appli- cations as Reno mattresses but can be used in areas where stone is unavailable in sufficient quantities. However, they are aesthetically as acceptable as the Reno mattress, which rapidly becomes covered in vegetation. 5. AM Stag Rx of r1264N BARE Nq5 rnicEt1 REFERENCES 1. New York Department of Transpor- tation, Division of Design and Construction. Bank and Channel Lining Procedures. 1971. 2. Bross, J.M. Engineering Evaluation of Erosion Protection for Water Courses in New Castle County, Delaware. 1970. 3. Maccaferri Gabions of America, Inc. Technical Literature. Flushing, New York. 4. Construction Techniques, Inc. Fabriform Literature. Cleveland, Ohio. 156 MEASURE 'TYPE- 90 2Po 6e. STABLLIZATION OF STREAM CHANNELS AND BANKS STREAMBANK PROTECTION WITH STONE OR CONCRETE REVETMENTS II.21 To prevent erosion of streambanks in critical areas which cannot be protected by grass (maximum velocity 5 fps) or other vegetation. ITI= G14ARALTE2IST 6 elvt4 APP I- VATioN. Any watercourse, particularly where it drains an urbanizing area, may need some stabilization. The most suscep- tible sites will be those with graded streams in the coastal plain, which flow through highly erodible soils. APVANITAea �S . 1. Protects valuable sites from erosion. 2. Eliminates dangerous undercut banks. DISADVANITACIE 1. Unless carefully carried out, revetments often result in loss of aesthetic value due to loss of riparian trees, etc. 2. In many cases, this will simply result in the shifting of the prob- lem area further up or downstream. 3. This is often seen as a permanent solution; in practice, it is rarely so. 4. Smooth linings speed flow which may aggravate scour problems downstream. A lined streambed will prevent an increase in bedload, often resulting in a scour hole downstream of the lined section. 5. Rigid concrete installations are often subject to undercutting and consequent collapse. R614 M1 OZITSKIA Qv1! 01)ILI.E irtGATtot\l.S Extent of Channel Linings or Revetments. Most failures of revetments or linings are due to an inadequate extent of lin- ing. The upper limit should generally be above design high water level. Bank protection should be terminated at bedrock or at the maximum depth of scour. There is no foolproof method of estimating scour, but Appendix 1I.18 gives a rough guide. Where lining cannot be extended to the desired depth, place rip rap at the toe and it will fall into the scour hole as it develops. Revetments may consist singly of stone, piling, etc., or in combination with vegetation. 157 Choice of a revetment type will depend on a survey of streamflow characteristics, soil type, and other criteria. Often the U.S.G.S. can provide data for discharge and velocity characteristics for streams of similar size to assist in deter- mining the most accurate revetment and lining design. 1. Sheet Piling. This must be driven to the point of refusal or to at least 1/'2 its length below the maximum depth of scour. Piling would generally be used only where a vertical bank is required, or where deep water is required close to the shore. 158 2. Rigid Concrete Revetments. Concrete revetments have the following character- istics: 2.1 Dewatering will probably be neces- sary before placing a concrete revetment. 2.2 They are aesthetically unappealing and often have low public accept- ance. 2.3 All rigid linings are liable to crack if settlement or undermining occurs. Thus, they should be used only on stable, well- compacted soils. 2.4 The lining should generally extend to the top of the bank which should be stabilized with a strip of sod; other disturbed areas should be seeded. The height of the revetment should be increased on the outside of bends. 2.5 Reinforcement should extend through all construction joints. 2.6 Extend the toe of the lining to the maximum anticipated depth of scour and protect it with rip rap. Rigid concrete linings and bank protection in small streams have an average life of about 20 years. 3- Grouted Stone Revetments. Grouting is sometimes used to stabilize dumped stone linings when stones of sufficient size to resist movement are unavailable or if it is found that movement is occurring. This can be effective, but the measure will reduce Manning's coefficient of roughness and, conse- quently, the velocity of flow will increase. This can result in a 'pluck- ing' action at any holes or flaws in the grouting, leading to failure and, thus, aggravating erosion problems at the ends of the revetments. Grout- ing also has the disadvantage of changing a flexible protection layer (dumped stone) into a rigid surface which will crack if settlement or undercutting occurs. 4. humped SLnne Linings and Revetments. Dumped stone forms a flexible lining which is therefore resistant to settle- ment and will not be so susceptible to undercutting as concrete lines, since stone will gradually slump into the scour hole. Its other major advantage is that it has a very rough surface which results in dissipation of the stream's energy, minimizing scouring problems at the ends of the revetment or lining. (A stone revetment also provides wave protection on larger rivers not considered here.) The maximum allowable velocity for various stone liners with side slopes of vary- ing gradient are shown in the Appendix to BMP 1I.18 (5). In designing stone linings, it must be remembered that ability to resist erosion depends principally on the size of stone used rather than the thickness of the lining. The minimum thickness of lining which should be used for various stone sizes is shown in the Appendix to BMP 11.18. 5. Placed Rip Rap or Bagged Concrete Linings and Revetments. Hand placed stone or rip rap generally consists of stones of 100 lbs. or more placed in a single layer. They are more subject to damage than dumped stone linings if there is any settlement or undercutting, because any shifting of the stone layer will expose bare soil beneath. Placed FROM Kt: EW-E9 •; c.6PaF` MAI% H41f SAGE Z'7 . •a- M1 Lizer2 wrru wu.10W Muu.7Zhru665 ,-,. it___, F- �ib MAX Alvr U v oFUR 3wN REFERENCES stone has a lower coefficient of rough- ness than dumped rock and, therefore, is more susceptible to scour at the end of lined sections. Bagged concrete forms a similar lining, however, placed stone is aesthetically one of the most acceptable protection techniques. 6. Soil Cement. May be useful for bank or channel protection in some cases. For more information, refer to "Soil- Cement Slope Protection," published by the Portland Cement Association. Avoid stream contact with fresh concrete. Maintenance of Dumped Stone. Shifted stones can be rearranged with backhoe. For large scale movement, dump more stone. Damage to concrete linings MUST BE REPAIRED IMMEDIATELY. Economic Considerations 1. Access. All these lining types require good access for construc- tion. Where access is difficult, it may increase the cost of the lining considerably; in such cases alternatives such as gabions should be considered. 2. Materials. The cost of hauling rock will be a significant factor in determining lining costs. Con- crete linings may be required where this is excessive. 3. Labor Costs. Where these are high and the cost of stone is low, use dumped stone. If vice versa, use hand placed stone. 1. New York Department of Transpora- tion, Division of Design and Construction. Bank and Channel Lining Procedures. 1971. 2. Bross, J.M. Engineering Evaluation of Erosion Protection for Water- courses in New Castle County, Delaware. 1970. 3. Leep, R.W. California Soil Conserva- tion District Streambank Stabiliza- tion Program. J. Soil and Water Conservation. Vol. 20 #1. 4. USDA, Soil Conservation Service. Engineering Field Manual for Conservation Practices. 1969. 5. U.S. Department of Transportation. Use of Rip Rap for Bank Protection. Hydraulic Engineering Circular 411. 159 MEPsURE TVPE MEASURES TO MINIMIZE RUNOFF POLLUTION FROM URBAN AREAS PREVENTION OF RUNOFF POLLUTION BY STREET CLEANING AND OTHER 'AT SOURCE' TECHNIQUES; TREATMENT OF RUNOFF FOR REUSE 1iJaPoSE Runoff from urban areas may be highly contaminated. [Runoff during the first hour of a storm can contribute as much pollutional load to receiving waters as the city's sanitary system during the same period (1).] sITE c 644,2NcrE21srtc avid APPLL GAT(C)N The amount of pollution found in urban runoff varies with density and type of land use. Industrial development (2,800 lbs. contaminants per road curb mile) was found to have the highest pollution runoff level. Residential (1,200 lbs.) wa: Next, and commercial only contri- buted 290 lbs. per curb mile. Density of land uses was important, and it may be assumed in this study that densities below Land Use 6 [residential equivalent of 1/8 -1/4 acre lot size do not have significant runoff pollution problems. ADVAIJTA, es 1. More attention to quality of runoff could result in significantly cleaner streets. 2. Control of urban runoff pollution would significantly reduce pollution loads in some streams draining Largely urbanized areas. 3. The control of urban runoff pollu- tion, along with use of stormwater could reduce the water demand of a community by 52.5% if treated to potable standards and by 46.5% if treated to subpotable standards (2). 916AD\/A. NTA4 E5 1. Existing street cleaning techniques are inefficient in picking up fine solids which account for only 5.9% of total solids but 1/4 of the oxygen demand and 1/2 of the algal nutrients (1). 2. Existing catch basin inlets may be a serious source of organic sludge pollution and are relatively inef- fective in controlling anything but the coarse solids fraction. 3. Runoff pollution may be serious enough to make the separation of storm and septic sewage of doubtful value. DES tf t�l Ge ITE A A and OUTLINE sPE_GIFILATlor■t5 1. 'At Source' Control of Runoff Pollution - Street Cleaning. More frequent and effective street cleaning can significantly reduce runoff pollu- tion. Improvements in street cleaning techniques should be aimed at picking up a larger proportion of the Fine Solids Fraction, a large portion of which are left behind by existing mach- inery (85 %). This could be achieved by the use of vacuum sweeps, and, as 78% 161 „t , ontaminants ar, found within h” of the curb, more frequent cleaning,with one pass up each gutter, rather than wider coverage. This may require tighter enforcement of parking restric- tions on cleaning days. Most street cleaning operations are carried out to get rid of aesthetically displeasing large solids, so operators should receive instructions that fine solids are as important from the pollution standpoint. Although concrete streets have been found to be generally cleaner than asphalt this is not a sole basis for recommending their use. However, if possible, porous pavements should not be used in areas susceptible to heavy loads of contaminants (BMP 1.3). Construction of broader concrete gut- ters could facilitate street cleaning efficiency. 2. Catch Basins. Catch basins, when regularly cleaned, are found to be effective in removing coarse solids but not fine solids. However, because few are cleaned frequently enough, (in many cities, once yearly; in some, once in 4 years), they may be a serious source of Organic sludge. Alternatively, catch basins could be more carefully designed to facilitate rapid cleanout with vactors and to exclude large material which cannot be pumped out by this means. 3. Design of Grass Swales. Grass swales should be carefully graded to eliminate any areas where potential runoff can pond and stagnate. This can be achieved by proper design and main- tenance. A well- vegetated drainage channel can be effective in filtering small discharges of polluted runoff which will tend to have a high concen- tration of contaminants. 4. Separation of Clean and Polluted Runoff. Where developers wish to make use of 'at source' disposal techniques for runoff (e.g., seepage pits, ditch drains, porous paving, etc.) (see BMP 1.2-1.4), they should avoid disposal of polluted runoff from streets, heavily used parking areas, or industrial sites without previously testing runoff samples from these areas. In some heavily - industrialized areas it may be more appropriate to direct highly -con- taminated stormwater into the sanitary sewage system. 5. Treatment of Polluted Runoff. Land uses of greater intensity than LU 6 should have provision for treating run- off prior to discharge into receiving waters. (In these cases, it may be economical for the developer to reduce the total quantity of runoff for treat- ment by infiltrating clean runoff, for example, that from roofs, at the source.) Minimum treatment would con- sist of settlement and chlorination. A high proportion of solids settle after 1 -2 hours; after this, the curve flat- tens out (3). (Organic nitrogen removal by settling was 37% and 44% at 1 and 4 hours, respectively.) Settling ponds used may be the same facilities as those for runoff and sediment con- trol. Design of the spillway for runoff control should allow for 75% of runoff to be retained in the pond for at least 1 -1/2 hours. However, since heavy storms will dilute runoff pollu- tion and minimize the problem, this minimum settling time need be achieved only for a 1 -year storm. Runoff should then be passed into a chlorination chamber and treated with 2 -6 mg /1 of chlorine for a minimum of 20 minutes which should kill 99.99% of coliforms and streptococci (3). 6. Treatment and Use of Stormwater. A pilot study (2) showed that 10 small reservoirs could be dispersed throughout a 1,140 -acre watershed and provide enough storage to receive 90% of the runoff from 1 -year storms without en- croaching on existing land development plans. The stormwater collected could 162 provide up to 52.5% of the demands of a typical residential urban development at an economical cost, if treated to potable standards and distributed through existing water supply mains. Water treated to subpotable quality could provide up to 46.5% of the water demands but would require a separate distribution system, making it more expensive than the potable treatment alternative. In some cases, such townhouse development around a golf course, impounded stormwater with minimal treatment can be used for irrigation purposes with a less elab- orate distribution system. Similarly, where there is a large demand for subpotable water by, for example, industrial establishments which require a less elaborate distribution system, this technique may be worthwhile. Al- though storage reduces the effectiveness of impoundments in controling runoff peaks, with careful design the runoff hydrographs can be maintained near those for a natural area. If, however, water is needed for domestic use, drawdown will occur and this may reduce the aesthetic value of such impoundments. 7. Prevention of Runoff Pollution During Emergencies -- Spills, Etc. It should be possible in the near future to isolate spills, when they occur, by using a portable unit capable of sur- rounding the source quickly with a foamed polyurethane barrier. It is recommended that such a unit, when developed, be available to all comm- unities and on industrial sites for rapid deployment in the event that serious spills occur. 8. 'Mop -Up' Techniques for Small Oil Slicks, Etc. Small oil slicks which find their way into ponds and lakes may be isolated by using floating booms and then 'mopped -up' with absorbent pads or blankets. One such product available at this time is a reusable hydrophobic material capable of absorbing 22 times its weight of #2 diesel fuel in 18 sec- onds. For larger spills in estuaries and large bodies of water, experimenta- tion is being carried out to develop hydraulic skimmers (5). Maintenance Control of runoff pollution 'at source' by improved street cleaning techniques, more frequent cleanout of catch basins, etc., is essentially a maintenance task in itself. Operation and maintenance of facilities to treat polluted runoff will vary according to the design of the system. The most important factor in designing a management and mainte- nance program for runoff pollution control ponds pollution is flexibility of use. The program will require modification if, for instance, the facility is also required to reduce runoff peaks, to function as a recrea- tion pond, etc. REFERENCES 1. URS Corporation. Water Pollution Aspects of Street Surface Contami- nants, U.S. Environmental Protection Agency. 1972. 2. Mallory, C.W. The Beneficial Use of Stormwater, Environmental Protection Agency, Office of Research and Monitoring. EPA -R1 -73 -139. 1973. 3. Evans, F.L. and others. Treatment of Urban Stormwater. 4. Conwed Corporation. Conwed Petroleum Sorbent Products. Minneapolis, Minnesota 55414. 5. EPA. Concept Development of a Hydraulic Skimmer System for the Recovery of Floating Oil. 1971. 163 MEA6UR E T/PE RCPOSE MEASURES TO MINIMIZE RUNOFF POLLUTION FROM URBAN AREAS OIL /GREASE SEPARATORS III.2 Oil, grease, and other petroleum prod- ucts can cause significant pollution, including toxic effects to fish. SITi✓ C1 -IA0QA i- i2.1 1 S avwd APPL! CATION Should be applied to any site with a likelihood of significant amounts of oil, grease, etc. in runoff, particu- larly service stations, garages, car washes, etc. A9Vat 1-1-A,clas Simple method of separating substances due to difference in density. 1)15h D VA QTA6leS Require periodic maintenance for oil/ grease removal. Maintenance must be enforced. Surcharge conditions will cause discharge of all accumulated oil /grease. PES4t4 C JTE (A avu4 OUT i t4 E -SPEGIFIGATIO t�(S The following information has been provided by the Washington Department of Ecology as a guide to the design of oil /grease separation facilities. It is intended only as a guide in that each installation must be designed for the specific petroleum component and flow rate involved. Oil separators discharging to a water- way require approval from the Depart- ment of Ecology. Design Design of a separator facility should be based upon flows resulting from a rainfall intensity of 1/2 inch per hour over the area intercepted to the separ- ator and provision of one hour retention time in the separator at that flow. In addition, the separator must be designed with a depth to width ratio of between 0.3 and 0.5. For further information on the design details of gravity type separators refer to the Department of Ecology's Guidelines for the Design of Gravity Oil -Water Separators (1). The effluent discharged from any oil removal treatment facility to the storm sewer must contain no visible oil and less than ten parts per million total oil. If discharge to a sanitary sewer is permissible, the acceptance level is no greater than one hundred parts per million of total oil. Configuration (References 1 and 2) 165 All wastewater must enter the separator through an inlet pipe. The top of the separator may be level with the floor if constructed inside a building. The separator should be covered with removable sections. Access and inspection covers, weighing not more than 30 lbs. and with suitable hand holds, are to be provided directly above the inspection "tee" and oil /grit collection compartment. Wastewater sources containing both detergents and oil contamination shall be routed through an oil separator distinct from that for wastewaters containing oily contamination only. Uncontaminated waters and stormwater runoff shall not be discharged to the separator unless specified in the initial design. Any pump mechanism shall be installed downstream of the separator to elimi- nate oil emulsification. No waste oils or solvents are to be discharged to the separator. Access to the separator is to be maintained to allow inspection at all times. Company inspection of the oil accumula- tion and effluent water shall be conducted at least once per week. Oil accumulation in the oil separation compartment shall not exceed three inches at any time. The effluent shut -off valve is to be closed during oil and grit removal and water re- filling operations. Following oil removal, the separator shall be hackfilled with clean water to prevent carry -over of oil to clear well. Waste nil accumulations removed from the separator shall not be disposed of to the ground surface or a state waterway. It is recommended that a permanent schedule for separator inspection and maintenance be posted adjacent to the separator and that employees sign and date it. Optional Separator Features Flow diffuser ports in distribution baffle Oil removal mechanism - skimmer - slotted pipe - float - valved outlet Waste oil storage tank Electronic /conductivity oil sensing probe - Automatic shut -off valve - Alarm, warning light Polishing filter in clearwell - Absorbent "Sandwich" +V4Ehh # IN6Pf:Cflot•1 GCVE 7 rn 166 1,==):90.Y/ • 'I //I \V TLET OIL Qztr SEPaZATORS Construction Materials Tank - concrete, steel plate, fiber- glass Baffles - concrete, steel plate, impervious wood Piping - cast iron, steel, plastic Maintenance Maintenance in the form of oil /grease removal must be carried out on a frequent, regular basis to ensure that overflow conditions do not occur. Any bypass or overflow may be considered detrimental to aquatic life. REFERENCES 1. Washington Department of Ecology. Guidelines for Design of Gravity Oil /Water Separators, as received by URS Company Seattle. January 31, 1977. 2. King County, Washington, Department of Public Works, Hydraulics Divi- sion. Professional Technical Guide Manual for Storm Drainage Control in King County. January, 1979. 167 MEASURES TO MINIMIZE RUNOFF POLLUTION FROM URBAN AREAS CONTROL OF FLOATING DEBRIS III.3 RO RPoSE. Floating debris may be a nuisance for the following reasons: (a) large debris may clog culverts, bridges, etc., causing overflow and possible damage; (b) aesthetic value of streams reduced; (c) debris may obstruct navigation of small craft. Srre GaraczAcTaz ISrC.S avki APPuO rtot.1 Floating debris may be a problem in any stream or river draining an urban area. The problem will be worse, however, where there has been a very large increase in runoff causing unstable streambank conditions, and, where flood - plains are extensive but heavily used. Where street cleaning is not regularly carried out, deterioration of the aesthetic quality of the stream is likely to occur due to floating trash and debris trapped in riparian vegeta- tion. ADVANTAGES 1. Improved street cleaning operations will result not only in reduction of floating debris, but improved urban conditions and an overall reduction in runoff pollution. 2. Streambank stabilization will result in not only a reduction in the quantity of floating debris (notably large trunks which may destroy bridges and other flood - plain installations) but also in sedimentation and deterioration of the stream's aesthetic quality. 3. Debris basins not only control floating debris but also reduce runoff peaks and cause the preci- pitation of a large quantity of sediment. DIISAkP\o/Ats47-464e. .s A certain amount of organic debris (branches, leaves, etc.) will be found in any stream or river. These measures are designed to control debris only where it is causing nuisance, danger (e.g., to bridges and culverts) or causing a serious loss of the stream's amenity value. PEE►U N G Z rrr.2 t,4 43148 OJ Lt KE. SPec 1FI CAT IOKIs 1. At- Source Control, Improved Street Cleaning and Maintenance of.Swales, Etc. More frequent street cleaning can reduce the amount of debris, particu- larly paper and plastic litter, which reduces the aesthetic value of streams draining urban areas. Also helpful is the installation of trash racks on 169 storm inlet structures although these of course, require frequent maintenance. They may also reduce the efficiency of the inlet if a great amount of material trapped. In most urban areas the most significant improvement in street cleaning efficiency could be achieved by parking control to allow more effec- tive use of equipment. Drainage swales, particularly those running along property boundaries, are often neglected and used as a convenient dump for rubbish. More rigorous maintenance of drainage channels is essential, including those on private lots. 2. At Source Control, Buoyant Materials in the Floodplain. Zoning to restrict urban development in the floodplain will both reduce the quantity of floating debris generated in these areas during times of flood and also reduce the amount of damage it causes to urban structures in the floodplain. However, even with enforced floodplain zoning, there will be buoyant materials. Their storage sites should be protected by a cyclone chain fence, the top of which should be above the 50 -year flood level. Any other buoyant materials should be securely fixed. 0,1541 r n��n�Lae Covey " ►, CATCH f5g51 N 'i h TUN RE5TR1 T R pEVIGE ic�iYU�1CLi n',e \\ p9' Inlet Jean OUf; Qft}e, sizeri mkt a601 3. Floodplain Management and Streambank Stabilization. In rural areas undergoing rapid urban development, streams will be subject to increased frequency and volume of floods. These are likely to cause streambank erosion and washouts in the floodplain. The instability of the stream thus will cause trees to fall. In the early stages it will be suffi- cient simply to remove threatened trees, to clear brush on the inside of bends and generally to keep the flood - plain free of accumulated debris. As runoff upstream increases, some stream - bank stabilization may be required. These measures are covered in BMP's II.20- II.21. 4. Debris Basins. Basins designed to (a) reduce runoff peaks, (b) remove sediments, and (c) to impound polluted runoff --will all func- tion as debris basins. Spillways on all these basins should be equipped with trash racks to prevent blockages, and, in addition, where a pipe -riser spillway is used, a trash rack can screen incoming flow so as to reduce the problems of removing debris from the surface of the pond. Frequent cleanouts are essential to maintain the design capacity of the intake channel or spillway. PIPE OR RODS 5. Debris Barriers. C M PIPE Where floating debris is a serious hazard due to stream instability and upstream development, local authorities should take measures to screen off debris above critical areas (bridges, urbanized areas of floodplain, etc.). These should take the form of permeable barriers placed across the whole width of the floodplain in an area where back -up of floodwater, caused by accu- mulating debris, will not cause a 170 problem. These facilities may be temporary and removed when the stream has readjusted to increased flows, etc., or they may be permanent. They should be designed by an engineer and enable debris to be cleared following flooding by machinery. A schematic design might consist of concrete piers or steel piles between which are fixed removable steel mesh screens. The barrier should be placed in a location where minor changes in streambed alignment due to accumulation of debris will not be a problem. Maintenance Improved street cleaning, floodplain management, and maintenance of drainage swales are all maintenance measures involving no construction. in de- signing such a program the essential instability of the stream must be recognized, and thus the maintenance program must be extremely flexible. Maintenance of debris basins is covered under specifi- cations dealing with their alternative functions (BMP I.10). Trash racks will need more frequent maintenance (monthly or following major rainfall) in order to maintain the design capacity of intake channel or spillway. Debris carriers should be designed for mechan- ical maintenance. REFERENCES 1. U.S. Department of Agriculture, Soil Conservation Service. Engineering Field Manual for Conservation Practices. 1969. 2. URS Corporation. Water Pollution Aspects of Street Surface Contami- nants. U.S. Environmental Protection Agency. 1972. 171 DRAFT ENVIRONMENTAL IMPACT STATEMENT FOR TUKWILA HOTEL PREPARED BY THE CITY OF TUKWILA TUKWILA PLANNING DEPARTMENT TUKWILA, WASHINGTON WITH THE ASSISTANCE OF R.W. THORPE AND ASSOCIATES Prepared in Compliance with The State Environmental Policy Act of 1971 Chapter 43.21c, Revised Code of Washington, as amended SEPA Guidelines, Effective January 16, 1976 -Chapter 197 -10, Washington Administration Code, as revised City of Tukwila Ordinance Number 1211 June 17 , 1982 TABLE OF CONTENTS Introduction Distribution List vi I. Summary 1 A. The Proposed Action 1 B. Impacts and Mitigating Measures 1 C. Alternatives 13 D. Unavoidable Adverse Impacts 14 II. Description of the Proposal 15 A. Name of the Proposal 15 B. Project Sponsor 15 C. Project Location 15 D. File Numbers of other Agencies Involved 15 E. Site Description 15 F. Description of the Surrounding Area 15 G. Major Physical and Engineering Aspects of the Proposal15 H. Relationship to Existing Laws, Plans and Policies 17 III. Existing Conditions, Impacts, and Mitigating Measures 22 A. Index of Elements of the Environment 22 B. Elements of the Physical Environment 23 C. Elements of the Human Environment 56 D. Sources and References Consulted 81 IV. Unavoidable Adverse Impacts 83 V. Short Term Use VS. Long Term Productivity 85 VI. Irreversible and Irretrievable Commitment of Resources 86 VII. Alternatives to the Proposal 87 VIII. Appendices A. Traffic Analysis B. Fiscal Impact Analysis C. Cultural Resource Evaluation D. Shoreline Management Program E. Flora F. Fauna G. Correspondence from Fire Department H. Correspondence from Police Department I. Geotechnical Report J. Fire Protection Standards for High Rise Buildings ii 111 Introduction .522jgat tan= Christensen Group, Incorporated 2500 NE Andresen Vancouver, Washington 98661 pf frommati Development of an 8 story hotel on a 5.47 acre parcel of land. The proposed development includes 274 guest rooms, dining room, cocktail lounge, banquet room, 5 meeting rooms, swimming pool, administrative offices, and parking spaces for up to 509 cars. A pedestrian bridge might be constructed to span the Green River connecting the Hotel to Christensen Trail. bacimottaufignm The 5.47 acre site is located at the southwest quadrant of the West Valley Highway /South 158th Street intersection in Tukwila. tnad tam= City of Tukwila Planning Department Resvaris i bte Off l ci-atm Brad Collins, Planning Director Planning Department City of Tukwila fkailmatbzimm Mark Caughey City of Tukwila Planning Department City Hall 6200 Southcenter Boulevard Tukwila, Washington 98188 Telephone: (206) 433 1849 A Ettnatagit=trit2taca This EIS was prepared under the direction of the City of Tukwila Planning Department; research and analyses were provided by the fol- lowing firms: R.W. Thorpe & Associates 815 Seattle Tower Building 3rd & University Seattle, Washington 98101 Telephone: (206) 624 6239 (Contact: R.W. Thorpe) iv Jensen, Krause and Schoenleber Architects 1962 NW Kearney Portland, Oregon 97209 Telephone: 624 6865 Beighley- Krause, Inc. Landscape Architects 12840 NW Correll Road Portland, OR 97229 Geo -Recon International, LTD Geophysics Archaeology Geology PO Box 55189 Seattle, WA 98155 Kegel & Associates Land Planning, Surveying, and Engineering 12360 NE 8th Bellevue, WA 98005 Kramer - Gehlen Associates, Inc. Consulting Structural Engineers 2712 Washington Street Vancouver, WA 98660 Shannon and Wilson Geotechnical Consultants 1105 N 38th St Seattle, WA 98103 The TRANSPO Group Transportation Engineers 23 148th Avenue SE Bellevue, Washington 98007 Lsriztsr.altraci±azroattaanzzaftmuthrgal Final Plat Approval Board of Architectural Review Approval Shoreline Management Substantial Development Permit Building Permits Flood Control Permit Site Plan Approval Hydraulics Permit Electrical Permits tacatfion gf Background Data R.W. Thorpe & Associates 815 Seattle Tower 3rd & University Seattle, Washington 98101 Occupancy Permits Sign Permits Grading Permit Flood Control Permit Mechanical Permit All other permits necessary to construct buildings and improvements proposed on the site. v Tukwila Planning Department City of Tukwila City Hall 6200 Southcenter Boulevard Tukwila, Washington 98188 atg gf tssue si 6ratt June 17, 1982 ihrtg Responses QIl Draft ut int Received Ity t ad tau= tuft to tf e July 23, 1982 10.00 All comments on this Draft EIS should be addressed to: Mark Caughey City of Tukwila Planning Department City Hall 6200 Southcenter Boulevard Tukwila, Washington 98188 vi RECIPIENTS OF THIS DRAFT ENVIRONMENTAL IMPACT STATEMENT f ggra1 Environmental Protection Agency Department of Housing and Urban Development Army Corps of Engineers, Seattle District Engineer Soils Conservation Service, Department of Agriculture U.S. Department of Interior, Fish and Wildlife Governor's Office Office of Program Planning and Fiscal Management Department of Ecology Department of Fisheries Department of Game Department of Transportation Department of Social and Health Services Ecological Commission Office of Archaeology and Historic Preservation Office of Public Archaeology, University of Washington Metro - Water Quality Division Metro - Transit Puget Sound Air Pollution Control Agency Puget Sound Council of Governments Seattle - King County Department of Public Health toad 2gsgrnment King County Department of Public Works, Hydraulics Division King County Building and Land. Development Division King County Planning and Community Development Department King County Soil and Water Conservation District City of Kent City of Renton City of Seattle ette Igkai Mayor City Council Planning Commission Public Works Department . Parks and Recreation Department Police Department Fire Department City Attorney SEPA Information Center Finance Department iftfifiitteslServtces South Central School District #406 Puget Sound Power and Light Washington Natural Gas Company Pacific Northwest Bell vii tihrAndem Tukwila Public Library Renton Public Library - Main Branch University of Washington Library, College of Architecture and Urban Planning King County Public Library hltIMPAREDIE Seattle Times Seattle Post- trttetl-tgertcer Datty dournat of Commerce Renton Record Chrortfcte H i gh l i ne Times ftisAte Drumnitamtbigna An¢ Ot h rs Tukwila Chamber of Commerce A. MIN $ iI The project sponsors propose to develop a 5.47 acre parcel for an 8 story hotel at the southwest quadrant of West Valley Highway and South 158th Street. The proponent is proposing to develop a 274 room hotel with dining room, cocktail lounge and banquet facili- ties. A swimming pool will be available for hotel guests. A pedestrian bridge may be constructed connecting the hotel to Chris- tensen Trail across the Green River. The completed hotel will rise approximately 92 feet above the existing grade. The proposed building will cover 30,715 square feet, or approximately 13 percent of the site. Paved areas will cover approximately 69 percent of the site. The remaining 39,315 square feet, or 18 percent of the site will be landscaped. The proponent also intends to landscape an additional 32,800 square feet along the riverbank and along the street frontage. The exterior of the b u i l d i n g w i l l be surfaced with painted con- crete, and /or painted Portland cement plaster, and solar bronze windows. A combined total of 509 parking spaces will be provided. The proposed development of the site will include associated im- provements and amenities, including floodproofing the building by raising its elevation with fill and constructing dikes. B. imgasta mu¢ tUJJ1mttag Milammx 1. Physr .r a t' E-rrvi-ronment a. Geology: Topography- Ansi Scats inumtm 1. A maximum of 80% of the topsoil of the site will be re- worked and covered with the building structure and parking lot. 2. Potential erosion during grading, filling, and land- scaping near the streambank. 3. Topographic changes range from 2 to 10 feet due to excavation and filling. id±igettna Measures 1. Earthwork and paving should be scheduled for the nor- mally dry weather months. If this is not possible, at a l l times, the recommendations of the soils engineer regarding earthmoving procedures applicable to periods of wet weather w i l l be followed. 2 ..rpop? t„.....- 4104),..e lw,....1..., ....,m!,_ ,„...:.-1 ,.- , Iplt, ,...4.4,(6,-..?---11.. ki2 1.■11.11 p: "2,141r-r---ropoznr-roulis \ VP' TNI pf4a" • tio t'aci44:70-41k.ANt4 1:1474' 1P4t. i'A,4i'VVid 10:kW Aggi.; I I Ogfr.-7,-, faMilkW 0.#14nificki Vet `c "ta,.4k Mil/11413 1 1 KIIMMillit„rji :/iluvlie6u1 ii,MiV,W4Maing, N.qirli:4174).iiilftlgrAgigotietrait It ll 1 . .....„-i— 46.4,.....,,, k 1 'II tl it" ill7:_fier*:77,tt_41.7,i';', 44' 4./eisii* tifsam6,,,,,, or-Iptivail ......„cm..,, rt ii' 4 .ii :ifitii 1 1! . 14 1 1 . giqoki:.iv•acm -7.---1:,..7-(:—. r_Orilti. 4 LI411N •-•'-.-- -'''. lii:lAk h. .4, ,„ 4,1....t: 41, irOm,b 9 ■ k,..., ,,:.,....,..i ...s-i Pk PP N5 ;..4r:orria.y....,'," / f ..- , 1 W109".11/61),\,1 Aeigr IIM fe-401,0 74 N. 00 400 1 --.51-zit, v.,2 -1N1'741 %matron , Ail lt ,.'llk_ U.S.G.S. BASE' +1,-=4000' NORTH 1. LOCATION MAP TUKWILA HOTEL R.W. THORPE AND ASSOCIATES ;A% 111111 1 NW 4 1, 41, 4 • Alb ' '." ,d7 • , k • 0) 5 2 a 6 -I 4 a I- 0 1 I 13 4 taw 3 I- 2. Test piles will be driven across the site to determine pile lengths and driveability, pile driving hammer and capacity. 3. A temporary runoff control system, including ditching, sumps, and pumping from the excavation cut should be employed by the building contractor. 4. A l l of the recommendations of the soils engineer re- garding soil bed preparation procedures will be fol- lowed. 5. The City's requirements on grading and excavation will be followed. 6. The proponent will install and maintain a vegetative buffer between the area containing the parking lot, fire lane, and the shoreline, which will provide erosion control and serve as a barrier impeding human activity along the shoreline. b. AIL Ouattty Imam= There will be a short -term increase in dust and fumes during construction contributing to particulate concentra- tions, which already exceed Washington State standards. Over the long -term under "worst case" conditions, the in- crease of 125 vehicles during peak hour can be expected to increase existing carbon monoxide levels by 1.1 parts per million during the evening peak hour. Increased violations of Washingon State standards for levels of hydrocarbons due to cumulative affects of this and other projects which generate traffic-will occur, Over the short -term, significant odors will be attributable to construction vehicles, dust, and asphalt paving during the construction. Automobile exhaust fumes will be per- ceived along the entrance driveway and parking areas. The hotel restaurant exhaust fumes may contribute marginally to odors perceived on the site. Mi"tio±i -ng Measures 1. Low - emission construction equipment could be used when- ever feasible. 2. Measures to control construction dust such as: water- ing, cleaning, and sweeping of streets at the end of hauling activities could be performed by the contractor. 3. Unnecessary motor vehicle engine idling during construction could be eliminated; engines could be shut off except when moving vehicles. 4. See Public Transportation - Impacts relating to "Traffic," page 65. c. Water tmpacts Increased surface runoff from the site. Increased levels of polluted surface runoff. Decreased infiltration of precipitation into groundwaters due to impermeable sur- faces. Potential addition of petroleum products, sedi- ments, and heavy metal traces from automobiles into the groundwater. Mitigabilla Measures 1. Fill material will be required to floodproof building sites which will prevent on -site flooding. 2. Stormwater runoff will be . collected in a 10 year design stormwater detention system and discharged into the river at the same outflow rate as exists in its present undeveloped state. 3. A temporary storm management system and the erosion control measures discussed under the "Soils" section, page 25, will be employed during construction. 4. Where possible, natural vegetation for silt control shall be maintained. . Temporary siltation and detention ponds shall be constructed by placing straw bales across swales. 6. All temporary siltation ponds shall be maintained in a satisfactory condition until such time that cleaning and /or construction is completed and the permanent drainage facilities are operational. 7. Rip -rap base (both sides) of bales shall be positioned as required for erosion control. 8. Cleaning of streets and parking areas sha l I be under- taken whenever necessary. 9. Frequent maintenance of the stormwater system shall be provided. 10. Grading operations during construction shall be limited to periods of normally dry weather. 11. Oil /water separators will be utilized to remove petroleum products from catch basins and screens will be included in the stormwater system to collect litter and debris. The hotel will shade the parking lot, which will help reduce the runoff water temperature. Cleaning of parking areas shall be undertaken whenever necessary. 1 2 . The riverbank w i l l be rip —raped around the stormwater outfall to prevent erosion and sedimentation. 13. All roof drains will be directed to the catch basins. d. Flora -Impacts Most vegetation within the property lines of the subject site will be removed. Some vegetation along the river will be disturbed due to reconstruction of the dike and con- struction of the fire access road. 101i-11-gatFnq Measures 1. A landscape plan has been prepared to assure good design practice and consistency throughout the site. 2. All vegetation along the riverbank, undisturbed by reconstruction of the dike and the fire access road, will be left undisturbed and maintained. Indigenous vegetation w i l l be planted and maintained inside the dike so that the entire length of the hotel's river frontage is landscaped with natural vegetation. 3. In addition to the 39,315 square feet of planned land- scaped area on site, 32,800 square feet of off —site landscaping is planned. These areas include the river- side area and along West Valley Road. e. Fauna -impacts Development of the site will cause an intrusion of human activity and remove all of the grassland used by small mammals, birds, and domestic grazing animals. Resident species will be driven off, displaced and, where alternative habitat is already occupied, their numbers will be reduced in competition for the limited habitat. Migratory and predatory species using the site as part of their feeding or resting area may be wholly or partially displaced, especially species not tolerant of human presence. Degradation of water quality in the Green River could have an adverse effect upon the fish population. Turbidity and high water temperature could particularly affect the health of fish. Mi-ttgattng Measures 1. An erosion control plan shall be followed during con- struction. 2. Natural vegetation shall be maintained along the stream bank. 3. Fill and grading operations will be limited to periods of normally dry weather. 4. Silt traps and oil /water separators shall be maintained and cleaned by the project owner whenever necessary. 5. The hotel and proposed landscaping will shade the parking lot, thereby possibly reducing the stormwater runoff temperature. f. Notse impacts During Construction activities, noise levels will increase considerably, with frequent noise peaks, depending on the type of equipment used. Traffic noise will increase with the additional traffic generated. M t sati rra Measures Electric equipment should be used in preference to gas or diesel powered, when available. Hydraulic or electric impact tools should be used when available, in preference to pneumatic tools, which require very noisy exhausts and compressors. g. Li-giit And Gtare -imp acts Low level lighting on the site. Mtttgattng Measures Parking lot lighting could be limited so that no direct light spills off the site. h. Land Use impacts Change in the land use of the site from an open field to a hotel. Mtttgattrrg Measures None. 1. Naturat Resources acts Consumption of some natural resources for construction. PM-Nat-Mg Measures None. 2. Human Errvtronmerrt a. Poputdti-arr. Ham AnA EmptoymeTlt Insignificant increase in population and employment. Increase in demand of approximately 18 housing units due to hotel employees who desire to move to Tukwila. Mfittgattrg Measures None. b. fransportafiron leirtcutar Transnartatton Generated acts The project will generate approximately 2,880 vehicle trips per day and about 190 vehicle trips during the peak evening hour. During the peak hour, the volume along West Valley Road is expected to increase between 4 and 6 percent due to the development. Mttrgattnq Measures 1. At some future date, if and when traffic conditions mandate such improvements, a traffic signal could be installed, turned to flashing operation and supple- mented with Washington State Patrol manual control during Longacres traffic periods. 2. A left turn lane will be installed at the northwest entrance. 3. The southernmost entrance will be restricted to right turn only for entering and exiting the site. 4. Metro transit information could be displayed in the lobby of the hotel. P_artng f ac ttt -es inuacta The proposed development will create 509 automobile parking spaces. 121±tig rrg Measures None. Movement And eircutatton Qf Peopi -e Aad Goods imuct A pedestrian bridge from the site across the river to the Christensen Trail may be constructed by the proponent if feasible. t ttgattrrg Measures None. Trattfic Hazards tmgagim Assuming accident rates in the vicinity remain at existing levels, the number of traffic accidents w i l l increase by approximately one accident per year within a one -mile radius of the site. 10 Mtttgati-nq Measures 1. Construct a left turn lane on West Valley Road for the northernmost entrance to the site. 2. Restrict the southernmost entrance of the hotel to right turns in and out only. c. Pubttc Servrces Ftre impacts Increased demand for fire protection services at the site. Mitigating Measures 1. The hotel will be fully sprinkled and conformed to each standard delineated in the City's Fire Protection Ordi- nance for High Rise Buildings. The Fire Marshal shall review the application prior to issuance of a building permit to ensure conformance to each standard. 2. Tax revenues from the proposed development will help offset the cost of additional services. Poi ice Demand for police protection services will increase. Mt1-t atrng Measures Tax revenues from the proposed development will help offset the cost of additional service. Park And Recreatton tm a Protect development may include a pedestrian bridge from the hotel to Christensen Trail across the Green River. Additional demand could be expected on Christensen Trail if the bridge is constructed. Attendance is expected to in- crease at Longacres Race Track. Visual and passive, rather than active pedestrian use of the project's shoreline is proposed. The area between the area containing the parking lot, fire lane and dike maintenance road and the shoreline is planned to be planted with groundcover, shrubs, con- iferous and deciduous trees. 11 Mtttgattng Measures 1. The project w i l l provide a swimming pool for use by hotel guests. 