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HomeMy WebLinkAboutSEPA E97-0023 - CITY OF TUKWILA / PUBLIC WORKS - RIVERTON CREEK STORMWATER QUALITY MANAGEMENT PLANRIVERTON CREEK STORMWATER QUALITY MANAGEMENT PLAN WATER QUALITY PLAN E97-0023 • • CITY OF TUKWILA DETERMINATION OF NONSIGNIFICANCE (DNS) DESCRIPTION OF PROPOSAL: WATER QUALITY PLAN FOR RIVERTON CREEK BASIN PROPONENT: PHIL FRASER LOCATION OF PROPOSAL, INCLUDING STREET ADDRESS, IF ANY: ADDRESS: 6200 SOUTHCENTER BL PARCEL NO: 359700-0282 SEC/TWN/RNG: LEAD AGENCY: CITY OF TUKWILA FILE NO: E97-0023 The City has determined that the proposal does not have a probable significant adverse impact on the environment. An environmental impact statement (EI'S) is not required under RCW 43.21c.030(2)(c). This decision was made after review of a completed environmental checklist and other information on file with the lead agency. This information is available to the public on request. *•***********•k•k•k•k*********k*k***4 *********k************** ***•k***********•** This determination is final and signed this 2P' day of )1/446,54- 1997. Steve Lancaster, Responsible Official City of Tukwila, (206) 431-3670 6300 Southcenter Boulevard Tukwila, WA 98188 Copies of the procedures for SEPA appeals are available with the Department of Community Development. I, AFFIDAVIT f Notice of Public Hearing ❑ Notice of Public Meeting O Board of Packet Li Board of Packet LI Planning Packet Adjustment Agenda Appeals Agenda Commission Agenda Short Subdivision Agenda Packet O Notice of Application for Shoreline Management Permit Li Shoreline Management Permit OF DISTRIBUTION hereby declare that: Determination of Non- significance D Mitigated Determination of Nonsignificance LDetermination of Significance and Scoping Notice fl Notice of Action Official Notice. Other Other was nal -led to each of the following addresses on 7-2-&-`1") Name of Projectg-t 0,1(4.S1�1/) Signature ` File Number E l'i - 07-Y2-5 AFFIDAVIT OF DISTRIBUTION I, , GlcA. :t PAbf l f'' hereby declare that: J Notice of Public Hearing fl Notice of Public Meeting Board of Packet OBoard of Packet LJ Planning Packet Adjustment Agenda Appeals Agenda Commission Agenda D Short Subdivision Agenda Packet O Notice of Application for Shoreline Management Permit 0 Shoreline Management Permit KDetermination of Non- significance 0 Mitigated Determination of Nonsignificance fl Determination of Significance and Scoping Notice fl Notice of Action Official Notice El Other Other was mailed to each of the following addresses on l ZlQ 1 . r� Name of Project \13.�it�f;�1n h 0 01�2�16 natur File NumberEQ1— Cai Aa n To: From: Date: Re: • City of Tukwila John W. Rants, Mayor Department of Community Development Steve Lancaster Director MEMORANDUM Steve Lancaster Michael Jenkins August 28, 1997 E97-0023, SEPA review of City of Tukwila Riverton Creek Stormwater Quality Management Plan Project Description: This SEPA review is for the Riverton Creek Stormwater Quality Management Plan, developed by Tukwila Department of Public Works. The study area covers approximately 434 acres, as indicated in the attached map. The plan includes the following goals: 1. Improve Riverton Creek Stream Habitat, including Water Quality 2. Minimize Riverton Creek Flooding 3. Develop a Stormwater Management Plan that is practical, easy to understand and will be implemented. From these goals, 8 activity categories were developed to implement the plan: 1. Citizen's Stream Restoration Project 2. Public Education and Involvement 3. New policies 4. New Hazardous Waste Ordinance 5. Interagency Agreements 6. Capital Improvement projects 7. Maintenance 8. Inventory and Monitoring Agencies with jurisdiction: Department of Ecology Summary of Primary Impacts: • Earth: • Air: • Water: • Plants: • Animals: • Energy/Natural Resources: • Environmental Health: • Land/Shoreline Use: N/A N/A N/A N/A N/A N/A N/A N/A 6300 Southcenter Boulevard Suite #100 • Tukwila, Washington 98188 • (206) 431-3670 • Fax (206) 431-3665 E97-0023 SEPA Checklist - City of Tukwila Public Works Riverton Creek Stormwater Quality Management Plan August 28, 1997 • Housing: N/A • Aesthetics: N/A • Light and Glare: N/A • Recreation: N/A • Historic/Cultural Preservation: N/A • Transportation: N/A • Public Services: N/A • Utilities: N/A SUPPLEMENTAL IMPACTS QUESTIONNAIRE 1. What are the objectives of the proposal • Improve Riverton Creek Stream Habitat and Water Quality • Minimize Riverton Creek flooding • Develop a stormwater management plan that can be implemented 2. What are the alternative means of accomplishing these objectives None. The only alternative to the plan is not adopting the plan or its implementation strategies. 3. Please compare the alternative means and indicate the preferred course of action. By not adopting a plan and implementation strategies, flooding, poor water quality and fish habitats would continue and be continually degraded. 4. Does the proposal conflict with policies of the Tukwila Comprehensive Land Use Policy Plan? No. The plan supports the following policies from the Tukwila Comprehensive Plan: • Goals 4.1, 4.5 • Goals 5.1 - 5.6, 5.9- 5.11 • Goals 12.1 • Goals 14.1-2 5. What are the proposed measures to avoid or reduce conflicts: No significant conflicts were noted during development of the plan. A Citizen Action Committee was developed to address and manage potential political conflicts. Recommendations: DNS • AFFIDAVIT AOuve_AQI)of tAcoAK Li Notice of Public Hearing fl Notice of Public Meeting L Board of Adjustment Agenda Packet O Board of Appeals Agenda Packet Planning Commission Agenda Packet Short Subdivision Agenda Packet O Notice of Application for Shoreline Management Permit LIShoreline Management Permit p�xe� was mai-3ed to each of the following • OF DISTRIBUTION hereby declare that: O Determination of Non- significance LI Mitigated Determination of Nonsignificance Determination of Significance and Scoping Notice ❑ Notice of Action Official Notice 11 Other Other addresses on FIZZ -II Name of Project cell File Number EC -oC-3 (Signature CITY OF TUKWILA NOTICE OF APPLICATION PROJECT INFORMATION The City of Tukwila has filed a SEPA environmental checklist for the Riverton Creek Stormwater Management Plan. The plan is a non -project action. A copy of the study area is attached. Permits applied for include: NONE Other known required permits include: • HPA Permit Studies required with the applications include: NONE FILES AVAILABLE FOR PUBLIC REVIEW The project files (E97-0023) are available at the City of Tukwila Department of Community Development (DCD), 6300 Southcenter Boulevard, Suite #100, Tukwila, WA. Project Files include: SEPA Checklist OPPORTUNITY FOR PUBLIC COMMENT Your written comments on the project are requested. They must be delivered to DCD at the address above or postmarked no later than 5:00 P.M., September 11, 1997. APPEALS You may request a copy of any decision, information on hearings, and your appeal rights by calling DCD at 431-3670. For further information on this proposal, contact Michael Jenkins at 431-3685 or visit our offices at 6300 Southcenter Boulevard, Suite #100, Monday through Friday, 8:30 a.m. to 5:00 p.m. Our telephone number is 431-3670 Application Filed: July 28, 1997 Notice of Completeness Issued: August 21, 1997 Notice of Application Issued: August 22, 1997 • City of Tukwila John W. Rants, Mayor Department of Community Development Steve Lancaster, Director NOTICE OF COMPLETE APPLICATION August 21, 1997 Phil Fraser City of Tukwila Public Works Department 6300 Southcenter Blvd., Suite 100 Tukwila, WA 98188 RE: SEPA Application for Riverton Creek Stormwater Management Plan, E97-0023 Dear Phil: Your SEPA application, on behalf of City of Tukwila, for the Riverton Creek Stormwater Managment Plan has been found to be complete on August 21, 1997 for the purposes of meeting state mandated time requirements. I have been assigned to this project. As this is a non -project action, there will be no requirements to post signs about the project. However, Notice of the SEPA application will be published in the Seattle Times with copies of this notice mailed to pertinent agencies and/or parties. This determination of complete application does not preclude the ability of the City to require that you submit additional plans or information, if in our estimation such information is necessary to ensure the project meets the substantive requirements of the City or to complete the review process. I will be contacting you soon to discuss this project. If you wish to speak to me sooner, feel free to call me at 431-3685. Sincerely, Michael Jenkins Assistant Planner cc: Reviewing City Departments c:\msoffice...sepa\9723comp.doc 6300 Southcenter Boulevard, Suite #100 • Tukwila, Washington 98188 • (206) 431-3670 • Fax (206) 4313665 City of Tukwila John W. Rants, Mayor Department of Community Development Steve Lancaster, Director MEMORANDUM TO: Michael Jenkins, Assistant Planner FROM: Gary Schulz, Urban Environmentalist DATE: August 14, 1997 RECEIVED CITY OF TUKWILA AUG 2 1 1997 PERMIT CENTER RE: Staff Review - Riverton Creek Draft Stormwater Quality Management Plan, SEPA File #E97-0023. As we discussed, the SEPA is complete as a draft stormwater quality plan has been provided including the planned components. The following comments are mostly specific text revisions that were coordinated with Phil Fraser, Public Works. The page numbers are followed by the specific comments for the Plan. Please contact me if there are questions or a need to discuss comments. 1) The first correction is an obvious one to me. Page i, spelling and title - Gary Schulz, Urban Environmentalist - Coordinator. 2) Page xiii, E. SWM is now WLRD - Water and Land Resources Dept. 3) Page xiii, Table 1 (B. $ figure seems high?) (H. $ figure seems high? Maybe this should be a range since part-time position is suggested). 4) Page 15 - Replacing open ditch drainages with piping is not usually considered a BMP. If flooding is a problem, piping usually transfers the problem downstream in the form of increased velocity, lack of groundwater recharge, and no water quality improvement. In addition, will any of the proposed piping projects affect regulated watercourses? The Flooding section does not address or mention the lack of detention or the need to replace this function in the upper watershed areas. Specifically the runoff associated with Hwy 99 development. 6300 Southcenter Boulevard Suite #100 • Tukwila, Washington 98188 • (206) 431-3670 • Fax (206) 431-3665 Riverton Stormwater Memo August 21, 1997 Page 2 5) Page 19 - City Comp Plan is not draft but was adopted in 1996. However, provisions of the Plan may not need to be revised but should be checked. All references to the Plan need to be checked such as page numbers and policy language. 6) Page 25 - Sediment and debris removal within stream channels is usually a direct conflict to providing fish cover and habitat. Also I did not find any mention of the Fish and Wildlife requirement for an HPA to work in waters of the State. 7) Page 28 - Chapter 2 of the Plan should also include Tree Regulations Ordinance - TMC 18.54. 8) Page 28 - SAO NO. 1599 section should include other identified wetlands in the basin: Sect 9 WL#5 & WL#18. & Sect. 16 WL#21. Should these wetlands be included on the watershed map? In addition to diversion or relocation, the SAO regulations for piping may also be worth mentioning in this section. Piping is generally not allowed except for access purposes. 9) Page 33 - Please check Page 25 & (6 above concerning the statements about woody debris and other cover in the stream that could reduce channel capacity. It appears to be a conflict in management of streams. 10) Page 36 Table 5 - E.1. SWM = WLRD, E.S. Why is Southgate Creek flow diversion included in this plan? 11) Page 43 - revise to indicate the Comp Plan is adopted. Restoring creeks by opening piped sections is a worthwhile effort but may only be effective as a code regulation. 12) Page 47 - Figure 15 appears to incorporate some fill into the restored corridor. The drawing is conceptual and the fill may be needed but stream corridor would have reduced capacity. 13) Page 48 - Not sure why volunteers can't be used for work within the WSDOT ROW? Doesn't Dept of Ecology use volunteers to clean up trash along highways? 14) Page 51 - Diversion of flood flow may be technically a viable way to preserve stream channels and still support a fishery. However, this engineering does not address treatment of the most polluted runoff water. Storm flows are shunted to the River where they are possibly diluted but still affect aquatic life and may contribute to pollution in the Puget Sound. • • Riverton Stormwater Memo August 21, 1997 Page 3 Site-specific watershed restoration should also include detention/retention for providing functions that have been lost over the years to intense development. 15) Page 52 - Re -design of Highway 99 does present an opportunity for new detention facilities. However, WSDOT would likely be required to only treat and handle the added impervious surface runoff. Roadside swale treatment has significant potential to restore lost functions but will require an education program. 16) Page 53 - Sedimentation Basins. Per the SAO standards, it will be more practical and economic to use existing watercourse area for sed. basins rather than altering wetland area. Wetland alteration requires DCD approval and replacement at a ratio of 1.5:1.0. 17) Page 54 - Roadside swales. This could be a very important contribution to improve water quality and provide public benefits and maintenance relief to City operations. Perhaps a tax break incentive could be used to stimulate interest.? 18) Page 55 - (Dept. of Community Dev.) The City's Urban Environmentalist performs some of the watershed management role. However, under current conditions could not be fully devoted to this new job function. 19) Appendix A.2 - Habitat Survey map. Typo correction - Balvue Stormwater... should be ValVue for ValVue Sewer/Water District. Thank you for the opportunity to review the Plan. I realize I have identified some issues. Please feel free to contact me for clarification. cc: Steve Lancaster, DCD Director Phil Fraser, PW Senior Engineer Dale Anderson, Entranco • • MEMORANDUM TO: Steve Lancaster FROM: Phil Fraser DATE: July 28, 1997 SUBJECT: Submit Environmental Checklist for Riverton Water Quality Managment Plan Included in the attached submittal for the Environmental Checklist for Riverton Water Quality Managment Plan are 17 copies of the checklist, 16 plan copies, and 10 copies of the Southgate Creek By -Pass Study. (associated report with plan) attachments file: 96-DR06.6 S P'i'. ; Jones S1 -54 Nici.FAknoivAs, Lyase (.0(-14:1 zi)NIP RECEIVED JUL 2 8 1997 COMMU f`Y DEVEL*PPJiENT •6 (—'go‘: p fft c YsP csNrG P L •l. C /-(k c, ( , CAiSDc?,77 OA- T : 5 UR T6�dfC.. 1. PCA ws .1 1 1 0 ;a TRAFF ECEIIVED 2 8 1997 JMUN,TY DEVELOPMENT Control No. Epic File No. f 17 oozes Fee: JPO Receipt No. ENVIRONMENTAL CHECKLIST A. BACKGROUND 1. Name of proposed project, if applicable: Riverton Creek Stormwater Quality Management Plan 2. Name of applicant: City of Tukwila 3. Address and phone number of applicant and contact person: 6300 Southcenter Blvd., Suite 100 Tukwila, WA 98188 433-0179; Phil Fraser 4. Date checklist prepared: 7/18/97 5. Agency requesting checklist City of Tukwila RECEIVED CITY OF TUKWILA J UL 2 0 1E07 PERMIT CENTER 6. Proposed timing or schedule (including phasing, if applicable): Water Quality, Stream Habitat, and Flood Control Planning Document for the Riverton Creek Basin to be adopted by Council September, 1997 7. Do you have any plans for future additions, expansion, or further activity related to or connected with this proposal? If yes, explain. Future CIP's, policies and BMP's (best management practices) recommended in the Plan to be implemented through the City's CIP and budgeting processes, and future updates of city planning documents. 8. List any environmental information you know about that has been prepared, or will be prepared, directly related to this proposal. This checklist. 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. Page 1 ENVIRONMENTAL CHECKLIST No. 10. List any government approvals or permits that will be needed for your proposal. Approval of the Plan by WSDOE and adoption by Tukwila City Council. 11. Give brief, complete description of your proposal, including the proposed uses and the size of the project and site. There are several questions later in this checklist that ask you to describe certain aspects of your proposal. You do not need to repeat those answers on this page. Section E requires a complete description of the objectives and alternates of your proposal and should not be summarized here. The Riverton Creek Stormwater Quality Management Plan is a comprehensive water quliaty, flood control and strteam habitat management plan for the Riverton Basin. The Riverton Basin is aproximately 434 acres in size and located in northwest Tukwila (See figures 1 and 2 in the Plan, after Page V). Riverton Creek drains the watershed via two principle tributaries, the east and west tributaries, which join at State Rout (SR) 599 near the Metro bus base. Riverton Creek then crosses SR 599 and runs adjacent to a large office park prior to discharging via twin, flap -gated culverts into the Duwamish Estuary just upstream of the Pacific Highway Bridge. This plan evaluates current conditions of stream habitat (water quality, water quantity and physical character), including pollutant loading to the Duwmaish Estuary from Riverton Creek and its causes. Also, the plan evaluates flooding conditions and causes of flooding. The Plan involves a Citizen Action Committee to develop goals and objectives of the Plan and also to assist in setting priorities. Finally, several recommendations come out of the Plan through its development and are summarized on Table 1 - see Page XIII). 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 Riverton Basin study area is 434 acres in size and is located in north portion of the City of Tukwila (See Figures 1 and 2, just after Page V in the Plan). The aproximate boundaries of the study area are S 140th Street on the South SR -599 on the East; the Duwmamish Estuary on the North; and, Military Road S on the West (west City limits). The study area is in sections 9, 10, 15, and 16, Township 23 North, Range 4 East, W.M., City of Tukwila, King County Washington. Page 2 • • ENVIRONMENTAL CHECKLIST 13. Does the proposal lie within an area designated on the City's Comprehensive Land Use Policy Plan Map as environmentally sensitive? Riverton Creek is contained within the study area. Portions of the study area include steep hillsides and also there are a few wetlands. Page 3 ENVIRONMENTAL CHECKLIST B. ENVIRONMENTAL ELEMENTS 1. Earth a. General description of the site (circle one): Flat, rolling, hilly, steep slopes, mountainous, other Upper Riverton Creek Basin is moderately steep with some deep ravines (hospital); the Central Basin has very steep and hilly slopes; and, the lower Basin is flat. b. What is the steepest slope on the site (approximate percent slope)? The maximum slope is approximately 100%. 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 soils are typical for this area and are glacially consolidated sand & silt. Also, clays, gravel and peat are encountered as well as muck in the lower Basin throughout SR -599. d. Are there surface indications or history of unstable soils in the immediate vicinity? If so, describe. Some areas of bank erosion exist during storm events which have created silting up of creek beds and high levels of turbity measured in our samples of the creek. e. Describe the purpose, type, and approximate quantities of any filling or grading proposed. Indicate source of fill. This is a programatic SEPA review. Therefore, there are no direct impacts on the physical enviornment. Implementing projects will be subjected to separate environmental reviews. f. Could erosion occur as a result of clearing, construction,or use? If so, generally describe. (See response under: "1. Earth, e" above) g. About what percent of the site will be covered with impervious surfaces after project construction (for example, asphalt or building). (See response under "1. Earth, e" above) Page 4 • • ENVIRONMENTAL CHECKLIST h. Proposed measures to reduce or control erosion, or other impacts to the earth, if any: (See response under: "1. Earth, e" above) 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. (See response under: "1. Earth, e" above) b. Are there any off-site sources of emissions or odor that may affect your proposal? If so, generally describe. (See response under: "1. Earth, e" above) c. Proposed measures to reduce or control emissions or other impacts to air, if any: (See response under: "1. Earth, e" above) 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. Riverton Creek and Duwamish Estuary (See Figure 2, after page V in Plan). Page 5 • • ENVIRONMENTAL CHECKLIST Will the project require any work over, in, or adjacent to (within 200 feet) the described waters? If yes, please describe and attach available plans. (See response under: "1. Earth, e" above) 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. (See response under: "1. Earth, e" above) 4) Will the proposal require surface water withdrawals or diversions? Give general description, purpose, and approximate quantities, if known. (See response under: "1. Earth, e" above) 5) Does the proposal lie within a 100 -year floodplain? If so, note location on the site plan. Some portions of lower Riverton Basin lie within the 100 -year floodplain. 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. Page 6 • • ENVIRONMENTAL CHECKLIST 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 materials 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. None. c. Water Runoff (including storm water): 1) Describe the source of runoff (including storm water) and method of collection and disposal, if any (include quantities, if known). Where will this water flow? Will this water flow into other waters? If so, describe. (See response under: "1. Earth, e" above) Page 7 • • ENVIRONMENTAL CHECKLIST 2) Could waste materials enter ground or surface waters? If so, generally describe. (See response under: "1. Earth, e" above) d. Proposed measures to reduce or control surface, ground, and runoff water impacts, if any: (See response under: "1. Earth, e" above) 4. Plants a. Check or circle types of vegetation found on the site: (See response under: "1. Earth, e" above) b. What kind and amount of vegetation will be removed or altered? (See response under: "1. Earth, e" above) c. List threatened or endangered species known to be on or near the site. (See response under: "1. Earth, e" above) Page 8 • • ENVIRONMENTAL CHECKLIST d. Proposed landscaping, use of native plants, or other measures to preserve or enhance vegetation on the site, if any: (See response under: "1. Earth, e" above) 5. Animals a. Circle any birds or animals which have been observed on or near the site or are known to be on or near the site: Birds:. (See response under: "1. Earth, e" above) Mammals: Fish: Other: b. List any threatened or endangered species known to be on or near the site. (See response under: "1. Earth, e" above) c. Is the site part of a migration route? If so, explain. (See response under: "1. Earth, e" above) d. Proposed measures to preserve or enhance wildlife, if any: (See response under: "1. Earth, e" above) Page 9 • • ENVIRONMENTAL CHECKLIST 6. Energy and Natural Resources a. What kinds of energy (electric, natural gas, oil, wood stove, solar) will be used to meet the completed project's energy needs? Describe whether it will be used for heating, manufacturing, etc. (See response under: "1. Earth, e" above) b. Would your project affect the potential use of solar energy by adjacent properties? If so, generally describe. (See response under: "1. Earth, e" above) c. What kinds of energy conservation features are included in the plans of this proposal? List other proposed measures to reduce or control energy impacts, if any: (See response under: "1. Earth, e" above) 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. (See response under: "1. Earth, e" above) 1) Describe special emergency services that might be required. (See response under: "1. Earth, e" above) 2) Proposed measures to reduce or control environmental health hazards, if any: Not applicable. Page 10 • • ENVIRONMENTAL CHECKLIST b. Noise 1) What types of noise exist in the area which may affect your project (for example: traffic, equipment, operation, other)? (See response under: "1. Earth, e" above) 2) What types and levels of noise would be created by or associated with the project on a short-term or long-term basis (for example: traffic, construction, operation, other)? Indicate what hours noise would come from the site. (See response under: "1. Earth, e" above) 3) Proposed measures to reduce or control noise impacts, if any: (See response under: "1. Earth, e" above) 8. Land and Shoreline Use a. What is the current use of the site and adjacent properties? (See response under: "1. Earth, e" above) b. Has the site been used for agriculture? If so, describe. (See response under: "1. Earth, e" above) c. Describe any structures on the site. (See response under: "1. Earth, e" above) Page 11 • • ENVIRONMENTAL CHECKLIST d. Will any structures be demolished? If so, what? (See response under: "1. Earth, e" above) e. What is the current zoning classification of the site? (See response under: "1. Earth, e" above) f What is the current comprehensive plan designation of the site? (See response under: "1. Earth, e" above) g. If applicable, what is the current shoreline master program designation of the site? (See response under: "1. Earth, e" above) h. Has any part of the site been classified as an "environmentally sensitive" area? If so, specify. (See response under: "1. Earth, e" above) i. Approximately how many people would reside or work in the completed project? (See response under: "1. Earth, e" above) 1• Approximately how many people would the completed project displace? (See response under: "1. Earth, e" above) k. Proposed measures to avoid or reduce displacement impacts, if any: (See response under: "1. Earth, e" above) 1. Proposed measures to ensure the proposal is compatible with existing and projected land uses and plans, if any: (See response under: "1. Earth, e" above) Page 12 ENVIRONMENTAL CHECKLIST 9. Housing a. Approximately how many units would be provided, if any? Indicate whether high, middle, or low-income housing? (See response under: "1. Earth, e" above) b. Approximately how many units, if any, would be eliminated? Indicate whether high, middle, or low-income housing. (See response under: "1. Earth, e" above) c. Proposed measures to reduce or control housing impacts, if any: (See response under: "1. Earth, e" above) 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? (See response under: "1. Earth, e" above) b. What views in the immediate vicinity would be altered or obstructed? (See response under: "1. Earth, e" above) c. Proposed measures to reduce or control aesthetic impacts, if any: (See response under: "1. Earth, e" above) Page 13 • • ENVIRONMENTAL CHECKLIST 11. Light and Glare a. What type of light or glare will the proposal produce? What time of day would it mainly occur? (See response under: "1. Earth, e" above) b. Could light or glare from the finished project be a safety hazard or interfere with views? (See response under: "1. Earth, e" above) c. What existing off-site sources of light or glare may affect your proposal? (See response under: "1. Earth, e" above) d. Proposed measures to reduce or control light and glare impacts, if any: (See response under: "1. Earth, e" above) 12. Recreation a. What designed and informal recreational opportunities are in the immediate vicinity? (See response under: "1. Earth, e" above) b. Would the proposed project displace any existing recreational uses? If so, describe. (See response under: "1. Earth, e" above) c. Proposed measures to reduce or control impacts on recreation, including recreation opportunities to be provided by the project or applicant, if any: (See response under: "1. Earth, e" above) Page 14 • • ENVIRONMENTAL CHECKLIST 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. (See response under: "1. Earth, e" above) b. Generally describe any landmarks or evidence of historic, archaeological, scientific, or cultural importance known to be on or next to the site. (See response under: "1. Earth, e" above) c. Proposed measures to reduce or control impacts, if any: (See response under: "1. Earth, e" above) 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. (See response under: "1. Earth, e" above) b. Is the site currently served by public transit? If not, what is the approximate distance to the nearest transit stop? (See response under: "1. Earth, e" above) c. How many parking spaces would the completed project have? How many would the project eliminate? (See response under: "1. Earth, e" above) Page 15 • • ENVIRONMENTAL CHECKLIST 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). (See response under: "1. Earth, e" above) e. Will the project use (or occur in the immediate vicinity of) water, rail, or air transportation? If so, generally describe. (See response under: "1. Earth, e" above) f How many vehicular trips per day would be generated by the completed project? If known, indicate when peak volumes would occur. (See response under: "1. Earth, e" above) g Proposed measures to reduce or control transportation impacts, if any: (See response under: "1. Earth, e" above) 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. (See response under: "1. Earth, e" above) b. Proposed measures to reduce or control direct impacts on public services, if any. (See response under: "1. Earth, e" above) Page 16 ENVIRONMENTAL CHECKLIST 16. Utilities a. Circle utilities currently available at the site: electricity, natural gas, water, refuse service, telephone, sanitary sewer, septic system, other. (See response under: "1. Earth, e" above) 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. (See response under: "1. Earth, e" above) C. 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. Signature: Date Submitted: 11 as 1 9 Page 17 ENVIRONMENTAL CHECKLO • D. 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 foregoing 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 objectives of the proposal? * Improve Riverton Creek Stream Habitat, including Water Quality * Minimize Riverton Creek Flooding * Develop a Stormwater Management Plan that is practical, easy to understand, and will be implemented 2. What are the alternative means of accomplishing these objectives? * Public Education and involvement * Capital Improvement Projects * Incoporate 6 new policies for protection of stream habitat, existing roadside swales, etc. through future update of planning documents. * Development of new Hazardous Waste Ordinance * Upgrade level of maintenance and implement annual inspection and claning of all storm drainage facilities - public and private. * Establishment of Watershed/Stream Steward fundtion in PW or DCD. * No action. Do nothing. 3. Please compare the alternative means and indicate the preferred course of action: * No action. Existing flooding, poor water quality and poor fish habitat would continue in a degraded state. * Under capital improvements: Alternative diversion of storm. The least cost diversion does not provide as much flood control benefit as the more costly alternative. It is anticipated that increased peak flows to Southgate Creek will be provided in such a manner as to not have any significant adverse impacts to Southgate Creek. This issue will continue to be refined and addressed through the final design and enviornmental review process for the proposed diversion piping from Pacific Highway to the Page 18 ENVIRONMENTAL CHECKLO • existing box culvert/72" diameter pipe in Interurban Ave S/S. 133rd Street.. The preliminary analysis of this issue was conducted through the May, 1997 Southgate Creek By -Pass Study by Perteet Engineering, Inc. (copy attached). Another alternative (Alt #4) to shunt high -flows for Pacific Highway North to the Duwamish River was also considered. * The City is planning on implementating a variety of structural and non-structural projects and/or programs to enhance the Creek. Its understood the structural programs have a greater certainty of benefit, but it is still important to do the non-structural programs which will effect daily operations of the stormwater system and can potentially change the public's operations & behaviors within the watershed to reduce or eliminate pollutants entering into Riverton Creek. 4. Does the proposal conflict with policies of the Tukwila Comprehensive Land Use Policy Plai ? No. In review of the the City's Comprehensive Plan the proposed actions were found to be consistent with the goals and policies of the City's Comprehensive Plan. 5. Proposed measures to avoid or reduce the conflict(s) are: No significant conflicts of any nature are recognized by the implementation of this Plan. The Citizen's Action Committee has given input to avoid potential conflicts. PF:prf:rivsepa.doc \phil\rivsepa.doc Page 19 • WASnIFIGTON STATE, OEPARTYENT OF ECOLOGY CO Riverton Creek Basin City of Tukwila, Washington E N T R A N C O Draft for City Review Water Quality, Stream Habitat, and Flood Control Riverton Creek Stormwater Quality Management Plan E9l- 0023 May 1997 DRAFT RIVERTON STORMWATER QUALITY MANAGEMENT PLAN WATER QUALITY, STREAM HABITAT, AND FLOOD CONTROL Prepared for City of Tukwila Prepared by ENTRANCO 10900 NE 8th Street, Suite 300 Bellevue, Washington 98004 (206) 454-5600 and TAYLOR ASSOCIATES and ENVIROVISION May 1997 DRAFT ACKNOWLEDGMENTS The following organizations and individuals participated in the development of the Riverton Creek Stormwater Quality Management Plan. Their participation is gratefully acknowledged by the City of Tukwila. Citizens Advisory Committee John Beal, I'm A Pal Foundation Bill Hitchman, Foster High School Sharon Barnhardt, Watershed Resident Denis Bourcier, Boeing Elemer Halasz, Watershed Resident Sue Kaufman, King County Surface Water Management Washington State Department of Ecology Kim McKee, Grant Officer City of Tukwila Entranco Ross Earnst, Public Works Director Ron Cameron, City Engineer Phil Fraser, Senior Engineer - Project Manager Gary Schultz, Land Use Planner Scott Moore, Construction Inspector John Howat, Crew Chief, Storm and Surface Water Ryan Partee, Fisheries Biologist - Stream Enhancement Dale Anderson, Project Manager Ralph Nelson, P.E., HSPF Modeling Analysis Mark Young, MLA, ASLA, Stream Habitat Restoration Joanne Wright, Stream Habitat Restoration David Morency, Water Quality Analysis Jory Oppenheimer, Monitoring Plan Tien Pham, Basin Mapping and HSPF Analysis Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basinpin (5/15/97) ss DRAFT Taylor Associates Envirovision Funding of Plan Joyce Carter, Word Processing Katherine Probert, Editing Anne Turner, Graphics Bill Taylor, Field Sampling and Automated Sampling Equipment Wendall Wiley, Stream Habitat Survey and Field Sampling Joy Michaud, Public Involvement Ecology Centennial Clean Water Fund Grant and the City of Tukwila ii Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basnpin (5/15/97) ss DRAFT TABLE OF CONTENTS Page ACKNOWLEDGMENTS EXECUTIVE SUMMARY INTRODUCTION v BASIN DESCRIPTION v PROBLEM SUMMARY v Stream Habitat Degradation ix Degraded Water Quality ix Flooding x GOALS AND OBJECTIVES xi RECOMMENDATIONS xii IMPLEMENTATION STEPS xiv ECOLOGY GRANT COMPLIANCE SUMMARY xv Chapter 1 EXISTING CONDITIONS INTRODUCTION 1 CITIZEN ACTION COMMITTEE - PERCEPTIONS OF PROBLEMS 2 CREEK WATER QUALITY/POLLUTANT LOADING TO DUWAMISH ESTUARY 4 STREAM HABITAT 12 FLOODING 14 Chapter 2 EXISTING PLANS, POLICIES, REGULATIONS AND PROGRAMS RELATED TO STORMWATER MANAGEMENT NATIONAL POLLUTANT DISCHARGE ELIMINATION SYSTEM (NPDES) 17 PUGET SOUND WATER QUALITY MANAGEMENT PLAN 18 STATE OF WASHINGTON GROWTH MANAGEMENT ACT 19 THE CITY COUNCIL RECOMMENDED DRAFT COMPREHENSIVE PLAN 19 SURFACE WATER MANAGEMENT COMPREHENSIVE PLAN 21 SURFACE AND STORMWATER MANAGEMENT ORDINANCE - NO. 1755 27 LAND -ALTERING ORDINANCE - NO. 1591 28 SENSITIVE AREAS ORDINANCE - NO. 1599 28 FLOODPLAIN MANAGEMENT ORDINANCE - NO. 1499 29 STORM AND SURFACE WATER UTILITY 29 SOLID AND HAZARDOUS WASTE PROGRAMS 30 FIRE PREVENTION INSPECTION PROGRAM 30 Chapter 3 STORMWATER QUALITY MANAGEMENT BASIN/STREAM RESTORATION CONCEPT 33 PLAN OVERVIEW 34 Citizen's Implementation Project—The Boeing Reach Project 38 Public Education and Involvement 41 Proposed Policies 43 Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basrpin (5/15/97) ss DRAFT Regulations and Enforcement 44 Interagency Agreements 45 Capital Improvement Projects (Structural Controls) 45 Tributary Sedimentation Basins 53 Maintenance 54 Inventory and Monitoring 55 REFERENCES PUBLISHED DOCUMENTS 57 PERSONAL COMMUNICATION 58 APPENDICES A - Riverton Creek Water and Sediment Quality B - Riverton Creek Stream Special Study C - Description of Drainage Improvement Projects from the 1993 Surface Water Management Comprehensive Plan D - Riverton Creek Habitat Enhancements - Boeing Section E - Hydrologic Analysis FIGURES Page 1. Project Vicinity vi 2. Riverton Creek Watershed vii 3. An example of a well-designed, well-maintained grass -lined swale in the upper watershed. 7 4. An example of a roadside ditch with excessively steep side slopes and soil slumping into the ditch. 7 5. Another example of good roadside conditions that protect against erosion. 8 6. Dirt from this temporary construction stockpile is located in the roadside ditch and could contribute to erosion during rainfall runoff conditions. 8 7. Streetside parking in this roadside ditch leads to Toss of grass cover and increased erosion potential. 9 8. Utility line construction adjacent to this roadside ditch also increases erosion potential. 9 9. Recent construction leaves exposed soils on relatively steep slopes 10 10. Another construction site showing exposed soils 10 11. Another post -construction situation with exposed soils on steep slopes just above a storm drain. 