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Permit L93-0009 - CITY OF TUKWILA - CENTRAL BUSINESS DISTRICT DRAINAGE STUDY / ENVIRONMENTAL IMPACT STATEMENT (EIS)
l93-0009 green river west south 180th street strander boulevard southeast central business district cbd drainage study sepa CITY OF TUKWILA ENVIRONMENTAL CHECKLIST SOUTHEAST CBD DRAINAGE STUDY January 14, 1993 h A. BACKGROUND 1. Name of proposed project, if applicable: Southeast CBD Drainage Study SEPA ENVIRONMENTAL IMPACT STATEMENT (Hartung/NC Machinery Basin Analysis) 2. Name of applicant: City of Tukwila 3. Address and phone number of applicant and contact person: CONTACT PERSON: Phil Fraser, PE. Senior Development/Surface Water Engineer Public Works Department 6300 Southcenter Blvd. Tukwila, WA 98188 Phone: (206) 433 -0179 4. Date checklist prepared: January 14, 1993 5. Agency requesting checklist: City of Tukwila 6. Proposed timing or schedule (including phasing, if applicable): 1 L'g3 -000q Report provides for recommendations to be approved and adopted in accordance with City's schedule for meetings. 7. Do you have any plans for future additions, expansions, or further activity related to or connected with this proposal? If yes, explain. This plan should be updated periodically based on zoning and land use considerations. 8. List any environmental information you know about that has been prepared, or will be prepared, directly related to this proposal. Drainage Report includes Wetland Report and Hydrogeology Report. F IV ilff 8 1993 DEVELOPMLNT 9. Do you know whether applications are pending for governmental approvals of other proposals directly affecting the property covered by your proposal? If yes, explain. No applications are known to be pending. 10. List any government approvals or permits that will be needed for your proposal, if known. City of Tukwila City Council approval. 11. Give brief, complete description of your proposal, including the proposed uses and the size of the project and site. There are several' questions later in this checklist that ask you to describe certain aspects of your proposal. You do not need to repeat those answers on this page. (Lead agencies may modify this form to include additional specific information on project description.) Recommendations include options to obtain drainage easements, revise development drainage requirements, seek funding sources, provide for stormwater monitoring, installation of additional culvert, maintaining existing ditch for biofiltration and adopting DOE's Stormwater Management Manual for the Puget Sound Basin. 12. Location of the proposal. Give sufficient information for a person to understand the precise location of your proposed project, including a street address, if any, and section, township, and range, if known. If a proposal would occur over a range of area, provide the range or boundaries of the site(s). Provide a legal description, site plan vicinity map, and topographic map, if reasonably available. While you should submit any plans required by the agency, you are not required to duplicate maps or detailed plans submitted with any permit applications related to this checklist. The S.E. CBD Drainage Basin extends to the Green River to the west, to South 180th Street to the south, to extended Strander Blvd. to the north and to the east to the eastern edge of the Burlington Northern right -of -way limits. 13. Does the proposal lie within an area on the City's Comprehensive Land Use Policy Plan Map designated as environmentally sensitive? Wetland designations were prepared as part of this report. B. ENVIRONMENTAL ELEMENTS 1. EARTH a. General description of the site (circle one): flat/rolling, hilly, steep slopes, mountainous, other. b. What is the steepest slope on the site (approximate percent slope)? 50% (2:1) side slopes along railroad embankments. c. What general types of soils are found on the site (for example, clay, sand, gravel, peat, muck)? If you know the classification of agricultural soils, specify them.and note any prime farmland? The study area lies on the alluvial plain the Green River and is underlain by river - deposited sediments consisting chiefly of sand and silt with some clay and peat. }";•i.t'.',': ' iii�5:?.,., t•,<.,.. -:�:.. Est••. ,,.�,n. o., ... �.-o.� d. Are there surface indications or history of unstable soils in the immediate vicinity? If so, describe. There are no known indications of unstable soils in the vicinity. e. Describe the purpose, type, and approximate quantities of any filling or grading proposed. Indicate source of fill. Does not apply. f. Could erosion occur as a result of clearing, construction, or use? If so, generally describe. g. A description of erosion control measures will be required for each site improvement within the study area in accordance with City of Tukwila standards. About what percent of the site will be covered with impervious surfaces after project construction (for example, asphalt or buildings)? Does not apply. h. Proposed measures to reduce or control erosion, or other impacts to the earth, if any: Temporary erosion control techniques should be employed during any construction activity. Seeding of exposed areas should be completed as soon after construction as reasonably possible. Maintaining existing drainage system is a recognized need. 2. AIR a. What types of emissions to the air would result from the proposal (i.e., dust, automobile, odors, industrial wood smoke) during construction and when the project is completed? If any, generally describe and give approximate quantities, if known. Does not apply. After construction there will be no new sources of emissions and the quantity of emissions should not increase over current conditions. b. Are there any off -site sources of emissions or odor that may affect your proposal? If so, generally describe. No c. Proposed measures to reduce or control emissions or other impacts to air, if any: Does not apply. 4 3. WATER a. Surface 1) Is there any surface water body on or in the immediate vicinity of the site (including year - round and seasonal streams, saltwater, lakes, ponds, wetlands)? If yes, describe type and provide names. If appropriate, state what stream or river it flows into. Report provides description of surface water drainage to Green River and Springbrook Creek. Will the project require any work over, in, or adjacent to (within 200 feet) of the described waters? If yes, please describe and attach available plans. No 3) Estimate the amount of fill and dredge material that would be placed in or removed from surface water or wetlands and indicate the area of the site that would be affected. Indicate the source of fill material. None 4) Will the proposal require surface water withdrawals or diversions? Give general description, purpose, and approximate quantities if known. No 5) Does the proposal lie within a I00 -year floodplain? If so, note location on the site plan. Yes, in two pockets along the eastern bank of the Green River, immediately south of Strander Blvd. 6) Does the proposal involve any discharges of waste materials to surface waters? If so, describe the type of waste and anticipated volume of discharge. No 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. No 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. Does not apply c. Water Runoff (including storm water): I) 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. Stormwater runoff will flow into and across the site from existing and future developments. Individual site improvements will be subject to City's permitting process. Combined runoff from the site will enter the groundwater by infiltration or will flow into the Green River or Springbrook Creek by pipes or ditches. 2) Could waste materials enter ground or surface waters? If so, generally describe. Does not apply d. Proposed measures to reduce or control surface, ground, and runoff water impacts, if any: The storm drainage system utilizes grass lined swales, groundwater recharge and preservation of wetlands. 4. PLANTS a. Check or circle types of vegetation found on the site: X deciduous tree: alder, maple, aspen, or other: Flowering Cherry evergreen tree: fir, cedar, pine, other X shrubs X grass X pasture crop or grain X wet soil plants; cattail, buttercup, bullrush, X skunk cabbage, other water plants: water lily, eelgrass, milfoil, other X other types of vegetation b. What kind and amount of vegetation will be removed or altered? Does not apply. c. List threatened or endangered species known to be on or near the site. None known d. Proposed landscaping, use of native plants, or other measures to preserve or enhance vegetation on the site, if any: In accordance with City standards. 6' 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: Starlings. sparrows. robins and other upland meadow species. Mammals: deer, bear, elk, beaver, other: Squirrels and other small upland species. Fish: bass, salmon, trout, herring, shellfish, other b. List any threatened or endangered species known to be on or near the site. None known c. Is the site part of a migration route? If so, explain. Study area is within "Pacific Flyway ". d. Proposed measures to preserve or enhance wildlife, if any: None • 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. Does not apply. b. Would your project affect the potential use of solar energy by adjacent properties? If so, generally describe. No c. What other 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: None 7. ENVIRONMENTAL HEALTH a. Are there any environmental health hazards, including exposure to toxic chemicals, risk of fire and explosion, spill, or hazardous waste, that could occur as a result of this proposal? If so, describe. No 1) Describe special emergency services that might be required. None 7 2) Proposed measures to reduce or control environmental health hazards, if any: None b. Noise 1) What types of noise exist in the area which may affect your project (for example: traffic, equipment, operation, other)? None 2) What types and levels of noise would be created by or associated with the project on a short - term or a Tong -term basis (for example: traffic, construction, operation, other)? Indicate what hours noise would come from the site. None 3) Proposed measures to reduce or control noise impacts, if any: None 8. LAND AND SHORELINE USE a. What is the current use of the site and adjacent properties? Strip industrial /commercial development along West Valley Highway, located east of the Green River and running north /south through study area. Railroad trackage located along east boundary. b. Has the site been used for agriculture? If so, describe. Not known although no agricultural use in last twenty years. c. Describe any structures on the site. Structures will be described on a project basis in accordance with individual project applications. d. Will any structures be demolished? If so, what? No e. What is the current zoning classification of the site? C-2, RA, M -1 and WL -12. f. What is the current comprehensive plan designation of the site? C -2, RA, M -1 and WL -12. g. If applicable, what is the current shoreline master program designation of the site? ing ounty /G n iver-Fleod- Gontro ne District. 8 h. Has any part of the site been classified as "environmentally sensitive" area. If so, specify. Wetlands analysis 'included in this report. i. Approximately how many people would reside or work in the completed project? None j. Approximately how many people would the completed project displace? None k. Proposed measures to avoid or reduce displacement impacts, if any: None 1. Proposed measures to ensure the proposal is compatible with existing and project land uses and plans, if any: None 9. HOUSING a. Approximately how many units would be provided, if any? Indicate whether high, middle, or low- income housing. None 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. None 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? Does not apply. b. What views in the immediate vicinity would be altered or obstructed? None c. Proposed measures to reduce or control aesthetic impacts, if any: None 9 11. LIGHT AND GLARE a. What type of light or glare will the proposal produce? What time of day would it mainly occur? None b. Could light or glare from the finished project be a safety hazard or interfere with views? None c. What existing off -site sources of light or glare may affect your proposal? None d. Proposed measures to reduce or control Tight and glare impacts, if any: None 12. RECREATION a. What designated and informal recreational opportunities are in the immediate vicinity? CF.50-13git b. Would the proposed project displace any existing recreational uses? If so, describe. No c. Proposed measures to reduce or control impacts on recreation, including recreation opportunities to be provided by the project 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. None known c. Proposed measures to reduce or control impacts, if any. None 10 14. TRANSPORTATION a. Identify public streets and highways serving the site, and describe proposed access to the existing street system. Show on site plans, if any. West Valley Highway b. Is site currently served by public transit? If not, what is the approximate distance to the nearest transit stop? Yes c. • How many parking spaces would the completed project have? How many would the project eliminate? Does not apply. 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). Does not apply. e. Will the project use (or occur in the immediate vicinity of) water, rail, or air transportation? If so, generally describe. Project area is crossed by the Burlington - Northern Railroad and the Union Pacific Railroad. f. How many vehicular trips per day would be generated by the completed project? If known, indicate when peak volumes would occur. This project will not generate additional trips. g. Proposed measures to reduce or control transportation impacts, if any: None 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: No b. Proposed measures to reduce or control direct impacts on public services, if any: None 16. UTILITIES a. Circle utilities currently available at the site: electricity, natural gas, water, refuse service, telephone, sanitary sewer, septic system, other: Cable TV 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. None SIGNATURE The above answers are true and complete to the best of my knowledge. I understand that the lead agency is relying on them to make its decision. Date Submitted: 93 11 D. SUPPLEMENTAL SHEET FOR NON- PROJECT ACTIONS 1. How would the proposal be likely to increase discharge to water; emissions to air; production, storage, or release of toxic or hazardous substances; or production of noise? The report provides recommendations for maintaining existing drainage courses which flow to the Green River and Springbrook creek based on existing physical constriants and accepted inter - jurisdictional drainage criteria. Proposed measures to avoid or reduce such increases are: Impacts are assocated with new development or redevelopment and will be addressed within the permitting pocess for each project. 2. How would the proposal be likely to affect plants, animals, fish or marine life? Same as above. Proposed measures to protect or conserve plant, animals, fish or marine life are: • Does not apply 3. How would the proposal be likely to deplete energy or natural resources? Does not apply Proposed measures to protect or conserve energy and natural resources are: None are required 4. How would the proposal be likely to use or affect environmentally sensitive areas or areas designated (or eligible or under study) for governmental protection; such as parks, n/li wilderness, wild and scenic rivers, threatened or endangered species habitat, historic or lD- culturalsites, wetlands, floodplains, or prime farmlands? �S �Jr414' ' Y��,I Report provides recommendations for development which include meth. a of maintaining :i existing sensitive areas. Proposed measures to protect such resources or to avoid or reduced impacts are: Incorporate individual project drainage analysis into drainage basins impacts, with identified impacts mitigated through developer requirements 5. How would the proposal be likely to affect land and shoreline use, including whether it would allow or encourage land or shoreline uses incompatible with existing plans? Report provides for review of new projects in relation to development standards to determine if a project is compatible or not. Proposed measures to avoid or reduce shoreline and land use impacts are: Determining project drainage compatibility and specific mitigation requirements in order to alleviate shoreline impacts as part of agency review process. • '13 6. How would the proposal be likely to increase demands on transportation or public services and utilities? Does not apply Proposed measures to reduce or respond to such demand(s) are: None required 7. Identify, if possible, whether the proposal may conflict with local, state, or federal laws or requirements for the protection of the environment. The Report has been prepared in accordance with the Green River Management Agreement and with coordination with each agency having regulatory jurisidction witin the described drainage basin. 8. Does the proposal conflict with policies of the Tukwila Comprehensive Land Use Policy Plan? If so, what policies of the Plan? Report does not conflict with the policies of the Tukwila Comprehensive land Use Policy Plan. Proposed measures to avoid or reduce the conflict(s) are: None required. 14- ••• E. SUPPLEMENTAL SHEET FOR ALL PROJECT AND NON PROJECT PROPOSALS The objectives and the alternative means of reaching the objectives for a proposal will be helpful in reviewing the aforegoing items of the Environmental Checklist. This information provides a general overall perspective of the proposed action in the context of the environmental information provided and the submitted plans, documents, supportive information, studies, etc. 1. What are the objective(s) of the proposal? The purpose of this report is to establish recommendations as to how future development and redevelopment of the area should address surface water runoff:` / Or� tv s 2. What are the alternative means of accomplishing these objectives? Best Management Practices (BMPs) have been described as: Alter this activity. Enclose the activity. Cover the activity. Segregate the activity. The actual means of accomplishing the necessary mitigation or construction activity would be determined during the review process for the individual project. 3. Please compare the alternative means and indicate the preferred course of action: BMP's will be incorporated into the approved drainage designs for new construction or redevelopment within the SE CBD drainage Study arca. 4. Does the proposal conflict with policies of the Tukwila Comprehensive Land Use Policy Plan? If so, what polices of the Plan? Report does not conflict with the policies of the Tukwila Comprehensive Land Use Policy Plan. Proposed measures to avoid to reduce the conflict(s) are: None required. • CITY OF TUKWILA SOUTHEAST CENTRAL BUSINESS DISTRICT ..N.Ne •'. NS 1° •• • v c2 0 • C a "CS A� $ t W " Z • C:, ° - • • • ,n,�•iid • o i'� :,'. i: ;GI -E;: 2 • u �• .00.. w�' �S : GOl= GARDNER CONSULTANTS, INC. January 26, 1993 Mr. Phil Fraser Senior Development /Surface Water Engineer Tukwila Public Works Department 6300 Southcenter Blvd. Tukwila, WA 98188 RE: Southeast CBD Drainage Study SEPA Checklist Dear Mr. Fraser: Attached, in accordance with our consultant services agreement, is our completed copy of the SEPA Checklist for the Southeast CBD Drainage Study Report previously submitted. Thank you for your assistance on this project. We appreciate the coordination and input you have provided. Please do not hesitate to call if you have any questions or comments. General Manager Enc. 111C11 -001 n /11:CR D1 f*t6.1; 81593 DEVELOP., 12720 GATEWAY DRIVE, SUITE 201 SEATTLE, WASHINGTON 9816B [2061242-9575 FAX [206) 242 -9617 GO GAIRDNEIR CONSULTANTS, INC. December 29, 1992 City of Tukwila Public Works Department 6300 Southcenter Boulevard Tukwila, WA 98188 RE: Southeast Central Business District Drainage Study GCI is pleased to submit thirty -five copies of the Final Report for the Southeast Central Business District Drainage Study in accordance with our consultant services agreement dated March 30, 1992. This report provides a description of the existing drainage basin, an evaluation of the drainage system and recommendations for establishing drainage parameters for future development. The recommendations are based upon existing physical constraints and are in accordance with accepted inter - jurisdictional drainage criteria. We have enjoyed the challenges and coordination incorporated into this project and appreciate this opportunity to assist the City of Tukwila. We hope to continue our working relationship on future public works projects in Tukwila. Very truly y• • GARD 1171° SUL ANTS, IN GE.RGE D. REYNOLDS General Manager 12720 GATEWAY DRIVE, SUITE 201 SEATTLE, WASHINGTON 98169 [206) 242 -9575 FAX (206) 242 -9617 CITY OF TU KWI LA SOUTHEAST CENTRAL BUSINESS DISTRICT DRAINAGE STUDY December, 1992 Prepared for: Public Works Department 6300 Southcenter Boulevard Tukwila, WA 98188 Prepared by: Gardner Consultants, Inc. 12720 Gateway Drive, Suite 201 Seattle, Washington 98168. (206) 242 -9575 TABLE OF CONTENTS PAGE EXECUTIVE SUMMARY INTRODUCTION 1 BASIN DESCRIPTION 2 EXISTING DRAINAGE SYSTEM 3 LOCAL AGENCY COORDINATION 4 SITE HYDROGEOLOGY 11 WETLAND ANALYSIS 12 NPDES PERMIT REQUIREMENTS 13 HYDRAULIC ANALYSIS 15 STORMWATER TREATMENT 19 STORMWATER POLLUTANTS AND THEIR EFFECTS 19 RECOMMENDATIONS 25 APPENDIX 1. CITY OF TUKWILA /RENTON INTERLOCAL AGREEMENT 2. B- TWELVE ASSOCIATES WETLAND ANALYSIS 3. HART- CROWSER SITE HYDROGEOLOGY REPORT EXECUTIVE SUMMARY CITY OF TUKWILA S.E. CBD DRAINAGE STUDY GCI initiated a study of the S.E. CBD Drainage Basin in April of 1992. The purpose of the study is to establish recommendations as to how future development and redevelopment of the area should address surface water runoff. Information was gathered from adjacent agencies and special interest authorities in regard to the existing control regulations and drainage infrastructure. This information was combined with survey information, a Site Hydrogeology Report and a Wetlands Analysis to prepare the comprehensive analysis of the existing hydrology of the area. The 147.2 acre basin is divided into a 37.9 acre sub -basin west of SR -181, and 109.3 acre sub - basin' east of SR -181. The west sub -basin has a series of constructed drainage systems connected directly to the Green River. The east sub -basin drains both directly and indirectly into Springbrook Creek via infiltration systems, detention ponds, constructed wetlands, natural wetlands and culvert systems. The relative differences between the SR -181 roadway elevation and the 100 -year Green River flood elevation Indicate that the roadway will drain to the river even when it is at its 100 -year flood stage. The east sub -basin flows through three 36 -inch culverts into the City of Renton. The combined capacity of these culverts is 75 cfs. The August 11, 1986 Interlocal Agreement with the City of Renton provides that Renton accept these flows. The D.O.E. has reviewed a number of Best Management Practices (BMP) methods for Improving surface water quality within the Puget Sound Basin. The recommended method for discharging storm runoff is to use infiltration trenches whenever practical. The recommendations resulting from the study are as follows: 1. If the City determines it is necessary to obtain easements to provide uniform maintenance for the regional drainage system, then acquire easements from Union Pacific and Burlington Northern Railroads for existing regional drainage system within railroad properties. 