Loading...
HomeMy WebLinkAboutSEPA E99-0012 - HILLSIDE HOMES - SUBDIVISIONTUKWILA SUBDIVISION HILLSIDE HOMES DEVELOPMENT OF SINGLE-FAMILY RESIDENCE 13217 40T" AVE. S. E99-0012 RECEIVED NOV 2 0 2000 COMMUNITY DEVELOPMENT November 16, 2000 City of Tukwila Department of Community Development Attn: Carol. Lumb, Associate Planner 6300 Southcenter Boulevard, Suite 100 Tukwila, WA 98188 CONSULTING ENGINEERS t t c RE: Tukwila Subdivision (L99-0023, L99-0024, E99-0012) Dear Ms. Lumb: 912-01-000-001 The name of the above referenced project has been changed to "Hillside Homes" Subdivision. Please make a note of this. All project correspondence from this point on will reference Hillside Homes. If you have any questions or need any other information, please call our office at (425) 415- 6144. Sincerely, Consulting Engine Roger J. Cecil, P.E. Project Engineer - F.IENGR\ESM•JOBS191210110001Documentslnamechangedoc • 11822 North Creek Parkway N. Suite 106 Bothell. WA 98011-8203 Tel (425) 415 6144 Fax (425) 415 0924 www.esmcivil.com Bellevue (425) 825 0455 Civil Engineering Project Management Land Surveying Land Planning Public Works Landscape Design • l rt AFFIDAVIT OF DISTRIBUTION hereby declare that: Notice of Public Hearing Notice of Public Meeting Board of Adjustment Agenda • Packet O Board of Appeals Agenda Packet • Planning Colau tis s io n Agenda' Packet Short. Subdivision Agenda Packet Notice of Application far Shoreline Management•Perm t Shoreline Management Permit Determination of -Non-. significance Mitigated Determination of Nonsignificance • JDetermination of Significance and Soaping Notice Notice of Action Official Notice Other Other was mailed to each of the following addresses an Name of Project File Number ‘11-00/2 Sicnatur Georgina Kerr 3834 S. 116th Street Tukwila, WA 98168 Hayden Thompson 13034 38th Avenue South Tukwila, WA 98168 Gary B. Greer Secure Capital P.O. Box 25127 Seattle, WA 98125 \OV) Donald H. DeBoer 14450 NE 31st Street J208 Bellevue, WA 98007 William H. Kirkland 13500 Pacific Hwy South #210 Tukwila, WA 98168 Joyce Wray 13025 38th Avenue South Tukwila, WA 98168 Resident 13016 38th Avenue South Tukwila, WA 98168 Donald Scanlon 13410 40th Avenue South Tukwila, WA 98168 Kurtis L. Marley 13038 38th Avenue South Tukwila, WA 98168 John & Kathy Stetson 13258 40th Avenue South Tukwila, WA 98168 Ms. Katherine Russell Triad & Associates tD\ 11814 115th Ave. NE Kirkland, WA 98034 Christa Mitchell 13217 38th Avenue South Tukwila, WA 98168 James & Linda Lewis 13020 38th Avenue South Tukwila, WA 98168 Mr. Michael Weinstein, Project Mgr Triad & Associates 11814 115th Ave. NE Kirkland, WA 98034 • Roselynn J. Primero 13212 38th Avenue South Tukwila, WA 98168 Roger L. Young 3415 South 130th Street Tukwila, WA 98168 Shirley & Curtis Robinson 13422 40th Avenue South Tukwila, WA 98168 Dwight & Nancy McLean 13015 38th Ave. South Tukwila, WA 98168 Aaron Hergert 13217 38th Avenue South Tukwila, WA 98168 Sandra Harrison 13040 38th Avenue South Tukwila, WA 98168 Ron Lamb 4251 S. 139th Street Tukwila, WA 98168 • CHECKLIST: ENVIRONMENTAL REVIEW/SHORELINE PERMIT MAILINGS ( ) U.S. ARMY CORPS OF ENGINEERS ( ) FEDERAL HIGHWAY ADMINISTRATION ( ) DEPT OF FISH & WILDLIFE OFFICE OF ARCHAEOLOGY TRANSPORTATION DEPARTMENT DEPT NATURAL RESOURCES OFFICE OF'THE GOVERNOR DEPT OF COMM. TRADE & ECONOMIC DEV. DEPT OF FISHERIES & WILDLIFE FEDERAL AGENCIES ( ) U.S. ENVIRONMENTAL PROTECTION AGENCY ( ) U.S. DEPT OF H.U.D. WASHINGTON STATE AGENCIES K.C. PLANNING & COMMUNITY DEV. BOUNDARY REVIEW BOARD FIRE DISTRICT #11 FIRE DISTRICT #2 K.C. WATER POLLUTION CNTRL SEPA OFFCL )/ TUKWILA SCHOOL DISTRICT V) TUKWILA LIBRARIES ( ) RENTON LIBRARY ( ) KENT LIBRARY ( ) CITY OF SEATTLE LIBRARY U S WEST SEATTLE CITY LIGHT PUGET SOUND ENERGY HIGHLINE WATER DISTRICT SEATTLE WATER DEPARTMENT TCI CABLEVISION OLYMPIC PIPELINE KENT PLANNING DEPT TUKWILA CITY DEPARTMENTS: ( ) PUBLIC WORKS ( ) POLICE ( ) PLANNING ( ) PARKS & REC. ( ) CITY CLERK ( .( ( FIRE FINANCE BUILDING MAYOR PUGET SOUND REGIONAL COUNCIL P.S. AIR POLLUTION CONTROL AGENCY SW K C CHAMBER OF COMMERCE MUCKLESHOOT INDIAN TRIBE DUWAMISH INDIAN TRIBE ( ) SEATTLE TIMES 07/09/98 C:WP51DATA\CHKLIST ( ) DEPT OF SOCIAL & HEALTH SERV. ( )) DEPT OF ECOLOGY, SHORELIND DIV / V DEPT OF ECOLOGY, SEPA DIVISION* ( ) OFFICE OF ATTORNEY GENERAL * SEND CHKLIST W/ DETERMINATIONS * SEND SITE MAPS WITH DECISION KING COUNTY AGENCIES ( ) K.C. DEPT OF PARKS ( J ) HEALTH DEPT (/ )) PORT OF SEATTLE ,V/ V) K.C.DEV & ENVIR SERVICES-SEPA INFO CNTR ( ) K.C. TRANSIT DIVISION - SEPA OFFICIAL SCHOOLS/LIBRARIES HIGHLINE SCHOOL DISTRICT K C PUBLIC LIBRARY SEATTLE MUNI REF LIBRARY SEATTLE SCHOOL DISTRICT RENTON SCHOOL DISTRICT UTILITIES (/) PUGET SOUND POWER & LIGHT /,VAL-VUE SEWER DISTRICT ( /WATER DISTRICT #20 VV WATER DISTRICT #125 ( ) CITY OF RENTON PUBLIC WORKS ( ) RAINIER VISTA ( ) SKYWAY CITY AGENCIES ( ) RENTON PLANNING DEPT ( ) CITY OF SEA -TAC ( ) CITY OF BURIEN ( ) TUKWILA PLANNING COMMISSION MEMBERS ( ) TUKWILA CITY COUNCIL MEMBERS ( ) CITY OF SEATTLE - SEPA INFO CENTER - DCLU ( ) SEATTLE OFFICE OF MGMNT & PLANNING* * NOTICE OF ALL SEATTLE RELATED PLNG PROJ. OTHER LOCAL AGENCIES ( ) METRO ENVIRONMENTAL PLANNING DIV. OFFICE/INDUSTRIAL 5,000 GSF OR MORE RESIDENTIAL 50 UNITS OR MORE RETAIL 30,000 GSF OR MORE MEDIA CITY OF TUKWILA DEPARTMENT OF COMMUNITY DEVELOPMENT 6300 Southcenter Boulevard, Tukwila,'WA 98188 Telephone: (206) 431-3670 AFFIDAVIT OF ItiSTALLATION AND POST OF PUBLIC I'\-FORVIATION SIGN(S) -State of Washington County of King City of Tukwila G I CERA 1 l--Witlo (Print Name) understand that Section 18.104.110 of the Tukwila Municipal Code requires me to post the property no later than fourteen (14) days following the issuance of the Notice of Completeness. I certify that on (c <j 6) the Public Notice Board(s) in accordance th Section 18.104.110 and other applicable guidelines were posted on the property located at 4-/0 1 5 130.4S� so as to be clearly seen from each right -of -way providing primary vehicular access to the property for application fife 'number -' 1-- 00 l2 Affiant (Applicant Signature) SUBSCRIBED AND SWORN to before me this day of , 19 NOTARY PUBLIC in and for the State of Washington residing at My commission expires on CITY OF TUKWILA DETERMINATION OF NONSIGNIFICANCE (DNS) DESCRIPTION OF PROPOSAL: SUBDIVISION TO CREATE 20 LOTS ON 7.11 AC. AND BLA AFFECTING 4 LOTS WITH EXISTING HOUSES IN VARIOU'S LOCATIONS WITHIN THE SUBDIVISION. PROPONENT: LOCATION OF PROPOSAL. INCLUDING ADDRESS: PARCEL NO: :;EE./TWN/RNG: LEAD AGENCY: 13217 40 ,AV S 734060-0901 NW 15-23-4E STREET ADDRESS. IF ANY: CITY OF TUKWILA FILE NO: E99-0012 The City has determined that the proposal does not have a probable significant adverse impact on the environment. An environmental impact statement (EIS) is not required under RCW 43.21c.03O(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. •kkkk•kb*******•k**kk•kk•kkk•kk**k*********kkkkk•kk******k1*k•kkk*kkkk•kkkkk•k*-k•kk•k•kk•kk 447 This determination is final and sinned this, day of 00k402/ - 199/. 0k 199 ._. _ Steve Lancaster, Responsible Official City of Tukwila. (206) 431-3670 6300 Southcenter Boulevard Tukwila, WA 98188 Copies of the procedures for '_CEPA appeals are available with the Department of Community Development. • 1 TUKWILA SUBDIVISION PLAT REQUIREMENTS FROM EXISTING CODE REQUIREMENTS The following items will be required of the applicant for the Tukwila Subdivision, as authorized or required by existing Tukwila Municipal Code. Required/Authorized by Sensitive Areas Ordinance or Land Altering Permit: 1. Peer review of geotechnical report. 2. Erosion Control Plan 3. Additional geotechnical analysis of: a. Grading of steep slopes on-site. b. Retaining walls and rockeries in steep slope areas. c. Affect of individual foundations and driveways on adjacent parcels within steep slope area. 4. On-site professional geotechnical engineer at all times during installation of utility systems, during land altering and during construction of roads and building pads. 5. Daily construction reports signed by on-site geotechnical engineer. 6. Director approval of piping of watercourses if a Type 3 watercourse if certain requirements are met or for purposes of access for all watercourses. Required Through Storm Water Management Ordinance 7. Review by Geotechnical Engineer of storm drainage report and site plans to ensure recommendations are coordinated and the site plan incorporates recommendations of both storm water and geotechnical reports. 8. Preparation of a Water Management Plan to incorporate recommendations of all consultants to control both ground and surface water flows. Required Through Tree Ordinance 9. Replacement of trees 4 -inches and larger in caliper removed from a sensitive area. Required Through Traffic Concurrency Ordinance 10. Payment of pro -rata share of traffic impact fee based on Concurrency Ordinance. Required Through Subdivision Ordinance 11. Pedestrian trail connection from subdivision through to South 38th Street. c:\carol\Tukwila Subdivision\plat-req.doc • City of Tukwila • John W. Rants, Mayor Department of f Communl y Development Steve Lancaster, Director MEMORANDUM October 1, 1999 To: Steve Lancaster, Director and SEPA Responsible Official Fm: Carol Lfiffi'b, Associate Planner Re: SEPA: Tukwila Subdivision (File No. E99-0012) Project Description: Subdivide an approximately 7.11 acre group of parcels into 20 single-family residential lots. The site will be developed as a planned residential development, with portions of the subdivision held as 2 separate open space tracts to contain a Class II stream, a Class III stream, their respective buffer areas and Class III Areas of Potential Geologic Instability. Proponent: Gary Greer, Secure Capital, LLC Location: The site will be accessed from 40th Avenue South Date checklist prepared: March 24, 1999 Lead Agency: City of Tukwila, Department of Community Development 6300 Southcenter Boulevar4 Suite #100 0 Tukwila, Washington 98188 ° (206) 431-3670 ° Fax (206) 431-3665 File E99-0012 • • Tukwila Subdivision SEPA Staff Report Challenges to Document: None Other Agencies of Jurisdiction: None Recommendation: Determination of Nonsignificance Documents submitted with SEPA Checklist: 1. Wetland Reconnaissance & Stream Relocation Concepts Study, Jones& Stokes Associates, August 13, 1998 2. Geotechnical Study, Squier/HGI Associates, July 15, 1998 3. Traffic Study, TSI, March 1, 1999 4. Proposed Project Plans, dated 3/25/99, revised 6/7/99 (Preliminary Plat/PRD; Boundary and Topographic Survey; Preliminary Utility Plan; Preliminary Grading Plan; Landscape/Recreation Plan; Tree Retention Plan/Slope Analysis; Building Elevations; Adjacent Land Uses) Summary of Primary Impacts: Earth The steepest slope on the site is approximately 48 percent, although the maximum slope within the area proposed for residential development is less than 30 percent. The site is generally underlain by native outwash, tills and consolidated fine-grained glaciolacustrine soils and over -consolidated sandy siltstone. The near -surface soils consist of stratified gravelly sand, fine to medium sand, sandy silt, and clayey silt. Most of the western half and southeast end of the site has been classified as a Class 3 area of potential geologic instability, under the City's Sensitive Areas Ordinance. A Class 3 area is one in which the landslide potential is high. The Geotechnical Report notes that some surficial evidence of slope instability was observed at the site during a site visit. A minor scarp -like feature was located downslope of the Pacific Highway drainage ditches near one of the test pits. No visible signs of recent landslide activity were noted, nor were there visible surface springs on the site. However, the Report notes that heavy vegetation on the site may have concealed seeps and springs and prevented a thorough visual survey. The Report recommends that once the site is cleared of undergrowth, the site be re-examined to check the initial c:\carol\tulcwila-subdivision\sepa-rpt.doc 2 File E99-0012 • Tukwila Subdivision SEPA Staff Report geotechnical observations. Peer review will be required as permitted by the City's Sensitive Areas Ordinance. Prior to issuance of the Land Altering Permit, additional geotechnical analysis will be required, such as more detailed information related to grading and retaining walls. Because construction is proposed in a Class 3 area of Potential Geologic Instability, the construction of the individual foundations must be addressed by the Geotechnical Report, particularly whether the construction of individual foundations and driveways on some of the parcels with steep slopes will adversely affect the side yard stability of the adjacent property. The Land Altering Permit also will be conditioned to require a registered professional geotechnical engineer to be on site at all times during the installation of the utility systems, during land altering activities and during the construction of the roads and building pads (foundations, foundation drains, driveways etc.). Daily construction reports will be required. These reports are to be prepared, signed and submitted to the City by the geotechnical engineer certifying that the work has been accomplished in accordance with the approved plans and specifications. Grading of the site will occur in the course of installing roads and utilities to serve the subdivision. Erosion could occur during the clearing and grading activities, particularly in the steep slope areas. An approved erosion control plan will be required prior to the issuance of a Land Altering Permit. The Checklist notes that possible erosion control methods to be used include silt fences, straw bales, temporary storm drainage features, minimizing soil disturbance during the rainy months and hydroseeding exposed soils and cleared areas after construction is complete. Approximately 35 percent of each building site will be covered with impervious surfaces. Air Emissions and dust particulates generated primarily by construction equipment will be produced during the construction phase of the project. Long term impacts to air quality are those typically associated with residential land use, such as vehicle emissions from increased trips by residents, and smoke from any wood burning fireplaces. Emissions during construction can be controlled by watering the site to control dust, although the sloped areas would need to be monitored for erosion. c:\carol\tukwila-subdivision\sepa-rpt.doc 3 File E99-0012 Tukwila Subdivision SEPA Staff Report Water The site lies within the 560 -acre Southgate Creek drainage basin, which drains into the Duwamish River. Southgate Creek branches into the North, Middle and South Forks upstream of a culvert under South 133rd Street. The project site lies between and includes the North and Middle Forks of Southgate Creek. The Middle Fork of Southgate Creek discharges under Highway 99 through a culvert, drains an area upslope of the highway as well as the south end of the project site before it flows under 40th Avenue South. A small tributary also discharges from a culvert under Highway 99, and then flows easterly across the southern portion of the site behind Lots 14-20. This tributary merges with the Middle Fork of Southgate Creek. The North Fork of Southgate Creek crosses the northeast corner of the project site before it also drains under 40th Avenue South. The Middle Fork and the tributary are both classified as a Type 2 stream. The North Fork is classified as a Type 3 stream under the City's Sensitive Areas Ordinance. These watercourses are mapped and inventoried as Watercourses #15-5 and 15-3 by the City's Sensitive Areas Ordinance inventory. The stream on the southern portion of the property is culverted in several areas as the stream flows toward 40th Avenue South. The applicant is proposing to place approximately 100 additional feet of the stream in a culvert where it currently flows on the northern side of Lot 18. The Sensitive Areas Ordinance (TMC 18.45. 080 D. 6.) governs when piping of watercourses is permitted. Generally, piping of any watercourse is to be avoided. Piping may be allowed if it is necessary for access purposes and also may be allowed for Type 3 watercourses if certain conditions are met. Before the additional culverting of the southern stream will be allowed, the applicant will be required to provide additional information on the type of watercourse (whether Type 2 or Type 30) in the area where the culverting is proposed, and whether placing the stream in the culvert is necessary for access purposes. Both of the streams will be placed in Open Space tracts along with their respective buffer areas (35 -feet for the Type 2 stream and 15 -feet for the Type 3 stream). The Tukwila PRD Wetland Reconnaissance and Stream Relocation Concepts report prepared by Jones and Stokes Associates looked at whether any wetlands are present on the site and assessed stream channel conditions in anticipation of the applicant submitting a proposal to relocate one of the stream channels. The possibility of relocating the stream channel is not being pursued by the applicant and no stream relocation is proposed. c:\carohtulcwila-subdivision\sepa-rpt.doc 4 File E99-0012 Tukwila Subdivision SEPA Staff Report • • Stormwater from the site will be collected in a series of catch basins and conveyed to a proposed detention/water quality facility. The detention/water quality facility is proposed to be located at the low end of the site, which is at the entrance to the subdivision on 40th Avenue South. The stormwater system must be designed in accordance with the King County Surface Water Design Manual and the City's adopted stormwater regulations. The geotechnical engineering study was prepared prior to both the storm drainage report and prior to completion of the proposed project plans. The geotechnical firm, Squier/HGI Associates, will be required to review both and determine whether the stormwater plans have incorporated the geotechnical recommendations. For example, the geotechnical engineering study states that control of the ground water is necessary in order to construct footings on firm natural deposits and recommends curtain drains, however the project plans do not appear to have incorporated this recommendation. It also does not appear that the curtain drain requirement has been incorporated into the surface water retention and detention calculations. In addition, the City's Storm Water Management Ordinance will require a water management plan that incorporates the recommendations made by all consultants to control both ground water and surface water flows. Each consultant will be required to review and sign the report. The project plans must be revised to incorporate the recommendations made in the water management report. Concerns have been expressed about the location of the aboveground stormwater detention facility at the entrance to the subdivision on 40th Avenue South. The location of the detention facility on the project site and whether it is an above- or belowground detention facility, will be reviewed and determined prior to the plat's review by the Tukwila City Council. Plants The SEPA Checklist notes that alder, maple, willow, hawthorn, fir and cedar trees are found on the site. With the exception of the steep slope areas, most of the vegetation in the proposed development area will be graded and removed to accommodate residential site preparation, roadway and utility installation. Street trees will be planted along the new public access street serving the subdivision as well as along 40th Avenue South. The City's Tree Ordinance requires replacement of trees 4 inches and larger in caliper if they are removed from a sensitive area. The applicant has submitted a Tree Retention Plan, with an inventory of trees to be removed, their sizes and the number of trees to be replaced. Ninety-three trees are c:\carol\tukwi la-subdiv ision\sepa-rpt.doc 5 File E99-0012 Tukwila Subdivision SEPA Staff Report • • proposed for removal that is subject to the City's tree ordinance. The Tree Retention Plan/Slope Analysis plan states two hundred and seventy-nine trees would need to be planted to replace the trees removed in the sensitive areas, per Tukwila's Tree Ordinance (TMC 18.54). The applicant has requested that an exception be granted to permit the planting of 175 seedlings in slope restoration areas in lieu of providing the full number of trees at the code required size. This request will be reviewed and a determination made prior to the subdivision's review by the City Council. The Planned Residential Development process (PRD) allows lot sizes and setbacks to be reduced up to 15% in order to minimize the impact of development on sensitive areas. The applicant has not proposed a reduction in lot sizes or setbacks. This may be an option to pursue t� reduce the number of trees needing to be cleared. Two open space tracts will be created, .21 and 1.95 acres in size, which will preserve existing native vegetation and provide protection to the stream channels and steep slope areas. Animals The checklist notes that songbirds, raccoons and rodents have been observed on or near the site. There is no threatened or endangered species known to be on or near the site nor is the site part of an identified migration route. Energy/Natural Resources Electricity will be the primary source of power serving the project; natural gas will be made available for heating and other needs associated with the future homes. The new home construction will conform to the most recent Uniform Building Code and Washington State energy code. Environmental Health The SEPA Checklist notes it is unlikely that any environmental health hazards will be encountered under the expected normal working conditions on the project site. State regulations regarding safety and the handling of hazardous materials would be enforced during the construction process. Equipment refueling areas would be located in areas where a spill could be quickly contained and where the risks of the hazardous material entering surface water is minimized. The predominant source of noise in the area is from vehicles travelling on Pacific Highway South, located on the property's westerly boundary. Short- c:\carol\tukwila-subdiv ision\sepa-rpt.doc 6 File E99-0012 Tukwila Subdivision SEPA Staff Report • • term impacts from noise would result from the use of construction equipment during site development. Construction will occur during daylight hours and construction equipment will not be allowed to idle for continuous periods of time to help mitigate the potential impacts of construction noise. Land/Shoreline Uses The proposed subdivision is located on a 7.11 -acre site on the west side of 40th Avenue South, just south of South 130th Street. Pacific Highway South (Tukwila International Boulevard) lies to the west; to the south is Southgate Park. Fortieth Avenue South borders on the east. The site slopes downward from west to east, with the west quarter of the site sloping downward steeply from Pacific Highway then sloping more gradually until the site is nearly level at 40th Avenue South. The site is currently occupied by several structures. A mobile home is located at the south end of the site, where Lot 20 is proposed. The mobile home will be relocated to a parcel just south of the proposed subdivision. A single-family residence on proposed Lot 1 will remain on that lot. Adjacent land uses consist of low-density single family homes. Tukwila International Boulevard lies to the west, with commercial and higher density multifamily uses. The slopes on the site buffer the project from Tukwila International Boulevard. The site is zoned Low Density Residential, LDR, with a minimum lot size of 6,500 square feet. Only two of the twenty proposed parcels in the subdivision are less than 7,000 square feet, with the majority of the lots ranging from 7000 square feet to 7,900 square feet. The average lot size is 7,560 square feet. Due to the sensitive areas on the site, steep slopes and the two forks of Southgate Creek, the project has been submitted as a Planned Residential Development (PRD). The PRD process permits flexibility in the application of certain zoning code requirements, such as minimum lot size, in order to encourage the retention of significant environmental features and create open space in residential developments. A 15% reduction of the required lot size (to 5,525 square feet) and 15% reduction in setbacks may be approved through the PRD process if certain conditions are met. The applicant has set aside the steep slope area and stream channels and their buffers in Open Space tracts as part of the PRD process. While the project has been submitted as a PRD, the applicant has not proposed any reductions in lot sizes or setbacks at this point. As noted under the section on "Plants," in order to reduce the number of trees proposed for clearing from the site, a reduction in lot sizes may be recommended. c:\carol\tukwila-subdiv ision\sepa-rpt. doc 7 File E99-0012 Tukwila Subdivision SEPA Staff Report • The Comprehensive Plan designates the site as Low Density Residential. The SEPA Checklist estimates that approximately 50 to 64 people may live in the proposed subdivision. Housing A total of 19 new single family homes will be constructed on the twenty lots in the proposed subdivision. One existing home will remain and one home will be relocated. Existing housing is being preserved through the boundary line adjustment process by separating out parcels with existing homes on them from the proposed subdivision. Aesthetics The new homes will be compatible with the surrounding residential neighborhood. Development of the site will change the visual character of the immediate area for adjacent existing residents. The applicant has submitted three sample designs of the homes that will be constructed. These designs will be reviewed by the City Council in the course of reviewing the proposed subdivision/PRD. Landscaping, street trees and house design will reduce aesthetic impacts. Light/Glare Street lights will be installed along the public road serving the proposed subdivision. Other light and glare that will be produced by this project is typical for single-family residential development — outside porch lights, etc. Recreation A walking trail proposed to run throughout Open Space Tract A can be accessed either at the end of the cul-de-sac of the public street serving the proposed subdivision or from 40th Avenue South. Given the sensitive nature of the slopes, the proposed trail will be eliminated. A pedestrian connection will be provided instead to 38th Avenue South, which in turn will provide pedestrian access to Tukwila International Boulevard to the west. Southgate Park is located in close proximity to the proposed subdivision. c:\carol\tukwila-subdivision\sepa-rpt. doc 8 File E99-0012 Tukwila Subdivision SEPA Staff Report 1 • Historic/Cultural Preservation There are no known landmarks or evidence of any significant historic, archaeological, scientific or cultural resources on or next to this site. If any historic or cultural evidence is encountered during construction, work would be halted and a State -approved archaeologist would be engaged to investigate and evaluate the found object. Transportation The site will be accessed from 40th Avenue South with a full street extending to the west and north, culminating in a cul-de-sac. There are also two private access tracts proposed that will provide access to 8 of the homes. The City is reviewing whether to require a through connection from the subdivision to 38th Avenue South. Metro Bus Route 174 provides transit service off Pacific Highway at the intersection of South 144th, South 139th, South 133"I and South 130th Streets. Route 184 stops at the intersection of South 144th Street and Pacific Highway. To the east, bus service is available on East Marginal Way South with Routes 34, 108 and 129 making stops at the intersections of South 133`' and 128th Streets. Approximately 220 vehicle trips per day are anticipated from the proposed project. The applicant may be required to pay a pro -rata share of a traffic impact fee based on the Concurrency Ordinance if the project impacts the streets identified in the Concurrency Ordinance. Any required fees will be paid prior to final plat approval. Public Services The new development will generate an increased need for public services, such as police and fire services, however, current service levels can accommodate this increase. Utilities Utilities currently available at the site include electric, natural gas, water, refuse service, telephone, and storm water. The site is served by Val Vue Sewer District and Water District #125. No additional utilities are anticipated to be needed as a result of the subdivision. c:\carol\tukwila-subdiv ision\sepa-rpt. doc 9 File E99-0012 Tukwila Subdivision SEPA Staff Report Conclusion • • The environmental impacts of the proposed project will be appropriately mitigated through the application of standard review procedures and requirements under the City's Sensitive Areas Ordinance, Surface Water Management Ordinance and other similar regulations. The proposal will therefore not have a significant adverse impact on the quality of the environment. Recommendation Determination of Nonsignificance c:\carol\tukwila-subdivision\sepa-rpt.doc 10 \s‘s 11.1s, ; l!1 !" 1;•. 1.‘ Zi i111 i s• • i ; : • -4; '; ; t . •/ , -4,ke4kgit • • 170.00; 14:477 • POR. OF NW 1/4, SEC. 15, TWP. 23N,RGE. 5E, W.M. 1 ! RECEIVED ,Itil 0 7 1999 C(.1.41VILINITY DEVELOPMENT / -1/•1•1, LEGEND 11M4 mr•••••••••••rm•F1� 0„.(R RAN •••••••••••••••••••••KVARO mAjERFR SERNCE mom ••••11...../.11111:71.1 0%7• CURS UK oxxo. Inn ----- CASEMENT ocomexxo Strox arc (0x3x) •••—. .... TCC:arfX/RWT"'S • •• .......... .. •••• r CINTOURS •••••••••••••••=•SIORTI OR. PIPE ROILAT:: .000c.(1TING 000,05. 101a I LAE mama. REEATSEARARC' YT('71." (NAVA 000010 000101100. C0.0.19C0 ROCKERY • - ROAR M•ATIOLE • CLD'91•ClI"'•••:TIR WAR 1/3/'. SVPACI DOUBLE WATER TARR Tr/ I. SERVICE ARE MYDRART AIR/VAC RELEASE MK CAA VAYE •-• 414 :77 0, BM • R •••*100110110 woo.. • CATCH BASRA tyPt • • CATCH OAS, TYPE • cower, •0 NITTuc ARA •,.., \, :11 ..;,1''. \‘'' '. .-' •;11' , . • \\\ \ , \ \ \\ ; • • • 1 • 1 % \ : ; % \ \\ s 1, ; ' ‘ .• \ % • 1, ' • 1 I, .,ip.,.11.••%.‘\1.1% *\,\ :• ,.•\3A:%;\ks\1% 1 ,\ •, , \, \ \ , \ , •\,,\:' \s' \ " \ VA\NN\ ‘ \ \ '' \s' \ \ \ 1 k \i's, .,, . • \ ,, \\.,, 0 \ ‘‘,., N ' \ ‘• \\c'sk.4.2 \ , , ' t•-, ,.; 1, *. 'y \ % , \''; \ ‘si‘ A \ ‘ ‘ 1, ‘ 1.. 1 \ i'l...--..1._\ _i ‘ \ ‘ \ N I ..--1"--1 1." .,/(/ • ‘.) Y'' ' ' * • ' \ • \ • \ * i 1 ' ' \ \ \ ‘ \ ." \ \ k \ i "3"rt.. .. .\.1,\\'\‘'s \:',. \\1,,‘j -IA \ .6 .',‘. ..i., ./ ! ‘'.,..\ `\ \ '., \ ., 1pw, e 4 . i , % \ , ' t . c.----7--- -...._ -, ..., , ! , i '''• . \ 0 \‘'' \ ' \ ..,, 4 • N .ki'..4%:\ `\. \\ \‘'. \\' \T% 11 1 181V‘ \ri 16-\ 7 4c.1 ri \A_:,"-',.-\--2., I\ \ I 1•\\I' ' - \ ;1•,„\\\\1011,0'11,?' 11\ 1 i I 1 .//i.:1------"--‘ '1'"' o. \ \\,,,f : , -c. \, . i „ I11 ii fi /Mit ii,q,-.)4-4.3; I f i ‘ I t i ; ,t,-1_,,.)/,/,,•/..---.-11.. — .., `V, i1,J.„e,;,.,A,- .., \ , \ r_-_-_-.7**--... ', \ \ ' \ \ \ 0 \\*A1W•\:.`1. \**.\\N\ ' i ,.. / ! i /I I i r!,,i-r i ! : 1 i , f ' ! 1 t .,...,,,-......z...i,....‹...._ _... ,, c•:..„, ,.;‘, , ;\ = \\,.,‘,,,,... 0 \ '' .1...-y,,,,-- . / - i . • • ,---:...--:-.1—•)=.. - • '• -... •...:',vi.:•-•••-• — ......." -- -,,—.-..- • . . \ \ \ /,` \--,- gl., \ .„!'..:,....-;,,,;....*:;., • ...\., 1, ..----,, 1,>4 ,, .,.,,,,,-.f.f...3.-=-...--...-:.-z..:-....„--..-- ......., \ ..,.., . •\ ,...,.-..,_,--s.-.:-.„......-2.-..---.-: v:....,,...\ ‘,1')i•-).1- \ • \ •••• - C\ \ ' \ <'•-•••'..0:5'.....----...-..•.------r..------•"'''.:..-:---..-.‘.-..:\.:,.:-:‘---"•::-...7-----"-----'' ‘-,..K.-A-e?-•-\\ \' \ ' • \\ •/'--/' ' ' •••,‘\\ .\-,.., \--- ---->',.... ,••••••••:--•.----,,.•.---------..\---,--2......_.__,. ---.,--;-....••._ -,\------..,-,-„,--•_---- .. ... --- .,••,,. 1 \ ,. • 'T ' .1•.:1 ///' t:•..-•-••".—- ... •- ..... . ...... IT: ....,\ \:‘,..::,. \ .....:•.. ,..„••• ..:::......• --• ....... . \ \ ' ' \ \ Nii..9.,i>.. T i 1E. , .•...,......1:,.._:......A.:.:..:.-‹ .A. vs.•.\\.:, . " — : \ ‘ \ \ , ‘ \ \ s. ` ` ' 1 1 1 : .% , v. _.•;:. 1:. -1:• 1 7".. 11. \ 114- \•;';'. 1 \•.,\ •:;``:4* -\1-,-.1...••• ; \ '. '. ' V,/.9", -,:r•;...5.2,-3-4,5.7-..-•. -77- •,,, ... -....._ \ ‘';'• \'• -'..:•:•, ,..\, :1): t \I ...);:).'1,-.::L ::---.-1-;. -........ _-- : . • ",\1%.•':::._:r:ei:f.\\ i I I : 1 \ ii,;:,.. -:::::::....---....:-.2.-• 0,1._,VE 0,1t,••• • • ; •‘1/4• ' ‘• :iii ••• . 9.1,T T.PT•: .1 s • YAM DRAM • WARR. STRUCTURE 3SE CURS PALM • MPRAP A WAD. A. 9. mat aopEs 737.. A.m., PARER.? Ei91ApALA , EJ ElCAA•AL C.CRITE E AMYL.. • eox ACRE SCALE, 1' - 30' 1 ••••• Aro TAPRRYR WASHINGTON 1 e g <10:**(103,1464.1 19.0 PA TSB 01101 11120 110 DAD • AIM 1337104111,1 97-223,, 3.8 • City of Tukwila John W. Rants, Mayor Department of Community Development. Steve Lancaster, Director MEMORANDUM TO: Carol Lumb, Associate Planner FROM: Gary Schulz, Urban Environmentalist DATE: September 24, 1999 RE: Tukwila Subdivision: Permit #'s L99-0023, L99-0024, L99-0025, E99-0012. The following comments are my technical review of the proposed subdivision. I. Wetland Reconnaissance 1. The wetland reconnaissance was conducted in August 1998 (Jones & Stokes Associates, Inc.) and includes some analysis of the watercourses on the site. During my site review I did not observe wetland areas and believe the report by Jones & Jones adequately describes and evaluates the areas that would have potential wetland. II. Proposed Tree Retention/Replacement Plan 1. The current landscape plan includes the replacement of trees removed along the lower, western slope for developing Lots #9 thru #14. Developing these lots requires tree replacement because of the 20 percent and greater slope conditions. Per TMC Chapter 18.54.140, the slope restoration proposed at the back of these Lots is appropriate and smaller plant material may be used. Where appropriate native tree seedlings can be planted but the recommended size is 3 — 4 feet in height. Depending on height, the 3 year 2-1 seedling stock may be acceptable. 2. However, because this project is a PRD these Lots can be reduced in size to as small as 5,525 square feet. Lot reduction in this slope area could provide more tree retention and reduce slope disturbance and retaining wall height. My initial estimate is that the total number of trees that could be saved is 15. If this is accurate then that would reduce replacement trees by a total of 48. The applicant will need to evaluate the potential lot reduction in order to reduce disturbance in this area. 6300 Southcenter Boulevard, Suite #100 • Tukwila, Washington 98188 • (206) 431-3670 • Fax (206) 431-3665N Tukwila Subdivision Memo September 24, 1999 Page 2 3. The plan's total, tree replacement number of 279 trees includes street trees. Street trees and any other required tree planting related to the subdivision cannot be used to meet the tree permit requirement. Trees that are planted as part of the detention facility to enhance or screen the pond may be used for the tree permit. III. Geotechnical Investigation 1. The geotechnical report (Squier/HGI Associates, 1998) includes a statement indicating grade cuts should be limited in steep portions of the site. 2. Groundwater seepage was observed as minimal to none. Also, it reviewing the tree survey the majority of trees on the steep western slope are bigleaf maple which indicates dryer conditions in the upper soil layers. Therefore, the recommendation to install a deep curtain drain at the top of slope should be designed .to not have a detrimental effect on existing trees growing on the slope. The curtain drain has the potential to divert water that is necessary for existing vegetation on the slope. 