11 12. Another post -construction site showing exposed soils and erosion in the vicinity of a storm drain inlet 11 13. Location of Drainage Improvement Projects 23 14. Proposed Improvements 39 15. Illustration of Improved Riparian Habitat 47 16. Subbasins Used for Flow Diversion Analysis 49 Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basinpin (5/15/97) ss DRAFT . TABLES Page 1. Summary of Riverton Creek Stormwater Quality Management Plan Recommendations xiii 2. Ecology Grant Milestone Progress Report xvi 3. Estimated Annual Pollutant Loading at the Mouth of Riverton Creek (1996) 5 4. Summary of Drainage Improvement Projects from the Surface Water Management Comprehensive Plan 1993 22 5. Summary of Riverton Stormwater Quality Management Plan Recommendations 34 6. Comparison of Existing, Pre -development (Forested), and Diversion Flow Scenarios (25 -year storm) for Selected Downstream Modeling Points in the Riverton Creek Basin 51 Riverton Stormwater Quality Management Plan - 1997 9'04-5 / reports / basrpin (5/15/97) ss iii Riverton Creek drains the watershed via two principal tributaries, the east and west tributaries, which join at State Route (SR) 599 near the Metro bus base. Riverton Creek then crosses SR 599 and runs adjacent to a Targe office park prior to discharging via twin, flap -gated culverts into the Duwamish Estuary just upstream of the Duwamish Estuary Bridge. Three ' major problem areas—degraded stream habitat, degraded water quality, and flooding—are summarized below. Riverton Stormwater Quality Management Plan - 1997 v 95035 / reports / bastripin (5/15/97) ss A948 95035-60 Riverton Creek (2/20/97) AGT N not to scale /West Seattle Freeway Project Site Kent. Des Moines Rd. © E N T R A N C O Figure 1 Project Vicinity 0 m Z 4 75 a z n 0 ata F}1a,1,t�1.lam`FY7Ti�.1 LZ1I c c al N A979 95035-60 Riverton Creek (2/20/97) AGT DRAFT EXECUTIVE SUMMARY Stream Habitat Degradation In conjunction with past site development and roadway construction activities, portions of Riverton Creek have been routed to underground culverts, relocated, channelized into long straight reaches, devegetated, and steepened. These actions have reduced stream habitat value and have hindered or impaired fish passage to upstream reaches. For example, there is a 2,250 -foot portion of the east tributary of the creek that passes through an underground culvert between South 126th Street and State Route (SR) 599. This may prohibit some salmon from attempting to reach the good habitat areas upstream of this location. Another fish passage barrier is located on the west tributary near 33rd Avenue South and South 125th Street where a 20 -foot -high waterfall (which resembles a staircase) has been constructed to carry the stream over a steep embankment. Another impact of urbanization on Riverton Creek is increased runoff in the basin. Hydrologic modeling indicates that existing peak flows are as much as 10 times greater than what occurred under undeveloped, forested conditions. These dramatic increases in peak flows mean increased erosional forces within the stream channel. Increased erosion in the upper stream reaches leads to increased sedimentation in the lower stream reaches, and subsequent reductions in stream habitat value for fish rearing and spawning. Another impact of increased stream flows is that higher stream velocities can physically overcome fish resulting in injury and removal from their rearing habitat. This kind of dislocation and injury can make the fish more vulnerable to predation and disease. Finally, flap gates at the two existing 48 -inch culvert pipes, which deliver Riverton Creek to the Duwamish Estuary, are closed for significant periods of time and also may represent a partial fish passage barrier to upstream migration. Stream channelization has reduced the number of natural pool areas for rearing, resting, and cover. Devegetation has resulted in lost fish food (insect) production, reduced shading (affecting temperature), and reduced cover for predator avoidance. In addition, sediment accumulation has covered over spawning habitat, and stream channelization/clearing has resulted in Toss of large rocks and Togs that contribute to overall habitat diversity and value. Degraded Water Quality Local residents have reported periodic water quality problems (turbid or discolored water) to the Department of Public Works. Because of the short duration of many water quality impacts, it has not been possible to Riverton Stormwater Quality Management Plan - 1997 95035 / reports / badnpin (5/15/97) ss ix EXECUTIVE SUMMARY Flooding DRAFT pinpoint the cause of such pollution, but the problems reported may be due to illegal dumping, past sewer line breaks, or short-term erosion/sedimentation impacts associated with construction in the watershed. Water quality monitoring conducted as part of this study, which was primarily performed during peak flow events (i.e. during rainstorms), showed high levels of fecal coliform bacteria, high levels of turbidity and total suspended solids, and periodic violations of water quality standards for toxic metals (copper, lead, mercury, and cadmium). These problems are attributed primarily to the relatively large amounts of polluted stormwater runoff (from streets, parking lots, etc.) discharged to the creek. Some of these pollutants drop out into the bottom sediments in the Lower Reach of Riverton Creek, but some are washed out into the Duwamish Estuary at the mouth of the creek. As a part of this study, estimates of annual pollutant loading (in kilograms per year) to the Duwamish River have been made. These pollutant loading estimates are provided in Chapter 1 and may be used in the future by resource managers to establish allowable pollutant loading limits for Riverton Creek. However, pollutant loading levels are expected to decline over time with implementation of pollution control measures recommended in this plan. A significant source of sediment load to the stream may be associated with the practice of street sanding used by Washington State Department of Transportation (WSDOT) on SR 99 and SR 599 and by the City of Tukwila on other local streets. In addition, there are diffuse (nonpoint) sources of erosion/sedimentation in the upper watershed due to poorly constructed roadside ditches. Periodic water quality degradation also may be due to: 1. Erosion/sedimentation during construction, 2. Accidental spills, 3. Illegal dumping, 4. Failing septic tank/drainfield systems, and/or 5. Leaking sanitary sewers. Despite the water quality problems that occur periodically during storm runoff events, low flow sampling (Appendix A) indicates that temperature and oxygen conditions are suitable for rearing juvenile salmon during summer months. There are several locations in the stream system that have experienced repeated flooding problems. One location is just west of East Marginal Way South at South 126th Street; another location is in the vicinity of Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basnpin (5/15/97) ss DRAFT EXECUTIVE SUMMARY South 130th Street between 35th and 37th Avenues South. These sites are both on the east tributary of the creek. Possible causes of flooding are undersized culverts, and/or culvert blockages due to sediment accumulation and/or debris accumulation. There is concern that sediment accumulation has dramatically reduced flood flow capacities of various culvert sections in the lower elevations of the basin (north of South 126th Street). For example, culverts discharging into and across SR 599 are more than half filled with sediment. This could contribute to existing flooding at South 126th Street, causing water to back up in the culvert system. It also might result in future flooding at additional sites if flood flow capacities are not restored. High flow conditions in December 1996 nearly resulted in building flooding at the Boeing complex near South 124th Street. Reduced stream channel capacity due to sediment accumulation also is considered a problem at this site. Potential future flooding problems due to continued sediment accumulation in culvert pipes and stream channels is considered the greatest flood issue in the basin. GOALS AND OBJECTIVES This next section defines the goals and objectives established by the Citizen Action Committee. Goal 1. Improve Riverton Creek Stream Habitat, including Water Quality Achieving these objectives will fulfill this goal: • Evaluate the current condition of stream habitat (water quality, water quantity, and physical character). • Evaluate the current and future pollutant loading to the Duwamish Estuary from Riverton Creek. • Determine causes of stream habitat degradation and pollutant loading. • Identify management options to: Improve water quality and physical character to support stream habitat needs and reduce pollutant loading. Manage water quantity to support stream habitat needs. Identify opportunities for volunteer participation in management efforts. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basirpin (5/15/97) ss xi EXECUTIVE SUMMARY DRAFT Goal 2. Minimize Riverton Creek Flooding Achieving these objectives will fulfill this goal: • Evaluate current flooding conditions associated with Riverton Creek. • Determine causes of flooding. • Identify management options for water quantity to minimize flooding. Goal 3. Develop A Stormwater Management Plan that is Practical, Easy to Understand, and will be Implemented Achieving these objectives will fulfill this goal: • Involve the Citizen Action Committee to establish citizen ownership of the management plan. • Focus on solutions that are acceptable to the citizens and City of Tukwila. • Focus on defining clear steps for plan implementation. • Pursue opportunities for public access trails and aesthetics when developing solutions on public property. RECOMMENDATIONS Recommendations for the Riverton Creek Stormwater Quality Management Plan are presented in table 1. There are eight categories of proposed activities. The only optional elements are contained in Category F - Capital Improvement Projects. For a more detailed discussion of the recommendations, the reader is referred to Chapter 3. xii Riverton Stormwater Quality Management Plan - 1997 95035 / reports / barn (5/15/97) ss DRAFT EXECUTIVE SUMMARY Table 1 Summary of Riverton Creek Stormwater Quality Management Plan Recommendations Management Plan Category Planning Level Cost Estimate A. Citizens Stream Restoration Implementation Project - The Boeing Reach Project - This is a stream habitat improvement project on 1,900 feet of the west tributary of Riverton Creek, adjacent to Boeing facilities. The project will include a barrel -type salmon egg incubator. Cost will be covered by the Boeing Company, City of Tukwila labor and equipment contributions, and citizen volunteer labor. B. Public Education and Involvement - This will involve best management practices (BMP) handbooks, storm drain stenciling, watershed signs, an annual stream clean up, newsletter stories, an Adopt -A -Stream program with school involvement, a citizen water watch, and a citizen brochure. C. Proposed Policies - Six new policies are proposed in support of (1) protecting and restoring stream habitat, (2) maintaining natural stream meander, (3) protecting existing roadside ditches and swales, (4) extending sewer service, (5) providing on-site waste water management in areas without sewers, and (6) minimizing sewer overflows. D. Regulations & Enforcement - A new Hazardous Waste Ordinance is proposed. E. Interagency Agreements - Interagency agreements would be developed with King. County SWM, King County Metro and WSDOT regarding coordinated stormwater management, and with the Rainier and Val Vue Sewer Districts regarding wastewater issues. F. Capital Improvement Projects (CIPs) - There is a list of 9 potential CIP projects including (1) tide gate removal or replacement, (2) selective sediment removal, (3) lower Riverton Creek habitat restoration, (4) culvert replacements and/or additions, (5) flow diversions, (6) roadside swale retrofit, (7) sedimentation basins, and (8) retrofit of SR 99 catch basins with spill control (SC) type oil/water separators and provide stormwater detention and treatment. There are two combinations of CIPs that may be approved by the City—Alternative A or B—see adjacent column. The basic difference between Alternatives A and B is whether to implement items 4 and 7 or item 5 (bolded in Alternatives). Additional design and cost data are needed from Perteet Engineering before a final recommendation can be made. $85,700 No new cost anticipated. It is assumed that these policies would be incorporated in city planning documents with the next update. $7,200 for preparation of the ordinance and presentation to the City Council. $12,000 cost for City staff to coordinate with other agencies, finalize agreements, and present them to the City Council for review and approval. Alternative A 1. Tide gate removal or tide gate replacement 2. Sediment removal 3. Lower creek restoration 4. Culvert replacements/additions 6. Roadside swale retrofit 7. Sedimentation basins (2) 8. Retrofit SR 99 w/SC oil/water separators and detention/ treatment for highway runoff only WSDOT Cost Range $750 $74,700 $20,000 $280,000 $638,000 $233,000 $606,000 $1,777,750 to $1,851,700 Alternative B 1. Tide gate removal, or tide gate replacement 2. Sediment removal 3. Lower creek restoration $750 $74,700 $20,000 $280,000 5. Flow diversion to Southgate Cr. $667,000 or flow diversion to SR 99 $1,500,000 6. Roadside swale retrofit $233,000 8. Retrofit SR 99 w/SC oil/water separators and detention/ treatment for highway runoff only WSDOT Cost Range $1,200,750 to $2,107,700 Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basfnpin (5/15/97) ss EXECUTIVE SUMMARY DRAFT Table 1 (Continued) Management Plan Category Planning Level Cost Estimate G. Maintenance - Annual inspection and cleaning of all storm drainage facilities—public and private—are recommended. This will require additional vactor truck use in the basin and additional work time for maintenance staff. H. Inventory and Monitoring - It is recommended that the City establish a new Watershed/Stream Steward function either in the Public Works Department or in the Department of Planning and Community Development. The Watershed/Stream Steward would oversee implementation of the Stormwater Quality Management Plan and help protect stream and watershed resources during the planning, design, and construction phases of new projects. This category also would include funds to perform additional water quality monitoring, inventory & mapping work in the basin, and to survey illegal storm drain connections. No additional equipment cost is anticipated because the City is in the process of acquiring a new vactor truck, which will be used part- time in the basin. The City Public Works Department will determine if re -prioritization of existing maintenance staff time or a new hire (part-time or full-time) will be needed to provide the increased level of maintenance activity in the basin. $2 82,000 The new Watershed/Stream Steward function could be filled by: (1) redefining the job duties of an existing staff person in the City, (2) by identifying an enthusiastic citizen volunteer, or (3) by hiring a new part-time or full-time person at the City. It is assumed that a full-time person would have City-wide responsibilities and would not just focus on Riverton Creek. Total Cost Range for the Stormwater Quality Management Plan $1,587,650 to $2,494,600 IMPLEMENTATION STEPS Plan implementation would involve the following steps. The dates indicate the month and year in which the steps are expected to be completed. 1. Review and comment on the Draft Plan 2. Preparation of the Final Plan 3. Presentation to the City of Tukwila Utilities Commission 4. Presentation to the City of Tukwila City Council 5. Adoption by the City Council 6. Prioritization of CIPs by Utilities Commission 7. Preparation of grant applications 8. Grant agreements 9. Final decisions on Plan Categories 10. Design reports (CIPs only) May 1997 June 1997 July 1997 August 1997 September 1997 October 1997 January 1998 October 1998 November 1998 April 1999 xiv Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basinpin (5/15/97) ss DRAFT EXECUTIVE SUMMARY 11. Environmental review and permitting (CIPs only) April 1999 12. Final design March 2000 13. Construction Summer 2000 Note: Performance monitoring and community education efforts would probably extend at least three years after construction is completed, depending on the availability of funding resources and citizen interest. ECOLOGY GRANT COMPLIANCE SUMMARY Several grant conditions/milestones were established between the City and Ecology as part of the grant agreement. Table 2 summarizes the status of meeting these grant conditions at the point of publishing the Draft plan. As one can see, City staff and Ecology approval of the Draft plan will trigger actions to fullfill the remainder of these grant conditions. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / barn (5/15/97) ss xv EXECUTIVE SUMMARY DRAFT Task No. Table 2 Ecology Grant Milestone Progress Report Task Description Ecology Grant Milestone Milestone Status Task 4.1 Steering Committee Participation a. Establish Steering Committee a. Achieved b. Steering Committee (SC) b. Pending Endorse Management Plan Task 4.2 Data Collection, Analysis, Modeling a. Collect flow data/model a. Achieved stream flows b. Monitoring Plan & Sampling & Map b. Achieved Task 4.3 Options for Addressing Water Quality Problems a. SC Prioritized Solutions a. Achieved b. Establish Goals/Objectives b. Achieved Task 4.4 Adoption of Water Quality Plan and Regulations a. Ecology Approves Plan a. Pending Task 4.5 Advisory Committee Participation a. City Establish Citizen Advisory Committee (AC) b. AC Establish Plan Implementation Strategy a. Pending b. Pending Task 4.6 Public Education/Awareness a. Produce Brochure/Flyers a. In Progress b. Hold Two Public Meetings b. Pending Task 4.7 Implementation of Community Project a. Select WQ Improvement Project b. Notices for Project Participation c. Project Outcome Evaluated a. Achieved b. Pending c. Pending Task 4.8 Interagency Coordination/ Commitment a. Agency Briefing on Results b. Draft Agreements c. Final Agreements a. Pending b. Pending c. Pending Task 5.1 Project Administration & Management "In Progress" "In Progress" Notes: City of Tukwila Contract Number: 95-106 - Ecology Grant Agreement: G9500201 City of Tukwila Project Number: 94-DRO6 XVI Riverton Stormwater Quality Management Plan - 1997 95035 / reports / baslnpin (5/15/97) ss DRAFT Chapter 1 EXISTING CONDITIONS INTRODUCTION The Riverton Basin is approximately 434 acres in size and is located in northwest Tukwila (figures 1 and 2). The relatively steep -sided slopes of the southern and western portions of the basin are occupied primarily by residential and commercial development, while the northern portion of the basin, which lies on the valley floor of the Duwamish Estuary, is occupied primarily by Tight industrial development. The cumulative impact of urban development has resulted in major impacts to Riverton Creek. The Creek has been channelized, relocated, straightened, devegetated, and piped throughout much of its length. It also has been impacted by increased flood flows, erosion/sedimentation, fecal coliform bacteria, and periodic violations of state water quality standards for metals. These cumulative impacts have dramatically reduced the capacity of Riverton Creek to support fish life. One of the City's major goals with this project is to implement cost-effective measures to restore Riverton Creek stream habitat and water quality and to enhance fish production. Another major goal is to correct existing flooding problems and prevent future ones. The City of Tukwila initiated the Riverton Stormwater Quality Management Plan in July of 1995 under a grant from the Washington State Department of Ecology (Ecology). Water quality sampling, stream flow measurements, and stream habitat surveys have been completed as part of this plan. The remainder of this chapter is devoted to summarizing existing stream habitat, water quality, and flooding problems in the basin. The first emphasis is to focus on problems identified by the Citizen Action Committee, followed by a discussion of existing problem conditions derived from: 1. Interviews with City staff, 2. Field observations, and 3. Results of water quality and flow monitoring conducted February through April 1996 and base flow measurements taken in June 1996. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basirptn (5/15/97) ss 1 CHAPTER 1 DRAFT CITIZEN ACTION COMMITTEE - PERCEPTIONS OF PROBLEMS Prior to this project, Tukwila citizens appointed to the Citizen's Advisory Committee, many who live and/or work within the Riverton Creek basin, reported the problems listed here. We were, however, not able to confirm all of these problems during our field monitoring and stream/watershed inventory work. • Sizable amounts of sediment have accumulated in one citizen's former trout pond. The pond is located on the west tributary, downstream of State Route (SR) 99 and receives runoff from a Targe residentially developed subbasin as well as SR 99 and associated commercial land uses. • The west tributary sometimes has a rusty brown color and may be due to runoff from Pacific Highway (SR 99) or adjacent land uses. • The west tributary is intermittently turbid or milky colored, and on some occasions may have foam and odors. The cause(s) of these problems has not been determined. • A sewer break occurred in the Rainier Vista area. This break has since been repaired and would not be a cause of water quality problems today. • There are relatively few salmon in the stream "today" as compared to the past. This may be due to construction of commercial buildings in the lower basin. • Floodgates stop upstream fish passage under almost all tide conditions. • The staircase ladder on the Boeing property is a physical barrier to fish passage in the west tributary. • Metro's oil/water separators are too small and are easily overloaded. • Stormwater from a tire shop,.copying business, and a local cafe have visible oil sheens and they don't have catch basins or oil/water separators. • The hospital site located off SR 99 has severe hillside erosion and sometimes has thick brown, chocolate colored runoff. There is a contamination problem which has been reported to Ecology and King County Surface Water Management (SWM). Riverton Stormwater Quality Management Plan - 1997 95nt5 / reports / basinpin (5/15/97) ss DRAFT CHAPTER 1 • A lot of petroleum -contaminated fill has been located near the creek—some near or on the SR 99 right-of-way and some at the hospital site. ■ There are existing flooding problems behind the S&L Cafe. • Stormwater runoff from the Boeing site is a problem. • In general, fish passage and upstream access to stream habitat is poor. In many cases, this is due to the stream being enclosed in culvert pipes. ■ Boeing is unable to control runoff from upstream portions of the watershed that drain to their property. • There may be problems with failing septic tank/drainfield systems. This could adversely affect stream water quality. • There are saturated soils and wetlands in the upper basin that cause increased surface water runoff and poor performance of septic tank/drainfield systems. • There is flooding at streamside residences near the S&L Cafe. • There is silt build-up in the stream channel near the S&L Cafe from upstream sources. • There is sediment build-up throughout the stream. • There is a need for improved communication regarding problems and solutions. • The stream lacks "bugs" (aquatic insects - fish food organisms) because of contamination. This is usually due to Toss of streamside vegetation and sediment accumulation. • Alder trees are dying due to oil contamination - you can tell when you cut into them. ■ Flood control is a big problem due to too much impervious surface area and lack of stormwater detention in the basin. This creates highly variable stream flows. This is compounded by steep slopes in portions of the watershed and wetland soils. • There are a variety of business types and industries within the watershed; these are potential contributors to stormwater pollution and impervious area. • Water temperature problems in the creek also contribute to water temperature problems in the Green/Duwamish Estuary. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basrpin (5/15/97) ss 3 CHAPTER 1 DRAFT • Lawn and garden debris is improperly disposed of over the bank at the Riverton Hospital. Improper disposal also may be a problem for residential property owners. • The cemetery in the upper watershed apparently uses a lot of pesticides. • Flooding problems at South 138th Street. • There is basement and crawl space flooding in the Cascade View area of the upper watershed. CREEK WATER QUALITY/POLLUTANT LOADING TO DUWAMISH ESTUARY This section presents a summary of water quality findings from the monitoring program conducted for this project. A more detailed discussion is included in Appendix A. • There are high fecal coliform bacteria levels throughout the stream system. State water quality standards were violated during each of the three storm sampling events. High bacteria levels are likely due to high stormwater pollutant loading from streets, parking Tots, etc. It may also be due to failing septic tank/drainfield systems, animal waste (pets, etc.), and/or exfiltration from leaking sanitary sewers. • Fecal coliform bacteria are indicators of the possible presence of water -borne disease organisms. However, the public health risk here is considered small since the stream is not used for domestic water supply or recreation. Fecal coliform contamination is not considered a direct threat to fish life, but may be an -indicator of other potential water quality problems for fish. • High levels of total phosphorus, turbidity, and total suspended solids were measured at Stations 1 and 4 on the east tributary. Field surveys in the upstream drainage area points to poor roadside ditch construction/maintenance and poor erosion control during construction as potentially significant sources of this kind of pollution. The practice of street sanding for roadway traction during snow and ice conditions is another potential source of suspended solids. • Acute and chronic standards were exceeded for copper in runoff from SR 99 and SR 599. High concentrations of copper in runoff from SR 99 contribute to the observed exceedance of the chronic standard at Station 1. This station is upstream of any existing stream habitat and therefore the high copper concentrations would not be expected to impact fish, because highway runoff is apparently Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basfnpin (5/15/97) ss DRAFT CHAPTER 1 diluted in the stream (there are no standard violations at stations downstream of Station 1 except for Station 4). Given the significant distance between SR 99 and Station 4, local street runoff is suspected as the source of high copper concentrations here. Concentrations of cadmium in SR 99 runoff also exceeded the chronic standard partly due to low water hardness at this site. There was no impact in the stream because stream water hardness is higher (metals are less toxic in hard water) and the concentration diluted. • The estimated annual pollutant loading, for selected parameters, is presented in table 3. The estimates are based on a watershed area of 434 acres and an average annual precipitation of 36 inches. Storm - water and baseflow loads were calculated separately and added to obtain the total. Stormwater pollutant concentrations are the average of three separate spring (February, March, and April 1996) runoff sampling events. Baseflow concentrations were from a single sample collection in June 1996. Hydrologic modeling was used to estimate the percentage of total annual runoff attributed to baseflow (64 percent) and stormflow (36 percent). Both pollutant concentrations and percent of base/stormflow can vary with time; therefore, the pollutant loads provided are estimates of actual amounts, which can vary considerably from season to season and year to year. Table 3 Estimated Annual Pollutant Loading at the Mouth of Riverton Creek (1996) Pollutant Annual Load Estimate Total Suspended Solids Total Petroleum Hydrocarbons Floating Oil and Grease Fecal Coliform Bacteria Total Phosphorus Ammonia Nitrogen Cadmium Copper Lead Mercury Biochemical Oxygen Demands 1. Concentration data from KCM 1992. 72.5 x 10' kg/year 592 kg/year 630 kg/year 113 x 10' organ isms/year 542 kg/year 363 kg/year No measurable quantity 15.4 kg/year No measurable quantity No measurable quantity 8.4 x 10' kg/year Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basinpin (5/15/97) ss 5 CHAPTER 1 DRAFT These pollutant load estimates may be used by resource managers at some time in the future to establish pollutant loading limits for the Riverton Creek basin. However, it should be noted that these pollutant Toads are likely to decline over time as elements of this Riverton Stormwater Quality Management Plan are implemented. Therefore, any future Toad limits should be based on updated pollutant concentration measurements. • Accidental spills and illegal dumping were identified as problems in the Fostoria basin based on review of Ecology records (Herrera Environmental Consultants 1996). It is expected that these problems also occur in the Riverton Creek basin. • Despite poor water quality during storm flow conditions and suspected periodic illegal dumping, chemical analysis of sediment samples near the mouth of the creek showed no contamination by heavy metals or organic chemicals. The analysis included testing for 13 heavy metals and 179 organic chemicals. • Stream banks throughout the stream system are relatively stable with no major cut banks or in -stream erosion observed along the stream segments that were inventoried. However, most of the natural stream has been replaced by straight, armored ditches and culverts. • Field surveys of residential neighborhoods upslope of SR 99 indicate that significant erosion/sedimentation could be due to poor construction of roadside ditches. • Additional erosion/sedimentation impacts are due to erosion during construction and/or the street sanding practices of WSDOT and the City (J. Howat, personal communication 1996). • Sedimentation in the Lower Reach of the stream system is a major problem. Sediment accumulation is reducing culvert capacities by as much as 50 to 75 percent, and fish spawning habitat (gravel or cobble substrate) is being covered over with undesirable silts and sands. A photo survey of drainage features in the upper Riverton Creek basin shows positive and negative aspects of erosion control (figures 3 through 12). Figure 3 shows an example of a very well-designed and maintained grass -lined swale. This type of drainage conveyance not only prevents erosion, but it also helps to detain and treat roadway runoff, thus protecting Riverton Creek from excessive peak flows and poor water quality. Another favorable roadside condition is shown in figure 5, where heavy vegetation (though not recently maintained) provides good ground cover and prevents soil erosion during storm conditions. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basinpin (5/15/97) ss DRAFT CHAPTER 1 Figure 3. An example of a well-designed, well-maintained grass -lined swale in the upper watershed. •l. •l;%f I. Figure 4. An example of a roadside ditch with excessively steep side slopes and soil slumping into the ditch. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basirpin (5/15/97) ss ( ) Figure 7. Streetside parking in this roadside ditch leads to Toss of grass cover and increased erosion potential. Figure 8. Utility Zine construction adjacent to this roadside ditch also increases erosion potential. CHAPTER 1 DRAFT Figure 9. Recent construction leaves exposed soils on relatively steep slopes. 104 • •- • 4.r s"y! 1110 ter.. v+. • +.f ���yj( ♦M i 7"-.4,74..:47.. iN i1.. w !. r• 4"4.41 _•T+�'1 yr .`� ,• Figure 10. Another construction site showing exposed soils. 10 Riverton Stormwater Quality Management Plan - 1997 95115 / reports / basrpin (5/15/97) ss DRAFT CHAPTER 1 Figure 11. Another post -construction situation with exposed soils on steep slopes just above a storm drain. Figure 12. Another post -construction site showing exposed soils and erosion in the vicinity of a storm drain inlet. Riverton Stormwater Quality Management Plan - 1997 95035/ reports / baslnpin (5/15/97) ss ,. 11 CHAPTER 1 DRAFT Other photos (figures 4, and 6 through 12) show examples of roadside drainage ditches and/or roadside or site construction practices that leave soils exposed to erosion forces during rainfall events. These photos show cases where: 1. Side slopes of roadside ditches are too steep leading to hydraulic undercutting and soil sloughing into the drainage course. 2. Soil stockpiles are located right in the middle of a roadside ditch creating much greater erosion potential in the event of rainfall and site runoff. 3. Roadside parking leading to Toss of grass cover and exposure of soils to erosion during rainfall/runoff conditions. 4. Utility line construction parallel to a roadside ditch with no post - construction revegetation to reduce erosion impacts. 5. Several other construction sites where post -construction revegetation was inadequate to protect against erosion. STREAM HABITAT A major beneficial use of Riverton Creek is the provision of stream habitat, which provides food, cover, refuge, and spawning area for salmonids and other aquatic organisms. Recent electro -shocking of the Lower Reach of Riverton Creek revealed the presence of juvenile coho salmon and cutthroat trout. Non -game species included sculpin spp., three-spined stickleback, and an unidentified sucker species. Existing problems affecting fish and stream habitat are summarized below. A more detailed discussion is provided in Appendix B. • There are two 48 -inch flap gates at the point where Riverton Creek discharges into the Duwamish Estuary. The gates are closed during periods of high tide and high river flow, and are, therefore, a partial fish passage barrier. • There is an extensive reach of approximately 2,250 feet of the east tributary of Riverton Creek which has been confined to underground culverts. This also may be an important fish passage barrier, preventing fish from swimming upstream to the remaining stream habitat in the east tributary, upstream of South 126th Street. 12 Riverton Stormwater Quality Management Plan - 1997 95035 / reports / bosinpin (5/15/97) ss DRAFT CHAPTER 1 • There is also a 20 -foot -high waterfall (which resembles a staircase) on the west tributary of Riverton Creek, just upstream of the Boeing property at South 125th Street. This is another fish passage barrier and prevents fish from reaching several hundred feet of useable stream habitat upstream of this location. • Culverts in the Lower Reach of Riverton Creek, which are partially filled with sediment, also may impede fish passage, especially larger adult fish. • There is a lack of good pool habitat on the west tributary. • Sediment has covered over much of the remaining spawning habitat in the creek. For example, Ryan Partee, the City's fish biologist, indicated that approximately 18 inches of sand and silt have accumulated in the man-made spawning channel that traverses the Metro property since it was last cleaned in 1990. • There is a lack of good streamside vegetation, especially in the Lower Reach of the stream from South 125th Street to the outlet. • There is also a lack of large organic debris (fallen trees, logs, root wads, etc.) for in -stream stream habitat. Much of this woody debris may have been hauled away as construction waste during property development and/or roadway construction. • Although juvenile coho salmon and cutthroat trout have been sighted in the creek, fish biologists have observed low numbers of both adult and juvenile fish throughout the stream system. This is probably due to the cumulative impacts of fish passage barriers, degraded spawning habitat, and degraded riparian habitat. • Poor water quality also is responsible for poor stream habitat in Riverton Creek. Poor water quality conditions appear to be most problematic during stormflow conditions. Monitoring conducted during summer low flow conditions indicates satisfactory temperature and dissolved oxygen conditions (R. Partee, personal communication). Good low flow conditions are believed to be due to the relatively high, groundwater contribution to base flow in this creek. Another potential source of danger to water quality and stream habitat is accidental spills or illegal dumping of pollutants. • Excessive flood flows in Riverton Creek also contribute to poor fish habitat. Hydrologic modeling shows that existing peak flows are as much as 10 times greater than what the creek experienced prior to human development of the watershed. Higher peak flows can cause increased erosion/sedimentation problems and also can be Riverton Stormwater Quality Management Plan - 1997 95035 / reports / baslnpin (5/15/97) ss 13 CHAPTER 1 DRAFT FLOODING responsible for physical injury to, and displacement of fish from their spawning and rearing habitats. These impacts can reduce reproductive success and make fish more susceptible to disease, predation, and direct physical mortality. In an urban stream like Riverton Creek, this is aggravated by the fact that much of the stream has been channelized and culverted and most of the large woody debris has been removed. In such stream reaches, there are few locations where fish can find low velocity resting places or off - channel refuge during high flows. • The single most significant potential flooding issue in the basin is the sizable accumulation of sediments in the Lower Reach of the stream system. As mentioned above, sediment accumulation is so great in some culverts that only 25-50 percent of the culvert capacity remains to convey peak flows. There is also significant sediment in the stream channels in the Lower Reach of the basin— perhaps as much as 18-36 inches. These conditions create a potential flood hazard condition in the event that clogged pipes and stream segments do not retain adequate capacity during flood conditions, especially if problems are worsened by blockages during major storms. Therefore, one of the City's highest priorities with this project is to clean out affected stream channels and culvert pipes. • Computer modeling confirmed existing and/or potential flooding problems at a number of locations throughout the watershed by showing that predicted flows would exceed pipe and/or channel flow capacities. This analysis was based on unrestricted pipe/channel flows and did not consider the additional potential impact of sediment accumulation further reducing peak flow capacities. • The east tributary stream course at South 126th Street floods due to sedimentation and/or an under -designed culvert. A preliminary City recommendation is to replace the existing 36 -inch culvert pipe with a 42- or 48 -inch pipe. This may be the most cost-effective solution, but flow diversion is also under consideration. • Similar problems occur near 34th Avenue South and South 128th Street—also on the east tributary. Culvert replacement also has been recommended at this location. • In 1994, the City began implementation of drainage improvements in the Cascade View neighborhood to alleviate localized ponding 14 Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basnpin (5/15/97) ss DRAFT CHAPTER 1 and flooding caused by poor soils and high water table conditions. Planned improvements involved 2,700 linear feet of new pavement in alleys and residential streets, and 3,850 linear feet of new storm drain pipes replacing roadside ditches. Because it was not possible to obtain construction easements from some private property owners, only a portion of this work was completed in 1995. These improvements likely contributed to increased peak flows downstream of SR 99 and may also have been a source of temporary erosion/sedimentation problems during construction. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basnpin (5/15/97) ss 15 DRAFT Chapter 2 EXISTING PLANS, POLICIES, REGULATIONS AND PROGRAMS RELATED TO STORMWATER MANAGEMENT NATIONAL POLLUTANT DISCHARGE ELIMINATION SYSTEM (NPDES) In 1990, the U.S. Environmental Protection Agency (EPA) adopted regulations establishing requirements for municipal and industrial stormwater discharges. Large municipalities, defined as those with over 250,000 residents, and medium-sized municipalities, with over 100,000 residents, are required to obtain an NPDES permit for stormwater discharges. Although Tukwila does not currently fall under these requirements, the City will be required to comply with the next phase (Phase II) of the program, which the EPA plans to establish for smaller municipalities. The schedule for Phase II implementation is uncertain at this time. The NPDES permit program requires implementation of best management practices (BMPs) to achieve water quality program objectives. It also requires a stormwater sampling program be conducted to assess the impact of stormwater discharges and a screening process be established to identify illegal discharges. The NPDES program also requires that certain industries obtain a permit and that organizations involved in land clearing activities affecting more than five acres obtain a permit. Although the City of Tukwila is not presently regulated under the NPDES program, the City has taken a number of actions, which are expected to be consistent with the intent of the NPDES permit program. These include adopting: The Surface and Storm Water Management Ordinance (No. 1755), The Land -Altering Ordinance (No. 1591), The King County Surface Water Design Manual (1990). The preparation and implementation of this Riverton Stormwater Quality Management Plan is another action, which is expected to be consistent with the Phase II NPDES permit program. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basrpin (5/15/97) ss 17 CHAPTER 2 DRAFT PUGET SOUND WATER QUALITY MANAGEMENT PLAN The Puget Sound Water Quality Management Plan (Puget Sound Water Quality Authority 1986, revised 1991) established a framework for stormwater management in the Puget Sound area and also established the Washington State Department of Ecology (Ecology) as the technical lead responsible for developing guidance on stormwater issues for local jurisdictions. The stated goal of the plan is: "to protect and restore beneficial uses of aquatic resources, including shellfish beds, stream habitat, and other resources, to prevent the contamination of sediments from urban runoff, and to achieve standards for water and sediment quality by reducing, as necessary, pollutant discharges from stormwater throughout Puget Sound." Under the plan, all cities and counties in Puget Sound are required to adopt ordinances that allow them to establish the following programs: • Stormwater quality controls for all new development and redevelopment projects. • An operation and maintenance program for all public and private stormwater facilities. The City of Tukwila has complied with these requirements with the passage and implementation of the Surface and Storm Water Management Ordinance (No. 1755). These program elements are intended to prevent increases in stormwater pollution. Ecology has prepared a guidance manual that establishes minimum requirements for stormwater controls called the Stormwater Management Manual for the Puget Sound Basin (also known as the Technical Manual, Ecology 1992). Local stormwater control programs must be consistent with the Ecology Technical Manual. Since Tukwila has adopted the King County Surface Water Design Manual, they are consistent with Ecology's Technical Manual. In addition to the basic program, densely populated urban areas are required to develop a comprehensive urban stormwater program. Although this requirement initially covers only the six largest cities and four largest counties in the region, by the year 2000 all urban areas, including Tukwila, will be required to implement a comprehensive urban stormwater program. This comprehensive program incorporates the following additional requirements: 18 Riverton Stormwater Quality Management Plan - 1997 9503. / reports / basnpin (5/15/97) ss DRAFT CHAPTER 2 • A water quality response program to investigate water quality problems and identify significant pollution sources and problem storm drains. • An inspection, compliance, and enforcement program. • Coordination with other jurisdictions to establish consistent and joint programs in basins shared by other jurisdictions. • A stormwater public education program that targets local residents, businesses, and industries. A schedule for implementing the comprehensive program also must be developed, with provisions to enable cities to require retrofitting of existing systems if the control measures listed above fail to adequately control stormwater pollution. In addition, cities must demonstrate that adequate funding is available to support the comprehensive stormwater program. STATE OF WASHINGTON GROWTH MANAGEMENT ACT The State of Washington Growth Management Act of 1990 (GMA) requires that jurisdictions prepare a comprehensive plan to establish guidelines for future development (RCW 36-70A). Included in the plan is a land use element that provides "guidance for corrective actions to mitigate or cleanse those discharges that pollute waters of the state, including Puget Sound or waters entering Puget Sound." The City of Tukwila prepared a Surface Water Management Comprehensive Plan'in April 1993 for the entire city. In addition, the City Council prepared a City Council Recommended Draft Comprehensive Plan in August 1995. Both plans are summarized below. THE CITY COUNCIL RECOMMENDED DRAFT COMPREHENSIVE PLAN The City Council Recommended Draft Comprehensive Plan is a land use plan and was prepared in response to the requirements of GMA. Some of the key provisions of the plan, which are in support of improved water quality, stream protection, and habitat improvement, are listed below: • The plan encourages replacement of septic tank/drainfield systems with sewers - page 47. • Stormwater policy encourages repair of drainage problems in residential areas - page 47. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basinpin (5/15/97) ss 19 CHAPTER 2 DRAFT • The plan encourages preservation and enhancement of the natural environment to promote recreational opportunities, visual relief, and drainage control/treatment - page 49. • Another planning policy is to retain and improve hillsides, wetlands, drainage courses for wildlife, recreation, water quality, and flood control - page 51. • The plan encourages clean water education programs for business and incentives for maintenance and replacement of existing stormwater systems - page 52. • The plan specifies inventory and classification of fish and wildlife priority habitats - page 53. • Enhancement of fish and wildlife habitat is encouraged via water quality controls and BMPs - page 53. • The plan also encourages joint neighborhood/City stream clean up, Adopt -a -stream, and trails and interpretive signs - pages 54-55. • Under the Shoreline Element, the plan encourages increased public access, recreation, and increased trees and landscaping adjacent to the river environment - pages 57-59. • The plan calls for the development of a River Access Plan and River design guidelines - page 69. • The plan supports implementation of the King County Green River Trail Master Plan - page 70. • The plan promotes the restoration, protection, and enhancement of natural habitat along the river, including planting trees for wildlife enhancement and for public and educational use - page 72. • The plan also promotes the restoration of degraded riverbanks and provision of interpretive signs - page 73. • The plan endorses erosion control and pollutant removal for waters discharging to the river - page 73. • It promotes a signage program identifying important surface drainage connections and corridors - page 161. • And finally, it supports the extension of sewer service and other improvements to residential streets - page 185. 20 Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basinpin (5/15/97) ss DRAFT CHAPTER 2 SURFACE WATER MANAGEMENT COMPREHENSIVE PLAN The Surface Water Management Comprehensive Plan, adopted in 1993, builds upon the stormwater program established when the Storm and Surface Water Utility was formed in 1989. The comprehensive plan was prepared to meet state (Puget Sound Water Quality Management Plan) and pending federal regulations (NPDES permit program) regarding stormwater. The objectives of the plan are listed below. • Enhance and maintain water quality in the Green/Duwamish Estuary and its tributaries to support beneficial uses. • Coordinate plans, systems, and policies of the program with those of other jurisdictions and governmental agencies within the Green River Management Agreement area. • Provide for the Tong -term storm drainage control needs of the city. • Protect the physical and biological integrity of wetlands, stream corridors, and associated habitats. • Establish and operate funding mechanisms that equitably allocate costs. • Encourage the development of regulations that are consistent, predictable, and equitable. • Build public understanding of surface water management problems as well as responsibilities and opportunities for individuals to improve water quality and drainage. • Emphasize the use of natural systems and nonstructural methods that focus on preventing and controlling runoff and pollution at the source. • Develop, implement, and maintain a comprehensive program to manage surface water in the city. Included in the comprehensive plan are a series of capital improvement projects that have been developed to address existing and future problem areas in the city. Five of the listed projects occur in the Riverton Creek basin. Their locations are shown in figure 13 and the projects are summarized in table 4. Detailed descriptions are located in Appendix C. It is noteworthy that the Surface Water Management Comprehensive Plan (SWMCP) identifies Riverton Creek as a potential fish enhancement project. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basnpin (5/15/97) ss 21 CHAPTER 2 DRAFT Table 4 Summary of Drainage Improvement Projects from the Surface Water Management Comprehensive Plan 1993 City of Tukwila Reference y Estimated and Project Name Project Description Cost Fostoria Basin Drainage Study 1986. • New Storm Drain System Parallel to Install a 36 -inch -diameter drainage pipe that $40,000 East Marginal Way - (F4) parallels East Marginal Way on the west side and ties into an existing 42 -inch drain pipe. (1989, ENR = 4771) Cascade View Annexation Priority Surface Water Management LIDs • Ditch Stabilization on South 132nd Stabilize ditch erosion through this reach using $67,000 Street Between 34th Avenue South and 45th Avenue South - (CVA6) log check dams and revegetation. (1990, ENR = 4960) • New High -Flow Bypass Pipeline Install 1,150 feet of 24 -inch -diameter pipeline $382,000 Along 37th Avenue South Between South 132nd Street and South 128th to intercept storm flows at the intersection of South 132nd Street and 37th Avenue South and (1990, ENR = 4960) Street - (CVA7) outfall to the existing creek at the northeast intersection of 37th Avenue South and South 128th Street. Install a special manhole where the existing 18 -inch -diameter pipeline discharges onto private property to maintain low flow to the existing creek corridor. • Local Collector Improvement on East Install approximately 540 feet of 18 -inch- $161,000 Marginal Way Between South 126th Street and South 128th Street - diameter collector pipeline along East Marginal Way South and South 126th Street to discharge (1990, ENR = 4960) (CVA8) on the downstream side of the creek culvert. • Culvert Replacement Under South Replace the partially plugged existing elliptical $55,000 126th Street Between East Marginal Way South and 37th Avenue South - CMP culvert with a 42 -inch -diameter RCP culvert. (1990, ENR = 4960) (CVA9) TOTAL COST FOR RIVERTON BASIN $705,000 LID = local improvement district CMP = corrugated metal pipe RCP = reinforced concrete pipe 22 Riverton Stormwater Quality Management Plan - 1997 95035 / reports / bapnpin (5/15/97) ss FIVIPW.-RMIffil:117,17T.TTRITI'ClaajaMi m — I Basin Boundary —•—•• Stream Course Z► not to scale (30 Source: Project F4 from the Fostoria Basin Drainage Study 1986. Projects CVA6 through CVA09 from the Cascade Views Annexation Priority Surface Water Management LID. See Table 4 for project descriptions. E N T R A N C O Figure 13 Location of Drainage Improvement Projects From the Surface Water Management Comprehensive Plan 1993 DRAFT CHAPTER 2 The SWMCP also includes a detailed discussion of Operations and Maintenance (O&M) of both public and private facilities. The O&M program includes inspection and maintenance activities for storm drains (pipes, manholes, catch basins, inlets), ditches, streams, and the flood control system (pump station, channels, levees) and also addresses the administrative aspects of O&M (staff needs, safety, training, education, public involvement, etc.). At the time of plan completion in 1993, the City of Tukwila Maintenance Department had divided the city into zones and performed routine maintenance on a three- to five-year rotating cycle. However, special attention was given to problem areas and citizen complaints. Some key aspects of the maintenance program, as practiced in 1993, are summarized below: • Manholes and catch basins are cleaned with a vactor truck when sediment depth is greater than six inches. Detention facilities (above and below ground) also are cleaned in a similar manner on an as needed basis. • Liquid vactor wastes are sent to the sanitary sewer and solids are sent to the Cedar Grove Compost Company or sanitary landfill. • Ditch maintenance involves vegetation and sediment removal with maintenance of hydraulic capacity a primary consideration. • Sediment and debris removal occurs in stream channels to maintain hydraulic capacity. However, maintenance activities are often limited by lack of a long boom (30 -foot) truck and limited access. • The City of Tukwila Maintenance and Fire Departments participate in the King County Division of Metropolitan Services hazardous spill response program. They are trained in the identification, containment, and clean up of hazardous materials. Recommendations included in the Surface Water Management Comprehensive Plan for improved O&M practices included the following: • Increase maintenance frequency in commercial and industrial areas to twice per year and once per year elsewhere, for improved water quality performance. • Identify and retrofit any catch basins that do not have sediment traps. • Perform inspections to identify needed system repairs. Riverton Stormwater Quality Management Plan - 1997 05035 / reports / basinpin (5/15/97) ss 25 CHAPTER 2 DRAFT • Modify zone boundaries to coincide with basin boundaries and perform facility inventory on GIS. • Use standard maintenance data entry forms. • Conduct TV inspections of storm drains to identify and correct illegal connections. • Develop vactor waste disposal policy consistent with Ecology programs. • Review vactor truck cleaning procedures to ensure crew safety. • Analyze decant solids and fluids to determine toxicity and disposal criteria. • Locate a vactor and street sweeping waste handling facility. • Complete a detailed facility inventory and complaint tracking system by basin. • Continue ditch maintenance on a five-year cycle with minimal vegetation removal so as to minimize erosion and maximize water quality treatment. • Prepare a drainage system map showing ditches and basin boundaries. • Complete restoration of hydraulic capacity of ditches in newly annexed areas. Provide erosion control and reseeding immediately following. • Convert ditches to pipe where slopes exceed 4 percent. • Convert ditches to swales where feasible to enhance water quality treatment. • Mow swales twice per year. Compost cut grass. Provide spot re- seeding in spring and fall. Clean sediment on a five-year cycle. • Inspect streams and stream culverts/channels annually and after major storms. • Review plunge pools and options to alleviate plunge pool conditions. • Improve inflow and outfall structures to include energy dissipation and outfall protection to reduce erosion potential. 26 Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basrpin (5/15/97) ss DRAFT CHAPTER 2 • Trace and eliminate sediment sources, including new construction sites, eroded channel sections, and earth stockpiles. • Develop a system for recording citizen complaints and the City's response. • Identify private outfalls into the Green/Duwamish Estuary as well as easements and rights-of-way along streams and ditches. • Develop a complete inventory of both public and private drainage facilities and features (pipes, culverts, ditches, streams). • Purchase another vactor truck so that one truck is used exclusively for drainage facility maintenance. • Rent a long -boom backhoe as needed for deep detention areas. • Continue staff training with emphasis on water quality, public education and maintenance system software. • Stencil catch basins with: "Drains to [Receiving Water Name], Dump No Pollutants". • Develop and distribute an educational brochure for citizens. SURFACE AND STORMWATER MANAGEMENT ORDINANCE - NO. 1755 The Surface and Stormwater Management Ordinance, adopted in December 1995, establishes requirements and standards for drainage design, plan review, permitting, critical drainage areas, maintenance, water quality, and performance bonds/securities for construction projects. Provisions relating specifically to water quality include: • Adoption of the 1992 King County Surface Water Design Manual, or as amended hereafter, and any more stringent requirements of Ecology. The manual requires stormwater quality controls for any new development or redevelopment creating more than 5,000 square feet of new impervious surface area. The ordinance also requires all drainage projects, irrespective of size, to provide controls necessary to maintain or enhance water quality. • The City may require the collection of baseline water quality data to evaluate treatment effectiveness and potential downstream impacts. • The ordinance includes provision for inspection and maintenance of both public and private, existing and new, storm drainage Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basnpin (5/15/97) ss 27 CHAPTER 2 DRAFT facilities. The ordinance also gives the City right of entry and enables the City to make necessary corrections and to charge private property owners for any maintenance not properly performed during a reasonable specified time frame. LAND -ALTERING ORDINANCE - NO. 1591 This ordinance regulates land -altering activities to prevent damage to public and private property (including stormwater systems) by controlling erosion and sedimentation, both during and following construction. The ordinance also protects water quality by reducing sediment -related pollution of surface water systems. Regulated activities include any operation that changes the natural cover or topography, including land clearing and grading, creation of impervious surfaces, excavation and fill projects, and material stockpiling. The ordinance establishes a permit program for construction projects, including required preparation of a land -altering plan. The plan must describe the proposed activity, identify proposed erosion and sedimentation control practices, and specify monitoring and maintenance programs to ensure proper performance of both temporary and permanent facilities. Control measures, including permanent controls, must be designed in accordance with the latest version of the King County Surface Water Design Manual. SENSITIVE AREAS ORDINANCE - NO. 1599 The Sensitive Areas Ordinance (SAO) establishes requirements for activities affecting wetlands, water courses, geologic hazards, abandoned.coal mines, and sites of archaeological importance. Setbacks, buffers and mitigation requirements are established for each type of sensitive area. Within the Riverton Creek basin, there are sensitive area designations for the various stream reaches, steep slopes, and a Type 2 wetland (within the southeast quadrant of the SR 99/SR 599 interchange). Buffer widths for Type 1, 2, and 3 water courses are 70, 35, and 15 feet, respectively. Buffer widths for Type 1, 2, and 3 wetlands are 100, 50, and 25 feet, respectively. Drainage maintenance activities in a water course, such as dredging and digging, are permitted with the approval of the Director of the Department of Community Development. Scheduling and performance of work must be conducted in a manner that minimizes impacts on water quality. Upon 28 Riverton Stormwater Quality Management Plan - 1997 95035/ reports / basinpin (5/15/97) ss DRAFT CHAPTER 2 completion, the affected area must be graded, replanted, and maintained to ensure successful restoration. Diversion or relocation of a water course also requires the Director's approval and must meet the following conditions: • A plan for mitigation, including monitoring, must be prepared and approved. • Work affecting critical fish or wildlife habitat will only be allowed if habitat is improved. FLOODPLAIN MANAGEMENT ORDINANCE - NO. 1499 The floodplain management ordinance establishes requirements for construction within or near a flood zone and for relocating water courses. Relocation of a water course requires approval by Ecology and the Federal Emergency Management Agency (FEMA). In addition, the ordinances require that altered or relocated stream channels be maintained to preserve flow -carrying capacity. STORM AND SURFACE WATER UTILITY The Storm and Surface Water Utility was established by ordinance in 1989 to operate and maintain the city storm drainage system. The ordinance establishes a storm and surface water utility fund to be financed through service charges applied to local residents and businesses. The fund is used to repair, maintain, and improve the existing drainage system and to purchase land or easements for the construction of regional stormwater facilities, as well as to support monitoring, inspection, enforcement, and administration activities necessary to implement City surface water policies. The Utility also conducts investigations to evaluate drainage conditions in the Tukwila service area as needed. For example, the City plans to install a permanent monitoring station on Southgate Creek at South 133rd Street and East Marginal Way South to continuously monitor flow in the stream. This information is needed to develop design parameters for instream channel improvements and also will document rainfall runoff relationships in this heavily urbanized stream. In addition, the City intends to install sampling equipment to allow collection of flow-composited samples for stream quality characterization. Similar monitoring is planned at two stations on Riverton Creek. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / baerpin (5/15/97) ss 29 CHAPTER 2 DRAFT SOLID AND HAZARDOUS WASTE PROGRAMS The Tukwila Department of Community Development sponsors a recycling program that indirectly assists in reducing stormwater pollution by encouraging local residents and businesses to recycle and properly dispose of solid and hazardous waste. This program is based on public education and technical assistance efforts that target local residents and businesses. For example, the City's recycling program regularly publishes articles in the city newsletter, Hazelnut, providing information to local residents about household hazardous waste disposal and recycling opportunities. The Hazelnut also publishes the locations and dates on which the King County hazardous waste mobile collection unit will be in the city to collect household hazardous wastes. In addition, the program routinely provides information to local residents about alternative products that can be used in place of more toxic household products, and also sells compost bins to the public at reduced rates. The City also sponsors an annual cleanup event for local residents to dispose of hard -to -recycle items (other than hazardous waste). Services for local businesses include publishing a newsletter twice a year to disseminate information on recycling opportunities and appropriate waste disposal practices, and providing technical assistance on how to set up a business recycling program. In addition, the City responds to questions from local businesses about disposal and recycling issues and refers them to local agencies and vendors that supply services in these areas. FIRE PREVENTION INSPECTION PROGRAM The Tukwila Fire Department is involved indirectly with stormwater pollution control through its fire prevention inspection program. Under this program, the department inspects every business in the city once every 18 months to document compliance with the Uniform Fire Code (Olivas, personal communication). The Uniform Fire Code covers a wide range of activities involving the storage, handling, and dispensing of hazardous and flammable materials. Although the Fire Department is concerned primarily with safety and fire prevention, its technical assistance efforts cover some issues of concern for stormwater pollution prevention. Topics particularly related to stormwater pollution include secondary containment for storage areas, spill and drainage controls, waste disposal, and employee training. In the course of inspecting hazardous material storage areas, the Fire Department often works with the City Building Department to ensure that hazardous material handling and storage areas are designed and constructed in accordance with accepted standards. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basirpin (5/15/97) ss DRAFT CHAPTER 2 Because Fire Department inspectors observe local businesses on a regular basis, they serve as a key point of contact with individual business owners and managers. It is uncertain whether the Fire Department would be able or willing to coordinate with the Storm and Surface Water Utility to facilitate evaluation of stormwater pollution control practices. However, because it has the most extensive knowledge of local business operations and housekeeping practices, the Fire Department represents a significant source of information for the utility. The Fire Department also staffs the hazardous materials response team. This team responds to spills reported within the city and initiates emergency spill containment. Spill cleanup is generally handled by Ecology. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / barn (5/15/97) ss 31 DRAFT Chapter 3 STORMWATER QUALITY MANAGEMENT BASIN/STREAM RESTORATION CONCEPT The draft Stormwater Quality Management Plan is based on an ecosystem approach to watershed/stream restoration, which focuses on the value of the stream and its water quality as stream habitat, as well as its function as a flood flow conveyance. In the ecosystem context, the City's approach to "water quality" is one that focuses on both preservation and enhancement of the physical/chemical/microbiological aspects of water quality, as well as the stream habitat value of the stream. The latter aspect of stream quality encompasses: ■ The quality of the streambed as it relates to production of aquatic invertebrates for fish food as well as its suitability as spawning habitat (well oxygenated gravel reaches not covered over with sediment). • The presence of quiescent pool areas in the stream, which function as rearing habitat for juvenile fish and also provide fish refuge during flood flows. • The presence of large woody debris in the stream, which reduces peak flow velocities and provides cover for fish so they have better opportunity to avoid perdition. • The presence of good natural riparian vegetation, which both shades the stream in summer months and provides additional habitat for fish food organisms (adult mayflies, etc. which fall into the stream and become fish food). The Riverton Stormwater Quality Management Plan is based on this ecosystem approach and is particularly important to Tukwila Mayor, John W. Rants. As a former commercial fisherman, he has a sincere interest in seeing streams restored to the point where they are once again capable of supporting healthy fish runs. Under his leadership, the City has hired a fishery biologist, Ryan Partee, to perform an inventory of City streams to assess their potential for restoration. Mr. Partee has completed his inventory work and has concluded that Riverton Creek has the greatest potential for restoration of any stream in the city. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basrpin (5/15/97) ss 33 CHAPTER 3 DRAFT PLAN OVERVIEW The Riverton Stormwater Quality Management Plan is a multifaceted plan comprised of the following elements: • Citizen's Implementation Project - The Boeing Reach • Public Education and Involvement • Policy Recommendations • Regulations and Enforcement • Interagency Agreements • Capital Improvement Projects • Maintenance • Inventory and Monitoring These elements are summarized in table 5 and described in detail in this chapter. Table 5 Summary of Riverton Stormwater Quality Management Plan Recommendations Preliminary Planning Level Brief Description Cost Estimates Recommendations A. Citizens Implementation Project - The Boeing Reach Project Install rock structures, install boulders, re -vegetate stream banks, remove sediment, and remove reed canarygrass. Install one barrel -type fish egg incubator. • Cost covered by the Boeing Company, City of Tukwila and citizen volunteers. B. Public Education and Involvement 1. Residential and Commercial Best Management Practices Handbooks Prepare two handbooks about best management practices for homeowners and businesses $27,000 2. Storm Drain Stenciling Use stencils to paint "Drains to Riverton Creek - Dump No Pollutants" near storm drain inlets and on pavement near roadside ditches. $5,500 Possible citizen project. 3. Watershed Signs Design, fabricate, and install 24 watershed signs to help identify watershed boundaries and creek location. $25,000 4. Annual Stream Clean Up Public Works sponsors an annual stream $2,000 expenses. See H.1. for clean up with watershed residents and City staff commitment. businesses. 34 Riverton Stormwater Quality Management Plan - 1997 951135 / reports / basinpin (5/15/97) ss DRAFT CHAPTER 3 Table 5 (Continued) Summary of Riverton Stormwater Quality Management Plan Recommendations Preliminary Planning Level Cost Estimates Recommendations Brief Description 5. Newsletter Stories 6. Adopt -A -Stream Program 7. Citizen Water Watch 8. Watershed Brochure The City will prepare 4 stories per year for 5 years to include in Hazelnut, the City newsletter. Public Works staff will work with teachers and students at the South Central School District to start an Adopt -A -Stream program. Covered by H.1. and other existing City program. $25,000 for equipment and supplies for 5 years. Labor by Watershed/Stream Steward (see H.1.). Public Works will identify citizen volunteers from the watershed to collect water samples and record observations about unusual water quality conditions. Distribute the Riverton Creek brochure to businesses and citizens in the basin. Costs covered by H.1. and H.3. $1,200 C. Proposed Policies 1. Stream Habitat Protection/Restoration Prohibit future piping and channelization of streams and promote opening and restoration of existing piped stream segments with redevelopment where cost-effective. 2. Natural Stream Meander 3. Roadside Ditches and Swales 4. Sewer Service Extension Prohibit straightening or channelizing of remaining natural stream segments. Protect existing roadside ditches and swales and promote use of swales for water quality treatment. If approved by the Department of Public Works and the City Council, policies would be included in subsequent revisions to City of Tukwila Comprehensive Plan (1995 - land use) and Surface Water Management Comprehensive Plan (1993). Same as C.1. Same as C.1. Encourage sewer hookup for residential properties still served by on-site wastewater treatment. Same as C.1. Also, the cost of sewer hook-up would be borne by private property owners. 5. On -Site Wastewater Management Encourage the Rainier Vista and Val Vue Sewer Districts to adopt on-site wastewater management services for non-sewered homes and businesses within their service areas. Same as C.1. Also, the additional cost of such a program would be assumed by the sewer districts and their on-site wastewater customers. 6. Minimize Inflow/Infiltration and Sanitary Sewer Overflows Encourage the Rainier Vista and Val Vue Sewer Districts to minimize sanitary infiltration/ inflow and associated sewer overflows to Riverton Creek. Same as C.1. Also, see D.2. below. D. Regulations & Enforcement 1. New Hazardous Waste Ordinance 2. New On-site Wastewater Management Ordinance Require appropriate businesses to prepare a hazardous waste management plan. To be acted on only if the Rainier Vista and Val Vue Sewer Districts decide not to provide this service. See item C.5 above. $7,200 See item C.S. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basinpin (5/15/97) ss 35 CHAPTER 3 DRAFT Table 5 (Continued) Summary of Riverton Stormwater Quality Management Plan Recommendations Preliminary Planning Level Cost Estimates Recommendations Brief Description E. Interagency Agreements 1. Interagency agreements with King County SWM and Transit and Washington State Department of Transportation (WSDOT) Develop agreements for joint review of stormwater detention & treatment facilities affecting Riverton Creek. $6,000 2. Interagency agreements with the Rainier Vista and Val Vue Sewer Districts Develop agreements regarding on-site wastewater management, sewer hook- up policy, and sanitary sewer overflow policy. $6,000 F. Capital Improvement Projects 1. Tide Gate Removal or Replacement. 2. Sediment Removal Remove tide gates on twin 48 -inch pipes at mouth of Riverton Creek at point of discharge to Duwamish Estuary. If removal would cause flood impacts, replace gate with "fish -passable" flap gate. 3. Lower Riverton Creek Restoration 4. Culvert Replacements and/or Additions (Previously Proposed Drainage Projects) 5. Flow Diversion 6. Stormwater Detention/Treatment 7. Roadside Swale Retrofit Remove accumulated sediment from pipes and stream channel segments to improve habitat and maintain hydraulic capacity. Approximately 1,900 feet of stream channel would be restored by (1) installing large woody debris, (2) installing streamside plantings (shrubs and trees - with topsoil), and (3) selectively placing spawning gravel. Removal $750 Replacement $74,700 $20,000 for selective removal from pipes, catch basins, and stream channel segments in the lower basin. $280,400 Install new and/or replace existing culverts at several select locations in the east tributary as described in table 4 and figure 13. Two diversion route alternatives are presented. The least -cost route ($667,000) would divert all flows from subbasin T7 and 50 percent of flows from subbasin T6. This route alternative would divert flows to the lower reaches of Southgate Creek and then to the Duwamish River. The other diversion route alternative would pick up flows from subbasins T7, T6, T2b and possibly K8, and route flows down SR 99 (to the north) and discharge directly to the Duwamish River. The SR 99 route is more costly at $1,500,000. Stormwater detention and treatment facilities would be needed for SR 99 highway runoff. $638,000 Southgate Creek Route - $667,000 SR 99 Route - $1,500,000 Cost will be covered by WSDOT. Replace 5,340 feet of existing roadside ditches with roadside swales to reduce ditch erosion and maintenance. $233,000 36 Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basinpin (5/15/97) ss DRAFT CHAPTER 3 Table 5 (Continued) Summary of Riverton Stormwater Quality Management Plan Recommendations Preliminary Planning Level Brief Description Cost Estimates Recommendations 8. Sedimentation Basins Construct two basins just downstream of South 126th Street on the east tributary and just downstream of the "steps" on the west tributary. $606,000 G. Maintenance 1. Storm Drainage Facility Maintenance Part-time use of new vactor truck and additional maintenance staff time to increase pipe and catch basin inspection and cleaning to once per year in the Riverton basin. No additional equipment cost is anticipated because the City is in the process of acquiring a new vactor truck, which will be used part-time in the basin. The City Public Works Department will determine if re -prioritization of existing maintenance staff time or a new hire (part-time or full-time) will be needed to provide the increased level of maintenance activity in the basin. 2. Private Drainage Facility Maintenance Inspect and clean annually. See G.1. 3. Roadside Swale Maintenance Annual inspection and maintenance is recommended. See G.1. 4. Construction Inspection Regular inspections and repair recommended in accordance with the City's Surface and Stormwater Management Ordinance See G.1. H. Inventory and Monitoring 1. Watershed/Stream Steward The Watershed/Stream Steward would oversee implementation of Stormwater Quality Management Plans and would also perform Environmental Impact Statement review, plan review and construction inspection to protect the resources that have been enhanced through plan implementation. The new Watershed/Stream Steward function could be filled by: (1) re -defining the job duties of an existing staff person in the City, (2) identifying an enthusiastic citizen volunteer, or (3) hiring a new part-time or full-time position at the City. It is assumed that a full-time person would have City- wide responsibilities and would not just focus on Riverton Creek. 2. Mapping and Inventory Aerial topographic mapping; pipe invert elevations and slope inventory along with stream channel dimensions at key locations; identify and map failing septic tank/drainfield locations; businesses using hazardous substances; Washington State Department of Ecology (Ecology) and WSDOT spill records; citizen drainage complaints. Aerial topographic survey - $75,000; pipe and channel survey/mapping - $15,200; other inventory mapping - $12,000 Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basirpin (5/15/97) ss 37 CHAPTER 3 DRAFT Table 5 (Continued) Summary of Riverton Stormwater Quality Management Plan Recommendations Preliminary Planning Level Cost Estimates Recommendations Brief Description 3. Performance Monitoring Provide continuous flow records at two permanent stations and a crest stage gage at the mouth of the creek for flow monitoring. Collect composite samples for three storm events and two base flow conditions each year. Analyze samples for the same parameters collected in the present study. Provide contingency fund for citizen water sample analysis. Analyze data and prepare annual report. Include benthic invertebrate sampling once per year in the summer at three stations. $15,600 per year for 5 years = $78,000 Benthic invertebrate sampling - $5,360 per year or $26,800 for 5 years. 4. Illegal Storm Drain Connection Survey Use a combination of pipe video surveys and tracer dye studies to determine if there are any illegal cross connections with the storm sewer system. Prepare preliminary engineering and costing for correction of problems. $75,000 Citizen's Implementation Project—The Boeing Reach Project Ryan Partee, fish biologist for the City of Tukwila, has held several coordination meetings with the Boeing Company to design stream improvements in the portion of the west tributary of Riverton Creek that runs through the Boeing property (figure 14). This design work has included coordination with John Beal and the Boeing Fish & Wildlife Club. Proposed stream improvements include: • Selective placement of rock structures to provide stream bank stabilization and improve in -stream pool formation and/or meander ■ Placement of boulders in the stream to enhance meander • Removal of reed canarygrass and revegetation of streambanks to improve shading and riparian habitat value and improve hydraulic capacity • Removal of 2-3 feet of accumulated sediment throughout this reach of the creek 38 Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basirpin (5/15/97) ss r• • • • • - • • -merlon reek 2 20 97 A Possible location of Stormwater Detention/Treatment Facility for SR99 Runoff Legend • Basin Boundary Area Proposed for Roadside Swale Retrofit Lower Stream Reach Restoration > SR 99 Peak Flow Diversion Route ----> Alternative Peak Flow Diversion Route Boeing Reach Citizens' Project 0 Existing Wetland Proposed Sedimentation Pond Figure 14 Proposed Improvements DRAFT CHAPTER 3 • Installation of one remote, barrel -type fish egg incubator to promote imprinting and return of fish for future years. The incubator is an important element of the overall plan and can produce up to 125,000 fry per year. Details of the proposed stream enhancement work on the Boeing Reach are presented in Appendix D. Boeing employees have formed a volunteer stream restoration team which is very interested in the project. The Boeing Company also has agreed to provide funding for construction materials and some construction labor. Streamside planting will all be done by citizen volunteers, including one or two local Boy Scout Troops. This project will satisfy the City/Ecology agreement, which specifies that a "citizen project" will be implemented under the grant. The Boeing Reach project work also has been coordinated with the Citizen Action Committee and will be identified in a citizen brochure about the stream along with other proposed restoration activities. Some stream restoration work has already been initiated by Boeing Company volunteers, who have removed much of the undesirable reed canarygrass in this segment of the stream. Reed canarygrass is undesirable because it competes against more desirable plant species, tends toward the formation of monocultures, reduces stream hydraulic capacity, and encourages flooding during peak flows by growing out into the stream channel. As part of the project, photographs and/or video tape records will be made before, during, and after stream restoration work, and will be used as an educational tool for local schools. The photographs/videos also may be used to provide first hand evidence of the project's benefits to citizens, City staff, the Mayor, City Councilmen, and local news media. The Boeing Reach Project will compliment past efforts by Bill Hitchman (teacher) and students of the South Central School District, who have planted salmon fry in Riverton Creek over the past 3 years. Public Education and Involvement This element of the Stormwater Quality Management Plan focuses on educating the public about the importance of the stream as a resource and how individuals and companies can help in restoring this resource. This element also focuses on ways to get the public actively involved in the project. The following describes seven actions that would be taken to achieve public education and involvement. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basinpin (5/15/97) ss 41 CHAPTER 3 DRAFT Residential and Commercial Property Best Management Practices (BMPs) Handbooks. As part of the public education and involvement element, the City would prepare and distribute separate BMP handbooks for residential and commercial property owners. Examples of residential BMPs are proper maintenance for on-site wastewater systems, proper disposal of household hazardous waste, etc. Additional residential BMPs could address the do's and don'ts or how to's of streamside activities such as fencing, streambank stabilization, landscaping, vegetation control, animal husbandry, etc. Some BMP literature is already available through the City of Tukwila (composting and recycling) and King County (recycling motor oil, pesticide -free gardening, and household hazardous waste mobile). King County also has a Hazardous Waste Directory for Small Businesses. The idea would be to identify and use existing BMPs prepared by other organizations such as (1) the Puget Sound Water Quality Authority - Public Information and Education Grant projects, (2) Ecology, (3) the U.S. Environmental Protection Agency (EPA), (4) the University of Washington, (5) King County and the cities of Seattle and Bellevue, (6) Washington State Department of Health, and (7) Seattle -King County Health Department. The available BMP literature from these organizations could be collected to obtain the best and most applicable ones for use in the Riverton Creek Basin. Copies of existing literature (brochures, etc.) could be obtained and distributed as part of the handbook, or the City could use this information to create their own watershed -specific handbooks. Storm Drain Stenciling. Storm drains would be stenciled with words like: "Drains to Riverton Creek - Dump No Pollutants". Special efforts may be needed to implement this kind of signage program in the Riverton Creek watershed where many residential areas have only roadside ditches or swales. In such areas, it may be possible to place concrete blocks in the ground near drainage ditches and swales as a platform for the sign, or stenciling could be done on the pavement. Watershed Signs. The City of Tukwila would work with high school students in the South Central School District to produce watershed signage artwork. The idea would be to come up with a unique Riverton Creek sign logo and to put up signs at important locations to indicate the boundaries of the watershed and the presence and value of the stream. Annual Stream Cleanup. The City of Tukwila would organize an annual community streamside cleanup event for the removal of trash, tires, appliances, etc. out of Riverton Creek. 42 Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basirpin (5/15/97) ss DRAFT CHAPTER 3 Newsletter Stories. The City would publish stories about the progress of stream restoration in the Hazelnut (a City of Tukwila Newsletter publication). An important part of this effort would be to publish information about the high levels of fecal coliform bacteria in the creek and the potential for water -borne disease for citizens using the stream. This public health advisory also could be published in other newspapers like the Seattle Times and Seattle Post-Intelligencer. Adopt -A -Stream. The City also would work with Bill Hitchman and the South Central School District to develop an Adopt -A -Stream program. This would include stream monitoring projects for students using the Adopt -A - Stream manual. Monitoring would include collecting and reporting data on bottom -dwelling organisms, flow, temperature, dissolved oxygen, annual stream walk, etc. Citizen Water Watch. The City also would develop a "Citizen Water Watch" group. The group would be comprised of citizen volunteers, who live adjacent to Riverton Creek. These citizens would be provided with sample collection bottles so that they could take water samples and bring them to the City for analysis whenever they suspect a water quality problem. Watershed Brochure. A watershed brochure is being prepared as part of this Stormwater Quality Management Plan. This brochure would be distributed to residents of the Riverton Creek Basin. Proposed Policies The following policies are recommended for improved protection and enhancement of stream water quality and habitat. These polices would be incorporated into subsequent updates of the Draft Tukwila Comprehensive Plan (1 995) and Surface Water Management Comprehensive Plan (1 993) if the policies are approved by the Utilities Commission and the City Council. These policies could be given regulatory authority by making appropriate modifications to the Sensitive Areas, Land -Altering, and Surface and Stormwater Management ordinances. Stream Habitat Protection/Restoration Policy. It is recommended that the City of Tukwila develop a policy of not enclosing remaining open -channel stream segments, and that existing closed segments be opened with property redevelopment where feasible and cost effective. Implementation of this policy could be facilitated by mapping existing open and closed stream channel segments. This policy would be consistent with other existing policies aimed at preserving and/or restoring stream habitat. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / bosimin (5/15/97) ss 43 CHAPTER 3 DRAFT Natural Stream Meander Policy. It is recommended that the City develop a policy of not allowing the remaining natural stream segments to be channelized into long, straight, box culverts or rip -rap channels and that the natural stream meander be retained. Natural stream meanders provide better hydraulics and better stream habitat. Roadside Swale Drainage Conveyance. It is recommended that the City develop a policy of retaining open roadside ditches and swales for drainage conveyance and enhanced water quality treatment, rather than using closed underground pipes. Roadside ditches would be converted to swales for improved water quality treatment where cost effective and feasible from an engineering perspective. Extension of Sewer Service. The Draft Tukwila Comprehensive Plan (1995) encourages the extension of sewer service to residences, which are presently served by on-site septic tank/drainfield systems. This policy is endorsed in this plan as a means of reducing fecal coliform bacteria contamination in Riverton Creek. It is suspected that high fecal coliform levels in the Creek may be partly attributed to failing or poorly performing on-site septic systems, especially during the rainy season. It is recommended that this policy be communicated in official correspondence to the Rainier Vista and Val Vue Sewer Districts. On -Site Wastewater Management. It is recommended that the Rainier Vista and Val Vue Sewer Districts develop programs to promote good management of on-site wastewater systems within their respective jurisdictions to reduce the possibility of fecal coliform bacteria contamination from failing or poorly performing on-site systems. This would include periodic inspection and regular pump out of septic tanks. Regulations and Enforcement Possible new ordinances that could be implemented to help prevent future water quality problems are addressed below: New Hazardous Waste Ordinance. A proposed new ordinance would be to require all businesses that handle hazardous materials to prepare a hazardous waste management plan (HWMP) including a list of all hazardous products, plans and specifications for any treatment facilities (e.g. industrial pre-treatment) and/or spill containment facilities, an emergency response plan, and ultimate disposal plan. The City would require review and approval of the HWMP prior to issuance of a hazardous waste permit. The plans and permits would be reviewed and updated every 5 years or whenever significant changes in property use are proposed. Riverton Stormwater Quality Management Plan - 1997 95035/ reports / baslrpin (5/15/97) s DRAFT CHAPTER 3 New On -Site Wastewater Management Ordinance. A proposed new ordinance would be to require an on-site wastewater system renewable permit issued once every five years. This would only be proposed in the event that the Rainier Vista and/or Val Vue Sewer Districts decided not to implement on-site wastewater management programs. The City would require septic system pumpout every five years and require inspection of the drainfield to assess hydraulic loading rates and performance. If drainfield failure was documented during inspection, the City would require repair or sewer hookup. As a part of the ordinance, the City could establish a low-interest loan program to help finance needed improvements to on-site septic systems and/or sewer hookups. Enforcement for these proposed ordinances could be similar to language contained in the Surface and Stormwater Management Ordinance giving the City the right to implement necessary corrections and bill the private property owner if the owner failed to take corrective action during a reasonable specified time frame. Interagency Agreements Agreements between agencies would be formalized to coordinate review and procedures. These agreements would avoid duplication of effort or contradictions between the different agencies policies. Washington State Department of Transportation and King County. Develop interagency agreements with WSDOT and the King County Transit to obtain and review stormwater quality facilities design and operation/maintenance measures/procedures to determine consistency with the Riverton Creek Stormwater Quality Plan. The interagency agreement would address both existing and proposed new facilities and would establish a retrofit policy. Rainier Vista and Val Vue Sewer Districts. It is recommended that the City of Tukwila work toward the development of interagency agreements with the Rainier Vista and Val Vue Sewer Districts regarding: (1) promoting the policy of extending sewer service to unsewered areas; (2) promoting on-site wastewater management practices in unsewered areas; (3) promoting additional infiltration/inflow studies and corrective actions to reduce sewer overflows to Riverton Creek during periods of high runoff. Capital Improvement Projects (Structural Controls) Several capital improvement projects are proposed that would contribute to the preservation and restoration of Riverton Creek. These projects would improve fish passage, correct existing flooding problems, reduce Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basi pin (5/15/97) ss 45 CHAPTER 3 DRAFT flood impacts on fish, reduce erosion/sedimentation problems, enhance stream habitat, and improve water quality. Tide Gate Removal or Replacement. Removal of the existing tide gates, at the twin 48 -inch outfall pipes discharging into the Duwamish Estuary, would provide year -around fish access into Riverton Creek and would eliminate this partial fish passage barrier. Tide gate removal also would restore normal tidal circulation in the Lower Reach of Riverton Creek, thus enhancing its value as a fish rearing area. A flood impact analysis would be conducted prior to removing the tide gates to assess whether any adverse flood impacts would occur as a result. If the flood impact analysis indicated adverse impact, then the existing standard tide gates could be replaced with a new "fish -passable" flap gate design developed by the Seattle District U.S. Army Corps of Engineers. Sediment Removal. Large amounts of sediment have accumulated in the drainage system (pipes and stream channel segments) north of South 126th Street. This portion of the basin is characterized by relatively flat terrain with low hydraulic gradients and correspondingly low flow velocities. This portion of the stream system also is often affected by tidal backwaters or backwaters due to high river elevations. These combined influences contribute to the settling of solids in the affected stream/pipe reaches. In some cases, 50 to 75 percent of culvert capacities have been lost due to sediment accumulation and Tukwila Public Works is concerned that flooding problems could occur in the near future unless the accumulated sediment is removed. The proposed sediment removal operations would selectively remove sediment that has accumulated in pipes and stream channel segments. This would be accomplished using vactor trucks and backhoe equipment. The City would coordinate similar sediment clean up operations with WSDOT and Metro. Lower Riverton Stream Restoration. Additional stream restoration work, similar to that proposed for implementation along the Boeing Reach, also would be performed on portions of the creek between the Boeing Reach and the creek mouth at the Duwamish Estuary (figures 14 and 15). Work would include: • Placement of boulders in the stream to enhance meander • Revegetation of streambanks to improve riparian habitat • Removal of sediment • Selective placement of spawning gravel • Placement of Togs and other woody debris to improve in -stream cover. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / bmirpin (5/15/97) ss A969 95035-60 Riverton Creek (2/20/97) AGT Existing .. 1 _il�_�1 c i ita - i�d 1. A_= 11- tl"",nal, -asn 1471'''_ Ir !<� Tuilli' r�.- ��lr7.n:�L. `7[ f- ` i�-M �-, L l ��it'�};F. 11'1=,.I _J-, '•'f C 0I i ,i .Il[.. 11„l ,�.�,- }�("�� :. ° �' ;-.1 1, -.1 Lys _ !='llrJi.1 tr �"c 4Lrt1_.• I's Existing Building ., Stream Channel Stream Corridor Parking Lot Proposed D and Driveway Existing Fence and Rock Gabions E N T R A N C O Stream Corridor with Riparian Planting VIZ _ -1: 1u 1� k:7.Il 'i=�'t1��-yR��[�'-�^ it� n,'ix=.:�rnz:ol4-;5-A9i it'''oir-i Parking Lot Figure 15 Illustration of Improved Riparian Habitat in the Lower Reaches of Riverton Creek Showing Existing and Post -Restoration Conditions CHAPTER 3 DRAFT Most work would occur in portions of the stream flowing through the SR 599 right-of-way, and would require close coordination with and approval by WSDOT. Because this portion of the project lies within WSDOT right-of- way, it would not be feasible to use volunteers. Therefore, the construction cost would be considerably higher than costs for the Boeing Reach. Culvert Replacement. There are two basic approaches to solving existing flooding problems in the basin. One is to replace some of the existing culverts that are acting as flow restrictors in the drainage system, and/or add parallel pipe capacity where existing stream channel capacity is limiting. These optional capital improvement projects are included in table 1, under Alternative A in the Executive Summary. This is the approach used in developing four of the five capital improvement projects identified in the Surface Water Management Comprehensive Plan (KCM 1993) for the Riverton Creek Basin (see table 4 and figure 13). These projects are being considered as an optional means of flood control in the Riverton Creek basin since they have yet to be implemented by the City of Tukwila. The cost of these projects, as presented in the Surface Water Management Comprehensive Plan (KCM 1993), is summarized below: Project F4 $40,000 Project CVA7 $382,000 Project CVA8 $161,000 Project CVA9 $55,000 Total $638,000 While this may be the least costly approach, the possibility exists that eliminating flooding at a given location, by increasing pipe size or adding pipe capacity, could lead to additional downstream flooding. This could occur if the increase in downstream flow causes capacity problems for other stream reaches or pipe sections, or if downstream flows are adversely affected by backwater conditions. A detailed assessment of such impacts is beyond the scope of this project, but could be made if data on pipe slopes was obtained along with detailed topographic survey data. Another disadvantage of this approach is that it would increase downstream peak flows impact on fish and fish habitat during flood events. The other basic approach for solving existing flooding problems is to divert peak runoff away from existing flood zones as discussed under Flow Diversions (next section). These optional capital improvement projects are included in table 1, under Alternative B in the Executive Summary. Flow Diversions. Three flow diversion scenarios (figure 16) were evaluated for the Riverton Creek basin: Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basinpin (5/15/97) ss A957 95035-60 Riverton Creek (2/20/97) AGT puwamish Estual_Y • T1 a • 11 • �1 t . 1 1 1. _. 1 •• t m. ', T1b• . , • \ not to scala , f ,\ VIt .. 1 i 1 `. ■ 1 t 1 1 '.. 5 : 1 1 \;. 1 ... 1: 1 1 ♦.•1'; 1 ♦ ':- T3 1+., \ 1 - :5 - 1t � ♦ IT2a 1.\ 1 •1 ♦. t_1` ii .S126St • -- • \. . 1 ' 1'){ -T5 . i 17 Subbasin Number - - - - Subbasins ▪ Stream Flow Direction - I _•.'-.1 ----,rs9c •/ .:�' \ , .•141.2bd. 1 , •` , .-- I( ; y - -- 1 1 ,, t•.,! ... `99b. 11 • `\ t T6 • b 1 • 1 • r. jai tt. 1 :72b • ( T6d •� N T7 1 9 1 • ♦ 1 t ` 1 5 1 + 5 1' 1 ------ --1 Figure 16 E N T R A N C O Subbasins Used for Flow Diversion Analysis CHAPTER 3 DRAFT ■ Scenario A - Diversion of peak flows from subbasins T6 and T7 ■ Scenario B - Diversion of peak flows from subbasins T6, T7, and T2 b • Scenario C - Diversion of peak flows from subbasins T6, T7, T2b, K8, and that portion of T2a west of SR 99 Scenario A was considered because it would potentially solve two existing flooding problems: • One along 37th Avenue South between South 128th and South 132nd Streets, and • One at South 126th Street just west of East Marginal Way South. Both of these existing flood impact areas are located on the east tributary of Riverton Creek. Scenario A would have the added benefit of reducing storm -related stream channel flows in the lower portion of Riverton Creek downstream of the Metro Bus Base (figure 14). This would mitigate flood impacts on in -stream fisheries, consistent with City goals for Riverton Creek. Scenarios B and C were considered because of the added potential benefit they could have in reducing peak flows to the Lower Reach of the west tributary as well as the portion of the stream downstream of the confluence of the east and west tributaries. Scenarios B and C would also reduce potential flood impacts to Boeing property (buildings were almost flooded in December 1996) and would benefit fishery resources by further reducing flood flows in the affected stream reaches. Since there is considerably more restorable stream habitat in the west tributary, the cost of diverting additional flows might be warranted. Results of HSPF (Hydrologic Simulation Program Fortran) modeling for selected subbasins are shown in table 6 for the three diversion scenarios. Additional information on HSPF modeling is presented in Appendix E. The benefit of diverting peak flows from subbasins T6 and T7 is evident in each scenario, with flow reductions of 42, 47, and 59 percent, respectively, at the downstream ends of subbasins T3, T4, and T6d. These flow reductions are expected to preclude the need for culvert replacements in the east tributary. Confirmation of this is recommended during engineering design, when accurate survey data and additional SR 99 drainage design information are available (see diversion discussion on the following page). In addition, they also would provide substantial Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basnpin (5/15/97) ss DRAFT CHAPTER 3 mitigation of flood flow impacts to salmon in lower stream reaches' . For example, the 25 -year peak flow at the mouth of Riverton Creek for subbasin Ti a would be reduced by 25 percent. However, even with this diversion, the 25 -year peak flow at Ti a would still be seven times greater than pre -development, forested conditions. Table 6 Comparison of Existing, Pre -development (Forested), and Diversion Flow Scenarios (25 -year storm) for Selected Downstream Modeling Points in the Riverton Creek Subbasin Locations for Predicted Flows - See Figure 16. Predicted 25 - Year Flow for Pre - development (Forested) Conditions Modeled 25 - Year Flow for Existing Developed Conditions Scenario A Diversion: Predicted Flows and Percent Reduction Compared to Existing Scenario B Diversion: Predicted Flows and Percent Reduction Compared to Existing Basin Scenario C Diversion: Predicted Flows and Percent Reduction Compared to Existing Subbasin T3 Subbasin T4 Subbasin T6d Subbasin T2a Subbasin T1 a 9 cfs 6 cfs 2 cfs 6 cfs 16 cfs cfs = cubic feet per second. 100 cfs 34 cfs 17 cfs 53 cfs 153 cfs 58 cfs 58 cfs 42% 42% 18 18cfs 47% 47% 7cfs 7cfs 59% 59% 49 cfs 44 cfs 8% 17% 114 cfs 109 cfs 25% 29% 58 cfs 42% 18 cfs 47% 7 cfs 59% 40 cfs 25% 106 cfs 31% Additional downstream flow reduction benefits would occur with Scenarios B and C. Comparing all three scenarios in table 6, we observe that total diverted flows for the 25 -year storm would be 38, 45, and 48 (cubic feet per second) cfs for Scenarios A, B, and C, respectively. For each flow diversion scenario, it is assumed that only peak flows (all flows greater than 0.64 times the 2 -year storm), and not base flows, would be diverted. It is essential to the support of fish populations in lower Riverton Creek that base flows continue to flow downstream. ' During winter flood flows juvenile salmonids can be washed out of their rearing habitat. This kind of flood impact can dramatically reduce the number of spawning adults in subsequent years. This also means that reduced numbers of juvenile fish would be spawned due to the lower number of returning adults. The impact of a single flood event can have repercussions on the salmon population for years. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basirpin (5/15/97) ss 51 CHAPTER 3 DRAFT Four different stormwater pipe diversion routes were evaluated in a separate report by Perteet Engineering (1997), including three routes to the east to the Lower Reach of Southgate Creek, and one route to the north along SR 99 to the Duwamish River/Estuary. One of the Southgate Creek diversion routes (the least -cost route) and the SR 99 diversion route are shown in figure 14. Diversion costs ranged from $667,000 for the least -cost Southgate Creek diversion route, to $1,500,000 for the SR 99 diversion route. In their assessment of diversion pipe routes, Perteet Engineering (1997) determined that all of subbasin T7 could be diverted to Southgate Creek, but only about 50 percent of subbasin T6 and none of subbasins T2b or K8. This means that flow diversion benefits would be about 25 percent lower than shown in table 6 for Scenario A. Although the SR 99 route is the most costly diversion route, it would provide the greatest benefit to fish and fish habitat mitigation because it would provide the greatest reduction in peak flows for both tributaries of Riverton Creek. If future increases in peak flows occur in subbasin K8 with new development of presently undeveloped property, this benefit will be even greater than shown in table 6. In contrast, the least -cost diversion route to Southgate Creek would increase peak flows in this already heavily impacted urban stream where fish habitat improvements also are planned (KCM 1992). A careful review of impacts to fish usage in the Lower Reach of Southgate Creek is recommended prior to finalizing a decision to adopt this as the preferred diversion route. A possible solution for avoiding additional fish habitat impacts in Southgate Creek would be to extend the diversion pipe all the way to the Duwamish River/Estuary. This would, of course, add to the cost. SR 99 Stormwater Detention and Treatment. Stormwater treatment of diverted flows will be accomplished by means of the roadside swale retrofit program described in the following section. In addition, it is recommended that WSDOT provide stormwater treatment for SR 99 highway runoff in a wetpond or constructed wetland facility located in WSDOT right-of-way near the Duwamish River/Estuary (figure 14). Stormwater detention of highway runoff may not be required. In addition, it is recommended that WSDOT provide spill control (SC) type oil/water separators and Type II catch basins in their drainage design for widening SR 99. These recommendations are consistent with standard WSDOT drainage control practice. No costs are shown as these facilities will be constructed as part of the SR 99 widening effort. 52 Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basirptn (5/15/97) ss DRAFT CHAPTER 3 Roadside Swale Retrofit. It has been estimated that there are about 5,340 linear feet of roadside ditches in the upper Riverton Creek basin. Almost all of these ditches are located in residential areas and help to convey stormwater runoff to the creek. However, many of these ditches are poorly designed and/or maintained, to such a degree that they are suspected as a significant source of high levels of suspended solids, turbidity, and nutrients in the creek. Many of these ditches are unsightly with uncut grass and weeds. In many cases, this is due to excessive side slopes which deter adjacent property owners from mowing and trimming. This unsightly aspect of upper basin roadside ditches also contributes to a neighborhood appearance which is less than desirable. If the roadside ditches were properly designed and maintained, they would look similar to the one shown in figure 3. Therefore, to reduce the contribution of roadside ditches to water quality degradation and to enhance the visual appearance of residential neighborhoods in the upper basin, it is recommended that all existing roadside ditches be upgraded, via redesign and reconstruction. In many instances, this would mean that a portion of the ditch would be located on adjacent private property. If so, construction easements would be required. In some cases, the slope of the swales would be such that vertical drop energy dissipaters and/or flow spreaders would be required to prevent rill erosion down the middle of the swale (per the Draft King County Surface Water Design Manual 1996). The estimated cost of roadside swale retrofit work is $233,000. Tributary Sedimentation Basins It is proposed that two sedimentation basins be constructed: one just upstream of South 126th Street on the east tributary and one just downstream of the "steps" on the west tributary (figure 14). These sedimentation basins are included in table 1, under Alternative A in the Executive Summary, because previously discussed culvert replacement will not remove sediment from the stream and improve water quality. The purpose of these facilities would be to trap sediment upstream of restored stream habitat. This would make it easier to perform sediment removal operations and minimize in -pipe or in -stream sediment removal in the future. Estimated cost for the two sedimentation basins is $606,000. This includes land and wetland mitigation costs for the east tributary facility. We did not include land costs for the west tributary facility since the proposed site is on Boeing property. It was assumed that Boeing would be willing to contribute land costs toward a facility that would help maintain stream channel capacities and reduce potential flood impacts to their buildings. However, this is an assumption that needs to be confirmed with Boeing. Riverton Stormwater Quality Management Plan - 1997 53 95005 / reports / bminpin (5/15/97) ss CHAPTER 3 Maintenance DRAFT The following maintenance measures would be implemented to preserve and restore Riverton Creek. Storm Drainage Facility Maintenance. Pipe and catch basin inspection and cleaning would be increased to once per year in the Riverton Basin, unless observation showed that a lower frequency would preclude sediment accumulations, which threaten hydraulic capacity and/or stream habitat value (e.g., covering of spawning grovel. The City is in the process of purchasing another vactor truck for use in drainage facility maintenance, which also will be used part-time in the Riverton Creek Basin. The new truck would be operated throughout the city and would be used as needed in the Riverton Creek Basin. Vactor-removed sediment and water would be disposed of at the City's new facility in accordance with Ecology (1995) BM Ps. Private Drainage Facility Maintenance. Private drainage facilities on commercial property in the lower watershed would be inspected annually at the time that public facilities are inspected. Critical facilities are those pipes, channels, and box culverts that carry the east and west tributaries of Riverton Creek through private property. If maintenance does not occur following adequate notification, the City is authorized to perform the maintenance and bill the property owner for the cost of services provided. Roadside Swale Maintenance. It is suggested that the City encourage a public/private cooperative maintenance program for roadside swales, once they are retrofitted. Under such a program, the adjacent property owner would be encouraged to mow the swale during summer months and the City would perform an annual inspection and sediment removal maintenance program. This work would be to remove any sediment accumulation in small sediment traps, energy drop structures, or the swales themselves. The City also would be responsible for reseeding or putting down new sod in any areas where restoration of grass cover is needed. Construction Inspection. Active construction sites would be inspected regularly to determine if erosion control measures were being properly implemented. If necessary, field adjustments would be made by the contractor to promote optimal erosion/sedimentation control and to minimize off-site erosion/sedimentation impacts—especially to Riverton Creek. Erosion and sedimentation control would be especially important with upcoming projects such as the widening of SR 99 and construction of drainage improvements proposed in this plan. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / badrpin (5/15/97) ss DRAFT CHAPTER 3 Inventory and Monitoring Watershed/Stream Steward. It is recommended that the City create a new Watershed/Stream Steward function, either in the Public Works or Planning and Community Development Department. One of the main functions of the Steward would be to oversee the implementation of the Riverton Creek and Southgate Creek Stormwater Quality Management Plans. This would include oversight of public involvement and education programs, capital facilities improvements, maintenance activities, and inventory and monitoring programs. Mapping and Inventory. It would be useful for future drainage planning and design in the watershed to have an updated aerial topographic survey. In addition, the drainage system inventory and mapping could be enhanced if invert elevations and slopes of pipe segments could be determined and catalogued, and if stream channel segments could be measured for dimensions at 50 -foot intervals. Additional inventory and mapping could involve (a) failing septic tank/drainfield systems from the Seattle/King County Health Department Records, (b) business types with an emphasis on those likely to utilize hazardous substances, (c) Ecology and WSDOT spill records on SR 99 and SR 599, and (d) City of Tukwila citizen complaints on drainage related issues. Performance Monitoring. It is recommended that water quantity and quality be monitored to determine how well BMPs and capital improvement projects are working. Since permanent flow monitoring stations were installed at Stations 3 and 4 (see Appendix A), it seems appropriate to recommend that future storm flow and water quality monitoring take place at these locations. In addition, it is recommended that monitoring be conducted at Station 8 for quality and that a crest stage gage at this location be checked periodically to assess peak flows. For water quality monitoring, three storm events and two base flow events would be sampled per year. It is recommended that a single composite sample be collected at each of the three stations for both storm and base flow conditions. Additional contingency laboratory costs would be planned to cover the cost of analyzing any water quality samples collected by citizens. Performance evaluation monitoring also would require field time for sample collection and office time for data interpretation and reporting. Annual monitoring of benthic invertebrates (fish food organisms) at three sites is also recommended. Illegal Storm Drain Connection Survey. A combination of dye studies and video monitoring would be used to identify illegal connections to the storm sewer system. The video monitoring also could be used to assess drainage pipe failures/corrosion. Riverton Stormwater Quality Management Plan 1997 95035 / reports / basirpin (5/15/97) ss 55 REFERENCES PUBLISHED DOCUMENTS Herrera Environmental Consultants 1996 Fostoria Basin Stormwater Quality Management Plan. Prepared for City of Tukwila Public Works Department Jones and Stokes 1990 City of Tukwila Watercourse Rating Data Sheets. Prepared for the City of Tukwila. King County 1996 Draft King County Surface Water Design Manual. King County Department of Public Works 1992 King County Surface Water Management Design Manual. January 1990, revised November 1992. King County Green River Trail Master Plan. KCM 1992 City of Tukwila Southgate Creek Fish Enhancement Project, Preliminary Design Report. Prepared for the City of Tukwila Public Works Department. Perteet Engineering 1997 Draft Report for Southgate Creek By -Pass Study - Southgate Creek and Riverton Drainage Basins. Prepared for the City of Tukwila. Puget Sound Water Quality Authority 1986 Puget Sound Water Quality Management Plan. 1986, revised 1991. Tukwila, City Council 1995 City Council Recommended Draft Comprehensive Plan. August 1995. Tukwila, City of 1995 Riverton Stormwater Quality Management Plan. July 1995. 1995 Draft Tukwila Comprehensive Plan. Riverton Stormwater Quality Management Plan - 1997 57 95035 / reports / baslnpin (5/15/97) ss REFERENCES DRAFT 1993 Surface Water Management Comprehensive Plan. April 1993. 1991 Cascade View Annexation Priority Surface Water Management LIDs. Prepared by Kramer, Chin & Mayo, Inc., for City of Tukwila. April 25, 1991. 1986 Fostoria Basin Drainage Study. Prepared by Kramer, Chin & Mayo, Inc., for City of Tukwila. May 1986. Washington State Department of Ecology (Ecology) 1995 Best Management Practices (BMPs) for Management and Disposal of Street Wastes. 1992 Stormwater Management Manual for the Puget Sound Basin. Technical Manual #91-75. Washington State Department of Transportation (WSDOT) 1995 Highway Runoff Manual. M 31-16. PERSONAL COMMUNICATION Howat, John. City of Tukwila Maintenance Division. Telephone conversation with David Morency, Entranco. 1996. Olivas. Tukwila Fire Department. 1995. 58 Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basnpin (5/15/97) ss APPENDIX A RIVERTON CREEK WATER AND SEDIMENT QUALITY ASSESSMENT Water Quality Assessment Water quality data were collected at 10 sampling stations throughout the Riverton Creek Watershed (figure A-1) during three storm events (February through April) and one base -flow event (May). In addition, one sediment sample was collected from an in -stream pond near the mouth of the creek. All data are appended. High fecal coliform levels were observed throughout Riverton Creek during both storm and non -storm flow conditions. These levels were well above the state water quality standards for Class A waters, making the stream unsuitable for drinking water purposes or public recreation. The risk to public health is regarded as low to moderate since there is no known use of the creek for drinking water and limited use for recreation. However, issuance of a public health advisory is recommended. During storm flows, some metals occurred at concentrations that could represent acute or chronic toxicity to fish. However, high levels only occurred in about 13 percent of the samples taken during storm events and risk of adverse impact to fish is considered low to moderate due to the short duration of exposure. No toxic metals concentrations were measured during base -flow conditions. Under high-flow conditions, turbidity, total suspended solids (TSS), and total phosphorus values were within the range of values typically reported for urban stormwater runoff. High suspended solids concentrations mean that relatively high sedimentation rates are occurring in the Lower Reach of the creek. Sediment accumulation is suspected as a possible contributing factor to flooding at some locations in the watershed and has resulted in pipe clogging and stream channel filling in the lower portions of the drainage system. Eventually, sediment removal will be required with its potential adverse impacts to stream habitat. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basIrpin (5/15/97) ss A.1 Balvue Stormwater and.Combined =! 'Sewer Overflow. Pipe '1:. BASE SOURCE: ENTRANCO OStream Water Quality Sampling Station and Crest Stage Gage O Sediment Sampling Station ▪ Permanent Flow/Quality Monitoring Station QRoadway Runoff Water Quality Sampling Station - Flow Direction 11111111 Stream Reach without Habitat Survey Stream Reach with Habitat Survey Basin Boundary Culvert Building NOT TO SCALE TAYLOR ASSOCIATES Riverton Creek Habitat Survey Monitoring Station Locations Figure 2 March 1996 Turbidity, TSS, and total phosphorus levels were generally higher in the east tributary than elsewhere in the creek. This appears to be due to erosion in the densely developed upper east tributary subbasin (above State Route [SR] 99), where drainage ditches, gravel shoulders, and some unvegetated slopes are exposed to erosive forces during storm runoff events. In contrast, much of the upper west tributary subbasin is overgrown with dense forest and undergrowth vegetation, especially in the vicinity of the stream channel. Storm flow temperature, pH, and dissolved oxygen values were typical for the February—April period and were within state standards. However, relatively low dissolved oxygen concentrations (lowest = 8.3 mg/I) suggest high levels of biochemical oxygen demand (not measured). Base -flow data for May were very good, but not necessarily representative of worst-case base -flow conditions, which are more likely to occur in August or September. Sampling Program. Water quality data were collected at 10 sampling stations in the Riverton Creek watershed (figure A-1). Samples at Stations 1 through 8 were taken from the creek, while Stations 9 and 10 sampled runoff from SR 99 and SR 599, respectively. Samples were collected from all 10 stations during rainstorms on February 17-18, 1996, March 22, 1996, and April 22, 1996. One set of low -flow samples was collected from Stations 1 through 8 on June 6, 1996. Where appropriate, the water quality results presented below are compared against Class A standards (Ecology 1992). Fecal Coliform Results. Fecal coliforms levels were very high during storm sampling at all stations. Fecal coliform levels ranged from 68 to 11,000 organisms per 100 milliliters (ml) across all 10 stations. Lowest values were reported for Stations 9 and 10 at SR 99 and SR 599, respectively. This is probably because there are fewer sources of contamination for highway runoff than for streams. There was some indication of a declining downstream trend with values ranging from 620 to 2,800 organisms per 100 ml at the most downstream stations (Stations 7 and 8), and 11 out of 18 values (61 percent of all measurements) higher than 2,800 in the six upstream stations. The geometric mean for all stations for the three storms was 1,937, 802, and 2,294 organisms per 100 ml, respectively, for the February, March, and April storms. These values are considerably higher than the Class A 1 Fecal coliform organisms are normal inhabitants of the intestinal tracts of birds and mammals, but are not disease -causing organisms themselves. Therefore, they are used as indicators of the possible presence of such water -borne diseases as cholera, typhoid fever, bacterial dysentery, polio, and hepatitis (Hodges 1977). Riverton Stormwater Quality Management Plan - 1997 05035 / reports / basrpin (5/15/97) ss A.3 standard of 100 organisms per 100 ml. Also, 9 out of 10 samples (90 percent of all samples) exceeded 200 organisms per 100 ml during each storm. These results also greatly exceed the standard of no more than 10 percent of samples to exceed 200 organisms per 100 ml. Although some of the individual measurements in Riverton Creek exceeded those reported for neighboring Southgate Creek (Herrera Environmental Consultants, Inc. 1996), the geometric mean at Southgate Creek was slightly higher than the highest geometric mean in Riverton Creek. Results reported for five stations at Southgate Creek, measured during a single storm event on March 8, 1995, ranged from 1,800 to 3,000 organisms per 100 ml, while 10 of the 24 Riverton Creek measurements were higher than the maximum value (3,000) at Southgate Creek. Nevertheless, the geometric mean at Southgate Creek was 2,321, and slightly higher than the highest geometric mean for Riverton Creek (2,294). During low -flow conditions, fecal coliform ranged from 160 to 3,400 organisms per 100 ml, with 88 percent of samples exceeding 200 organisms per 100 ml (under state standard no more than 10 percent can exceed 200 organisms per 100 ml). The geometric mean for the low -flow samples was 760, nearly as high as one of the storm data sets, and well above the state water quality standard of 100 organisms per 100 ml. Under existing conditions, it would neither be safe to drink the water from Riverton Creek, nor for children to play in it due to the risk of infection from water -borne disease during storm flows and for safety reasons. Possible sources of fecal coliform contamination in Riverton Creek include failing septic drainfields, domestic animals (cats, dogs, geese, etc.), and wild birds and animals. Metals Results. Concentrations of cadmium, copper, lead, and mercury were measured during the storm sampling program. Out of 120 total measurements there were 8 samples that exceeded the acute standard and an additional 8 samples that exceeded the chronic standard1 . Therefore, standards were exceeded in only 13 percent of the samples. Out of the 16 standard violations, 10 were measured in runoff from SR 99 or SR 599. There are acute and chronic standards for metals and these are established primarily to protect fish life. The acute concentration is higher than the chronic concentration and cannot be tolerated for very long before death occurs. The chronic concentration may be tolerated for relatively long periods of time without mortality, but chronic concentrations may cause impaired health, increased susceptibility to predation and/or reduced reproductive success. Because the toxicity of metals is lower with increasing water hardness, toxicity must be calculated for each measurement based on hardness. This is why there is no single number standard. Reference to exceedances in this text indicate that the acute or chronic level was exceeded without reference to frequency of occurrence criteria, since it would take many more samples to establish whether or not the frequency of occurrence criteria are violated. For example, the chronic criteria for metals is based on "a 4 -day average concentration not to be exceeded more than once every three years on the average." (WAC 173- 201A 1992 Water Quality Standards for Surface Waters of the State of Washington) Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basinpin (5/15/97) ss Standards violations were more common in highway runoff primarily because of lower hardness in runoff samples compared to stream samples. Dilution may also play a role in reducing the concentrations in the creek. Creek violations occurred at Stations 1, 4, 5, 6, and 8, with no apparent upstream or downstream trends. There were only two acute standard violations in Riverton Creek and those were both for copper; all other creek violations were at chronic levels. Copper was the metal most frequently above standard, accounting for 10 of the 16 violations. Lead concentrations exceeded standard three times, mercury two times, and cadmium only once. Copper levels were higher than in neighboring Southgate Creek, with peak values in Southgate Creek of 3.7 p.g/I (Herrera Environmental Consultants, Inc. 1996) and peak values in Riverton Creek of 11.5 µg/I. High metals concentrations in urban runoff are typically due to the normal wear of metal parts of motorized vehicles. However, some contamination may be due to illegal dumping of waste materials containing metals (e.g., batteries, copper wire, etc.). Concentrations of cadmium, lead, and mercury were all below the limit of detection during base -flow conditions. Copper was the only metal above the limit of detection during base -flow conditions, ranging in concentration from less than 1.0 to 2.1 141. These concentrations would not be toxic to fish under base -flow conditions, because of higher water hardness (118 to 135 mg CaCO3/I). Turbidity and Total Suspended Solids. Turbidity and TSS were relatively high, especially in the east tributary of Riverton Creek. Average turbidity was 47 NTUs (nephelometric turbidity units1 ) in the east tributary compared to 11 NTUs in the remainder of the creek. A similar pattern was observed in TSS concentrations with an average TSS of 97 mg/I in the east tributary compared to 43 mg/I for the rest of the stream. In general, there was a trend of declining turbidity and TSS toward the downstream segments of the stream. This may be due to reduced pollutant loading rates for downstream land uses compared to upstream land uses (Stahre and Urbonas [1990] report higher TSS levels for residential land uses compared to commercial land uses). It may also reflect the higher erosion potential of steeper terrain in the upper watershed, and dropping out of sediment in the upper end of low velocity reaches on the valley floor. 