2. Tax revenues from the proposed development w i l l hel p offset the cost of additional service. Matmterrance imaztota Over the short -term, vehicles involved with construction at the site can be expected to carry dust and mud off the site into the adjacent streets, thus impacting the street cleaning activities with the Public Works Department. Mfttgatfing Measures 1. The contractor could provide wheel washing for any vehicles exiting the site during excavation. 2. Regular street cleaning could be provided by the applicant, as necessary. Energy tweets Increase in demand for electrical power. Mtttgattng Measures Utilize insulation in the roof and walls. d. U-t- E l fiti-es Impacts Existing water supply and system will experience some additional demand. Sewer facilities will experience increased sewage flows. Demand for solid waste collection will increase. MitF ti•ng Measures All work and materials will be in complete accordance with the standards and specifications of the City of Tukwila, the State Department of Social and Health Services, and the Washington State Department of Ecology. 12 e. Aesthetics imaata Visual appearance of the site will be altered. Northerly views of the office complex south of the site will be blocked. gig Measures None.. f. ArchaeotggtcafItfistofcat imuezta Potential uncovering of archaeologically significant finds during construction. Mittgattng Measures A qualified archaeologist should conduct on -site monitoring during land clearing, access road construction and building site preparation. g. Ecorronri c fmpacts innuata Net municipal income generated by the project is estimated to be approximately $30,895 annually. Short -term employ- ment for construction workers and Tong -term employment for hotel employees will result. .Mtl:tcaLtinu Measures None. 13 C. ALTERNATIVES TO THE PROPOSAL Alternative 1 - No Action Descrintion Under the "no action" alternative, the site could continue to be used for pasture until some other proposal for development is approved by the City. Impacts All positive and negative impacts of the proposal would, for the time being, be avoided. Feasibility Under current conditions, this alternative is impractical for anything other than the very limited future. The pending development of other properties on the valley floor will substantially increase the pressure for development of this site at a higher use as the inventory of land suitable for development is reduced. Alternative 2 - Light industriai Development Description This option would be in conformance with the existing zoning designa- tion for this site. However, it would not conform to the commercial use designation of the Comprehensive Plan. This alternative would allow those uses allowed in C -1 and C -2 zones as well as Tight manu- facturing plants, warehouses, meat processing, salvage processing, spray painting or paint mixing, stamp dieing, shearing or punching of metal not exceeding on- eighth inch in thickness and similar uses. Impacts This alternative could potentially increase impacts on Noise, Odor, Aesthetics, Economics, and Land Use. It is probable that traffic generation would be reduced and air quality would be less impacted, as would soils, natural resources, public utilities, and services. This type of development would be less visible in the general vicinity. However, it could be less compatible with the surrounding land uses and would become a legal non - conforming use once the existing zoning code is replaced this year. Feasibility It is unlikely permits could be acquired prior to the proposed change in zoning. Further, the proponent has not, nor intends to propose a Tight industrial use for the site. .14 D . UNAVOIDABLE ADVERSE I MACTS Soils 1. The reworking and loss of productivity at a maximum of 835 of the topsoils of the site. 2. Potential for minor uncontrollable erosion of soils near the streambank.during construction of driveway and parking lots adja- cent to the streambank. Topography Chanties of contours of site, including excavation depths of a maximum of 10 feet. Air 1. Increased air pollution from automobile emissions 2. Increased particulate levels due to construction activity and additional traffic volumes 3. Short -term odors during construction Water 1. Urban pollutant levels will increase in storm water runoff, par - ticularly.during construction 2. A potential increase in peak runoff from the site 3. Potential decrease in groundwater quality F' fora Reduction of most of the natural vegetation on the site Fauna A reduction in the number of species on the site will result from project development.. Noise Increased noise levels over the short term due to construction activity, and over the long -term due to human activity and increased traffic. Light and Glare Additional light and glare will be emitted from the site to surrounding properties. 15 f Dmamotathaami jJ ftmgmmat A. hFame 9f inimmmod Tukwila Hotel B. Christensen Group 2500 NE Andresen Vancouver, Washington 98661 C. f The project is proposed to be located on a 5.47 acre site, ap- proximately one -third mile east of Southcenter. The site is bounded by the Green River to the west and south, West Valley Highway to the east, and South 158th Street, if extended to the north. (See the Vicinity Map, Page 2.) D. fithac Agancfnm Ratatainfng films mn None. E. The site contains approximately 5.47 acres of level farmland. Two sides of the site border on the Green River. The site was altered slightly with man -made levees along the river bank. It is level, except for that portion of the levee 1 to 2 feet above the major portion of the site. The remainder of the site slopes slightly to the west. F. Dmiasainfinn gE fix JImatanding Area The Green River flows along the southern and western edge of the site, and West Valley Highway forms the eastern boundary. A single family residence is north and adjacent to the site. The character of the general vicinity is office and light warehouse across the river west of the site, Longacres race track and associated uses east of West Valley Highway; and mixed highway commercial and residential uses along West Valley Highway. (See Land Use - Exist- ing Conditions, Page 53.) G. tbdmr namitclit mnd ftcpiarcarfia hamesfm gf tint P Construction of the hotel will take 10 months. Beginning con- struction date is scheduled for late 1982 or early 1983. The amount of fill required for the development of the site is approximately 23,500 cubic yards. Floodproofing of the hotel will require a dike with an elevation of 27.8 feet, approximately 2.8 to 3.8 feet above the site's existing elevation. 16 -ail MO M \ SITE ,t ■■■■! I■■■! MUM OWN f■■■■ SOMME ■ ■■i ■■•1 ... .... MEM IN MULTI FAMILY RESIDENTIAL: _ - _SINGLE FAMILY ...... RESIDENTIAL ■■MOSS MINIM RETAIL____ fgtli(r PARKS AND . PUBLIC SERVICES _COMMERCIAL WHOLESALE UNDEVELOPED _SERVICES .... .... _ DISTRIBUTION . PROCESS ..MANUFACTURING. 3EXISTINQ LAND USE 4. SCALE-1-'2;1200' TUKWdA HOTEL NORTH A.W. THORPE AND ASSOCIATES 17 H. Retattorrshtg ±2 faiz±ing taws Pot'tci es. And fAmm 1. L±±y _aj Tukwtta Comprehensive Land Use Pottcy Pfan The City of Tukwila adopted the Comprehensive Land Use Policy Plan in 1977. The Comprehensive Land Use Plan Map shows the subject property suited for commercial uses with special development considerations. Refer to Figure 4, Page18 of this EIS. The Goals, Objectives and Policies of the Comprehensive Plan pertaining to this area are as follows: COMPATIBILITY Policy #1 "Encourage the grouping of uses w h i c h w i l l mutually and economically benefit'each other or provide necessary services. Comment The proposed development is ideally situated near 1 -405 and 1 -5, as well as close proximity to Southcenter Shopping Center, Tukwila and Renton Commercial and Industrial areas, and Long - acres Race Track. Policy #2 "Allow for the location of new commercial and industrial areas and the expansion of exis- ting ones when this expansion is compatible with surrounding land use and not detrimental to the public welfare." Comment The proposed development is compatible with all the surroun- ding land uses, with the exception of the few single family residences in the general vicinity. However, the area is a developing commercial area and. is supported as such by the Comprehensive Plan Map and Zoning Code. DESIGN Policy #3 "Encourage aesthetic building and site design in working and trade areas." Comment Under Conditional Use Permit requirements, the Planning Com- mission shall ensure that the development shall be generally compatible with the surrounding land uses in terms of traf- fic, pedestrian circulation, and building and site design. 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' irp111111111! Mr • h. 1014111111•W I I I II tc-b, I I I lEd • ,vp • :IN. C 11 • . g • ,1* 1110111111111_ 11111111111 • u. GI! 3. 3. • • t2 it* 19 Policy 114 "Encourage the use of live landscaping in all developments." Comment The proposed development will be required(to meet the minimum landscaping requirements of ten feet in the front yard, and five feet in the side yards. I n addition, detailed landscape plans shall be submitted to the City for approval. Policy 17 "Promote adequate provisions for parking for all land uses." Comment The proposed site plans call for a total of 509 parking spaces to be constructed on -site which is in compliance with the zoning requirements and is considered adequate parking provisions for the proposed hotel. GROWTH Policy 118 "Encourage a diversity of business uses to pro- mote maximum occupancy." eomment The hotel industry owes its vitality to a variety of uses including commercial /industrial uses, as well as recreational and tourism. As the economy fluctuates, some uses supportive of the hotel industry may decline, while others improve. However, due to the significant growth in retail and commer- cial services in the Tukwila area (see the discussion of "Employment - Existing Conditions "), the proposed hotel is expected to maintain a high occupancy rate. ENVIRONMENTALLY SENSITIVE AREAS The subject site lies in an area designated as requiring special development considerations, specifically Shoreline Management guidelines. This designation does not preclude development; rather it depicts areas where urban development must respond sensitively to certain environmental factors. Comment The proposed development conforms to the Shoreline Management Program (included as Appendix D of this FEI. 20 2. hull= @rd finance : ebbe Ad Tukwf fia 3. The City of Tukwila has updated the Zoning Code to better reflect the goals and policies of the 1977 City of Tukwila Comprehensive Land Use Policy Plan. The City Council adopted the new zoning code in May 1982. The previous zoning designa- tion for the subject site was light industry (M -1). The zoning map now designates the site as Regional Retail (C -2). The proponent has obtained preliminary approval to waive the height restriction in order to construct the proposed 8 story hotel. Prior to construction, Board of Architectural Review will be required. In addition, the shoreline permit requirement discussed below applies to portions of the site as an "overlay" zone. Comment The proposed development will be in conformance with the Tukwila Zoning Code upon approval of the Board of Architecture Review. The Washington State Shoreline Management Act applies to that portion of the site within 200 feet from the ordinary high water mark of the Green River. The law stipulates that a permit must be obtained from the City of Tukwila for any substantial development occurring within this zone. The Green River has also been designated as a "Shoreline of Statewide Signifi- cance." Within shorelines of this designation, the City has been entrusted to ensure that development will preserve the natural character, ecology and resources as well as increase public access to the shoreline. The Shorelines Management Act is directed at enhancement of shorelines rather than restric- tion of use. The Shoreline Master Program for the City of Tukwila desig- nates the entire Green River Shoreline as an "urban environ- ment" which allows high intensity land uses including resi- dential, commercial and industrial development. The City of Tukwila classifies the 200 foot shoreline into three manage- ment zones: the river zone is 40 to 50 feet from the mean highwater line; the low impact zone is outside the River zone and within 100 feet of the mean high water I i ne; and the high impact zone is outside the low impact zone and extends 200 feet from the mean high water line. Refer to Appendix D - General Regulations. Comment The site plans of the proposed development are in conformance with the General Regulations as listed in Appendix D. The building and parking lot shall be constructed beyond the 40 foot River zone setback line. TUKWILA - R -A Agricultural C -2 Regional Retail C -P Planned Business Center C -M Industrial Park M-1 Light Industry SCALE: 1"=:1200 NORTH (Gent RENTON. G ' Single Family Residential B-1 Business Park B -P Business Parking M-P Manufacturing Park H-1 Heavy Industry SS.ZONING TUKWILA HOTEL R.W. THORPE AND ASSOCIATES 22 III. EXISTING CONDITIONS, IMPACTS AND MITIGATING MEASURES INDEX Et-EMEaa !ti f?NtftRONMENT A. EtfMENTS DE MM PWtS1 At ENYtRONMENT Page Earth Geology 24 Soils 24 Topography 27 Unique features 27 Erosion 25 Accretion /Avulsion NA At r Climate 30 Quality 30 Odor 34 Microclimate 30 Water Surface water movement 35 Surface water quantity 35 Surface water quality 38 Runoff /absorption 35 Floods 35 Groundwater quantity 38 Public water supplies 74 Ftora Numbers or diversity of species 40 Uniquespecies 40 Agricultural Crops 42 F aura Numbers or diversity of species 43 Unique species 44 Barriers and /or corridors NA Fish or wildlife habitat 43 JVotse 46 tight Anst Gtare Land 11.9g 53 Naturat Resources Rate of use 55 Nonrenewable resources 55 Risk gf Jxpi osfon Qt Hazardous Emtsstons NA 23 B. EtEMENTS DE ThE .1M811 ENVIRONMENT Page. Population on 56 Housing 57 Emptoyment 58 Transportati"o"n /Crrcu tat'ron Vehicular transportation generated 60 Parking facilities 64 Transportation systems 65 Movement /circulation of people and goods 65 Waterborne, rail and air traffic 66 Traffic hazards 66 Pub t-tc Services Fire 68 Police 68 Schools NA Parks and other recreational facilities 69 Maintenance 70 Other governmental services NA Energy Amount required 72 Source /availability 73 Ut t ities Energy 73 Communications 73 Water 74 Sewer 74 Storm water 35 Solid waste 75 Human Neatth NA Aesthetics 76 Recreation 69 Archaeo togrca f /Hi-stortcat 79 Economic actors 80 24 g� EtEMENTs QE DE .t ENVI R©MMENT 1. EARTH a. 2252±2= Exi-stf ng Condt1tons The site of the proposal is located within the Green River Valley. The geologic history of the entire Puget Lowland is dominated by the advance and retreat of at least four great ice sheets, the last of which (the Vashon) retreated from the region approximately 14,000 years ago. The general terrain of the region as it presently exists, has resulted from the action of these glaciers upon the pre - existing landscape. The area of present Puget Sound was deeply excavated by glacial movement. As the Vashon Glacier retreated north, ice - marginal and north flowing rivers were dammed, creating temporary lakes south of the glacier. Post glacial l acustr i ne sediment was deposited in the Green River Valley during this point. Subsequent to the glacier retreating north, the ocean invaded and extended into Puget Sound and the lower Green Valley. This embayment has slowly filled with alluvium deposited by the flood waters of the White, Cedar, Black, and Green Rivers to its present level. f mph None. Excavations or fill should affect only surface soils. MTtlgati-ng Measures None proposed. tfiavo-i•dabte Adverse tm2=±1 None. b. miffs g Condi-ttons A Geotechnical Report, submitted by Shannon and Wilson, Inc., on March 12, 1982, is included as Appendix 1 of this DEIS. The following description of soil characteristics and recommenda- tions for the building foundation design are based on the analysis presented within that report. The site is underlain, to a depth of more than 100 feet by alluvium, most of which can be assumed originated from White River deposits. Beneath the alluvium is dense weathered basalt bed rock. 25 The soil type of the project site, as indicated by the Soil Conservation Service Soil Survey of King County, 1973, is Urban land (UR). This soil has been modified by disturbance of the natural layers with additions of fill material similar to the natural alluviam soils of this area. Five boring samples were taken at the site in 1973 and four additional borings were taken in January and February of 1982. These boring Togs are mapped on Figure 2 of Appendix 1. The borings indicate that the site is underlain by approximately 60 feet of sand. The upper 35 feet of sand is loose to medium dense, becoming denser with depth. Underlying the sand is a variable thickness of layered soft to stiff clayey silt and silt. This compressible layer varies thickness from approximately 18 feet to 35 feet. However, this layer was not observed in the most easterly boring. Beneath the clayey layer, dense, gravelly silty sand with shells to sand with gravel was observed. Water levels, according to readings taken on January 8, 1982, were indicated at 15 feet. Because of the proximity of the Green River to the site and the pervious nature of the near - surface soils, the groundwater levels would be about the same as the river level. The soil characteristics are closely related to that of Newberg silt loam (Ng), the soil common to the lowlands adjacent to the stream corridors in the valley. Newberg silt loam has good permeability, but is subject to a periodic high water table. The suitability of this soil for building foundations can be poor under natural conditions in which no flood control is provided. This so i l is suitable for hay, pasture, and vegetables, and represents one of the best and most easily worked soils in King County. The seasonal high water table drops below the rooting depth during the growing season. The rate of erosion of this soil is slight. The Puget Sound region is located within a seismically active area. The soil type of the site, and the associated soils of the lower Green River Valley, are considered susceptible to "liquefaction" during earthquakes. This phenomenon occurs as ground shaking causes a loss of supporting capacity within loose, fine, or organic soils, which are heavily water satu- rated. Structures supported within or above the soil can undergo significant settlement and possible tilting. The esti- mated recurrence interval for an earthquake with a Richter magnitude of 5.0 is five years, for 6.0, thirty years, and for 7.0 and above, 150 years or greater. fimpacts The proposed building site is underlain with normally consoli- dated alluvial soils of which the thick clayey silt is compres- sible. Consequently, the hotel tower and lounge and dining areas will be supported on relatively long end - bearing piles. 26 Pile lengths could range from approximatly 80 to 125 feet, measured from the existing ground surface. Piles should pene- trate into the dense soils below the compressible clayey silt. A maximum of 83% of the topsoil of the site w i l l be reworked and covered with the building structure and parking lot, thus losing its current productivity. Some erosion of the fill material and worked natural soils is likely prior to construction of the building. The potential exists for water to seep into the foundation cut during con- struction, requiring temporary drainage. The movement of heavy earth moving equipment over the surface of the site during construction wi I I compact the soil, causing some pooling of water during periods of precipitation. This condition, coupled with the removal of vegetation, may contribute marginally to erosion of surficial soils. Existing levees along the stream - bank will have to be protected during construction to minimize the potential for streambank erosion. It is likely, however, that grading and landscaping near the streambank will precipi- tate some erosion of soils beyond the control of the procedures utilized to minimize erosion. Mttroattng Measure 1. Earthwork and paving should be scheduled for the normally dry weather months. If this is not possible, at all times, the recommendations of the soils engineer regarding earth - moving procedures applicable to periods of wet weather will be followed. 2. Test piles will be driven across the site to determine pile lengths and driveabliity, pile driving hammer and capacity. 3. A temporary runoff control system, including ditching, sumps, and pumping from the excavation cut should be em- ployed by the building contractor. 4. All of the recommendations of the soils engineer regarding soil bed preparation procedures will be followed. 5. The City's requirements on grading and excavation will be followed. 6. The proponent will install and maintain a vegetative buffer between the area containing the parking lot, fire lane, and the shoreline, which will provide erosion control and serve as a barrier impeding human activity along the shoreline. Unavofdabie Adverse tmpacts 1. The reworking and loss of productivity of a maximum of 83% of the topsoils of the site. 27 2. Potential for minor uncontrollable erosion of soils near streambank during construction of driveway and parking lots adjacent the streambank. 3. Potential for minor erosion of soils near streambanks due to potential presence of human activity. c. icamgna24 d. Existtng condttrons The site is very level, averaging 24 feet and varying only three feet in elevation. The top of the levee, along the river bank is generally two to three feet higher than the center of the site, however, along much of the south side there is very little variation in elevation. Fill material into the "River Zone" is not an allowed use except for those uses described in the City of Tukwila Shore- line Master Program, Use Regulations (See Appendix D). tmpacts Topographic changes ranging from 2 to 10 feet will occur due to excavation and filling during construction. These changes will occur in order to construct a basement, and provide floodproofing ( i . e . , dikes and i l l I to raise elevations above the maximum discharge elevation of Howard Hansen Dam. See Unique Physical Features, page 27 ). The building and parking lot sha l i be constructed beyond the 40 foot "river zone" set- back line. M ittgattng Measures None. Urtavo ftabte Adverse impacts Changes in the contours of the site, including excavation depths of a maximum of 10 feet. Fxtsttna Cond-i-tions Due to the proximity of the Green River to the site, the potential of flooding is increased. Consequently, dikes have been constructed along the bank of the river. King County Hydraulics Division reviews applications for State Flood Con- trol permits. The proponent of a development adjacent to the River is required to provide dikes, or build at an elevation 2 feet above the maximum discharge elevation of the Howard Hansen Dam (27.8 feet). /1!O•J/7A1Q•a' / lee N/YIY? JD 111y ME( /FJi •N' i /Nl' AR17•N' I N. 4, Nsc•04' ICQ 01 lrohJ N ea 111 7199r 71Y At A7 AP Al, /NYr /dl /7 /r "or 1171. bow m.00 r 1 .a� /r eel A'OO" AVM / 'U11.fi707 'J fO e' �f 1 CS • .e rYfr r Id G10 TOP /x e7 f /A/ /f// it /1•0•11 l o AEA!• /.VE /100 1' �NY11.f0 1• ' ti atrrof "s' _ 1111? iOO / CM Ot7AK di .. 1 N. lea !A!Il - ` \ MAC Igill era- wiz / ava/eat 1111E00 /1t i me .we emir µ C?CNGIJ /Y '1/ M 1I / I !MY 4900 f 1 jimang A NAV* DAIIMENT ROOlf 1 111 /Y d'b nrez 1•(70 Mt am AT' 4W 11/0. e' S. 84th S1. Ca '9 Woo 'zoo e" :. LAVE OP N5IrTATKlN CQ '/O /Y/Y I 70/ /41.27 /Alf 14.CO•G" • 01 011V GREEN ■9/1"'R ACM Or lAS 41MT CO/V°1 401NS /N r • I( /1Y•NO .1R M w1Ty WC/44W *VI Al 4 IO/►YO eY "WAVOYAS /N70 /W1 4f1CN/. /i' f ,04,1. /0 1/00 Y/r /IAAo 1Y1M. &11M MAY 400 A1.4W/1.11.V4ZV 401 111 AMC aft 7//1 NA! AfCM'ltj ?1T Af4Y fe• LEGEND — /4f5' LVlY C /N1 PITYVVA77 CcYf•A' -N- 1r.UT /.Ml COYVIOd?J — ' 4Q O' WAY L/A7J .0YYZW.41Y NJGy AAleA' l/Nf. NAF4C CO 4'•4M9! new LGYA110 +—+- 1Qsf a 11 /mAtt PAIVAGA/l //i e.YCOVTO!/AV NA/1.6V AlPiAICAP &OM /116111,7149T ROO" At41N1 • 1..AIG1 al' iA>t /1NT/!A IT /r•lvxot RIP afratrc ■ 1 KEGEL & ASSOCIATES INC. kni LAND PLANNING ENGINEERING & SURVEYING 9000 EVERGREEN WAY EVERETT.WA. 91104 REVENUE OFFICE 12160N.E.Rt11STREE T i 102 101LE VUE. W A. 9800S P. (2061 491.1115 M.M.. 111 0.11 4111 114.• /1 /202. CMICuO .. O•l 1,11011LC184111.4 t* MX STORM WATER DRAINAGE AND GRADING PLAN .. For the Tukwila Hotel SHEET 3 OF 4 FTIE NO. 28243 28 29 impacts Project development will necessitate floodproofing the hotel. The proposed development shows a dike along the southern lot boundary and grades around the hotel between 28 and 30 feet in elevation. Mfittga1tng Measures None. tlnavotdabte Apturmg Impacts None. 30 2. AIR a. Li i=±2 mafie Extsttng Condttfons The site is located in the Green River valley and has a typical Northwest Pacific Coast marine climate. during the fall and winter, prevailing winds are from the south and southwest, and during the late spring and summer from the north and northwest. Low level temperature inversions may occur in the Valley which, coupled with low wind speed, can result in the trapping of pollutants. This condition is most prevalent during the winter months. The Washington State Department of Ecology (DOE) has been designated as the responsible agency to obtain statewide a i r quality monitoring data needed to determine the status of compliance with the National Ambient Air Quality Standards. DOE's monitoring sites are located where worst air quality conditions are expected to exist. b. ii Oualto 1) Ex rsttng Cond illons Particulates are minute particles of matter (often referred to as "dust ") suspended in the atmosphere. The particles may be toxic or irritating to lung tissue. Particulates represent the visible component of air pollution locally, often seen as a "haze" during periods of air stagnation. Prevailing winds can play a role in distributing particu- lates from high concentration areas in central Seattle and Tacoma to the general vicinity within which the project site is located. Data accumulated by the Puget Sound A i r Pollution Control Agency (PSAPCA) indicates that the con- centration of suspended particulates in the Tukwila area has generally increased with increased urbanization of the Valley. The following table summarizes particulate data collected at a number of air monitoring stations in the general vicinity: Location 31 TABLE 1 Subp tided Parttcvtate earrcerrt-rattons Imkxtim )�Cea tnniuml eeometrfic an micrograms per cubic meter Distance Wash. from site State (mi) 1981* 1980 1979 1978 1977 1976 1975 Std. Renton Municipal Building 2.50 -- 53 59 55 51 50 37 .60 Southcenter .38 62* 48 50 46 48 45 34 60 12026 42nd Ave S 2.87 75* 57 58 53 52 49 37 60 (King County) S 2nd St & Lake Ave S 2.00 59* 53 59 55* -- -- 60 (Renton) (Source: Puget Sound Air Pollution Control Agency, Air Pollution Control Agency, All- Ouattty Data Summary--1977, 1978, 1979, 1980, 1981, Quarterly Air Monitoring Data Summary; Department of Ecology, State of Washington, June 1981). *Based on less than 12 months data. 2) The Table indicates the particulate levels have exceeded the Washington State Ambient Air Quality Standards. Based on the proximity of the site to the monitoring stations, it is expected that the air quality conditions are most simi- lar to those recorded at the Southcenter monitoring site. Ext5 i•nat Condtttons Carbon monoxide (CO) is a by- product of internal combustion and accumulates in areas of heavy, slowly moving traffic. CO can reduce the oxygen carrying capacity of blood, re- sulting in drowsiness and loss of vigor. Levels of CO vary by location more readily than particulates, therefore, it is difficult to interpolate accurate readings to unmoni- tored sites. In addition to carbon monoxide, automobiles emit two other chemicals, hydrocarbons, and nitrogen oxides, which react 32 in the presence of sunlight to produce ozone. This reac- tion occurs over a period of time, therefore, ozone concen- trations are highest near major urban areas. Table 2 outlines the three automobile generated pollutants as measured at a monitoring station nearest the site by the State Department of Transportation. TABLE 2 Araimmatim t d P, F I utant bevel's + .11L find Location (# on map) Nitrogen Hydro Dtoxtde Distance Carton Monoxide Carbons Study From Site Period 1 Hour 8 Hour 6 -9 AM Period (Miles) (Mo.,Yr.) Max. Max. Avg. Avg. Puget Power Transformer Yd (Renton) 2.33 6 -7, 1977 3.2 3 -4, 1977 4.2 10- 11,1976 8.1 6 -7, 1976 2.2 2.0 3.3 6.6 1.3 0.37 0.28 0.02 0.01 0.04 State Ambient 35.0 9.0 0.24 0.05/ Air Quality Annual Standard Average (Source: Washington State Department of Transportation 1977 Monitoring) 3) The CO levels monitored were within the State standards. Although those levels were measured at a monitoring station closest the project site, and under traffic conditions roughly similar to those near the site, they are not neces- sarily representative of current CO levels there. The hydrocarbons were, as shown, at levels above the State three hour average during both times measured between 6 and 9 AM. Ex:tattoo Condition Sulfur dioxide (SO 2 ) pollution is produced through the burning of fossil fuels and is associated with a variety of respiratory ailments. The nearest station monitoring sul- fur dioxide is located at the Duwamish Pump Station, 4500 East Marginal Way, Seattle, approximately 8 miles from the site. 33 The sulfur dioxide levels measured (for 1980) are well below Washington State standards. According to Stuart Clark of DOE, sulfur dioxide is not anticipated to be a problem in Tukwila. Levels there should be equal or better than those recorded at the Duwamish Pump Station. Sulfur dioxide levels are typically high near pulp mills, or smelters; automobiles emit very little sulfur dioxide and are not considered as a source by the Department of Ecology. (Telephone conversation with Stuart Clark, De- partment of Ecology, March 2, 1981.) tmpacts 1. Short -term generation of particulates will occur as construction commences. Dust particles would be raised by earthmoving activities. Suspended particulate con- centrations which already exceed Washington State stan- dards will further increase due to project development. However, air quality impacts are not site specific and would occur regardless of project site location. 2. Noxious odors would be emitted by diesel powered ve- hicles and from asphalt paving operations. 3. Some Tong -term increases in motor vehicle generated pollutants will occur due to the traffic generated by the proposed projects. Impacts would be most severe at identified points of congestion. Higher pollutant concentrations could cause air quality standard viola- tions to occur or persist longer than if no development were constructed. 4. Based on the "Simplified Analysis Technique for Estab- lishing Carbon Monoxide Concentrations Near Highway Facilities," the maximum levels of carbon monoxide during the peak traffic movement hour created solely by the proposed project will add approximately 1.1 ppm of carbon monoxide to the existing levels. Levels will decrease with wind speeds in excess of 2 mph and with distance from Southcenter. Cumulatively, carbon monox- ide levels will be significantly less than the 1 hour maximum standard of 35 ppm. Furthermore, as more stringent federal motor vehicle emission controls take effect, there could be an overall decl ine in veh i c l e- related pollutants. 5. Increase in violation of Washington State standards for levels of hydrocarbons will occur due to the cumulative effects of this and other projects which generate auto- mobile traffic. However, air quality impacts are not localized and would occur regardless of project site location. 34 Mfttgattng Measures 1. Low - emission construction equipment could be used when- ever feasible. 2. Measures to control construction dust such as: water- ing, cleaning and sweeping of streets at the end of hauling activities could be performed by the contractor. 3. Unnecessary motor vehicle engine idling during con- struction could be eliminated; engines could be shut off except when moving vehicles: 4. See Public Transportation - Impacts relating to "Traffic," page 65. Unavo-idab to Adverse tmpacts 1. Increased air pollution from automobile emissions will contribute to hydrocarbon levels which already exceed Washington State Standards. 2. Increased particulate levels, which already exceed Washington State Standards, due to construction ac- tivity and additional traffic volumes. b. Odor t x tsttng Cond i-ttorrs The site is currently devoid of any discernible odors, except for potential occasional odors attributable to sheep grazing on site and north of the site, and odors emanating from the adja- cent river bed during periods of low stage. tmpacts 1. The hotel restaurant exhaust fumes may contribute mar- ginally to odors perceived on the site. 2. Automob i le exhaust fumes w i l l be perceived along the en- trance driveway and parking areas. 3. Over the short term, significant odors will be attributable to construction vehicles, dust, and asphalt paving during the construction phase. Mtttgattng Measures None. Unavotdabte Adverse fnvtronmental impacts Short -term odors during construction. 35 3. WATER a. IML±AQ2 NA±ME gt0MdftbU±LUMfta Extsthng Condlttons The subject property is adjacent to the Green River. Man -made dikes protect the site and general vicinity from flooding from the Green River. However, due to the dikes, internal drainage is restricted from flowing into the river with resultant pon- ding during heavy rains. The level of the Green River is regulated by the Howard Hanson Dam, approximately 35 miles upstream from the project site. The flood level of the river is thus dictated by the maximum discharge of the dam. The maximum flood stage of the river at the site has been determined to be at elevation 25.8 feet. The major portion of the site lies within this flood plain. The site lies within the Green River flood control zone. A permit for any development within this zone must be obtained from the King County Hydraulics Division, acting as the dele- gated authority for the State of Washington. The subject site is located in an area designated "floodway fringe" where new development is only allowed when the King County Hydraulics Division determines the development has adequate floodproofing for a 100 year storm. I n accordance with the direction of the Tukwila Public Works Department, storm drainage runoff will be filtered and chan- neled into the Green River. The present policy is to move surface water runoff, from properties adjacent to the river, into the river as quickly as possible for the purpose of drain- ing those lands before the river reaches its flood capacity of 12,000 cfs (controlled by Howard Hanson Dam). tmpacts I n conformance with the State Flood Control Permit require- ments, fill material will be utilized to bring building eleva- tions above 100 year flood levels. A substantial increase in surface water runoff volumes would occur due to the creation of paved areas over approximately 82 percent of the site. This surface water will be collected in a storm drainage system and emptied into the Green River at the same rate as presently exists in its undeveloped state. Since the site has previously been diked, surface water was prevented from draining into the River, increasing potential of flooding. The proposed development will decrease this poten- tial by pumping surface drainage water into the river as quick- ly as possible. Although this drainage system will be designed in accordance with City and County regulations, the system could contribute marginally to peak river flows due to the runoff from impervious surfaces. Although the level of the tee •..? /r/V s"- 70 AIM /IAA •10. I ea '1 ryfri 7 Ilia NV /sir •1 ea pry z-A- A' a" ra• mit alto .WY /3/7 /8 11, N se0-9. 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STORM WATER DRAINAGE AND GRADING PLAN For the Tukwila Hotel SHEET 3 OF 4 FILL NO. 28248 36 37 river is controlled by the Howard Hanson Dam, minor uncontrol- lable fluctuations in river flow could contribute to minor streambank erosion downstream from the system outfall. The potential also exists for minor uncontrollable erosion of surficial streambank soils into the river during construction and landscaping. Mtttgat i-rrg Measures 1. Fill material will be required to floodproof building sites which will prevent on —site flooding. 2. 2. A stormwater detention system designed for a 10 year storm capable of detaining 8,252 cubic feet of water is proposed to be installed. Stormw ater will be stored in oversized pipes under the parking lot and detention areas (depres- sions) on the parking lot. The gravity flow system is designed to discharge stormwater into the Green River at the same rate as the existing discharge rate. The City of Tukwila shall approve stormwater drainage plans prior to issuance of the building permit. 3. A temporary storm management system and the erosion control measures discussed under the "Soils" section, page 25 will be employed during construction. 4. Where possible, natural vegetation for silt control shall be maintained. 5. Temporary siltation and detention ponds shall be constructed by placing straw bales across swales. 6. All temporary siltation ponds shall be maintained in a satisfactory condition until such time as cleaning and /or construction is completed and the permanent drainage facil- ities are operational. 7. Rip —rap base (both sides) of bales sha l I be positioned as required for erosion control. 8. Cleaning of streets and parking areas shall be undertaken whenever necessary. 9. Frequent maintenance of the stormwater system shall be provided. tinavofdab 1 e Adverse Impacts 1. A decrease in the quality of the runoff from the site. 2. A potential increase in peak runoff from the site. 38 b. 5113dg= tAlegm Y Ex-i-sttnq Condtttons In the past, surface water has drained into the groundwater. No pollutants currently impact surface water quality on -site. "M►Pacts Through contour grading, filling, and paving, on -site storm water will flow into a closed storm water system. Ten catch basins w i l l be located on the site to collect water. Precast oil/water separator tanks, which have been accepted for use adjacent to streams by the Department of Ecology, will be included in the system. The o f I /water separator tanks w i l l have a built-in baffling system which not only separates out the oils, but also dissipates the velocity of storm water flow to further settle out sands and silts before discharge into the river. Mfitfigatr nq Measures 1. Grading operations during construction shall be limited to periods of normally dry weather. 2. Oil/water separators w i l l be uti l ized to remove petroleum products from catch basins and screens will be included in the storm water system to collect litter and debris. The hotel will shade the parking lot, which will help reduce the runoff water temperature. Cleaning of parking areas shall be undertaken whenever necessary. 3. The riverbank will be rip -raped around the stormwater outfall to prevent erosion and sedimentation. 4. All roof drains will be directed to the catch basins. Urravotdalrte Adverse tmpacts Urban pollutant levels w i l l increase in storm water runoff, particularly during construction. c. Groundwater euarrhttv/@oattty Ercfsti ng Condrttons The groundwater within the property is subject to a periodic high water table, however, ponding has not been observed on this site. Groundwater levels observed during drilling by Shannon and Wilson, Inc., Geotechn i ca l Consultants, were at elevation 15 feet. Due to the proximity of the Green River to the site, and the pervious nature of the near surface soils, 39 the groundwater levels are approximately the same as the sur- face water level of the river. impacts Infiltration of precipitation into groundwaters through the surface soils will be reduced, becoming mainly surface runoff, which will be directed to the Green River. The addition of automobile traffic will replace nutrients from vegetation and rainwater with pollutants from paved surfaces, petroleum products, sediments, and heavy metal traces from automobiles. I t i s expected that groundwater l e v e l s w i l l not change as a result of development due to the proximity of the River. Mtttgatfng Measures None. Unavotdabte Adverse tmpacts Potential decrease in groundwater quality. 40 4. FLORA €xfsttng Bond i-ttons a. Emmtmr SZL Dimanotta n± Ummtmanituum load= The site of the proposed project is located within the Green River Valley, an area which has undergone considerable altera- tion in vegetation types due to urbanization and agricultural activities. The original habitat of the Green River valley consisted of mixed coniferous and deciduous, and riparian forest (in the lowland areas adjacent stream corridors). Pre- sent day forest stands consist largely of red alder, and iso- lated stands of doug l as fir, western red cedar, and hemlock. Pioneer shrub species, grasses, agricultural, and grazing crops are common in the predominately open areas. The vegetation at the project site is representative of other lowland types in the valley which are subject to periodic high water table conditions. With the exception of a small scatter- ing of cottonwoods, maples, berries, and shrub species, the site consists primarily of grasses which have been introduced because of their suitability for grazing purposes. Many "weed" species are represented as well. The portions of the site presently utilized for grazing are dominated by bluegrass and fescue, with clover, buttercup, plantain, and other weeds subdominant. Only those plants in- edible to sheep, or able to withstand heavy grazing pressure have been able to reach maturity, including barley, mullein, and sourdock. A list of located and probable plant species at the site of the proposal is presented in Appendix E. The small number of deciduous trees which are located on the project site include two 80 foot big leaf maples, and one 120 foot black cottonwood. The trees are in very poor condition, as evidenced by spotty foliage and weak and broken limbs. The landscape architect has recommended removal of the trees because of their poor condition. The levee along the southern boundary of the site is covered by a mix of cottonwoods, Oregon ash, and pacific willow. All of the trees on the site are representative of species tolerant of periodic standing water, or high water table conditions. No rare or endangered species were discovered on the site. cc EXISTING COTTONW TO BE REMOVED EXISTING MAPLE TO BE REMOVED EXISTING MAPLE TO BE REMOVED TREES TO REMAIN WEST VALLEY HIGHWAY TREE REMOVAL PLAN aJENSEN KRAUSE S. SCHOENLEBER ARCHITECTS & PLANNERS PC AIA I O VW WS /1/10111111, 11.011117taND 0•6• WP•0111 MOs •w MIN TUKWILA HOTEL TUKWILA, WASHINGTON eihley Landscape Architecture, Panning pc 12840 Northwest Comil1 Road • Portland. Orson 97229 42 b• Ag-tcufiturat Crops-: The Green River Valley has developed as the primary agriculture region in the greater Seattle area. The general v i c i n i t y of the project site is in various stages of agricultural and post agricultural activities. Much of the land in the area has been previously farmed or grazed and has undergone urbanization through construction of manufacturing parks, retail stores, roads, and residences. Sheep currently graze just north of and on the project site, where pasture makes up the majority of the land area. The fine sand and silty soils of the site, and within the valley are considered good for crop production, however, this area primarily supports pastures and hay l ands. Portions of the site which are not heavily grazed exhibit a succession of growth to pioneer brush and weed species. These small areas could be utilized for pasture, if replanted and continually grazed. tmpacts Most vegetation within the property lines of the subject site will be replaced. Approximately 18 percent of the site will be landscaped with ornamental vegetation. Reconstruction of the dikes and construction of the fire access road will disturb some of the existing vegetation along the river. attiZsittlig Measures 1. A landscape plan has been prepared to assure good design practice and consistency throughout the site. 2. All vegetation along the riverbank, undisturbed by recon- struction of the dike and the fire access road, will be left undisturbed and maintained. All trees on the riverbank will be left undisturbed. (See Tree Removal Plan, page 41) Indigenous vegetation will be planted and maintained inside the dike so that the entire length of the hotel's river frontage is landscaped with natural vegetation. 3. In . addition to the 39,315 square feet of planned landscaped area on site, 32,800 square feet off -site landscaping is planned. These areas include the riverside area and along West Valley Road. tinavotdabfe Adverse impacts Reduction of most of the natural vegetation on the site. 43 5. FAUNA Extsti-nq Fondfi Eons Number cgr Dtversfty j Specfes /tintque Spec i es /Terrestrrat Wttd-htte : The wildlife habitats provided by the Green River Valley have been altered and reduced through the clearing of the original coniferous and riparion forests and the drainage of the lowlands. The vegetative communities which previously supported numerous terrestrial 'wildlife types varied from wetland and marsh, to established douglas fir and early successional deciduous and riparion types. Most of the forest was cleared for agricultural purposes. Most of the wetlands of the valley were eliminated by drainage projects associated first with farming activities and later with industrial developments. The majority of the project site consists of pasture. Due to heavy grazing, the herbaceous vegetation on the project site does not in itself support a diversity of wildlife comparable to the brush or tree habitats on the site, (which provide ade- quate cover and food). Wildlife species likely to occur at the site, as well as those common to the area, are listed in Appen- dix F. Mammals located on the project site include a significant number of moles (indicative of relatively productive topsoil) and other small common mammals, including rabbits, mice, and raccoons. Migratory waterfowl have been observed in the fresh water and shore habitats provided by the Green River bordering the project site and by an oxbow pond north of the project site. The number and variety of birds which can be found at the site will fluctuate considerably by season. Urbanization and in- creases in traffic levels have reduced the presence of certain birds not tolerant of urban conditions. The project site is located directly adjacent to the Green River, which receives the combined runoff of 211 creeks and tributaries of the Green River watershed. The fish habitat associated with the Green River has been severely impacted by removal of riparion vegetation, straightening of channels, and septic tank usage. In spite of the fact that the water quality and the overall environment for fish production have been and are being degraded, the fisheries of the Green River have remained an important intrinsic and economic resource. The planting of juvenile hatchery - reared salmon contributes the majority of anadromous fish which populate the Green River. 