3. The need for a slope setback along proposed Lots #9 thru #14 appears less critical if retaining structures are used. 4. In order to reduce the amount of disturbance to the steep, western slope, I recommend the pedestrian trail be relocated of the slope and considered as a connection to the north onto 38th Avenue S. This may be a safer route and could be used by more people and include bikes. cc: Jack Pace, Planning Manager Steve Lancaster, DCD Director Jim Morrow, PW Director TO: FROM: SUBJECT: City of Tukwila John W Rants, Mayor Department of Public Works JamesE Morrow, P.E., Director Director, Community Development Director, Public Works Department Tukwila Subdivision, SEPA Comments E99-0012 DATE: August 25, 1999 The Public Works Department has completed its review of the SEPA Checklist. Included are comments and recommended SEPA conditions. Before you make a SEPA Determination Decision, it is requested that we meet and discuss the proposed project. In my review I have come to realize that there may be several areas of confusion. As an example, the Applicant has proposed a cul-de-sac in lieu of a through street that would connect 40th Ave. South and 38th Ave. South. Supposedly his proposal reflects public comment, yet it does not meet the City's policy of providing through streets. Another example is the provision of a pedestrian trail that traverses the western and southern portions of the site. I cannot determine why this has been added. I am concerned about disturbing these areas in light of the steep slopes. As we have agreed, our two departments need to reach an agreement before we present the Applicant with the findings. 6300 Southcenter Boulevard, Suite #100 • Tukwila, Washington 98188 • Phone: (206) 433-0179 • Fax: (206) 431-3665 FILE: APPLICANT: ADDRESS: DATE: PLAN REVIEWER: SEPA REVIEW COMMENTS PUBLIC WORKS DEPARTMENT E99-0012 Tukwila Subdivision 40t Ave. S. and S. 130th St. August 24, 1999 Jim Morrow; telephone (206) 433-0179 The Public Works Department has completed its review of the SEPA Checklist. Included in the review were: • July 15, 1998 Geotechnical Engineering Study prepared by Squier/HGI Associates; • December 30, 1998 Preliminary Storm Drainage Report prepared by Triad Associates; • March 1, 1999 Traffic Study prepared by Transportation Solutions, Inc., • August 13, 1999 Wetland Reconnaissance and Stream Relocation Concepts report prepared by Jones & Stokes Associates • Revised March 24, 1999 project plans (submitted June7, 1999) prepared by Triad Associates. Based upon this review, the following comments and recommended SEPA conditions are provided. General Comments 1. The proposed pedestrian trail that traverses the western and southern portion of the development is to be eliminated. These areas are extremely steep and/or sensitive and should not be disturbed. 2. There does not appear to have been any coordination between the different consultants. The proposed plans do not incorporate the recommendations made by the geotechnical engineering study and the storm drainage report does appear to incorporate the effects of providing curtain drains to control ground water flow. 3. A significant number of rockeries are being proposed, some as retaining walls in steep slope areas. No rockery will be permitted over 4 feet in height. Further, for those areas where steep slopes are present, an engineered retaining wall will be required. • • Geotechnical Engineering Study 1. A peer review of the geotechnical study will be required. 2. Squier/HGI Associates is to evaluate the stability of the slopes and the suitability of the subgrade for each individual lot. 3. Because construction is proposed in a Class 3 Area of Potential Geologic Instability, the construction of the individual foundations needs to be addressed. Is it feasible to construct each foundation and driveway separately? In other words, can each foundation and driveway be constructed without adversely impacting the neighbor's yard (Side yard stability). Can slope stability be maintained or should a "series" of foundations be constructed at one time? 4. Given that the geotechnical engineering study was prepared before both the storm drainage report and the project plans were completed, Squier/HGI Associates should review both and provide an evaluation as to whether the plans have incorporated the geotech's recommendations. 5. The geotechnical engineering study stated that control of the ground water was necessary in order to construct footings on firm natural deposits and recommended curtain drains. Further, the study states that careful control of surface water runoff is important to prevent landslides. Therefore the proposed surface and subsurface drainage plan needs to be evaluated by Squier/HGI Associates and an evaluation prepared. 6. A registered professional geotechnical engineer is to be on site at all times during the installation of the utility systems, during land altering activities, and during the construction of the roads and building pads (foundations, foundation drains, driveways, etc.). Daily construction reports are to be prepared, signed, and submitted to the City Of Tukwila by the geotechnical engineer certifying that the work has been accomplished in accordance with the approved plans and specifications. Surface Water Management 1. The Storm Drainage Report mentions the existence of an existing stream within the project's boundaries but does not provide any analysis as to its effects upon surface water management. 2. The Storm Drainage Report also mentions the possible need for a Hydraulic Permit because of the aforementioned stream but does not provide any analysis as to the actual requirement for the permit. • 3. The Geotechnical Engineering Study identifies the need for curtain drains to properly control the groundwater, but the Storm Drainage Report does not include this requirement in the surface water retention and detention calculations. 4. The project plans do not appear to have incorporated the comments and recommendations made by the different consultants — plans do not show any curtain drains, as an example. Traffic Analysis 1. Potential traffic impact and concurrency mitigation costs can be addressed prior to final plat approval. 2. There appears to have been considerable discussion about whether the development's access from 40th Ave South should be a through street and connect to 38th Ave South. The Applicant, in response to public comment, has proposed a cul-de-sac. Even though some residents may object to the proposed access being a through street, the City has a policy of promoting through streets where possible. Additionally, the Applicant is proposing that on street parking be allowed. In order to accommodate on -street parking, the road must be 51 feet in width — 41 feet from back of curb to back of curb; 10 feet is needed for the sidewalks on both sides of the road. 3. Tract D Access should be relocated to the other side of Lot 18. RECOMMENDED SEPA CONDITIONS 1. A peer review of the geotechnical study will be required, at the Applicant's expense. 2. Squier/HGI Associates shall be required to evaluate the stability of the slopes and the suitability of the subgrade for each individual lot. As part of the evaluation, an analysis of the proposed retaining walls shall be conducted. The project plans are to show the locations where key and benching is required. 3. Squier/HGI Associates shall be required to evaluate the feasibility of constructing the foundations and driveway access for each building site. Can slope and side yard stability be maintained if each building pad is built individually or should there be a proposed construction sequencing? 4. Squier/HGI Associates shall be required to review the Storm Drainage Report and the project plans to ensure that adequate provisions have been made to maximize slope stability. • 5. A Water Management Plan shall be required that incorporates the recommendations made by all consultants to control both ground water and surface water flows. Each consultant will be required to review and sign the report. The project plans are to incorporate the recommendations made in the Water Management Plan. 6. A registered professional geotechnical engineer is to be on site at all times during the installation of the utility systems, during land altering activities, and during the construction of the roads and building pads. Daily construction reports are to be prepared, signed, and submitted to the City by the geotechnical engineer certifying that the work has been accomplished in accordance with the approved plans and specifications. SQUIER/HGI ASSOCIATES GEOTECHNICAL & ENVIRONMENTAL CONSULTANTS Secure Capital Investments #2, LLC P.O. Box 25127 Seattle, Washington 98125 Attn: Mr. Gary Greer Re: Subsurface Investigation for Proposed Tukwila R.R.D. King County, Washington Dear Mr. Greer: � file Geri EH -colt. 7981 168th Avenue N.E., Suite 109 Redmond, Washington 98052 425.702.0185 • FAX 425.881.6616 98349 July 15, 1998 _RECEIVED MAR 2 5 199 COMMUNITY DEVELOPMENT We have completed a geotechnical engineering study, including a geologic hazards evaluation, for the 7.5 -acre proposed residential subdivision site located between Pacific Highway 99 South and 40th Avenue South in Tukwila, Washington. The location of the site is shown on the Vicinity Map (refer, Figure 1). The conceptual plan for the site, as developed by Triad Associates on May 1, 1998, is to build seventeen single-family housing units on lots ranging from about 5,500 to 6,500 square feet in size. The remaining areas are set aside for open space, stream buffers, a roadway, and a stormwater detention pond. In June 1998, two acres of the total 7.5 acres of land at the southeast portion of our study area were added to the original 5.5 acres due to proposed property acquisitions. A conceptual plan for this additional area was not provided to us prior to implementing this study. The overall purpose of our study was to conduct a geotechnical engineering study and report on the subsurface conditions observed at the site, and on the geotechnical requirements for development of the proposed subdivision, and evaluate stability and drainage characteristics for the site in general. Our study did not include recommendations for design and construction of individual properties. Review of "sensitive area" maps at the City of Tukwila revealed that the site is classified as a Class 3 Area of Potential Geologic Instability for most of the western half and southeastern portions of the site, and that the eastern portion of the site near 40th Avenue South is largely outside Areas of Potential Geologic Instability. A Class 3 Area of Potential Geologic Instability is identified as an area where landslide potential is high. These include areas sloping between 20% and 40%, which are underlain by relatively impermeable soils or by bedrock and also include all • SQUIER/HGI ASSOCIATES areas sloping more steeply than 40%. Title 18 of Tukwila's Municipal Code recognizes that Areas of Potential Geologic Instability can be modified or the project can be designed so that potential impact to the project and surrounding properties is eliminated and slope stability is not negatively affected. BACKGROUND INFORMATION Site Description The proposed residential subdivision site is roughly rectangular in shape. The main portion of the area of investigation measures approximately 540 by 600 feet. The site is bounded by Highway 99 on the west and 40th Avenue on the east, as shown on Vicinity Map (refer, Figure 1) and Site Survey (refer, Figure 2) prepared and provided by Triad Associates. The site is approximately 7.5 acres in size and consists of a combination of seven City of Tukwila tax parcels of land. Currently, the subject site is occupied by an old wood and concrete water tank structure at the northwest comer, an old abandoned log cabin on the northeast parcel, and three single family houses along 40th Avenue South. One of these houses is a mobile home and another has been recently abandoned. Vegetation covers the majority of the site. It consists mostly of deciduous trees (e.g., maple, alder, willow, fruit), vine plants, grasses, and a few remnants of cultivated agricultural plants. Ground cover consists largely of vine plants and grasses. Vine plants are primarily blackberry bushes and have grown to a height of 15 feet at some locations within the site boundaries. The site descends to the east from Pacific Highway South with a maximum slope of approximately 30 percent along the western side of the property and grades to approximately 12 percent in the eastern portion of the site. The southern limits of the site have the steepest grade change. The western limit of the site begins at elevation 194 feet at its highest point and slopes east to a low elevation of 74 feet near 40th Avenue South. The topography of the western and southern portions of the site is moderately steep (approximately 30 percent grade) and grade to a much more gentle slope (approximately 10 to 15 percent grade) near the central and eastern portions of the site. Approximately one-half of the land within the site boundaries is below 15 percent grade. Surface water runoff in the vicinity of the site likely flows northeasterly from the upland till plain towards the Duwamish River Valley as sheet flow or shallow subsurface flow. Due to controlling topography, surface water drainage at the site likely flows to the east-northeast into the 40th Avenue South ditch line. The small drainage ditches located on the southwestern portion of 2 • SQUIER/HGI ASSOCIATES the property are directly fed by two 18 -inch drainage culverts emerging beneath the Pacific Highway 99 embankment fill at the western portion of the site. Sensitive area protection easements surround a small stream channel on the south side of the site and a steam channel at the northeast parcel of the site. The stream at the northeast parcel has created a ravine approximately 15 feet in depth and 20 feet wide. Some surficial evidence of slope instability was observed at the site on June 18, 1998. A minor scarp -like feature was located downslope of the Pacific Highway 99 drainage ditches near Test Pit #8. However, there were no visible signs of any recent landslide activity on the site that could be observed at the time of the investigation, nor were there visible surface springs on thesite on ::. this date. Heavy vegetation may have concealed seeps and springs and prevented a thorough visual survey. As a consequence, we recommend that we revisit the site to check our initial observations once the site has been cleared of undergrowth during site development. The narrow rectangular portion of the site which extends north to 38th Avenue in the most northwestern section of the site was investigated to determine suitability for a building site. The surface conditions indicated surface water ponding in the southeast comer of the above narrow section, approximately 60 feet southwest of . a house located on an adjacent property. Approximately one-third of this narrow section is located on a steep slope with buildings located upslope. It is unclear if this slope is an embankment fill slope or a cut slope due to abundant vegetation which covers the embankment. Lower portions of the slope revealed garbage debris mixed in with soil indicating some fill material may be present. If housing is proposed in this area, some additional field investigation might be required to better evaluate the slope's possible fill and subgrade condition. Geologic Setting Existing reconnaissance -level geologic mapping of the Des Moines Quadrangle (Waldron, 1962) indicates that the site is underlain by Pre-Vashon drift deposits along the eastern edge of glacial till in the upland area. Our field investigation revealed that a veneer of Vashon glacial till extends over much of the site and is, in tum, underlain' by advance outwash and glaciolacustrine deposits. Pleistocene glacial deposits in the site area were largely directly or indirectly derived from the Puget Lobe of the Cordilleran ice sheet about 14,000 years ago during the Vashon Stade. These glacial deposits have been glacially overridden by several thousand feet of glacial ice. The till generally consists of a poorly sorted to nonsorted mixture of clay, silt, sand, pebbles, cobbles, and boulders in variable amounts, with a concrete -like appearance. Though generally quite sandy, it locally contains much clay and its poor sorting reflects mixing of materials overridden and 3 • • SQUIER/HGI ASSOCIATES incorporated by the ice. The Advance Outwash typically consists of stratified clean pebbly sand with fine-grained sand and some silt in the lower part of the unit. Where large areas of advance outwash have been exposed to subaerial weathering, much of it has been oxidized to brown and reddish -brown in contrast to its usual gray color. It is generally well drained and provides stable foundation material. Moisture sensitivity is low to medium. Glaciolacustrine deposits consist of silt and clay deposited in ice -marginal lakes or ice -walled depressions. These deposits consist mostly of massive to laminated clay, silt, and fine sand, and are generally poorly drained. The glaciolacustrine deposits may grade up into the base of the overlying advance outwash. Moisture sensitivity of fine-grained glaciolacustrine soils is normally high. FIELD EXPLORATIONS General The subsurface conditions underlying the site were explored with eight test pits on June 18, 1998. The locations of the test pits, designated Test Pit #1 through Test Pit #8, are shown on the Site Survey, Figure 2. In addition to the eight test pits, six hand auger explorations were conducted to a maximum depth of 4.8 feet. The locations of the hand holes, designated HA -1 through HA -6, are shown on the Site Survey, Figure 2. The procedures and techniques used to accomplish the explorations, collect samples, and other field techniques are described in detail in the following paragraphs. Unless otherwise noted, all soil sampling and classification procedures followed applicable ASTM standards. Test Pits Eight test pits were made to observe subsurface conditions and materials within the proposed subdivision. The test pits were excavated to about depth 9 to 14 feet using a Komatsu trackhoe. A representative from our firm located the general areas for the excavations and maintained detailed descriptive soil Togs of the explorations. Representative disturbed samples were taken at selected depths in the test pits for classification and for physical testing. The samples were sealed in glass jars or placed in plastic bags. The unconfined compressive strengths of the fine- grained soils exposed in the sidewalls 'of the test pits were evaluated using a pocket penetrometer and a Torvane shear device. 4 i SQUIER/HGI ASSOCIATES Logs of Test Pits The logs of all explorations are presented on Figures 4 through 17. The logs show the various types of materials that were encountered and the depths where the materials and/or charac- teristics of these materials changed, although the changes may be gradual. The types of samples taken during excavation, along with their identification numbers, are shown to the right of the classification of materials. Further to the right are plotted the natural water (moisture) contents, and undrained shear strength values. To the left on each log, where applicable, observed water seepage is noted. A natural ground water table was not observed during our excavations; however, slight seepage was observed in some of the test pits at a depth of 9 feet below the existing ground surface (refer, Logs of Test Pits, Figures 4 through 11). The Togs of all hand augers are presented on Figures 12 through 17. LABORATORY TESTS All the soil samples were returned to our laboratory for further examination and check classifi- cation. During classification, certain physical characteristics of each sample were noted; for example, color, distinguishing odors, degree of plasticity and whether the sample was dry, moist, wet or saturated. The terminology used in the soil classifications and other modifiers are defined in Table 1. The natural moisture (water) content of selected samples were measured. The moisture content is the ratio of the weight of water to dry weight of soil, expressed as a percentage. The moisture contents are plotted on the test pit logs. DISCUSSION OF SUBSURFACE CONDITIONS Soil Conditions The site is generally underlain by native outwash, tills, and consolidated, fine-grained glaciolacustrine soils and over -consolidated sandy siltstone. The near -surface soils consist of stratified gravelly sand, fine to medium sand, sandy silt, and clayey silt. Numerous cobbles were observed in a majority of the test pits and occasionally boulders (up to two feet in diameter) were observed in a few of the test pits. Deeper penetration was prevented by existence of cobbles or boulders in the hand auger holes. The generalized stratigraphic sequence of soil and rock units on site are as follows: 5 SQUIER/HGI ASSOCIATES Soil/Rock Units A. A veneer of loose organic silty sand ,topsoil, on average one to two feet in thickness, mantles the heavily vegetated site. B. Glacial till which consists of clayey, sandy silt with gravel ranging from stiff to hard, and generally well -sorted and highly consolidated and moist. Its extent ranges from below the organic topsoil unit to a poorly sorted, highly laminated hard silt unit beneath it. Its thickness ranges between approximately three to four feet in all test pit locations. C. Native outwash sand underlies the till in the eastern portion of the site and ranges from loose to dense and contains occasional cobbles to a maximum size of about eight inches in - diameter. D. Silt strata are typically laminated brown and tan, with fine-grained sand and clay lenses. Mottling was present in this unit in a majority of the test pits. The silt unit is hard, moist to dry and easily stands vertical when cut with the trackhoe bucket. E. A gray, hard, fine sandy silt unit immediately underlies the hard, tan laminar silt. The overconsolidated silt grades to siltstone approximately one foot beneath its contact with the overlying silt strata. The gray silt and siltstone is laminated with fine sand in most samples. The gray siltstone unit was encountered in Test Pits #2, #3, #4, #5, #7, and #8. No evidence of disturbed native material or artificially -placed, non-native fill was present in any of the test pits. One of the hand auger holes, HA -6 (located in a narrow strip in the northern portion of the site), however, revealed man made debris at approximately 1.5 feet indicating some fill at that location. Hand auger borings HA -3 and HA -4 revealed angular 34 -inch minus angular driveway gravel. The soil in the vicinity of HA -5 was observed to be a wet, highly organic, fine sandy silt. Ground Water Conditions Ground water seepage was not observed in the upslope Test Pits #2, #3, #4, and #5. In fact, soils in these test pits were only slightly moist to dry. No naturally occurring springs were observed during the investigation although the dense vegetation may have prevented their visual discovery. Ground water seepage was encountered in all of the lower elevation test pits (#1, #6, #7, and #8). The ground water inflow rates on June 18, 1998 ranged from approximately 0.5 to 2 gallons per minute from the side walls of these test pits. The zone of inflow was apparently an outwash sand 6 • SQUIER/HGI ASSOCIATES layer which was present at 9 to 9.5 feet below the existing ground surface in the test pits immediately above an impermeable silt laver The ground water is likely to be higher during the wet winter months and after significant storm events, and migration patterns are likely to occur laterally along the outwash sand layer due to the highly impermeable consolidated and over -consolidated siltstone encountered beneath the sand. Perched ground water in significant quantities possibly could be trapped on the glaciolacustrine aquitard (low permeability layer) during periods of heavy precipitation or if water is artificially introduced into the subsurface. Water will infiltrate into the outwash deposit and migrate down- ward along the contact with the glaciolacustrine deposits, until it emerges in springs at the lower elevations of the site. Relatively loose soils near the ground water table observed in lower elevation test pits may be caused by rapid seepage of ground water downhill on the west slope that undermines the outwash sand deposits. CONCLUSIONS AND RECOMMENDATIONS General. Based on the soil conditions encountered in our subsurface explorations, our opinion is that the proposed development is feasible in most areas of the site from a geotechnical engineering viewpoint. Footing foundations placed in the firm, undisturbed, natural deposits underlying fill and weathered soft or loose topsoil may be used for supporting single-family residences. Over -excavation and backfilling of footing trenches may be required in areas where excessive thickness of fill or loose soils is encountered. Control of ground water seepage will likely be necessa in order to construct footin • s on firm natural de • osits. GEOLOGIC HAZARDS Landslide Hazard. The site has been classified as a Class 3 Area of Potential Geologic Instability for most of the western half and southeast end of the site with the steep slopes. A Class 3 Area of Potential Geologic Instability is identified as an area where landslide potential is high, which include areas sloping between 20% and 40%, and which are underlain by relatively impermeable soils or by bedrock. Landslides are most likely to occur at the site after clear cutting in the form of debris flows where a few feet of relatively loose, surficial soil over the denser and less permeable underlying consoli- dated soil becomes saturated. Based on the combination of slope, geology, soil types, and ground water conditions at the site, our opinion is that the potential for shallow debris flow -type landslides at the site is moderate in the southwestern and western portions of the site and low in 7 SQUIER/HGI ASSOCIATES the eastern half of the site. Careful control of surface water runoff is important to prevent debris flows. Surficial soil movement may occur if significant cuts are made during construction. The steeper portions of the site may become unstable if excessive amounts of water are applied to the slope or if ground water levels increase. Due to the steepness of the slope at portions of the site, cuts should be limited, and the drainage system and shoring in those areas should be incorporated into foundation and road designs. Occasionally, glaciolacustrine soils and bedrock fail on steep slopes. Our current opinion, however, is that a deep-seated landslide at the site is unlikely to occur due to the degree of consolidation of underlying soils and rock, slope inclination, and general geologic characteristics of the slope. Based on current information, our opinion is that the potential for this type of slope failure is very low. Erosion Hazard and Control. The potential erosion hazard is high for a Class 3 Landslide Hazards Area when it is devegetated. Soil erosion, primarily by uncontrolled surface water runoff, can cause significant problems in areas of the site undergoing development on the slopes between 20 and 40 percent, unless measures are taken to control surface water flow. Ground water discharge of springs along the slopes on the site (if any) may cause erosion of downslope soils, particularly where flow velocities become high. In unpaved areas, if ground vegetation cover is maintained and concentrated discharge of storm water onto slopes is diverted to appropriate collection pipes and ditches, the erosion hazard at the site should be low. Several additional measures are available to minimize the effects of erosion. Typical are the following: • The building pads and any other exposed areas, such as lay down yards and haul roads, should be protected by crushed rock base as soon after exposure as practical to protect the exposed subgrade from softening and erosion. • Sediment control barriers, such as hay bales, or a pre -manufactured barrier, such as Envirofence by Mirafi, may be constructed to intercept silt -laden runoff, and to prevent sedimentation offsite. Such barriers are used to shorten runoff paths. • Sediment basins may be constructed at the head of runoff ravines, also, to minimize sedimentation offsite. • Any natural vegetation removed outside of the development area should be replanted or reseeded as soon as possible. A silt fence should be erected along the downhill sides of the construction area to contain sediments. 8 • • SQUIER/HGI ASSOCIATES We are available to work with you to identify appropriate erosion and sedimentation control measures, as the rainy season progresses, and as the needs for the project become apparent. Site Preparation and Earthwork The site should be stripped and grubbed within the limits of any new construction so as to remove all grass, roots, organic soil; and, locally, tree roots larger than 1 inch. Based upon our explora- tions, stripping over most of the site should remove about the top 12 inches. Locally, organic zones or Targe roots may require; deeper stripping and grubbing. The exposed subgrade should be probed -(during the rainy season) or proof -rolled (during the dry season) with a rubber -tire vehicle, such as a partially loaded dump truck, to reveal soft/weak unsuitable areas that may exist in the subgrade. Any soft/weak areas disclosed should be overexcavated to firm ground and the grade restored with suitable backfill material placed in thin lifts and compacted. Because of the fine-grained soils encountered, we recommend that earthwork be accomplished during the summer construction season, generally considered to extend between mid-June and late October of any given year. At other times, earthwork and vehicular traffic may cause excessive soil "pumping", rutting and/or other soil disturbances, resulting in additional site prep- aration treatment and greater than expected site development costs. Further, as discussed below, the fine-grained native soils are highly moisture sensitive and difficult to place and compact when the natural moisture is above optimum for compaction. Excavation and Slopes The maximum slope within the area of proposed residential development is Tess than 30%. The setback requirement in the City of Tukwila Municipal Code for . a residential area is 10 feet. Normally in the Seattle area, setbacks are based on a 40% or more slope. We do not anticipate that additional setback will be required by the City of Tukwila based on slope within the proposed developmental plan area. Some of the proposed residences may have daylight basements cut into the slope which may require the design of embedded retaining walls. An engineered retaining wall would likely be necessary for a residential structure built in the north narrow section within the most northwest portion of the site, if the slope was to be altered for building foundations. Where excavation is required, the cut slopes should not be greater than the limits specified by local, state and national government safety regulations. Temporary cuts greater than 4 feet in height should be sloped no steeper than 1 H:1 V in the natural deposits of the gravelly sand of the Advance Outwash or in the 9 SQUIER/HGI ASSOCIATES clay and silt of the glaciolacustrine deposits. Footing trenches excavated into the loose fill or topsoil may be as steep as the bank stays stable, if no workers are to be sent into the trenches; otherwise, the trench banks should not be steeper than 1'/H:1V. The above recommendedt excavation slo • es assume • round water wi n • t be ncounter-d • urin • ons Should ground water be encountered, the excavation should be immediately halted and the slope stability re-evaluated. The excavation slopes may have to be flattened and other measures taken to stabilize the slopes. Permanent fill embankments, if required, should be constructed in accordance with the recommendations in the Structural Fill section of this report, andkhould be no steeper thanZ H:1 V, Surface runoff should not be allowed to flow uncontrolled over the top of cut slopes into excavated areas. Exposed temporary cut slopes should becovered with plastic sheets during construction to minimize erosion and sloughing from rainwater. Permanent cut slopes or fill embankments should be vegetated or covered with erosion protection matting for long-term stability. The vegetation should be maintained until it is established. Structural Fill Restoration of grade in overexcavated areas, and the raising of site grades within the access roads, buildings, and behind basement walls might require compacted structural fill. The material for the structural fill may consist of onsite silt or an imported granular material, such as sand and gravel or crushed rock, or reject crushed rock. With the silt or reject crushed rock material, the water content at the time of compaction becomes important. If too wet for optimum compaction, the material will be difficult to place and to compact to a suitable density. Because of the need for moisture control, the silts and similar fine-grained materials, as well as reject crushed rock, generally are not suitable for use during the wet rainy season. However, if construction of the structural fill proceeds during the summer, such silt and reject crushed rock materials can be considered for use in the structural fill. With respect to the onsite soils, the average natural moisture content is about 20 to 30 percent. Our experience suggests that this moisture content is about 5 to_10_.percent wet of optimum moisture for suitable compaction. Hence, some drying by aeration most likely will be required. Based upon our experience, the placement of the silt in thin lifts over a wide area combined with aeration by tilling during the summer construction season can dry the silt to optimum moisture for compaction. If imported material is used for structural fill, it should consist of sand, or sand and gravel, or crushed rock, with not more than 5 percent passing the No. 200 sieve (wet sieve analysis, ASTM 10 • • SQUIER/HGI ASSOCIATES D1140). During periods of no precipitation, reject crushed rock may be selectively hauled onsite for use in structural fills. The substitution could be a field decision at the time of fill placement. Placing fill against a slope steeper than 4H:1V requires some site preparation to prevent slippage of the fill -natural slope contact. The site preparation should include benching into the existing slope with a bulldozer. A relatively level work area wide enough for a bulldozer and compactor should be prepared. Each lift should be relatively horizontal and further benched into the slope in a "stair -step" fashion as the fill is constructed. Granular fill material should be placed in lifts not exceeding 12 inches (loose); whereas silt or other fine-grained fill materials should be placed in lifts ,not exceeding 9 inches (loose). Each lift should be compacted to at least 95 percent in the upper 12 inches and lower layers should be minimum 90 percent of the modified- maximum dry density determined in accordance with ASTM D1557 or AASHTO-180. A medium weight (48 -inch diameter drum) smooth steel -wheeled vibratory roller probably would prove to be effective in compaction of granular material. Compactors with pad foot drums would probably be effective on silt and fine-grained fill material. Wet Weather Construction If wet weather construction is necessary in order to meet project schedules, we recommend that additional steps in construction be considered in order to minimize subgrade disturbance. Prolonged rains tend to weaken any exposed subgrade, and cause pumping and softening of the • subgrade under wheel loads of construction equipment, along with foot traffic. In order to control subgrade pumping and softening, we recommend that all haul roads consist of a minimum 18 inches of crushed rock aggregate. A separation geotextile, such as a Mirafi 140N, will strengthen some soft subgrades and minimize rutting and other forms of subgrade failure, such as excessive pumping. A geotextile will also prevent contamination of the base aggregate by subgrade silt, allowing the aggregate to be used elsewhere, at a Tater time. Use of a separation geotextile can be a field decision made at the time of the construction. At other locations, care should be taken to cover all exposed surfaces with crushed aggregate as soon as possible after exposure. Particularly important would be the covering of the subgrade for the road with the recommended base rock course ortl_y after exposure. 