1 Turbidity is a measure of the cloudiness of the water, as measured by the ability of the sample to scatter light in NTUs. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basinOn (5/15/97) ss A.5 Based on field reconnaissance and aerial photo interpretation, it appears that higher concentrations in the upper east tributary (above SR 99) are due to more intense land use. The upper east tributary is almost entirely occupied with dense residential development, while the upper west tributary has an estimated 50 acres of undeveloped forest lands. In the upper east tributary, we observed various drainage ditch and roadway shoulder and side slope conditions that could contribute to erosion and in - stream turbidity/TSS problems during storm runoff events. In contrast, the densely vegetated forested lands adjacent to the upper west tributary are providing effective slope stability, stream channel stability, and erosion control under present conditions. Total suspended solids concentrations under storm runoff conditions were similar to those found in urban stormwater runoff. For example, Stahre and Urbonas (1990) reported median TSS concentrations of 67 and 101 mg/I for mixed and residential land uses, respectively. Total suspended solids concentrations were very high for SR 99 during the March and April storms at 464 and 489 mg/I, respectively. However, turbidity was relatively low during all three storms ranging from 12-21. Both turbidity and TSS were low on SR 599, with turbidity ranging from 6- 14, and TSS ranging from 9-27 mg/I. High rates of sedimentation are a drainage maintenance problem in the creek. Sediment accumulation is suspected of contributing to flooding at the east tributary culvert crossing under South 126th Street and in the vicinity of the South 130th Street/35th Avenue South intersection. In addition, sediment accumulation at the twin 36 -inch culvert crossing under SR 599 has occupied approximately 75 percent of pipe volume and is a concern with respect to future flooding potential at this location. Sedimentation may have had an historical impact on fish spawning habitat in the Lower Reach of the creek by covering over and in -filling natural gravel spawning beds. However, no sediment coring studies have been performed to determine whether gravel stream bed conditions existed in the lower stream reaches under pre -development conditions. Since existing stream substrates are composed primarily of sands, silts, and clays in the lower stream reaches under existing conditions, there is no concern about future adverse impacts to future spawning habitat. However, high rates of future sedimentation could be detrimental to aquatic life in the lower stream reaches if the rates are so high as to cover over bottom - dwelling organisms that serve as a food supply for fish. In view of the degree of sediment accumulation in the downstream reaches of both east and west tributaries, as well as the mainstream downstream of the confluence of the two forks, it is evident that future sediment removal operations, which will be necessary to maintain pipe and channel Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basinpin (5/15/97) ss capacities during flood conditions, will have an adverse impact on fish habitat unless carefully timed, executed, and mitigated. Under low -flow conditions turbidity and TSS levels were substantially lower than during storm conditions, with turbidity measurements ranging from 1.1 to 1.8 NTU, and TSS measurements ranging from 1.7 to 10 mg/I. These measurements compare with the in -stream storm flow turbidity and TSS ranges of 3 to 55 NTU and 18 to 216 mg/I, respectively. Total Phosphorus and Ammonia. Total phosphorus (TP) concentrations were relatively high with concentrations in the range typically found in urban stormwater runoff. The TP concentrations might be high enough to produce undesirable algal growth during summer months, especially in the pond near the mouth of the creek. In contrast, ammonia concentrations were relatively low; at the levels observed, ammonia concentrations would not be toxic to fish. Both parameters showed a pattern similar to turbidity and TSS, with high concentrations in the east tributary, and lower concentrations in the rest of the stream. Average TP and ammonia concentrations were 242 and 86 µg/I, respectively, in the east tributary, and only 118 and 42 µg/I, respectively, in the remainder of the stream. For comparison, median stormwater TP concentrations for residential and mixed land uses, respectively, are reported at 383 and 263 µg/1 (Stahre and Urbonas 1990). Total phosphorus concentrations in SR 599 runoff were relatively low, ranging from 24 to 86 µg/I, and ammonia concentrations were similar to those found in Riverton Creek, and ranging from 44 to 59 µg/I. The TP values in the SR 99 runoff were higher and more typical of runoff concentrations, ranging from 107 to 377 µg/I, while ammonia levels ranged from 70 to 271 µg/I. In -stream base -flow concentrations of TP and ammonia ranged from 35 to 105 µg/1 and 18 to 84 µg/I, respectively. Temperature, pH, and Dissolved Oxygen. During storm flow conditions, temperatures ranged from 8 to 12 degrees C and were well below the maximum of 18 degrees C, as expected for this time of year. The pH values ranged from 6.7 to 7.8 and were also within the standard range of 6.5 to 8.5. Dissolved oxygen values ranged from 8.3 to 11.5 mg/I and were also above the 8.0 mg/I minimum specified by the state standard. The low value of 8.3 is quite low for this time of year and suggests the influence of high levels of chemical and/or biochemical oxygen demand. There was a tendency for dissolved oxygen concentrations to decrease in a downstream direction. This may be due to steeper slopes and more turbulence in the upper watershed compared to the lower watershed. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basirpin (5/15/97) ss A.7 During the base -flow sampling in May, temperature and dissolved oxygen measurements ranged from 14.0 to 15.6 degrees C, and 9.4 to 11.1 mg/I, respectively. The pH measurements ranged from 7.4 to 7.9. All these measurements are well within state water quality standards. However, they may not reflect worst-case conditions, which are likely to occur in August or September. Oil and Grease Results. Oil and grease concentrations ranged from <0.25 mg/I (limit of detection) to a high of 1.7 mg/I in the various stream stations and in runoff from SR 599. The only station with high concentrations was SR 99 where oil and grease ranged from 2.3 to 13.2 mg/I. Concentrations are high enough to warrant spill control (SC) type oil/water separators in the SR 99 drainage system. In view of the potential for adverse impacts to Riverton Creek in the event of an accidental fuel, oil, or hazardous chemical spill on SR 99, additional mitigation may be warranted. In -stream low -flow oil and grease concentrations were below the limit of detection. Sediment Quality Assessment A sediment sample was collected near the mouth of Riverton Creek and tested for EPA priority pollutants (13 metals and 179 organic compounds). All 13 metals were found to be above the limit of detection, but only 11 organic compounds were above the limit of detection. All sediment concentrations were below the Marine Sediment Standards and were not considered a threat to aquatic life. Sediment sampling is often conducted because contaminants that might be discharged into the water for a relatively short period of time (like an accidental spill for example) might be missed by water grab sampling techniques if the time of sampling does not coincide with the time of the spill. However, evidence of a spill could show up in sediment sampling if it was missed in water sampling efforts. Therefore, sediment sampling may give a better indication of the recent history (1-5 years or more depending on the rate of sediment deposition) of stream contamination when compared to the "snapshot" picture provided by water grab sampling. Sampling Program. A single grab sample was collected from an in -stream pond near the mouth of Riverton Creek using a stainless steel, 6 -inch, petite ponar sediment sampler. Sampling was performed on March 13, 1996. Sediments were placed in containers and transported to the laboratory. Metals analyses were performed by Aquatic Resources, Inc. of Seattle. Organic chemistry testing was performed by Sound Analytical. A.8 Riverton Stormwater Quality Management Plan - 1997 95035 / reports / badnpin (5/15/97) ss Sediment Metals Results. The single sediment sample was 34 percent solids and was a fine-grained material, with silts and clays comprising over 90 percent of the sample by weight. Riverton Creek sediment metals concentrations are presented in table A-1 along with corresponding Marine Sediment Standards (WAC 173-204)1 . Marine Sediment Quality Standards (MSQS) do not legally apply to freshwater sediments but are the best "ruler" against which freshwater sediment concentrations can be compared at this time. As indicated in table A-1, all sediment metals concentrations in Riverton Creek are below the corresponding MSQS. Based on these results, we conclude that there has been no major metals discharges from any use in the watershed in recent years. However, these results do not negate the significance of water quality test results, which show periodic standards violations for some metals. Organic Chemicals. Three major groups of organic chemicals were tested: (1) organochlorine pesticides; (2) semivolatile organics; and (3) volatile organics2 . Out of a total of 179 chemicals tested, all were below the detection limit except for 9 semivolatile organics and 2 volatile organics. The majority of detected organics are classified as polycyclic aromatic hydrocarbons (PAHs), which are derived from petroleum products, incomplete combustion of petroleum products, and asphalt. No organochlorine pesticides were detected. Organic compounds detected in the sediment are shown in table A-2 in comparison with MSQS. Results indicate that those compounds detected were well below standard. Therefore, we have concluded that organic chemicals in Riverton Creek sediments are not likely to have an adverse impact on aquatic life. 1 Marine sediment quality standards are used for comparative purposes, since there are no freshwater sediment standards at this time. 2 Volatile compounds vaporize or evaporate quickly. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / baslnpin (5/15/97) ss A.9 Table A-1 Riverton Creek Sediment Metals Data Compared to the Marine Sediment Standards (all values reported as mg/kg dry weight). Sediment Metal Riverton Creek Sediment Marine Sediment Standards.' Antimony Arsenic Beryllium Cadmium Chromium Copper Lead Mercury Nickel Selenium Silver Thallium Zinc <2.5 10.7 0.6 2.2 40.7 66.1 91.4 0.2 36.3 <2.5 <1.0 <1.0 378 NS 57 NS 5.1 260 390 450 0.41 NS NS 6.1 NS 410 1. Marine sediment quality standards are used for comparative purposes, since there are no freshwater sediment standards at this time. NS = No Standard. Marine Sediment Standards have no criteria set for these metals. Table A-2 Riverton Creek Sediment Organic Chemical Data Compared to Marine Sediment Standards (all values expressed as mg/kg dry weight). Sediment Organic Riverton Creek Sediment Marine Sediment Standards.' High Molecular Weight Polycyclic Aromatic Hydrocarbons (HPAHs) Benzo(a)anthracene 0.5 110 Benzo(a)pyrene 0.5 99 Benzo(b)fluoranthene 0.8 230 Chrysene 0.5 110 Fluoranthene 1.1 160 Pyrene 1.0 1,000 Indeno(1,2,3-cd)pyrene 0.4 34 Miscellaneous Organic Chemicals Acetone 0.2 NS Benzoic Acid 0.9 650 bis(2-Ethyl hexyl)Phthalate 2.5 47 Toluene Trace NS 1. Marine sediment quality standards are used for comparative purposes, since there are no freshwater sediment standards at this time. NS = No Standard. Marine Sediment Standards have no criteria set for these chemicals. A.10 Riverton Stormwater Quality Management Plan - 1997 95035 / reports / basinpin (5/15/97) ss Annual Loading Estimates for Selected Parameters. Coordination with Ecology (S. Butkus and K. Fitzpatrick, personal communication) indicates that the majority of state standards violations in the lower Duwamish River are related to violations of Marine Sediment Quality Standards. Since sediment testing near the mouth of Riverton Creek showed no exceedances of the Marine Sediment Quality Standards, it has been concluded that there is no need to apply any loading restrictions to Riverton Creek in connection with TMDL (total maximum daily load) planning efforts.1 Water quality violations in the lower Duwamish River have occurred for temperature, dissolved oxygen, pH, fecal coliform, and ammonia. From the data collected and presented in this report, it has been concluded that Riverton Creek is an unlikely contributor to temperature, pH, or ammonia standards violations in the Duwamish River. Therefore, loading calculations have not been performed. However, it seems that Riverton Creek may contribute to standards violations of dissolved oxygen and fecal coliform bacteria in the Duwamish River, depending on the proximity of the mouth of the creek to the ambient monitoring stations where past violations have occurred. Therefore, loading calculations for biochemical oxygen demand (BOD) and fecal coliform bacteria may be useful in Ecology's TMDL assessment. The annual load for Riverton Creek fecal coliform bacteria is estimated at 113 billion organisms. A load calculation for BOD is not possible since BOD was not collected under the monitoring program. Other parameters of possible interest to Ecology are total nitrogen and metals. It is not possible to calculate a load for total nitrogen because TKN (total Kjeldahl nitrogen) was not measured under the monitoring plan. From the metals data collected, it is only possible to calculate load estimates for mercury since this is the only metal for which total metals concentrations were obtained. Only dissolved concentrations of copper, cadmium, and lead were measured, for comparison with state water quality standards, so it is not possible to calculate a total annual load for these metals. In future stream monitoring efforts, the City of Tukwila may want to include TKN, BOD, and total metals measurements for a better assessment of TMDL significance. 1 TMDL is a water quality control approach which involves quantification of watershed -wide pollutant loading rates (in pounds or kilograms per year) for parameters that have exceeded water quality standards and then establishes loading goals for both point and nonpoint sources of pollution. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / baJrpin (5/15/97) ss A.11 References Ecology 1992 Water Quality Standards for Surface Waters of the State of Washington. WAC 173-201A. Herrera 1996 Fostoria Basin Stormwater Quality Management Plans. Prepared for City of Tukwila Department of Public Works. Hodges, L. 1977 Environmental Pollution. Holt, Rinehart and Winston. Second edition. Stahre, P. and B. Urbonas 1990 Stormwater Detention for Drainage, Water Quality, and CSO Management. Prentice Hall. Personal Communications Butkus, Steve and Kevin Fitzpatrick. Ecology - Olympia and Bellevue, respectively. 303d fax transmittals of parameters exceeding water or sediment quality standards and phone conversations with David Morency, Entranco, relating to the 303d list and total maximum daily load analysis. June 1996. A.12 Riverton Stormwater Quality Management Plan - 1997 95035 / reports / badnpin (5/15/97) ss APPENDIX A RIVERTON CREEK STORM AND BASE FLOW WATER QUALITY DATA 9 TAYLOR ASSOCIATES 722 North 102nd Street Seattle, Washington 98133 (206) 781-3490 ENTRANCO JUN 2 8 1996 TO: DAVID MORENCY, ENTRANCO ENGINEERS RECEIVED FROM: WENDALL WILLEY DATE: JUNE 21, 1996 SUBJECT: FIELD MEASUREMENTS COLLECTED DURING BASE -FLOW SAMPLING ON RIVERTON CREEK Dear Dave, Please find below a summary table of field data collected during our base flow sampling of Riverton Creek on June 6, 1996. Field measurements were collected at Stations 1 through 8 concurrently with water quality sampling. Water samples collected at Stations 1 through 8 were immediately delivered to Aquatic Research Inc. for subsequent analysis. Flow rates (where applicable) were measured using a Swoffer propeller velocity meter and topset rod. Conductivity, Temperature, and Dissolved Oxygen were measured using a Corning Inc. Checkmate hand held field meter which was calibrated according to the manufactures specifications prior to sample measurements. Table 1. Summary of Field Measurement Results forRiverton Creek Stations 1- You should be receiving laboratory results for this base -flow sampling event shortly. If you have any questions or need any further information, please feel free to call me at 814-4536 or Bill Taylor at 781-3490. Sincerely, do g Wendall S. Willey Taylor Associates Cnn.vultiu,t; in the C'c rini and Freshwater .Se/C/! e Field Measurements Station # Time Collected I Flow Rate (cfs) Stage (ft) Temp. (C) Conductivity (micro-seimens) Dissolved Oxygen m 1 13:00 -- -- 15.6 228 9.4 2 13:30 -- -- 14.6 282 10.6 3 13:45 0.55 0.3 14.0 298 11.1 4 14:00 0.33 0.35 15.5 290 9.7 5 16:00 0.33 63.05 15.3 291 9.9 6 14:45 0.79 38.55 14.7 294 10.3 7 15:30 1.13 72.70 15.5 284 10.3 8 15:00 1.44 46.40 15.3 285 9.7 You should be receiving laboratory results for this base -flow sampling event shortly. If you have any questions or need any further information, please feel free to call me at 814-4536 or Bill Taylor at 781-3490. Sincerely, do g Wendall S. Willey Taylor Associates Cnn.vultiu,t; in the C'c rini and Freshwater .Se/C/! e AQUATIC RESEARCH INCORPORATED LABORATORY & CONSULTING SERVICES 3927 AURORA AVENUE NORTH, SEATTLE, WA 98103 PHONE: (206) 632-2715 FAX: (206) 632-2417 EN00906: En0296 CASE FILE NUMBER: EN009-06 REPORT DATE: 07/02/96 PAGE 1 DATE SAMPLED: 06/06/96 DATE RECEIVED: 06/06/96 FINAL REPORT, LABORATORY ANALYSIS OF SELECTED PARAMETERS ON WATER SAMPLES FROMENTRANCO / RIVERTON CREEK CASE NARRATIVE Eight water samples were delivered to the laboratory in good condition. The samples were analyzed according to the chain of custody. No difficulties were encountered in the preparation or analysis of these samples. Sample data follows while QA/QC data is ccntained on subsequent pages. SAMPLE DATA TURBIDITY TSS TPH FOG FECALS TOTAL -P AMMONIA SAMPLE ID (NTU) (mg/1) (mg/1) (mg/1) (#/100m1) (mg/1) (mg/1) STATION 1 1.5 3.7 <0.25 <0.25 420 0.105 0.023 STATION 2 1.5 10 <0.25 <0.25 est 160 0.035 0.018 STATION 3 1.6 8.1 <0.25 <0.25 440 0.048 0.023 STATION 4 1.8 4.0 <0.25 <0.25 640 0.065 0.050 STATION 5 1.6 1.7 <0.25 <0.25 est 400 0.068 0.073 STATION 6 1.1 4.9 <0.25 <0.25 est 3400 0.104 0.023 STATION 7 1.7 3.9 <0.25 <0.25 est 1800 0.092 0.084 STATION 8 1.8 2.4 <0.25 <0.25 est 2400 0.090 0.067 WATER DATA DISSOLVED METALS TOTAL HARDNESS CADMIUM COPPER LEAD MERCURY pH SAMPLE ID (mgCaCO3/1 (mg/1) (mg/1) (mg/1) (mg/1) STATION 1 135 <0.0002 0.0020 <0.0010 <0.00010 7.46 STATION 2 120 <0.0002 0.0016 <0.0010 <0.00010 7.55 STATION 3 131 <0.0002 0.0015 <0.0010 <0.00010 7.82 STATION 4 130 <0.0002 0.0021 <0.0010 <0.00010 7.87 STATION 5 121 <0.0002 0.0015 <0.0010 <0.00010 7.78 STATION 6 118 <0.0002 <0.0010 <0.0010 <0.00010 7.71 STATION 7 132 <0.0002 0.0015 <0.0010 <0.00010 7.52 STATION 8 126 <0.0002 0.0014 <0.0010 <0.00010 7.45 Cnrsultin, in t/ie Cristal incl Frrslnrutrr Scan(c c Date: Rainfall Total Riverton Creek Stormwater Sampling Sample Event Number 1 February 17, 1996 for Storm Event 0.56 inches Sampling Location * Time Sample Collected Sample Type Discharge (cfs) ** Field Measurements Dissolved Oxygen (mg/L) Temperature (C) Conductivity (micro -semens Station 1 Station 2 Station 3 Station 4 Station 5 Station 6 Station 7 Station 8 Highway 599 Highway 99 15:40 16:00 05:39 - 04:39 16:30 17:50 16:45 17:30 17:00 17:45 17:20 Grab Grab Composite Grab Grab Grab Grab Grab Grab Grab 2.23 1.30 1.78 3.35 10.32 9.74 10.1 9.8 10.3 9.8 9.7 10.2 10 9.7 10 11.5 113 181 223 143 145 210 148 162 122 35 10.1 10.1 10.2 9.9 9.3 9.2 8.3 8.4 8.4 9.6 * See attached site schematic for station locations ** Discharge not calculated for Stations 1, 2, Hwy 599 and Hwy 99. Discharge for Stations 3 and 4 recorded from Marsh-McBirney flow meters. All other Station Discharge estimates calculated from site specific stage discharge equations. Riverton Creek Stormwater Sampling Storm Event #1 Hourly Rainfall Totals 0.1 0.08 a) o 0.06 c co c 0.04 .(0 0.02 0 1 1 00:30 Period of Grab Sample Collection 111111111 I 1 I 04:30 08:30 12:30 16:30 Date and Time I'1 SII 1 1 t 20:30 00:30 Rainfall Data recorded by ISCO, Inc. Model 674L tipping -bucket rain gauge located at SeaTac Airport. TAYLOR ASSOCIATES Riverton Creek Stormwater Sampling Sample Event Number 2 Date: March 22, 1996 Rainfall Total for Storm Event 0.22 inches Field Measurements Sampling Location * Time Sample Collected Sample Type Discharge (cfs) ** Temperature (C) Conductivity (micro -semens Dissolved Oxygen (mg/L) Station 1 Station 2 Station 3 Station 4 Station 5 Station 6 Station 7 Station 8 Highway 599 Highway 99 07:50 08:15 07:45 - 13:30 08:45 10:30 09:25 10:00 09:45 10:45 11:30 Grab Grab Composite Grab Grab Grab Grab Grab Grab Grab 1.66 1.13 1.08 3.12 5.69 8.30 8.6 8.9 8.6 8.6 9 9 8.9 9.2 8.7 10.2 174 246 271 192 169 205 160 165 137 19.7 10.5 10.6 10.6 10.2 9.9 9.9 9.2 9 10.2 10.3 * See attached site schematic for station locations ** Discharge not calculated for Stations 1, 2, Hwy 599 and Hwy 99. Discharge for Stations 3 and 4 recorded from Marsh-McBirney flow meters. All other Station Discharge estimates calculated from site specific stage discharge equations. Riverton Creek Stormwater Sampling Storm Event #2 Hourly Rainfall Totals 0.05 0.04 IsT 00.03 c c 0.02 •cu 0.01 Period of Grab S 0 I I I I•I•I•I•I 00:00 ample Collection 11 , 04:00 08:00 12:00 Date and Time 16:00 20:00 1 1 1 00:00 Rainfall Data recorded by ISCO, Inc. Model 674L tipping -bucket rain gauge located at SeaTac Airport TAYLOR ASSOCIATES Riverton Creek Stormwater Sampling Sample Event Number 3 Date: April 22, 1996 Rainfall Total for Storm Event 2.54 inches Field Measurements Sampling Location * Time Sample Collected Sample Type Discharge (cfs)** Temperature (C) Conductivity (micro -semens) Dissolved Oxygen (mg/L) Station 1 12:45 Grab 12.4 91.3 11.2 Station 2 13:15 Grab 11.4 204 10.9 Station 3 10:00 - 09:00 Composite 1.90 10.7 244 11.5 Station 4 13:45 Grab 2.51 12 144 11 Station 5 14:55 Grab 4.50 12.6 107 11 Station 6 14:00 Grab 4.03 11.8 177 9.9 Station 7 14:35 Grab 8.14 12.4 124 9.8 Station 8 14:20 Grab 9.18 12.3 147 9.5 Highway 599 15:15 Grab 12.1 93.7 9.7 Highway 99 13:55 Grab 13.6 11.25 10.3 * See attached site schematic for station locations ** Discharge not calculated for Stations 1, 2, Hwy 599 and Hwy 99. Discharge for Stations 3 and 4 recorded from Marsh-McBirney flow meters. All other Station Discharge estimates calculated from site specific stage discharge equations. Riverton Creek Stormwater Sampling Storm Event #3 Hourly Rainfall Totals 0.20 0.05 Period of Grab Sample Collection 0.00 lillll111llflli1111fl11ll11111ll1111 08:00 12:00 16:00 20:00 00:00 04:00 08:00 12:00 16:00 Date and Time 419 Rainfall Data recorded by ISCO, Inc. Model 674L tipping -bucket rain gauge located at SeaTac Airport TAYLOR ASSOCIATES AQUATIC RESEARCH INCORPORATED LABORATORY & CONSULTING SERVICES 3927 AURORA AVENUE NORTH, SEATTLE, WA 98103 PHONE: (206) 632-2715 FAX: (206) 632-2417 EN00901:EN0296.XLS CASE FILE NUMBER: EN009-01 REPORT DATE: 03/08/96 PAGE 1 DATE SAMPLED: 02/17,18/96 DATE RECEIVED: 02/19/96 FINAL REPORT, LABORATORY ANALYSIS OF SELECTED PARAMETERS ON WATER SAMPLES FROM ENTRANCO / RIVERTON CREEK CASE NARRATIVE Ten water samples were delivered to the laboratory in good condition. The samples were composited and analyzed according to the chain of custody. No clifficultias were encountered in the preparation or:utalysis of these samples. Sample data follows while QA/QC data is contained on subsequent pages, SAMPLE DATA TURBIDITY TSS TPH FOG FECALS TOTAL -P AMMONIA SAMPLE ID (NTU) (mg/1) (mg/1) (mg/1) 0/100ml) (mg/1) (mg/1) HWY 99 12 22 2.3 2.5 68 0.127 0.271 HWY 599 7.0 8.2 <0.25 0.26 420 0.036 0.059 STATION 1 55 78 0.38 0.38 4200 0.210 0.074 STATION 2 22 47 <0.25 <0.25 10800 0.110 0.056 STATION 3 6.0 19 <0.25 <0.25 est 240 0.077 0.020 STATION 4 50 66 <0.25 <0.25 7800 0.208 0.091 STATION 5 38 45 <0.25 0.29 7600 0.154 0.095 STATION 6 15 33 <0.25 <0.25 7200 0.113 0.052 STATION 7 25 27 x.25 0.28 est 2000 0.115 0.057 STATION 8 23 27 0.28 0.34 est 2800 0.112 0.078 WATER DATA DISSOLVED METALS /1.F1 HARDNESS CADMIUM SAMPLE ID (mgCaCO3/1) (mg/l) =',lie COPPER LEAD MERCURY (mg/1) (mg/1) (mg/1) HWY 99 16.0 _+ 0.0005. 0.0171 <0.0010 <0.00010 I WY 599 45.5 <0.0002 0.0103 4 0.0027 <0.00010 STATION 1 51.9 <0.0002 0.0078 <0.0010 <0.00010 STATION 2 81.4 <0.0002 0.0024 <0.0010 <0.00010 STATION 3 102 <0.0002 0.0077 <0.0010 <0.00010 STATION 4 61.0 <0.0002 0.0115 <0.0010 <0.00010 STATION 5 60.2 <0.0002 0.0045 <0.0010 <0.00010 STATION 6 87.3 <0.0002 0.0023 <0.0010 <0.00010 STATION 7 76.8 <0.0002 0.0033 <0.0010 <0.00010 STATION 8 71.7 <0.0002 0.0056 <0.0010 <0.00010 r G z .Edi AQUATIC RESEARCH INCORPORATED LABORATORY & CONSULTING SERVICES 3927 AURORA AVENUE NORTH, SEATTLE, WA 98103 PHONE: (206) 632-2715 FAX: (206) 632-2417 EN00903:EN0296.XLS CASE FILE NUMBER: EN009-03 REPORT DATE: 04/16/96 PAGE 1 DATE SAMPLED: 03/22/96 DATE RECEIVED: 03/22/96 FINAL REPORT, LABORATORY ANALYSIS OF SELECTED PARAMETERS ON WATER SAMPLES FROMENTRANCO / RIVERTON CREEK CASE NARRATIVE Ten water samples were delivered to the laboratory in good condition. The samples were composited and analyzed according to the chain of custody. No difficulties were encountered in the preparation or analysis of these samples. Sample data follows while QA/QC data is contained on subsequent pages. SAMPLE DATA TURBIDITY TSS TPH FOG FECALS TOTAL -P AMMONIA SAMPLED) (NTIJ) (mg/1) (mg/1) (mg/1) (#/100m1) (mp./1) (mg/1) STATION 1 67 216 1.0 1.0 7200 0.441 0.059 STATION 2 6.1 19 <0.25 <0.25 560 0.047 0.023 STATION 3 3.1 23 <0.25 <0.25 est 100 0.035 0.029 STATION 4 50 74 0.33 0.32 est 2600 0.216 0.054 STATION 5 37 46 0.27 0.29 est 3000 0.130 0.064 STATION 6 5.8 18 <0.25 <0.25 1180 0.077 0.031 STATION 7 19 28 0.32 0.33 620 0.099 0.063 STATION 8 17 26 0.27 0.28 920 0.082 0.084 HWY 99 18 464 9.8 9.7 est 260 0.107 0.179 HWY 599 5.5 8.7 <0.25 <0.25 est 200 0.024 0.044 WATER DATA DISSOLVED METALS b2 HARDNESS CADMIUM COPPER LEAD MERCURY SAMPLE ID (mgCaCO3/1) (mg/1) (mg/1) (mg/1) (mg/1) pH STATION 1 71.5 <0.0002 0.0029 <0.0010 <0.00010 7.53 STATION 2 107 <0.0002 0.0019 <0.0010 <0.00010 7.69 STATION 3 122 <0.0002 0.0053 <0.0010 <0.00010 7.39 STATION 4 85.1 <0.0002 0.0044 <0.0010 <0.00010 7.48 STATION 5 81.1 <0.0002 0.0092 <0.0010 0.00010 7.62 STATION 6 99.9 <0.0002 0.0020 <0.0010 0.00018 7.81 STATION 7 68.6 <0.0002 0.0043 <0.0010 <0.00010 7.28 STATION 8 74.3 <0.0002 0.0030 <0.0010 <0.00010 7.36 HWY 99 10.5 <0.0002 0.0072 0.0010 <0.00010 7.12 HWY 599 51.9 <0.0002 0.0138 0.0046 <0.00010 6.81 ! AQUATIC RESEARCH INCORPORATED LABORATORY & CONSULTING SERVICES 3927 AURORA AVENUE NORTH, SEATTLE, WA 98103 PHONE: (206) 632-2715 FAX: (206) 632-2417 EN00905:En0296 CASE FILE NUMBER: EN009-05 REPORT DATE: 05/20/96 PAGE 1 DATE SAMPLED: 04/22/96 DATE RECEIVED: 04/23/96 FINAL REPORT, LABORATORY ANALYSIS OF SELECTED PARAMETERS ON WATER SAMPLES FROMENTRANCO / RIVERTON CREEK CASE NARRATIVE Ten water samples were delivered to the laboratory in good condition. The samples were analyzed according to the chain of custody. No difficulties were encountered in the preparation or analysis of these samples. Sample data follows while QA/QC data is contained on subsequent pages. SAMPLE DATA TURBIDITY TSS TPH FOG FECALS TOTAL -P AMMONIA SAMPLE ID (NTU) (mg/1) (mg/1) (mg/1) (#/100m1) (mg/1) (mg/1) STATION 1 32 139 1.6 1.7 8800 0.315 0.036 STATION 2 29 75 0.27 0.29 est 2800 0.207 0.016 STATION 3 25 120 <0.25 <0.25 4600 0.174 <0.010 STATION 4 52 109 0.41 0.42 est 8000 0.315 0.081 STATION 5 46 97 0.52 0.53 est 11000 0.271 0.027 STATION 6 17 95 0.61 0.65 600 0.160 0.024 STATION 7 21 43 0.30 0.32 est 2800 0.183 0.045 STATION 8 27 48 0.38 0.40 est 1800 0.179 0.050 HWY 99 21 489 9.4 13.2 est 100 0.377 0.070 HWY 599 14 19 <0.25 <0.25 1340 0.086 0.044 WATER DATA DISSOLVED METALS HARDNESS CADMIUM COPPER LEAD MERCURY pH SAMPLE ID SmgCaCO3/1 (mg/11 (mg/1) (mg/1) (mg/1) STATION 1 40.6 <0.0002 :00087' <0.0010 <0.00010 7.07 STATION 2 91.6 <0.0002 0.0046 <0.0010 <0.00010 7.09 STATION 3 80.1 <0.0002 0.0053 <0.0010 <0.00010 6.76 STATION 4 63.6 <0.0002 0.0052 <0.0010 <0.00010 6.92 STATION 5 44.9 <0.0002 0.0058 <0.0010 <0.00010 6.99 STATION 6 66.3 <0.0002 0.0053 <0.0010 <0.00010 6.96 STATION 7 59.1 <0.0002 0.0055 0.0010 <0.00010 6.99 STATION 8 65.9 <0.0002 0.0083 <0.0010 <0.00010 6.95 HWY 99 20.8 <0.0002 10:0061,"~, <0.0010 <0.00010 7.39 HWY 599 40.6 <0.0002 •0:0141,,. 0.0051 <0.00010 6.97 Hca( � �Gvr-viti•-+-rte.. APPENDIX B RIVERTON CREEK SEDIMENT QUALITY DATA 10 article AQUATIC RESEARCH INCORPORATED CASE FILE NUMBER: EN009-04 REPORT DATE: 05/22/96 PAGE 1 DATE SAMPLED: 04/19/96 DATE RECEIVED: 04/19/96 LABORATORY ANALYSIS OF GRAIN SIZE ON SEDIMENTS FROM ENTRANCO ENGINEERING PERCENT FINER BY WEIGHT 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 0.001 1 U.S. STANDARD SIEVE SIZE G O `2. N 9 d' ru a fa Lu It W W 0.01 0.1GRAIN SIZE id MILLIMETERS 10 r -43- SED. POND —I— SED. POND DUP 100 1000 SILT OR CLAY SAND FINE MEDIUM COARSE GRAVEL FINE COARSE COBBLES SAMPLE IL) IJESCRUP 1 ION JLiJ. 1 VINL 'Stu. FUIN J uur 1VLU 1J MUL u u U 0 u 0 Laboratory Director AQUATIC RESEARCH, INC. 3927 AURORA AVENUE, N. SEATTLE. WA 98103 (206)632-2715 EN009-02:EN0296.XLS AQUATIC RESEARCH INCORPORATED LABORATORY & CONSULTING SERVICES 3927 AURORA AVENUE NORTH, SEATTLE, WA 98103 PHONE: (206) 632-2715 FAX: (206) 632-2417 CASE FILE NUMBER: EN009-02 REPORT DATE: 04/10/96 PAGE 1 DATE SAMPLED: 03/13/96 DATE RECEIVED: 03/13/96 FINAL REPORT, LABORATORY ANALYSIS OF SELECTED PARAMETERS ON WATER SAMPLES FROM ENTRANCO / RIVERTON CASE NARRATIVE One soil sample was delivered to the laboratory in good condition. The sample was analyzed according to the chain of custody. No difficulties were encountered in the preparation or analysis of this sample. Sample data follows while QA/QC data is contained on subsequent pages. SAMPLE DATA TOTAL METALS SOLIDS ANTIMONY ARSENIC BERYLLIUM CADMIUM CHROMIUM SAMPLE ID (%) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) RIVERTON CR POND 30.22% <2.50 10.7 0.579 2.24 40.7 TOTAL METALS COPPER LEAD MERCURY NICKEL SELENIUM SILVER SAMPLE ID (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) RIVERTON CR POND 66.1 91.4 0.248 36.3 < 2.50 <1.00 TOTAL METALS THALLIUM ZINC SAMPLE ID (mg/kg) (mg/kg) RIVERTON CR POND < 1.00 378 EN009-02:EN0296.XLS AQUATIC RESEARCH INCORPORATED LABORATORY & CONSULTING SERVICES 3927 AURORA AVENUE NORTH, SEATTLE, WA 98103 PHONE: (206) 632-2715 FAX: (206) 632-2417 CASE FILE NUMBER: EN009-02 PAGE 2 REPORT DATE: 04/10/96 DATE SAMPLED: 03/13/96 DATE RECEIVED: 03/13/96 FINAL REPORT, LABORATORY ANALYSIS OF SELECTED PARAMETERS ON WATER SAMPLES FROM ENTRANCO / RIVERTON QA/QC DATA CONVENTIONALS, METALS QC PARAMETER METHOD DATE ANALYZED DETECTION LIMIT DUPLICATE SAMPLE ID ORIGINAL DUPLICATE RPD SPIKE SAMPLE SAMPLE ID ORIGINAL SPIKED SAMPLE SPIKE ADDED % RECOVERY QC CHECK (mg/I) FOUND TRUE % RECOVERY BLANK SOLIDS (%)_ EPA 160.3 03/14/96 1.00 ANTIMONY ARSENIC BERYLLIUM CADMIUM CHROMIUM (nig/kg) (Tng/k) (mg/kg) (rmikg) (mg/Lg) EPA 205.2 04/03/96 2.50 EPA 206.2 04/02/96 0.300 EPA 200.7 03/26/96 0.200 EPA 200.7 03/26/96 0.200 EPA 200.7 03/26/96 1.00 RIVERTON CR PND 30.22% 30.52% 0.99% RIVERTON CR PND < 2.50 < 2.50 NC RIVERTON CR PND 10.7 9.12 15.90% RIVERTON CR PND 0.579 0.579 0.00% RIVERTON CR PND 2.24 2.58 13.95% RIVERTON CR PND 40.7 36.6 10.53% NA RIVERTON CR PND < 2.50 21.7 20.7 104.78% RIVERTON CR PND 10.7 76.5 82.7 79.54% RIVERTON CR PND 0.579 76.2 82.7 91.39% RIVERTON CR PND 2.24 79.5 82.7 93.45% RIVERTON CR PNU 40.7 106 82.7 78.82% NA 0.0238 0.0250 95.00% 0.0239 0.0250 95.4.% 0.101 0.100 101.40% 0.994 1.00 99.35% 1.05 1.00 104.90% NA < 2.50 <0.300 <0.200 <0.200 <0.100 RPU = RELATIVE PERCENT DIFFERENCE. NA = NOT APPLICABLE OR NOT AVAILABLE. NC = NOT CALCULABLE DUE TO ONE OR MORE VALUES BEINO BELOW THE DETECTION LIMIT. OR = RECOVERY NOT CALCULABLE DUE TO SPIKE SAMPLE OUP OF RANGE OR SPIKE TO LOW RELATIVE TO SAMPLE CONCENTRATION. EN009-02:EN0296.XLS AQUATIC RESEARCH INCORPORATED LABORATORY & CONSULTING SERVICES 3927 AURORA AVENUE NORTH, SEATTLE, WA 98103 PHONE: (206) 632-2715 FAX: (206) 632-2417 CASE FILE NUMBER: EN009-02 REPORT DATE: 04/10/96 PAGE 3 DATE SAMPLED: 03/13/96 DATE RECEIVED: 03/13/96 FINAL REPORT, LABORATORY ANALYSIS OF SELECTED PARAMETERS ON WATER SAMPLES FROM ENTRANCO / RIVERTON QA/QC DATA METALS QC PARAMETER METHOD DATE ANALYZED DETECTION LIMIT DUPLICATE SAMPLE ID ORIGINAL DUPLICATE RPD SPIKE SAMPLE SAMPLE ID ORIGINAL SPIKED SAMPLE SPIKE ADDED % RECOVERY QC CHECK mg/1 FOUND TRUE % RECOVERY BLANK COPPER (mg/kg) LEAD (mg/kg) ETA :39 2 04/02/96 0.100 MERCURY (mg/kg) EPA 243.1 03/28/96 0.020 NICKEL (mg/kg) EPA 200.7 03/26/96 0.500 SELENIUM (mg/kg) EPA 270.2 04/02/96 2.50 SILVER (mg/kg) EPA 200.7 04/03/96 1.00 EPA 200.7 03/26/96 0.500 RIVERTON CR PNU 66.1 64.6 2.28% RIVERTON CR PND 91.4 80.9 12.21% RIVERTON CR PND 0.248 0.263 5.83% RIVERTON CR PND 36.3 38.9 6.82% RIVERTON CR PNU <2.50 <2.50 NC RIVERTON CR PND <1.00 <1.00 NC RIVERTON CR PND 66.1 134 82.7 82.33% RIVERTON CR PND 91.4 132 41.4 99.31% RIVERTON CR PND 0.248 0.611 0.414 87.64% RIVERTON CR PND 36.3 108 82.7 87.24% RIVERTON CR PND <2.50 16.4 20.7 79.22% RIVERTON CR PND <1.00 13.6 16.5 82.30% 1.07 1.00 107.00% 0.0257 0.0250 102.80% 0.00357 0.00350 102.00% 1.06 1.00 106.00% 0.0242 0.0250 96.80% 0.947 1.00 94.71% <0.500 <0.100 <0.020 <0.500 <2.50 <1.00 RPD= RELATIVE PERCENT DIFFERENCE. NA = NOT APPLICABLE OR NOT AVAILABLE. NC= NOT CALCULABLE DUE TO ONE OR MORE VALUES BEING BELOW TIIE DETECTION LIMIT. OR = RECOVERY NOT CALCULABLE DUE TO SPIKE SAMPLE OUT OF RANGE OR SPIKE TO LOW RELATIVE TO SAMPLE CONCENTRATION. EN009-02:EN0296.XLS AQUATIC RESEARCH INCORPORATED LABORATORY & CONSULTING SERVICES 3927 AURORA AVENUE NORTH, SEATTLE, WA 98103 PHONE: (206) 632-2715 FAX: (206) 632-2417 CASE FILE NUMBER: EN009-02 PAGE 4 REPORT DATE: 04/10/96 DATE SAMPLED: 03/13/96 DATE RECEIVED: 03/13/96 FINAL REPORT, LABORATORY ANALYSIS OF SELECTED PARAMETERS ON WATER SAMPLES FROM ENTRANCO / RIVERTON QA/QC DATA TOTAL METALS, CYANIDE QC PARAMETER METHOD DATE ANALYZED DETECTION LIMIT DUPLICATE SAMPLE ID ORIGINAL DUPLICATE RPD SPIKE SAMPLE SAMPLE ID ORIGINAL SPIKED SAMPLE SPIKE ADDED % RECOVERY QC CHECK mg/I FOUND TRUE % RECOVERY PREP BLANK THALLIUM ZINC (mg/kg) (nig/Kg) EPA 279.2 04/02/96 1.00 EPA 200.7 03/26/96 0.300 RIVERTON CR PND RIVERTON CR PND < 1.00 378 < 1.00 385 NC 1.74% RIVERTON CR PND RIVERTON CR PNU < 1.00 8.65 10.3 83.70% OR 0.0269 1.03 0.0250 1.00 107.60% 102.70% < 1.00 <0.300 RPD - RELATIVE PERCENT DIFFERENCE. NA - NOT APPLICABLE OR NOT AVAILABLE. NC ...NOT CALCULABLE DUE TO ONE OR MORE VALUES BEING BELOW THE DETECTION LIMIT. OR - RECOVERY NOT CALCULABLE DUE TO SPIKE SAMPLE OUT OF RANGE OR SPIKE TO LOW RELATIVE TO SAMPLE CONCENTRATION. SUBMITTED BY: Seve. Laboratory Director CHAIR—OF—CUSTODY RECORD CL:ENT: c0 Aquatic Research Incorporated 3927 Aurora Ave. N / Seattle, WA 98103 / (206) 632-2715 SAMPLING DATE: _ ;//j/' G - SAMPLERS: /..i elv.%t% I C•✓ , / ' SAMPLE INFORMATION SAMPLE ID re, DATE/TIME COLLECTED PARAMETERS SHEET / OF PROJECT ID: CASE FILE NO.: floc 9 - O:Z DATA RECORDED BY 1 • O T T MN • 111=1111111111111111111111111 11111111111111111111111111 11111111111111111111111111111 1111111111111111111111111111 111111111111111111111111111 MEM ■■■w■ NUMMENIM IMUMIUMM ■t ■t ■t t■ MEM MI NMI INN ii OMMIMUMMini NM NM .f?c;'U in :041(16 lJ NOTES Printed Name Signature Affiliation Reliruis e ry/, _/� Da�lTi� J l��-/moi ) , /G' %6 e; r/b, (fxs-ct Received By eJ,!;5 (cLr t15 Date/Time 3/J- 1 J5'•Z° Miscellaneous gotes (Hazardou, Materials, Quick turn -around time, etc.): .,9" /ate,,. 1 A s-�,-f /"c- ( i4 ypJ33 En0296 AQUATIC RESEARCH INCORPORATED LABORATORY & CONSULTING SERVICES 3927 AURORA AVENUE NORTH, SEATTLE, WA 98103 PHONE: (206) 632-2715 FAX: (206) 632-2417 CASE FILE NUMBER: EN009-04 REPORT DATE: 05/22/96 PAGE 1 DATE SAMPLED: 04/19/96 DATE RECEIVED: 04/19/96 FINAL REPORT, LABORATORY ANALYSIS OF SELECTED PARAMETERS ON WATER SAMPLES FROM ENTRANCO / RIVERTON CREEK CASE NARRATIVE One sediment sample was received by the laboratory in good condition and analyzed according to the chain of custody. No difficulties were encountered in the preparation or analysis of this sample. Sample data follows while QA/QC data is contained on subsequent pages. Analysis for trace organics are included as separate reports. SAMPLE DATA - DRY WEIGHT BASIS SAMPLE ID SOLIDS (%) TOC (mg/kg) SEDIMENT POND 34.32% 40186 AQUATIC RESEARCH INCORPORATED LABORATORY & CONSULTING SERVICES 3927 AURORA AVENUE NORTH, SEATTLE, WA 98103 PHONE: (206) 632-2715 FAX: (206) 632-2417 CASE FILE NUMBER: EN009-04 PAGE 2 REPORT DATE: 05/22/96 DATE SAMPLED: 04/19/96 DATE RECEIVED:. 04/19/96 FINAL REPORT, LABORATORY ANALYSIS OF SELECTED PARAMETERS ON WATER SAMPLES FROM ENTRANCO / RIVERTON CREEK QA/ QC DATA QC PARAMETER METHOD DATE PREPARED DATE ANALYZED DETECTION LIMIT DUPLICATE SAMPLE ID ORIGINAL DUPLICATE RPD SPIKE SAMPLE SAMPLE ID ORIGINAL SPIKED SAMPLE SPIKE ADDED % RECOVERY QC CHECK FOUND TRUE % RECOVERY BLANK SOLIDS TOC (%) (mg/kg) EPA 160.3 EPA 415.1 04/22/96 05/17/96 0.10% 200 SBD POND BATCH 34.32% 27496 34.39% 31099 0.20% 12.30% NA NA 2190 1996 NA 109.72% NA <200 RPD = RELATIVE PERCENT DIFFERENCE. NA = NOT APPLICABLE OR NOT AVAILABLE. NC = NOT CALCULABLE DUE TO ONE OR MORE VALUES BEING BELOW THE DETECTION LIMIT. OR = RECOVERY NOT CALCULABLE DUE TO SPIKE SAMPLE OUT OF RANGE OR SPIKE TO LOW RELATIVE TO SAMPLE CONCENTRATION. SUBMITTED BY: Laboratory Director En0296 SOUND ANALYTICAL SERVICES, INC. Client Name Aquatic Research, Inc. Client ID: RIVER CR. SED. POND Lab ID: 56112-01 Date Received: 4/22/96 Date Prepared: 4/24/96 Date Analyzed: 4/24/96 % Solids 33.5 Organochlorine Pesticides and PCBs by USEPA Method 8080 Recovery Limits Surrogate % Recovery Flags Low High TCMX 138 50 150 Decachlorobiphenyl 145 50 150 Sample results are on a dry weight basis. Result Analyte (ug/kg) PQL Aroclor 1016 ND 280 Aroclor 1221 ND 280 Aroclor 1232 ND 280 Aroclor 1242 ND 280 Aroclor 1248 ND 280 Aroclor 1254 ND 280 Aroclor 1260 ND 280 Aldrin ND 5.7 alpha -BHC ND 5.7 beta -BHC ND 5.7 delta -BHC ND 5.7 gamma -BHC (Lindane) ND 5.7 Chlordane (technical) ND 57 4,4' -DDD ND 11 4,4' -DDE ND 11 4,4' -DDT ND 11 Dieldrin ND 11 Endosulfan I ND 5.7 Endosulfan II ND 11 Endosulfan sulfate ND 11 Endrin ND 11 Endrin aldehyde ND 11 Heptachlor ND 5.7 Heptachlor epoxide ND 5.7 Methoxychlor ND 57 Endrin ketone ND 11 Flags SOUND ANALYTICAL SERVICES, INC. Organochlorine Pesticides and PCBs by USEPA Method 8080 data for 56112-01 continued... Result Analyte (ug/kg) PQL Flags Toxaphene ND 570 3 SOUND ANALYTICAL SERVICES, INC. Client Name Aquatic Research, Inc. Client ID: RIVER CR. SED. POND Lab ID: 56112-01 Date Received: 4/22/96 Date Prepared: 4/23/96 Date Analyzed: 4/23/96 % Solids 33.5 Semivolatile Organics by USEPA Method 8270 Recovery Limits Surrogate % Recovery Flags Low High Nitrobenzene - d5 84 23 120 2 - Fluorobiphenyl 90 30 115 p - Terphenyl - d14 73 18 137 Phenol -d5 97 24 113 2 - Fluorophenol 89 25 121 2,4,6 - Tribromophenol 107 19 122 Sample results are on a dry weight basis. Result Analyte (ug/kg) PQL Phenol ND 590 bis(2-Chloroethyl)ether ND 590 2 -Chlorophenol ND 590 1,3 -Dichlorobenzene ND 590 1,4 -Dichlorobenzene ND 590 Benzyl Alcohol ND 1200 1,2 -Dichlorobenzene ND 590 2-Methylphenol ND 590 bis(2-Chloroisopropyl)ether ND 590 3- & 4-Methylphenol ND 590 N-nitroso-di-n-propylamine ND 590 Hexachloroethane ND 590 Nitrobenzene ND 590 Isophorone ND 590 2-Nitrophenol ND 590 2,4 -Dimethylphenol ND 590 Benzoic Acid 940 2900 bis(2-Chloroethoxy)methane ND 590 2,4-Dichlorophenol ND 590 1,2,4-Trichlorobenzene ND 590 Naphthalene ND 590 4-Chloroaniline ND 1200 Hexachlorobutadiene ND 590 4-Chloro-3-methylphenol ND 1200 2 -Methylnaphthalene ND 590 Hexachlorocyclopentadiene ND 590 Flags J 4 SOUND ANALYTICAL SERVICES, INC. Semivolatile Organics by USEPA Method 8270 data for 56112-01 continued... Result Analyte (ug/kg) PQL Flags 2,4,6 -Trichlorophenol ND 590 2,4,5 -Trichlorophenol ND 590 2-Chloronaphthalene ND 590 2-Nitroaniline ND 2900 Dimethylphthalate ND 590 Acenaphthylene ND 590 2,6-Dinitrotoluene ND 590 3-Nitroaniline ND 2900 Acenaphthene ND 590 2,4-Dinitrophenol ND 2900 4-Nitrophenol ND 2900 Dibenzofuran ND 590 2,4-Dinitrotoluene ND 590 Diethylphthalate ND 590 4-Chlorophenylphenylether ND 590 Fluorene ND 590 4-Nitroaniline ND 2900 4,6-Dinitro-2-methylphenol ND 2900 N-Nitrosodiphenylamine ND 590 4-Bromophenylphenylether ND 590 Hexachlorobenzene ND 590 Pentachlorophenol ND 2900 Phenanthrene ND 590 Anthracene ND 590 Di-n-butylphthalate ND 590 Fluoranthene 1100 590 Pyrene 1000 590 Butylbenzylphthalate ND 590 3,3'-dichlorobenzidine ND 590 Benzo(a)anthracene 510 590 J Chrysene 450 590 J bis(2-Ethylhexyl)phthalats 2500 590 B1 Di-n-octylphthalate ND 590 Benzo(b)fluoranthene 750 590 Benzo(k)fluoranthene ND 590 Benzo(a)pyrene 480 590 J Indeno(1,2,3-cd)pyrene 400 590 J Dibenz(a,h)anthracene ND 590 Benzo(g,h,i)perylene ND 590 5 SOUND ANALYTICAL SERVICES, INC. Lab ID: Date Received: Date Prepared: Date Analyzed: Solids Method Blank - PE542 4/24/96 4/24/96 Organochlorine Pesticides and PCBs by USEPA Method 8080 Recovery Limits Surrogate % Recovery Flags Low High TCMX 104 50 150 Decachlorobiphenyl 99 50 150 Sample results are on an as received basis. Result Analyte (ug/kg) PQL Aroclor 1016 ND 100 Aroclor 1221 ND 100 Aroclor 1232 ND 100 Aroclor 1242 ND 100 Aroclor 1248 ND 100 Aroclor 1254 ND 100 Aroclor 1260 ND 100 Aldrin ND 2 alpha -BHC ND 2 beta -BHC ND 2 delta -BHC ND 2 gamma -BHC (Lindane) ND 2 Chlordane (technical) ND 20 4,4' -DDD ND 4 4,4' -DDE ND 4 4,4' -DDT ND 4 Dieldrin ND 4 Endosulfan I ND 2 Endosulfan II ND 4 Endosulfan sulfate ND 4 Endrin ND 4 Endrin aldehyde ND 4 Heptachlor ND 2 Heptachlor epoxide ND 2 Methoxychlor ND 20 Endrin ketone ND 4 Flags 6 SOUND ANALYTICAL SERVICES, INC. Organochlorine Pesticides and PCBs by USEPA Method 8080 data for PE542 continued... Result Analyte (ug/kg) PQL Flags Toxaphene ND 200 7 SOUND ANALYTICAL SERVICES, INC. Blank Spike/Blank Spike Duplicate Report Lab ID: PE542 Date Prepared: 4/24/96 Date Analyzed: 4/24/96 QC Batch ID: PE542 Organochlorine Pesticides and PCBs by USEPA Method 8080 Blank Spike BS BSD Result Amount Result BS Result BSD Compound Name (ug/kg) (ug/kg) (ug/kg) % Rec. (ug/kg) % Rec. RPD Flag Aldrin 0 20 20.4 102 20.2 101 0.99 gamma -BHC (Lindane) 0 20 15.8 79.1 15.8 78.8 0.38 4,4' -DDT 0 50 41.1 82.2 40.1 80.1 2.6 Dieldrin 0 50 44.3 88.7 43.5 87.1 1.8 Endrin 0 50 44.8 89.5 44.6 89.2 0.34 Heptachlor 0 20 17.9 89.3 17.7 88.6 0.79 8 SOUND ANALYTICAL SERVICES, INC. Matrix Spike/Matrix Spike Duplicate Report Client Sample ID: RIVER CR. SED. POND Lab ID: 56112-01 Date Prepared: 4/24/96 Date Analyzed: 4/24/96 QC Batch ID: PE542 Organochlorine Pesticides and PCBs by USEPA Method 8080 Sample Spike MS MSD Result Amount Result MS Result MSD Compound Name (ug/kg) (ug/kg) (ug/kg) % Rec. (ug/kg) % Rec. RPD Flag Aldrin 0 232 221 95.5 214 90.9 4.9 gamma -BHC (Lindane) 0 232 165 71.1 165 70 1.6 4,4' -DDT 0 463 208 45 135 28.8 44 X7 Dieldrin 0 463 492 106 512 109 2.8 Endrin 0 463 493 107 485 103 3.8 Heptachlor 0 232 171 74 153 64.9 13 9 SOUND ANALYTICAL SERVICES, INC. Lab ID: Date Received: Date Prepared: Date Analyzed: % Solids Method Blank - SV863 4/23/96 4/23/96 Semivolatile Organics by USEPA Method 8270 Recovery Limits Surrogate % Recovery Flags Low High Nitrobenzene - d5 76 23 120 2 - Fluorobiphenyl 88 30 115 p - Terphenyl - d14 77 18 137 Phenol - d5 98 24 113 2 - Fluorophenol 87 25 121 2,4,6 - Tribromophenol 76 19 122 Sample results are on an as received basis. Result Analyte (ug/kg) PQL Phenol ND 200 bis(2-Chloroethyl)ether ND 200 2 -Chlorophenol ND 200 1,3 -Dichlorobenzene ND 200 1,4 -Dichlorobenzene ND 200 Benzyl Alcohol ND 400 1,2 -Dichlorobenzene ND 200 2-Methylphenol ND 200 bis(2-Chloroisopropyl)ether ND 200 3- & 4-Methylphenol ND 200 N-nitroso-di-n-propylamine ND 200 Hexachloroethane ND 200 Nitrobenzene ND 200 Isophorone ND 200 2-Nitrophenol ND 200 2,4 -Dimethylphenol ND 200 Benzoic Acid ND 1000 bis(2-Chloroethoxy)methane ND 200 2,4-Dichlorophenol ND 200 1,2,4-Trichlorobenzene ND 200 Naphthalene ND 200 4-Chloroaniline ND 400 Hexachlorobutadiene ND 200 4-Chloro-3-methylphenol ND 400 2 -Methylnaphthalene ND 200 Hexachlorocyclopentadiene ND 200 Flags 10 SOUND ANALYTICAL SERVICES, INC. Semivolatile Organics by USEPA Method 8270 data for SV863 continued... Result Analyte (ug/kg) PQL 2,4,6 -Trichlorophenol ND 200 2,4,5 -Trichlorophenol ND 200 2-Chloronaphthalene ND 200 2-Nitroaniline ND 1000 Dimethylphthalate ND 200 Acenaphthylene ND 200 2,6-Dinitrotoluene ND 200 3-Nitroaniline ND 1000 Acenaphthene ND 200 2,4-Dinitrophenol ND 1000 4-Nitrophenol ND 1000 Dibenzofuran ND 200 2,4-Dinitrotoluene ND 200 Diethylphthalate ND 200 4-Chlorophenylphenylether ND 200 Fluorene ND 200 4-Nitroaniline ND 1000 4,6-Dinitro-2-methylphenol ND 1000 N-Nitrosodiphenylamine ND 200 4-Bromophenylphenylether ND 200 Hexachlorobenzene ND 200 Pentachlorophenol ND 1000 Phenanthrene ND 200 Anthracene ND 200 Di-n-butylphthalate ND 200 Fluoranthene ND 200 Pyrene ND 200 Butylbenzylphthalate ND 200 3,3'-dichlorobenzidine ND 200 Benzo(a)anthracene ND 200 Chrysene ND 200 bis(2-Ethylhexyl)phthalate 250 200 Di-n-octylphthalate 240 200 Benzo(b)fluoranthene ND 200 Benzo(k)fluoranthene ND 200 Benzo(a)pyrene ND 200 Indeno(1,2,3-cd)pyrene ND 200 Dibenz(a,h)anthracene ND 200 Benzo(g,h,i)perylene ND 200 Flags 11 SOUND ANALYTICAL SERVICES, INC. Matrix Spike/Matrix Spike Duplicate Report Client Sample ID: RIVER CR. SED. POND Lab ID: 56112-01 Date Prepared: 4/23/96 Date Analyzed: 4/23/96 QC Batch ID: SV863 Semivolatile Organics by USEPA Method 8270 Sample Spike MS MSD Result Amount Result MS Result MSD Compound Name (ug/kg) (ug/kg) (ug/kg) % Rec. (ug/kg) % Rec. RPD Flag Phenol 0 28800 28100 97.6 26400 92.5 5.4 2 -Chlorophenol 0 28800 21800 75.6 21300 74.8 1.1 1,4 -Dichlorobenzene 0 28800 24200 84 24800 86.9 3.4 N-nitroso-di-n-propylamine 0 28800 20600 71.5 21300 74.7 4.4 1,2,4-Trichlorobenzene 0 28800 25500 88.4 25900 90.7 2.6 4-Chloro-3-methylphenol 0 28800 28800 100 30900 109 8.6 Acenaphthene 0 28800 25000 86.7 23200 81.4 6.3 4-Nitrophenol 0 28800 26300 91.4 27600 96.6 5.5 2,4-Dinitrotoluene 0 28800 21800 75.8 20000 70.1 7.8 Pentachlorophenol 0 28800 23800 82.6 22600 79.2 4.2 Pyrene 1000 28800 25900 86.4 25000 84.1 2.7 12 SOUND ANALYTICAL SERVICES, INC. 4813 PACIFIC HIGHWAY EAST, TACOMA, WASHINGTON 98424 • TELEPHONE 206-922-2310 • FAX 206-922-5047 DATA QUALIFIERS AND ABBREVIATIONS B1: This analyte was detected in the associated method blank. The analyte concentration was determined not to be significantly higher than the associated method blank (less than ten times the concentration reported in the blank). B2: This analyte was detected in the associated method blank. The analyte concentration in the sample was determined to be significantly higher than the method blank (greater than ten times the concentration reported in the blank). C: Additional confirmation performed. D: The reported result for this analyte is calculated based on a secondary dilution factor. E: The concentration of this analyte exceeded the instrument calibration range. J: The analyte was analyzed for and positively identified, but the associated numerical value is an estimated quantity. MCL: Maximum Contaminant Level MDL: Method Detection Limit N: See analytical narrative. ND: Not Detected PQL: Practical Quantitation Limit X 1: Contaminant does not appear to be "typical" product. Elution pattern suggests it may be X2: Contaminant does not appear to be "typical" product. Further testing is suggested for identification. X3: Identification and quantification of peaks was complicated by matrix interference; GC/MS confirmation is recommended. X4: RPD for duplicates outside advisory QC limits. Sample was re -analyzed with similar results. X4a: RPD for duplicates outside advisory QC limits due to analyte concentration near the method practical quantitation limit/detection limit. X5: Matrix spike was diluted out during analysis. X6: Recovery of matrix spike was outside advisory QC limits. Sample was re -analyzed with similar results. X7: Recovery of matrix spike outside advisory QC limits. Matrix interference is indicated by blank spike recovery data. X7a: Recovery and/or RPD values for MS/MSD outside advisory QC limits due to high contaminant levels. X8: Surrogate was diluted out during analysis. X9: Surrogate recovery outside advisory QC limits due to matrix composition. 13 CASE FILE NUMBER: SAMPLE ID NO. . DATE COLLECTED : DATE RECEIVED : DATE ANALYZED : DATE OF REPORT : DATA FILE Aquatic Research Inc. 3927 Aurora Ave. N. , Seattle, WA 98103 1 (206) 632-2715 VOLATILE ORGANIC CHEMICAL REPORT Results of Analysis by EPA Method 8240 Measurement of Purgeable Organic Compounds by Capillary Column Gas Chromatography/Mass Spectrometry ENOO9-04 Riverton Ck. MATRIX 04/19/96 SAMPLE WT. 04/19/96 DILUTION FACTOR 04/30/96 o SOLIDS 05/13/96 ANALYST 0430_13.D SUPERVISOR'S INITIALS: SOIL 3.369 G 1 34.32% KOB Page 1 of 2 CAS# NAME OF COMPOUND AMOUNT (ppb) FLAG 108-86-1 74-97-5 74-83-9 104-51-8 135-98-8 98-06-6 56-23-5 108-90-7 75-00-3 74-87-3 95-49-8 106-43-4 96-12-8 106-93-4 Bromobenzene Bromochloromethane Bromomethane n-Butylbenzene sec-Butylbenzene tert-Butylbenzene Carbon tetrachloride Chlorobenzene Chloroethane Chloromethane 2-Chlorotoluene 4-Chlorotoluene 1,2-Dibromo-3-Chloropropan 1,2-Dibromoethane 11 11 11 11 11 11 11 11 11 11 11 11 11 11 74-95-3 Dibromomethane 11 U 95-50-1 1,2 -Dichlorobenzene 11 U 541-73-1 1,3 -Dichlorobenzene 11 U 106-46-7 1,4 -Dichlorobenzene 11 U 75-71-8 Dichlorodifluoromethane 11 U 75-34-3 1,1-Dichloroethane 11 U 107-06-2 1,2-Dichloroethane 11 U 75-35-4 1,1-Dichloroethene 11 U 156-59-4 cis-1,2-Dichloroethene 11 U 156-80-5 trans-1,2-Dichloroethene 11 U 78-87-5 1,2-Dichloropropane 11 U 142-28-9 1,3-Dichloropropane 11 U 590-20-7 2,2-Dichloropropane 11 U 563-58-6 1,1-Dichloropropene 11 U 10061-01-5 cis-1,3-Dichloropropene 11 U 10061-02-6 trans-1,3-Dichloropropene 11 U 87-68-3 Hexachlorobutadiene 11 U 98-82-8 Isopropylbenzene 11 U 99-87-6 4-Isopropyltoluene 11 U 75-09-2 Methylene chloride 11 U 91-20-3 Naphthalene 11 U 103-65-1 n-Propylbenzene 11 U 100-42-5 Styrene U CAS# NAME OF COMPOUND AMOUNT (ppb) FLAG 630-20-6 1,1,1,2 -Tetrachloroethane 11 U 79-34-5 1,1,2,2 -Tetrachloroethane 11 U 127-18-4 Tetrachloroethene 11 U 87-61-6 1,2,3-Trichlorobenzene 11 U 120-82-1 1,2,4-Trichlorobenzene 11 U 71-55-6 1,1,1 -Trichloroethane 11 U 79-00-5 1,1,2 -Trichloroethane 11 U 79-01-8 Trichloroethene 11 U 75-69-4 Trichlorofluoromethane 11 U 96-18-4 1,2,3-Trichloropropane 11 U 95-63-6 1,2,4-Trimethylbenzene 11 U 108-67-8 1,3, 5-Trimethylbenzene 11 U 75-01-4 Vinyl chloride 11 U BTEX 71-43-2 Benzene 11 U 108-88-3 Toluene 8.3 J 100-41-4 Ethylbenzene 11 U 75-25-2 p/m-Xylene 11 U 95-47-6 o -Xylene 11 U TRIHALOMETHANES (THM) 87-66-3 Chloroform 11 U 75-27-4 Bromodichloromethane 11 U 124-48-1 Dibromochloromethane 11 U 75-25-2 Bromoform 11 U KETONES, CS2, 2-CEVE 87-64-1 Acetone 210 J,PP ---2-2O . j.XP" 591-78-6 2-Hexanone 11 U 108-10-1 4-Methyl-2-Pentanone 11 U 75-15-0 Carbon Disulfide 11 U 110-75-8 2-Chloroethylvinylether 11 U Aquatic Research Inc. 3927 Aurora Ave. N. , Seattle, WA 98103 (206) 632-2715 VOLATILE ORGANIC CHEMICAL REPORT Results of Analysis by EPA Method 8240 Measurement of Purgeable Organic Compounds by Capillary Column Gas Chromatography/Mass Spectrometry CASE FILE NUMBER: EN009-04 SAMPLE ID NO. Riverton Ck. DATE COLLECTED : DATE RECEIVED DATE ANALYZED DATE OF REPORT : DATA FILE MATRIX 04/19/96 SAMPLE WT . 04/19/96 DILUTION FACTOR 04/30/96 % SOLIDS 05/13/96 ANALYST : 0430_13.D SUPERVISOR'S INITIALS: SOIL 3.369 G 1 34.32% KOB Page 2 of 2 CAS# NAME OF COMPOUND AMOUNT (ppb) FLAG Soil CAS# NAME OF COMPOUND AMOUNT (Ppb) FLAG 107-13-1 Acrylonitrile 220 U,PP 67-72-1 Hexachloroethane 11 U 107-05-1 Allyl Chloride 11 U 74-88-4 lodomethane 11 U 100-44-7 Benzyl Chloride 11 U 128-98-7 Methacrylonitrile 220 U,PP 109-69-3 1-Chlorobutane 11 U 96-33-3 Methyl Acrylate 220 U,PP 110-82-7 Cyclohexane 11 U 1634-04- Methyl -t -Butyl Ether 11 U 110-57-6 trans-1,4-Dichloro-2-Butene 11 U 80-62-6 Methyl methacrylate 220 U,PP 60-29-7 Diethyl Ether 11 U 98-95-3 Nitrobenzene N/A U,PP 97-83-2 Ethyl Methacrylate 220 U,PP 79-46-9 2-Nitropropane N/A U,PP 76-13-1 Freon 113 11 U 78-01-7 Pentachloroethane 11 U 622-96-8 4-Ethyltoluene 11 U 109-99-9 Tetrahydrofuran 220 U,PP 142-82-5 Heptane 11 U 108-05-4 Vinyl Acetate 11 U 110-54-3 Hexane _ 11 U FLAGS: U Indicates compound was analyzed for, but not detected at the specified detection limit. 8 Blank contaminated with this analyte. J Estimated value - compound positively identified, but below specified detection limit. E Estimated value - compound exceeded calibration range. D Compound analyzed at a secondary dilution factor of from data file: PP Compound Purges Poorly, requiring elevated detection limit. NOTE: ppb Amounts are in pg/KG dry weight. CAS# R.T.. COMPOUND 18.92 Unknown, alkane 19.29 Unknown, alkane 19.53 Unknown, alkane 2958-76-1 19.75 Naphthalene, decahydro-2-methyl- 19.96 Unknown, alkene 2958-78-1 20.13 Naphthalene, decahydro-2-methyl- 20.6 Unknown 20.75 Unknown, alkane 112-40-3 20.92 Dodecane 21.21 Unknown, alkane 21.37 Unknown, alkane 54676-39-0 21.87 Cyclohexane, 2-butyl-1,1,3-trimethyl- 22.13 Unknown, alkane 22.31 Unknown, alkane 22.45 Unknown, alkane TENTATIVELY IDENTIFIED COMPOUNDS REL. CONC. 24 12 13 13 17 16 12 26 45 81 18 27 24 60 16 The above compounds have been tentatively identified as present. In general. specific identities of isomers of alkanes/alkenes is not possible to resolve. SURROGATE RECOVERIES %Rea. QC limits Water Soil Dibromofluoromethane 118% 86-118% 80-120% Toluene -d8 100% 88-110% 81-117% 4-Bromofluorobenzene 99% 86-115% 74-121 % 1,2 -Dichlorobenzene -d4 88% 80-120% 80-120% CASE FILE NUMBER: SAMPLE ID NO. . DATE COLLECTED : DATE RECEIVED . DATE ANALYZED . DATE OF REPORT : DATA FILE Aquatic Research Inc. 3927 Aurora Ave. N. , Seattle, WA 98103 J (206) 632-2715 VOLATILE ORGANIC CHEMICAL REPORT Results of Analysis by EPA Method 8240 Measurement of Purgeable Organic Compounds by Capillary Column Gas Chromatography/Mass Spectrometry EN009-04 Riverton Ck. Duplicate MATRIX 04/19/96 SAMPLE WT. 04/19/96 DILUTION FACTOR 04/30/96 o SOLIDS 05/13/96 ANALYST : 0430.14M SUPERVISOR'S INITIALS: SOIL 4.886 G 1 34.32% KOBS Page 1 of 2 CAS# NAME OF COMPOUND AMOUNT (ppb) FLAG 108-86-1 74-97-5 74-83-9 104-51-8 135-98-8 98-06-6 58-23-5 108-90-7 75-00-3 74-87-3 95-49-8 106-43-4 96-12-8 106-93-4 Bromobenzene Bromochloromethane Bromomethane n-Butylbenzene sec-Butylbenzene tert-Butylbenzene Carbon tetrachloride Chlorobenzene Chloroethane Chloromethane 2-Chlorotoluene 4-Chlorotoluene 1,2-Dibromo-3-Chloropropan 8 8 8 8 8 8 8 8 8 8 8 8 8 1,2-Dibromoethane 8 74-95-3 Dibromomethane 8 U 95-50-1 1,2 -Dichlorobenzene 8 U 541-73-1 1,3 -Dichlorobenzene 8 U 108-46-7 1,4 -Dichlorobenzene 8 U 75-71-8 Dichlorodifluoromethane 8 U 75-34-3 1,1-Dichloroethane 8 U 107-06-2 1,2-Dichloroethane 8 U 75-35-4 1,1-Dichloroethene 8 U 156-59-4 cis-1,2-Dichloroethene 8 U 156-60-5 trans-1,2-Dichloroethene 8 U 78-87-5 1,2-Dichloropropane 8 U 142-28-9 1,3-Dichloropropane 8 U 590-20-7 2,2-Dichloropropane 8 U 563-58-6 1,1-Dichloropropene 8 U 10081-01-5 cis -1, 3-Dichloropropene 8 U 10061-02-6 trans-1,3-Dichloropropene 8 U 87-68-3 Hexachlorobutadiene 8 U 98-82-8 Isopropylbenzene 8 U 99-87-6 4-Isopropyltoluene 8 U 75-09-2 Methylene chloride 8 U 91-20-3 Naphthalene 8 U 103-65-1 n-Propylbenzene 8 U 100-42-5 Styrene 8 U CAS# NAME OF COMPOUND AMOUNT (ppb) FLAG 630-20-6 1,1,1,2 -Tetrachloroethane 8 U 79-34-5 1,1,2,2 -Tetrachloroethane 8 U 127-18-4 Tetrachloroethene 8 U 87-61-6 1,2,3-Trichlorobenzene 8 U 120-82-1 1,2,4-Trichlorobenzene 8 U 71-55-6 1,1,1 -Trichloroethane 8 U 79-00-5 1,1,2 -Trichloroethane 8 U 79-01-6 Trichloroethene 8 U 75-69-4 Trichlorofluoromethane 8 U 96-18-4 1,2,3-Trichloropropane 8 U 95-63-6 1,2,4-Trimethylbenzene 8 U 108-67-8 1, 3, 5-Trimethylbenzene 8 U 75-01-4 Vinyl chloride 8 U BTEX 71-43-2 Benzene 8 U 108-88-3 Toluene 6.9 J 100-41-4 Ethylbenzene 8 U 75-25-2 p/m-Xylene 8 U 95-47-6 o -Xylene 8 U TRIHALOMETHANES (THM) 67-66-3 Chloroform 8 U 75-27-4 Bromodichloromethane 8 U 124-48-1 Dibromochloromethane 8 U 75-25-2 Bromoform 8 U KETONES, CS2, 2-CEVE 67-64-1 Acetone 180 PP 78-93-3 2-Butanone 150 U,PP 591-78-8 2-Hexanone 8 U 108-10-1 4-Methyl-2-Pentanone 8 U 75-15-0 Carbon Disulfide 8 U 110-75-8 2-Chloroethylvinylether 8 U CASE FILE NUMBER: SAMPLE ID NO. . DATE COLLECTED : DATE RECEIVED DATE ANALYZED - DATE OF REPORT : DATA FILE Aquatic Research Inc. 3927 Aurora Ave. N. , Seattle, WA 98103 1 (206) 632-2715 VOLATILE ORGANIC CHEMICAL REPORT Results of Analysis by EPA Method 8240 Measurement of Purgeable Organic Compounds by Capillary Column Gas Chromatography/Mass Spectrometry EN009-04 Riverton Ck. Duplicate MATRIX 04/19/96 SAMPLE WT. 04/19/96 DILUTION FACTOR 04/30/96 o SOLIDS 05/13/96 ANALYST : 0430_14.D SUPERVISOR'S INITIALS: SOIL 4.886 G 1 34.32% ``ROB Kt Page 2 of 2 CAS# NAME OF COMPOUND AMOUNT (ppb) FLAG Soil CAS# NAME OF COMPOUND AMOUNT (ppb) FLAG 107-13-1 Acrylonitrile 150 U,PP 67-72-1 Hexachloroethane 8 U 107-05-1 Allyl Chloride 8 U 74-88-4 lodomethane 8 U 100-44-7 Benzyl Chloride 8 U 126-98-7 Methacrylonitrile 150 U,PP 109-69-3 1-Chlorobutane 8 U 96-33-3 Methyl Acrylate 150 U,PP 110-82-7 Cyclohexane 8 U 1634-04- Methyl -t -Butyl Ether 8 U 110-57-6 trans-1,4-Dichloro-2-Butene 8 U 80-62-6 Methyl methacrylate 150 U,PP 60-29-7 Diethyl Ether 8 U 98-95-3 Nitrobenzene N/A U,PP 97-63-2 Ethyl Methacrylate 150 U,PP 79-46-9 2-Nitropropane N/A U,PP 76-13-1 Freon 113 8 U 76-01-7 Pentachloroethane 8 U 622-96-8 4-Ethyltoluene 8 U 109-99-9 Tetrahydrofuran 150 U,PP 142-82-5 Heptane 8 U 108-05-4 Vinyl Acetate 8 U 110-54-3 Hexane _ 8 U FLAGS: U B J E D PP Indicates compound was analyzed for, but not detected at the specified detection limit. Blank contaminated with this analyte. Estimated value - compound positively identified, but below specified detection limit. Estimated value - compound exceeded calibration range. Compound analyzed at a secondary dilution factor of from data file: Compound Purges Poorly, requiring elevated detection limit. NOTE: ppb Amounts are in pg/KG dry weight. CAS# R.T.. COMPOUND See original run for TIC'a TENTATIVELY IDENTIFIED COMPOUNDS REL. CONC. The above compounds have been tentatively identified as present. In general. specific identities of isomers of alkanes/alkenes is not possible to resolve. SURROGATE RECOVERIES %Rec. QC limits Water Soil Dibromofluoromethane 105% 88-118% 80-120% Toluene -d8 99% 88-110% 81-117% 4-Bromofluorobenzene 100% 86-115% 74-121% 1,2 -Dichlorobenzene -d4 90% 80-120% 80-120% Aquatic Research Inc. 3927 Aurora Ave. N. , Seattle, WA 98103 1 (206) 632-2715 VOLATILE ORGANIC CHEMICAL REPORT CASE FILE NUMBER: SAMPLE ID NO. DATE COLLECTED DATE RECEIVED DATE ANALYZED DATE OF REPORT DATA FILE Results of Analysis by EPA Method 8240 Measurement of Purgeable Organic Compounds by Capillary Column Gas Chromatography/Mass Spectrometry EN009-04 Method Blank MATRIX 04/19/96 SAMPLE VOL . 04/19/96 DILUTION FACTOR 04/30/96 05/13/96 ANALYST 0430_12.0 SUPERVISOR' S INITIALS : WATER 25 1 ROB ML Page 1 of 2 CAS# NAME OF COMPOUND AMOUNT (ppb) FLAG 108-86-1 Bromobenzene 74-97-5 Bromochloromethane 74-83-9 104-51-8 135-98-8 98-06-6 56-23-5 108-90-7 75-00-3 74-87-3 95-49-8 Bromomethane n-Butylbenzene sec-Butylbenzene tert-Butylbenzene Carbon tetrachloride Chlorobenzene Chloroethane Chloromethane 2-Chlorotoluene 106-43-4 4-Chlorotoluene 98-12-8 1,2-Dibromo-3-Chloropropane 108-93-4 1,2-Dibromoethane 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 74-95-3 Dibromomethane 0.5 U 95-50-1 1,2 -Dichlorobenzene 0.5 U 541-73-1 1,3 -Dichlorobenzene 0.5 U 108-48-7 1,4 -Dichlorobenzene 0.5 U 75-71-8 Dichlorodifluoromethane 0.5 U 75-34-3 1,1-Dichloroethane 0.5 U 107-08-2 1,2-Dichloroethane 0.5 U 75-35-4 1,1-Dichloroethene 0.5 U 158-59-4 cis-1,2-Dichloroethene 0.5 U 156-60-5 trans-1,2-Dichloroethene 0.5 U 78-87-5 1,2-Dichloropropane 0.5 U 142-28-9 1,3-Dichloropropane 0.5 U 590-20-7 2,2-Dichloropropane 0.5 U 583-58-6 1,1-Dichloropropene 0.5 U 10081-01 cis-1,3-Dichloropropene 0.5 U 10081-02 trans-1,3-Dichloropropene 0.5 U 87-88-3 Hexachlorobutadiene 0.5 U 98-82-8 Isopropylbenzene 0.5 U 99-87-6 4-Isopropyltoluene 0.5 U 75-09-2 Methylene chloride 0.5 U 91-20-3 Naphthalene 0.5 U 103-85-1 n-Propylbenzene 0.5 U 100-42-5 Styrene 0.5 U CAS# NAME OF COMPOUND AMOUNT (ppb) FLAG 830-20-8 1,1,1,2 -Tetrachloroethane 0.5 U 79-34-5 1,1,2,2 -Tetrachloroethane 0.5 U 127-18-4 Tetrachloroethene 0.5 U 87-61-6 1,2,3-Trichlorobenzene 0.5 U 120-82-1 1,2,4-Trichlorobenzene 0.5 U 71-55-6 1,1,1 -Trichloroethane 0.5 U 79-00-5 1,1,2 -Trichloroethane 0.5 U 79-01-6 Trichloroethene 0.5 U 75-69-4 Trichlorofluoromethane 0.5 U 96-18-4 1,2,3-Trichloropropane 0.5 U 95-63-8 1,2,4-Trimethylbenzene 0.5 U 108-67-8 1,3, 5-Trimethylbenzene 0.5 U 75-01-4 Vinyl chloride 0.5 U BTEX 71-43-2 Benzene 0.5 U 108-88-3 Toluene 0.5 U 100-41-4 Ethylbenzene 0.5 U 75-25-2 p/m-Xylene 0.5 U 95-47-6 o -Xylene 0.5 U TRIHALOMETHANES (THM) 67-86-3 Chloroform 0.5 U 75-27=4 Bromodichloromethane 0.5 U 124-48-1 Dibromochloromethane 0.5 U 75-25-2 Bromoform 0.5 U KETONES, CS2, 2-CEVE 87-84-1 Acetone 10 U,PP 78-93-3 2-Butanone 10 U,PP 591-78-8 2-Hexanone 0.5 U 108-10-1 4-Methyl-2-Pentanone 0.5 U 75-15-0 Carbon Disulfide 0.5 U 110-75-8 2-Chloroethylvinylether 0.5 U Aquatic Research Inc. 3927 Aurora Ave. N. , Seattle, WA 98103 1 (208) 632-2715 VOLATILE ORGANIC CHEMICAL REPORT CASE FILE NUMBER: SAMPLE ID NO. DATE COLLECTED : DATE RECEIVED DATE ANALYZED DATE OF REPORT : DATA FILE Results of Analysis by EPA Method 8240 Measurement of Purgeable Organic Compounds by Capillary Column Gas Chromatography/Mass Spectrometry EN009-04 Method Blank MATRIX 04/19/96 SAMPLE VOL . 04/19/96 DILUTION FACTOR 04/30/96 05/13/96 ANALYST 0430_12.D SUPERVISOR'S INITIALS : WATER 25 1 KOB KOS ML Page 2 of 2 CAS# NAME OF COMPOUND AMOUNT (ppb) FLAG Soil CAS# NAME OF COMPOUND AMOUNT (ppb) FLAG 107-13-1 Acrylonitrile 10 U,PP 67-72-1 Hexachloroethane 0.5 U 107-05-1 Allyl Chloride 0.5 U 74-88-4 lodomethane 0.5 U 100-44-7 Benzyl Chloride 0.5 U 128-98-7 Methacrylonitrile 10 U,PP 109-69-3 1-Chlorobutane 0.5 U 96-33-3 Methyl Acrylate 10 U,PP 110-82-7 Cyclohexane 0.5 U 1834-04- Methyl -t -Butyl Ether 0.5 U 110-57-6 trans-1,4-Dichloro-2-Butene 0.5 U 80-62-8 Methyl methacrylate 10 U,PP 60-29-7 Diethyl Ether 0.5 U 98-95-3 Nitrobenzene N/A U,PP 97-83-2 Ethyl Methacrylate 10 U,PP 79-48-9 2-Nitropropane N/A U,PP 78-13-1 Freon 113 0.5 U 76-01-7 Pentachloroethane 0.5 U 622-96-8 4-Ethyltoluene 0.5 U 109-99-9 Tetrahydrofuran 10 U,PP 142-82-5 Heptane 0.5 U 108-05-4 Vinyl Acetate 0.5 U 110-54-3 Hexane 0.5 U FLAGS: U B J E D PP Indicates compound was analyzed for, but not detected at the specified detection limit. Blank contaminated with this analyte. Estimated value - compound positively identified, but below specified detection limit. Estimated value - compound exceeded calibration range. Compound analyzed at a secondary dilution factor of from data file: Compound Purges Poorly, requiring elevated detection limit. NOTE: ppb Amounts are in pg/L CAS# COMPOUND TENTATIVELY IDENTIFIED COMPOUNDS REL. CONC. The above compounds have been tentatively identified as present. In general. specific identities of isomers of alkanes/alkenes is not possible to resolve. SURROGATE RECOVERIES %Rec. QC limits Water Soil Dibromofluoromethane 102% 86-118% 80-120% Toluene -d8 101% 88-110% 81-117% 4-Bromofluorobenzene 105% 86-115% 74-121% 1,2 -Dichlorobenzene -d4 103% 80-120% 80-1 20% IA, Aquatic Research Inc. 3927 Aurora Ave. N. , Seattle, WA 98103 1 (206) 632-2715 VOLATILE ORGANIC CHEMICAL REPORT Results of Analysis by EPA Method 8240 Measurement of Purgeable Organic Compounds by Capillary Column Gas Chromatography/Mass Spectrometry CASE FILE NUMBER: SAMPLE ID NO. : DATE COLLECTED DATE RECEIVED DATE ANALYZED DATE OF REPORT EN009-04, voc 4 ppb, v4add 10 ppb Riverton Ck. Matrix Spike MATRIX 04/19/96 SAMPLE AMT. 04/19/96 % SOLIDS 04/30/96 DATA FILE 05/13/96 ANALYST SUPERVISOR'S INITIALS: SOIL 3.72 G 34.32% 0430_15.D KOBB ✓ Page 1 of 2 CAS# NAME OF COMPOUND 108-86-1 74-97-5 74-83-9 104-51-8 135-98-8 98-06-6 56-23-5 108-90-7 75-00-3 74-87-3 95-49-8 106-43-4 96-12-8 106-93-4 Bromobenzene AMOUNT (ppb) 95% Bromochloromethane 139% Bromomethane n-Butylbenzene 99% 56% sec-Butylbenzene 67% tert-Butylbenzene 89% Carbon tetrachloride 94% Chlorobenzene Chloroethane Chloromethane 2-Chlorotoluene 4-Chlorotoluene 1,2-Dibromo-3-Chloropropan 1,2-Dibromoethane 96% 105% 97% 85% 82% 100% 138% 74-95-3 Dibromomethane 153% 95-50-1 1,2 -Dichlorobenzene 74% 541-73-1 1,3 -Dichlorobenzene 74% 108-46-7 1,4 -Dichlorobenzene 74% 75-71-8 Dichlorodifluoromethane N/A 75-34-3 1,1-Dichloroethane 104% 107-06-2 1,2-Dichloroethane 130% 75-35-4 1,1-Dichloroethene 106% 156-59-4 cis-1,2-Dichloroethene 105% 158-60-5 trans-1,2-Dichloroethene 103% 78-87-5 1,2-Dichloropropane 109% 142-28-9 590-20-7 563-58-6 1,3-Dichloropropane 2,2-Dichloropropane 1,1-Dichloropropene 130% 100% 100% 10061-01 cis-1,3-Dichloropropene 109% 10061-02 trans-1,3-Dichloropropene 116% 87-68-3 Hexachlorobutadiene 27% 98-82-8 Isopropylbenzene 88% 99-87-6 4-Isopropyltoluene 65% 75-09-2 Methylene chloride 119% 91-20-3 Naphthalene 66% 103-65-1 n-Propylbenzene 84% 100-42-5 Styrene 96% CAS# NAME OF COMPOUND AMOUNT (ppb) 630-20-6 1,1,1,2 -Tetrachloroethane 101% 79-34-5 1,1,2,2 -Tetrachloroethane 135% 127-18-4 Tetrachloroethene 126% 87-61-6 1,2,3-Trichlorobenzene 35% 120-82-1 1,2,4-Trichlorobenzene 35% 71-55-6 1,1,1 -Trichloroethane 102% 79-00-5 1,1,2 -Trichloroethane 131% 79-01-6 Trichloroethene 107% 75-69-4 Trichlorofluoromethane 105% 96-18-4 1,2,3-Trichloropropane 140% 95-63-6 1,2,4-Trimethylbenzene 76% 108-67-8 1,3,5-Trimethylbenzene 76% 75-01-4 Vinyl chloride 102% BTEX 71-43-2 Benzene 102% 108-88-3 Toluene 100% 100-41-4 Ethylbenzene 96% 75-25-2 p/m-Xylene 95% 95-47-6 o -Xylene 95% TRIHALOMETHANES (THM) 67-66-3 Chloroform 104% 75-27-4 Bromodichloromethane 107% 124-48-1 Dibromochloromethane 105% 75-25-2 Bromoform 101% KETONES, CS2, 2-CEVE 67-64-1 Acetone N/A 78-93-3 2-Butanone N/A 591-78-6 2-Hexanone N/A 108-10-1 4-Methyl-2-Pentanone N/A 75-15-0 Carbon Disulfide N/A 110-75-8 2-Chloroethylvinylether N/A Aquatic Research Inc. 3927 Aurora Ave. N. , Seattle, WA 98103 1 (206) 632-2715 VOLATILE ORGANIC CHEMICAL REPORT Results of Analysis by EPA Method 8240 Measurement of Purgeable Organic Compounds by Capillary Column Gas Chromatography/Mass Spectrometry CASE FILE NUMBER: SAMPLE ID NO. . DATE COLLECTED : DATE RECEIVED DATE ANALYZED DATE OF REPORT : EN009-04, voc 4 ppb, v4add 10 ppb Riverton Ck. Matrix Spike MATRIX 04/19/96 SAMPLE AMT . 04/19/96 DILUTION FACTOR 04/30/96 DATA FILE 05/13/96 ANALYST • SUPERVISOR'S INITIALS: SOIL 3.72 34.32% 0430_15.D ROB (4e/3 G Page 2 of 2 CAS# NAME OF COMPOUND AMOUNT (ppb) Water CAS# NAME OF COMPOUND AMOUNT (ppb) 107-13-1 Acrylonitrile N/A 67-72-1 Hexachloroethane 38% 107-05-1 AIIyI Chloride 91% 74-88-4 lodomethane 94% 100-44-7 Benzyl Chloride 97% 126-98-7 Methacrylonitrile N/A 109-69-3 1-Chlorobutane 96% 96-33-3 Methyl Acrylate N/A 110-82-7 Cyclohexane 90% 1634-04- Methyl -t -Butyl Ether N/A 110-57-6 trans-1,4-Dichloro-2-Butene 116% 80-62-8 Methyl methacrylate N/A 60-29-7 Diethyl Ether 122% 98-95-3 Nitrobenzene N/A 97-63-2 Ethyl Methacrylate 114% 79-48-9 2-Nitropropane N/A 76-13-1 Freon 113 93% 76-01-7 Pentachloroethane 76% 622-96-8 4-Ethyltoluene 73% 109-99-9 Tetrahydrofuran N/A 142-82-5 Heptane 51% 108-05-4 Vinyl Acetate 46% 110-54-3 Hexane 73% FLAGS: U B J E D PP Indicates compound was analyzed for, but not detected at the specified detection limit. Blank contaminated with this analyte. Estimated value - compound positively identified, but below specified detection limit. Estimated value - compound exceeded calibration range. Compound analyzed at a secondary dilution factor of from data file: Compound Purges Poorly, requiring elevated detection limit. NOTE: ppb Amounts are in pg/L or pg/KG dry weight. CAS# COMPOUND TENTATIVELY IDENTIFIED COMPOUNDS REL. CONC. The above compounds have been tentatively identified as present. In general. specific identities of isomers of alkanes/alkenes is not possible to resolve. SURROGATE RECOVERIES %Rec. QC limits Water Soil Dibromofluoromethane 109% 86-118% 80-120% Toluene -d8 99% 88-110% 81-117% 4-Bromofluorobenzene 91 % 86-115% 74-121 % 1,2 -Dichlorobenzene -d4 76% 80-120% 80-120% 1CHAIN-OF-CUSTODY RECORD CLIENT: En -wart co Aquatic Research Incorporated 3927 Aurora Ave. N / Seattle, WA 98103 / (206) 632-2715 SHEET OF PROJECT ID: CUedflut IAMPLING DATE: 1/(///1. CASE FILE NO.: �i(� P��C�_ Q�� AMPLERS: (�enGl( 1-(1, /16/ DATA RECORDED BY: i SAMPLE INFORMATION / N. u-cn 5( P1,at'Ty Pa//uhi,7T-Sf4; ' SAMPLE ID . ,-.,,t- .4..- DATE/TIME COLLECTED v 'j O PARAMETERS '?9c- v 6-11-11 - ©gid -PeA NOTES .o 1".."..."1".."..."R4!1°i ./ - 6" -e `' V.._T To. ,'/i, , srcc; 4I L r 1 .,4T. t «N'�w► K T # yer�Grl (r. geef1'4 PO/i Pat/ [/�%e/1G /S.,,, /Pew APPENDIX B Riverton Creek Stream Special Study RIVERTON CREEK STREAM SPECIAL STUDY LEVEL 1 STREAM SURVEY FINAL REPORT Prepared for CITY OF TUKWILA DEPARTMENT OF PUBLIC WORKS AND ENTRANCO Prepared by TAYLOR ASSOCIATES 722 N. 102nd Street Seattle, WA 98133 (206) 781-3490 March 1996 RIVERTON CREEK STREAM SPECIAL STUDY TABLE OF CONTENTS 1.0 EXECUTIVE SUMMARY 1 2.0 INTRODUCTION 2 3.0 METHODS 3.1 Review of Existing Background Information 2 3.2 General Site Survey 4 3.3 Level 1 Basic Stream Survey 4 4.0 GENERAL SITE SURVEY RESULTS 4.1 Review of Existing Background Information 10 4.2 Natural Drainage System Configuration and Stream Classification 10 4.3 Riparian Zone Land Uses 11 4.4 Riparian Vegetation 11 4.5 Riparian Soils, Bank Stability, and Channel Morphology 12 4.6 Substrate Composition 13 4.7 Large Woody Debris and Pool Quality 13 4.8 Fish Habitat and Utilization 13 5.0 LEVEL 1 BASIC STREAM SURVEY RESULTS 5.1 Habitat Survey 15 5.2 Fish Habitat Requirements and Seasons of Use 24 6.0 HABITAT FACTORS LIMITING FISH SPAWNING AND REARING SUCCESS 25 REFERENCES 27 APPENDIX A 28 List of Figures and Tables Figure 1. Site Location Map 3 Figure 2. Riverton Creek Habitat Survey Surveyed Streams 5 Figure 2 (cont.). Photograph Plates 6-9 Figure 3. Riverton Creek Longitudinal Profile 19 Table 1. Habitat data for the Snoqualmie River following King County SWM (1991) format and category descriptions. 16-17 Table 2. Percentage of total area for habitat units by stream reach for Riverton Creek habitat inventory data. 21 1.0 EXECUTIVE SUMMARY Riverton Creek is a small tributary to the Duwamish River in the central Puget Sound area (Figure 1). The creek is entirely within the Tukwila city limits. Taylor Associates, under contract to Entranco, Inc. conducted a stream habitat survey of Riverton Creek for the City of Tukwila Department of Public Works. The purpose of the stream survey was to identify and inventory existing stream habitat, determine the quality of existing habitat for fish spawning and rearing, and evaluate anadromous barriers in the basin. Taylor Associates conducted a stream habitat survey of Riverton Creek between the months of January and March 1996. Methodologies for field data collection and the subsequent report format follow the King County Surface Water Management guidelines. The survey area was separated into three stream reaches: The Lower Reach, from the mouth of the creek to immediately south of SR 599; and reaches 2 and 3, the West and East tributaries, respectively, from the point of their confluence to SR 99 (see Figure 2). The King County Sensitive Areas Folio identifies Riverton Creek as a Class 2 stream (both perennial and salmon bearing) through much of the West Tributary. The Lower Reach and East Tributary are unclassified at this time. Riverton Creek channel morphology and stream habitat were found to be extremely diverse throughout the survey reaches due to the slope characteristics of the drainage basin. The upper reaches of the East and West tributaries flow through the high gradient hillsides of Riverton Heights, resulting in stream habitats dominated by riffles. Farther downstream the gradient decreases substantially and the East and West tributaries, as well as the entire Lower Reach, assume characteristics of low gradient streams, with much of their habitat dominated by long slow flowing glides. The Lower Reach is low enough in elevation to experience the tidal influence that occurs in the Duwamish River. This reach experiences tidal inundation on a regular basis. Riverton Creek is a moderately degraded stream that has been altered by human development, including: stream channel rerouting, channel straightening, and extensive culverting. The most common habitat types found on the Lower Reach (by percentage of total area) include: Pool (65%), Glide (28%) and Culvert (7%). The three most common habitats on the West Tributary are: Low Gradient Riffle (44%), Run (19%) and Culverts (14% of total reach habitat). The East Tributary's three most prevalent habitat types are: Glide (40% by area), followed by Culverts (37%), and Low Gradient Riffle (16%). Salmonid species which utilize the Duwamish River include chinook (Oncorhynchus tshawytscha), coho (0. kisutch), and chum (0. keta) salmon. Steelhead and resident rainbow trout (0. mykiss) and cutthroat trout (Salmo clarki) are also present. These salmonids all use the Duwamish River for transportation and rearing. Because Riverton Creek drains into the Duwamish River it may be used for spawning, rearing, and protection from high flood flows by salmonid species present in the Duwamish River. Of the salmon species listed above it is known that coho salmon utilize the Lower Reach and the West Tributary of Riverton Creek. It is suspected that cutthroat trout also utilize these stream reaches. Spawning habitat accessible to salmonids is limited to the West Tributary of Riverton Creek. All other areas are either unreachable due to barriers or do not possess appropriate habitat required for successful spawning. Coho rearing and cover habitat is present throughout the entire Lower Reach and through much of the low gradient portions of both the East and West tributaries, although poor water quality may limit its potential. Removal of the tide gate to improve adult passage and development of instream and riparian cover in the West Tributary could improve spawning potential for coho salmon. Improvement in spawning could then provide a source of juveniles to fill this existing rearing habitat. 1 2.0 INTRODUCTION Riverton Creek is a small tributary to the Duwamish River located in the central Puget Sound area (Figure 1). All portions of this creek are located within the Tukwila city limits. Taylor Associates, under contract to Entranco, Inc. conducted a stream habitat survey of Riverton Creek for the City of Tukwila Department of Public Works. The purpose of the stream survey is to identify and inventory existing stream habitat, and to determine the quality of existing habitat for fish spawning and rearing. Further objectives include: identifying all barriers to upstream fish passage and identifying and prioritizing factors limiting fish spawning and rearing success on Riverton Creek. This draft report reflects information gained from background research and completed field reconnaissance and evaluation. A final report will be submitted when all editorial comments and suggestions received from Entranco, Inc. have been reviewed and incorporated into this draft document. 3.0 METHODS 3.1 Review of Existing Background Information The following information was reviewed prior to performing field work in order to identify the natural drainage system features of the Riverton Creek basin within the study area boundaries: U.S. Geological Survey. Topographic Map, 7.5 minute series quadrangle map, Burien, Washington (USGS 1983). King County Sensitive Areas Ordinance (King County, 1990). King County Sensitive Areas Map Folio, Map #4 (King County, 1990). Riverton Creek Basin Base Map (Entranco, Inc., 1996) Washington State Department of Fisheries Catalog of Washington Streams and Salmon Utilization (Williams et al., 1975), Duwamish River Basin (WRIA Basin #09), Lower Duwamish River. Washington State Department of Fisheries, Washington State Department of Wildlife, and Western Washington Treaty Indian Tribes. 1993. 1992 Washington State Salmon and Steelhead Stock Inventory (Washington State Department of Fish and Wildlife [WDFW], 1993). 