2. Encourage new development or redevelopment to use infiltration systems to dispose of storm drainage where soil investigations indicate infiltration will function properly. 3. Seek appropriate funding sources (i.e. Green River Flood Zone Control District and /or Corps of Engineers) for construction of a levee south of Strander Boulevard where the existing river bank has a tendency to erode. 4. Continue monitoring the City of Renton Springbrook Creek /P -1 channel studies to ensure that they provide for stormwater flow under the B.N. Railroad tracks. 5. Construct a 24 -inch diameter culvert under the proposed bicycle trail at Station 59 +50 with an invert elevation of 20.5. 6. Maintain existing ditch and wetlands and /or improvealong the west side of the proposed trail to provide for continued natural biofiltration. 7. The City of Tukwila should adopt by reference the Department of Ecology " Stormwoter Management Manual for the Puget Sound Basin" and the " Stormwater Program Guidance Manual for the Puget Sound Basin ". li S.E. CBD DRAINAGE STUDY INTRODUCTION: GCI was retained by the City of Tukwila in April of 1992 to prepare a study to review the existing drainage systems which were in place in the S.E. CBD Drainage Basin. This review Included mapping of the existing facilities including the wetland. The purpose of this study is to evaluate existing drainage systems and establish drainage parameters for future development. The recommended requirements for future development and redevelopment are based upon the existing physical constraints within the basin and are in conjunction with accepted inter - Jurisdictional drainage criteria. The scope of work for this study includes the following: 1. Prepare a map of the drainage basin using the existing Tukwila topographic map as a base map. 2. Evaluate regulations and requirements which determine future drainage solution parameters. 3. Review the area hydrogeology 4. Evaluate surface water characteristics with regard to the following: a) What "best management practices" (BMPs) are practical to improve the drainage water quality in this already developed basin. b) What is the condition of the SR -181 WSDOT drainage system. c) Possible NPDES permit constraints within the S.E. CBD Basin. d) Existing drainage capacity. e) Potential future drainage needs at buildout. 1 0 Existing wetlands constraints and potential uses. g) Surface water hydraulic characteristics. 5. Make recommendations for future development with regard to: a) Detention requirements. b) Best Management Practices (BMP). 6. Recommend basin wide capital improvements which address overall water quantity and quality solutions for the future. This study is intended to be used as a guide for reviewing drainage designs for future developments within the basin to ensure compatibility with the comprehensive quantity and quality requirements of the area. BASIN DESCRIPTION: The S.E. CBD Drainage Basin is bounded to the west by the Green River, to the south by South 180th Street, to the north by Strander Boulevard, and to the east by the eastern edge of the B.N. right -of -way Limits. The drainage basin is approximately 147.2 acres in total area. West Valley Highway (State Route 181) extends north /south, parallel to the Green River, through the length of the drainage basin. The SR -181 drainage, combined with the private property west of it, drains directly into the Green River through numerous storm drain outfalls. West of SR -181 which flows directly into the Green River has a 100 -year flood elevation of 26.8 feet at South 180th Street and 23.8 feet at Strander Boulevard. These elevations restrict building construction west of SR -181. The property east of SR -181 slopes toward Springbrook Creek located along the basin's east boundary. A portion of the drainage within this part of the basin infiltrates Into shallow permeable lenses of sand. The balance of the drainage flows Into adjacent wetlands and then to Springbrook Creek via culverts under the Union Pacific and Burlington Northern Railroad tracks. 2 The area east of SR -181 has a 100 -year flood elevation of 17.2 at South 180th Street and 14.8 at S.W. 27th Street (the approximate alignment of Strander Boulevard extended to the east). There are localized areas within this drainage basin which are lower than existing culvert systems along the railroad tracks and which may have to be Jeff in tact. Otherwise, redevelopment can be accomplished with drainage directed to the Springbrook Creek system. The City of Renton is obligated by the August 11, 1986 interiocal agreement with the City of Tukwila (see appendix) to allow drainage to pass easterly through the railroad corridor. EXISTING DRAINAGE SYSTEM: West Sub -basin - The drainage system for SR -181 and the area west of it consists of small pipe outfalls Into the Green River. Eleven of these are public outfalls ranging in size from 8 -inch to 24 -inch diameter. There are also private development outfalls for which complete information is not yet available. These drainage systems are direct discharge systems which flow into the Green River. Most of the drainage is routed through catch basins which are not equipped with oil separators. The existing drainage system for the 37.9 acre west subbasin, with its numerous direct discharges to the Green River, has more than adequate capacity to carry all the drainage it receives. East Sub -basin - This basin is characterized by infiltration systems and constructed wetland infiltration systems to dissipate stormwater runoff. It appears that the majority of this runoff migrates into shallow sand lenses and then into adjacent wetlands. From the wetlands, the drainage flows through culverts under a Puget Power access road and the railroad tracks Into Springbrook Creek in the City of Renton. The culvert system under the railroad beds has more than sufficient capacity to serve the 109.3 acre sub -basin by directly discharging drainage into the City of Renton. The Union Pacific culverts control the amount of drainage which can flow through to Springbrook Creek. Three primary culverts of 24 -Inch, 36 -inch and 48 -inch diameter have capacities of 15 cfs, 25 cfs and 60 cfs respectively. The 24 -inch culvert has an invert elevation of 19.36, the 36 -inch culverts invert is elevation 18.35 and the 48 -inch culvert invert is 20.67. The 48 -inch diameter culvert under the Puget Power access road between wetlands No.3 and No.1 has 3 invert elevations lower than the U.P. culvert. This culvert allows for equalization of water levels in the wetlands before it actually will transport water to the U.P. culvert. LOCAL AGENCY COORDINATION: A list of all agencies having possible Involvement and regulatory jurisdiction over the basin has been established. The agencies were then contacted and asked to provide any requirements and standards applicable to drainage in the basin. The following is a summary of their comments in alphabetical order by agency name. Burlington Northern Railroad: Dan Morris, (467 -3229) - Mr. Morris is a field engineer with Burlington Northern. In conjunction with a field Investigation of the study area, he Informed us of three 36 -Inch diameter culverts crossing the Burlington Northern tracks. These culverts drain to the east. FEMA: Larry Basich, (487 -4703) - Mr. Basich stated the 100 -year floodplain did not extend into the study area. Therefore, FEMA has no concerns with this study. Kent: Tom Tezuma, (859 -3383) - Mr. Tezuma stated that the City of Kent concerns are covered in the 'Green River Management Agreement'. Richard Chase - Mr. Chase stated that the City of Kent occasionally monitors stormwater discharge into the Green River. However, there are no strict quality regulations that the City must follow for storm drainage discharge at this time. King County/Green River Flood Control Zone District: Andy Lesveque, (296 -8379) - Mr. Lesveque stated that some of some of the King County concerns are listed in the Pump Operations Procedures Plan of the 'Green River Management Agreement'. The management plan was developed by the Green River Interlocal Agreement comprised of King County, Kent, Renton and Tukwila. This plan states that existing outfalls into the Green River are satisfactory. An increase in the size of existing outfalls, or any additional outfalls must be approved by the interlocal agencies if the increase in flow is greater than 30 cfs. 4 Also any new outfall system to the Green River must be shut down when the river reaches a flow rate of 12,000 cfs at the Auburn gauge. Storage capacity for a 100 -year 7 day storm is required for new drainage systems in conjunction with the shutdown of outfalls during 12,000 cfs events in the river. Renton: Ron Straka, (277 -5547) - The City of Renton has adopted the 1990 King County Surface Water Management Design Manual. New development drainage flowing into Renton from Tukwila must comply with the requirements as stated In the manual. Tukwila: Phil Fraser, (433 -0179) - The City of Tukwila has adopted the 1990 King County Surface Water Management Design Manual, and is planning to adopt a stormwater management ordinance which addresses development water quality issues. The City aiso has a Sensitive Areas Ordinance which regulates water courses and wetlands; and provides guidelines for wetland mitigation associated with development. Union Pacific Railroad: Ray Oneida, (764 -1467) - Mr. Oneida stated that Union Pacific has two culvert crossings along their tracks within the study area. U.S. Army Corps of Engineers: Joe Webber, (764 -3661) - The Corps has no discharge constraints for this size of study area. Tom Mueller, (764 -3495) - The Corps is only interested if fill Is being placed in existing wetlands. Water quality concerns are handled by the NPDES. Gail Teryzi - There are various fill permits issued by the Corps of Engineers. The type of permit required depends on the classification of wetland, and the area covered by the proposed fill. U.S.D.A. Soil Conservation Service (SCS): Rod Denherder, (764 -3325) - The SCS is not interested in discharges into the Green River. They do, however, need to know projected flows Into Springbrook Creek in order to update their model. The SCS may require retention /detention for flows to Springbrook Creek when the creek is in a flooding state. The SCS uses a 100 -year 24 hour design storm. 5 Washington State Department of Ecology: Helen Presley, (438 -7089) - Currently, the EPA's NPDES permit requirement for existing storm drainage systems applies to municipalities with a population greater than 100,000. The Department of Ecology will list their criteria for storm drainage in their forthcoming 'Stormwater Management Manual - for the Puget Sound Basin' which is expected to be published in September, 1992. Ann Wessel, (438 -7077) - There is a possibility that NPDES permits for existing storm drainage systems could require co-permitees in the future. In this case, the agency applying for the permit would include in the permit those municipalities contributing runoff upstream of their jurisdictional boundaries. Stan Ciuba, (438 -7042) - NPDES pen-nits are necessary for construction activities, industrial facilities and municipal improvements involving a disturbed surface area of greater than 5 acres in size. A number of people with the Department of Ecology both in Bellevue and in Olympia were questioned in regard to the advisability of stormwater injection wells. The Department of Ecology does not encourage the use of injection wells except in cases where they must be used to maintain a distinct quantity of water in an aquifer and then only with the use of pre- treatment. Pretreatment of storm drainage discharge into injection wells must meet criteria for groundwater quality, per WAC 173 -200. The principles governing Washington State's underground infection control program are defined in WAC 173 -218. The States Waste Discharge Permit Program (WAC 173 -216) also requires a municipality to treat and monitor injected stormwater. Washington State Department of Fisheries: Joe Roebel, (753 -2980) - Mr. Roebel stated that Fisheries would like stormwater flowing into Springbrook Creek and the Green River to be treated by blofiltration. The Department of Fisheries main concern for discharge into the Green River is water quality, not quantity. 6 Fisheries standards state that for storm events less than a 2 -year event, the amount of discharge into the Springbrook Creek can be no greater than 1/2 the 2 -year pre - development flow. For storms of greater intensity than the 2 -year design storm, the discharge rate Into the creek shall be no greater than the pre - development rate. The Department of Fisheries requires new development proposals to biofilter all flows less than the 2 -year event as a condition of their HPA permit. Washington State Department of Transportation: Bob Winter, (562 -4463) - Mr, Winter stated that WSDOT requires that local detention ordinances be followed. WSDOT also needs to be assured that additional flows do not 'silt up' their drainage transport systems, and will not compromise the existing water quality. WSDOT does not allow detention systems which will back -flow into their culverts or against their roadway fills. DOT Standards state that the depth of flow in a curb and gutter system cannot exceed 0.12 feet for a 10 -year storm, and that a head water culvert design shall not exceed 1.25 D. Jim Olson, (872 -6470) - Mr. Olson stated that WSDOT does not allow new drainage to enter their system unless it historically flowed in that direction. New drainage must also use existing culverts to be carried under a highway. In addition to the information received from the above agencies, the following documents outline parameters which development and redevelopment must include. 1. City of Tukwila Sensitive Areas Ordinance as modified by Ordinance No. 1608. 2. 1985 Green River Management Plan. 3. 1992 Green River Basin Program Interlocal Agreement 4. City of Renton Black River Water Quality Management Plan and Eastside Green River Watershed Plan. 5. 1992 Eastside Consultants, Inc. McLeod Exhibition Facility Drainage Analysis. 6. 1988 KCM Nelson Place /Longacres Way Storm Drainage System Preliminary Design. 7. 1986 KCM Nelson Place /Longacres Drive Basin Drainage Study. 8. 1991 R.W. Beck /City of Renton, Eastside Green River Watershed Plan, Project Summary Document, 7 9. 1992 R.W. Beck /City of Renton, Hydraulic Analysis Report. 10. 1991 R.W. Beck /City of Renton, Hydrologic Analysis. 11. 1991 R.W. Beck /City of Renton, Eastside Green River Watershed Plan, Current Conditions Document. 12. 1991 R,W. Beck /City of Renton, Water Quality Monitoring and Quality Assurance Project Plan for the Black River Water Quality Management Plan. 13. Jones & Stokes Associates, Inc., Wetland Inventory Black River Water Quality Management Plan /ESGRW. 14. Green /Duwamish Watershed Nonpoint Action Plan. 15. King County Flood Hazard Reduction Plan Eastside Green River Watershed Plan, Eastside Green River Watershed Plan, The following shows the permit requirements of regulatory agencies who have jurisdiction in the portion of the Springbrook Creek /Green River basin located within the study area. AGENCY Burlington Northern Railroad FEMA PERMIT REQUIRED No No 8 PERMIT NAME COMMENTS Storm discharge review by City of Tukwila in coordination with B.N. Permit required for work performed within B.N. right - of -way. Study area not within 100 - year floodplain, therefore, FEMA has no involvement. AGENCY Renton Tukwila Tukwila Union Pacific Railroad U.S. Army Corps of Engineers Washington State Department of Ecology PERMIT REQUIRED No Yes Yes Yes Yes Yes Yes PERMIT NAME Flood Zone Control Permit Street Use Permit Storm Drainage Various NPDES 9 COMMENTS Storm drainage review of flows into Springbrook Creek by Tukwila. Tukwila coordinates with City of Renton In analysis of flows. Permit required for all work within the City of Tukwila right -of -way. Permit for all drainage contributed to Tukwila's system. Storm discharge review by City of Tukwila In coordination with U.P. Permit required for work performed within U.P. right of way. Corps of Engineers required permit to fill in natural wetlands. NPDES required if drainage categorized as Industrial area discharge for a development project 5 acres or larger in size. PERMIT PERMIT AGENCY REQUIRED NAME COMMENTS Washington State No Utility Permit required when Department of work within WSDOT right -of- Transportation way. Otherwise, storm discharge review by City of Tukwila in coordination with WSDOT. DESIGN CRITERIA: The design criteria for new development or redevelopment within the basin is determined by the requirements of a number of sources. Specifically, the design criteria and associated agency are listed below: King County Surface Water 10 -year, 24 hour storm (detention) Management: 25 -year, 24 hour storm (conveyance) If Green River reaches 12,000 cfs, then must detain for 100 -year, 7 day storm. Renton: 10 -year, 24 hour storm (detention) 25 -year, 24 hour storm (conveyance) 10 Soil Conservation Service: Washington State Department of Fisheries: City of Tukwila: If Springbrook Creek or Green River reaches flood stage then must detain for 100 -year 24 hour storm For storm events larger than a 2 -year event, discharge Into Springbrook Creek will not exceed the pre - development flow. For a 2 -year or less event, discharge into Springbrook Creek will be at no greater than 1/2 the 2 -year pre - development flow. The City of Tukwila has adopted the 1990 King County Surface Water Design Manual as the basis for approving all development and redevelopment projects within the City. Supplemental to this document, all development within the S.E. CBD Drainage Basin must meet the more stringent requirements as imposed by other jurisdictional agencies for the Green River /Springbrook Creek drainage basins. Future requirements will be instituted as a result of the adoption of the Tukwila Development Standards and Stormwater Management Ordinance. SITE HYDROGEOLOGY: The firm of Hart- Crowser was responsible for the preparation of a hydrogeology report for the site based upon existing geotechnical reports which were available. Their work did not include field or laboratory testing. Their report is contained in the appendix of this study. The main points of their report are: 1. The study area Iles on the alluvial plain of the Green River and is underlain by river - deposited sediments consisting chiefly of sand and silt with some clay and peat. 11 2. Typical of river deposits, the strata underlying the basin are limited In areal extend. 