11 SQUIER/HGI ASSOCIATES Utility Trench Backfill All utility trenches should be backfilled with material that is suitable for compaction. The accept- ability of trench backfill material should be in accordance with the same criteria described for structural fill, whether it is native silt or imported sand or crushed rock. The backfill should be compacted to at least 90 percent of the maximum modified Proctor dry density (ASTM D1557) below one foot from the surface, and compacted to at least 95 percent in the upper 12 inches. Utility trench backfill in landscaped areas may be compacted to 85 percent (ASTM D1557) maximum dry density. Base Course Prior to paving the silt subgrade should be proof -rolled or probed as described in the section entitled, Site Preparation and Earthwork. Any soft/weak areas disclosed should be improved by overexcavating to firm ground and backfilling with compacted structural fill. The base course for pavement should be 1% -inch minus crushed rock, which passes Washington State Highway Department specifications. A leveling course of 3/4 -inch minus crushed rock may be used to cap the top 2 inches of the base rock section. The base course should be compacted to 95 percent of the maximum modified dry density (ASTM D1557). Compaction, in our opinion, would be best accomplished using a medium weight (48 -inch diameter) smooth -wheeled vibratory roller. Foundations Spread footings may be used for supporting columns and continuous footings for residential buildings. Footings should be founded on .compacted structural fill or firm native, undisturbed, glacial till, outwash sand, or the glaciolacustrine silt or siltstone underlying the fill and surficial topsoil. Over -excavated footing trenches, where excessively thick fill or unsuitable material is encountered, may be backfilled with Control Density Fill (CDF) or structural fill.. CDF is a flowable, low -strength mixture of cement, fly ash, and aggregate that is commercially available in ready -mix form. If structural fill is used for supporting footings, the structural fill should extend laterally for a horizontal distance beyond the edges of footings at least one-half the depth of the structural fill. The structural fill should be constructed in accordance with recommendations in structural fill section. When _ground water is encountered, the footing. trenches should. be_backflled with. flinch 12 SQUIER/HGI ASSOCIATES minus crushed rock to at least 6 inches above water level. In lieu of structural fill, over -excavated footing trenches may be backfilled with CDF to support footings. Moisture should not be allowed to accumulate in excavated footing trenches. Disturbedsoil should be completely removed or thoroughly re -compacted prior to pouring concrete for the footings. If ground water levels potentially could rise at the lower elevations of the site, it would be prudent to increase the elevation of this area of the site by using structural fill. For footings constructed as recommended above, our recommended design criteria for footings are as follows: • Allowable soil bearing pressure for ,footing,including dead and liveloads, should be no greater than 2,000 psf. • Minimum depth to bottom of perimeter footing below adjacent final exterior grade should be no Tess than 18 inches. • Minimum depth to bottom of the interior footing below lowest adjacent grade or top of floor slab should be no less than 12 inches. • Minimum width of wall footings should be no Tess than 18 inches. Minimum lateral dimension of individual footings should be no less than 24 inches. A one-third increase in the above allowable soil bearing pressures may be used when considering short-term transitory wind or seismic loads. Based on our experience of single-family residential structures supported on similar soil conditions and for the above allowable soil bearing pressures, we estimate that the maximum total post -construction settlement should be % inch or less and the differential settlement across the building width should be 1/4 inch or less. Lateral Earth Pressure on Retaining Walls Retaining walls will most likely be required in the major cut or fill areas or in the daylight basement areas. Lateral earth pressure on retaining walls depends on the type of wall (i.e., yielding or non - yielding wall), the type and method of placement of backfill against the wall, the magnitude of surcharge weight on the ground adjacent to the wall, and the slope of the backfill. A summary_ of design earth pressures for level _backfill or a_backfill slope of 4H _1V_or flatter, and for different types of backfill materials is presented in the following table. 13 SQUIER/HGI ASSOCIATE* s Embedded Wall Backfill: Earth Pressures e of Wall ackfill Yielding Clean crushed rock Onsite silt without gravel 45 Non -Yielding Clean crushed rock 50 Onsite silt without gravel 60 Note: Assumes_backslone of 4H•1V slope or flatter Loading adjacent to the top of the wall which acts as surcharge on the retaining wall, can be taken into account by dividing the vertical surcharge Toad, expressed in psf by 100. The resultin quotient, expressed in feet, is an equivalent height of backfill which is added to the retainingg height, H, of the wall. The passive earth pressure on an embedded wall, which would provide a component of resistance against sliding can be computed on the basis of an equivalent fluid density of 200D, where "D" is the thickness of the permanent backfill against the embedded footing (feet). The magnitude of passive earth pressure is significantly influenced by the amount of lateral displacement of the wall and footing into the soil. Therefore, to minimize the displacement the recommended value of passive pressure includes a factor of safety of 1.5. All footings should be poured neat against undisturbed soil, or backfilled with compacted structural fill. Further lateral resistance for the retaining walls can be provided by friction along the footing. This frictional resistance can be expressed as the vertical multiplied by a coefficient of friction of 0.35 (native silty soils). A factor of safety of 1.5 should be used in calculation of overall sliding resistance. Equivalent Fluid( CF) 35 Backfill above anyg_walls should be graded to drain surface runoff away from the wall and to drains to ,prevent.psndiggid infiltra ion of rainfall, and to minimize entrance of water through embedded walls and into building. g Backfill placed against the retaining walls should only be moderately compacted, i.e., between 85 and 90 percent of the modified Proctor maximum dry density, ASTM D1557. Heavy compac- tion equipment should not be allowed closer than 5 feet to embedded walls to prevent inducing higher lateral earth pressures. 14 SQUIER/HGI ASSOCIATES• Note: The above recommendation regarding the retaining walls are site specific general (geotechnical parameters) recommendations; however; we should review the design parameters for the actual designed retaining walls higher than 4 feet. Site Drainage Surface Drainage. The finished ground around buildings should be graded such that surface water is directed away from the residence. Water should not be allowed to stand within building limits or in areas where footings or pavements are to be constructed. Final site grades should allow surface runoff to be collected by catch basins and drain lines, and tightlined to drain into a permanent storm drain system. We suggest that the ground be sloped at a gradient of 3 percent minimum for a distance of at least 10 feet away from the buildings,except in areas that are to be paved. Ground Water Drainage. Should ground water seepage be encountered during construction, we recommend that the bottom of excavation be sloped to collect water into small sump pits or ditches from which the water can be pumped and discharged into a storm drain. A subdrain system should be installed behind all embedded walls. If a basement option is adopted for the buildings, the lower floor may require subdrains underneath the slab and behind the building walls.. The footing drain should consist of a 4 -inch minimum diameter, perforated, rigid, drain pipe laid below the footing level with a sufficient gradient to generate flow by gravity. The drain line should be bedded on, surrounded by, and covered with a free -draining washed rock, pea gravel, or other free -draining granular material, wrapped with a layer of non -woven filter fabric, such as Mirafi 140N or equivalent. Once the drains are installed, the excavation within an 18 -inch horizontal distance behind the footing or foundation walls should be backfilled with a granular structural fill, except the top twelve inches should be a layer of compacted, impermeable, native soil. This impermeable soil cap should be separated from the underlying granular soil by a layer of non -woven filter fabric. The ground surface should be sloped to drain away from the buildings. Alternatively, the ground can be sealed with asphalt or concrete pavement. Water collected by the footing drains should be tightlined to drain into a permanent storm drain system or to be dispersed over a large, well -vegetated area at a sufficient distance away from the proposed residence. Under no circumstance should roof downspouts drain lines be connected to the footing drain system. All roof downspout drains must be separately tightlined to discharge to 15 SQUIER/HGI ASSOCIATES • • the permanent storm sewer system. The footing drain system should have a minimum of 12 inches of vertical fall _before itis connected to the storm water system We recommend that sufficient cleanouts be installed at strategic locations to allow for periodic maintenance of the footing and downspout drain systems. Curtain Drains. To control surface water and shallow subsurface ground water flow on to the site from Pacific Highway 99, and to minimize slope instability of the hillside due to seepage, a curtain drain should be designed and installed near the top of the west slope parallel to the highway at potential flowpath locations. This curtain drain should penetrate into the highly consolidated glaciolacustrine silt or siltstone, beneath permeable outwash deposits,: and tightlined down the slope into a stormwater sewer line. In addition, a curtain drain should be designed and installed in a similar manner at apprnximatPly the 114_to 120 -foot c ur Into capture any water from seepage and springs discharging from the slope to decrease ground waterlevels at lower elevations of the site. The curtain drains or .interceptor trench drains should be at least 18 inches wide and minimum 5 feet deep (24 inches into the glaciolacustrine silt or siltstone). A 4 -inch perforated, rigid PVC pipe should be embedded near the bottom of the trench. The trench should be backfilled with the drain pipe completely surrounded by pea gravel or drain rock. The bottom of the trench and the drain pipe should have sufficient gradient (minimum 0.5 percent) to generate gravity flow. The drain pipe should be tightlined at low points to discharge collected water into a permanent storm sewer system. Otherwise, the water should be discharged within the property at minimum 50 feet away from the slope and proposed buildings. The discharge points should be well -vegetated areas and discharge over a Targe area to minimize erosion potential from discharged water. Additional Services We should be retained to review the project plans and specifications of each building, retaining wall, fill, and roadway to evaluate if they are in substantial conformance with the conclusions and recommendations contained in our report, and to evaluate compatibility with site conditions. We further recommend that we observe all footing subgrade conditions and cut/fill slopes for each residence to assure compliance with our recommendations. Also, we should observe the excavated curtain drain trenches to confirm the presence of low permeability soils. Unless we have the opportunity during construction to confirm our assumptions, interpretations and analyses, we cannot be held responsible for applicability of our conclusions and recommendations to conditions that are different from those anticipated. 16 . • SQUIER/HGI ASSOCIATES RISK EVALUATION STATEMENTS There is an inherent risk of soil movement in developing steep -sloped sites. The conditions of the site, however, are not unique to the local area of the site, and developments of sites with similar conditions have been successfully completed. The risk of soil movement on the steep slope can be reduced by careful planning, proper design, suitable foundation supports, and prudent construction practices. In our judgment, if the recommendations of this report are satisfied during construction and after the completion of the development, the areas disturbed by construction will be stabilized and remain stable and should not increase the potential for soil movement. In our opinion, the risk of damage to the proposed development and from the development to adjacent properties from soil instability should be acceptable. Detailed plans and specifications of the proposed development were not available at the time of this study, and should be reviewed by us when available. LIMITATIONS The stability of the slopes and the suitability of the subgrade for each individual lot should be evaluated and checked by us prior to construction and after footing excavations are completed. This report is prepared for the specific application to this project and the exclusive use of Security Capital, Inc., and their associates and representatives. We recommend that this report, in its entirety, be included in the project contract documents for the information of the prospective contractors for their estimating and bidding purposes. The conclusions and interpretations in this report, however, should not be construed as a warranty of the subsurface conditions. The scope of this study does not include services related to construction .,safety precautions and our recommendations are not intended to direct the contractor's methods, techniques, sequences or procedures, except as specifically described in this report for design considerations. Our recommendations and conclusions are based on soil conditions encountered in our test pits, hand augers, our engineering analyses, and our experience and engineering judgement. The conclusions and recommendations are professional opinions derived in a manner consistent with the level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area. No warranty, express of implied, is made. The recommendations in this report are based on the site surface conditions observed and subsurface conditions encountered in our site exploration. Soil and ground water conditions may 17 SQUIER/HGI ASSOCIATE", vary from those actually encountered during exploration. The nature and extent of such variations may not become evident until construction. If variations appear then, we should be retained to re-evaluate the recommendations of this report, and to verify or modify them in writing prior to proceeding with the construction. The scope of our services did not include any environmental assessment or investigation for the presence or absence of wetlands or hazardous or toxic materials in the soil, surface water, ground water, or air, on or below or around this site. Any statements in this report or on the test pit/hand auger logs regarding odors noted or unusual or suspicious items or conditions observed, are solely for the information of our client. We are pleased to be of serviceCo. you on this project. If you have any report or need further consultation, please feel free to call us. questions regarding this Yours very truly, Squier/HGI Associates by L,., _ Glen C. Strachan, R.G., C.E.G. Principal Geologist by Arlan H. Rippe, P.E. Senior Vice President GCS/SB/AHR/ph Encl: Table 1 Figures 1 through 17 98349.wpd I EXPIRES: 7-6.00 • • REFERENCES City of Tukwila, "Sensitive Area Overlay" Title 18 of Tukwila Municipal Code, 10/10/98. GeoEngineers, "Geologic Hazards Evaluation Report," Prepared for City of Tukwila, Washington, undated. Economic and Engineering Services, Inc. et al., South King County Ground Water Management Plan, Volume II, April 1991. Triad Associates, "Proposed Tukwila R.R.D. Layout Plan," Kirkland, Washington, 5/1/98. Triad Associates, "Tukwila P.R.D. Boundary and Topographic Survey Drawing," Kirkland, Washington, 6/8/98. U.S. Geological Survey, "Des Moines, Washington," 7.5 Minute Series Topographic Map, 1962, Photorevised 1973. TABLE 1 TERMINOLOGY USED TO DESCRIBE SOIL SAMPLES AND CLASSIFICATION OF ROCK SAMPLES Soils exist in mixtures with varying proportions of components. The predominant soil, i.e. greater than 50 percent based upon total by weight, is the primary soil type, i.e., sand, gravel, silt or clay. Lesser percentages of other soils in the mixture are indicated by use of modifier words in general accordance with standard practice (ASTM D2488-93). For sand and gravel, the following modifiers are used: Term trace/clean with silt/clay silty/clayey with sand sandy with gravel gravelly Portion of Total Sample < 5% minus No. 200 5% - 15% minus No. 200 15% - 50% minus No. 200 z 15% sand • 30% plus No. 200, predominantly sand • 15% gravel z 30% plus No. 200, predominantly gravel Soil sample identification based upon visual examination is in general accordance with Visual -Manual Procedure (ASTM D2488-93). If the field sample contains any cobbles or boulders, use "with cobbles" or "with cobble and boulders" and list maximum size. Group symbols and descriptions are based on the portion passing the 3 -inch (75mm) sieve, and are limited to naturally occurring soils. Plasticity characteristics are based upon the minus No. 40 sieve fraction. Description of Relative Density for Granular Soils Relative Density very loose loose medium dense dense very dense Standard Penetration Resistance (N -values) blows/ft. 0 - 4 4 - 10 10 - 30 30 - 50 over 50 Description of Consistency for Fine -Grained (Cohesive) Soils Consistency very soft soft medium stiff stiff very stiff hard Standard Penetration Resistance (N -values) blows/ft. less than 2 2-4 5-8 9-15 16-30 over 30 Unconfined Compressive Strength tons/sq.ft. less than 0.25 0.25 - 0.5 0.5 - 1.0 1.0 - 2.0 2.0 - 4.0 over 4.0 Sandy silt materials which exhibit general properties of granular soils are given relative density descriptions. 1 TABLE 1 (Cont'd.) TERMINOLOGY USED TO DESCRIBE SOIL SAMPLES AND CLASSIFICATION OF ROCK SAMPLES Scale of Rock Strength Approximate Range of Unconfined Compressive Description Designation Strength. lbs./sq.in. Very low strength R1 100-1,000 Low strength Moderate strength R2 R3 Medium high strength R4 High strength 1,000-4,000 4,000-8,000 8,000-16,000 R5 16,000-32,000 Very high strength R6 32,000 Field Identification Crumbles under firm blows with point of geology pick; can be peeled by a pocket knife. Can be peeled by a pocket knife with difficulty; shallow indentation made by firm blows of geology pick. Cannot by scraped or peeled with a pocket knife; specimen can be fractured with a single firm blow of geology hammer. Specimen requires more than one blow with a geology hammer to fracture it. Specimen requires many blows of geology hammer to fracture it. Specimen can only be chipped with geology pick. Correlation of RQD and Rock Quality Description of RQD. Percent Rock Quality 0 25 50 75 90 25 50 75 90 100 very poor poor fair good excellent Descriptive Terminology for Joint Spacing or Bedding Spacing of Joints Less than 2 inches 2 inches - 1 foot 1 foot - 3 feet 3 feet - 10 feet Greater than 10 feet 2 Descriptive Term very close close moderately close wide very wide (massive) NOTE: Features shown are for illustrative pu Proposed Subdivision Tukwila, Washington VICINITY MAP FIGURE 1 • AFFIDAVIT Notice of Public Hearing Notice of. Public Meeting Board of Adjustment Agenda Packet Board of Appeals Agenda Packet Planning Commission Agenda Packet Short Subdivision Agenda Packet 0? DISTRIBUTIO N hereby declare that: J Notice of Application for Shoreline Management Permit Shoreline Management Permit Determination of Non- significance Mitigated. Determination of Nonsignificance JDetermination of Significance and Soaping Notice Notice of Action Official—Notice 'ther Other Alice 12LLca-c_a was mailed to each of the fallowing addresses on Name ' ito-D Alsoc / 5ccx0 Car- ii.4UG51+> Tib -L LQ 51,47pco 51 °"l4 of Project File Number b`11 -00 Z.3 CRq_oolz S i cr.ature -OM • City of Tukwila John W Rants, Mayor Department of Community Development Steve Lancaster, Director Notice of Application PROJECT INFORMATION. Triad Associates acting for Secure Capital Investments, has filed applications for development of a 20 lot subdivision at 13217 40 Av. S. The project, currently called Tukwila Subdivision, will create a new public street at approximately S 133 St. and two private access roads. The subdivision.will include underground utilities for sewer, water, storm drainage, electricity, cable, and telephone as well as a pedestrian path. Approval requested: • Preliminary Plat approval • Planned Residential Development Other known required permits include: • Land Altering permit • State Environmental Policy Act (SEPA) Determination • Utility Permit • Boundary Line Adjustment FILES AVAILABLE FOR PUBLIC REVIEW The files are available at the City of Tukwila. To view the files, come to the Department of Community Development at the address at the bottom of this page. Files Numbers include: • L99-0023 (Planned. Residential Development) • L99-0024 (Preliminary Plat) • L95-0025 (Boundary Line Adjustment) • E99-0012 (SEPA) OPPORTUNITY FOR PUBLIC COMMENT Yourcomments on the project are requested. There will be a public meeting on July 22, 1999 from 6-7:30 p.m. at the Foster Library at 4060 S. 144 St. This will be your opportunity to meet the applicant, review the plans and speak with a City staff member regarding the decision process. Written comments to DCD may also be submitted or postmarked by no later than 5:00 P.M., Thursday July 30, 1999. Opportunity will be provided for additional oral and written public comments at a public hearing before the Tukwila City Council. The date for that hearing is not yet scheduled. APPEALS & CITY OFFICE LOCATION You may ask about hearings, request a copy of the decision, and ask about your appeal rights on this proposal by contacting Carol Lumb at 431-3661 or visiting our offices. Monday through Friday, 8:30 a.m. to 5:00 p.m. Application Filed: March 25, 1999 Notice of Completeness Issued: June 16, 1999 Notice of Application Issued:July 9, 1999 6.300 Southcenter Boulevard Suite #100 • Tukwila,. Washington 98188 • (206) 431-3670 • Fax (206) 431-3665 152304 9053 Nell Marshall & Marshall Timmi Nka 708 Shoreland Dr SE Bellevue, WA 98004 192080 0035 Stephen Parris 3949 S Angeline St Seattle, WA 98118 733240 0015 Roger Young 3715 S 130th St Seattle, WA 98168 733240 0030 Joyce Wray 13025 38th Ave S Seattle, WA 98168 733240 0050 Randy Nunez 3803 S 130th St Tukwila, WA 98168 733240 0055 Roger Purdmon 13026 38th Ave S Tukwila, WA 98168 734060 0800 Daniel Brundage 13039 40th Ave S Seattle, WA 98168 734060 0803 Keystar 6752 Lake Washington Blvd Kirkland, WA 98033- 734060 0803 Keystar 6752 Lake Washington Blvd Kirkland, WA 98033 734060 0880 David More 13204 40th Ave S #1 Seattle, WA 98168 152304 9157 L S McGinnis 4661 138th Ave SE Bellevue, WA 98006 733240 0005 Pete & Socorro Castro 3705 S 130th St Seattle, WA 98168 733240 0020 Philip & Eleanor Smith PO Box 68233 Seattle, WA 98168 733240 0035 Roderick Ross 5578 NE Admiralty Way #175 Hansville, WA 98340 733240 0053 Mohammad Khan 323526th Ave W Seattle, WA 98199 733240 0070 Dennis Eck 14106 6th Ave SW Seattle, WA 98166 734060 0801 Paul Walldey 13035 40th Ave S Tukwila, WA 98168 734060 0803 Keystar 6752 Lake Washington Blvd Kirkland, WA 98033 734060 0824 Gale Shub 13000 E Marginal Way S Tukwila, WA 98168 734060 0881 Jonathan & Therese Tweet 13212 40th Ave S Tukwila, WA 98168 192080 0025 John Schroeppel 13023 40th Ave S Seattle, WA 98168 733240 0010 Richard Vranjes 3711 S 130th St Tukwila, WA 98168 733240 0025 Dwight & Nancy McLean 13015 38th Ave S Seattle, WA 98168 733240 0045 Alan Glore 3809 S 130th St Seattle, WA 98168. 733240 0054 James & Linda Diane Louis 13020 38th Ave S Tukwila, WA 98168 733240 0075 Timothy & Penny Severson 16103 188th Ave SE Renton, WA 98058 734060 0803 Keystar 6752 Lake Washington Blvd Kirkland, WA 98033 734060 0803 Keystar 6752 Lake Washington Blvd Kirkland, WA 98033 734060 0825 George Richard & Paula Huls 13937 15th P1 SW Seattle, WA 98166 734060 0882 Edward Lucero 13219 E Marginal Way S Seattle, WA 98168 734060 0884 SOUTH CENTRAL SCH DIST 406 , 13100 E Marginal Way S , WA 734060 0903 CHASE MORGAN PROPERTIES 5190 S 166th St Tukwila, WA 98.188 734060 0906 David & Nadine Morgan 5190 S 166th St Tukwila, WA 98188 734060 0909 Paul Houser PO Box 59 Renton, WA 98057 734060 0922 Joseph & Anita Wade 13200 37th Ave S • Tukwila, WA 98168 734060 0925 Ping & Earline Tom 1919 S Jackson St Seattle, WA 98144 734060 0927 Kurds Marley 13038 38th Ave S Tukwila, WA 98168 734060 0940 SCI MANAGEMENT CORP 1929 Allen Pkwy Houston, TX 77019 734060 0962 William Strand Jr. 14117 30th Pl S Seatac, WA 98168 734060 0966 J Sturgeon 13232 40th Ave S Seattle, WA 98168 734060 0900 William James Muir 13215 40th Ave S Seattle, WA 98168 734060 0904 CHASE MORGAN PROPERI'1hS 5190 S 166th St Tukwila, WA 98188 734060 0907 Rolf Flaten 4216 S 173rd St Seatac, WA 109604 734060 0920 Pamela Longshore 13264 38th Ave S Seattle, WA 98168 734060 0923 Stephen & Debra McClung 25432 163rd P1 SE Kent, WA 98042 734060 0926 Ping & Earline Tom 1919 S Jackson St Seattle, WA 98144 734060 0928 Brian Gadzuk 13041 38th Ave S Tukwila, WA 98168 734060 0960 Leonard Meagher 13242 40th Ave S Seattle, WA 98168 734060 0963. Jacob Sturgeon 13232 40th Ave S Seattle, WA 98168 734060 0980 James & Barbara Guess 28020 201st Ave SE Kent, WA -109604 734060 0902 Paul Houser PO Box 59 Renton, WA 98057 734060 0905 CHASE MORGAN PROPERTIES 5190 S 166th St Tukwila, WA 98188 734060 0908 Paul Houser PO Box 59 Renton, WA 98057 734060 0921 Sandra Harrison 13040 38th Ave S Tukwila, WA 98168 734060 0924 Tommie Lee Kanunerzell 13217 38th Ave S Seattle, WA 98168 734060 0926 Ping & Earline Tom 1919 S Jackson St Seattle, WA 98144 734060 0931 Frances Primero 22109 SE 277th St Kent, WA 98042 734060 0961 John Stetson III 13258 40th Ave S Seattle, WA 98168 734060 0965 Laverne Crossen 13250 40th Ave S Seattle, WA 98168 734060 0981 James & Barbara Guess 28020 201st Ave SE Kent, WA 109604 735860 0075 SALLE FAMILY LIMITED LIABILIT 13207 35th Ave S Seattle, WA 98168 735860 0180 Theresa Isley 13317 35th Ave S Tukwila, WA 98168 735860 0190 Julie Carlton 13305 35th Ave S Seattle, WA 98168 735860 0215 Blanche Cooper , 13314 35th Ave S - Seattle, WA 98168 735860 0230 Rodney & Gloria Sjol 13336 35th Ave S Seattle, WA 98168 735860 0250 Shauna Bailey & K Wal Terri 13354 35th Ave S Seattle, WA 98168 735860 0270 Jody Unmuth 13349 37th Ave S Tukwila, WA 98168 735860 0285 Tuyen Hoai Bac Nguyen 13333 37th Ave S Tukwila, WA 98168 735860 0310 Harry Bowen 31025 Military Rd S Auburn, WA 98001 735960 0670 Terrance Yoshikawa 2416 32nd Ave W Seattle, WA 98199 735860 0170 L J Rushmeier 13327 35th Ave S Seattle, WA 98168 735860 0185 Mark McGuire 13313 35th Ave S Seattle, WA 98168 735860 0200 Mack & Joyce Wilkerson 12049 Standring Ct SW Seattle; WA 98146 735860 0220 Ilia Pomeroy 13322 35th Ave S Seattle, WA 98168 735860 0231 Tuan Tai & Phuong Tuye Truong 13332 35th Ave S Tukwila,. WA 98168 735860 0255 Regina Wheeler 13356 35th Ave S Seattle, WA 98168 735860 0275 Paul & Maria Toth 13345 37th Ave S Seattle, WA 98168 735860 0290 Kathleen Eisenman 13325 37th Ave S Tukwila, WA 98168 735860 0320 BUTLER BUILDING CORPORATIO 12035 Palatine Ave N Seattle, WA 98133 735960 0680 Terrance Yoshikawa 2416 32nd Ave W Seattle, WA 98199 735860 0175 Tim & Maureen Jean Lippens 13321 35th Ave S Tukwila, WA 98168 735860 0188 James Michels 13307 35th Ave S Seattle, WA 98168 735860 0205 Michael & Larue Butler. 13308 35th Ave S Tukwila, WA 98168 735860 0225 Jeffrey Knight 13326 35th Ave S Seattle, WA 98168 735860 0240 Larry & Betsy Tucker 13344 35th Ave S Tukwila, WA 98168 735860 0260 David Skrogstad 13357 37th Ave S Tukwila, WA 98168 735860 0280 Ralph Albanese 3261 S 152nd St Seatac, WA 98188 735860 0300 Gintana & Playngam Ongpituk 1331737thAveS Seattle, WA 98168 735860 0325 Security Title 5151 E Broadway Blvd Tucson, AZ 85711 735960 0770 Ha Shofar Beth 13001 37th Ave S Seattle, WA 98168 734060 0981 James & Barbara Guess 28020 201st Ave SE Kent, WA 109604 734060 1003 Joanne Konrad Poirier 13405 43rd Ave S Tukwila, WA 98168 734060 1011 CITY OF TUKWILA 6200 Southcenter Blvd Tukwila, WA 109604 734060 1020 William Kirkland 13500 Pacific Hwy S #20 Tukwila, WA 98168 734060 1023 Heinz Klotzbuecher 3215 E Madison St Seattle, WA 98112 734060 1026 CITY OF TUKWILA 6200 Southcenter Blvd Tukwila, WA 109604 734060 1041 Patricia Willis 13502 37th Ave S Seattle, WA 98168 734060 1064 Kenneth Ray Ball 13629 28th PI S Seattle, WA 98168 735860 0025 Roy- Wilder 13206 34th Ave S Tukwila, WA 98168 735860 0055 SALLE FAMILY LIMITED LIABILIT 13225 35th Ave S Seattle, WA 98168 734060 0983 Elizabeth Springer 13325 Macadam Rd S Tukwila, WA 98168 734060 1004 Donald Scanlon 13410 40th Ave S Tukwila, WA 98168 734060 1012 Konrad Joanne Poirier 13405 43rd Ave S Seattle, WA 98168 734060 1021 Lillian Spagnole 13325 Pacific Hwy S Tukwila, WA 98168 734060 1024 Steven Fleisclunan ''917 N 130th St Seattle, WA 98133 734060 1027 William Kirkland 13500 Pacific Hwy S Seattle, WA 98168 734060 1042 Ellsworth Gronewold 13335 Pacific Hwy S Seattle, WA 98168 734060 1067 William Looney PO Box 66098 Seattle, WA 98166 735860 0040 Mary Norris & Mary Norris 13216 34th Ave S Tukwila, WA 98168 735860 0065 SALLE FAMILY LIMITED LIABILIT 13219 35th Ave S Seattle, WA 98168 734060 1001 Curtiss Robinson 13422 40th Ave S Tukwila, WA 98168 734060 1005 Curtiss Robinson 13422 40th Ave S Tukwila, WA 98168 734060 1012 Konrad Joanne Poirier 13405 43rd Ave S Seattle, WA 98168 734060 1023 Heinz Klotzbuecher 3215 E Madison St Seattle, WA 98112 734060 1025 E Gronewold 13335 Pacific Hwy S Seattle, WA 98168 734060 1027 William Kirkland 13500 Pacific Hwy S Seattle, WA 98168 734060 1062 DUJARDIN DEVELOPMENT COMP PO Box 5308 Everett, WA 98206 735860 0005 Michael Mastro 601 Union St Seattle, WA 98101 735860,0050 SALLE FAMILY LIMITED LIABILIT 3420 S 133rd St Tukwila, WA 98168 735860 0070 SALLE FAMILY LIMITED LIABILIT 13215 35th Ave S Seattle, WA 98168 735960 0775 Beth Ha Shofar 13001 37th Ave S Seattle, WA 98168 735960 0795 Rebecca Mae Harlan 13029 37th Ave S Seattle, WA 98168 735960 0815 BOARDWALK INVESTMENTS 4210 SW Oregon St Seattle, WA 98116 - 735960 0836 Karen Stewart 13015 37th Ave S Tukwila, WA 98168 735960 0870 Nell Marshall & Marshall Timmi Nka 708 Shoreland Dr SE Bellevue, WA 98004 734160-0165 JOSEPH & SANDRA CHARON 13039 27111 ST SW SEATTLE WA 98168 734160-0005 SOUTH CENTRAL SCH DIST 406 4640 SOUTH :144TH 'STREET TUKWILA WA 98168 734160-0171 WILLIAM STANLEY 13029 41ST STREET AVE S SEATTLE WA 98168 735960-0789 Shellie Lynn Fackrell 13027 37th Ave S. Tukwila, WA 98148 735960 0780 Thomas McLeod 13017 37th Ave S Seattle, WA 98168. 735960 0796 T W Edwards - -13031 37th Ave S Seattle, WA 98168 735960 0825 - William Dietz 13030 35th Ave S Seattle, WA 98168 735960 0845 Michael Mastro 601 Union St Seattle, WA 98101 735960 0885 SALLE FAMILY LIMITED LIABILIT NO STREET NAME or NUMBER ,WA 735960 0790 Tom Wayne & Lisa Ann McLeod NO STREET NAME or NUMBER WA 735960 0810 Grace Hickey 3510 S 132nd St Seattle, WA 98168 735960 0830 Raul Manac 13020 35th Ave S Seattle, WA 98168 735960 0855 Nathaniel Mettler 13209 37th Ave S Seattle, WA 98168 734060 0884 Current Resident , 13100E Marginal Way S Tukwila, WA 734060 0903 Current Resident 13045 40th Ave S Tukwila, WA 98168 734060 0906 Current Resident 13047 40th Ave S Tukwila, WA 98168 734060 0909 Current Resident NO STREET NAME or NUMBER Tukwila, WA 734060 0922 Current Resident 13200 37th Ave S Tukwila, WA 98168 734060 0925 Current Resident 13222 37th Ave S Tukwila, WA 98168 734060 0927 Current Resident 13038 38th Ave S Tukwila, WA 98168 734060 0940 Current Resident 13350 Pacific Hwy S Tukwila, WA 98168 734060 0962 Current Resident 13235 E Marginal Way S Tukwila, WA 98168 734060 0966 Current Resident 13232 40th Ave S Seattle, WA 98168 • • 734060 0900 Current Resident- 13215 esident13215 40th Ave S Seattle, WA 98168 734060 0904 Current Resident 13043 40th Ave S Tukwila, WA 98168 734060 0907 Current Resident 13053 40th Ave S Tukwila; WA 11872 734060 0920 Current Resident 13264 38th Ave S Seattle, WA 98168 734060 0923 Current Resident NO STREET NAME or NUMBER Tukwila, WA 734060 0926 Current Resident 13228 37th Ave S Tukwila, WA 98168 734060 0928 Current Resident 13041 38th Ave S Tukwila, WA 98168 734060 0960 Current Resident 13242 40th Ave S Seattle, WA 98168 734060 0963 Current Resident NO STREET NAME or NUMBER Tukwila, WA 734060 0980 Current Resident 13305 42nd Ave S Tukwila, WA 11846 734060 0902 - Current Resident NO STREET NAME or NUMBER Tukwila, WA 734060 0905 Current Resident NO STREET NAME or NUMBER Tukwila, WA 734060 0908 Current Resident NO STREET NAME or NUMBER Tukwila, WA 734060 0921 Current Resident 13040 38th Ave S Tukwila, WA 98168 734060 0924 Current Resident 13217 38th Ave S Seattle, WA 98168 734060 0926 Current Resident 13228 37th Ave S Tukwila, WA 98168 734060 0931 Current Resident 13212 38th Ave S Tukwila, WA 98168 734060 0961 Current Resident 13258 40th Ave S Seattle, WA 98168 734060 0965 Current Resident 13250 40th Ave S Seattle, WA 98168 734060 0981 Cu nt Resii nt 13319 2 d"AveS Tukwila, A 11846 734060 0981 Current Resident 13319 42nd Ave S Tukwila, WA 11846 734060 1003 Current Resident 13407 42nd Ave S Tukwila, WA 98168 734060 1011 Current Resident NO STREET NAME or NUMBER Tukwila, WA 11874 734060 1020 Current Resident 13409 40th Ave S Tukwila, WA 98168 734060 1023 Current Resident 13350 37th Ave S Tukwila, WA 98168 734060 1026 Current Resident NO STREET NAME or NUMBER Tukwila, WA 11874 734060 1041 Current Resident 13502 37th Ave S Seattle, WA 98168 734060 1064 Current Resident NO STREET NAME or NUMBER Tukwila, WA 73 ' : 60 002., Curre I sident 13206 Ave S Tukwila, 98168 735860 0055 Current Resident 13225 35th Ave S Seattle, WA 98168 734060 0983 Current Resident NO STREET NAME or NUMBER Tukwila, WA 734060 1004 Current Resident 1341040th Ave S Tukwila, WA 98168 734060 1012 Current Resident 13415 43rd Ave S Tukwila; WA 98168 734060 1021 Current Resident 13325 Pacific Hwy S Tukwila, WA 98168 734060 1024 Current Resident 13535 Pacific Hwy S Tukwila, WA 98168 734060 1027 Current Resident 13500 Pacific Hwy S Seattle, WA 98168 734060 1042 Current Resident 13545 Pacific Hwy S Tukwila, WA 98168 734060 1067 Current Resident NO STREET NAME or NUMBER Tukwila, WA 735860 0040 Curre Resident 13216AveS Tukwila, WA 98168 735860 0065 Current Resident 13219 35th Ave S Seattle, WA 98168 734060 1001 Current Resident 13422 40th Ave S Tukwila, WA 98168 734060 1005 Current Resident NO STREET NAME or NUMBER Tukwila, WA . 