2 BASE SOURCE: THOMAS BROS. MAPS, KING PIERCE AND SNOHOMISH COUNTIES, 1993 0 1 2 4 MILE TAYLOR ASSOCIATES Riverton Creek Habitat Survey Site Location Map Figure 1 March 1996 3.2 General Site Survey A Level 1 habitat survey was conducted on all portions of Riverton Creek between the creek mouth (confluence of the Duwamish River) and SR 99. The following features were evaluated during the general site survey: 1. Natural drainage system configuration and stream classification; 2. Riparian zone land uses; 3. Riparian vegetation; 4. Animal habitat and utilization; 5. Riparian soils, bank stability, and channel morphology; 6. Substrate composition; 7. Large woody debris and pool quality; and 8. Fish habitat and utilization. The general site survey was qualitative, based on information obtained through review of existing background documents and observations made during site evaluation. Results of the general site survey should not be viewed as a systematic, quantitative evaluation of the features listed. More quantitative evaluations were performed during the Level 1 basic stream survey, discussed in Section 5. 3.3 Level 1 Basic Stream Survey A Level 1 basic stream survey was conducted on Riverton Creek between the months of January and March 1996. The overall study area totalled more than 9,800 feet in length, and was surveyed to this length to incorporate all of the important stream channels in Riverton Creek, as determined by Entranco and the City of Tukwila. The entire study area was divided into three study reaches. Reach one included approximately 1,900 feet from the mouth of Riverton Creek to the confluence of the East and West tributaries; reach two, the West Tributary, approximately 3,400 feet; and reach three, the East Tributary, consisting of approximately 4,500 feet. A detailed site schematic showing the Riverton Creek drainage basin is provided in Figure 2. General conventions were followed for this stream survey relating to stream bank identification and river mile location references. Stream banks were identified by first facing in the downstream direction and then assigning left bank to the left hand side (West bank) and right bank to the right hand side (East bank) of the stream channel. The stream survey consisted of a general site survey and a stream habitat inventory conducted following the procedures outlined in the Region 5 U.S. Forest Service Fish Habitat Relationships (FHR) technical bulletin (McCain et al., 1990). This approach classifies a stream using naturally occurring pool -riffle -run units where homogeneous areas of habitat equal to or greater than one channel width were recorded as distinct habitat units. The stream habitat survey forms used were modified by King County Surface Water Management personnel (see Appendix B, King County SWM, 1991) from methods developed by the 4 Lower Reach Lower Reach ;— TAYLOR ASSOCIATES Riverton Creek Habitat Survey Lower Reach Figure 2 - cont'd. March 1996 West Tributary West Tributary TAYLOR ASSOCIATES Riverton Creek Habitat Survey Lower Reach Figure 2 - cont'd. March 1991 West Tributary East Tributary TAYLOR ASSOCIATES Riverton Creek Habitat Survey Lower Reach Figure 2 - cont'd. March 1996 East Tributary .sa _.�y.+h.•-'.�:w"�'..-.4 .4 ••••, •,'-;�j.'.�&' �M! �y.�• L East Tributary TAYLOR ASSOCIATES Riverton Creek Habitat Survey Lower Reach Figure 2 - cont'd. March 1996 USDA Forest Service. This method evaluates .instream habitat as well as riparian conditions, substrate types, and the presence, orientation,' variety, and condition of large woody debris within the channel. Photographs were taken at 100 -foot intervals to document existing habitat on Riverton Creek. These photographs can be seen in Appendix A. Pool quality indexing (PQI) was performed according to the criteria developed by Platts et al. (1987). This index rates pool habitat quality based on pool diameter, depth, and fish cover conditions. Pools are assigned a rating of 1 to 5, with 1 being of little habitat value and 5 being of superior habitat value for salmonids. Large woody debris (LWD) or large organic debris (LOD) are defined for this study as pieces of woody debris in excess of 8 inches in diameter and 5 feet in length which interact directly with the stream channel in some way. Normally, woody debris would have to be larger than this to be considered LWD; however, due to the small channel sizes found throughout Riverton Creek, the criteria used to classify LWD was modified accordingly. 4.0 GENERAL SITE SURVEY RESULTS 4.1 Review of Existing Background Information Riverton Creek is identified in the King County Sensitive Areas Map Folio (King County, 1990) as a Class 2 stream in various sections. This designation refers to streams which flow year around during years of normal rainfall, or those that are used by salmonids. The West Tributary is identified as a Class 2 perennial stream with salmonids present; however, this classification changes to a Class 2 perennial stream without salmonids in the upper reaches. The Lower Reach and East Tributary are presently unclassified in the King County Map Folio. It is the conclusion of this study that this classification should be changed to Class 2 for the Lower Reach, as this section of Riverton.Creek flows year around and most likely contains salmonid fishes, at least for a portion of their life history. Riverton Creek is not identified in the Washington State Department of Fisheries WRIA Stream Catalog (Williams et al., 1975) due to its small size. The catalog does; however, indicate that chinook (Oncorhynchus tshawytscha), coho (0. kisutch), and chum (0. keta) salmon use the Duwamish River for transportation and rearing. Because Riverton Creek drains into the Duwamish River, it may be used for spawning, rearing, and protection from high flood flows by salmonid species which are present in the Duwamish River. 4.2 Natural Drainage System Configuration and Stream Classification The Riverton Creek basin drains an area of approximately 434 acres in size located in the northwestern part of the City of Tukwila. The creek originates from springs that emerge from the steeply sloping hillsides of Riverton Heights. Riverton Creek forms in two distinct and separate tributaries as it travels in a northerly direction down the steep valley wall to the Duwamish River. The West Tributary flows through low to moderate density residential areas 10 in its upper reaches, and extensively developed commercial property through the Lower Reach. The channel has been rerouted and extensively channelized through the Lower Reach. The East Tributary flows through moderate to high density residential property in its high gradient upper reach, and is culverted and ditched through all of its lower gradient reach. The Lower Reach of Riverton Creek (downstream of the confluence of the East and West Tributaries to the stream mouth) is similarly artificially rerouted and channelized under and around man-made developements; specifically State SR 599 and the Gateway North Office Complex. The Lower Reach is low enough in elevation to experience the tidal influence of daily diurnal tides which affect the Duwamish River. The entire Lower Reach experiences tidal inundation on a regular basis. 4.3 Riparian Zone Land Uses Land use along Riverton Creek consists of a variety of commercial, industrial and residential development, as well as highways and local roads throughout the basin. Land use in the Lower Reach and low gradient portion of the East and West Tributaries is dominated by large tracts of commercial and industrial property and state highways, including a 35 -acre Metro support facility, several large buildings of the Boeing Company's Tukwila Plant, the Gateway North Commercial/Office complex, and SR 599. Land use in the riparian zone becomes dominated by low to high density residential property in the upstream reaches of both tributaries as stream gradient increases. Both tributaries flow through private property (back -yards) and through culverts in the upper reaches. The West Tributary flows through less intensively developed property (fewer culverts) and more undeveloped property than does the East Tributary. Riparian zone land uses upstream of the habitat survey area consist of moderate to high density residential property, light commercial and institutional (hospital and cemetery) uses, and numerous roads including SR 99. 4.4 Riparian Vegetation Riparian vegetation on both banks of the Lower Reach of Riverton Creek consists primarily of reed canarygrass (Phalaris arundinacea), blackberries (Rubus spp.), Scot's broom (Sytisus scoparius) and other shrubs. Red alder (Alnus rubra), cottonwood (Populus spp.) and Western red cedars (Thuja plicata) are also found along this portion of the creek, especially in the area between SR 599 and the mouth. Portions of the Lower Reach riparian zone have also been landscaped with ornamental trees and shrubs; specifically, within the boundaries of the Gateway North Commercial/Office complex. The low gradient portion of the East Tributary which flows parallel to the south side of SR 599 has a riparian zone similar to that described above for Riverton Creek's Lower Reach. Dominant vegetation is reed canary grass which grows abundantly on both stream banks. Thick patches of blackberries are found on the left bank interspersed with coniferous trees that have been planted along Metro's property line at equally spaced intervals, 11 approximately thirty feet apart. Red alder and willow (Salix spp.) trees are also found in the lower portion of the East Tributary. Riparian vegetation in the upper reach of the East Tributary consists of a mixture of grasses (Poa spp.), blackberries, herbaceous shrubs, and coniferous and deciduous trees. Landscaped backyards also frequently abut the upper reach of the East Tributary. Many of these landscaped backyards contain unidentified ornamental shrubs and trees planted in the riparian zone and on the stream banks of the East Tributary. Riparian vegetation along the West Tributary stream corridor is extremely uniform throughout the entire low gradient portion. Vegetation consists of aquatic sedges and grasses that cover the narrow stream corridor which has been channelized around the Boeing property line. Some deciduous trees, including willow, cottonwood and alder, are planted along the stream corridor in places. As the gradient increases towards the south end of Boeing property, the riparian zone improves greatly with an increase in the quantity and diversity of vegetation. The upper reaches of the West Tributary have riparian areas which consist of Western red cedar (T plicata), Western hemlock (Tsuga heterophylla), cottonwood (Populus spp.), oak (Quercus spp.) and vine maple (Acer circinatum). Salmonberry and blackberry (Rubus spp.), sword fern (Polystichum munitum) and lady fern (Athyrium felix-femina) are among the most common ground cover vegetation in the West Tributary survey area. 4.5 Riparian Soils, Bank Stability, and Channel Morphology Similar to other stream channels, Riverton Creek riparian soils, bank stability, and channel morphology are greatly influenced by channel gradient. The lower portions of both the East and West Tributaries, as well as the entire Lower Reach of Riverton Creek, exhibit alluvial sandy riparian soils and channel. banks that show few signs of current erosion. These conditions exist because of the low gradient of these lower reaches. As gradient increases, however, riparian soils tend to become dominated by organic matter mixed with small to large gravels. Stream banks have the potential to become less stable where there is a greater likelihood of stream downcutting that could result in steeper banks; however, bank stability is relatively good along both tributaries of Riverton Creek. No areas were found that showed evidence of contributing silt or other eroded material to the stream. This is partially due to sufficient vegetative cover that holds the streambanks together and channel structural modifications which prevent mass wasting in areas where the stream banks are steep. The channel morphology of Riverton Creek has been extensively modified by urban development, especially in the lower gradient portions of the creek. The channel has been extensively rerouted, channelized and culverted around commercial and industrial parks in this area. Channel morphology thus tends to consist of long stretches of straight U-shaped channels with very few meanders or stream bends. This type of channel promotes the rapid conveyance of water for drainage purposes during high flow periods. During low flow conditions, the channel does assume a more natural low gradient stream morphology by meandering across the depositional alluvium through which it flows. The upper reach of the East Tributary shows a similar pattern of being culverted around and under commercial developments and roadways. The West Tributary has a channel morphology that is more typical of the natural condition of a small, high gradient stream. It is more meandering and highly variable, with a greater variety of stream habitats exhibited in the upper reach. 12 4.6 Substrate Composition Riverton Creek's substrate composition consists almost exclusively of sand and silt throughout the entire Lower Reach and through the low gradient portions of the East Tributary. Due to the low gradient in these areas of Riverton Creek, sediment accumulates readily and builds up until a flow event of sufficient size clears the sediment out to the Duwamish River. Although the majority of the low gradient stream reaches are dominated by sand and silt substrates, the low gradient portion of the West Tributary is dominated by small and large gravels. Substrate size increases as stream gradient increases upstream of the low gradient portion in both Riverton Creek tributaries. In general, substrate composition was a combination of small and large gravels mixed with pockets of sand in a great majority of the habitat units observed. The West Tributary was found to have a better substrate composition with longer sections of stream channel with cleaner gravel of larger size than that observed in the East Tributary. Stream substrates in the East Tributary tended to contain a relatively high proportion of fine sediments with many stream segments showing no gravels at all. 4.7 Large Woody Debris and Pool Quality Large woody debris (LWD) provides structural support to the stream channel, which leads to the creation of more diverse and complex habitats and subsequently provides forage and cover for fish. Riverton Creek was found to have no LWD in the stream channels surveyed. Few pools were observed during the habitat survey. Of the pools encountered, only two rated a pool quality index (PQI) of 5. These pools consisted of the sediment pond in the lower reach and a mid -channel pool in the East Tributary. The West Tributary had only two small pools which both rated a PQI of 3. The East Tributary had the most diverse pool habitat and the largest number of pools of any stream reach. The PQIs achieved were not very high on this tributary, however, with most pools earning PQIs of 3. Pool quality ratings were low in the East Tributary due to their small size, depth and limited vegetative cover. One pool had a PQI of 4, while the remaining pool scored only a 2. 4.8 Fish Habitat and Utilization Fish habitat in the Lower Reach of Riverton Creek is considered fair. The slow flowing and tidally influenced water potentially provides a unique habitat for fish inhabiting the Duwamish River. During periods of high flow in the Duwamish River, the Lower Reach can be used as a slow flowing refuge area for both adult and juvenile fish. In addition, juvenile coho may use the lower reach during their smolt transformation before their ocean migration. Riparian zone vegetation, which provides overhanging cover and shaded areas for fish, is abundant in this reach, and increases habitat value for salmonids and other species of fish. Despite low morphological variation which decreases habitat complexity, the Lower Reach 13 contains enough instream structure to provide cover and resting habitat for fish. No spawning occurs in the Lower Reach; however, due to substrate composition, which lacks both small and large gravel. Fish habitat on the West Tributary is the most diverse and probably the most widely used in Riverton Creek. The long, slow flowing glides found in the low gradient lower portion of the West Tributary provide a fair amount of rearing habitat for juvenile salmonids. Large amounts of quality riparian zone vegetation are lacking in this area, however, so it is less attractive to juvenile fish than it could be. As the channel gradient increases and gravel substrates become more prevalent, riffle spawning areas can be seen. A large amount of spawnable gravel is located in the channel west of buildings at the south end of the Boeing property. This constitutes the only area throughout the entire Riverton Creek basin where spawning could be successful. Adult coho salmon have been observed in the channel below the spawning gravels by Boeing employee Clay Kean (personal communication). However, it is not known if spawning actually occured. Important pool habitat is lacking on the West Tributary. Pools are used by adult salmon as resting areas during their upstream migration and by juvenile salmon, especially coho, for rearing. No pools were observed on the West Tributary downstream of an artificial 20 -foot -high . cascading waterfall that acts as a complete barrier to upstream fish migration. The waterfall is located just upstream of the spawning riffles. The lack of pools and overhanging riparian vegetation constitute serious deficiencies in the West Tributary stream habitat. Fish habitat on the East Tributary is limited to rearing and cover areas found in the channel parallel to SR 599. The slow flowing glides and the one large pool on the East Tributary are usable by both adult and juvenile salmonids during the winter when streamflows are fairly constant. During the summer dry period, this channel may not contain enough water to support fish. No spawning can occur in this channel due to excessive amounts of sediment and few patches of small gravel. A small section of pool and riffle habitat is available for spawning upstream of the 2,250 -foot -long culvert on the East Tributary. The riffles in this area contain both small and large gravels that could be used by salmon spawners. The habitat is degraded and apparently is used moderately by children who have trampled the streambanks in places. Coho salmon have been known to spawn in habitat similar to this. It is doubtful that spawning does or will occur here because the long culvert is likely a barrier to upstream fish migration. It is certain that no spawning occurs in the upstream portion of the East Tributary due to numerous impassable culverts. 14 5.0 LEVEL 1 BASIC STREAM SURVEY RESULTS 5.1 Habitat Survey The Level 1 stream habitat survey was conducted on Riverton Creek between the months of January and March 1996, using the US Forest Service Fish Habitat Relationships (FHR) methodology (McCain et al., 1990). The survey was conducted on both the East and West Tributaries of Riverton Creek and included more than 9,800 feet in total length. Only habitat units which were at least one stream width long were identified and recorded in the survey. Stream channel data collected for all survey reaches of Riverton Creek are presented in Table 1. Photographs representing existing habitat can be seen in Appendix A. Habitat types (McCain et al., 1990) encountered in the survey included: Low Gradient Riffle (LGR)--Shallow reaches with swiftly flowing, turbulent water with some partially exposed substrate. Gradient <4%, substrate is usually cobble dominated. High Gradient Riffle (HGR)--Steep reaches of moderately deep, swift, and very turbulent water. Amount of exposed substrate is relatively great. Gradient is >4%, and substrate is boulder dominated. Cascade (CAS) --The steepest riffle habitat, consists of alternating small waterfalls and shallow pools. Substrate is usually bedrock and boulders. Plunge Pool (PLP) --Found where stream passes over a complete or nearly complete channel obstruction and drops steeply into the streambed below, scouring out a depression, often large and deep. Substrate size is highly variable. Lateral Scour Pool (LSP) --Formed by flow impinging against one stream bank or against a partial channel obstruction. The associated scour is confined to <60% of wetted channel width. Channel obstructions include rootwads, woody debris, boulders, and bedrock. Run (RUN) --Swiftly flowing reaches with little surface agitation and no major flow obstructions. Often appears as flooded riffles. Typical substrates are gravel, cobble and boulders. Mid -Channel Pool (MCP) --Large pools formed by mid -channel scour. The scour hole encompasses more than 60% of the wetted channel. Water velocity is slow, and the substrate is highly variable. Glide (GLD)--A wide shallow pool flowing smoothly and gently, with low to moderate velocities and little or no surface turbulence. Substrate usually consists of cobble, gravel, and sand. 15 Table 1. Habitat data for three stream reaches of Riverton Creek following King County SWM (1990) format and category descriptions (except where otherwise noted). Habitat Unit # Habitat Type * Lower Reach 1 Double 48" Culvert 2 Glide 3 Sediment Pond 4 Glide 5 Double 48" Culvert 6 Glide West Tributary 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 36" Culvert Box Culvert 36" Culvert Run Glide 36" Culvert Run Low Gradient Riffle Low Gradient Riffle 36" Culvert Low Gradient Riffle Glide Low Gradient Riffle Cascade Low Gradient Riffle Lateral Scour Pool Low Gradient Riffle Mid -Channel Pool Low Gradient Riffle Cascade Low Gradient Riffle Cascade Low Gradient Riffle 30" Culvert Low Gradient Riffle High Gradient Riffle Low Gradient Riffle Concrete Pond Chute High Gradient Riffle 24" Culvert Avg. Width'" Avg. Depth " (ft.) (ft.) 4-4 2-4 8-12 2-6 60-80 3-6 6-10 2-5 3-4 1-4. • 3-8 1-5 Streamside Length Structure Substrate Appendix A (ft.) LB—RB Type PQI Photo # 100 — — 1 300 3-3 2-3 2-4 300 4-3 2--3 5 5- 7 780 3-3 2-3 8 - 13 320 — — 14 120 3-4 2-3 15 - 16 3 1 - 3 220 — 2-3 17 - 18 5 1.5 100 0-0 2-3 19 3 1.5 100 — — 6 1.5 160 3-3 2-3 20 4 1 300 0-0 3-4 21 - 22 3 1 50 — 3-4 3 1 225 2-0 3-4 23 - 24 3 0.8 160 2-0 4-5 25 - 26 3 0.6 200 0-0 4-5 27 - 28 3 0.8 175 — — 2 1 150 4-0 4-5 29 - 31 3 1 80 4-0 4-3 3.5 0.4 240 2-2 4-5 32 - 36 4 0.3 50 2-2 Concrete 37 4 0.3 180 2-2 5-4 38 2 1 10 2-2 4-2 3 4 0.3 40 2-2 5-4 2.5 1 10 2--2 4--3 3 4 0.3 50 2--2 5-4 3.5 0.5 30 2-2 7-6 39 4.5 0.2 65 2-0 5--4 40 2 0.8 15 2-0 7-6 3 0.4 135 2-0 5-4 41 - 43 2 0.5 50 — 5-4 44 4 0.4 120 1-1 5--6 44 2 0.8 30 1--1 5--6 3 0.3 140 1-1 4--5 45 30 80 0-0 -- 46 3 0.4 100 0-0 5-4 3 0.3 100 • 2-2 5-4 1 0.3 50 — — * Culverts are not habitat categories in the FHR (USDA, 1990) methodology but appropriately describe the channel here. "" Two widths and depths are given for the Lower Reach habitat descriptions to represent low tide and high tide conditions, respectively. CODES Streamside Structure 0 = No Riparian Zone 1 = Mature Complex Forest 2 = Immature/Even-Aged/Disturbed 3 = Shrub -Dominated 4 = Grassland/Meadow/Pasture 5 = Wetland ABBREVIATIONS LB -RB = Left Bank -Right Bank PQI = Pool Quality Index, defined in Methods section. 16 Substrate Type 1 = Bedrock 2 = Silt/Organic 3 = Sand 4 = Gravel (<25 mm) 5 = Gravel (25 mm -100 mm) 6 = Cobble (100 mm -256 mm) 7 = Boulder Table 1 (cont.) Habitat data for three stream reaches of Riverton Creek following King County SWM (1990) format and category descriptions (except where otherwise noted). Habitat Unit # Habitat Type * East Tributary 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 Streamside Avg. Width Avg. Depth Length Structure Substrate Appendix A (ft.) (ft.) (ft.) LB --RB Type PQI Photo # Glide Mid -Channel Pool Glide 36" Culvert 24" Culvert Glide Mid -Channel Pool Glide Mid -Channel Pool Glide Low Gradient Riffle Glide Low Gradient Riffle 24" Culvert Plunge Pool Low Gradient Riffle Mid -Channel Pool Low Gradient Riffle Mid -Channel Pool 36" Culvert Low Gradient Riffle Glide 24" Culvert Low Gradient Riffle Low Gradient Riffle Glide 24" Culvert High Gradient Riffle Low Gradient Riffle Low Gradient Riffle 12" Concrete Pipe Sump Low Gradient Riffle 8 1 480 2--4 2--3 47 - 52 10 2 60 2--4 2--3 5 53 6 1.5 175 2-4 2--3 54 - 55 2 -- 2250 -- -- 55 2 -- 75 -- -- 58 3.5 0.8 30 0-0 3--7 59 3 2 10 0--3 2--6 4 59 3.5 0.8 10 3--3 2--6 59 3 1.5 20 3--3 2--6 3 59 3.5 0.8 75 3--3 2--3 60 4 0.4 30 3--3 3--6 61 3 1 25 0--2 2--3 3 0.4 50 0--0 4--5 62 1 0.4 50 -- -- 5 1.5 20 2--0 2--4 3 63 4 0.3 95 2-0 4--5 64 5 1.5 12 0--2 2--3 2 64 5 0.2 40 0--0 4--5 5 0.8 15 0--0 4--6 3 65 1.5 -- 120 -- -- 65 4 0.2 25 0--0 4--6 66 3 0.6 10 0--0 4--5 67 1.5 0.4 25 -- -- 3 0.3 200 0--0 4--5 68 - 69 2 0.6 50 4--4 3--4 70 3 0.5 50 4--4 2--3 71 1 0.1 175 -- -- 72 2 0.2 40 0--0 5--6 73 3 0.2 60 0--0 4--5 74 - 75 4 0.2 100 2--1 4--5 76 1 0.4 50 -- -- 77 3 -- 10 -- -- 2 0.5 40 0--0 3--4 78 - 79 * Culverts are not habitat categories in the FHR (USDA, 1990) methodology but appropriately describe the channel here. CODES Streamside Structure 0 = No Riparian Zone 1 = Mature Complex Forest 2 = Immature/Even-Aged/Disturbed 3 = Shrub -Dominated 4 = Grassland/Meadow/Pasture 5 = Wetland ABBREVIATIONS LB -RB = Left Bank -Right Bank PQI = Pool Quality Index, defined in Methods section. Substrate Type 1 = Bedrock 2 = Silt/Organic 3 = Sand 4 = Gravel (<25 mm) 5 = Gravel (25 mm -100 mm) 6 = Cobble (100 mm -256 mm) 7 = Boulder Culverts --Not habitat units as defined by the USFS FHR methodology, but are included in this survey to describe areas that have been tightlined in concrete or corrogated metal pipes to convey water under or around roads and developed areas. Riverton Creek has a very diverse morphology and drainage pattern that changes with increased elevation from the mouth to the headwaters. The longitudinal stream profile for Riverton Creek (Figure 3) shows the general stream profile for both the East and West Tributaries as well as the Lower Reach. The Riverton Creek drainage basin has a relatively flat low gradient portion in the lower reaches and a higher gradient in the upper stream reaches. The differing channel characteristics, morphologies and habitats that are observed and reported in this stream habitat survey are largely the result of the changing channel gradients throughout the drainage basin. Because of the diverse habitats found within the Riverton Creek drainage basin, the survey area was separated into three stream reaches: the Lower Reach, the West Tributary, and the East Tributary. Stream habitat found within each stream reach is discussed below. General drainage patterns and unique identifying landmarks found on or along each stream reach are provided in Figure 2. Photographs reflecting representative stream segments or showing unique stream features are included on four photograph plates after Figure 2. Location and direction of these reference photographs are marked on Figure 2. LOWER REACH Riverton Creek enters the Duwamish River from the left bank at approximately River Mile (RM) 5.0 through two 4 -foot -diameter metal culverts. The culverts run through the levee and are each equipped with large metal flap gates that appear to close relatively tightly around the ends of the culverts. The westernmost flap gate, however, was observed on at least one occasion to not close tightly, due to a small piece of woody debris that has lodged between the end of the pipe and the flap gate. The gap created by the piece of wood was wide enough to allow fish entry into the culvert. During low tide the twin culverts are exposed and can be observed above the water surface of the Duwamish River. During high tide, however, the culverts become inundated and water backs up in the channel upstream. This channel flows in an east -west orientation between the Gateway North Commercial/Office complex and SR 599. Habitat within the channel is largely homogenized into slow flowing glides during inundated high tide periods. During low tide and low flow conditions, the channel shows a more varied flow pattern as some small riffle and pool sequences appear, although the majority of the habitat remains as glides. A large sediment pond is located in the Lower Reach of Riverton Creek. The pond is relatively large, and fluctuates in size with the tide (Figure 2, Photo 1). Pool quality indexing (PQI) on the pond showed a high rating of 5, which constitutes superior habitat for salmonids. The high rating was acheived due to the pool depth and large diameter. Despite the high PQI rating, much of the habitat is degraded in the pond and both up and downstream. Years of dumping trash, tires, and even large appliances into the channel have led to the degraded condition found in this area of Riverton Creek. 18 Riverton Creek Longitudinal Profile 210 180 — 150 5120 0 90 — a 60 w 30 20 15 0 Lower Reach -- Area of Tidal Inundation Highway 99 Crossin Anadromous Barrier -- 20 foot Cascade WaterFall ighway 599 Crossing Anadromous Barrier -- 2,250 foot Concrete Tightlined Culvert I I I 0 1000 2000 3000 4000 5000 6000 7000 Distance from Mouth (ft) Lower Reach — West Tributary — East Tributary Figure 3. Riverton Creek Longitudinal Profile — — — — — — Upstream of the sediment pond, the channel continues to flow in an east -west direction with the Gateway North Commercial/Office complex on the right bank and SR 599 on the left bank. The channel is fairly incised and much lower in elevation than the surrounding landscape (Figure 2, Photo 2). Most of the riparian areas were probably filled during development of this area, especially the Gateway North Property. This can be seen by the steepness of the right bank in relation to the left bank, which gently slopes up to meet the SR 599 right-of-way in most places. The channel is conveyed under SR 599 via two 48 -inch culverts that extend more than 320 feet in length in a north -south direction from one end of SR 599 to the other. The culvert on the left bank has filled with a substantial amount of sediment which has reduced its water transport capacity. The right bank culvert is functioning properly, despite a small build-up of sediment in the pipe. The Lower Reach ends just south of SR 599 as the East and West Tributaries converge. Very few habitat types were identified in the lower reach of Riverton Creek. This is largely due to the gentle gradient through which the stream flows. Of all the habitat types observed in the lower reach, Pool habitat was predominant (65 percent of total habitat as measured in square feet). Glide habitat was second most prevalent with 28 percent of the total habitat. Culverts made up the remaining 7 percent of total habitat by area (Table 2). WEST TRIBUTARY The West Tributary flows in a north -south direction beginning at the confluence with the East Tributary (see Figure 2). The lower portion of the West Tributary flows through a series of 36 -inch culverts and an open box culvert which divert the creek through and around Metro's Transportation Support Facility. The creek flows in long expanses of open channel upstream of the Metro property and on the west side of buildings in Boeing's Tukwila Plant. The open channel throughout the lower portion of the West Tributary has been straightened and apparently widened for flood control purposes. Glide habitat occurs just upstream of the Metro property and west of Boeing property (Figure 2, Photo 3). The channel is in fairly good condition in this area with a moderate amount of vegetation on both banks. A combined sewer overflow (CSO) pipe is located on the left bank just upstream of Metro property (Figure 2). This pipe originates from the Balvue sewer pump station west of SR 99. Mr. Bruce Barrow, Metro's Environmental Compliance Chief, stated that on at least two occasions, raw sewage has spilled into Riverton Creek via this CSO pipe over the last three-year period (personal communication). The vegetation decreases on both banks as the creek flows through Boeing property. Sedges and grasses grow profusely along the stream channel between the stream banks, which have been riprapped, gabioned, or otherwise reinforced throughout the Boeing property. The channel has a typical U -shape through much of this low gradient reach. Substrates are predominately silt and sand deposited in this area due to the low gradient and slow stream flows. During periods of low discharge, the stream flows in a small distinct channel that 20 Table 2. Percentage of total area for habitat units by stream reach for Riverton Creek habitat inventory data. Habitat Total Area Percentage Area Type (sq. ft.) by Reach Lower Reach Pool 18000 65% Glide 7680 28% Culvert 2080 7% 27760 100% West Tributary Low Gradient Riffle 4897 44% Run 2135 19% Culvert 1610 14% Glide 1440 13% High Gradient Riffle 360 3% Cascade 335 3% Chute 300 3% Pool 45 0% 11122 100% East Tributary Glide 5547 40% Culvert 5143 37% Low Gradient Riffle 2310 16% Pool 955 7% High Gradient Riffle 80 1% 14035 100% 21 meanders through the sand and grasses on the bottom of the streambed. During higher streamflow, the small distinct channel disappears as the width and depth of water increase in the channel creating a straight flowing glide. As stream gradient begins to increase toward the south end of Boeing property, habitat improves greatly as Low Gradient Riffles become predominant. Both small and large gravel become the dominant substrate through this area of the stream. As described above, during low to intermediate streamflow periods, a small distinct channel tends to meander back and forth between the hardened rip -rapped banks (Figure 2, Photo 4). During periods of increased discharge the stream overflows the small distinct channel and widens to fill the entire stream cross-section from bank to bank. As gradient increases even farther upstream, the channel becomes wider and gravel size increases. Riparian vegetation also increases on both streambanks and includes numerous shrubs and some large deciduous and coniferous trees, all of which shade the stream and provide cover for fish when foliage is present. Just upstream of the southernmost building on Boeing's property is a 20 -foot -high cascading waterfall about 40 feet in length (Figure 2, Photo 5). This artificial concrete structure was built to convey water down the steeply sloping hillside with a minimum of erosion. The artificial waterfall does function well to protect the stream from erosion; however, it acts as a complete barrier to fish. Despite being a barrier to all upstream fish migration, the concrete waterfall is a neccesary structure due to the extremely high stream gradient here. Without the artificial waterfall to prevent erosion, mass wasting of the surrounding soil would probably occur during periods of high discharge. Upstream of the cascading waterfall, the stream flows through a few hundred feet of undeveloped Boeing property. Riparian areas are very healthy with large mature trees and numerous small shrubs. Stream habitat includes alternating riffles and small pools with small and large gravel substrates. This type of riparian zone vegetation and stream habitat continues upstream as the channel flows through very low density residential properties. Residents in this area have largely let the stream channel flow in its natural drainage pattern with little interference or landscaping modifications. Upstream of the South 126th Street stream crossing, riparian habitat is the most undisturbed of the entire Riverton Creek basin surveyed. This is due to the high gradient of the stream and undeveloped parcels of land in this area. The stream channel meanders through this undeveloped land and into the backyards of private residences. One resident has impounded the stream by creating a large cement pond which may be used as a small hobby fish hatchery. Upstream of this residence, the water has been channelized to flow directly into the pond via a concrete chute. The survey area ends where the channel crosses 34th Avenue via a 24 -inch cantilivered culvert. Overall, the West Tributary offers the best habitat of the three stream reaches surveyed. Stream habitat in the West Tributary is dominated by Low Gradient Riffle (44% by area), followed by Run (19%), Culverts (14%) and Glide habitat (13% by area). Other habitat types observed include High Gradient Riffle, Cascades and one long Chute, each contributing 3% to total reach habitat as measured in square feet. It is interesting to note that pool habitat constitutes less than 1% of total stream habitat in this reach. This indicates a serious habitat deficiency in the West Tributary. 22 EAST TRIBUTARY The lower portion of the East Tributary flows in an east -west direction on the south side of SR 599 (see Figure 2). The channel is a low lying depression that resembles a large drainage ditch running in a straight channel for approximately 750 feet parallel to the highway. Habitat in the channel is dominated by glides which flow smoothly through the narrow channel during both high and low flow periods. One fairly large pool was observed in between two large sections of glide habitat. The pool rated a high PQI, indicating that it is of superior habitat value for salmonid fishes. This pool may be of particular importance for any juvenile fish that use this channel for its protective cover during high stream flows, and for refuge during low stream flows. Substrates within the channel show that this low gradient portion of the tributary is a depositional area. Large amounts of sand and silt have settled out in the channel. In many places, the sediment is more than 2 to 3 feet deep. At the far eastern end, a 36 -inch culvert diverts the channel in a north -south direction (Figure 2, Photo 6). This culvert is very long, paralleling East Marginal Way South a distance of more than 2,250 feet. The culvert consists of one long continuous pipe that does not daylight from one end to the next. Land use along East Marginal Way South, in the vicinity of this culvert, includes commercial and industrial Metro and Boeing properties, a truck tire sales/repair shop, and buildings related to commercial warehousing and shipping. The 36 -inch culvert conveys not only the East Tributary but also collects stormwater from several catch basins along East Marginal Way South and the commercial properties listed above. The 36 -inch culvert continues along East Marginal Way South beyond the survey area. The East Tributary is connected to this culvert via another 24 -inch pipe that drains into the 36 -inch culvert. The East Tributary daylights upstream of this 24 -inch culvert (Figure 2, Photo 7). The open channel in this area is moderately incised with steep, highly vegetated streambanks on both sides of the stream. Channel habitat is relatively complex and shows a heterogenous mixture of alternating glides and small pools. Further up the channel the streambanks lose their steep slope and highly vegetated character, although patches of thick vegetation are present in some areas. The channel begins to run through residential property and some small businesses in this area. Stream gradient increases upstream of the culvert, and stretches of Low Gradient Riffle habitat begin to develop. The East Tributary crosses under South 126th Street via a 24 -inch corrogated metal pipe (CMP). More Low Gradient Riffle habitat occurs upstream of South 126th Street where the channel meanders through more low density residential property. Despite having good gravels and some large trees near the stream, the habitat is severely degraded due to the dumping of trash, tires, and general misuse of the riparian zone by land owners and children. The East Tributary is culverted again to divert it around the Becker/Trans World Express Trucking Company property, which is located between most of South 126th Street and South 128th Street. This culvert is very steep with a gradient of more than 10 percent. The upper portion of the East Tributary continues upstream of the Becker/Trans World Express Trucking Company property, and is characterized by alternating sections of 23 open channel habitat and culverts that flow through predominantly mid- to high-density residential properties and. streets. The open channel habitat areas observed were of varying quality throughout the upper reach of the East Tributary. Upstream of the trucking company, the open channel habitat areas were generally dominated by riffles which flowed through residential backyards (Figure 2, Photo 8). Most of the landowners in this upper reach have taken care of the stream by cleaning up trash and incorporating the stream in their landscaping. Riparian vegetation has suffered, however, by being replaced with ornamental plants and bushes of lesser quantity and quality along much of the stream. Despite the presence of good riffle and glide habitat, the habitat is unusable by fish due to the presence of numerous steep gradient culverts throughout this stream reach. Although culverts account for more than 60% of the East Tributary's total stream length in linear feet, they constitute only 40% of the total stream habitat as measured in square feet. Glide habitat follows closely with 37% of the total. Low Gradient Riffle, Pools, and High Gradient Riffle complete the list of habitat types observed on the East Tributary contributing 16%, 7%, and 1% of total reach habitat, respectively (Table 2). 