44 The Washington State Department of Fisheries operates a fish hatchery located on the Soos Creek tributary. Freshwater angling is permitted in the lower Green - Duwamish Rivers. The average annual salmon catch, according to surveys conducted between 1964 and 1966, was 270. More than 655 fish were reported caught in 1966. A 1966 survey showed that 111,450 angler days produced 22,550 steelhead from the Green River drainage. Elliot Bay, which supports over 60,000 angler days annually, i s a favorite salmon sport - fishing area asso- ciated with the Green River runs. tadmaiteigt gD Ttrreatened Svecfes: The ranges of four bird species listed as endangered or threat- ened are known to include the Green River area. These species include the Aleutian Canada goose, the American and arctic peregrine falcons and the northern bald eagle. No sightings of these species are known to have occurred in the general vicini- ty of the project. acts Development of the site w i l l cause an intrusion of human acti- vity and remove a l l of the grassland used by small mammals, birds, and domestic grazing animals. Resident species will be driven off, displaced and, where alternative habitat is already occupied, their numbers will be reduced in competition for the limited habitat. Migratory and predatory species using the site as part of their feeding or resting area may be wholly or partially displaced, especially species not tolerant of human presence. Degradation of water quality in the Green River could have an adverse effect upon the fish population. Turbidity and high water temperature could particularly affect the health of fish. Mtfl ng Measures 1. An erosion control plan shall be followed during construc- tion. 2. Natural vegetation shall be maintained along the stream bank. 3. Fill and grading operations will be limited to periods of normally dry weather. 4. Silt traps and oil /water separators shall be maintained and cleaned by the project owner whenever necessary. 5. The hotel, and proposed landscaping, will shade the parking lot, thereby possibly reducing the stormwater runoff tem- perature. 45 Unavotdabte Adverse impacts A reduction in the number of spec i es on the site will result from project development. 46 6. NOISE Existi-ng Land i t i ons The predominant source of noise affecting the site and adjacent areas is traffic on the West Valley Highway. Noise monitorings were undertaken for a similar site on Interurban Avenue last summer for the Expanded Environmental Checklist for Best Way Motor Freight Terminal Development, July, 1980. Due to simi- larities in sites, traffic patterns and topography, it is expected the noise levels of the suject site are similar to those of the site monitored. The sound levels have been com- puted for L10, L50, and L90 percentage levels. The L90 statis- tic indicates the sound level exceeded 90% of the time (the low level); the L0 indicates the sound level exceeded 50% of the time (the median level); and the L1 indicates the sound level exceeded 10% of the time (the high 4evel). Sound level measurements were taken during the morning rush hour to represent a worst case analysis. Measurements were also taken in the evening to represent the hours when there is the least amount of noise. The L20, L50, and L90 levels for the site are as follows: TABLE 3 SUMMARY QE RESULTS Qf SOUND MEASUREMENTS Location Sound Surces Time Date High LAvvgLLow dBA dBA dBA Intersection of Interurban S 143rd St and traffic, mower, 7:55AM 7/2/80 68 61 58 Maule Ave (100') aircraft n n Interurban traffic, Oak 12:40PM 7/2/80 61 56 53 Harbor Trucks Interurban traffic, air- 8:10PM 7/2/80 61 56 51 craft, train General Radio 1565 -D sound level meter with attached windscreen was used for monitorings. The sound level meter was calibrated with General Radio 1987 calibrator before and after each set of measurements. There are a number of standards for noise assessment which can be used for comparison purposes. The Federal Highway Admini- stration recommends a design noise level (L 10) of 70 dBA for 47 outdoor residential areas. The U.S. Environmental Protection Agency (EPA) Region X Guidelines recommend that for adequate speech communication, the median noise level (L50) should not exceed 55 dBA. The EPA does not have regulatory standards. The noise level measurements taken at the Maule Avenue site was below the levels recommended by the Federal Highway Admini- stration. EPA recommended levels were slightly exceeded. The aforementioned levels pertain to residential areas. Single family residences lie to the north and south of the site. However, the vicinity is zoned for commercial use and commer- cial uses may replace the single family residences in the foreseeable future. -impacts Ambient noise levels will be increased as a result of short — term construction activities and the additional traffic generated. Construction equipment can generate noise peaks in the range of 85 to 95 dBA. The following tables present maximum anticipated noise levels from construction equipment, and immediate abate- ment potential of construction equipment noise level. 48 Table 4 ANTICIPATED MAXIMUM NOISE LEVELS FROM CONSTRUCTION EQUIPMENT Phase and Duration Equipment Used Noise (dBA) Maximum at 50 feet* At 100 Feet* Phase I: Clearing and Demolition Phase II: Excavation Phase III: Foundation Phase IV: Frame, Roof and Skin Phase V: Finishing Dump Truck Bulldozer Vibrating Grader Backhoe Bulldozer Dump Truck Concrete Truck Dump Truck Saw Concrete Truck Generator Concrete Vibrator Crane Dump Truck Air Compressor Welding Generator Concrete Truck Concrete Pump Dump Truck Air Compressor Saw Jackhammer 80 -90 80 76 85 85 80 91 85 91 78 85 78 76 83 91 81 78 85 82 91 81 78 88 85 74 70 79 79 74 85 79 85 72 79 72 70 78 85 75 72 79 76 85 75 72 82 *(Source: Dash Point Heights DEIS, King County) A 49 Table 5 IMMEDIATE ABATEMENT POTENTIAL OF CONSTRUCTION EQUIPMENT NOISE LEVEL IN dBA AT 50 FEET Equipment Important With Feasible Noise Present Noise Contrail Sources2 Usage3 Earthmoving front loader 79 75 E C F I H 40 backhoes 85 75 E C F I H 16 dozers 80 75 E C F I H 16 tractors 80 75 E C F I W 40 scrapers 88 80 E C F I W 40 graders 85 75 E C F I W 8 truck 91 75 ECFIT 40 paver 89 80 E D F I 10 Materials Handling concrete mixer 85 75 E C F W T 40 concrete pump 82 75 E C H 40 crane 83 75 E C F I T 16 derrick 88 75 E CFI T 16 Stationary pumps 76 75 E C 100 generators 78 75 E C 100 compressors 81 75 E C H I 100 Impact pile drivers 101 95 W P E 4 jack hammers 88 75 P W E C 10 rock drills 98 80 W E P 4 pneumatic tools 86 80 P W E C 16 Other saws 78 75 W A vibrator 76 75 W E C 40 1Estimated levels obtainable by selecting quieter procedures or machine and implementing noise control features requiring no major redesign or extreme cost. 2In order of importance: T Power Transmission System, Gearing C Engine Casing E Engine Exhaust P Pneumatic Exhaust F Cooling Fan W Tool -Work Interaction H Hydraulics I Engine Intake 3Percentage of t? *te equipment is operating at noisiest mode in most used phase on site, (Sorrce: Dash Point IIeights DEIS, King County) 50 Noise impacts due to additional traffic generated wi I I also occur, although it appears the impacts will not be significant. By way of comparison, the following table gives levels of common noise - sources: Table 6 dBA LEVELS OF COMMON NOISE SOURCES Source of Noise Noise Level dBA Jet. takeoff 120 (200 feet) Auto horn 115 (3 feet) Riveting machine 110 Jet takeoff 105 (2,000 feet) Garbage truck 100 Heavy truck 90 (50 feet) Pneumatic drill 85 (50 feet) Alarm clock 80 Freight train 75 (50 feet) Freeway traffic 70 (50 feet) Air - conditioning unit 60 (20 feet) Light auto traffic . • . 50 (100. feet) Living room 45 Bedroom 40 Library 35 (Source: Dash Point Heights DEIS, K.C.) 51 Given a dBA computation of loudness for annoyance level, the loudness or annoyance doubles for each 10 dBA increment in level. The traffic report (Appendix A) estimates the volume of traffic on West Valley Highway to be approximately 20,000 to 23,000 vehicles per day for two -way traffic. The report also esti- mates maximum "worst case" vehicle trips to and from the pro- posed project to be approximately 2,880 vehicles per day. This represents an increase of approximately 14 %. This addition of vehicular traffic will not significantly in- crease the decibel level of noise. A property of the decibel scale is that the sound pressure levels of two separate sounds which have different dBA levels, the lower level adds less to the higher as this difference increases. For example, adding a 60 dBA sound to a 70 dBA sound only increases the total sound pressure level less than 1/2 dBA. Mitigating Measures Electric equipment should be used in preference to gas or diesel powered, when available. Hydraulic or electric impact tools should be used when available, in preference to pneumatic tools, which require very noisy exhausts and compressors. Unavoidabie Adverse Impacts Increased noise levels over the short -term due to construction activity, and over the long -term due to human activity and increased traffic. 52 7. LIGHT AND GLARE Extsttng Conditions Because the site is presently undeveloped, no light or glare is generated from the site. Impacts The proposed hotel would replace the open field. Light would be emitted from hotel rooms, lobby, restaurant banquet rooms, parking lot lighting, and automobiles. Mfittgathnq Measures Parking lot lighting could be limited so that no direct light spills off -site. Unavotdabte Adverse tmpacts Additional light and glare will be emitted from the site to surrounding properties. 53 8. LAND USE Existing Condittions The site is presently undeveloped and used on occasion for sheep grazing. The surrounding area is a mixture of vacant lands, agricultural lands, single family, commercial and office uses. The subject site and single family residence north and adjacent to the site are separated from other land uses by the Green River to the west and south, West Valley Highway to the east and 1 -405 to the north. Land uses along West Valley Highway, though well established, appear to be transitional commercial uses which typify suburban highways (ie. restau- rants, car dealership, single family homes, insurance company, gas station, and agricultural lands). A predominant land use across the highway from the site is Longacres Race Track. Associated land uses such as pasture, and auction barn, cumula- tively define a large portion of the vicinity. Across from the river, land uses are predominantly office and, to a lesser degree, I i ght warehouse land uses. Single family homes are situated on the lots immediately north and south of the site. Impacts The project will alter the current character of the site in that it will commit 5.47 acres of undeveloped land to hotel use. The proposed development will not only change the land use within the project boundaries, but could have an indirect impact on other land uses in the general site vicinity as a result of increasing property values of surrounding property and providing the potential for associated land uses to the hotel. The proposed action precludes alternative land uses for the site during the life of the buildings. Mit gattng Measures None. Unavotdatrte Adverse Impacts 1. Loss of potential agricultural lands. 2. Preclusion of alternative land uses for the site during the life of the buildings. 54 -impacts The project will alter the current character of the site.in that it will commit 5.47 acres of undeveloped land to hotel use. The proposed development will not only change the land use within the project boundaries, but could have an indirect impact on other land uses in the general site vicinity as a result of increasing property values of surrounding property and providing the potential for associated land uses to the hotel. The proposed action precludes alternative land uses for the site during the life of the buildings. Mfiti- gattng Measures None. Urravotdafrte Adverse Impacts 1. Loss of potential agricultural lands. 2. Preclusion of alternative land uses for the site during the life of the buildings. 55. 9. NATURAL RESOURCES Extsti ng Cond tttons As mentioned under Flora, "Agricultural Crops" (page 42), the site is primarily open pasture suitable for grazing and, poten- tially, cultivation of certain row crops and berries. This agricultural and open space resource could be considered to be ,valuable locally. The site is not known for any valuable mineral resources, or as a critical or unique ecosystem. con- sumption of natural resources, such as energy required to construct and operate the complex, is discussed in separate sections on the respective resources. Impacts The potential agricultural resource at the site and the open space amenity represented by the site will be eliminated. Construction of the building will consume natural resources, including energy and raw materials used in concrete, steel, aluminum, glass, copper, and other materials, of varying scar- city. The building may be demolished at the end of its econo- mic life. In the foreseeable future, when materials are scar- cer, demolition of the building may take place. The energy used for demolition will not be recoverable. The materials will be largely nonsalvageable, though some copper wiring and piping may be salvageable from the building's utility cores, along with windows, wood and some nonstructural parts of the interior. Mtttgatfng Measures None. tfnavatdabi-e Adverse Impacts 1. Consumption of building materials and energy 2. Conversion of natural open space to commercial use 56 B. EtEMENTS QE HUMAN EMBIONMENT 1. POPULATION Extsftng Corrditfons The population in the City of Tukwila has not changed signifi- cantly in the past 10 years. The U.S. Census of Population and Housing shows a 2 percent increase from 1970 to 1980, while King County experienced a 9.5 percent increase over the same period of time.) The Puget Sound Council of Governments (PSCOG) made the follow- ing projections of AAM Districts 3650 and 3800, which include large portions of Tukwila and Renton: TABLE 7 ;$ ____ ECTt8NS.2 Percent Percent AAM District 1980 1990 Change 2000 Change 3650 3800 TOTAL 1 2 4555 5474 20.2 5989 9.4 410 1248 104.4 1566 25.5 4965 6722 35.4 7555 12.4 1980 Census of Population and Housing Final Population and Housing Unit Counts Puget Sound Council of Governments Activity Allocation Model 1979 The proposed hotel will not produce a significant increase in the area's population. The expected hotel employment of 175 would prompt some non -local employees to relocate near the site. I f so, it could create a minimal increase in the local population. Mtti- gating Measures None. Unavo-idat,te Adverse tmpacts None. 57 2. HOUSING Extsti nq Cond i.t ions Housing in the City of Tukwila has increased 15.8 percent between 197Q and 1980 compared to 23.7 percent experienced in King C?unty. The 1980 Tukwila housing count was 1938 dwelling units. 11980 Census of Population and Housing Advanced Report - March 1981. Housing forecasts computed by the Puget Sound Council of Gov- ernments for the general vicinity are as follows: TABLE 8 tietStNO GROWTH Percent Percent Location 1980 1990 Change 2000 Change General Vicinity 2038 2631 29.1 2987 13.5 Vacancy rate for the subject area was approximately 1.6 percent in 1979. Based on projected housing and population growth for this area. Vacancy rates are expected to increase only slightly. impacts Project development will not significantly increase housing demand in the Tukwila area. It is expected that some of the employees will come from the area's unemployed ranks. Based on the City's ratio of 9.89 employees per dwelling unit, an increase of 175 employees due to hotel employment would indicate an increase in housing demand by approximatly 18 housing units. This represents approximately .9 percent of the existing housing stock. M'rttgattng Measures None. Unavo'rdabte Adverse Impacts None. 58 3. EMPLOYMENT Existing Conditions Total employment has increased significantly in the past few years, already exceeding King County's 1990 employment projection figures. The rate of growth is expected to continue at a lesser rate in the near future with the greatest growth occurring in retail and commercial services. Land Use Table 9 EMPLOYMENT 1978 1979 1980 % Change Commercial Services 3,308 4,770 6,816 106.0 Distribution - Retail 4,833 4,952 5,716 18.3 Distribution - Wholesale 3,658 4,356 4,388 19.9 Processing 934 1,878 1,825 101.0 Public Service Facilities 166 205 252 51.8 Communications /Utilities 33 53 177 436.3 TOTAL 12,932 16,214 19,174 48.3 Source: City of Tukwila, 1980 Employment Survey, City of Tukwila Planning Department, 1981 Employment forecasts for the general vicinity are as follows: Table 10 enal323Mit General Commercial Communities Government & Total Vicinity Retail Service Manufacturing & Utilities Education Employment 1980 4,936 4,029 1990 6,177 6,367 2000 6,721 6,606 1,388 4,699 303 15,355 1,574 5,460 427 20,005 1,776 5,246 527 20,876 Source: Puget Sound Council of Governments Main Model Allocation - 1979 tmpacts (short-termY Project development will require approximately 35 construction workers over a ten month period of time. Construction is scheduled to begin in late 1982 or early 1983. 59 Impacts (long-term) The project, when fully developed, is estimated to provide full time employment for approximately 175 distributed over three shifts. (Telephone conversation with Jerry Baysinger, AIA of Jensen, Krause, and Schoenleber Architects on December 14, 1981.) This would make the subject hotel the 12th largest employer in the City and increase Tukwila's employment base by 0.9%. Thus the project will require a demand for approximately 175 skilled and semi - skilled workers. Some of these positions can be expected to be filled by the unemployed Tukwila work force. Mi-tigattng Measures None. Unavoidab to Adverse tmp-acts None. 60 4. TRANSPORTATION (See also detailed consultants report, Appendix A a. Veh-i-cutar Transportatl'on Generated Extsting Condtttons The site is served by West Valley Road, a major north -south arterial extending from Grady Way through Auburn. West Valley Road is a 5 lane road (2 lanes in each direction with a center 2 -way left turn lane) except in the-intersection south of the site to Strander Boulevard where the road narrows to 4 lanes. To the north of the 1 -405 interchange, the road intersects with Grady Way, Southcenter Boulevard, and north onto 1 -5. North of Grady Way, the name of the road changes to Interurban Avenue. To the south, Strander Boulevard is one of two major east -west arterials south of the site. Strander Boulevard is 4 lanes wide, but widens to 5 at its intersections with north -south cross streets to permit left turn lanes. Southcenter Boulevard is the primary east -west arterial that lies north of the site. Southcenter Boulevard is a 2 -lane roadway with stabilized gravel shoulders toward its western end as it intersects with Interurban Avenue. Grady Way is also a 2 -lane road north of the site. Traffic signals in the vicinity of the site are located at the following intersections: Interurban Avenue and Southcenter Boulevard, West Valley Road and S.W. Grady Way, West Valley Road and 1 -405 interchange, West Valley Road and Strander Boulevard (see Figure A -6). Where volumes are lighter, STOP sign control is used to control the minor volume side street traffic so the major through volumes can pass uninterrupted. In addition to this permanent traffic control, the Washington State Patrol assigns two to three officers to control traffic between 1 -405 and the main entrance to Longacres Race Track (South 158th Street) during the racing season. ENTRANCO Engineers has prepared a transportation improvement program for the City of Tukwila. This program, combined with the most recent (1982) transportation improvement program, shows a number of major improvements proposed for this area (see Figure A -8). Of top priority is the rebuilding of the Grady Way bridge over the railroad just north of 1 -405. Next is the realignment of Southcenter Boulevard to intersect Grady Way and provide better access into Andover Business Park and Southcenter Regional Shopping Center. Other near term improve- ments include: addition of a right turn lane at the West Valley Road - Strander Boulevard intersection, new channelization and signalization at the Strander Boulevard- Andover Park East intersection, sidewalks and other street improvements are pro- posed along Interurban Avenue. Long term improvements include: 61 widening of Andover Park East and Strander Boulevard East to 5 f u l l lanes. Existing traffic volumes on streets in the area were assembled from State of Washington Department of Transportation records and reflect counts made between 1979 and 1981. These counts were adjusted to reflect 1980 traffic volumes and are displayed in Figure A -10. Immediately adjacent to the site, West Valley Road carries between 20,000 and 23,000 vehicles per day (vpd). The volume is slightly less north of Southcenter Boulevard, approximately 17,500 vpd. Volumes on roads internal to Andover Business Park are approximately 8,000 to 10,000 vpd. Roads surrounding and immediately adjacent to Southcenter Regional Shopping Center range from 14,000 to 19,000 vpd. Longacres Race Track generates a significant increase in traffic volumes during racing season (May through October). Unfortunately, there are no known traffic counts reflecting this special condition. However, discussions with the State Department of Transportation and the Washington State Patrol indicate peak surges in traffic volumes occur between 3:00 and 3:30 PM, and 8:00 and 9:00 PM on weekdays, and 11:00 and 11:30 AM and 6:00 and 7:00 PM on weekends. I n these situations, at least 2 Washington State Patrol officers are used to control traffic at the entrance of South 158th Street. Peak hour traffic volumes generally fall between 4:15 and 5:15 on weekdays, averaging between 10 and 16 percent of the average weekday traffic volumes. The evening peak hour traffic volumes of West Valley Road range between 2300 and 3000 vehicles per hour (vph). Approximately 55 percent of the traffic flow at this time is northbound and 45 percent southbound. Techniques have been developed to determine what these traffic volumes mean in terms of congestion and delay. These techniques have been called Levels of Service (LOS), and combine the influence of various road and traffic volume conditions. These Levels of Service range from LOS A, which is very good, to LOS F, which reflects a traffic flow that has deteriorated to a start — and —stop condition. In urban areas, most traffic engineers design improvements to operate at LOS C, but consider LOS D acceptable during peak periods as long as these conditions do not extend more than one hour within the peak period. An analysis of the major intersections in the vicinity of the site under average weekday peak hour conditions shows that the Strander Boulevard —West Valley Road intersection currently operates at LOS C, while the westbound off —on ramp —West Valley Road intersection operates at LOS D to LOS E. These levels do not reflect the influence of traffic when Longacres is operating. -Based on conversations with the Washington State Department of Transportation and Washington State Patrol, it 62 appears that conditions along West Valley Road between Grady Way and South 158th Street deteriorate to an "at or near capacity" condition just prior to the opening of the track and following its closure. tmpacts Trip generation statistics by the Institute of Transportation Engineers and the Arizona State Department of Transportation shows the average trip generation rates for hotels and motels range between 10.1 and 10.5 daily trips per occupied room. During the weekday evening peak hour when traffic conditions are at their worst, the Tukwila Hotel would be expected to generate between .65 and .73 one -way vehicle trips per occupied unit. These trip generation rates reflect conditions where restaurants, cocktail lounges, meetings in banquet facilities, or convention facilities, and other retail and small shops are included as part of the hotel. When these trip generation rates were applied to the proposed Tukwi la Hotel, they yielded a total daily trip generation of 2,880 one -way trips. During the evening peak hour, the project is expected to generate approximately 190 vehicle trips, with approximately 95 vehicles traveling inbound, and 95 vehicles traveling outbound. These figures assume the hotel is fully occupied on weekdays. During the weekend day, the Tukwila Hotel would be expected to generate between 750 and 1,300 vehicles per day. Further, typical weekend day /evening peak hour traffic volumes are sub- stantially lower than during the weekdays. In the project area, the peak weekend day traffic occurs during the mid- afternoon due to the traffic generated by the retail activity at Southcenter and due to the traffic generated by Longacres during the racing season. It is expected that approximately 55 percent of the daily traffic and 65 percent of the peak hour traffic generated by the proposed Hotel will travel north on West Valley Road. (See Figure A -22). The proposed Hotel is expected to generate approximately a 7 percent increase in the daily travel along West Valley Road. During the peak hour, the volume along West Valley Road north of the site is forecasted to increase to about 125 vehicle trips per hour at evening peak hours, with the volumes being approximately equally split northbound and southbound, repre- senting a 4 to 6 percent increase. To the south, the increase amounts to less than 7 percent on a daily basis (1300 vpd) and less than 3 percent during the peak hour (20 vpd). (See Figure A -19.) In terms of Level of Service (LOS), projected to 1983, intersections in the vicinity of the - project will be impacted as follows: 63 Table 11 LEVEL OF SERVICE SUMMARY Existing Development Development 1 -405 WB ramps /W Valley Hwy D -E E . E 1 -405 EB ramps /W Valley Hwy C D D -E Strander Blvd /W Valley Hwy C -D' D D Longacres (S 158th) /W Valley Hwy* E E E *Represents conditions during the Longacres racing season All other intersections within the surrounding area are not expected to be noticeably impacted by the additional volumes generated by this project. Peak traffic volumes at Longacres do not occur at the same time as the hotel peaks. However, traffic patterns generated by Longacres were examined to determine potential conflicts. It is estimated that between 500 and 750 vehicles per hour use the southbound turn into Longacres during its operation. The pro- posed project is expected to generate between 90 and 110 vpd with inbound and outbound volumes split about equally. The principal conflict appears to be between cars exiting the subject site (eastbound to northbound left turns) and cars making left turns into Longacres. The outbound left -turn vol- ume will amount to about one car per minute. Such a low volume would not cause a noticeable delay to Longacres traffic. Dur- ing the peak times, when traffic control is not provided by the Washington State Patrol, the exiting hotel traffic may not be able to find an acceptable gap in the traffic flow along West Valley Road, and motorists may become frustrated by the delay and travel south (turn right) to Strander Boulevard and make a "U" turn at the signalized intersection. Access to the site will be provided by two exit /entrances off West Valley Road. The first w i l l be opposite 158th and w i l l provide access for both right and left turns in and out. The second access lies approximately 370 feet south of the primary access. Traffic in and out of this entrance will be restricted to right turns only. Traffic entering the site will circulate to the north of the building under a canopy where baggage and passengers will be loaded and unloaded. The aisles for parking will serve as the internal road system. The proposal includes provision of a left -turn lane on West Valley Road at the northerly entrance to the site. A sketch illustrating the design is presented in Figure A -26. Based on an analysis of the daily and peak hour traffic volumes in the vicinity of the northerly entrance, the need for a traffic s i g n a l is not warranted. W h i l e there w i l l be selected times when signal warrant criteria are satisfied (e.g., following Longacres closing), warrants cannot be met for the full 8 -hour 64 period. A traffic signal may, in fact, add to the congestion at the northern entrance, because it could simultaneously re- spond to the peak surges generated by Longacres and maintain coordination with the traffic signals at 1 -405. Mtttgattng Pleasures 1. A traffic signal could be installed, turned to flashing operation and supplemented with Washington State Patrol manual control during the Longacres traffic periods. 2. A left turn lane will be installed at the northernmost entrance. 3. The southernmost entrance will be restricted to right turn only for entering and exiting the site. 4. Metro transit information could be displayed in the lobby of the hotel. Unavotdabl-e Adverse tmpacts Traffic impacts in a worst case analysis will increase due to a total daily trip generation of 2,880 trips and 190 vehicle trips during the evning peak hour. b. fffEtitag Pazfiti•t-i-es fxtsttng Cond1ti-ons The undeveloped site is not currently used for parking. A no parking sign has been posted on the site, presumably to discourage parking by customers of Longacres race track. tmpacts The proposed development will create 509 automobile spaces, 419 of which will be standard size, 83 designated for compact cars, and 7 designed for the handicapped. This complies with the proposed City of Tukwila Parking requirements. Parking for the hotel is intended to be used by customers of the Hotel facilities only. A service court is designed in the back of the hotel which will accomodate truck deliveries. MttFgattng Measures • None. Unavotdabte Adverse tmpacts None. 65 c. iimagEttimaLystml Exrstrnq Cond?ttons The Tukwila site is served by 3 transit routes, including the 154 Seattle- Auburn, and 158/159 Seattle -Kent East Hill route. These 3 routes provide a total of 14 runs during the morning and afternoon peak periods. The fares during the peak hours are 60s/ for one zone and 90i for two zones. Recent counts on these buses show that the majority operate at less than fu l I capacity during the morning and afternoon peak hours in the vicinity of the project. impacts It is expected that an insignificant number of guests will use the bus service. However, the hotel will sponsor a shuttle service to and from the Seattle- Tacoma Airport, which lies approximately 3 miles west of the site. Mtttgatirra Measures None. linavotdabte Averse fmQac s-t None. d. Mliummat and/or C rcutattorr g± f vgam Ar¢ � Ex'rsti-rrg Condtttorrs Although no accurate counts of pedestrians and bicycle volumes in the vicinity are available, observations during various times of the day demonstrate that there is very little activity near the project site. This can be attributed to long walking distances between activity nodes and, most off - street parking appears to be adequate to serve any of the demands by specific businesses. However, during the horse racing season, some spectators park away from the track and walk to avoid parking fees and to avoid evening traffic congestion exiting the race track. The Christensen Trail on the west side of the River is used by both pedestrians and bicyclists. tmnacts I t is unlikely any hotel guests will make trips by bicycle or on foot, However, the proponent may construct a pedestrian bridge from the subject site across the river to the Christen- sen Trail. If this is constructed, it is expected that guests and people coming to the restaurant and lounge would also use 66 this pedestrian bridge to cross the river between the business park and the site, or simply to take a stroll. Should the bridge be constructed, it would then become more feasible to extend the trail along the east side of the river to the north and eventually up to Fort Dent Park. Mtttgatinq Measures None. Unavotdabte Adverse hnpacts None. e. W+ terbvrne. 2Aiil gC Air Tn-dff l c Extstfnq Condtttorrs There are two rail 1 ines which run north -south and which lie east of West Valley Road. Both lines are active and serve a substantial amount of rail travel, including freight service into Andover Business Park off spur lines which are located south of Strander Boulevard. The Green River is categorized as a navigable waterway and can be used by small boats up to its present location, but as a practical matter, it is not considered usable by commercial watercraft. _impacts None. Mtttgattnti Measures None. Unavotdabte Adverse, impacts None. f. Icalitca =ant Ex rsttnq CondUtrorrs Traffic accident statistics were assembled from the records maintained by the Washington State Department of Transportation District 1. These statistics are summarized in Figure 6 in Appendix A. The highest number of average annual accidents occured at Strander Boulevard and West Valley Road (4.0), with the next highest accident location falling at West Valley Road and South 158th Street (3.0). Midway between these two 67 intersections, the average annual number of accidents dropped to 1.5 per year. North of the site, 1.5 accidents per year occured at both the Southcenter Boulevard- Interurban Avenue and Westbound 1 -405 on -off ramp -West Valley Road intersections. The high number of accidents occuring at Strander Boulevard and West Valley Road can be attributed to the new signal at this intersection. Some of the accidents may have occured prior to the signal's installation. Also, typically, the number of accidents at newly signalized intersections increase until people become accustomed to its existence and operation. acts Due to an increase in traffic volumes generated by the proposed hotel, it is expected the number of traffic accidents would also increase. It is estimated the project would increase the average number of accidents by approximately one accident per year within a one -mile radius of the site. Mitt gattng Measures 1. Construct a left turn lane on West Valley Road for the northernmost entrance to the site. 2. Restrict the southernmost entrance to the Hotel to right turns in and out only. Unavatdabte Adverse tmpacts Potential increase in traffic accidents. 68 5. PUBLIC SERVICES a. F re Servrce Extstina Conditions Fire protection to the proposed development will be provided by the Tukwila Fire Department. Fire and emergency responses will be from the station located at 444 Andover Park East in Tukwila, approximately 1/2 mile southwest of the subject site. The Andover East station has three pumpers, one 100 foot aerial ladder, aid car and support vehicles, with full time personnel on duty 24 hours a day. The maximum emergency response time would be 2 minutes or less. Emergency medical aid will also be provided by the Andover East station by an aid car and person- nel. The fire rating in Tukwila is class 4 in a scale of 1 to 10 with 1 as excellent. tmpacts According to a representative of the Tukwila Fire Department, the project w i l l increase the work load. (Refer to Appendix G for correspondence with Fire Marshall, Jim Hoel.) The proposed hotel will rise approximately 92 feet above existing grade and between 89 and 90 feet above finished grade. Iitti-gattnq Measures 1. The hotel will be fully sprinkled and conform with each standard delineated in the City of Tukwila's fire Protection Standards, Ordinance for High Rise Buildings Number 1167. (See Appendix J) The Fire Marshal shall review the application prior to issuance of a building permit to ensure conformance to each standard. 2. The proposed hotel is designed to have 2 passenger elevators and one service elevator in the middle of the building. A fourth elevator shaft will be provided for a future elevator i f needed. Stairs on the north and south ends of the hotel will also be provided. 3. Tax revenues from the proposed development will help offset the cost of additional service. Unavai-dable Adverse Impacts Increased demand for fire service._ b. fatuto ervkw Extsti n4 Corrd fti'orrs Police protection will be provided by the City of Tukwila Police Department, located in the City Hall less than three 69 quarters of a mile northwest of the subject site. The force currently consists of 27 commissioned officers. Emergency response time would average between two and three minutes. Present service level is considered adequate. During Longacres season, the Washington State Patrol provides local traffic control on West Valley Highway. There were seven reported accidents in the general vicinity in 1981. However, during the horse racing season, minor traffic accidents have been handled by the Washington State Patrol and not reported to Tukwila. -Impacts The proposed development could create adverse impacts on the service level to the rest of the City. The increase in tax revenue contributed by this development could help negate this impact. Lieutenant Patrick Phelan, Administrative Commander of the Tukwila Police Department expects a broad variety of police problems will occur due to the hotel. Problems which could occur are: car prowls, burglaries, and alcohol related problems. (Refer to Appendix H for correspondence with Lt. Patrick Phelan, Administrative Commander.) Mfittgating Measures Tax revenues from the proposed development will help offset the cost of additional service. Unavoi-dabte Adverse -I-mpacts Increased demand for police service. c. Lodi =I Egframxtima Exiting Condittons Several recreation facilities are in the vicinity of the site. Bicentennial Park is a one acre neighborhood park located 1/4 mile south of the site on Green River and accessed by Strander Boulevard. The park has a sheltered picnic area and is acces- sible to the River for fishing. Tukwila Park is 1/3 mile north of 1 -405 on 65th Avenue South. This 6.5 acre neighborhood park has picnic grounds, tennis courts, children's play area, and restrooms. Fort Dent Park is the nearest regional park, located north of 1 -405 on Interurban Avenue. This 50 acre park, 2/3 m i l e from the site, has facilities for field games, tennis, and track, and is equipped with restrooms. Longacres race track is visible from the site. Horse racing is seasonal, lasting from April to October. 7Q The Green River provides an important recreational feature adjacent to the site, both from the standpoint of a passive visual amenity, as well as for fishing. The City of Tukwila Park and Open Space Program (1976 -1981) does not identify any park needs in the general vicinity of the subject site. Goals for the Southcenter neighborhood in which the site is located are as follows: 1. "Encourage shopper and employee use of Christensen Road." 2. "Encourage employers to provide some on -site recreational opportunity to employees." 3. "Encourage open areas in developments for the enjoyment of customers and employees." The Trails and River Park Concept of the Plan identifies either side of the Green River as a R i verf ront Park. However, the Preliminary Park Plan for the section of River which the sub- ject site is on, does not show any park facilities on the east side of the River. tmaacts Project development may include a pedestrian bridge from the hotel to Christensen Trail across the Green River. Additional demand could be expected on Christensen Trail if the bridge is constructed. Attendance is expected to increase at Longacres. Passive use of the project's shoreline is proposed. The area between the area containing the parking lot, fire lane and dikes, maintenance road, and the shoreline is planned to be improved with the addition of groundcover, shrubs, and conif- erous and deciduous trees. Mlgattrro Measures 1. The project will provide a swimming pool and j acuzz i for use by hotel guests. 2. Tax revenues from the proposed development will help offset the cost of additional service. Urravotdabte Adverse tmpacts None. d. Malrit uduL The maintenance of existing public facilities is undertaken by the City's Street and Sewer Departments. 71 Impacts Over the short -term, vehicles involved with construction at the site can be expected to carry dust and mud off the site into the adjacent streets, thus impacting the street cleaning acti- vities with the Public Works Department. Mfti-gattng Measures 1. The contractor could provide wheel washing for any vehicles exiting the site during excavation. 2. Regular street cleaning could be provided by the applicant, as necessary. Unavuit abte Adverse Envtronmenta1 Impacts None. 72 6. ENERGY Existing Cond-i ttorrs The site is not presently occupied and does not consume energy resources. impacts The use of electrical energy is discussed in the following section on Public Utilities. The initial energy investment requirement (estimated according to the Department of Energy State Energy Conservatton P tart Handbook, page 77), would be approximately 63,000 BTU's per (1980) dollar, or roughly 945 b i l I i on BTU's. This estimate i nc l udes energy for activities such as transporting building materials to the site, energy investment in various types of materials, and fuel used by construction equipment. Eatigmting Measures 1. Utilize insulation in roof (R -19) and walls (R -11). Unavoi-datrte Adverse Impacts Increased demand for electrical energy. 73 7. UTILITIES a. Energy Ex'rsttng Condrttons Puget Power and Light Company would provide electrical energy to the proposed development. The Renton Junction substation southeast of the site on West Valley Highway serves the vicinity. The Washington Natural Gas Company would provide natural gas service to the development should the developer opt for the energy source in the future. At present, the site could be served,by a four inch high pressure line located on West Valley Highway. Impacts During construction significant amounts of electrical energy will be necessary, estimated to equal approximately 81,000 BTU's per one dollar of construction cost (Department of Energy, 1978). Mttfgating Measures The hotel is designed to have R -11 insulation in the walls and R -19 in the roof. Unavotdabte Adverse tmpacts Increased demand for electrical energy. b. eammunlcatfon Extstf-ng Condttfons The proposed development is within the service area of Pacific Northwest Bell Telephone Company. They have the ability to supply the needed line capacity for all development in the area as long as they are aware of the need well in advance. hmpacts Telephone lines will need to be extended to the site. Mrttgath-ng Measures 1. All telephone lines will be installed underground. 2. Installation of telephone lines will be coordinated with installation of electrical lines. 74 Unavo idabl e Adverse impacts None. c. Azimizatz ExistFng Conditions Water in the vicinity is supplied by the City of Tukwi la and "Independent Water Company." A six inch water main owned by Independent Water Company lies approximately 40 feet northeast of the northeast corner of the site. The line is connected to a fire hydrant on the west side of West Valley Road, which has a pressure of approximately 90 psi. Independent Water Company also has a twelve inch line approximately 470 feet east of the site on South 158th Street, and The City of Tukwila owns a ten inch main approximately 480 feet south of the site. The water pressure is between 125 and 150 psi. Average demand in the City is approximately 6,000,000 gallons per day. Impacts The proponent intends to use the City of Tukwila water line south of the site. This ten inch main could adequately supply the hotel. I n order to connect with this I i ne, the proponent would install an extension of approximately 490 feet. The development will result in increased water demand. Mitigating Measures All work and materials will be in complete accordance with the standards and specification of the City of Tukwila and the State Department of Social and Health Services. Unavoi-dab--te Adverse tmpacts Increased demand on water supply. d. tneza Exfsttng Condtti-ons Sewer service is provided by the City of Tukwila. The nearest sewer pipe is eight inches in diameter, located approximately 220 feet east of the subject site. Sewage is discharged into the Metro Renton Sewage Treatment Plant, which is already operating above capacity. 75 Impacts An eight inch sewer line will be installed by the proponent to serve the site. The development will result in increased sewage flows. Mtt igati-ng Mea ores All work and materials shall be in complete accordance with the specifications and standards of the City of Tukwila and the Washington State Department of Ecology. UnavotdabI e Adverse .impacts Sewage generated by the development would contribute to above capacity discharges at the Renton Metro Sewage Treatment Plant. e. tztblitczte Existing Conditions The businesses and residences in the surrounding vicinity are currently served by Sea -Tac Disposal. Dumpsters and compactors can be rented from them. The solid waste is taken to the King County Transfer Station. tmpacts The proposed development will increase demand for solid waste collection, which can adequately be provided by Sea -Tac Disposal. Mtttgattng Measures None. Unavoidable Adverse -impacts None. 76 8. AESTHETICS Extst-i nq Conditions The site, located on the bank of the Green River, is currently an undeveloped open field used occasionally for grazing. The River flows a l ong the southern and western boundaries of the site. Single family homes lie to the north and south. Commer- cial strip development, Longacres Race Track, and supplementary land uses l i e along West Valley Highway, immediately east of the site. Office and light warehouse uses are west of the site. Some of the most dominant visual elements in the general vicinity are; Longacres Race Track facilities, West Valley Highway, 1 -405, River View Office Buildings, and the Green River. The residential neighborhood on McMicken Heights, approximately one mile west of the site has easterly views toward the Cascades across Tukwila CBD and the subject site. The residential area is between 300 and 400 feet above the valley floor. The residential neighborhoods on Tukwila Hill, northwest of the site, generally are not on slopes oriented toward the subject site. They are generally oriented due south or east. Buildings west of the site along Christensen Road face Andover Park East, backyards are along Christensen Road. Impacts Development of the site will convert an open field into an eight story hotel. The development will be visible from much of the surrounding community. However, only a few neighboring properties will have views obstructed due to the project. Northerly views from the 3 story River View Office Complex south and from Christensen Trail, across the river from the site, would have views blocked. Other views will be altered when traveling by car on 1 -405 and West Valley Highway. The change in character due to the hotel development will be determined as a positive element of the man -made environment by some residents, workers, . and commuters in Tukw i la and as a detrimental aesthetic impact by others. Mftfgattng Measures None. Unavoidable Adverse fmpacts Obstruction of some views of adjacent property owners and change in character of the general vicinity. U.S.G.S. BASE 4,1"=2000" NORTH 9. VIEW ASSESSMENT TUKWILA HOTEL R.W. THORPE AND ASSOCIATES 78 1 10. VIEW BLOCKAGE TUKWILA HOTEL NORTH R.W. THORPE AND ASSOCIATES 79 9. ARCHAEOLOGICAL /HISTORICAL Ext sttng Conditions Duwamish Indians inhabited the Green River drainage system. Their v i I l ages often moved, forced by the changing course of the river, cultural preference for relatively clean surroun- dings, and the necessity to seek food and supplies as they became available. The Duwamish No.1 site, located downstream from the project area on the Duwamish Waterway, appears to have been occupied. The oldest dendro- corrected C-14 date obtained is 670 AD and the youngest is 1690 - 1800 AD. Another site, located along the abandoned channel of the Black River near Renton, was occupied somewhere between 200 and 1000 AD and again between 1900 and 1920. An archaeological survey was undertaken on the site. There is no indication from the survey of any archaeological significant artifacts on the site. (See Appendix C) - impacts Potential uncovering of archaeologically significant finds during construction. Mfttgating Measures A qualified archaeologist should conduct on -site monitoring during land clearing, access road construction and building site preparation. Urravo r-dab' Fe Adverse impacts Potential removal of an archaeological site. 80 10. ECONOMIC FACTORS Existing Condrtions Currently, the undeveloped site is generating a negligible amount of municipal revenue through property taxes. There are no municipal expenditures associated with the site. cts The proposed $11 million dollar development would generate approximately $47,837 annually upon completion. Building and plan check fees would accrue approximately $16,914 prior to development. The School District would realize approximately $23,705 as a result of the development. Metro would receive approximately $29,922. Total municipal expenditures created by the development can be expected to approximate $16,942. The net affect of the proposed project is a municipal income of approximately $30,895 annually. (Refer to Appendix B) MfitPgattng Measures None. Unavotdabi a Adverse Impacts None. 81 SOURCES AND REFERENCES CONSULTED o Egrth 1. "Soil Survey King County Area" 1973 by U.S. Soil Conservation Service. 