734060 1012 Current Resident 13415 43rd Ave S Tukwila, WA 98168 734060 1023 Current Resident 13350 37th Ave 'S Tukwila, WA 98168 734060 1025 Current Resident 13475 Pacific Vac Hwy S Tukwila, WA 734060 1027 Current Resident 13500 Pacific Hwy S Seattle, WA 98168 734060 1062 Current Resident S 137th St/42nd Ave S Tukwila, WA 98106 735860 0005 Current Resident 13224 35th Ave S Tukwila, WA 98168 735860 0050 Current Resident 3420 S 133rd St Tukwila, WA 98168 735860 0070 Current Resident 13215 35th Ave S Seattle, WA 98168- • 735860 0075 Current Resident - 13207 35th Ave S Seattle, WA 98168 735860 0180 Current Resident 13317 35th Ave•S Tukwila, WA 9.8168 735860 0190 Current Resident 13305 35th Ave S Seattle, WA 98168 735860 0215 Current Resident 13314 35th Ave S Seattle, WA 98168 735860 0230 Current Resident 13336 35th Ave S Seattle, WA 98168 735860 0250 Current Resident 13354 35th Ave S Seattle, WA 98168 735860 0270 Current Resident 13349 37th Ave S Tukwila, WA 98168 735860 0285 - Current Resident 13333 37th Ave S Tukwila, WA 98168 735860 0310 Current Resident 13311 37th Ave S Tukwila, WA 98168 735960 0670 Current Resident 3418 S 132nd St Tukwila, WA 98168 735860 0170 Cent Resi 1335 Ave S Seattle/ A 98168 735860 0185 Current Resident 1331335th Ave S Seattle, WA 98168 735860 0200 Current Resident NO STREET NAME or NUMBER Tukwila, WA 735860 0220 Current Resident 13322 35th Ave S Seattle, WA 98168 735860 0231 Current Resident 13332 35th Ave S Tukwila, WA 98168 735860 0255 Current Resident 13356 35th Ave S Seattle, WA 98168 735860 0275 Current Resident 13345 37th Ave S Seattle, WA 98168 735860 0290 Current Resident 13325 37th Ave S Tukwila, WA 98168 735860 0320 Current Resident 13305 37th Ave S Tukwila, WA 98168 735860 0175 Current Resident 13317 35th Ave S Tukwila, WA 98168 735860 0188 Current Resident 13307 35th Ave S Seattle, WA 98168 735860 0205 Current Resident 13308 35th Ave S Tukwila, WA 98168 735860 0225 Current Resident 13326 35th Ave S Seattle, WA 98168 735860 0240 Current Resident 13344 35th Ave S Tukwila, WA 98168 735860 0260 Current Resident 13357 37th Ave S Tukwila, WA 98168 735860 0280 Current Resident 13335 37th Ave S Tukwila, WA 98168 735860 0300 Current Resident 13317, 37th Ave S Seattle, WA 98168 735860 0325 Current Resident 35th Ave S Tukwila, WA 73560 06 6 7 960 0770. Curre esident Cu t Resident 3412 "1 nd St iJ 1300 7th Ave S Tukwila, A 98168 Tukwila, WA 98168 735960 0775 Current Resident - - .13013 37th Ave S Tukwila, WA 98168 735960 0795 Current Resident 13029 37th Ave S Seattle, WA 98168 735960 0815 Current Resident 13042 Pacific Hwy S- Tukwila, WA 98168 7359600836 Current esident 13015 3'7, S Tukwila, W 98168 735960 0870 Current Resident 37th Ave S Tukwila, WA 735960 0780 Current Resident 13017 37th Ave S Seattle, WA 98168 735960 0796 Current Resident 13031 37th Ave S Seattle, WA 98168 735960 0825 Current Resident 13030 35th Ave S Seattle, WA 98168 735960 0845 Current Resident 35th Ave S Tukwila, WA 735960 0885 Current Resident NO STREET NAME or NUMBER Tukwila, WA 735960 0790 Current Resident 13027 37th Ave S Tukwila, WA 98168 735960 0810 Current Resident 3510 S 132nd St Seattle, WA 98168 735960 0830 Current Resident 13020 35th Ave S Seattle, WA 98168 735960 0855 Current Resident 1320937th Ave S Seattle, WA 98168 • 152304 9053 Current Resident ,37thAveS Tukwila, WA 192080 0035 Current Resident 13027 40th Ave S Tukwila, WA 98168 733240 0015 Current Resident 3715 S 130th St Seattle, WA 98168 733240 0030 Current Resident 13025 38th Ave S Seattle, WA 98168 733240 0050 Current Resident 3803 S 130th St Tukwila, WA 98168 733240 0055 Current Resident 13026 38th Ave S Tukwila, WA 98168 734060 0800 Current Resident 13039 40th Ave S Seattle, WA 98168 734060 0803 Current Resident 3827 S 130th St Tukwila, WA 98168 734060 0803 Current Resident 3827 S 130th St Tukwila, WA 98168 734060 0880 Current Resident 13204 40th Ave S Seattle, WA 98168 152304 9157 Current Resident 35th Ave S Tukwila, WA 733240 0005 Current Resident 3705 S 130th St Seattle, WA 98168 733240 0020 Current Resident 13016 37th Ave S Tukwila, WA 98168 733240 0035 Current Resident NO STREET NAME or NUMBER Tukwila, WA 733240 0053 Current Resident 13016 38th Ave S Tukwila, WA 98168 733240 0070 Current Resident 13030 38th Ave S Tukwila, WA 98168 734060 0801 Current Resident 13035 40th Ave S Tukwila, WA 98168 734060 0803 Current Resident 3827 S 130th St Tukwila, WA 98168 734060 0824 Current Resident 13060 E Marginal Way S Tukwila, WA 98168 734060 0881 Current Resident 13212 40th Ave S Tukwila, WA 98168 • 192080 0025 Current Resident 13023 40th Ave S Seattle,, WA 98168 733240 0010 Current Resident 3711 S 130th St Tukwila, WA 98168 733240 0025 Current Resident 13015 38th Ave S Seattle, WA 98168 733240 0045 Current Resident 3809 S 130th St Seattle, WA 98168 733240 0054 Current Resident 13020 38th Ave S Tukwila, WA 98168 733240 0075 Current Resident 13034 38th Ave S Tukwila, WA 98168 734060 0803 Current Resident 3827 S 130th St Tukwila, WA 98168 734060 0803 Current Resident 3827 S 130th St Tukwila, WA 98168 734060 0825 Current Resident 13041 E Marginal Way S Tukwila, WA 98168 734060 0882 Current Resident 13219E Marginal Way S Seattle, WA 98168 City of Tukwila • • John W. Rants, Mayor Department of Community Development Steve Lancaster, Director NOTICE OF COMPLETE APPLICATION DATED June 16, 1999 Michael Weinstein Triad Associates 11814 115 Av. NE Kirkland, WA 98034 Subject: L99-0024 Tukwila Subdivision L99-0023 Tukwila Subdivision PRD E99-0012 Tukwila Subdivision Environmental Review Dear Michael: I have reviewed your June 7, 1999 resubmittal and appreciate your comprehensive response to our comments. We have determined that your application is complete. The next step is for you to install the notice board on the site within 14 days of the date of this letter. You received information on how to install the sign with your application packet. If you need another set of those instructions, you may obtain them at the Department of Community Development (DCD). After installing the sign with the laminated notice, you need to return the signed Affidavit of Posting to our office. I will be out of the office until June 28, 1999. If you have any questions please call my supervisor Jack Pace at 431-370 or wait and callme when I return. Sincerely, Moira Carr Bradshaw Associate Planner Cc: Fire Public Works Urban Environmentalist 6300 Southcenter Boulevard, Suite #100 • Tukwila, Washington 98188 • (2O6) 431-3670 • Fax (206) 431-3665 City of Tukwila John W. Rants, Mayor Department of Community Development Steve Lancaster Director June 7, 1999 Katherine Russell Triad Associates 11814 115 Avenue NE Kirkland, WA 98034-6923 Subject: Tukwila Subdivision PRD No. L99-0023 Dear Katherine: I told Ron Guest that the application form and feefor a design review is not .required for the above project. However, the project is subject to compliance with the design review criteria per the Tukwila Zoning Code, PRD Chapter, Relationship of this chapter to other sections and other ordinances section. TMC 18.46.060(G) As Ron was the "applicant" for the project and some one else from Triad will be assuming his duties, please provide new signature pages for us so that we have an accurate and official record of who will be the contact on this project. Call me at 431-3651 with any questions. Thank you, Yours truly, Moira Carr Bradshaw Associate Planner 6300 Southcenter Boulevard, Suite #100 • Tukwila, Washington 98188 • (206) 4313670 • Fax (206) 431-3665 CITY OF TUKWILA Department of Community Development Permit Center 6300 Southcenter Blvd, #100, Tukwila, WA 98188 (206)431-3670 RECEIVED JUN 07 1999 DEVELOPMENT e{�%!. fy/ , /,((� / 341�j,� rte..x f ~fif iy~� �j11 y s'" ,� : .Y yx� q X 'r �'3. 'x y y >W « ^ £ Y ✓..•, g >-y} iit• ...m,< ave . +if7�vi f 'T< •rtfY'°£S 3:.diS%i<iv�.L •ti ;° g oz ,✓. ..:� . <•+•..�.�.s.fe.,r.,..«< •;n •r: ee-.< J I ^ C ' ht » Y0%Kf$ �SS't,���;q.)8x Aiy��,'.,Mf3 Vs 4Tf�f{4 gJY�'a Xi bt Date: (DILC; (g 9 Ca Response to Incomplete Letter ❑ Response to Correction Letter ❑ Revision after Permit Issued Project Name: Plan Check/Permit Number: L9.C(- Dbz3 -J— Lctor -no 2f -- Project Address: I', Contact Person: Phone Number: Otik Summary of Revision: -��lL 9�C1S4___)Z \ c� 6)yie-t5-YvvPik_fiYet 40Incompq Sheet Numbers) "Cloud" or highlight all areas of revisions and date revisions. Submitted to City of Tukwila Permit Center ❑ Entered in Sierra on 3/4/99 June 4, 1999 Mr. Steve Lancaster, Director City of Tukwila 6300 Southcenter Boulevard, Suite 100 Tukwila, WA 98188 141a /Mr IML G., 1 TRIAD ASSOCIATES Project Management Civil Engineering Land Surveying Land Use Planning Landscape Architecture Site Design RE: Tukwila Subdivision PRD No. L99-0023, Tukwila Subdivision No. L99-0024 Triad Job No. 97-223 Dear Steve: Pursuant to the regulations stipulated in Tukwila Code Section 1,8.54.140, I am writing to request an exception from the tree replacement requirements stipulated in Section 18.54.130.3. I believe that this request for exception does meet the criteria cited in 18.54.140.2. I came to this conclusion after carefully reviewing the number of trees that would be removed during the mass grading operation. According to City Code Section 18.54.130.3, the number of required replacement trees had increased to the astounding number of 279. Given the density of trees on those portions of the site that will remain undisturbed, planting that number of trees cannot be accomplished on this site. Instead, we propose, as indicated on the revised submittal plan, planting 104 trees and 175 native evergreen seedlings within "slope restoration areas". I believe that this approach satisfies the intent of the Tree Regulations Chapter, as well as creating a more aesthetically pleasing, more viable project for the applicant. I appreciate your consideration in this matter. Should you have any question regarding this request, please do not hesitate to call me. Sincerely, TRIAD ASSOCIATES atherine E. Russell Planner 11814 115th Avenue NE. Kirkland. Washington 98034-6923 Phone 206.821.8448 Toll Free 800.488.0756 Fax 206.821 3481 • June 4, 1999 Moira Bradshaw City of Tukwila 6300 Southcenter Blvd Tukwila, WA 98188 RECEIVED IML ._ : o AMIN JUN 07 1999WINIAMINIIMMI COMMUNITY DEVELOPMENT TRIAD ASSOCIATES Project Management Civil Engineering Land Surveying Land Use Planning Landscape Architecture Site Design RE: Tukwila Subdivision PRD No. L99-0023, Tukwila Subdivision No. L99-0024 Triad Job No. 97-223 Dear Moira: Pursuant to your letter dated April 21, 1999, Triad Associates has revised the above referenced submittal package to reflect your comments. The following is a list of changes and/or comments, in order as they appear in your, letter, necessary for the above referenced application to be considered complete: 1. Pursuant to your May 4th telephone conversation with Ron Guest of Triad Associates, The Design Review requirement has been waived for this project; 2. A listing of architectural materials has been provided on sheet seven of this submittal; and 3: The location and type of exterior building lighting has been indicated on sheet seven of this' submittal. Additionally, your April 21st letter raised a number of issues that you indicated should be addressed. In regard to the street system you stated that the internal street system should be extended to 38th Street, as the proposed PRD boundary abutted 38th Street. During the past several months, the applicant has had the opportunity to speak with some of the neighbors and inform them of the proposed subdivision. Consistently, their primary concern was that a connection to 38th Street not be a part of this development. This would avoid increasing traffic on 40th and associated disturbances. In response to this request and to be sensitive to the neighbors' concerns, the applicant has elected to remove that portion of the property abutting 38th Street from this proposal. • Your letter also stipulated that cul-de-sac length should not exceed 600 feet. Triad has measured the cul-de-sac length and confirmed that it does not exceed 600 feet. Lastly, your letter stated that sidewalks would be required on both sides of the street. The revised plans now include this rrequirement..Not referenced in your letter, but discussed during our May 4th meeting, is the proposed hammerhead turn -around depicted on the original submittal. As it is unlikely that this would be acceptable to the City, Triad has revised the plans to indicate a cul-de-sac turn -around built to City standards. 11814 115th Avenue NE, Kirkland, Washington 98034=6923 Phone 425.821.8448 Toll Free 800.488.0756 Fax 425.821.3481 Internet www.triadassoc.com Page 2 Moira Bradshaw City of Tukwila June 4, 1999 Regarding the proposed trail, we have, pursuant to your request, extended it to the edge of property for connection with Pacific Highway. Your letter also indicated a number of problems with our initial submittal regarding the on-site utility system. The sewer line connections have been checked and modified pursuant to your letter. The distance between fire hydrants has been modified such that the distance between hydrants does not exceed 300 feet. Likewise, a hydrant has been added in the vicinity of lots 4, 5, and 6 so that the 150 foot distance from the hydrant to the outside of the house is not exceeded. As you and I have discussed, both during the May 4th meeting and over the telephone, the location of the detention pond is based on the:topography;of the site. In order to maintain the aesthetic, value of the site, Triad has provided significant landscaping to adequately screen the detention pond. The last item referenced in your letter is that the City does not allow subdivision entry monument signs in single-family neighborhoods. I would like to clarify that the note "landscape/entry monument easement" depicted on sheet five of this submittal is specifically called out for landscape treatment/natural "monumentation" such as tastefully placed rockformations and'is not indicative of signage. The last issue that I would like to point out is the revised tree retention count. After carefully reviewing the number of trees that would be removed during the mass grading operation, the number of required replacement trees, pursuant to Tukwila Code Section 18.54.130.3, has increased to the astounding number of 279. Given the density of trees on those portions of the site that will remain undisturbed, planting that number of trees cannot be accomplished on this site. Instead, we'propose, as indicated on the revised submittal plan, planting 104 trees and 175 native evergreen seedlings within "slope restoration areas". I believe that this approach satisfies the intent of the Tree Regulations Chapter, as well as creating a more aesthetically pleasing, more viable project for the applicant. Pursuant to Section 18.54.140, a letter to the Director is enclosed requesting an exception to the specific requirements of Section 18:54.130.3. I trust that this submittal addresses all of the issues you have raised, both in the May 4th letter and in conversation. Should you have any questions or need additional information regarding this submittal, please do not hesitate to call me. Sincerely, ASSOCIATES Katherine E. Russell Planner • City of Tukwila John W. Rants, Mayor Department of Community Development Steve Lancaster, Director April 21, 1999 Ronald Guest Triad Associates 11814 115 Av. NE Kirkland, WA 98034 Subject: Notice of Incompleteness `L99-0024 TukwilaSubdivision L99-0023 Tukwila Subdivision PRD Dear Mr. Guest I have received and reviewed your documentation for the above referenced applications. The following items are needed in order to consider the above two applications complete: 1. A Design Review application (see application checklist for potential additional materials) and fee ($900) 2. Architectural Materials to be used 3. Location and type of exterior building lighting Upon receipt of these items, the City will continue processing your applications. Please provide these materials together as'a package. These applications will expire if we -do not receive the package within 90 days of the date of this letter; unless an extension is granted pursuant to Section 18.104.070(E) of the Tukwila Municipal Code. Substantively there are a number of issues that will need to be addressed. These comments are preliminary in nature, not comprehensive but significant. Several Tukwila Design Standards are not met in your proposal. The most significant issue from the planning perspective is the overall layout of the subdivision and its relationship with surrounding subdividable land and streets. Specific standards are listed below. 6300 Southcenter Boulevard, Suite #100 • Tukwila, Washington 98188 • (206) 431-3670 • Fax (206) 431-3665 • Streets 17.20.030© Extension. Proposed street systems shall extend existing streets. Where appropriate existing streets shall extend to the boundaries of the plat to ensure access to, neighboring properties. 38th Street is a natural extension into this subdivision and is ignored. There may also be opportunities to the north and south of your site where access through your plat would be appropriate. 6. (b) 1) Cul-de-sacs standard length should not exceed 600 feet. 6. © 5) Sidewalks are required along all street frontages. 17.20.030 E. Blocks. Residential. block lengths should be -within 300 and 1,000 feet. Width should allow a two-tier layer of lots. The Subdivision Code has an exception section, TMC 17.32, that you may use for the above elements. There are specific criteria that must be applied to requests for exceptions from the standards. Trails. We would like to see the proposed trail extended to Pacific Highway, where pedestrians are likely to travel to access transit and commercial services. Utilities. Sewer. It appears that you are making sewer connections to the storm drain system. See lots 4 & 3 and 21 & 22. Water. Maximum spacing between fire hydrants is 300 feet and the distance between lots 7 and 11 exceeds that standard. The Fire Department has also indicated that the minimum distance of 150 feet from hydrant to any outside portion of a building will not be met for lots 4, 5 & 6; therefore an additional hydrant that is looped into the system will be required at this location.. Storm Water Detention. The location, contouring and landscape treatment of the detention system at the entrance to the subdivision does not seem appropriate or inviting. Can it be given a different treatment and designed to fit more naturally with the terrain and layout? Signs. Subdivision monument signs are not allowed in single family neighborhoods. Public Works and our Environmental Planner have your project under review. When they have their comments together we can meet to discuss these issues and any other issues comprehensively. Please call me at 431-3651 with any questions. Moira Carr Bradshaw Associate Planner Enclosure Cc: Fire Public Works Urban Environmentalist CITY OF UKWILA Department of Community Development 9 6300 Southcenter Boulevard, Tukwila, WA 98188 Telephone: (206) 431-3670 RECEIVED MAR 2 5 1999 COMMUNITY DEVELOPMENT ENVIRONMENTAL REVIEW (SEPA) APPLICATION To submit for SEPA review, provide the items listed above to the Planning Division at 6300 Southcenter Boulevard, Room 100. 8 copies of the completed and signed environmental checklist. You may use the City's pre-printed form or you may re -type the questions on your computer. If you choose to re -type the form into your computer, be sure to do so accurately. Mistakes or omissions will increase the review time. ❑ 8 sets of the full size plans needed to clearly describe the proposed action. ❑ One PMT set of plans reduced to 8.5" x 11". ❑ Four copies of supporting studies. ❑ One copy of the checklist application. ❑ One set of mailing labels .for all properties 500' from the subject property. (See address label worksheet.) ❑ $325 filing fee. The checklist contains several pages of questions which you are asked to answer. It covers a comprehensive set of topics. As a result, several of the questions may not apply to your project. If a particular question does not apply, simply write N/A undemeath. HOWEVER, be aware that many questions apply despite appearing not to. Care needs to be taken in reading and answering the questions to ensure the appropriate response is provided. It is important that accurate and clear information be provided. You may not know all of the answers. Answer each question to the best of your ability. If we find an answer to be insufficient, the City may contact you to ask for more information. Sometimes, after reviewing the checklist, the City will ask you provide additional studies or information. Commonly requested information includes traffic analysis, site topography, soils studies and tree surveys. • Tukwila PRD - City of Tukwila SEPA Checklist Purpose of Checklist: The State Environmental Policy Act (SEPA), chapter 43.21 C RCW, requires all governmental agencies to consider the environmental impacts of a proposal before making decisions. An environmental impact statement (EIS) must be prepared for all proposals with probable significant adverse impacts on the quality of the environment. The purpose of this checklist is to provide information to help the City of Tukwila's Responsible Official and any other agencies with jurisdiction to identify impacts from a proposal (and to reduce or avoid impacts from the proposal, if it can be done) and to help the City of Tukwila decide whether an EIS is required. A. BACKGROUND 1. Name of proposed project, if applicable: Tukwila PRD 2. Name of proponent: Secure Capital, LLC 3. Address and phone number of proponent and contact person: Proponent: Contact Person: Gary Greer Secure Capital, LLC P.O. Box 25127 Seattle, WA 98125 (206) 361-8023 Ronald E. Guest, PE Triad Associates Kirkland, WA 98034 Phone: (425) 821-8448 Fax: (425) 821-3481 4. Date checklist prepared: March 24, 1999 5. Agency requesting checklist: City of Tukwila Department of Community Development 6. Proposed timing or schedule (including phasing, if applicable): Once the grading permit and subsequent approvals have been granted, all on-site and off-site improvements will be constructed for the project. It is anticipated that development of the project will take place following approval of the building permit. Construction will proceed as one phase. 7. Do you have any plans for future additions, expansions, or further activity related to or connected with this proposal? If yes please explain. There are no additional plans anticipated at this time. 1 rcE et -Py FOR AGENCY USE ONLY RECEIVED MAR 2 5 1999 COMMUNITY DEVELOPMENT • 1 Tukwila PRD - City of Tukwila SEPA Checklist FOR AGENCY USE ONLY 8. List any information you know about that has been prepared, or will be prepared, directly related to this proposal. The following environmental information has been prepared for the PRD and is included as supplemental information to this Checklist: a) Wetland Reconnaissance & Stream Relocation Concepts Study prepared by Jones & Stokes Associates, Inc. dated August 13, 1998. b) Geotechnical Study prepared by Squier/HGI Associates dated July 15, 1998. c) Traffic Study prepared by TSI dated March 1, 1999. 9. Do you know whether applications are pending for governmental approvals of other proposals directly affecting the property covered by this proposal? No. 10. List any governmental approvals or permits that will be needed for your proposal, if known. * Preliminary & Final Plat Approval * PRD Approval * SEPA Threshold Determination * Clearing and Grading Permits * Road and Storm Drainage Approval * Sewer Extension Approval * Water Extension Approval * Building Permits * Boundary Line Adjustment City of Tukwila City of Tukwila City of Tukwila City of Tukwila City of Tukwila Val Vue Sewer District Water District #125 City of Tukwila City of Tukwila 11. Give brief, complete description of the 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. The proposal is for the development of 22 single-family residences on approximately 7.11 acres located in the City of Tukwila's Low Density Residential Zone (LDR). The project will be accessed off of 40th Avenue South and will be served by public water and sewer. 12. Location of the proposal. Provide 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 available. The subject property is situated on approximately 7.11 acres, located within the City of Tukwila in the NW 1/4 of Section 15, Township 23 North, Range 4 East. The site is located east of Pacific Highway South (Highway 99), west of 40th Avenue South, and north of Southgate Park. Please refer to attached legal description, site plan, vicinity map and topographic map. 2 • • Tukwila PRD - City of Tukwila SEPA Checklist B. ENVIRONMENTAL ELEMENTS 1. Earth FOR AGENCY USE ONLY a. General description of the site (circle one): flat, rolling, hilly, steep slopes, mountainous. b. What is the steepest slope on the site (approximate percent slope)? The steepest slope on the site is approximately 48 percent. However, the maximum slope within the area of proposed residential development is Tess than 30 percent. c. What general types of soils are found on the site (for example, clay, sand, gravel, peat, and muck)? If you know the classification of agricultural soils, specify them and note any prime farmland. The site is generally underlain by native outwash, tills, and consolidated, fine- grained glaciolacustrine soils and over -consolidated sandy siltstone. The near -surface soils consist of stratified gravelly sand, fine to medium sand, sandy silt, and clayey silt. Please refer to the Geotechnical Report prepared by Squier/HGI Associates submitted as part of the PRD Application. d.. Are there surface indications or history of unstable soils in the immediate vicinity? If so, describe. The site has been classified by the City of Tukwila's Sensitive Areas Ordinance (SAO) as a Class 3 Area of Potential Geologic Instability for most of the western half and southeast end of the site with the steep slopes. A Class 3 Area of Potential Geologic Instability is identified as an area where landslide potential is high, which include areas sloping between 20% and 40%, and which are underlain by relatively impermeable soils or bedrock. Based on the combination of slope, geology, soil types and groundwater conditions at the site, the potential for shallow debris flow -type landslides at the site is moderate in the southwestern and western portions of the site and low in the eastern half of the site. Please refer to the Geotechnical Report prepared by Squier/HGI Associates submitted as part of the PRD Application. e. Describe the purpose, type, and approximate quantities of any filling or grading proposed. Indicate source of fill. Grading of the site would be necessary to build the roads and prepare building pads for lots. The amount of material involved for grading and filling activities has not been estimated at this time. f. Could erosion occur as a result of clearing, construction, or use? If so, generally describe. Some erosion could occur on-site as a result of construction activities, however, temporary erosion and sedimentation control measures approved by the City of Tukwila will be employed to reduce erosion impacts. Please refer to the Geotechnical Report prepared by Squier/HGI Associates submitted as part of the PRD Application. 3 • • Tukwila PRD - City of Tukwila SEPA Checklist g. FOR AGENCY USE ONLY About what percent of the site will be covered with impervious surfaces after project construction (for example, asphalt or buildings)? It is anticipated that about 35 percent of each lot created will be covered with impervious surfaces. h. Proposed measures to reduce or control erosion, or other impacts to the earth, if any: During construction, the contractor will follow an approved temporary erosion and sedimentation control plan meeting City of Tukwila standards. Measures to be employed include the use of silt fences, straw bales, and temporary storm drainage features. Minimizing the soil disturbance during the rainy months and hydroseeding exposed soils and cleared areas after construction is complete will also reduce the potential for erosion. 2. Air a. What types of emissions to the air would result from the proposal (i.e., dust, automobile, odors, and industrial wood smoke) during construction and when the project is completed? If any, generally describe and give approximate quantities if known. Construction Impacts: Emissions and dust particulates generated primarily by construction equipment will be produced during the construction phase of the project. The amount of emissions to the air will be minimal and will occur during the actual construction of the development. Long -Term Air Quality Impacts: Long-term impacts would be those typically associated with residential land uses. Sources of long-term emissions and odor could include vehicle emissions from increased vehicle use generated by new residents, and smoke from any wood burning fireplaces, if permitted. The additional vehicular emissions in these areas is not anticipated to concentrate and therefore are not anticipated to create a health hazard to the residents or surrounding areas. b. Are there any off-site sources of emissions or odor that may affect your proposal? If so, generally describe. There are no known off-site sources of emissions or odors that could potentially impact this project. c. Proposed measures to reduce or control emissions or other impacts to air, if any: Frequent watering of the site during the construction phase of the project could help control dust and other particulates generated on the site. 4 • • Tukwila PRD - City of Tukwila SEPA Checklist 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, and wetlands)? If yes, describe type and provide names. If appropriate, state what stream or river it flows into. There are two open drainages on site and they are both mapped and inventoried Watercourses #15-5 and #15-3 per the City of Tukwila Sensitive Areas Ordinance (SAO). The site lies within the 560 -acre Southgate Creek drainage basin, which drains into the Duwamish River. Upstream of a culvert under South 133rd Street, Southgate Creek branches into the North, Middle, and South Forks, draining an area 248 acres in size (Herrera Environmental Consultants 1996; KCM 1992). The project site lies approximately between and includes the North and Middle Forks of Southgate Creek. The Middle Fork Southgate Creek, discharging under Highway 99 through a culvert, drains an area upslope of the highway as well as the south end of the project site, before it flows under 40th Avenue South. A small tributary also discharges from a culvert under Highway 99, and then flows easterly across the southern portion of the site in behind Lots 14-22. The North Fork Southgate Creek crosses the northeast corner of the project site before it also drains under 40th Avenue South. The Middle Fork and the tributary are both classified as Type 2 channels under the City of Tukwila's Sensitive Areas Ordinance (SAO). In addition, the North Fork is a Type 3 channel under Tukwila's SAO. 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. Work near the Type 2 and 3 streams will be necessary for the grading of lots and building pads. However, no activity will take place within the required 35 -foot, Type 2 buffer and the 15 -foot, Type 3 buffer. 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. There will be no filling or dredging of the Type 2 or Type 3 streams. 4) Will the proposal require surface water withdrawals or diversions? Give general description, purpose, and approximate quantities if known. There are no proposed surface water withdrawals or diversions. 5) Does the proposal lie within a 100 -year floodplain? If so, note location on the site plan. According to the Flood Insurance Map, there are no documented floodplains within the site. 5 FOR AGENCY USE ONLY • • Tukwila PRD - City of Tukwila SEPA Checklist FOR AGENCY USE ONLY 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. Some pollutants normally associated with residential development could enter surrounding surface water off-site, however the amount would be minimal since the on-site drainage will include the use of storm drainage conveyance, detention and treatment facilities in conformance with Department of Ecology Surface Water Management practices. b. Ground: 1) Will ground water be withdrawn, or will water be discharged to ground water? Give general description, purpose, and approximate quantities if known. The proposed development will be served by public water; therefore no ground water will be withdrawn to serve future residences. 2) Describe waste material that will be discharged into the ground from septic tanks or other sources, 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 the system(s) are expected to serve. Sanitary sewers will serve the project; therefore no waste material from septic systems will be discharged into the ground water system. 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. On-site stormwater run-off will primarily be generated from the single-family residential structures, associated roadways and driveways. Stormwater will be collected in a series of catch basins and conveyed into an approved stormwater detention system and discharged at its naturally occurring location. The conveyance, detention, treatment and discharge system will be designed in conformance with Department of Ecology Management practices. 2) Could waste materials enter ground or surface waters? If so, generally describe. Some pollutants normally associated with residential development could enter the surface water, however, the amount would be minimal since the on-site drainage will include the use of treatment facilities in conformance with current Department of Ecology standards. d. Proposed measures to reduce or control surface, ground, and runoff water impacts, if any: Stormwater runoff will occur as a result of the proposed development. The stormwater runoff will be collected and conveyed to an onsite detention/water quality facility. The detention facility will be designed and constructed per Department of Ecology standards. 