3. Portions of the original topography have been modified and filled with sand and gravel for construction purposes. 4. There are several wetlands in the basin supported by precipitation and overland flow, The wetlands appear to be perched above the local water table. 5, The direction of groundwater flow is usually toward the Green River except at times of high river stage when the direction of groundwater flow may be away from the river. The flow from the Green River does not appear to be directly connected to Springbrook Creek because large changes in the Green River elevations are not reflected by changes in the level of Springbrook Creek. 6. The horizontal hydraulic conductivity of the alluvial deposits is estimated to be 10-3 to 10-5 centimeter /second (cm /sec) as inferred from in situ well tests performed in monitoring wells located at the perimeter of the basin, 7, Except for the Puyallup fine sandy loam, the soils in the basin have low infiltration rates and are generally not feasible for induced infiltration of stormwater. If there is limited induced infiltration, it would best be accomplished by the use of surface structures such as grasslined basins rather than by the use of dry wells. 8. Water migrates from wetland No.3 through a culvert in the fill on the power line right - of -way to wetland No.1. This migration is a major source of water for wetland No,1. WETLAND ANALYSIS: The firm of B- twelve Associates, Inc. was responsible for the preparation of a wetlands analysis for the S.E. CBD Drainage Basin which is contained in the appendix of this report. The following is a listing of the mapped wetlands within the basin and their classification based upon the City of Tukwila Sensitive Areas Ordinance. Figure No.1 (page 27), and Exhibit C In Appendix 2 provide the location of each wetland. 12 MAMA No.1 No.2 No.3 No.4 No.5, 6 & 7 No.8 No.9 No.10 No.11 CITY CLASSIFICATION Type 2 Type 2 Exempt (Constructed) Type 2 Type 3 Type 2 Exempt (Constructed) Type 2 Type 1 The wetlands are connected together by both existing culverts and pervious fill In the power line access road. The setbacks for the wetlands, as required by the City of Tukwila Sensitive Areas Ordinance, do not exist because development occurred prior to SAO and extends to the edge of the wetlands. It appears that the constructed drainage systems are a major source of water for the natural wetlands. The runoff flows through culverts fill which were installed for the power line access road. If the access road is developed into a trail, consideration should be made for the continued flow of water between the natural wetlands. If the existing flow is interrupted, the water quality of the natural wetlands could degrade to a septic condition. NPDES PERMIT: Congress has amended the Federal Clean Water Act to require the U.S. Environmental Protection Agency (EPA) to control stormwater discharges through the National Pollutant Discharge Elimination System (NPDES) permit program. The Washington State Department of Ecology (DOE) is responsible for implementing EPA requirements for stormwater permits in Washington State. The federal regulations apply only to "point source" stormwater discharging to surface waters and storm sewers. The goals for the new NPDES regulations are as follows: 1. Stop the illegal discharge of wastewaters and other pollutants into storm sewers, which should be used only for stormwater and other legally permitted discharges. 13 ' "0, •■•■ ow. 2. Reduce the amount of pollutants in stormwater. 3. Establish a permit system for stormwater discharged by municipalities over 100,000 In populations. 4. Establish a permit system for stormwater discharged from industrial sites; and 5. Eliminate water quality standards violations caused by stormwater discharges Industrial activities which may be required to have permits are as follows: 1 Industrial plant yards 2. Immediate access roads and rail lines used or traveled by carriers of raw materials, manufactured products, waste material, or by-products used or created by the facility. 3. Material handling sites 4. Refuse sites 5. Sites used for the application or disposal of process waste waters (as defined as 40 CFR part 401); 6. Sites used for the storage and maintenance of material handling equipment 7. Sites used for residual treatment, storage or disposal 8. Shipping and receiving areas 9. Manufacturing buildings 10. Storage areas (including tank farms) for raw materials, and Intermediate and finished products; and . 14 11. Areas where industrial activity has taken place in the past and significant materials remain and are exposed to stormwater Municipal activities which may be required to have permits are as follows: 1. Sand and gravel mining 2. Crushed and broken stone operations, and rip rap mining and quarrying 3. Landfills, land application sites, and open dumps that receive or have received industrial waste 4. Transportation services which have vehicle maintenance shops, equipment cleaning operations, or airport de -icing operations 5. Sewage treatment plants with a design flow above one million gallons per day 6. Construction activities, including clearing, grading or excavating sites which disturb five acres or more Municipalities over 100,000 in population (currently this Includes King, Pierce and Snohomish Counties, Seattle, and Tacoma) are also subject to federal regulations requiring system wide permits for their storm sewer systems. Industries and municipal operations which discharge their surface water runoff into infiltration systems are not subject to the NPDES permit requirements. The specific NPDES permit requirements are still being developed by the DOE and should be available in September, 1992. HYDRAULIC ANALYSIS: The S.E. CBD Drainage Basin consists of a 37.9 acre west sub -basin and a 109.3 acre east sub - basin. The west basin drains to the Green River and the east basin drains to Springbrook Creek, 15 The physical characteristics of the two drainage basins are distinctively different, West Basin: The drainage from the west basin is collected by many different small pipe systems and has eleven public ouffalls (see attached map) in addition to the outfalls from private property which directly discharge stormwater into the Green River. The drainage is collected by small Type 1 catch basins without oil /water separators. There are two small areas outside at the riverbank which are susceptible to flooding (see attached map). Portions of the existing river side is protected with levees. One part of the riverbank which is unprotected and susceptible to flooding is the area just south of Strander Boulevard. The drainage systems function very well under most conditions. There can be backwater conditions for the ouffalls when the Green River is in a flood stage. The 100 -year flood elevation varies from 26.8 feet at South 180th Street to 23.8 feet at Strander Boulevard. The elevation of SR -181 which forms the boundary between the west and east basin is 33.0 near South 180th Street and 27.5 at Strander Boulevard. The following table lists the eleven different ouffalls along with pertinent hydraulic data: 6 Hr. 25 Yr. Storm Flow Unused 'Outfall Outfall Tributary • • .a o Hydraulic Hydraulic •1 -S ... 1 ... 1. 18" 0,35 0.062 26.0 0.3 25.7 2. 12" 0.60 0.038 7.0 0.5 6.5 3. 12" 0.55 0.045 7.6 0.4 7.2 4. 12" 0.35 0.065 9.2 0.3 8.9 5. 18" 0.85 0.057 25.0 0.7 24.3 6. 18" 1.50 0.046 22.0 1.2 20.8 7. 8" 0.55 0.048 2.7 0.4 2.3 8. 24" 5.00 0.036 43.0 3.9 39.1 9. 8" 0.85 0.067 3.2 0.7 2.5 10. 18" 1.25 0.065 27.0 1.0 26.0 11. 12" 1,30 0.036 6.7 1.0 5.7 ' Outfall locations beginning at South 180th Street (1) proceeding to Strander Boulevard (11). 16 The table shows that the hydraulic capacity of the existing DOT drainage system is In excess of the existing transport needs. A 6 hour 25 -year design storm for the maximum buildout under existing land use conditions was selected to evaluate the capacities of the drainage transport system. This design storm is compatible with the design storm used throughout the City to evaluate storm drainage transport systems. The SCS Type 1a distribution pattern for the storm was used to evaluate the peak flows in the transport system. The small drainage systems which serve the 37.9 acre west basin will function even when the Green River is in flood stage. The difference between the Green River flood elevation and the elevation of SR -181 provides for an adequate hydraulic gradient for storm drainage runoff. It may be possible that future development east of SR -181 could be constructed at an elevation that would allow for its drainage to be handled by the existing drainage system. This may be possible after the City accepts ownership and operation and maintenance responsibility for the roadway. The existing public storm drain systems in SR -181 will be exempt from the D.O.E. NPDES permit process as it is currently written. The private drainage systems which discharge directly into the Green River were not mapped because we did not have complete plans for the systems. The private systems, which are industrial sites may be required to acquire NPDES permits from the D.O.E. The conditions of the permits are still not known. East Basin: The east basin is distinctly different from the west basin. It does not have the network of pipes to carry drainage directly to Springbrook Creek. There is an existing 48 -inch diameter culvert and a proposed 24 -Inch diameter culvert under the Puget Power access road which work in conjunction with a series of culverts under the Union Pacific and Burlington Northern Railroad tracks to carry surface runoff. The U.P. tracks have a 24 -inch diameter culvert with an inlet elevation of 19.36, a 36 -inch diameter culvert with an inlet elevation of 18.35 and a 48 -inch culvert with an inlet elevation of 20.67. Overland flow which passes under the U.P. tracks then flows under the Burlington Northern tracks. The inlet elevations of the 36 -inch culverts (from south to north) are 18.71, 18.72 and 21.17. (See attached map) 17 GCI and B- twelve located an existing 48 -inch diameter culvert which directly discharges from west of the Puget Power right -of -way to the culverts crossing the U.P. railroad tracks. It appears that the development drainage flows into constructed retention ponds or infiltration trench systems. It then flows and percolates into natural wetlands which outlet through the railroad culverts. Without surcharging, the capacity of the U.P. culverts are 15 cfs for the 24 -inch diameter culvert, 25 cfs for the 36 -inch diameter culvert and 60 cfs for the 48 -inch diameter culvert. The existing development's use of retention and infiltration systems retards flows to the culvert system. The Hydrology Report prepared by Hart- Crowser indicates that there is little percolation into the groundwater aquifer. The east basin developments do not have point discharges and, therefore, are exempt from acquiring an NPDES permit as the requirements are now written. If the basin is analyzed in the traditional manner the basin overland flow can be divided into that going into the 24 -inch diameter culvert, the 36 -inch diameter culvert and the 48 -inch diameter culvert under the Union Pacific Railroad tracks. This scenario will require that a culvert be constructed under the proposed pedestrian /bicycle trail west of the Union Pacific railroad track north of the railroad spur. The 6 hour 25 -year transport storm which flows to the 24 -inch and 36 -inch diameter culverts from their 61.1 acre tributary area is 11.4 cfs. The 6 hour 25 -year storm which flows to the 48 Inch diameter culvert from its 16.5 acre tributary area is 4.1 cfs. The hydraulics of this analysis indicate that there is capacity in the railroad culvert system to handle the 6 hour 25 -year storm as long as the overland flow can flow under the trail which is now under design. The elevation of the water flowing through the 24 -inch and 36 -inch culverts is approximately elevation 21. The hydraulic grade line can be projected back across the wetland to the building lot areas to see what the relative elevation of the drainage at the building pads would be. The hydraulic grade line can be projected back at a slope of 0.2% from the high water in the 24 -inch and 36 -inch diameter culverts. The hydraulics of the piped /wetland transport drainage system downstream from the Union Pacific railroad track culverts Is very straight forward. The capacity of the Burlington Northern track culverts is more than double the capacity of the Union Pacific track culverts. The flow from the B.N. culverts at Invert elevations of 18.7 flows into a wetland in the City of 18 Renton and into Springbrook Creek which has a normal bottom elevation at S. 180th Street of 7.5 and a 100 -year flood elevation of 17.2. The City of Renton is responsible for ensuring that a channel for storm drainage be maintained between the B.N. culverts and Springbrook Creek (see attached Renton Maps). The three 36 -inch diameter culverts which cross under the Burlington Northern Railroad track have a capacity of 25 cfs each, for a total of 75 cfs. The City of Renton Is responsible for providing facilities to accept this flow. STORMWATER TREATMENT: A number of approaches are being taken in an attempt to control stormwater pollution so that the water quality of receiving water is minimally impacted. The Department of Ecology's present approach to improving water quality is to use Best Management Practices (BMP). This involves developing standards "by evaluating receiving water conditions under a variety of watershed developments and BMP use scenarios." The D.O.E. is continuing to research the best approach to establishing water quality standards. The D.O.E. now recommends that infiltration systems be the preferred BMP for reducing stormwater runoff where it is feasible. The following excerpt from The D.O.E. Stormwater Management Manual for the Puget Sound Basin" outlines the basis for the D.O.E.'s concern about stormwater quality. STORMWATER POLLUTANTS AND THEIR EFFECTS: To appreciate the need for Best Management Practices to minimize pollution of urban stormwater runoff we begin with an overview of the types of pollutants commonly found In this runoff. • 011 and grease: Concentrations in stormwater from commercial and Industrial areas often exceed the Washington Department of Ecology (Ecology) guideline of 10 mg/ 1. 19 • Nutrients: Phosphorus and nitrogen can cause excessive or accelerated growth of aquatic vegetation. Such growth can significantly affect lakes and may also be of concern In Puget Sound. • Oxygen demanding organics: Natural organic materials washed from paved surfaces are consumed by bacteria present in receiving waters. Oxygen may be depleted in the process, threatening higher organisms such as fish. • Metals: Stormwater contains metals such as lead, zinc, cadmium, and copper at concentrations that often exceed water quality criteria. Research in Puget Sound has found that metals and toxic organics concentrate in sediments and at the water surface (microlayer) where they interfere with the reproductive cycle of many biotic species as well as cause tumors and lesions in fish. • Bacteria and viruses: Research has shown that stormwater contains disease- causing bacteria and viruses, although not at concentrations found in sanitary sewage. Shellfish along Puget Sound near urban areas are usually unsafe for consumption due to these bacteria. • Eroded soil: Erosion of soil during construction carries soil particles into streams. These sediments destroy the desired habitat conditions for fish. The sediment may be carried to lakes or Puget Sound where they may be toxic to marine life and make dredging necessary. TYPICAL POLLUTANT CONCENTRATIONS: Research in Western Washington has shown that the concentrations of pollutants In stormwater from residential, commercial and industrial areas exceed Ecology's water quality standards and guidelines. Examples are shown In the following Table. Although little data exist for specific land uses such as shopping centers, it is expected that research would produce similar results. 20 What are BMPs? In its long range plan, the Puget Sound Water Quality Authority cites stormwater control as one of 12 key action programs. Their control strategy Is to emphasize the use of Best Management Practices. Best Management Practices (BMPs) are defined as physical, structural and /or managerial practices, that when used singly or in combination, prevent or reduce pollution of water and have been approved by Ecology. BMPs may be placed Into two general groups: source control BMPS and runoff treatment BMPs. The former group includes those BMPs which keep a pollutant from ever coming in contact with stormwater; the latter group consists of various methods of treating stormwater. Source control BMPs are preferred as they are generally less expensive and are frequently very effective in eliminating the source of pollution prior to its entry into runoff. BMP STRATEGIES AND PREFERENCES: There are many types of BMPs, some of which represent general strategies for dealing with stormwater. Listed below are several of these BMPs in order of their preference as related to their effectiveness. 21 10 O L O U a D U .0 o c O c,) o• 'O 0 c Q �L o• CV Sri 0 O zz • 4-C) E cn p j o o• o o a N< •V N Cr U w N � O 0 N \ N C co U L.L. C +_ J 0 M O a O V 0 O 0 O U�o ci o c CI• D) 0. coN 2 E " o o• in o w 0 Q o co o 0 0 8 O 0 N O 5 c N 0 0 0 O 3 [L ti O_ Ea a � O a) ° g °m 0 O _ N U a • O 5 iii H C a) a c ^� g o O. v . 0_ CD a ° E O rn0 0 U cn j `n o v = o 0 z O N N '_ 0 C N CA 0 O > wv • .- a CO u CO 0 N CO N O• 4) O0 U 0 U E w 0o 0 E w U o a° U 0 - N O Fecal Particulate fraction values apply to concentration data for commercial and industrial land uses only. Acute criteria for freshwater at a hardness of 20 ppm. Ecology effluent guideline (mg /1); all other values are receiving water standards. Ecology criteria for class AA water. Alter the activity: The preferred option is to alter any practice that may contaminate surface water or groundwater by either not producing the pollutant to begin with or by controlling it in such a way as to keep it out of the environment. An example would be recycling used oil rather than dumping it down a storm drain. Illicit or unintentional connection of indoor drains to the storm drain, rather than to the sanitary or process sewer is a significant source of stormwater contamination. Research and local experience have demonstrated the importance of identifying and correcting these connections. Enclose the activity: If the practice cannot be altered, it should be enclosed In a building. Enclosure accomplishes two things. It keeps rain from coming into contact with the activity, and since drains inside a building must discharge to sanitary or process wastewater sewers or a dead -end sump, any contamination of runoff is avoided. Cover the activity: Placing the activity inside a building may be Infeasible or prohibitively expensive. A less expensive structure with only a roof may be effective although it may not keep out all precipitation. Internal drains must be connected to the sanitary sewer to collect water used to wash down the area as well as any rain that may enter along the perimeter. Segregate the activity: Segregating an activity that is the most significant source of pollutants from other activities that cause little or no pollution may lower the cost of enclosure or covering to a reasonable level. If the segregated activity cannot be covered, it may be possible in certain situations to connect the area to the public sanitary sewer subject to the approval of the local Sewer Authority. Or, drains may be connected to a business' own process wastewater system if the business operates independently of the local authority, Discharge stormwater to the process wastewater treatment system: Many industries have their own process wastewater treatment system with final disposal directly to the receiving water. Here, stormwater from areas of significant pollution sources can be plumbed to the process treatment system as long as its capacity is not exceeded. 23 Discharge small, high freauencv storms to public sanitary sewer: This BMP would be limited to those few outside activities that contribute unusually high concentrations of pollutants and /or pollutants of unusual concern. Limited entry of these few special cases may not overtax the public sanitary sewer. It is important, however, to first have the approval of the local Sewer Authority. The entry of stormwater to the sanitary or combined sewer can be limited to the small high - frequency storms that carry off the majority of pollutants over time. Storm flows in excess of the hydraulic capacity of the sanitary or combined sewer would be discharged to the storm drain. Discharge small. high frequency storms to a dead -end sump: This BMP would be limited to those few activities which contribute unusually high concentrations of pollutants and /or pollutants of unusual concern. This option would be used when discharge into a sanitary sewer or process wastewater treatment is not available or feasible. This option requires the capability to have the sump pumped out regularly and the pumpage disposed of in an appropriate manner. Treat the stormwater with a stormwater treatment BMP: The treatment of stormwater is the least- preferred option for several reasons. As noted previously, source control BMPs keep the pollutants completely away from stormwater. In contrast, stormwater treatment devices are not 100% effective. Note, the table on page 22 shows that even if a stormwater treatment is 75% effective, freshwater criteria may still not be met for commercial areas. In addition, Inadequate maintenance can reduce a system's expected efficiency. THE IMPORTANCE OF EFFECTIVE MAINTENANCE: BMPs require regular attention to ensure their effectiveness. For example, containers for Dangerous Wastes must be kept closed if they are stored outside. Allowing the entry of rain to an open container may cause the overflow of its contents to nearby street drains. Stormwater treatment devices such as oil /water separators must be cleaned frequently. Unfortunately, due to lack of experience or oversight by the owner, inadequately maintained facilities are common. 