2. "Geotechn i ca I Report" 1982 by Shannon and Wilson, Inc., Geotechn i - cal Consultants. o tdi tuatitz lEztioa 1. State of Washington Department of Ecology 1981 Quarterly Air Monitoring Data Summary, June 29, 1981.. 2. Washington State Air Monitoring Data, April 1980, Department of Ecology, July 1981. 3. Washington State Department of Transportationn, 1977 Air Quality Monitoring. 4. Telephone conversation with Stuart Clark, Department of Ecology, March 2, 1981. 5. Environmental Protection Agency, "Compilation of Air Pollutant Emission Factor" with revisions. o flgra _and fmanm 1. East Side Green River Watershed, King County, Washington, DEIS, prepared by U.S. Soil Conservation Service, November 1978. 2. Field Analysis, R.W. Thorpe & Associates, December 1981. o No I se 1. Noise measurements monitored by R.W. Thorpe and Associates 1980 2. Dash Point Heights DEIS, King County o Pavutattan ABA 1. United States Bureau of Census, 1980 Census of Population and Housing Advanced Report. 2. Puget Sound Council of Governments, Main Allocation Model, 1979. o Effiztampirt iggiztaa 1. Employment Center Background Report, 1980, King County Planning Division. 2. City of Tukwila 1980 Employment Survey, 1981, City of Tukwila Planning Department. 82 o facial= State Energy Conservation Ptan Handbook by Washington State Department of Energy o PutiTc =MI-es SEct k n 1. Mr. Perry Capps, Puget Power (Telephone Conversation) 2. Jim Walker, Washington Natural Gas (Telephone Conversation) 3. City of Tukwila Department of Public Works - Phil Fraser, Water Department - Dave Grage, Sewer Department - Ray Doss (Telephone Conversations) 4. Pacific Northwest Bell o Traffic Analysis, March 1982, The TRANSPO Group o Patrftc Servrces 1. Fire Marshall James Hoel, City of Tukwila, 1981 (See letter re: Fire Services, Appendix G) 2. Lieutenant Patrick L. Phalan, Administrative Commander, City of Tukwila Police Department (See letter re: Police Services, Appen- dix H) o isimblimiagjimittlittmcbart Cultural Resourece Evaluation, January 1982, Geo -Recon International, LTD. o fconamfic Factors 1. City of Tukwila Preliminary Budget 1982 2. "Fiscal Impact Guidebook - Estimating Local Costs and Revenues of Land Development" 1979 by Rober Burchell and David Listokin 3. "Trends in the Hotel Industry in the Pacific Northwest" 1981 Edi- tion, by Pannell Kerr Forster, CPA 4. "Real Estate Research Report" 1981, by Seattle Real Estate Re- search Committee 83 IV. UNAVOIDABLE ADVERSE IMPACTS So-f t-s 1. The reworking and loss of productivity at a maximum of 83% of the topsoils of the site. 2. Potential for minor uncontrollable erosion of soils near the streambank during construction of driveway and parking lots adja- cent to the streambank. 3. Potential for minor erosion'of soils near streambank due to poten- tial presence of human activity. Igugrcahv Changes in the contours of the site, including excavation depths of a maximum of 10 feet. hit 1. Increased air pollution from automobile emissions contributing to hydrocarbon levels which already exceed Washington State Standards. 2. Increased particulate levels, which already exceed Washington State Standards, due to construction activity and additional traf- fic volumes 3. Short -term odors during construction MAIELEC 1. Urban pollutant levels will increase in storm water runoff, par- ticularly during construction 2. A potential increase in peak runoff from the site 3. Potential decrease in groundwater quality F-bra Reduction of most of the natural vegetation on the site fmarca A reduction in the number of species on the site will result from project development. Notre Increased noise levels over the short term due to construction activity, and over the long -term due to human activity and increased traffic. 84 tigt±AMilbM Additional Tight and glare will be emitted from the site to surrounding properties. 85 V. SHORT -TERM USE VERSUS LONG -TERM PRODUCTIVITY The hotel development proposed for the site will be a long term use of the land. The hotel can be expected to remain for at least 50 years or the life of the building. The development will prevent short term use of the land for agricultural use. However, because the site is located on a major arterial and conveniently located near 1 -405 and I- 5, and because the site is not proposed for purchase in the agricul- tural retention program, long term agricultural use may not occur on the site whether or not the project i s implemented. Long term estab- lishment of commercial use other than hotel use on the site w i l l be precluded. Realization of the project would result in economic benefits to private investers, as well as increased employment opportunities and tax base. Therewould be secondary economic benefits to existing commercial businesses in Tukwila due to their convenient location to hotel guests. These benefits are balanced against the permanent loss of pasture land and 5.47 acres of open space and the adverse environmental impacts described on page 1. Benefits of deferring development or reserving the area for future options would include: no immediate increase in local traffic volumes, the retention of existing vegetation and soils, preservation of habitat areas, no immediate change in land use character. On the other hand, deferring development would present some disadvan- tages. Development at some future time would face increased costs, because of inflation and the potential scarcity and increasing costs of building materials. Development in another area less suitable for hotel use might result. Further, deferral of the project would not necessarily eliminate or alleviate the level of environmental impacts associated with this project. 86. VI. IRREVERSIBLE AND IRRETRIEVABLE COMMITMENT OF RESOURCES Completion of the proposed action will result in the long term commitment of the entire site containing soils suitable for grazing to use for building, parking lot, and landscaped areas. Most soils could be reclaimed in the future, though some local changes in the soil profile by excavation and addition of new materials could render this infeasible. Long term use of the hotel will commit additional energy resources for heating and maintenance at this location. The use of various construction and building materials required for development of the proposed project can be considered an irreversible commitment of these materials, as well as the energy utilized in providing them. The proposed project will require a long term commitment of energy resources, and solid waste facilities. All electrical power and water expended and the waste treatment and solid waste facilities utilized during construction, operation, and maintenance of the proposed project are considered irreversible and irretrievable commitments. All positive and negative impacts of the proposal would, for the time being, be avoided. Feast b I City Under current conditions, this alternative is impractical for anything other than the very limited future. The pending development of other properties on the valley floor will substantially increase the pressure for development of this site at a higher use as the inventory of land suitable for development is reduced. tEttlaarttsm 2 = Itutt intaitthEt Devetopment Descri-ptiyon This option would be in conformance with the existing zoning designa- tion for this site. However, it would not conform to the commercial use designation of the Comprehensive Plan. This alternative would allow those uses allowed in C -1 and C -2 zones as well as light manu- facturing plants, warehouses, meat processing, salvage processing, spray painting or paint mixing, stamp dieing, shearing or punching of metal not exceeding on- eighth inch in thickness and similar uses. impacts This alternative could potentially increase impacts on Noise, Odor, Aesthetics, Economics, and Land Use. It is probable that traffic generation would be reduced and air quality would be less impacted, as would soils, natural resources, public utilities, and services. This type of development would be Tess visible in the general vicinity. However, it could be less compatible with the surrounding land uses and would become a legal non - conforming use once the existing zoning code is replaced this year. Feast -b-i -t 'tty It is unlikely permits could be acquired prior to the proposed change in zoning. Further, the proponent has not, nor intends to propose a Tight industrial use for the site. 88 VIII. APPENDICES A. Traffic Analysis B. Fiscal Impact Analysis C. Cultural Resource Evaluation D. Shoreline Master Program (General Regulations) E. Flora F. Fauna G. Correspondence from Fire Department H. Correspondence from Police Department I. Geotechnical Report J. Fire Protection Standards TUKWILA HOTEL MARCH 1982 prepared for: The Christensen Group. Inc: The City of Tukwila - - prepared by: The TRANSPO Group 23 - 148th Ave SE Bellevue, WA 98007 TRANSPO Grove INTRODUCTION This report summarizes a traffic analysis for the proposed Tukwila Hotel and is intended to supplement a transportation /circulation element of a more comprehensive Draft Environmental Impact Statement (DEIS). The purposes of this analysis are to identify any positive or negative traffic related impacts generated by construction and occupancy of this project and, where appropriate, to outline policies, programs, and /or physical improvements to minimize or eliminate the effects of these impacts. The proposed Tukwila Hotel is located on a site south of I -405 and east of the Southcenter regional shopping center. The site is bordered on the east by West Valley Road and on the west and south by the Green River. Figure 1 shows that the site is central to much of the Puget Sound urban areas, with Seattle and Bellevue north of the site; Renton is several miles to the east; and Kent, Auburn and Tacoma are to the south. The proposed hotel is to include 274 guest rooms, a restaurant that seats between 180 and 200 persons, and a lounge with a capacity of 125 people. Also included are five meeting rooms with a capacity of 10 to 12 persons. Another area will be convertible from 3 rooms serving 100 to 150 persons each to 1 room with a capacity of 400 to 500 persons. The hotel has been planned primarily to cater to business people, with tourists and vacation travelers considered as a secondary market. The hotel will sponsor a shuttle service to /from the Seattle - Tacoma Airport, which lies approximately 3 miles west of the site. The restaurant and lounge are targeted to serve primarily the hotel guests but may also capture some of the lunchtime customers coming from business areas that lie west and south of the site, plus generate some dinner trade within the surrounding areas. It is not anticipated or proposed that either the restaurant or the lounge will capture a significant share of those persons traveling to and from Longacres. • - - = - - • - ep Anpl.i i "Nan n 417"r7 moats • ft, 01 run Qm _ r ri send • •.t• ',al, � 6y •..nrs kw" rta,1 11 Arlington are SNOHOMISH 1, • I Note m • t Granite e Falls A �'" Lake rr.uitn. 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F.Inr.il4 ML .fJ.rdi► ;! `J/ �W TUKWILA HOTEL FIGURE 1 VICINITY AND LOCATION MAP The TRANS! @row Access to the site will be provided via two exit /entrances off West Valley Road . The first will be opposite 158th and will provide access from all directions (both right and left turns in and out). The second access lies approximately 370 feet south of the primary access. Traffic in and out of this entrance will be restricted to right turn in and right turn out only. Traffic entering the site will circulate to the north of the building under a canopy where baggage and passengers will be loaded and unloaded. The aisles for parking will serve as the internal road system. Presently, the plan calls for development for approximately 508 automobile spaces, 20 percent of which will be designated for compact cars. A proposed feature of the project that is still under consideration is a pedestrian bridge that crosses the Green River to the south connecting a public open space and trail system with the site. This bridge could be used by guests who wish to take a walk to the other side of the river to the open space area or by business people in the business park area west of the Green River who wish.to walk to the hotel/restaurant for lunch or dinner. In the area surrounding the site there are a wide variety of uses. Immediately to the east is the Longacres thoroughbred horse racing track. West of the river, as mentioned above, is a very substantial business park including a wide variety of office, commercial, warehousing, and light industrial users. Along West Valley Road exists a number of commercial and retail activities including restaurants, and roadside support services. As mentioned earlier, the Southcenter regional shopping center lies approxi- mately 2 miles west of the site and can be accessed via Strander Boulevard to the south or I -405 or Southcenter Boulevard to the north. Further to the west I -405 intersects with I -5 which runs north -south from Vancouver, B.C. to California. Further west I -405 changes designation to State Route 518 and connects this area with the Seattle- Tacoma International Airport. More immediate to the site, the area north of the.site is presently occupied with a single family home and several acres of vacant land. Likewise, to the south of the site there is a single family residence and some other commer- cially zoned properties. TUKWILA HOTEL FIGURE 2 SITE PLAN The TRANSPO Grove 4' EXISTING CONDITIONS This section describes the existing transportation conditions in the vicinity of the project site, including the street system, traffic control devices, traffic operations, parking conditions, transit services, and pedestrian and bicycle activity. This discussion is intended to serve as a basis for subsequent analysis of project generated traffic. Roadway System The street system in the vicinity of the Tukwila Hotel is depicted on Figure 3 and is dominated by I -405, a limited access interstate freeway that serves as a bypass to I -5 and as a main roadway connecting several major cities along the east side of Lake Washington. This road is a 4 -lane divided roadway and has a full interchange at West Valley Road. West Valley Road is a 5 -lane road (2 lanes in each direction with a center 2 -way left turn lane) except in the section south of the site to Strander Boulevard where the road narrows to 4 lanes. To the north of the I -405 ramps, the road intersects with Grady Way (which connects with Renton), Southcenter Boulevard, and north onto I -5. North of Grady Way the name of the road changes to Interurban Avenue. To the south, Strander Boulevard is one of two major east /west arterials south of the site. Strander Boulevard is 4 lanes wide but widens to 5 lanes at its intersection with north /south cross streets to permit a left -turn storage lane. Strander Boulevard provides an excellent connection to the Southcenter regional shopping center and the Andover Business Park. The road forms a T- intersection with West Valley Road with special channeli- zation that provides for one left turn and one right turn lane on the east- bound approach. 1. Southcenter Boulevard is the primary east /west arterial that lies to the north of the site and connects West Valley Road with City Hall, one of Tukwila's primary residential areas, and to the bridges that connect this section of the city to Southcenter and Andover Business Park. South - center Boulevard is a two -lane roadway with stabilized gravel shoulders toward its western end as it intersects with Interurban Avenue. SoutAcent•r Blvd Tukwila Pkwy Si STATE PATROL MANUAL CONTROL DURING LONGACRES RACING SEASON Evans -Black Dr Baker Blvd • lof •> wk •'s 016 Andover Park E Strander Blvd LEGEND: TRAFFIC SIGNAL _ STOP SIGN • • TUKWILA HOTEL FIGURE 3 STREET SYSTEM & TRAFFIC CONTROL —6— Grady Way is a two -lane road that provides a connection between Renton and Tukwila. This road is parallel to and north of I -405. Traffic control in the vicinity of the project is provided by traffic signals at the higher volume intersections shown on Figure 3. Where volumes are lighter, STOP sign control is used to control the minor volume side street traffic so the major thru volumes can pass uninterrupted. In addition to this permanent traffic control, the Washington State Patrol assigns officers to control traffic between I -405 and the main entrance to Longacres Race Track (S 158th Street) during the racing season. This often requires two to three officers when the track opens during the 2 -3:00 hour and on/ weekends between 11:00 AM and noon. Most speed limits in the area are posted at 35 mph except for the portion of Strander Boulevard east of Andover Park E at 30 mph, and SW Grady Way, which is posted at 25 mph. Programmed Roadway Improvements The City of Tukwila has had Entranco Engineers prepare a transportation improvement program and it, in combination with the most recent (1982) transportation improvement program, show a number of major improvements proposed for this area. Of top priority is the rebuilding of the Grady Way bridge over the railroad just north of I -405. This project is a joint Renton /Tukwila sponsored effort. Next is the realignment of Southcenter Boulevard to intersect with Grady Way and provide better access into Andover Business Park and Southcenter regional shopping center. A proposed align- ment for this improvement is reflected on Figure 4. Another near term improvement calls for adding a right turn lane at the West Valley Road/ Strander Boulevard intersection and new signalization and channelization at the Strander Boulevard /Andover Park East intersection. Both these projects are scheduled for implementation in 1982. In 1984, sidewalks and other street improvements are proposed along Interurban Avenue north of Southcenter Boulevard and longer range improvements call for the widening of Andover Park East north and south of Strander Boulevard and Strander Boulevard east and west of Andover Park East. This widening will bring these roads to a full 5 lane section. -7- SIDEWALKS & OTHER STREET IMPROVEMENTS 1984 REALIGN ROADWAY 1983 Southcentar Blvd REPLACE BRIDGE -1982 1_ •61 aNON Tukwila Pkwy \ \ St Evans -Black Dr Baker Blvd O • • e • cr c. 0' J• mew a. r • • O WIDEN TO 5 LANES 1985 -1987 mOW Strander Blvd 1a1111iarrriIllI11IlIIIu 0 • •A NEW SIGNALIZATION • AND CHANNELIZATION •. 1982 G0 TUKWILA HOTEL FIGURE 4 PROGRAMMED ROAD IMPROVEMENTS -8- Traffic Volumes and Patterns Traffic volumes on streets in the area of the proposed Tukwila Hotel ' were assembled from State of Washington Department of Transportation records and reflect counts made between 1979 and 1981. These counts were adjusted to reflect a 1980 traffic volume and are displayed on Figure 5. Weekday traffic volumes were found to be substantially higher than weekend day traffic volumes and as such were used for the purpose of analyzing the impacts associated with this project. Furthermore, the combination of traffic - generated traffic volumes and existing non - project traffic volumes are expected to be highest during the weekday. Immediately adjacent to the project site, West Valley Road carries approximately 20,000 to 23,000 vehicles per day (vpd). The volume drops slightly north of Southcenter Boulevard to approximately 17,500 vpd. I -405 carries between 85,000 and 88,000 vpd. To the south, Strander Boulevard west of West Valley Road carries approximately 8,500 vpd. Volumes on roads in- ternal to the Andover Business Park drop somewhat to 8,000 to 10,000 vpd, while roads surrounding or immediately adjacent to the Southcenter regional shopping center are somewhat larger, ranging from 14,000 to 19,000 vpd. A review of counts made over the 1979 through 1981 time frame shows significant fluctuation that suggests a reduction in traffic volumes to this area. To be conservative, however, a higher than average value was used to evaluate traffic conditions. Another factor unique to this area relates to the significant in- crease in traffic volume that occurs when the Longacres race track is in full operation (between May and October each year). Unfortunately, traffic volumes associated with the Longacres operation were not available, and none of the State's traffic counts nor any of the counts contained in the Entranco Engineers Transportation Improvement Plan reflected these special conditions. Based on discussions with the State Department of Transportation and the Washington State Patrol, it was found that there are peak surges in traffic volumes between 3:00 and 3:30 p.m. and 8:00 8 700 (1300) 11 400 (1400) 4700 BOUtAcenter Blv 61 87.400 N/A 85:100 N/A Tukwila Pkwy st st 11,700 (1530) A 0, • •. u' •s ait 0 Evans -Black Dr aws■► Baker Blvd Andover Park E 10.100 (1200) TUKWILA HOTEL FIGURE 5 ESTIMATED 1980 DAILY AND PM PEAK HOUR TRAFFIC VOLUMES -10- until 9:00 p.m. on weekdays and 11 :00 to 11 :30 a.m. and 6 :00 to 7:00 p.m. on weekend days. In these situations, at least two Washington State Patrol officers are used to control traffic at the entrance off S 158th Street. In certain circumstances, three officers are required to direct traffic. The very heavy left turn demand as people exit from I -405 onto West Valley Road and then turn east on S 158th Street necessitates this manual traffic control. On an average weekday (a day without Longacres traffic volume), West Valley Road serves as a primary arterial feeding traffic to and from I -405. As one follows West Valley Road south, volumes diminish, suggesting that this road acts as a major collector- distributor arterial to Andover Business Park and Southcenter. Likewise, north of I -405, volumes on Interurban Avenue tend to decrease as one follows the road north toward I -405. South - west Grady Way serves as a bypass to I -405 for some people traveling be- tween Renton and Tukwila. While daily traffic volumes provide a general impression of travel patterns, it is appropriate to examine the peak hour traffic conditions as this is the time when traffic congestion normally becomes most notice- able. In the vicinity of the project site, the peak hour varies from one location to another and from one time to another, but, on the average, falls between 4 :15 and 5:15 p.m. on weekdays. The peak hour volume rep- resents between 10 percent and 16 percent of the average weekday traffic volumes which is higher than the regional average of 8 percent to 12 per- cent. This higher range can be explained by the fact that these roads serve major employment concentrations which typically are higher peak hour traffic generators. The evening peak hour traffic volumes on West Valley Highway ranges between 2300 and 3000 vehicles per hour (vph). In the evening the dominant flow is northbound, traveling toward I -405 (about 55 percent northbound and 45 percent'southbound). These peak hour patterns tend to reflect the strong influence of I -405 as a facil- ity that collects trips off the local streets to carry them to residential areas within the region. While these traffic volumes can give some impression of traffic patterns, they unfortunately do not give a perception of the congestion that exists along the road system. Techniques have been developed to assess the congestion levels that result with different street and traffic volume conditions. These techniques are described in the High- way Capacity Manual, 1965, the Traffic Engineering Handbook, and, most recently, in the Transportation Research Board's Circular 212. These techniques are referred to as levels of service (LOS) which range from LOS A, which is very good, to LOS F, which reflects a traffic flow that has deteriorated to a start - and -stop condition. In urban areas, most traffic engineers design improvements to operate at LOS C, but consider LOS D acceptable during peak periods as long as these conditions do not extend more than one hour within the peak period. LOS A suggests that traffic is flowing with minimal delay'at STOP signs or traffic signals. LOS E indicates that the roadway is operating at capacity such that in- creases in traffic volume will tend to increase the length of queues rather than maintaining or reducing the length of the backup. An analysis of the major intersections in the vicinity of the site under average weekday peak hour conditions shows that the Strander Boulevard /West Valley Road intersection currently operates at LOS C to LOS D. The eastbound off -on ramp /West Valley Road intersection operates at LOS C, while the westbound off -on ramp /West Valley Road intersection operates at LOS D to LOS E. These calculations do not reflect the in- fluence of traffic when Longacres race track is in session. Based on conversations with Washington State Department of Transportation and Washington State Patrol, it appears that conditions along West Valley Road between Grady Way and S 158th Street deteriorate to an "at or . near capacity" condition just prior to the opening of the track and following its closure. The levels of service calculated for these pri- mary intersections tend to be confirmed by the Transportation Improvement Plan prepared by Entranco Engineers. Any differences in the results tend to reflect improvements that have been madetto the intersections or ad- justments in traffic volume that have occurred within the last several years. Traffic Accident Conditions Accident data within the vicinity of the project was limited to the State roadways. Records maintained by WSDOT District 1 for 1979 and 1980 were evaluated as part of this study, and the results are presented on Figure 6. The results of this analysis show that the highest number of average annual accidents occurred at Strander Boulevard and West Valley Road (4.0), with the next highest accident location falling at West Valley Road and S 158th Street (3.0). Midway between these two inter- sections, the average annual number of accidents dropped to 1.5 per year. North of the site, 1.5 accidents per year occurred at both the Southcenter Boulevard /Interurban Avenue intersection and the signalized ramp intersection south of I -5. The lowest number of average annual accidents occurred at the intersection of SW Grady Way /westbound on -off ramp /West Valley Road intersection. One possible reason for the high number of accidents occurring at Strander Boulevard and West Valley Road could be the fact that this intersection has just been signalized, and some of the accidents may have occurred prior to the signal being installed. Regardless, the number of accidents at a newly signalized intersection generally in- creases until people become accustomed to its existence and operation. While the number of accidents generally increase at a newly signalized intersection, the type of accidents are substantially less severe (e.g., they are rear -end type accidents as opposed to right angle accidents). Transit Service The Tukwila Hotel site is served by three transit routes, in- cluding the 154 Seattle- Auburn, and 158/159 Seattle -Kent East Hill route. These routes travel north to I -405 and continue into Seattle. There are several other routes which provide express service into the area, but these fall beyond a reasonable walking distance from the site and thus are not considered to be logical routes for use by hotel em- ployees or guests. -13- 154- 158 -159 Bouthcenter Blvd Tukwila Pkwy 240 -340 Evans-Black Dr Baker Blvd TRANSIT ROUTES 154 SEATTLE - AUBURN 158 - 159 SEATTLE -KENT EAST HILL 145 - 146 SEATTLE- RENTON 240 BELLEVUE -SEA TAC 340 AURORA V 1LLAGE-SOJ11< LATER Andover Perk E LEGEND: Hnll' TRANSIT ROUTE • BUS STOP TUKWILA HOTEL FIGURE 6 1979 -1980 ANNUAL AVERAGE ACCIDENT SUMMARY AND TRANSIT ROUTES -14- Routes 154, 158 and 159 all are oriented to provide peak hour service, combining to provide a total of about 14 runs during the morning peak period and the afternoon peak period. The schedules are oriented to pro- vide service into downtown Seattle, and thus the schedules may run too early to serve this site. The fares during the peak hours are 60Q for one zone and 90Q for two zones. Recent counts on these buses show that the majority operate at less than full capacity during the morning and afternoon peak hours in the vicinity of the project. Parking Parking associated with businesses in the vicinity of the project site is generally accommodated in off - street parking lots. While some roads have shoulders that are wide enough to serve as parking areas, field observa- tions suggest that people rarely use these areas because of longer walking distances, and because most off - street parking appears to be adequate to serve any of the demands generated by specific businesses. Pedestrian, Bicycle, and Equestrian Activity There was no record of pedestrian or bicycle counts in the vicinity of the project. During field surveys, no pedestrian or bicycle activity was observed. This seems reasonable because of relatively long walking dis- tances between buildings and because there are not logical combinations of trip origin generators and trip destination attractions that fall within reasonable walking distances. It is observed that most people use their car to travel from one location to another, even when the travel distance is relatively short. While there are sidewalks along the edge of most of the roads in the newer, more densely developed areas that are located west of the Green River, West Valley Road is bordered only by shoulders. At several locations, these shoulders become relatively narrow and, in combination with the higher speed and higher volume traffic, they do not appear to provide a comfortable walking area for pedestrians. -15- Along the western bank of the Green River and east of Christiansen Road, is a narrow strip of land often referred to as the Christiansen Green Belt. Presently there is a trail system that follows along the river from Strander Boulevard which ends at the south edge of I -405. This trail system starts up again north of I -405 in the vicinity of Fort Dent Park. Presently there is not a convenient connection between these two trail segments. There are no plans to have the trail system follow the east edge of the river across the project site. There have been plans to make pedestrian crossing improvements north of the site across I -405 that would link the two above - mentioned trail segments. Rail, Air and Waterborne Transportation There are two rail lines that operate in the vicinity of the project. Both run north -south and lie east of the West Valley Road. These railroads cross over low clearance bridges at S 158th Street, but travel under I -405 and SW Grady Way. Both rail lines are active and serve a substantial amount of train travel, including freight service into the Andover Business Park off spur lines which are lo- cated south of Strander Boulevard. The Green River is categorized as a navigable waterway and can be used by small boats up to its present location, but as a practical matter, it is not considered usable by commercial watercraft. FORECASTS OF TRAVEL DEMAND AND TRAFFIC ANALYSIS This section of the report outlines the assumptions and steps taken to arrive at an estimate of future traffic volumes associated with the Tukwila Hotel, and discusses the potential impacts of additional traffic on streets in the vicinity of the site. The process used a standard trans- portation planning approach for forecasting travel demand, using the following steps: 1. Trip Generation - How many people will make trips? 2. Mode Split - What methods will people use (automobile, transit, bicycle, or walk)? 3. Trip Distribution - Where are their destinations (Seattle, Seattle- Tacoma Airport, Renton, Tukwila, etc.)? . Travel Assignment - Which routes will people use when making their trips (specific streets, sidewalks or transit routes)? The steps taken to estimate these future traffic levels are described below. To insure that impacts would not be underestimated, the analysis which follows generally reflects a "worst case" condition. "Worst case" is defined here to reflect the high end of the reasonably expected range of conditions. NON- PROJECT TRAFFIC Before estimating the traffic that is expected to be generated by the project, it is important to understand that traffic volumes along most streets in the vicinity of the project will grow regardless of any new development on this site. To estimate these changes, historical trends were observed. As noted in the Existing Conditions section, in recent years this trend has suggested that traffic volumes have been declining, but over the long term, traffic volumes have been on the increase. Considering the large amount of vacant land in the area,it is expected that development will occur and will result in increased volumes. For the purpose of this analysis, 1983 was used as a target year for forecasting, since by this time the hotel would be constructed and in full operation. Based on historical trends, traffic volumes were estimated to increase at a rate of approximately 2 percent per year. As a result of this increase, the volumes reflected on Figure 7 result. It can be noted that a slightly smaller than 2 percent average annual increase was applied to I -405 in order that the volume using the free- way balanced with those forecasted to travel along the local street system. Trip Generation Trip generation statistics assembled by the Institute of Trans- portation Engineers and the Arizona State Department of Transportation suggest that the average trip generation rates for hotels and motels range between 10.1 and 10.5 daily one -way trips per occupied room. A daily trip generation rate of 10.5 vehicle trips per unit (5.25 round trips) were used for this analysis. By applying this higher trip generation rate, a factor of safety will be introduced and a more conservative analysis will result. During the weekday evening peak hour when traffic conditions are at their worst, the Tukwila Hotel would be expected to generate between .65 and .73 one -way ve- hicle trips per occupied unit. These peak hour trips are relatively balanced, such that approximately an equal number of trips enter and leave the parking area. For the purpose of this analysis, a peak hour trip generation rate of 0.70 vehicle trips per occupied unit was applied (0.35 vehicle trips inbound and 0.35 vehicle trips out- bound). These trip generation rates reflect conditions where restaurants, cocktail lounges, meetings in'banquet facilities or convention facili- ties, and other retail and small shops are included as part of the hotel. Consequently, it was not necessary to derive separate trip generation rates for the restaurant, lounge, and meeting room space. When these trip generation rates were applied to the proposed Tukwila Hotel, they yielded a total daily trip generation of 2,880 trips (1,440 round trips). During the evening peak hour, the project Bovthoenter Blvd Andover Park E Strandar Blvd LEGEND: DAILY V/0 PROJ ECT DAILY W/ PROJ ECT XXXXX XXX XXXXX XXX P M PEAK r/0 PROJECT 4 P M PEAK r/ PROJECT TUKWILA HOTEL FIGURE 7 1983 TRAFFIC W/ AND W/O PROJECT -19- is expected to generate approximately 190 vehicle trips, with about 95 vehicles traveling inbound and about 95 vehicles traveling outbound. For the purposes of this report, the weekday occupancy was assumed to be 100 percent. This occupancy is substantially higher than averages observed in the hotel industry (67.4 percent for transient hotels in the Washington, Oregon, Idaho area - "Trends in the Hotel Industry in the Pacific Northwest ", 1981 Edition, Pannell, Kerr, Forester). This high occupancy was used to represent a maximum worst case condition. On a weekend day hotels generate between 8 and 9.5 vehicle trips per occupied room. This reflects lower levels of meeting, conference, and restaurant use. Furthermore, the occupancy on weekends in suburban hotels and motels drops substantially to between 30 percent and 50 percent capacity. As a consequence of these reductions, the average weekend daily traffic volume can be as low as 750 vehicles per day, and is usually not higher than 1,300 vehicles per day. Because this is substantially lower than the average weekday traffic volume, traffic conditions on weekends were not evaluated in significant detail. Typically, the weekend day evening peak hour traffic volumes are usually substantially lower. Although not a weekly occurrence, the one unique weekend use characteristic is the use of the assembly and banquet rooms for large parties. Because these surges in traffic volume generally occur in the late evening, they are not expected to create a noticeable impact since they occur when the adjacent street traffic volumes are very low. In this project area, the peak weekend day traffic occurs during the mid - afternoon due to the traffic generated by the retail activity in the vicinity of Southcenter, and due to the traffic generated by Longacres during . the racing season. Mode Split The next step in estimating traffic demand is to estimate the pro- portion of persons who might use alternate modes of transportation that travel to the hotel. There is no universally accepted approach for determining this mode split, inasmuch as mode choice is affected by a large number of factors. In the case of hotels, however, research shows that a very small number of people use public transportation or walk. People will, however, use private group transportation in the -20- form of limousine service. While this could account for a reduction of 10 to 20 percent in the overall guest travel, there has been no extra allowance given in order that the analysis presented in this report remains very conservative. Trip Distribution and Traffic Assignment Once the number of automobiles traveling to and from the site is known, it is necessary to identify the origins and destinations of these trips. Since this hotel is targeted to market itself primarily to weekday business activity, it is expected that traffic volumes will be about evenly distri- buted north and south. While the facility is expected to serve a primary market in the industrial commercial area south and west of the site, there will continue to be a substantial orientation to I -405 where traffic will split east to Renton and the Valley Freeway and west to I -5 and the Seattle - Tacoma Airport. As a consequence, approximately 55 percent of the daily traffic and 65 percent of the peak hour traffic is estimated to travel north on West Valley Road. The remainder of the daily traffic will be oriented to and from the south on West Valley Road, and a small percentage will use local roads on the west side of the Green River and walk across the pedestrian bridge. Once traffic reaches I -405, it is expected to split so that approximately 15 percent travels east to Renton and Bellevue and the remaining 35 percent travels west to I -405 and the Seattle- Tacoma International Airport. Approximately 5 percent of the daily traffic and 10 percent of the peak hour traffic is expected to use Interurban Avenue to travel north to I -5. While this is a very direct route to and from I -5, it is not expected to be used by many of the guests at the hotel because it is not well known. Local residents and people who travel in this area on a regular basis (e.g., employees) are erected to use this route, and this is why the peak hour travel distribution is higher. When this percentage distribution is applied to the trip generation, the traffic volumes presented on Figure 8 result. This shows that there will be an increase in the traffic volume along West Valley Road of ap- proximately 1,580 vehicle trips per day. This represents less than a 7 Bouthcantar Blvd Tukwila Pkwy Evans -Black Or • 7 • • • Andover Park E LEGEND X OF DAILY PROJECT TRAFF I CN )O % )OC( X OF PM PEAK PROJECT TRAFFIC i XX DAILY PROJECT TRAFFIC 1 PM PEAK PROJECT TRAFFIC NEG = NEGLEG I BLE TUKWILA HOTEL FIGURE 8 PROJECT GENERATED TRAFFIC -22- percent increase in the daily travel. During the peak hour the volume along West Valley Road north of the site is forecasted to increase to about 125 vehicle trips per hour, with the volumes being approximately equally split northbound and southbound, representing a 4 to 6 percent increase. To the south, the increase amounts to less than 7 percent on a daily basis (1,300 vpd) and less than 3 percent during the peak hour (20 vph). Traffic Analysis As discussed earlier in the section on non - project traffic volumes, the only accurate way to assess the true impact of a proposed project like the Tukwila Hotel is to compare the traffic volume at some future year (1983) with and without the project. This shows that West Valley Road north of the site could carry approximately 25,000 vehicles per day (vpd). South of the site the volume drops slightly to approximately 23,000 vpd. The majority of the travel to and from the south will be generated out of Strander Boulevard and further south from 180th Avenue S. To the north, a major increase in volume is forecasted to occur west of the site toward I -5 and the Seattle- Tacoma International Airport. The 1983 peak hour volumes were analyzed using the level of service methods described in the Existing Conditions section of this report. This analysis shows that without the project, the level of service at the I -405 eastbound ramps /West Valley Road intersection will operate at LOS D. With this project, the level of service may drop to LOS D -E. To the north at the I -405 westbound ramp /Grady Way /West Valley Road intersection, the level of service with or without the project will drop to LOS E. South of the site at the Strander Boulevard /West Valley Road intersection, the level of service is forecasted to be LOS D with or without the project. All other intersection locations within the surrounding area are not expected to be noticeably impacted by the additional volumes generated by this project. As noted earlier, the peak hour traffic volumes represent a relatively low percentage of the daily traffic volumes (about 5 %) when compared with other land uses including residential development (the peak hour is 8 -12% of the daily traffic volume) or employment centers (the peak hour traffic volumes represent 18 -25% of the daily traffic volume). -23- Lonqacres Traffic The other times used for evaluating traffic conditions coincided with the time Longacres opened and closed. Unfortunately, none of the traffic counts made in the vicinity of the project reflected exact vol- umes. Discussions with the State DOT, State Patrol and Longacres staff clearly indicated the Longacres traffic arrives and departs in peak surges that are relatively short in duration. On weekdays, the first peak starts about one hour before opening (2:15 to 2:30 PM), then tapers off until 4 :00 PM, when volumes increase again, but are not as high as during pre- opening when the State Patrol is on duty to control inbound traffic. The other peak occurs after the last race of the day (8:00- 9:30 PM). On weekends there are only two peaks -- one before the races start (11:30 AM to 1:00 PM) and one following the close of racing (6:00 to 7:30 PM). Because these peak surges are not forecasted to occur at the same time as the hotel peaks, they were not analyzed in the same detail as was evening peak hour congestion. Examination of forecasted traffic patterns with Longacres was, nonetheless, examined to determine the impact on congestion when Long - acres is in operation. It is estimated that between 500 to 750 vehicles per hour use the southbound left turn into Longacres. The project is expected to generate between 90 to 110 vph with inbound and outbound volumes split about equally. The principal conflict appears to be between cars exiting the site (eastbound to northbound left turns) and cars making left turns into Longacres. The outbound left -turn volume will amount to about one car per minute. Such a low volume would not cause noticeable delay to Longacres traffic. During the peak times, when traffic control is not provided by the Washington State Patrol, the exiting hotel traffic may not be able to find an acceptable gap in the traffic flow along West Valley Road, aria motorists may become frus- trated by the delay and travel south (turn right) to Strander Boulevard and make a "U" turn at the signalized intersection. In summary, the additional hotel volumes are not expected to create any noticeable impact on Longacres traffic flow, but the high volume generated by Longacres is expected to delay, and possibly inconvenience, cars attempt- ing to make left turns out of the hotel site. -24- Entrance Traffic Control Probably the most visible concern regarding this site relates to access directly on and off the site on West Valley Road. The main en- trance to the site is expected to attract the majority of traffic in and out of the development, provided the West Valley Highway will be modified to permit left turns in and left turns out of the driveway. A sketch illustrating such a design is presented on Figure 9. In addition to these channelization modifications, there is some question as to the need for a traffic signal that would serve both access into 158th Street (Longacres Race Track) and the project. Based on an analysis of the daily and peak hour traffic volumes in the vicinity of the northerly entrance, the need for a traffic signal is not warranted. While there will be selected times when signal warrant criteria are satisfied (e.g., following Longacres closing), warrants cannot be met for the full 8 -hour period. A traffic signal may, in fact, add to the congestion at the northern entrance, because it could not simultaneously respond to the peak surges generated by Longacres and maintain coordina- tion with the traffic signals at I -405. If a traffic signal were installed, it would probably need to be turned to flashing operation and supplemented with Washington State Patrol manual control during the peak Longacres traffic periods. Another option for access control is to provide left -turn access in and out of the property, restricting the northern entrance to right -turn traffic in and out, and emphasizing the southerly entrance to the site as a major entrance. This would then divide the concentration of traffic volume in this area to two intersections (one at South 158th Street, and the other at the southerly entrance). Because these entrances are spaced a reasonable distance apart (about 250 feet), safety hazards typical of closely spaced entrances should not present a significant problem. The drawback to the southerly entrance is that it would create out -of- direction travel through the parking area and access would not work as efficiently as would the northerly entrance. It is recognized that many people may not be familiar with or under- stand the underlying philosophy supporting traffic signal warrant criteria. Thus, it is often useful to draw a comparison with similar existing N Ol • • TUKWILA HOTEL t FIGURE. 