6 • • Tukwila PRD - City of Tukwila SEPA Checklist 4. Plants FOR AGENCY USE ONLY a. Check or circle types of vegetation found on the site: deciduous tree: alder, maple, aspen, other: willow hawthorne evergreen tree: fir, cedar, hemlock, pine, other shrubs grass pasture crop or grain wet soil plants: cattail, buttercup, bulrush, skunk cabbage, other... water plants: water lily, eelgrass, milfoil, other: b. What kind and amount of vegetation will be removed or altered? With exception to areas of steep slopes, most of the vegetation within the proposed development area will be graded and removed to accommodate residential site preparation, roadway and utility installation. c. List threatened or endangered species known to be on or near the site. There are no known threatened or endangered species on or near the site. d. Proposed landscaping, use of native plants, or other measures to preserve or enhance vegetation on the site, if any: A street tree plan has been included with this proposal. However, a site specific landscape plan is not included for all proposed lots with this submittal. In addition, the two open space tracts will be retained, thus preserving areas of the existing native vegetation and the protection of streams and steep slope areas. As many of the significant trees as possible would be retained within the landscaped areas. 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: raptors mammals: deer, bear, elk, beaver, other: rabbits, raccoons, other: rodents fish: bass, perch, salmon, trout, herring, shellfish, other b. List any threatened or endangered species known to be on or near the site. None to our knowledge. c. Is the site part of a migration route? If so, explain. No. d. Proposed measures to preserve or enhance wildlife, if any: None. 7 • • Tukwila PRD - City of Tukwila SEPA Checklist 6. Energy and Natural Resources a. What kinds of energy (electric, natural gas, oil, wood stove, solar) will be used to meet the completed project's energy needs? Describe whether it will be used for heating, manufacturing, etc. Electrical energy will be the primary source of power serving the needs of the project and natural gas will be made available for the purpose of heating and other needs associated with single-family residential living. 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: The future homes that will be constructed as a result of this project will meet or exceed the applicable single-family residential energy conservation/consumption requirements in the City of Tukwila & Uniform Building Codes. 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. It is unlikely under normal working conditions environmental health hazards would be encountered. All project -related construction will meet or exceed current, local, city, state and federal laws. 1) Describe special emergency services that might be required. In the event of an explosion or spill, the City of Tukwila Fire Department is in close proximity to the site and would respond to any emergency. 2) Proposed measures to reduce or control environmental health hazards, if any: State regulations regarding safety and the handling of hazardous materials would be enforced during the construction process. Equipment refueling areas would be located in areas where a spill could be quickly contained and where the risks of the hazardous material entering surface water is minimized. b. Noise 1) What types of noise exist in the area which may affect your project (for example: traffic, equipment operation, other)? The predominant source of noise in the areas is from vehicles travelling on Pacific Highway South (SR -99), located on the property's westerly boundary is not project related or generated. 8 FOR AGENCY USE ONLY • • Tukwila PRD - City of Tukwila SEPA Checklist 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: traffic, construction, operation, other)? Indicate what hours noise would come from the site. Short-term impacts would result from the use of construction equipment during site development. Construction would occur primarily during the daylight hours and always in compliance with the Noise Code. Heavy equipment, hand tools, and the transporting of construction equipment generate construction noise. At 200 feet from the construction, approximate levels of noise would be: Activity Decibels Clearing 71-72 Excavation 59-77 Foundations 65 Building Erection 60-72 Finishing 62-77 Long-term impacts would be those associated with the increase in users. Future users would generate additional traffic. Sound levels for various noise sources could include: Sound Level at Noise Source 100 feet (dba) Automobile Starting 50-55 Closing Car Door 50-55 Loud Voices 50 Automobile/Truck Traffic 50 3) Proposed measures to reduce or control noise impacts, if any: No measures are proposed to reduce off-site traffic noise from Pacific Highway South (SR -99). Construction activity will be limited to daytime hours and construction equipment will not be allowed to idle for continuous periods of time, which will help to mitigate the impacts of potential construction noise. 8. Land and Shoreline Use a. What is the current use of the site and adjacent properties? The Tukwila PRD is a 7.11 -acre site located west of 40th Avenue South, east of Pacific Highway South (Highway 99), and north of Southgate Park. The site slopes downward from west to east. The west quarter of the site slopes downward steeply from Highway 99. Thereafter the slope becomes more gradual until it becomes nearly level adjacent to 40th Avenue South. The site is primarily undeveloped, however, there is one mobile home located on proposed Lot 20. This mobile home will be moved directly south of Lot 20 to a new lot created through the BLA process. The site is generally covered with grass, understory, thickets and trees. Adjacent land uses consist of low- density single-family residences to the north, south and east of the subject property. In addition, there is one structure located directly adjacent to the property in the central portion of the site that has been excepted out of the property through a boundary line adjustment. 9 FOR AGENCY USE ONLY • • Tukwila PRD - City of Tukwila SEPA Checklist b. Has the site been used for agriculture? If so, describe. Not known. c. Describe any structures on the site. One single-family residence on proposed Lot 1 will remain as a part of this proposal. d. Will any structures be demolished? If so, what? Yes. One garage on proposed Lot 1 will be removed and the mobile home on proposed Lot 20 will be moved directly south to a new lot created in the BLA process. No other structures will be removed or demolished as part of this proposal. e. What is the current zoning classification of the site? The site is zoned Low Density Residential (LDR). f. What is the current comprehensive plan designation of the site? The area is designated Single -Family Residential. g. If applicable, what is the current shoreline master program designation of the site? N/A h. Has any part of the site been classified as an "environmentally sensitive" area? If so, specify. No. i. Approximately how many people would reside or work in the completed project? j• Assuming 2.5 to 3.2 people per household, approximately 55 to 70 people would reside in the completed project. Approximately how many people would the completed project displace? None. k. Proposed measures to avoid or reduce displacement impacts, if any: None. I. Proposed measures to ensure the proposal is compatible with existing and projected land uses and plans, if any: The project will be developed in accordance with applicable City of Tukwila development and land use codes to ensure the project is consistent with the goals and policies of the Comprehensive Plan as adopted at the time of this application. 10 FOR AGENCY USE ONLY Tukwila PRD - City of Tukwila SEPA Checklist 9. Housing a. Approximately how many units would be provided, if any? Indicate whether high, middle, or low-income housing. A total of 22 new single-family middle income units will be developed, and one existing single-family residence will remain. b. Approximately how many units, if any would be eliminated? Indicate whether high, middle, or low-income housing. None. c. Proposed measures to reduce or control housing impacts, if any: Adherence to existing zoning and growth management planning goals would ensure that housing development is consistent with those policies stated in the applicable land use plan. 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? No specific building plans are included with this phase of the project, however, it is anticipated that houses built on the site would conform to the City of Tukwila Zoning Code height restrictions. b. What views in the immediate vicinity would be altered or obstructed? Development of the site would change the visual character of the site for the nearest existing residences from that of a currently undeveloped site to that of single-family unit neighborhood. c. Proposed measures to reduce or control aesthetic impacts, if any: Landscaping and building designs will be constructed in accordance with the City of Tukwila's development and land use codes. 11. Light and Glare a. What type of light or glare will the proposal produce? What time of day would it mainly occur? Light and glare that will be produced by this project will be that which is typically generated by single-family residential development. Light and glare from the completed project would mainly occur during the evening hours. b. Could light or glare from the finished project be a safety hazard or interfere with views? Not under normal circumstances. 11 FOR AGENCY USE ONLY • • Tukwila PRD - City of Tukwila SEPA Checklist 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: None. 12. Recreation a. What designated and informal recreational opportunities are in the immediate vicinity? A walking trail will be designed to run throughout Open Space Tract A behind Lots 11 through 19. Access to the trail will be gained through either 38th Avenue South or 40th Avenue South. In addition, the property is located in close proximity to Southgate Park. Please refer to attached site plan. b. Would the proposed project displace any existing recreational uses? If so, describe. The project would not displace any existing recreational uses. c. Proposed measures to reduce or control impacts on recreation, including recreation opportunities to be provided by the project or applicant, if any: None. 13. Historic and Cultural Preservation a. Are there any places or objects listed on, or proposed for, national, state, or local preservation registers known to be on or next to the site? If so, generally describe. None known. b. Generally describe any landmarks or evidence of historic, archaeological, scientific, or cultural importance known to be on or next to the site. There are no landmarks or evidence of any significant historic, archaeological, scientific or cultural resources known to be on or next to the site. c. Proposed measures to reduce or control impacts, if any: If any such historic or cultural evidence was encountered during construction or installation of improvements, work would be halted in the area and a state - approved archaeologist/historian would be engaged to investigate, evaluate and/or move or curate such resources, as appropriate. 12 FOR AGENCY USE ONLY • • Tukwila PRD - City of Tukwila SEPA Checklist 14. Transportation FOR AGENCY USE ONLY a. Identify public streets and highways serving the site, and describe proposed access to the existing street system. Show on site plans, if any. The proposed project is accessed from 40th Avenue South with a full street extending to the west and ultimately north to a hammerhead turnaround. In addition, there are two access tracts that will provide access to lots 3-6 and lots 20-22. Please refer to attached site plan. b. Is site currently served by public transit? If not, what is the approximate distance to the nearest transit stop? Route 174 provides service off of SR -99 at the intersections of South 144th, 139th, 133' and 130th. In addition, Route 184 stops at the intersection of South 144th Street. Please refer to the Traffic Study prepared by TSI. c. How many parking spaces would the completed project have? How many would the project eliminate? None. 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). Yes, the proposed project will require the development of an internal roadway system. e. Will the project use (or occur in the immediate vicinity of) water, rail, or air transportation? If so, generally describe. No. f. How many vehicular trips per day would be generated by the completed project? If known, indicate when peak volumes would occur. g. Approximately 220 vehicle trips per day are anticipated as a result of this project. Please refer to the Traffic Study prepared by TSI. Proposed measures to reduce or control transportation impacts, if any: The applicant will pay a pro -rata share traffic impact fee based on Mitigation Proportionate Fair -Share Costs Transportation Element Table. Please refer to Traffic Study prepared by TSI. 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 completed project would result in a slight increased need for police and fire protection as well as emergency medical service. There would also likely be an increase in school enrollment and a slight increase in demand for area recreational facilities. 13 • Tukwila PRD - City of Tukwila SEPA Checklist b. Proposed measures to reduce or control direct impacts on public services, if any. None proposed. 16. Utilities a. Indicate utilities currently available at the site: Electricity, Natural Gas, Water, Telephone, Sanitary Sewer, Septic System, Other. All utilities will be extended to and through the site. 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. Sanitary Sewer: Val Vue Sewer District Water: Water District #125 Electricity: Puget Sound Energy Natural Gas: Puget Sound Energy Telephone: U.S. West Cable TV: TCI Cable Refuse Service: Sea -Tac Disposal C. SIGNATURE The above answers are true and complete to the best of my knowledge. I understand that the lead agency is re - the/ ake its decision. Signature: Ar f oug St. leton Planner Date Prepared: March 24, 1999 14 FOR AGENCY USE ONLY Pipeline Video and Cleaning 35849 Military Rd S. Auburn. WA 98001 800.1v.A.PIPE 253.661.0828 Assigned ID: 31107 PO or Job# Client: Cunningham Development Project Name: Hillside Homes Address: 13243 40th Ave S. City: Tukwila State: WA Weather: Clear Truck Number: 3 Video Inspection Report Date: 4/3/2003 Legal description or orientation: 40th Ave 133rd Tukwila Technician: Paul Bendel Inspector: None - NewCastle Cleanliness: Minimal debris Grade: Poor Condition: Poor Joint type: Unk Joint length: 20' Starting Structure. Oepth. Ending Structure. Depth: Direction: Video Ref: Line Length: CB 16 10'6" CB 17 6'10" Upstream 0:00:00 68.7 Line Type: Pipe Type: Size: : Ref. Ball: Air Test: Air Quality:: Ventilated: Mandrel': Pass: Storm HDPE 12" none No Good No No N/A Cleaned: _ Comments: I Tape: Yes •1 Footage Position Comments Severity Notes Photo Clip Vid Ref 1 -0.1 Start of inspection - 0:00:0 2 4. 13.3 12 o'clock Joint - '.i.f-711 0:03:01 3 15.2 3 o'clock Hole in pipe -41tie ig /dx\ A,,, P� 0:04:03 a 15.2 6 o'clock grade change /�P� ` ` J �R(� 0:04:29 5 19.6 6 o'clock grade change end of ponding 0:05:27 6 68.7 • End of inspection - 0:08:03 • Page 1 of 20 Pipeline Video and Cleaning 35849 Milicary Rd S. Auburn, WA 98001 800.N.A.PIPE 253.661.0828 Assigned ID: 31107 PO or Job# Client: Cunningham Development Project Name: Hillside Homes Address: 13243 40th Ave S. City: Tukwila State: WA Weather: Clear Truck Number: 3 Cleanliness: Clean Video Inspection Report Date: 4/3/2003 Legal description or orientation: 40th Ave 133rd Tukwila Technician: Paul Bendel Inspector: None - NewCastle Grade: Good Condition: Poor Joint type: Gasket Joint length: 20 Starting Structure: Depth: Ending Structure: Depth: Direction: ; Video Ref: Line Length: CB 14 5'11" CB 12 4'9" Downstream 0:21:56 83 • Line Type: Pipe Type: I Size: j Ref. Ball: Air Test: Air Quality: ; Ventilated: i Mandrell: Pass* Storm HDPE 12" none No Good No No N/A Cleaned: Comments: Yes Footage Position 1 1 0.0 2 ' 8.0 Comments rTape: 2 Severity Notes Photo Clip Vid Ref Start of inspection - 0:21:56 3 36.0 5 o'clock Hole in pipe -- 4 60.8 Deflection egg shaped 5 8.0 End of inspection - 0:26:06 0:28:15 0:29:14 Page 5 of 20 Pipeline Video and Cleaning 35849 Miliary Rd S. Auburn. WA 98001 800.7V.A.PIPE 253.661,0828 Assigned ID: 31107 PO or Job# Client: Cunningham Development Project Name: Hillside Homes Address: 13243 40th Ave S. City: Tukwila Weather: Clear Cleanliness: State: WA Truck Number: 3 Video Inspection Report Date: 4/3/2003 Legal description or orientation: 40th Ave 133rd Tukwila Technician: Paul Bendel Inspector: None - NewCastle Grade: Condition: Joint type: Joint length: Starting Structure: Depth: Ending Structure: Depth: Direction: Video Ref: Line Length: CB 12 4'9" CB 13 4'8" Upstream 0:29:56 26.2 Line Type: Pipe Type: I Size: ! Ref. Ball: Air Test: ! Air Quality. Storm HOPE 12" none No Good Cleaned: Comments: Yes Footage Position Comments 1 0.0 Start of inspection - 2 20.1 Deflection egg shaped 3 24.1 grade change end of ponding 4 26.2 End of inspection - 5 9.8 Ventilated: Mandrel!: Pass: No No N/A Tape: 2 Severity Notes Photo Clip Vid Ref 0:29:56 0:32:00 0:34:34 Page 6 of 20 Pipeline Video and Cleaning 35849 Milicary Rd S. Auburn, WA 98001 800.N.A.PIPE 253.661.0828 Assigned ID: 31107 PO or Job# Client: Cunningham Development Project Name: Hillside Homes Address: 13243 40th Ave S. City: Tukwila Weather: Clear Cleanliness: State: WA Truck Number: 3 Video Inspection Report Date: 4/3/2003 Legal description or orientation: 40th Ave 133rd Tukwila Technician: Paul Bendel Inspector. None - NewCastle Grade: Condition: Joint type: Joint length: Starting Structure: Depth: Ending Structure: Depth: Direction: Video Ref: Line Length: - CB .12 4'9" CB 9 7'7" Downstream 0:34:46 130.4 Line Type: Pipe Type: Size: i Ref. Ball: Air Test: Air Quality: L Ventilated: Mandrell: Pass: Storm HOPE 12" none No Good No No N/A Cleaned:: Comments: Yes Tape: 2 Footage Position Comments Severity Notes Photo Clip Vid Ref 1 ` 0.0 : Start of inspection - 0:34:46 2 i 29.2: Joint - egg shaped 0 OK. 0:36:59 3.116,1.. 3 o'clock Hole in pipe T ria 4 120.1 3 o'clock Hole in. pipe �l 4 it -10:41:39 5 ; 123.3 .11 o'clock Hole in pipe - 0:42:44 6 126.6 grade change ponding G[z 7/ 0:44:12 7 128.3 12 o'clock Deflection jjjj I 0:45:32 8 129.2 2 o'clock Deflection 0:46:11 9 130.4 End of inspection - 0:46:59 Page 7 of 20 Pipeline Video and Cleaning 35849 Milicary Rd S. Auburn. WA 98001 800.1V.A.PIPE 253.661.0828 Assigned ID: 31107 PO or Job# Client: Cunningham Development Project Name: Hillside Homes Address: 13243 40th Ave S. City: Tukwila State: WA Weather: Clear Truck Number: 3 Cleanliness: Clean Video Inspection Report Date: 4/3/2003 Legal description or orientation: 40th Ave 133rd Tukwila Technician: Paul Bendel Inspector None - NewCastle Grade: Poor Condition: Good Joint type: Gasket Joint length: 18' Starting Structure: Depth: Ending Structure: Depth: Direction: ':. Video Ref: Line Length: CB 10 2'2" CB 11 3'7" Upstream 0:50:26 34.3 Line Type: ! , Pi. •e: j Size: ; Ref: Ball: Air Test: Air Quality: I Ventilated: Mandrell: Pass: Storm DIP 12" none No Good No No N/A Cleaned: Comments: i Tape: i I - 3 Yes Footage 0.0 8.8 15.7 34.3 13.1 2 Position Comments Severity Notes Photo Clip Vid Ref Start of inspection - 0:50:26 Ponding - 1/4 Pipe c14-0` 0:51:23 Ponding - 1/3 pipe % 0:52:15 End of inspection - 0:54:00 VG414 ( AMA of PL" 15 AttavActt. Page 9 of 20 Pipeline Video and Cleaning 35849 Military Rd S, Auburn. WA 98001 800.N.A.PIPE 253.661.0828 Assigned ID: 31107 PO or Job# Client: Cunningham Development Project Name: Hillside Homes Address: 13243 40th Ave S. City: Tukwila State: WA Weather: Clear Truck Number: 3 Cleanliness: Clean Video Inspection Report Date: 4/3/2003 Legal description or orientation: 40th Ave 133rd Tukwila Technician: Paul Bendel Inspector: None - NewCastle Grade: Good Condition: Poor Joint type: Gasket Joint length: 20' Starting Structure: Depth: Ending Structure: Depth: Direction: l Video Ref: Line Length: CB 3 11. CB 8 9'8 Upstream 0:57:20 68.5 Line Type:___ _ Pipe Type: Size:.,_,I Ref. Ball: Air Test: Air Quality_ Ventilated: Mandrel': Pass: Storm HOPE 12" none No Good No No N/A Cleaned: Comments: ! Tape: Yes Footage Position Comments 0.0 : Start of inspection - 8.7 ' Joint - wide • 32.0 12 o'clock Hole in pipe 35.3 12 o'clock Hole in pipeitit - 2 Severity Notes Photo Clip Vid Ref 0:57:20 0:59:06 Yes 1:01:40 Yes 1:04:46 1:07:34 1:08:29 1:09:19 5 63.5 : 6 66.7 7 68.5 8 -1.4 grade change end of ponding Transition to Control structure End of inspection - Page 11 of 20 Pipeline Video and Cleaning 35849 Military fad S. Auburn. WA 98001 800.N.A.PIPE 253.661.0828 Assigned ID: 31107 PO or Job# Client: Cunningham Development Project Name: Hillside Homes Address: 13243 40th Ave S. City: Tukwila Weather.- Clear State: WA Truck Number: 3 Video Inspection Report Date: 4/3/2003 Legal description or orientation: 40th Ave 133rd Tukwila Technician: Paul Bendel Inspector- None - NewCastle Cleanliness: Clean Grade: Good Condition: Fair Joint type: Gasket Joint length: 20' Starting Structure: Depth: Ending Structure: Depth: Direction: Video Ref: Line Length: CB 4 9'8" Existing 2'5" Downstream 1:32:14 41.3 • Line Type: I Pipe Type: Size: ' Ref. Ball: Air Test:: Air Quality: i Ventilated: ! Mandrels: Pass: • Storm HDPE 24" none No Good No No N/A : Cleaned:: Comments: Tape: Yes : 2 Footage Position Comments Severity Notes Photo Clip Vid Ref 1 0.0 Start of inspection - �1 1:32:14 2 ; 0.0 grade change ponding 1:34:11 3 7.8 grade change end of ponding 1:36:06 4 ; 17.0: Deflection � lato�' 1:36:13 5 ; 36.4 6 o'clock Deflection ' _ 1� �� \ 1:37:59 s 41.3 End of inspection - , �j �j 1:38:40 Page 15 of 20 Pipeline Video and Cleaning 35849 Military Rd S. Auburn, WA 98001 800.TV.A.PIPE 253.661.0828 Assigned ID: 31107 PO or Job# Client: Cunningham Development Project Name: Hillside Homes Address: 13243 40th Ave S. City: Tukwila Weather: Clear State: WA Truck Number: 3 Video Inspection Report Date: 4/3/2003 Legal description or orientation: 40th Ave 133rd Tukwila Technician: Paul Bendel Inspector: None - NewCastle Cleanliness: Clean Grade: Poor Condition: Poor Joint type: Gasket Joint length: 20' Starting Structure: Depth: Ending Structure: Depth: Direction: Video Ref: Line Length: 08 21 5 DETPOND N/A Downstream 1:38:44 23.8 . Line Type: Pipe Type: Size: , Ref. Ball: Air Test: Air Quality: ; Ventilated: Mandrell: Pass: Size: Storm HDPE 12" none No N/A No No N/A Tape: 2 Cleaned: Comments: Yes... _ .. -.. . Footage Position Comments Severity Notes Photo Clip Vid Ref 0.0 Start of inspection - 1:38:44 18.8 ` grade change ponding 1:40:48 22.8 6 o'clock Break - 1:45:12 i 23.8 ; End of inspection - 1:48:21 Page 16 of 20 Pipeline Video and Cleaning 35849 Military Rd S. Auburn, WA 98001 800.TV.A.PIPE 253.661.0828 Assigned ID: 31107 PO or Job# Client: Cunningham Development Project Name: Hillside Homes Address: 1324340th Ave S. City: Tukwila State: WA Weather: Clear Truck Number: 3 Cleanliness: Starting Structure: Depth: CB 20 5'5" Line Type: j Pipe Type: Storm HOPE Cleaned: Comments: Yes __. Video Inspection Report Date: 4/3/2003 Legal description or orientation: 40th Ave 133rd Tukwila Technician: Paul Bendel Inspector: None - NewCastle Grade: Good Condition: Good Joint type: Gasket Joint length: 20' Ending Structure: Depth: Direction: Video Ref: Line Length: CB 19 8'10" Downstream 1:48:26 122.3 Size: Ref. Ball: Air Test: ` Air Quality: I Ventilated: 18" none No Good No Footage Position Comments i 0.0 Start of inspection 2 48.9 Joint - wide I _ 3 49.8 11 o'clock Hole in pip 4 : 76.7 12 o'clock Deflection- ! S 105.5 3 o'clock Deflection 6 117.3 grade change pondin 7 120.2 • Deflection 8 122.3 End of inspection - 9 ! 120.7 Severity Notes Mandrel!: Pass: No N/A Tape: 2 Photo Clip Vid Ref 1:48:26 1:53:53 1:55:22 1:57:49 2:00:10 2:02:48 2:03:56 2:04:29 Page 17 of 20 • • Pipeline Video and Cleaning 35849 Milicary Rd S. Auburn, WA 98001 800.TV.A.PIPE 253.661.0828 Assigned ID: 31107 PO or Job# Client: Cunningham Development Project Name: Hillside Homes Address: 13243 40th Ave S. City: Tukwila State: WA Weather: Clear Truck Number: 3 Video Inspection Report Date: 4/3/2003 Legal description or orientation: 40th Ave 133rd Tukwila Technician: Paul Bendel Inspector: None - NewCastle Cleanliness: Clean Grade:Good Condition:Poor Joint type: Gasket Joint length: 20' • Starting Structure: Depth: Ending Structure: Depth: Direction: Video Ref: Line Length: CB 19 8'10" Outfall N/A Downstream 2:04:28 128.4 • Line Type: Pipe Type: j Size: Ref. Bali: Air Test: Air Quality: Ventilated: Mandrell: Pass. Storm HDPE 18" none No N/A No No N/A Cleaned: . Comments: 1. Yes ':. Tape: 2 Footage Position Comments Severity Notes Photo Clip Vid Ref i 1 I 0.0 . Start of inspection - 2:04:28 11.0 . 6 o'clock Deflection 2:06:08 44.6 • grade change ,� \ 2:08:40 53.3,. 12 o'clock Hole in pipe - 55.1 11 o'clock Hole in pipe �~ 1�+� Yes 2:11:17 6 57.3 11 o'clock Hole in pipe - Yes 2:12:59 7 : 66.7 Pipe out -of -round - egg shaped 2:14:38 8 81.3 Deflection 2:16:30 91 83.7 Hole in pipe 2:17:53 10 88.1, , Joint - wide 0 . f 2:19:33 11 i 107.8 grade change 2:21:33 /2-1128.4 I End of inspection - 2:23:30 . 13 1133.2 Page 18 of 20 Pipeline Video and Cleaning 35849 Military Ad S. Auburn, WA 98001 800.TV.A.PIPE 253.661.0828 Assigned ID: 31107 PO or Job# Client: Cunningham Development Project Name: Hillside Homes Address: 13243 40th Ave S. City: Tukwila State: WA Weather: Clear Truck Number: 3 Video Inspection Report Date: 4/3/2003 Legal description or orientation: 40th Ave 133rd Tukwila Technician: Paul Bendel Inspector: None - NewCastle Cleanliness: Clean Grade: Good Condition: Good Joint type: 0-Rinq Joint length: 20' Starting Structure: Depth: Ending Structure: Depth: Direction: : Video Ref: Line Length: CB 2A 9'8" CB 1 N/A Downstream 2:31:07 95 • Line Type_ _ Pipe Type: Size: 1 Ref. Ball: Air Test: Air Quality: Ventilated: Mandrell: Pass: Storm HDPE• 30" none No N/A No No N/A Cleaned: Comments: Yes Footage Position Comments 0.0 Start of inspection - 95.0 End of inspection - Tape: 2 Severity Notes Photo Clip Vid Ref 2:31:07 2:36:48 Page 20 of 20 CITY OFtUKWILA Department of Community Development 6300 Southcenter Boulevard, Tukwila, WA 98188 Telephone: (206) 431-3670 • RECEIVED MAR 2 5 1999 COMMUNITY. DEVELOPMENT SEPA APPLICATION CHECKLIST FOR STAFF USE ONLY Planner: File Number: q 7- 00 (oa. Receipt Number: Cross-reference files: 2,( i 7-© 48 Applicant, notified of incomplete,application: ,Applicant notified of complete application:: Notice of appiication'issued: A. NAME OF PROJECT/DEVELOPMENT: B. LOCATION OF PROJECT/DEVELOPMENT: (address and accessors parcel number(s)) THE SUBJECT PROPERTY IS SITUATED ON APPROXIMATELY 7.3 ACRES, LOCATED EAST OF PACIFIC HIGHWAY SOUTH: "', (HIGHWAY 99), WEST OF 40TH AVE SOUTH, AND NORTH OF SOUTHGATE PARK. PARCEL NOS. 734060-0901,x%9029,'9030 ADDRESS: 13223 and 13242 40TH AVE SOUTH. 734060-9041, 0 Quarter: NW Section: 15 Township: 23 Range: 4E (This information may be found on your tax statement) C. PROJECT DESCRIPTION: THE PROPOSAL IS FOR THE DEVELOPMENT OF 23 SINGLE-FAMILY RESIDENCESr0N APPROXIMATELY 7.1ACRES_LOCATED IN THE CITY OF TUKWILA's LOW DENSITY RESIDENTIAL ZONE. THE PROJECT WILL BE ACCESSED OFF. OF 40TH AVE SOUTH AND WILL :W' RVEL W F PUBLIC T A D D. APPLICANT: NAME: GARY GREER c/o SECURE!_CAPTIAL,: LLC ADDRESS: P.O. ,BOX 25127 S PHONE: 206 -361 - SIGNATURE: VAIN/ OPP' w A DATE: • TSI Transportation Solutions, Inc. 16310 NE 80th Street, Suite 100 Redmond, WA 98052-3861 (425) 8834134 (800) 2854134 FAX: (425) 867-0898 March 1, 1999 Mr. Gary Greer Secure Capital PO'Box 25127 Seattle, Washington 98125 Subject: Tukwila Residential -'"Traffic Study_ Dear Mr. Greer: ftt'ccio, RECEIVED MAR 2 51999 COMMUNITY DEVELOPMENT e99- oo/Z This letter summarizes the traffic impacts associated with the proposed detached single family residential units in Tukwila, Washiigton.1The purpose of this analysis is to comply with the City of Tukwila standards by identifying traffic -related impacts generated by the construction and operation of the proposed proie ct and to outline policies, programs, and/or physical improvements to mitigate the effects of these impacts. Cumulative impacts have been evaluated in this report by combining existing traffic volumes, future non -project traffic annual growth and project -generated traffic volumes in the immediate vicinity of the site. Introduction The scope of this traffic analysis was defined through discussions with the City -of Tukwila -- Department of Public Works staff and foliowing'the Traffic Concurrency Standards, - Chapter 9.48 in the Tukwila Municipal Code. this traffic impact study addresses an analyses of the following: Intersection Level o 1S�ervice (LOS), driveways accessing 40th Avenue South, on-site parking and circulation, available transit service, and traffic impact fees.. Project Location, fiiescription, and Operation TI.^enty-three detached single family resider+:alnits are proposed on a combination of twc adjacent parcels of land located west ef:40` ^Avemae South, -east of Pacific Highway South, and south of South -130 Street. The1site_cuently is occupied by several structures _ 1 rr that will be removed before development: -Each parcel will provide its own parking area. Access will be provided by driveways via 40`h A �enu South. Figure 1' shows the general location for the proposed project: Fieuie 2 shows the pwposed site plan. Rcpon :.doc Secure Capiiai - • Existing Conditions This section of this report summarizes a description of the existing road network and traffic conditions in the immediate vicinity of the site. LThis information forms the basis for evaluating future traffic conditions. Page 2- 411 Tukwila Residential Road Conditions 40th Street South is a two-lane roadway with one -to two foot -wide paved shoulders. This roadway transverses north to south, parallel with SR 99 to the west and I-5 to the east. Adjacent to the site, 40th Street South stretches for 0.5 miles starting in the north intersecting with South 126" Street and heading south past the site and intersecting with South 136" Street. The posted speed limit is 30 -miles per hour (m.p.h.). State Route 99 (Pacific Highway South) is a four to five -lane roadway. Both sides of the highway have four to five foot -wide paved shoulders. The roadway is oriented north to south on the western edge of the site. The roadway begins in the north at the City of Everett and transverses south past the site to theCity of Des Moines where it turns into SR 509. The posted speed is 45 m.p.h. South 130th Street is a two-lane, 22 -foot wide roadway with gravel and paved shoulders. Adjacent to the site, South 30th Street.extends for less than 0.5 miles. This roadway begins to the west at State Route 99 and transverses eastward to MacAdam Road South. The posted speed is 25 m.p.h. Traffic Control The intersections in the immediate area arecontrolled with stop signs and traffic signals. TSI followed the City of Tukwila's Municipal Code (Chapter 9.48 — Traffic Concurrency Standards) for evaluating intersections impacted with proposed project trips. As described in the Code, any intersection impacted with five or more peak hour trips should be evaluated. The intersections analyzed in this analysis that would be impacted by five or more peak hour trips are as follows: 1. South 130"' Street/East Marginal Way 2. 40" Avenue South/East Marginal Way 3. Site Access/40' Avenue South 1 4. South 133'" Street/SR 599 Southbound Ramps 5. South 133`d Street/Gateway Drive (Interurban Avenue South) 6. SR 599 Northbound Off-Ramp/Interurban Avenue 7. I-5 Southbound Off-Ramp/Interurban Avenue rsi Transportation Solutions Inc Secure Capital Traffic Volumes Page 3 - Tukwila Residential The weekday AM and PM peak hour traffic volumes used in this analysis were gathered by the City of Tukwila, WSDOT and conducted byTraffiCount. The AM and PM peak periods were selected for this analysis because it_represents the highest total traffic volume (background traffic and project -generated traffic) These counts indicate that during the weekday PM peak hour, South 130th Street carries approximately 280 vehicles per hour (vph) in both directions adjacent to the site; 40`h Avenue South carries approximately 250 vph in both directions adjacent to the site. Figure 3 illustrates the existing traffic volumes in the vicinity of the site. To evaluate the ability of the road network serving these volumes, an intersection level of service analysis was conducted. This analysis measures the ability of a given intersection to serve the traffic on the street system. The level of service methodology used was developed by the Transportation Research Board and is summarized in the Highway Capacity Manual (HCM-1994). Table 2, presented later in this report, summarizes the level of service analysis performed along at the impacted intersections. Transit Service TSI evaluated the transit service available in the vicinity of the site. SR 99 and East Marginal Way South both offer transit services.The locations and routes are listed below. State Route 99 - Route 174 stops at the intersections of South 144th, 139th, 133rd, and 130`h Street. Route 184 stops at the intersection of South 144t Street. East Marginal Way South - Routes 34, 108 and 1-29 stop at the intersections of South 133rd and 128th Streets. Route 124 stops at the intersection of South 128th Street. 