5.2 Fish Habitat Requirements and Seasons of Use Salmonid species inhabiting the Duwamish River system include chinook (0. tshawytscha), coho (0. kisutch), and chum (0. keta) salmon (Williams et al., 1975), steelhead and resident rainbow trout (0. mykiss), and cutthroat trout (0. clarki). Although the specific life history characteristics, behavior patterns, and water use areas vary considerably for each of the anadromous salmonids, their general life history patterns are similar. It is currently unknown which of these species of salmonids currently inhabit Riverton Creek. However, visual observation of adult coho spawners has been confirmed in the West Tributary. Cutthroat trout are also likely to be found in Riverton Creek, although this is not confirmed. Adult salmon spawn in the fall, primarily between September and December, when water temperatures range between 42 and 58 degrees F. The eggs hatch in approximately 2 months, depending on water temperature, and the young emerge from the gravel 2 to 3 weeks later. Coho fry remain in fresh water (their native stream or in the mainstem Duwamish River) for 1 to 2 years before migrating to the ocean. Chinook fry spend a variable amount of time in fresh water before migrating to the ocean, ranging from a few days to 3 years. Chum salmon fry move downstream immediately after emergence, primarily at night, and are in fresh water only a matter of days (Wydoski and Whitney, 1979). Juvenile salmon utilize extensive areas of the mainstem Duwamish River for rearing and refuge habitat before migrating downstream to the ocean. Steelhead, rainbow and cutthroat trout usually spawn in the spring, between February and June, with a peak occurring in mid-April. Normally, trout fry hatch and emerge from the gravel redds between April and July. Steelhead juveniles usually remain in freshwater for 1 or 2 years while anadromous cutthroat may remain in freshwater for 2 to 9 years. Resident rainbow and cutthroat trout utilize the Duwamish River year around for rearing and refuge habitat, and depend on many tributary streams for spawning. 24 Adult salmonid spawners require large pools and other slow -water habitats for resting and cover during spawning. After salmonid young emerge from the redds they also require cover or refuge habitat that offers protection from predation and high water velocities. Coho fry normally prefer deep pools, while steelhead and chinook use a wide variety of habitats and prefer to remain close to gravel substrates near the streambed. Coho, chinook, and steelhead juveniles are all territorial during their freshwater rearing phase, and defend habitat areas to a certain extent. Salmonids predominantly feed on both aquatic and terrestrial insects (Diptera, mayflies, stoneflies), macrobenthic invertebrates, including worms and amphipods, and juvenile fishes. 6.0 HABITAT FACTORS LIMITING FISH SPAWNING AND REARING SUCCESS All streams have a limited fish production capacity. Normally, the full capacity is not reached because something limits fish productivity and growth. This can be readily observed by the fact that most streams are not teeming with fish. Stream ecosystems typically have one or more limiting factors which lead to a reduction in fish production and growth. A limiting factor can be defined as anything that impedes the potential rate of growth of any organism or population. Salmonid habitat attributes that could be limiting factors include water quality, spawning habitat, summer- and winter -rearing habitat, cover, stream flows, and food (Hunter, 1991). Although there may be numerous limiting factors affecting fish production on any one stream at the same time, only one of the factors is actually limiting the fish population. It can be said that a hierarchy of limiting factors exists on a stream. That is, the primary or the most important limiting factor limits the population. If that limiting factor were to be removed the next most important limiting factor would limit the population, and so on. Riverton Creek exhibits numerous limiting factors which affects its ability to produce and support fish populations. These factors are listed and prioritized below beginning with the most important limiting factor. These are the main habitat attributes that could be inhibiting salmonid production on Riverton Creek. 1. Anadromous Barriers and Migration Obstructions. Adult coho are limited in their upstream migration by the 20 -foot -high waterfall on the West Tributary and by the 2,250 -foot -long culvert on the East Tributary. Adults are unable to reach available spawning habitat upstream of these barriers. The tide gate at the mouth of Riverton Creek may at times actually physically prevent migration upstream and so becomes in effect an intermittant anadromous barrier. In addition, although they do not prevent migration, numerous culverts in the Lower Reach and West Tributary make it difficult for adults to migrate upstream. Reports by observers indicate that adult coho that do migrate upstream of the culverts are physically damaged and appear exhausted (personal communication with Mr. Clay Kean). 25 2. Spawning Habitat. Only limited spawning areas are accessible to adult salmonids on the West Tributary. These areas are capable of providing limited spawning success as they exist now. However, several factors could be improved to augment coho spawning success. These include limiting sediment inputs which deposit on gravel substrates, increasing riparian vegetative cover and instream structural elements, and increasing pool habitat for use as adult resting areas. 3. Rearing Areas Underseeded or Underutilized by Juveniles. Riverton Creek is underseeded with juvenile salmonids. Due to the lack of adult spawners there are few juvenile salmonids to inhabit the available rearing areas on the East and West Tributaries as well as the Lower Reach. The Lower Reach may be utilized by juveniles that have immigrated into Riverton Creek from the Duwamish River. However, these few immigrants will not fill up all of the habitat that is available. 4. Lack of Rearing/Resting Areas on the West Tributary. The rearing habitat that exists at present is located downstream of spawning habitat in the low gradient reach of the West Tributary. This habitat consists of glides with very little vegetative cover. Very few rearing areas exist throughout the spawning area. Any juveniles that emerge from the spawning gravels have to migrate downstream to find adequate cover and rearing areas. The presence of large high quality pools in the channel amongst the spawning riffles would provide the neccessary habitat for both rearing juveniles and resting or holding adult spawners. 5. Low Summer Streamflows. Although winter streamflows are adequate to support both adult spawners and overwintering juveniles, low summer streamflows may limit the amount of rearing area available for juveniles. As streamflow decreases, wetted habitat areas may be reduced to a point were juveniles cannot be supported. If this occurs, rearing habitat may be abandoned by juveniles, in favor of emigration to the Duwamish River. 6. Poor Water Quality. Water quality may act as a limiting factor by physiologically damaging salmonid juveniles and adults. Chemicals used by residents upstream, pollution from roadway runoff and parking lots, and high sediment loads during storms can all contribute to a decrease in fish survival and overall fish population health. 26 REFERENCES Hunter, C. J. 1991. Better Tout Habitat, A Guide to Stream Restoration and Management. Montana Land Reliance. Washington D. C. and Covelo, California. Island Press. King County. 1990. King County sensitive areas folio. Seattle, WA. King County. 1990. King County sensitive areas ordinance. Seattle, WA. King County Surface Water Management (SWM). 1991. Stream survey report criteria. Seattle, WA. McCain, M., D. Fuller, L. Decker and K. Overton. 1990. Stream classification and inventory procedures for Northern California. U.S.F.S. fish habitat relationships Technical Bulletin, Number 1. Pacific SouthWest Region, Arcata, California. Personal Communication to Mr. Bruce Burrow, METRO Environmental Compliance Chief, regarding combined sewer overflow pipe from Balvue pump station, 1996. Personal Communication to Mr. Clay Kean, Boeing employee, regarding observation of adult coho salmon spawner in West Tributary of Riverton Creek, 1996. Platts, W.S., G. Armour, G.D. Booth, M. Bryant, et al. 1987. Methods for evaluating riparian habitats with applications to management. USDA Forest Service, General Technical Report INT -221. U.S. Geological Survey (USGS). 1983. 7.5 minute series quadrangle map, Burien, Washington. Denver, CO. Washington State Department of Fisheries, Washington State Department of Wildlife, and Western Washington Treaty Indian Tribes. 1993. 1992 Washington State salmon and steelhead stock inventory. Olympia, WA. Williams, R.W., R.M. Laramie, and J.J. Ames. 1975. A catalog of Washington streams and salmon utilization. Volume 1, Puget Sound region. Washington Department of Fisheries. Olympia, WA. Wydoski, RS. and R.R. Whitney. 1979. Inland fishes of Washington. Seattle, WA and London, England. University of Washington Press. 27 giver tc-, Cree K Nio ...44.821Pa 0,*!;.r. • . •••• . ) v --"N'- _, --".- ii. ...a: ,,....;?....7,.,....1.-1 ...e) ).C. Locvfe" lE'cfc-11 Lit,' Tt Get COrlif .74; on 5. •-• • ''. ;4-Witif • • • 1- istuaq ..„?...,./...-. - . '-....- -- • .. .1..,... '1 :'-, ! 1 e."•,, / •';'...:.:: .;•-'7. P. . . ' '..*,, ' , '.. • • . .-. - „: yi;.4.•:-..S4.16. ' .- ". '-I e .„ --4.--;, , ' . ,:...., , • t • . -ha _.,. .iv.g, ..,,,,,,,i.)1,,...,..,. 1,,,.,r. .,. • , ,, ,., ,•,,,,, -. 1,(:a..,k--. • e„ 1.- -., '•••• .„,•-:-A- • • ..---'• • =„;,\I-. - •.,%:-. ----<,..v..e,... - • _•7%,,,r.• .,....;,1 ,,,,. i - -.---„,- • ''-' J. • .....,-14.,:, , '••',-,., , , . - A V . iffitl'' • v‘.011‘,1, „ ,, -,,;,•,- 1:::ii,71.4.1.L1'177-: .1 .. . ,. .., v. ,... -... --- . • . • ; A 41>N01:-.A.v. . .;•::- :"..",7",. , ... ,1..•,:.7----...y&., 11. g .C. 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' ' ' ' • ..'N... t .•, • \ i . . . • ..,.,!;., ' ••• ,..„,0• ; 17 .1 • •••".A. 'to P.oadfr.51'1'• /V-.4 -ct.•/f L -f '3j •giZtE n1• 11 , ••••,t •',:l?';.4 , ••Aey, C.7!: • APPENDIX C Description of Drainage Improvement Projects from the 1993 Surface Water Management Comprehensive Plan City of Tukwila Surfacewatcr Managment Program - . Program Element CAPITAL IMPROVEMENT PROGRAM MANAGEMENT MEASURE SOURCES CONTROLLED RESPONSIBLE AGENCY CONTACT/PHONE DESCRIPTION GOALS/OBJECTIVES REFERENCE ESTIMATED COST RATING NEW STORM DRAIN SYSTEM PARALLEL TO MARGINAL WAY Surface runoff quantity King County Install a 36 -inch diameter drainage pipe that parallels East Mar- ginal Way on the west side and ties into an existing 42" drain pipe- Improve drainage by increasing system capacity in vicinity of So. 126th Street and 37th Avenue So. City of Tukwila: Fostoria Basin Drainage Study, 1986 (Common Improvement Element 4) $40,000 (1989, ENR = 4771) TIE TO EXISTING_ 42" • LINE INSTALL so" DICAINACrE LINE POORLY DICAINED AICEA City of Tukwila Surface Water Management Program PROJECT NUMBER 6 MANAGEMENT MEASURE: DITCH STABILIZATION ON SOUTH 132ND STREET BETWEEN 34TH AVENUE SOUTH AND 35TH AVENUE SOUTH SOURCES CONTROLLED: Surface Runoff Quantity and Quality RESPONSIBLE AGENCY: City of Tukwila CONTACT/PHONE: SWM Engineer/443-0179 DESCRIPTION: Stabilize the ditch erosion through this reach using log check dams and revegetation. GOALS/OBJECTIVES: Increase capacity of ditch to accommodate 25 -year storm flows under ultimate development conditions and promote increased water quality. REFERENCE: City of Tukwila: Cascade View Annexation Priority Surface Water Management LIDs • ESTIMATED COST: 567,000 (1990, ENR = 4960) ILLUSTRATION: STABILIZE 150 LF OF ROADSIDE DITCI-! w L �2G w L_ 1) 133rd ST w (0 r 1! N LO r•. City of Tukwila Surface Water Management Program PROJECT NUMBER 7 MANAGEMENT MEASURE: NEW HIGH-FLOW BYPASS PIPELINE ALONG . 37TH AVENUE SOUTH BETWEEN SOUTH 132ND STREET AND SOUTH 128TH STREET SOURCES CONTROLLED: Surface Runoff. Quantity RESPONSIBLE AGENCY: City of Tukwila CONTACT/PHONE: SWM Engineer/443-0179 DESCRIPTION: Install 1,150 feet of 24 -inch diameter pipeline to intercept storm flows at intersection of South 132nd Avenue and 37th Avenue South and outfall into existing creek at the northeast intersection of 37th Avenue South and South 128th Street. Install special manhole where existing 18 -inch diameter pipeline discharges onto private property to maintain low flow to existing creek corridor. GOALS/OBJECTIVES: REFERENCE: ESTIMATED COST: ILL iISTRATION Increase capacity of existing system to accommodate 25 -year storm flows under ultimate development conditions. City of Tukwila: Cascade View Annexation Priority Surface Water Management LIDS 5382,000 (1990, ENR = 4960) NE\,1J 24.4) PIPE -' 38th AVE s 35th AVE S EXIST I8%0 PIPE WITI-! SPECIAL MANHOLE INSTALLED AT. EXIST NG C2EE.< OUTFALL 37th AVE Creek _c City of Tukwila Surface Water Management Program PROTECT NUMBER 8 MANAGEMENT MEASURE: LOCAL COLLECTOR IMPROVEMENT ON EAST MARGINAL WAY BETWEEN SOUTH 126TH STREET AND SOUTH 128TH STREET SOURCES CONTROLLED: Surface Runoff Quantity RESPONSIBLE AGENCY: City of Tukwila CONTACT/PHONE: SWM Engineer/443-0179 DESCRIPTION: Install approximately 540 feet of 18 -inch diameter collector pipeline along East Marginal Way South and South 126th Street to discharge on downstream side of creek culvert. GOALS/OBJECTIVES: REFERENCE: ESTIMATED COST: Eliminate street flooding during 25 -year storm event under ultimate development conditions. City of Tukwila: Cascade View Annexation Priority Surface Water Management LIDS $161,000 (1990, ENR = 4960) ILLUSTRATION: N co N ree 38th AVE S 37th AVE S c a5 18'4) COLLECTOR PIPELINE City of Tukwila Surface Water Management Program PROJECT NUMBER 9 MANAGEMENT' MEASURE: CULVERT REPLACEMENT UNDER SOUTH 126TH STREET • BETWEEN EAST MARGINAL WAY SOUTH AND 37TH AVENUE SOUTH SOURCES CONTROLLED• Surface Runoff Quantity RESPONSIBLE AGENCY: City of. Tukwila CONTACT/PHONE: SWM Engineer/443-0179 DESCRIPTION: Replace partially plugged existing eliptical CMP culvert with 42 - inch diameter RCP culvert. GOALS/OBJECTIVES: Adequate conveyance of 25 -year storm flows without major backup or road overtopping. REFERENCE: City of Tukwila: Cascade View Annexation Priority Surface Water Management LIDs ESTIMATED COST: 555,000 (1990, ENR = 4960) ILLUSTRATION: 37th AVE S REPLACE EXISTING EL 1PTICAL CMP CLLLVE T UNDER S 126TH ST W/ 470 RCP CULVERT i1 cs MPRC\NPL 38th AVE 5 Nt1P( NEW COLL EC T O2 PIPELINE IDENTIFIED IN PROJECT = 8 APPENDIX D Riverton Creek Habitat Enhancements - Boeing Section Note: the recommendations in this appendix were formulated as a joint effort of the Boeing Company and the City of Tukwila, and have not been reviewed by Entranco for engineering feasibility. RIVERTON CREEK HABITAT ENHANCEMENTS: Boeing Section Produced by: Ryan R. Partee, Fisheries Biologist for the City of Tukwila. Consistent with the Citizens Advisory Committee's priority on fisheries restoration within the Riverton drainage, a fisheries restoration design has been developed to serve as the implementation element as required in the grant funded and administered by the Department of Ecology. The City has been working with members of The Boeing Company to provide fisheries enhancement in the section of Riverton Creek which passes through their property (Figure 1), and are prepared to construct and complete these improvements in the Spring of 1997. Simple habitat restoration techniques will be the methodology employed during this phase. These techniques will then be evaluated for the potential use in other restorative projects within the City. The recommended habitat improvements to this drainage include the modification of the existing creek bed as well as augmentations to the surrounding streamside vegetation. This includes instream structures and the utilization of a variety of selected vegetation (Table 1). Due to the nature of fisheries enhancement projects, the specific treatments listed in the following section may be changed or altered in order to accommodate undiscovered idiosyncrasies. It is recommended that restoration in this portion of the Riverton drainage begin immediately and be completed prior to the emergence of the currently incubating coho which will begin leaving the incubator as early as mid- March. Recommended future enhancements should include; the incorporation of sediment traps, storm water energy dissipaters, and make improvements in water quality. These items are not addressed in this portion of the enhancement effort. Habitat improvement recommendations for Riverton Creek: This reach of the Riverton drainage has been subdivided into manageable sections (in general 25m units, Figure 2). Each individual section has been given a specific enhancement treatment designed to best make use of the existing characteristics. When completed, these modifications should greatly increase the ecological diversity and complexity of this system. The recommendations for each section are as follows: Section 1. (Sta. 1-2, 0 - 25m) Streambed: The stream bed should be deepened by a depth of 2-3 ft through removing the accumulated depositional material. Recreate a natural stream bed with exposed gravel substrate. Place a rock structure (to a height of 1/3 the channel depth) across the stream channel to provide pool habitat at 15m (Figure 3). Stream banks: Bioengineer for erosion control. Remove invasive vegetation and replant with available streamside and riparian vegetation (Figure 4). Section 2. (Sta. 2-3, 25 - 50m) Streambed: The stream bed should be deepened by a depth of 2-3 ft through removing the accumulated depositional material. Recreate a natural stream bed with exposed gravel substrate. Place several 1-2 person rocks into stream bed to create slight meander (Figure 5). Place a rock structure at 50m to provide pool habitat. Stream banks: Bioengineer for erosion control. Remove invasive vegetation and replant with available streamside and riparian vegetation. Section 3. (Sta. 3-4, 50 - 75m) Streambed: The stream bed should be deepened by a depth of 2-3 ft through removing the accumulated depositional material. Recreate a natural stream bed with exposed gravel substrate. Place several 1 person rocks into stream bed to create slight meander. Stream banks: Bioengineer for erosion control. Remove invasive vegetation and replant with available streamside and riparian vegetation. Section 4. (Sta. 4-5, 75 - 100m) Streambed: The stream bed should be deepened by a depth of 2-3 ft through removing the accumulated depositional material. Remove reed canary grass, Phalaris arundinacea. Recreate a natural stream bed with exposed gravel substrate. Place several 1 person rocks into stream bed to create slight meander. Stream banks: Bioengineer for erosion control. Remove invasive vegetation and plant with available streamside and riparian vegetation. Section 5. (Sta. 5-6, 100 - 125m) Streambed: The stream bed should be deepened by a depth of 2-3 ft through removing the accumulated depositional material. Remove reed canary grass, Phalaris arundinacea. Recreate a natural stream bed with exposed gravel substrate. Place several 1 person rocks into stream bed to create slight meander. Stream banks: Bioengineer for erosion control. Remove invasive vegetation and plant with available streamside and riparian vegetation. Section 6. (Sta. 6-7, 125 - 150m) Streambed: The stream bed should be deepened by a depth of 2-3 ft through removing the accumulated depositional material. Remove reed canary grass, Phalaris arundinacea. Recreate a natural stream bed with exposed gravel substrate. Place several 1 person rocks into stream bed to create slight meander. Place a rock structure (to a height of 1/3 the channel depth) across the stream channel to provide pool habitat at 150m. Stream banks: Bioengineer for erosion control. Remove invasive vegetation andplant with available streamside and riparian vegetation. Section 7. (Sta. 7-8, 150 - 175m) Streambed: The stream bed should be deepened by a depth of 2-3 ft through removing the accumulated depositional material. Remove reed canary grass, Phalaris arundinacea. Recreate a natural stream bed with exposed gravel substrate. Place several 1 person rocks into stream bed to create slight meander. Stream banks: Bioengineer for erosion control. Remove invasive vegetation and plant with available streamside and riparian vegetation. Section 8. (Sta. 8-9, 175 - 200m) Streambed: The stream bed should be deepened by a depth of 2-3 ft through removing the accumulated depositional material. Remove reed canary grass, Phalaris arundinacea. Recreate a natural stream bed with exposed gravel substrate. Place a rock structure (to a height of 1/3 the channel depth) across the stream channel to provide pool habitat at 190m. Stream banks: Bioengineer for erosion control. Remove invasive vegetation and plant with available streamside and riparian vegetation. Section 9. (Sta. 9-10, 200 - 285m) Streambed: Remove sand and sediment from culvert to improve flow. Armor upstream end of culvert to minimize additional undercut. Stream banks: None. Section 10. (Sta. 10-11, 285 - 310m) Streambed: The stream bed should be deepened by a depth of 2 ft through removing the accumulated depositional material. Remove reed canary grass, Phalaris arundinacea. Recreate a natural stream bed with meander and exposed gravel substrate. Place a rock structure (to a height of 1/3 the channel depth) across the stream channel to provide pool habitat at 292m and 305m. Stream banks: Plant with available streamside and riparian vegetation. Remove or replace unnecessary chain link fencing. Section 11. (Sta. 11-12, 310 - 335m) Streambed: The stream bed should be deepened by a depth of 2 ft through removing the accumulated depositional material. Remove reed canary grass, Phalaris arundinacea. Recreate a natural stream bed with meander and exposed gravel substrate. Place a rock structure (to a height of 1/3 the channel depth) across the stream channel to provide pool habitat at 312m and 330m. Stream banks: Plant with available streamside and riparian vegetation. Remove or replace unnecessary chain link fencing. Section 12. (Sta. 12-13, 335 - 360m) Streambed: The stream bed should be deepened by a depth of 2 ft through removing the accumulated depositional material. Remove reed canary grass, Phalaris arundinacea. Recreate a natural stream bed with meander and exposed gravel substrate. Place 1-2 person rocks in stream bed to create meander. Place a rock structure (to a height of 1/3 the channel depth) across the stream channel to provide pool habitat at 360m. Stream banks: Plant with available streamside and riparian vegetation. Remove or replace unnecessary chain link fencing. Section 13. (Sta. 13-14, 360 - 385m) Streambed: The stream bed should be deepened by a depth of 2 ft by removing the accumulated depositional material. Remove reed canary grass, Phalaris arundinacea. Recreate a natural stream bed with meander and exposed gravel substrate. Place 1-2 person rocks in stream to create meander. Stream banks: Plant with available streamside and riparian vegetation. Remove or replace unnecessary chain link fencing. Section 14. (Sta. 14-15, 385 - 410m) Streambed: The stream bed should be deepened by a depth of 2-3 ft through removing the accumulated depositional material. Remove reed canary grass, Phalaris arundinacea. Recreate a natural stream bed with meander and exposed gravel substrate. Place 1-2 person rocks in stream to create meander. Stream banks: Plant with available streamside and riparian vegetation. Remove or replace unnecessary chain link gate and fencing. Section 15. (Sta. 15-16, 410 - 435m) Streambed: The stream bed should be deepened by a depth of 2-3 ft through removing the accumulated depositional material. Remove reed canary grass, Phalaris arundinacea. Recreate a natural stream bed with meander and exposed gravel substrate. Place 1-2 person rocks in stream bed to create meander. Stream banks: Plant with available streamside and riparian vegetation. Remove or replace unnecessary chain link fencing. Section 16. (Sta. 16-17, 435 - 460) Streambed: The stream bed should be deepened by a depth of 2-3 ft through removing the accumulated depositional material. Remove reed canary grass, Phalaris arundinacea. Recreate a natural stream bed with meander and exposed gravel substrate. Place 1-2 person rocks in stream bed to create meander. Stream banks: Plant with available streamside and riparian vegetation. Remove or replace unnecessary chain link fencing. Section 17. (Sta. 17-18, 460 - 486m) Streambed: The stream bed should be deepened by a depth of 3-5 ft through removing the accumulated depositional material. Remove sediment from culvert which begins at 468m. Remove reed canary grass, Phalaris arundinacea. Recreate a natural stream bed and exposed gravel substrate. Stream banks: Plant with available streamside and riparian vegetation. Remove or replace unnecessary chain link fencing. Section 18. (Sta. 18-19, 486 - 580m) Streambed: The stream bed should be deepened by a depth of 2-3 ft through removing the accumulated depositional material. Remove reed canary grass, Phalaris arundinacea. Recreate a natural stream bed with meander and exposed gravel substrate. Place a rock structure (to a height of 1/3 the channel depth) across the stream channel to provide pool habitat at 500m, 525m, 555m, and 575m. Stream banks: Plant with available streamside and riparian vegetation. Remove or replace unnecessary chain link fencing. Section 19. (Sta. 19-20, 535 - 560m) Streambed: The stream bed should be deepened by a depth of 2-3 ft through removing the accumulated depositional material. Remove reed canary grass, Phalaris arundinacea. Recreate a natural stream bed and exposed gravel substrate. Place 1-2 person rocks in stream to create meander. Stream banks: Plant with available streamside and riparian vegetation. Remove or replace unnecessary chain link fencing. Table 1. Vegetation for proposed enhancement planting. * Zone A. Selected riparian vegetation. Common Name Trees: Western Hemlock Sitka Spruce Western Red Cedar Red Alder Big Leaf Maple Black Cottonwood White Birch Bitter Cherry Pacific Crab Apple Oregon Ash Pacific Dogwood Zone B. Selected streamside vegetation. Common Name Shrubs: Highbush Cranberry Red Elderberry Sitka Mountain Ash Salmonberry California Wax Myrtle Pacific Willow Red Osier Dogwood Vine Maple Fern: Deer Fern Sword Fern Lady Fern Horsetails: Giant Horsetail Iridaceae: Blue Eyed Grass Golden Eyed Grass Wild Flag Saxifragaceae: Red Stemmed Saxifrage Piggyback Plant Ranunculaceae: Broad Leaved Marsh Marigold Rosaceae: Silverweed Apiaceae: Water Parsnip Lamiaceae: Northern Water Horehound Asteraceae: Newcombe's Butterweed Menyanthaceae: Deer Cabbage Araceae: Skunk Cabbage Zone C. Selected aquatic vegetation. Common Name Aquatics: Arrow Grass Water Plantain Cattail Diverse -Leaved Water-Starwort Scientific Name Tsuga heterophylla Picea sitchensis Thuja plicata Alnus rubra Acer macrophyllum Populus balsamifera ssp. trichocarpa Betula papyrifera Prunus enarginata Malus fusca Fraxinus latifolia Cornus nuttalli Scientific Name Viburnum edule Sambucus racemosa Sorbus sitchensis Rubus spectabilis Myrica californica Salix lucida ssp. lasiandra Cornus stolonifera Acer circinatum Blechnum spicant Polystichum munitum Athyrium ftlix femina Equisetum telmatiea Sisyrinchium idahoence Sisyrinchium califonicum Iris serosa Saxifraga lyallii Tolmiea menziesii Caltha bijlora Potentilla anserina Sium suave Lycopus unijlorus Senecio newcombei Fauria crista-galli Lysichiton americanum Scientific Name Triglochin maritimum Alisma plantago- aquatica Typha latifolia Callitriche heterophylla Seasonality Coniferous Coniferous Coniferous Deciduous Deciduous Deciduous Deciduous Deciduous Deciduous Deciduous Deciduous Seasonality 9 Deciduous Deciduous Deciduous Evergreen Deciduous Deciduous Deciduous Evergreen Evergreen 9 9 Perennial Perennial Perennial Perennial Perennial Perennial Perennial Perennial Perennial Perennial Perennial Perennial Seasonality Perennial Perennial Perennial 9 • Use of these species is subject to their availability. Listed species are not necessarilly restricted to a singular environment as many are found in areas outside of this generalization. Additional species not listed may also be utilized. ' ' 127 St ' ' ' ' 1 - IC np� li Figure 1. Riverton Creek drainage. 0 Sao '.0 44 q S 120 Place uoIlaas 2u►aog S116St r Remote site incubator location 1 S126St S128St 1 V S St Cidily of Tukwila a CITY OF TUKWILA Public Works Engineering 6300 Southcenter Boulevard Tukwila WA 98188 (206) 433-0179 fRIWN RY• !L. 11442.1%— REVISED BY: 7112 i1AML: DATE: Lau.: m,r ry xau Ouwa ish RIVer�y } i 11i k' + 1 iC y�1 f;�l t.1 ;A: !YA:f J _ p,k.+r,?Tr-y''�`t�:-�.,�• Sediment; Pond GATEWAY NORTH COMMERCIAL PROPERTY BalvueStormwater and Combined Sewer..Overflow Pipe `1 'BOEING PROPERTY Small Tributary Draining from HWY 99 1.: BASE SOURCE: ENTRANCQ NOT TO SCALE Photo Location and Number (see Figure 2 - cont.) Flow Diection — — — — Basin Boundary Stream Reach without Habitat Survey ■ ■� Stream Reach with Habitat Survey Culvert Building Proposed sediment trap* Pac. Hwy. Drainage --\1/4 Op. STA. 5 �' STA. 4 STA. 3 _ Proposed rock structure 2 ri J STA. 6 c STA. 2 LC -1 's STA. 1 Incubator location Proposed rock structure Chainlink fencing Proposed sediment trap Proposed rock structure P STA. 7 STA. 8 7. , STA. 9 L Proposed rock structure 85m Railroad tie retaining wall STA. 10 STA. 11 Continued on sheet 2 Chainlink fencing Proposed rock structure Proposed rock structure * Future installation Figure 2. Riverton Creek, Boeing section sheet 1. Cigy of Tukwila CITY OF TUKWILA Public 'OrkS Engineering 6300 Southcenter Boulevard Tukwila ' ./A 98188 (2047 433-0179 IDRAWN BY: Ryan R. Patter REVISED BY: FILE NAME: Boein section Riverton Creek DATE: I I/1&% DATE: SC.'LE: NOT ro SCALE SHEET NUMBERS Blackberry i STA. 14 STA. 16 STA. 17 STA. 15 _ w From sheet 1 Pedestrian bridge :S I: Chainlink fencing i Proposed rock structure STA. 18 94m STA. 19 COO STA. 20 744+ijy4c[7w. - ,--fxre x-c+QY4. 0 \-- Gabion retaining wall Fire hydrant Figure 2. Riverton Creek, Boeing section sheet 2. City of Tzkwlla CITY OF TUKWILA Public Works Engineering 6300 Southcenter Boulevard Tukwila WA 98198 f ZO6r 433-0179 IDRAWN BY: Rvan R. Partee 1 DATE: 11n REVISED BY: FILE NAME: Boeing section Riverton Creek DATE: SZ.LE: NOT TO SCALE SHEET NUMBERS 2 Armored section typical. Figure 3. Rock structure to create pool habitat. Unarmored section typical. City of Tukwila CITY OF TUKWILA Public Works Engineering 6300 Soutncenter Boulevard Tukwila VQ 98188 (Z06) 433-0179 naLxv RY• DAT!' REVISED BY: DATE: )ILL NASAL: ..vr }v xxts Zone A. Largcr riparian vegetation ) :67; • 7. .. • •.. • • • "4'. ‘. • • t • Zone B. Smaller strcamside vegetation Zone C. Aquatic vegetation Zone B. Smaller streamside vegetation • :757 • k •1:;r•li .! • . • .„. • ..^ Zone A. Largcr riparian vegetation Figure 4. Proposed riparian, streamside, and aquatic re -vegetation typical. City of Tukwila CITY OF TUKWILA Public Vorks Engineering 6300 Southcenter Boulevard Tukwila VA 98188 C2•34) 431.3171 ntAvt4 ny..--r?4,ZTge- REVISED 111,TP, DATE: Ha. AS111.. 0‘//1 93 - Nwr Figure 5. Rock placement to create stream meander. City of Tukwila CITY OF TUKWILA Public Works Engineering 6300 Southcenter Boulevard Tukwila VA 98188 caw q7-0171 (1171.WI4 AY. 2. 64(21—G REVISED BY: n.rr• //n17�' DATE t lLt :(Al1L wr to--sCEli APPENDIX E Hydrologic Analysis APPENDIX E HYDROLOGIC ANALYSIS Riverton Stormwater Quality Management Plan - 1997 E.1 95035 / reports / appetext (5/20/97) lc APPENDIX E DRAFT Model Description and Calibration Results The U.S. Environmental Protection Agency (EPA) hydrologic model, Hydrologic Simulation Program - Fortran (HSPF), was used as the computer modeling tool for the Riverton Creek project. The model provides a continuous simulation of stream flow based on recorded rainfall records, and has a distinct advantage over event -based models, which only predict flow responses for single storm events. Various rainfall -runoff relationships are represented in the model, providing a means to continuously predict changes in the moisture stored within the watershed, as well as the amount of runoff generated by surface and subsurface flow. Surface flow is that portion of the rainfall that runs directly off either pervious or impervious land surface, rather than rainfall that either infiltrates into the soil or evaporates. Subsurface flow includes interflow (shallow lateral groundwater flow that commonly occurs in the soil mantle above relatively impermeable till or hardpan layers) and deeper groundwater flow. The HSPF model was configured to represent the various soils, land cover and surface topography represented in the Riverton Creek watershed. Soils data were obtained from Soil Conservation Service maps. Land cover represents coverages of forest, grass -covered open space or impervious surfaces and is based upon land use as shown on a recent aerial photograph of the basin. A total of eleven subbasins were defined to assist in the model assessment (see figure 16 in the main text). The HSPF model developed for the Riverton Creek basin was "calibrated" by comparing measured and simulated inflows. Measured flows were obtained from two continuous flow gage sites at stations 3 and 4, and from crest stage gages located at other sites in the basin. Rainfall data was obtained from nearby SeaTac Airport. Rainfall and flow data were obtained for the period February, March, and April of 1996. Adjustments were made to the HSPF parameters to obtain the best match between predicted and measured runoff peaks and baseflows. Predicted (simulated) flows are shown for each subbasin for the 2-, 10-, 25-, and 100 -year storm events for both forested (pre -development) and existing land use conditions (see tables attached). A comparison of these tables shows that peak flows under existing land use can be up to 10 times greater than flows prior to development. The dramatic increases in peak flows result in increased flooding potential, increased erosion/ sedimentation problems in the stream system, and increased stream velocities during peak flow periods. E.2 Riverton Stormwater Quality Management Plan - 1997 95035 / reports / appetext (5/20/97) Jc DRAFT APPENDIX E The model was also used to assess three different flow diversion options ("scenarios" in the main text). Different combinations of subbasins were diverted under options A, B and C (see tables attached). As shown in the tables, diversion of subbasins T6, T7, T2b, K8, and the western portion of T2a (Option C) provided the greatest reductions in downstream flows. Option C also would require the greatest investment in new storm diversion pipe construction to achieve potential downstream flow reduction benefits. A preliminary comparison was made of downstream flows versus existing stream channel/pipe capacity at selected locations. This analysis showed that pipe capacity was inadequate to handle peak flows for some storms. This result was consistent with known flooding problems in the basin. However, the level of detail provided as input to the capacity analysis includes assumptions that need to be verified by field survey. The recommended field survey should include: (1) stream channel slopes and cross sections, and (2) culvert pipe invert elevations, slopes and extent of sedimentation. It is recommended that additional model analysis be performed as part of facility design to re -check the capacity analysis for individual pipe segments. This will also make it possible to confirm the downstream flood control benefits of the flow diversion alternatives. Riverton Stormwater Quality Management Plan - 1997 95035 / reports / appetext (5/20/97) lc E.3 Riverton otormwater Plan 12/17/9610:33 AM 7.00 6.00 5.00 0 4.00 c 3.00 LL 2.00 Station 4 (HSPF Reach 7) 1.00 — - s; • • o ' n 9, LL • • f 1 I I .0 in `m co m u lira) i 2 2 N QS N N g- N Date Simulated Recorded Page 1 Riverton - flow predictions - existing land use 1/9/97 Stream Tributary Predicted Peak Annual Flow Rate Sub -basin Reach Area (ac) 2 -yr 10 -yr 25 -yr 100 -yr T1 a 1 435 99.7 136.3 152.5 174.7 T1 b 2 393 94.1 132.6 149.7 172.9 T2a/K8 3 147 31.9 45.7 53.3 65.4 T2bd/SR99c 4 45 8.2 11.2 12.5 14.4 T2b 5 34 5.7 7.5 8.2 9.2 T3 6 234 61.6 88.1 100.6 118.5 T4/SR99a 7 151 36.5 52.9 59.9 69.2 T5 8 25 6.2 7.9 8.7 9.7 T6d/SR99b 9 45 10.8 15.3 17.3 19.8 T6 10 33 7.6 10.4 11.5 12.8 T7 11 81 20.9 30.0 33.5 37.8 Predicted flow rates are based upon a 43 year continuous simulation using HSPF and SeaTac rainfall Riverton - flow predictions - forested conditions 1/9/97 Stream Tributary Predicted Peak Annual Flow Rate Sub -basin Reach Area (ac) 2 -yr 10 -yr 25 -yr 100 -yr T1 a 1 435 5.7 12.1 16.2 23.3 T1 b 2 393 5.4 8.7 15.2 22.0 T2a/K8 3 147 2.6 4.8 6.2 8.5 T2bd/SR99c 4 45 1.7 2.5 2.9 3.6 T2b 5 34 1.6 2.2 2.5 3.0 T3 6 234 2.6 6.6 9.2 13.9 T4/SR99a 7 151 1.8 4.3 6.1 9.3 T5 8 25 0.3 0.6 0.9 1.3 T6d/SR99b 9 45 0.6 1.4 1.9 2.9 T6 10 33 0.5 1.1 1.5 2.2 T7 11 81 0.9 2.6 3.8 6.3 Predicted flow rates are based upon a 43 year continuous simulation using HSPF and SeaTac rainfall Existing impervious surfaces are assumed to be flat -sloped, forest -covered till soils. Riverton - flow predictions - bypass option A 1/9/97 •Stream Predicted Peak Annual Flow Rate Sub -basin Reach 2 -yr 10 -yr 25 -yr 100 -yr T1 a 1 75.0 91.2 114.3 132.9 T1b 2 67.7 94.2 107.3 126.6 T2a/K8 3 29.6 42.3 49.2 60.2 T2bd/SR99c 4 8.2 11.2 12.5 14.4 T2b 5 5.7 7.5 8.2 9.2 T3 6 37.6 51.5 57.7 66.3 T4/SR99a 7 12.0 16.4 18.0 20.1 T5 8 6.2 7.9 8.7 9.7 T6d/SR99b 9 4.5 5.9 6.5 7.2 T6 10 7.6 10.4 11.5 12.8 T7 11 20.9 30.0 33.5 37.8 Bypass structures Bypass outlet 24.3 34.7 38.2 42.2 T7 diversion to east trib. 2.1 2.3 2.4 2.5 to bypass 18.9 27.9 31.4 35.7 T6 diversion to east trib. 1.7 1.8 1.8 1.9 to bypass 6.7 9.7 10.6 11.5 Predicted flow rates are based upon a 43 year continuous simulation using HSPF and Sea Tac rainfall Diverting excess flows from sub -basins 77 and T6. Changes in Peak 2 -yr 10 -yr Annual Flow (%) 25 -yr 100 -yr -25% -28% -7% 0% 0% -39% -67% 0% -58% 0% 0% -33% -29% -7% 0% 0% -42% -69% 0% -61% 0% 0% -25% -28% -8% 0% 0% - 43% -70% 0% - 62% 0% 0% -24% -27% -8% 0% 0% -44% -71% 0% -64% 0% 0% Riverton - flow predictions - bypass option B 1/9/97 Stream Predicted Peak Annual Flow Rate Sub -basin Reach 2 -yr 10 -yr 25 -yr 100 -yr T1a 1 71.6 96.9 109.1 127.1 T 1 b 2 64.1 89.3 101.8 120.5 T2a/K8 3 26.1 37.5 43.9 54.4 T2bd/SR99c 4 4.4 5.7 6.4 7.4 T2b 5 5.7 7.5 8.2 9.2 T3 6 37.6 51.5 57.7 66.3 T4/SR99a 7 12.0 16.4 18.0 20.1 T5 8 6.4 7.8 8.1 8.3 T6d/SR99b 9 4.6 5.9 6.4 7.0 T6 10 7.6 10.4 11.5 12.8 T7 11 20.9 30.0 33.5 37.8 Bypass structures Bypass outlet 27.7 39.7 44.7 51.0 T7 diversion to east trib. 2.1 2.3 2.4 2.5 to bypass 18.9 27.9 31.4 35.7 T6 diversion to east trib. 1.7 1.8 1.8 1.9 to bypass 6.7 9.7 10.6 11.5 T2b diversion to west trib. to bypass Predicted flow rates are based upon a 43 year continuous simulation using HSPF and SeaTac rainfall Diverting excess flows from sub -basins T7, T6 and T2b. Changes in Peak 2 -yr 10 -yr Annual Flow (%) 25 -yr 100 -yr -28% -32% -18% -46% 0% • -39% -67% 3% -57% 0% 0% -29% -33% -18% -49% 0% -42% -69% -1% -61 % 0% 0% -28% - 32% -18% - 49% 0% - 43% - 70% -7% - 63% 0% 0% -27% -30% -17% -49% 0% -44% -71% -14% • -65% 0% 0% Riverton - flow predictions - bypass option C 1/9/97 Stream Predicted Peak Annual Flow Rate Sub -basin Reach 2 -yr 10 -yr 25 -yr 100 -yr T1 a 1 69.3 93.8 105.7 123.3 T1b 2 61.7 85.7 97.8 115.9 T2a/K8 3 23.7 34.2 40.3 50.3 T2bd/SR99c 4 4.4 5.7 6.4 7.4 T2b 5 5.7 7.5 82 9.2 T3 6 37.6 51.5 57.7 66.3 T4/SR99a 7 12.0 16.4 18.0 20.1 T5 8 6.2 7.9 8.7 9.7 T6d/SR99b 9 4.5 5.9 6.5 7.2 T6 10 7.7 10.4 11.3 12.1 T7 11 20.9 30.0 33.5 37.8 Bypass structures Bypass outlet 29.9 42.9 48.3 55.4 T7 diversion to east trib. 2.1 2.3 2.4 2.5 to bypass 18.9 27.9 31.4 35.7 T6 diversion to east trib. 1.7 1.8 1.8 1.9 to bypass 6.6 9.7 10.9 12.3 T2b diversion to west trib. to bypass Predicted flow rates are based upon a 43 year continuous simulation using HSPF and Sea Tac rainfall Diverting excess flows from sub -basins T7, T6, T2b, K8 and westem portion of T2A. Changes in Peak 2 -yr 10 -yr Annual Flow (%) 25 -yr 100 -yr -30% -34% -26% -46% 0% -39% -67% 0% -58% 1% 0% -31% -35% -25% -49% 0% -42% -69% 0% -61 % 0% 0% -31% -35% -24% -49% 0% -43% -70% 0% -62% -2% 0% 0% -29% -33% -23% -49% 0% -44% -71 % 0% -64% -5%