9 DETAILED 1985 DAILY TRAFFIC W /PROJECT The IRIANSPO Crovp development to illustrate the types of traffic conditions that may be created when a proposed development is completed. Such a comparable location exists along Pacific Highway S. east of the Seattle- Tacoma Airport. Here there are several hotels with primary access off Pacific Highway S. at.unsignalized driveways. Pacific Highway S. is a five -lane (two lanes in each direction with a center two -way left - turn lane) State highway (SR 99) that serves both through traffic and provides local access to roadside business including hotels. This road carries about 32,200 vehicles per day (about 9000 more cars per day than West Valley Road), and traffic control is provided by traffic signals at intersections with principal cross streets that fall within 300 to 1000 feet of the driveways serving hotels used as examples in this comparison. The hotels are the Holiday Inn and the Sea -Tac Red Lion Motor Inn which have 255 rooms and 850 rooms, respectively. Both hotels have restaurants and lounges, and both have meeting rooms; the Sea -Tac Motor Inn strongly markets this space for seminars and group meetings. Observation of traffic patterns at both locations shows there are sufficient gaps in the traffic flow to permit left turns in and out of the parking area without excessive queuing in the center two -way, left -turn lane or in the parking lot. While some traffic is required to wait for a gap in the traffic flow, the wait was not observed to be any longer than the average waiting time for a traffic signal to change, except in the situation when there was a heavy surge in exiting traffic (e.g., when a seminar ends). Therefore, it is recommended that the intersection of West Valley Road /S. 158th Street be rechannelized to permit left turns in and out of the site, but a signal should not be installed. If extraordinary congestion problems result, then one of two improvements should be made: • Close the northerly entrance to left turns and rechannelize West Valley Road at the southerly entrance to permit left turns in and out of the site, or • Install a traffic signal system at the West Valley Road /S. 158th Street intersection even if it needs to be switched to flashing operation during Longacres' peaks. In any case, the applicant should agree to pay their proportional share of costs for installing a signal, since they would derive some benefit from -27- such an improvement. The applicant's share should be based on the pro- portion of traffic generated by this project divided by the total traffic volume passing through the intersection. In summary, the additional traffic volumes generated by the Tukwila Hotel would have a moderate impact on traffic movement in the vicinity of the project, especially north of the site. The relative increases created by traffic volumes generated by the Tukwila Hotel are somewhat similar to the fluctuation in traffic volumes from one day to the next within a given week (e.g., the difference between volumes on a Wednesday compared with those on a Thursday). As a consequence, they will contribute to additional delay and congestion, but their impact will be relatively small. In some cases, the impact will be too small to actually measure. Congestion on I -405 is significant today and will be made worse in the future with or without this project. While this project will contribute somewhat to additional volumes on this roadway, the majority of the project - generated traffic is oriented to and from the west, and thus will have ti possibly less impact than if the majority of traffic were oriented to and from the east. Parking As indicated in the introduction of this report, the project will in- clude 508 parking spaces as part of the project. This complies with City of Tukwila's proposed parking requirements. The City of Tukwila parking requirements appear to fall above generally accepted standards for hotels like the Tukwila Hotel and thus based on experience at other hotels in the area, it is concluded that there should never be a situation where there would be spillover parking onto the adjacent street system as a result of insufficient parking on -site. t, One possible impact relating to parking could be a situation where some people park in the lots serving the office and business park buildings west of the Green River and walk across the proposed pedestrian bridge to the hotel. If this phenomenon exists, it would be expected to occur during the middle part of the day (likely during lunch). This phenomenon is not expected to happen often, both because the walking distance is relatively long (over 1/4 mile) and because it would likely occur only on days when weather was favorable. Nonetheless, such an impact is mentioned as a potential. -28- Safety Hazards Because there will be an increase in traffic volumes along streets in the vicinity of the project, there is the implicit potential for an increase in the number of accidents. Research shows that the number of accidents in an area generally increases in equal proportion to the increase in traffic volumes. Following this approach, it could be expected that the traffic generated by this project would increase the average number of accidents by about one accident per year within a one -mile radius of the site. The most logical location for any increase in access would be at the main entrance to the site. This is where new potential conflicts would be created by left -turn movements in and out of the site. Some of the accident potential can be decreased as a result of the access design by restricting one of the two entrances to right -turns in and right -turns out only. Bicycle and Pedestrian Activity A potential element of this project is a pedestrian bridge that crosses the Green River to the south. Because this bridge will connect to the Christiansen Green Belt and the pedestrian trail within that green belt, it could be expected that the bridge would be used for both hotel - generated and general public. It is expected further that the Christiansen trail might be extended along the east side of the river to the north and even- tually up to Fort Dent Park. It may also be possible that this bridge and path system would be used by cyclists. In terms of hotel - generated traffic, it is expected that guests and people coming to the restaurant and lounge would also use this pedestrian bridge to cross the river between the business park area and the site, or simply to take a stroll. There is not expected to be a noticeable amount of hotel-generated pedestrian or bicycle traffic using or crossing West Valley Highway. Rail, Waterborne and Air Travel The only possible impact that might be created by this project would be the result of the potential pedestrian bridge crossing the river. Presently -29- the Green River is a navigable waterway and as such, there may be some additional review required to permit the construction of the bridge across the river. From a practical standpoint, however, observation of waterborne travel in this area shows there are no large watercraft that use this section of the river. From time to time there are smaller motor powered pleasure boats and row boat /canoes that use the river. There is not expected to be any adverse impact associated with rail travel or safety associated with rail crossings. All the main line rail- roads in the area are grade- separated from the roadway system and thus, the potential for interruption of rail service or conflicts with automobile traffic will not present a problem. There are several rail spurs that cross Strander Boulevard and other streets in the Andover Industrial Park, however, most of the activity associated with any rail movement in these areas is concentrated during the evening and is very infrequent and low volume. As a consequence, it is concluded there will be no adverse impact to rail move - ment or as a result of railroad traffic. While the proposed hotel will have a shuttle service between the site and the airport, it is not expected that the hotel will precipitate any noticeable increase in air travel, rather, the hotel is responding to the increased business activity some of which will involve guests who travel by air and use the Seattle- Tacoma International Airport. Consequently, there is not expected to be any adverse impact created as a result of this project. LEVEL OF SERVICE SUMMARY Future w/o Future w/ Existing Development Development I -405 WB ramps /West Valley Hwy. D -E E E I -405 EB ramps /West Valley Hwy. C D D -E Strander Blvd /West Valley Hwy. C -D D D Longacres (S 158th) /West Valley Hwy. 1) E E E 1) Represents conditions during the Longacres racing season. B Fiscal- Impact Analysis Two models are designed for determining fiscal impacts on non - commercial uses. The Proportional Valuation Method and the Employment Anticipation Method. The Proportional Valuation Method recognizes municipal costs increase with the intensity of land use. The Employment Anticipation Method predicts a change in municipal costs based on an anticipated change in local employment levels and per capita municipal costs. This latter method was determined inappropriate because of the disproportionate number of employees to residents in Tukwila comparitive to comparable sized towns delineated in the model. The Proportional Valuation Method separates existing municipal expenditures associated with non - residential uses from total municipal expenditures by using proportional valuations and refinement coefficients. The future municipal costs associated with the proposed hotel are estimated by using proportional valuation and refinement coefficients applied to total municipal costs induced by the growth created by the hotel. These costs generated by the hotel are then assigned to service categories (general government, public safety, public works, health and welfare, recreation and culture). The associated revenues and expenditures of the proposed hotel incurred by the City of Tukwi la is an approximation based on analysis of the City of Tukwila 1982 Budget and a fiscal impact model referred to as "Proportional Valuation Method" by Burchell and Listokin, authors of the "Fiscal Impact Guidebook, Estimating Local Costs and Revenues of Land Development. Secondary sources of revenue are not computed in these figures. These sources include revenue generated from an increase in local employment during and after construction. Additional Services and goods demanded by hotel guests and associated taxes for goods and services. Expenditures The Proportional Valuation Method requires the following data: Total Municipal Expenditures: Total Real Property Value: Commercial /Industrial Real Property Value: Proposed Hotel Property Value: $ 4,329,080 702,681,000 562,144,800 11,000,000 Non- Residential real property value is not a statistic available from King County Assessors or City of Tukwila Finance Department. This figure was computed by multiplying the average 1980 sales price of single family, apartment, and condominium units in the Tukwila area by the total number of dwelling units in Tukwila. This approximate total residential market value is subtracted from the total real property value to compute the approximate non - residential property value. B ".1 TOTAL AND AVERAGE MARKET VALUES. BY USE Number of Dwelling Approximate Land Use Units or Businesses Total Market Value Average Market Value Residential 2,038 $ 93,662,950 Commercial /Industrial 814 (1978) 562,144,800 Other N/A 46,873,250 $ 45,958 690,595 N/A TOTAL $702,681,000 TOTAL AVERAGE RES-WENTtAL SALES Number of Average Sales Approximate Use Dwelling Units Price - 1980 Total Market Value Single Family Apartments Condominiums 695 1,255 88 $59,741 37,341 60,000 $41,519,995 46,862,955 5,280,000 TOTAL 2,038 - - -- $93,662,950 Total property values for utilities, agricultural lands, public service facilities and vacant lands have been estimated to be approximately 5 percent of the total property value of all uses. Thus, commercial /industrial property values have been computed to be approximately 80 percent of the total property values, or approximately $562,144,800. Commercial /Industrial Municipal Expenditures are computed by multiplying the total municipal expenditures times the ratio of Commercial /Industrial Property Value by Total Property Value. LOCAL COMMERCtAL-f INDUSTRIAL LIE COST PROJECTION Commercial /Industrial Commercial /Industrial Total Municipal Property Value Municipal Expenditure = Expenditure x $16,942 $3,463,264 Total Property Value $ 11,000,000 x x .25 $562,144,800 1 The refinement coefficient is based from case studies by Rutgers University in 1977.. "Fiscal Impact Guidebook" by Burchell and Listokin The approximate municipal expenditures expected to be created by the pro- posed hotel is $16,942. B 2 Burchell and Listokin in "Fiscal Impact Guidebook, Estimating Local Costs and Revenues of Land Development" have estimated the average percentage distribution of total costs to municipal service categories, as listed below: TYPICAL IMPACT OF PROPOSED HOTEL ON LOCAL- PUBLIC SERVICE CATEGORIES Municipal Service Percentage Dollars General Government 6 $ 1,017 Public Safety 75 $ 12,706 Public Works 15 $ 2,541 Health and Welfare 2 $ 339 Recreation and Culture 2 $ 339 TOTAL 100 $ 16,942 Revenuer A.Property Taxes- The estimated value of the proposed project is approximately $ 11,000,000. The breakdown of property taxes for this project is shown in the following table: PROJECTED PROPERTY TAXES (25 Percent of Current Fund) Levy Millage Rate Revenue Percentage City 2.082 $ 22,902 21.75 State 4.740 52,140 49.3 School 2.155 23,705 22.4 G.O. Bond .503 5,533 5.2 Emergency Svcs .129 1,419 1.3 TOTAL 9.609 $105,699 100.0% The proposed project represents an approximate increase of 2.11 percent in property tax revenue to the City. B. Sales Taxes - The estimated revenue generated by the hotel will be approximately $5,000,000 per year. REVENUE GENERATED BY PROPOSED HOTEL1 Number of Rooms Expected Revenue Revenue Generated Per Room Per Year by Proposed Hotel 274 $18,201 $4,987,074 1 "Trends in the Hotel Industry in the Pacific Northwest," 1981 Edition, Pannell Kerr Forster, CPA The breakdown of sales taxes on this project is shown on the following table: B3 PROJECTED SALES TAX (51 Percent of Current Fund) Levy, Rate Revenue Percent City Metro State TOTAL .5 $ 24,935 85 .6 29,922 9 5.5 274,289 83 6.6 $332,750 100% The proposed project represents an approximate increase of 1.0 percent in sales tax revenue to the City. Cumulatively property and sales taxes account for approximately $47,837 in additional revenue to the City. C. Permit Fees - Permit fees were estimated to total $25,987 on the basis of the City of Tukwila's fee schedule for commercial development with an estimated uilding valuation of $11 million. Building permit fees are expected to be $9,837 ($887 for first $500,000 valuation and $1 per $1000 valuation thereafter). Plan check fee is expected to be $6,427,(65% of building permit fee. Conditional Use Permit fee is $240, Design Review (BAR) $60, Shoreline Permit $240, Threshold Determination $60. Cumulative- ly, the proponent will be required to pay approximately $16,914 in fees prior to construction. These fees will help offset municipal service costs prior to project completion. Conclusion - The City of Tukwila does not have a formula with which to allocate tax revenues to individual service categories. Therefore, a comparison of revenue to cost by service function is not possible. However, the estimated total revenue generated by the proposed project ($47,837 annually) exceeds the estimated total municipal service costs ($16,942) by $30,895. This figure does not include the $16,914 in building and plan check fees, and the secondary sources of revenue generated from an increase in local employment during and after construction, additional private services and goods demanded by guests of the hotel and associated taxes for such goods and services. REVE•-NU, IQ TUKW I LA Permit Fees (first year only) $ 16,914 Property Tax $ 22,902 Sales Tax 24,935 Total (annual) $ 47,837 64 REVENUE TO OTHER JURISDICTIONS Property Tax to School District Property Tax to Emergency Services Property Tax to G.O. Bond Property Tax to State Sales Tax to Metro Sales Tax to State $ 23,705 1,419 5,533 52,140 29,922 274,289 Total (annual) $387,008 B 5 C J -82 -208 CULTURAL RESOURCE EVALUATION OF THE PROPOSED TUKWILA HOTEL SITE TUKWILA, WASHINGTON SUBMITTED TO: CHRISTENSEN GROUP, INC. 2500 NORTHEAST ANDRESEN VANCOUVER, WASHINGTON 98661 SUBMITTED BY: GEO -RECON INTERNATIONAL, LTD. P.O. BOX 55189 SEATTLE, WASHINGTON 98155 /?//2/744!_,>&4Pt_, RINITA DALAN Approved by: STEVE WILKE STAFF ARCHAEOLOGIST VICE PRESIDENT JANUARY 29, 1982 ACKNOWLEDGEMENTS Numerous individuals provided assistance or information during this project. Appreciation is due Mr. Jon Potter of R. W. Thorpe and Associates, Mr. Ken Baines of Christensen Group, Inc., and Mr. George Yamane and Mr. Tom Grutowski of Shannon & Wilson, Inc. Ms. Helen Nelsen and Ms. Sidonia Nelsen Kettering generously shared their knowledge of the area's history and land use. INTRODUCTION This report presents the results of an archival and field investigation designed to determine if the lands encompassed by the proposed Tukwila Hotel were associated with any people or events or contained any physical remains of potential local, regional or national significance. LOCATION AND DESCRIPTION OF PROPOSED DEVELOPMENT The proposed Tukwila Hotel site is located within the Southwest Quarter of the Southwest Quarter of Section 24, Township 23 North, Range 4 East, Willamette Meridian. The site is bordered on the south and west by the Green River, and on the east by West Valley Highway. The total acreage of the site is 5.47 acres (Figure 1). Approximately 90 percent of the site will be developed. Available information states that the proposed development will include an eight story hotel with space for approximately 270 guest rooms and a paved area with parking for 534 vehicles. ENVIRONMENTAL SETTING Geology and Hydrology The proposed hotel site lies within the northern portion of the Puget Trough physiographic province as defined by Franklin and Dyrness (1973). The geology and topography of this northern portion, known as the Puget Sound Basin, have resulted almost entirely from the occupation of the region by a lobe of the Cordilleran ice sheet during the Pleistocene (Folsom 1970, Mark and Ojamaa 1972). There were apparently at least four distinct episodes of glaciation during the Pleistocene, the Vashon glaciation being the most recent. Glacial episodes were separated by nonglacial intervals; during which erosion, weathering, and nonglacial sedimentation occurred. During the Vashon glaciation, the lower Green River Valley was scoured to its present width and to a depth of over 15 meters below present sea level. As the ice sheet retreated, it dammed the northern end of the valley, and a lake of over 76 meters in depth was formed. As the ice continued to melt, the lower valley became a marine embayment much like other arms of the present Puget Sound. Following the glacial retreat, the Green River quickly incised a meandering path across the Black Diamond area instead of resuming the more northerly route it had followed during pre - glacial times. The river then flowed into the arm of the Sound occupying the lower valley. For some time during, and possibly after the retreat of the glacier, the Cedar River flowed southwest into the Green. By 13,000 years ago, however, it followed a more direct route to the Sound along its present path and built a fan across another arm of the valley to form Lake Washington. About 5,000 years ago, the Osceola mudflow swept down from the upper slopes of Mt. Rainier, flowed down the White River valley and spilled out across the lowland, flow- ing on into the narrow lower Green Valley arm of the Sound, -3- and eventually came to rest just north of Auburn as a submarine deposit. As the White River channel was obliterated, the river cut a channel northward and joined the Green River at the present site of Auburn. The White River deposited coarse debris eroded from the mudflow deposit and sediment derived from the Mt. Rainier area to form a massive fan into the lower valley. Finer sediments were carried beyond the fan into the marine embayment. In this manner, the combined flows of the White, Green, and eventually the Black Rivers contributed sediment to a narrow delta which gradually crept northward and filled the lower valley (Dunne and Dietrich 1979: A- 5 -A -6). During the last 75 years, numerous changes have occurred in the stream pattern of the Green River. Prior to this time, the Green River joined the White River near the site of present -day Auburn. This combined stream was known as the White River Valley to the point where it was joined by the Black River near Tukwila. From the Black River to Elliott Bay, the river was known as the Duwamish. The waters of Lake Washington had an outlet through the Black River, and the Cedar River could flow into either the Black River or Lake Washington. During.a serious flood in 1906, debris blocked the main channel of the White River, which then cut its way southward into the Stuck River, which flowed into the Puyallup River and hence to Commencement Bay at Tacoma. In subsequent flood - control efforts, the diversion of the White River was made permanent. In 1913, dredging and straightening began on the lower Duwamish in order to create a. waterway by which oceangoing liners might come into Seattle (Cleveland High School 1974:72). In 1917, the Lake Washington Ship Canal and Government Locks at Ballard were created, causing the level of Lake Washington to fall. This practically stopped the flow of the Black River, which today remains as only.a small drainage ditch. The Cedar River was also permanently dredged into Lake Washington to assure sufficient water for operation of the locks at Ballard (Pence 1946:26, Lane 1973b:9 -12). Since these changes have occurred, the Green River is now the correct name for the stream in the entire valley. The valley has historically been subject to flooding on an annual and semi - annual basis caused by high run -off resulting from a combination of snow melt and excessive precipitation. Early attempts to control this flooding consisted of dikes constructed by local interests and the operation of two drainage districts. Next came gauging stations and surveys to find a solution to stopping the bank overflows. The danger of severe floods was not averted until Howard A. Hanson Dam began operating in 1962 (Jones and Jones 1979). Levees have been constructed along the portions of the project area that border the river. It should also be noted that sequential topographic surveys and aerial photographs for the Green River covering the period from 1898 to 1978 show that river meanders have shifted across the floodplain at average rates of up to 18 meters per year, although the majority of rates below Auburn have been less than three meters per year. Flooding and channel changes potentially'have affected cultural resources along the river's length. The deposition of sediments over resources also hinders their recognition. Soils The soils of the lower Green River Valley have developed from the enormous quantities of alluvium deposited in post- glacial times. Soils in the lower valley belong to the Oridia- Seattle- Woodinville association. These somewhat poorly drained and very poorly drained soils occur in all the major stream. valleys in King County and are the most suitable soils for farming. The Oridia- Seattle - Woodinville association consists of approximately 17 percent Oridia soils, 13 percent Seattle soils, and 10 percent Woodinville soils. The remaining 60 percent is comprised of soils of small extent including Briscot, Edgewick, Newberg, Nooksack, Pilchuck, Puget, Puyallup, Renton, Si, Sultan, Snohomish, Shalcar, and Tukwila soils. The soil within the study area is classified as a Sultan silt loam, high bottom. Climate The climate of the study area is a mid - latitude, west coast marine type characterized by a well defined dry season in the summer and a rainy season in the winter. Precipitation is light in the summer, increases in the fall, reaches a peak in the winter, and then decreases in the spring, with a slight increase in May and June followed by a sharp drop near the first of July. Seventy -five percent of the annual precipitation falls between October and March. December has the highest precipitation while the least precipitation falls in July. Maritime air has a moderating influence on summer and winter temperatures while surrounding hills and mountains shield the area from the more intense Pacific winter storms. The prevailing wind is from the southwest in the fall and winter, gradually shifting to the northwest in late spring and summer (Phillips 1968:4 -12). The mean annual temperature is generally around 51° to 52 °F in the lower valley with July being the warmest month and the coolest temperatures occurring in January. The length of the growing season is approximately 175 days (U.S. Army 1949:26). Flora and Fauna The study area lies within the Puget Sound area of the Tsuga heterophylla zone, one of the major vegetational areas defined by Franklin and Dyrness (1973). Major forest tree species in this zone include Douglas -fir (Psuedotsuga menziesii), western hemlock (Tsuga heterophylla), and western red cedar (Thuja plicata). Black cottonwood (Populus trichocarpa) and Oregon ash (Fraxinus latifolia) with bigleaf maple (Acer macrophyllum) and red alder (Alnus rubra) are species which are found along the major watercourses. Franklin and Dyrness (1973) describe a spectrum of understory communities arranged along moisture gradients within this zone. In the Puget Sound area, the most common species are vine maple. (Acer circinatum), broadleaf rhododendron (Rhododendron macrophyllum), Pacific dogwood (Cornus nuttalii), red huckleberry (Vaccinium parvifolium), Oregon grape (Berberis nervosa), salal (Gaultheria shallon), and trailing blackberry (Rubus ursinus). The Green River area supports a diverse fauna due to the presence of numerous habitat types, including riparian woodland, fields, marshes, shrub swamps, ponds, mixed forest, coniferous forest, developed areas, and the river itself. -7- A variety of mammals utilizes the forests, meadows, and waters of the area. Significant numbers of avian species have been observed. The lower Green River Valley is a significant wintering area and migration corridor for waterfowl in the Puget Sound area. Amphibians, including various species of frogs and salamander, are found in shallow ponds, sloughs and slow moving streams. The reptilian fauna is not particu- larly diverse, but several species of snakes and lizards do occur (Erkmann 1979). The river itself supports a varied ichthyofauna, particularly in the sections under tidal influence. Salo and McComas (1979) list 44 different species of fish utilizing the river estuary system. CULTURAL HISTORY Prehistory The prehistory of the lower Green River Valley is not well known. Few professional cultural resource surveys have been conducted and although three sites in the vicinity have been excavated (45- KI -23, 45- KI -51, and 45- KI -59), excavation reports are not yet available. The Duwamish No. 1 Site (45- KI -23), located downstream from the project area on the Duwamish Waterway, appears to have been occupied prior to the contact period. The oldest dendro- corrected C -14 date obtained is 670 AD and the youngest is 1690 -1800 AD (Sarah Campbell, personal communication). Although C -14 dates are not yet available for 45- KI -59, it is felt that this site was occupied somewhere between 200 -1000 AD. This date is assigned on the basis of the presence of small corner - notched projectile points. This site, along with 45- KI -51, is located along the abandoned channel of the Black River near Renton. 45 -KI -51 appears to be the remains of a proto- historic longhouse occupied during the first two decades of the 19th century (45- KI -51D) and the remains of what may have been a series of small dwellings occupied for a brief period in the mid -19th century (45- KI- 51A)(Jim Chatters, personal communication). Excavations at both 45 -KI -59 and 45 -KI -51 indicate a primarily riverine adaption of their inhabitants, with a primary focus on salmon. Hunting and gathering also appear to have been practiced, and marine resources were utilized to some extent. There appears to have been more of an emphasis on marine resources at 45- KI -23, a probable result of its location close to the Sound. A check of site files maintained by the Office of Public Archaeology at the University of Washington reveals that in 1963, a shell midden site (45 -KI -6) was located just north of the study area. The site was recorded as containing shell, charcoal, fire-cracked rock, wood, and chipped stone. The site lay in the path of a relocation channel for the Green River and was hence completely destroyed. Helen Nelsen, daughter of James Nelsen who settled in the area in 1884, states that Indians camped at this point on the river when her family settled in the area (Helen Nelsen, personal communication) . Ethnography Ethnographic sources record several Native American groups inhabiting the Green River drainage system. The Duwamish inhabited the area from the river's mouth up to -9- and including the Black and Cedar Rivers; the Sammamish and Sktahlmish were the Lake Washington groups; the Smulkamish were located at what was then the head of the White River, the Skopamish people lived on what was then the upper Green River, and the Stkamish lived on what was then called the main White River (from the confluence of the White and Green Rivers to the mouth of the Black River)(Lane 1973a). All groups were included together under the Treaty of Point Elliot, signed January 22, 1855. The settlement pattern of these groups was seasonal. In the winter months, people gathered in politically autonomous groups at permanent winter village sites. These permanent villages were occupied by the entire village group only during the winter, at other times of the year, portions of the population dispersed to secure food and other supplies as they became available. Houses at the winter village sites were constructed on bits of high, well drained ground. Village size varied from one to three houses, with each house large enough for four to six families (Smith 1940:4). Houses were rectangular and were constructed of cedar planks. These planks were fastened to a superstructure built of large cedar logs (Lorenz et al. 1976:19). After the settlement of the valley by non - Indians, the house style changed. Instead of multi- family dwellings, several began to build homes for single families (Noel 1980:11). In the spring, people began to disperse from their winter villages to the beach areas where mollusks and other Marine resources were collected. Certain species were consumed on the spot while others were processed for later -10- use (Lorenz et al. 1976:21). Following the gathering and processing of the winter shellfish supply, the women went to root and berry collecting stations (Haeberlin and Gunther 1930) . The men were involved in the pursuit of fish from the beginning of the summer until November. Four species of salmon and the steelhead were the most sought after fish. Indian fisheries existed throughout the drainage system from the upper reaches of the tributaries to the waters of the Sound. Fish weirs probably accounted for the bulk of the fish taken, but considerable numbers were secured with other devices including funnel snares, grills, nets, and spears (Lane 1973b:1 -8). Although most of the summer subsistence activities centered on fishing and plant gather- ing, there was also some hunting of terrestrial mammals. As people dispersed in the spring and summer to gather foodstuffs, temporary summer homes were constructed from woven mats. Poles were set up and mats, carried from the interior walls of the permanent houses, were laid over the poles and attached with strips of hide, nettle, or cedar bark twine (Noel 1980:10). According to Haeberlin and Gunther (1930), Puget Sound summer homes were constructed as single family dwellings and were either teepee- shaped or square. A check of ethnographic sources has revealed several village sites and temporary camps within the Green River drainage system, however, none are located within project boundaries. Daughters of early settler James Nelsen both stated that no Indians camped within the project area during their lifetimes (Helen Nelsen and Sidonia Nelsen Kettering, personal communication). History The first settlers in what is now King County settled near the mouth of the Green River in 1850 and 1851. With the opening of the road through Naches Pass in 1853, a new wave of settlers arrived in the valley. From 1853 to 1855 numerous settlers acquired land in the valley under the Federal Donation Land Act. One of these settlers, Henry Meter (Meader) claimed land encompassing the project area. The Henry Meter claim is shown on the 1862 General Land Office (GLO) plat map, although no structures or improvements are indicated on the property. The first task facing these early settlers was to clear the land. In the area bordering the river, except for the few natural prairies, the growth was particularly dense. Maple, vine maple, cottonwood, ash, and alder were interspersed with conifers. The Native Americans in the region were often employed to help with clearing and with the planting of crops (Bagley 1929:693). Logging operations were deferred in the valley, as fir and cedar grew either in scattered stands or in a tangle of unmerchantable growth. In addition, the sandbars and meandering course of the lower Green River made the stream unsuitable for floating rafts or logs to the mills (Pence 1946:76). These early settlers were occupied with farming, although many of them had been trained in other trades. This dependency of the economy on agriculture has remained constant through time, although the principal source of farm income has changed. Up to the 1940's, industrial development of the valley was limited. After this time, however, industrial development became more rapid, especially in the lower valley. Flat lands provided suitable factory sites when Seattle industries began to spread up the Duwamish Waterway. The river served as the main avenue of transportation for the early settlers. Trails were also used, as well as crude roads built mainly by the settlers, often with puncheons laid over swampy areas. The coming of the railroads in the 1880's, however, brought an end to the dominance of river transportation. Small towns and centers that had already sprung up at various crossroads and steamship landings grew into thriving farming centers. Mainly, these centers became important transfer stations for local farmers anxious to send their produce to Seattle and receive manufactured goods in return. With the advent of good roads and automobiles, many of these centers, dependent as they were on the railroad, were not able to survive. A check of files maintained by the King County Office of Historic Preservation shows that the James Nelsen house, built in 1905, lies just north of the study area. This house is also shown on a 1907 Duwamish - Puyallup survey map provided by the U.S. Army Corps of Engineers. In 1884, James Nelsen homesteaded 20 acres in the Renton junction area. Ultimately, he acquired 280 acres of land in the valley. Around 1900, James sold,100 acres to his brother, Fred, who developed a prosperous dairy farm. By 1927, James also had a prosperous dairy farm. In 1934, James leased 107 acres to the Washington Jockdy Club. He later sold the land to them. Today it is known as Longacres Racetrack. When James and his wife Mary Dobler married, they lived in a small house at 16010 West Valley Road. In 1905, Mary consulted with a local carpenter to design a new home. This is the home referred to in the King County Office of Historic Preservation records. James and Mary had four children: Harry J. (1885- 1975), Frank A. (1890 - 1972), Sidonia (1895- ), and Helen A. (1906- ). These latter two children were both interviewed and provided considerable information on the history of the project area. A 1935 aerial photograph shows only a portion of one structure lying within the project area. A barnyard or turnaround is also shown to the west and south of this building. The rest of the project area appears to be in pasture at this time. FIELD METHODS AND RESULTS A complete coverage survey of the proposed Tukwila Hotel site was conducted on January 26, 1982. Surveyors walked transects across the site, with spacing between surveyors varying from seven to 10 meters. Because surface views were hindered by a cover of grass, the surface was cleared with a shovel every five to 10 meters. As the river was quite high, surveyors were not able to inspect the river bank. The project area was also systematically cored with a one -inch push tube sampler. Cores were taken every 30 to 35 meters to a depth of two meters, except in the northeastern portion of the site where rock fill prevented coring. Approximately 16 cores were taken, however, no cultural soils or modifications such as ash lenses, fired soils, or organic staining were noted (Figure 1). The on -foot inspection revealed a large concrete foundation located partially within the northeastern corner of the unit (Figure 1). The foundation measured 30.3 meters north /south and was 13.6 meters wide on its north end and 19 meters wide on its south end. Bases of wood posts were still evident as were water spigots. Plywood and milled boards were piled on top of the foundation. According to informants, this foundation was that of a barn built around 1903. It was originally used as a dairy barn but then came to be used as an auction barn. In 1969, it was moved east across the West Valley Highway where it stands today (Helen Nelsen and Sidonia Nelsen Kettering, personal communication) . Associated with the barn was a barnyard filled with gravel and rock. Part of this area has grassed over. This barnyard area covered much of the northeastern quarter of the project area (Figure 1). According to Mrs. Kettering, part of this rock was brought in by developers (Sidonia Nelsen Kettering, personal communication). Near the center of the site, in a six meter square area surrounding two pizometer tubes, small pieces of shell in a grey /black fine sand and solidified oil were noted lying on the surface (Figure 1). Five cores were taken within this area to a depth of 2.7 meters (Figure 1). The scatter of shell on top of the ground surface proved to be two to three centimeters -15- thick. No shell layer was encountered below the soil horizon. A few small flecks of charcoal and one piece of shell were recovered in two separate cores at a depth of 60 to 70 centi- menters. A four -inch bucket auger was also employed to a depth of one meter, but no cultural soils were noted. Contact with personnel at Shannon & Wilson, Inc., who had conducted soil borings at the site in 1973 and again in 1982, revealed that the shells had come from a depth of 101 -119 feet (30.8 -36.3 meters). The depth of this layer and its location above a very dense, grey, silty sandy gravel suggests that it is a natural not a cultural deposit. It was most likely deposited following the retreat of the glacial ice sheet when the lower valley was a marine embayment (refer to page 2). Also noted were an area containing numerous broken cement slabs and a large (76 X 4 meter) linear pile of milled boards and posts (Figure 1). Associated with this wood dump were a metal trough, part of a wagon, bed springs and ceramic pipe. According to Mrs. Kettering, this lumber and other debris came from the interior of the auction barn when it was remodeled (Sidonia Nelsen Kettering, personal communications). Modern debris including styrofoam, metal, plastics, beer bottles, glass, wood and cement were scattered throughout the project area. CONCLUSIONS AND RECOMMENDATIONS On the basis of our investigation, it is concluded that no remains of local, regional or national significance are present within the bounds of the proposed Tukwila Hotel site. Therefore, within the limits of the methods employed, it is believed that the proposed development should have no adverse effect on significant cultural resources. In light of the poor ground visibility and the probability of a large amount of alluvial deposition over the area, however, it is recommended that a qualified archeologist conduct on -site monitoring during land clearing, access road construction and building site prepara- tion. In the absence of on -site monitoring, should cultural materials be uncovered during the development of the property, a qualified archeologist should be immediately contacted and the materials evaluated. )C A tib X REDEPOSITED ?'� _ SHELL X X x xl _/ X 'r PROPERTY LINE "Th. 1 X r BARN ' FOUNDATION x 1�- BARNYARD KEY: x APPROXIMATE LOCATION APPROXIMATE CORE LOCATION NOTE: DRAWING ADAPTED FROM JENSEN KRAUSE & SCHOENLEBER SITE PLAN' DATED NOVEMBER 1981. 11 0 GREEN RIVER 1 1 1 i0 SCALE IN FEET GEO -RECON INTERNATIONAL PROPOSED TUKWILA HOTEL SITE CULTURAL RESOURCE INVESTIGATION JANUARY 1982 L J -82 -20e FIG. 1 BIBLIOGRAPHY Bagley, C. B. 1929 The History of King County. S. J. Clarke Co., Chicago. Cleveland High School 1974 The Duwamish Diary (second printing), Shorey Facsimile Reproduction, Seattle. Dunne, T. and W. E. Dietrich 1979 Geomorphology and hydrology of the Green River. Appendix A in A River of Green, a planning report to the King County Department of Planning and Community Development by Jones and Jones. Erckmann, J. 1979 Habitat and wildlife assessment for the upper and lower Green River valleys. Appendix C in A. River of Green, a planning report to the King County Department of Planning and Community Development by Jones and Jones. Folsom, M. M. 1970 The glacial geomorphology of the Puget lowland, Washington and British Columbia: comments and selected references. Northwest Science 44(2):143 -146. Franklin, J. F. and C. T. Dyrness 1973 Natural vegetation of Oregon and Washington.' USDA Forest Service, General Technical Report PNW -8. Haeberlin, H. and E. Gunther 1930 The Indians of Puget Sound. University of Washington Publications in Anthropology 4(1):1 -84, University of Washington Press, Seattle. Jones and Jones 1979 A River of Green. Planning report to the King County Department of Planning and Community Development. Lane, B. Lane, B. 1973a Anthropological report on the identity and treaty status of the Muckleshoot Indians. Unpublished Ms. 1973b Anthropological report on the traditional fisheries of the Muckleshoot Indians. Unpublished Ms. Lorenz, T. H., G. R. Spearmann, and J. V. Jermann 1976 Archaeological testing at the Duwamish No. 1 Site, King County, Washington. Office of Public Archaeology, University of Washington, Reconnaisance Report 8, Seattle. Mark, D. M. and P. M. Ojamaa 1972 The glacial geomorphology of the Puget lowland, Washington and British Columbia: further comments and references. Northwest Science 46:336 -338. Noel, P. S. 1980 Muckleshoot Indian History. Auburn School District No. 408, Auburn, Washington. Pence, W. R. 1946 The White River Valley of Washington. MA thesis, Department of Geography, University of Washington, Seattle. Phillips, E. L. 1968 Washington climate for these counties: King, Kitsap, Mason, Pierce. Cooperative Extension Service, College of Agriculture, Washington State University, Pullman. Salo, E. and R. L. McComas 1979 Aquatic resources of the Green - Duwamish River; with enhancement possibilities. Appendix B in A River of Green, a planning, report to the King County Department of Planning and Community Development by Jones and Jones. Smith, M. 1940 The Puyallup - Nisqually. Columbia University, Contributions to Anthropology 32. U. S. Army Corps of Engineers 1949 Green and Duwamish Rivers, and Duwamish Waterway, Seattle Harbor, Washington. 