1 Future Conditions Without and With the iroject This section of the report outlines the assumptions and steps taken to forecast future traffic volumes without and with the proposed residential development. It discusses the potential impacts of additional automobile traffic in the site vicinity generated by the proposed project and the impacts associated with other transportation issues including site access and on-site circulation. Background Traffic Volumes Between now and 2001, when this project is expected to be completed and occupied, there will be growth in traffic volumes that is unrelated to the project. To reflect this traffic growth, an annual average growth factor of 1.0 %l was applied to the existing traffic TSI Transportation Solutions Inc. Secure Capital Page 4- • Tukwila Residential volumes. This was based on conversations w4 -City of Tukwila staff. Figure 4 illustrates the traffic volumes in the 2001 Future Background Conditions without the project. Project Generated Traffic Volumes TSI used a generally accepted transportation planning approach that includes the following steps for forecasting travel demand: • Trip generation - How many people will_make trips? • Mode split - What modes will people usle (automobile, transit, other)? • Trip distribution - What are people's origins/destinations? • Travel assignment - Which routes will people take to make their trips? Trip Generation The AM and PM peak hour periods were analyzed to calculate the impact to traffic in the vicinity of the site. This is the time period when -proposed project trips could have the rr 1 1 • n gr Table 1: Trip Gen ?ration Information Time Period Quantity Trip Rate Gross New Trips 1 AM Peak Hour 23 DU 0.75 17 vph PM Peak Hour 23 DU 1.01 23 vph It l v Daily 23 DU 9.57 220 vpd DU — Dwelling Units Vph — vehicles per hour, vpd — vehicles per day TSI forecast the trip generation for the site during the weekday AM and PM peak, and daily time periods. A total of 17 vehicles per hour (vph) and 23 vph are forecast to be generated during the AM and PM peak periods, respectively. Both time periods (AM and PM peak hours) were analyzed in this summary -report with the project. A total of 220 vehicles per day (vpd) are forecast for the average daily traffic. Mode Split For the purpose of this analysis, it was assumed -that all of the trips to this development would travel via passenger vehicles. This would_ensure a `worst case' scenario for this analysis. TSI Transportation Solutions Inc. Secure Capital Trip Distribution • Page 5 • Tukwila Residential The trip distribution for this analysis was based on existing traffic patterns and knowledge of land uses in the vicinity of the site. General trip distribution trends were developed from this information, and the resulting percentages were then superimposed on the road system to identify the specific routes that cars would tra iel to and from the site. Figure 5 illustrates the trip distribution in the vicinity of the site. Travel Assignment The trip distribution was converted to vehicle trips by multiplying the percentage assigned to each roadway by the trip generation. Figure 6 reflects the assignment for the project. These project generated traffic volumes are then superimposed on the 2001 background traffic volumes. This combination of volumes is -referred to as the "2001 Traffic Volumes with Project" and is depicted on Figure 7. Traffic Analysis Consistent with the analysis scope defined by the City of Tukwila for this traffic analysis, TSI examined the traffic operations and safety at the proposed driveways to serve the site. This included an evaluation of the level of service and an assessment of sight distance and road channelization needs. —' Level of Service Table 2 illustrates the intersection and driveway -levels of service for the existing, future conditions without and with the project. The City of Tukwila guidelines for intersection LOS is a minimum of LOS -D for all minor and6llector arterials in predominately residential area. Following the table is a summary description of the results. Table 2: Existing and Future Levels of Service LOS — Level of Service V/C — Volume to Capacity Ratio Delay — Seconds of vehicle delay i31 Transportation Solutions Inc. [Existing Future Without Project Future With Project Intersections L; OS, Delay LOS, Delay LOS, Delay South 130th Street/East Marginal Way South 1 1B, 6.7 B, 7.1 B, 7.1 South 133'd Street/40th Avenue South '—'A, 0.8 A, 0.8 A, 1.0 Site Access/40th Avenue South NA NA A, 0.2 South 133rd Street/SR 599 SB Ramps 1 1B, 5.4 B, 5.8 B, 6.3 Interurban Avenue South/South 133' Street 1 C, 15.5 C, 16.1 C, 16.0 Interurban Avenue South/SR 599 NB Off-Rampl B, 6.7 B, 6.8 B, 6.8 Interurban Avenue South/I5 SB Off -Ramp FIB, 7.3 ' B, 7.3 B, 7.4 LOS — Level of Service V/C — Volume to Capacity Ratio Delay — Seconds of vehicle delay i31 Transportation Solutions Inc. Secure Capital Page 6 - Tukwila Residential For future intersection level of service without and with the project, all of the intersections impacted with project generated traffic will operate at LOS -C or better. Therefore, there will be no intersection LOS deficiencies at any of the impacted intersections. Sight Distance Entering and stopping sight distances were measured along 40th Avenue South to determine if the proposed driveway locations satisfy City of Tukwila minimum design requirements. Table 3 shows the entering and stopping site distances for both directions of travel at each proposed driveway. Table 3: Driveway Site Distance Driveway Direction & Typexi sting Condition King County Road Standards Tract C Northbound ESD '—' 700+ feet 430 feet Northbound SSSD r- 700+ feet 220 feet Southbound ESD I I 460 feet 430 feet Southbound SSSD I I 430 feet 210 feet Tract D Northbound ESD H. 960 feet . I) 920 feet 430 feet 220 feet (southern most) Northbo• und SSSD Southbound ESD U 435 feet 430 feet Southbound SSSD _ 400 feet 210 feet ESD — Entering Sight Distance; SSSD — Safe Stopping Sight Distance The City of Tukwila has established sight distance requirements based on A Policy on Geometric Design of Highways and Streets (AASHTO, 1990 Edition). These requirements apply to determination of adequate vertical alignment for all roads, and streets and proper intersection design. The 40th Avenue South driveways for Tract C and D meet the entering and safe "stopping sight distance requirements On-site Circulation A 50 -foot wide street will be constructed on-site ((Tract. C) with one lane flowing in each direction. On -street parking will be provided along this.street. Curb, gutter, and.sidewalk will be constructed on both sides of the roadways. Stop sign control will regulate traffic at the driveway access`via 40th Avenue South. These roadways meet City of Tukwila guidelines. TSI Transportation Solutions Inc. Secure Capital Pagel • Tukwila Residential Traffic Impact Fee The City of Tukwila requires developments to pay a pro -rata share traffic impact fee. This payment must be paid prior to the issuance of th jbuilding permit for this proposal. The traffic impact fee is based on Mitigation Proportionate Fair -Share Costs Transportation Element Table (Figure 8 attached). This proposed project would not impact any of the projects listed in this table. Therefore, the development would not be subjected to a cost per trip mitigation payment. U Conclusion Based on this analysis, TSI concludes that the proposed project will have minimal impact on the surrounding road network. The intersections in the vicinity of the site will operate at LOS -C with the addition of the proposed project. The proposed driveways along 40`x' Avenue South would operate at LOS -A. The driveways meet stopping and entering site guidelines, therefore would operate safely. The -on street and individual parking spaces for each dwelling unit will adequately serve the site. Also, frontage improvements will be made by the proposed project and will follow C ty of Tukwila acceptable guidelines. Finally, the proposed project would not be subjected to a Mitigation Proportionate Fair - Share Cost because it would not impact any of the intersections listed in the City of Tukwila's Transportation Element list of projects. I trust this provides you and the City of Tukwila -with an understanding of the traffic impacts associated with this site. If you or theyhaveany questions, we invite you to contact us at any time. Sincerely, Transportation Solutions, Inc. Michael H. Hennessey Transportation Engineer Attachments TSI Transportation Solutions Inc. TSI Transportation Solutions, Inc. Figure 1 Vicinity Map Secure Capital Tukwila 0 r. 14 i : g 14, Ee te vat ELI\ lJi a � � .. ... . of 2 -..r.. . 1 + ;- IL_ IL_ 1 a 1 II 14\ : ,.. 1i ‘ \ 1 •- ` )`, i •\ a / )1•. i ' • 1 f l♦ • !' k \ \ / � 1 • w4 • Yi4 \ / 44 1 894VMSC O a •. • ki • TSI Transportation Solutions, Inc. Figure 2 Secure Capital Site Plan Tukwila • • TSI Transportation Solutions, Inc. Figure 3 1998 Existing PM Peak Hour Traffic Volumes Secure Capital Tukwila 'AI 4 �11LA 17 4 68-0 • X92 24— 4-48 �1l • • 4\4 ` / m ` /:49--tbjefLet--\512158 l7014�ilir� 7 m TSI Transportation Solutions, Inc. Figure 4 Secure Capital 2001 Future Background PM Tukwila Peak Hour Traffic Volumes • • . TSI Transportation Solutions, Inc. Figure 5 Secure Capital PM Peak Hour Tukwila Trip Distribution • • /__44414.7 ` /j\ /_4t44 I 1—�o-_ tl 0 © 3�©4-12 tCy f°1 t <\1.1 114:F7 t`//‘ © \‘. / d\ 0Q TSI Transportation Solutions, Inc. Figure 6 Secure Capital PM Peak Hour Tukwila Trip Assignment • /aj 68�04-92 17 ‘-4 68 25—* d-48 \II*/ • 8—� 53-4 4-518 /� 87 —Co ©�-137 � A/ _ ��� 0 14\w/—�70 TSI Transportation Solutions, Inc. Figure 7 Secure Capital 2001 Future with Project PM Tukwila Peak Hour Traffic Volumes x • • :„ - • • • • • • So tutr:tnter Pk Wy/168 W Valley/Stranar NB dual left turn lanes • Interurban Bridge _ wideritor dual 5,236 7,760 2,524 31,200,000 347S 790 1.453 663 5250,000' .S377 1.441 3,078 637 3250.000* 3392 2.425 3.324 899 50 sa,7 3,433 4.316 883 S250.000* 5283 2.831 3.945 • 1.114 S1,250,000* 51,122 *1--141,21,17,1 level" es rintare. r re-wr fiA, e uture (Beyc a 6 year4(2000)): Minkler (APW SointtC4dtcr PkWy) r31 /2.3/36o vsTpoomm q7 .0 1.015 1,015 construct 3 lane ser S 178 St (Southdenter PkWy-WCL) rea:ip (cap/safety/transit) Ancicver PkWy (T PkWy-180) wicktn :o .5 lar.es Andover Pk E (T PkWy-180) widen to 5 lanes @ ints. Scutt:miter PkWy (180.200) dOnstrat 3 and 5 lane strut . 4 eiv -789 1.424 635 1,112 1.833 721 970 1.420 450 408 1,600 1.192 1-2-14 21i 350D ;.. 3 • Nove:nber 1993 • Md/001 tramNni Wd2T:E0 86 P'2 TUKWILA City of Tukwila, Washington Preliminary Storm Drainage Report Revised: December 30, 1998 Prepared by: Geoff E. Tamble Reviewed by: Mark A. Reeves, P.E. /MI 1MM MIIM TRIAD ASSOCIATES ENGINEER'S STAMP NOT VALID UNLESS SIGNED AND DATED EXPIRES: 4/26/q' October 27 1998 Triad Job No. 97-223 TABLE OF CONTENTS INTRODUCTION 1 VICINITY MAP 2 DRAINAGE CONCEPT 3 DETENTION CALCULATIONS 4 Existing Conditions 5 Allowable Release Rates 6 Developed Conditions 7 Bypass Developed Conditions 8 Level Pool Routing 11 Live Storage 11 Dead Storage 11 APPENDIX Curve Number Table Volume Correction Factor Table Soil Classification Table 2, 10, & 100 -Year Isopluvials Existing Conditions Tributary Area Map Developed Conditions Tributary Area Map COMPUTER OUTPUT Level Pool Table Summaries Stage Discharge Tables Hydrograph Summaries Basin Summaries PRELIMINARY STORM DRAINAGE REPORT FOR TUKWILA - PAGE - i ' PRELIMINARY STORM DRAINAGE REPORT FOR TUKWILA - PAGE - 1 • • VICINITY MAP Not to Scale PRELIMINARY STORM DRAINAGE REPORT FOR TUKWILA - PAGE - 2 DRAINAGE CONCEPT Since the existing stream within the project may require a Hydraulic Permit from the Washington State Department of Fish and Wildlife, the storm drainage systems for the proposed project were designed with reference to standards found within the Washington State Department of Ecology (DOE) Standards. The onsite drainage system will convey runoff from the developed site and all of the frontage improvements within a tightline drainage system to a combined detention/wet pond facility located adjacent to 40th Ave. South. The detained storm drainage will connect to an existing 24" culvert located under 40th Ave. South just east of the site. The detention facility is designed to provide peak rate runoff control for the 2, 10, and 100 -year, 24-hour storm events. The facilities were designed such that the post - developed peak runoff rates are attenuated to the pre -developed peak runoff rates for each of the 2, 10, and 100 -year, 24-hour storm events. The 2 year release rate is adjusted to allow one half of the pre -developed 2 year flow. To account for bypass, the release rates for all storm events are adjusted so that the sum of the hydrographs of the bypass area and the release rate hydrographs do not exceed the release rates from the predeveloped conditions. A 30 -percent volume correction factor (factor of safety) will also be applied to the live storage volume for the facility. Water quality enhancement will be provided within the facility through the use of "dead" storage. The amount of "dead" storage provided is equal to the volume of the "water quality" (6 -month) storm event. Based on (DOE) standards the precipitation to be used for the water quality storm event is 64% of the 2 -year, 24-hour precipitation. PRELIMINARY STORM DRAINAGE REPORT FOR TUKWILA - PAGE - 3 DETENTION CALCULATIONS PRELIMINARY STORM DRAINAGE REPORT FOR TUKWILA - PAGE - 4 Existing Conditions Total Area = 6.97 Ac Impervious Area = 0.27 Ac @ CN -98 Pervious Area = 6.70 Ac @ CN -76.7 (Calculated) 6.50 Ac * 76 (Older Forest) + 0.50 Ac * 86 (Lawn) = 76.7 6.70 Ac Time of Concentration = 29.18 min. (see computer output for basin ID Al, 2, 3) Reach 1: 300' Sheet Flow @ 28.0%; 'n' = 0.4 (Forest with light underbrush) Reach 2: 400' Shallow Concentrated Flow @ 12.0%; 'k' = 3.0 (Forest with groundlitter) Existing Condition Hydrograph Rainfall Type User 1 Time of Conc. 29.18 min. Baseflows 0.00 cfs Total Area 6.97 Ac Abstraction Coeff. 0.20 Pervious Area 6.70 Ac @ CN=76.70 Time Interval 10.00 min. Impervious Area 0.27 Ac @ CN=98 Existing Condition Hydrograph Summaries Storm Precip. [in] Peak Flow [cfs] Volume [Ac -ft] Time of Peak [min.] 2 -Year 2.0 0.31 0.28 490 10 -Year 2.9 0.98 0.61 480 100 -Year 4.0 2.07 1.08 480 PRELIMINARY STORM DRAINAGE REPORT FOR TUKWILA - PAGE - 5 • Developed Conditions Total Area = 6.60 Ac Impervious Area = 2.68 Ac @ CN=98 (Pavement, Roofs) Pervious Area = 3.92 Ac @ CN=82.58 (Calculated) 0.37 Ac*86 (Undeveloped Grass) + 2.15 Ac*86 (Lawn) + 1.40 Ac*76 (Forest) = 82.43 3.92 Ac Time of Concentration = 10.10 min. (see computer output for basin ID B1, 2, 3) Developed Condition Hydrograph Rainfall Type User 1 Time of Conc. 10.10 min. Baseflows 0.00 cfs Total Area 6.60 Ac Abstraction Coeff. 0.20 Pervious Area 3.92 Ac @ CN=82.58 Time Interval 10.00 min. Impervious Area 2.68 Ac @ CN=98 Developed Condition Hydrograph Summaries Storm Precip. [in] Peak Flow [cfs] Volume [Ac -ft] Time of Peak [min.] 2 -Year 2.0 1.71 0.61 480 10 -Year 2.9 2.98 1.03 480 100 -Year 4.0 4.65 1.52 480 Water Quality 1.28 0.82 0.32 480 PRELIMINARY STORM DRAINAGE REPORT FOR TUKWILA - PAGE - 7 Bypass Developed Conditions Lot l: Total Area = 0.21 Ac Impervious Area = 0.105 Ac @ CN=98 (Pavement, Roofs) Pervious Area = 0.105 Ac @ CN=86 (Lawn) Time of Concentration = 10.02 min. (see computer output for basin ID Cl, 2,3) Developed Bypass Condition Hydrograph Rainfall Type User 1 Time of Conc. 10.02 min. Baseflows 0.00 cfs Total Area 0.21 Ac Abstraction Coeff. 0.20 Pervious Area 0.105 Ac @ CN=86 Time Interval 10.00 min. Impervious Area 0.105 Ac @ CN=98 Developed Bypass Condition Hydrograph Summaries Storm Precip. [in] Peak Flow [cfs] Volume [Ac -ft] Time of Peak [min.] 2 -Year 2.0 0.07 0.02 .480 10 -Year 2.9 0.11 0.04 480 100 -Year 4.0 0.17 0.06 480 Lot 12: Total Area = 0.16 Ac Impervious Area = 0.08 Ac @ CN=98 (Pavement, Roofs) Pervious Area = 0.08 Ac @ CN=86 (Lawn) Time of Concentration = 6.3 min. (calculated to be 4 min, 6.3 is minimum allowed) Developed Bypass Condition Hydrograph Rainfall Type User 1 Time of Conc. 6.3 min. Baseflows 0.00 cfs Total Area 0.16 Ac Abstraction Coeff. 0.20 Pervious Area 0.08 Ac @ CN=86 Time Interval 10.00 min. Impervious Area 0.08 Ac @ CN=98 PRELIMINARY STORM DRAINAGE REPORT FOR TUKWILA - PAGE.- 8 • 1 Developed Bypass Condition Hydrograph Summaries Storm Precip. [ink Peak Flow [cfsj Volume [Ac -ft[ Time of Peak [min.] 2 -Year 2.0 0.05 0.02 480 10 -Year 2.9 0.09 0.03 470 100 -Year 4.0 0.13 0.04 470 Pond Outflow Check Using the water works program we added the outflow of the pond to the outflow of the hydrographs generated from the developed bypass basins. The addition of these two hydrographs for the 2, 10, and 100 year storms cannot exceed the calculated release rates for the entire site. From the table below we see that they do not exceed the calculated release rates. HYDROGRAPH SUMMARY DESCRIPTION HYD NUM PEAK (CFS/ TIME [Min] VOLUME [CF] AREA [Ac] 2 -YR OUTFLOW + BYPASS 14 0.151 480 11046 6.97 10 -YR OUTFLOW + BYPASS 15 0.674 780 29884 6.97 100 -YR OUTFLOW + BYPASS 16 1.570 540 54860 6.97 PRELIMINARY STORM DRAINAGE REPORT FOR TUKWILA - PAGE - 9 i • STAGE STORAGE TABLE RECTANGULAR VAULT ID No. STOR1 Description: OPEN VAULT Length: 82.00 ft. Width: 61.00 ft. COMBINATION DISCHARGE ID No. CMB 1 Description: COMBO ORIFACE/RISER Structure: RIS1 Structure: Structure: DIS 1 Structure: Structure: MULTIPLE ORIFICE ID No. DIS 1 Description: DISCHARGE ORIFACE Outlet Elev: 67.10 Elev: 65.10 ft Orifice Diameter: 1.0620 in. = 1-1/16 " RISER DISCHARGE ID No. RIS1 Description: RISER Riser Diameter (in): 18.00 elev: 71.79 ft Weir Coefficient...: 3.782 height: 72.20 ft Orif Coefficient...: 9.739 increm: 0.10 ft STAGE \ STORAGE \ DISCHARGE STAGE [FT] STORAGE [CF] STORAGE [Ac -FT] DISCHARGE [CFS] 67.10 0 0.0000 0.0000 67.50 2001 0.0459 0.0194 68.00 4502 0.1033 0.0290 68.50 7003 0.1608 0.0362 69.00 9504 0.2182 0.0422 69.50 12005 0.2756 0.0474 70.00 14506 0.3330 0.0521 70.50 17007 0.3904 0.0564 71.00 19508 0.4478 0.0604 71.50 22009 0.5053 0.0642 72.00 24510 0.5627 1.4736 72.50 27011 0.6201 7.2414 73.00 29512 0.6775 9.4348 1. - PRELIMINARY STORM DRAINAGE REPORT FOR TUKWILA - PAGE - 10 • Level Pool Routing The following level pool table summary represents the results of routing the developed area 2, 10, and 100 -year hydrographs through a theoretical detention structure. Please note that in all cases the discharge rates are less than or equal to the allowable release rates. Please refer to the Water Works outputs located in the Appendix. THEORETICAL LEVEL POOL TABLE SUMMARY Description Inflow Storage Discharge P. Stage Volume Outflow P. Time [CFS] ID ID [FT] [CF] [CFS] [Min] 2 -YR OUTFLOW 1.71 STOR CMB1 71.72 23125.85 0.069 1470 10 -YR OUTFLOW 2.98 STOR CMB1 71.90 24032.48 0.640 780 100 -YR OUTFLOW 4.65 STOR CMB1 72.00 24519.48 1.495 540 Live Storage The theoretical volume of live storage required is 24,519 cubic -feet. In addition to the 27% volume correction factor required by the Department of Ecology and additional 3% factor of safety was applied to the live storage volume to account for inaccuracies during facility construction. Therefore, the actual volume of live storage required is 31,874 cubic feet (1.30 x 24,519 ft3). The actual detention facility was designed to provide 31,987 cubic feet of live storage (68' x 96' x 4.9' ). Dead Storage The facility will be designed to provide "dead" storage in the amount equal to the volume of the water quality storm event. The volume of the water quality hydrograph (64% of the 2 year precipitation) was determined to be 0.33 Ac -ft or 13,825 cubic -feet as stated previously in the Developed Condition Hydrograph Summary. A 3 % factor of safety was then applied to account for inaccuracies that may occur during facility construction. The required volume of dead storage is therefore 14,240 cubic feet). The actual detention facility was designed to provide 19,584 cubic feet of dead storage (68' x 96' x 3'). The detention facility will have a total depth of 7.9 feet. PRELIMINARY STORM DRAINAGE REPORT FOR TUKWILA - PAGE - I 1 • APPENDIX • III -1-12 FEBRUARY, 1992 STOR MANAGEMENT MANUAL FOR THE P•ET SOUND BASIN FIGURE III -1.1 Volume Correction Factor to be Applied to Streambank Erosion Control BMPs Based on Site Impervious Cover 50 45 40 35 Z 30 2'1° 25 u 0 20 15 10 0 20 0 40 60 SITE IMPERVIOUS COVER 010 80 100 III -1-3 FEBRUARY, 1992 STORMW/R MANAGEMENT MANUAL FOR THE PU•T SOUND BASIN Table 1114.6 Hydrologic Soil Groups for Soils in the Puget Sound Basin Soil T Agnew Ahl Aits Alderwood Arents, Alderwood Arents, Everett Ashoe Baldhill Barneaton Baumgard Beausite Belfast Bellingham Bellingham variant Boistfort Bow Briscot Buckley Bunker Cagey Carlsborg Casey Cassolary Cathcart Centrale Chehalis Cheraw Cinebar Clatam Clayton Coastal beaches Kapowain Karina IGlchis Kitsap Klaus Kione Lates Lebam Lummi Lynnwood Lystair Mal Manley Mashel Maytowa McKenna McMurray Melbourne Menzel Mixed Alluvial Molson Mukilteo Naff Nargar National Neilton Hydrologic Soil Group C B C C Soil Type Colter Custer Dabob Delphi B Dick 8 Dimal B Dupont B Earlmoot C Edgewick B Eld B Elwell C Esquatzel D Everett C Everson B Galvin D Getchell D Giles C Godfrey B Greenwater C Grove ND Harstine ND Hartnit C I{oh B Hoko B Hoodaport B Hoogdal A Hoypus B Huel C. Indianola B Jonas variable Juarpe C/D Kalaloch C Renton C Republic C Riverwash ND Rober ND Sala! C Salkum B Sammamish ND San Juan ND Scamman ND Schneider C Seattle B Sekiu B Semiahmoo C Shalcar B Shano ND Shelton B Si ND Sinclair variable Skipopa B Skykomish C/D Snahopiah 8 Snohomish A Solduc ND Sollcks A Spans Hydrologic Soil Group C ND ND D ND D D C B B B A D D' A B D A C C ND ND ND ND C ND ND ND B ND C D B variable C C B D ND D B D ND D D B C C C D B ND D B ND D III -1-9 FEBRUARY, 1992 KING COUNTY, WIIING'fON, SURFACE W•ER DESIGN MANUAL (2) CN values can be area weighted when they apply to pervious areas of similar CN's (within 20 CN points). However, high CN areas should not be combined with low CN areas (unless the low CN areas are less than 15% of the subbasin). In this case, separate hydrographs should be generated and summed to form one hydrograph. FIGURE 3.S.2A HYDROLOGIC SOIL GROUP OF THE SOILS IN KING COUNTY SOIL GROUP HYDROLOGIC GROUP* SOIL GROUP HYDROLOGIC GROUP* Alderwood C Arents, Alderwood Material Arents, Everett Material Beausite Bellingham Briscot Buckley Coastal Beaches Earlmont Silt Loam Edgewick Everett Indianola Kitsap Klaus Mixed Alluvial Land Neilton Newberg Nooksack Normal Sandy Loam C- C. - Variable -C. - Variable D C. A/B A C C Variable A B C D Orcas Peat Oridia OvaII Pilchuck Puget Puyallup Ragnar Renton Riverwash Salal `Sammamish Seattle Shacar SI Silt Snohomish Sultan Tukwila Urban Woodinville D D C C_ D 8 D Variable C D D D C D C D Variable D HYDROLOGIC SOIL GROUP CLASSIFICATIONS 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 soils have a high rate of water transmission. 8. (Moderately low runoff potential). Soils having moderate infiltration rates when thoroughly wetted, and consisting chiefly of moderately fine to moderately coarse textures. These soils have a moderate rate of water transmission. C. (Moderately high runoff potential). Soils having slow infiltration rates when thoroughly wetted, and, consisting chiefly of soils with a layer that Impedes downward movement of water, or soils with moderately fine to fine textures. These soils have a slow rate of water transmission. D. (High 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 permanent high water table, soils with a hardpan or clay layer at or near the surface, and shallow soils over nearly impervious material. These soils have a very slow rate of water transmission. From SCS, TR -55, Second Edition, June 1986, Exhibit A-1. Revisions made from SCS, Soil Interpretation Record, Form #5, September 1988. 3.5.?-? 11/92 STORMWAT• MANAGEMENT MANUAL FOR THE PUGET SOUND BASIN • 124 123 122 121 25 — S NE 35 3025 30 25 - 25 • CENT 20 WASHINGTON 10 0 10 20 30 40 MILES Figure 25 ISOPLLNIALS F 2 -YR 24 -HR PRECIPITATII N IN TENTHS OF A INCH 124 Ar 25"_ NOAA ATLAS 2, Volume IX Prepared by U.S. Department of merce National Oceanic and Atmospheric •ministration National Weather Service, Office of Hydrology Prepared for U.S. Department of A iculture. Soil Conservation Service, Engineer g Division 123 122 121 III -1-44 FEBRUARY, 1992 STORMWATER MANAGEMENT MANUAL FOR THE PUGET SOUND BASIN 1 24 49 123 122 121 IIL REMME UN TI S'. OLGA PORT STANL:Y 48 47 46 4 40 50 50 0 15 :A I AMS WASHINGTON 10 0 10 20 30 40 Figure 27 ISOPLUVIALS i F 10 -YR 24 -HR PRECIPIT IN TENTHS OF AN INCH MILES 124 30 VAN .11 4�s t�l 1` f OAA ATLAS 2, Volume eIX TION 0 Prepared by U.S. Department of Commerce National Oceanic and Atmospheric Administration National Weather Service, Office of Hydrology Prepared for U.S. Department of Agriculture, Soil Conservation Service, Engineering Division 123 122 121 III -1-45 FEBRUARY, 1992 49r. STORMWATER MANAGEMENT MANUAL FOR THE PUGET SOUND BASIN 45� ;.158085 1 ►iilC-'r HAR OFi 3. 30/ ' T u �(.k2 15 4 8' 47 46 15 80 85'. 90\ 100\ 10d� 90� 6 6 6 55 rat 5 55 tCKLI 10 0 10 20 30 40 i r----) MILES 10 Figure 30 ISOPLUVIALS F 100 -YR 24 -HR PRECIPITATION IN TENTHS OF N INCH /5 50 55 60 65 Prepared by U.S. Department of coerce ; NationalOceanicandAtmospheric ministration National Weather Service, Office ofHydrology ' Prepared for U.S. Department of A iculture, Soil Conservation Service, Engineer ng Division An -111015 NOAA ATLAS 2, Volume IX 124 123 122 12 III -1-46 FEBRUARY, 1992 • • MML7er ,SJO' S. 130TH ST. woo:rut •o of \} 1t ; � .,� \1'1`, \ i`/ "Lit ` \ ‘Ii, ,l lip`;i ' 1 t\ j l; \\ I ;\1`;' 1_( ji 11yWj' tl 3 l \\ �� ( t,' I\ , .12B, \i ! 1 `\ , , . l ? r ), ! ,\i' j 1 ., ilii 4 .,,i5,. ..•1 ;� \17 t i tt 01 1 .,\. • wnn:,. \ ` 1,i' � \\\, z \ 1 \ \ \ ( %I, '\\'\ \ \'\; ,. \\;; \ \ \\ ' 7.., 7 `I � \'\\',11.\\\ ,moi` � \i ,`' � \ x\\\\\ \\1N\ \,N\—.\‘ \\\ \\\\\\\ k.\ ;%1' \ \s, ,i \ l I l�''F��V'L�`;1T \\ c�� `\��1 i I \ i \ \ ol` , \\;,‘,N,' \;1 : 1 \N\‘ , \\‘\\,\.,:,,f\i\. \ ,. \\ \''..."1\...\ANC77\i\J 11 .\/,,,\,‘\.‘,‘,‘•,,\'‘.1 ,\�',�� I! 11��\I\ti\I \ \\li 1 \ \ \ \ ;� T. \\\\' V \‘‘, Ali\ \ \ "A \,1\ : \\ \\\ \ 1`,.''',1\\\:s1, \\ . \I\ \ \ \ \ : \ .\\\\ ‘ s '\ \ \ ' s ' 1 \\:::, t ,� \ \ \ 4 / /• t! -H,n `! ? 1 t J ' if . ? 77am_. �,�.� r \� �\ ` 7 , : cif �\\ t-_ _. 'N• ;,./.,_54 r1:„.........„.,',.\,' /ji t ', 7,,,•:\.N1.:,\. '''/!.>:::-..-'..- . : ;://4.... - .- ..... ... • ' ---- n• N \ 1 • 1 rk -ao— rt 40 80 160 PREDEVEL OPED CONDITIONS MAP • 1.73nIT 71,13. S. 130TH ST. 1.917-511 moolrist 0,99-17.5r.to 0.00" r. • f BYPASS 0.16 AC 211 , • TRACT / ).. 'I! OPEN SPACE TRACT P%___zE_IYPASS 0.21 AC "' J/ • . • SCALE: 1" = 80' 0 40 80 160 DEVELOPED CONDITIONS MAP • • &kOS 12/29/98 TUKWILA DECEMBER 29, 1998 GEOFF TAMBLE page 1 BASIN ID: A 1 SBUH METHODOLOGY TOTAL AREA..: 6.97 Acres RAINFALL TYPE..: USER1 PRECIPITATION..: 2.00 inches TIME INTERVAL..: 10.00 min TIME OF CONC..: 29.18 min ABSTRACTION COEFF : 0.20 BASIN SUMMARY NAME: 2 -YR EXISTING BASEFLOWS : 0.00 cfs PERVIOUS AREA AREA..: 6.69 Acres CN..: 76.70 IMPERVIOUS AREA AREA..: 0.27 Acres CN..: 98.00 TcReach - Sheet L: 300.00 ns:0.4000 p2yr: 2.00 s:0.2800 TcReach - Shallow L: 400.00 ks:3.00 s:0.1200 PEAK RATE: 0.31 cfs VOL: 0.28 Ac -ft TIME: 490 min BASIN ID: A2 SBUH METHODOLOGY TOTAL AREA..: 6.97 Acres RAINFALL TYPE..: USER1 PRECIPITATION..: 2.90 inches TIME INTERVAL..: 10.00 min TIME OF CONC..: 29.18 min ABSTRACTION COEFF : 0.20 NAME: 10 -YR EXISTING BASEFLOWS : 0.00 cfs PERVIOUS AREA AREA..: 6.69 Acres CN..: 76.70 IMPERVIOUS AREA AREA..: 0.27 Acres CN..: 98.00 TcReach - Sheet L: 300.00 ns:0.4000 p2yr: 2.00 s:0.2800 TcReach - Shallow L: 400.00 ks:3.00 s:0.1200 PEAK RATE: 0.98 cfs VOL: 0.61 Ac -ft TIME: 480 min BASIN ID: A3 SBUH METHODOLOGY TOTAL AREA..: 6.97 Acres RAINFALL TYPE..: PRECIPITATION..: TIME INTERVAL..: USER1 4.00 inches 10.00 min TIME OF CONC..: 29.18 min ABSTRACTION COEFF : 0.20 NAME: 100 -YR EXISTING BASEFLOWS : 0.00 cfs PERVIOUS AREA AREA..: 6.69 Acres CN..: 76.70 IMPERVIOUS AREA AREA..: 0.27 Acres CN..: 98.00 TcReach - Sheet L: 300.00 ns:0.4000 p2yr: 2.00 s:0.2800 TcReach - Shallow L: 400.00 ks:3.00 s:0.1200 PEAK RATE: 2.07 cfs VOL: 1.08 Ac -ft TIME: 480 min • &kOS 12/29/98 TUKWILA DECEMBER 29, 1998 GEOFF TAMBLE page 2 • BASIN ID: B 1 SBUH METHODOLOGY TOTAL AREA..: 6.60 Acres RAINFALL TYPE..: USER1 PRECIPITATION..: 2.00 inches TIME INTERVAL..: 10.00 min TIME OF CONC..: 10.10 min ABSTRACTION COEFF : 0.20 BASIN SUMMARY NAME: 2 -YR DEVELOPED BASEFLOWS : 0.00 cfs PERVIOUS AREA AREA..: CN..: IMPERVIOUS AREA AREA..: CN..: TcReach - Sheet L: 250.00 ns:O.1500 p2yr: 2.00 s:0.2480 TcReach - Channel L: 500.00 kc:42.00 s:0.1120 3.92 Acres 82.43 2.68 Acres 98.00 PEAK RATE: 1.71 cfs VOL: 0.61 Ac -ft TIME: 480 min BASIN ID: B2 SBUH METHODOLOGY TOTAL AREA..: 6.60 Acres RAINFALL TYPE..: USER1 PRECIPITATION..: 2.90 inches TIME INTERVAL..: 10.00 min TIME OF CONC..: 10.10 min ABSTRACTION COEFF : 0.20 NAME: 10 -YR DEVELOPED BASEFLOWS : 0.00 cfs PERVIOUS AREA AREA..: 3.92 Acres CN..: 82.43 IMPERVIOUS AREA AREA..: 2.68 Acres CN..: 98.00 PEAK RATE: 2.98 cfs VOL: 1.03 Ac -ft TIME: 480 min BASIN ID: B3 SBUH METHODOLOGY TOTAL AREA..: 6.60 Acres RAINFALL TYPE..: USER1 PRECIPITATION..: 4.00 inches TIME INTERVAL..: 10.00 min TIME OF CONC..: 10.10 min ABSTRACTION COEFF : 0.20 NAME: 100 -YR DEVELOPED BASEFLOWS : 0.00 cfs PERVIOUS AREA AREA..: 3.92 Acres CN..: 82.43 IMPERVIOUS AREA 2.68 Acres CN..: 98.00 PEAK RATE: 4.65 cfs VOL: 1.57 Ac -ft TIME: 480 min &kOS 12/29/98 TUKWILA DECEMBER 29, 1998 GEOFF TAMBLE page 3 BASIN ID: CI SBUH METHODOLOGY TOTAL AREA..: 0.21 Acres RAINFALL TYPE..: USER1 PRECIPITATION..: 2.00 inches TIME INTERVAL..: 10.00 min TIME OF CONC..: 10.02 min ABSTRACTION COEFF : 0.20 TcReach - Sheet BASIN SUMMARY NAME: 2 -YR BYPASS, LOT 1 BASEFLOWS : 0.00 cfs PERVIOUS AREA AREA..: 0.11 Acres CN..: 86.00 IMPERVIOUS AREA AREA..: 0.11 Acres CN..: 98.00 L: 115.00. ns:0.1500 p2yr: 2.00 s:0.0450 PEAK RATE: BASIN ID: C2 SBUH METHODOLOGY TOTAL AREA..: 0.21 Acres RAINFALL TYPE..: USER1 PRECIPITATION..: 2.90 inches TIME INTERVAL..: 10.00 min TIME OF CONC..: 10.02 min ABSTRACTION COEFF : 0.20 0.07 cfs VOL: 0.02 Ac -ft TIME: 480 min NAME: 10 -YR BYPASS, LOT 1 BASEFLOWS : 0.00 cfs PERVIOUS AREA AREA..: 0.11 Acres CN..: 86.00 IMPERVIOUS AREA AREA..: 0.11 Acres CN..: 98.00 TcReach - Sheet L: 115.00 ns:0.1500 p2yr: 2.00 s:0.0450 PEAK RATE: 0.11 cfs VOL: 0.04 Ac -ft TIME: BASIN ID: C3 SBUH METHODOLOGY TOTAL AREA..: 0.21 Acres RAINFALL TYPE..: USER1 PRECIPITATION..: 4.00 inches TIME INTERVAL..: 10.00 min TIME OF CONC..: 10.02 min ABSTRACTION COEFF : 0.20 TcReach - Sheet 480 min NAME: 100 -YR BYPASS, LOT 1 BASEFLOWS : 0.00 cfs PERVIOUS AREA AREA..: 0.11 Acres CN..: 86.00 IMPERVIOUS AREA AREA..: 0.11 Acres CN..: 98.00 L: 115.00 ns:0.1500 p2yr: 2.00 s:0.0450 PEAK RATE: 0.17 cfs VOL: 0.06 Ac -ft TIME: 480 min • &kOS 12/29/98 TUKWILA DECEMBER 29, 1998 GEOFF TAMBLE page 4 • BASIN ID: DI SBUH METHODOLOGY TOTAL AREA..: 0.16 Acres RAINFALL TYPE..: USER1 PRECIPITATION..: 2.00 inches TIME INTERVAL..: 10.00 min TIME OF CONC..: 6.30 min ABSTRACTION COEFF : 0.20 BASIN SUMMARY NAME: 2 -YR BYPASS, LOT 12 BASEFLOWS : 0.00 cfs PERVIOUS AREA AREA..: 0.08 Acres CN..: 86.00 IMPERVIOUS AREA AREA..: 0.08 Acres CN..: 98.00 PEAK RATE: 0.05 cfs VOL: 0.02 Ac -ft TIME: 480 min BASIN ID: D2 SBUH METHODOLOGY TOTAL AREA..: 0.16 Acres RAINFALL TYPE..: USER1 PRECIPITATION..: 2.90 inches TIME INTERVAL..: 10.00 min TIME OF CONC..: 6.30 min ABSTRACTION COEFF : 0.20 NAME: 10 -YR BYPASS, LOT 12 BASEFLOWS : 0.00 cfs PERVIOUS AREA AREA..: 0.08 Acres CN..: 86.00 IMPERVIOUS AREA AREA..: 0.08 Acres CN..: 98.00 PEAK RATE: 0.09 cfs VOL: 0.03 Ac -ft TIME: 470 min BASIN ID: D3 SBUH METHODOLOGY TOTAL AREA..: 0.16 Acres RAINFALL TYPE..: USER 1 PRECIPITATION..: 4.00 inches TIME INTERVAL..: 10.00 min TIME OF CONC..: 6.30 min ABSTRACTION COEFF : 0.20 NAME: 100 -YR BYPASS, LOT 12 BASEFLOWS : 0.00 cfs PERVIOUS AREA AREA..: 0.08 Acres CN..: 86.00 „MPERVIOUS AREA AREA..: 0.08 Acres CN..: 98.00 PEAK RATE: 0.13 cfs VOL: 0.04 Ac -ft TIME: 470 min &kOS 12/29/98 TUKWILA DECEMBER 29, 1998 GEOFF TAMBLE page 5 BASIN ID: WQ SBUH METHODOLOGY TOTAL AREA..: 6.60 Acres RAINFALL TYPE..: USER' PRECIPITATION..: 1.28 inches TIME INTERVAL..: 10.00 min TIME OF CONC..: 10.10 min ABSTRACTION COEFF : 0.20 BASIN SUMMARY NAME: WATER QUALITY STORM BASEFLOWS : 0.00 cfs PERVIOUS AREA AREA..: 3.92 Acres CN..: 82.43 IMPERVIOUS AREA AREA..: • 2.68 Acres CN..: 98.00 TcReach - Sheet L: 250.00 ns:0.1500 p2yr: 2.00 s:0.2480 TcReach - Shallow L: 50.00 ks:27.00 s:0.1250 TcReach - Channel L: 500.00 kc:42.00 s:0.1120 PEAK RATE: 0.82 cfs VOL: 0.32 Ac -ft TIME: 480 min • &k0S 12/29/98 TUKWILA DECEMBER 29, 1998 GEOFF TAMBLE page 6 • HYDROGRAPH SUMMARY DESCRIPTION HYD NUM PEAK [CFS] TIME [Min] VOLUME [CF] AREA [Ac] 2 -YR EXISTING 1 0.308 490 12367 6.97 10 -YR EXISTING 2 0.980 480 26559 6.97 100 -YR EXISTING 3 2.066 480 47154 6.97 2 -YR DEVELOPED 4 1.709 480 26773 6.60 10 -YR DEVELOPED 5 2.979 480 44870 6.60 100 -YR DEVELOPED 6 4.651 480 68482 6.60 2 -YR BYPASS (LOTS 1 & 12) 7 0.120 480 1762 0.37 10 -YR BYPASS (LOTS 1 & 12) 8 0.198 480 2851 0.37 100 -YR BYPASS (LOTS 1 & 12) 9 0.298 480 4238 0.37 WATER QUALITY STORM 10 0.818 480 13825 6.60 2 -YR VAULT OUTFLOW 11 0.069 1470 9284 6.60 10 -YR VAULT OUTFLOW 12 0.640 780 27032 6.60 100 -YR VAULT OUTFLOW 13 1.495 540 50622 6.60 2 -YR OUTFLOW + BYPASS 14 0.151 480 11046 6.97 10 -YR OUTFLOW + BYPASS 15 0.674 780 29884 6.97 100 -YR OUTFLOW + BYPASS 16 1.570 540 54860 6.97 &kOS 12/29/98 TUKWILA DECEMBER 29, 1998 GEOFF TAMBLE page 7 STAGE STORAGE TABLE RECTANGULAR VAULT ID No. STOR1 Description: OPEN VAULT Length: 82.00 ft. Width: 61.00 ft. STAGE [FT] STORAGE [CF] STORAGE [Ac -FT] 67.10 0 0.0000 67.50 2001 0.0459 68.00 4502 0.1033 68.50 7003 0.1608 69.00 9504 0.2182 69.50 12005 0.2756 70.00 14506 0.3330 70.50 17007 0.3904 71.00 19508 0.4478 71.50 22009 0.5053 72.00 24510 0.5627 72.50 27011 0.6201 73.00 29512 0.6775 &kOS 12/29/98 TUKWILA DECEMBER 29, 1998 GEOFF TAMBLE page 8 STAGE DISCHARGE TABLE COMBINATION DISCHARGE ID No. CMB 1 Description: COMBINED ORIFACE/RISER Structure: RIS 1 Structure: Structure: DISI Structure: Structure: STAGE [FT] DISCHARGE [CFS] 67.10 0.0000 67.50 0.0194 68.00 0.0290 68.50 0.0362 69.00 0.0422 69.50 0.0474 70.00 0.0521 70.50 0.0564 71.00 0.0604 71.50 0.0642 72.00 1.4736 72.50 7.2414 73.00 9.4348 &kOS 12/29/98 TUKWILA DECEMBER 29, 1998 . GEOFF TAMBLE page 9 STAGE DISCHARGE TABLE MULTIPLE ORIFICE ID No. DIS1 Description: DISCHARGE ORIFACE Outlet Elev: 67.10 Elev: 65.10 ft Orifice Diameter: 1.0620 in. STAGE [FT] DISCHARGE [CFS] 67.10 0.0000 67.50 0.0194 68.00 0.0290 68.50 0.0362 69.00 0.0422 69.50 0.0474 70.00 0.0521 70.50 0.0564 71.00 0.0604 71.50 0.0642 72.00 0.0677 72.50 0.0711 73.00 0.0743 • • &kOS 12/29/98 TUKWILA DECEMBER 29, 1998 GEOFF TAMBLE page 10 STAGE DISCHARGE TABLE RISER DISCHARGE ID No. RIS1 Description: RISER Riser Diameter (in): 18.00 elev: 71.79 ft Weir Coefficient...: 3.782 height: 74.00 ft Orif Coefficient...: 9.739 increm: 0.10 ft STAGE [FT] DISCHARGE [CFS] 71.79 0.0000 71.80 0.0146 71.90 0.5330 72.00 1.4058 72.50 7.1702 73.00 9.3604 &kOS 12/29/98 TUKWILA DECEMBER 29, 1998 GEOFF TAMBLE page 11 LEVEL POOL TABLE SUMMARY Description Inflow Storage Discharge P. Stage Volume Outflow P. Time [CFS] ID ID [FT] [CF] [CFS] [Min] 2 -YR OUTFLOW 1.71 STOR CMB1 71.72 23125.85 0.069 1470 10 -YR OUTFLOW 2.98 STOR CMB1 71.90 24032.48 0.640 780 100 -YR OUTFLOW 4.65 STOR CMB1 72.00 24519.48 1.495 540 • rite c019k/ CO /Z DECEIVED T'ukwil'a PRD :Wetland Reconnaissance and Stream `Relocation Concepts; Prepared Triad .Associates Kirkland, Washington Contact: Doug Stapleton Jones`&Stokes Associates; Inc. Bellevue, Washington August 13, 1998 • Tukwila PRD Wetland Reconnaissance and Stream Relocation Concepts Prepared for: Triad Associates 11814 - 115th Avenue NE Kirkland, Washington 98034 Contact: Doug Stapleton • Prepared by: Jones & Stokes Associates, Inc. 2820 Northup Way, Suite 100 Bellevue, Washington 98004-1419 425/822-1077 August 13, 1998 Table of Contents Page Tukwila PRD Wetland Reconnaissance and Stream Relocation Concepts 1 SITE DESCRIPTION 1 Vegetation 1 Soils.3 Streas 3 WETLAND RECONNAISSANCE 5 STREAM CHANNEL ANALYSIS 6 Channel Characteristics 6 Streamflow and Channel Capacity 7 Aquatic Resources 8 RECOMMENDATIONS FOR CHANNEL RELOCATION 8 Alternative 1: Redefine Lot 7 Boundary (Do Not Relocate Stream A) 10 Alternative 2: .Relocate Stream A with "Best Fit to Existing Lot Boundary" 10 Alternative 3: Relocate Stream A with "Best Fit to Slope" 13 ADDITIONAL RECOMMENDATIONS 15 CITATIONS 16 Appendix A. City of Tukwila Stream Rating Forms 7RIAD/IUICWILA PRD 08/1Y98e • 1 List of Tables and Figures Page Table 1 Summary of Development Attributes and Issues by Alternative 9 Figure 1 Site Location Map 2 2 Existing Conditions 4 3 Alternative 1 11 4 Alternative 2 12 5 Alternative 3 14 TRUDTJKW1LA PRD 08/13198e 11 • Tukwila PRD Wetland Reconnaissance and Stream Relocation Concepts This report presents the results of a wetland reconnaissance and stream relocation assessment of the Tukwila PRD project site. The primary objectives were to (1) determine if any jurisdictional wetlands are present on the site, (2) assess stream channel conditions on and adjacent to the development site t� identify appropriate design elements for the relocation of one of the channels, and (3) prepare a conceptual stream relocation plan. Jones & Stokes Associates conducted a site visit on April 30, 1998. SITE DESCRIPTION The Tukwila PRD project site is a 5.4 -acre parcel located west of 40th Avenue South, east of Pacific Highway South (Hwy 99), and north of Southgate Park (S15, R4E, T23N) (Figure 1). The site slopes downward from west to east. The west quarter of the site slopes downward steeply from Hwy 99. Thereafter the slope becomes more gradual until it becomes nearly level adjacent to 40th Avenue South. The site is largely undeveloped although one residence and one abandoned house are located in the northeast portion of the site. Vegetation Vegetation on the project site consists of wooded areas in the west half of the site, partially wooded pastures in the central portion, and grassy areas associated with the residences in the east third of the site. A wooded area would be maintained as an open space greenbelt on the steepest slopes between the development and Hwy 99. Likewise, most of the existing buffers on the three streams on the site would be maintained. The wooded areas are dominated by4ig-leaf maple and red alder ranging from 12 to 30 inches in diameter. The shrub layer consists of both native and non-native species, including red elderberry, salmonberry, Indian plum, and occasional Hunalayan blackberry, Grecian laurel, willow, and Douglas' hawthorn. Groundcover species include sword fern, lady -fern, red raspberry, stinging nettle, bleeding heart, slender -stemmed waterleaf, and patches of English ivy. TRIAWNKWILA PRD 08/13/9& 1 , . , cas guar - 1",PY A i + 9411WWI "T" ' \`\ +1y� s r s,m go 1. ,,,mr..... e® sS � [�I 1 ff� en -71A A 4.111145/VIIIIIPE --- - - -- Na.i.' \‘t;. , - ..