24 King County has found that public and private storm drainage control systems must be Inspected by the public authority at least annually to insure proper maintenance. The D.O.E. is continuing to search the best approach to establishing water quality standards. The D.O.E. now recommends that infiltration systems be the preferred BMP for reducing stormwater runoff where it is feasible. The specific BMPs which should be used for a project will depend upon the contaminants which are contained in the storm drainage leaving the protect site, the physical constraints of the project site, and the contaminant removal requirements. RECOMMENDATIONS: The following recommendations are based upon the information provided in the proceeding chapters and upon potential changes which may effect the stormwater runoff within the S.E. CBD area. The scope of this study was limited by budgetary considerations. This study provides recommendations based on general information obtained from reports and studies which cover the area. The following recommendations are not site specific and in order to evaluate development or redevelopment projects site specific studies must be done. These studies may include the following: mapping of the wetlands, detailed soil inventory, groundwater variation study and the 100 -year flood plain elevation determination within each site. 1. If deemed appropriate by the City of Tukwila, the City may pursue the acquisition of easements from the Union Pacific and Burlington Northern Railroads for the existing regional drainage system within the railroad property. This will allow the City to maintain the drainage systems without requiring prior approval from the railroads. 2. Encourage new development or redevelopment to use infiltration systems to dispose of storm drainage where soil investigations indicate infiltration will function properly. The D.O.E. concurs with this recommendation as the best way to mitigate peak runoff problems, 25 3. Seek appropriate funding source (Corps of Engineers) for construction of a levee south of Strander Boulevard where the existing river bank has a tendency to erode. This area is now susceptible to peak flow erosion problems. 4. Continue to monitor the City of Renton's development of Springbrook Creek /P -1 channel studies to ensure that they continue to provide for stormwater flow under the B.N. Railroad tracks. The east portion of the S.E. CBD drainage basin flows into the City of Renton and that outlet must be maintained. 5. The City should construct a 24 -inch diameter culvert under the proposed bicycle trail at Station 59 +50 with an invert elevation of 20.5. This culvert will equalize high water levels and thus limit flooding potential. 6. The existing ditch and wetlands should be maintained and possibly improved along the west side of the proposed trail to provide for continued natural biofiltratlon. This will help mitigate the formation of stagnate water pools which form during the summer. 7. The City of Tukwila should adopt by reference the Department of Ecology " Stormwater Management Manual for the Puget Sound Basin" and the " Stormwater Program Guidance Manual for the Puget Sound Basin ", The adoption of these documents will provide the City with an authoritative basis to request mitigation of drainage issues for development and redevelopment projects. Job No. 110G92031 192/92!(HRkCa)(ww) 12/31/92 26 CITY OF TUKWILA /RENTON INTERLOCAL AGREEMENT APPENDIX 1 A •c C F'l.c n DATE f /,i1{' -4) INTERLOCAL AGREEMENT REGARDING RiCIPROC L AEXAfi1ris THIS AGREEMENT is entered into between the City of Tukwila, hereinafter referred to as "Tukwila ", and the City of Renton, hereinafter referred to as "Renton ". WHEREAS, the Cities of Renton and Tukwila are authorized by Chapter 39.34 RCW to enter into agreements for the purpose of interlocal cooperation, and WHEREAS, the Tukwila City Council has passed Resolution No. 1008 , which indicates Tukwila's willingness to accept annexation to Tukwila of certain property currently located within Renton and more particularly described on Exhibit A attached hereto and incorporated herein by this reference as if fully set forth to Tukwila, and calls for certain property currently located within Tukwila and described on Exhibit B attached hereto and incorporated herein by this reference as if fully set forth to be annexed to Renton, and WHEREAS, the Renton City Council has passed Resolution No. oZ�Si , which calls for certain property currently located within Renton and more particularly described on Exhibit A to be annexed to Tukwila and indicates Renton's willingness to accept annexation of certain property currently located within Tukwila and more particularly described on Exhibit B to Renton, and WHEREAS, both Resolutions recognize that there are issues of concern to both Renton and Tukwila that must be mutually resolved and Renton and Tukwila desire to enter into an interlocal agreement to resolve these issues, now, therefore FOR AND IN CONSIDERATION OF the mutual benefits and conditions hereinafter contained, the parties hereto agree as follows: 1. Scope and Effect of Agreement. It is the intent of the parties to resolve issues of mutual concern with respect to pending reciprocal annexations. This Agreement shall become effective and shall bind the parties upon completion of the latter of the annexation of the property described on Exhibit B to Renton and annexation of the property described on Exhibit A to the City of Tukwila. In the event that, for any reason, one or both of the above referenced annexations are not completed, then this Agreement shall be null and void. 2. Strander Boulevard /S. W. 27th Street Improvements. Local costs of the future crossing of the railroad tracks by Strander Boulevard /S. W. 27th Street should be shared equitably between the two parties. In pursuit of this Agreement, both Cities agree to designate the aforementioned improvement of Strander Boulevard /S. W. 27th Street as a high priority item on each City's Transportation Improvement Plan, and each provide one -half of the local funds needed to match an 80% federal funding for this road improvement project. Because the timing of this street extension is uncertain, Renton and Tukwila agree to monitor development and, as development warrants, to acknowledge that the route is needed and that both jurisdictions will cooperate to insure that an appropriate connection is designed and constructed. Because the crossing will be located entirely within Tukwila upon completion of the annexation, the final decision as to the time for improvement shall be left to the discretion of Tukwila. If federal funding is unavailable, then Renton and Tukwila will negotiate an equitable funding option as necessary, such that each cities' share of the local costs of the improvement shall be 50 %. 3. S. W. 43rd Street /S. 180th Street Improvements. If a proposed grade separated crossing of S. W. 43rd and the railroad tracks is undertaken to improve traffic safety and capacity, the Interlocal Agreement Regarding Reciprocal Annexations Page 2 local costs should be shared equitably between Renton and Tukwila. The two Cities shall support the S. W. 43rd Street /S. 180th Street improvement in the same manner as the Strander Boulevard /S. W. 27th Street railroad crossing. By support, it is meant that both Cities will designate this road improvement as a high priority item on each Cities' Transportation Improvement Plan and each provide one -half of the local funds needed to match an 80% federal funding for this road improvement project. If federal funding is unavailable, then Renton and Tukwila will negotiate an equitable funding option as necessary, such that each cities' share of the local costs of such road improvement shall be 50 %. Because the improvement will be located entirely within Tukwila upon completion of the annexation, the final decision as to the time for the improvement shall be left to the discretion of Tukwila. 4. P -1 Channel. The P -1 Channel is a storm drainage improvement to be located within that property described on Exhibit B which will be annexed to Renton. Renton agrees to assume what would have been Tukwila's share of the cost of construction and maintenance for that portion of the P -1 Channel which will be located in said area. The City of Tukwila shall retain the right to connect to and use the P -1 Channel. 5. Green River Dike Maintenance. Renton's share of the cost of the Green River Dike Maintenance Plan was 22% prior to the reciprocal annexations. Construction and maintenance costs for the Green River Dikes should be revised to reflect the fact that Renton will not have Green River frontage after the reciprocal annexations are completed and that therefore Renton should have no obligation for dike maintenance or rehabilitation. 6. Frank Zepp Bridge. Upon completion of the reciprocal annexations, the Frank Zepp Bridge at S. W. 43rd Street /S. 180th Street will be located entirely within the City of Tukwila. Tukwila agrees to assume all costs of maintenance and future widening for the bridge. Both parties understand that with the annexation of the property described on Exhibit A to Tukwila, the responsibility for maintenance and operation of the traffic signals at the intersection of S. W. 43rd Street and West Valley Road (SR -181), formerly shared by the Cities of Renton and Kent, should be assumed in total by the City of Kent. 7. Utilities. Both parties understand that Renton has existing utilities serving a portion of the area to be annexed to the City of Tukwila bordered by S. W. 43rd Street, West Valley Highway, the existing Renton City limits and the Union Pacific Railroad right -of -way. Renton shall retain ownership of the said existing utilities and shall be responsible for all costs of operation and maintenance of the same. Tukwila shall be responsible for providing sewer and water service to all other areas annexed to Tukwila as part of the reciprocal annexations. Neither party shall impose a surcharge upon utility users within the newly annexed areas solely because of their annexation. 8. SR -181. The City of Renton should enter into an agreement with the State of Washington regarding the transfer of costs to the State for improvements to SR -181 between S. W. 43rd Street and 1 -405. The City of Tukwila shall bear no responsibility for such costs by virtue of the execution of this Agreement. 9. Future Annexations. Renton and Tukwila will coordinate review of future annexation petitions received by the parties consistent with the boundary line shown on Exhibit C attached hereto and incorporated herein by this reference as if set forth in full. EXHIBIT A Lands to be Annexed to Tukwila from Renton The lands proposed to be annexed to the City of Tukwila from the City of Renton are listed below and shown in Figure 1. SECTION - TOWNSHIP -RANGE PARCEL ACREAGE NW 1/4 of Sec. 24, Twn. 23, Rqe. 4 27 (portion) 3.62 12 SW 1/4 of Sec. 24, Twn. 23, Rge. 4 63 2.35 32 0.27 28 3.85 7 MDC 4.55 NW 1/4 of Sec. 25, Twn. 23, Rge. 4 38 1.84 0.91 8 MDC (p) 2.91 1.14 9 MDC (p) 3.05 43 2.15 50 0.84 51 0.72 23 2.16 6 6.70 2.16 24 (portion) 44.10 21 MDC 2.45 2.16 22 (portion) 10.47 SW 1/4 of Sec. 25, Twn. 23, Rge. 4 21 1.61 59 0.37 20 2.14 33 3.69 17 5.93 3.01 23 (portion) 10.43 24 (portion) 5.44 44.10 22 3.01 NW 1/4 of Sec. 36, Twn. 23, Rge. 4 97 3.00 57 8.69 62 6.40 61 0.17 11 6.83 43 0.10 37 0.17 38 0.14 39 0.14 53 0.14 14 0.12 13 0.12 29 0.32 10 0.14 9 0.19 59 0.15 8 0.17 1.7 0.12 35 2.84 34 5.54 36 3.09 TOTAL I 45 parcels 101.65 EXHIBIT B Lands to be Annexed to Renton from Tukwila The lands proposed to be annexed to the City of Renton from the City of Tukwila are listed below and shown in Figure 1. SECTION - TOWNSHIP -RANGE PARCEL ACREAGE SW 1/4 of Sec. 25, Twn. 23, Rge. 4 41 19.05 4 23.44 NW 1/4 of Sec. 25, Twn. 23, Rge. 4 42 16.03 SW 1/4 of Sec. 25, Twn. 23, Rge. 4 19 40.21 SE 1/4 of Sec. 14, Twn. 23, Rge. 4 0160 (portion) 11.79 0145 .29 0155 (portion) 1.29 0150 1.49 0320 .28 0330 .02 Lot #2 .12 TOTAL 11 parcels 114.01 F re i Renton-Tukwi 1 Boundary /Boundary Adjustment Map of Affected Areas Lands to Renton LOmGACRES VIC Lands to Tukwila Lands to Renton Lands to Tukwila LoWill t; F Ire 1 Renton -Tukwi Boundary Adjustment Map of Affected Areas Lands to Renton LGNuACRES Lands to Tukwila Lands to Renton Lands to Tukwila CIT-, T1 L 1.11.1• aoad' EXHIBIT C Areas Subject to Joint Tukwila-Renton Review of all Future Annexation Petitions kijrnommietaR241 ahlialUg„310; -‘=4i .411-1BMitrifitt;Lz„.„"; CITY OF TUKWILA WASHINGTON RESOLUTION NO /6'67 . A RESOLUTION OF THE CITY OF TUKWILA, WASHINGTON, ESTABLISHING INTENT TO ANNEX CERTAIN AREAS FROM THE CITY OF RENTON, WASHINGTON, REQUESTING THE CITY OF RENTON TO ANNEX CERTAIN AREAS CURRENTLY WITHIN THE CORPORATE LIMITS OF THE CITY OF TUKWILA, SPECIFYING TERMS AND CONDITIONS OF SUCH ANNEXATIONS AUTHORIZING THE MAYOR AND CITY CLERK TO EXECUTE AN AGREEMENT WITH RENTON ACCORDING TO SUCH TERMS AND CONDITIONS AND REPEALING RESOLUTION NO. 1002 OF THE CITY COUNCIL. WHEREAS, the current location of the common corporate boundary between the City of Renton and the City of Tukwila is irregular and does not follow an easily identified natural feature, and WHEREAS, the current boundary is difficult for residents, businesses, and public officials to recognize and use, and WHEREAS, the current irregular boundary limits the ability of one respective jurisdictions to plan for future land use and logical service areas, and WHEREAS, realigning and simplifying the common boundary would be in the mutual interest of Renton and Tukwila, and WHEREAS, a realigned boundary would provide more logical service areas, including emergency service response areas, and WHEREAS, a realigned boundary would clarify land use planning responsibilities and provide more logical mailing addresses, and WHEREAS, staff members of the respective Cities have explored the potential areas of fiscal and administrative concern in detail, and WHEREAS, the City of Renton, acting as lead agency for purposes of SEPA, a Determination of Non - Significance for a proposed realignment of boundaries between the two Cities to be accomplished by reciprocal annexations pursuant to RCW 35.10.217, now, therefore, THE CITY COUNCIL OF THE CITY OF TUKWILA, WASHINGTON HEREBY RESOLVE AS FOLLOWS: 2. S. W. 43rd Street /S. 180th Street Improvements. If a proposed grade separated crossing of S. W. 43rd and the railroad tracks is undertaken to improve traffic safety and capacity, the local costs should be shared equitably between Renton and Tukwila. The two Cities shall support the S. W. 43rd Street /S. 180th Street improvement in the same manner as the Strander Boulevard /S. W. 27th Street railroad crossing. By support, it is meant that both Cities will designate this road improvement as a high priority item on each City's Transportation Improvement Plan and each provide one -half of the local funds needed to match an 80% federal funding for this road improvement project. If federal funding is unavailable, then Renton and Tukwila will negotiate an equitable funding option as necessary, such that each cities' share of the local costs of such road improvement shall be 50 %. Because the improvement will be located entirely within Tukwila upon completion of the annexation, the final decision as to the time for the improvement shall be left to the discretion of Tukwila. 3. P -1 Channel. The P -1 Channel is a storm drainage improvement to be located within that property described on Exhibit B which will be annexed to Renton. Renton agrees to assume what would have been Tukwila's share of the cost of construction and maintenance for that portion of the P -1 Channel which will be located in said area. The City of Tukwila shall retain the right to connect to and use the P -1 Channel. 4. Green River Dike Maintenance. Renton's share of the cost of the Green River Dike Maintenance Plan was 22% prior to the reciprocal annexations. Construction and maintenance costs for the Green River Dikes should be revised to reflect the fact that Renton will not have Green River frontage after the reciprocal annexations are completed and that therefore Renton should have no obligation for dike maintenance or rehabilitation. 5. Frank Zepp Bridge. Upon completion of the reciprocal annexations, the Frank Zepp Bridge at S. W. 43rd Street /S. 180th Street will be located entirely within the City of Tukwila. Tukwila agrees to assume all costs of maintenance and future widening for the bridge. Both parties understand that with the annexation of the property described on Exhibit A to Tukwila, the responsibility for maintenance and operation of the traffic signals at the intersection of S. W. 43rd Street and West Valley Road (SR -181), formerly shared by the Cities of'Renton and Kent, should be assumed in total by the City of Kent. 6. Utilities. Both parties understand that Renton has existing utilities serving a portion of the area to be annexed to the City of Tukwila bordered by S. W. 43rd Street, West Valley Highway, the existing Renton City limits and the Union Pacific Railroad right -of -way. Renton shall retain ownership of the said existing utilities and shall be responsible for all costs of operation and maintenance of the same. Tukwila shall be responsible for providing sewer and water service to all other areas annexed to Tukwila as part of the reciprocal annexations. Neither party shall impose a surcharge upon utility users within the newly annexed areas solely because of their annexation. 7. SR -181. The City of Renton should enter into an agreement with the State of Washington regarding the transfer of costs to the State for improvements to SR -181 between S. W. 43rd Street and I -405. The City of Tukwila shall bear no responsibility for such costs by virtue of the execution of this Agreement. 8. Future Annexations. Renton and Tukwila will coordinate review of future annexation petitions received by the parties consistent with the boundary line shown on Exhibit C attached hereto and incorporated herein by this reference as if set forth in full. - 3 - EXHIBIT A Lands to be Annexed to Tukwila from Renton The lands proposed to be annexed to the City of Tukwila from the City of Renton are listed below and shown in Figure 1. SECTION - TOWNSHIP -RANGE PARCEL ACREAGE NW 1/4 of Sec. 24, Twn. 23, Rqe. 4 27 (portion) 3.62 TETT SW 1/4 of Sec. 24, Twn. 23, Rge. 4 63 2.35 32 0.27 28 3.85 7 MDC 4.55 NW 1/4 of Sec. 25, Twn. 23, Rge. 4 38 1.84 0.91 8 MDC (p) 1.91 1.14 9 MDC (p) 3.05 43 2.15 50 0.84 51 0.72 23 2.16 6 6.70 2.16 24 (portion) 11717 21 MDC 2.45 2.16 22 (portion) 10.47 SW 1/4 of Sec. 25, Twn. 23, Rge. 4 21 1.61 59 0.37 20 2.14 33 3.69 17 5.93 3.01 23 (portion) 0.43 24 (portion) 5.44 -44717 22 3.01 NW 1/4 of Sec. 36, Twn. 23, Rge. 4 97 3.00 57 8.69 62 6.40 61 0.17 11 6.83 43 0.10 37 0.17 38 0.14 39 0.14 53 0.14 14 0.12 13 0.12 29 0.32 10 0.14 9 0.19 59 0.15 8 0.17 1.7 0.12 35 2.84 34 5.54 36 3.09 TOTAL 45 parcels 101.65 ; re 1 \ Renton-ruw"..0 Boundary Adjustment Map of Affected Areas Lands to Renton :IK Lands to Tukwila 2000. Lands to Renton Lands to Tukwila CITY OF TU 0042.010.009 JEH /ko 12/01/86 01/06/87 WASHINGTON RESOLUTION NO. 1 nag <WILA A RESOLUTION OF THE CITY COUNCIL OF THE CITY OF TUKWILA, WASHINGTON, ANNEXING CERTAIN REAL PROPERTY TO THE CITY OF TUKWILA FROM THE CITY OF RENTON. WHEREAS, Resolution No. 2651 of the City of Renton requested that the City of Tukwila annex certain real property located in the City of Renton as part of a common effort by Renton and Tukwila to simplify their common boundaries, and WHEREAS, Resolution 1008 of the City of Tukwila declared the City of Tukwila's willingness to accept such annexation upon certain conditions and requested that the City of Renton annex certain property located within the City of Tukwila as a reciprocal measure designed to simplify the common boundary, and WHEREAS, the City of Renton and the City of Tukwila entered into an interlocal agreement providing for shared responsibilities with respect to the areas to be annexed by both cities, and WHEREAS, the King County Boundary Review Board has reviewed the proposed annexations and boundary change and same, and WHEREAS, pursuant to RCW 35.10.217 and upon has approved the proper notice, a public hearing was held on the proposed annexation before the City Council of the City of Tukwila on January 5, 1987, at which all persons who were interested in the annexation were allowed to participate, and WHEREAS, after such public hearing, the City Council of the City of Tukwila has determined to annex the area, now, therefore THE CITY COUNCIL OF THE CITY OF TUKWILA, WASHINGTON, HEREBY RESOLVE AS FOLLOWS: Section 1. Annexation of Area from Renton. Pursuant to RCW 35.10.217, the real property previously located in the City of Renton and legally described on Exhibit A attached hereto and incorporated herein by this reference as if set forth in full, l ExHIBIT A Lands to be Annexed to Tukwila from Renton The lands proposed to be annexed to the City of Tukwila from the City of Renton are listed below and shown in Figure 1. SECTION - TOWNSHIP -RANGE PARCEL ACREAGE 3.62 NW 1/4 of Sec. 24, Twn. 23, Rge. 4 27 (portion) 12.79 SW 1/4 of Sec. 24, Twn. 23, Rge. 4 63 2.35 32 0.27 28 3.85 7 MDC 4.55 NW 1/4 of Sec. 25, Twn. 23, Rge. 4 38 1.84 0.91 8 MDC (p) 2.91 1.14 9 MDC (p) 3.05 43 2.15 50 0.84 51 0.72 23 2.16 6 6.70 2.16 24 (portion) ITTU- 21 MOC 2.45 2.16 22 (portion) TETT- SW 1/4 of Sec. 25, Twn. 23, Rge. 4. 