1(.)HN SI'ELLMAN Governor STATE OF WASHINGTON OFFICE OF ARCHAEOLOGY AND HISTORIC PRESERVATION 111 West Twenty-First Avenue, KL -11 • Olympia, Washington 98504 • (206) 753 -4011 Rick Seaborne R.W. Thorpe & Associates 815 Seattle Tower 3rd & University Seattle, WA 98101 JAC( )1i 11 a )MA', Dirrt.1 Date: January 15, 1982 Log Reference: 282-C -KI -03 Project Title: proposed hotel development Tukwila Dear Applicant: We have reviewed the materials forwarded to us for the above referenced project and would like to make the following comments: REVIEW RESULTS: A search of our records, including the National and State Registers of Historic Places and the Washington State Archaeological and Historic Sites Inventories, indicates the following for the project area: project area has not been surveyed for the presence of cultural resources. _ project area has been surveyed for historic/ archaeological resources: intensive survey/ reconnaissance survey/ partial survey. X surveys have been conducted in the general vicinity of the project area. _ sites as noted below have been identified in the project vicinity: historic sites: National Register/ State Register/ Inventory. archaeological sites: National Register/ State Register/ Inventory. X known site distributions, ethnohistoric sources, and /or consultation with others indicates that the project area has X high /__ moderate/ low potential for the occurrence of previously unidentified cultural resources. _ no sites have been recorded in the immediate project vicinity, however, this may be due more to a lack of information than an actual lack of resources; please note above whether or not the project area has been professionally surveyed for cultural resources. IMPACT ASSESSMENT: Based on the information provided for our review, we have determined that the proposed project /plan: _ will have no effect on cultural resources. _ will have no adverse effect on cultural resources. will have an adverse effect on cultural resources noted below: we do not have sufficient information to determine whether or not the project or proposal will affect cultural resources. RECOMMENDATIONS: Based on the results of our records searches, consultations, and the materials provided for our review, we make the following recommendations: no further consideration is necessary at this time. _ site preparation and other ground disturbing activities should be monitored by a professional archaeologist. X professional surveys of the project area should be conducted prior to further action: historic/ x archaeological/ architectural. _ resources have been identified as noted above; the current condition of these resources and the potential for impact to them should be professionally assessed prior to further action. a plan to adequately mitigate anticipated impacts should be devised in consultation with this office and implemented prior to further action. we do not have sufficient information on which to base recommendations. The above comments are based on the information available at the time of this review. Should additional information become available, our assessment may be revised. In the event that cultural materials are inadvertently discovered during construction, work in the immediate vicinity should be discontinued and this office notified. Please indicate the log reference number noted above in further communications concerning this project. A copy of these comments should be included in subsequent environmental documents. Sheila Stump Archaeologist db Form AHP R -5 (2/81) CHAPTER 5 - ENVIRONMENTS The designation of shoreline environments is based on: 1) the existing shore, channel and cultural values as determined in the inventory of shoreline characteristics; 2) the existing land uses and those proposed in the Comprehensive Plan; and 3) the manage- ment objectives. In summary, the majority of the natural and cultural values inven- toried in the designation of environments process were located along the edge of the river shore. All of the land within the 200 foot jurisdiction of the Act is either zoned industrial or presently developed under urban uses. The management objectives are directed at minimizing adverse impacts on the river and shore- line ecology, maximizing the aesthetic quality and recreational opportunities of the river shore, and recognizing the rights and privileges of property owners. In response to these considerations, the shoreline environment is designated as follows: Urban Environment: DEFINITION: The urban environment shall include the total two hundred (200 feet from tkWe mead high_ waark T is designation shall encompass the entire length of the Green • River Shoreline within the City of Tukwila corporate"rtmits. The urban environment includes areas to be managed in high intensiye inn' uses, including— resideen-t`ra'r; commercial and in ustrial development and accessory uses, while providing for restoration and preservation to ensure long -term protection of natural and cultural resources within the shoreline. This designation is considered to be the most equitable of the alternatives examined and provides a uniform basis for regulating uses. 5.1 D CHAPTER 6 - USE REGULATIONS Use regulations are the legal tools for implementing the manage- ment objectives and the goals and policies of the Master Program. Compliance wth the Use Regulations is a condition for obtaining a shoreline development permit. For the purpose of the Shoreline Master Program, shoreline uses include all structures and accessory facilities associated with industrial, commercial, residential and recreational activities. These regulations apply to the property owner, contract purchaser and leasee. General Regulations ALL SHORELINE USES MUST CONFORM TO THE FOLLOWING GENERAL REGULATIONS: 1. The use is not in conflict with the regulations of the City of Tukwila Zoning Code. 2. The use does not conflict with the goals and policies of the Master Program or the intent of the Shoreline Management Act. 3. No structures or accessory facilities shall be located over the river unless such structure is needed to protect or promote the public interest. 4. There shall be no disruption of existing trees or vegetation along the river shore unless necessary for public safety or flood control. 5. Erosion control measures shall be consistent with the standards of the Soil Convervation Service, United States Department of Agriculture. 6. The use of pesticides, herbicides and /or fertilizers shall be consistent with the standards and regulations of the Washington State Department of Agriculture, Washington State Department of Ecology, and the United States Environmental _a_ P=ote_ction Agency. 7. No effluent shall be discharged into the Green.River which exceeds the water quality classification as established by the State Department of Ecology for the adjacent portion of the river. 8. All state and federal water quality regulations shall be strictly complied-with. 9. Wildlife habitat in and along the river shall be protected. 6.1 10. All perimeters of land fills shall be provided with vegetation, retaining walls or other satisfactory mechanisms for erosion prevention. 11. All necessary permits shall be obtained from federal, state, county or city agencies. 12. Dredging for purposes other than for navigational improvements or flood control is prohibited. 13. Mining is prohibited along the river shoreline. 14. Solid waste disposal is prohibited along the river shoreline. 15. No property will be acquired for public use without just compensation to the owner. 16. Off- premise advertising signs are not allowed within two hundred (200) feet of the mean high water mark. In addition to the general regulations, the following specific regulations will apply to the three management zones: RIVER ZONE: The River Zone is an impact buffer area which provides for resource protection, flood control maintenance, pollution control and land- scape enhancement. This zone shall conform with one of the following, either A or B: A. The River Zone shall consist of 50 feet, as measured on a horizontal plane, from the mean high water mark and shall contain no uses other than the following shoreline uses: 1. Access roads not to exceed 24 feet in width. 2. Railroad lead tracks, as defined within this Program. 3. Public and /or private foot paths or trails. 4. Recreation facilities such as benches, tables, view- points, overlooks, etc. 5. Recreation structures such as picnic shelters not to exceed fifteen feet in height. 6. Support facilities for pollution control such as run- off ponds and filter systems, provided they are on or below grade. 7. Information and direction signs conforming to the underlying zoning district. 6.2 8. Diking for flood control purposes. B. The River Zone shall consist of 40 feet, as measured on a horizontal plane, from the mean high water mark and shall contain no uses other than: 1. Public and /or private foot paths or trails. 2. Recreation facilities such as benches, tables, view- points, overlooks, etc. 3. Recreation structures such as picnic shelters not to exceed fifteen (15) feet in height. 4. Support facilities for pollution control such as run- off ponds and filter systems, provided they are on or below grade. 5. Information and direction signs conforming to the underlying zoning district. 6. Diking for flood control purposes.. River Zone Uses Shall Conform to the Following Standards: 1. Access roads shall be located no closer than twenty -five (25) feet to the mean high water mark. 2. The centerline of railroad lead tracks shall be located no closer than forty (40) feet to the mean high water mark. 3. The River Zone shall be landscaped with suitable plant material from the appropriate set -back line or edge of road or track to- the river, consistent with flood control measures, as follows: a. Large hardy shade trees at a maximum of 30 feet on center such as sycamore, maple, willow, oak, beech, walnut, ash, alder, poplar, cottonwood, birch and black locust. b. One of the following: 1. Live groundcover at a maximum of 18. inches on center such as ivy, salal, salmonberry, oregon grape. 2. Natural grass such as red fescue, field grass, clover. 3. Addition to the existing natural vegetation where appropriate. 4. Recreation structures shall not be located closer than twenty - five (25) feet to the mean high water mark. 6.3 5. Other,facilities such as pumps, pipes, etc. shall be suitably screened with hardy plant material. 6. Utility easements where necessary shall be landscaped with live groundcover or natural grass cover. LOW IMPACT ZONE: The Low Impact Zone is a transitional area outside the River Zone and within 100 feet of the mean high water mark intended to minimize physical and visual impact on the River Zone while accommodating shoreline development and shall contain no uses other than those allowed in the River Zone and the following: 1. Structures not to exceed thirty -five (35) feet in height. 2. Parking /loading and storage facilities. 3. Railroad lead and spur trackage. 4. Utilities and signs not to exceed regulations of the under- lying zoning district. Low Impact Zone Uses Shall Conform to the Following Standards: 1. Structures shall be sited and appropriately landscaped in accordance with underlying zoning district regulations . (Appendix C). 2. Access roads shall be located no closer than ten (10) feet to buildings, spur tracks or parking /loading and storage facilities and the effective set -back area shall be suitably landscaped. This shall not prohibit access and egress points between an access road and the described facilities. 3. Where access roads exist parking /loading and storage facilities shall he appropriately screened :from the river with: a. A solid evergreen screen of a minimum six ( 6 ) foot height. OR b. Decorative fence six (6) feet high. (NOTE: Chain link fence shall be planted with ivy or other trailing vine.) OR c. Large hardy shade trees as per requirements for access roads. OR d. Earth berms at a minimum of four (4) feet high suitably planted with live groundcover or natural grass. 6.4 4. Lead trackage shall be no closer than fifteen (15) feet to parking /loading and storage facilities, and shall be suitably landscaped. High Impact Zone Regulations SHORELINE USES ALLOWED IN THE HIGH IMPACT ZONE ARE: 1. All uses allowed in the underlying zoning district (Appendix C). High Impact Zone Uses Shall Conform to the Following Standards: 1. All regulations in conformance with the underlying zoning district and the general use regulations of the Master Program. 6.5 Vegetation Found at the Site Common lime TREES: Black Cottonwood Sig -leaf Maple Oregon Ash SHRUBS: Pacific 4.'i l low Japanese Knotweed Himalayan Blackberry Red Elderberry HER5ACEOUS PLANTS: Stinging nettle Sourdock Buttercup var. Clover var. Foxglove Common !'uI lein English Plantain Mayweed Chamomile Hairy Cats -ear Wild Lettuce Common Tansy Common Dandelion Fescue -grass var. Foxta i I Barley Bluegrass var. Source: R.W. Thorpe and Associates Scientific Nc,ne Popu1us trichocarpa Acer macrophy I 1 urn Fraxinus latifolia Salix lasiandra Polygonum cuspidatun Rubus discolor Sarnbucus racenosa Urtica Iyallii Rumex cr i spus Ranunculus sp. Trifoliurn spp. Digitalis purpurea Verbascum thapsus Plantago lanceolata Anthenis cotula Hypochaeris radicata Lactuca sp. Tanacetun vulgar:' Taraxacum officinale Festuca sp. Hordeurn muri nun Poo sp. Mammals of the Lower Green River Watershed Common Name American Oppossum Cinerous Shrew Vagrant Shrew Dusky Shrew !later Shrew Marsh Shrew Trowbr i dges' s Shrew Shrew-mole Townsend' s Mole Coast Mole Various Bats Eastern Cottontail Snowshoe Hare Mountain Beaver Townsend's Chipmunk Eastern Gray Squirrel Fox Squirrel Douglas's Squirrel Northern Flying Squirrel Deaver Common. Mouse Mountain Deer `Mouse Bushy- Tailed Wood Rat Gapper's Red - Backed Mouse Townsend' s Meadow house Long-tailed Meadow Mouse Oregon Meadow i louse Muskrat Norway Rat Black Rat House Blouse Pacific Jumping Mouse Porcupine Nutria Coyote Red Fox. Black Sear Raccoon Short-tailed Weasel Long-tailed Weasel Mink Spotted Skunk Striped Skunk River Otter Bobcat Black- Tailed Deer Scientific Name Didelphis marsupialis Sorex cinereus -Sorex vagrans Sorex obscurus Sorex palustris Sorex bendirei Sorex Trowbr i dge i lleurotrichus gibbsi Scapanus townsendi Scapanus orarius Ch1roptera Sylvilagus floridanus Lepus americanus Aplodontia rufa Eutamias townsendi Sciurus carolinensis Sciurus niger Tamiasciurus douglasi Glaucomys sabrinus Castor fiber Peromyscus man1cu1atus Peromyscus oreas Neotoma c1nerea Clethrionomys gapperi °1 i crotus townsendi iiicrotus longicaudus ^'1 crotus oregon1 Ondatra zibethicus Rattus norvegicus Rattus rattus Mus muscu I us Zapus trinotatus Erethizon dorsatum (iyocastor coypus Canis Iatrans Vulpes vulpes fulva Ursus americanus Procyon lotor Mustela erm1nea Mustela frenata Lutreola Iutreola Spilogale putorius "Mephitis mephitis Lutra canadensis Lynx rufus Odocoileus hernionus Source: East Side Green River W atershed DE I S, U.S. So i I Conversation Service, 11/78 Birds of the Lower Green River Watershed Common Name Common Loon Horned Grebe Western Grebe Pied - Billed Grebe Double- Crested Cormorant Great Blue Heron Green Heron American Bittern W h i s t l i n g Swan Canada Goose White-Fronted Goose Snow Goose Mallard Gadwall Pintail Green - Winged Teal Blue - Winged Teal Cinnamon Teal European L' i geon American Wigeon or Baldpate Shoveler Wood Duck Redhead Ring- Necked Duck Canvasback Greater Scaup Lesser Scaup Common Go I deneye Bufflehead Harlequin Duck White-winged Scoter Surf Scoter Common Scoter Ruddy Duck Hooded Merganser Common Merganser Red - Breasted Merganser Goshawk Sharp - shinned Hawk Red - Tailed Hawk Bald Eagle Marsh Hawk Osprey Gyrfalcon Peregrine Falcon Pigeon Hawk Sparrow Hawk Ruffed Grouse California Quail Ring- Necked Pheasant Virginia Rail Scientific Name Gavia irnnier Podiceps auritus Aechmophorus occidentalis Podilymbus podiceps Phalacrocorax auritus Ardea herodias Butorides virescens Botaurus lentiginosus Olor columbianus Branta canadensis Anser albifrons Chen hperborea Anas platyrhynchos Anas strepera Anas acuta Anas carolinensis Anas discors Anas cyanoptera Mareca penelope Mareca americana Spatula clypeata Aix sponsa Aythya americana Aythya collaris Aythya valisineria Aythya marila Aythya Affinis Bucephala clangula Bucephala albeola Histrionicus histrionicus Melanitta deglandi Melanitta perspeicillata Oidemia nigra Oxyura jamaicensis Lophodytes cucullatus Mergus merganser Mergus serrator Accipiter gentilis Accipiter cooperii Buteo jamaicensis Haliaeetus leucocephalus Circus cyaneous Panion haliaetus Falco rusticolus Falco peregrinus Falco cclumbarius Falco sparverius Bonasa umbel I us Lophortyx californicus Phasianus colchicus Rallus Iimicola American Coot K i l l d e e r Common Snipe SpottedSandpiper Greater Yellowlegs Lesser Yellowlegs Pectoral Sandpiper Least Sandpiper Dunlin Long - billed Dowitcher !Western Sandpiper Wilson's Phalarope Glaucous- winged Gull Western Gull California Gull. Ring- billed Gull New Gu I I Bonaparte's Gull Band - Tailed Pigeon Rock Dove Mourning dove Barn Owl Snowy Owl Spotted Owl Short -Eared Owl Common Nighthawk Black Swift Vaux's Swift Anna's Hummingbirdd Rufous Hummingbird Belted Kingfisher Red- Shafted Flicker Hairy Woodpecker Trail's Flycatcher Western Flycatcher Western Wood Pee flee Olive -Sided Flycatcher Horned Lark Violet -Green Swallow Tree Swallow Bank Swallow Rough - Winged Swallow. Barn Swallow Cliff Swallow Purple Martin Steller's Jay Common Crow Black- Capped Chickadee Chestnut - Backed Chickadee Common Dushtit Winter Wren Bew i ck' s V!ren Long-Billed Marsh Wren Robin Varied Thrush Fulica americana Charadrius vociferus Capella gallinago Actitis macularia Totanus melanoleucus Totanus flavipes Erolia melanotos Erolia minutilla Erolia alpina Limnodromus scolopaceus Ereunetes mauri Steganopus tricolor Larus glaucescens Larus occidentalis Larus californicus Larus delawarensis Larus canus Larus philadelphia Columba fasciata columba livia Zenaidura macroura Tyto alba iIyctea scandiaca Strix occidentalis Asio flammeus Chordeiles minor Cypseloides niger Chaetura vauxi Calypte anna Selasphorus rufus Megaceryle alcyon Culaptes cafer Dendrocopos Pubescens Empidonax traillii Empidonax difficilis Contopus sordidulus Nuttallornis borealis Fremophila alpestris Tachyccineta thalassina Iridoprocne bicolor Riparia riparia Stelgidopteeryx ruficollis Hirundo rustica Petrochelidon pyrrhonota Progne subis Cyanocitta stelleri Corvus brachyrhynchos Parus atricapillus Parus rufescens Psaltriparus minimus Troglodytes troglodytes Thryomanes becw i ck i i TeImatodytes palustris Turdus migratorius I xoreus Naev i us Swa i nson' s Thrush Mountain Bluebird '.Western Bluebird Golden-Crowned Kinglet Ruby - Crowned Kinglet Water Pipit Cedar Waxwing Northern Shrike Starling Solitary Vireo Red -eyed Vireo Warbling Vireo Orange - Crowned Warbler Hermit Warbler Yellow Warbler Townsend' s Warbler Black- Throated Gray Warbler Yellowthroat Wilson's Warbler House Sparrow Western Meadow I arkk Red - !tinged Blackbird Bullock's Oriole Brewer's Blackbird Brown- Headed Cowbird Western Tanaer Black - Headed Grosbeak Pine Grosbeak Purple Finch House Finch Pine Siskin American Goldfinch White-Winged Crossb i 1 1 Rufous -Sided Towhee Slate-colored Junco Savanna Sparrow Chipping Sparrow White- Crowned Sparrow Golden - Crowned Sparrow !White- throated Sparrow Fox Sparrow Lincoln's Sparrow Song Sparrow Hylocichla ustulata Sialia currucoides Sialia mexicanna ^egulus satrapa Regulus calendula Anthus spinoletta Bobycilla cedrorun Lanius excubitcr Sturnus vulaaris Vireo solitarius Vireo olivaceus Vireo gilvus Vermivora celata Dendroica occidentalis Dendroica petechia Dendroica townsendi Dendroica nigrescens Geothlypis tichas ,',i Isonia pusi I la Passer donesticus Sturnella neglecta Euphagus cyancophalus Icterus bullocki1 Euphagus cyancophalus Molothrus ater Piranga ludoviciane Iesper i phony:, vespertine Pinicola enucleator Carpodaccus purpureus Carpodacus mexicanus Spinus pinus Spinus tristis Loxia leucoptera Pipilo erythrophthalmus Junco hyemalis Passerculus sandwichensis Spizella passerine Zonotrichia leucophrys Zonotrichia artricpilla Zonotrichia albicollis Passerella iliaca Melospiza lincolnii `,lelospiza nelodia Source: East Side Green River !Watershed DEIS, SCS, November, 1978. Fish Species of the Green River Common Name Prickly Sculpin Threespine Stickleback Brown Bullhead Large -mouth Slack bass Chum Salmon Coho Salmon Chinook Salmon Yellow Perch Mountain whitefish Long -Nose Dace Speckled Dace Cutthroat Trout Steelhead Trout Rainbow Trout Dolly Varden Trout Starry Flounder Scientific Name Cottus asper Gasterosteus acu1eatus Ictalurus nebulosus °iicropterus salmoides Oncorhynchus keta Oncorhynchus kisutch Oncorhynchus tshawtscha Percy flavescens Prosopium williamsoni Rhinichtays cataractac Rhinichtays oculus Salmo clarki Salmo gairdneri Salmo gairdneri Salvelinus malma Prosopium stellatus Source: East Side Green River Watershed DEIS, SCS, November, 1978. Cityof l�K VU~. ^ .^X�� - Frank Todd � �U��� K�U � ����»��'��~, `` � Mayor Fire Department Hubert H.Crawley Fire Chief Jon Potter, APA R.W. Thorpe & Associates 815 Seattle Tower Third & University Seattle, WashinsAton 98101 Dear Mr. Potter: December 11, 1981 With re�ard to your ouestionnaire of December 7; 1, Total number of alarms for the year of 1981 will be about 1500, 2, Approximately 60-65% of our responses are for emergency aid. 3. Type of responses are widely varied^ - Vehicular, coronary, industrial accidents, etc. 4^ Fire flow almost anywhere in the City.is adeouate and usually better than in surrounding Jurisdictions, 5^ 25 Firefighters, 1 Chief, 1 Fire Marshal/Asst.Chief, & 1 Fire Prevention Officer, 3 pumpers, one 100 ft. aerial ladder, aid car & support vehicles. 6. Response time to your proposed site would be 2 minutes or less. 7^ Fire Rating = Class IV 8^ Any Project of this magnitude will naturally increase the work load on all City Departments and Services. 9, See attached Ordinance copy, Yours truly, The Tukwila Fire Prevention Bureau cc:TFD file Planning Depf, Enc|.:Ord|nanca No. 1167 City of Tukwila 1 Fire Department, 444 Andover Park East, Tukwila, Washington 98188 (206) 575-4404 H City of Tukwila 6200 Southcenter Boulevard Tukwila, Washington 98188 Mr. Jon Potter, APA R.W. Thorpe & Associates 815 Seattle Tower 3rd & University Seattle, Washington 98101 Dear Mr. Potter: 'apartment 433 -1808 The following information is being supplied to you pursuant to your request of December 7, 1981. I hope that you will find it helpful. We have responded to your questions point by point: 1. 27 Commissioned Officers. 2. There have been seven reported accidents in the area in 1981, one of which was injury. During Longacres season the Washington State Patrol is on duty there and there are several low speed "fender bender" type accidents that are handled by them and not reported to Tukwila. 3. None known to us at this time during 1981. 4. Emergency Response. Time probably averages betwen 2 -3 minutes. 5. Present service level is adequate in the City. 6. This project will definitely create adverse impacts on the service level to the rest of the City. Experience with this type of establishment already in the City indicates that a broad variety of police problems will be encountered ranging from car prowls and burglaries, to alcohol related problems such as customer problems, assaults, and Driving While Intoxicated. Time spent by the police on,problems generated by this proposed establishment will definitely have an adverse impact on the service level currently provided. 7. Particular care must be taken to plan.. for ingress /egress to the property for both vehicles and pedestrians. This is a very heavily travelled area at both morning and evening rush hours. The traffic problem becomes severe during the Longacres racing season. Given the close proximity of this complex to the horse racing track it is only logical to assume that there will be an increase in both foot and vehicle traffic between this area and the track. Careful plan- ning and quality engineering must be done to insure that we do not create a traffic situation which will endanger both life and property. Sincerely, Lt. Patrick L. Phelan Administrative Commander slj PREAMBLE GEOTECHNICAL REPORT The firm of Shannon and Wilson, Inc. provided the proponent with two studies to determine the most feasible foundation for the proposed hotel. The January 1982 study examined both a mat foundation and a pile foundation based on six soil borings. The March 1982 study examined both mat founda- tion and pile foundation based on three additional borings. The consul- tants concluded the hotel supported on p i I i ngs would be a cost effective foundation yet preclude adverse impacts associated with site preparation for a mat foundation. Both studies are included in this appendix. 7 CONSULTANTS William L Shannon, P.E. Stanley D. Wilson, P.E. SHANNON & WILSON, INC.. W- 3919 -02 Geotechnical Consultants 1105 North 38th Street •Seattle, Washington 98103• Telephone: (206) 632 -8020 • Cable: GEOSAW March 12, 1982 Jensen, Krause & Schoenleber 1962 NW Kearney Portland, OR 97209 Attn: Mr. Norm Krause ADDITIONAL GE OTECHNI CAL ENGINEERING STUDIES TUKWILA HOTEL, TUKWILA, WASHINGTON We have completed drilling three additional deep borings within the hotel tower area and made additional engineering studies in general accordance with our letter dated February 19, 1982. The purpose of this additional work was to evaluate a mat -pile foundation system which, we understand, would consist of a three to five -foot thick mat supported with relatively short timber piles. SUBSURFACE CONDITIONS We originally proposed to drill two 100 -foot deep borings near the east and west ends of the hotel tower. These additional borings were to supplement the deep boring (B -6) accomplished for our initial studies, in order to estimate the thickness of the compressible clay beneath the tower and the consequent estimated settlements. However, the lower clay layer was not penetrated in our second boring, B -8. Therefore, another boring was drilled 35 feet to the west of B -8. A boring location plan is presented in Figure 1, which includes all of the borings drilled at this site. The logs of Borings B -7, B -8 and B -9 are presented in Figures 2, 3 and 4. A generalized subsurface profile through the long axis of the hotel tower is presented in Figure 5. In general, the site was underlain by about 60 feet of sand. The upper 35 feet of sand was loose to medium dense, becoming denser with depth. The bottom of the sand layer was at about elevation -42 feet. Underlying the sand was a variable thickness of layered soft to stiff, clayey silt and silt. As illustrated in Figure 5, this compressible layer varied in thickness from about 18 feet in Boring B -7, 35 feet in B -6, 22 feet in B -9 and was not observed in Boring B -8. Beneath this clayey layer, dense, gravelly, silty sand with shells to sand and gravel was encountered in all four borings. The groundwater levels observed during drilling for this phase were at elevation 15 feet, which is near the bottom of the proposed mat. CONCLUSIONS AND RECOMMENDATIONS The long-term performance of the hotel tower supported with a mat -pile foundation would be directly related to the consolidation and long -term compression characteristics and thickness of the lower clay layer. Since the proposed structure is large, it is our opinion that ultimately the pile and /or mat load would eventually be Raymond P. Miller, P.E. George Yamane, P.E. Senior Vice President and Manager Vice President Maurice D. Veatch, P.G. Harvey W. Parker, P.E. Vice President Vice President Seattle • Spokane • Portland Fairbanks • St. Louis • Houston Jensen, Krause & Schoenleber Attn: Mr. Norm Krause March 12, 1982 Page 2 W- 3919 -02 transferred to the lower clay layer. Assuming various timber pile capacities ranging from 30 to 100 kips with spacings from about 6 to 10 feet and a pile tip elevation of -25 feet, we estimate the following short -term or consolidation and long-term or secondary compression settlements: Estimated Settlement Boring No. Short -Term Long-Term inches inches B -7, B -9 2 to 3 2 B -6 3 to 4 - 4 B -8 1/2 to 1 NA As indicated, short -term differential settlements between Borings B -6 and B -8 could range from 2 to 4 inches. These short -term settlements are estimated to occur in about 25 to 160 days. Additional long -term settlements resulting from secondary compression of the lower clay layer are estimated to occur over a period of approximately 20 years and at a decreasing rate. The range of estimated settlements is directly related to the thickness of the underlying clay layer. If the thicknesses were uniform, and if the mat is relatively rigid with the piles loaded uniformly, then short -term settlements would be relatively uniform, such as those estimated for Borings B -6, 7 and 9, and a mat -pile foundation scheme would be a reasonable alternative. However, long -term secondary compression settlement would still occur over a period of approximately 20 years as indicated, in our opinion. Long-term differential settlements could range from 1 to 3 inches or more. Based on the recent boring information, we recommend that either the structure be supported on deep -end bearing piles ranging in length from 80 to 125 feet, or the site be preloaded as presented in our January 21, 1982 report. We recommend that we be retained to review the plans and specifications for the foundation scheme selected. Sincerely, SHANNON & WILSON, INC. George Y : m : ', P.E. Vice Pre•ident TMG /abc Encl: Figures 1 through 5 its • i r\w • . t• ti i t.. \�� C:3'. �\ -\ kJ u • «4T_.2 _s,E c E.-. -. O' 40' -.1 A • • 2 51 Fas a ^6 / ZS 34 .QJET QA%NS NOTES 1) BASE DRAWING PROVIDED BY JENSEN KRAUSE & SCHOENLEBER ARCHITECTS & PLANNERS, PORTLAND, OR, UNTITLED, DATED JANUARY 5, 1982. 2) BORING LOCATIONS ARE APPROXIMATE, BUT WERE LOCATED WITH REFERENCE TO KEGEL & ASSOCIATES TOPOGRAPHY WORKSHEET DATED 2/7/82, JOB NO. 28248. • :.N ■ / / \. :214..4 ZOG}+( / \ / / \ B -2 J ♦ / t .►. - -_ �' ± —� —* ._ 4' __ ._ — + —_ T / / B'6 N O B -3 / \ _.....S...._+ ,-, , ....., 1 ••■I , it, ......). i 431 B-9 . ... . • -"se,. F...---grr % B-7 (El F. , "/ ,k • — 's∎ I 1 t. tout? - -- + a- 1.O1!!4t L cr014_ I %-+ �_� D,u, I ! 1 I ! N'1 i. - I v a r / 1 b ,\ I , 1 `` J. Ii b b °'r • b, /Or 0 II.1 • 0 60 120 SCALE IN FEET 180 24 t+e B -4® B -6 19 B -7 ED s LEGEND APPROXIMATE BORING LOCATION & DESIGNATION, BY S &W, 1973 APPROXIMATE BORING LOCATION & DESIGNATION, JANUARY 1982 APPROXIMATE BORING LOCATION & DESIGNATION, FEBRUARY 1982 GENERALIZED SUBSURFACE PROFILE LOCATION CHRISTENSEN GROUP, INC. TUKWILA HOTEL TUKWILA, WASHINGTON BORING LOCATION PLAN FEBRUARY 1982 W- 3919 -02 SHANNON & WILSON, INC. I FIG. Geoteehnical Consultants SOIL DESCRIPTION Surface E levation: APPROX. 25 F EET = J a a. i La Q N GROUND WATER DEPTH, ft. Standard Penetration Resistance (140 Ib. weight. 30" drop) ♦ Blows per foot 0 20 40 60 Loose, brown, silty to slightly silty SAND, with organics. 0 1 = OBSERVED 2 -24 -82 `Q H) CO v an tT p W N .+ 0 0 0 0 - - -. —0 0 0 0 0 0. • 2= 6" Loose to medium dense, brown, clean SAND, 3= 4 = 5= 21 Medium dense, black, clean SAND with a trace of organics. 6 1 ` 7= 8= 9 = 10 = • rt 111 12 1 13= .70. 61 Loose, black, silty, fine SAND. 14= ,_ 66 Soft to medium stiff, gray, slightly clayey to clayey . . SILT with a trace of sand and organics. 15 = • 16 = 17 = . 84 18= Medium dense to very dense, shelly, gravelly, silty SAND. 89.0 19= .. . '50/6" • . BORING COMPLETED 2.23 -82 . . . LEGEND • % Water content 12" O.D. split spoon sample , Impervious seal I[ 3" O.D. thin.wall sample 2 Water level ' Piezometer tip CHRISTENSEN GROUP, INC. *Sample not recovered TUKWILA HOTEL P Sample pushed Atterberg Limits: TUKWILA, WASHINGTON 1T1-.-- Liquid limit ��— Natural water content LOG OF BORING B-7 Plastic limit MARCH 1982 W- 3919.02 NOTE; The stratification lines represent th• approximate boundaries SHANNON & WILSON, INC.I between soil types and the transition may be gradual. Geotechnical Consultants FIG. 2 SOIL DESCRIPTION Surface Elevation: APPROX. 25 FEET = w J n 0 g GROUND WATER DEPTH, ft. Standard Penetration Resistance 1140 Ib. weight, 30" drop) A Blows per foot 0 20 40 60 Medium dense, brown, gravelly, silty, fine SAND with numerous organics. r 1.5 1 Z OBSERVED 2 -25 -82 11 V 0) A W N o 0 0 0 0 0 0 0 Very loose, brown, silty. fine SAND with shelly and clean layers. 2= 31 11 Medium dense to dense, brown grading to black, clean SAND with a trace of shell and wood fragments, slightly layered. 4= 5= 61 81 9 I 68 10 = .. 11= 121 131 75_ - 62.5 14 = Very dense, gravelly, silty SAND with scatterod shells. 95/9" ON 66.1 15x• .... 5011' -ar BORING COMPLETED 2.24 -82 .. ... NOTE: BORING COULD NOT BE ADVANCED FURTHER DUE TO OBSTRUCTION AT 66 FEET. . • LEGEND • % Water content 1 Y' O.D. split spoon sample tc-� Impervious seal fl 3" O.D. thin -wall sample 2 Water level Piezometer tip *Sample not recovered CHRISTENSEN GROUP, INC. P Sample pushed TUKWILA HOTEL Atterberg Limits: TUKWILA, WASHINGTON 1--0--1-0-- Liquid limit �� Natural water content LOG OF BORING B-8 Plastic limit MARCH 1982 W- 3919 -02 NOTE; The stratification lines represent the approximate boundaries between soil types and the transition may be gradual. SHANNON & WILSON, INC.) Geotechnical Consultants FIG. 3 SOIL DESCRIPTION Surface Elevation: APPROX. 24 FEET 41 CII La I-• a. a. la p g GROUND WATER DEPTH, ft. Standard Penetration Resistance (140 lb. weight, 30" drop) A Blows per foot 0 20 40 60 Medium dense to dense, brown to black. clean SAND with a trace of shells, organics, fine gravel and silt. _ • 0 64 71 81 76 9 1 101 85.5 • 89.5 111 WATER LEVEL COULD NOT BE TAKEN DURING DRILLING co V 01 !77 A W tV -a o. 0 0 0 0 0 0 0 0 0 • • .... . ....... _ _ .. _._. ._ • . • ,... .......__ . . . . . . . . . ..... • . • • • - • . . . . . . Soft to stiff, gray SILT with fine sand and occasional clayey silt layers. Stiff , gray, clayey SILT, slightly layered, numerous shells at tne base. Dense, gray, shelly, gravelly, silty SAND BORING COMPLETED 2-25-82 . LEGEND c Impervious seal ,2 Water level Piezometer tip P Sample pushed approximate boundaries may be graduaL. • % Water . • content 1 r' 0.0. split spoon sample II 3" 0.0. thin-wall sample *Sample not recovered Atterberg Limits: 1-4--i....- Liquid limit \-- Natural water content \ limit CHRISTENSEN GROUP, INC. TUKWILA HOTEL TUKWILA, WASHINGTON LOG OF BORING B-9 MARCH 1982 W-3919-02 Plastic NOTE; The stratification lines represent the between soil types and the transition SHANNON & WILSON, INC] G eotechnical Consultants FIG. 4 EAST 30 0 1- .W -30 W u. z z 0 1- 4 us -60 W -90 -120 7 B -6 7 LEGEND 35 -64 -85.5 —89.5 EXISTING GROUND SURFACE HOTEL TOWER APPROX. MAT ELEVATION, 15 FT. - ---- ? — 1 /8a -11.5 Soft to stiff, layered, 7 Loose, silty SAND with organics - - -7 Loose to medium dense SAND -32— —. — -_ —.7__ Dense SAND, locally medium dense -66 ? clayey SILT and SILT with a trace of sand -101 Dense, gravelly, silty SAND with shells to SAND and GRAVEL —123.4 APPROXIMATE BORING LOCATION AND DESIGNATION a 2/24 WATER LEVEL AND DATE OBSERVED —89 BOTTOM OF BORING AND DEPTH IN FEET O 30 60 90 1-i • 1-� 1 SCALE IN FEET 7 — NOTES 1. SEE FIGURE 1 FOR BORING, BUILDING AND SECTION LOCATION. 2.SUBSURFACE PROFILE IS GENERALIZED FROM MATERIALS ENCOUNTERED IN THE BORINGS. VARIATIONS BETWEEN THIS SUBSURFACE PROFILE AND ACTUAL CONDITIONS MAY EXIST. 7 =2_J -35 - -7 66 —? -84--- 89 WEST A' 30 0 1- -30W W z z 0. 1- 4 > -60 -90 -120 CHRISTENSEN GROUP, INC: TUKWILA HOTEL TUKWILA, WASHINGTON GENERALIZED SUBSURFACE PROFILE FEBRUARY 1982 W- 3919 -02 SHANNON & WILSON, INC. I FIG. 5 Geotechnical Consultants CONSULTANTS William L. Shannon. P.E. Stanley 0. Wilson, P.E. 7.1 I SHANNON & WILSON, INC. W- 3919 -01 Geotechnical Consultants 1105 North 38th Street • Seattle, Washington 98103•Telephone: (206) 632 -8020 • Cable: GEOSAW March 12, 1982 Jensen, Krause dr Schoenleber 1962 NW Kearney Portland, OR 97209 Attn: Mr. Norm Krause TRANSMITTAL OF REPORT: GEOTECHNICAL REPORT TUKWILA HOTEL, TUKWILA, WASHINGTON Enclosed are the original and seven copies of the above report, dated January 1982. The 1973 borings and recently completed boring indicate that the site is underlain with sands over a thick layer of compressible clayey silt and then dense sand and gravel. If a mat foundation is selected, we recommend that the site be preloaded and the near - surface loose sands should be densified. We estimate that preloading could take about 4 to 7 months. Another alternative would be to support the structures on long end - bearing piles ranging in length from 100 to 125 feet below existing ground surface. Shorter friction piles are not recommended. Because of the complexity of the site conditions, we recommend that a meeting be held with the design team to determine that our recommendations are compatible with your design. We appreciate the opportunity to be of service. If you have any questions, or if we can be of any further assistance, please call. Sincerely, SHANNON & WILSON, INC. George Y an .E. Vice Pres•dent TMG/lcl Enclosure: Report (Original + 7 copies) Raymond P. Miller, P.E. George Yamane, P.E. Senior Vice President and Manager Vice President Maurice D. Veatch. P.G. Harvey W. Parker. P.E. Vice President Vice President Seattle • Spokane • Portland Fairbanks • St. Louis • Houston W- 3919 -01 TABLE OF CONTENTS Page I. Introduction 1 II. Site and Project Description 1 III. Subsurface Explorations 2 IV. Laboratory Testing 3 V. Subsurface Conditions 3 VI. Conclusions and Recommendations 4 A. General 4 B. Mat Foundation 4 1. Estimated Settlements 4 2. Preloading 4 3. Densification 5 4. Subgrade Modulus 5 5. Post - Construction Settlement Estimates 6 C. Footings and Floor Slabs 6 D. Structural Fill Placement and Compaction 6 E. Pile Foundations 7 F. Lateral Earth Pressures 8 G. Lateral Resistance 9 H. Drainage 10 I. Excavations, Dewatering, and Safety 10 J. Roads and Parking Areas 10 K. Weather Considerations 11 VII. Limitations 12 i List of Figures Figure No. 1 Vicinity Map 2 Boring Location Plan 3 Log of Boring B -6 4A thru Consolidation Test, Boring B -6, Sample S -21 4E 5A thru Consolidation Test, Boring B -6, Sample S -21 5E 6A thru Consolidation Test, Boring B -6, Sample S -22 6E 7A thru Unconfined Compression Test, Boring B -6, Sample S -21 7B 8 Settlement Plate Detail 9 Subdrainage & Backfilling TABLE 1 TABLE 2 List of Tables Summary of Laboratory Test Data Pile aiui Driving Equipment Data W- 3919 -01 Attachment A 1973 Shannon & Wilson, Inc. Boring Logs and Laboratory Test Results ii GEOTECHNICAL REPORT TUKWILA HOTEL TUKWILA, WASHINGTON I. INTRODUCTION This report presents the results of previous and current subsurface explorations, and geotechnical engineering at the site of the proposed Tukwila Hotel, the location of which is shown in Figure 1. The purpose of our work is to provide recommendations based upon field explorations, laboratory testing, and engineering analyses to assist you with the foundation design. This work was accomplished in general accordance with our revised proposal letter dated December 8, 1981, and was authorized by Kenneth W. Baines, President of the Christensen Group, Inc., by signing the proposal letter on December 17, 1981. II. SITE AND PROJECT DESCRIPTION The site is relatively level, being at about elevation 23 feet. It is currently used as a pasture. Topography of the site is illustrated in Figure 2, Boring Location Plan. As shown in Figure 2, the high -rise portion of the hotel (8- stories) is about 62 by 297 feet in plan dimension. A basement will be within this area and at elevation 19 feet. We currently understand that the banquet and dining room areas will be near elevation 30 feet, requiring about 6 feet of fill. Column loads for the banquet dining room would be up to 100 kips and founded on spread footings embedded within the fill. A 3 to 5 -foot thick mat foundation is being considered for the support of the hotel tower. Bottom elevation of the mat would be approximately 16 to 19 feet, requiring an excavation of about 10 feet. Gross mat pressure will vary from 1100 to 1100 pounds per square foot (psf). Based upon a discussion with the structural engineer, a realistic gross mat pressure would be 1250 psf. With this gross pressure the net pressure reacting against the soil would be about 900 psf. This soil pressure was used in our analysis. The site will be preloaded if this scheme is selected. If a preload is not selected, then the structures would be pile- supported. 1 III. SUBSURFACE EXPLORATIONS Five borings designated B -1 through B -5 were drilled at this site in 1973. Their locations are included in Figure 2. These boring logs, along with pertinent laboratory test results, are included in Attachment A. For this current study one deep rotary boring, designated B -6, was accomplished on December 17 to 22 by Kring Drilling. Boring B -6 was located by cloth taping from prominent site features and the elevation was interpolated from the ground surface elevation contours shown in Figure 2. Samples were obtained from these borings at selected depth intervals with either a 2 -inch O.D. Standard split -spoon sampler or a standard 3 -inch O.D. thin -walled push tube sampler. Standard Penetration Resistance tests were performed in conjunction with sampling. These tests involve driving the standard split -spoon sampler a total of 18 inches, with a 140 -pound hammer falling a distance of 30 inches. Blow counts are recorded for each 6 -inch interval, and the total of the last 12 inches of penetration is designated as the Standard Penetration Resistance or N- value. N -value is an empirical parameter which generalizes the consistency of cohesive soils and the relative density of granular soils. All drilling and sampling operations were observed and recorded by an experienced geologist from our firm who also collected and field - classified samples and completed detailed field boring logs. All samples were sealed in jars to preserve the natural moisture and were returned to our laboratory. Two observation wells were installed in boring B -6. One well was set at the bottom of the boring and the other at a depth of about 25 feet. Both wells consisted of a 2 -foot length of 2 -inch diameter slotted plastic well screen connected to a 3/4-inch plastic riser pipe. The drill hole was backfilled with pea gravel and separated with an impervious bentonite seal at a depth of about 70 feet. A seal was also placed at the ground surface. Log of boring B -6 is presented in Figure 3. Shown graphically on the right side of these logs are sample number, type of sampler, depth, and plot of N- values. On the left side of the boring logs is our interpretation of the subsurface conditions. 2 IV. LABORATORY TESTING Laboratory tests were performed on selected representative soil samples to confirm the field classifications and to evaluate the engineering properties of the subsurface materials. Soil classification tests consisting of Atterberg limits and natural moisture contents were performed. These tests are summarized on Table 1. Three tube samples were tested to determine consolidation properties of the clay. Three/ consolidation tests were performed on clay samples from boring B -6. In these tests, the samples were carefully trimmed and fitted into a rigid ring. Porous stones were placed on the top and bottom of each specimen to allow drainage. Vertical loads were then applied in increments and the specimen allowed to consolidate under each load increment. Rebound was measured during each load decrement. Each test specimen was unindated at approximately its overburden pressure. The test results are presented in Figures I, 5 and 6. One unconfined compression test was accomplished on a relatively undisturbed sample from boring B -6. The results are presented in Figure 7. V. SUBSURFACE CONDITIONS The near - surface soils, generally to a depth of 10 to 15 feet, consisted of very loose to loose, fine sandy silt to silty fine sand. Beneath this silt to a depth of about 70 feet a layer of loose to dense sand was penetrated. The sand generally was denser at a depth of about 35 feet (Elev. -11 ft.). All of the borings indicated that the upper 35 feet of soil at this site have a relative density on the order of 20 to 30 percent, as determined from the N- values. Approximately a 35 -foot thick layer of medium stiff, silt and clayey silt with scattered organics was penetrated below the dense sand in boring B -6. The depth and thickness of this compressible soil was about the same as was observed in the 1973 boring B -5. Underlying the compressible clayey soils was medium dense to dense sands and gravels. Water levels were read in borings B -3 and B -6 on January 8, 1982 at a depth of about 15 feet (Elev. 9 ft.). Because of the proximity of the Green River to the site and the pervious nature of the near - surface soils, the groundwater levels would be about the same as the river level. VI. CONCLUSIONS AND RECOMMENDATIONS A. General The proposed building site is underlain with normally consolidated alluvial soils of which the lower thick clayey silt is compressible. Consequently, the hotel tower can either be supported on relatively long end - bearing piles or supported with a mat or raft, provided that the in situ soils are improved. Soil improvements for a mat foundation should include preloading and soil densification. The purpose of preloading would be to preconsolidate the lower clayey silt to reduce post- construction settlements to acceptable amounts. It should be noted that the lower clayey silt will settle indefinitely, even after preloading, but at a decreasing rate. The purpose of densifying the loose sand would be to reduce settlements and lessen the risk of soil liquefaction during a strong earthquake. B. Mat Foundation 1. Estimated Settlements. We estimate total settlements without preloading to be on the order of 3 to 6 inches with differential settlements of 2 to 4 inches under the load of the mat foundation and surrounding 6 feet of fill. About 70 percent of these settlements would occur within 2 years and the remainder over a period of about 20 years, but at a decreasing rate. In addition, the near- surface loose silts and sands would also cause settlement during seismic loading. These additional settlements are estimated to be on the order of 2 to 6 inches or more. Therefore, we recommend the site be preloaded and densified to reduce these potential settlements. 2. Preloading. We recommend that the mat and dining room area be preloaded with at least 15 feet of fill. (top elevation 39 feet). This preload should extend full height at least 25 feet beyond the edge of the proposed structure. Preload settlements are estimated to range from 3 to 12 inches. The duration for the preload fill to be in- place is estimated to be about 4 to 7 months. It is recommended that the preload settlements be monitored with about 12 settlement plates to determine at what time the preload can be removed. A detail of the settlement plate is presented in Figure 8. We recommend that we select the plate locations on the contract drawing when it becomes available. 4 The 6 feet of site fill required to -support the banquet - dining area should be structural fill. The preload fill should not have more than 20 percent of nonplastic fines passing the No. 200 sieve and should be compacted by routing haul equipment and dozers. 