- 20Th t • 1 * 599 .',0Erief _ \ \ _R. \ , Iill trAl ; \. ‘ \ • EEE \\\ "D 11 I 3:snt SMINIM a, -.i den al ii2.11,11101MT SOK .ailta..11L ......__,,, 8• N. otzu /K • E MILNE A ON1411TI ik NEN Min 0. my 1.1001 l Willi l� NX 15 .i.. 7 ,:... '� I4 2, \�� s 16 » I Pro ect Site .ru. a - M' . �trr , u ie. CakIfOr maims F7 N _ Lo � i< roam M ) • a MX -. Erb g u U„.111111 I :, . 1 1P Einv i N Sr14 V xs i"I. ®`i rf It l ±• > I 1 r•�F . S} : A Ira ` 1' R -.41111111111,�]Jh4ILirflJI , auri - 1 III 558.LAO I Ebb��._._ ' •, dli�r� \ ^f..� ,23• ®� I� ii K; Al 1 .,..._ .\ .�.-moi _ '� iY 1``11�� IfO4IX TACOMA INTERNATIONAL AIRPORT su tea of COMM ,1 r K,41,---(ot 4 S 160TH Illr;itreS-. 4 •��1I!( Ilk , P ` '�C O GN!w7 59 1P} S r , Milli( , D 'I s l�lil” "° rA ,�� .x C yr J ..K, 7'° �V : �� oy _ N 1 s .�i_�l�■Vai� .. I � �. ^ SIRANOER EMIL' I i`�`I © ■ 98-114 08/11/98 Figure 1. Site Location Map 7RIAD/NKWILA PRD 08/13/9& 2 Soils Cohesive silt and clay -sized sediments underlay the coarse-textured glacial outwash soils, and are exposed intermittently in the streambeds. This clay -like subsoil is compact and platy in appearance, and appears to have resisted deep scour in these small channels. The coarse-textured banks (consisting of gravelly loam soils) above this compact layer are severely eroded and will probably continue to slough and contribute sediment indefinitely because of the depth of incision of the channels. The compact till is of particular concern because it is relatively impermeable and causes temporary perching of water in the coarse-grained soils above it during storm periods. This shallow groundwater is responsible for much of the landslide activity in the Seattle area during the fall and winter months. Therefore, changing the hydrologic and hydraulic characteristics of channels bedded in these materials requires caution. Streams The site lies within the 560 -acre Southgate Creek drainage basin, which drains into the Duwamish River. Upstream of a culvert under South 133rd Street, Southgate Creek branches into the North, Middle, and South Forks, draining an area 248 acres in size (Herrera Environmental Consultants 1996; KCM 1992). The project site lies approximately between and includes the North and Middle Forks of Southgate Creek. The Middle Fork Southgate Creek, discharging under Hwy 99 through a culvert, drains an area upslope of the highway as well as the south end of the project site, before it flows east under 40th Avenue South. A small tributary, referred to as Stream A, also discharges from a culvert under Hwy 99, and then flows easterly across a portion of Lot 7 to its confluence with the Middle Fork near the south site boundary, approximately 340 feet west of 40th Avenue South (Figure 2). The project proposal includes the relocation of Stream A and its confluence with the Middle Fork upslope so that Lot 7 can be adequately graded and prepared for residential development. The North Fork Southgate Creek crosses the northeast corner of the project site before it also drains east under 40th Avenue South. The Middle Fork and Stream A are both classified as Type 2 channels under the Tukwila sensitive areas ordinance primarily because of their wide, diverse, multi -canopied riparian corridor. The North Fork is a Type 3 channel because of its degraded condition and low -value riparian corridor. Rating forms are included in Appendix A. Type 2 streams require a 35 -foot buffer and Type 3 streams require a 15 -foot buffer. TRIAwr1KWILA PRD 3 OB/I3/98e • 1 1 1 ,1 1 1 1 I / I I 1 1 1 1 / 11 I t 1 1 I 1 1 1 1 1 t I 11 1 1 1 ►t \ 1\ 1 1 1 1 ► 1 1 1 y \ \ \ I 1 \ \ 1 \ \ \ 1 ►: \\\ \\I 1\`111 \\1 E--111 ►\\ `1` \`1 `\� I1 `11 1 1 I 1\ \ 1 . \\ 1 1\ 1 1 \ 1 1\ 1 \\ \\ 1\ 1 1 1 ; r \► ; \\ \\ \ I \ `\ \\\C--)11 \� ►1 11 `\ \ ( 0 �L;11 1 \ \ `\ 11 1\ 1 \ \ 1 \\ \\ `\ 1\ �►� 1`\ 1 ; 1; `' `► 1► \1 1 \\: \� ` `\ \\\1, \`. hI 0 i \ 1 1` 11 11 I 1 11 ` 1 \ \\ 11 \I �i`� \\ \ 1 1 1 I 1 1 \ \ U. 11 1 1 11 \ y , 1t I 1 1 ; \ 1 '\ 1 1 1\ 1 I 1 1 ► 1 \, \ `\ 1 1 1 1 1 1 1 \ \ I y t 11 1 1 \ \ 11 1 I 1 `\ }� 1 1 11 i 1 1 i \1 1 \ 1 ` t t 1 1 1 1 1 1 1 1 1 I I 11 1 1 1 1 1 1 ; 1 1 1 11 1 1 1 1 1 1 1 1 I 01 ^ i 1 1 1�1 1 ,/�. I H ) D t (0) It I I I 1� I1 1 / I / / / / / / // , //./ e1 \ .� \ 1 1 1 I I / / // 1 / / / 1 / / l / 1 / t / /�� 11 \N \� I / '.-- \ \ \ \� - •�.----- / \ \.,. \1 \\ •`-....--.\ \\ \ \ \ 1 \ 1 / • /' •fes •O` / -7::::....7.---17e. - :AD,:• ^\\�// \1•Ga \ \\ \ \\ \ 1 r\ \ \ \ •\ \ • \ VC \ \ 1 ` \ \ iii �\ I //// . \ 1 \\I 1\111\11 \ `1111 �• \ ' 11I\`\ 1\;\:111\1 \ / /. )j l / • • ` —\ � \ • 1 / / / j--/ '1-= - • \ • 20' 0 20' 40' Scale: 1" = 40' Legend: - --- Buffer Boundary Lot 7 Boundary oO Tree Q Stream �-- -) Stream Segment Figure 2: Existing Conditions TRIAD/IUKWILA PRD 08/IY98e 4 • • WETLAND RECONNAISSANCE Jones & Stokes Associates biologists surveyed the entire site. Areas that included plant species that are typically found in wetlands were examined for evidence of wetland hydrology and hydric soils. Areas examined include the upper slope on the west part of the site, the riparian area associated with the North Fork, and the yard and pasture west of the house immediately south of the North Fork. While some of these areas have some indications of being seasonally wet, none meet all three criteria for wetlands as defined in the 1987 U.S. Army Corps of Engineers Wetlands Delineation Manual (i.e., presence of wetland soils, vegetation, and hydrology). The upper slope is dominated by facultative and upland plant species (facultative species are adapted to grow in both wetlands and uplands). Within the wooded slope, soils were sampled near the south stream channels, near the center of the site, and near the north boundary. Soils sampled were very dark grayish brown (10YR 3/2) in the surface layer overlaying dark brown (10YR 3/3) to • dark yellowish brown (10YR 3/4 to 4/4) below. These soils had high chromas ranging from 2 to 4 and no mottles. Chromas of 3 or higher are indicators of upland soil conditions. A chroma of 2 without mottles is considered upland soil, while a chroma of 2 with mottles or a chroma of 1 with or without mottles is an indicator of hydric soils. Soils were well drained and not saturated at the time of the site visit. The riparian area associated with the North Fork is dominated by Himalayan blackberry, a plant that most often grows in uplands. Other species in the area include morning-glory, an upland plant, and common horsetail and purple nightshade, both facultative species. This area consists of deposition piles of sand eroded from upstream areas. The stream has cut multiple channels 3 to 4 feet deep amongst the deposits. Soils sampled were sands and were damp at the time of the site visit, but were not saturated and no mottles were present. Immediately upslope of the stream deposition areas, the soils were brown (10YR 5/3) loam with low soil moisture content. This area has only a marginally wetland plant community and lacks hydric soils. The sandy soils are too well -drained to support wetland hydrology. The gently sloping area behind the house south of the North Fork was examined due to the presence of creeping buttercup, a species typically found in wetlands. Other plant species in the yard include ornamental trees and shrubs, Himalayan blackberry, dandelion, and Kentucky fescue, all of which are typically non -wetland plants. Soils were damp but not saturated at the time of the site visit. The surface layer of soil to 14 inches was very dark brown loam (10YR 2/2) but lacked mottles. Below 14 inches the soil was dark grayish, brown (10YR 4/2) gravelly loam with dark yellowish brown (10YR 3/6) mottles. This indicates that the lower soil layer is seasonally saturated with subsurface runoff probably perched above the till layer. However, saturation must occur within the upper 12 inches to create wetland conditions. Therefore, this area does not meet the criteria for a wetland. Further upslope is a pasture dominated primarily by upland species including apple trees, Himalayan blackberry, dandelion, and vetch, and includes one Douglas' fir tree. Wetland species present included creeping buttercup, and two facultative species, velvet grass and northern bentgrass. The soils sampled were very dark brown (10YR 2/2) gravelly loams with no mottles. TRIADRUKWILA PRD 08/13/98e 5 • • At the upper edge of the pasture is a narrow bench perhaps 8 feet wide that was wetter than the surrounding slopes. The vegetation consisted of a mix of upland and wetland species. Upland species included Himalayan blackberry, Indian plum, sword fern, Kentucky fescue, and dandelion; wetland species included red alder, Douglas' hawthorn, creeping buttercup, Sitka willow, and large - leaved avens. Soils were saturated at 10 inches. Soils were very dark grayish brown (10YR 3/2) gravelly loam without mottles to 12 inches. Below this surface layer, a few dark yellowish brown (10YR 4/4) mottles were observed. The lack of mottles in the upper layer indicates that while water is present within the surface layer, it drains through the soil quickly enough that it does not become anaerobic, which is the key factor to creating wetland conditions. Therefore, this area also fails to meet the criteria for a wetland. STREAM CHANNEL ANALYSIS The second project objective is to provide recommendations for relocating the confluence of Stream A with the Middle Fork Southgate Creek in order to allow room to regrade Lot 7 for development. Jones & Stokes Associates evaluated the two streams to identify issues and potential locations for the new stream segment and confluence. Channel Characteristics Stream A flows 270 feet at an average gradient of 25% from its outlet at a 24 -inch concrete culvert under Pacific Highway South to its existing confluence with the Noddle Fork. The apparent bankfull channel width ranges from approximately 3 to 5 feet, and the channel bed is incised 2 to 6 feet below the surrounding landform. The channel has cut down fairly rapidly through the glacially - derived, gravelly-cobbly loam soils to its current profile, as indicated by unvegetated, nearly vertical lower banks (approximately 2 feet high), a low width -depth ratio, and the lack of significant pools. Bed material ranges from sand to small boulders; the median particle size is estimated to be that of small or large cobbles (2.5 to 10 inches). The Middle Fork Southgate Creek flows 230 feet at a gradient of about 20% adjacent to the project site and upstream of its existing confluence with Stream A. The channel has a top width of 6 to 8 feet and is incised 2 to 8 feet in the surrounding landform. As with Stream A, evidence suggests the channel cut fairly rapidly downntbrough the coarse-textured soils. Bed material ranges from sand to small boulders; the median particle size is estimated to be that of small or large cobbles (2.5 to 10 inches). Downslope of the confluence with Stream A, the Middle Fork decreases to a gradient of approximately 10% and a width of 1.5 feet as it flows across residential property into a 24 -inch corrugated metal pipe that drains east under 40th Avenue South. 7RIAD/RJKWILA PRD 0V131%e 6 Streamflow and Channel Capacity Peak streamflow in these channels is probably torrential during heavy rain events as evidenced in the raw, gullied appearance of short sections of these channels. However, at the time of Jones & Stokes Associates' visit, the streams were flowing at a combined rate of <0.1 cubic feet per second (cfs) downstream of the confluence, and Stream A was nearly dry. Flows were estimated to be only slightly higher during a site visit by Jones & Stokes Associates in March 1998. Stream A is therefore assumed to be intermittent. The Middle Fork may also flow intermittently during dry summer months. Herrera Environmental Consultants (1996) suggests base flows in the Noddle Fork are maintained by springs on the steep slope west of Hwy 99, but no springs were observed during our site visit. Despite the apparently large bankfull or top widths of both the Nfiddle Fork and Stream A described above, these streams are believed to be smaller than the current channel dimensions would indicate. As a result, channel widths at the ordinary high water marks (OHWM) are probably much less than the estimated bankfull widths, perhaps on the order of 1 to 2 feet for Stream A, and 3 to 4 feet for the Middle Fork. Vegetative indicators of the OHWM are generally absent due to the difficulty of revegetating raw, oversteepened banks. Likewise, continued bank sloughing masks many of the indicators of fluvial scour, although some fine sediment deposition in the channels indicates that flows are not typically high. In addition, the smaller size and increased stability of the Nfiddle Fork channel as it flows across the yard of a residence to 40th Avenue South suggest that peak discharges in the hillslope channel segments do not approach the potential bankfull discharge. As a result, we can assume that only a small portion of the cross-sectional areas of the upper channels experiences streamflow. There are several potential reasons behind the discrepancy between small streamflows and oversized channel dimensions in the upper stream segments. Undoubtedly, higher streamflow velocities on the steeper slopes in highly erodible soils caused rapid downcutting and undermining of channel sideslopes, resulting in channels with larger cross-sectional areas relative to typical streamflows. Anecdotal information from area residents suggests there has been a reduction in flow volume as a result of streamflow diversions. Markedly lower flows during the last year or two may be the result of a cable trench which crossed the streams upstream of Pacific Highway South and may have inadvertently diverted some of the water (Reeves pers. comm.). Another possibility is a reduction in source area resulting in a smaller volume available for runoff. KCM (1986) reports a watershed area of the North and Middle Forks of Southgate Creek of over 100 acres upstream of the confluence with the South Fork. Herrera Environmental Consultants (1996) accounts for only about 36 acres of watershed area for the North and Middle Forks upstream of 40th Avenue South, but indicates that storm drain mapping west (upslope) of Hwy 99 is incomplete. Development of the storm drain network in this area over the past 12 years may have significantly reduced the size of the Middle Fork watershed. 7RIAD/TUKWILA PRD 08/13/98e 7 Aquatic Resources Water quality is degraded in most reaches of the Southgate Creek network because of industrial and other urban developments. Fish habitat in the watershed could support an anadromous fishery, but is of poor quality due to severe sediment deposition. In addition to the loss of fish habitat, sediment plugs culverts, increases flooding, and increases maintenance costs. The City of Tukwila has begun efforts to improve stormwater quality (Herrera Environmental Consultants 1996) and fish habitat (KCM 1992). Although Jones & Stokes Associates did not survey for fish, the stream's high gradient, lack of physical structure, and intermittent flows in Stream A make it unsuitable for fish. Similarly, fish habitat in the Middle Fork Southgate Creek adjacent to the project site is negligible, and fish are unlikely to use this segment of the stream. A few hardy individuals may survive if larger, deeper pools exist upstream of the site and downstream of Pacific Highway South. However, fish that have been stocked in a small pool on a residential lot manually supplied with water from the Middle Fork reportedly die after the first major storm event each season (Herrera Environmental Consultants 1996). RECOMVIENDATIONS FOR CHANNEL RELOCATION The project proposal includes the relocation of Stream A to avoid Lot 7. This requires moving its confluence with the Middle Fork Southgate Creek upslope and generates several issues: • Where is a stable site for a new confluence? • Can the Mddle Fork handle the additional flow from Stream A between the existing and proposed confluences? • How should the new channel segment be constructed to adequately convey flow, minimize site disturbance, and maintain slope stability? • How can costs to the developer be minimized? Three alternatives were evaluated, inclgding (1) redefining the Lot 7 boundary, (2) relocating Stream A with best fit to the existing Lot 7 boundary, and (3) relocating Stream A with best fit to the hillslope. The alternatives and recommendations provided are based on the following assumptions: • Each of the alternatives discussed below is viable from a landscape point -of -view. Table 1 summarizes some of the key features and issues associated with each alternative. TRIAD/RIKWILA PRD O8/1Y98e Table 1. Summary of Development Attributes and Issues by Alternative Attribute/Issue Alternative 1 Alternative 2 Alternative 3 Theme do not relocate Stream A; maximize lot modification relocate Stream A to avoid lot modification (best fit to lot) relocate Stream A with minor lot modifications (best fit to slope) Modifications to current proposal for Lot 7 boundary maximized; shift lot boundary to coincide with boundary of existing Stream A buffer, net loss of 0.02 acres avoided through stream location minor, small upslope decreases offset by expanded frontage on proposed road; irregular lot but no net loss of lot acreage Cutbank excavation avoided assumes steeper, higher cutbank which requires some terracing and revegetation for stability assumes minor to moderate stabilization of cutbank is required Slope stability issues involving clayey soils avoided yes; unknown extent yes; unknown extent Cost to developer no costs associated with modification of stream buffer, but this savings must be weighed against lost revenues on reduced acreage greatest cost cost less than Alternative 2 Stable site for confluence not applicable yes yes Capacity of Middle Fork for combined flow of both channels not applicable probably; requires hydrologic/hydraulic modeling with final design features probably; requires hydrologic/hydraulic modeling with final design features Wetlands impacted none none none tRUW/IUKWILA PRD 9 �� • • • The current channel dimensions of the Middle Fork and Stream A are larger than required to contain peak flows for reasons which may include a reduction in source volume, a reduction in source area, historic peak flows during a period of channel downcutting, or other reasons unknown at this time. • Site grading requirements (especially for Lot 7) can be met by matching recontoured areas with the existing slopes within the Type 2 stream buffer of the relocated stream (i.e., regrading Lot 7 will avoid disturbance to the buffer). Alternative 1: Redefine Lot 7 Boundary (Do Not Relocate Stream A) The existing channel location does not bisect Lot 7 to the extent originally thought—only about 5 linear feet of the stream actually lie in the south corner of the lot. However, since the City of Tukwila sensitive areas ordinance requires a 35 -foot buffer on. Stream A (a Type 2 stream), the buffer becomes the issue which precludes site development. If grading plans for site development do not require it, relocation of Stream A can be avoided by simply modifying the boundary of Lot 7 to coincide with the stream buffer (Figure 3). Relocating the Lot 7 boundary results in a 12% reduction in lot area from approximately 6,166 square feet (0.14 acres) to 5,400 square feet (0.12 acres). This alternative assumes that site development can be shown to not affect the buffer, thus avoiding the 10 -foot residential setback requirement. The reduced lot is 125 square feet below the minimum lot area of 5,525 square feet shown on Triad site plans, but discussions with City of Tukwila personnel indicated a willingness to waive minimum lot size requirements (Schulz pers. comm.). This alternative avoids the cost of stream relocation, but this savings must be weighed reduced property values. Tukwila's sensitive areas ordinance permits the reduction of buffer requirements by half where the channel gradient is less than 20% and compensatory practices are used such as planting to mitigate the impacts of development and improve the residual buffer. The portion of Stream A whose buffer area conflicts with the lot has a 24% gradient, so a mitigation approach is not possible. The City does not consider any other buffer averaging techniques (Schulz pers. comm.). Alternative 2: Relocate Stream A with "Best Fit to Existing Lot Boundary" In order for Lot 7 to lie entirely outside the buffer of Stream A, the stream centerline should be constructed as shown at segments a, b, and c in Figure 4. This alignment loses 20 feet of elevation over 80 linear feet for an average bed gradient of 25.5%. A maximum gradient of 45% would occur over 21 feet as segment c traverses down the incised side slope of the Middle Fork Southgate Creek. There are two curves in the new alignment, one to the right at approximately 70 degrees, and one to the left at about 15 degrees. TRIAD/IUKwILA PRD Os/IY98e 10 \ t \ E TI G \ \\\ \\1 + \ \ , t \ 11 Al \ \ \ t +' 1 \ \+ \ \ + i 11 1 1 1 1\ \\ 1 1 1 11 it \\I `+\ \ It • ► t l 1 +\ •' L 1 \ + \\ 1\ 1 `\ \\\ _` \ \ \ \ / 11 1 1 ! 1 r 1l \ /// // // i // ///// �/ /// 1 11\ r / �/ \\� 0' I 1 11 : ‘i t 1 \11 1 ! l ` \ \ // ,L \ \ Al11 • \ 11 `11\111\\ \+1\'�!/\\ \\\\ \\ \\ l\\\‘1\ •-- \....... \\ It\�, \ 1 \\ \ .... � \ \ .� N. \ AA \ \t (\11 '1\\\\�\ � • \\\\\y \� j/ + a\1\ +\\ \\\,:".A.\ \ \ `\ \\/ \1 i/ �/ / ; \ \ 1 1 \1\ \\ + 1 T \ \ 1 •�) i ( / 1 \I'R \\\\\ i ` \\ 1 1 \ 11 1 `\ \\ \\\ \ \\ \\ \\ 1y 11\\\` DO �� \\+1\ 1 / I 1` \•\;_ U \+\ �1\`\ 1 / I I , / /I j, r 1 I 1 / / ) ! 1 1 ! l e /// r / C•F `-� \ \ \ \\ •' / rl /;�.�=��'4 `.`\\ `\\\� \1/ -Z —� • �\�/ •moi 1; \ \' - // // / r�L —V— /// _� .�... \` • • 1 1 1 I11•• • • Scale: 1" = 40' Legend: - - - Buffer Boundary Lot 7 Boundary • Stream �—. •• —� Stream Segment Figure 3: Alternative 1 TRIAD/IUKWILA PRD 08JIY98e 11 ,\ 1\ �\ (pit 1 , 1 \ 1 1 1 1 ! 1 • 1 , + ) \ \ \,`� 1 \ \ 1 / I t I I 1 1 1 I 1 1 1 \\` + ; 1 ; j1 1 1 1 1 1 1 I I I 1 1 I 1 1 1 I 1 \ 1 \ t\ 1 1 ; 1 1 1 1 \ I i \ I 1 1 i . 1 1 \ 1 1 1 \ 1\ 1\ \ \ 1 1 *PI* \ `1 1 (p1 \ �, \ \•%1\1 \1 \ \ \ 11 \\ \\ 1\ \ \` \ 1 1 1 t i \, \ b:1 \ ,0 �� \ \ , , \ \ 1 \ 4,r>r \ 1 \ t , \ \ 1 1 \ \ , \ 1 1 \ \ 1�C 1 1 \ , t 40 ►'���,�'� \\ 1 q� , \ 1 1 1 \ 1 \ 1 1 1 \ ` 1 1 1 , \ , \ 11 1 �1/ 1 1 1 1 1 \ t' 1 t 1 1 1 1 \o\ \, \ \ �\\1,111'\;\111, ,1 \\\ -� 1 i \ \ 1t 1` ',1 '\1 1\\ \\, \\ X. t!I 0 1 1 1 i 1 \ 1` \ \\\ 1 t 11 \1 I 1 t 1 \ 1 `; \\ i �•;� t t \ \ \\ \1 1 I I 1 t 1 1 \ "",�` 1 \ 1 1 1 1 1 111 \ \ \ � 1 \1 11 1 , 1 1 t 1 \ 1 1 1 \\ 1 1 1! ►.� ;1 I 1 1 1 1 \ 1 { I 1 1 l \\ 1,11\ ` 11 \\ i 1 (lir/ 1 1 11 ‘11\ 1%1\ 11 111 1 ` `1 til \\ \1 \\ 11 11 \, 1;\ 1 1 ! 1 1 \1 1 1 \ 1 1 t 1. \ 1 \ 1 1 1, 1 1 1y \1 11 i 1 '; 11 •a 1 1t // \\\ \1 \ \\ \\\ `1 .. 11 1 � 1 11 11 11 \\ 1 • 1 1 \\ 1 1 1 1 ' 1 1 1 1 1 1 ( 1 \f O 1 \ 1 1 \ ,/ \\ 1 ; \1 1 1 1 , • ; 1 s 1 1 1 /1 /1 1/ 11� / / �o / , I r is 1 m , 1 , 1 0 ! 1 l ! / / ,1 1 \r // 1 r 11 1 ri r; 1 I '� r 11_1' l l 1 ��; ;1 1/'// / 11/11 1111 11 1 t I r �, !,-�'_/��` 1 1 �, // // / / J / / 1 I r l 1 / I i I 1----f \\ \ 11 l/ �: / / / / / J / 1 i / / �• \\ 1 1 11 \ // // // / / 1 • / 1 V/ /i/�---.11:-.1,11:21.1(;!:: �� \ \ \ \11 / / / // / / ! /!/ / /1// / 1 / ///„.• \ /\` \ \ ; `11 1 1/// 1/• �/ // \ \ i it1 \ \�► \1.1 , lit�l 1 t l \ ;('p -j\ \\\L \\ \ •\. is evGl�^L. /-_r-- 11 1{ \11 1 \ 1 \ \ t \\\ \ �� / \ \ '` st 1/ /� - \1\1\t:\ :tr \\1\:11\ 1\1 1 1�"% `y \\ \ \\ \\ \\ 1\ �V, �..."1;";/,.../.:#/•1 � _/e•--� 1 \ 111\\� i1 �/� �J /_i\ O,\\\•\\\ \`\�\ //!/� ////�/t _ 4` �` -�. • • • __ ........... . . _. T\I\�1 111\ \ \•\• • • \ ♦ \\ \\ \\ t / �= /_ _ ___ 1111 \\\ \•1•X \ \1 1 \ \-.\1. /* 1._11 ` 1 1 1/1 /! i /) `- ` '. - _.�'... \1\I1 1 11 •r-- \ 1 \ \\ \ 1 , 1 / ti, I / / `\ _ i1•4 • 1 rt‘ 1\\ \\\1 \ \\ \ 1 1 1 1 I/lt �� -' -.l ....... • \\‘‘1%\.. \� t\\1� \\ 1 11y 1 ) 1 j �11J,�� ��r ---', ````\\ `,`\ �- 11 / 1 -;^\ •` \\ \1111` \ % /l I ( • i ` 1 1 1 1 t 1 01 ' •\ 0 \\ \1 ..�i 20' 0 20' 40' Scale: 1" = 40' \ • 1• • • \ Legend: mum mil Buffer Boundary ` " Lot 7 Boundary Stream ,a, -) Stream Segment Tree Figure 4: Alternative 2 TRIADVRIKWILA PRD OR/1398c 12 • • This alternative relocates Stream A as far upslope as necessary to avoid a conflict between the stream buffer and Lot 7. In doing so the channel location cuts across the toe of a steep incline in the hillslope profile. Channel excavation would generate a steep cutbank on the right bank (upslope side) of segment b that could require terracing or other methods of recontouring in order to stabilize the slope. The stability of the proposed confluence with the Middle Fork is aided by large cobble and small boulder substrate. However, localized pockets of gravel in the bed and coarse, unconsolidated sediments in the streambanks will require construction of a protective apron at and downstream of the confluence to withstand the additional stream energy. In addition, the right bank of the Middle Fork (opposite Stream A) will require reinforcement. The angle of the confluence should be less than 70 degrees to further reduce scour and deposition processes at the confluence. Given the previously described assumption that both Stream A and the Middle Fork have low flows relative to channel size, we suspect that the 136 feet of the M ddle Fork channel between the existing and proposed confluences has sufficient capacity to handle the additional streamflow without requiring additional erosion control measures to maintain or improve channel stability. This would be confirmed with the implementation of hydraulic modeling in conjunction with final design criteria. Cross-sectional area of the finished channel, based on field estimates obtained upstream on Stream A, should be approximately 5 square feet. Excavation of the channel cross-section would have to exceed 5 square feet in order to accommodate stability and erosion control features necessary to maintain the channel. Also, cross-sectional area may be modified pending completion of an open channel water surface profile which incorporates both the channel roughness of these final design features and a design storm event involving refined watershed area estimates (see "Streamflow and Channel Capacity" above). Channel stability and erosion control features may include bank stabilization on bends, terraced cut bank on segment b, armoring of the entire streambed, installation of a clay liner or geotextile fabric, excavation to the clay layer and embedding control into this layer, placing log weirs in the channel, utilization of a half 48 -inch -diameter culvert with baffles on segment c, installation of an apron and log weir downstream of the new confluence, and armoring of the right streambank on the Middle Fork at the new confluence. Alternative 3: Relocate Stream A with "Best Fit to Slope" This alternative is quite similar to Alternative 2, but generates a "better fit" of the channel to the hillslope. If the stream centerline is constructed as shown in Figure 5, the alignment would lose 20 feet of elevation head over 70 linear feet for an average bed gradient of 28.6%. A maximum gradient of 45% would still occur over 21 feet as the channel traverses down the incised side slope of the Middle Fork Southgate Creek. There are two curves in this alignment, one to the right at approximately 70 degrees, and one to the left at about 30 degrees. TRIAD/IUKWILA PRD OR/ IY98e 13 \ 0 1 • \ \ 1 1 1 j 1 �I 1 1 1 I 1 I I 1 1 i 1 1 1 1 ' i 1 \ 1 I \ \ \ 1 \ \ 1 I \\\ \\ 11\ \\\ \\\ •\1 11 \ \ 1 1 \ \ . 1 1 \ 1 \1 \ \ 1 1 1\ \; I\ \ 1\ \\ 1 \\ rC \1 1 \\ \\ 11 \ \ \\ \ \ 111 11 \\\, t\ G0 \1 1\ \ \' 1 \1 \,` 1 \ 1 t 1 1 1 1 \\ 1, I 1 1 O\i \\ 1 1 1 I 1 1 1 1 1 \ 1 1 I 1 I 1 1 I 1 11 1 1 1 1 1 1 1 1 1 1 I 0 \ ♦\ \\ \ \ 1 \ 1 \ O{ • \\ 1 I /! i / li /i /,---- - \ =__`�/\ :/ ,r' •`\ 00_ —� _� \�-_♦ -•• -•�� \ ! i .. •\ \ \ \\� *A\ \ 1 1 j/ / - - ��`�` %\ • ♦�1♦\\\ \\ `` \\ 0v�.:%:i' ;/•__�_ I`--1,\ \ `\\ \\ \\ /� 1 � /r/ • ice --�� - _ - --✓� \\\, \\a `\ \\ \\ \ O `� . \ //, //..-'' _ -,`- \ , .\\ ,..,..,\\ „ \ ., N, A ii il, i'l / 1/1/1.1-',- -- • -- • - - - "-- • 11\\! 1 t •/ i%/ // 7 0 20' /. // / / / , 1 t 1\ • 20' 40' Scale: 1" = 40' Legend: IMM 411•1•11 Buffer Boundary ` " Lot 7 Boundary Oo Tree Stream E- .a. -) Stream Segment Figure 5: Alternative 3 TRIADRUKWILA PRD Oe/IY98e 14 • This alignment differs from Alternative 2 in that it follows more closely a very narrow bench or break in the hillslope gradient. As a consequence, it would require smaller -angle channel bends and a somewhat smaller cut bank on the upslope side of segment b. Although the overall gradient is about 3% steeper, this is more than compensated by even small reductions in the amount of excavation and the sharpness of the channel bends. However, in creating this alignment, the Type 2 stream buffer would occupy about 27 square feet of the southernmost corner of the current proposed Lot 7. This area could be more than compensated (and the lot enlarged) by extending the lot near the eastern corner toward the buffer of the Middle Fork Southgate Creek, as shown in Figure 3. Cross-sectional area recommendations, considerations for the stability of the Middle Fork at and downstream of the confluence, and recommendations for channel stability and erosion control features remain the same as for Alternative 2. ADDITIONAL RECOMMENDATIONS • A geotechnical review of the site should be conducted to consider the extent and effect of the soil structure (coarse, unconsolidated fill material over compacted silty clay) on site development (grading, foundation design, etc.). Final site design for any work involving the relocation of Stream A should also pass a geotechnical inspection prior to implementation. • An hydraulic analysis model for Stream A and the Middle Fork Southgate Creek should be completed once watershed areas are reviewed and refined and channel stability design elements are decided. The model should confirm the adequacy of the capacities of the new Stream A design and the Middle Fork downstream of the proposed confluence. • Herrera Environmental Consultants (1996) reports that springs in the vicinity of the site maintain base flow in the streams. We did not observe any springs contributing to Stream A in the field. However, to protect against continued flow, erosion, or structural damage associated with springs feeding the remnant Stream A channel (should it be relocated as in Alternatives 2 or 3 above), the developer should be prepared to address potential drainage problems in the remnant channel. For example, if the remnant channel continues to collect water from seeps during the rainy season, a perforated pipe may need to be installed prior to backfilling to prevent erosion of the backfill soil into the Middle Fork Southgate Creek. ThereforLe,,we recommend that, if the channel is to be backfilled, the developer wait at least one wet season in order to observe the extent of water collection in the channel. TR1AD/TUKWILA PRD OB/1 Y9& 15 CITATIONS Herrera Environmental Consultants. 1996. Fostoria Basin Stormwater Quality Management Plan. Prepared for City of Tukwila Department of Public Works. March 1996. KCM. See Kramer, Chin, & Mayo, Inc. Kramer, Chin, & Mayo, Inc. 1992. Southgate Creek Fish Enhancement Project Preliminary Design Report. City of Tukwila Department of Public Works. July 1992. . 