21 1.61 59 0.37 20 . 2.14 33 3.69 17 5.93 3.01 23 (portion) 10.43 24 (portion) 5.44 arra- 22 3.01 NW 1/4 of Sec. 36, Twn. 23, Rge. 4 97 3.00 57 8.69 62 6.40 61 0.17 11 6.83 43 0.10 37 0.17 38 0.14 39 0.14 53 0.14 14 0.12 13 0.12 29 0.32 10 0.14 9 0.19 59 0.15 8 0.17 1.7 0.12 35 2.84 34 1 5.54 1 1 36 1 3.09 1 1 TOTAL 1 45 parcels 101.65 l3.nseZ A•rrAGww+Wr SUGGESTED LEGAL DESCRIPTION (From City of Renton to City of Tukwila - North Part) All that portion of the City of Renton as annexed by City Ordinance ►io. 1764 lying westerly of the east margin of BURR Company (N.P. Ry) main track right of way all being located in the Si of the UW} of Section 24, Township 23 North, Range 4 East, W.M. Together with all that portion of Ordinance No. 1764 lying westerly main track right of way all being 23 North, Range 4 East, W.M. Together with all that portion of Ordinance No. 1764 lying westerly main track right of way all being 23 North, Range 4 East, W.M. King 9/16/86:JRB the City of Renton as of the east margin of located in the SW} of the City of Renton as of the east margin of located in the NW* of County, Washington annexed by City BNRR Company (U.P. Ry) Section 24, Township annexed by City BNRR Company (N.P. Ry) Section 25, Township B- TWELVE ASSOCIATES WETLAND ANALYSIS APPENDIX 2 1 \I 1 . •I �rymm�'I} jh)uhI'l!Iiiilh ,I - =�° tuar;111 1 B- twelve Associates , Inc. bli- �?�V.wpfaM)n.f GARDNER CONSULTANTS, INC. DEC 2 B 1992 December 23, 1992 Keith Harris Gardner Consultants, Inc. 12720 Gateway Drive Suite 201 Seattle, Washington 98168 RE: Southeast CBD Drainage Basin Study - Revised Wetland Report. B- twelve Job#92 -100 Dear Keith, I have enclosed one original and one copy of the Southeast CBD Drainage Basin Study - Revised Wetland Report. If you have any questions regarding this report please call me at (206) 859 -0515. Sincerely, B- twelve Associates, Inc. Ed Sewall Senior Wetland Ecologist Encl: Revised Wetland Analysis Report (1 original & 1 copy). 92110- 01.doc 521 South Washington Ave. • Kent, WA 98032 • 206/859 -0515 • Fax: 206/852 -4732 egts B- twelve Associates, Inc. SOUTHEAST CBD DRAINAGE BASIN STUDY CITY OF TUKWILA REVISED WETLAND ANALYSIS REPORT PREPARED FOR GARDNER CONSULTANTS, INC. 12720 GATEWAY DRIVE, SUITE 201 SEATTLE, WASHINGTON 98168 BY B- TWELVE ASSOCIATES INC. 521 SOUTH WASHINGTON AVE. KENT, WASHINGTON 98032 DECEMBER 16, 1992 JOB #92 -110 521 South Washington Ave. • Kent. WA 98032.. 206/859 -0515 • Fax: 206/852 -4732 t luw„ 4.0411CAI B- twelve Associates, Inc. SOUTHEAST CBD DRAINAGE BASIN STUDY CITY OF TUKWILA REVISED WETLAND ANALYSIS REPORT 1.0 INTRODUCTION The purpose of this study was to assess surficial hydrologic features (wetlands, streams, ditches) between the Green River on the west, Tukwila City line on the east (Burlington Northern tracks), S. 180th Street (aka SE 43rd Street) on the south and Strander Boulevard on the north (see Exhibit A). This information is to be used to assist in future planning of development within the study area. Specifically, this report describes hydrologic features, and the possible impacts of development on these features. This study describes and generally locates all surficial hydrologic features within the study area. In addition, hydrologic connections and drainage patterns throughout the study area are described resulting from our field study and review of various maps, documents and aerial photographs. A discussion of the regulations protecting these features is also included. 2.0 FIELD METHODS Ed Sewall of B- twelve Associates, Inc., identified wetlands within the study area on March 26 and April 3, 20 & 23 and May 22, 1992. Gary Schulz of the City of Tukwila accompanied Ed Sewall on April 23, and May 22, 1992, on site visits. A combination of field indicators (including vegetation, soils, topography, and hydrology) were used to identify wetlands. The wetlands on site were identified using methodology in the Federal Manual for Identifying and Delineating Jurisdictional Wetlands (Interagency Committee for Wetland Delineation, 1989). This is the methodology currently recognized by the City of Tukwila for wetland determinations and delineations. It should also be noted that the wetlands identified would be considered wetlands using the methodology described in Corps of Engineers Wetland Delineation Manual (Environmental Laboratory, 1987). The location and size of the wetlands described in this report are approximate and were derived from aerial photographs and field verification (see Exhibit C). The wetland edges were not flagged or surveyed for this project. The edges along the Puget Power right -of -way were flagged by B- twelve for the Tukwila Trail project. However, the delineation associated with the Tukwila Trail project does not cover all wetlands within the CBD Basin study area, nor the entire wetland edge of many of those wetlands that are within the CBD Basin study area. 521 South Washington Ave. • Kent, WA 98032 • 206/859 -0515 • Fax: 206/852 -4732 Southeast CBD Drainage Basin Study /Job #92 -110 B- Twelve Associates Inc December 16, 1992 Page 2 3.0 OBSERVATIONS 3.1 Uplands The topography of the site is generally flat, with steep fill banks dropping into the wetlands along the railroad tracks and power line access road. The upland portions of the site consist of railroad tracks on gravel fill, paved surfaces, buildings and other structures, and areas containing dumped trash and woody debris. The dominant plant in upland areas is Blackberry (Rubus discolor). Other common species found within the uplands consist of Cherry (Prunus emarginata), Red Alder (Alnus rubra), Willows (Salix spp.), Black Cottonwood (Populus trichocarpa), Reed Canary Grass (Phalaris arundinacea), Thistle (Cirsiwn spp.), Yarrow (Achillea spp.), Bracken Fern (Pteridium aquilinum), Mullein (Verbascum thapsus), Rose (Rosa spp.) and Stinging Nettle (Urtica dioica). The remaining buffer surrounding the wetlands within the study area has been heavily impacted by development. Very little vegetated buffer exists within the study area, and that remaining is generally in very poor condition. 3.2 Soils There are five major soil types mapped for the study area according to the Soil Survey of King County; Urban Land (Ur), Woodinville silt loam (Wo), Puyallup fine sandy loam (Py), Puget silty clay loam (Pu), and Newberg silt loam (Ng) (see Exhibit B). The Woodinville and Puget soil series are considered hydric soils according to the publication Hydric Soils of the United States. The Puyallup and Newberg soils are well drained, and like the other soil types mapped for this area, formed in alluvium. With few exceptions, soils within the wetlands in the study area were either fill or inundated with 1 foot or more of water and could not be observed. 3.3 Hydrology 3.3.1 Existing surficial hydrology. All of the wetlands within the study area appear to retain large quantities of stormwater. These wetlands are depicted on Exhibit C. To assist in identifying locations of culverts, station numbers are used. These stations are from the HDA survey for the Tukwila Interurban Trail (see Exhibit C). Following rainfall on 4- 30 -92, Wetland "3" was observed to have an increased volume of water compared to previous observations. This water appears to flow from the area referred to as the detention pond (by overflowing a small berm) eastward into the ditch. Water within the ditch had a very slight northward flow. Approximately halfway down the ditch, in the vicinity of the sewer line crossing, flow is less than observable. The wetlands located to the west of the access road are hydrologically connected to those located to the east through a 48" culvert located at the north end of wetland #2, approximately 34' north of station 23+00. Water within Wetland "1" is hydrologically connected to Wetland "11" by a 24" culvert that passes under the Union Pacific Railroad tracks to the east, approximately 20' south of station 16 +00 (see Exhibit D). There was no detectable flow within this pipe, although the pipe was approximately half full of water. It is suspected that water does flow from Wetland "1 ", to the east into Wetland "11" during periods of heavy precipitation. Generally, the pipe appears to act as an equalizer between these two wetlands. Southeast CBD Drainage Basin Study /Job #92 -110 B- Twelve Associates Inc December 16, 1992 Page 3 Wetland "11" appears to receive water from direct precipitation, possibly groundwater, and surface water flow directed through culverts from Wetlands "1", "2" and "8". Although a surficial flow pattern is not evident within this wetland, water does exit through two 36" culverts at a constant rate and is directed into the large wetland complex, located off -site to the east of the BNR track (off -site wetland W -3 and uninventoried forested wetland). There is also a culvert connecting to an uninventoried wetland located to the east, within the City of Renton. There was no water in this culvert. Although evidence of flow (water born debris) was observed in the culvert, it is suspected to occur only during periods of very high water levels. Surface water within Wetland complex "3" flows through a 48" culvert (located approximately 34' north of station 23 +00) into Wetland #2. The inverts of this culvert indicate flow travels to the west. However, when a head of water builds up within Wetland complex "3" this water flows through the culvert to the east entering Wetland "2 ". This wetland appears to have once been part of Wetland "1 ", but was historically separated by the placement of fill. Surface water flows from Wetland "2" into Wetland "11" through the east end of a 36" culvert located approximately 34' south of station 23 +00. All water within Wetland "2" appears to be from direct precipitation, overland flow and at certain times of the year, possibly groundwater. Wetlands 4,5,6,7,9 and 10 all appear to be "isolated ". These wetlands have no apparent surface connection to any other wetlands or surface water feature. Water enters these wetlands from overland flow, direct precipitation and possibly groundwater. Evaporation and transpiration being the most obvious outlets for water within these features. It is also possible that a subsurface hydrologic connection between these wetlands and those in close proximity exists. This appears dependent upon the permeability of the highly variable fill surrounding each wetland. 3.3.2 Possible Impacts from changes in hydrology. Most of the wetlands located to the east of the Puget Power access road appear to have a highly fluctuating water table. If the hydrology of these wetlands were modified, significant changes will likely occur in the plant communities. Increased water into these wetlands, especially a longer residence time, would probably result in a shift in species composition to more flood tolerant species. This shift could change not only species composition, but structural composition as well. The portions of these wetlands which appear to be most susceptible to change are dominated by Black Cottonwood. These areas are generally seasonally flooded. A shift to a much wetter water regime would likely eliminate these trees. Black Cottonwoods do not typically withstand long periods of inundation as do willow dominated wetlands. The willow dominated wetlands appear more successful at surviving long periods of inundation. Areas wetter than the Willow dominated areas (semipermanently flooded) in the study area are dominated by shrub species such as Douglas Spirea. A radical change to an intermittently exposed or permanently flooded water regime would likely result in these scrub -shrub areas becoming emergent marshes. Wetland #W -3 located off -site to the east of the BNR tracks, appears to have undergone this transformation. This 6 acre wetland is referred to in the City of Renton's Wetland Inventory as wetland W -3 (Orillia Pond). Many snags (4 -6 inch dbh) remain in what is now an emergent marsh. These snags are the remainder of a forested area, probably wetland, which was transformed into a marsh by a change in water regime. This change is most likely due to an increase in water to the wetland from the west, and /or a Southeast CBD Drainage Basin Study /Job #92 -110 B- Twelve Associates Inc December 16, 1992 Page 4 blocked drainage causing water to be retained in the wetland nearly year round. According to the City of Renton Wetland Inventory, this wetland is blocked with no outlet. Historically, water appears to have exited this wetland into a slough, located to the east. This slough appears to be the historic channel of Springbrook Creek. Review of topographic maps taken from aerial photos from 1962, reveals a stream, exiting the northeast side of Orillia Pond, and leading directly to within 100 feet of the slough. At this point, the maps show the stream to end, probably because the channel was obstructed from view during photo interpretation. Although not shown on any maps, a ditch was observed in the field to lead from the southeastern end of this wetland, under a dirt road in a culvert, in the direction of Springbrook Creek. This ditch is blocked with fill and waste (ground rubber) near the bend of the dirt access road entering the property bordering the east side of Orillia Pond. Review of April 1992 aerial photographs of the site indicates water exits the north end of Orillia Pond, flowing to the north under the railroad spur. This flow occurs in a ditch directed to wetlands to the northeast, in the City of Renton. The ditch appears to be surrounded by an uninventoried forested wetland for most of its length. At a point parallel to the end of Oaksdale Blvd., this ditch takes a right angle turn to the east, connecting to wetlands adjacent to Springbrook Creek. This ditch is depicted on maps 4 & 5 of the Streams and 100 Year Floodplains in the King County Sensitive Areas Map Folio (see Exhibit E). At the point where the ditch turns to the east, it proceeds along City of Renton inventoried wetland "W -13" (see Exhibit G). This wetland is described as being hydrologically connected to Springbrook Creek, which is also listed as its outlet. The wetland adjacent to Springbrook Creek and to the east of "W -13" is known as wetland W -12 according to the City of Renton Critical Areas Inventory map. According to the Critical Areas Inventory Report (Jones & Stokes 1991), wetland W -12 is a 41 acre wetland that is the highest ranked wetland within the City of Renton. This wetland contains high quality wildlife habitat and is hydrologically connected by stream flow, to Springbrook Creek to the east. Although connections between wetlands on -site and Springbrook appear to exist on the photographs and in City of Renton Documents, we did not conduct a thorough field check of this off -site area to verify this connection. An inspection of this connection is necessary to positively determine this connection. 4.0 WETLAND DESCRIPTIONS - (SOILS- VEGETATION - HYDROLOGY) This section describes the characteristics of each wetland located within the study area. Some of these wetlands are depicted on the National Wetlands Inventory maps (See Exhibit G). Wetland 1 The wetland is linear in shape and, like most on the site, is very obviously defined by the steep, topographical break of the power line road and the railroad. This wetland contains both forested and scrub -shrub classes. The forested areas are dominated by Sitka Willow (Salix sitchensis), with a shrub layer comprised of Red -Osier Dogwood (Cornus stolonifera), Douglas Spirea (Spirea douglasii), and Sitka Willow. According to the US Fish and Wildlife Wetland Classification methodology (Cowardin et al. 1979), this area would be classified as PFO1C (Palustrine, Forested, Broad - leaved deciduous, Seasonally Flooded). The scrub -shrub areas are dominated by the previously mentioned shrubs with the addition of Salmonberry (Rebus spectabilis). Scrub shrub appears to be the dominant wetland class and would be classified as PSSC (Palustrine, Scrub - shrub, Seasonally Flooded). Southeast CBD Drainage Basin Study /Job #92 -110 B- Twelve Associates Inc December 16, 1992 Page 5 This wetland contained up to 36 inches of standing water during our site inspection on April 3, 1992. The water regime for most of the wetland appears to be seasonally flooded, however, portions may have a semipermanently flooded water regime (Cowardin et al. 1979). A corrugated pipe (approximately 24 inches in diameter) links the northern end of this wetland to Wetland "11 ", located between the Union Pacific Railroad tracks and the Burlington Northern Railroad tracks, approximately 20' south of station 16 +00. Due to its small size, two wetland classes and a forested wetland class, this wetland would be considered a Type 2 wetland according to the City of Tukwila Sensitive Areas Ordinance. However, due to its hydrologic connection to a Type 1 wetland (Wetland "11"), the City may choose to interpret this wetland as a Type 1 wetland. Typically, Type 2 wetlands receive a 50 foot buffer and Type 1 wetlands receive a 100 foot buffer. However, there is no remaining undisturbed buffer surrounding this wetland. Wetland 2 This wetland contains a forested wetland class (PFO1= Palustrine, Forested, Broad - leaved Deciduous, Seasonally Flooded) dominated by Black Cottonwood (Populus trichocarpa) with lesser amounts of Pacific Willow (Salix lasiandra), Sitka Willow, and Oregon Ash (Fraxinus latifolia). The scrub -shrub (PSS1C= Palustrine, Scrub - shrub, Broad - leaved Deciduous, Seasonally Flooded) portions of the wetland are comprised of Red -Osier Dogwood, Douglas Spirea, and Sitka Willow. There is also a large emergent area dominated by Cattails (Typha latifolia) which would be classified as PEM1F (Palustrine, Emergent, Persistent, Semipermanently Flooded). The forested and scrub -shrub portions of the wetland appear to have a seasonally flooded water regime, while the emergent area appears to have longer inundation, resulting in a semipermanently flooded water regime. Surface water flows from Wetland "3" into Wetland "2 ", entering through a 48" culvert with its east end located approximately 46' north of station 23 +00. Surface water exits Wetland "2" into Wetland "11" through a 36" culvert located approximately 34 feet south of station 23+00. There was approximately 3 inches of water flowing to the east in this culvert. Due to its small size, three wetland classes and a forested wetland class, this wetland would be considered a Type 2 wetland according to the City of Tukwila Sensitive Areas Ordinance. However, due to its hydrologic connection to a Type 1 wetland (Wetland "11"), the City may choose to interpret this wetland as a Type 1 wetland. Typically, Type 2 wetlands receive a 50 foot buffer and Type 1 wetlands receive a 100 foot buffer. However, there is no remaining undisturbed buffer surrounding this wetland. Wetland Complex 3 This wetland system consists of three distinct sections of wetland hydrologically connected by what appears to be a man-made drainage ditch on the west side of the Puget Power access road. These three sections consist of an emergent wetland (Wetland 3A), an area abutting Wetland 3A to the north with wetland characteristics used as a detention pond (Wetland 3B), and a forested wetland (Wetland 3C). The ditch that hydrologically connects these three wetlands is vegetated with scrub -shrub vegetation such as Red -Osier Dogwood, Sitka Willow and Douglas Spirea. Some areas are dominated by emergents consisting of Reed Canary Grass and Cattail. Water was observed to stand 1 -3 feet deep in this ditch with no visible movement. According to the US Fish and Wildlife Wetland Classification methodology (Cowardin et al. 1979), the ditch would be classified as PSSC ( Palustrine, Scrub - shrub, Seasonally Flooded) and portions classified as PEM1C ( Palustrine, Emergent, Persistent, Seasonally Flooded). Southeast • BD Drainage Basin Study /Job #92 -110 B- Twelve ssociates Inc December 6, 1992 Page 6 Wetland c A is a small area of emergent wetland, dominated by a Reed -Canary Grass monocult