3. Densification. It is recommended that the loose sands beneath the structures be densified to a depth of about 35 feet (elev. -11 ft.) and to a minimum SPT N -value of 30 blows per foot. This corresponds to a relative density of 75 to 80 percent. Soils should be densified laterally beyond the edge of the structures a distance of 25 feet. Densification should be evaluated with rotary borings to determine N- values and with Dutch cone probes to delineate any silt layers. A densification program should be designed and accomplished by an experienced contractor. The program should be reviewed by our firm. Our experience indicates that vibroflotation would be a suitable method for densifying the sands at this site. If dynamic consolidation, which consists of dropping a weight in a systematic pattern, is proposed, a test section with borings, etc. should be done prior to any production densification. The contractor should also submit, in detail, his design and procedures for review by our firm. We recommend that utility connections between structures be flexible. 4. Subgrade Modulus. We have made an analysis of a uniformly loaded 62 by 297 -foot mat. For this case a five -foot thick mat is still relatively flexible and the modulus of subgrade reaction would not vary significantly across the mat. However, the vertical displacement of the mat is a function of the stiffness of the subgrade soils. For the densified case we estimate central elastic displacement to be about 1 inch with differential displacement on the order of 1/2 -inch and recommend a modulus of subgrade reaction of 15 pci. Without densification, we estimate central elastic displacement on the order of 3 to 1 inches with differential displacement on the order of 1 to 2 inches or more, and a subgrade modulus of 3 pci. Elastic displacement is the movement of the mat due to compression of the sand and does not include the consolidation settlement due to the consolidation of the underlying clayey silts. These elastic displacements are expected to occur essentially as the load is applied. 5 W- 3919 -01 5. Post - Construction Settlement Estimates. We estimate that about 2 to 3 inches of settlement will occur due to secondary compression of the lower clayey soils which have been preloaded. This settlement would take place at a decreasing rate and over a period of approximately 20 years following construction. This .additional settlement would probably take place over the entire area in a dish - shaped pattern. The above described settlements are estimates; i.e., they are based upon the results of two deep borings and laboratory and office studies. The actual settlements could be somewhat different, particularly if subsurface conditions are different from the borings. Preload settlement data would assist in evaluating post- construction settlements. C. Footings and Floor Slabs The banquet- dining room structure may be founded on spread footings which are embedded in structural fill. An allowable soil bearing pressure of 3 ksf is recom- mended. This pressure could be increased by 1/3 for seismic loading. Minimum footing width and embedment below the lowest adjacent grade should be 21 inches. Footings should be founded on at least 3 feet of compacted structural fill, which should extend beyond the edges of footings a minimum distance equal to the thickness of the fill. A vapor barrier consisting of plastic sheeting should be placed beneath the floor slab over a 6 -inch minimum thick layer of washed 3/1 to 1/9 -inch gravel or washed pea gravel. The gravel should be provided as a capillary break, and should be hydraulically connected to drain into a storm sewer system. A two -inch layer of crushed rock on top of the gravel and compacted with 1 complete coverages of a vibrating plate compactor would assist in providing a working surface on which to place reinforcement and concrete. D. Structural Fill, Placement and Compaction Structural fill material should consist of a reasonably well- graded (from fine to coarse) sand or sand and gravel, free of organics and debris, with a maximum particle size of about 3 inches and having not more than 12 percent fines by weight passing a No. 200 mesh sieve, based upon wet sieving the minus 3/4 -inch fraction. If earthwork takes place in wet weather, no matter what time of the year or within wet 6 W- 3919 -01 excavations, the fines content of structural fill material should be limited to not more than 5 percent passing the No. 200 sieve, based upon the minus 3/1 -inch fraction. Fines should be nonplastic. Compaction should achieve a dense, unyielding surface and at least 95 percent of the Modified Proctor (ASTM: D 1557 -70, Method C or D) maximum dry density. The loose lift thickness before compaction should be 8 inches maximum for heavy equipment compactors and should not exceed 9 inches for hand - operated compactors. Structural fill should be placed in horizontal lifts. Any soft, loose, wet or spongy areas detected during fill placement should be removed and replaced with structural fill. All lifts should be compacted at the time they are placed so that uncompacted material is not exposed to water. The fill material should have a near optimum moisture content during compaction. Where wet conditions are encountered in the bottom of excavations, we recom- mend that the excavation be pumped dry and an initial lift of clean sand and gravel containing not more than 5 percent fines be placed. This initial lift should be about 18 inches thick. All excavated subgrades and all fill placement and compaction should be monitor- ed and tested by an experienced person from our office. The on -site soils are not suitable for structural fill. E. Pile Foundations As mentioned, another foundation alternate would be to support the hotel tower and banquet - dining areas on relatively long end - bearing piles. Depending on the situation, pile lengths could range from approximately 100 to 125 feet, measured from the existing ground surface. Piles should penetrate into the dense soils below the compressible clayey silt. 7 W- 3919 -01 If 3 or more feet of fill is placed to raise site grades around and /or beneath the structures, the piles will be subject to downdrag loads. Downdrag occurs when loose or soft soils consolidate and soils above settle, gripping the piles and applying downward loads to the piles. Another alternate would be to design all the structures with basements or hollow crawl spaces such that the site soils are loaded as little as possible and not settle. The following table presents the design capacities for 1i -inch concrete and steel pipe piles, with and without downdrag. Pile Type 11" Oct. Prestressed Concrete 14" Pipe Pile, 3/8" wall (closed -end) * Below existing ground surface Estimated Pile Length* (feet) Downdrag Load (kips) 120 to 130 210 120 to 130 180 Design Capacity with without Downdrag Downdra (kips) kips 90 200 80 200 If pile foundations are selected we recommend about 10 test piles be driven across the site to evaluate pile lengths and driveability, pile- driving hammer, and capacity. Driving test piles should be about 130 feet long. If a pile foundation is selected, we recommend that we be retained to review the hammer size required. The data listed in Table 2 will be required in the final hammer selection. We recommend that the WEAP program be used to select the hammer and to determine pile driving criteria. We recommend that the upper loose silts and sands be densified to provide lateral pile resistance from wind or seismic loading, and that the densification be accomplished after pile installation. F. Lateral Earth Pressures The lateral earth pressure against a wall is dependent on the . method of backfill placement and degree of compaction, the backfill slope, the type of backfill material, the drainage provisions and, above all, whether or not the wall can yield laterally after or during placement of backfill. When a wall is restrained against lateral movements or tilting, the soil pressure exerted on the wall is the at -rest soil pressure. Wall restraint may occur if a rigid structural network is constructed prior to backfilling or 8 W- 3919 -01 if the wall is inherently stiff. However, if the wall is freestanding, or if it is allowed to move horizontally, or to rotate so that the top of the wall moves an amount equal to about 0.001 times its height, then the soil pressure exerted against the wall drops to the active value. Theoretically, this is the minimum pressure that a soil can exert against a wall. For the active case, we recommend an equivalent fluid pressure of 35 pounds per cubic foot (pcf) and for the at -rest condition and equivalent fluid pressure of 55 pcf. These pressures assume drained conditions behind the wall and hydrostatic pressure should be included. The analysis of walls should also take into account any surcharges, such as caused by floor, traffic or other loads. For a uniformly distributed surcharge load behind a wall, a uniformly distributed lateral pressure equal to 35 and 50 percent of the surcharge loading should be added for the active and at -rest case, respectively. Backfilling and compaction criteria are presented in Figure 9. For 95 percent compaction, settlements on the order of 1/2 percent times the wall height could occur and if this is deemed objectionable, floors should be reinforced accordingly. Where 95 percent compaction is required clean granular backfill is recommended because this material requires less compactive effort and moisture control than silty soils in order to achieve the desired density. G. Lateral Resistance Lateral forces from wind or seismic loadings would be resisted, in part, by passive earth pressure against the buried portions of the structure. An equivalent fluid pressure of 320 pounds per cubic foot (pcf) is recommended for passive earth pressure. The above value includes a factor of safety of 1.5. We recommend that a coefficient of friction between concrete and soil of 0.5 be used with an appropriate factor of safety to calculate the resistance to sliding at the base of footings. 9 W- 3919 -01 H. Drainage Our recommendations for drainage behind permanent walls are presented in Figure 9. These include compaction criteria for backfill, types of underdrain pipe, and gradation requirements of drainage material. ■ I. Excavations, Dewatering, and Safety For safe working conditions and prevention of ground loss, excavation slopes should be the responsibility of the contractor, since he would be at the job site to observe the work. Furthermore, all current and applicable safety regulations regarding excavation slopes and shoring should be followed. For planning purposes only, temporary excavation slopes should not be steeper than 1V:1.5H. Where loose soils, seepage zones or clean sand are encountered, flatter slopes may be required. Fill and natural soils at this site are erodable when exposed to heavy rains. Measures to prevent this erosion, such as covering the slope with visqueen, etc., should be the responsibility of the contractor. In addition, the contractor should be made responsible for the adequate control of any ground or surface water wherever encountered. In this regard, sloping, slope protection, ditching, sumps, dewatering and other measures should be employed as necessary to permit proper completion of the work. J. Roads and Parking Areas All soft, loose, organic soils and other objectionable debris should be removed prior to placement of road fill. Road fills should then be placed in 12 -inch lifts and compacted to at least 92 percent of the Modified Proctor maximum dry density. Some select preload materials may be used for road fill. All road excavation surfaces should be proofrolled to detect soft or loose sols. The excavated surface should be leveled to promote uniform compaction. 10 W- 3919 -01 Proofrolling could be accomplished with a minimum 5 -ton (static weight) vibra- tory roller, where granular soils are exposed at the surface. If clay /silt soils are exposed at the surface, proofrolling could be accomplished with a loaded 10 -cubic yard dump truck. At least four complete coverages should be accomplished to detect any soft or loose areas. Should proofrolling reveal the presence of soft or loose areas, they should be removed and replaced with structural fill or dried out and recompacted until a firm, unyielding surface is achieved. The top 12 inches of pavement subgrades should be compacted to a dense, unyielding state and to at least 95 percent of the Modified Proctor maximum dry density. We recommend that a subgrade CBR of 3 percent be used for flexible pavement design. Pavements should be protected from frost action. We recommend that a total of at least 12 inches of pavement, base course and /or granular subbase be provided beneath exterior pavement. The base course and granular subbase should be nonfrost susceptible, i.e., should contain less than 3 percent material by weight, finer than 0.02 mm. They should be compacted to at least 98 percent of the Modified Proctor maximum 'dry density. Prior to asphalt paving, a loaded dump truck should proofroll the entire base course area. If yielding areas are observed, they should be removed and replaced with suitably compacted materials so as to achieve a dense, unyielding surface for paving operations. K. Weather Considerations The rainy season in western Washington normally encompasses the period begin- ning mid -October and extending through about May, and this usually has a large effect on construction projects involving earthwork. The soils that will be exposed at the proposed subgrade elevations at the site are generally silty or clayey. These soils contain sufficient fines to produce a cohesive mixture when wet. Such soils are highly susceptible to changes in water content and become soft and difficult to handle when wet. Proofrolling or compaction may become impossible when the moisture content of these soils is above optimum. It is generally not feasible to dry out such soils during wet weather once they become wet. We, therefore, recommend that earthwork and paving be scheduled for the normally dry weather months. 11 W- 3919 -01 However, rainy weather can occur at any time of the year. The following recommendations are applicable should wet weather occur during this work: 1. The ground surface in the contruction area should be sloped to whatever extent is possible to promote the runoff of precipitation and to prevent ponding of water. Temporary ditches should be provided where appropriate. 2. Earthwork should be completed in small sections to reduce exposure of excavations to rain. Placement and compaction of any structural fill, subbase and base would provide protection for clayey or silty soils. The placement and compaction of granular materials should occur on the same day that excavation takes place in an area. 3. Fill materials, including base or subbase materials, should not be left uncom- pacted so as to soak up water. A rubber -tired roller, or equivalent, should roll the surface to seal out as much water as possible. 1. Work should take place only during non -rainy periods. Following rain, construction equipment should not operate upon the soil until drying occurs suffi- ciently to avoid disturbance. (The clayey and silty soils are more subject to disturbance and softening than cleaner granular soils.) Delays should be anticipated when conditions are too wet. 5. If time for drying the wet soils is not available, soils that are or become too wet for compaction should be removed. For such removal, it may be necessary to use lightweight equipment and /or excavation by wide -track loader, "Gradall" or equal, in order to protect against disturbance. Replacement soil and all fill material (structural fill) should be a clean granular soil of which not more than 5 percent by weight of material will pass the No. 200 sieve, based upon wet sieving the minus 3/1 -inch soil fraction. The fines should be nonplastic. 6. The Contractor, in preparing his bid, should consider the probable weather and site drainage conditions that may be encountered during the time limitation of his contract. He should be made responsible for conducting his operations accordingly. 7. Earthwork to include excavation, proofrolling, filling and compaction of all materials should be monitored on a full-time basis by an engineer or technician experienced in earthwork. Vil. LIMITATIONS The analyses, conclusions, and recommendations contained in this report are based on site conditions as they presently exist, and further assume that the exploratory borings are representative of the subsurface conditions throughout the site, i.e., the sub- surface conditions everywhere are not significantly different from those disclosed by the explorations. If, during construction, subsurface conditions different from those encountered in the exploratory borings are observed or appear to be present beneath 12 W- 3919 -01 excavations, we should be advised at once so that we can review these conditions and reconsider our recommendations where necessary. If there is a substantial lapse of time between the submission of this report and the start of work at the site, or if conditions have changed due to natural causes or construction operations at or adjacent to the site, it is recommended that this report be reviewed to determine the applicability of the conclusions and recommendations considering the changed condi- tions and time lapse. This report was prepared for the exclusive use of the Owner, Architect, and Engineer in the design of the subject facility. It should be made available to prospective contractors and /or the contractor for information on factual data only, and not as a warranty of subsurface conditions, such as those interpreted from the boring logs, and the discussion of subsurface conditions included in this report. We recommend that we be retained to review the plans and specifications. We also recommend that we be retained to observe construction, particularly excavation and grading, the proofrolling and compaction of subgrades, over - excavation requirements, structural filling, footing excavations, densification, pile driving, preloading, and such other field observations as may be necessary. Unanticipated soil conditions are commonly encountered and cannot be fully deter- mined by merely taking soil samples from borings. Such unexpected conditions frequently require that additional expenditures be made to attain a properly constructed project. Therefore, some contingency fund is recommended to accommodate such potential extra costs. SHANNON do WILSON, INC. omas M. Gurt:wski, P.E. Principal Engineer George Ya Vice Presid 13 �ILR • ASK, row w 1 ^ o � � 0� 1/4, Z F S EG\�i 1 — _sT/QNAI -t;gli NOTE DRAWING ADAPTED FROM THOMAS BROS. MAP. 0 1/2 1 SCALE IN MILES CHRISTENSEN GROUP, INC. TUKWILA HOTEL TUKWILA, WASHINGTON VICINITY MAP JANUARY 1982 W.3919.01 SHANNON E IILSON, INC. GEOTECNNICAL CONSULTANTS FIG. 1 tc, . '. " N.. '''' ...`'44,• *s....... - --,.. ...,,,..1 j/ -..!_•-•,..s.. '":--- --:.:../7 • 0 Ni4-1 riaTEZ EL. ri.o• --27P 54.4 4.0 wW,.-i r -6 p4 ■••••E NOTE BASE DRAWING PROVIDED BY JENSEN KRAUSE & SCHOENLEBER ARCHITECTS & PLANNERS. POR TLAND, OR, UNTITLED, DATED JANUARY 5, 1982. 7_1 BO UE-r IZGO!-'15 2t211 23:2 (Pr B-3 4 4.- --cwraz .: .71.a. 01-17— 1 :IT (wiz..., ex ;et 6-2,c7e) ,acse-.00 "Alb' osAos. B-6 %JP,- • • a...ow!. 1 F = 4 1 , 1 el. - 0 6 I Li! 001.111 I . i • • • ; r 1 ; 1 ! : 1 1 1 1 1 c>,,....... , 1 B-1 1 1 • i • 1 -\ 4— X X t B-5 1 a 1-11 , . I / e 1'1'111 ii 1 i ! 1 ; 11 II 1 1 .11 i 1 1 a Will 1 Iii,i,1 4' I I I • I 24.42-6 i I 0 1-4 1-4 If -4 60 . 120 180 SCALE IN FEET -z4 -2.4P /1 11 / / 1/ / s- N —_e_otLIHSI-1nlim B-4® B-6 8? LEGEND APPROXIMATE LOCATION & D BY S&W, 1973 APPROXIMATE LOCATION & D THIS STUDY BOR ING ESIGNATION, BORING ESIGNATION, CHRISTENSEN GROUP, INC. TUKWILA HOTEL TUKWILA, WASHINGTON BORING LOCATION PLAN JANUARY 1982 W-3919-01 SHANNON & WILSON, INC. I Geotechnical Consultants FIG. 2 SOIL DESCRIPTION Surface Elevation: Approx. 24 ft. 1- o. W 0 ^\ Very loose, slightly silty SAND with organics. r 1 Soft, brown, sandy SILT with organics. r Loose, brown to gray, silty, fine SAND, slightly layered, with a trace of organics. Loose to medium dense, black, clean, fine to medium SAND, with a trace of wood fragments. Similar to above except medium dense to very dense,, Medium dense, gray, layered, clean SAND and SILT. Medium stiff to stiff, gray SILT with sand. Medium stiff to stiff, locally soft, gray, clayey SILT, locally silty CLAY, with a trace of fine sand. Medium dense to dense, gray, gravelly, sandy SILT, with GRAVEL layers, scattered sheik. 1 2.5 11.5 31 61 66 76 101 N W J a. 2 N 1L 2= 41 5.1 6= 7= 8= 9= 10 111 12 13 14 1 151 161 171 18 JIG 19 HP 20 UP 21 IIP 22 UP 23 lP 2411P 2511P 261 27I. 119 281 (CONTINUED ON RIGHT) NOTE: The stratification lines represent the approximate boundaries between soil types and the transition may be gradual. 0¢ Z W 7� 0.4 Kg t7 1 2 MM- OBSERVED 1.842 S 1- a. W 0 0 10 20 30 40 50 60 70 80 90 100 110 120 Standard Penetration Resistance (140 Ib. weight, 30" drop) A Blows per foot 0 20 40 60 • • • • • • • • 76 • • 1 t•• 1 •• • A • • . . . . . . . . . . . . . . . . . . • • 20 40 • % Water content 60 SOIL DESCRIPTION Very dense, gray, silty, sandy GRAVEL BOTTOM OF BORING COMPLETED 12 -22-81 d 2 4 co) OK Z W 04 tc 123.4 29 = 1 I P- o- w O 120 130 Standard Penetration Resistance (140 Ib. weight, 30" drop) A Blows per foot 0 20 40 60, i I 2" 0.D. split spoon sample 11 3". O.D. shin wall sample Sample not recovered Atterberg Limits: Liquid limit LEGEND Natural water content Plastic limit Impervious seal Water level Piezometer tip P Sample pushed G GUS sample 20 40 60 • 16 Water Content CHRISTENSEN GROUP, INC.. TUKWILA HOTEL TUKWILA, WASHINGTON LOG OF BORING B-6 JANUARY 1082 W- 3919 -01 SHANNON & WILSON, INC. I FIG. 3 Geotechnical Consultants • • • • .11.!!!...E."— • A /TM Nf AAA A' YMa Jr p�i KEGEL & ASSOCIATES INC. SAND Pl ANNING ENGINEERING & SURVEYING am IIIIIfall• WAY IYIIIII,f1,l Mlf• MAMA OIIKI IlMMI 'N I.I MIIIYN.wA IWl 1\. 1200 111.1111 AA M _ A/ N AM! u AM r •r arr r 11 ai �►Alr' LA / 2 MAMA AM /MNIY apt enwer ■!AN �!!!Y !!M CAC AIM! WM All AA" JAW PALMHAEL—AIMIA ati ASO !Z ANP !IAt r lermn+v AY a1 AV •0AS. f —GA!!N A!✓OR JA Al RN AWAY' (Mw r~WAS AVIAN AN* AVM MAYA, 41Af! Al AffaMI Or •••••• .q1 AY' 414•0•14 DUMPS !.00 r4• AAA OVA NOM ,AP AO Al • wlY J1)4 AM Al ABA A /A AsO AV Mir AI SAWA LEGEND • ._ • aW0/6 A1vr/r(IAIIA4• d A. SI AA AMWAY AIM.�IYf - _ n_ /MOW/ AIHMfaI a/Ir a+l Alf +.l AA M�4Ylf AWAr AKHOI ®s•rml Ar Maw! C.,14Se13014. STORM WATER DRAINAGE AND GRADING PLAN AA M Tukwila Hotel J CITY OF TUKWI WASHINGTON ORDINANCE NO. //� 7 AN ORDINANCE ESTABLISHING CERTAIN FIRE PROTECTION COUNCIL ACTION MEETING TVE DATE 'GEK ∎A ITEM ACTION rlw 11,y 1 j P µ.4► �w 5�17 1 I 2r, gal J a. -7)4 / STANDARDS FOR THE CONSTRUCTION OF HIGH -RISE BUILDINGS. WHEREAS, the City of Tukwila is concerned about the health, wel- fare and safety of persons working or residing in high -rise buildings, and WHEREAS, the City wishes to provide appropriate standards for construction of high -rise buildings. NOW, THEREFORE, THE CITY COUNCIL OF THE CITY OF TUKWILA, WASHINGTON, DO ORDAIN AS FOLLOWS: Section 1. Definition: Story. As used herein, the definition of "story" shall be as contained in Section 16.04.050, as amended, of the Tukwila Municipal Code. Section 2. Scope and Construction of Ordinance. This ordinance shall apply only to buil ings in excess of four stories, In all other re- spects the provisions of the Uniform Building Code, as found in the Tukwila Municipal Code 16.04.010 and the Uniform Fire Code as found in the Tukwila Municipal Code 16.16.011 shall be generally applicable to this ordinance including, but not limited to, provisions for the issuance of permits and collection of fees therefor, and provisions for penalties for violations and establishing administrative appeal procedures. If, in any specific case, this ordinance specifies materials, , methods of construction or other requirements which are different from those specified in any other part of the Tukwila Building Code (Tukwila Municipal Code 16.04), the more restrictive requirement shall govern. Section 3. High Rise Fire Protection Required. 1. Every building shall be fully sprinklered in accordance with the standards set down in NFPA (National Fire Protection Association) #13. 2. Fire hose racks shall be provided with 75 feet of lined 1 -1/2 inch, single - jacket hose and adjustable shut -off plastic nozzles. The hose racks shall have a 2 -1/2 inch valve from the sprinkler riser with a 2 -1/2 inch to 1 -1/2 inch reducer provided for each rack. Additional racks, if required for approved coverage, may be taken off of the sprinkler cross - mains. The reducer shall not be required in these racks, which will have a•1 -1/2 inch Naive. 0.ul111 hull, 11 1111 '1,111 '111,0 - 01,1 11111111 1111 1/11.111 ». 411. '■nil., .1 1111 '1,111 '11111 11 1.111 1381 - pN11 [I0 [. E. E. [I E. [ [ 11111 10 0,111 0011 '11111 e1 I111t Illlitl. ,.01.11 evil •01110 VI 4.7t 14111 •.1/.l 1,.0 - N, 0 If If 11 lluld.o u1.ds —a _ uo1ld,1osa0 IIoS e3uelslsau 111.41 uopeJlaued I•"wo plepuelS Z�8 ' 1111111 41 its 111111@011 141 put 11411 111 1111114 11111e@n11 1,.1.11/ 041 1111.10,1 00111 1.11111, 11,111 041 1.1.111. ,. eeeee2 '11117 1110111 'sell.. 1 0•11 '1.911 ' - fill Lc [tl . .. .. . . ._ .. .. . _ S I,uht1111 me 11 00111 1111 1111 1.4,11 '1111 I. 11,11 1111. 1111 snipe, 11 0v11 • '11111 .n11w 11 .7111 - OMII St [I I [I I [• 1 Ce 1 1.111 It Allis 1114111/ 'P11111' evil '11111 el @sell '111.1 11 1,111 1111 - Qil► [t [t 11111 l• 11111 .Ill 'Ipe,e 0v11 ',..11 '.1..1 11.1 - Ill1 [t [t S [l 0 It 14 t1 uolldposep II°S leo.a 12 ad mall • aouelslsou UOIleilaued pjepuelS AK IRA :31i0" pua6ai 5601 OUIJO8 ! ! ! ! ! ! • ! ! ! • ! ! ! ! • ! ! Boring Logs Legend B•3 11,,,,,1 rwl« Standard Penetration Resistance • et.. per K o.otaK Soil Description 1 OBSERVED 1.8 -82 11 11 11 — -- • - - - - - -- .,_ _ - --- • -- - -- -- — 0 1 1111 - 1111 11.... 111.a. 1 U. ..sir. 11th true 41 5 1] I] 10 ] 1 1] 1114 - Vero sun to loos.. bros. to U.el. woos 11mo 1111111. 11111 — — - — _____ . _... 15 1] 1 ] p 1 1] 30 qp ill 3 J 117 1100 - lets 1.11.. 11.•1.1 mulls, 1 . 1.11 to 111,1. 1111 t. .1d1.. 1111 .ee.II a.l 1111 1 111* s./ toed lls(...t. 111.1 11 loot . . ••... .. .. ... ... .. .. ... ., ..... NOTE: Ids .Irs1111 oo11u Ilan rgn/l.1 IM .yonll..t. ►1,nd.11.. ketoses 5511 ..... and 111 lunllll.s .y n'WM. B•4 p.m w.1« Standard Penetration Resistance • BI p•1 R D.pt11.K Soil Description 1 11 11 11 . _ • - -- -- 0 1 5 11 ! - Inn. If.a. 11.. 01.1.14. 1111 1 r. .111 11.11 - - ...- - • -- I] 1] a] 1] 1] 20 1] 1410 - Inn 0. nts 1.00.. Iota to block. tors 140 10 111, trellised. 1110111 11111 .. .. o . .] 25 11] 1111 - 1,110, . . 1rn. 10 116(1. (l1, te 1.11.0 In10,1 • \111J - 1111 11 0111.■ 11111. Inr. 11111. //'' 111111111 111, 1a0t. hull. I 30 11 ] 35 'I] 40 45 14] SD 1i] ' .. -, 1111 0 .11 »1 - .0 .. 11. 011(0. 1111 1. n 0, il. 1.111110 .Iltt 1. 11110. 1111 00000l.n1 11151 11 loop 1111 • . oo .. • .. . . .. ... ... ... — — — — — Boring Logs Legend tom: B•5 Standard Penetration Resistance • Illo•s pet It Dpt41t Sop Description 0 5 10 15 Ltd - lerr Inn. Item. 1116 11113 .1 1111 11111, 1 111 11161 1] 1111 - lets leers. dote 1,864. Ilse monde 20 25 111_10 - teen 11 oodles dense. In■a 1e IU.3. Ilse is molly. ,64leed 11] 11] I3] 11] 14] 11] CMp - I.Ils. block. Ile. le 1.41.• . . ellb 1.1,,1.1111 elopes 1111 1.3.64 n1 ,,no 161d Indsesle Is. tlnllllttll.e 11.., up m•1 IIH .00nt loan bonaletl,t bot.16a tell 111.1 and Ito l,.e.11l,. •e1 16 gradual. B.5 cont'd Oioud Wotan Standard Qenetration nealstance • slaw. per IL Dp11i.R Soil Description 0000000 11/3' oantti 11 1 1, 11] 70 111 31] 31 33 11] 14110 - Usu. 411st. 1121. 1111611, Ilene. 11111, m111 .stn 114.1 II11 Segos 11111111 1111 - Ill/ 1311 It molls 11111. 41,t I /eo to 1111410 11111. alien, 11111113 Ilse kelp• 6.11,116 14iUalrod 64ed 111,86111. 161s 1 1 e0000.lo 646 14d .4.11 11] - loop ten.. pees le 61111. 14,81111. 110 64.1,. . nip 1111,: I.1tbseel 111.11 urain size Classification • 100 90 •0 " 0 W • 50 10 0 Borings B.1, B.2, B.3 Sieve Analysis Hydrometer Analysis. Size of Opening In Inches 1 Number of Mesh per In., U11.131andard Ofeln Size In mm. •oo •s 0 n . LI • re 0 Cs 10 o z CI SI, Y1 .4 evi ••■ 10 . NO el. CY Grain Size In Millimeters to, 0 Cs 0 tJ 93 CO Cobbles Coorso Flno Coorso Modlum Flno Fines t revo _ Sample No. Dopth•11. USA Classification M:s --- - ...N, PL _ B-1, S-2 8-2, S-9 0-3.5-0 - --- -- - Blown lino sandy SILT, 1 loco 01 fools Black SAND, I ono 01 wood li ayon Is 01 ack lino to mull urn SAND • - - -- • . -- --- - _ .. . _ .. ._ .. . ._ . - -- - - .- 1_11.1_1____ S.9 •-• - - -- ._ - • Li _ . - - ... - - - . . — ._:LL _ - - _ ._______ - - \ I. --' • ' - - -- • - i _ _ — -- ----- --• J -- ---- - -- -- ---- -- ---• - -- — . . --- - -- ----- - ----- --- - • -• __L.2___I I --S.6 - - - - - • - I_L 1. I_ . - - L....I - _ - . 1.11_111_l --• - _I - .:1_ - _ _._ _ ------ ---- =I CI SI, Y1 .4 evi ••■ 10 . NO el. CY Grain Size In Millimeters to, 0 Cs 0 tJ 93 CO Cobbles Coorso Flno Coorso Modlum Flno Fines t revo • on. Sample No. Dopth•11. USA Classification M:s U. PL PI B-1, S-2 8-2, S-9 0-3.5-0 5. D-0. 5 22.5-24.0 15.0-10.5 Blown lino sandy SILT, 1 loco 01 fools Black SAND, I ono 01 wood li ayon Is 01 ack lino to mull urn SAND • 17.2 21.4 0.8 I 0 50 50 0 50 60 50 0 90 100 ;45!eM Aq iasreo3 ;uao Jad Grain Size Classification Per cent Finer by Weight Boring B•5 Sieve Analysis . Hydrometer Analysis Size oI Oponino In Inches 1 tlumbor of Moth per In.. U.S.Slandard Grain Size In mm. 100 10 00 10 10 !0 10 30 10 10 o •.-1_ 0 0 ^ 0 1L .1_1_1 _.l .l_ n • S•8 .1111 I..II 1_:1 • Po .1111. 1 1 1. 1 r . n 0 0 0 0 0 0 r 0 0 0 0 Grain Sizo In Millimolors . n o 0 0 0 0 0 0 0 0 a • 0 0 0 0 0 Cobblos \ 7l Coereo Modium Fino S.4 -_. __. ..—.. Deplh•II. U.S.C. Classification wGZ 11 Pt. Pt S -2 5.0 -8.5 Brown slily line SANG 9. ) . 5 -4 10.0 -11.5 Dark -brown line sandy SILT • 24.3 — S -8 20.0 -21.5 Black line to medium SAND 29.4 • S -20 13.0 -11.5 - Black slightly clay line sandy SILT • Grain Sizo In Millimolors . n o 0 0 0 0 0 0 0 0 a • 0 0 0 0 0 Cobblos Coareo Fine Coereo Modium Fino Flnoe r r11vo an Sample ; Deplh•II. U.S.C. Classification wGZ 11 Pt. Pt S -2 5.0 -8.5 Brown slily line SANG 9. ) 5 -4 10.0 -11.5 Dark -brown line sandy SILT • 24.3 S -8 20.0 -21.5 Black line to medium SAND 29.4 • S -20 13.0 -11.5 - Black slightly clay line sandy SILT • 0 10 11 10 40 eo 10 10 10 00 100 145iaM Aq JasJeoo luau Jad per cent settlemont 0 5 10 1 20 25 b�,S•1J LStress in Tons per Sq.Ft. D.01 2 3 4 5 6 7 90.1 3 4 6 7 891.0 2 3 4 5 6 T 891 2 , ! 5 QJJ9 Boring Samplo Depth•11. WC's Heigh! In. Dia. In. Classification Beloro Alt r 8-5 S-19 10. -12.5 36 28 0.942 2.11 Organic Slit— medium s.tlII, dark grey with fine sandy silt laminations 4. One standpipe /riser will penetrate the roof and be provided with a 2 -1/2 inch wye outlet and valves. The portion of the standpipe /riser which penetrates the roof shall be protected from freezing by appropriate insulating materials. 5. An on site emergency water supply shall be provided with a capacity of not,iess than 15,000 gallons. 6. Two stand by fire pumps shall be provided and shall have auto- matic controls to utilize the emergency water supply. One pump shall be diesel powered. The other shall be electric and shall be capable of being powered from the building emergency power generator. 7. An emergency power generator shall be provided and shall provide power for the following: (a) Emergency elevator; (b) Minimum lighting, including all Exit stairs, Exit lights and Exit corridors; (c) Stair tower pressurization; (d) Emergency communications system, including phone jacks; (e) Fire alarm system; (f) Electric Fire pump; (g) Smoke removal equipment (if otherwise required); (h) Emergency evacuation notification system; (i) Fire Department control room. 8. Emergency stair towers shall be pressurized when an..a:larm condition is detected. 9. If the building is not provided with openable windows on each floor, 10% of the windows on each floor shall be tempered glass with a 1 -3/4 inch diameter RED circle on the upper left -hand corner of each window. 10. The building shall be provided with an approved smoke /heat detector system combined with manual pull - stations. Smoke detectors shall be installed in the elevator lobby of each floor and outside of the emergency stair tower doors on each floor. Fixed temperature heat detectors shall be installed in all mechanical equipment rooms. Both this detector system and the sprinkler system shall be monitored by an approved central station alarm agency, providing 24 -hour supervision. 11. An'emergency communications system shall be provided with jacks on each floor of each emergency stair tower and beside the emergency elevator. A minimum of six handsets shall be stored in a room, the location of which shall be designated by the Chief of the Tukwila Fire Department. 12. The room referred to in (11) above shall be of fire resistive construction (according to the standards set out in Part VII of the Uniform Building Code), shall ordinarily remain locked (the lock shall automatically release upon activation of either the fire detection or sprinkler system), and shall contain the following: (a) Emergency communication system controls; (b) Fire alarm and sprinkler flow annunciator panels; (c) Controls to manually start and shut down the fire pumps; (d) An outside line telephone (Pacific Northwest Bell); (e) Smoke evacuation controls; (f) Elevator status panel. • c 0.01 'n n STRESS, KG_ /CM? 0.1 1.0 10 100 CONSOLIDATION TEST BORING B -6 SAMPLE S -19 DEPTH '74.4' .JAN IBB2 U- 3919 -01 SHANNON AND UILSON.INC. GFDTF.CIINICRL CONSULTANTS S H N N N U.N : CONSOLIDATION TEST NO. C -101 : Tested Calc Check. bte AB hw ND Ow "nth: Date 12/29/81 Date 01/05/R2 Date .4' r ! r HeiEht: in. Diameter: ins. Wet Unlit Wt.: mcf EIry Unit Wt.?' pcf Water content: % Void ratio LOAD I:KG) 0.2 0,5 1.0 2.0 5.0 10,0 20.0 10,0. 2040 40.0 10.0 • BEFORE AFTEP TEST TEST .789 2.504 112.5 12945 81.0 98.0 38,9 32.1 1.0820 STRESS (KG/CM2) • 0.066„ 0.165 0.330 0.660 1,650 3.301 6.601 3.301 6.601 13.:03. 3,30.1 0.660 DIAL READINC (0,01MM) 3.1, 1:.8 25.0 39.4 62.6 111.3 -0540 19R.0 210.7` 300,0 284.9 263.2 W I L S O N : INC. + Job! No, W- 39.19 -0.1 Burin, . B -6 Sample S -19 De¢thI 7444' Unified clan =if. ML Fines: % Liquid limit: 38. Plastic limit: % 27. Plasticity index: % 11, I taJ- i c content: % S- ecific Gravity 2.7 MACH. DEFL, SETTLEMENT VOID CORRECTION RATIO ( 0.0 I M i1). 0.4 2.2 5.0 9 +5 13,9 18.4 23.7 18.4 23.7 29.6 r.'l.. 4 0.13 0.53 1.04 1.49 2,43 4,64 9.05 8,96 6 7,.33. 13.49 13 +97 1? 11 1; 0 7 9 2 1.0710 1,0603 1.0509 1.0314 ;.9855 0.8936 0.8954 0.8877 ,x,,8011 0.7912 n.8090 MG. 48 TIME IN MINUTES 0. 1 1.0 10 100 1000 66 G CM2) 0 660 (KG /CM2) 0 N O Gig 1.650 (KG /CM2) 3.301 (KG /CM2) • CONSOLIDATION TEST 7 IME— SETTLEMENT CURVES BORING B -6 SAMPLE 5-19 DEPTH 7L1.4/ CHRISTENSEN GROUP; INC. TUKWILA HOTEL TUKWILA, WASHINGTON JAN. 1982 W- 3919 -01 SHANNON 'b WILSON, INC. GEOTECHNJCPL CONSULTANTS FIG. 4C TIME IN MINUTES 1.0 10 100 1000 1• 1161 17 '_ 3.301 ('s;G /CM2) I:d: �ii������ ' itrit�L ':iit`iiul�:��:i�N1ill��_•. �,� ''' 6.601 (KG /CM2) •IIhflllNiIiIhii CONSOLIDATION TEST TIME— SETTLEMENT CURVES BORING B -6 SAMPLE S -19 DEPTH 74.14' CHRISTENSEN GROUP, INC. TUKWILA HOTEL TUKWILA, WASHINGTON JAN. 1982 W- 3919 -01 SHANNON b WILSON, INC. GEOTECHNICAL CONSULTANTS FIG. 4D 00. N TIME IN MINUTES 1.0 10 _00 1000 _ 11 , 0.660 (KG /CM2) IlII1�1���1i� 61 3.301 ( K0/ CM2 Oiv 0 m 0 O m 13.203 (KG /CM2 CONSOLIOR7ION 7E37 T IME— SETTLEMENT CURVES BORING D -6 SAMPLE S -19 DEPTH 7L. y' CHRIS7ENSEN GROUP, INC. 7UKWILR HOTEL TUKWILR, WRSHING7ON JAN. 1932 W- 3919 -01 SHRNNON b WILSON, INC. GEO7ECHNICPL CONSULTANTS FIG. 4E 11 fF�E� KG.. /F.M. C 0.01 (1. 1 1. (1 1 (1 10(1 O C.ON 5OL I DAT I ON TEST BORING 13-6 SAMPLE S -21 DEPTH `v'`I.Z .IRN 1902 5.'1RNNGN RNA WILbcN.'NC. nizTEc:1N:r9L cGNSuLTRNT;, • - - - • 1.7.1 T-I n-- I ,t Pr; 0'; 0-- IN 6-1 -I 1' C.J 0 n--I ri t.--t 0 r, 0 u4 (.• =T r4 .-I rI 0 PI PI 1.-.• 1-1 I- I() "rir 1- V) =-4 s0 V) 14 C-2 4-,, n-I (1 1 • 0 a C.1 C.1 CT C./ C-1 0 0 0---' Ct- C.t, (2.. 1 'T 1'4 =-4 CJ :-.). a- 1-4 4 -,3 ,r-i -,I ,4 1---F T.! :-.1 -TI -,4 0 •":"' 0 CV t) 1.-.1 •.tj 4-1 t.i.-) ;...'... 1 1 t • 1- 11 •• (.. •.1- --- , 4.. • at tli ,r4. ;,-..! ill -1-:`, -I- I: •r1 "'• .0 C' 'I-I La .-' to .,. 1.rt t...: 2,1# > ....1 t...! C.) =-1 i- w -0 l',. V- V.. ,-; e-i i'.4• 1r.0 0 Tit ID kfi +3' -.4 . -i -1.) IV 1-- '' -7- 17: .--. f: 10 -.4 G ' - C.: C. 1--- _ -T-I 0. --1----. *-1: '''' -14 j0 0 (I 11.1 • - T4 T-1 T.-1 vi .0 r•-•-' • E7- it. 0' -r4 F-4 -1-1. 0 u) 1.1 0 1.0' III ::,*. 1--1 -g- I 0 71 Ilii .11.1.1 -4:1 13' - - 0: 0 11 - et II .. -C1 -04 -r4 -4 ..4--, -. - -.4 i.0 -.-4 4-1' -0 17.: -I Z. w iii It ci . ti., 0 •-#.:4::: • IN. of to- tit 21.1..-;. L.- •-4 •■••4 r--1..-1 I.. (#; (4 1-... t D. Li, ...I O. O. &.t 0) • C..2.12: ... hi „.-# t.-:, ct c4f--4,) t::.. 1.1:t-.. i) C-1 tot ...r tp.c., --4. -I ei -1 (-1 C-1--' f.t.: 2....1 ..- fr- #.1 (.Cl 1 I h71 0 WI I • 1 I- 1.0 1 1 • - - 1 CD X...: • I I, -4-.1,) I . Z - - CO e•-4 If) if) 4.2 CO -C# le) C-I 0 04; ,-.• :) 0-- t=4 _.,1 1-4 ,-I -'4•-• - 2". ri -:-I .C-.1 A. 1 ,-4 a a4 f.1) C.,- ifl 1.1) uni f.-i- ' er -... - •-4 Cei -1- 0.. :---I ,---1 (-4 I0 -,-.4 0, 4 a. .--i I-- 17) -t %,...• .',. V-% CI 1.&J0 CI 4.-1 -el pl prt cl :- 0-- I iv 10 I .Li 41: --. Z 0 (i0 I , L(} - '.., •,.... IV C3 0) (0 NO 0- iv P) 1') I.- .. :2- • C-1 1-.4 .A1 L. 41 III 0 , , 0 :-.. 0 ,i f."").-7.;i bi I- U.... hl CO ..1- .0 I.il .." al . - - 0 ei ----. - E. . 44 lb #1.; Cl e--# ID C-1 ..-0 ill 0 CI, al JO e.-4 lij .,-; (1 if) O. i- -1-) er) --i) ,...# 2.0 :E '0-'0 V) 1) ,-T it- iv .0. 0 00-0- lel to to lo to 4.- cp- ' .01 (..) • 0 -I 19 NO -0 el 11) Cei WI .-,4 C..1 -.0 110 111 CrI C:I C'.i 0 CI 1--- -. 0. D. 1- 2..:1 (..:. C.' i:..'" C, 74 r.1 '0 4.) -0 I) let t i •• 0) '.:.e.: . ,.-.1 ..... ..lo .. .. ..0 .... 1 - 1 Ci ill i...-# i 1:-. • 1-. z ii-„i • ,T4 4-' -4--' 0.I e # 1- - C. 73 7...i: 4.) CI . 1. =II -.11 ;## --4 •, C.: -e1 e I i----: .C1 _CI ..1:1 i--- -11.) 4-4 0 -f-. 1 r---; •, Ill ..4 -e-1 0 ill I _1 'CI . .#-I -#-:' c C.: 2- a 2.1) 1 CI ID • ...../. .C.' ill 17, Li 2- 0 'LK 1 4.) Li 0 01 E. al -0 ..... re. 01 r-I jI 1 0 33 al. ...C. 1 _•1 1- - • 11) )4 -0 0 4. 41 0 LI b`.# 0 0 CI 0 0 0 0 0 T-I ID C) o C. #:-.) 0 0 ri •-4 C4 <1- 4 0 z 1. C C U.; CL -J cc TIME IN MINU 7 ES 0.1 1.0 10 100, 1000 p .: N • . 1 1 ,' 0.165 0.066 (KG /CM2) (KG /CM2) le' ■ 0.330 p p Iiiii (KG /C 2) CD 0 659 (KG /CM2) r. C 1.648 (KG /CM2) co 0 0 0 N 3.295 (KG /CM2) C C M CONSOLIDR7ION 7E57 T IME- SETTLEMENT CURVES !30RING B-6 SAMPLE 5 -21, DEPTH 89-.8 CHRIS7ENSEN GROUP, INC. TUKWILA HOTEL 7UKWILA, WASHINGTON JAN. 1982 W- 3919 -01 SHANNON b WILSON, INC. GEO7ECHNICPL CONSULTANTS FIG. 5C c0. 1 0 0 (N O (N O (D N TIME IN MINUTES 1.0 10 _00 1000 2) CONSOLIDATION 7E37 7IME- 3E77LEMEN7 CURVES BORING B -6 SAMPLE S -21 DEPTH S +.S CHRI57ENSEN GROUP, INC. 7UKWILA HOTEL 7UKW I LA, • WASH I N G7 ON JAN. 1932 W- 3919 -01 SHANNON & WILSON, INC. GE07ECHNICPL CONSULTANTS FIG.5D 11 11 1 \ 1 1 n-- 3.295 (KG /CP Cit /CM; (KG 6.591 6.591 (KG /CM2) 2) CONSOLIDATION 7E37 7IME- 3E77LEMEN7 CURVES BORING B -6 SAMPLE S -21 DEPTH S +.S CHRI57ENSEN GROUP, INC. 7UKWILA HOTEL 7UKW I LA, • WASH I N G7 ON JAN. 1932 W- 3919 -01 SHANNON & WILSON, INC. GE07ECHNICPL CONSULTANTS FIG.5D z J O H 0. 1 TIME IN MINUTES 1.0 10 _00 '000 1 V N 0 - -. N it O GO N ° CO N O IIIIIIIIL1 1111111riddlilliar ' �C.659 (KG /CMi ) Cr r: N-__.:. 7)--r' O WRIT Ill MN III III _:......c......:,.�:a...IL��wtit 3.295 (KG /CM2) l 13.182 (KG /CM2) Cr) 0 LO Cr) O CONSOLIDATION TEST 7 IME— SETTLEMENT CURVES BORING B -6 SAMPLE 3 -21 DEPTH 1-3(+8 CHRISTENSEN GROUP, INC. TUKWILA HOTEL TUKWILA, WASHINGTON JAN, 1932 W- 3519 -01 SHANNON b WILSON, INC. GEOTECHNICPL CONSULTANTS FIG. 5E - • 0 0 r1 -n 0.01 S FRES3 . Kr7. /rm. 0. 1 1.0 10 100 e z3— CONSOLIDATION TES( BORING 8 - -6 SAMPLE S - -22 DEPTH 89.3' JAN 1 P2 14-391S-01 ZHANNCN AND IILSGN.ING. Gf.CTEStlNICNL CGN ULTANTs 4-1 • . z • 45• 3-1 1 C.. ..ii ,-i 1.1 r-f .ri r.1 r-I ,.7) (7) 0 0 0 -.2- o, ci , 1•1 -.0 C4 PI 1 1 I . :,-!. 1- 4T4 CO 0- ... Z CO • : ! 7:!: .. at W 4.- i---•!. lal 4-" 4-'1 X •r I .... -111 17. -r4 141 -',.- hi 0 r's `.0 "4 11.1 '''4 0 '0 1171 0. 0) • 01 ... 0 1... ti1 ..> ...., ?,!,. 0 C.4 I- V- 0 01 al m 4, •„4 -ri +., co 1--, *. C ' 4 ...0 • W • • • CT: C i••• . • i--- .,C, 0 0 0 .,.4 t4:1 IX.1 ID co C4 Al CL ..4 it -4-:* ....1 E .*4 :111 0 0 4,1 r-1 ,i 1-.! Xi t- fil -O. - O 0 w cil cl •,--f ,--4 +-", 0 , 01 771 a CO (.0 / ... ,!: ,--1 •.-1 (1 -1.: 0 0 el" ...I ea .'. 4:1 -.4 -.4 .-4 4.. • , -r4 141 .r1 -0 .0 C *1 --; Z (4- ii4 :1 W 314 444 f,4 IL. 43 ..-4 C r At 11.4 .441 lb , 14) 474 ---- C -,4 -.4 .-4 ...1 1:-. a : i- i- t: 1 LL. _1 11. CL 474 co : •• 144 ---4 '4= 1---, 0- V- 1,-. O. 1'. 44.- N LCI 0. ' V X CA: 0 . . . . 4 C 41 CC • 0 C4 1' 1,-- 1*-1 -0 -4 •0 .-4 N. 44 0 a o c• -I •-• ci ,-1 ci 3:4 ,--1 r o --- • N C'.1 CD -.0 -.-4- 1,, '0 0- ..0 10 b) 3:3:3 *1' C-1 11-4 4:4' 1-4 •-0 (7,1 r's ,1 11..1 a1 '0 '13 CO 0 0, 0 N. f...4 Is- 0 C.). 0. 0- P, C• C4 e4 r4 14) 4- 4- • 0 < ,.--; ,---1 0 0 0 0 0- Et- a at af at (s. .7..7 cs.: LLi 1:14 i i ix' -0 10 1 • .-.., 1- 141 1 1 . -.. • 1 •.:) :E Li_ 1:-. 1 1 j... -1:4 el 1 C.: Cr i" Z ,t',. ..41, 0 -,4- 0 iy. 0 i....3 ..., 0 c-, .1*-; , .. . .J.: . ....?... VI r-4 CI 1 .,i ..4 1-4 ,4 a ai .:.:, 0 0) CO il 1-4 <r. • I:1 RIO --4 C., .4. 0- 0- 0) 0 0) V- bl. 0 ' .r.1 s . r1t ... ..-. ;pi 1 O. V) 9,' 1 Id *-4 --4 (1.174 (\I. 1-1- • 2: I) f.i 0 ki cr.: }- 0 ril 0) '0 ID 12' 10 i'. . . • C-1 ,--11A1 Lt. 1.1.1 CO 0 - • • • 0 -,--4 0 ..-1 11.1 1- F.-- Iil -.--4 0 0- 0 •E 7. 3::74 * • .-4 111 PO ......3 es. ( C ID Qv Oft 1- .,4 0, 4 I 4-, 4) 4) -:-.4 .01 -to W 0.,/ 4- 4-- RIO 11::::1 . 1.0 41.1 al a4 a, , ...... . . . , . . 0 0 ";-!: C- I 1 - . .... .. 4..) 1.-1 I -:, ....- 441 ...... 0 1.11 4, Xi C: • 4 C. 1 8-4 .1.: 2, 0.4 - -.4 4-.1 4-:. 114 i 1-- 17:: 17-1 ; 4-:' C.; 1 ...L. 3:i ' III :i• • t•• •• C: • ei 1 47.4. 4.4 .C4 .4.1 L.. 0 ...i..) C4 4-, 1 1-4 .. (41 ...4 •r4 0 01 at .."... 1 --.1 .1:1 • 0 0 C C. 1:. 'a. 0 C.101 ;C:, 0 0. 0. .:::". 0 •:--, 0 0 .C.-, 1 0 di .. .z..: -C 411 =1 =1 f- 0 i III .0 0 0 A t... Q.1 -1:1 -41 --- 14 • -4. .,.. • WI 4-1 64 4.7.4 11.4 44 57 -.4 (44 -1....' 13-3- ..4 31' ..-4 ej L.: W 0 i 4.) 1-- ■:.:-. 13 a D ,•::, 3: - :.. .. _ . . _ .. .. _.• _ . C �co O z Z C CC W 04 o _JO CL's 0 O N 0. 1.0 TIME IN MINUTES 10 100 0.066 (KG /CM2) I I I I I I! 0 165 (KG /CM2) 1000 0.330 ( KG L_ 0.659 (KG /CM2) '4' 1.648 (KG /CM2) II 3.295 (KG /CM2) CONSOLIDATION TEST T BORING B -6 SAMPLE 3-22 DEPTH 89.3' IME- SETTLEMENT CURVES CHRISTENSEN GROUP, INC. TUKWILA HOTEL TUKW I LA, WASHINGTON JAN. 1982 W- 3919 -01 SHANNON 6 WILSON, INC. GEOTECHNICPL CONSULTANTS FIG. 6C 00. 1. TIME IN MINUTES 1.0 10 100 _000 ,.... 0 N _ i O CD 1lI C 0 .. I. C thlicii, 3.295 (KG /CM2 RI lini _Nunn 1Uiih.ui.iI!!!iJII' If'' _ N 6 7-1 591 �(KG /CM N 0 N 6.591 1 (KG /CM2) ii • N 0 __ N = M -. N 2) CONSOLIDATION TEST T IME- SETTLEMENT CURVES BORING B -6 SAMPLE 5-22 DEPTH 89.3' CHRIS T ENSEN GROUP, INC. TUKWILA HOTEL TUKW I LA , WASHINGTON JAN. 1932 W- 3919 -01 SHANNON b WILSON, INC. GEOTECHNICAL CONSULTANTS FIG. 6D 00. 1 co 0 O O N z O �+N 0 O z N 0. cc OL O J CO O N ►-1 O O m O N m O m TIME IN MINUTES 1. 0, 10 _00 1000 11111 I 111111131 0 659 (KG/CM2) i 611111411, 11111 1 mummun rumilimm-m:.2": iiIiIiilliiiiIIIllhIiIiiiiiiIIIii' .295 (KG /CM2) 11 3.182 (KG /CM2)- CONSOLIDATION TEST TIME — SETTLEMENT CURVES BORING 9 -6 SAMPLE 3-22 DEPTH 39.3' CHRISTENS EN GROUP, INC. TUKWILA HOTEL TUKWILA,• WASHINGTON JAN. 1982 W- 3919 -01 SHANNON b WILSON, INC. GEOTECHNICPL CONSULTRNTS FIG. 6E ,NC:IN ' NED C0VPRESS [1\ TEST W- 3919 -01 +) + + + 5. 0 BORING 6 -6 SAMPLE .S -21 DEPTH 83.8' 1 1 A.0 10.0 1 S. 0 20.0. 30. 0 AXIAL STRAIN, FAILURE SKETCH 11 SHANNON 6 WILSON, INC. CHRISTENSEN GROUP, INC. CEOTECHNICAL CONSULTANTS TUKWILA HOTEL S EAT T L E, WASH i N GT ON I UKW I LA , WASHINGTON JAN. 1982 FIG. 7A 2.84 2.05 Wet Un4t Wt.* wr.f Dr y Wt.! SpeA4men Und:.sturbed INSTRUMENT CCNSTANTS Def'ormation! Loed- AXIAL nEF. gEAD. 5.0 10,0 25.0 100,0 125.0 150.0. '00.0 300,0 400.0 500.0 00.0 700,0 Jo, No. W.-71:919-0 Toot No. 9H-101 ?orint cemPlo S-21 tooth Cleosificatinn MEDIUM STIFF, DARK GRAY! SILTY CLAY TO CLAYEY SILT. Water Content A!ter Toot 49.0 001 1.098 Stress Controlled Test Ave. train Rate 0.85297 %/min ; owl STRAIN STRESS READ. A TSF 0.0 0,09 0.00 1 ' 040 0.17 0.00 43 . 1.7 0 0.05 5.0 0.86 0.14 1.29 g:.12'24) 12.0 1.72' 0,32 H 17.0 2.15 0.46 21.0 2.58 0.56 1 27,0 3.44 0.72 5415 0.80 30.7 27.5 6.87 0.70 0,62 , 24.5 8.59 1 19.5 10.7.1 0.4e 1 i6.0 17';07 C-,75' ■ FIG. 78 FINISHED SURCHARGE FILL SURFACE —\ PIPE COUPLINGS rxrx% "STEEL PLATE EXCAVATION -' OPTIONAL • o. •)rprii STANDARD PIPE PLUG WITH 2 VENT HOLES INSTALL PLATE AND r PIPE RISER TO THIS POINT BEFORE PLACING FILL r STANDARD STEEL PIPE EXISTING ..� GROUND SURFACE g: po 8e e SEE DETAIL BELOW rxrx% PLATE eL GRAVEL POCKET fr — CONCRETE SAND r'STANDARO PIPE PIPE COUPLING WELD ALL AROUND NOTE: SETTLEMENT MARKERS ADJACENT TO EXISTING BUILDINGS TO CONSIST OF STEEL PIPE OR ROD DRIVEN 4 FEET OR MORE INTO GROUND TO PROVIDE FIRM SETTLEMENT MONUMENT. CHR ISTENSEN GROUP, INC. TUKWILA HOTEL TUKWILA, WASHINGTON SETTLEMENT PLATE DETAIL JANUARY 1982 W.3919-01 SHANNON $ WILSON, INC. . CEOTECNMICAL COMSVLTIMTI FIG. 8 PAVEMENT OR 18' IMPERVIOUS SOIL ONSITE SOIL. (SEE NOTE 2) SLOPED TO DRAIN AWAY FROM STRUCTURE EXCAVATION SLOPE CONTRACTORS RESPONSIBILITY 12" MIN. COVER OF DRAINAGE SAND & GRAVEL 16" MIN. ON SIDES OF PIPE) SUBDRAIN PIPE EXTERIOR WALL. DAMP PROOFING DRAINAGE SAND & GRAVEL OR WASHED PEA GRAVEL WEEP HOLES (SEE NOTE 1) WASHED PEA GRAVEL MATERIALS DRAINAGE SAND & GRAVEL WITH THE FOLLOWING SPECIFICATIONS: SIEVE SIZE 1.1/2'" 3/4" 1/4" NO. 8 NO. 30 NO. 50 NO. 200 (by wet sieving) PERCENT PASSING BY WEIGHT 100 90 to 100 70 to 90 60 to 85 20 to 65 3 to 20 0 to 2 (non - plastic) SUBDRAIN PIPE 4" MINIMUM DIAMETER PERFORATED OR SLOTTED, CONCRETE, M ETAL, ASBESTOS. CEMENT OR PLASTIC PIPE; TIGHT JOINTS; SLOPED TO DRAIN .(4 "1100' MIN. SLOPE); PROVIDE CLEAN •UTS. PERFORATED PIPE HOLES (3/16 "TO 1/4" DIA.) TO BE IN LOWER HALF OF THE PIPE WITH LOWER QUARTER SEGMENT UNPERFORATED FOR WATER FLOW. SLOTTED PIPE TO HAVE 1/8" MAXIMUM WIDTH SLOTS. NOT TO SCALE VAPOR BARRIER 18 MIN. %••'.�` 6" MIN. NOTES 1. DRAINAGE GRAVEL BENEATH FLOOR SLAB SHOULD BE HYDRAULICALLY CONNECTED TO SUBDRAIN PIPE. USE, OF 2" DIA. WEEP HOLES AS SHOWN IS ONE APPLICABLE METHOD. 2. IF WET CONDITIONS RENDER ONSITE SOIL UNSUITABLE FOR COMPACTION, BACKFILL THE ZONE SHOWN ABOVE WITH FREE• DRAINING GRANULAR SOIL WITH NOT MORE THAN 5% (BY WEIGHT BASED ON MINUS 3/4" PORTION) PASSING NO. 200 SIEVE (BY WET SIEVING) WITH NO PLASTIC FINES. 3. BACKFILL WITHIN 18" OF WALL SHOULD BE COMPACTED WITH HAND -OPERATED EQUIPMENT. HEAVY EQUIPMENT SHOULD NOT BE USED FOR BACKFILL, AS SUCH EOUIPMENT OPERATED NEAR THE WALL COULD INCREASE LATERAL EARTH PRESSURES AND POSSIBLY DAMAGE THE WALL. 4. ALL BACKFILL SHOULD BE PLACED IN LAYERS NOT EXCEEDING 6" LOOSE THICKNESS AND DENSELY COMPACTED. BENEATH PAVED OR SIDEWALK AREAS, COMPACT TO AT LEAST 95% MODIFIED PROCTOR MAXIMUM DENSITY (ASTM: D1557, METHOD C). OTHERWISE COMPACT TO 90% MINIMUM. CHRISTENSEN GROUP, INC. TUKWILA HOTEL TUKWILA, WASHINGTON SUBDRAINAGE & BACKFILLING JANUARY 1982 W- 3919 -01 SHANNON & WILSON, INC. Geot•chnial Consultants FIG. 9 TABLE 1 SUMMARY OF LABORATORY TEST DATA w- 3919-01 Mrla{ Iuahal In or lapis euaesr Ospth, loaf Weis( sr Dleaf /D" ihssr Strsatlh TSF Dry Dsnf11T kf hstsr Cen bnt,S Ittnbsr6 halts Dthsr Tests Supls Clseslllestlea LL IL 11 8-6 5 -1 0.0 -1.5 1,2,1 14.: To; 1.0': very loose, dark brown, slightly silty, fine to medium SAND; numerous roots and organics. 31.6 Bottom 0.3': soft, brown, fine sandy SILT; some roots and organics. 5 -2 3.0 -4.5 1,2,4 31.5 Medium stiff, brown, fine sandy, SILT; some roots and organics. 5-3 5.0-7.0 1.2,4 27.0 Loose, grey - brown, silty, fine SAND; trace of organics. S -4 8.0 -9.5 3,6.7 23.6 Medium dense, grey - brown, silty, fine SAND; trace of organics. S -5 10.5-12.0 1,2,2 30.3 Top I.0': , loose, grey- brown. silty, fine SAN`; trace of organics. 29.5 Bottom 0.3': loose, dark grey, fine to medium SAND. S -6 13.0 -14.5 2,3,4 29.2 Loose, dark grey, fine to medium SAND. S -7 15.5-17.0 6,11,17 21.8 (tedium dense, dark grey, fine to medium SANO. 5-8 18.0 -15.5 10,12,15 27.0 Medium dense, dark grey, fine to medium SAND. 5 -9 23.0 -24.5 3.5,5 32.2 Medium dense, dark grey. fine to medium SAND. 5 -10 28.0 -29.5 8,9,9 33.0 Medium dense, dark grey, fine SAND; some meciuT sand; one large wood fragment. 5 -11 33.0 -34.5 15,20,21 27.0 Dense, dark grey, fine to medium SAND. 5 -12 39.0 -39.5 13.23.23 29.9 Dense, Jark,grey, fine to medium SAND. 5 -13 43.0 -44.5 12,13,15 30.3 Medium dense, dark grey. Fine SAND; some medi- um sand; one j" laver of fine sandy silt. 5 -14 48.5 -49.5 18,30,30 26.9 Very dense, dark grey, fine SAND; trace of medium sand. S -15 53.5-54.5 25,28,32 29.8 Very dense, dark grey, fine SANO; trace of medium sand. 5 -16 56.0 -59.5 23,35,41 25.2 Very dense, dark grey, fine SAND; trace of medium sand. S -17 63.0 -64.5 5.9.11 33.1 Very stiff, dark grey, fine sandy SILT tc silty fine SAND; oxidizes rapidly. 5 -18 6C.0 -69.2 GUS 38.2 Stiff, dark grey, SILT; trace fine sand; oxi- dizes rapidly. 5 -19 73.0 -75.5 SHELBY 0.3(TV) 81.0 38.5 38 27 11 CCISOL :tedium stiff; dark grey, fine sandy, clayey SILT; oxidizes rapidly. 5 -20 79.0 -80.5 SHELBY 0.3(TV) 46.8 .'tedium stiff. dark grey, silty CLAY to clayey 0.5(PP) SILT; trace of fine sand; oxidizes rapidly. S -21 83.0 -85.5 SHELBY 0.9(TV) 0.7(PP) 74.9 45.3 46 27 19 COHSOL Medium stiff to stiff, dark grey; silty. CLAY, to clayey SILT; oxidizes rapidly. 0.4(QU) 75.7 49.0 2u 5 -22 88.0 -90.5 SHELBY 0.2(PP) 42.7 To 0.3': Soft. light grey, CLAY; highly plastic. 0.7(TV) 0.6(PP) 80.0 39.5 37 26 11 CONSOL Bottae 1.0': Stiff, grey, clayey SILT ;some layers contain a trace of fine sand; mixed varved and blocky texture; some oxidation. 5 -23 93.0 -95.5 SHELBY >1.0(TV) 0.5(PP) 51.4 Top 1.5': Stiff, dark grey, clayey SILT; trace fine sand; oxidizes rapidly. 0.2(TV) 55.6 Bottom 0.2': Same as top, except soft. 0.1(CP) 5 -24 98.0 -100.5 SHELBY 50.7 Very soft to soft, dark gray, fine sandy, clayey 51LT; oxidizes rapidly. 5 -25 103.0 -105.5 SHELBY 40.2 Dark grey, clayey, silty, fine SAND; trace of medium sand, clay laminations, and shell fragments. 5 -26 108.0 -109.5 15,19,14 31.1 Dense, grey. clayey, silty, fine SAND and SHELL FRAGMENTS; some fine gravel. 5 -27 113.0 -114.5 5.7.9 -- No recovery. • TABLE 1 SUMMARY OF LABORATORY TEST DATA w-39t9-Ot Whit Itself Ieo a Su11s tamest Oe1th, bet Su/1er •t Ileee /O' Sheer ilren th :SF Ors :entity ICF toter lCsnten,f Melberg limits 00et Tests :smell CUsNllotlen l FL 11 B -6 5 -22 5 -29 116.0 -119.5 123.0 -123.4 10,10,50 50/5" 19.0 16.2 12.9 Top 1.0'; Very stiff, green -gray, fine to coarse sandy, clayey SILT; trace of fine gravel; oxidizes rapidly (TILL - LIKE). Bottom 0.5'; Very dense, blue -gray, fine to coarse sandy, clayey, silty, fine GRAVEL; oxidizes rapidly. Very stiff, blue -grey, fine to coarse gravelly, fine to coarse sandy, clayey SILT; oxidizes rapidly (TILL- LIKE). • Shoot 2 of 2 TABLE PILE AND DRIVING EQUIPMENT DATA Contract No.: Structure Name and /or No' Project' County N I- C 2 W la t ▪ O G t O r- ANVIL HAMMER RAM Pile- Driving Contractor or Subcontractor: ( Piles dri•ea by ) Manufacturer: Model Type: Serial No.: Rated Energy: Cd Length of Stroke Explosive Force • (For diesel hemmers) Rom Weight: Ram Length: Rom Cross Sectional Area: A NVI L (with diesel hemmers) ( Por diesel bammsrs ) Anvil Weight: Material: , Are CAPBLOCK Thickness Modulus of Elasticity - E (P,S.L) Coefficient of Restitution -e Helmet D------1 PILE CAP — Bonnet — Weight: Anvil Block Drive heat: CUSHION PILE Cushion Material: A►eo* Thickness: Modulus of Elasticity - E (PS.L) Coefficient of Restitution -e Type :. Pile Si:e : Length (In Leads ) - Diameter- Wall Thickness: Taper: Material: Weight /Ft.• Design Pile Capacity' (Tons) Description of Splice c Tip Treatment Description :. FINAL ENVIRONMENTAL IMPACT STATEMENT FOR TUKWILA HOTEL PREPARED BY THE CITY OF TUKWILA PLANNING DEPARTMENT TUKWILA, WASHINGTON WITH THE ASSISTANCE OF R.W. THORPE AND ASSOCIATES, INC. Prepared in Compliance with The State Environmental Policy Act of 1971 Chapter 43.21c, Revised Code of Washington, as amended SEPA Guidelines, Effective January 16, 1976 Chapter 197 -10, Washington Administration Code, as revised City of Tukwila Ordinance Number 1211 November 23, 1982 TABLE OF CONTENTS INTRODUCTION DISTRIBUTION LIST iv LOCATION MAP vi ILLUSTRATION vii' COMMENT LETTERS: Written Comments and Responses to Comments: 1. United States Department of Army, Corps of Engineers 2. Washington State Department of Ecology 3. Washington State Department of Game 4. Washington State Department of Transportation 5. Puget Sound Air Pollution Control Agency 6. King County Conservation District 7. Municipality of Metropolitan Seattle 8. City of Tukwila Public Works Department Letters Not Requiring Response: 1. Office of Archaeology /Historic Preservation APPENDIX: Traffic Analysis 2 8 10 13 17 19 21 24 27 INTRODUCTION Project Sponsor: Christensen Group, Incorporated 2500 NE Andresen Vancouver, Washington 98661 Nature of Proposal: Development of an 8 story hotel on a 5.47 acre parcel of land. The proposed development includes 274 guest rooms, dining room, cocktail lounge, banquet room, 5 meeting rooms, swimming pool, administrative offices, and parking spaces for up to 509 cars. A pedestrian bridge might be constructed to span the Green River connecting the Hotel to Christensen Trail. Project Location: The 5.47 acre site is located at the southwest quadrant of the West Valley Highway /South 158th Street intersection in Tukwila. Lead Agency: City of Tukwila Planning Department Responsible Official: Brad Collins, Planning Director Planning Department City of Tukwila Contact Person: Mark Caughey City of Tukwila Planning Department City Hall 6200 Southcenter Boulevard Tukwila, Washington 98188 Telephone: (206) 433 1849 Authors and Principal Contributors: This EIS was prepared under the direction of the City of Tukwila Planning Department; research and analyses were provided by the fol- lowing firms: R.W. Thorpe & Associates 815 Seattle Tower Building 3rd & University Seattle, Washington 98101 Telephone: (206) 624 6239 (Contact: R.W. Thorpe) Jensen, Krause and Schoenleber Architects 1962 NW Kearney Portland, Oregon 97209 Telephone: 624 6865 Beighley- Krause, Inc. Landscape Architects 12840 NW Correll Road Portland, OR 97229 Geo -Recon International, LTD Geophysics Archaeology Geology PO Box 55189 Seattle, WA 98155 Kegel & Associates Land Planning, Surveying, and Engineering 12360 NE 8th Bellevue, WA 98005 Kramer - Gehlen Associates, Inc. Consulting Structural Engineers 2712 Washington Street Vancouver, WA 98660 Shannon and 'Wilson Geotechnical Consultants 1105 N 38th St Seattle, WA 98103 The TRANSPO Group Transportation Engineers 23 148th Avenue SE Bellevue, Washington 98007 Actions, Permits and Licenses Required: Final Plat Approval Board of Architectural Review Approval Shoreline Management Substantial Development Permit Building Permits Hydraulics Permit Flood Control Permit Site Plan Approval Electrical Permits ii Occupancy Permits Sign Permits Grading Permit Flood Control Permit Mechanical Permit Puget Sound Air Pollution Control Agency's "Notice of Construction" and "Notice of Completion" All other permits necessary to construct buildings & improvements proposed on the site. Location of EIS Background Data: R.W. Thorpe and Associates 815 Seattle Tower 3rd and University Seattle, WA 98101 Tukwila Planning Department City of Tukwila City Hall 6200 Southcenter Boulevard Tukwila, WA 98188 Cost to Public of Copies of Final EIS: No cost Date of Issue of Draft EIS: June 17, 1982 Date of Issue of Final EIS: November 23, 1982 NOTICE The distribution of this Final Environmental Impact Statement has exceeded the 75 day time period normally required by the lead agency (City of Tukwila) by section WAC 197 -10 -550 of the SEPA Guidelines. Due to the complexity of the issues pertinent to this project, especially as presented in comments from the WSDOT, and the necessity to fully disclose all impacts and mitigating measures, the City of Tukwila extended the 75 day time period. iii RECIPIENTS OF THIS FINAL ENVIRONMENTAL IMPACT STATEMENT Federal Environmental Protection Agency Department of Housing and Urban Development Army Corps of Engineers, Seattle District Engineer Soils Conservation Service, Department of Agriculture U.S. Department of Interior, Fish and Wildlife Department of Energy, Region X State Governor's Office Office of Program Planning and Fiscal Management Department of Ecology Department of Fisheries Department of Game Department of Transportation Department of Social and Health Services Ecological Commission Office of Archaeology and Historic Preservation Office of Public Archaeology, University of Washington Regional Metro - Water Quality Division Metro - Transit Puget Sound Air Pollution Control Agency Puget Sound Council of Governments Seattle - King County Department of Public Health Local Government Ring County Department of Public Works, Hydraulics Division King County Building and Land Development Division King County Planning and Community Development Department King County Soil and Water Conservation District City of Kent City of Renton City of Seattle City of Tukwila Mayor City Council Planning Commission Public Works Department Parks and Recreation Department Police Department Fire Department City Attorney SEPA Information Center Finance Department Utilities /Services South Central School District #406 Puget Sound Power and Light Washington Natural Gas Company Pacific Northwest Bell Libraries Tukwila Public Library Renton Public Library - Main Branch University of Washington Library, College of Architecture and Urban Planning King County Public Library Newspapers Seattle Times Seattle Post - Intelligencer Daily Journal of Commerce Renton Record Chronicle Highline Times Private Organizations and Others Tukwila Chamber of Commerce The Greater Renton Chamber of Commerce Rainier Audubon Society v ut ` iT � 7%nien it r a �uvw�A aF'► w. � � w. �T� \�. E � a���►il ca, *It Ng Et A ilp:k rag, Mo4,-ag ruectuiek,.. ‘h4:4140,g7g* iik t �.� '0 4 , ' \l i" �'..��.� tilt �L .' . g.Ak\1 11 I. r-P#17.1rirr,,---,„,,-1_,,:instirg„ w � �; fiNW ` !liar .� I.1!w 1 §MOVI, loom 111010431:40.2rtfil 147147V51r4f la sizq 1 +� tea._. :• 1 1.( a r log; ,�j "mot Eh AlEtr intik ,z0/ U.S.G.S. BASE +1"=4000' NORTH 1. LOCATION MAP TUKWILA HOTEL A.W. THORPE AND ASSOCIATES vi WRITTEN COMMENTS AND RESPONSES TO COMMENTS 1 NPSEN -PL -ER c DEPARTMENT OF THE ARMY SEATTLE DISTRICT, CORPS OF ENGINEERS P.O. BOX C -3755 SEATTLE. WASHINGTON 98124 Mr. Mark Caughey Planning Department City of Tukwila 6200 Southcenter Boulevard Tukwila, Washington 98188 SUDS -» JUL 26 1982 C OF TUKWILA ' .NNtNG DEPT. V r: 7S n ;-n ti m is 5`: • . •z.• r3 Dear Mr. Caughey: We have reviewed the draft environmental impact statement (EIS) for the Tukwila Hotel, Tukwila, Washington, with respect to the U.S. Army Corps of Engineers' areas of responsibility for flood control, navigation, and regulatory functions. We have the following comments. - • a. Please refer to the last paragraph on page 35 and to item 2 under Mitigating Measures on page 37. It is not clear whether interior runoff will be pumped or drained by gravity. b. The EIS states that'existing site is diked 'and surface runoff prevented from draining to the Green River (last paragraph on page 35). However, both the preceding paragraph and item 2 under Mitigating Meas- ures on page 37 state that surface water will be drained to the Green River at the same rate as presently exists. This inconsistency should be resolved. c. There is no discussion of the engineering involved in designing the interior drainage system. Some assurance should be provided that the plan will function if the Green River is at maximum controlled flow and the design interior storm occurs at the same time. d. Please refer to figure 6 on page 28 and figure 7 on page 36. We recommend deleting the note on these figures. With respect to the Corps of Engineers' storm water discharge policy, the notes are misleading. To clarify the basis for this recommendation, a copy of a recent letter we sent to King County is attached (inclosure 1). This letter describes our authority to manage water resources within the Green River Basin. e. Please refer to page 35, second paragraph, fifth line. Elevation should be 24.2 feet instead of 25.8 feet. P R. Lm. u "a r p �t lR r . r. r^� c :; 1 C-1 SUBJECT ' L S +dld 2 • J NPSEN -PL -ER Hr. Mark Caughey PRE' Vf:z SUBJECT TO REVSM4 f. There is a flood danger to individuals using the basement because the floor is proposed at elevation 19 feet, which is about 5 feet below the maximum flood level. We recommend the city of Tukwila develop flood warning procedures to notify the hotel management that a flood danger could exist to occupants and contents in the basement. Although this flood threat is remote, a warning system should be developed to assure safety of hotel occupants. g. The pedestrian bridge, which may be constructed to span the Green River, should be clear span to prevent obstruction to floodflows and potential collection point for debris. h. The project area would be inundated by a basin wide standard project flood. Thank you for the opportunity to review this statement. If you have any questions regarding our comments, please contact Dr. Steven F. Dice, telephone (206) 764 -3624, of my staff. 1 Incl As stated • Sincerely, R . I SUBJECT TO REVISION 3 . ‘,,•"" • - . • 4+- 'f'�`�'^S :�•eo -��... '� : - • - - MPSEN -PL -FE Janes W. Guenther, Director - input for the county's basin vater.sanagement plan. If you have any ques- tions, please contact Ms. Linda Smith, Study Manager, at telephone (206) 764-3620. • Copy furnished: Lynn Brown, Acting State Conservationist Soil Conservation Service, Boom 360 D.S. Courthouse Spokane, Washington 99201 Earold Robertson. Manager Planning Division Ling County Courthouse, W217 Seattle, Washington 98104 Mr. Wes Edens Federal Emergency Management Administration 130 228th Street Southvest Bothell, Washington 98011 Sincerely, R.P. SELLEVOLD, P.E Chief, Engine, ing Division 5 Responses to Comments from the United States Department of the Army, Corps of Engineers Comment Number: 1 Comment noted. The last paragraph of page 35 of the DEIS is hereby amended as follows: "Since the site has previously been diked, surface water was partially prevented from draining into the River, resulting in periodic on -site flooding. The proposed development will decrease this potential by releasing surface drainage water into the river. A gravity flow system is designed to discharge stormwater at the same rate as the existing discharge rate. A sump pump will be used to drain stormwater from the loading dock area located at the north side of the building to the gravity flow drainage system. Although this drainage system will be designed in accordance with city regulations, the system could contribute marginally to peak river flows due to the runoff from impervious surfaces. Although the level of the river is controlled at Howard Hansen Dam, minor uncontrollable fluctuations in river flow could contribute to minor streambank erosion downstream from the system outfall." Comment Number: 2 Correction noted. Paragraph 1 on page 35 of the DEIS is hereby amended as follows: "The subject property is adjacent to the Green River. Man -made dikes protect the site and general vicinity from flooding from the Green River. However, due to the dikes, internal drainage is somewhat restricted from flowing into the river. Resultant drainage follows three courses: some flows northerly to the adjacent property, some percolates into the groundwater. and some drains directly into the Green River." (Also, please refer to response to Comment Number 1 for the Department of Army, Corps of Engineers) Item 2 under Mitigating Measures on page 37 of the DEIS is correct in stating "The gravity flow system is designed to discharge stormwater into the Green River at the same rate as the existing discharge rate." Comment Number: 3 Comment noted. Mitigating Measures on page 37 and page 5 are hereby amended to include the following: "A one -way gate valve will be installed at the outfall of the stormwater control system in order to prevent water backing up into the site's drainage facility from the Green River during periods of maximum controlled flow." 6 Comment Number: 4 Correction noted. Figures 6 and 7 of the DEIS are hereby amended. The notes on said graphics are deleted. Please refer to the following Storm - water Drainage and Grading Plan. Comment Number: 5 Correction noted. Line 5, second paragraph on page 35 of the DEIS is hereby amended as follows: "The maximum flood stage of the river at the site has been determined by the Army Corps of Engineers to be at elevation a.2 feet." Comment Number: 6 The basement is designed for storage, laundry facilities, mechanical room and meeting rooms. Mitigating Measures, pages 37 and 5, are hereby amended to include the following: "The City of Tukwila could develop a flood warning procedure to notify the hotel management that a flood danger could exist to occupants and contents of the basement during peak flows of the Green River. At the time such warning is received, the Hotel would require closure of the basement." Comment Number: 7 Comment noted. Should the pedestrian bridge be constructed, permits shall be obtained from the Army Corps of Engineers prior to construction to insure adequate structural clearance above design flood flows. Comment Number: 8 Comment noted. Impacts on page 35 is hereby amended to include the following: "Portions of the Green River Basin, including the site would be inundated by a basin wide standard project flood." 7 v AI Ito v rl.T/'M• 10. .1 1P/r/ 1 !/r/I Jr -w (I nIY.Or / A• ,1170 / NA NO Nq A/ NI •aY / /J{'.O' I•W NI).y Nr0 r M!' Apia Afe 1 I4LV •1J A•O r wt AY Jr •O 1 40 1 `0..,.1- — — 4 asm_n_ 1 � 4 ml KEGEL L ASSOCIATES INC. l4 — LAND PLANNING ENGINEERING 1 a SURVEYING e'J7rA. NM llgr UK rY QraraV • 90 mg 1 W •D •• AAa••• IN, — f-- G/Y/f.Y /1 /Ny{/fST ti LEGEND /aYrIn. !Awe • ',fawn nsr.w.9 - -r•_ _- II/J//AV CONIAVII - - - -. MAr..14. AI3 1INlJ arawJs, .496.3 Am,* t•YI, rM n -Ay Nd /.I. NLrO 1*'3110 - �---r- LOG[ aa,7.0 ftIn• yr ��N /AvSv OVIOOMJ LIN/0V M✓LNL /1 J(oY AWN iamr •. /N1 m4 40.71 •p1f,N Jur A was IVI.Ga1111 WAY 11/1.111•W^. wru• NUM' 01101 1,161.1 OAS Ig11•Iv MIl1YV1 wA. 01111111 04 13041 411 1(1* a..'atl.N rlK x/11 STORM WATER DRAINAGE AND GRADING PLAN Pa 01• Tukwila Hotel 0•011 0 01 • 101 110. ]0740 JOHN SPELLMAN Governor STATE OF WASHINGTON DEPARTMENT OF ECOLOGY Mail Stop PV -11 • Olympia, Washington 98504 • (206) 459-6000 July 19, 1982 Mr. Mark Caughey City of Tukwila Planning Department 6200 Southcenter Boulevard Tukwila, Washington 98188 Dear Mr. Caughey: DONALD W. MOOS Director Thank you for the opportunity to review the draft environmental impact statement for the Tukwika Hotel. As noted in the EIS, a flood control zone permit is required from the Department of Ecology. An application should be submitted to the Department of Ecology, Northwest Regional Office, 4350 - 150th Avenue, NE, Redmond, Washington 98052. If you have any questions, please call Mr. Herman Huggins, Northwest Regional Office, at 885 -1900. BJR: lc cc: Herman Huggins Sincerely, ' Y �Ifi Barbara J. Ritchie Environmental Review Section Response to Comments from Washington State Department of Ecology Comment Number: 1 A State Flood Control Zone Permit application was submitted to the King County Surface Water Management Division May 24th, 1982, per the instruc- tions provided in the "Procedure for Filing State Flood Control Zone Appli- cations." Permit processing has not been completed at this time. 9 • JOHN SPELLMAN Governor STATE OF WASHINGTON DEPARTMENT OF GAME 6IX) North Capitol Way, G/-11 • Olympia, Washington 98504 • (206) 753 -5700 July 27, 1982 Mark Caughey City of Tukwila Planning Department City Hall 6200 Southcenter Boulevard Tukwila, Washington 98188 •Dear Mr. Caughey: FRANK LOCKARD Director JUL 2 9 1982 DRAFT ENVIRONMENTAL IMPACT STATEMENT: Tukwila Hotel Your document was reviewed by our staff as requested; our comments follow. The riparian buffer zone proposed along the Green River is inadequate 'to protect water quality and streamside habitat. A buffer zone does not fulfill its functions if major construction such as dikes and a fire access road is done within it. We recommend a minimum undisturbed buffer of 100 feet along the Green River at the project site. Dikes and the fire access road should be constructed outside this buffer. Areas disturbed from construction of the storm water outlet should be revegetated with native plant species. Our specific comments on the EIS are: Page 19, paragraph 5; page 20, paragraph 6. The proposed development does not conform with the Shoreline Management Program described in Appendix D. An eight -story hotel building within 100 feet of the river does not meet the use regulation that no structures exceeding 35 feet in height be built within the Low Impact Zone (Appendix D, page 6.4). Page 38, paragraph 4. A maintenance schedule for the oil /water separators should be specified prior to approval of the storm water drainage plans by the city of Tukwila. \Page 43, paragraph 1. Past reductions in wildlife habitat make the remaining habitat all the more important. Pages 43 -44, Fish; This section presents good information on the existing fish resources of the Green River. However, the project as proposed will impact fish habitat along the Green River. The decrease &CIO 3 l 1 2 J= J 4 5 Mark Caughey July 27, 1982 Page Two in quality of site runoff plus the lack of an adequate riparian buffer will degrade the aquatic habitat and impact the fish resource. Thank you for sending us your document. We hope you find our comments helpful. BW:cv cc:. Agencies Region Sincerely, THE DEPARTMENT OF GAME Betsy Wolin, Applied Ecologist Environmental Affairs Program Habitat Management Division 11 1 5 Responses to Comments from Washington State Department of Game Comment Number: 1 The dike is planned to be reconstructed at its existing location. The planned dike location and fire access road are in conformance with the Shoreline Master Program for the City of Tukwila. (Please refer to Appendix D of the DEIS.) It is acknowledged that construction of the dike and fire access road will impact understory vegetation along the river (please refer to Impacts, page 42 of the DEIS) which may degrade the quality of habitat (please refer to Impacts, page 44 of the DEIS). However, indigenous trees of significant growth along the river bank will be retained, and understory vegetation damaged in the course of construction will be restored in accordance with the standards contained in the Tukwila Shoreline Zone (TMC.18.44.130 lc) Comment Number: 2 The proposed development does conform with the City of Tukwila Shoreline Management Program. (Please refer to Appendix D of the DEIS). The 8 -story portion of the hotel is located beyond the 100 foot "Low Impact Zone." That portion of the hotel which is within the "Low Impact Zone" does not exceed 35 feet in height. Comment Number: 3 The City of Tukwila Public Works Department presently does not have a policy for insuring a maintenance schedule of oil /water separators. However, under RCW 90.48 "Water Pollution Control," no oil discharge is permitted in State waters. In the event a complaint is filed in regard to a problem with pollution, the Department of Ecology would intervene and insure the problem is rectified, should the City of Tukwila fail to. Comment Number: 4 Comment noted. Generally, this statement is true. However, the site presently does not support rare or unique wildlife habitat. (Please refer to Existing Conditions, page 43 of the DEIS.) Potential degradation of the river habitat is noted extensively. (Please refer to Impacts and Mitigat- ing Measures, page 44 of the DEIS.) Comment Number: 5 Comment noted. Impacts on fish habitat are acknowledged. (Please refer to Impacts, page 44 of the DEIS.) 12 JOHN SPELLMAN Governor STATE OF WASHINGTON DEPARTMENT OF TRANSPORTATION Office of District Administrator • 0-1, 6431 Corson Ave. So., C -81410 • Seattle, Washington 981019 July 23, 1982 Mr. Mark Caughey City of Tukwila Planning Department City Hall 6200 Southcenter Boulevard Tukwila, WA 98188 Dear Mr. Caughey: DUANE BERENTSON • Secretary SR 181 City of Tukwila DEIS Review Tukwila Hotel (K -434) We have reviewed the above noted document and due to the projected traffic volumes generated by this project, mitigation will be re- quired as follows: 1. The projected traffic volumes indicate a traffic signal is warranted at the intersection of SR 181 and S. 158th Street. • 1 This signal system must be coordinated with emergency pre- emption. 2. The installation of a signal will severely add to Longacres peak traffic hour problems. To resolve this problem, two 2 southbound left turn lanes will be required to improve the level of service. 3. A southbound deceleration right turn lane into the Hotel may be required. J 4. The above noted mitigation items necessitate the modification) 4 of the existing illumination system. 5. Additional highway right of way will be necessary to accommodate 5 the required traffic mitigation measures. None of the above items are contained within this department's cur- rent operating budget; therefore, funding of these mitigating mea- sures will have to come from other sources. Mr. Mark Caughey July 23, 1982 Page Two Thank you for the opportunity to review this proposal. If you have any questions regarding this matter, please call me at 764 -4356. PRL:dp Very truly yours, J. D. ZIRKLE, P.E. District Administrator HAROLD L. MORGAN, -.E. Acting Design Engineer 14 Responses to Comments from Washington State Department of Transportation (Please refer to Appendix of this document, Traffic Analysis) Comment Number: 1 In response to the WSDOT July 23 comment regarding the need for a traffic signal, one must compare the traffic volume shown against the warrant outline in the Manual on Uniform Traffic Control Devices (MUTCD), and must consider the WSDOT policy regarding interpretation of these warrants. For background, it has been the standing policy of the WSDOT not to issue a signal permit for construction of a traffic signal on a state highway if only Warrant 2 (the interruption of continuous traffic warrant) was satis- fied. Traditionally, WSDOT requires that either the minimum volume warrant or one of the other volume or traffic safety warrants must be met in order to justify construction of a traffic signal. The warrants outlined in the manual on uniform traffic control devices require that average daily traffic volumes be used as a basis for satis- fying the traffic signal warrants. For the purpose of the analysis pre- pared in our traffic report, we assumed the condition with Longacres in operation even though this condition exists less than half the year. Under this condition, none of the warrants outlined in the Manual on Uniform Traffic Control Devices are satisfied. Even Warrant 8, combination war- rant, although very close to minimum criteria, does not satisfy warrants. In the event this warrant were satisfied, two factors should be kept in perspective: 1. A signal should not be installed under this warrant alone unless, "Adequate trial of other remedial measures which cause less delay and inconvenience to traffic" preceed such installation" (MUTCD -Page 4C -7) 2. If a signal is warranted after these trial measures are proven ineffective, the costs thereof should be borne by benefitting property owners in pro- portion to their contribution to total traffic volumes that exist during those hours when traffic signal warrants are satisfied, assuming WSDOT does not have the resources to provide the improvements. Comment Number: 2 As the WSDOT letter points out, the installation of the traffic signal could have a significant adverse impact on peak traffic conditions at the S. 158th St./West Valley Highway intersection which may in turn impact properties and businesses in the vicinity, including Longacres and the Tukwila Hotel. This is one reason why installation of a traffic signal was not recommended as a mitigation strategy for the hotel project. The addition of southbound left - turn lanes, as suggested, is only one of many optional capacity- improvement features which could be explored in the context of any future signal /intersec- tion design,, and is not necessarily the optimal solution at this time. 15 Comment Number: 3 The need for a southbound deceleration right -turn lane into the hotel does not appear warranted based on the traffic volumes that are forecasted to be gene- rated by this project. Because the hotel traffic demand is spread out over the entire day, there are not the typical peak surges in traffic volume that are typically generated by other land uses like office or residential devel- opment. Moreover, the peak traffic flow in the evening peak hour is north- bound on West Valley Highway, while the peak flow into this hotel is expected to be split evenly by traffic traveling northbound and southbound on West Valley Highway. Comment Number: 4 At such time as a traffic signal system is warranted, it seems only reasonable that the existing illumination system be upgraded. Any additional right -of- way which might be necessary to accommodate the improvements associated with a traffic signal and any additional turn lanes could be incorporated as part of the costs of that improvement. Like costs associated with the traffic signal, these right -of -way costs should be distributed in proportion to the traffic volumes that will utilize the intersection. Comment Number: 5 Comment noted. 16 SERVING: KING COUNTY 200 West Mercer St. P.O. Box 9863 Seattle. 98109 (206) 344.7330 KITSAP COUNTY Dial Operator for Tot Free Number Zen to 8385 Bainpriage Island Residents Dial 344.7330 PIERCE COUNTY 213 Hess Budding Tacoma, 98402 (206) 3835851 SNOHOMISH COUNTY (2061 259.0288 BOARD OF DIRECTORS HENN JUL 231982 C OF TUKWtLA .NNJNG DEPT. 1r. Mark Caughey City of "Tu1 ila Planning Department City Hall 6200 Southcenter Boulevard Tukwila, WA 98188 Dear Mr. Caughey : Tukwila Hotel 200 West MercerlStreet, Room 205, P.O. Box 9863 Seattle, Washington 98109 (206) 344.7330 July 22, 1982 The following comments are submitted in response to the draft environmental iupact statement for the Tukwila Hotel. The proponent should be encouraged to implement the first three mitigating measures under "Air Quality" listed on page 4 and on page 34. Mitigating measure number 4 (on page 5 and on page 34) states:. "See Public Transpor- tation - impacts related to 'Traffic', page 65." Yet on page 65 there are no mitigating measures listed under either section c - Transportation Systems or section d - Movement and /or Circulation of People and Goods. his should be clarified. On page iv, under Actions, Perrits and Licenses Required, the Puget Sound Air Pollution Control Agency should be added, since it is probable that the proposed hotel may have fuel -burning equipment, an incinerator, paint spray booth, gasoline storage tank or other equipment that requires approval under this Agency's Notice of Construction program. On page 33, the last sentence in paragraph 4 under impact, could be reworded` as follows: "A herunre, as more stringent federal motor vehicle emission controls and the Washington State vehicle emission inspection and maintenance program take effect, there could be an overall decline in vehicle- related pollutants." Thank you for the opportunity to comment. Very truly yo 1 1 sj CHAIRMAN: Gene Lobe. Commissioner Kitsap County: Joe Stortni. Councilman for Booth Garoner, Pierce County Executive: Doug Sutnenana. Mayor Tacoma Arthur R. •_A, s oehler Air Pollution Control Officer James B. Haines. Councilman SnonomIsn County, Randy Reveller. King County Executive: Charles Royer. Mayor Seattle 17 William E. Moore. Mayor Everett: 1 2 3 VICE CHAIRMAN: Harvey 5. Poll, Member at Lar,E Gene Nelson. Mayor Bremerlor A. R. Dammkoenler. Air Pollution Control Office Responses to Comments from Puget Sound Air Pollution Control Agency Comment Number: 1 Comment noted. Comment Number: 2 Correction noted. Mitigating Measure number 4 under Air Quality, pages 5 and 34 of the Draft EIS, is hereby deleted. Comment Number: 3 Correction noted. Aetions; Permits; and Licenses Required is hereby amended to include Puget Sound Air Pollution Control's "Notice of Construction," and "Notice of Completion." Comment Number: 4 Comment noted. Impact number 4 under Air Quality, page 33 of the Draft EIS, is hereby amended as follows: "Based on the 'Simplified Analysis Technique for Establishing Carbon Monoxide Concentrations Near Highway Facilities,' the maxi- mum levels of carbon monoxide during the peak traffic movement hour created solely by the proposed project will add approximately 1.1 ppm of carbon monoxide to the existing levels. Levels will decrease with wind speeds in excess of 2 mph and with distance from Southcenter. Cumulatively, carbon monoxide levels will be significantly less than the 1 hour maximum standard of 35 ppm. Furthermore, as more stringent federal motor vehicle emission controls and the Washington State Vehicle Emission Inspection and Maintenance Program take effect, there could be an overall decline in vehicle - related pollutants." 18 King County Conservation District 35 SOUTH GRADY WAY RENTON, WASHINGTON 98055 MOE JUN 2 8 1982 • OF TUk T .A F'_.ANN1NG DEPT. Ju Mr. Mark Caughey City of Tukwila Planning Dept. Tukwila City ?jHall 6200 Southceriter Blvd. Tukwila, WA. 98188 Rem Tukwila Hotel DEIS Dear Mr. Caughey: 24, 1982 We have reviewed the Tukwila Hotel DEIS and find it thoroughly addresses our concerns. We recommend that the King County Conservation District review the Temporary Erosion - Sedimentation Control Plan (TESCP) to check the adequacy of this plan to assure that clean water enters ' the Green River. cc: file Sincerely, Robert T. Gavenda Water Quality Planner 19 CONSERVATION - DEVELOPMENT - SELF- GOVERNMENT Response to Comments from Ring County Conservation District Comment Number: 1 The temporary erosion /sedimentation control plan will most likely be submitted along with the site grading and utility infrastructure drawings at the construction permit review stage. The temporary Erosion /Sedimenta- tion Control Plan will be referred to the Ring County Conservation District for review and comment. 20 atia • S Municipality of Metropolitan Seattle Exchange Bldg. • 821 Second Ave., Seattle, Washington 98104 July 20, 1982 Mark Caughey City of Tukwila Planning Department City Hall 6200 Southcenter Boulevard Tukwila, Washington 98188 Draft Environmental Impact Statement Tukwila Hotel Dear Mr. Caughey: fJUL 22 2 1982 TU �J OEPT�'•- OF .NNING Metro staff has reviewed the proposal and offers the following comments. Wastewater Facilities We note the proposal is within Metro's Renton treatment plant service area. Metro has prepared a facilities plan for the Renton system with a grant from DOE and EPA, in part because the Renton treatment plant has reached "design" capacity and,continued development is occurring within the service area. A final plan for the Renton service area was adopted by the Metro Council in November 1981 and contains a recommended;program for upgrading the Renton system so that water quality and health will con- tinue to be protected. The plan calls for these improve- ments to be on line in the summer of 1986. Water Quality In order to maintain water quality, all mitigating measures included on pages 26, 37 and 38 should be implemented. In addition, an oil /water separator should be included in the design of the stormwater detention system. The drainage/ detention system must be maintained on a regular schedule to be effective. This schedule should be developed with the proponent committed to implementation. Mitigating measures for water resource impacts (p. 37) include straw bales as a primary temporary erosion control technique. Use of this technique has not proven effective in all cases. We recommend that the proponent consult with the King County Conservation District for advice on designing and implementing an effective erosion and sedi- mentation control plan. `? . ss 4;'x It 21 Mark Caughey DEIS /Tukwila Hotel July 20, 1982 Page two Construction and Water Quality (available from King County) is a good reference manual for several techniques and specific applications effective in protecting water quality in the Seattle -King County region. Transportation Excellent peak -hour bus service is available along West Valley Road to and from downtown Seattle. It is likely that some hotel guests might wish to use this service if it were accessible. A raised sidewalk should be provided to connect the hotel to this road in order to provide a safe walkway through the parking lot. Proponents should consult with Chuck Gehrts, Metro Transit Planner, at 447 -6367, concerning bus -stop locations prior to commencing construction. The construction of the pedestrian bridge over the Green River would offer the opportunity for hotel guests to walk to major attractions on the west side of the river, perhaps resulting in some small reduction in auto traffic and congestion otherwise resulting from this project. Thank you for the opportunity to review and comment. Very truly yours, Rodney G. Proctor, Manager Environmental Planning Division RGP:ssj 22 J6 7 Response to Comments from Municipality of Metropolitan Seattle Comment Number: 1 Comment noted. Comment Number: 2 Comment noted. Comment Number: 3 Comment noted. Mitigating Measure number 2, page 38 of the DEIS, is hereby amended as follows: "Oil /water separators will be utilized to remove petroleum pro- ducts from catch basins and screens will be included in the storm - water system (including the drainage detention system) to collect litter and debris. The hotel will shade the parking lot at cer- tain times of the day, which will help reduce runoff water tem- perature. Cleaning of parking areas shall be undertaken whenever necessary." Comment Number: 4 Please refer to response to comment number 3 from Washington State Department of Game, page 12 of this FEIS. Comment Number: 5 Comment noted. Comment Number: 6 Comment noted. Comment Number: 7 The availability of transit service on the West Valley Road corridor is noted; however, the proponent anticipates that public transportation patronage by hotel guests and employees will be minimal. The suggested provision of a designated pedestrian crossing path through the hotel parking lot from the highway frontage is indeed valid, although a "raised sidewalk" is not compatible with the project's internal circulation pattern. Alternative pedestrian path designation techniques (at grade) will be evaluated during the construction permit review phase. Comment Number: 8 Comment noted. 23 SIGNED WEOTFORM ® 45 472 SIGNED SEND PARTS 1 AND 3 WITH CARBON INTACT - PART 3 WILL BE RETURNED WITH REPLY. DATE r rn s. POLY PAK (50 SETS) 4P472 Response to Comments from City of Tukwila Public Works Department Comment Number: 1 The site is inside the Independent Water District boundaries. An agreement will need to be reached between the City, Independent Water District, and project proponent to establish the availability and adequacy of water service. 25 1 - — — — — — JOHN SPELLMAN Governor STATE OF WASHINGTON OFFICE OF ARCHAEOLOGY AND HISTORIC PRESERVATION 111 West Twenty -First Avenue, K1 -11 • Olympia, Washington 98504 • (206) 753 -4011 June 23, 1982 Mr. Mark Caughey City of Tukwila Planning Department City Hall - 6200 Southcenter Boulevard Tukwila, Washington 98188 JACOB THOMAS Director MINECEM [JUN 2 8 1982 C:TY OF TUKWILA PLANNING DEPT. RE: 323- C -KI -10 Tukwila Hotel -DEIS Dear Mr. Caughey: A staff review has been completed of your draft environmental impact statement. The document exhibits a well considered concern for the cultural environment. The document adequately considers known and anticipated cultural resources and the potential for impact to these. We concur with the consultant's recommendation that professional monitoring be conducted of the project activities. Thank you for your consideration of our cultural heritage. and Sincerely, rte- �• �.,,� �� Robert G. Whitlam, Ph.D. Archaeologist APPENDIX Traffic Analysis Transportation Engineering & Planning Consultants September 25, 1982 Jon Potter R. W. Thorpe and Associates 815 Seattle Tower 3rd and University Seattle, WA. 98101 SUBJECT: TUKWILA HOTEL EIS Dear Mr. Potter: This letter responds to the. September 7 request of Mr. Mark Caughey, associate planner, city of Tukwila, regarding the,need for a quantative response to the state department of transportation (WDOT) July 23, 1982 comment on the draft environmental impact statement. Attached please find a summary of hourly traffic volumes at the South 158th Street /West Valley Highway intersection. These volumes had been developed using WSDOT traffic counts along roads feeding into the site, manual traffic counts made by The TRANSPO Group, and estimates of projected demand volumes for the new hotel made by the Transpo Group. These summaries show traffic volume conditions with and without Longacres in operation. We have also attached a summary of the signal warrant checks that form the basis of our conclusions. In response to the WSDOT July 23 comment regarding the need for a traffic signal one must compare the traffic volume shown against the warrant outline in the Manual on Uniform Traffic Control Devices (MUTCD), and must consider the WSDOT policy regarding interpretation of these warrants. For background, it has been the standing policy of the WSDOT not to issue a signal permit for construction of a traffic signal on a state highway if only Warrant 2 (the interruption of continuous traffic warrant) was satisfied. Traditionally WSDOT requires that either the minimum volume warrant or one of the other volume or traffic safety warrants must be met in order to justify construction of a traffic signal. The warrants outlined in the manual on uniform traffic control devices require that average daily traffic volumes be used as a basis for satisfying the traffic signal warrants. For the purpose of the analysis prepared in our traffic report we assumed the condition with Longacres in operation even though this condition-exists less than half the year. Under this condition none of the warrants outlined in the Manual on Uniform Traffic Control Devices are satisfied. Even Warrant 8, combination warrant, although very close to minimum criteria, does not satisfy warrants. In the event this warrant were satisfied, two factors should be kept in perspective: The TRANSPO Group, Inc. • 23 -148th Avenue SE, Bellevue, Washington 98007 • (206) 641 -3881 TING TRANSPO 1. A signal should not be installed under this warrant alone unless, "Adequate trial of other remedial measures which cause less delay and inconvenience to traffic" preceed such installation" (MUTCD- Page 4C -7) 2. If a signal is still warranted after these trial measures are proven ineffective it will be triggered by the volumes generated by prop- erties located east of West Valley Highway using S. 158th Street. Thus any costs should be borne by those property owners in whole or in proportion to the traffic volumes that exist during those hours when traffic signal warrants are satisfied, assuming WSDOT does not have the resources to provide the improvements. As the WSDOT letter points out, the installation of the traffic signal could have significant impact on the peak traffic conditions that are generated by Longacres and could require an additional southbound left turn lane to improve the level of service. This is exactly one of the reasons we did not recom- mend installation of a traffic signal. Again, the volume that warrants addi- tional turn lane capacity is being generated by properties east of West Valley Highway and thus the costs should be borne by these property owners. The need for a southbound deceleration right turn lane into the hotel is not warranted based on the traffic volumes that are forecasted to be generated by this project. Because the hotel traffic demand is spread out over the entire day, there are not the typical peak surges in traffic volume that are typic- ally generated by other land uses like office or residential development. Moreover, the peak traffic flow in the evening peak hour is northbound on West Valley Highway, while the peak flow into this hotel is expected to be split evenly by traffic traveling northbound and southbound on West Valley Highway. At such time as a traffic signal system is warranted, it seems only reason- able that the existing illumination system be upgraded. Any additional right - of -way might be necessary to accommodate the improvements associated with a traffic signal and any additional turn lanes could be incorporated as part of the costs of that improvement, Like costs associated with the traffic signal, the right -of -way costs should be distributed in proportion to the traffic volumes that will utilize the intersection. I trust this summary of our analysis and the attached traffic volume forcasts provide Mr. Caughey with the information he needs to approve issuance of the Final Invironmental Impact Statement for the Tukwila Hotel project. If you or he have any questions regarding our analysis I encourage you to call me at your convenience. Sincerely, The TRANSPO Group, Inc. David D. Markley, jj / Principal attachment j , , M_�•••••1 ■■ • ■/ • • OM I • • ■■- ,IRZIKV ■ ■O ■ ■r i T N` vv s7 . VA- y • 6. isiS5 -7 r.+... : 6 J-rL . : Now-rt+Slcuoip ; .50/7HSGU,..ho . 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WA2 v7 Z/ /0 AS .(.,5 /n/` I#77E6 V 71- 3 /irr./1r.S 2. 5A"7 s S F t EIS w t-f-EJ R GO ma rn/ A-7 rO,n/ o f 5A"7cSFf1 7) A 90 AAr z ar 4A/ icKiiceAc,c AZ24J75 r zc.c3 1 [-7-11 Ku /(.A- ( -Io-rE c Si v■/ vk/Aet r .sv� P - ,ey The TRANSPO Crovp Grove