1986. Fostoria Basin Drainage Study. City of Tukwila. May 1986. Reeves, Mark. Triad Associates, Kirkland, WA. April 30, 1998 - field meeting. Schulz, Gary. Urban Environmentalist. City of Tukwila Department of Community Development, Tukwila, WA. May 5, 1998 - telephone conversation. TRUD/NKWILA PRD 08A v98e 16 City of Tukwila Stream Rating Form Stream Segment Name Middle Fork Southgate Creek Stream Segment Description Channel whose location is unchanged; segment includes existing and proposed confluence with Stream A Overall Stream Segment Type Type 2 Parameter Value Subscore Score Left Bank Right Bank INSTREAM ELEMENTS Width (OHWM) 4 2 2 2 Capacity Ample 3 3 3 Stability Obvious scour -1 -1 -1 Fish use No fish 0 0 0 Fish habitat N/A 0 0 0 SUBTOTAL INSTREAM 4 4 CORRIDOR FEATURES Corridor quality 9 9 Width of unmaintained vegetation from OHWM LB 100 3 RB 100 3 Vegetation diversity LB Diverse, multi -layered 3 RB Diverse, multi -layered 3 Barrier function (% dense) 2 2 LB 75 — RB 75 — Surrounding land use -1 -1 LB Urban, residential — RB Urban, residential — SUBTOTAL CORRIDOR 10 10 ENHANCEMENT POTENTIAL (noted by "A7.) TOTAL SCORE, SEGMENT 14 14 WATERCOURSE TYPE, BANK Type 2 Type 2 Jones & Stokes Associates STRMRATE.WK4 05/05/98 City of Tukwila Stream Rating Form Stream Segment Name Stream A Stream Segment Description Channel Proposed for Relocation near Lot 7 Overall Stream Segment Type Type 2 Parameter Value Subscore Score Left Bank Right Bank INSTREAM ELEMENTS Width (OHWM) 2 2 2 2 Capacity Ample 3 3 3 Stability Obvious scour -1 -1 -1 Fish use No fish 0 0 0 Fish habitat N/A 0 0 0 SUBTOTAL INSTREAM 4 4 CORRIDOR FEATURES Corridor quality 9 9 Widthof unmaintained vegetation from OHWM LB 100 3 RB 100 3 Vegetation diversity LB Diverse, multi -layered 3 RB Diverse, multi -layered 3 Barrier function (% dense) 2 2 LB 75 — RB 75 — Surrounding land use -1 -1 LB Urban, residential — RB Urban, residential — SUBTOTAL CORRIDOR 10 10 ENHANCEMENT POTENTIAL (noted by "A") L w TOTAL SCORE, SEGMENT 14 14 WATERCOURSE TYPE, BANK Type 2 Type 2 Jones & Stokes Associates STRMRATE.WK4 05/05/98 City of Tukwila Stream Rating Form Stream Segment Name North Fork Southgate Creek Stream Segment Description Channel adjacent to log cabin on 40th Ave S Overall Stream Segment Type Type 3 Parameter Value Subscore Score Left Bank Right Bank INSTREAM ELEMENTS Width (OHWM) 3 2 2 2 Capacity Insufficient 0 0 0 Stability Obvious scour -1 -1 -1 Fish use No fish 0 0 0 Fish habitat N/A 0 0 0 SUBTOTAL INSTREAM 1 1 CORRIDOR FEATURES Corridor quality 1 1 Width of unmaintained vegetation from OHWM LB 15 1 RB 5 1 Vegetation diversity LB Not diverse, one -layered 1 RB Not diverse, one -layered 1 Barrier function (% dense) 3 3 LB 99 — RB 99 - Surrounding land use -1 -1 LB Urban, residential — RB Urban, residential — SUBTOTAL CORRIDOR 3 3 ENHANCEMENT POTENTIAL (noted by "A") A A TOTAL SCORE, SEGMENT 4A 4A WATERCOURSE TYPE, BANK Type 3 Type 3 Jones & Stokes Associates STRMRATE.WK4 05/05/98 August 13, 1998 Mr. Doug Stapleton Triad Associates 11814 115th Ave NE Kirkland, WA 98034 SUBJECT: Tukwila PRD Wetland and Stream Reports Dear Doug: RECEIVED MAR 2 5 1999 CUNITY DENITY EPM Attached are the two reports for the Tukwila PRD project, Tukwila PRD Wetland Reconnaissance and Stream Relocation Concepts and Tukwila PRD North Fork Southgate Creek Restoration. These documents provide baseline information from our site visit and alternatives and recommendations for site improvements that will facilitate site development. Thank you for the opportunity to work with you. Please call if you have any questions or we may be of further assistance. Sincerely, �rna..G1 Cama -ate Sarah Cassatt Project Manager Jones & Stokes Associates, Inc. 2820 Northup Way, Suite 100 • Bellevue, WA 98004-1419 • Fax 425/822-1079.425/822-1077 August 13, 1998 Mr. Doug Stapleton Triad Associates 11814 - 115th Avenue NE Kirkland, WA 98034 SUBJECT: Tukwila PRD North Fork Southgate Creek Restoration Dear Doug: This letter presents our observations of channel conditions along the North Fork of Southgate Creek, on property proposed for development by your client on 40th Avenue South in Tukwila. As you requested, this information is being presented separate from a report addressing wetlands and the relocation of a stream channel on the project site. We visited the site on April 30, 1998 to assess channel conditions and identify restoration opportunities. Site Description Upstream of the development property, the North Fork discharges under SR 99, flowing easterly down gradients of 10% to more than 20%. It then flows for 250 feet across the northwest corner of the property—from south to southeast to east around an abandoned log house. Channel gradient ranges from 7.5% to 10%, but drops to 5% just upstream of where the stream splits into two channels immediately southwest of the log house. The two channels reconverge about 65 feet downstream, then flow another 35 feet before passing under 40th Avenue South in a 24 inch concrete culvert. Channel width is approximately 4 feet. Substrate consists of sand, gravel, and patches of fine organic debris. The stream offers little or no fish habitat because of the consistent gradient, fine bed material, and few, small pools. Vegetation near the channel is dominated by dense blackberry thickets. Channel Condition and Discussion The North Fork is in poor condition on the development property. The landform on the site, an alluvial fan, results from the deposition of sediments possibly associated with a historic hillslope slump and subsequent storm events. The channel split is the result of streamflow directed around debris deposited at the slope break. The left (north) channel has down -cut 5 feet through the debris deposit. The right (south) channel is deeply undercutting its right bank, placing a fence and the Jones & Stokes Associates, Inc. 2820 Northup Way, Suite 100 • Bellevue, WA 98004-1419 • Fax 425/822-1079.425/822-1077 Mr. Doug Stapleton August 13, 1998 Page 2 backyard of another house at risk of loss. Sediment eroded by the stream at this site is transported downstream where it impacts sites with greater potential aquatic habitat lower on Southgate Creek. The North Fork Southgate Creek is a Type 3 channel under the City of Tukwila's Sensitive Areas Ordinance (see attached rating form). Its degraded condition and low value riparian corridor are the primary factors behind its low rating. As a Type 3 stream, a 15 -foot buffer is required to maintain water quality. KCM (1992) and Herrera (1996) identified the North Fork Southgate Creek as one of the primary sources of sediment in the Southgate Creek watershed. KCM (1992) identified the North Fork immediately above 40th Avenue South as a potential site for a stormwater detention pond. Herrera (1996) recommends both the re -installation of a sediment trap and the stabilization of the channel as stormwater quality improvement projects. Recommendations for Site Restoration In light of the previously identified need for stabilization and the mitigation of existing downstream impacts, channel modifications made to facilitate residential development and improve property values can also be designed to provide multiple other benefits for fish, flood control, and protection of private and public property. It is important to recognize, however, that the site is naturally prone to the deposition of sediment and debris which may become obstructions and flow deflectors. Long-term periodic maintenance is likely to be needed to provide continued flow conveyance or protection of in -channel structures. Alternatives to restoration of the North Fork may include the following approaches. • Construct a narrow detention pond where the channel now splits into two (where deposition occurs). A gated weir or vertical standpipes of different elevations and diameters could be used to maintain the pond during both high- and low -flow periods. ■ Excavate a new channel approximately down the center of the two split channels, then fill in the existing channels. • Excavate a new channel as above, and shorten the 150 feet of channel on the property upstream of the split by straightening the channel. Re -locating the upstream channel in this fashion would increase the gradient and could increase the sediment transport capacity of the stream, reducing the potential for sediment deposition on the site. Jones & Stokes Associates, Inc. 2820 Northup Way, Suite 100 • Bellevue, WA 98004-1419 • Fax 425/822-1079.425/822-1077 • • Mr. Doug Stapleton August 13, 1998 Page 3 The second and third alternatives would require hydraulic modeling to verify that stream energy can be maintained to minimize sediment deposition. The channel would require armoring and bank reinforcement to maintain channel stability. All alternatives would require further design and coordination with the City of Tukwila. Jones & Stokes Associates has been pleased to provide this brief review of the North Fork Southgate Creek. Please call if you have questions or if we can help you further develop and refine development alternatives on your client's property. :lr Attachments TRIAD/IUKWILA PRD 08/13/98u Sincerely, ikaka b. 06-ecty-Qt Michael Wolanek Hydrologist Jones & Stokes Associates, Inc. 2820 NoNwp Way, Suite 100 • Bellevue, WA 980041419 • Fax 425/822-1079.425/822-1077 \ \\ 1 \ \ \ \ I----1- ---- JL LIGAL DEBCRPTMW \ I =r,IRA. 11\ u"`% yW10iOWMvrOrwmaoua ?COI1 IOIL!IS VC A/344? 6111. M Fd. MCI weer mom Jfl5 m:.vi VC SOU go... P0•07 R1 MT to A ran N Mm uaw-.1 yam' oma aMO M10 ' /110011/001 2a aro..r un g Mr• .:: 0/ MM.. VOW •411012 LI •214/ .gc1MOcaEweawm /6e ALM VO �...rmJ,.RMIT •Ceir 02 100 11 A 1101•03 LI r. 100 01•00 Mall EOM 0.1.1. WIT ILlft oar or 1.11111.11. Cr PC 01041/2/01 PO 0092 RAM • > MT24274100 01 460 IWO 010/ /0121/ .r'ie°srJ�, Mt an 1172 NM1,12-0 I MOM 0/702r FM/ NN sars ay. oar* era. Aar Sao, mI re oar o nrwr Nrer+rn.nl NOM 00./061 00211 FM /0 01/ LW 020001/ q nacfrws 001111iO4;... `ix un 000 11rr CI"'"Frr1LSI 10A6IY Ih 10 PEW temiersrae Mrs re a1 rmoor A r. Rlq W.I.rr n. .010 Of .6i LyC O el 00.0111 CI 10 MUCIN rd MT 01f 400 Arr. TO r 06 MO �00 SAO1 C Mr IO. Nr MT r 10, XV re4TJON 1151 MCI. 0.0.01•1. Saar .001-01.010- POWwNN 00011.0 0.101 MUM. 10 De 0022n11P Nr. MI POW. o NAI 0. 1.004 1.410.0.1 MONO A1o.2044 POO 0/ N MOM 110001.1 •�W(l4oL.0:000 MKT 42.AMETOLMN6 =MOM M01021.00.2 I.r .I O4 DRi 04451001.00 M 45.0 MY/0* r Saar.7. r4tea re 4 NN' d Nr �m Ne 64545«10, 4e33450 move m• Fax Dew N45OAVM. ALOE 0Y My 10 PC LOT LiVwO 00113,.= Am AKMr.NS rJ1.m1N VAT VC OM IUD WC. 1.10000 . 170Sna MKS MOM wane tar .ftow ALJORVI O4T IV4M er 4t*{CI Or1DC'IARKHYID0N19 q00 MA/ / Al PC rVMa14.4�1�4511124 /M6CfT Ir. NEIN'1YOr 4 iv1Cl WM O.i.1N MN v 0001 �- ..O 1 ,01 \\ I 81- --- I -f - \ \ I \ I COSMO SAMTMY Meg , CASOO/T 42 A 7T S ys: LOSpq WI SS C S umnn .at NOa I A POR. OF NW,1/4 OF SEC.16,TWP. 23N,RGE. 4E.W.M. 1 i CT 8 ORM SPACE TRACT • IOOf Sr RNr630/0 10 DS � rO14000 al.. N AN 4OpI /O. 7.0c =T re.NOAI O(A ma.M Yq'a1 10.0 rise =firer 1.001001 Nom " eofLON F1 11040 SOWN AO IMMO MOW. W.1.w 450 301 De 02102 004 A rnrn aT moo /�OKddl� r .1110( alai= EcMM. 0 42122 It( 1.01010 Tale 42F N 1110 0,4« 012 4 307 -r 7wer 70 ILv> 003M n mr 1 ,,-.7.:__ wrp 7 a n..etn 1y0... 1 ,N aMn..�'urw�+«v44 .wS w`'�m." i0 o Iua ra.s 6.45,«.0 4Mo:., ' C' soar Nr4aM IM> ;„m Jr: «fan-aarr4®aL.A---t _ I l4/llfan MwflO K.OWIIi Ar1ORS450 N 1141.0.0101, R MPOgUVY.NpCPCO� �4 V LI NaN P1.02111 , . 0. 50.0 o100=11=7.0.11.4V-0,-11.'"' 10 b of 040-YOr Asp MMR 045004. DORIAI.M FAIL 1014 110S 040/Cf 0•0 040004 NOM 01.4In. 1.111 MINOICt 10001•1 I ."nr ar1M1.nA 0.10 04.101 nr Nr�45 non roe 1/102.46N.n047 N r rev 10 OC SR 01101.0. SO... . .0212 0L003 WO wVC wr nwe r.l Jws1. ar L4C 011C 4n Jr u�r a1. INN SROPC LJ1Nr r x LT a�nncrsenr r �� n Far x Nor 001107 Mwrr .1112.120, o Muer0 10..1. connN•07201"rwc0Or/01 MU, wr 1mNa year Mr MC. 0reFerrie.aro reneo Aar 0610, ,r I RI e(J4. RI IJIT 0•/Mr MM MrMr 001. r+Mal.MOT 0 a. wrTO 00 202 MCI MOP Pa..0111,Nae,. 111.14010 DOM Mo 2000100 WV TIM 1-1 MCI MOM COWS. 411 P.M 11/12.0r 1 • I100. SAM 00100. 1.1 marl 11 1 f I I 1 1 • M014Cd1101 ONAI[D DNOU04 ILA PROCESS 1 LXSTM 756010 IV MOW eNSrIN /36!4.4 N S ACVOL01 ONOIMI AU PROCESS Ipansv/amo rra, veass 1 710) \ 11 ))1( ice_ _ ^ 1 11 0!!I i% 1 \ 1 I :A NOTES - EASEMENTS AVERAGE LOT WIDTH 1 ` 1,1.:(2420 a1w1 w M 0u -Ml 1111010.00 r PPM= 611 - -- m d POCr rA.'"O aNlQi 10 F 7 r.IW 4/33[�Ay04x0N•rr 070LO1OM.LPA L. .N• /M M OwLal 1'' 1O ALN a... N A N ANTM. ra 4451.1 bIJ 011 m1RwLM. `r .401 0 1.1 0 •, ▪ p` �mM. N AM As ecofrr moo Alr"',ro+,amr"W 001 ram . 0111.! ,fir. 4 LPC kOPTNar Ao1N A1N A '‘."'"•01''''' anw M rA.m L I i... N'07mo �M 'S1O 14.('0!4 Or'''OR rrwvl ` rJ OJ6® 0161 .. wr ro 401 1 Lm n re l I. 1 1 1 1 1 1 Lot IA 110. WI lot 14 Let IF Lot 12 LOT 1.4 LOT 00 LOI6 0150.4 66/0.0 'V' 07 4011 CENT LOT GRATED IDLSw/w eu PICA=S N�re MAP SITE DATA OOR N10R 0221401100/ 10/02040 400• 421240/ 0400 ACO® WA/7r r0R 11.10.0 LvIRON meMe4 041110 017200 20100 IIIDEX OF BIPETB Gar 001, 7.AI 011 100000, N LLC PO M 20-NEI034 (JON Lan WO KM .. C sante rArK r NW Burr wog IICURE .4011 014272000 4 Lit PO Oar imi41-04J MAO •s'.YOvAlf ono MN 0.000. lin MON (NAvrly.45 1/240 41002.113 11014 MIN. r.NJJN 101.1 011 S R41 11.0 SnInt 10 111101 NCt PUNT 0002 0101041.1007 101.00 0.1101.1.1.2 002000. t S 4 a -5 7 8 PREL8MARY PLAT DOtICARY AND TOPOORAPTIC SURVEY PREL8eLARY UTILITY PLAN PRELDIENEY GRAMNO PLAN LANDSCAPE PLAN SLOPEND A !WENT ARCIIT:CTGML ELEVATIONS ADJACENT LAND USE EXTENT RECEIVED ------MAR 2 5 1999 COMMUNITY DEVELOPMENT TRIAD ApOdATIS 04 W- 1.0 re MK M. II errs w ti 1.220 0•240 YYYRR ••u,rm et W •� O t ti LLI hC E ,33 pm 44.m SCALE: 1 .50.50' elan IrM 4= 040 N899751'W 1091 ' 51"W 120.08' N00'53'2 75.70 ® TEST PIT LOCATION • : HAND AUGER BORING LOCATION Proposed. Subdivision Tukwila, Washington -SQUIER/HGI ASSOCIATES Drawn By. Checked By ill/ u 18 -too 1'M 8QT°FJt 3 .2 �%1�_ � \ ,� 948 .: W � �: �- •�: . ��� � - _. (/ �� MINOR. �I 1 ;. SCARP LINE . + FEATURE I1 �, SITE SURVEYRECEivED MAR 2 5 1999 FIGURE2 DEOELMUNIIEEF' CAD\SITESURV 7/9/98 tom 160 1"=20'V 120 100 A • • • GEOLOGIC CROSS SECTION A to A' : PROPOSED SUBDIVISION SITE , TUKWILAWASHINGTON II TOPSOIL: organic, sandy SILT and siltySAND ROADWAY FILL: angular roadway embankment fill Highway 99 R.O.W. TILL and OUTWASH: stiff, brown, sandy SILT with i I silty clay, gravel and cobbles; some sand lenses LAMINATED SILT: highly consolidated tan and brown glaciolacustrine SILT with sand and clay lenses SILTSTONE: over consolidated gray fine sandy SILTSTONE, lenses of fine sand and silt; grades to fine grain Sandstone in some locales Unit boundaries are inferred between test pit locations. Actual unit boundaries and characteristics may vary throughout the site. TP#1 (el. 100') • (el. 140') TP#5 (eI. 186' )TP#3 Xi II' It '-,r 1 , ' ' r , • * .i , 1 1 1 t 4 SQUIER /• HGI ASSOCIATES ifo b !2s 100 leo 210 1"=40'H NOTE: Features shown are for illustrative purposes only and are approximate Eby: 'Original Dab: 6/30,98 'Revision: 'Revision: Latest Revision: OD 4410 52.6 Proposed Subdivision Tukwila, Washington GEOLOGIC CROSS SECTION FIGURE 3 PROJECTS.98 Dab: June.lggg (Job. No. ge349 1 11 1 it Remarks Depth Feet Surfaoe Elevatilliret: CLASSIFICATION OF MATERIAL Log De linill Feet Stunples 6, Dry Density, P.C.F. otural il NaWater Con ent, % 50 130 . .%:%.• X'.% • 0.0 TOPSOIL: Soft dark brown sandy SILT with trace clay and occasional gravel, numerous organic fibers; i,..-04; • • '.: *.- . X• .% • .44.•:*.- moist : % r • *% 1_,t. ... • • • ' X' a • 1.0 TILL: Medium stiffbrown silty fine1 to coarse SAND with gravel; trace clay; subrounded to rounded; tin' occasional organics; moist t .1 s-1 FAO x• • a'. ii2 . • 1ft, ••.*- .r.i.f.1 t S-2 A A 0 • X. ..a.1 Grades to sandy clayey SILT; medium plasticity; micaceous 3 .. ... 4 I-.1. 4 ....X%..t% .• x• a • x• - • •A ..-. .% *: x. .a. ..‘..:*' 5.5 OUTWASH: Loose to medium dense gray brown silty fine to coarse SAND with gravel and cobbles; rounded 411; : It- ;1 f S-3 A A i x• .a.- x• ' a.: to subrounded; moist to wet 411 A.T 6 a. • a. - •.....a. .444f, , , ..A..; % #1.1 7 • • till . .„ S4 •.‘ .. - • .x. • .a*, % • '. • Ground water seepage Grades to SAND with silt, gravel and cobbles :-1. 1 8 I . x• . • • • • .% .; % • X- .%• *.- .."14•1 .i'.; • A.• •a• ' at 9.0 feet • 4 f: . x.. .a.. (1 gpm) 9.3 Cobbles and boulders k.) °i. 9.5 End Test Pit (6/18/98) LEGEND 00 25 5.0 Shear Strength, T.S.F. (approx.) 1 = 2.0" O.D. Split Spoon Sample•Torvane 11 = 3.0" O.D. Thin -Walled Sample ‘-7 Ground Water Level as = Not Recovered -V- Measured on Date Shown •• Pocket Penetrometer • Sample (May Vary with Time of Year) (83 - Jar Sample • TEST PIT #1 o - Bag Sample ATTERBERG LIMITS Proposed Tukwila Subdivision 9 = CBR Test Sample 1 -111 -1 -4 -Liquid Limit Tukwila, Washington = Seepage —4"-------: Natural Water Content NOTE: Plastic Limit Lines representing the interface between soiVrock units of differing description 4 SQUIER/ HGI ASSOCIATES arexi tem,..._vr_...._•t!1._..._.,adma and mayindicate ual transition 6/26/98 98349 , — ' . - . —..-...-...,...-vvi A Reviewed i44 Pagelo Reviewed age 1 o „I fil Remarks Depth Feet Surface Elevatifeet: CLASSIFICATION OF MATERIAL Log De Irne Samples Feet DensityP.C.F. 6, Dry , • Natural Water Contatt, % 0 50 130 • A ' ..‘.• i x- ..A• 0.0 TOPSOIL: Soft brown silty fine to coarse SAND with gravel; trace clay; subangular; numerous organics; moist .°-2-4: ., . /.,,k 4, 0 •* • ..' . X' • a• • .‘ •.; 4C. . • • .X •.' * • X' • .a• •.' * i•i'..si S; • '' ” '0 ti • .X ..%• • X •.' * X' • .a• .. .. . I, .%1 li • ' .' • • 2 S-1 • X ••• X x• .• •s‘ 1, • ••% ,'. ',I• /, ' •a • X • • x• •a '.. *. No ground water seepage 2.5 TILL: Very stiff gray brown SILT with fine sand; trace clay and gravel; mottled; low plasticity; moist - • . . • A x' - • .It ••• 4c., x- ..a. observed • •• . . 3 S 4 I 1-2 ci5 .A ..- * • . . - '.‘'.. i 'I • X. • .1t• ••• * . .. . • • 4 ' . .X . • . • . • • • • x• "A', . . ' • 5 - • • • .A ••. a.-1 x• .a, • . . • • - • • ••- .‘ .* * - 6.0 GLACIOLACUSTRINE DEPOSITS: Hard tan brown SILT with clay; trace fine sanklaminated with fine sand. • I: . .. • • 6 •_. .••. • .A ••• * A •..•:;•• and clay lenseslow plasticityoverconsoldated '.*.•. 8-3 -I '• .••. 4•* .....•...•' 7 •-.•'•......-....... .•••• . . •' • •....' 8.5 Veylow strength (R1) gray fine sandy SLSTOE; massive, severely weathered; dense .xA : 9 _.2AAh . . 9.1 End Test Pit (6/18/98) LEGEND 00 Shear Strength, T.S.F. (approx.) " 1 = 2.0O.D.Split Spoon Sample H = 3.0" O.D. Thin -Walled Sample x-7 Ground Water Level as 4- Measured on Date Shown • Torvane •• Pocket Penetrometer • = Sample Not Recovered (May Vary with Time of Year) 0 = Jar Sarnple TEST PIT #2 0= Bag Sample ATTERBERG LIMITS Proposed Tukwila Subdivision 9 CBR Test Sample I-0-1-0- Liquid Limit Tukwila, Washington seepage ' .'"`------......r.---.....:: Ndural Water Content • Limit NOTE: are approximate only and may indicate gradual transition descriPptilasotinc S SQUIEFt/ HGI ASSOCIATES Lines representing the interface between soil/rock units of differing I 6/26/98 98349 . _ _ 1 - . ... miTiiT TO r 4 Reviewed age 1 o 1 M Remarks Depth Feet Surface Sievel ike:a: CLASSIFICATION OF MATERIAL Log DAP In Feet Sainples 6, Dry Density, P.C.F. 0. Natural/ Water Content, Y. so 130 •x.. . .‘ ..*" 0.0 TOPSOIL: Loose dark brown silty SAND with cobbles; trace rounded gravel; ntunaous organics; moist .•4 k A ..• ... f,..,t•fr. 0 0,..r... s• ' % • .s •••'*- '.* • ' :ir...i .1-!...= 1 s• • .‘ •.: *.- ..k ..: *.. 1.0 TILL: Medium dense tan silty fine SAND with cobbles; trace fine to coarse gravel; subangular; lit i '41 4fit i a' a . • . • • X' •a •!Hi • micaceous; occasional organics; moist 2 . . . .s •• % • ' %'• .1 1.. . .41.. 1 s- . •::.: .1.: • '.: * . No ground water seepage 3.1...ir .A • x'• A. a. a . • . • . observed :1'1 - • .. . I, .‘ •: a,• X- .a ..‘ ..' * '.%' 3.5 GLACIOLACUSTRINE DEPOSITS: Hard tan fine sandy SILT with clay, larninated; overconsolidated; -.... • 4 s• ..‘ •-• * x• •.%. mottled; moist to dry I . .. • . . - s• •.s' ..‘ ..' * • X• ..a. ..' • • • 1 . . -.... ..- .% * x• '.%' '.s*•• * '.%. .• .. 5 s• ..A ..' * X' ..a' -• •.• . • s• '.%* ..A ••• * X' ..4t. ' •.•..• i . . •. •.. . • . • .X •.' * s• • .a' I •. • . . • •.•..• S-2 X • X• .a. .s*.• *• • I . ' •. • . ..- I 7 .s '.- *• .. • . - . •,. ..• I . • . . .I ' • • 8 ..A.: * . . I . . • . • .. . .1 ... • •. • . . • .. 9 s• • .%" I '•I-.- .. 1 ' - 10.0 Very low strength (R1) gray SJLTSTONE; remolds to silt with trace fine to coarse sand; silt lenses; massive; j __ _,,, _—..._=._: 10 S-3 , s• '.%", dense x- • a.. --.... At. • ... ..".-=,=: 12.0 End Test Pit (6/18/98) 12 LEGEND 00 2.5 5.0 T.S.F. 1 = 2.0" O.D. Split Spoon Sample n = 3.0" O.D. Thin -Walled Sample T-7 Ground Water Level as • = Sample Not Recovered -Y-- Measured on Date Shown ' Shear Strength, (approx.) Torvane 69 Pocket Penetrometer (May Vary with Time of Year) 21 = Jar Sample TEST PIT #3 0 — Bag Sample ATTERBERG Limns Proposed Tukwila Subdivision 8 = CBR Test Sample FAD—I '41- Liquid Limit Tulcwila, Washington ••^1. = Seepage . '''''''-- Ndural Water Content NOTE: Plastic Limit Lines representing the interface between soit/rock units of differing description SQUIERJ HGI ASSOCIATES 0 are approximate only and may indicate gradual transition '6 6/26/98 98349 Reviewed mpg Page 1 of 1 Remarks Depth Feet Surface Ekv4110 Feet: CLASSIFICATION OF MATERIAL r �• • s x. 2 t• t t. 1 .x r a. X. x• % r• : *. X. %- �.: z • a .t A.: * x••r• . ; .: %. • x. x. r t• i. t• a •. ‘ r• t• .X.:%: �., •%Y X. . X. t • X- *. X. : A'•.s. .;.•. X' : t• • 1t.:% Z. • t. • -.s••r, s.: i. % . z• . . I= II= i; . _ O • NOTE: Liness �.. No ground water seepage observed LEGEND 0.0 TOPSOIL: Loose dark brown silty SAND with numerous organics; moist 1.0 TILL: 24 inch weathered granite boulder Log Iv:., • :,I+; 3.0 GLACIOLACUSTRINE DEPOSITS: Dense brown SILT with fine sand and clay; overconsolidated; close laminations of fine sand; mottled; low to medium plasticity; micaceous; moist 7.5 8.5 11.0 •••-• Very dense gray SILT with fine sand; close laminations of silt; moist Grades to very low strength (R1) gray SILTSTONE; remolds to silt with trace fine sand; micaceous; close laminations; numerous lenses of clayey silt; dense 2.0" O.D. Split Spoon Sample 3.0' O.D. Thin -Walled Sample Sample Not Recovered Jar Sample Bag Sample CBR Test Sample Seepage End Test Pit (6/18/98) Ground Water Level as Measured on Date Shown (May Vary with Time of Year) ATTERBERG LIMITS 1--r1---J-4-Liquid Limit Natural Water Content Plastic Limit representing the interface between soil/rock units of differing description are approximate only and may indicate gradual transition ,/ y7 1 Reviewed 4 g 1 DO Samples Fed 0 2 3 4 5. 6 7 8 9 10 11 0 Dry Density, P.C.F. • Natural Water Content, % 0 50 130 • • S-2 vi Shear Strength, T.S • Torvane Pocket Penetrometer .F .(approx.) TEST PIT #4 Proposed Tukwila Subdivision Tukwila, Washington SQUIER/ HGI ASSOCIATE. r 6/26198 98349 Page 1 of 1 FIGURE '7 • m 2 Remarks Depth Feet Surface Ririe:km11111: CLASSIFICATION OF MATERIAL Log Depl In Feet 0 Samples i L Dry Density, P.C.F. e Natural Water Content, % cl50 130 -.74'771 .% .. * • x• '.%' • IE 0.0 TOPSOIL: Loose dark brown silty SAND; numerous organics; moist •& l.. 4, 0 ... • . X. • %. 1 • • 3- - .. . 1.0 TILL: Dense gray brown silty fine to coarse SAND with clay, gravel, and cobbles; rounded to subangular; yfti ; .i.# 3. %. 3.. .. weathered cobbles; moist4-1;1.1 ,.... I 1'11 2 x• • * 3- •... ft F tt: 'A..:% • A -... ,E. No ground water seepage :Fill t 3 ..1'...: •.%..- observed i7.111. .4' IV S-1 fil * 4 , A ••• * • A .• *• 1 :{i I 1 4.1.•1111, rill 5 . A .. t . % •• *, Al !IV •.% •*. *.• * • . • . • • .% .: *.• Petrified wood V iia- . 'iri•ff 6 S-2 ifi a• • ;L' . • . • • 6.0 GLACIOLACUSTRINE DEPOSITS: Hard tan silty fine SAND with close laminations of silt and clay; dryI 1 .... • . •• • . . .% .' % .. . . X' •.k. ..• 1 • . 7 ' .% '.• * x• '.%' '.%'•: *. I •.•..: x• .% • .% -.' * • X' •.*• .A.: * x• '.%* ' .%'•• * • •• • . . - 1. . 8 x• .*. • .**: * X' •.k. • A •.; * .1%. -. •. •.. ..• X• .%• x• -.%' . . . I -. •.. .: I •.- 9 x• •.*' • .%••• *• •.%• • . I • 1 • X' .A.: *• *• •.•..• I. • -. • . . • • • 10 .%•-• .% ••'. *- i •. • . ..• . " . .%••• *.• • x• ' % • •' 11.0 Very low strength (RI) gray SILTSTONE; occasional fine sand lenses; remolds to silt with clay and trace fme• ;-.7"._ 11 x••v*- x• • .%', •A'.• *, sand; dense — __ _ x• • z% •.'.•• --- --_-7,-_—. 12 It. , . X' •.Z. .%••• *• ..71.: -- S-3 _____ 13.0 End Test Pit (6/18/98) 13 LEGEND 00 25 5.0 1 = 2.0" O.D. Split Spoon Sample la = 3.0' O.D. Thin -Walled Sample t-7 Ground Water Level as = 44- Measured on Date Shown • Sample Not Recovered Shear Strength, T.S.F. (approx.) Torvane .. Pocket Penetrometer (May Vary with Time of Year) Jar Sample ID = TEST PIT #5 o - Bag Sample ATTERBERG LIMITS Proposed Tukwila Subdivision a - CBR Test Sample 1-40--1-4-Liquid.Limit Tukwila, Washington Seepage ...--7---..*--............_-- Neural Water Content NOTE: Plastic Limit Lines representing the interface between soiVrock units of differing description * SQUIER/ HGI ASSOCIATES are approximate only and may indicate gradual transition 6/26/98 98349 _ — - Reviewed AV Page 1 of 1 FIG .bc - Remarlcs Depth Feet Surfce aElevation in Feet: CLASSIFICATION OF MATERIAL Log Depth In Fee Samples Dry Density, P.C.F. • Natural Water Content, % 0 50 100 A * A • .%*.• *. • .% ••• * • .X .' * • A.' * • A •..2 x• • A • .% ••: %. x• A ".%•-: %. • x• •% x % "•• * • • % .....* x.. • • .A ••' A ...z-..:.: x• • % 3. ' % x• • % . . • . x• % x• * % x• • % • •A .•;.%. A' .A • .A ••' A A' • A A' • A . . • . .A .• % A' • A• x• • % • .A.-; A. A' A • • • • .A •• % • x.• • -%: .A .• A , X',..w: % .• % .x. • a• . . • . A -: %.x• . . . . .A •• a • - • .A •: A. x• % - • .A ••• A • • . .% •• % • - • - Ground water seepage at 9.0 feet (0.5 gpm) . 0.0 2.0 • 9.0 10.0 14.0 TOPSOIL: Loose dark brown silty SAND with numerous organics; moist •_!.-, ,, .,... G ..f.. I-- .0 ,i . *• 1. ,' 0 ti ,. ...__i i 3 4 5 6 7 8 9 10 11 12 14 TILL: Stiff tan brown clayey SILT with lux to coarse sand, gravel and cobbles; weathered cobbles; subangular; mottled; medium plasticity; moist ..__ 7, / / 7/ / / / / / / / / / X 11 . S -I s iiel • OUTWASH: Medium dense brown silty SAND with scattered gravel; moist to wet IJ• 7 4:11111- f . Medium dense tan orange silty fine to medium SAND with gravel; occasional silt lenses; wet • . - S-2 4 0 End Test Pit (6/18/98) LEGEND 25 5.0 Shear Strength, T.S.F. (approx.) 1 - 2.0" O.D. Split Spoon Sample ti n = 3.0" O.D. Thin -Walled Sample v-7 Ground Water Level as -II- Measured on Date Shown - Sample ". Pocket Penetrometer • Not Recovered (May Vary with Time of Year) IS) = Jar Stunt* TEST PIT #6 o - Bag Sample ATTERBERG LIMITS Proposed Tukwila Subdivision a - CBR Test Sample 1.. -0 -1 -01 -Liquid Limit Tukwila, Washington ,.....0 - seepage .. 'Ig--_- N&u•al Water Content NOTE:Plastic Limit Lanes representing the interface between soil/rock units of differing description % SQUIER/ HGI ASSOCIATES . *: \. are ),.....= t=i..................... jradmate and indicategradual munition . ' 6/26/98 98349 _ — . ---....-........." ... Reviewed il41'A age 1 0 _ w Remarks Depth Feet Surface Elcin Feet: CLASSIFICATION OF MATERIAL Log In Feet Samples Q Dry Density, P.C.F. Natural Water Con ent, %0 50 100 X. % • 0.0 TOPSOIL: Loose brown SAND with silt; moist ''''—r"• ^s 0 —�- • x x . *.: 0.5 TILL: Dense tan fine to coarse SAND with silt and cobbles; trace clay and gravel; subangular to �}:t j t.4 f �` ' 1 .x.•: subrounded; weathered cobbles; occasional organics; moist 1 r x x .x..1: 1} . f... k 2 -"— X : x • x x• • •I , ` -41-4 —�--- x• .x. • %•,: x.a 1 I4 i x x• ' x'• S-1 X11 12r— x x• ".%"... x; }. t' 1 + } • • 1:11 n -ti: iii ft4 5 •x. 4-1 NI.x x• �. 6 x . x• .x • {'ar I •: }F x •x jj • it If -r _ 1 H 4' 8 . 1.. {`'`r x xt x• ,x. 11.4:4 x' •x • x x • 9.0 OUTWASH: Medium dense tan silty SAND with gravel; wet — . A..•} • x ,x • x• x•: Ground water seepage ,. : 10 ".%'.: 'x: • x.• ' at 9.5 feet (1 gpm) 10.0 Loose tan orange sandy GRAVEL with cobbles; trace silt; wet * fprm..• ..4 - . t►�� x x �:4A ,...• s 11 ••• A. x . • 111 x x x i x' :x ' x'. 12.0 GLACIOLACUSTRINE DEPOSITS: Hard tan SILT with clay; trace fine sand; close laminations of silt and ..1... 1 I '. 12 x: x lenses of fine sand; mottled; wet I 1 : x: •• x 13.0 Very low strength (RI) gray SILTSTONE; occasional lenses of fine sand; dense — _ . 13 S-2 „ . x•x• — --- 14.0 End Test Pit (6/18/98) 14 - LEGEND 15.0 2-.5- 570 Shear Strength, T.S.F. (approx. 1 = 2.0" O.D. Split Spoon Sample L[ = 3.0" O.D. Thin -Walled Sample Ground Water Level as = Sample Not Recovered . - Measured on Date Shown Torvane ". Pocket Penetrometer ® = Jar Sample (May Vary with Time of Year) TEST PIT #7 O = Bag Sample ATTERBERG LLIVIITS Proposed Tukwila Subdivision B = CBR Test Sample HD— -a-Liquid Limit Tukwila, Washington ."� = Seepage -.‘� Natural Water Content NOTE: Plastic Limit Lines representing the interface between soil/rock units of differing description •SQUIERI HGI ASSOCIATES approximate only and may indicate gradual transition 6/26/98 98349 R ewed /41,8 Page 1 of 1 E10 Y — Remarks Depth Fal Surface eet: CLASSIFICATION OF MATERIAL Log In Fat Samples Q Dry Density. P.C.F. • Natural Water Content, % 0 50 130 • x .Z 0.0 TOPSOIL: Soft dark brown sandy SILT; trace clay and gravel; numerous organic fibers; moist '— - r; .' 1+ 1 r .x :g. : i x t. •._ •.: t - 1.0 TILL: Stiff brown silty fine to coarse SAND with clay and gravel; rounded to subangular; moist Ill ;. y x• :• 4- ; i':•}• x• 't • • s':t +'r � •.�. • • II- 1 ' S-1 ►4 1 �.:} x .t. x-•• .x- 1'v 3 t• i _ 1- x• _t•. x .t -d-.. 4 x. •%. x• '.t x. .z , � .A.-.a- N - •x' t x• t• :x.•: ill i 41 ' t• x •2 . 4! 4 6 0. 11 .s'•:'r • .: i 7.0 OUTWASH: Medium dense brown silty SAND with gravel and cobbles; rounded; wet S-2 ' 1 • x ••• x• . .>.•%: Increasing sand 8 .:. i.. x• .t. Ground water , - .‘•• x' t' : a.%(<0.5 Page at 9.0 feet gpm) 9.0 GLACIOLACUSTRINE DEPOSITS: Very stiff tan SILT with trace clay, close laminations; wetI I 9 •x '• :: 9.0 I.I • .s'•: x.- x• x' ••x';'x.• 10.0 Very low strength (R1) gray SILTSTONE; remolds to,„.-`_— fine to coarse sandySILT; trace subangular vel; . _ S-3 ♦ x .x massive; dense 11.0 End Test Pit (6/18/98) LEGEND t 1 Shear Strength, T.S.F. (approx.) 1 = 2.0" O.D. Split Spoon Sample II = 3.0" O.D. Thin-Walled Sample Ground Water Level as Q Measured on Date Shown Torvane '. Pocket Penetrometer • =Sample Not Recovered ® = Jar Sample (May Vary with Time of Year) TEST PIT #8 o _ S -{ATTERBERG LIMITS Proposed Tukwila Subdivision 8 =C Sample F--1-a--Liquid Limit Tukwila, Washington f� Natural Water Content ..,� = Seepage NOTE: Plastic Limit S SQUIER/ HGI ASSOCIATES Lines representing the interface between soil/rock units of differing description 498349 are . • roximate onl and ma indicate : • . ual transition . 6/26/98 .-...,••,tmt' 11 Reviewed r -•r agelo Remarks Depth Feet Surface ElevaFeet: CLASSIFICATION OF MATERIAL Log De In . Samples Feet A Dry Density, P.C.F. • Natural Water Content % 0 50 130 0.0 1.0 5.0 TOPSOIL: Dark brown silty SAND with gravel; moist i i • • TILL: Brown sandy SILT with gravel; moist Increasing cobbles and gravel End Hand Auger Boring (6/18/98) 0 2 3 4 5 LEGEND = 2.0" O.D. Split Spoon Sample 11 = 3.0" O.D. Thin -Walled Samplc • = Sample Not Rcco tg) — Jar Sample 0 = Bag Sample ▪ CBR Test Sample seepage NOTE: Lines representing the are approximate only vered Ground Water Level as -Y- Measured on Date Shown (May Vary with Time of Year) ATTERBERG LIMITS 1 • l -4 -Liquid Limit Natural Water Content Plastic Limit between soil/rock units of differing description indicate gradual transition interface and may ' 00 2.5 Shear Strength, T.S.F. (approx.) • Torvane Pocket Penetrometer 5 0 HAND AUGER HA -1 Proposed Tukwila Subdivision Tukwila, Washington SQUIER/ HGI ASSOCIATES 6f26/98 98349 Reviewed MAO Page 1 of 1 FIGURE 12 ..AL _ g Fr. Remarks Depth Feet Surface Elevatileeet: CLASSIFICATION OF MATERIAL Log De Feet Samples A DrY Density, P.C.F. • Natural Water Content % 0 50 130 0.0 TOPSOIL: Dark brown organic sandy SILT with gravel; moist : i 1__.• 1. . . . .st i . ' 1 1.0 TILL: Brown sandy SILT with gravel; trace clay; moist • 2 •• • Increasing cobbles and gravel . _. . .._ • 3 3.5 End Hand Auger Boring (6/18/98) ,.. 4 • 5 5.0 LEGEND 0.0 25 Shear Strength, T.S.F. (approx.) 1 = 2.0" 0.D. Split Spoon Sample r[ = 3.0" O.D. Thin -Walled Sample t-7 Ground Water Level as 4-. Measured on Date Shown Torvane m• Pocket Penetrometer • = Sample Not Recovered (May Vary with Time of Year) 0 = Jar Sample HAND AUGER HA -2 o - Bag Sarnple ATTERBERG LIMITS Proposed Tukwila Subdivision 9 = CBR Test Sample 1-411--I -01-Liquid.Limit Tukwila, Washington = seepage Water Content NOTE: Plastic Limit , 'SQUIER/ HGI ASSOCIATES Lines representing the interface between soil/rock units of differing description , S are approximate only and may indicate gradual transition ' • 6/26/98 98349 Reviewed Page 1 of 1 14 03 w Remarks Depth Feet Surface eel: CLASSIFICATION OF MATERIAL Log ;•;•;• i'i'i' ppp. -410 In t Samples A • 0 Dry Natural Density, Water P.C.F. Con 50 ent, % Igo 0.0 1.0 5.0 FILL: 3/4 -inch minus crushed rock TILL: Brown sandy SILT with gravel; trace clay; moist Increasing cobbles and gravel lit 11 :.;1/ . 11 411 I 11) 1 • III 2 3 4 End Hand Auger Boring (6/18/98) 0 0 Shear • Strength, Torvane Pocket Penetrometer -2.5 T.S.F. (approx.) 5.0 LEGEND Spoon Sample SampleGround Water Level as Q Measured on Date Shown (May Vary with Time of Year) ATTERBERG LIMITS I-0-1, .Limit .4"--7----.._____-- Nahtrai Water Content Plastic Limit interface between soil/rock units of differing description and may indicate gradual transition 1 = 2.0" O.D. Split I[ = 3.0" O.D. Thin -Walled = Sample Not Recovered ® = Jar Sample o = Bag Sample B = CBR Test Sample -.no _ page NOTE: Lines representing the are approximate only ■ HAND AUGER HA -3 Proposed Tukwila Subdivision Tukwila, Washington 686/98 HGI ASSOCIATES SQUIER/ 98349 f r,__- r -CI tt,iriTTDV 1d Reviewed !' )f m — m u: Remarks Depth Feet Surface ElevaiIP Feet: CLASSIFICATION OF MATERIAL Log Depth In Samples Q Dry Density, P.C.F. • Natural Water Content, 0 50 100 0.0 4.2 FILL: 3/4 -inch minus crushed rock •••••• •0.5 0 TILL: Brown sandy SILT with gravel; trace clay; moist Increasing cobbles and gravel "• 11� r lli . 11 • �1� •till 1111 111 .,a! ip11111 2 3 4 End Hand Auger Boring (6/18/98) 5 LEGEND Sample Sample interface and may indicate Ground Water Level as Q Measured on Date Shown (May Vary with Time of Year) ATTERBERG LIMITS .0.0 Shear • 2 576 Strength, T.S.F. (approx.) Torvane Penetrometer 1 = 2.0" O.D. Split Spoon II = 3.0" O.D. Thin -Walled • = Sample Not Recovered ® = Jar Sample ❑ = Bag Sample B = CBR Test Sample ',"‘c• = Seepage • NOTE: Lines representing the areapproximate only ". Pocket TEST PIT HA -4 Proposed Tukwila Subdivision Tukwila, Washington SQUIER/ HGI ASSOCIATES �� 6/26/98 98349 Liquid Limit I R— Natural Water Content Plastic Limit between soiVrock units of differing description gradual transition Reviewed I' ri4 Page 1 of 1 FIGURE 15 aa_ � w Remarks Depth Feet Surface Devat. . CLASSIFICATION OF MATERIAL Log De In - Feet r Samples Dry Density, P.C.F. Natural Wa er Con ent 0 50 100 0.0 1.0 4.2 TOPSOIL: Dark brown organic sandy SILT with' gravel; medium plasticity; wet/, ' `: • �_�• ..7 rr. ..Si I t TILL: Brown sandy SILT with gravel; trace clay; moist Increasing cobbles and gravel ril )11 i .t 101 �. /15.I 2 Ji 3 1. 4 4 End Hand Auger Boring (6/18/98) 5 5.0. LEGEND Spoon Sample SampleGround Water Level as Q Measured on Date Shown (May Vary with Time of Year) ATTERBERG LIMITS 1 -0—i -4 -Liquid Limit �� Natural Water Content Plastic Limit % interface between soil/rock units of differing description and may indicate gradual transition 0 U Shear 23 Strength, T.S.F. (approx.) Torvane Pocket Penetrometer 1 = 2.0" O.D. Split II = 3.0" O.D. Thin -Walled • = Sample Not Recovered O = Jar Sample p =Bag Sample 8 = CBR Test Sample = Seepage NOTE: Lines representing the are approximate only ■ TEST PIT HA -5 Proposed Tukwila Subdivision Tukwila, Washington SQUIER/ HGI ASSOCIATES 686/98 98349 - _ t I,T!"'TTr. V 1K Reviewed Alf age Y ^ mw Remarks Depth Feet Surface El n Feet: _ CLASSIFICATION OF MATERIAL Log In J Feet Samples Q 0 Dry Natural Density. Wa er P.C.F. Content, 50 % too 0.0 3.0 TILL: Brown fine sandy SILT with gravel; artifictii debris at 1 foot; moist . (possible fill slope) . . 0 1 2 3 End Hand Auger Boring (6/18/98) LEGEND Sample Sample interface may indicate P Ground Water Level as Q Measured on Date Shown (May Vary with Time of Year) ATTERBERG LIMITS Liquid Limit 1-0-1-4-Liquid Shear 3 so Strength, T.S.F. (approx.) Torvane Pocket Penetrometer 1 = 2.0" O.D. Split Spoon 11 = 3.0" O.D. Thin -Walled • = Sample Not Recovered ® =Jar Sample ❑ = Bag Sample B = CBR Test Sample '� = Seepage NOTE Lines representing the are approximate only and •■ TEST PIT HA -6 ,Proposed Tukwila Subdivision Tukwila, Washington /A SQUIER/ HGI ASSOCIATES 6/26/98 98349 Natural Water Content Plastic Limit between'soiVrock units of differing description gradual transition Reviewed /41/7/3 Page 1 of 1 FIGURE 17 -SD "›<:. L— IV ILI4 I • ! ••s"1: ";. / TRACT "Er's \ \ \ \ ----- • Pi OF 11 NO C \B. .1 12 1 13. MA. 11111101111111 Y. • r" c.p. fl3 \ \ C.E. #1\2 `C.B. #:14 1 \ \ \1 17 i,,, iv _ .:-) \ , \ ,, ' \ \ ' \ 15 \ ..C.BN #8 • „CIO!, io-r-fgRWILA ELLA.1 1j O. LDD -0026 -11_ TRACT "I) 111 I --_, • 1 ' '1 3 115( UTILITY )f - ) EASEMENT • - ( (s* PI - \ ) C.B.(#2A ! ... • . .PARCEL 4406' I OF TUKWILA;i1J—A. NO. • LD07-6025 ...... ,, .. TL. 4 C.B. #11 T.L C.B. #10 C.B. #4 .< TLW CC > ° PC TL. 0 101x20' T CO STRUC EA EMENT (-is° •-• C.B. TL.