re, and located adjacent to the south side of the area referred to as the detention pond (W tland 3B). This wetland is regulated by the City as well as the ACOE. This area would be classified as PEM1C ( Palustrine, Emergent, Persistent, Seasonally Flooded). This area wou d be considered a Type 3 wetlands according to the City of Tukwila Sensitive Areas Ordinan - . Typically, Type 3 wetlands receive a 25 foot buffer. The buffer of this wetland is complete y developed on the west, but consists of wetland (Wetland 3B) and pasture on all other sid s. Wetland in an old the City Tukwila Renton, area con appears t through t B consists of a forested wetland dominated by Black Cottonwood which has formed detention pond abutting the southern end of the ditch. According to Gary Schulz of f Tukwila, this detention pond was built in the 1970's, and is exempt from City of egulation. The 1962 aerial photograph topography maps produced for the City of how the detention pond areas as a cultivated field. During our site visit, this forested 'ned 18 inches of standing water which had overflowed its berm into the ditch. It at the runoff from adjacent commercial and industrial sites enters this ditch indirectly e detention pond overflow, or overland flow on its banks. II Wetland C is a forested wetland located behind the Hartung facility (north end of wetland complex). This wetland hydrologically connects the Wetland 3 complex to Wetland "2" by a 48" culv:rt, with its west end located approximately 34' north of station 23 +00. Due to the presence • f a forested class, this wetland would be considered a Type 2 wetland according to the City f Tukwila Sensitive Areas Ordinance. Typically, Type 2 wetlands receive a 50 foot buffer, h wever, there is no remaining undisturbed buffer surrounding this wetland. Building , paved surfaces, and the access road currently occupy the buffer. However, due to its hydro ogic connection to a Type 1 wetland (Wetland "11"), the City may choose to interpret his wetland and /or wetland complex as a Type 1 wetland. Accordin to the City of Tukwila Sensitive Areas Ordinance, constructed wetlands are exempt from the etland regulations. Those areas of this wetland that have been constructed as a drainage facility (the ditch and Wetland 3B) may be exempt from City regulation. Although the City rimy not regulate the "detention pond" and ditch portion of the wetland, the ACOE is consideri ng them regulated "adjacent" wetlands. They base this decision on the mapped soil unit for t e area being hydric, and a dominance of hydrophytic vegetation. Wetland 4 Histori 1y, this wetland appears to have been the northern portion of Wetland "2" prior to the cons ction of the rail spur now separating them. This wetland is dominated by a forested wetland lass (PFO1C) ( Palustrine, Forested, Broad leaved deciduous, Seasonally Flooded) with sm er scrub -shrub areas (PSS1C) (Palustrine, Scrub - Shrub, Broad leaved deciduous, Seasonal Flooded) also present. The forested portion of the wetland is dominated by Black Cottonw with a shrub layer of Red -Osier Dogwood, Sitka Willow, Pacific Willow, Salmonb rry and Douglas Spirea. Some forested portions of the wetland are dominated by willows. The Scrub -shrub class is comprised of the above described shrub species. Skunk Cabbage (Lysichitum americanum) is also commonly found in the herbaceous layer. There were no urficial hydrologic connections found connecting this wetland with any of the adjacent etlands. However, a subsurface hydrologic connection is probable due to the close proximity of groundwater and the coarse and variable nature of the fill separating these wetlands) Southeast CBD Drainage Basin Study /Job #92 -110 B- Twelve Associates Inc December 16, 1992 Page 7 observed in the center of each depression. This water was stagnant with no visible movement. There does not appear to be any hydrologic connection of these wetlands to any of the surrounding wetlands. There were no surficial hydrologic connections found connecting this wetland with any of the adjacent wetlands. However, a subsurface hydrologic connection is probable due to the close proximity of groundwater and the coarse and variable nature of the fill separating these wetlands. These areas are vegetated with Douglas Spirea, Reed Canary Grass and Blackberry (Rubus spp.). Garbage and fill has intruded into these wetlands leaving very little functional value other than a small water storage capacity. According to the US Fish and Wildlife Wetland Classification method (Cowardin et al. 1979), these wetlands would be classified as PSS1C (Palustrine, Scrub - Shrub, Broad leaved deciduous, Seasonally Flooded). Due to the small size and single wetland class, these areas would be considered Type 3 wetlands according to the City of Tukwila Sensitive Areas Ordinance. Typically, Type 3 wetlands receive a 25 foot buffer, however, there is no remaining undisturbed buffer surrounding these wetlands. Buildings, paved surfaces, and the access road currently occupy the buffer. Wetland 8 Three wetland classes are present in this wetland; forested (PFO1C: Palustrine, Forested, Broad leaved deciduous, Seasonally Flooded), scrub -shrub (PSS1C: Palustrine, Scrub - Shrub, Broad leaved deciduous, Seasonally Flooded) and emergent (PEM1F: Palustrine, Emergent, Persistent Semipermanently Flooded). The forested section is dominated by Pacific Willow with smaller quantities of Black Cottonwood and Sitka Willow in the overstory. The shrub layer in the forested portion of the wetland is vegetated with saplings of the same species in addition to Red -Osier Dogwood and Salmonberry. The scrub -shrub sections of the wetland contain Red -Osier Dogwood, Salmonberry and Douglas Spirea, in addition to Blackberry along the edges. The emergent section is dominated by a mix of Cattail, Reed -Canary Grass and Nightshade (Solanum spp.). This wetland contained up to 36 inches of standing water during our site inspections. The water in this wetland appeared relatively stagnant. However, a 36 inch corrugated pipe was found at the end of a ditch at the north end of the wetland (located approximately 30' north of station 63 +00). This pipe provides a hydrologic connection to wetlands located to the east. Water appears to enter this pipe and flow to the east under the Union Pacific tracks into Wetland "11", a Type 1 wetland. Due to the three wetland classes and a forested wetland class, this wetland would be considered a Type 2 wetland according to the City of Tukwila Sensitive Areas Ordinance. However, due to its hydrologic connection to a Type 1 wetland (Wetland "11"), the City may choose to interpret this wetland as a Type 1 wetland. Typically, Type 2 wetlands receive a 50 foot buffer and Type 1 wetlands receive a 100 foot buffer. However, there is no remaining undisturbed buffer surrounding this wetland. Southeast CBD Drainage Basin Study /Job #92 -110 B- Twelve Associates Inc December 16, 1992 Page 8 Wetland 9 This emergent wetland is located in a shallow depression between the access road and a building. Soils within this wetland consist of fill, primarily sand and gravel. The dominant plant species within this wetland consist of Cattail and Reed Canary Grass. During our site inspection water was observed to stand at a depth of 10 inches in this wetland. There were no surficial hydrologic connections found connecting this wetland with any of the adjacent wetlands. However, a subsurface hydrologic connection is probable due to the close proximity of groundwater and the coarse and variable nature of the fill separating these wetlands. According to the US Fish and Wildlife Wetland Classification method (Cowardin et al. 1979), this wetland would contain areas classified PEM1F ( Palustrine, Emergent, Persistent, Semipermanently Flooded). This area appears to be a portion of the constructed ditch that was separated by fill. As a constructed wetland it would not be protected under the regulations. Wetland 10 This wetland consists primarily of a forested area dominated by an overstory of Black Cottonwood, with a shrub layer of Salmonberry and Blackberry. Unlike the other wetlands located on the site, the soils found within this wetland did not consist of fill. Soils were found to have 12 inches of saturated, 1OYR 2/2 sandy loam, overlying a sandy loam with a matrix of 2.5Y 3/2 and 1OYR 3/4 mottles. There is a ditch along the east side of this wetland that appears constructed and contained approximately 1 foot of standing water. The wetland around the ditch consisted of the same soils as the forested area, but was entirely vegetated with Reed Canary Grass. There were no surficial hydrologic connections found connecting this wetland with any of the adjacent wetlands. However, a subsurface hydrologic connection is probable due to the close proximity of groundwater and the coarse and variable nature of the fill separating these wetlands. According to the US Fish and Wildlife Wetland Classification method (Cowardin et al. 1979), this wetland would contain areas classified as PEM1F ( Palustrine, Emergent, Persistent Semipermanently Flooded), PEM1C ( Palustrine, Emergent, Persistent Seasonally Flooded), and PFO1C ( Palustrine, Forested, Broad leaved deciduous, Seasonally Flooded). Due to the presence of a forested class, this wetland would be considered a Type 2 wetland according to the City of Tukwila Sensitive Areas Ordinance. Typically, Type 2 wetlands receive a 50 foot buffer, however, there is no remaining undisturbed buffer surrounding this wetland. Wetland 11 This is a very large wetland which contains a mosaic of wetland classes. There are Forested (PFO1C: Palustrine, Forested, Broad - leaved deciduous, Seasonally flooded), Scrub -Shrub (PSS 1 C: Palustrine, Scrub - shrub, Persistent, Seasonally Flooded), Emergent (PEM1C: Palustrine, Emergent, Persistent, Seasonally Flooded & PEM1F: Palustrine, Emergent, Persistent, Semipermanently Flooded), and Unconsolidated Bottom (PUB3F: Palustrine, Unconsolidated bottom, Mud, Semipermanently Flooded) wetland classes found within this wetland complex. The forested wetland classes consist of both Willow (S. sitchensis & S. lasiandra) dominated areas and Black Cottonwood /Red Alder dominated areas. Shrub species within the willow dominated zones consist primarily of Red -Osier Dogwood and Willow seedlings and saplings. The shrub layer in the Black Cottonwood areas usually contains a greater amount of Salmonberry and Blackberry, although the previously mentioned species are Southeast CBD Drainage Basin Study /Job #92 -110 B- Twelve Associates Inc December 16, 1992 Page 9 also quite common. The herb stratum is very sparse in all of the forested wetlands, and in some areas, could not be observed due to inundation. Species that were observed included Skunk Cabbage and Reed -Canary Grass. The scrub -shrub areas are typically monotypic stands of Willow saplings and seedlings, monotypic stands of Douglas Spirea, or a mix of Spirea, Red -Osier Dogwood, Salmonberry, and Willows. Emergent wetland classes consist of monotypic stands of Reed -Canary Grass, and Cattail (7ypha latifolia) dominated marshes. Also observed within the marsh areas were Water Plantain (Alisma plantago- aquatica), Smartweed (Polygonum spp.), Nightshade (Solanum spp.) and Duckweed (Lemna spp.). There are also areas of unconsolidated mud bottom, which are inundated with water levels fluctuating enough so as to prohibit most vegetative growth. These areas appear to have a semipermanently flooded water regime. Due to the size (>5 ac.) and the number of wetland classes (4 classes), this wetland would be considered a Type 1 wetland according to the City of Tukwila Sensitive Areas Ordinance. Typically, Type 1 wetlands receive a 100 foot buffer, however, there is no remaining undisturbed buffer surrounding this wetland. 5.0 WETLAND FUNCTIONS /VALUES The most obvious function that these wetlands provide is the storage of stormwater runoff. Essentially, these wetlands act as a regional detention facility for the surrounding businesses and industries. They also appear to have the ability to store a significant amount of runoff following storm events. Most of the stormwater is directed into the wetlands on the western side of the access road. Runoff drains primarily from businesses along the east side of West Valley Highway. Although water appears to drain into this wetland system, flow within the system appears blocked at numerous points. Water movement appears to be negligible to non- existent as a result of blocked culverts and /or filled drainage ways. Wetlands to the east of the access road are hydrologically connected to those located to the west of the access road by a 48" culvert. Wetlands located to the east of the access road are hydrologically connected to wetlands between, and east of the railroad tracks via several culverts. Flow through these wetlands appears to occur primarily during periods of elevated water levels and storm events. Another important function these wetlands perform is the improvement of water quality. This is especially true of the emergent portions of the wetlands. Vegetation within the wetland functions to trap sediment and remove contaminants from the surface water. Aquatic plants have been effective in treatment of a number of pollution problems, including nutrient removal, uptake of metals and organics, reductions of pathogenic bacteria, and neutralizing extremes of pH (Kulzer, 1990). The emergent wetland classes observed throughout the wetland complex containing Reed -Canary Grass, Cattail (7ypha latifolia), and Soft Rush (Juncus efusus) are especially adept at performing heavy metal and nutrient contaminant removal. These wetlands may be isolated from the regional groundwater system, being perched on an impervious layer. However, test borings indicate it is probable that a perched groundwater system does influence these wetlands. Test borings in the vicinity of the wetlands along S. 180th Street indicate groundwater is at an elevation of approximately 16'. The surface of the wetlands in this area is approximately 20', with the bottoms more likely between 16' -19' elevation, and the saturated zone lower than this. Due to close proximity of groundwater elevations to the wetland elevations, it is likely that a perched groundwater system does interface with the wetlands at some time during the year. Southeast CBD Drainage Basin Study /Job #92 -110 B- Twelve Associates Inc December 16, 1992 Page 10 It is also likely that the natural wetlands in the area formed in what was historically the floodplains of the Green River and Springbrook Creek. As a result of diking and development, these wetlands no longer appear to be hydrologically connected to the Green River. However, wetlands #1,2,3,8 & 11 are hydrologically connected to Springbrook Creek. Although heavily impacted by man, these wetlands still offer good habitat to many species of wildlife. They offer one of the few remaining undeveloped tracts of land in the area. This large wetland complex offers a refuge to wildlife from the surrounding urban land uses; in addition, it offers aesthetic appeal as open space. Waterfowl commonly utilize the emergent portions of the wetlands. Species observed utilizing the wetlands include Great Blue Heron, Green Heron, Mallards, Canada Geese and Redheads. Songbirds are also plentiful within the wetlands with Red - winged Blackbirds, Goldfinches, Marsh Wrens and various warblers being observed. Raptors such as Red -tail Hawks, Rough - legged Hawks, Marsh Hawks and Kestrals were also observed on the site and its immediate vicinity. Skunks, Raccoons, Opossums, and Garter Snakes are also common inhabitants of the site. 6.0 REGULATIONS In addition to the City of Tukwila wetland regulations previously described for each wetland, certain activities (filling and dredging) within "waters of the United States" may fall under the jurisdiction of the US Army Corps of Engineers (ACOE). If fill is to be placed within wetlands that fall under Federal Jurisdiction, then a Section 404 Permit from the Army Corps of Engineers will be required. If the wetlands on this site were considered "isolated" or "headwaters ", a Nationwide Permit would be appropriate. However, telephone conversations and a site walkthrough with Jack Kennedy and Gail Terzi of the Regulatory Branch of the Seattle District, ACOE revealed that all of these wetlands (except for constructed portions) would be considered adjacent to Springbrook Creek and /or the Green River unless a natural break or separation exists or did exist. Our research indicated taht there is no natural break, therefore, Ms. Terzi stated that these wetlands are considered "adjacent" by the ACOE. Constructed areas not regulated by the City may be regulated by the Corps if they were mapped as containing hydric soils in the soil survey and maintained other wetland characteristics. Therefore, it is possible that the detention pond area, the ditches and Wetland "9" may be regulated by the Corps as adjacent wetlands. Any work within any of the wetlands within the project area would require going through the Individual Permit process. Since none of the wetlands within the study area were delineated for this study, a site specific wetland analysis and delineation should be performed for any future development in and around these sensitive areas. If you have any questions regarding this report, please call us at 859 -0515. Sincerely, B- twelve Associates, Inc. Edgar K. Sewall III Senior Wetland Ecologist Southeast CBD Drainage Basin Study /Job 1/92 -110 B- twelve Associates, Inc. December 16, 1992 Page 12 - REFERENCES REFERENCES Cowardin, L., V. Carter, F. Golet, and E. LaRoe. 1979. Classification of Wetlands and Deepwater Habitats of the United States. U.S. Fish and Wildlife Service, FWS /OBS- 79 -31, Washington, D. C. Environmental Laboratory. 1987. Corps of Engineers Wetlands Delineation Manual, Technical Report Y -87 -1. U. S. Army Corps of Engineers Waterways Experiment Station, Vicksburg, Mississippi. Federal Interagency Committee for Wetland Delineation. 1989. Federal Manual for Identifying and Delineating Jurisdictional Wetlands. U.S. Army Corps of Engineers, U. S. Environmental Protection Agency, U.S. Fish and Wildlife Service, and U.S.D.A. Soil Conservation Service, Washington, D.C. (Cooperative technical publication). Hitchcock, C. and A. Cronquist. 1976. Flora of the Pacific Northwest. University of Washington Press, Seattle, Washington. King County Planning Division. 1983. King County Wetlands Inventory Notebook, Vol.s 1- 3. King County Courthouse, Seattle, Washington. Kulzer, L., 1990. Water Pollution Control Aspects of Aquatic Plants. Seattle Metro, 38p. Munsell Color. 1988. Munsell Soil Color Charts. Kollmorgen Instruments Corp., Baltimore, Maryland. Reed, P., Jr. 1988. National List of Plant Species that Occur in Wetlands: Northwest (Region 9). 1988. U. S. Fish and Wildlife Service, Inland Freshwater Ecology Section, St. Petersburg, Florida. Snyder, D., P.. Gale, and R. Pringle. 1973. Soil Survey King County Area Washington. U.S.D.A., Soil Conservation Service, Washington, D.C. Steward, A. , L. Dennis, and H. Gilkey. 1963. Aquatic Plants of the Pacific Northwest. Oregon State University Press, Corvallis, Oregon. U.S.D.A. Soil Conservation Service. 1988. Soil Taxonomy. Robert E. Krieger Publishing Company, Malabar, Florida. Jones and Stokes, 1991. Critical Areas Inventory, City of Renton Wetlands and Stream Corridors. Southeast CBD Drainage Basin Study /Job#92 -110 B- twelve Associates, Inc. December 16, 1992 Page 13 - PLANTS PLANTS OBSERVED IN WETLANDS AT SOUTHEAST CBD DRAINAGE BASIN Indicator Categories Obligate Wetland (OBL). Occur almost always (estimated probability >99 %) under natural conditions in wetlands. Facultative Wetland (FACW). Usually occur in wetlands (estimated probability 67 % -99 %), but occasionally found in nonwetlands. Facultative (FAC). Equally likely to occur in wetlands or nonwetlands (estimated probability 34%-66%). Facultative Upland (FACU). Usually occur in nonwetlands(estimated probability 67 % -99 %), but occasionally found in wetlands (1%-33%). Not Listed (NL). Do not appear on the list. Usually upland plants, or groups of plants (e.g. mosses) not included on the list. NI,. Appear on the list, but have not been assigned an indicator status. + More frequently found in wetlands. - Less frequently found in wetlands. Trees Acer macrophyllum Alnus rubra Fraxinus latifolia Populus balsamifera Salix lasiandra Salix scouleriana Salix sitchensis Shrubs Acer circinatum Cornus stolonifera Corylus cornuta Cytisus scoparius Holodiscus discolor Lonicera involucrata Oemleria cerasiformis Prunus emarginata Pyrus fusca Rhamnus purshiana Ribes bracteosum Big Leaf Maple Red Alder Oregon Ash Black Cottonwood Pacific Willow Scouler Willow Sitka Willow Vine Maple Red -osier Dogwood Beaked Hazelnut Broom Oceanspray Twinberry Indian Plum Bitter Cherry Wild Crabapple Cascara Stink Currant Indicator Status FACU FAC FACW FAC FACW+ FAC FACW FACU+ FACW NI NL NL FAC NL NL FAC+ NI FAC Southeast CBD Drainage Basin Study /Job#92 -110 B- twelve Associates, Inc. December 16, 1992 Page 14 - PLANTS Herbs Ribes sanguineum Ribes spp. Rosa nutkana Rubus discolor Rubus laciniatus Rubus spectabilis Rubus spp. Salix spp. Salix lasiandra Salix scouleriana Salix sitchensis Sambucus racemosa Spiraea douglasii Symphoricarpos albus Cirsium spp. Dicentra formosa Elodea nuttallii Epilobium angustifolium Epilobium ciliatum Galium spp. Geranium robertianum Geum macrophyllum Iris pseudacorus Lysichitum americanum Lythrum salicaria Mentha arvensis Oenanthe sarmentosa Polygonum hydropiperoides Ranunculus repens Rumex crispus Rumex spp. Solanum dulcamara Solidago spp. Stachys cooleyae Tolmiea menziesii Trifolium spp. 7ypha latifolia Urtica dioica Utricularia minor Veronica scutellata Sedges /Rushes /Grasses /Ferns Agrostis alba Agrostis spp. Alopecurus pratensis Alopecurus sp. Athyrium filix-femina Red- flowering Currant Currant Nootka Rose Himalayan Blackberry Evergreen Blackberry Salmonberry Blackberry Willow Pacific Willow Scouler Willow Sitka Willow Red Elderberry Hardhack Snowberry Thistle Pacific Bleedingheart Nuttall's Waterweed Fireweed Hairy Willow -herb Bedstraw Robert's Geranium Large- leaved Avens Yellow Iris Skunk Cabbage Purple Loosestrife Field Mint Water Parsley Marsh Pepper Smartweed Creeping Buttercup Curly Dock Dock Bittersweet Nightshade Goldenrod Cooley's Hedge - nettle Piggy -back Plant Clover Cattail Stinging Nettle Bladderwort Marsh Speedwell Redtop Bentgrass Bentgrass Meadow Foxtail Foxtail Grass Lady Fern NL NI FACU- FACU+ FAC FACW+ FAC FACW FACU FACW FACU NL OBL FACU+ FACW- --- NL FACW+ OBL OBL OBL FAC OBL OBL FACW FACW FAC FACW FAC OBL FAC+ OBL OBL FACW FACW FAC Southeast CBD Drainage Basin Study /Job#92 -110 B- twelve Associates, Inc. December 16, 1992 Page 15 - PLANTS Carex deweyana Carex obnupta Carex sp. Equisetum arvense Equisetum sp. Festuca arundinacea Glyceria elata Glyceria spp. Juncus acuminatus Juncus effusus Juncus ensifolius Juncus tenuis Juncus spp. Lemna minor Phalaris arundinacea Polystichum munitum Pteridium aquilinum Scirpus microcarpus Short-scale Sedge Slough Sedge Sedge Field Horsetail Horsetail Kentucky Fescue Tall Manna Grass Mannagrass Tapered Rush Soft Rush Dagger -leaf Rush Slender Rush Rush Duckweed Reed Canary Grass Sword Fern Bracken Fern Small - fruited Bulrush FAC+ OBL FAC FACU- FACW+ OBL FACW + FACW FAC OBL FACW NL FACU OBL NORTH EXHIBIT A : Vicinity Map COX, SAT! HAIRGINCY Reproduced with permission gauged by THOMAS BROS. MAPS. This map is copyrighted by THOMAS BROS. MAPS. It is 'unlawful to copy or reproduce all or any part thereof, whether for personal use or resale, without permission. B- twelve Associates, Inc. Ecological Systems Design & Management 521 South Washington Ave. • Kent, WA 98032 Job No.: 9z -fro Date: Drawn By: fKs Checked By: Revised: 21 IG-4L By: 4-3 -1i TUKWILA BASIN STUDY I CITY OF TUKWILA, WA NORTH EXHIBIT B: Soils Map This map taken from the Soil Survey of King County Area, Washington (Snyder et al. 1973). KEY Ur - Urban Land Wo - Woodinville silt loam* Pu - Puget silty clay loam* Py - Puyallup fine sandy loam Ng - Newberg silt loam * - indicates hydric soil B-twelve Associates, Inc. Ecological Systems Design & Management 521 South Washington Ave. • Kent, WA 98032 Job No.: 42-1/0 Date: 3-17. Drawn By: filS Checked By: Revised: /2.-/G-qt. By: TUKWILA BASIN STUDY CITY OF TUKWILA, WA WETLAND 1 EXHIBIT D: Surface Water Flow Chart "3" WETLAND L LAL rD "9 ►► Isolated (non regulated) Through 48" CMP 1 WETLAND "10" Isolated WED "4" Isolated WETLAND Isolated WETLAND Isolated WETLAND Isolated WETLAND "1" WETLAND "2" WETLAND Through 36" CMP Through 24" CMP )WETLAND "11",‘ "Through 48" CMP Through 36" CMP Through 36" CMP "8 ►► •►$ If City of Tukwila 111111111111111111111111111111111111111111111 111/11111 1111111111 /1111111111111111111111111111 11111111111111111 ORILLIA POND (W-3) ' City of Renton UNINVE TORTE ()RESTED WETLAND Through culvert and ditch > DITCH Adjacent to ditch NORTH "W-13" ,Through culvert ? "W-12" Adjacent to Creek ----> SPRINGBR OK CREEK B- twelve Associates, Inc. Ecological Systems Design & Management 521 South Washington Ave. • Kent, WA 98032 Job No.: 92-i to Date: Drawn By: fits Checked By: Revised: 12.- l & -1Z. By: L'- 3-17. TUKWILA BASIN STUDY . CITY OF TUKWILA, WA EXHIBIT E: King County Stream & 100 Year Floodplain Map NORTH KEY ��• - Class 1 Stream •- . Class 2 Stream (wilth salmonids) Class 2 stream (perennial; salmonid use undetermined) - Class 3 Stream -- - Unclassified. This map taken from the Sensitive Areas Map Folio, King County Washington, Dec. 1990. B- twelve Associates, Inc. Ecological Systems Design & Management 521 South Washington Ave. • Kent, WA 98032 Job No.: 42 -tio Date: I.-3 -1z Drawn By: f Ks Checked By: Revised: 12,- 14-17- By: TUKWILA BASIN STUDY 1 CITY OF TUKWILA, WA � NORTH EXHIBIT F: City of Renton Wetland Inventory Map LEGEND S -1 = Streams W -1 =Wetlands MAP LIMITATIONS This map is not intended to determine regulatory boundaries. Wetland boundaries are approxi- mate and are intended to provide an indication of the presence of wetlands. Further field verifica- tion will be necessary to deter- mine exact wetland boundaries' 6/25/91 B- twelve Associates, Inc. Ecological Systems Design & Management 521 South Washington Ave. • Kent, WA 98032 Job No.: 9z -sto Date: Drawn By: Ears Checked By: Revised: ' /_-!4'11 By: 3 -12 TUKWILA BASI J STUDY CITY OF TUK [LA, WA EXHIBIT G: National Wetlands Inventory Map nage posaL - -- ol∎".•' W 1. I -;; i,a17 1'' x . ngacrei' I ; katf -?' PEMC ••war =.- :' -� '( '" i ��i_ : ism e c , ?rack . .� _;, I; I r. L, � z ,. _ - ,;ice.. 4 • µ ▪ ' ti, � �� DFOC 'OM PFOC E ` PEMC •'— -� J V PEMC : ' ' "" ;S-S=C= ▪ 1 i PFOC 1/ PFOA • 1/ = PSSC DMM Q PEMC L 1i 25. 41 •.. egI7]Ed 1 PSSC' p� JliFOC .. 1.,.. EI ill P EMC PFOC. PAIS% ' .1 PSSF PSSF PSSC PuBH PSSF aes YOlr • • PFOC x • PSSC PSSCi G'4 This map is a portion of the National Wetlands Inventory map, Renton quadragle, dated 1988. US Dept. of Interior. Fish and Wildlife Service. All wetland locations and size are approximate. NORTH Job No.: q2 -tio Date: Drawn By: /KS Checked By: Revised: 1z -F. - "z. By: 4.- 3-1z B- twelve Associates, Inc. Ecological Systems Design & Management 521 South Washington Ave. • Kent, WA 98032 TUKWILA BASIN STUDY . CITY OF TUKWILA, WA II- twelve Associates, Inc. Job # 9L-1 /0 Wetland tr Upland Other WETLAND DETERMINATION FORM Applicant Application Name: ca F.1 OT #: State: u,F} County Date: -3 -9Z Plot #: Idtti 1 Vegetation Species Ind. Status Trees 1. - 2. 3. Saplings /shrubs 4. CC.,-.~ s s 4-0 1CW. ,.P, 5. Spp.; �.. Jo i,14 6. �, n v s seedC n. /, Ft-cw Project Name: Sas.� 5r.,dY Sample Name: Determined by: £d // Herbs 7. 8. 9. Woody vines 10. 11. 12. Species % of spp. OBL, FACW, and /or FAC: i r, Comments: Hydrophytic vegetation: Yes /No . Basis: /o0% hioQ11}4.s Soil Series and Phase: On hydric soils list? Depth (0 in) in. in. in. Fi << Yes No_. Munsell Color matrix/mottle Ind. Status Subgroup: Texture Remarks Comments: Hydric soils: Yes ✓ No _. Basis: 4.,.,,,,1 .41,1 >3o 01w =3 clv.•,;. ttv. Hydrology Inundated: Yes ✓ No . Depth of standing water: 36" Saturated soil: Yes ✓ No Depth to sat. soil: s,,,.ia c.x. Other indicators: Wetland Hydrology: Yeses No . Basis: sAfwathi > 3 o d.7, do,.e&I 4&. q��w��� seas.' Atypical situation: Yes .No ✓ . Normal circumstances: Yes ✓ No Wetland Determination: Wetland ✓ Nonwetland Comments: B- twelve Associates, Inc. Applicant Name: crf. f Ttuw�l State: IA/R Date: 4 —2P-9 L Vegetation Species Trees 1. Qc�i..s 2, so.r, Trl 'chp[M04 3. Saplings /shrubs 4. s..l, K S, Job11 qL—) /O Wetland ✓ Upland Other WETLAND DETERMINATION FORM Application #: County k; rd Plot #: lvrt' /A.,, Ind. Status FP�W 5. Co. -NKS 5fa10 I PVC r/}-c-' Herbs Project Name: -71u%ocw ;1., bas: ST„dY Sample Name: Determined by: f Se w.► // 7. Species rip 1. .4/ F., i. 8. PA./-r-: 9. Woody vines 10. 11. 6. 12. 7U of spp. OBL, FACW, and /or PAC: /,v Comments: Hydrophytic vegetation: Yes ,/ No. Basis: /e,0% 611ro P\ 4&s Soil Series and Phase: Fill On hydric soils list? Yes No_. Depth Munsell Color (0 in) matrix/mottle ‚'in. in. Ind. Status Obi F/lG L-1 Subgroup: Texture s*1.1 t ,,.t I Remarks in. in. Comments: Hydric soils: Yes ✓ No _ . Basis: s, i..•.J4d 1 ,;...,„d,11 >30 cI s s e s o.r . ,� _ veil" Hydrology Inundated: Yes ✓ No . Depth of standing water: Saturated soil: Yes ✓ No Depth to sat. soil: Other indicators: / z — 3 G ./ Wetland Hydrology: Yes ,i No . Basis: s4fw,1-41 > 3 c ei■r, daf•e•-, OA. 31Vvrer -, e4J••' Atypical situation: Yes "No ✓ . Normal circumstances: Yes ✓ No Wetland Determination: Wetland ✓ Nonwetland Comments: Job# 92-IIo Wetland ✓ Upland Other WETLAND DETERMINATION FORM Applicant Application Project Name: C, 1-1 #: Name: T�vt,',1.� .- s - 5 State: vs/q- County K,'n Sample Name: Date: 4 -3 -9 z Plot #: wet -.,I 3 Determined by: d f./ Vegetation Species Ind. Status Species Ind. Status Trees Herbs 1. 7. A.,4ti -,s ...,„...d. .- ......... FA.cw 2. 8. 3. Saplings /shrubs 4. 5. j/J,reti JdV)h. S• 9. Woody vines 10. prck./ 11. 6. 12. % of spp. OBL, FACW, and /or FAC: boy . Comments: Hydrophytic vegetation: Yes ✓ No_. Basis: ioo'i, :,,Jiro r . Soil Series and Phase: Subgroup: On hydric soils list? Yes No . Depth Munsell Color Texture Remarks (0 in) matrix/mottle ` /s in. criv.c/ f sue.... in. in. in. Comments: Hydric soils: Yes ✓ No ^ Basis: > zvdn.. • Hydrology Inundated: Yes ,/ No . Depth of standing water: 'Z- 34 Saturated soil: Yes ✓ No _. Depth to sat. soil: 5,,-A, u Other indicators: Wetland Hydrology: Yes ✓ No Basis: ) 3o s,,, _ �. Sts s�� Atypical situation: Yes No Normal circumstances: Yes No Wetland Determination: Wetland 7 Nonwetland Comments: IV 13- twelve Associates, Inc. Job}/ gL-ito Wetland ✓ Upland Other WETLAND DETERMINATION FORM Applicant Application Project Name: c. � of T,,Kw;l., #: Name: 7-01.Cw;1 a bas STAY State: t,,,,c1 County K;N1 Sample Name: Date: 4. -.2b-9L Plot #: wc>''l,i.ak 4 Determined by: £d Se w.. 1/ Vegetation Species Ind. Status Species Ind. Status Trees 1. / 2. 3. Saplings /shrubs 4. r- F1 ,L 5. . ' $I f[ ��1.rS� s F/4-CL-1 Herbs 7. ..r.. �.. 8. 9. Woody vines 10. 11. 6. !=, , :....b- ..._Fns'/2. s,./.'/ iS F/4-c. 12. io of spp. OBL, FACW, and /or FAC: ivy . Comments: Hydrophytic vegetation: Yes ✓ No . Basislov % 4,�kpp�„� }�S Soil Series and Phase: Fi l\ Subgroup: On hydric soils list? Yes_ No . Depth Munsell Color Texture Remarks (0 in) matrix/mottle t din. sit',vv.,/ 7i %/ in. in. in. Comments: Hydric soils: Yes ✓ No . Basis:- s, ilerwi I f ,. vAJi I > 30 41w1,, d✓r,,, 4‘.4- 9.owl•N' Sea, s o.4 . Hydrology Inundated: Yes ✓ No Depth of standing water: 6— 2-4'' Saturated soil: Yes ✓ No _. Depth to sat. soil: Other indicators: Wetland Hydrology: Yeses No . Basis: sAw,fi/ a t;,.,►,.4„ f4#/ > '3 o Aar d ✓��',. 1r...0-, sem.., Atypical situation: Yes 'No ✓ . Normal circumstances: Yes V No Wetland Determination: Wetland ✓ Nonwetland Comments: II- twelve Associates, Inc. Applicant r Name: c4f� pT T.jww: State: tA,� Date: 4 -W-9 z.. Vegetation Species Species Trees 1. 2. Job tl Wetland ✓ Upland Other WETLAND DETERMINATION FORM Application Project #: Name: ., gas, ST„dY County k; Nl Sample Name: Plot #: with-) C Determined by: £ d Se h.A I/ 3. Saplings /shrubs 4. sort", d.h., 43,',' 5. Ind. Status Herbs 7. Phut 8. 9. Woody vines 10. 2,b,s 11. R, b ,s PA<L-✓ 6. 12. % of spp. OBL, FACW, and /or FAC: 50 . Comments: Hydrophytic vegetation: Yes ✓No Ind. Status .4S%04 r T, _..J /4 a F/+c v -r- Soil Series and Phase: Fi It On hydric soils list? Yes_ No_. Depth Munsell Color (0 in) matrix/mottle l Spin. in. Basis: So etie VII ke f \ 1 #4s Subgroup: Texture s1 t ?I-.A4 Remarks 7ti %( in. in. Comments: Hydric soils: Yes ✓ No . Basis: s4 iv. SJ.% f ,;•v,.,r47411 > 30 4i.,3 4v #.•:•) 411.4. 9rour 'Na, s s o.. • Hydrology Inundated: Yes ✓ No . Depth of standing water: Co - / Saturated soil: Yes ✓ No . Depth to sat. soil: Other indicators: Wetland Hydrology: Yeses No. Basis: s.it...41.d 10 41.73 d,..,',., 4'i.. qr•••'', Ste0,' Atypical situation: Yes 'No ✓ . Normal circumstances: Yes V No Wetland Determination: Wetland ✓ Nonwetland Comments: • II- twelve Associates, Inc. Job JJ qL -) /D Wetland ✓ Upland Other WETLAND DETERMINATION FORM Applicant r Application Project Name: cr+ p7 TJKN�11 #: Name: Z-uticw; \.. gas.,., sdrvdY State: k,,,A County K Sample Name: Date: -4 -2-a -9 z Plot #: Determined by: 1/ Vegetation Species Ind. Status Species Ind. Status Trees 1. 2. Herbs 7. PA44,,'s FA-6 w 8. 3. 9. Saplings /shrubs Woody vines 4. sip« d>v, /A5,',' FA - 10. gv1, ,s 5. 11. d /StDI* 6. 12. ro of spp. OBL, FACW, and /or PAC: G (. • Comments: Hydrophytic vegetation: Yes i/No_. Basis: GG °!e Soil Series and Phase: Fi It Subgroup: On hydric soils list? Yes_ No_. Depth Munsell Color Texture Remarks (0 in) matrix/mottle 14 in. s t 9�'"^`1 P. %( in. in. in. Comments: Hydric soils: Yes ✓ No Basis: el 4~W i:- wPJ,4c • > 3o ot.��,y dtop►;.y k. 9.ow +'�� s e•, . Hydrology Inundated: Yes ✓ No . Depth of standing water: 6, –/ Saturated soil: Yes ✓ No —. Depth to sat. soil: Other indicators: Wetland Hydrology: Yes ✓ No. Basis: s4fti.Af41.+ riww►,f.,it 3 o A„, d,,,.e,...) 0e,. yrev+11. -7 se4,10,0 Atypical situation: Yes 'No ✓ . Normal circumstances: Yes ✓ No Wetland Determination: Wetland ✓ Nonwetland Comments: 13-twelve Associates, Inc. Job f qL Wetland ✓ Upland Other WETLAND DETERMINATION FORM Applicant Application Project Name: crfl ,f Tokala, #: Name: -r-otcw;\., 61s:,. ST44 State: ,,,) f} County Kt./5 Sample Name: Date:4 -1D-9 t. Plot #: wetA.-) Determined by: £d Sc ....Ai/ Vegetation Species Ind. Status Species Ind. Status Trees 1. 2. 3. Saplings /shrubs 4• Sp rat d,, Thai, • 5. F Herbs 7. , ��.,'s a,r-ve•-gl pct. FA-C. U./ $. 9. Woody vines 10. g,/,,s _ ,..5ro(ir- PAc V 11. 6. 12. io of spp. OBL, FACW, and/or FAC: G Comments: Hydrophytic vegetation: Yes fNo . Basis: GG 9'e Soil Series and Phase: Fi Subgroup: On hydric soils list? Yes No_. Depth Munsell Color Texture Remarks (0 in) matrix/mottle thin. s ►t ?�.► ( 7/ 7( in. in. in. Comments: Hydric soils: Yes ✓ No Hydrology Inundated: Yes ✓ No . Depth of standing water: -/ Fr Saturated soil: Yes ✓ No Depth to sat. soil: Other indicators: Wetland Hydrology: Yes ,i No. Basis: s4f , ) + 4~4A/ > s o d■73 d,,,.,'," 41.t sc,0•" • Basis: $4 > 30 4,3 aver'," 9.0,.,►•�} s eti s o,r . Atypical situation: Yes 'No ✓ . Normal circumstances: Yes ✓ No Wetland Determination: Wetland ✓ Nonwetland Comments: • 5. Project Name: t< I3as.',r Sr./Ay Sample Name: Determined by: fet Species Ind. Status Herbs 7. P /...rs 8. 9. Woody vines 10. feu 11. vs d,s.rJ,.• 6. RV 6,•3 st„ rf:;l�, i.5 I. -;r C 12. % of spp. OBL, FACW, and /or FAC: 8'8 . Comments: Hydrophytic vegetation: Yes ✓ No . Basis: ' ' % hN iro /4\14es Soil Series and Phase: Fi it On hydric soils list? Yes No . Depth Munsell Color (0 in) matrix/mottle t `e in. in. ("fjGl.,i Subgroup: Texture s...04.1. Remarks fi %r in. in. Comments: Hydric soils: Yes ✓ No . Basis: sot i'►...ftA • 4••••••^,44 >30 oidiv d✓et:1 4hc g.oweol Sea. s o.+ • Hydrology Inundated: Yes ✓ No . Depth of standing water: Saturated soil: Yes ✓ No . Depth to sat. soil: Other indicators: Wetland Hydrology: Yes ✓ No . Basis: s4fw„fii 3 o co..13 d,,���,. 9rewt'. -7 sc44•4.• 36" s c.e, Atypical situation: Yes No ✓ . Normal circumstances: Yes ✓ No Wetland Determination: Wetland ✓ Nonwetland Comments: II- twelve Associates, Inc. Job// 9L"IlQ Wetland V. Upland Other WETLAND DETERMINATION FORM Applicant Application Name: co-.1 #: State: k„IA County K ;,/5 Date:1- -2 ° -9 Z. Plot #: wet/4.1 er Vegetation Species Ind. Status Trees Herbs 1. 2. 3. Saplings /shrubs 4. 5. Project Name: T,14,..;1.. 13 .s.N ST,.& Sample Name: Determined by: £d Sc ww 1/ Species Ind. Status 7. T177)4., /`� �,Fo /.:L c61 g. / Aa /Ar..S M �O� • ^�' �t t �� c 9. Woody vines 10. 11. 6. % of spp. OBL, FACW, and /or FAC: Comments: Hydrophytic vegetation: Yes ,/ No Soil Series and Phase: Fi l\ On hydric soils list? Yes_ No_. Depth Munsell Color (0 in) matrix/mottle t gin. in. . Basis: ioa% 4►�ke����ss Subgroup: Texture 50/01 7rovrc Remarks 7/ r� in. in. Comments: Hydric soils: Yes ✓ No Basis: $4lvr.►f<01 f t:-.' di,1,# >3oS.ts dam... -, irOWeNl se.,so... Hydrology Inundated: Yes ✓ No . Depth of standing water: Saturated soil: Yes ✓ No —. Depth to sat. soil: Other indicators: Wetland Hydrology: Yes_ No . Basis: sst...,f<iI e 0,..+4.4.114 4/ > 30 (A013 doreel 44. !rows'', Se-'"T"' / o /r rr Fti vL. Atypical situation: Yes 'No ✓ . Normal circumstances: Yes V No Wetland Determination: Wetland ✓ Nonwetland Comments: B- twelve Associates, Inc. Job// Wetland ✓ Upland Other WETLAND DETERMINATION FORM Applicant Application Project Name: e,s ,F T4.41,, #: Narne: i v4twi.ia B,s ,-, 5 t,.o17 State: 1.,,, F}- County KI`A., Sample Name: Date: 4 -2.o - qa Plot #: the f U /6 Determined by: 5-- - -41 Vegetation Species Ind. Status Species Ind. Status Trees 1. Poeyiv5 +ritLfw.pt py C- 2. 3. Saplings /shrubs 4. (2- Srci-401115 FA-C_ Herbs 7. pin, i � ; 8. pAe 9. Woody vines F/kC 10. l?. at, o� o %� 5. 11. 6. 12. % of spp. OBL, FACW, and /or FAC: 754 . Comments: Hydrophytic vegetation: Yes No . Basis: ?5% 4,71' • p4,3 S Soil Series and Phase: On hydric soils list? Yes_ No . Depth (0 in) /rin. in. in. Munsell Color matrix/mottle ioYa- Z./7 7. s'y 31.2. Subgroup: /0 Y/2 3/4 n.fh•r Texture s...d"I /a.� -, Remarks Comments: Hydric soils: Yes VNo Hydrology Inundated: Yes No V Saturated soil: Yes ./No Other indicators: Wetland Hydrology: Yes . Basis: c �p � 1 .t z /� . at�,s Depth of standing water: _. Depth to sat. soil: �No_ Basis: Atypical situation: Yes No . Normal circumstances: Yes No Wetland Determination: Wetland �onwetland Comments: B- twelve Associates, Inc. Job H q Z- — 110 Wetland ✓ Upland Other WETLAND DETERMINATION FORM Applicant Application Project Name: G/F� ,f -11,16.11 ., #: Name: TutCw ;1., l3As.',✓ ST,,dy State: t,,,ii County K; N5 Sample Name: Date: 4 -3 -n. Plot #: lve#,,.J 1l Determined by: £d Se WA It Vegetation Species Ind. Status Species Ind. Status Trees Herbs 1. 2 . 5, /4 s, i� ,d j-c, �/ w r 3. (bears fr,c4, Corr,\ �4L Saplings /shrubs 4. S. s /IcLis, 3 F/;-C w 5. 5, / s F 1.-./ 7. 77 J1 lti7', 61 8. A/,s,••,\ ,;,.,f� � � .,�f,�� obi 9, /124.10,••vr+ Woody vines 10. 11. Sfl' 6. COM ✓3 .:4v /ON/ryti p:,4ct.../ 12. ro of spp. OBL, FACW, and /or FAC: /4, ; Comments: Hydrophytic vegetation: Yes./ No_. Basis: % 611,-e Q \14-4s Soil Series and Phase: Fi It Subgroup: On hydric soils list? Yes_ No_. Depth Munsell Color Texture Remarks (0 in) matrix/mottle 1 din. P. %/ in. in. in. Comments: Hydric soils: Yes ✓ No Basis: s, iVevacol f 440/.0/474t1 > 30 4,3 d,,, �y. 9.oweol S es. s o.+ • Hydrology Inundated: Yes ✓ No . Depth of standing water: 1.?_ -3 (,e/ Saturated soil: Yes ✓ No Depth to sat. soil: s,,. Other indicators: Wetland Hydrology: Yes ✓ No . Basis: sarfv.,44) > s o A.r, lire, 5r.w�#., se..'' Atypical situation: Yes 'No ✓ . Normal circumstances: Yes V No Wetland Determination: Weiland v- Nonwetland Comments: HART- CROWSER SITE HYDROGEOLOGY REPORT APPENDIX 3 . RIM 11 HIIRTCROWSER Earth and Environmental Technologies Tukwila Basin Study Site Hydrogeology Prepared for Gardner Consultants, Inc. June 23, 1992 J -3572 Seattle • Tacoma • Richland • Anchorage • Portland • San Francisco • Long Beach TUKWILA BASIN STUDY SITE HYDROGEOLOGY SUMMARY Hart Crowser J -3572 The study area lies on the alluvial plain of the Green River and is underlain by river - deposited sediments consisting chiefly of sand and silt with some clay and peat. ► Typical of river deposits, the strata underlying the basin are limited in areal extent. ► Portions of the original topography have been modified and filled with sand and gravel for construction purposes. ► There are several wetlands in the basin supported by precipitation and overland flow. The wetlands appear to be perched above the local water table and serve to recharge the groundwater system via infiltration through the bottom of the wetland soils. ► The direction of groundwater flow is usually toward the Green River except at times of high river stage when the direction of groundwater flow may be away from the river. ► The horizontal hydraulic conductivity of the alluvial deposits is estimated to be 10 to 10 centimeter /second (cm /sec) as inferred from in situ well tests performed in monitoring wells located at the perimeter of the basin. ► Except for the Puyallup fine sandy loam, the soils in the basin have low infiltration rates and are generally not feasible for induced infiltration of stormwater. PROJECT BACKGROUND The purpose of this study was to define the hydrogeology, including the site geology and occurrence and flow pattern of groundwater in an area located in the Green River valley north of South 180th Street (S.W. 43rd Street), south of Strander Boulevard, west of the Tukwila city line Page 1 Hart Crowser 3 -3572 of the Burlington Northern Railroad, and east of the Green River in the city of Tukwila (Figures 1 and 2). This is an area of low topographic relief covered by industrial facilities which border several wetlands. Two particular topics of interest to the study were the relationship of wetlands identified on the site to the groundwater table and the capacity of the local soils to receive induced infiltration of stormwater. This study is to provide information pertinent to an environmental impact study being prepared for the City of Tukwila in compliance with the Washington State Environmental Policy Act (SEPA). The study was performed using available information. No field work was performed for this study. REGIONAL HYDROGEOLOGY The Green River valley was carved during the Pleistocene Epoch by glaciers advancing south from British Columbia (Leisch et al., 1963). Sediments filled the valley as the glaciers retreated and later as the Green River reworked glacial deposits and carried soils toward Puget Sound. Relatively steep walls on uplands and a broad alluvial plain with local topographic highs characterize the valley in the vicinity of the site. Complex meanders of the Green River, flooding, and reworking of older glacial sediments have created sandy and silty soils with discontinuous zones of silt and clay. These soils have been mapped as alluvium (EES et al., 1991). The description of alluvium as chiefly sand and silt with some clay and peat closely describes the soils which were reported in the sources reviewed. Shallow groundwater in the valley generally flows from the uplands toward the Green River. EES et al. (1991) report in the South King County Groundwater Management Plan that groundwater in the vicinity of the project site flows to the northwest, toward the Green River. Locally, groundwater may flow in other directions preferentially through more permeable soil or fill materials. Groundwater in deeper aquifers (greater than 100 feet below ground surface) most likely flows parallel to the river. Page 2 Hart Crowser J -3572 SUBSURFACE STRATIGRAPHY A review of geotechnical reports for construction sites located on the perimeter of the basin area indicates that three main stratigraphic units exist beneath the project site: fill materials; loose, silty, alluvial sediments; and denser sandy sediments. Figures 3 and 4 show the general stratigraphic sequence in geologic cross sections A -A' (north - south) and B -B' (east- west); the locations of the cross sections are indicated on Figure 2. Soil and geotechnical information were obtained from the City of Tukwila and from Hart Crowser in -house files. Portions of the original surface topography have been modified and filled with sandy gravel and gravelly sand for construction purposes. Fill depth varies around the site area. Below the fill to a depth of approximately 30 feet exists a complex alluvial system composed of interlayered fine sand, silty sand, sandy silt, clayey silt, silty clay, and peat. Boring logs reviewed for this work depict soil units to be approximately 2 to 5 feet thick but the units do not appear to be continuous between boreholes separated by more than several hundred feet. The amount of fines, such as clayey silt and silty clay, appears to increase to the south where a silt and clay unit approximately 20 feet thick was observed (Figure 3). A zone of organic accumulation (peat), almost 5 feet thick was observed at a depth of approximately 25 feet at the northern end of the site and near a depth of 30 feet to the south. A dense to very dense, medium to fine sand with interbedded silt and scattered organics was observed beneath the loose, alluvial deposits. The sand appears to be more continuous than the upper soil units as it was observed in nearly all the deeper explorations. Silt lenses are described as "laminations" and reported thicknesses range between 2 and 12 inches. This unit appears to extend to a total depth of approximately 70 feet. Below that depth, cone penetrometer data (Hart Crowser, 1974) suggest the existence of alternating layers of silt, sandy silt, and silty sand. GROUNDWATER OCCURRENCE AND FLOW Based on estimated ground surface elevations, groundwater should exist between 1 foot and 15 feet below the ground surface. Water table Page 3 Hart Crowser J -3572 elevations measured in monitoring wells in the basin and surveyed test pits indicate that shallow groundwater occurs at elevations between 7 and 18 feet above mean sea level (MSL). The majority of groundwater level elevations reported in the documents we reviewed were between 15 and 18 feet (MSL). Deviations from this range may be due to aquifer heterogeneities or seasonal fluctuations. Hart Crowser (1978) reported groundwater elevations of 16 to 17 feet (MSL) near the southwest corner of the basin area. EES et al. (1991) report groundwater elevations between 8 and 11 feet (MSL) in the basin area. Water level elevations and their measurement dates are presented on Figure 3. Based on the data reviewed, it appears that surface water in the basin infiltrates to groundwater. B- twelve Associates, Inc. (1992) have identified several wetlands in the area (Figure 2) which are supported by precipitation and local surface water drainage. Several of the wetlands are connected via ditches and culverts with excess surface water draining easterly towards Springbrook Creek. B- twelve Associates, Inc. (1992) report that the surface of the basin area is at an elevation of approximately 20 feet (MSL) with saturated conditions extending to depths of 4 feet or more. They describe saturated soils extending from the surface to depths and elevations at which the water table has been locally observed. The locally observed water table appears to occur at a depth of less than 5 feet below ground surface. The water stored in the wetlands may provide recharge to the groundwater system via infiltration through the bottom of the wetlands. The shallow groundwater observed beneath the site appears to be hydraulically connected with the Green River with groundwater flowing toward and discharging to the river during most of the year. The surface elevations reported for the river are similar to those of the groundwater table. In 1978, Hart Crowser measured the groundwater elevation near the south end of the basin area at 16 to 17 feet (MSL). Review of historical USGS river discharge data for 1978 and recent communication with USGS personnel provided an updated estimate of the river surface elevation near the project site. The river surface elevation (stage) was reportedly between elevation 5 and 14 feet (MSL) during 1978, based on a river gradient of between 0.001 ft /ft and 0.0001 ft /ft. These river elevations fit well with the regional groundwater flow map presented by EES et al. (1991). The elevation of the groundwater Page 4 Hart Crowser J -3572 table near the river is higher than the surface of the river, with groundwater flow toward the river. It is likely that groundwater flows away from the river during wet periods when the river stage is high. Hart Crowser personnel observed groundwater fluctuations of 5 feet in a monitoring well along SW 43rd Street, measured between December 1973 and April 1974. Fluctuations of the water table may exceed 5 feet at other locations in the basin. Springbrook Creek does not appear to be directly connected to the Green River via groundwater because large changes in the stage of the Green River are not reflected by changes in stage at Springbrook Creek. It is likely that the predominantly fine - grained sediments in the Green River valley limit the extent of a reversal in groundwater flow direction when the Green River's stage is high. A horizontal hydraulic conductivity estimate of 10'3 to 10'5 cm /sec was derived from in situ falling and rising head tests performed in monitoring wells completed in the upper groundwater table and on the perimeter of the basin area. The saturated strata were described as silty sand and the depth to water was 7 feet. The estimated groundwater elevation was approximately 15 to 16 feet at the test site. Vertical hydraulic conductivity values are typically lower by one to two orders of magnitude due to the orientation of clay particles and layering of the strata. Published values of hydraulic conductivity in silts and clays are in the range of 10'5 to 10'' cm /sec. Locally, discontinuous zones of more permeable strata likely exist within the generally fine - grained matrix. WATER INFILTRATION POTENTIAL The United States Department of Agriculture (USDA, 1973) has mapped a total of 5 soil types in the basin. The soil series and the associated infiltration rate and Hydrologic Soil Group determined (via the soil type) by using Washington State Department of Ecology (Ecology 1991) draft guidelines are as follows: Page 5 Hart Crowser 3 -3572 Infiltration Hydrologic Soil Rate in Inches/Hour Soil Group Puyallup fine sandy loam (Py) 1.02 B Newberg silt loam (Ng) 0.27 C Woodinville silt loam (Wo) 0.27 C Puget clay loam (Pu) 0.09 D Urban Land (Ur) NA NA Based on Ecology (1991) draft guidelines, the Puyallup fine sandy loam (Pu) soil has an infiltration rate of approximately 1.02 inches/hour making it an acceptable soil for stormwater infiltration. Puyallup fine sandy loam is located in the southwestern corner of the site and extends north along the banks of the Green River. Induced infiltration would best be accomplished by use of surface structures such as grass -lined basins rather than by use of dry wells. This is because of the shallow depth to groundwater; Ecology (1991) recommends a good thickness of unsaturated soil beneath an infiltration structure. In addition, the pollutants in stormwater runoff are adsorbed by grass; dry wells do not share this advantage. The four other soils, which make up the majority of the surficial deposits on the site, do not fall into the classification of soils with feasible stormwater infiltration rates, as defined by Ecology (1991). The Newberg silt loam is in some areas classified as a very fine sandy loam and as such may be acceptable for stormwater infiltration systems. It is not known whether the soil on site is a silty loam or a very fine sandy loam. Urban land is considered too diverse for classification as it may consist of fill material. Infiltration rates and soil classification must be done on a site -by -site basis. Page 6 REFERENCES Hart Crowser J -3572 B- twelve Associates, Inc., 1992. Tukwila Basin Study, City of Tukwila Wetland Analysis. Prepared for Gardner Consultants, Inc., Tukwila, WA. Job 92 -110. EES, Hart Crowser, Pacific Groundwater Group, and Robinson and Noble, 1991. Title Prepared for Municipality of Metropolitan Seattle. 42 pp and Appendices. Hart Crowser, 1974. Soils and Foundation Engineering Study for Preliminary Design of the S.W. 43rd. Street Improvements, J -125. Hart Crowser, 1978. Soils and Foundation Engineering Study, Proposed New Facility for the Howard Cooper Corporation, Renton, Washington, J -643. Leisch, B.A., E.C. Price, and K.L. Walters, 1963. Geology and Ground -Water Resources of Northwestern King County, Washington, Water Supply Bulletin 20. Washington State Department of Conservation and United States Geological Survey: 59 pp. United States Department of Agriculture, 1973. King County Area, Washington, Soil Survey, Soil Conservation Service. United States Geological Survey, 1978. Water Resources Data for Washington, Vol 1 and 2, United States Department of the Interior. Washington State Department of Ecology, 1991. Draft Stormwater Management Manual for the Puget Sound Basin, Olympia, WA. Page 7 Vicinity Map 0 112 Scale in Miles ILI OW HART J-3572 6/92 Figure 1 1 all 0 \a A a • ; ? Note: Base map prepared from drawing provided by GC! Consultants entitled 'S.E C8D Drainage Basin Study'. dated May 1992 08 -1 Boring Location and Number •P -1 Probe Location and Number Wetland Area and Identifier (B— twelve Associates.1992) Cross Section Location and Designation i�.�.�ii;ii 0 e1 Sca Cross Section Location and Designation t (366t'sateroossy eMeM —g) Jaijpuapi pue easy pueiteM 188d ui aieos 0 Generalized Subsurface Cross Section A -A' Tukwila Basin Study A (South) 40 - 20 kn M • TD 0 u. c 0 0 w 0 -20 _40 Intersection of Cross Section B-B' Loose. wet, dark brown, fine SAND with SILT. Damp, brown, sandy SILT. Loose to medium dense,moist to wet. silty,fine SAND to sandy SILT with areas of FILL (.Sandy GRAVEL). Approximate Ground Surface --It - - - - - -_ 26/78 Stiff to medium stiff, gray-brown,— 10/74 moist to wet. clayey SILT to silty CLAY. ALL with organics ALL (sandy GRAVEL) Loose to very loose, moist to wet, gray to brown, interbedded fine sandy SILTS. silty fine SANDS. fine to medium SANDS,and clayey SILT with zones of organics (peat). 121/80 Dense to very dense, moist to wet, black to gray, medium to fine SANDS with interbedded SILT layers and scattered organics. A' (North) RLL (gravelly SAND) 2 Loose to medium 9/85 dense. moist to wet, silty, fine SAND to sandy SILT. Zone of Organic Accumulation Note: Drawing based on subsurface data provided by City of Tukwila. Gardner Consultants. Inc.. and Hart Dowser. Inc. SL Water Table Level 10/74 (Date Indicated) Horizontal Scale in Feet 0 500 0 20 Vertical Scale in Feet Vertical Exaggeration x 25 1000 40 gneralized Subsurface Cross Section A -A' Wier Basin Study A (South) 40 20 -40 - Intersection of Cross Section 6-13• Loose, wet, dark brown, fine SAND with SILT. Damp. brown, sandy SILT. Loose to medium dense,moist to wet, silty.fine SAND to sandy SILT with areas of FILL (Sandy GRAVEL). Approximate Ground Surface FILL with organics FILL (sandy GRAVEL) FILL (gravelly SAND) — — — — — _ 26/78 2 Stiff to medium stiff. gray-brown ,-- 10/74 moist to wet. clayey SILT to silty CLAY. Loose to very loose. most to wet. gray to brown, interbedded fine sandy SILTS. silty fine SANDS. fine to medium SANDS,and clayey SILT with zones of organics (peat). Dense to very dense. moist to wet, black to gray, medium to fine SANDS with interbedded SILT layers and scattered organics. 21/80 A' (North) _ 2 Loose to medium 9/85 dense, moist to wet, silty, fine SAND to sandy SILT. Zone of Organic Accumulation Note: Drawing based on subsurface data provided by City of Tukwila. Gardner Consultants. Inc.. and Hart Dowser. Inc. Q Water Table Level 10/74 (Date Indicated) Horizontal Scale in Feet 0 500 0 20 Vertical Scale in Feet Vertical Exaggeration x 25 1000 40 J -3572 6/92 Figure 3 .0 Be N Of Intersection of Cross Section A -A* B B 8 -2A -28 P -1 8 -3 P -2 8 8 20 - �� Solt to madam sell. ly SAND e �- 1 clayey SILL and sandy SILT with some loose �, -' silty sand layers.— . _ _ _ jao- s a - Trail may_ _ Loosasilly_SAND and sandy Sal wdh some madun — — :EC. -iark- 'Sr _czcsm_sitt. - Solt to medium still. silly CLAY and clayey SILT with some saw sill to W -20 -40 d GRA E FILL Medium dense to dense SAND with some silty sand and clayey sill layara. still Gay and sill aro & 1 r -� and silly sand layers./ / layers. Silly SAND and GFUWEL FILL Medium stiff to still,clayey SILT and sandy SILT. Medium dense to dense. line to medium SAND. Loose to medium dense. silty SAND and SAND and layers of meclum stiff to stlff,clayey SILT and sandy SILT with scattered organics. 8 -3 Boring Number Note: Contact between soil units are based upon Interpolation between borings and represents P -1 Probe Number our Interpretation of subsurface conditions • based on currently available date. Exploration Location (Source: Hart Crowser, 1974) Horizontal Scale in Feet O 300 • 600 G O 20 40 Vertical Scale in Feet 1 1 %(1 100 TEAR ROOD ELEV. • 26.8 17 12" 17 18" ��LF • L � f 250 0 EXHIBIT C: WET Li"' Li 250 500 750 SCALE IN FEET DE7N 36• CAW LE 18.35 LE 18.25 / / 24• r, f I I f ni,; f' ; � Ns • ` 4 s, BY ARFIIS r� Sn.DY SPOWING 10D YEAR FLOOD AREAS EEYO D RIVER BANG —J 48• LE 161 LE 18.46 NOTE: CM STP. E P. RR. 0 36• GNP LE 1871 /E 1Z56 B.N.R.R. 100 YEAR ROOD ELEV. -17.2 24• CM" 1 LE 19.36 LE 19.28 .This map provided to B- twelve Associates, Inc. by Gardner Associates, Inc. .Map depicts approximate locations of wetlands identified by B- twelve Associates Inc. Wetland edges were mapped off April 1992 aerial photographs. Wetland edges were not delineated or formally surveyed. ti r ,� �t "c.1t FFOSTRESf37 T°R1 TLAW SEE CITY OF RENTON DRAWING FOR SPRINGBROOK CREEK - P -1 CHANNEL ALTERNATES tO 9 36- C P LE 16.72 1.E 16.79 a DRAINAGE COURSE EAST OF CILVERT IS NOT APPARENT UVINVE TO IED CITY CF RENTON WETLAND W-13 TO SPRINGBROOK CREEK VIA WETLAND W -12 SPRINCIROOK CREE‹ 100 TEAR ROOD E EV.- 14.6 AT STRANDS? EXTENDED B- twelve Associates, Inc. Ecological Systems Design & Managemen 521 South Washington Ave- • Kent. WA 980: TUKWILA BASIN STUDY CITY OF TUKWILA, WA 1 gat: dcsiannf!U.k 11,w. ucxn l'.5:.1''9'd c`!ck ^d t ,..7'.r .92 f :`f... Ca L.4 :k ^a •ay„u� • ly�.r . .; ,�� r�hr �cVLs":. a� �'. yh wed •'f`�( `yam•, - • !i�! ti'r:�1? - s` ? -. -moil,. ..L� ___ .'.:1.1.31[07,1=031 r c rtZ .77. FL':9'1 °. 174 A 1. ^.0 amp ...c.c. am : ucu. w Grr:.r -nr S.E. CBD JAINAG,_ =,c,SI • .0 ) t .l � lr . ri Y_ !,-� '^` ' - J �r� l�L (� nI �(' _ �; 1 rr��lr �lol Ij1 ESL jU ti _ I ='� �Ji fir! J- - EI10INEERING- STREETS- WATER - SEWER- PARKS- BUILDING- _\ I S I T\G D.L.-1—,. ' <- —. ...n - 100 YEAR R.000 ELEV. • 26.8 k /7 18' GQEE-A/ /2" 250 0 i . Li 11L1 • 250 500 750 SCALE DV FEET 5: M3.. DI tri 0 u[S7i" AV. S. IT // --I ti "- i ri : En . ! • , ....; . '`c • '"•• .'.. 1 ; .1111', •/', -. / _il 'LI i ; .. . • .k. \ • Ti_____I Ir/: /,-,,.; ‘- v. \ ,--z \cr. . 36- C40 _ 7. 7 1/ LE 18.35 c..t;z:.„...46........ 24" - 17 ,/ • .. • LE raso_J i I /), 8- LE 18.46 HI-- I EXHIBIT C: WETLAND MAP C> AREAS MAPPED BY 1989 F.EMA STIAT SPIOWING 100 YEAR FLOOD AREAS BEYOND RIVER EIANC 43' 0E7N i t tilt 0 ,---- -- ----- -- 0 -..- '''' ----- CM ST.P. EP. QR. 100 YEAR FLOOD ELEV. - 23.5 --" HJ PROPOSED 24- CU-YERT - __LE 20.5 •- — • 36' CMP LE 20.97 \ LE 2L17 0 36 CA40 LE 18.71 IE 17.56 CE: fij 24* CMF' LE 19.36 LE 19.28 100 YEAR FLOOD ELEV. -17.2 s map provided to B-twelve :iates, Inc. by Gardner Associates, p depicts approximate locations of nds identified by B-twelve Associates Wetland edges were mapped off April aerial photographs. Wetland edges not delineated or formally surveyed. 40.074q,c1t. 0 LNINVIENITORIED FORESTED WETLAND - • - • - • - • - 7- — • 1 SEE CITY OF RENTON DRAWING FOR SPRINGBROOK CREEK - P-1 CHANNEL ALTERNATES (I) 36- CM' LE 16.72 LE 16.79 I 0 DRAINAGE COARSE EAST OF CtLVERT IS NOT APPA/aENT UVANENTC,RieD cirr CF RENTON WETLAND W-13 TO SPRINGBROOK CREEK VIA WETLAND W-12 SPRINGS/ROOK CREEK' 100 YEAR FLOOD ELEV.- 14.6 AT STRAW ER EICTENDED B-twelve Associates, Inc. Ecological Systems Design 84 521 South Washington Ave. Management • Kent. WA 98032 46- LE. 20.69' LE 20.5a TUKWILA BASIN STUDY CITY OF TUKWILA, WA ri 1 \ tiCi ----iJ4L-11:::1EY CIAVC-2.1r.-7,-)F--1-r;-----1 :-----11----------='.7-.2—:11.7 1 r • I drat nof.otr, 414'" 4711 ,._,__,.,._;_r. . _ : , .,. i T • f„:-F-.. :f; ] r. '; '- .-.:- 5.E. CD DRAINGE 34-..siNi STUDY t'fined:°.:',.:';-,97., chtiktd 1 .■:,.....:,17,-.., . ' -ENGINEERING-STREETS-WATER-SEWER-PARKS-BUILDING- .z. ) \ISITNG -),L.—i_.. :-....i•zriT.D5,,t-vn r*,..:Tr r.K1111-0_7_1,.,54*If.5, 3: -1;-2- ,:.:., ‘4.1.141 rr.D,L =i :21 :4A711.f. lt• ixe) :41-13,: i. DS-01 r:77-4:711"12..''.99.—}1/ 100 YEAR ROOD ELEV. -26.8 EV 250 0 2°.A 500 SCALE ZI $T 150 _--1-1. -I ' 11 ti\ m — — a �--f 1 1 I ' t U 4�IA'/ G I L J ll Ce - �J � _ -o u + ��� ►►► ► � -- _,as DCTIV 11i , ;1 C a b I C:1 I 3 xCM.3P 5 n d I l 1r :', It11111 1 I tltl 48 I G 1 ■ ° C1 QI ® 1.2 ,D 1LE 18. ._t 1� � i LE 16.46 _ � � - - -- -- -- �_ � � n o � iL —. � I I �3 -.. w.rr_= _ - - -- I si E -F-i H t-1 w / �T.�h[a1�rw•© - - - C - rrc�ic-_r� 33 li � GAZ ST.P. F P. RR. Ui i O I I I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 '1 11 111111111: 111111111111111111111111111111111 _ •_ _ � - - -- t 1, 1 1 1 1 1 1 1 1,1,1,1,1,1,1,1,1,1,11111 r I; AREAS MAPPED BY 1989 FEMA. S71-10Y SNOWING 100 YEAR ROOD AREAS BEYOND RIV BANG 36- cMP (.E /8.71 LE (7.56 100 YEAR ROOD ELEV. - 17.2 p0p 1n 24' CMP \° (iC LE 19.36 (j LE 19.28 qTrj-L 171C--1 - Ef0IQ1N11MAI G-STREETS•WATER- SEWER- PARKS- SWLDINCIl- [ LNINVHVTOR/ED FORESTED WETLAND SEE CITY OF REVTON DRAWING FOR SPR/NGBROOK CREEK - P-I CHANNEL ALTERNATES 36" CMP LE I.E. (6.72 r r679 / II o C DRAINAGE COLRSE EAST OF CLLV6ZT IS I 4E LE LE NOT APPARENT 1 I UVInNEVTORIED CITY OF REVTON VVE7LAAD W -13 TO SPRINGaROOK CRS VIA WETLAND W -12 SPRINGEROOK CREEK 100 YEAR 19.000 ELEV.- 14.6 AT STRAWER EXTEi1DED �0�3c�Li37�� S.E. CBD DRAINAGE_ BASIN STUDY EXISITNG DATA date r o o o 500 SCALE 5.4 T 100 YEAR FLOOD S.EV. - 2618 750 AREAS MAPPED BY 1989 FENA. STUDY SHOWING 100 YEAR FLOOD AREAS BEYOND RIVER BAN: 100 YEAR MOOD ELEV. • 23.5 WEST VALLEY RO �J i PR0POSG ! 24' CLLj2T •' ..„l.E 20.5 11 — t L. P,22 48'CMPIi I.E 20.695 1.E 20.5Cj CM ST.P. E P.Z. crsIL 100 YEAR FLOOD ELEV. -17.2 24' CMP \o� ICE /98 , ' 1 1 36' CM° LE an LE 17.56 LNINVIEVTORED � FORESTED 1WETLAAD SEE CITY OF RENTON DRAWING FOR SPRINGBROOK CREEK — P—I CNAIIVEL ALTERNATES f TO SPRNK FOOL CRS' VIA WETLAND W-12 36' CMP LE 16.72 1E16.79 DRAINAGE COLRSE EAST OF CLLVERT IS NOT APPARENT LNIM ITOR1® CITY OF RENTON WETLAND W -13 SPRAGEIROOK CSC 100 YEAR FLOOD ELEV.- 14.6 AT STRANDS? E T15\V S.E. CBD DAINAGE BASIN STUDY EXISITNG DATA WMAN D WL-12. EXHIBIT H: CITY OF TUKWILA WETLAND IN A113 NO1N311 4C • .• • • • • • • - • • • . - NOTES • NORTH t WETLAND 13 B-twelve Associates, Inc Ecological Systems Des 521 South Washington Ave. TUKWILA BASJ TUKWILA, WA Job No.: ci7-//0 I Drawn Bv: Lie 5 C Revised: - 1 WEI LAN 0 WL-12. EXHIBIT H: CITY OF TUKWILA WETLAND INVENTORY _S4111'111 Ai13 NOIN311 ;I: IORTH rAlk WETLAND WL-I3 AID B-twelve Associates, Inc. Ecological Systems Design & Management 521 South Washington Ave. • Kent, WA 98032 TUKWILA BASIN STUDY TUKWILA, WA Job No.: 92.-//c) Date: Drawn By: Lx5 Checked By: Revised: By: