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Home My WebLink AboutCAG-92-120 c IMPLEMENTATION STRATEGY Renton/Lake Washington Pollution Abatement Program Prepared for: City of Renton Surface Water Utility t� .0 1 June1994 CMMI HERRERA ENVIRONMENTAL CONSULTANTS i 100%Re yded P - IMPLEMENTATION STRATEGY Renton/Lake Washington Pollution Abatement Program Prepared for: City of Renton Surface Water Utility 200 Mill Avenue South Renton, Washington 98055 Prepared by: Herrera Environmental Consultants, Inc. 1414 Dexter Avenue North, Suite 200 Seattle, Washington 98109 and R.W. Beck and Associates 2101 Fourth Avenue, Suite 600 Seattle, Washington 98121 and Bredouw P.O. Box 30705 Seattle, Washington 98103 June 1994 This project has been funded in part by the Washington Department of Ecology Centennial Clean Water Fund IMPLEMENTATION STRATEGY Renton/Lake Washington Pollution Abatement Program Prepared for: City of Renton Surface Water Utility June 1994 CONTENTS Abbreviations.................................................................................................................vi 1. Introduction .............................................................................................................. 1 Goalsand Objectives .............................................................................................4 TechnicalApproach...............................................................................................5 2. Drainage Basin Characteristics..................................................................................7 StormDrainage System ......................................................................................... 8 North Renton Basin Storm Drainage System ................................................ 8 West Hill Basin Storm Drainage System.......................................................9 LandUse ............................................................................................................. 10 Land Use in North Renton Basin ................................................................ 10 LandUse in West Hill Basin....................................................................... 11 Aquatic Resources in Lake Washington............................................................... 12 Shoreline (Riparian) Vegetation.................................................................. 12 North Renton Basin Stormwater Outfall............................................ 12 West Hill Basin Stormwater Outfall .................................................. 13 LittoralZone .............................................................................................. 13 WaterColumn................................................................................... 14 Aquatic Macrophyte Beds ................................................................. 15 Sediment and Sediment/Water Interface............................................ 15 BusinessInventory............................................................................................... 16 Business Inventory of North Renton Basin ................................................. 18 NPDES-Permitted Facilities in North Renton Basin.......................... 18 Hazardous Waste Generators in North Renton Basin......................... 19 Contaminated Sites in North Renton Basin........................................20 Business Inventory of West Hill Basin........................................................ 21 NPDES-Permitted Facilities in West Hill Basin.................................22 Hazardous Waste Generators in West Hill Basin............................... 22 Contaminated Sites in West Hill Basin..............................................22 Housekeeping Practices in North Renton and West Hill Basins............................22 SpillRecords .......................................................................................................24 Summary of Drainage Basin Characteristics ........................................................25 3. Contaminant Source Characterization......................................................................27 Storm Drain Sampling Program................................................... ...........28 OutfallSampling .......................................................................................28 Outfall Sampling Methods.................................................................28 Outfall Sampling Results...................................................................28 SubbasinSampling..................................................................................... 36 North Renton Basin Sampling Stations.............................................. 36 West Hill Basin Sampling Stations.................................................... 37 Subbasin Sampling Methods.............................................................. 38 Subbasin Sampling Results................................................................ 38 Sediment Sampling Program................................................................................45 Sediment Sampling Methods......................................................................46 Freshwater Sediment Guidelines.................................................................46 Historical Sediment Data............................................................................ 47 Urban Street Dust Data...............................................................................47 ii Sediment Sampling Results ........................................................................ 48 Metals ...............................................................................................48 OrganicCompounds..........................................................................49 Illicit Connection Survey..................................................................................... 51 Storm Drain Sampling Methods.................................................................. 51 Storm Drain Sampling Results....................................................................52 Fecal Coliform Bacteria..................................................................... 52 Turbidity, pH, Temperature, and Dissolved Oxygen.......................... 53 Total Petroleum Hydrocarbons.......................................................... 53 AncillaryTesting............................................................................... 53 Hach Field Parameters....................................................................... 53 Storm Drain Monitoring Recommendations................................................ 54 HistoricalData..................................................................................................... 54 Boeing Stormwater Sampling Data............................................................. 54 Paccar Stormwater Monitoring Data........................................................... 56 Contaminant Source Characterization Summary .................................................. 56 NorthRenton Outfall.................................................................................. 57 North Renton Subbasin Monitoring................................................... 58 North Renton Illicit Connection Monitoring...................................... 59 North Renton Outfall Sediment Sampling ......................................... 59 WestHill Outfall........................................................................................60 West Hill Subbasin Monitoring.........................................................60 West Hill Illicit Connection Monitoring ............................................ 61 West Hill Outfall Sediment Sampling................................................ 61 4. Existing Renton City Pollution Control Activities...................................................63 SewerUtility........................................................................................................63 SurfaceWater Utility...........................................................................................63 WaterUtility........................................................................................................66 FireDepartment...................................................................................................66 SolidWaste Utility .............................................................................................. 67 RentonMunicipal Airport....................................................................................67 Parks and Recreation Department ........................................................................ 69 5. Pollution Abatement Criteria...................................................................................71 6. Evaluation of Pollution Abatement Alternatives.......................................................73 WaterQuality Program........................................................................................ 73 Storm Drainage System Maintenance Activities ......................................... 74 Procedures to Maximize Pollution Removal in Storm Drainage System .................................................. 74 StaffTraining.................................................................................... 76 Storm Drainage System Inspections .................................................. 77 TechnicalAssistance................................................................................... 78 Nonstructural Source Controls for Local Businesses andResidents.................................................................. 78 Inspection and Technical Assistance Staff Training........................... 84 Business Inspection and Source Control Efforts ................................ 85 Educational Workshops..................................................................... 87 Coordination with Other City Programs ............................................ 87 Individual Site Cleanup Actions........................................................ 87 Enforcement of Pollution Abatement Program Objectives................. 88 iii Monitoring and Record-Keeping Programs................................................. 89 Water Quality Program Record-Keeping........................................... 89 WaterQuality Sampling.................................................................... 90 Illicit Connection Surveys.....................................................:...........92 Preservation and Enhancement of Natural Drainage Systems...................... 93 Coordination of Spill Control and Containment Capabilities....................... 93 PublicEducation..................................................................................................94 Existing Water Quality Education Efforts...................................................95 Cityof Renton................................................................................... 95 KingCounty..................................................................................... 97 Washington Department of Ecology................................................ 100 Puget Sound Water Quality Authority............................................. 101 Waste Information Network............................................................ 101 Public Education Options ......................................................................... 101 Options for the General Public ........................................................ 101 Options for Businesses.................................................................... 108 Recommended Public Education Program................................................ 109 Coordination with Comprehensive Storm and Surface Water Management Plan.................................. 110 Storm Drain Stenciling Program...................................................... III Best Management Practices Workshop for Airport Tenants............. Ill Interdepartmental Briefing on Program Coordination...................... 112 Environmental Education Coordinator............................................. 112 School Curriculum Programs........................................................... 112 Public Informational Media............................................................. 113 Structural Controls for Stormwater Treatment................................................... 113 Biofilter.................................................................................................... 115 Pollutant Removal Mechanisms of Biofilters................................... 116 Biofilter Performance...................................................................... 116 Applicability of Biofilters in North Renton and West Hill Basins.... 117 CompostFilter.......................................................................................... 119 Pollutant Removal Mechanisms of Compost Filters......................... 119 Compost Filter Performance............................................................ 120 Applicability of Compost Filters in North Renton and West Hill Basins........................................................... 120 Oil/Water Separator.................................................................................. 123 Pollutant Removal Mechanisms of Oil/Water Separators................. 123 Oil/Water Separator Performance.................................................... 123 Applicability of Oil/Water Separators in North Renton and WestHill Basins........................................................... 124 SedimentTrap.......................................................................................... 124 Sediment Trap Performance............................................................ 125 Applicability of Sediment Traps in Renton...................................... 125 CatchBasin Insert..................................................................................... 125 Pollutant Removal Mechanisms of Catch Basin Inserts.................... 125 Catch Basin Insert Performance....................................................... 126 Applicability of Catch Basin Inserts in North Renton and WestHill Basins........................................................... 126 WetPond and Wet Vault.......................................................................... 127 iv Removal Mechanisms of Wet Ponds and Vaults.............................. 127 Wet Pond and Wet Vault Performance ............................................ 127 Applicability of Wet Ponds and Vaults in North Renton and WestHill Basins........................................................... 127 7. Summary and Recommendations .......................................................................... 129 WaterQuality Program...................................................................................... 130 public education Program .................................................................................. 132 8. References............................................................................................................. 135 APPENDICES Appendix A Figures Appendix B Tables Appendix C Hydrologic Analysis Appendix D Business Inventory Appendix E Data Quality Assurance Report Appendix F Available Stormwater Publications Appendix G Waiver Form for Volunteers v FIGURES (APPENDIX A) 1 Study area for the Lake Washington pollution abatement project 2 Sampling stations and business locations within the North Renton drainage basin 3 Sampling stations and business locations within the West Hill drainage basin 4 Storm drains and facilities at Renton Municipal Airport 5 Land use in the North Renton drainage basin 6 Land use in the West Hill drainage basin 7 Bathymetry of the littoral zone in Lake Washington near Renton 8 Contour map showing areal distribution of milfoil and other aquatic plants in Lake Washington at the city of Renton 9 Sewer service areas in the West Hill drainage basin 10 Copper concentrations in storm and base flow samples compared with water quality standards 11 Lead concentrations in storm and base flow samples compared with water quality standards 12 Zinc concentrations in storm and base flow samples compared with water quality standards 13 Boeing NPDES stormwater sampling station locations 14 Stormwater sampling stations at the Paccar site 15 Aquifer protection area zones in the North Renton drainage basin vi TABLES (APPENDIX B) 1 Land use in the North Renton and West Hill drainage basins 2 Riparian plant species observed on April 27, 1993 in the vicinity of the North Renton and West Hill basin outfalls to Lake Washington 3 Generators of hazardous waste in the North Renton and West Hill drainage basins 4 Contaminant spills reported in North Renton and West Hill drainage basins, 1990-1993 5 Washington Department of Ecology surface water quality standards for Class AA freshwaters 6 Results for conventional pollutants in stormwater samples collected at North Renton and West Hill storm drain outfalls 7 Results for metals in stormwater samples collected January 19, 1993 at North Renton and West Hill storm drain outfalls 8 Results for organic pollutants in stormwater samples collected January 19, 1993 at North Renton and West Hill storm drain outfalls 9 Base flow water quality results for subbasin monitoring stations in North Renton and West Hill drainage basins 10 Storm flow water quality results for subbasin monitoring stations in North Renton and West Hill drainage basins 11 Exceedances of water quality standards for copper, lead, and zinc 12 Comparison of metals concentrations in stormwater samples collected from the North Renton and West Hill drainage basins 13 Average annual runoff volume estimates for the North Renton and West Hill drainage basins 14 Average annual stormwater pollutant loading arising from the North Renton and West Hill drainage basins 15 Stormwater pollutant concentrations and total loadings arising from subbasins within the North Renton and West Hill drainage basins 16 Stormwater pollutant loading ranking by subbasin within the North Renton basin 17 Stormwater pollutant loading ranking by subbasin within the West Hill basin vii 18 Average annual areal stormwater pollutant loading arising from the North Renton and West Hill drainage basins 19 Stormwater pollutant concentrations and areal loadings arising from subbasins within the North Renton and West Hill drainage basins 20 Areal stormwater pollutant loading ranking by subbasin within the North Renton basin 21 Areal stormwater pollutant loading ranking by subbasin within the West Hill basin 22 Contaminant concentrations in sediment samples collected in Lake Washington offshore of the North Renton and West Hill storm drain outfalls, compared to sediment quality guidelines and historical data 23 Concentrations of miscellaneous organic compounds detected in sediment samples collected in Lake Washington offshore of the North Renton and West Hill storm drain outfalls, compared to historical data and marine sediment criteria 24 North Renton and West Hill drainage basin illicit connection survey results 25 Stormwater monitoring data for the Boeing Renton plant site 26 Stormwater monitoring data for the Paccar site 27 Summary of results for selected parameters measured in water samples collected from North Renton and West Hill storm drains 28 Summary of existing public education programs 29 Average pollutant removal efficiencies for selected stormwater treatment technologies 30 Information on permitting, regulatory compliance, cost, and urban applicability of selected structural controls 31 Estimated cost of the recommended pollutant abatement program for the Renton/Lake Washington study area viii ABBREVIATIONS API American Petroleum Institute ASA Automotive Service Association BMP best management practice BOD biochemical oxygen demand CERCLIS Comprehensive Environmental Response, Compensation, and Liability Information System (Superfund database) cfs cubic feet per second cfu colony-forming units EC50 effective concentration, median Ecology Washington Department of Ecology FINDS Facility Index System (U.S. EPA database) HPAH high molecular weight polycyclic aromatic hydrocarbon IBA Independent Business Association LC50 lethal concentration, median LPAH low molecular weight polycyclic aromatic hydrocarbon Metro King County Department of Metropolitan Services (formerly Municipality of Metropolitan Seattle) mg/kg milligrams per kilogram µg/L micrograms per liter mg/L milligrams per liter mL milliliter µmhos/cm micromhos per centimeter MMS maintenance management system MTCA Washington Model Toxics Control Act NPDES National Pollutant Discharge Elimination System NTU nephelometric turbidity units NURP Nationwide Urban Runoff Program °C degrees Celsius (centigrade) PAH polycyclic aromatic hydrocarbon PCB polychlorinated biphenyl PIE public involvement and education PSEP Puget Sound Estuary Program RAINEV a rainfall computer analysis model (Sutherland and Green 1989) RCRA Resource Conservation and Recovery Act SIC standard industrial classification SR state route SRP soluble reactive phosphorus SWM King County Surface Water Management Division TPH total petroleum hydrocarbons TPPS toxicant pretreatment planning study TSS total suspended solids U.S. EPA U.S. Environmental Protection Agency USGS U.S. Geological Survey WAC Washington Administrative Code WIN Waste Information Network WSDOT Washington State Department of Transportation ix 1. INTRODUCTION The Renton/Lake Washington Pollution Abatement Program has been undertaken to characterize stormwater quality conditions in the North Renton and West Hill drainage basins and to develop a program to correct existing and future stormwater pollution problems that may develop in these two basins. These highly urbanized basins, comprising 1,236 acres and 736 acres respectively, are located in the city of Renton and drain to the southern end of Lake Washington (Figure 1 in Appendix A). They have been selected for study to further the understanding of point and nonpoint pollution sources that exist within these and other similar basins of the city. The North Renton and West Hill drainage basins contain a variety of development including residential neighborhoods and commercial and industrial properties. Therefore, the stormwater quality problems identified in these two basins will likely be similar to those experienced in other urban areas in the city of Renton. As a result, many of the solutions selected for the North Renton and West Hill basins will be applicable to other areas of the city. The purpose of this project is to provide the city with a framework and strategy with which to begin implementing stormwater controls in the two study basins that could also be applied to other areas in the city. This report is organized into separate chapters focusing on drainage basin characteristics, contaminant source characterization and problem identification, evaluation of alternatives, and recommendations. The basin and source characterization chapters describe the results of an intensive investigation conducted to develop an understanding of the stormwater issues and concerns associated with the two drainage basins. The problems identified during these efforts define the goals and requirements of the pollution abatement program. The final chapter presents recommendations for an integrated stormwater quality program that could be implemented within the Renton Surface Water Utility. Figures and tables cited in the report are presented in Appendices A and B. BACKGROUND Stormwater runoff has long been recognized as a significant contributor to nonpoint pollution in urban watersheds. Pollutants that accumulate on streets and urban soils are washed off during rainstorms and transported to nearby receiving waters in surface runoff. The numerous nonpoint sources contributing to urban stormwater pollution are often difficult to control. Potential nonpoint sources responsible for urban stormwater pollution include atmospheric deposition of airborne pollutants from residential home heating systems, industrial emissions, and automobile emissions; accidental spills and leaks from automobiles; improper storage and disposal of hazardous materials; fertilizers and pesticides used in urban landscaping; and domestic pet waste. While the primary concern with stormwater in the past has focused on flooding and related impacts, stormwater controls in highly urbanized and developing areas must now also focus on the protection of receiving water quality. Recently, the U.S. Environmental Protection Agency (U.S. EPA), the Washington Department of Ecology (Ecology), and many local jurisdictions have begun to develop and implement programs to address urban stormwater pollution. U.S. EPA has expanded the National Pollutant Discharge Elimination System (NPDES) permit program to include stormwater from medium 255C\LWTASK3 I Herrera Environmental Consultants and large municipalities, construction activities, and certain industrial activities. Because Renton's population does not exceed 100,000, the city is not currently required to obtain a municipal NPDES stormwater permit. However, in the near future the NPDES program is likely to be expanded to cover smaller municipalities like Renton. In 1987, the Puget Sound Water Quality Authority adopted the Puget Sound Water Quality Management Plan, which required local governments to develop and implement stormwater management programs. The goal of these programs is to protect existing resources by reducing pollutant contributions from stormwater throughout the Puget Sound region. The plan, updated in 1991, requires that all cities and counties at a minimum adopt ordinances requiring stormwater controls for new development and requiring maintenance of public and private stormwater systems. In addition, the six largest cities (i.e., Seattle, Bellevue, Tacoma, Everett, Bellingham, and Bremerton) are required to develop and implement stormwater management programs incorporating the following elements: source identification and characterization, operation and maintenance of storm drain systems, compliance inspections and enforcement, and coordination with other local agencies. Although these requirements initially are limited to the six largest cities, all urban areas in the Puget Sound basin eventually will be required to implement stormwater management programs. In response to requirements of the Puget Sound Water Quality Management Plan, Ecology (1992a,b) has recently established guidelines for managing stormwater runoff in its stormwater management and stormwater program guidance manuals for the Puget Sound basin. The management manual (technical manual) presents criteria for designing stormwater control and treatment facilities for new development and redevelopment, while the program manual provides guidelines for developing stormwater programs that comply with the requirements of the Puget Sound Water Quality Management Plan. The Ecology technical manual uses many of the designs developed by King County (1990/1992) in its Surface Water Design Manual, which Renton adopted in its Storm and Surface Water Drainage Ordinance. The King County manual is being updated to comply with the Ecology technical manual. Renton has also recently embarked on several projects that have begun to fulfill the requirements established in the Puget Sound Water Quality Management Plan. For example, the Renton Surface Water Utility is in the process of developing a Comprehensive Storm and Surface Water Management Plan. The plan, scheduled to be completed in 1995, will provide an integrated approach for managing surface water in the city of Renton, incorporating water quality and quantity issues as well as programmatic requirements for operations of the utility. The following basin plans also have been completed or are underway to address surface water quality issues associated with the individual drainage basins that make up the city of Renton watershed: ■ Black River Basin Water Quality Management Plan. Completed in 1993, this plan addresses surface water quality issues in the Black River basin, a subbasin of the Green-Duwamish watershed which encompasses areas in Tukwila plus the southern portion of Renton. The plan identifies surface water quality problems and recommends actions that should be taken to 255C\LWTASK3 2 Herrera Environmental Consultants correct these problems. Corrective actions identified in the plan include implementing a basinwide monitoring program, inventorying hobby farms and unsewered areas, conducting an illicit connection survey, implementing a storm drain inspection and maintenance program, and coordinating with other city utilities and adjacent communities. In addition, the plan identifies specific capital improvement projects to improve fish passage and reduce stream bank erosion. ■ Lower Cedar River Basin and Nonpoint Action Plan. This joint project between Renton and King County addresses surface water issues in the lower Cedar River basin, which encompasses the eastern portion of the Renton watershed plus portions of unincorporated King County. As part of the project, Renton will conduct a survey of the city drainage system in the Cedar River basin to locate possible sewer cross-connections. The city will also investigate a number of businesses in the basin to identify possible illicit connections to the storm drain system that could damage water quality. The investigation will target approximately 50 businesses. Businesses will be selected by reviewing the business licenses issued in the city. The final plan is scheduled for completion in 1995. ■ May Creek Basin Plan. This plan is currently being developed by King County to address drainage, water quality, and aquatic habitat issues in the May Creek basin. The May Creek watershed is located directly north of the North Renton basin, but only the lower portion of the watershed is within the city of Renton. The project is scheduled for completion in August 1994. ■ East Side Green River Watershed Plan. This plan is an ongoing effort by the city of Renton to develop a comprehensive flood control program for the Renton Valley that minimizes impacts on the watershed and if possible enhances environmental resources in the watershed, which includes Springbrook Creek and Panther Creek. This planning effort began in the 1960s under the direction of the U.S. Soil Conservation Service. Several of the flood control features recommended by the Soil Conservation Service have been constructed, including the Black River pump station and forebay, a portion of the P-1 channel, and the Grady Way and state route (SR)-405 box culverts. However, construction of the remaining features (i.e., completion of the P-1 channel and the P-9 channel/Panther Creek wetlands project) was halted in 1988 because of concerns about the adequacy of the original environmental impact statement. The current plan includes a new hydrologic and hydraulic model of the watershed, an aquatic resource evaluation, a water quality evaluation, a wetland inventory and assessment, a flood control alternatives analysis, and a financial and policy analysis. Environmental elements of the plan were developed under the Black River Basin Management Plan described above. The final East Side Green River Watershed Plan is scheduled to be completed in 1995. 255C\LWTASK3 3 Herrera Environmental Consultants In addition, the Renton Transportation Division is updating the Renton Municipal Airport Master Plan, which focuses on service and facility issues related to Renton Municipal Airport operations. The western portion of the airport lies within the West Hill basin and constitutes the only industrially zoned property in the basin. The Airport Master Plan will include a discussion of environmental issues. In particular, the need for a centralized aircraft wash facility will be evaluated. The Renton/Lake Washington Pollution Abatement Program focuses on the two remaining drainage basins in the city that are not covered by any of the previous plans, the North Renton and West Hill basins. Because of project schedules, the Renton/Lake Washington program report will be completed before the comprehensive plan. Therefore, although the Renton/Lake Washington plan focuses on problems specific to the North Renton and West Hill basins, it also identifies and describes program elements within the Surface Water Utility that are needed to support citywide stormwater pollution abatement activities. Water duality data and nonpoint source control information developed as part of the Renton/Lake Washington Pollution Abatement Program will provide guidance to the city in developing source control strategies to be implemented as part of these other planning efforts. GOALS AND OBJECTIVES The overall objectives of the Renton/Lake Washington Pollution Abatement Program are 1) to characterize and improve the quality of runoff generated within the North Renton and West Hill drainage basins, and 2) to provide baseline data in anticipation of future compliance with NPDES stormwater permit requirements. This program will meet these objectives by providing the city with a framework and strategy with which to begin implementing nonpoint source controls in the North Renton and West Hill basins. To develop a stormwater pollution abatement strategy for the two basins, the following specific goals have been identified as part of the program: ■ Identify the types and numbers of potential nonpoint source contributors within each basin ■ Quantify the volume of stormwater runoff and pollutant loadings generated within the North Renton and West Hill basins ■ Create a monitoring record to document stormwater quality (including NPDES parameters of concern) at the outfalls to Lake Washington from the North Renton and West Hill basins ■ Determine the number and types of businesses operating within each basin, and evaluate potential pollutant contributions from these businesses ■ Investigate possible illicit connections to the storm drainage system 255C\LWTASK3 4 Herrera Environmental Consultants ■ Develop and implement a public awareness program that promotes actions to protect and enhance stormwater quality within these urban basins ■ Identify and evaluate actions that could be taken by the Surface Water Utility to improve operation of existing stormwater control facilities and to ensure that appropriate source controls are implemented by local businesses and residents. TECHNICAL APPROACH The approach used to identify stormwater pollution problems and evaluate abatement program requirements in the North Renton and West Hill drainage basins is summarized below: ■ Determine the stormwater quality concerns and identify the potential pollutant sources in each drainage basin ■ Develop criteria for evaluating pollution abatement alternatives ■ Research existing programs implemented by other city departments that address stormwater pollution issues ■ Identify and evaluate applicable abatement alternatives ■ Prioritize activities to establish a recommended pollution control program. The first step in assessing stormwater pollution abatement needs for the two Renton/Lake Washington drainage basins involved characterizing existing conditions in the North Renton and West Hill basins. Basin characteristics were determined by several means: reviewing available information on land use from the city comprehensive plan (Renton 1993) and available aerial photographs, conducting field surveys in the two basins to evaluate general housekeeping practices employed by businesses operating in the basins, reviewing agency files, and compiling a list of businesses operating in the basins. This information was then used to identify potential pollutants of concern and assess potential contaminant sources in each basin. In addition, the two drainage basins were divided into smaller subbasins to facilitate identification of problem areas and pollutant sources. A stormwater sampling program was then designed and implemented to characterize the quality of stormwater runoff, evaluate potential impacts on the receiving water environment, and identify illicit connections to the storm drainage system. Once the problems associated with each basin were identified, criteria were developed to evaluate possible abatement alternatives. The abatement criteria were formulated to focus the city's efforts on activities that would directly improve stormwater quality. In conjunction with the development of criteria, ongoing activities related to pollution source control within the Surface Water Utility and other city departments were also evaluated. This review was conducted to identify areas where the Surface Water Utility could build on other existing programs and coordinate with other city agencies to facilitate pollution control efforts throughout the city. 255C\LWTASK3 5 Herrera Environmental Consultants Based on these criteria and on the types of stormwater pollution problems discovered in the North Renton and West Hill drainage basins, the following three pollution abatement alternatives have been identified: ■ Develop a water quality program within the Surface Water Utility to direct source control activities and provide technical assistance to the local community as well as other city departments regarding appropriate best management practices. ■ Implement a public education program to encourage the local community to employ best management practices to reduce nonpoint pollution. ■ Construct stormwater treatment facilities to remove pollutants from the runoff generated from the North Renton and West Hill drainage basins prior to discharge to Lake Washington. The final phase of the study involved selecting the appropriate components from each of the three alternatives to develop an integrated plan for addressing stormwater issues in the North Renton and West Hill drainage basins. It is intended that this program eventually be expanded to other areas of the city and serve to complement the pollution control efforts conducted by other city departments. 255C\LWTASK3 6 Herrera Environmental Consultants 2. DRAINAGE BASIN CHARACTERISTICS Because stormwater quality is largely determined by land use, it is important to understand the characteristics of the contributing watershed prior to initiating any stormwater investigation. To characterize conditions in the North Renton and West Hill basins, a comprehensive review of the drainage system layout and land use distribution in each basin was conducted. Available storm drain inventory and topographic maps from the city of Renton were reviewed and field-verified to delineate drainage basin boundaries. This information was then used in conjunction with available data on land use to divide the two primary basins into smaller subbasins to facilitate analysis of source contributions and identification of possible problem areas that could be targeted for subsequent field sampling. Land use information was obtained from recent aerial photographs of the area (WSDOT 1992), windshield surveys conducted in each basin, and business inventories maintained by the Washington Department of Labor and Industries. Windshield surveys (i.e., informal observations noted while driving through the area) were also used to assess the housekeeping practices employed by local businesses, to identify possible pollution sources and typical contaminants of concern associated with businesses operating in the basins. Additional information concerning possible contaminant sources in the study area was obtained from agency records, summarized below: ■ Ecology NPDES records ■ Ecology Toxics Cleanup Program site list ■ Ecology spill response records ■ U.S. EPA Comprehensive Environmental Response, Compensation, and Liability Information System (CERCLIS) ■ U.S. EPA Resource Conservation and Recovery Act(RCRA) notifiers list ■ U.S. EPA Facility Index System(FINDS). In addition, a hydrologic analysis was performed to evaluate annual runoff contributions from each of the major basins. This information was then combined with available stormwater quality data obtained during the field sampling effort conducted as part of this study to assess pollutant loading contributions. Pollutant loadings were used to prioritize problem subbasins. Finally, a preliminary survey of the littoral (near-shore) zone in Lake Washington offshore of the North Renton and West Hill storm drain outfalls was conducted to assess habitat conditions for fish and wildlife. This information was used in conjunction with available stormwater and sediment quality data to assess possible impacts on the receiving water environment. 255C\LWTASK3 7 Herrera Environmental Consultants STORM DRAINAGE SYSTEM North Renton Basin Storm Drainage System The storm drainage system serving the North Renton basin is shown in Figure 2. The North Renton drainage basin is located east of the Cedar River, in the northeastern part of the city, encompassing approximately 1,236 acres. The basin generally slopes from east to west. The drainage system serving the basin consists of a network of roadside ditches and pipes. Runoff from the primarily residential areas in the upper part of the basin is collected in roadside ditches and conveyed to a network of collector storm drains installed along the major roadways. In the lower basin, which is composed primarily of industrial property, most runoff is collected and conveyed through a series of underground pipes. Although most of the natural drainage system in the North Renton basin (i.e., John's Creek) has been either channelized or enclosed in pipes, a few remnants of the original stream channel remain in the lower basin. The remaining open-channel sections are located between Interstate 405 (I-405) and Houser Way in the vicinity of North Eighth Street and west of Lake Washington Boulevard where the drainage system enters Coulon Beach Park. Flow from the I-405/Houser Way channel enters a culvert at North Eighth Street and is piped along North Eighth Street to Garden Avenue North, then along Garden Avenue North to Lake Washington Boulevard. Near the entrance to Coulon Beach Park, the Garden Avenue drain merges with three other drains serving the remaining areas in the northern and southern portions of the North Renton basin. Flow from these four drains is routed under Lake Washington Boulevard in a series of culverts that discharge into a broad, open channel that passes through Coulon Beach Park. This lower channel is routed under driveways accessing the park and other lakefront properties through a series of culverts before discharging into Lake Washington. Salmonids have been observed in this lower section of the drainage basin. Runoff from the 382-acre area north of Sunset Boulevard (subbasins N4 and N6 in Figure 2) passes under Lake Washington Boulevard via a 36-inch storm drain. Two 72-inch drains that serve most of the southern portion of the basin(780 acres in subbasins N2, N3, and N5 in Figure 2) also converge at Lake Washington Boulevard. The 72-inch drain that runs along the center of Garden Avenue North receives runoff from a portion of the Boeing Renton East Base site (number 175 in Figure 2) and all of the Paccar Defense Systems site (number 63 in Figure 2), as well as from other industrial and commercial areas between Park Avenue North and Garden Avenue North. Several oil/water separators are installed at the Boeing facility to treat runoff before it enters the 72-inch drain. The Paccar site has been redeveloped for construction of the Kenworth truck facility. Site drainage has also been modified as part of the redevelopment. Runoff from this property passes through onsite detention and treatment ponds before entering the 72-inch drain. The other 72-inch drain that runs along the eastern side of Garden Avenue North collects runoff from the I-405/Houser Way channel described above and from storm drains serving the primarily residential areas located in the eastern part of the study area. However, the two 72- inch drains are interconnected at several locations along Garden Avenue North. Therefore, runoff from the various catchment areas can mix, depending on rainfall and flow conditions. 255C\LWTASK3 8 Herrera Environmental Consultants A fourth drain (30-inch) that serves approximately 19 acres of industrial and commercial property located along the northern end of Houser Way (subbasin N7) crosses under Lake Washington Boulevard near the entrance to Coulon Beach Park. Runoff from approximately 55 acres in the extreme southwestern corner of the basin enters the lower channel west of Lake Washington Boulevard via a 48-inch storm drain (subbasin N1 in Figure 2). This drain primarily serves the Boeing Renton plant area but also collects runoff from a short section of Park Avenue North and adjacent properties. Several oil/water separators are installed at the Boeing plant to treat runoff before it enters the 48-inch storm drain. Two types of oil/water separators are installed at the Boeing Renton plant. Coalescing plate separators have typically been installed since about 1991, while those installed prior to 1991 are API (American Petroleum Institute) separators (Nelson 1993 personal communication). The Boeing Company has implemented a program to replace the API separators with coalescing plate units as new construction occurs or if activities in the drainage basin change sufficiently to warrant an immediate upgrade. All separators are inspected quarterly; floating debris and oil are removed as necessary. In addition, a complete cleaning is performed annually at each separator. Catch basins in the yard areas are also cleaned regularly, typically on a 12- to 18-month schedule, depending on the need at each catch basin location. West Hill Basin Storm Drainage System The storm drainage system serving the West Hill basin is shown in Figure 3. The 736-acre West Hill basin is located west of the Cedar River in the northwestern section of Renton (see Figure 1): As shown in Figure 3, only the eastern part of the basin is located within the city of Renton. The majority of the basin is outside the city limits and is under King County jurisdiction. A ridge runs diagonally across the basin from northwest to southeast, separating the northern and southern portions of the basin. The northern part of the basin (approximately 240 acres in subbasins W2, W3, and W4) slopes from west to east. Runoff is collected in three primary drains and routed to a large interceptor drain, the Black River culvert, which runs east of Rainier Avenue North under West Perimeter Road (along the western edge of Renton Municipal Airport) and discharges into Lake Washington at the northern end of the airport. The southern part of the basin (approximately 404 acres in subbasins WI and W6) generally slopes from north to south. Runoff flows from the hillside in a series of ditches and is collected in a single ditch that runs from west to east near the southern border of the basin. The ditch enters a 24-inch storm drain near the east end of Renton Avenue South, which then connects into the Black River culvert on West Perimeter Road. The Renton Municipal Airport covers approximately 81 acres on the far eastern side of the basin (subbasin W5 in Figure 3). Runoff from the western side of the runway to the western edge of the airport is collected in a number of small storm drains that discharge directly into the Black River culvert (Figure 4). Runoff from only a small portion of the airport property is treated before discharge to Lake Washington. Runoff from the Boeing refueling facility located at apron B at the southwestern end of th airport is routed through an oil/water separator before 255C\LWTASK3 9 Herrera Environmental Consultants entering the Black River culvert. This separation is designed to contain spills in the refueling area. The remainder of the airport property discharges directly to the culvert without treatment. LAND USE Both the North Renton and West Hill drainage basins are nearly fully developed. Open space and undeveloped areas consist primarily of scattered city parks and largely undevelopable land on steep hillsides. Less than 15 percent of the total area in each basin is undeveloped or wooded. Land use in the two basins is summarized by acreage in Table 1. The predominant land use in both basins is residential. The North Renton basin contains a larger proportion of commercial and industrial property (28 percent) than the West Hill basin (17 percent). Land Use in North Renton Basin Land use in the North Renton drainage basin is shown in Figure 5. Residential development (665 acres) covers approximately 54 percent of the 1,236-acre North Renton basin. Approximately 70 percent (467 acres) of the residential development consists of single family housing. Nearly all of the residential property in the basin lies east of the I-405 corridor. The area west of 1-405 is zoned primarily for industrial use, with a small amount of commercial use. A large city park (Coulon Beach Park) is also located on the western side of the basin. The Boeing Company and Paccar Defense Systems (now Kenworth) occupy the two largest industrial sites in the basin, comprising over 90 percent of the industrially zoned property. The Boeing Renton plant covers approximately 107 acres in the southwestern portion of the North Renton basin. Operations at the plant include aircraft part assembly, painting, hazardous materials storage, and photofinishing. The Paccar site encompasses about 85 acres in the southwestern corner of the basin. From 1907 until about 1988, rail cars and military vehicles (tanks and trucks) were manufactured at this plant. Foundry and metal galvanizing operations were also conducted. Paccar has completed a cleanup program to remediate contaminated soil and ground water at the site. The northern half of the property has been converted to a truck manufacturing plant (Kenworth). Plans for the southern part of the property have not yet been developed. Redevelopment of the Paccar site has included construction of the Houser Way stormwater bypass, which routes surface runoff from the southern half of the Paccar site and offsite areas south of the property around the manufacturing areas in the northern part of the property to the city storm drain system on North Eighth Street. in addition, a 72-inch storm drain was installed in Garden Avenue North between North Eighth Street and Lake Washington Boulevard. The new drain connects to an existing 72-inch drain in Garden Avenue North, providing additional conveyance capacity for the Paccar site as well as the surrounding drainage area. 255C\LWTASK3 10 Herrera Environmental Consultants A small portion of the basin located on the western side of the I-405 corridor near the southern end of the basin is zoned for light industrial use. Facilities operating in this area include several automotive repair and painting operations, as well as a small industrial machine factory. Commercial development covers approximately 10 percent (126 acres) of the basin. The majority of the commercial development is concentrated along the Sunset Boulevard/Park Avenue corridor between Edmonds Avenue NE and Monroe Avenue NE. Several small shopping centers are located in this area. Typical businesses include service stations, laundromats, groceries, photography studios, roofing contractors, and small repair shops. Other businesses interspersed throughout the basin include contractors (general construction, plumbing, electrical, roofing, and paving), gardening services, building maintenance services, and convenience stores. The I-405 corridor runs through the eastern part of the basin. Total highway drainage area is estimated at approximately 53 acres, or 4 percent of the basin. Land Use in West Hill Basin Land use in the 736-acre West Hill drainage basin, shown in Figure 6, is primarily residential (480 acres). The Renton Municipal Airport, located along the eastern edge of the basin, is the only industrially zoned area within the basin (81 acres). Several small aircraft charter and flight service facilities operate from the western side of the airport. In addition, Boeing operates a fueling station at apron B near the southwestern end of the airport (see Figure 4). As explained earlier, runoff from the apron B refueling area passes through an oil/water separator before entering the Black River culvert. Runoff from other areas at the airport are tightlined (piped) directly to the Black River culvert without benefit of oil/water separation. While the refueling area at apron B handles the larger aircraft, planes, the smaller commercial and private aircraft that use the Renton airport are refueled by mobile fuel truck. Consequently, refueling operations can occur anywhere at the airport. Because areas outside apron B are not served by oil/water separators, any spills that occur during these remote fueling operations or due to accidents on the runway would enter the Black River culvert and discharge directly to Lake Washington. Fuel tanker trucks are supplied from underground storage tanks. The locations of fuel storage tanks are shown in Figure 4, which also shows the locations of other major airport facilities including aircraft storage hangars and maintenance facilities. Aircraft washing operations also occur at various locations around the airport. Washwater is collected in nearby catch basins and discharged to Lake Washington via the Black River culvert. The storm drains at the airport were cleaned in 1991 to remove sediment that was deposited in the drainage system when the airport was inundated by a Cedar River flood. A single sediment sample collected from approximately 20 cubic yards of sediment that was removed from the drains contained 1,700 milligrams per kilogram (mg/kg) of total petroleum hydrocarbons. Because this concentration exceeds the state Model Toxics Control Act (MTCA) method A cleanup level for soil (200 mg/kg), the sediments were disposed of at the Cedar Hills landfill. 255C\LWTASK3 I 1 Herrera Environmental Consultants Commercial operations in the West Hill basin are concentrated almost exclusively along Rainier Avenue North, although a few small facilities (including several nurseries, small building contractors, and a rental car agency) are interspersed throughout the basin. Typical commercial facilities along Rainier Avenue North are automotive parts and repair facilities, restaurants, office buildings, and equipment rental facilities. Commercial land use constitutes less than 10 percent of the basin (44 acres). AQUATIC RESOURCES IN LAKE WASHINGTON The shoreline and littoral (i.e., near-shore aquatic) habitats at the North Renton and West Hill basin stormwater outfalls are influenced either directly or indirectly by land uses in each of the basins and along the waterfront. Existing habitat conditions in these areas are described here based on the best available information, along with field observations made during sediment monitoring. In addition, the observed or potential impacts on these habitats are presented and discussed. Observations of the following habitat types are limited to the shoreline and littoral areas within the vicinity of the outfalls. Shoreline (Riparian) Vegetation Historic and existing land uses have significantly reduced the amount, type, and quality of remaining riparian vegetation in the vicinity of both stormwater outfalls. Most of the historic coniferous forest and wetlands in the southern end of Lake Washington have been lost to residential, commercial, and industrial development. The following descriptions of the remaining riparian vegetation near the North Renton and West Hill basin stormwater outfalls are based on observations made on April 27, 1993 and recent aerial photographs. North Renton Basin Stormwater Outfall The shoreline area and riparian vegetation around the stormwater outfall of the North Renton basin has been modified by various development activities. Most of the shoreline has been artificially hardened by a mixture of breakwaters, boat launches, marinas, landscaping, and park facilities. The North Renton stormwater outfall is located at Coulon Beach Park on the shore of Lake Washington. The outfall is the terminus of John's Creek, which is artificially constrained and confined by riprap along its channel through Coulon Beach Park. Although much of the shoreline around the stormwater outfall and Coulon Beach Park consists of bulkheads, buildings, boat docks, parking lots, and park lands, there is some riparian vegetation around the stormwater outfall, consisting entirely of plantings of native and introduced species. That portion of John's Creek flowing through Coulon Beach Park supports a narrow band of upland and riparian vegetation. The dominant plant species observed during the April 27, 1993 survey are listed in Table 2. These species form a three-tiered, multistory canopy of trees (20 to 25 feet), shrubs (3 to 15 feet), and emergent vegetation (1 to 5 feet) over the short elevational gradient from the crest of the stream banks to the water level. The continuum of vegetational communities from the stream bank crest is generally trees to shrubs to emergent 255C\LWTASK3 12 Herrera Environmental Consultants vegetation. Each of these communities forms a more or less discrete, uniform, narrow band extending along the creek to the lakeshore. Although riparian vegetation is disconnected from nearby upland forests, it provides important functional values including habitat for fish and wildlife. Tree and shrub communities provide rearing, resting, feeding, and nesting habitat for various species of perching birds. During the brief habitat survey, three species of birds were observed using these communities (i.e., song sparrow, red-winged blackbird, and house sparrow). Emergent vegetation similarly provides habitat for fish and wildlife. Cattails, rushes, and shrubs that overhang the water provide cover and food for amphibians, reptiles, and juvenile salmonids and other fishes. Riparian vegetation also provides limited water quality protection, slowing high flows and filtering suspended sediments and adsorbed pollutants. Furthermore, riparian vegetation is an important source of organic matter, which provides food and nutrients to various aquatic plants and animals. West Hill Basin Stormwater Outfall The shoreline area and riparian vegetation in the vicinity of the West Hill basin stormwater outfall has been completely altered by various developments. The West Hill basin stormwater outfall, located approximately 180 meters west of the Cedar River delta, emerges from beneath a restaurant at the northwestern perimeter of Renton Municipal Airport. There is essentially no remaining natural riparian vegetation around the West Hill basin outfall. Cedar stumps in the littoral region of the lake near the Cedar River delta are all that remains of historical riparian, forested wetlands. The outfall, which is submerged where it enters Lake Washington, is surrounded by hardened shoreline. Riparian vegetation has been lost to assorted commercial, industrial, and residential shoreline development, including the Renton Municipal Airport, private boat docks and bulkheads, and the Boeing industrial complex. The only remaining riparian vegetation consists of small, narrow bands of invasive species (e.g., Himalayan blackberry and reed canarygrass). These small communities of invasive vegetation generally have limited habitat value. Although invasive riparian vegetation provides some cover and food for wildlife, few species of wildlife are likely to use these areas because of their isolation and small size. Riparian vegetation near the West Hill basin outfall is completely isolated from remaining upland forests. Therefore, there is no linkage or lake travel corridor between larger habitats of potentially higher quality and the isolated riparian vegetation along the shoreline. Consequently, the observed riparian vegetation is likely to be used only by a few small mammals (e.g., rodents) and birds that are adapted or accustomed to high levels of human activity. Littoral Zone The littoral zone is a shallow, near-shore interface region between uplands and deep-water (pelagic) areas of a lake (Wetzel 1975). The littoral zone in the vicinity of the stormwater outfalls can be subdivided into three distinct microcosms or environments: the water column, aquatic macrophyte beds, and the sediment and sediment/water interface. Some of the inhabitants of these environments, their functions and values, and observed or expected effects 255C\LWTASK3 13 Herrera Environmental Consultants of stormwater discharges are described in the sections below. The discussion of these habitat areas is limited to the general region bounded by the Renton Municipal Airport to the west and Coulon Beach Park to the east. Water Column The littoral zone of southern Lake Washington near the North Renton and West Hill basin outfalls is shown in Figure 7. The depth of the water column in these near-shore areas is strongly influenced by sediment carried by the Cedar River. Planktonic plants and animals inhabit the water column. Phytoplankton and flora of the littoral zone are important sources of organic matter, contributing to the productivity of the entire lake system (Wetzel 1975). Composition and productivity of the planktonic lake community influence the production and structure of higher trophic levels, such as the economically important sockeye salmon. Although plankton sampling is beyond the scope of the present study, results of sampling conducted on May 25, 1993 indicate the presence of unexpected, primarily deep-water plankton species near the outfalls (Litt 1993 personal communication). Few littoral plankton species were observed in these samples. Although it is uncertain whether stormwater discharges at the North Renton and West Hill outfalls have adversely affected water quality and plankton community composition, stormwater runoff from urban areas typically contains pollutants that can degrade water quality and harm plankton communities. Stormwater runoff from urban areas often contains elevated levels of suspended solids, nutrients, polycyclic aromatic hydrocarbons (PAHs), other organic compounds, and metals (Galvin and Moore 1982; U.S. EPA 1983; Pitt and Bissonnette 1984; Elfish 1986). These pollutants may have acute or chronic effects on plankton and other organisms that inhabit the water column. Some of these potential effects include changes in species diversity and abundance, reduced light penetration, and reduced primary productivity. Primary productivity in phytoplankton can be decreased by increases in suspended sediments that contribute to reduced light penetration, abrasion and disruption of cells, and sorption of nutrients or other elements essential to productivity (Jeffries and Mills 1990; Fairchild et al. 1987). Because Lake Washington is a large body of water, stormwater-borne pollutants, especially toxicants, generally are likely to be diluted below levels that cause acute effects. Acute and chronic effects of toxicants are often related to other factors including total organic carbon, alkalinity, and hardness. In addition, although chronic effects (e.g., decreased fecundity) may occur in individual organisms or possibly local populations of organisms that dwell in the water column, long-term stormwater effects on these organisms are unlikely. There are several reasons to expect that acute or chronic effects on littoral plankton and other water column organisms are short-lived in Lake Washington. First, many pollutants are rapidly diluted to low levels by the large volume of water in the lake. Second, many pollutants (e.g., various forms of metals and PAHs) bind with suspended sediments or organic matter and settle out of the water column, thereby becoming unavailable to biota and reducing the possibility of exposure. In a comparison of metals concentrations observed in stormwater runoff in a Bellevue urban runoff study, Pitt and Bissonnette (1984) report that metals levels in the receiving water are unlikely to exceed levels established for the protection of aquatic life (U.S. EPA 1986) or to 255C\LWTASK3 14 Herrera Environmental Consultants significantly affect receiving water quality during most rainfall events. In addition, exposure to these pollutants is limited to periods during and shortly after rainfall events, when stormwater runoff occurs. Finally, even if localized adverse impacts on water column organisms occur, organisms from other populations of unaffected littoral areas can be expected to rapidly recolonize the affected areas. Aquatic Macrophyte Beds Over the past several years, several surveys of macrophytes (i.e., larger aquatic plants) have been conducted in the area near the North Renton and West Hill stormwater outfalls. Compared to other parts of the lake, aquatic macrophyte beds in this vicinity are rather sparse (Figure 8). It is uncertain whether low macrophyte density and coverage are a result of disturbance or pollution, or whether macrophyte communities have always been sparse in this area. The extent and composition of these aquatic macrophyte communities vary from year to year. These communities are composed of Potamogeton crispus, Elodea species, Najas species, and Myriophyllum spicatum. Reported coverage of these macrophyte communities has ranged from approximately 36 acres in 1981 to approximately 30 acrei in 1985 (Metro 1985). These vascular aquatic macrophyte communities have several important functional values. They are important sources of organic matter for other producers and consumers and thereby influence various trophic levels and lake ecology as a whole. Furthermore, macrophytes support a unique assemblage of organisms, including epiphytes and periphyton (organisms that grow on the surfaces of plants or other submerged objects), as well as the organisms that feed on them. Macrophytes provide habitat for salmonids and other fish species and help stabilize littoral zone sediments. It is likely (although not well documented) that juvenile sockeye use the littoral zone and aquatic macrophyte beds as a rearing area prior to migrating to the pelagic zone of the lake (Simenstad 1993 personal communication). Traynor (1973) estimates that young of the year use the littoral zone for 2 to 3 months before migrating to deeper water. Therefore, adverse impacts on macrophytes could affect salmonids and other members of these communities. Although stormwater impacts on macrophytes were not observed during the present study, stormwater may have several types of adverse impact. Decreases in water clarity and light transmission from increases in nutrient loading (i.e., eutrophication), as well as increases in suspended sediment loading, may inhibit photosynthesis, decrease macrophyte production, and decrease areal extent and diversity of aquatic macrophyte beds. Epiphytic and periphytic communities living on the macrophytes may also be similarly affected. However, except for undesirable milfoil beds, the existing macrophyte communities are relatively far from the stormwater outfalls (approximately 50 to 100 meters). Therefore, stormwater discharges are unlikely to directly affect these communities (see Figure 8). Sediment and Sediment/Water Interface Sediment size and composition characteristics were visually estimated at the outfalls. Sediments are generally dark gray to black silts with varying amounts of organic matter and sand. Silts and fine sands are the dominant particles. Based on their dark color, many samples appeared to be 255C\LWTASK3 15 Herrera Environmental Consultants relatively rich in organic matter. Several of the samples contained clearly recognizable and identifiable organic matter such as leaves and twigs. Sediment and the sediment/water interface form an important environment in Lake Washington. Sediments and sediment flora and fauna are important to the processes of pollutant retention, storage, and biotransformation; nutrient cycling; and decomposition. Sediments and the sediment/water interface also support benthic (bottom-dwelling) organisms that are important sources of food for assorted species of fish and wildlife. Diving ducks such as buffleheads, pie- billed grebe, and golden eye feed on benthic invertebrates. Benthic organisms are important food sources for salmonids and other fishes, which in turn are important to the diets of various piscivorous bird species including cormorant, merganser, kingfisher, and osprey. Adverse impacts on sediment from stormwater runoff are well documented. Stormwater runoff is known to contain certain types of pollutants (e.g., metals and PAHs), many of which are associated with sediment or particulate organic matter. Increases of these pollutants in sediments may result in acute or chronic effects on benthic invertebrates and other organisms that inhabit or use the sediment and sediment/water interface environment(e.g., sculpins and diving ducks). Among the impacts reported by various investigators are reduction in species diversity or abundance, increases in pollution-tolerant species, and decreases in pollution-intolerant organisms (Heliovaara and Vaisanen 1993; Welch 1992). Metro (1984a) found that aquatic invertebrate diversity and abundance were negatively correlated with silt particles and metals concentrations. Although the investigators concluded that it was impossible to differentiate between effects from metal toxicity and substrate composition, it was clear that both the benthic invertebrate abundances and the toxicant concentrations, including metals and PAHs, were strongly related to silt particles. The highest toxicant concentrations were associated with silty sediments. Furthermore, these finer sediments were inhabited primarily by chironomids, some species of which are generally acknowledged as pollution-tolerant organisms (Welch 1992). In addition to observed decreases in the numbers of pollution-intolerant organisms, Welch (1992) indicates that pollution-tolerant organisms often increase in abundance. Therefore stormwater discharges are likely to influence sediment particle distribution, sediment toxicant concentrations, and benthic invertebrate community composition (i.e., pollution-tolerant forms). These effects are likely to be limited to those areas receiving contaminated sediment from the stormwater outfalls. In addition, these impacts may be further limited, particularly at the North Renton basin outfall, by the influence of the Cedar River on sediment composition and distribution. BUSINESS INVENTORY An inventory of businesses operating in the North Renton and West Hill drainage basins was compiled to identify the types and locations of commercial operations and to assess their potential to contribute pollutants to the storm drainage system. Industrial and commercial facilities are potential sources of pollutants to surface water and ground water. The primary transport pathways for pollutants discharged from these facilities are stormwater runoff, accidental spills, leaks from equipment and chemical storage facilities, and direct discharges from permitted facilities (i.e., facilities operating under NPDES or state wastewater discharge permits). Pollutants associated with commercial and industrial discharges vary depending on 255C\LWTASK3 16 Herrera Environmental Consultants facility operations. However, pollutants commonly found in urban runoff include total suspended solids, petroleum hydrocarbons, metals, nutrients, fecal coliform bacteria, and in some cases organic contaminants such as solvents. A list of licensed businesses in the Renton area was obtained from the Washington Department of Labor and Industries. The list includes a standard industrial classification (SIC) designation for each business, which is used to identify the type of operation. Although the original list includes all licensed businesses, the list was revised to include only those types of businesses that are considered potential contaminant sources based on the nature of their operations (e.g., manufacturing, businesses that store and use potentially hazardous chemicals as part of their operations, and businesses that generate hazardous materials). For example, restaurants, professional offices, and most retail facilities whose operations are not expected to contribute significantly to stormwater pollutant loading were dropped from the list. Although these commercial areas can contain a high percentage of impervious land surface associated with parking areas, pollutant loadings from these areas are primarily transportation-related and are not typically affected by commercial activities. The following categories of businesses are considered potential contaminant sources. ■ All manufacturing facilities ■ Automotive repair, sales, rental, and service stations ■ Car washes ■ General and special trade contractors (e.g., plumbing, painting, electrical repair, building construction) ■ Paint retailers ■ Printers, graphics shops, film developers ■ Laundries and dry cleaners ■ Nurseries and gardening services ■ Transportation-related facilities (e.g., couriers, bus maintenance facilities, airports, trucking companies) ■ General equipment repair facilities. Locations of these businesses of concern in the North Renton and West Hill basins are shown in Figures 2 and 3. Detailed lists containing each facility name, street address, and SIC code, sorted by map identification number, facility name, and SIC code, are provided in Appendix D. A brief description of the businesses of concern found in each basin is provided in the following sections. 255C\LWTASK3 17 Herrera Environmental Consultants Business Inventory of North Renton Basin There are 71 businesses operating in the North Renton basin that can be considered potential sources of pollution to the storm drainage system (see Figure 2 and Appendix D). The two largest categories of businesses represented in the basin are general and special contractors (21 businesses) and automotive facilities (14 businesses). The contractor category includes general building contractors, plumbers, electricians, painters, carpenters, roofing contractors, and flooring specialists. Contaminants associated with these types of operations generally consist of cleaning products, solvents, paints, and wood preservatives. Automotive facilities include car dealerships, automotive repair shops (e.g., service stations, automotive painting), and towing operations. Pollutants associated with these types of facilities include petroleum hydrocarbons, solvents, and degreasers. Other businesses operating in the North Renton basin include lawn and garden services, industrial machine equipment manufacturers, retail paint stores, building maintenance services, laundromats and dry cleaners, specialty repair services (for electrical equipment, appliances, and small machinery), and a medical clinic. In addition, two large manufacturing facilities, the Boeing Renton plant and the Paccar/Kenworth site, are located in the North Renton basin. NPDES-Permitted Facilities in North Renton Basin The Boeing Renton plant is the only active NPDES-permitted discharge in the North Renton basin. Boeing is permitted to discharge 75,600 gallons per day of noncontact cooling water to a 48-inch drain that runs along Lake Washington Boulevard (subbasin N 1 in Figure 2). Effluent limits for the cooling water discharge include temperature (220C), pH (6.0 to 9.0), and total oils (15 milligrams per liter [mg/L], no visible sheen). This drain also carries surface water runoff from approximately 55 acres of the Boeing Renton plant site. The Puget Power property located north of Lake Washington Boulevard near the intersection with Park Avenue is permitted to discharge boiler blowdown water from its Shuffleton reserve power plant directly to Lake Washington at a point approximately 1,100 feet west of the North Renton outfall. Cooling water from the plant has not been discharged to the North Renton drainage system. The plant has been closed since 1989, when it operated for a short period of time for emergency power generation. Given its location along the Lake Washington shoreline, most runoff from the plant site probably discharges to Lake Washington, although areas along the eastern edge of the property may drain to the North Renton outfall channel. The NPDES permit is currently being revised to incorporate stormwater discharges from the Puget Power property (Barnes 1993 personal communication). Under the new NPDES regulations, stormwater runoff from certain industrial facilities and construction sites larger than 5 acres is also subject to NPDES permit requirements. These facilities are required to develop a stormwater pollution prevention plan that incorporates applicable best management practices by October 1, 1993. Plans must be implemented by October 1, 1994. In addition, the facility must conduct two annual inspections (one during wet weather and one during dry weather) to verify that the best management practices are adequate. J 255C\LWTASK3 18 Herrera Environmental Consultants Only three facilities in the basin qualify for an NPDES stormwater permit: Boeing, Paccar/Kenworth, and the Renton School District school bus facility. The school bus facility will likely be covered under Ecology's baseline general permit. Boeing has applied for an individual industrial permit and has completed the part 2 application, which included collecting a storm flow sample from each of five representative storm drains. One of these drains is located in the North Renton drainage basin. Sample results for this drain are included in the discussion of historical data. The Paccar site is currently undergoing a voluntary cleanup to remediate contaminated soil and ground water. Routine monitoring of surface water and stormwater quality is also being conducted as part of the cleanup action plan. Remediation is complete, and a truck manufacturing facility has been constructed on the northern half of the site. Plans for development of the southern half of the site were undetermined at the time of this report. Hazardous Waste Generators in North Renton Basin There are three large-quantity generators, six small-quantity generators, and two conditionally exempt generators of hazardous waste within the North Renton drainage basin (Table 3). Large- quantity generators are those that accumulate more than 2,200 pounds per month (or per batch) of dangerous waste or more than 2.2 pounds per month (or per batch) of extremely hazardous waste. Large-quantity generators are subject to all of the generator requirements specified under Washington Administrative Code (WAC) 173-303. Small-quantity generators are those that accumulate less than 220 pounds per month (or per batch) of dangerous waste or less than 2.2 pounds per month (or per batch) of extremely hazardous waste. Small-quantity generators are not subject to the dangerous waste regulations if they treat or dispose of dangerous waste in an onsite facility or ensure delivery to a permitted offsite facility. Conditionally exempt generators are those that generate more than 220 pounds but less than 2,200 pounds per month (or per batch) of dangerous waste or less than 2.2 pounds per month (or per batch) of extremely hazardous waste. Conditionally exempt generators must comply with most of the requirements under WAC 173-303, but record-keeping requirements for these facilities are less extensive and storage time limits are less restrictive than for large-quantity generators. Registration as a hazardous waste generator does not necessarily indicate that a facility is an active pollutant source. However, handling of large quantities of hazardous materials increases the potential for release of these materials due to spills or accidents. Each large-quantity generator is required to prepare and implement a contingency plan for responding to emergencies involving hazardous waste. These plans generally describe procedures for containing the spilled material to prevent contamination of surface and ground water supplies. Conditionally exempt and small-quantity generators are not required to implement contingency plans, although conditionally exempt facilities must designate an on-scene coordinator who is capable of notifying the proper authorities in the event of a spill or other emergency. In addition, conditionally exempt facilities must comply with the containment requirements for hazardous waste storage areas that apply to large-quantity generators, while small-quantity generators are exempt from these requirements. 255C\LWTASK3 19 Herrera Environmental Consultants Contaminated Sites in North Renton Basin The following three sites in the basin are included on the Ecology Model Toxics Cleanup Program list of contaminated sites in Washington: ■ Paccar Defense Systems ■ Performance Apex auto shop ■ Renton Highlands landfill. A brief description of each site is provided in the following sections. Paccar Defense Systems The Paccar site is included on the National Priorities List of Superfund sites. Paccar manufactured rail cars and military vehicles at the Renton facility from about 1907 until it closed in 1988. A foundry and galvanizing plant also operated at the site to support manufacturing activities. Soil, ground water, surface water, and sediments at the site are contaminated. The following contaminants have been identified at the site (Ecology 1991a): ■ Polycyclic aromatic hydrocarbons (PAHs) ■ Polychlorinated biphenyls (PCBs) (in localized areas due to spills from transformers) ■ Metals (arsenic, lead, and chromium) ■ Volatile organic compounds (benzene, toluene, ethylbenzene, xylenes, tetrachloroethene, trichloroethene, and 1,2-dichloroethane). The site is undergoing cleanup under MTCA and has been redeveloped for use as a truck manufacturing facility. Excavation of contaminated soil was required for construction of new factory buildings and in isolated hotspot areas. In other areas, contaminated soils may be permanently covered. A separate plan to remediate contaminated ground water will be implemented independently of the soil remediation and redevelopment plan. In 1991, a stormwater bypass pipeline was constructed to route runoff from the southern half of the property (which has yet to be redeveloped), and from offsite areas located south of the property, away from the new truck manufacturing facilities in the northern half of the property. Surface water runoff from the site and the bypass enters the North Renton drainage system near the intersection of North Eighth Street and Garden Avenue North. As part of the site remediation activities, Paccar has implemented a monitoring program to evaluate the quality of stormwater entering and exiting the site. The concentrations of metals (copper, lead, and zinc) in samples of surface water leaving the site periodically exceed the chronic toxicity criteria for aquatic life. However, the quality of runoff is generally comparable to that found in runoff from local urban areas such as Bellevue. Volatile organic compounds, pesticides, and PCBs were not detected in any surface water samples collected from the site (see section on historical data for a 255C\LWTASK3 20 Herrera Environmental Consultants discussion of Paccar stormwater data). An ongoing surface water monitoring program will be implemented as part of the final cleanup plan (Ecology 1991 a). Performance Apex Auto Shop This former auto repair shop is classified by Ecology as C2 (potential hazardous substance site). Soil contamination at the site has been confirmed, and the potential for ground water contamination also exists. Contaminants associated with this site include petroleum products and solvents (halogenated and nonhalogenated organic compounds) resulting from leaks from onsite storage tanks and improper handling practices. Renton Highlands Landfill This former landfill is located on approximately 11 acres just outside the North Renton drainage basin, south of NE Fourth Street and NE Third Street between Jefferson Avenue and Harrington Avenue (site 218 in Figure 2). The landfill received a variety of waste material from 1940 until sometime in the late 1960s (Seattle/King County Department of Public Health 1985). No records of waste disposal activities at the site are available. However, because of its proximity to industrial areas in Renton, it is believed that industrial waste may have been disposed of in this landfill. Because the landfill is located outside the North Renton basin, runoff from this site would not affect stormwater quality in the North Renton drainage system. Leaching of contaminants present in the fill and transport through the ground water system would be the primary contaminant pathway from the landfill to the North Renton drain, if such movement of ground water is occurring. Business Inventory of West Hill Basin There are 59 businesses operating in the West Hill basin that can be considered potential sources of pollution to the storm drainage system (see Figure 3 and Appendix D). Automotive facilities (23 businesses) constitute the largest category of these businesses in the basin. These facilities include new and used car dealerships, auto parts stores, auto repair shops (general repair, transmission, lubrication, and muffler shops), and motorcycle dealerships. Petroleum hydrocarbons, cleaners, and degreasers are the primary contaminants associated with automotive activities. Airport-related services such as flight service, aircraft repair, and air freight businesses (7 businesses) are the second largest business category in the basin. Contaminants associated with these types of businesses are similar to those associated with automotive repair shops, with the addition of aviation fuel as a potential contaminant of concern. Other potential pollutant sources in the basin include general and specialty contractors (building contractors, carpenters, floor installers, roofing contractors, glass installers), nurseries, manufacturers of industrial testing equipment, heating oil suppliers, building maintenance services, car washes, dry cleaners, and miscellaneous equipment repair services. 255C\LWTASK3 21 Herrera Environmental Consultants NPDES-Permitted Facilities in West Hill Basin There are no NPDES-permitted discharges of industrial wastewater into the West Hill drainage system. As explained earlier, businesses in certain industrial categories are required to obtain an NPDES permit for their stormwater discharges. The following businesses operating in the West Hill basin are subject to NPDES stormwater permit requirements: ■ Sound Flight, Inc. ■ Northwest Seaplanes ■ The Boeing Company ■ JVC Aviation, Inc. ■ Lane Aviation ■ Action Aviation, Inc. As discussed above, Boeing has elected to obtain an individual permit. The other facilities may be covered by either a general baseline permit or a group permit. In either case, these facilities are required to prepare a stormwater pollution prevention plan by October 1, 1993 and to implement the plan by October 1, 1994. Hazardous Waste Generators in West Hill Basin One large-quantity generator, three small-quantity generators, and two conditionally exempt generators of hazardous waste are located in the West Hill basin (see Table 3). As explained above in the discussion of hazardous waste generators in the North Renton basin, classification as a generator does not necessarily imply that these facilities are contributing pollutants to the drainage system. The designation simply applies to facilities that handle large quantities of hazardous materials as part of their normal operations. With proper waste storage and handling procedures, the potential risk of releases to stormwater drains can be greatly reduced. Contaminated Sites in West Hill Basin There are no Ecology cleanup sites or U.S. EPA Superfund sites located in the West Hill basin. HOUSEKEEPING PRACTICES IN NORTH RENTON AND WEST HILL BASINS A windshield survey was conducted as part of the field reconnaissance and sampling activities to evaluate general housekeeping practices of businesses operating in the North Renton and West Hill basins. When possible, a brief drive-through of individual sites was conducted to evaluate maintenance practices such as equipment and material storage, waste disposal, and general yard maintenance. Otherwise, observations were made from the street. Photographs were taken to record typical housekeeping practices, and observations were recorded in the field notes. Although many smaller businesses were surveyed, the larger industrial sites such as Boeing and Paccar were not accessible. For the larger industrial facilities, inspections are usually handled by Ecology as part of permit enforcement and oversight activities. 255C\LWTASK3 22 Herrera Environmental Consultants In general, many of the businesses in the two basins could improve their equipment and material storage practices. Equipment and materials are commonly stored outdoors without a roof or covering to prevent contact with stormwater. In addition, waste storage areas often have no secondary containment to prevent spills and leaks from entering the local storm drainage system. At several locations, staining was evident on the ground around storage facilities, indicating past spills that may have contaminated site runoff. Oil sheens were also observed at many of the sampling and reconnaissance locations, suggesting that waste storage and disposal practices could be improved. Waste disposal practices were difficult to evaluate during the one-time inspections. More frequent inspections and contact with the local businesses are needed to better evaluate disposal practices. Questionnaires mailed to local businesses would also be useful in obtaining information about waste disposal practices. Following are typical examples of specific observations at small business sites. North Renton Basin ■ 903 Houser Way: Pallets containing fertilizer stored outdoors with no protection to prevent contact with rainwater and no containment for spills or leaks. ■ 1101 Lake Washington Boulevard: Numerous transformers stored outdoors in an open yard area with no secondary containment facilities for spills or leaks and no roof to prevent contact with rainwater. ■ 350 Sunset Boulevard: Extensive material and waste storage area containing sheet metal, wood, and other debris located outdoors behind building. No roof or containment provided. West Hill Basin ■ 559 Rainier Avenue North: Equipment and material storage area under roof, but little containment provided for spills. ■ 515 Rainier Avenue North: Soil around maintenance shed is stained. Absorbent material deployed outside shop area. Sheen observed in runoff from property. ■ 453 Renton Avenue North: No containment provided for drum storage area. ■ 505 Park Avenue: No containment provided for drum and container storage area. ■ 919 Houser Way North: No containment or roof provided for drum storage area. 255C\LWTASK3 23 Herrera Environmental Consultants SPILL RECORDS Accidental spills from commercial or industrial facilities and transportation-related sources represent a potential threat to surface and ground water quality in the North Renton and West Hill basins. Uncontrolled releases resulting from spills or leaks are often difficult to track because they are not always reported. Consequently, these releases may not be adequately cleaned up, allowing contaminant residues remaining in soil or ground water to act as long-term pollutant sources. The general public often contributes to the problem by improperly disposing of household wastes. Improper disposal of used crankcase oil is probably the best example of how individual practices can aggravate a basinwide water quality problem. Used crankcase oil generated from home automotive maintenance activities is often improperly disposed of in nearby catch basins or dumped on the ground. Although individually these discharges may seem insignificant, the cumulative effect from many individual discharges can significantly degrade water quality. Loftness (1981) estimates that 8 million gallons of motor oil are sold each year in Washington state for use in home automotive maintenance activities. Earlier studies conducted by the U.S. EPA (1973) and the Oregon Department of Environmental Quality (1978) estimate that 40 to 60 percent of waste oils generated by home auto repair operations is disposed of improperly (e.g., dumped on the ground, poured into storm drains or sanitary sewers, or placed in garbage cans). Recent public education efforts conducted by the King County Department of Metropolitan Services (Metro) and Ecology to encourage recycling of waste oils and other household products have likely improved public waste disposal practices. Ecology also operates a recycling hotline to provide information on recycling opportunities. Locally, the Renton Solid Waste Utility has implemented a public education program to promote use of nonhazardous household products and to encourage recycling efforts. Information on the locations of local oil recycling centers has also been distributed. Oil recycling centers are located in both the North Renton and West Hill drainage basins. Spills that occurred in the two drainage basins between 1990 and 1993 and were reported to Ecology are summarized in Table 4. Most spills are reported to Ecology's regional spill response unit. Since 1990, spill reports received by the northwest regional office, which covers the Renton area, have been entered on a computer database. Records of spills that occurred prior to 1990 are stored chronologically in paper files at the regional office. Records for the entire northwest region are combined. Information on many of the earlier spills is often incomplete. Therefore, this review focuses on the most recent spills for which information is readily available through the Ecology database. Between 1990 and 1993, 16 spills in the North Renton basin and 11 spills in the West Hill basin were reported to Ecology. In many cases, the source, the quantity, and even the type of material spilled were not identified. However, it appears that most spills have involved less than 100 gallons of material. Oil and other petroleum products were the most common type of material released. In the North Renton basin, most spills have occurred along roadways or have been released on the ground adjacent to industrial and commercial businesses. The majority of the oil and petroleum spills have been caused by vehicular (automobile, truck, aircraft, or ship) accidents. 255C\LWTASK3 24 Herrera Environmental Consultants In the West Hill basin, most of the spills have occurred at the airport, involving oil and petroleum products. Because most catch basins at the airport are plumbed directly to adjacent storm drains (e.g., the Black River culvert), these spills end up in nearby surface waters such as Lake Washington or the Cedar River. With the exception of the Boeing refueling operation located at apron B in the southwestern portion of the airport, there are no oil/water separators or other containment devices installed in the portion of the airport drainage system that contributes to the Black River culvert. Once spilled material reaches a catch basin, it is conveyed directly to nearby waterways (i.e., Lake Washington or the Cedar River). Other spills reported in the West Hill basin have generally occurred at small commercial or industrial facilities. These spills have involved oil, petroleum pro lucts, and unspecified hazardous materials. The largest reported release occurred in 1991 and involved a 75-gallon oil spill that seeped into the ground and reportedly entered the undei'ying ground water system. SUMMARY OF DRAINAGE BASIN CHARACTERISTICS The 1,236-acre North Renton basin and the 736-acre West Hill basin are both highly urbanized drainages, with predominately residential land use (approximately 54 percent of the North Renton basin and approximately 65 percent of the West Hill basin are in residential development). Little undeveloped land remains in either basin. Future changes in land use would primarily involve redevelopment rather than new development. The North Renton basin contains a slightly higher proportion (18 percent) of industrial development than the West Hill basin (I I percent). The Renton Municipal Airport comprises all of the industrially zoned property in the West Hill basin, wh:le the North Renton basin supports a more diverse industrial community. Boeing and Paccar/K_enworth are the two largest industrial facilities in the North Renton basin, although a few small industrial facilities (e.g., a hydraulic machinery manufacturer and an electric power utility) are also located in the basin. Commercial development in both basins is primarily concentrated along major transportation corridors (e.g., Sunset Boulevard and I-405 in the North Renton basin, and Rainier Avenue in the West Hill basin). A variety of retail, service, and professional businesses operate in the two basins. However, with respect to potential impacts on stormwater quality, the primary businesses of interest in the two basins consist of automotive repair and service shops, general and specialty contractors (e.g., roofing, flooring, and building construction), small equipment repair shops, nurseries, and building maintenance services. A brief windshield survey of the two basins revealed that, although problems are not widespread, housekeeping practices at some of the small commercial and industrial businesses could be improved to reduce the potential for these operations to adversely affect stormwater runoff quality. (The larger industrial facilities were not accessible for a windshield survey.) Equipment and waste storage are the two primary areas where housekeeping practices could be improved. Containment for these areas is often inadequate, allowing spilled or leaked material to enter the stormwater drainage system. Provision of secondary containment for storage areas or relocating storage facilities indoors to prevent contact with stormwater runoff would greatly reduce the potential for contamination. 255C\LWTASK3 25 Herrera Environmental Consultants Accidental spills represent another pathway for contamination of surface water runoff. Over approximately the past 4 years, 16 spills in the North Renton basin and 11 spills in the West Hill basin have been reported. Oil and petroleum products were the materials most commonly spilled, with most spills involving less than 40 gallons of material. Most of the spills in the two basins were caused by transportation-related accidents. In addition, two small industrial spills have been reported in the North Renton basin, one involving industrial wastewater that entered nearby surface waters, and one involving a hazardous material spill on a roadway. In the West Hill basin, incidents at the airport accounted for more than half of the reported spills. Because the airport is located adjacent to Lake Washington and the Cedar River, the potential for spilled materials to enter these waterways is high. Other potential sources at the airport include refueling and aircraft washing operations. Spill containment facilities are installed only at the Boeing refueling area at apron B. Refueling and washing of smaller private and commercial aircraft occur at remote locations throughout the airport property where there are no containment facilities. Any spills associated with these operations would be collected in nearby catch basins and discharged directly to Lake Washington or the Cedar River. 255C\LWTASK3 26 Herrera Environmental Consultants 3. CONTAMINANT SOURCE CHARACTERIZATION To make the most efficient use of available city resources, it is important to focus source control efforts on the specific contaminants and sources that affect stormwater quality in the North Renton and West Hill basins. In support of these efforts, potential sources of contaminants to the storm drain systems have been characterized. This information has been used 1) to identify contaminants of concern, 2) to identify and prioritize specific problem areas and sources in the two basins, and 3) to assess the potential effects on the receiving water environment from stormwater discharges. This information also will be used in the future to develop source control alternatives. The first step in the source characterization effort involved compiling and reviewing available data on stormwater quality as well as known and suspected pollutant sources. For the most part, available data from other investigations conducted in the study area are limited to data from contaminated sites that have been investigated by Ecology (e.g., Paccar and Performance Apex auto shop) or investigations conducted by individual businesses as part of a permit application (e.g., Boeing NPDES stormwater permit application). No basinwide stormwater quality data are available. Because existing data are limited, a sampling program was also implemented to develop the information necessary to evaluate conditions in the two basins. The sampling program was designed to characterize the quality of stormwater runoff, evaluate potential impacts on the receiving water environment, and identify illicit connections to the storm drainage system. The sampling effort involved four main tasks: outfall sampling, subbasin sampling, sediment sampling, and a survey of illicit connections. The objectives of each task are described below: ■ Outfall monitoring. Samples were collected at the downstream end of each drain to characterize the quality of stormwater entering Lake Washington. ■ Subbasin monitoring. Samples were collected from individual subbasins within each of the two larger basins to identify and characterize problem areas. ■ Sediment survey. Sediment samples were collected in Lake Washington offshore of the two outfalls to further characterize contaminant contributions (including historical impacts) and to evaluate possible effects on the receiving environment. ■ Illicit connection survey. Field screening procedures were used to measure a variety of source indicator parameters under base flow conditions at various locations in the two basins tc, identify illicit connections to the storm drainage system. Details of the sampling plan and quality control procedures that were employed to ensure that data quality objectives were met are described in the sampling and analysis plan (Herrera 1992). The following sections present the results of the sampling effort and summarize data from other studies conducted in the two basins. 255C\LWTASK3 27 Herrera Environmental Consultants STORM DRAIN SAMPLING PROGRAM Outfall Sampling Samples were collected from the North Renton and West Hill storm drain outfalls during a storm event that occurred on January 19, 1993. Total rainfall measured on that date at Seattle-Tacoma International Airport was approximately 0.59 inches. Samples were collected from access points located near the downstream end of each system to evaluate the overall quality of stormwater entering Lake Washington from the two basins (see Figures 2 and 3). A brief description of the two sampling stations is provided below: ■ North Renton outfall. The sample was collected from the stream channel in Coulon Beach Park approximately 100 feet upstream of the outfall in Lake Washington. This site is located opposite an existing flow gauging station. ■ West Hill outfall. The sample was collected from manhole 11, 134-24 (city of Renton storm drain inventory map). The manhole is located just north of the airport entrance between the guard rail and the fence on the eastern side of West Perimeter Road, approximately 1,000 feet upstream of the outfall. Outfall Sampling Methods Grab samples were collected every 20 minutes for a period of 3 hours during the storm event (a total of 9 grab samples were collected at each station). Flow rate in the drain was measured at the time each grab sample was collected. At the end of the 3-hour sampling event, a single flow rate composite sample from each outfall was prepared and submitted for chemical analysis. Flow at the North Renton outfall averaged about 16 cubic feet per second (cfs) during the 3-hour monitoring period, and flow at the West Hill outfall averaged about 8 cfs. The difference in flow reflects the greater drainage basin area served by the North Renton drain (1,236 acres) compared to the West Hill drain (736 acres). Samples were analyzed for NPDES parameters following NPDES sampling protocols, so that these data can be used to fulfill permit application requirements in case Renton is required to obtain an NPDES stormwater permit in the future. Outfall Sampling Results Results for the samples collected from the North Renton and West Hill storm drain outfalls are described in the following sections. For most of the pollutants analyzed, available stormwater quality data for other urban areas are presented in the data summary tables for comparative purposes. These other data from regional and local stormwater studies represent pollutant levels 255C\LWTASK3 28 Herrera Environmental Consultants that are typical of general urban runoff. Where available, separate values for residential and commercial stormwater runoff quality are provided. Under the Nationwide Urban Runoff Program (NURP) study (U.S. EPA 1983), stormwater samples were collected from 28 sites across the United States during multiple storm events. This study is the most comprehensive study available of urban stormwater quality. Although the Bellevue data are included in the NURP data set, they are displayed separately, along with recent data for storm drains in the city of Seattle, to characterize local stormwater quality. Both drains discharge to Lake Washington and are therefore subject to Class AA water quality standards (WAC 173-201). Water quality standards for Class AA freshwaters are summarized in Table 5. Conventional Pollutants Results for conventional pollutants analyzed in stormwater discharged from the North Renton and West Hill drainage basins are presented in Table 6. The quality of stormwater discharged from the two Renton drains is comparable to runoff from other urban areas. Without exception, the concentrations of conventional pollutants analyzed in the outfall samples fall within the ranges reported for other residential and commercial areas. These results indicate that Renton has nonpoint pollution problems typical of other urban areas. Total suspended solids concentrations measured in the outfall samples collected during the January 19, 1993 storm (80 mg/L) were about 4 to 20 times greater than the concentrations measured in the stormwater samples collected at the individual subbasin monitoring stations during the April 8 and April 26, 1993 storms and as much as 100 times greater than in base flow samples. The reported 24-hour rainfall for the January 19 storm (0.59 inches at Sea-Tac International Airport) was similar to the two April storms (0.83 and 0.52 inches on April 8 and April 25, respectively). However, antecedent conditions were quite different. For the January 19 storm, no rainfall was reported during the 3 days prior to the storm, with only trace amounts occurring during the previous 10 days. In comparison, both April storms had measurable amounts of rainfall within 24 hours of the sampling events. The longer antecedent dry period allowed a larger quantity of pollutants to accumulate on road surfaces within the basin, likely resulting in greater pollutant washoff during the January storm than during the two April storms. Biochemical oxygen demand and chemical oxygen demand concentrations in both outfalls were generally low, (7.5 to 8.3 mg/L and 40 to 47 mg/L, respectively) below the average concentrations reported in runoff from residential and commercial areas. Biochemical and chemical oxygen demand are measures of the quantity of organic matter (e.g., litter, debris, and animal waste) present in stormwater. Organic matter can be decomposed both biologically (by bacteria present in the receiving water environment) and chemically. Because both degradation processes generally require oxygen, high concentrations of organic matter can deplete oxygen levels in the receiving water environment. Given the relatively low biochemical and chemical oxygen demand concentrations measured in the outfall samples, it appears that stormwater runoff does not adversely affect dissolved oxygen levels in Lake Washington near the North Renton and West Hill outfalls. 255C\LWTASK3 29 Herrera Environmental Consultants Nutrient concentrations measured in the two storm drain outfalls are also within the ranges reported for stormwater runoff from other urban areas. However, total phosphorus and nitrite+nitrate nitrogen levels in the outfalls are greater than the concentrations measured in streams in the Puget Sound region (Metro 1989, 1990, 1991) as shown below: Puget Sound Renton Parameter (mg/L) Streams Storm Drains Total phosphorus 0.016 - 0.214 0.223 - 0.375 Ammonia-nitrogen 0.014 - 1.09 0.101 - 0.422 Nitrite+nitrate nitrogen 0.0008 - 0.025 0.267 - 0.559 These results reflect the overall urban nature of the two Renton drainage basins. Fertilizer, erosion of nutrient-rich urban soils, pet waste, and street litter are the primary sources of nutrients in urban watersheds. The watersheds of most of the streams monitored during studies conducted by Metro contain significant amounts of undeveloped land, with urban development generally confined to the lower basins. In comparison, the North Renton and West Hill drainage basins are nearly totally developed. Nitrogen and phosphorus are essential nutrients for algae and other plants in freshwater ecosystems. Phosphorus is of particular concern because it is the limiting nutrient for most lakes in the Puget Sound region, including Lake Washington. Therefore, inputs of large quantities of phosphorus can cause excessive algal growth and a general decline in the quality of the lake. Total phosphorus concentrations in the two Renton outfalls (0.223 to 0.375 mg/L) exceed the level considered acceptable for discharge into lakes to prevent cultural eutrophication (0.05 mg/L). The total phosphorus concentration measured at five near-shore stations in Lake Washington averages about 0.02 mg/L (Metro 1991), which indicates that stormwater discharges from the two Renton storm drains contribute to degradation of water quality in the lake. However, because the North Renton and West Hill basins represent less than 1 percent of the 300,000-acre watershed contributing to Lake Washington, it is unlikely that these two drains have a significant effect on overall water quality in the lake. Influence is likely limited to the local near-shore areas adjacent to the outfalls. Fecal coliform bacteria concentrations in waters of both outfalls (720 colony-forming units [cfu] per 100 milliliters [mL] at the North Renton outfall and 600 cfu/100 mL at the West Hill outfall) exceed the Ecology water quality standard for Class AA freshwaters of 50 cfu/100 mL. Fecal coliforms are present in the intestinal tracts of warm-blooded animals (human and nonhuman) and therefore are commonly used in water and wastewater analyses as indicators of contamination by fecal material and associated pathogens. The presence of these bacteria suggests that fecal contamination has occurred in the recent past. However, it is not possible from the standard fecal coliform test to determine the source(s) or the human health risk posed by these bacteria in stormwater. In an urban environment, sources may be as diverse as domestic pets, birds, or other urban wildlife but may also include human sanitary sewage. The numbers of fecal coliform bacteria observed in waters at both basin outfalls is not unusual for urban stormwater. Concentrations of fecal coliform bacteria in urban runoff are highly variable 255C\LWTASK3 30 Herrera Environmental Consultants and during warmer periods of the year may be approximately 20 times greater than numbers observed during colder months (U.S. EPA 1983). The presence of greater numbers of fecal coliform bacteria in stormwater samples collected during warmer periods of the year is not necessarily associated with a greater risk to human health. Stormwater can contain fecal contamination from a variety of nonhuman sources. Although humans can be infected by some pathogenic microorganisms carried by animals, infection from human enteric viruses is of greater concern. Because the fecal coliform test does not distinguish between human and nonhuman sources, tilis test alone does not provide sufficient evidence to evaluate potential risks to human health(O'Shea and Field 1992). Studies have found little correlation between fecal coliform densities and incidence of gastrointestinal illness in swimmers (Dufour 1984; Cabelli 1983). A significant portion of illnesses related to swimming is associated with exposure to non-enteric pathogens such as Staphylococcus, Pseudomonas aeruginosa, Klebsiella, and adenoviruses. In addition, results of limited virological sampling of stormwater in the Puget Sound area show that human enteric viruses are not present in local runoff(Tomlinson et al. 1980). Therefore, while the numbers of fecal coliform bacteria in urban runoff may be high, the risk to human health may not be great (U.S. EPA 1983). Furthermore, because most rainfall in western Washington occurs in the winter months when outdoor activities generally decline, tL. risk of human exposure to contaminated stormwater is somewhat lower than in other areas of the country where a greater proportion of annual rainfall occurs in the summer. In addition, warm weather stormwater discharges from the North Renton and West Hill drains may be more rapidly diluted in Lake Washington because of the smaller volume of runoff occurring in the summer months compared to the winter wet season. Potential health risks from fecal coliform bacteria in stormwater discharges would likely be greater in the North Renton basin than in the West Hill basin, because there is more opportunity for public contact at the outfall and along the discharge channel in Coulon Beach Park. The West Hill drain is enclosed in pipes throughout most of the basin, and the outfall near the Renton Municipal Airport is not readily accessible to the public. Metals Metals results for the stormwater samples collected from the North Renton and West Hill storm drain outfalls are presented in Table 7. Of the 13 priority pollutant metals analyzed, only copper, lead, and zinc exceed state water quality standards. The concentrations of these three metals exceed both the chronic and acute toxicity for aquatic life. Copper, lead, and zinc are the metals most commonly found in urban runoff and were detected in more than 95 percent of the samples analyzed as part of the NURP study (U.S. EPA 1983). These metals are generated primarily by traffic-related sources (Krenkel and Novotny 1980): 255C\LWTASK3 31 Herrera Environmental Consultants Pollutant Traffic-Related Source Copper Thrust bearings, bushings, and brake linings Lead Leaded gas, transmission fluid, babbitt metal bearings Zinc Motor oil and tires A brief discussion of the toxicity of these three metals is presented in the following sections. Copper--Copper is highly toxic to most freshwater invertebrates, with LC50 values (i.e., the concentration that is lethal to 50 percent of the test organisms) ranging from 0.006 mg/L to greater than 225 mg/L (Moore and Ramamoorthy 1984a). As with other metals, toxicity is inversely related to water hardness. The low hardness of the Renton stormwater samples (25 to 35 mg/L as calcium carbonate [CaCO31 greatly increases copper toxicity. However, the presence of organic chelates in solution can significantly reduce toxicity. Some species such as the isopod Asellus meridiannus (sow bug) can adapt to high levels of copper. The 48-hour LC50 value reported for individuals from a highly polluted river is 2.5 mg/L, compared with 1.2 mg/L for animals from a less polluted site (Brown 1976). Copper is also toxic to fish, with LC50 values ranging from 0.017 to 1.0 mg/L (Moore and Ramamoorthy 1984a). Acute toxicity depends largely on water hardness; ionic copper (Cu+2) and ionized hydroxides (CuOH+, CuOH2+2) are the most toxic. Copper toxicity is highly species-dependent. Some of the more sensitive species include fathead minnow, guppy, and golfen shiner. Copper can also exert chronic or sublethal effects. Concentrations of 0.02 to 0.2 mg/L have been shown to reduce survival, growth, and the reproductive rate in various fish species (Chapman 1978). In soft water (<75 mg/L hardness as CaCO3), egg survival may be inhibited at concentrations as low as 0.004 mg/L. Copper is also toxic to most aquatic plants, with growth inhibition occurring at concentrations of 0.1 mg/L or less regardless of test conditions and species (Moore and Ramamoorthy 1984a). Blue-green algae are particularly sensitive to copper because it inhibits nitrogen fixation, although many algae species can adapt to elevated levels of copper (Ernst 1975). Lead—Lead is less toxic to invertebrates than are copper and zinc. Acute effects generally occur at concentrations of 0.1 to 10 mg/L, but mortality may occur within the range of 0.002 to 670 mg/L, depending on various environmental factors such as light, temperature, pH, hardness, and dissolved oxygen (Moore and Ramamoorthy 1984a). Chronic effects may or may not appear at concentrations below the LC50 level. As with other metals, chelators such as organic acids bind ionic lead, reducing its toxicity. Some invertebrates may develop physiological adaptations that provide tolerance to lead. The 96-hour LCS0 value for total lead generally falls within the range of 0.5 to 10 mg/L. As with other metals, toxicity is affected by water hardness. In hard waters, LC50 values may exceed 350 mg/L. Lead is also less toxic than copper to aquatic plants. Acute and chronic effects generally occur at concentrations of 0.1 to 5 mg/L, with toxicity affected by light, temperature, and water 255C\LWTASK3 32 Herrera Environmental Consultants chemistry. Some species such as Chlorella and Chlarnydomoras are relatively tolerant, showing no detectable effects at 5 and 50 mg/L lead, respectively (Hutchinson 1973). Zinc—Acute toxicity of zinc to freshwater invertebrates is relatively low, with LC50 values generally in the range of 0.5 to 5 mg/L, although some species are particularly sensitive to zinc (Moore and Ramamoorthy 1984a). For example, the 48-hour LC50 for the cladoceran Daphnia hyalina is only about 0.055 mg/L (Baudouin and Scoppa 1974). According to Moore and Ramamoorthy (1984a), a number of insect and crustacean species are relatively tolerant to zinc, with LC50 values exceeding 55 mg/L, which may reflect adaptability to zinc. Generally, immature life stages of invertebrates are more sensitive to zinc than are adults. The acute zinc toxicity level for fish is generally within the range of 0.5 to 5.0 mg/L (Moore and Ramamoorthy 1984a). However, physicochemical and biological factors may extend this range to between 0.09 and>100 mg/L. Toxicity is largely species-dependent. Goldfish (24-hour LC50 = 100 mg/L) and rainbow trout (24-hour LC50 = 5,000 mg/L) are particularly tolerant. However, studies have shown that the stage of development also affects zinc toxicity; adults are more tolerant than immature life stages (Chapman 1978). Temperature also influences toxicity, as temperature stress increases the susceptibility of most fish species to zinc (Moore and Ramamoorthy 1984a). Zinc toxicity to aquatic plants is highly variable, with LC50 values ranging from 0.0075 to greater than 50 mg/L (Moore and Ramamoorthy 1984a). Unicellular species such as englenoids and flagellates appear to be most sensitive. Studies have shown that zinc concentrations as low as 0.0075 to 0.075 mg/L Zn+2 can cause 20 to 100 percent reductions in Englena gracilis within 48 hours (Mills 1976). Other unicellular species such as Stigeoclonium, Ulothirx, Hormidium, and Microspora can adapt to high levels of zinc, while some species of blue-green algae can produce chelating agents that act to protect the cells from zinc. Toxicity of Metals in Stormwater—Metals are most toxic to aquatic biota in the free ionic or dissolved form. Metals in urban runoff are usually sorbed onto particulate matter, which reduces their bioavailability. For example, only about 5 to 20 percent of the total lead found in urban runoff is present in dissolved form; the majority is bound to particulates (Wanielista and Yousef 1993). This partitioning between dissolved and particulate-bound forms greatly reduces the potential toxicity of lead and other metals in stormwater. Water quality standards have been derived based on laboratory studies that typically use relatively particulate-free water. Consequently, these standards would be more appropriately applied to dissolved metal concentrations rather than total metal concentrations. Paulson and Amy (1993) used a chemical equilibrium model to evaluate metals data from two of the NURP study sites. The model predicted that less than 6 percent of the total copper and lead concentrations and about 10 to 35 percent of the total zinc concentrations in stormwater were bioavailable (defined as the free and inorganically complexed metals). The analyses performed on the stormwater samples collected from the North Renton and West Hill basins represent total metals concentrations. These total metals concentrations frequently exceeded state water quality standards. However, if the total metals concentrations are adjusted to account for only the portion that is bioavailable (using the factors calculated from the NURP data set), none exceed the water quality standards. 255C\LWTASK3 33 Herrera Environmental Consultants In addition, the water quality standards pertain to conditions in the receiving water environment. Direct comparison with in-pipe stormwater conditions does not take into account the dilution that occurs as the discharge enters Lake Washington. Although both the North Renton and West Hill drainage systems are accessible to fish, little suitable fish habitat remains in either basin. Most of the natural drainages have been piped or channelized over time as these basins have developed. For example, approximately the lower 650 feet of the West Hill drainage system is enclosed in the Black River culvert. The only remaining open-channel sections consist of a 350- foot reach upstream of Renton Avenue South, and shallow ditches that drain the hillside along the southern side of the basin. Salmonids have been observed in the lower reaches of the North Renton drainage, below Lake Washington Boulevard where remnants of the John's Creek stream channel still exist (Fisher 1993 personal communication). With the exception of a short of en-channel section along Houser Way, the rest of the drainage system is largely confined to underground pipes and culverts. Because much of the fish habitat in the North Renton and West Hill basins has been damaged or destroyed, it is unlikely that these two drainages support extensive fish populations. Fish would most likely be exposed to contaminants present in the stormwater runoff at locations offshore of the outfalls, after the stormwater mixes in the lake. Organic Compounds Results for organic compounds analyzed in the storm drain outfalls are presented in Table 8. Most organic contaminants were undetc ted. Consistent with the NURP study (U.S. EPA 1983), PAHs and phthalates were the most f :quently detected organic contaminants in the Renton storm drain outfalls. PAHs, particularly the high molecular weight PAHs (HPAHs) that are generated by the combustion of fossil fuel (e.g., automobile exhaust and heating oil use), as well as phthalates (plasticizers used in a variety.of household products), are ubiquitous in the urban environment. Concentrations of these compounds in the storm drain outfalls were within the ranges reported by the NURP study. Polycyclic Aromatic Hydrocarbons—With the exception of chrysene (0.5 to 0.6 micrograms per liter [[tg/L]), the concentrations of all the organic compounds detected in the Renton stormwater samples were below available criteria or MTCA cleanup standards. However, the concentrations of chrysene found at both outfall locations exceed the MTCA method B cleanup level for freshwater (0.0296 µg/L). Method B cleanup levels are based on a human health risk assessment in which the primary exposure pathway is the consumption of contaminated fish. Estimated bioconcentration factors for PAHs range from about 100 to 500 for low molecular weight PAHs (LPAHs) and from about 1,100 to 44,600 for HPAH compounds (Moore and Ramamoorthy 1984b). Studies have found that PAH residues in fish are usually low, except at site-specific discharge points. Fish uptake of PAHs from water is rapid and increases with concentration. However, these compounds are usually rapidly excreted by fish, with half-lives on the order of 1 to 2 days. Therefore, fish tissue accumulation effects resulting from stormwater discharges are expected to be fairly short-term. 255C\LWTASK3 34 Herrera Environmental Consultants From an aquatic life standpoint, PAHs are not highly toxic to aquatic organisms. The concentrations of PAH compounds in the stormwater effluent (0.5 to 2.7 µg/L) are well below the reported acute toxicity levels for invertebrates (300 to >325,000 µg/L), for fish (1,700 to >560,000 µg/L), and for aquatic plants (500 to 33,000 jag/L) (Moore and Ramamoorthy 1984b). In addition, studies have shown that PAHs in urban runoff are primarily associated with particulate matter, which greatly reduces bioavailability (Galvin and Moore 1982). PAH residues, especially benzo(a)pyrene, pyrene, and fluoranther_e, have been detected in tissues of invertebrates such as oligochaetes and insect larvae inhabiting a tributary of the Great Lakes. Tissue concentrations generally correlate with sediment residues (Eadie et al. 1982). Although PAHs are generally not highly toxic to fish, chronic or sublethal effects such as reductions in growth and reproduction, as well as behavioral abnormalities (loss of equilibrium, avoidance, and increase in spontaneous activity), have been observed. The early life stages of several fish species appear to be more susceptible to PAH than are adults. Pacific salmon are more sensitive in marine water than freshwater due to osmotic stress (Malins and Hodgins 1981). Phthalates—Of the two phthalates detected in the outfall samples, only bis(2- ethylhexyl)phthalate (5.9 µg/L in the North Renton outfall and 3.7 µg/L in the West Hill outfall) exceeded the MTCA method B cleanup leve! (3.56 µg/L). B;s(2-ethylhexyl)phthalate, a suspected carcinogen, is a plasticizer used in the manufacture of polyvinyl chloride and is also used in vacuum pumps. Although the compound is not highly toxic, studies have shown chronic effects on aquatic organisms. In tests conducted on five freshwater invertebrate and five fish species, LC50 values for bis(2-ethylhexyl)phthalate range from about 89 to 1,500,000 µg/L (U.S. EPA 1987). Reductions in survival and reproduction rates have been evaluated. Chronic toxicity levels for bis(2-ethylhexyl)phthalate range from 8.366 µg/L for rainbow trout fry (Salmo gairdneri) to 358 µg/L for Daphnia magnia and 31,770 µg/L for the fathead minnow (Pimphales promelas). Uptake of bis(2-ethylhexyl)phthalate from water has been shown to be inversely related to water concentration (U.S. EPA 1987). Bioconcentration factors for invertebrates range from 14 for the isopod Asellus brevicaudus to 3,600 for the amphipod Ganimarus pseilohninaeus (Mayer 1976). Bioconcentration in fish is on the order of 114 to 1,380 times (Mehrle and Mayer 1976). Other studies have shown that bis(2-ethylhexyl)phthalate is not highly toxic to aquatic plants. Reductions in the growth of green algae (Selenastrum capriconutum) exposed to 410 µg/L for a period of 5 days were less than 50 percent (Richter 1982 personal communication). Davis (1981) reports EC50 values (i.e., median effective concentration) between 408,000 and 7,492,000 µg/L for duckweed (Lemna gibba). Miscellaneous Organic Compounds—Other organic compounds detected in the outfall samples include benzoic acid (North Renton), 4-methylphenol (North Renton), 1,3-dichlorobenzene (North Renton and West Hill), and toluene (North Renton and West Hill). However, concentrations do not exceed MTCA cleanup standards. Benzoic acid is commonly used in alkyd resins, flavors and perfumes, and as a tobacco seasoning, a food preservative, a plasticizer, and an antifungal agent. The phenolic compoui:d 4-methylphenol (p-cresol) is used in phenolic resins, synthetic food flavors, herbicides and surfactants, and as a disinfectant and chemical 255C\LWTASK3 35 Herrera Environmental Consultants intermediate. The hydrocarbon 1,3-dichlorobenzene is primarily used as a fumigant and insecticide. Toluene is a solvent used in a variety of products. Subbasin Sampling The intent of the subbasin monitoring was to divide the two relatively large basins into smaller subbasins for analysis. This approach aids in the identification of specific problems areas which can then be targeted for additional investigation and source control efforts. Subbasins that do not experience serious water quality problems and do not contribute a significant amount of pollution to the storm drain system can be eliminated from future investigations. The subbasin sampling program involved collecting water samples at 10 stations in the two basins (six stations in the North Renton basin and four stations in the West Hill basin) to characterize stormwater quality under base flow and storin flow conditions. Subbasin sampling station locations are shown in Figures 2 and 3. S upling stations were selected primarily on the basis of land use and the layout of the storm drain system. A brief description of the subbasin sampling stations is provided below: North Renton Basin Sampling Stations ■ Station NR-1—Manhole 13, B3-9 on the 24-inch storm drain located on Edmonds Avenue near the intersection with Sunset Boulevard NE. This drain collects runoff from the northeastern part of the basin (approximately 154 acres, subbasin N6 in Figure 2). Land use is predominantly residential, with commercial use concentrated along Sunset Boulevard. ■ Station NR-2—Manhole 12, F5-4 9n the 24-inch storm drain at the intersection of North Eighth Street and Houser Way North. This drain collects runoff from approximately 452 acres located in the southeastern portion of the basin (subbasin N5 in Figure 2). Land use is primarily residential, with commercial use limited to areas along Sunset Boul, vard and several small, isolated commercial properties interspersed throughout the subbasin. ■ Station NR-3—At the outlet of a 72-inch culvert under Lake Washington Boulevard near the intersection with Park Drive NE. This drain runs along the center line of Garden Avenue North serving the western part of the basin between Park Avenue North and Garden Avenue North (approximately 34 acres in subbasin N2 in Figure 2). Land use in subbasin N2 is entirely industrial, comprising all of the Paccar property and a portion of the Boeing Renton plant. This 72-inch drain is connected at several locations with a new 72-inch drain (installed by Paccar) located on the eastern edge of Garden Avenue North. The new drain carries runoff from the entire southeastern portion of the drainage basin (see the station NR-4 description below) 255C\LWTASK3 36 Herrera Environmental Consultants ■ Station NR-4—At the outlet of a 72-inch culvert under Lake Washington Boulevard near the intersection with Park Drive NE. This recently constructed drain runs along the eastern edge of Garden Avenue North and collects runoff from approximately 746 acres in subbasins N3 and N5 (see Figure 2), including all of the area served by station NR-2 (452 acres) in the upper subbasin, plus an additional 294 acres of industrial land in the lower portion of the subbasin. ■ Station NR-5—At the outlet of a 36-inch culvert under Lake Washington Boulevard near the intersection with Park Drive NE. This drain collects runoff from approximately 382 acres north of Sunset Boulevard (subbasins N4 and N6 in Figure 2), including the area served by station NR-1. Land use in subbasin N4 is primarily residential. Land use in subbasin N6 includes a mixture of residential and commercial properties. ■ Station NR-6—At the outlet of a 48-inch culvert under Lake Washington Boulevard near the intersection with Park Drive NE. This drain collects runoff from about 55 acres in the western portion of the North Renton basin between Burnett Avenue North and Garden Avenue North (subbasin N1 in Figure 2). Land use in the subbasin is entirely commercial and industrial. The eastern portions of the Boeing Renton plant site occupy most of the subbasin. West Hill Basin Sampling Stations ■ Station WH-1—Manhole 11, D5-3 on the 36-inch storm drain located on Rainier Avenue North between South 119 Street and South 118 Street. This drain collects runoff from approximately 115 acres in the northern portion of the basin (subbasin W4 in Figure 3). Land use in the subbasin is primarily residential, although several professional office buildings are located along Rainier Avenue North. ■ Station WH-2—Manhole 11, E7-1 on the 24-inch storm drain located at the intersection of Taylor Avenue and Rainier Avenue North. This drain collects runoff from about 95 acres in the central portion of the West Hill basin (subbasin W3 in Figure 3). Land use is primarily residential, with commercial use (automotive repair, equipment repair, and equipment rental businesses) concentrated along Rainier Avenue North. ■ Station WH-3—Manhole 16, E2-4 on the 12-inch storm drain located at the intersection of Hardie Avenue NW and NW Third Place. This storm drain collects runoff from about 30 acres in the southeastern part of the basin (subbasin W2 in Figure 3). Land use is primarily residential. Commercial operations (equipment repair, marine equipment, and automotive parts stores) are confined to the area along Rainier Avenue North. 255C\LWTASK3 37 Herrera Environmental Consultants ■ Station WH-4—At the entrance to the 24-inch culvert (16, D4-14) under Taylor Avenue NW. This drain collects runoff from approximately 337 acres in the southwestern part of the basin (subbasin WI in Figure 3). Land use is almost exclusively residential, with some commercial properties interspersed along Renton Avenue South. Subbasin Sampling Methods At each station, grab samples were collected once during base flow and once during storm flow conditions. Base flow samples were collected on April 20, 1993. No rain was reported in Renton during the two days prior to sampling. Storm flow samples were collected during storms that occurred on April 8, 1993 and April 26, 1993. Rainfall (measured at Sea-Tac Airport) on these two days was 0.83 and 0.52 inches, respectively. No rain was measured the day prior to either storm. As expected, flow rates in the storm drains under base flow conditions were low, ranging from about 0.0004 to 0.0009 cfs per acre in the West Hill subbasins and from about 0.00002 to 0.002 cfs per acre in the North Renton subbasins (Table 9). Base flow represents ground water contributions to the drainage systems, although base flows at station NR-6 also include NPDES- permit discharges of noncontact cooling water from the Boeing plant (75,600 gallons per day). Flows increase by as much as 3 to 100 times under storm flow conditions (Table 10). All samples were analyzed for conventional pollutants (temperature, dissolved oxygen, pH, specific conductance, turbidity, total suspended solids, fecal coliform bacteria, and hardness), nutrients (total phosphorus, soluble reactive phosphorus, ammonia-nitrogen, and nitrite+nitrate nitrogen), total petroleum hydrocarbons, and metals (total copper, lead, and zinc). Flow rate was also measured at each station. Subbasin Sampling Results Results for the base flow and storm flow samples collected at the 10 subbasin monitoring stations in the North Renton and West Hill storm drains are presented in Tables 9 and 10. Base flow and storm flow quality conditions at the subbasin sampling stations are described and evaluated in the following sections. Conventional Pollutants and Nutrients Only three of the conventional pollutants analyzed (i.e., pH, fecal coliform bacteria, and total phosphorus) exceed water quality standards c r guidelines under base flow or storm flow conditions. Typically, both the number and magnitude of exceedances are greater under storm flow than base flow conditions. In addition, there are marked differences between base flow and storm flow quality in both basins. A description of the results for individual pollutants is provided in the following sections. 255C\LWTASK3 38 Herrera Environmental Consultants pH—None of the samples collected from the 10 subbasin stations exceeded the Class AA standard for pH under base flow conditions. However, storm flow pl i values at four of the 10 stations (WH-1, WH-2, WH-3, and NR-6) were below the standard pH range (6.5 to 8.5). The pH values at these four stations ranged from 6.03 to 6.4, while pH values at the other seven stations ranged from 7.3 to 7.6. With the exception of station WH4, pH values at the six stations that met water quality standards were typically higher under storm flow conditions (7.3 to 7.6) compared with base flow conditions (7.01 to 7.67). However, the opposite trend was observed at the other four stations, with storm flow pH values always less than base flow pH values. Fecal Coliform Bacteria—Base flow samples exceeded the fecal coliform bacteria standard for Class AA waters (50 cfu/100 mL) at all but four of the sampling stations, and storm flow samples exceeded the standard at all stations. The Class AA standard was met only in the base flow samples collected at stations WH-3, NR-1, NR-4, and NR-6. Elevated fecal coliform counts are commonly observed in urban stormwater runoff. A recent study conducted in the Pipers Creek watershed in north Seattle found that fecal contamination in stormwater runoff was contributed entirely from animal sources (i.e., dog, cat, and bird) rather than human sources (Herrera 1993a). This study used a forensic method based on genetic labeling techniques to differentiate fecal contamination contributed from various animal species and humans. The greatest number of matches between receiving water and source isolates were of domestic cat origin. However, due to the limited number of samples, it is unclear whether cats were the primary source of fecal contamination in the stormwater samples. Given the predominance of residential land use in the Renton basins and the potential for large concentrations of domestic animals, it is reasonable to assume that animal waste is also a major source of fecal contamination measured in stormwater samples collected from the two Renton storm drains. However, it is unlikely that animal waste is the primary source of the fecal contamination found in the base flow samples. Under base flow conditions, contributions from surface runoff are negligible, as most base flow is contributed from ground water. Therefore, there is little opportunity for base flows to come in contact with animal waste that is deposited on the ground. The primary sources of fecal contamination in base flow samples are likely to include: ■ Leaks from sanitary sewers that infiltrate into the storm drain system ■ Failing septic tanks that contaminate local ground water ■ Cross-connections between the sanitary and storm drain systems (i.e., illicit connections). Most of the North Renton drainage basin and a little more than half of the West Hill basin are served by sanitary sewers. Given the age of most of the residential development in these basins (40 to 50 years), it is possible that some of the existing sanitary sewer pipes may need repair or replacement. The Renton Sewer Utility is currently evaluating the condition of sewer pipes within its service area. Results from this study will be available within the next few months. The entire North Renton basin is located within the city of Renton sewer service area. Only a small area in the northern portion of the basin along Edmonds Avenue NE between NE 16th Street and NE 18th Street is unsewered. The rest of the basin is served by sanitary sewer. 255C\LWTASK3 39 Herrera Environmental Consultants The West Hill basin is located partially within the Renton, Skyway, and Bryn Mawr sewer service areas (Figure 9). The Renton and Bryn Mawr service areas are entirely sewered. A large portion of the Skyway service area (from 84th Avenue South to the western border of the basin between South 124 Street and South 132 Street) remains unsewered (Figure 9). Seattle/King County Department of Public Health records for 1965 through 1992 indicate that many septic tank failures have occurred in this area, particularly in the area bordered by 76th and 80th avenues south, and South 124 and South 128 streets (Figure 9). Although residents are not typically required to tie in when a new sewer line is installed, they are charged for service by the local sewer districts regardless of whether they hook up to the sewer. Therefore, it is likely that most residences and businesses located in sewered areas within the North Renton and West Hill basins are connected to the sewer. Contributions from illicit connections u id infiltra6 n frcm surrounding sewer lines are difficult to confirm. A survey was conducted as part of this study to identify possible illegal connections to the two storm drain systems. The results are described in detail elsewhere in this report. Fecal coliform bacteria concentrations were elevated in only three of approximately 40 stations surveyed (20 in the North Renton basin and 20 in the West Hill basin). Further investigation is needed to identify the cause of the elevated fecal coliform bacteria levels observed in base flow samples. Temperature—Storm flow and base flow samples were collected in early spring. Therefore, water temperatures are fairly consistent, ranging from about 90C to 12°C. The only difference noted in the base flow sample collected at station NR-6 (13.2°C) was probably associated with NPDES-permitted discharges of noncontact cooling water from the Boeing plant. Specific Conductance and Hardness-Specific conductance and hardness in base flow samples (140 to 340 micromhos per centimeter [µmhos/cm] and 56 to 153 mg/L as CaC')3, respectively) are both consistently higher than in the storm flow samples collected at each station (20 to 183 µmhos/cm and 11 to 74 mg/L as CaCO3, respectively). These differences highlight the importance of ground water contributions to base flow in the study area. Ground water typically contains greater concentrations of dissolved solids, which are reflected in higher specific conductance and hardness. The median concentrations for specific conductance and hardness measured in wells in King County are 165 kLmhos/cm and 64 mg/L as CaCO3, respectively (Turney 1986). Total Suspended Solids—With the exception of stations WH-1 (21 mg/L) and WH-3 (37 mg/L), total suspended solids concentrations i.i the bz_se flow samples are fairly low (<1 to 5 mg/L). Stations WH-1 and WH-3 are located s_ manholes just west of Rainier Way North at the bottom of a steep section of pipe. It is possible that base flows at these two stations are scouring sediments deposited in the storm drains from previous rainfall events. Further investigation of these two systems is recommended to determine whether storm drain cleaning is warranted. Although typically greater than in base flow samples, suspended solids concentrations in the storm flow samples are relatively low, ranging from 3.5 to 23 mg/L. These concentrations are at the low end of the range reported in other urban runoff samples, reflecting the older age of the developments in the North Renton and West Hill basins. As a result, there is little land 255C\LWTASK3 40 Herrera Environmental Consultants disturbance associated with new construction. Most of the neighborhoods are well established and have little potential for soil erosion. Nutrients—Nutrient concentrations are generally within the ranges reported in runoff from other urban areas, although nitrate+nitrite nitrogen concentrations often exceed the average concentrations reported for residential areas. With the exception of station WH-4 (storm flow and base flow sample = 1.68 mg/L), nitrite+nitrate nitrogen concentrations are typically greater in the base flow samples than in the storm flow samples. In most cases, nitrite+nitrate nitrogen concentrations in the base flow samples are between 2 and 8 times greater than in the storm flow samples. However, base flow concentrations at stations NR-1 and NR-2 are 43 and 17 times greater, respectively than the corresponding storm flow samples. Higher concentrations in base flow samples reflect contributions from ground water. The nitrite+nitrate nitrogen concentrations measured in the base flow samples collected from subbasin monitoring stations in both drainage basins (0.315 to 5 mg/L) are considerably higher than the median concentration (0.1 mg/L) reported for ground water samples collected in King County (Turney 1986). These differences suggest that local ground water contains elevated concentrations of nitrite+nitrate nitrogen, possibly due to failing septic tanks or leaks in the sanitary sewer lines. These results are consistent with the fecal coliform bacteria concentrations, which are also elevated in many of the base flow samples. Ammonia concentrations in base flow and stormwater samples are low in all samples collected from the North Renton and West Hill storm drains, with concentrations ranging from 0.012 to 0.5 mg/L in base flow samples and from less than 0.01 to 0.359 mg/L in stormwater samples. None of the samples exceed the chronic or acute criteria for freshwater aquatic life. Total phosphorus concentrations at most stations exceed the level considered acceptable for discharge into lakes to prevent cultural eutrophication (0.05 mg/L). These results are consistent with the concentrations in the outfall monitoring samples, which also exceed the phosphorus criterion. Only station NR-6 meets the phosphorus criterion in both base flow and stormwater samples. No apparent trend was observed at the other stations. Base flow concentrations are greater than storm flow concentrations at some stations, while at other stations this trend is reversed. The only consistent trend shows phosphorus present primarily in particulate form, with the soluble fraction making up between 10 and 48 percent of the total phosphorus. As explained earlier, because phosphorus is a limiting nutrient in Lake Washington, increases in phosphorus loadings could stimulate excessive algal growth. Metals Metals exhibit the same pattern as many of the conventional pollutants, with concentrations generally lower in the base flow samples than in the storm flow samples (see Tables 9 and 10). However, water quality standards were exceeded under both base flow and storm flow conditions. The number and magnitude of exceedances are portrayed graphically in Figures 10 through 12. Under base flow conditions, lead problems were most widespread, as lead exceeded the chronic toxicity level for aquatic organisms a; six of the 10 stations sampled. Concentrations ranged 255C\LWTASK3 41 Herrera Environmental Consultants from 0.5 to 10.1 µg/L. The largest exceedances occurred at stations WH-3 and NR-6, where the concentration of lead in the base flow samples was nearly 10 times greater than the chronic toxicity level. In addition to lead, copper (34.7 µg/L) and zinc (168 µg/L) in base flow samples at stations NR- 3 and NR-1, respectively, exceeded the acute toxicity criteria for aquatic life. The concentrations of these metals were between 2 and 30 times greater than the concentrations measured at other stations in the two basins. The copper concentration also exceeded the criterion for chronic toxicity at station NR-6. Metals concentrations and the number of exceedances of water quality standards increased dramatically in the storm flow samples, particularly at stations NR-4, NR-5, and NR-6, which exceeded the acute toxicity criteria for copper, lei d, and zinc (Table 11) In general, with respect to the three metals analyzed as part of the investigation (copper, lead, and zinc), stormwater quality is better in the West Hill basin than in the North Renton basin. Although stormwater collected from all stations in the West Hill basin exceeded the chronic toxicity criterion for at least one metal, acute toxicity criteria were exceeded only at station WH- 2 (copper and zinc). In comparison, all stations sampled in the North Renton basin exceeded the acute toxicity criterion for at least one metal. Zinc was the most prevalent, with exceedances at all six stations in the North Renton basin. As shown in Figure 12, the largest exceedance (by a factor of nearly 10) occurred at station NR-6. Copper and lead concentrations in stormwater samples exceeded the acute toxicity criteria at stations NR 4, NR-5, and NR-6. The overall range of metals concentrations_and averages for all stations sampled are compared in Table 12 for the North Renton and West Hill basins. OveraL basin averages are calculated using the results from all subbasin monitoring stations in a particular basin. Outfall results are included in the calculation of average stormwater concentrations. In general, the concentrations of metals in stormwater samples collected from the two basins are comparable. However, some minor differences are evident in the base flow samples. For example, the overall basin averages for copper and zinc in the North Renton basin are approximately double the averages calculated for the West Hill basin. The exact opposite is noted for lead, where the average concentration in the West Hill basin is approximately double the average for the North Renton stations. Base flow samples generally represent ground water contributions. Therefore, these apparent trends probably reflect differences in the quality of ground water rather than surface water quality in the two drainage basins. Total Petroleum Hydrocarbons Total petroleum hydrocarbons were detected in only one base flow sample (280 µg/L at station WH-3). Concentrations were generally higher in the stormwater samples, consistent with observations made during the stormwater sampling events (visible sheens were reported at several of the sampling stations). There are currently no surface water standards for total petroleum hydrocarbons, although the criteria for aesthetic quality apply. Aesthetic quality criteria are subjective, allowing no impairment that would offend the senses of sight, smell, 255C\LWTASK3 42 Herrera Environmental Consultants touch, or taste. The noticeable sheens observed at stations NR-4 and WH-2 would qualify as aesthetic quality impairment. MTCA cleanup standards have not yet been established for total petroleum hydrocarbons. A cleanup level of 1,000 µg/L has been established under MTCA for contaminated ground water. The ground water cleanup standard is based on prevention of adverse aesthetic characteristics. Therefore, it is used here for comparison purposes to evaluate stormwater quality results. Petroleum hydrocarbon concentrations measured in stormwater samples collected at stations NR- 1 (1,370 µg/L) and NR-5 (1,570 µg/L) exceeded the MTCA method A cleanup level for ground water (1,000 µg/L). These two stations are located in subbasins N4 and N6, which cover the entire area north of Sunset Boulevard. Further investigation of possible petroleum contaminant sources in this area is warranted. Pollutant Loading Estimates Estimates of average annual pollutant loading have been calculated for each of the 10 subbasin monitoring stations as well as the North Renton and West Hill outfall stations. Pollutant loadings were then used to rank the individual subbasins so that source control efforts can be prioritized. Loadings for the following pollutants were calculated from the product of the average annual runoff volume and the average pollutant concentration measured during the base flow and storm flow sampling events: ■ -Total suspended solids ■ Nutrients ■ Metals ■ Fecal coliform bacteria. Because total petroleum hydrocarbons were detected in only a limited number of samples, loadings have not been calculated. Hydrologic Analysis Average annual runoff volumes were estimated for the 10 subbasins corresponding to the subbasin monitoring stations in the North Renton and West Hill drainage basins. Runoff estimates were calculated using the U.S. Soil Conservation Service TR-55 curve number model. Because TR-55 is a single-event runoff model, estimates were calculated for several storm sizes, then summed based on the distribution of rainfall events for an average year. A detailed discussion of the hydrologic analysis is presented in Appendix C. Based on previous studies, 1959 was selected as representing the average year, for distribution of rainfall events, based on data from Sea-Tac International Airport. Rainfall analysis was performed using RAINEV, a rainfall analysis computer model (Sutherland and Green 1989). The model results indicate that approximately 176 rainfall events occur during the average year, with daily rainfall amounts ranging between 0.01 and 3.5 inches. Rainfall events of 0.5 inches 255C\LWTASK3 43 Herrera Environmental Consultants or less account for approximately 87 percent of the total number of storms occurring each year, while 56 percent of the storms are less than or equal to 0.2 inches. Larger storms occur infrequently; storm events of 1 inch or more account for less than 4 percent of the total number of storms each year. The results of the hydrologic analysis are summarized in Table 13. Average annual runoff from the 1,236-acre North Renton drainage basin is estimated at 1,490 acre-feet per year. Average annual runoff from the 736-acre West Hill basin is estimated at 708 acre-feet per year. Subbasins N3 (408 acre-feet) and N5 (472 acre-feet) account for approximately 59 percent of the total runoff from the North Renton basin, while subbasins W 1 (252 acre-feet) and W5 (193 acre- feet) contribute about 63 percent of the total runoff in the West Hill basin. Because of the large runoff volumes, these subbasins can also be expected to contribute a significant fraction of the overall pollutant loading in the basins. Loading Analysis Estimates of the average annual stormwater pollutant loadings within the North Renton and West Hill basins were calculated using the results from both the outfall and subbasin monitoring efforts. The pollutant concentration measured at each station (the mean of the storm and base flow events for the subbasin monitoring station) was multiplied by th(, average annual runoff as calculated in the hydrologic analysis. Results are summmari_,ed in Tabie 14. In addition, annual pollutant loadings for each of the subbasins located .--ithi 1 the larg.r basins were calculated (Table 15). A pollutant loading ranking by subbasin derived from the total annua: loadings is presented in Tables 16 and 17. The ranking shows that in the West Hill basin, subbasins W1 and W5 contributed the highest pollutant loadings, while in the North Renton basin, subbasin N3 was ranked as the highest contributor for total loadings of all pollutants. Because each basin and subbasin generally contains a mixture of residential, commercial, and industrial land uses, areal pollutant loadings (in pounds per acre per year) were also calculated for each basin and subbasin to provide an understanding of the relative runoff contribution derived from activities within the two basins. When average annual pollutant loadings for the North Renton and West Hill basins were calculated on an areal basis (Table 18), the loadings per acre for those parameters tested were observed to vary between basins. The loadings per acre were highest in the North Renton basin for the following pollutants: total suspended solids, soluble reactive phosphorus, copper, zinc, and fecal coliform bacteria; while in the West Hill basin, total phosphorus and nitrite+nitrate nitrogen areal loadings were higher. Per-acre lead loadings were the same in the North Renton and West Hill basins. Pollutant loadings were also calculated on an areal basis for the subbasins within the North Renton and West Hill basins (Table 19). Pollutant loadings were then ranked based on the areal contribution generated within each subbasin (Tables 20 and 21). The ranking shows that the greatest pollutant loading by area does not always coincide with the total pollutant loadings calculated previously. 255C\LWTASK3 44 Herrera Environmental Consultants In the West Hill basin, subbasin W5 was identified as the highest generator of pollutants based on the overall ranking of areal loadings. (Loadings for subbasins W5 and W6 were based on calculated loadings using pollutant concentrations derived from other studies of similar land use.) Subbasin W5 was followed by subbasins W6 and W4. Thus, on a relative basis, subbasin W5 contributes the greatest amount of pollutant runoff per subbasin area. From the standpoint of total annual pollutant loading, subbasin W5 may also be considered the largest contributor to runoff pollutant loading within the West Hill basin. However, subbasin W1, while last in areal pollutant contribution, ranks second in total pollutant loading for the basin. When pollutant runoff from the North Renton subbasin was ranked according to areal pollutant loadings, it was observed that subbasin N2 generated the highest areal loading, followed by subbasins NI and N3. However, while subbasin N2 ranks highest in areal pollutant loading, it ranks only fifth based on total pollutant loadings. Similarly, subbasin N1, which ranks second in areal loading, ranks last in total pollutant loading for the basin. The areal pollutant loadings calculated for subbasins of the West Hill and North Renton basins have provided information with which to characterize the level of urban activity contributing to pollutant runoff. From the overall ranking of stormwater pollutant loadings presented above, it can be shown that those subbasins with the greatest urban activity contributing to runoff pollution are W5 and W6 in the West Hill basin and N2 in the North Renton basin. While it is not possible, based on the calculated loading rankings, to specify the type or level of urban activity contributing stormwater pollutants, the rankings provide a focus for the examination of possible sources within these basins. SEDIMENT SAMPLING PROGRAM The sediment sampling program was conducted to characterize the quality of sediments that have accumulated in Lake Washington offshore of the North Renton and West Hill storm drain outfalls. The goal of the sediment sampling program is to provide additional information for characterizing pollutant sources that mz:.✓ not have been identified by the stormwater sampling program. Another objective of the sediment sampling program is to evaluate the potential effects of stormwater on benthic organisms that inhabit receiving waters. Many pollutants present in urban runoff(e.g., nutrients, metals, and organic contaminants) tend to sorb onto particulate material. Particulate-bound pollutants are then deposited in low-energy areas such as the lake bottom offshore of the storm drain outfalls. As sediments accumulate over time, they provide a historical perspective of stormwater quality, combining the contributions from numerous storm events. Because of this compositing effect, sediment samples are often preferable to single-event stormwater samples for evaluation of long-term effects on the receiving water environment. Methods and results of the sediment sampling program are presented in the following sections. 255C\LWTASK3 45 Herrera Environmental Consultants Sediment Sampling Methods Surficial sediment samples were collected on April 27, 1993 in Lake Washington at the North Renton and West Hill outfalls. The North Renton outfall is a 45-foot-wide stream channel, and the West Hill outfall is an 8-foot-wide box culvert. To reduce the effects of special variation, a composite sediment sample composed of five grab samples was collected at each outfall. The grab samples were collected at evenly spaced intervals across the width of each outfall along two transects located approximately 20 feet and 30 feet from the mouth of the outfall. Water depth ranged from 7 to 10 feet at the North Renton locations and from 9.5 to 12.5 feet at the West Hill locations. Sediment samples were collected from a boat using a stainless steel van Veen bottom grab sampler, following Puget Sound protocols (PSEP 1986) and methods described in the sampling and quality assurance plan (Herrera 1992). The Surficial 2 centimeters of sediment from each undisturbed grab sample was transferred to a stainless mixing bowl for compositing. Sediment characteristics (e.g., texture, color, debris, oily sheen, and odor) were recorded in the field notebook. After debris and gravel larger than 2 centimeters in particle size were discarded, the grab samples were thoroughly mixed, and the homogenized sample was transferred to prelabeled sample containers. The samples were immediately placed on ice in a cooler and delivered to the laboratory on the day of collection. The sediment samples were analyzed for die 'allowing constituents according to U.S. EPA approved methods identified in the sampling and quality assurance plan (Herrera 1992): ■ Total solids ■ . Total organic carbon ■ Priority pollutant metals ■ Semivolatile organic compounds ■ Chlorinated pesticides and PCBs. Laboratory data were validated according to objectives and procedures identified in the sampling and quality assurance plan (Herrera 1992). No analytical problems or limitations on use of the data are identified in the quality assurance report(Appendix E). Freshwater Sediment Guidelines Freshwater sediment quality guidelines used to evaluate relative levels of contamination and potential effects on benthic organisms in Lake Washington are presented in Table 22. The guidelines were developed for the protection and management of freshwater sediments in Ontario, Canada and are the most comprehensive set of freshwater sediment quality guidelines currently available. They are currently being evaluated by Ecology (1991 b) for future development of freshwater sediment quality standards for Washington state. The Ontario (1992/93) guidelines are based on the following three levels of toxicity: ■ No-effect level: The no-effect level represents contaminant concentrations that do not affect fish or be thic organisms. do not transfer through the food 255C\LWTASK3 46 Herrera Environmental Consultants chain, and do not affect water quality. Sediments that fall into this category would be considered unpolluted. ■ Lowest-effect level: Sediment contaminant concentrations that exceed the lowest-effect level are not expected to affect the majority of benthic organisms but may adversely affect sensitive organisms. These sediments would be considered moderately polluted. ■ Severe-effect level: Contaminant concentrations that exceed the severe-effect level are likely to affect the health of benthic organisms. These sediments would be considered highly polluted. Historical Sediment Data For comparative purposes, historical se�'Iiment data from a survey conducted in Lake Washington (Metro 1984b) are also presented in Table 22. The values presented are the average concentrations measured in sediment samples collected in Lake Washington immediately offshore of four storm drain outfalls and at two near-shore background (control) locations. The storm drain outfalls are located adjacent to the following residential areas: Madison Park (Seattle), Madrona (Seattle), the northern end of Mercer Island, and the southeastern end of Mercer Island. The control stations are located adjacent to Lake City (Seattle) and in Juanita Bay. One composite sediment sample was collected at each of these locations, with the exception of two samples collected from the northern end of Mercer Island, for a total of five storm drain samples and two control samples. In the calculation of mean values, the analytical detection limit was used for undetected values. Results from recent samples collected from the Cedar River delta are also included in Table 22 for comparative purposes. Five composite sedimen` samples collected from 10 stations at depths of zero to 8 feet were analyzed prior to excavating sediments from the delta located at the southern end of Lake Washington. Dredging was conducted to reduce threats to aircraft at the Renton Municipal Airport posed by foraging birds attracted to the shallow delta area (Golder 1992). Urban Street Dust Data Available data for urban street dust are also provided in Table 22 for comparison with the outfall sediment chemistry results (Galvin and Moore 1982). Street dust samples were collected from 14 locations in Bellevue and Seattle, representing residential, commercial, and light industrial uses. Because sediment that accumulates offshore of storm drain outfalls is expected to mix with lake bottom sediments, street dust data represent an upper bound for contaminant levels in offshore sediments. 255C\LWTASK3 47 Herrera Environmental Consultants Sediment Sampling Results The composite sediment samples collected offshore of the two drains exhibited similar physical characteristics. Both samples consisted of a dark gray to black mixture of organic debris (leaves and sticks) and silt with small amounts of fine sand. Sediments at both stations also exhibited a slight oil sheen. Analytical results for the two outfall sediment samples are presented in Table 22. Metals Concentrations of heavy metals were similar in the sediment samples collected offshore of the two outfalls, generally falling between the lowest-effect and severe-effect levels defined under the Ontario (1992/93) guidelines (Table 22). These results indicate a moderate level of pollution that likely affects the health of more sensitive benthic organisms. All sediment metals exceeded the background levels measured in Lake Washington, which suggests that stormwater discharges have affected sediment quality in the lake. Cadmium(2.9 to 3.4 mg/kg) exhibited the largest elevation above the background concentration (0.13 mg/kg). Studies have shown that fish feeding on benthic organisms can bioaccumulate cadmium (Moore and Ramamoorthy 1984a). However, because cadmium is accumulated primarily in major organs rather than in edible muscle tissue, accumulation is not usually a threat to most freshwater fishery resources (Walsh et al. 1977). The concentrations of other metals were generally within the range of 2 to 6 times the background levels. The concentrations of antimony, cadmium, copper, and zinc in the sediments offshore of the two Renton outfalls are approximately 2 to 10 times greater than the average concentration measured in the Metro (1984b) study. In addition, the concentration of silver in the sediment offshore of the North Renton storm drain outfall (19.8 mg/kg) is nearly 200 times greater than the concentration measured offshore of other storm drains in Lake Washington (0.1 mg/kg). The concentrations of other metals are comparable to the levels reported by Metro (1984b) for sediments offshore of other storm drains in Lake Washington. Metro (1987) found elevated concentrations of silver in sediments offshore of the Denny Way combined sewer overflow in Seattle. Silver contamination at this site was attributed to discharges from photographic laboratories in the drainage basin. However, there is only one photographic studio in the North Renton drainage basin, and unlike Seattle, the Renton drainage basins are served by separate storm and sanitary sewer systems. Therefore, it is unlikely that photographic processing contributed to the silver contamination observed at this site. The source of the silver contamination is not known. Metals concentrations in the sediment offshore of the two Renton outfalls ranged from about 2 to nearly 100 times greater than the concentrations measured in the Cedar River delta sediments. The greatest differences were observed for cadmium (2.9 to 3.4 mg/kg offshore of the outfalls versus 0.04 to 0.07 mg/kg in the delta) and lead (207 mg/kg offshore of the outfalls versus 6.3 to 11 mg/kg in the delta). 255C\LWTASK3 48 Herrera Environmental Consultants Differences in sediment chemistry are likely associated with differences in the physical sediment characteristics and relative contributions from sources in the two Renton drainage basins compared to the entire Cedar River watershed. Although it is a depositional area, the Cedar River delta is subject to greater currents due to the large input from the river (the average annual flow is 670 cfs) than are the sediments offshore of the storm drains. As a result, sediment in the delta consists primarily of coarse-grained particles (>90 percent sands and gravels), while the sediments offshore of the storm drain outfalls contain a greater proportion of fine-grained particles (estimated at >50 percent silt, clay, and organic material). Fine-grained sediments usually contain a greater concentration of contaminants than do coarse-grained sediments because of their larger surface-area-to-volume ratio, which makes them more effective in adsorbing the contaminants present in runoff. The 184-square-mile Cedar River watershed also contains a large proportion of undeveloped, forested land, compared to the two Renton basins. High-density development, which is characteristic of the entire North Rented and West Hill drainage basins, is confined to the lower portions of the Cedar River watershed. Consequently, contaminants in urban runoff contributed from sources in the lower Cedar River basin are diluted by discharges from the upper basin. Metals concentrations in sediments offshore of the two Renton outfalls were generally within the range of concentrations reported in urban street dust (see Table 22). Exceptions include concentrations of cadmium, selenium, silver, and zinc that exceed the highest value measured in street dust. Organic Compounds As in the case of metals, the concentrations of organic compounds observed in the sediments offshore of the North Renton and West Hill storm drain o itfalls were similar (see Table 22). Based on comparisons with the available historical data for Lake Washington sediments, the concentrations of the following groups of compounds may be considered elevated: ■ Total organic carbon ■ LPAHs and HPAHs ■ Phthalates ■ PCBs. Concentrations of these compounds exceed levels measured offshore of other storm drain outfalls in Lake Washington (Metro 1984b) and also exceed the Ontario (1992/93) guidelines for lowest effects on benthic organisms but not for severe effects. High levels of total organic carbon are detrimental to benthic organisms because decomposition of organic matter depresses oxygen levels in the sediment. The total organic carbon concentrations observed in outfall sediments (3.5 to 3.7 percent) suggest that the most sensitive species of benthic organisms may be affected by organic matter in stormwater discharged from the two basins. PAH compounds originate from fossil fuels and are commonly found in urban runoff. Potential sources of PAHs in urban stormwater include direct discharge via spills (e.g., leaks from 255C\LWTASK3 49 Herrera Environmental Consultants automobiles and improper disposal of used crankcase oil) and atmospheric deposition of combustion products from automobile exhaust and other combustion sources (e.g., coal and home heating oil). PAHs, particularly the higher molecular weight compounds, have low aqueous solubilities. Consequently, these compounds are usually associated with particulate material and are transported in stormwater as suspended solids. Concentrations of LPAHs and HPAHs in the Renton outfall sediments are approximately 4 times higher than the mean levels measured offshore of other storm drains in Lake Washington and are 20 to 100 times greater than the background levels reported in Lake Washington (Metro 1984b). The concentrations of PAH compounds in the sediments offshore of the two Renton storm drain outfalls also exceed the concentrations found in the Cedar River delta sediments. PAH compounds, particularly the LPAHs, have not been detected in sediments from the delta. Again, these differences can be explained by the different particle size distribution in the sediments collected from these areas. The coarse sediments found in the delta area are not capable of adsorbing large amounts of contaminants. LPAH and HPAH concentrations in outfall sediments also exceed the Ontario (1992/93) lowest- effect criteria but not the severe-effect criteria. According to these criteria, outfall sediments are moderately contaminated with LPAHs and HPAHs to a level that likely affects the health of more sensitive benthic organisms. LPAH concentrations in the sediment offshore of the two Renton outfalls is comparable to the levels measured in urban street dust. However, HPAH concentrations in the offshore sediments are about 2 to 3 times greater than in urban street dust. HPAH compounds are characteristic of fossil fuel combustion. Studies have shown that the PAH mixtures found in combustion product residues are similar, regardless of the type of fuel material that is burned (Lee et al. 1977). Therefore, the predominance of HPAH compounds in the sediments offshore of the two outfalls indicates a combustion-related source. In addition, HPAH compounds are typically more difficult to degrade than LPAH compounds, which may result in a greater accumulation of HPAHs than LPAHs in the receiving environment. Phthalates are used as plasticizers in a variety of products and therefore tend to be ubiquitous in the urban environment. Guidelines for phthalates in freshwater sediments have not been established. Concentrations of total phthalates in the North Renton and West Hill outfall sediments are similar to the mean concentration reported by Metro (1984b) for sediments offshore of other storm drain outfalls in Lake Washington, but they exceed the reported background concentration by a factor of 22 to 27 and are 10 to 50 times greater than the concentrations measured in the Cedar River delta. PCBs were historically used as insulating oil in a variety of electrical equipment (e.g., transformers and capacitors) and were also commonly used as plasticizers. Although their production has now ceased, they persist in the environment. PCBs are a widespread contaminant in invertebrates and fish because they readily bioaccumulate (Moore and Ramamoorthy 1984b). Concentrations of total PCBs in the sediments offshore of the North Renton and West Hill outfalls are 2 to 26 times greater than average concentrations measured offshore of other storm drains in Lake Washington (Metro 1984b) and the control sites. (Metro [1984b] reports that one of the control sites was inexplicably contaminated with PCBs.) These levels also exceed the lowest-effect criterion for total PCBs, but not the severe-effect criterion. Thus, the North 255C\LWTASK3 50 Herrera Environmental Consultants Renton and West Hill outfall sediments are moderately contaminated with PCBs to a level that may affect the health of the more sensitive benthic organisms. Most other organic compounds (e.g., pesticides, chlorinated hydrocarbons, and phenolic compounds) were undetected. In addition to the general categories of contaminants described above, the following individual compounds were also detected in the outfall sediments: Compound Use Carbazole Manufacture of dyes, explosives, insecticides, lubricants, rubber antioxidants, and odor-inhibiting detergents; ultraviolet sensitizer for photographic plates Dibenzofuran Insecticide 4-Methylphenol Disinfectant, phenolic resins, chemical intermediate, manufacture of herbicides, surfactant, synthetic food flavors Because freshwater sediment guidelines and Metro historical data are not available for these compounds, outfall results are compai d to other data sources in Table 23. This comparison shows that concentrations of these compounds in the outfall sediments are similar to concentrations in uncontaminated areas of Lake Washington and are higher than concentrations in the marine waters of Puget Sound. Marine sediment criteria are also presented in Table 23, showing that the only criterion exceedance was for 4-methylphenol at the North Renton outfall. Thus, sediments at the North Renton outfall appear to be moderately contaminated with 4- methylphenol to a level that may affect the health of benthic organisms. ILLICIT CONNECTION SURVEY A survey of each basin was conducted to determine if pollutants are being illegally discharged into the city storm drain system via illicit connections, discharges, or dumping. A total of 16 stations were sampled in the North Renton basin (see Figure 2), and 14 stations were sampled in the West Hill basin (see Figure 3). 'Sampling stations within each of the basin storm drain systems were chosen based on their access, proximity to other stations, and location within the overall drainage system. Storm Drain Sampling Methods Water samples were collected manually (i.e., grab samples) within each basin from manhole access points. Sample collection took place during base flow conditions (i.e., after at least 72 hours of dry weather) to minimize interference from stormwater runoff. Field measurements were made and recorded at the time samples were collected. The following field measurements were recorded using field instruments: 255C\LWTASK3 51 Herrera Environmental Consultants ■ Temperature ■ pH ■ Dissolved oxygen ■ Specific conductance. In addition to the field measurements, field testing was conducted using a commercially available water test kit (trade name Hach). Field tests were conducted to screen for the presence of the following contaminants in the storm drain system: ■ Chlorine ■ Copper ■ Detergent ■ Phenols. All samples collected were also analyzed for turbidity ai-d ;cal coliform bacteria. The bacteria samples were collected in sterile laboratory sample bottles -,-nd held on ice during transport to the laboratory. Turbidity was analyzed within 24 hours using a turbidimeter (model 800, Engineered Systems and Designs). Storm Drain Sampling Results Results of the monitoring for illicit connections are presented in Table 24. Because not all of the stations were observed to have flowing water, not all were sampled. Only nine stations (of 16) in the North Renton basin were sampled, and only nine stations (of 14) in the West Hill basin contained water and were sampled. Fecal Coliform Bacteria All stations were tested for the presence of fecal coliform bacteria to determine if a sanitary sewer connection or sewer line breakage is contributing sanitary wastewater to the storm drain. During storm events it is not unusual to observe high concentrations of fecal coliform bacteria in stormwater. However, during base flow conditions, fecal coliform bacteria concentrations are expected to be low unless a sanitary source is connected to the drainage system. Only one drain in the North Renton basin exhibited what may be considered an unusually high concentration of fecal coliform bacteria. Manhole 17, F2-3 had 1,160 cfu per 100 mL. In the West Hill basin, four of nine stations sampled exhibited elevated concentrations of fecal coliform bacteria. These were 11, 136-16; 11, D8-12; Taylor Avenue ravine; and 15, G4-2, which exhibited the following respective concentrations: 420, 200, 860, and 2,200 cfu per 100 mL. Each of these drains may receive flow from a sanitary source. However, only three of these drains (17, 172-3; 11, 136-16; and 11, D8-12) also exhibited the presence of chlorine, which suggests that potable water is present. (Potable water might also be expected if a sanitary connection to the storm drain exists.) 255C\LWTASK3 52 Herrera Environmental Consultants Turbidity,pH, Temperature, and Dissolved Oxygen Turbidity values for all illicit investigation samples except two were low (i.e., less than 10 nephelometric turbidity units [NTU]). A single station in the North Renton basin (12, D6-2) was very turbid (161 NTU) and also exhibited high specific conductance (1,287 µmhos/cm). Only one station in the West Hill basin (11, 136-16) was observed to be turbid (34 NTU). These results suggest that, of the drains tested, the two noted above may be receiving inputs from inappropriate sources. The elevated turbidity may indicate either the discharge of washwater that contacts and erodes exposed soils, or a similar inappropriate activity within the subbasin. All drainage waters sampled exhibited pH values within a range that indicates no unusual discharge. All pH values were within Ecology freshwater quality standards (i.e., 6.5 to 8.5). Temperature and dissolved oxygen measurements were recorded for drains in the North Renton basin. However, due to equipment failure, these measurements are not available for the West Hill basin drains. Measurements in the North Renton basin drains indicate that dissolved oxygen is reasonably high (i.e., greater than 5.0 mg/L) in all drainage waters except one (12, 136-2). This drain exhibited a dissolved oxygen concentration of 0.7 mg/L, likely because of stagnant water conditions that exist at this station. (As noted previously, turbidity and specific conductance were also elevated in water from this drain.) Total Petroleum Hydrocarbons A visible sheen was noted in one of the North Renton drains (12, D6-2), and a sample was collected and analyzed by the laboratory for the presence of total petroleum hydrocarbons. However, none were detected (analytical detection limit of 0.25 mg/L). This sample also exhibits high turbidity (161 NTU) and high specific conductance (1,287 µmhos/cm). Ancillary Testing A single sample from the North Renton basin (12, H2-2) exhibiting high specific conductance was submitted to the laboratory and analyzed for th,; presence of copper, lead, and zinc. The results of this testing (0.0711 mg/L, 0.0031 nig/L, and 0.076 mg/L, respectively) reveal the presence of these metals only at low levels. Thus, the presence of an illicit discharge of these metals to the upstream storm drain system is not indicated. Hach Field Parameters Field testing using a Hach portable test kit revealed only the presence of chlorine in four of the North Renton drains (07, E7-2; 12, F5-6; 12, H6-6; and 17, F2-3) and three of the West Hill drains (11, 136-16; 11, D8-12; and 128 Street ravine). All observed chlorine concentrations were low (i.e., less than 0.3 mg/L) and were indicative of potable water rather than an industrial source of chlorine. The field test kit results did not reveal the presence of copper, detergent, or phenols. 255C\LWTASK3 53 Herrera Environmental Consultants Storm Drain Monitoring Recommendations Based upon the illicit connection studies described above, it appears that at least two areas in the North Renton basin warrant further investigation. These areas include those portions of subbasin N2 draining to station 12, D6-2 and those portions of subbasin N3 draining to station 17, F2-3. The former station exhibits elevated specific conductance and turbidity and low dissolved oxygen, while the latter station exhibits traces of chlorine and an elevated fecal coliform bacteria level. These findings suggest the presence of illicit connections or detrimental activities occurring within the subbasins served by the storm drain system. In the West Hill basin at least four subbasin areas may warrant further investigation of illicit connections or source tracking. These areas include those portions of subbasin W1 draining to station 15, G4-2; those portions of subbasin W3 draining to station 11, D8-1.2 and the Taylor Avenue ravine; and those portions of subbasin W4 draining to station 11, 136-16. Activities in these areas appear to be contributing to fecal coliform contamination:f ire drainage system, and in the case of subbasin W4, turbidity sources may also be a problem. HISTORICAL DATA Historical stormwater quality data are available for only two sites, Boeing and Paccar. Both of these sites are located in the North Renton basin. Basinwide stormwater data for the North Renton and West Hill basins are generally not available. Existing information for the Boeing and Paccar sites is summarized in the following sections. Boeing Stormwater Sampling Data The Boeing Renton East Base facility covers approximately 107 acres in the western portion of the North Renton basin (Figure 13). In addition, Boeing leases property at the Renton Municipal Airport in the West Hill basin. In 1993, Boeing collected stormwater samples from five storm drains in support of its part 2 NPDES stormwater permit application. Data from two Boeing sampling stations (001 and 017) have been compiled to provide additional information on stormwater quality in the North Renton and West Hill basins. Boeing station 001 is located on a storm drain on Lake Washington Boulevard. This drain collects runoff from about 58 acres at the Boeing Renton plant and also receives noncontact cooling water from the Renton plant. The area contributing to station 001 is approximately the same as subbasin N1 in Figure 2. Under its NPDES industrial wastewater permit, Boeing is permitted to discharge 75,600 gallons per day of noncontact cooling water. Boeing station 017 is located on a storm drain that serves the apron D area adjacent to the Cedar River. Although this drainage area is outside the North Renton and West Hill basins, Boeing has identified this station as representative of other areas on the Boeing property, particularly the Boeing airport facilities that drain to the Black River culvert in the West Hill basin. Activities in this basin that are similar to those at the airport include airplane deicing, oil storage, and unloading operations. 255C\LWTASK3 54 Herrera Environmental Consultants Boeing collected 24-hour composite samples during a storm that occurred March 13-15, 1993. Total rainfall for the event was 0.47 inches. Parameters analyzed in the samples collected from each station were selected based on the activities and pollutants associated with the individual basins. Boeing sample results are summarized in Table 25. Comparisons with surface water quality standards and available data for urban runoff from other areas are also provided. With the exception of total suspended solids at station 017, the concentrations of most conventional pollutants are similar to concentrations measured in urban runoff from Seattle and in samples collected across the United States for the Nationwide Urban Runoff Program (NURP) (U.S. EPA 1983). The Seattle data are representative of industrial runoff, while the NURP data represent runoff from commercial areas. Although the data are limited, some differences are evident between the two Boeing sampling stations. In particular, the total suspended solids concentration at station 017 (51 mg/L) was about 10 times greater than at station 001 (4.4 mg/L) and was about 2 times greater than the average concentration measured in runoff from industrial areas in Seattle. In addition, nitrogen compounds (total Kjeldahl nitrogen and total nitrogen) were about 2 times greater at station 001 than at station 017. The total phosphorus concentrations in stormwater collected at the two Boeing stations (0.087 and 0.118 mg/L) exceed the level generally considered acceptable for discharge into lakes to prevent cultural eutrophication (0.05 mg/L). However, these concentrations are similar to the concentrations measured at other stations in the North Renton drainage basin (0.051 to 0.124 mg/L). Therefore, it does not appear that the Boeing site represents a significant source of phosphorus in the North Renton drainage basin. The concentrations of the cadmium, copper, silver, and zinc in stormwater collected from station 001 exceed the state water quality standards for acute and chronic toxicity to aquatic life. These results are typical of urban runoff. As shown in Table 25, the metals concentrations measured at station 001 were similar to the concentrations measured in runoff from other urban runoff. Only the lead concentration was different, with concentrations in runoff at station 001 lower than in runoff from industrial areas in Seattle by approximately a factor of 18. The concentrations of copper (30 µg/L) and zinc (183 µg/L) in the Boeing stormwater sample collected at station 001 were also greater than the concentrations measured at other stations in the North Renton basin sampled as part of this study (2.5 to 12.7 µg/L copper and 47 to 114 µg/L zinc). However, the lead concentration in the Boeing stormwater sample was similar to the concentrations measured at other stations in the North Renton basin. These results, although limited, suggest that the Boeing site may be a source of copper and lead to the North Renton drainage system. Metals were not analyzed at station 017. Water quality standards have not been established for the organic compounds measured at the two stations. However, concentrations of organic compounds were below MTCA cleanup standards. The volatile organic compound 2-butanone was detected at station 017, while chloroform, 4-methyl-2-pentanone, 1,1,2-trichlorotrifluorethane, benzoic acid, di-n-butyl phthalate, and bis(2-ethylhexyl)phthalate were detected at station 001. 255C\LWTASK3 55 Herrera Environmental Consultants Paccar Stormwater Monitoring Data A stormwater monitoring program has been implemented as part of ongoing remediation activities at the Paccar site. The Paccar site covers about 85 acres located in subbasin N3 in the southwestern corner of the North Renton basin (see Figure 2). Stormwater samples have been collected at two onsite stations and one offsite (background) station (Figure 14). The background station, located at the southeastern corner of the site, represents runoff from other industrial areas in the North Renton basin. Samples have been analyzed for metals (arsenic, chromium, copper, lead, nickel, and zinc) and select organic compounds (PCBs, total petroleum hydrocarbons, benzene, and vinyl chloride). Results for samples collected at the Paccar site in 1990-1992 are summarized in Table 26. Copper, lead, and zinc concentrations in site runoff frequently exceed the acute and chronic toxicity criteria for aquatic life. However, the concentrations are generally within the range typically found in urban runoff. With the exception of lead, the concentrations of most pollutants in runoff from the Paccar site are also similar to the concentrations measured at the background station. Average lead concentrations in onsite runoff are about 20 times greater than those found at the background station. However, the concentrations of lead and the other metals analyzed in the Paccar storm drains are similar to those measured at the six subbasin stations in the North Renton basin that were sampled as part of this study. These results indicate that runoff from the Paccar site is comparable to runoff in other urban areas and does not constitute a significant source of metals in the North Renton basin. Total petroleum hydrocarbons, the only organic compound detected in runoff from the site, were detected during only one sampling event and were also detected at the background station during this event. CONTAMINANT SOURCE CHARACTERIZATION SUMMARY The North Renton and West Hill drainage basins are highly urbanized. Each basin supports approximately 60 businesses that can be considered potential sources of pollution to the storm drainage system. Even though the primary source of most stormwater pollutants is atmospheric deposition, including wet fall and dry fall (Schueler 1987), stormwater pollution problems can also arise from the illegal or illicit discharge of many commercial chemicals and even household chemicals. The assessment of existing point and nonpoint pollu!ant sources presented here for the North Renton and West Hill drainage basins is intended to provide information with which to begin the formulation, evaluation, and selection of stormwater pollution abatement alternatives. The source characterization studies presented here attempt to focus on specific contaminants and sources that affect stormwater quality in the North Renton and West Hill basins. A compilation of data for known and suspected pollutant sources, coupled with the basinwide sampling of storm drains, is used to characterize the quality of runoff, evaluate potential impacts on the 255C\LWTASK3 56 Herrera Environmental Consultants receiving water environment of Lake Washington, and identify illicit connections to the storm drain system. North Renton Outfall Those water quality pollutants of concern measured in the stormwater sample collected from the North Renton basin outfall to Lake Washington include the following: ■ Total phosphorus (0.223 mg/L) ■ Copper(20 µg/L) ■ Chrysene (0.6 µg/L) ■ Lead (26 µg/L) ■ Fecal coliform bacteria(720 cfu/100 mL) ■ Zinc (28 µg/L). The concentrations listed above exceed either recommended guidelines for surface water quality or state water quality standards for freshwater. However, the levels of these and other pollutants are all within and, in most cases, at the low end of the ranges observed in urban runoff characterized locally and elsewhere in the United States. It is generally recommended that the total phosphorus concentration in streams discharging into any lake or reservoir not exceed 0.05 mg/L to prevent nuisance growth of algae and aquatic plants (U.S. EPA 1976). Although the total phosphorus concentration found in the North Renton outfall (0.223 mg/L) is more than 4 times greater than this recommended limit, it is unlikely that stormwater from the North Renton basin will have a significant adverse impact on water quality in Lake Washington, for the following reasons: ■ Stormwater discharges do not typically coincide with the plant growing season (most rainfall in western Washington occurs during the winter months). ■ The 1,236-acre drainage basin represents less than 1 percent of the total area contributing to Lake Washington (302,000 acres). Therefore, contributions from the North Renton basin are expected to be small relative to other basins contributing to Lake Washington. Metals, particularly copper, lead, and zinc, are commonly found in urban runoff. Sources of these materials include erosion of urban soil and contributions from vehicular traffic (e.g., automotive emissions and abrasion of street surfaces). The concentrations of copper, lead, and zinc in the outfall sample exceed the acute toxicity criteria for aquatic life. These results are based on analysis of an unfiltered sample containing both dissolved and particulate components. Recent studies show that most metals in stormwater runoff are present in particulate rather than dissolved form (Pitt and Bissonnette 1984; Galvin and Moore 1982). Because particulate-bound pollutants are generally not biologically available, it is unlikely that these compounds are toxic to aquatic life. Although salmonids have been observed in the lower portion of the North Renton drainage system, most fish are likely to be exposed to runoff in the lake offshore of the outfall, where concentrations of most pollutants are considerably lower due to dilution with the surrounding lake water. Because water quality standards are based on receiving water concentrations, direct 255C\LWTASK3 57 Herrera Environmental Consultants comparisons with undiluted stormwater may not be representative of actual environmental conditions. The concentration of chrysene (a PAH compound) in the North Renton outfall sample exceeds the MTCA method B cleanup level. PAHs, particularly the HPAH compounds, are byproducts of fossil fuel combustion. Consequently, the presence of chrysene in the outfall sample is likely due to a number of diffuse sources (e.g., automobile emissions and home heating oil use), which are more difficult to control, rather than a single source. The method B cleanup levels are established for protection of human health, based on consumption of contaminated food products (e.g., fish and water) as the primary pathway of exposure. Because fish and humans are not usually directly exposed to stormwater, these standards may be conservative. Therefore, chrysene is not considered a serious threat to human health in the North Renton basin. The number of fecal coliform bacteria measured in the outfall sample (720 cfu/100 mL) exceeds the state Class AA water quality standard of 50 cfu/100 mL. Fecal coliform bacteria are commonly found in urban runoff. Typical sources of these bacteria in stormwater runoff include birds, domestic pets, cross-connections between storm and sanitary sewer systems, and failing septic tanks. Although the presence of elevated levels of fecal coliform bacteria in the North Renton outfall is indicative of urban pollution, the concentrations are well within the range of concentrations found in runoff from other urban areas. North Renton Subbasin Monitoring Subbasin runoff monitoring within the North Renton basin has revealed widespread exceedances of acute and/or chronic toxicity water quality criteria for lead, copper, and zinc. During storm flows, all basins exceeded the acute or chronic toxicity criteria for two or more of these metals. During base flows, criteria exceedances were significantly reduced. Only four subbasins (N1, N2,N5, and N6) exhibited criteria exceedances(acute or chronic toxicity) for one or more of the three metals. For fecal coliform bacteria, the state standard was exceeded in all subbasins during storm flows and in subbasins N2, N4, and N5 during base flow. During storm flows, total phosphorus concentrations exceeded the recommended threshold level for discharge to lakes in all subbasins except N 1. Base flow total phosphorus exceedances were observed in subbasins N1, N2, and N3+N5. Base flow samples are usually representative of ground water contributions to the storm drain system. Typical sources of phosphorus in ground water include contact with native soil in the watershed, failing septic tanks, leaks from sanitary sewers, and cross-connections between storm and sanitary sewer systems. Because most of the North Renton basin is served by sanitary sewers, failing septic tanks are not a likely source. Therefore, ground water contributions and sewer cross-connections are the two most likely sources of elevated phosphorus in base flow samples. As described below, the illicit connection program identified a few locations in the basin where sanitary waste may be entering the storm drain system. Given the age of the sanitary sewer system that serves the North Renton basin (most of the basin was developed in the 1940s and 1950s), leaks caused by breaks in the sanitary sewer pipes may represent an additional source of phosphorus to the storm drain system. The Renton Sewer Utility is currently evaluating the condition of the sewer system throughout the city. Results 255C\LWTASK3 58 Herrera Environmental Consultants from this study should be reviewed to determine whether sanitary sewers are a likely source of phosphorus and other pollutants such as fecal coliform bacteria. Results of the subbasin monitoring program are summarized in Table 27. Concentrations of most pollutants analyzed during this study are comparable to the concentrations found in runoff from other urban areas, suggesting that water quality problems in the North Renton subbasins are likely caused by a variety of diffuse sources rather than a few clearly identifiable (and easily controlled) sources. North Renton Illicit Connection Monitoring Base flow monitoring investigations in the North Renton basin reveal that only three subbasins exhibit the presence of pollutants that may suggest illicit connection sources (i.e., fecal coliform bacteria and chlorine). These subbasins are N3,N4, and N5. North Renton Outfall Sediment Sampling The sediment sample collected offshore of the North Renton outfall contained elevated concentrations of the following pollutants: ■ Metals (antimony, cadmium, copper, lead, mercury, nickel, silver, and zinc) ■ Total organic carbon ■ Organic compounds (PAH, phthalates, and PCBs). The concentrations of these pollutants at the North Renton outfall typically exceed the concentrations reported for background sediments in Lake Washington and fall between the lowest-effect and severe-effect levels for benthic organisms as defined by Ontario (1992/93). These results indicate that stormwater discharges have affected lakeshore sediment quality in the areas offshore of the outfall. However, because sampling was limited to a single composite sample, it is not possible to determine the zone of influence from the stormwater discharge. With the exception of silver, pollutant concentrations in the offshore sediment sample are typically within the range of concentrations reported in urban street dust. The silver concentration (19.8 mg/kg) was nearly 40 times greater than the highest concentration measured in urban street dust and exceeded background concentrations in Lake Washington sediments by a factor of nearly 250. Silver was not detected (at a detection limit of 3 µg/L) in the stormwater sample collected from the North Renton outfall and was not analyzed in any of the subbasin samples. However, the sediment results indicate that there is a significant source of silver in the North Renton drainage system. Other pollutants detected in the offshore sediment sample include 4-methylphenol (0.71 mg/kg), carbazole (0.37 mg/kg), and dibenzofuran (0.09 mg/kg). Sediment quality standards have not yet been established for these pollutants. However, the concentrations measured offshore of the North Renton outfall are within the ranges reported for sediments collected from reference 255C\LWTASK3 59 Herrera Environmental Consultants stations in Lake Washington. Therefore, it appears that storm drain discharges have not had a significant effect on the concentrations of these three contaminants in offshore sediments. West Hill Outfall Those water quality parameters of concern measured in stormwater from the West Hill basin outfall include the following: ■ pH (5.37) ■ Copper (16 µg/L) ■ Fecal coliform bacteria (600 cfu/100 mL) ■ Lead(33 µg/L) ■ Total phosphorus (0.375 mg/L) ■ Zinc (90 µg/L). ■ Chrysene (0.5 µg/L) These concentrations exceed either recommended guidelines for surface water quality or state water quality standards for freshwater. But, as noted for the North Renton outfall, the levels of these pollutants are within the pollutant ranges observed in urban runoff characterized locally and nationally. The generally low levels of pollution found in the West Hill outfall are typical of an urban watershed, suggesting that water quality problems are likely caused by a variety of diffuse sources. The pH level in the outfall sample (5.37) was well below the acceptable range defined by state water quality standards(6.5 to 8.5). Although the source of the depressed pH levels is unknown, the results from the outfall sample are consistent with the results from the subbasin monitoring program, where three of the four stations were below the recommended pH limits. The number of fecal coliform bacteria in the West Hill outfall sample was similar to the number measured in the North Renton outfall. However, unlike the North Renton basin, a large portion of the West Hill basin is unsewered. Septic tank failures have been fairly widespread in the West Hill basin. Therefore, septic tanks constitute a potential source of fecal coliform bacteria contamination(in addition to possible contributions from animal waste, sanitary sewer leaks, and cross-connections). Sources of phosphorus and metals present in the West Hill outfall are probably similar to those described for the North Renton outfall. In addition, like the North Renton outfall, the West Hill outfall likely exhibits only minor effects on water quality in Lake Washington. As explained earlier, although the concentration of chrysene measured in the West Hill outfall sample exceeded the MTCA method B cleanup level, chrysene is not considered a serious direct threat to human health. West Hill Subbasin Monitoring Subbasin runoff monitoring results indicate less frequent violations of water quality standards at the West Hill outfall than at the North Renton outfall. However, lead exceeded the chronic toxicity criterion in all subbasins during storm flow and only in subbasins W2 and W4 during base flow; zinc exceeded the acute and chronic toxicity criteria only in Subbasin W3 during 255C\LWTASK3 60 Herrera Environmental Consultants storm flow; and copper exceeded the chronic toxicity criterion in subbasins W2 and W3 and also the acute toxicity criterion in subbasin W3 during storm flow. The fecal coliform bacteria standard was exceeded in all subbasins during storm flows and in all but one subbasin (W2) during base flow. Total phosphorus concentrations exceeded the recommended threshold level for discharge to lakes in all but one subbasin during storm and base flows. The one exception was subbasin W2 during storm flow. Results of the subbasin monitoring program are summarized in Table 27. Concentrations of most pollutants analyzed during this study are comparable to the concentrations found in runoff from other urban areas, suggesting that water quality problems in the West Hill basin are likely caused by a variety of diffuse sources rather than a few clearly identifiable (and easily controllable) sources. West Hill Illicit Connection Monitoring Base flow monitoring investigations reveal that three subbasins (WI, W3, and W4) exhibit the presence of pollutants that may suggest the presence of illicit connections (i.e., fecal coliform bacteria and chlorine). Failing septic tanks are another potential source of the elevated numbers of fecal coliform bacteria observed during the illicit connection survey. A large portion of the West Hill drainage basin is not served by sanitary sewer, and Seattle/King County Department of Public Health records indicate that there have beer. numerous septic failures in the basin. West Hill Outfall Sediment Sampling The sediment sample collected offshore of the West Hill outfall contained elevated concentrations of the following pollutants: ■ Metals (antimony, cadmium, copper, lead, mercury, nickel, silver, and zinc) ■ Total organic carbon ■ Organic compounds (PAH, phthalates, and PCBs). The concentrations of these pollutants at the West Hill outfall typically exceed the concentrations reported for background sediments in Lake Washington and fall between the lowest-effect and severe-effect levels for benthic organisms as defined by Ontario (1992/93). Pollutant concentrations in the offshore sediment sample are typically within the range of concentrations reported in urban street dust. These results indicate that stormwater discharges have affected lakeshore sediment quality in the areas offshore of the outfall. However, because sampling was limited to a single composite sample, it is not possible to determine the zone of influence from the stormwater discharge. Other pollutants detected in the offshore sediment sample include 4-methylphenol (0.46 mg/kg), carbazole (0.53 mg/kg), and dibenzofuran (0.15 mg/kg). Sediment quality standards have not yet been established for these pollutants. However, the concentrations measured offshore of the West Hill outfall are within the ranges reported for sediments collected from reference stations 255C\LWTASK3 61 Herrera Environmental Consultants in Lake Washington. Therefore, it appears that storm drain discharges have not had a significant effect on the concentrations of these three contaminants in offshore sediments. 255C\LWTASK3 62 Herrera Environmental Consultants 4. EXISTING RENTON CITY POLLUTION CONTROL ACTIVITIES This section provides information on existing programs related to stormwater pollution prevention, control, and abatement that are currently being implemented by various departments and utilities within the Renton city government. SEWER UTILITY The Renton Sewer Utility is not currently involved in efforts directly related to stormwater and surface water pollution prevention. However, the Sewer Utility works with Metro to educate businesses about industrial waste handling and disposal issues, to minimize the amount of industrial waste and other materials discharged to the sanitary sewer. Although not proactive in this regard, the Sewer Utility maintains information that can be dispensed in response to calls related to industrial waste issues (Christensen 1993 personal communication). The Sewer Utility is currently in the process of replacing a large number of aging and failing sanitary sewers in the North Renton basin (Christensen 1993 personal communication). Many of these old sewers have contaminated surrounding soils and continue to contaminate them through leaks of untreated wastewater. Leaks caused by breaks in the sewer lines can contaminate ground water and surface water supplies if allowed to continue for long periods of time. The sewer repair and replacement program should serve to reduce these problems in the future. Because the sanitary sewers in the West Hill basin are much newer than those in the North Renton basin, the Sewer Utility has no immediate plans to remove or replace pipelines in the West Hill basin (Christensen 1993 personal communication). SURFACE WATER UTILITY The Surface Water Utility is currently developing its Comprehensive Storm and Surface Water Management Plan. The plan will provide an integrated approach for managing surface water in the city of Renton, incorporating water quality and quantity issues as well as programmatic requirements for operations of the utility. Items specifically related to stormwater quality include the following: ■ An inspection, maintenance, and enforcement program handbook ■ A citywide water quality monitoring program that meets the expected requirements of the NPDES regulations ■ A preliminary water quality analysis to evaluate water quality issues and proposed alternatives for improvement ■ Recommended design criteria for stormwater treatment and best management practices to be implemented by new development and by known pollutant sources that are identified within the city service area 255C\LWTASK3 63 Herrera Environmental Consultants ■ An evaluation of potential regional stormwater facilities as well as opportunities to modify existing detention facilities to provide water quality treatment. The Renton Maintenance Division is responsible for upkeep and repair of the city storm drain system. The division maintains two field crews, one dedicated to operating the city's vactor truck for cleaning catch basins and manholes, and the other responsible for small construction and repair work. Catch basins and manholes are cleaned every 1 to 5 years, as necessary. The city operates two vactor decant stations, one in the north district and one in the south district, for disposing of decant water from the vactor trucks. A third vactor decant station is planned for the central district. The city also participates on the Regional Vactor Waste Planning Committee sponsored by King County Surface Water Management Division, which is constructing a drying shed for vactor solids at the county maintenance facility. Decant stations are plumbed to the sanitary sewer. If decant stations are not accessible to the vactor crew, the crew may pump decant water back to the storm drain system. Standard practice is to discharge no more than the volume of the sumps in the manholes or catch basins, so that the decant water remains in the system until the next storm event and does not immediately discharge to area receiving waters. Vactor truck sediments are discharged onto an asphalt-paved area at the maintenance shop and allowed to dewater before transport to the landfill for disposal. The city is currently responsible for maintaining storm drains located only on city property or city rights-of-way. Retention/detention systems installed in newer residential developments and other privately owned systems (e.g., those serving commercial or industrial facilities) are maintained by individual property owners. The city has recently completed an inventory and inspection of residential and commercial systems to evaluate the condition of these systems. Private industrial storm drain systems are scheduled to be inspected this summer. The city does not have the authority to order owners of private systems to conduct routine cleaning and maintenance, nor does the city have authority to use city crews to maintain private systems and bill the owners for the work. The Maintenance Division has recently modified its standard procedures for cleaning and maintaining roadside ditches and wet pond systems. The previous practice was to use backhoes and other mechanical equipment to clear out accumulated sediments and vegetation in order to restore hydraulic capacity. The division now primarily uses hand tools for these operations to minimize the disturbance of these natural systems. Crews are directed to leave as much vegetation as possible when performing cleaning operations. In addition to performing routine maintenance operations, city crews also respond to trouble calls regarding spills or leaks of materials into the storm drain system, and crews may collect samples to identify the type of material and possible sources. All crew members attend a water quality training class offered by Metro that explains basic procedures for collecting samples to evaluate spills and for responding to calls concerning water quality problems. The 3-hour class describes sampling procedures, provides information on appropriate chemical analyses to perform, and discusses personal protection and safety concerns. 255C\LWTASK3 64 Herrera Environmental Consultants The Maintenance Division also works with the city land use compliance officer to enforce city codes pertaining to stormwater pollution control. The primary authority arises from state water quality regulations, which require that no wastes be discharged to waters of the state. Maintenance crews report any problems observed at local businesses while conducting routine maintenance operations (e.g., leaking waste oil storage containers). If a code violation is noted, the compliance inspector can then issue a citation requiring the property owner to correct the situation. The city also has the authority to levy fines in cases of criminal infraction. The compliance officer may also coordinate with Ecology to require businesses to implement best management practices in situations where there is no applicable city code provision. LAND USE COMPLIANCE OFFICER As described above, the land use compliance officer is responsible for enforcing all city codes and ordinances. The compliance program is administered by the Developmental Services Division of the Renton Planning/Building/Public Works Department. Under Title IV-33 of the Renton Municipal Code, the compliance officer is authorized to conduct compliance inspections at local businesses and residences. If code violations are discovered during these inspections, the officer then issues an order to correct the violation, identifying the nature of the violation, recommending specific corrective actions, and specifying a schedule for compliance. Violators who fail to comply with an order are issued a citation. Depending on the nature of the violation, the municipal court may levy a fine against the violator. In extreme cases, business licenses can be revoked if the violator does not comply with code requirements. The compliance officer also reviews all applications for business licenses that are filed in the city and can stipulate conditions of approval requiring the applicant to implement specific controls and practices. Depending on the type of business, these conditions may address stormwater pollution issues. Enforcement of conditions for business licenses and plat approvals is conducted by the compliance officer. At this time, there is only one compliance officer responsible for the entire city. Although the officer is authorized to conduct investigations of individual businesses and properties, because of staffing limitations the division has primarily responded to complaints rather than proactively investigating compliance issues. To date, only one stormwater pollution citation has been issued to a business located in the Renton Valley area. The violator was discharging washwater from a steam cleaning operation to an onsite detention system that discharged to a nearby stream (Arthur 1994 personal communication). It is difficult to evaluate the effectiveness of this program in improving stormwater quality. The current record-keeping and program tracking system is unable to efficiently track the nature and locations of businesses where orders to correct violations have been issued or to easily identify the types of violation. The city is in the process of filing all notices of violation and citations issued by the program in a computerized database, which will enable the division to better track the status of compliance efforts. However, the database retrieval system is not yet operational. 255C\LWTASK3 65 Herrera Environmental Consultants WATER UTILITY The Renton Water Utility has implemented a pollution prevention and permitting program to support the city Aquifer Protection Ordinance. The ordinance establishes requirements for the use, storage, and production of regulated substances (including flammable and combustible liquids, hazardous materials, dangerous waste as defined by WAC 173-303, and a number of other substances specifically described in the ordinance) within designated aquifer protection areas in the city. Boundaries of these areas have been delineated based on the estimated time required for ground water to reach city water supply wells. Ground water underlying aquifer protection area zone 1 can travel to the supply wells in one year or less (based on horizontal pathway and flow rates). Aquifer protection area zone 2 includes those areas where travel time to the area of capture for city wells is greater than 1 year. As shown in Figure 15, portions of the North Renton drainage basin are located within a designated aquifer protection area. Only a small area in the extreme southern end of the basin is located in the most restrictive zone 1. The northern and eastern ends of the basin are located in zone 2. No portion of the West Hill drainage basin is located within the aquifer protection area. The ordinance requires businesses located within a designated aquifer protection area that use, store, or handle more than 5 gallons of any one regulated substance, or 20 gallons aggregate, to obtain a permit from the Water Utility. Permit requirements include providing secondary containment for material storage areas and work areas, educating employees about the ordinance and associated concerns, providing spill cleanup materials, preparing spill contingency plans, and reporting spills (Hornsby 1993 personal communication). In addition, businesses located within aquifer protection area zone 1 that exceed the quantity limits for regulated substances may be required to install ground water monitoring wells and implement a monitoring plan within 5 years of the effective date of the ordinance. The Water Utility also conducts inspections annually (or more frequently as necessary) as part of this program, to assist businesses in developing effective pollution controls and to enforce the ordinance. The Water Utility also has an aquifer protection education program to complement its enforcement efforts. The educational program includes presentations to local schools and mailings of written information to businesses within the protection zone summarizing water quality concerns and ordinance requirements (Hornsby 1993 personal communication). The Water Utility has established a full-time position to carry out this program. FIRE DEPARTMENT The Renton Fire Department conducts an annual inspection of every commercial business in the city to ensure compliance with the requirements of the Uniform Fire Code and to catalog the quantities and types of flammable materials stored onsite so that this information can be made available to firefighters responding to fire calls. The Uniform Fire Code establishes requirements consistent with recognized safe practices for storing, handling, and dispensing hazardous materials. Topics particularly related to stormwater pollution include secondary containment for storage areas, spill and drainage control, waste disposal, permitting requirements, and employee training. Some businesses are also required to implement spill response and reporting plans, depending on the amounts of hazardous materials they use or 255C\LWTASK3 66 Herrera Environmental Consultants generate. The Fire Department works with these businesses to help them develop effective plans (Andrews 1993 personal communication). Although the Fire Department's concerns are safety and fire prevention, its technical assistance efforts cover some issues of concern for stormwater pollution prevention. Because Fire Department inspectors are required to observe local business operations on a regular basis, they serve as a key point of contact with individual business owners and managers. It is not known whether the Fire Department would be able or willing to evaluate stormwater pollution control practices as part of its annual inspections. In any case, because it has the most extensive knowledge of operations and housekeeping practices employed by local businesses, the Fire Department represents a significant source of information for the Surface Water Utility, to identify businesses in need of source control efforts. SOLID WASTE UTILITY The Renton Solid Waste Utility is involved in a variety of projects designed to promote recycling, proper disposal of household hazardous wastes, use of nonhazardous cleaning materials, and environmentally sound gardening practices. This comprehensive program has been successful in reducing the amount of solid waste (and some liquid waste such as used motor oil) that is disposed of or dumped by businesses and residences in Renton, and thus has reduced the associated pollution that previously occurred. The city has implemented a curbside collection program for recyclable materials such as newspaper, plastic, glass, tin, aluminum, and cardboard from single- and multifamily residences. The city has not sponsored a collection program for commercial and industrial properties, primarily because businesses cannot be required to use the services of a city recycling contractor, and also because recyclers typically charge a higher fee to collect from commercial locations (Brown 1994 personal communication). Thus, the Solid Waste Utility has relied primarily on educational efforts to encourage local businesses to recycle and has also hired a consultant to provide technical assistance to businesses setting up their own recyclii a programs (Knight 1993 personal communication). The utility's public education efforts are described in the public education section of Chapter 6. RENTON MUNICIPAL AIRPORT The city, in its role as manager of the Renton Municipal Airport, oversees airport operations. However, the city's involvement in activities at the airport is limited to overseeing leases to private companies that store, maintain, and repair aircraft. To date, the city's involvement in providing technical assistance, particularly for stormwater problems, has been limited because the airport does not have the authority to require tenants to implement best management practices or construct structural stormwater controls. The NPDES program requires certain industrial facilities, such as airport facilities that perform aircraft maintenance or washing operations, to obtain a permit for stormwater discharges. Because the city functions solely as the airport manager and is not directly engaged in providing flight services or maintaining equipment (other than airport facilities such as buildings, hangars, 255C\LWTASK3 67 Herrera Environmental Consultants and utilities), the city has not been required to obtain an NPDES permit for airport operations. However, under the NPDES program, individual tenants engaged in aircraft maintenance, washing, or deicing activities must obtain a permit. Ecology has allowed airports the following three options for NPDES permits: ■ A single permit covering all airport tenants ■ Separate permits for individual tenants engaged in aircraft maintenance and washing activities, with the airport lisied as a co-permittee ■ Separate permits for individual tenants engaged in aircraft maintenance and washing activities, without involving the airport. The city has functioned as a clearinghouse, disseminating information to all airport leaseholders on the NPDES permit requirements and applicable best management practices. Of the nine active leaseholders (The Boeing Company leases approximately 40 percent of the airport property), three tenants are reported to engage in aircraft maintenance operations and therefore are required to comply with NPDES stormwater permit requirements. If any of the remaining tenants allow sub-lessees to wash aircraft on leased property, those tenants are also subject to NPDES requirements. Under the NPDES program, a permitted facility is required to implement a variety of best management practices to prevent stormwater pollution and must prepare a stormwater pollution prevention plan. Tenants that are not covered by Ecology's NPDES program are not required to develop stormwater pollution prevention plans specific to their own facilities. All leaseholders must comply with applicable city, state, and federal regulations. However, because there are no local regulations that require non-NPDES businesses to implement stormwater pollution controls, there has been little effort on their part to improve airport stormwater facilities. Construction of centralized aircraft fueling and washing facilities has been considered, but because of space limitations and the difficulty in providing service to the various types of planes that use the airport (e.g., seaplanes, piston engine aircraft, and turbine engine aircraft), this option has not been pursued. Almost all of the available land at the airport is leased under long-term arrangements (i.e., beyond 2010). Proposals for installation of centralized fueling and washing areas by the individual leaseholders have not been well received because these facilities would consume valuable leased property (Reed 1993 personal communication). Furthermore, it is difficult for the airport to obtain funding to construct water quality facilities. Federal Aviation Administration funding is typically available only for facilities directly related to flight services and operation. The Airport Master Plan is currently being updated, with completion estimated in August 1994. Although this document will focus primarily on assessing facility needs associated with flight services, it may also contain information on stormwater pollution prevention issues. The plan will incorporate relocation of all general aviation facilities to the western side of the airport to consolidate these activities (Reed 1993 personal communication). This change will improve the practicality of installing centralized fueling and washing facilities to serve these planes. The 255C\LWTASK3 68 Herrera Environmental Consultants master plan will address the issue of centralized facilities within existing siting constraints and with limited land availability. PARKS AND RECREATION DEPARTMENT The Renton Parks and Recreation Department is committed to limiting the amount of pesticides (i.e., herbicides, insecticides, and fungicides) and fertilizers used to maintain vegetation in the parks throughout the city. The following city parks are located in the West Hill and North Renton basins: North Renton Basin West Hill Basin Windsor Hills Park Kiwanis Bicentennial Air Park Highlands Park Bryn Mawr Park Sunset Court Park Coulon Beach Park Herbicides are applied to the turf in city parks once each year between April and June, depending on weather conditions. Application frequency and rate are limited as much as possible. (Frank 1993 personal communication). Herbicides are applied occasionally to flower beds, when necessary to prevent the invasion of undesirable species. Fertilizer use is also carefully controlled. Only the minimum amount necessary for plant growth is applied, with most applications typically occurring in the spring. Insecticides have not been sprayed on trees in city parks for several years because of citizen concerns (Frank 1993 personal communication). 255C\LWTASK3 69 Herrera Environmental Consultants 255C\LWTASK3 70 Herrera Environmental Consultants 5. POLLUTION ABATEMENT CRITERIA Pollution abatement criteria have been established to aid in the development of reasonable and effective abatement alternatives and to enable the city to evaluate the effectiveness of any stormwater pollution programs or activities that may be implemented in the North Renton and West Hill drainage basins. These criteria are simply a more specific presentation of the general goals and objectives of the overall project described in Chapter 1. The criteria are intended to be used to facilitate periodic review of the Surface Water Utility's pollution abatement program by 1) evaluating program effectiveness, and 2) identifying areas where adjustments are needed. The most direct way of evaluating the effectiveness of city source control efforts in the North Renton and West Hill basins would be to routinely collect stormwater samples from various locations in these two basins to determine whether water quality improves. Under this approach, specific goals would be established for individual pollutant parameters (e.g., meeting state water quality standards for metals). However, because stormwater quality is variable and can change depending on the frequency and intensity of individual storms, as well as on land use and source control practices, an extensive data collection effort is usually required to accurately distinguish changes in water quality. Such monitoring efforts are typically expensive and require a significant commitment of both staff and equipment that could otherwise be directed toward source control efforts. An alternative approach requiring less effort on the part of the utility has been developed to provide a mechanism for evaluating program effectiveness. Because stormwater quality is largely affected by human activities and land use practices in the contributing watershed, the city's pollution abatement efforts in the North Renton and West Hill basins should focus on source control and public education rather than stormwater treatment. The effectiveness of these efforts could be evaluated by focusing on the behavior and practices of local businesses and residents regarding stormwater pollution. This program would track the types of stormwater pollution problems observed in each basin to evaluate the overall performance of those involved in reducing the discharge of pollutants to storm drains (i.e., local businesses and residents, as well as the utility itself and the maintenance department). Recommended pollution abatement criteria are listed below: ■ Reduce the number of incidents related to stormwater pollution in the North Renton and West Hill basins that are reported each year to Ecology's 24-hour spill response line and Metro's trouble call line ■ Reduce the number of complaints received, notices of violation, and citations issued by the Renton land use compliance officer that are related to stormwater pollution ■ Increase the number of inspections conducte-i each year at local businesses and at privately owned storm drain systems ■ Increase the awareness of local businesses and residents regarding stormwater pollution concerns and source control practices 255C\LWTASK3 71 Herrera Environmental Consultants ■ Reduce the number of illicit connections that are identified each year in the North Renton and West Hill basins ■ Reduce the number of emergency response service calls made by the Maintenance Division ■ Generate the information required to comply with future NPDES permit requirements. These criteria are intended to enable the city to evaluate the effectiveness of businesses and local residents in implementing best management practices to reduce the amount of pollutants entering the city storm drain system. Reductions in pollutant loadings that are achieved by improving housekeeping practices and changing local attitudes toward stormwater pollution will have a direct effect on the quality of stormwater discharged to Lake Washington from the North Renton and West Hill drainage basins. Therefore, although this approach will not directly measure improvements in local stormwater quality, it will provide an indirect measure by assessing local source control efforts designed to reduce stormwater pollution. 255C\LWTASK3 72 Herrera Environmental Consultants 6. EVALUATION OF POLLUTION ABATEMENT ALTERNATIVES This chapter presents a discussion of stormwater pollution abatement alternatives that could be applied to the North Renton and West Hill basins. Three alternatives for improving stormwater quality in these two basins have been identified and are evaluated in this section: ■ Develop and implement a water quality program within the Surface Water Utility to oversee and carry out water pollution control efforts throughout the city ■ Develop and implement a public education program to encourage local residents and businesses to implement best management practices for stormwater pollution control ■ Modify the existing storm drainage system to provide improved pollutant removal capability by constructing stormwater treatment facilities. The water quality program section describes various nonstructural controls (i.e., best management practices) that could be implemented by the Surface Water Utility and the Maintenance Division to improve the performance of existing stormwater quality features, as well as activities that could be conducted to ensure that local businesses employ appropriate practices in their daily operations. This section describes maintenance procedures, compliance inspections, technical assistance activities, enforcement authority needs, and coordination with other departments within the city, all of which must be addressed to develop an integrated program to reduce the amount of pollutants generated within the city service area. The second abatement alternative, public education, is an integral part of any source control effort. Specific recommendations are provided for a public education program that targets local residents and businesses in the North Renton and West Hill basins to increase their awareness of stormwater quality issues and understanding of appropriate best management practices to reduce stormwater pollution. The section on structural controls identifies technologies that are currently available to treat urban runoff, describes the pollutant removal mechanisms used by each technology, evaluates the expected performance of these systems, and identifies possible applications within the North Renton and West Hill basins. WATER QUALITY PROGRAM This section describes the basic elements of a water quality program that could be implemented by the Surface Water Utility to control stormwater pollution in the North Renton and West Hill drainage basins. The emphasis of the water quality program is on implementation of nonstructural controls and coordination with existing programs to achieve an integrated system for identifying and dealing with water quality issues. Nonstructural controls, commonly referred to as best management practices or 13MPs, include a variety of activities designed to reduce the amount of pollution generated by nonpoint sources. In the North Renton and West Hill basins, 255C\LWTASK3 73 Herrera Environmental Consultants these controls would target businesses and residential development as well as utility operation and maintenance activities. The discussion is separated into the following primary areas, each of which is relatively independent of the others, but all of which should be managed as a concerted effort: ■ Storm drain maintenance ■ Technical assistance to local businesses and residents ■ Monitoring and record-keeping to evaluate program effectiveness ■ Preservation and enhancement of natural drainage systems ■ Coordination of spill control and containment capabilities. The following paragraphs outline subcomponents that should be considered for implementation within each of these five water quality program categories. Storm Drainage System Maintenance Activities The water quality program should strive to maximize the pollution abatement capability of the existing storm drainage system facilities in the North Renton and West Hill basins. This can be accomplished by developing and implementing standard procedures to optimize the pollution removal capability of existing drainage system features, training maintenance crews, and scheduling routine inspections to evaluate the condition of drainage facilities and determine maintenance needs. While many of these activities are currently being undertaken to some extent within the Maintenance Division, a coordinated effort by all those involved would greatly improve the effectiveness of these activities. Procedures to Maximize Pollution Removal in Storm Drainage System Maintenance procedures that can be undertaken to enhance the pollution removal capability of existing storm drainage system features in the North Renton and West Hill basins include the following: Ditch Maintenance For effective filtration, it is important that the plant height in biofiltration swales and filter strips be greater than the depth of flow. Therefore, it is recommended that vegetated roadside ditches be periodically mowed to maintain a grass height of approximately 3 to 6 inches. The West Hill basin in particular contains numerous roadside ditches, most of which have good grass cover. Roadside ditches that are eroding or earth-lined with no vegetation should be seeded and protected with mulch or jute matting to promote vegetation growth. As explained below in the section on structural controls, vegetation performs an important function because plant stems and leaves filter pollutants out of stormwater. Seeding should occur in the spring or summer to ensure that vegetation is well established before the onset of winter rains. 255C\LWTASK3 74 Herrera Environmental Consultants Storm Drain Sediment Removal Sediment that accumulates in catch basins, manholes, regional retention/detention facilities, and at culvert entrances should be periodically removed, to prevent these materials from being flushed downstream during larger storm events and to restore system capacity. Many pollutants adhere to particulates and are transported along with the sediment in urban runoff. As a result, sediment, debris, and muck that deposit in the drainage system can carry a variety of pollutants. By increasing the cleaning frequency of catch basins (and storm sewer pipes), pollutant loadings to Lake Washington can be significantly reduced. The Maintenance Division has implemented a routine storm drain cleaning program. With one crew dedicated to cleaning operations, it is estimated that approximately 5 years will be needed to complete one round of the city system, although certain parts of the system are cleaned more frequently to prevent excessive accumulation of sediment. This program should be continued and expanded as needed. Cleaning operations should be reviewed, and periodic inspections should be conducted after the entire system has been visited, to evaluate cleaning frequency requirements at various locations in the drainage system. For example, catch basins in the North Renton drainage basin are of greater concern for cleaning than those in the West Hill basin, due to land use conditions and the condition of the drainage system serving these areas (Stein 1993 personal communication). The city plans to install a third vactor decant station in the central_ district. The city also participates on the county's Regional Vactor Waste Planning Committee, which is constructing a drying shed for vactor solids. In addition, the city should evaluate the need for and feasibility of constructing a sediment storage facility similar to those being constructed at the King County maintenance shop, where sediments removed from the drainage system can be temporarily stored, dewatered, and tested prior to disposal. Improvements to Existing Facilities Grassy areas (and other unpaved areas) adjacent to parking lots on city property that may function as filter strips for parking lot runoff should be maintained and enhanced where possible. If the grass cover is sparse or is experiencing erosion problems (e.g., if rills and channelization are evident), or if it is otherwise ineffective ,.t filtering pollutants in runoff, the area should be reseeded or sodded and protected with mulch or matting until the vegetation is well established. The city should also investigate opportunities to incorporate stormwater treatment capabilities into existing systems. For example, whenever storm drains are scheduled for major repair in the West Hill and North Renton drainage basins, consideration should be given to replacing underground pipes with grass-lined swales where grade requirements and land availability allow conversion to open-channel systems. Options for retrofitting existing drainage systems are described below in the section on structural controls. Surface Water Utility staff should coordinate with the Maintenance Division to exchange information about advances in stormwater treatment technologies and innovative approaches to system maintenance, and to keep in touch with conditions in the city service area. It is recommended that Maintenance Division and Surface Water Utility staff meet on a regular basis 255C\LWTASK3 75 Herrera Environmental Consultants (e.g., quarterly). The Surface Water Utility should also coordinate with other city agencies such as the Transportation Division to exchange this type of information so that the responsible parties can carry out the desired maintenance procedures. Staff Training Maintenance crews and Surface Water Utility staff participating in the water quality program should be trained to recognize problems affecting stormwater quality and to proceed with appropriate pollution abatement measures once a problem has been identified. Although maintenance crews currently attend Metro's water quality training class, additional training is needed to educate crews and utility staff about appropriate best management practices, regulatory requirements, and standard maintenance procedures. When performing routine maintenance and inspection activities, maintenance crews are encouraged to look for unusual runoff conditions such as oil sheens, unusual odors or color, evidence of detergents (e.g., excessive foam or suds), or flow where none is usually present. In addition, because maintenance crews spend more time in the field and are more familiar with basin activities, they should also be observant of general housekeeping practices employed by those businesses operating in the basin. Examples of items for crews to note while in the field include the following: ■ Outdoor material and waste storage areas lacking roofs or cover to prevent rainfall from coming in contact with the materials, or lacking adequate containment structures to prevent any spills or leaks from reaching the drainage system. ■ Evidence of improper disposal of waste products (e.g., soil staining or stressed vegetation). Depending upon the circumstances, it may be beneficial to collect stormwater samples, to identify the pollutants present in the discharge when problems are observed and to facilitate source identification. Maintenance crews currently carry a Metro sampling kit when they are in the field. The sampling kit should include: ■ Sample bottles: - Metals: 250-mL glass or plastic preserved to pH 2 with HNO3 - Fecal coliform bacteria: 250-mL amber glass - Volatile organic compounds: two 40-mL glass vials with Teflon- lined septum - Semivolatile organic compounds: 1-L glass - Conventional parameters (total suspended solids, nutrients, turbidity): 250-mL plastic 255C\LWTASK3 76 Herrera Environmental Consultants - Biochemical oxygen demand: glass bottle (with ground glass stopper) ■ Field equipment (pH meter, thermometer, conductivity meter) ■ Chain-of-custody and analysis request forms ■ Personal protective equipment (gloves, boots, eye protection) ■ Ice chest ■ Absorbent material for small spills ■ Emergency phone numbers (e.g., Ecology 24-hour spill response team, Fire Department hazardous materials team). Precleaned sample bottles should be obtained from an analytical laboratory and stored in a cooler under chain-of-custody seal to prevent them from becoming contaminated prior to use. Crews should have access to a knowledgeable contact person at the Surface Water Utility for advice on sampling protocols, chemical hazards, and the pollutants of concern associated with various types of discharges that may be encountered. Standard procedures for responding to water quality problems should also be developed. At a minimum, maintenance crews should understand their role in responding to problems that they may encounter. In particular, crews should know whom to contact in the event of a spill or other emergency situation. Storm Drainage System Inspections The Maintenance Division currently inspects roadside ditches, culverts, catch basins, and other runoff conveyance, detention, or treatment features in the North Renton and West Hill basins twice each year. These routine inspections facilitate evaluation of maintenance requirements and identification of pollution problems. Two types of inspections are recommended: ■ Dry season inspections to identify illegal discharges and to evaluate the condition of drainage structures ■ Wet season inspections to observe possible capacity limitations and stormwater pollution. More frequent inspections should be conducted in the rainy season, when problems are most prevalent and are readily identified. Therefore, inspections of all drainage facilities in the North Renton and West Hill basins should be conducted at least monthly between October and April. Water quality problems that are discovered by maintenance crews should be recorded in a field log and reported to the maintenance supervisor. If additional work is required, a service request should be filed. In addition, the Surface Water Utility aria the land use compliance officer should be advised of any problems caused by an illegal discharge or improper business practice. 255C\LWTASK3 77 Herrera Environmental Consultants The Maintenance Division should also implement a regular inspection program to assess the condition of privately owned storm drains, retention/detention structures, and stormwater treatment facilities. The city has recently completed a first-time survey of residential and commercial drainage systems and plans to investigate industrial systems during summer 1994. This program should be expanded to include periodic inspections to ensure that these systems are adequately maintained and operated. Technical Assistance Businesses and residents in the North Renton and West Hill basins must be encouraged to implement appropriate best management practices to reduce the amount of pollutants discharged to the Renton storm drain system. To be effective, the city will need to work actively with the local community to educate citizens about best management practices as well as to enforce local codes and ordinances that address stormwater issues. A business-oriented stormwater pollution program would entail conducting regular visits of businesses operating in the two basins to assess business practices, to identify necessary corrective actions, to document compliance with local requirements, and to provide businesses with the information necessary to accomplish effective pollution control. Specific activities to be incorporated into the program include such items as: ■ Compiling and developing best management practices for the kinds of operations conducted by local businesses ■ Training city employees who will participate in the inspection program ■ Coordinating with other city departments ■ Overseeing individual site cleanup actions ■ Enforcing pollution abatement objectives. For the residential community, the utility should emphasize public awareness to promote a better understanding of stormwater pollution issues. A public education plan developed as part of this project is described in a separate section below. This section describes recommended actions regarding development and compilation of best management practices for residential activities related to stormwater pollution in support of the public education efforts and to respond to questions from the general public. Nonstructural Source Controls for Local Businesses and Residents The Surface Water Utility should maintain a file on best management practices applicable to the types of activities occurring in the North Renton and West Hill drainage basins. Best management practices are standard procedures that have been developed to reduce the amount of pollution generated by nonpoint sources. Best management practices address a wide variety of 255C\LWTASK3 78 Herrera Environmental Consultants activities, including waste minimization, recycling, alternative product use, waste disposal practices, material and waste storage practices, spill containment and response, fertilizer and pesticide use, and automobile washing. Information on nonstructural source controls that are effective and applicable to local businesses and residences can be obtained from publications produced by agencies in the region, including the Stormwater Management Manual for the Puget Sound Basin (Ecology 1992a) and the draft King County Water Quality Best Management I ractices Manual (1993). A list of available publications and brochures that deal with stormwater and related issues is provided in Appendix F. As part of the Business Partners for Clean Water program, the city of Bellevue has developed manuals describing best management practices for facilities serving construction, automotive, landscaping, food, and maintenance operations. In addition, Metro maintains an extensive library of information on best management practices as part of King County's local hazardous waste management program. Additional ideas and related information should be continuously developed and tested by the Surface Water Utility, as appropriate. The information on best management practices that is obtained and developed by the Surface Water Utility should be assembled in a single location for access by utility staff and to support technical assistance and public education efforts. Licensed businesses currently operating in the Renton/Lake Washington study area that are considered potential sources of stormwater pollution because of the nature of their operations are listed in Appendix D. These businesses include: ■ Landscaping, greenhouses, nurseries, and lawn and garden services ■ Specialty contractors: concrete contractors, painters, carpenters, plumbers, electricians, and roofers ■ Automotive services: repair shops, sales lots, service stations, and car washes ■ Airport services ■ Dry cleaners and laundromats. Although there are many businesses other than those described above operating in the two Renton/Lake Washington basins (e.g., restaurants, professional offices, and retail facilities), these other facilities are not considered to pose a significant threat to stormwater quality. These other businesses can be combined into a general category and addressed as time and funding permit. The following discussion provides a brief explanation of the types of nonstructural source controls and associated activities that should be included in a program targeting the above-listed groups of businesses and the residential community. 255C\LWTASK3 79 Herrera Environmental Consultants Landscaping, Nurseries, and Related Businesses These businesses typically store and apply fertilizers, lime, ash, pesticides (i.e., herbicides, fungicides, and insecticides), and other raw materials. Receiving water quality can be degraded by spills and leaks from storage areas and, after application, by residues washed off or eroded from surface soils and transported to nearby surface water supplies in stormwater runoff. Nonstructural source controls for these types of businesses emphasize isolating and containing material storage areas, storing and transporting materials in watertight containers, and limiting the use of pesticides and fertilizers. Business managers and employees in this category should be educated in the principles of integrated pest management, which emphasize appropriate use of these materials. In particular, employees responsible for scheduling and performing pesticide and fertilizer applications should be familiar with standard practices to minimize potential environmental damage. For example: ■ Applications should be avoided when precipitation is expected and should follow the manufacturer's suggested methods and application rates ■ Fertilizers should be tilled into the soil after application to reduce runoff potential ■ Materials should be stored in protected locations when not in use. Construction Contractors This category includes a variety of small-scale contractors. The common problem shared by these businesses in terms of stormwater contamination concerns is that work tends to be performed outdoors or in unenclosed locations where materials and equipment are exposed to rainfall and are subject to runoff. The best means of preventing runoff contamination from these construction activities is to prevent contaminants associated with blasting, painting, masonry work, concrete work, and other similar activities from escaping collection. The source control practices that should be emphasized for construction contractors include the following: ■ Use drip pans, ground cloths, and windblock tarps to the maximum extent possible ■ Use buckets or tubs to hold paint cans, tools, and other materials when they are not in use ■ Contain runoff from areas where concrete is mixed and poured ■ Contain runoff from areas where paints are mixed and applied ■ Provide daily collection and proper disposal of debris, grit, paint chips, and concrete aggregate ■ Place all work materials under a protective cover overnight. 255C\LWTASK3 80 Herrera Environmental Consultants Education of employees is especially important for controlling pollution from construction sites. Automotive Services Gas stations, automobile body shops, automotive parts stores, and engine repair shops can be significant sources of pollution to storm drains due to the nature of their work and the toxicity of many of the chemicals used. Best management practices applicable to automotive businesses primarily aim to keep oil, fuel, cleaning solvents, engine fluids, paints, and contaminated liquids from coming in contact with precipitation and runoff. Source control practices that should be emphasized for automotive businesses include the following: ■ Perform all repair work indoors ■ Use drip pans or other drip col'ection devices or materials beneath all transfers of engine fluids ■ Cover fueling areas ■ Provide containment (such as perimeter drains or curbing) around fueling, oil storage, and work areas to collect leaked and spilled fluids before they contact precipitation or runoff ■ Minimize wastes by recycling or reusing solvents and other chemicals ■ Eliminate the use of soap or detergent to wash vehicles. Nonstructural source controls can substantially reduce the amount of stormwater pollution generated from these automotive facilities. However, because these facilities use a number of materials that can have significant detrimental effects on the receiving water environment, and because spills and leaks can never be entirely eliminated, runoff from automotive shops should ideally be treated onsite in oil/water separators or other devices before being discharged to the city drainage system. Airport Services The Renton Municipal Airport is an obvious target for pollution abatement efforts because of the types of activities that take place there and its proximity to Lake Washington. An estimated three of the nine active airport tenants are required to obtain an NPDES stormwater discharge permit from Ecology. NPDES stormwater regulations require these facilities to implement source control practices. Although Ecology currently administers the NPDES stormwater program in Renton, the city may assume this responsibility in the future if U.S. EPA extends the NPDES program to include smaller municipalities with populations less than 100,000. The city of Renton should actively work with both NPDES-permitted and nonpermitted airport tenants to ensure that they are using effective source control practices. Pollutants that escape 255C\LWTASK3 81 Herrera Environmental Consultants from airport operations enter Renton storm drains and are discharged directly to Lake Washington via the Black River culvert. Thus, it is in the city's best interest to understand what types of best management practices are appropriate for airport operations, and the city should also oversee implementation of best management practices at the airport. Specific source control practices that should be considered for the airport are discussed below. Waste Oil Collection—A waste oil disposal and recycling facility could be established at the airport, by either the airport or individual tenants Such a facility existed there previously but proved ineffective because it was undersized and because of problems that occurred when the recycling contractor accepted waste oil from non-Renton residents who used the airport (Reed 1993 personal communication). These problems should not be difficult to resolve with proper planning and contractual arrangements. Fuel System Test Disposal—Individual aircraft operators should be required to properly dispose of or recycle excess fuel that is generated by routine fuel system inspections conducted in preparation for takeoff. Pilots commonly inspect a valve on the plane's fuel system to check for the presence of water or sediment prior to takeoff. The small quantity of fluid extracted during the process (i.e., a few ounces), which consists of a mixture of fuel and water, is routinely dumped on the ground (Reed 1993 personal communication). This practice violates the Uniform Fire Code, which prohibits the discharge of flammable and combustible liquids and petroleum waste products to the surrounding environment (e.g., streets, sidewalks, surface water bodies, and storm drainage systems). Although the amount of fuel per plane disposed of in this manner is minor, the cumulative effect from all aircraft using the airport could be significant. Residues containing PAH and other fuel additives can be washed off the tarmac by rainfall and discharged to nearby surface water bodies (i.e., Lake Washington and the Cedar River). This excess fuel should be collected. If this material cannot be reused, it should be disposed of in accordance with state and local regulations. Hangar Drain Inspection—The Surface Water Utility should work with the airport manager to schedule routine inspections at general aviation hanga,•s to evaluate the need for source control efforts and to advise tenants of appropriate source control practices. The airport manager has reported that none of the hangars owned by the city have interior floor drains, but that other hangars built by private companies may have floor drains. Floor drains, if present and plumbed to the airport drainage system, represent a direct pathway for pollutants to reach Lake Washington, and they are of particular concern where airplane maintenance and washing operations are involved. In addition to conducting a physical inspection, available plans for hangar utilities should be reviewed to identify locations of floor drains that may not be visible during the inspection. Dye tests should be performed if there is any question about floor drain plumbing connections. Spill Containment—The Surface Water Utility should work with the airport manager to evaluate the feasibility of incorporating spill containment into the airport drainage system. Currently, the airport has little control over the refueling of private aircraft, which is often conducted by individual owners or operators who have little if any training in fuel handling and 255C\LWTASK3 82 Herrera Environmental Consultants dispensing procedures. In addition, many of the airport tenants are not complying with Uniform Fire Code requirements for fuel dispensing, which increases the potential for spills to occur. The evaluation of spill containment features should focus on those areas used for refueling operations. Aircraft Wash Facility—The airport should consider installing a centralized aircraft wash facility for the tenants. Ecology does not allow untreated aircraft washwater to be discharged to surface water. Therefore, the airport manager has prohibited the washing of aircraft on airport property. However, this rule will likely be difficult to enforce and does not provide a long-term solution for tenants who want to wash their planes. Therefore, it is recommended that a washpad that is plumbed to the sanitary sewer be installed at the airport. Although approval from Metro is required, if the volume of washwater generated is less than 25,000 gallons per day, the airport will probably not be required to obtain a permit for the washpad. However, Metro will require that provisions be made to prevent stormwater from entering the sanitary sewer. In addition, installation of an oil/water separator will be needed to keep the concentration of all nonpolar fats, oils, and grease in the discharge below 100 mg/L. Dry Cleaners and Laundromats Chemicals and detergents used by dry cleaners and laundromats can be a threat to stormwater runoff quality if they are not handled and stored properly. Source control practices for these businesses should be geared toward preventing contact of product storage containers with precipitation and runoff. Bags, boxes, bottles, and miscellaneous containers that previously contained chemicals and detergents should be stored in designated containers prior to collection or disposal. These containers should be sheltered from wind and rainfall, elevated above the ground or surrounded by a containment curb or berm, and equipped with tight-fitting lids. Other Businesses All businesses in the North Renton and West Hill drainage basins should be targeted for source control activities. A variety of simple measures should be incorporated into daily or weekly operations to prevent pollutants from contacting precipitation and reaching site runoff. Examples include the following: ■ Frequently sweep work and parking areas and properly dispose of collected materials ■ Inspect solid waste containers to ensure that they are covered and adequately sized for the waste loads ■ Stock spill cleanup materials in an accessible location known to all employees ■ Keep storm drains, gutters, and other drainage features free of dirt and debris. 255C\LWTASK3 83 Herrera Environmental Consultants Residential Community A variety of source control practices should be implemented within the local community to reduce stormwater pollution. Many of the pollutants observed in stormwater and base flow samples collected from the North Renton and West Hill drainage basins are associated primarily with residential rather than commercial and industrial activities (e.g., phosphorus and fecal coliform bacteria). Fertilizers, pet waste, and failing septic systems are common sources of these pollutants. Information on the following best management practices should be compiled by the utility for use in subsequent public education efforts: ■ Collect and dispose of pet wastes from yards, parks, and other outdoor areas where pets are allowed to roam. ■ Use proper methods for applying and disposing of excess fertilizers and pesticides used on gardens and lawns. ■ Use proper methods for washing automobiles. Automobiles should be washed without soaps or detergents. If soaps or detergents are used, automobiles should be washed on vegetated areas (i.e., lawns), or washwater should be directed to vegetated areas to prevent this material from discharging to the storm drain system. ■ Collect and dispose of or compost leaves, twigs, grass clippings, and other organic debris to prevent this material from entering the storm drain system. ■ Mechanically clean driveways and sidewalks instead of hosing them down to a nearby storm drain. The Renton Solid Waste Utility is currently involved in extensive outreach efforts directed at household hazardous wastes, recycling, and waste reduction. The Surface Water Utility should coordinate with the Solid Waste Utility to ensure that issues regarding stormwater pollution are included in these outreach efforts. Inspection and Technical Assistance Staff Training Surface Water Utility staff and maintenance crews responsible for providing technical assistance to individual businesses should be properly trained both to recognize stormwater pollution problems that they may encounter in the field and to understand nonstructural source control options that are applicable in various situations. This requires knowledge of the businesses and their operations as well as source control practices and their related costs. To provide a brief overview of conditions and standard practices, a preliminary windshield survey of businesses in the basins is recommended prior to embarking on a detailed inspection and nonstructural source control program. 255C\LWTASK3 84 Herrera Environmental Consultants Business Inspection and Source Control Efforts After applicable information on best management practices has been researched and assembled and the staff is adequately trained, the Surface Water Utility will be prepared to implement the nonstructural source control program at individual businesses in the North Renton and West Hill basins. It is recommended that the city start by educating local businesses about the water quality program and the city's intent to conduct inspections and workshops to encourage businesses to implement best management practices. This notification could be attached to utility bills. The notice should include a brief schedule of upcoming activities. Follow-up notification should then be sent to individual businesses to obtain permission to access the property prior to conducting a site inspection. For the North Renton and West Hill basins, it is recommended that the city initially target automotive businesses (automotive repair, parts, sales, and service stations) and airport facilities. A list of licensed businesses in the two basins obtained from the Washington Department of Labor and Industries, Data Analysis Section, is provided in Appendix D. The locations of these business are plotted on Figures 2 and 3. This information should be periodically updated to keep the utility informed about local business operations. One way to accomplish this would be to monitor and log business license applications approved in the city of Renton. Those businesses considered to be a potential source of stormwater pollution could then be targeted for technical assistance. The land use compliance inspector currently reviews all business applications. The Surface Water Utility should work with the inspector to develop a system for logging business license approvals, as a means of routinely updating the list of active businesses in the Renton service area. There are several possible approaches to implementing the business inspection program. The city could elect to have utility staff perform all inspections. This approach would provide the utility with total control of the program but would require additional staff dedicated to performing inspections. The North Renton and West Hill basins contain approximately 120 businesses that are considered potential sources of pollution to the city storm drain system (of which approximately 37 are categorized as automotive and nine are airport services. At least one staff person would be needed to conduct the business inspections and oversee activities in the basins. Another approach would use other existing resources and programs to support water quality program activities. For example, as part of the local hazardous waste management program, Metro and the Seattle/King County Department of Public Health currently staff four field teams (audit, survey, onsite consultation, and response teams) to inspect and advise businesses in King County about appropriate practices and regulatory requirements for small-quantity generators of hazardous waste. This plan, developed by King County in response to the State Hazardous Waste Management Act, is funded by fees applied to local utility bills throughout the county. The program has been in operation for about 3 years. The onsite consultation team is available upon request to perform audits of local businesses. The survey team visits all businesses within selected geographic areas to observe hazardous waste handling practices, provide technical assistance to local businesses, and develop a database of local businesses and practices for future program efforts. It is expected that the survey team will eventually reach all small-quantity generators in King County. Recently, Renton's aquifer 255C\LWTASK3 85 Herrera Environmental Consultants protection program was able to schedule the Metro survey team to visit all businesses operating within the zone 1 and zone 2 aquifer protection areas (Boatsman 1994 personal communication). The survey team generally performs one-time site inspections to review business operations and advise facilities of appropriate source control practices for hazardous waste management. The Metro team could be used to complete an initial survey of businesses in the North Renton and West Hill basins to give the utility an idea of the problems that exist and the areas needing attention. The utility should coordinate with the survey team to ensure that stormwater issues and concerns are addressed. Follow-up inspections and technical assistance could then be provided by the Surface Water Utility. Similarly, the local hazardous waste management onsite consultation team responds to requests from individual businesses to conduct audits and provide specific recommendations on waste minimization and pollution prevention opportunities. This team also visits ail new hazardous waste generators who report to Ecology and qualify as small-quantity generators. The Surface Water Utility should use this team as a resource by referring those businesses that are experiencing particular waste management problems to the team for advice. The local hazardous waste management program also operates a business waste hotline that local businesses can call for advice on waste issues (206/296-3976). It is uncertain to what extent the local hazardous waste management teams will be available to support other local programs, particularly as more municipalities become aware of and make use of this service. Therefore, it is recommended that the Surface Water Utility use the hazardous waste teams as a resource to complement its in-house program, rather than relying on these teams to form the basis of a water quality program. For the success of any program directed at local businesses, it is impor'.ant that the city stimulate a spirit of cooperation within the business community rather than taking an adversarial stance. This can be achieved by using an informal approach to dealing wi,h local businesses and by developing an informational exchange between businesses and the ciiy. Inspections should be conducted with the intent of forming a working relationship with the business and therefore should be prearranged with the property owner. While onsite, city inspectors should try to elicit information about business operations that generate or use materials that can be toxic to the receiving water environment, identify source control procedures that may already have been implemented, and encourage businesses owners to talk openly about problems they have experienced in implementing best management practices. This information will be useful to the inspector in developing site-specific recommendations that can be easily implemented. When advising local businesses, it is helpful to provide them with some guidance on expected implementation costs. Inspections should be followed up in writing to document any problems identified and to provide additional information on source control recommendations. The utility should make use of available expertise in other agencies, such as Ecology's urban bay program and the King County consultation team, to develop appropriate recommendations on source controls. It is essential that businesses understand that the city is committed to accomplishing pollution abatement. To convey this message, city staff must be available to work with local businesses to satisfy the water quality program objectives. The city of Bellevue Storm and Surface Water 255C\LWTASK3 86 Herrera Environmental Consultants Utility has implemented a similar program, called Business Partners for Clean Water, which has been successful at achieving pollution abatement. It is recommended that Renton contact Bellevue utility staff members to obtain information on the program and to get their perspective on the most efficient ways to work with local businesses. Educational Workshops The Surface Water Utility should conduct educational workshops as a cost-effective means of conveying pollution abatement information to businesses that share many of the same operations and source control requirements. One such audience that is already being targeted is the Renton Municipal Airport tenants. A workshop is being developed and will be presented to the airport tenants as part of this project. The workshop will describe appropriate procedures for activities such as aircraft washing; storage, handling, and transport of liquid materials (e.g., solvents and fuel); fuel dispensing; waste minimization and recycling; waste disposal; aircraft deicing; and spill prevention and emergency cleanup. In addition, a brief discussion will be provided on structural controls that could be installed (e.g., oil/water separators, centralized refueling station, and aircraft wash station). Consideration should also be given to conducting workshops with other business groups in the North Renton and West Hill basins, such as automotive service businesses. Workshops provide a forum for hearing the concerns of several businesses at one time, as well as guaranteeing that educational materials are received by the appropriate people. Coordination with Other City Programs Effective implementation of best management practices at businesses in the North Renton and West Hill drainage basins will require coordination with the Renton Water Utility's aquifer protection program, the Fire Department's annual inspection program, the land use compliance inspection program, the Maintenance Division, and the Renton Municipal Airport manager. Information that is relevant to stormwater pollution abatement concerns is already being collected by these other departments. An interdepartmental network should be established to facilitate the sharing of information among the various city departments. In addition, this network could be used to coordinate business inspections, thereby minimizing the overlap between departments. The aquifer protection program is already working with the Fire Department to coordinate inspections in designated city aquifer protection areas and is assisting the Fire Prevention Bureau with computer programs to enhance code enforcement. Other opportunities for resource sharing should also be explored. Individual Site Cleanup Actions The Surface Water Utility should continue to coordinate with Ecology and U.S. EPA on individual cleanup actions conducted at sites in the North Renton and West Hill basins to ensure that cleanup plans adequately address stormwater quality issues and comply with local 255C\LWTASK3 87 Herrera Environmental Consultants ordinances. One example is the Paccar/Kenworth site located in the North Renton basin, which is undergoing cleanup of contaminated soil and ground water. Paccar has constructed wet ponds to treat stormwater runoff before it leaves the site and enters the city storm drain system. Under MTCA, Ecology is the lead agency for most site cleanups. The city does not have the authority to regulate specific cleanup activities but should have input on actions that affect city operations (e.g., Surface Water, Sewer, and Solid Waste Utilities and Transportation Division). However, Renton should be proactive in dealing with contamination issues by notifying Ecology of any contaminated sites it may discover and working closely with Ecology to ensure that contaminated sites in Renton are cleaned up in a timely manner. Enforcement of Pollution Abatement Program Objectives It is unlikely that all businesses and residents in the North Renton and West Hill basins will readily comply with the recommended pollution abatement procedures. Therefore, a system for enforcing the requirements of the pollution abatement program should be developed. The existing Renton Storm and Surface Water Drainage Ordinance stipulates drainage and treatment requirements for runoff generated by new development and redevelopment, but the ordinance does not specifically address existing development or requirements for source control. The city has limited enforcement authority under Title IV-33 (Civil Penalties) of the Renton Municipal Code. Although the land use compliance officer has used this ordinance to require businesses to implement source control activities, stormwater quality and pollution control requirements are not specifically addressed by any city code or ordinance. The Storm and Surface Water Drainage Ordinance and the Aquifer Protection Ordinance both include provisions that address water quality, but neither is applicable citywide. For example, the Storm and Surface Water Drainage Ordinance (Title IV-22) requires new developments to prepare a drainage plan that describes drainage control, water quality controls, and erosion control practices that will be incorporated into site development. However, this requirement does not apply to existing facilities in the city. Likewise, the Aquifer Protection Ordinance requires businesses located within a designated aquifer protection area to implement best management practices to meet specific requirements for source control, but this ordinance does not apply to businesses located outside the aquifer protection area. Other municipalities have passed ordinances establishing legal authority to control the discharge of contaminants, as authorized under the federal Clean Water Act. For example, in 1992 King County passed an ordinance (No. 10636) prohibiting the discharge of any contaminants into surface water or stormwater and authorizing the Public Works director to require that best management practices be implemented to control pollution sources. The city of Renton could consider enacting a similar ordinance to provide city agencies with clear authority to enforce best management practices. The need for additional ordinances will be addressed in the Comprehensive Storm and Surface Water Management Plan. In the interim, the city should continue to its the Civil Penalties Code to enforce city codes that apply to stormwater and should refer other cases where there are no applicable city codes to Ecology for enforcement. 255C\LWTASK3 88 Herrera Environmental Consultants Monitoring and Record-Keeping Programs The third major component of the water quality program is development and implementation of a system for evaluating the effectiveness of pollution abatement control activities. This section describes program record-keeping and monitoring efforts needed to support the water quality program. Water Quality Program Record-Keeping The Surface Water Utility should develop a record-keeping system for tracking stormwater pollution problems that occur within the city service area. This will help the city not only to understand the nature of stormwater quality problems affecting its drainage system but also to maintain up-to-date information on source control efforts and the status of future enforcement actions. In addition, an efficient record-keeping system will be needed to document the effectiveness of the overall pollution abatement p )gram. The following records should be maintained in Surface Water Utility files: ■ Drainage system inspection and maintenance logs, including results from any samples that may be collected to document pollutant discharges (these should continue to be recorded in the city maintenance management system [MMS]) ■ Business inspection reports ■ Spills reported within the service area that affect the storm drain system (coordinate with Ecology and Metro to obtain spill records) ■ Notices of violation and citations issued by inspectors ■ Illicit connection survey results ■ Capital improvement projects constructed for stormwater quality control. Many of these record-keeping tasks may be as simple as developing a form to be completed for each activity, which can then be filed to enable the utility to track its stormwater pollution control activities. Other tasks will require coordination with other city departments and agencies to obtain and compile the necessary information. For example, the Maintenance Division has developed a system to track and schedule future work orders. The utility should coordinate with maintenance staff to develop a standard system for recording and retrieving information required to support the water quality program (e g., inspection reports, recurring problem areas in the two basins, work orders related to stormwater qualit;,, and discharger reports to Ecology or the land use compliance officer). The land use compliance program is developing a database system using the SIERRA computer program to facilitate tracking of code violations. This relational database system will track city code violations by maintaining up-to-date records of the number and types of businesses that 255C\LWTASK3 89 Herrera Environmental Consultants typically experience compliance problems. This information would be useful to the Surface Water Utility's water quality program. Ecology also maintains a database on spills that have been reported and investigated by the agency. Currently, this information can be retrieved by geographical area, affected media (e.g., surface water, ground water, or soil), date of spill, and material spilled (e.g., oil/petroleum, hazardous material, or wastewater). The Surface Water Utility should coordinate with Ecology to obtain records and track cleanup actions on spills that occur in the city service area. Initially, it will be possible to operate a manual filing system to maintain program records. However, as the water quality program grows, particularly if drainage basins other than the North Renton and West Hill basins are included in the program, a manual filing system may become inefficient, and conversion to a computer-based tracking system may be warranted. Many city agencies already use computerized databases. The Surface Water Utility should examine the systems used by other city offices to determine whether any of these could be easily modified to fulfill water quality program requirements. Implementation of an efficient record-keeping system will help to streamline the preparation of annual summaries that are useful for assessment of program development and progress and for accounting purposes. As explained earlier, it is recommended that the stormwater program be evaluated based on its effectiveness in improving practices used by local businesses and residents that affect stormwater quality (rather than attempting to directly measure water quality improvements). The following items, which affect stormwater quality, should be tracked to assess whether their frequency of occurrence is reduced after the utility's water quality program is implemented: ■ Spills and other trouble calls reported to Ecology and Metro hotlines ■ Complaints received by the land use compliance program related to stormwater pollution ■ Illicit connections identified in the storm drain system ■ Emergency service calls conducted by the Maintenance Division. The utility should also maintain a list of businesses inspected each year, as well as a tally of the number and types of improper housekeeping practices discovered during these inspections, to evaluate improvements in local business practices. Water Quality Sampling Development and implementation of a basinwide water quality monitoring program in the North Renton and West Hill basins is not recommended. As explained in Chapter 5, stormwater monitoring is often expensive, because an extensive data collection effort is usually needed to track source control improvements in stormwater quality against the background of a wide range of natural variation in stormwater discharges. Although the results of the sampling effort conducted as part of this project indicate that stormwater discharged from the two Renton/Lake 255C\LWTASK3 90 Herrera Environmental Consultants Washington basins commonly exceeds the state water quality standards for metals (copper, lead, and zinc) and fecal coliform bacteria, in most cases the quality of runoff discharged from these two basins is comparable to the runoff from other urban areas in Puget Sound and across the United States. Instead of basinwide sampling, a few small, focused investigations should be conducted targeting specific stormwater quality problems and problem chemicals that have been identified in the two basins. The primary goal of these projects would be to identify the responsible sources so that source control activities can be implemented. Stormwater quality problems discovered during the drainage basin characterization effort conducted as part of this study and warranting additional investigation include: ■ Elevated concentrations of total petroleum hydrocarbons were observed in stormwater samples collected from stations NR-1 (subbasin N6) and NR-5 (subbasins N4 +N6). ■ The concentration of silver in the sediment sample collected offshore of the North Renton outfall was nearly 200 times greater than the concentrations measured offshore of other storm drain outfalls in Lake Washington. ■ Large numbers of fecal coliform bacteria observed in base flow samples collected from several stations in the North Renton and West Hill basins indicate the possible existence of illicit connections in these areas. Investigation of petroleum contamination in subbasins N4 acid N6 should begin with an initial survey conducted during a storm event to qualitatively evaluate the extent of petroleum-related contributions in these two subbasins. This survey would entail inspecting major junctions in the storm drain system for signs of petroleum contamination (i.e., oil sheens) to assess whether petroleum is a problem throughout these subbasins or whether this contamination results from a few localized problem areas within each subbasin. Likely areas to target during these inspections are large commercial developments such as the two shopping centers located along Sunset Boulevard. Depending on findings of the initial field survey, additional sampling may be necessary to identify responsible sources prior to assessing source control and treatment options. The presence of silver in concentrations that greatly exceed those measured in the sediments offshore of other storm drains in Lake Washington suggests that there may be a significant source or sources of silver in the North Renton basin. Further investigation is to confirm that silver is a problem and to determine whether the contamination is caused by historical or ongoing sources. It is recommended that additional sediment samples be collected offshore of the North Renton storm drain outfall to determine the extent of contamination. If silver contamination is confirmed, then a focused source identification investigation should be conducted. It is often difficult to conduct source tracking investigations for pollutants such as silver, which are usually present in very low concentrations in stormwater (i.e., below standard analytical detection limits). Therefore, source tracking studies are often based on an analysis of sediment that has accumulated in the storm drain system, rather than on bulk stormwater samples: Storm drain sediment deposits serve as a sink for contaminants like metals that adhere to the 255C\LWTASK3 91 Herrera Environmental Consultants particulates present in runoff. Recommendations for conducting source tracking studies in urban storm drain systems are provided by Tetra Tech (1988). Illicit Connection Surveys Based on the findings of the pollutant source characterization study, it is apparent that further efforts are needed to identify and eliminate potential illicit discharges, especially in subbasins N2 and N3 in the North Renton basin and in subbasins W1, W3, and W4 in the West Hill basin. Discharge of non-stormwater flows from maintenance shop floor drains, industrial waste systems (e.g., cooling water from mechanical equipment), and inadvertent sanitary sewer cross- connections to city storm drain systems are recurring problems in urban areas. Illicit discharges that may exist in the Renton/Lake Washington drainage basins could contribute significant pollutant loading to Lake Washington. Under base flow conditions, the following sites were found to have elevated specific conductance or elevated concentrations of fecal coliform bacteria or chlorine, suggesting that there may be illicit connections in these areas (see Figures 2 and 3): West Hill Basin' North Renton Basina Manhole 15, G4-2 Manhole 12, D6-2 Manhole 11, D8-12 Manhole 17, F2-3 Manhole 11, 136-16 Taylor Avenue ravine a Manhole descriptions correspond to city drainage inventory map numbers. It is recommended that the city conduct more thorough investigations in these areas to identify and eliminate any illicit connections that may exist. This will require additional efforts on the part of city maintenance crews and Surface Water Utility staff to coordinate the necessary field sampling and to work with the local community. Available city drainage and sewer maps should be reviewed to identify appropriate sampling locations. Sample collection should begin in the downstream area and proceed upstream, to pinpoint possible source locations. Samples should be collected during dry weather conditions to minimize interference from stormwater runoff. Depending on the size of the drainage system, a period of 2 to 3 days of antecedent dry conditions is recommended prior to sampling. Analysis of fecal coliform bacteria, an indicator species that inhabits the intestinal tract of warm- blooded animals (including humans), can be used to locate possible cross-connections between the sanitary sewer and the storm drain system. Laboratory costs are approximately $30 per sample. Some utilities have also used reagent kits that measure the concentration of ammonia:nitrogen to locate sanitary sewer connections (Glanton et al. 1992). Reagent kits, while less sensitive and less accurate than laboratory methods, offer the advantage of generating results in the field, thereby reducing the time required to track illicit connections. Surveys in primarily residential areas should be conducted during the early morning hours when most residents are arising and preparing for the day, and discharges from sanitary cross-connections are greatest. In commercial areas, surveys should be conducted during normal business hours. 255C\LWTASK3 92 Herrera Environmental Consultants Once a contaminant source has been identified or traced to a particular segment of the drainage system, dye tests can then be used to verify the exact location so that the cross-connection can be eliminated. Other indicator parameters will be needed to track the location of illicit connections that do not involve sanitary waste. For example, temperature measurements can be used to locate cooling water discharges from industrial sources. Specific conductance, which provides a measure of the dissolved solids content of the water, can often be used to locate process water discharges, such as metal plating wastes that contain elevated concentrations of metallic salts. Preservation and Enhancement of Natural Drainage Systems Natural drainage systems tend to have better pollutant removal capability than constructed conveyance channels and closed pipe systems. Natural systems also provide habitat for fish and wildlife. Therefore, it is desirable to preserve natural drainage systems to the maximum extent possible. Examples of natural drainage systems in the study area that should be preserved include the following: ■ The last remnants of John's Creek are located west of the SR-405 corridor, and in Coulon Beach Park near the outlet to Lake Washington, in the North Renton basin. These two sections are in good condition, with thick vegetation growing along the stream banks. The wetland areas surrounding the reach along SR-405 also help to filter pollutants present in the runoff and serve as -wildlife habitat. ■ Vegetated ravines exist along the hillside above Rainier Avenue and along Renton Avenue South in the West Hill basin. These ravines provide good quality wildlife refuge and habitat, in addition to their ability to infiltrate and treat stormwater runoff. Coordination of Spill Control and Containment Capabilities The Surface Water Utility should coordinate with the Fire Department and Ecology to assist in responding to spills and other emergencies involving the city storm drain system. Utility staff and the Maintenance Division should review drainage system plans and inspect appropriate sites within the drainage system to identify opportunities for spill control and containment, so that spills that may occur in the North Renton and West Hill basins can be prevented from reaching Lake Washington. The areas to target are the major transportation corridors within the two basins where spills associated with vehicular accidents are most likely to occur (e.g., SR-405, Sunset Boulevard, and Rainier Avenue). This will require coordination with city and state transportation agencies. 255C\LWTASK3 93 Herrera Environmental Consultants PUBLIC EDUCATION This section recommends public education efforts that could be implemented by the city of Renton to improve stormwater quality and local awareness of stormwater quality issues, particularly in the North Renton and West Hill drainage basins. The basin characterization and source identification efforts conducted as part of this study indicate that stormwater quality problems in these two basins are similar to those experienced in other urban areas (e.g., frequent exceedances of state water quality standards for fecal coliform bacteria and metals such as copper, lead, and zinc). These pollutants tend to be ubiquitous in urban basins and are generally contributed from a variety of diffuse sources rather than a few individual sources or problem areas. In only a few cases were uniq-:j problems related to site- specific conditions identified. For example, oil sheens were observed in runoff from several locations, and fecal contamination was observed during base flow conditions in a number of drains, particularly in the West Hill basin. Pollutants found in stormwater runoff from the North Renton and West Hill basins and likely sources of these compounds are listed below: Pollutant Probable Sources Metals (copper, lead, Roadways, automobiles.(tire wear, gasoline, motor and zinc) oil, bearings) Fecal coliform bacteria Failing septic tanks, cross connections with sanitary sewers, domestic pets and wildlife Petroleum hydrocarbons Roadways, automobiles, improper disposal of waste oils, automotive maintenance activities Nutrients (phosphorus) Pet and animal wastes, fertilizers, soil erosion Given the general nature of stormwater quality problems experienced in the North Renton and West Hill basins, appropriate public education efforts are those that cover a broad range of land use activities, targeting the general public as well as local businesses. This public education plan has been developed to complement other ongoing programs by addressing issues or fulfilling public education and information needs that are not already covered by existing programs. The first section of the plan describes public education programs that have been implemented by the city of Renton and other jurisdictions addressing stormwater quality and management issues. The second section explores options for providing additional public education to fill any gaps in coverage. The final section describes recommendations for public education activities that the Renton Surface Water Utility could implement in the North Renton and West Hill basins and in other city drainages. Although the public education program targets the two study basins, the plan will also be applicable citywide because the Lake Washington basins share many of the same stormwater problems experienced by other drainages in the city. The recommendations focus both on actions that are not already covered by water quality education efforts sponsored by Renton or 255C\LWTASK3 94 Herrera Environmental Consultants other governmental agencies, and on actions that are expected to have the greatest effect on reducing the pollutants found in the North Renton and West Hill basins. It is expected that public education efforts would begin in the North Renton and West Hill basins, then gradually expand into other areas of the city as funding and staffing allow. Full review and adoption of this plan will be carried out as part of phase 2 of the Surface Water Utility comprehensive plan, which also is intended to include a public education component and other city water quality efforts. Existing Water Quality Education Efforts This section describes efforts that local jurisdictions are undertaking to improve water quality through public education. Many government agencies, as well as educational institutions and volunteer groups, currently participate in public education efforts in order to improve water quality throughout Puget Sound, including Lake Washington. Agencies charged with environmental protection through solid waste management, surface water management, ground water protection, fire protection, and sewage treatment all use public education to improve water quality. This section documents a number of those efforts that are best suited to address the types of stormwater quality problems identified in the North Renton and West Hill basins. Existing public education programs are summarized in Table 28. City of Renton Many city departments and divisions provide public education designed to reduce water pollution either directly or indirectly through implementation of sound environmental practices. Currently there is no formal coordination among these many efforts, nor is there a consolidated reference center on water quality education for city staff use. Ongoing Renton public education efforts are described in the following sections. Surface Water Utility Phase 1 of the utility's comprehensive plan includes a needs assessment, a policy review, a utility rate study, and a public involvement program. Phase 1 is still under review by the city of Renton. Phase 2 will include utility policies and programs to accomplish operation and maintenance, basin planning, surface water quality improvement, capital improvement projects, and public involvement and education. The approach that is currently favored for a citywide public education program is to encourage community involvement in watershed issues by enhancing the community's understanding of watershed concepts and water quality issues (Barton 1994 personal communication). In addition to the comprehensive plan, the utility has completed one individual basin plan to date, the Black River Basin Water Quality Management Plan. The city is in the process of preparing two other basin plans, the May Creek Basin Plan and the Cedar River Basin Plan, in cooperation with the King County Surface Water Management Division (SWM). SWM is expected to begin development of the Green River Basin Plan with the cooperation of Renton and other valley communities in 1994 (Jennings 1994 personal communication). Each of these 255C\LWTASK3 95 Herrera Environmental Consultants basin plans contains a public education component, which should be coordinated with other city programs. Water Utility The city has adopted an Aquifer Protection Ordinance, which requires businesses located within designated aquifer protection areas to obtain a permit from the city to handle hazardous materials or other chemicals that could threaten the city's water supply. The pennit specifies requirements for storage and handling of these materials. Education is being used as a primary means of ensuring compliance with the ordinance. An aquifer protection specialist visits businesses operating within designated aquifer protection areas, to explain ordinance requirements and to assist businesses in complying with the ordinance. Technical assistance has also been provided by Metro hazardous waste survey and onsite consulting teams (described below). Public education efforts carried out or planned by Renton's Water Utility focus on aquifer protection, hydrogeology, drinking water quality, water conservation, less toxic alternatives to commonly used hazardous products, hazardous waste minimization, recycling, and waste disposal. An educational slide show is frequently presented to civic and technical organizations. Signs and billboards promote aquifer protection, and an educational ;+isplay has been developed for community fairs. In addition, day camps and "water walks" arc, offered in the summer. A school curriculum focusing on aquifer protection has been developed for second, fourth, and eighth grades, and teacher workshops are provided throughout Renton schools. Other education programs include a popular magic show that teaches children about protecting water resources in an entertaining format, and the "water wizard," a volunteer dressed in a costume designed by school children, who entertains and educates children at school assemblies. The utility has also printed two brochures that serve as public education tools: Water Quality, It's up to You is an older brochure focusing on protecting aquifer water quality, and Understanding the Aquifer Protection Ordinance is currently being used to educate Renton's citizens and business community about the ordinance. Solid Waste Utility The primary focus of the solid waste public education program is to promote the use of nonhazardous home products. Utility staff members conduct workshops for local community groups (e.g., Kiwanis and PTA) on safe home cleaning and gardening practices. The Clean and Green Resource Guide is distributed in conjunction with the workshops. This guide is a binder containing brochures and educational materials produced by other agencies, providing information on how to reduce the amount of toxic products used in homes. The guide focuses on household cleaners, green gardening, automotive care, aquifer awareness, and other resources available to readers. Many copies of the guide already have been distributed to West Hill residents. 255C\LWTASK3 96 Herrera Environmental Consultants The used motor oil recycling program is an important part of the utility's efforts to reduce water pollution. This year, utility staff distributed 500 "draintainers" (containers for collecting used motor oil) and 500 quarts of recycled motor oil, in addition to information about locations in Renton where citizens can take used motor oil for recycling. Based on the volume of oil received at the local oil recycling collection centers (i.e., Al's Auto Supply, Shuck's Auto Supply, and various BP Oil Company stations), the program appears to be successful. The utility also uses the Renton River Days and semiannual recycling days (during which used oil and antifreeze also are collected) to advertise this and other available environmental programs administered by local jurisdictions. Within the study area, the Solid Waste Utility coordinates with a King County master recycler composter in the North Renton basin who maintains a public information display at the public library. The utility also coordinates with the King County Solid Waste Division's master recycler program, the King County local hazardous waste management program, and the Metrocenter YMCA master home environmentalist program to make full use of available public education information and materials. In 1994-95, the Solid Waste Utility will focus its efforts on promoting the use of worm bin composters to reduce the solid waste stream, distributing information about alternative home cleaning products and conducting children's workshops (in conjunction with the Renton Parks and Recreation Department). Fire Department The Renton Fire Department indirectly provides water quality education through its annual inspections of commercial businesses in the city. These inspections address storage of flammable materials, containment, and handling of hazardous materials. King County Public Works Department, Surface Water Management Division SWM is involved in many public education activities pertaining to water quality. Its public involvement unit administers the community stewardship program, which trains citizen volunteers for revegetation projects as part of county-sponsored capital construction projects in water-quality-sensitive locations (contact Debbie Cornell at 206/296-8368). The unit also organizes water quality workshops, although fewer workshops may be provided in the future because of falling attendance. The public involvement unit also manages the signage program, intended to educate the public about the need for drainage facilities (e.g., retention/detention ponds). A list of available public education materials, as well as SWM's resource library contents, is provided in Appendix F. Seattle/King County Department of Public Health The Health Department has jurisdiction over septic tanks in unsewered areas of Renton and King County, including those areas within the North Renton and West Hill basins that are not served 255C\LWTASK3 97 Herrera Environmental Consultants by sanitary sewers (i.e., portions of the Skyway Water and Sewer District and the city of Renton service area). The Health Department conducts home inspections and mails informational brochures to individuals upon request. These brochures provide information on septic system maintenance, including the proper use and cleaning of septic tanks. A videotape that describes septic tank maintenance procedures is also available for viewing in the office. The Health Department also sends as-built plans of newly installed septic systems to homeowners 3 years after construction is completed. The department's most recent survey was conducte '. in the Skyway Water and Sewer District and May Creek areas. No additional effort in Renton is currently planned. Sanitary surveys are conducted only when requested and are funded by a city or sewer district. Maps showing septic system failures are located in the Eastgate office. The Eastgate office serves the area north of Petrovitsky Road (contact Sid Forman, inspector, at 206/296-9736). The Health Department is also active in the local hazardous waste management program (as is the city of Seattle and the King County Solid Waste Division), described below under Department of Metropolitan Services. Washington State Universi /Coo erative Extension - King County g ty P The King County land and water stewardship program is a volunteer educator program modeled after the master gardener program. Volunteers receive 100 hours of training on water quality practices, then perform a minimum of 100 hours of public service. Volunteers work with their neighborhood, homeowners association, Kiwanis Club, church, or school to provide information on land and water conservation practices. The trained volunteer in Renton is Sue Kinser (206/228-9623). The Cooperative Extension (206/296-3900) also conducts conferences and workshops on water quality, small farms, wetlands, and stormwater issues. (See reference to the master gardener program below under Public Education Options, Resources in Other Organizations. Department of Development and Environmental Services The Environmental Resource Planning section (206/296-7590) offers two slide shows, Doing it Right and Regional Heritage, designed to promote discussion of sound development practices. The Environmental Education section (206/296-6602) conducts erosion control and water quality workshops for developers, farmers, landowners, and environmental activists. The agency also provides training on the county Sensitive Areas Ordinance for teachers and realtors. Department of Metropolitan Services (Metro) Local Hazardous Waste Management Program—The local hazardous waste management program, administered in part by Metro, focuses its efforts toward businesses (specifically, small-quantity generators of hazardous materials) and residents (for household hazardous waste). The program is a cooperative effort involving Metro, Seattle Solid Waste Utility, King County 255C\LWTASK3 98 Herrera Environmental Consultants Solid Waste Division, Seattle/King County Department of Public Health, and suburban cities in King County. As part of this program, Metro maintains a hazardous waste library at 130 Nickerson Street in Seattle (206/689-3051), which is open to the public and could be used by Renton in developing future programs. A list of publications available from the library is provided in Appendix F. Through the small-quantity generator program, Metro works with all businesses in its service area (i.e., all of King County) to provide information and technical assistance on proper handling and storage of moderate- to hazardous-risk wastes. The program staffs four field teams that work directly with local businesses. Three of the teams are staffed by Metro personnel: 1) the survey team, which makes uninvited visits to all businesses in selected geographic areas, 2) the onsite consultation team, which visits businesses at their request, and 3) the response team, which acts on complaints from other agencies or flue public. A fourth field team, the audit team, is staffed by the Seattle/King County Department of Public Health. The audit team, which focuses on high-priority business categories, canvasses the county, vi,iting a'.1 businesses of a certain type and providing owners with information on applicable regulations and proper waste handling, reduction, and disposal methods. The audit team is currently targeting automotive body shops and has visited about half the body shops in King County (contact Rosemary Byrne at 206/296-3974). Metro's survey team focuses on selected geographic areas, visiting all businesses regardless of the category of operations. The team inspects each site to observe the facility's waste handling practices and also to provide information on best management practices and services available to small businesses. One of the objectives of these surveys is to obtain information on general housekeeping practices employed by local businesses, to determine the materials needed for the long-term education of businesses in King County. The survey teams visit about 1,200 businesses each year. Metro survey teams have visited the businesses in Renton's aquifer protection area and could upon request visit the businesses in the West Hill and North Renton basins in 1994. The small-quantity generator program is supported by the education and technical assistance group, which produces and distributes brochures, fact sheets, and other materials to local businesses describing regulatory requirements and best management practices for handling hazardous waste. The group performs a range of public relations activities such as issuing press releases, publishing articles in local trade journals, and participating in local trade shows. The technical assistance group also maintains a list of vendors that dispose of hazardous waste (contact Gayle Savina at 206/689-3062). A list of publications available from the technical assistance group is provided in Appendix F. The technical assistance group does not conduct workshops but provides onsite consultation teams to review conditions at business sites and offer advice on regulations, containment, and cleanup. The speaker liaison program provides speakers and literature upon request to business groups and associations (contact Dave Waddell at 206/689-3069). Presentations are tailored to specific audiences and can be general or technical. These offices are intended to assist businesses in implementing proper hazardous waste disposal practices and have no enforcement function. 255C\LWTASK3 99 Herrera Environmental Consultants The school program offers classroom lectures on hazardous waste and its effects on water quality, and maintains a public hazardous waste library with materials available by mail. In addition to classroom work, the program provides workshops for teachers, projects for the Girl Scouts and Boy Scouts, and videos for adults on hazardous waste. The program will soon offer a teacher guide describing numerous activities for classroom curricula. All of these services and materials are available to Renton and other jurisdictions upon request (contact Gayle Gensler at 206/689-3082). A separate department provides public education for local residents in support of the household hazardous waste program. Metro's outreach and education program, which produces educational materials on household hazardous waste directed toward adults, is staffed by Annette Frahm (206/689-3064). The program has developed a "safe alternatives" poster and an accompanying brochure; has instituted a green gardening program of garden tours and chemical workshops; and has produced calendars designed to promote appropriate use of pesticides in gardens, as well as a homebuyer's guide on the use of chemicals in construction, and three brochures on eliminating chemicals in gardens. The program is developing a radio campaign to reduce pesticide use and, together with the Washington Toxics Coalition, is developing a buyer's guide for household products. Metro also distributes a brochure on paint disposal (contact Ann Moser at 206/689- 3051). Water Quality Program—The general water quality education program for grades kindergarten through 12 offers classroom workshops that focus on the water cycle. Topics include water availability, water use and wastewater disposal, sources of pollution, and ways to keep the water clean. Work sheets and reading materials are provided for students to take home and use with their families (contact Lexi Truman at 206/684-1160). Washington Department of Ecology Ecology provides numerous water quality education programs through its administration of federal and state grant monies. Ecology's business education program, coordinated by Dave Misko (206/649-7014), offers free workshops for businesses that are registered generators of hazardous waste (i.e., those that have a U.S. I?PA identification number). In addition, the liaison for technical assistance to businesses, Leighton Pratt (206/407-7018), can refer businesses or agencies to the appropriate regional office staff to address problems or questions. Ecology also manages educational programs for hazardous waste management and underground storage tanks. Educational programs for the general public are coordinated through the Office of Public and Environmental Education, which has available two curricula for grades kindergarten through 12, Away with Waste and Discover Wetlands (contact Rhonda Hunter at 206/407-6147). The Ecology publications distribution office offers water quality educational materials such as brochures and fact sheets. A summary of water quality publications is provided in Appendix F. Three publications of special note for Renton are A Guide to Technical Assistance from Ecology (#92-106), Designing Community Environmental Programs: A Guide for Local Government (992-99), and Environmental Education Resources Directory (#90-72). An index of publications is available from Rachel C,_mens (266/407-747?1. 255C\LWTASK3 100 Herrera Environmental Consultants Puget Sound Water Quality Authority The Puget Sound Water Quality Authority administers the Centennial Clean Water Fund, which provides funds for local governments to conduct watershed protection planning. Proposals to address stormwater pollution and nonpoint pollution are accepted during the first year of each biennium. The agency has published two books describing the uses and successes of its public involvement and education program (known as the PIE fund) and will sponsor a conference in the fall of 1994 on this program. The program manager for the PIE program is Bob Steelquist (206/407-7300). The two publications, Public Involvement and Education Model Projects Fund: 47 Success Stories from Puget Sound, and Educating for Action: More Success Stories from Puget Sound, provide a comprehensive list of water quality education options, many of which are described below (PSWQA 1991, 1993). Waste Information Network The Waste Information Network (WIN) is an organization of representatives from local businesses, trade associations, schools, environmental groups, regulatory agencies, and environmental service providers, which provides technical assistance and education to local businesses. Its primary emphasis is on promoting sound waste management practices. WIN has produced industry-specific brochures describing typical hazardous waste issues, providing tips on waste reduction and recycling opportunities, and listing available resources and contacts on hazardous waste issues. The group distributes an annual hazardous waste management guide for local businesses. In addition, WIN is a major sponsor of the annual Northwest Waste Information Expo, which features seminars on waste management and environmental exhibits from local vendors of waste management products and services. The exposition is oriented toward teaching small businesses how to become more environmentally responsible. WIN also conducts monthly meetings that feature speakers on hazardous waste issues. Meetings are held at the Metro office at 130 Nickerson Street in Seattle (contact Alice Rice at 206/689- 3050). Public Education Options This section summarizes options that Renton could employ to educate the general public and small businesses about water quality issues, primarily those relating to nonpoint source water pollution. Two lists of options available to Renton to reach these two audiences are provided. Many of these efforts have been initiated by other jurisdictions, as noted in the sections below. Options for the General Public City Environmental Education Coordinator A full-time staff position could be established to consolidate the environmental education efforts of the various city departments into a single office. This position would be responsible for 255C\LWTASK3 101 Herrera Environmental Consultants producing printed and audiovisual materials; coordinating household and business programs, school programs, and special events; and establishing relations with the local news media to promote and advertise these programs. Program topics could include watershed planning, solid and household hazardous waste disposal, best management practices for stormwater, recycling, water conservation, aquifer awareness and protection, and drinking water quality. In addition, this staff position could serve to coordinate efforts by other city agencies involved in environmental education. This position also would handle phone inquiries and hotline calls; serve as the contact for complaints, violations, or spills; and be responsible for coordinating and updating printed material available from other jurisdictions. Eventually, a city watershed interpretive specialist could be assigned to support this position, to initiate and coordinate activities on watershed education for selected Renton watersheds. The interpretive specialist, who should have a background in parks, water quality, or forestry with an educational and interpretive emphasis, would be in charge of community efforts and public outreach for watershed management issues, including working with citizens, community groups, and city schools. Kiosk and Hotline A continually updated kiosk could be rotated among various public outlets in the city such as libraries, senior centers, schools, government offices and community centers, to make information available to the general public on water quality, solid and hazardous waste disposal, recycling, watershed management, and other pertinent subjects. In addition, a city hotline could be established to respond to questions and complaints from the local community. Informational Brochure An informational brochure could be developed.describing the water quality programs planned and currently underway in the city of Renton. The brochure could also reference other agency brochures on pertinent topics (see Appendix F) and could include telephone numbers to call for assistance with water quality problems. Suggested topics for brochures are listed below: ■ Utility functions and programs ■ Problems caused by disposal of chemicals and oil in storm drains ■ Locations of oil and antifreeze recycling stations ■ Proper use of fertilizers and pesticides ■ Environmentally safe pest control practices 255C\LWTASK3 102 Herrera Environmental Consultants ■ Disposal of pet waste ■ Proper composting techniques ■ Erosion control ■ Effects of littering and dumping (including yard waste) ■ Proper methods for using, storing, and disposing of chemicals, paints, and other household hazardous waste ■ Methods for identifying failing septic tanks (if not on city sewer) and telephone numbers for reporting ■ Septic tank maintenance procedures ■ Drainage ditch and swale maintenance procedures ■ Home streamside guidelines ■ Waterfowl feeding. Agency telephone numbers that could be listed on the brochure include the following: ■ Ecology recycling hotline: 800/732-9253 ■ Ecology spills hotline: 206/649-7000 ■ Hazardous waste: 206/296-3976 (for businesses) and 206/296-4692 (for households) ■ Metro trouble reporting: 206/684-1231. A brochure describing the various city programs could be distributed to all Renton residents through direct mail, or to residents of specific watersheds by carrier sort, or through visits by volunteers to each household. Some of the recommended brochure topics may already be covered in the Clean and Green Resource Guide binder distributed by the Solid Waste Utility. Alternatively, water-related topics that are not included in the binder could be added, and distribution of the binder could be coordinated within the city to achieve wider coverage. Newsletter The Surface Water Utility could also produce a newsletter or use the existing city newsletter, the Renton Reporter, to disseminate information about utility programs and activities and other utility issues. The newsletter would be distributed to all city residents. Because distribution of 255C\LWTASK3 103 Herrera Environmental Consultants the existing newsletter is already well established, this may be a more cost effective vehicle for disseminating information. The utility could arrange with the Renton Reporter staff to include regular articles and advertisements about upcoming events and programs. Realtors and New Utility Customers: Information for Newcomers New city residents and businesses could be given a packet of information that explains water quality issues and best management practices, describes city programs, and identifies key contact persons. Information packets could be distributed by realtors, city utilities, Puget Power, a visitors bureau, or the Chamber of Commerce. Poster Many communities have furthered awareness of water quality problems and best management practices through use of a well-designed poster that is attractive enough to appear on many walls in businesses, schools, community centers, and private homes. Another idea for an educational poster is one depicting the water bodies and wetlands in the city of Renton or in targeted neighborhoods. If pursued, this option would probably be best used citywide and would not be specific to the North Renton and West Hill basins. Watershed Signage Roadside signage could be installed informing citizens when they are entering certain key watersheds in the city. The Public Works Department could prepare signs to heighten awareness among residents about watershed management and water quality issues for the Renton basins. Because few natural drainage features remain (most stormwater runoff is collected in closed pipe systems), this option is probably not appropriate for the North Renton and West Hill basins. If implemented, this program should be coordinated with the city aquifer signage program. Interpretive Displays Signage and displays can be developed for key watersheds to explain their functions and the ways in which individuals contribute to the water quality of Lake Washington and Puget Sound. City parks, retention/detention facilities, road crossings, or other areas could be targeted for displays. The most likely location for a display in the Lake Washington study area is at Coulon Beach Park in the North Renton basin, where one of the last open-channel sections of the John's Creek drainage system remains. Media Program The utility could work with the local media (e.g., Valley Daily News) to run informational pieces or a regular column on water quality issues. This approach ensures continued high visibility and community awareness by making information easily accessible to citizens, to 255C\LWTASK3 104 Herrera Environmental Consultants assure their understanding and participation in water quality issues. To help cultivate a relationship with individual reporters and editors, the utility could also develop regular press releases or press kits for local media to use whenever a water quality event, activity, or program takes place. Watershed Awareness Week An annual watershed awareness week could be established as a cooperative citywide event with participation from local community groups and other city departments. It could be planned around Earth Day in April, Renton River Days in August, or Coastweeks in October. Activities could include a school poster contest, a park cleanup campaign, and other informational activities. This event would provide an annual focal point to encoLl.rage community organizations to work together on educational activities and stimulate local involvement. It may be possible to coordinate with People for Puget Sound for this event. The group currently sponsors Kids for Puget Sound, an annual day of activities that take place throughout the Puget Sound area. In addition, People for Puget Sound provides a speakers bureau for clean water issues, helps to organize conferences, conducts research, produces brochures on water quality, conducts citizen workshops on clean water and pollution monitoring, places information in public libraries, helps other groups maintain wetlands, and publishes a quarterly newsletter. Information is available from Pam Johnson(206/382-7007). Annual Creek Cleanup Days Citywide creek cleanup events could be organized to remove debris from local streams and roadside ditches and provide general cleanup on an annual basis. Efforts should be coordinated with regional and local political organizations to broaden awareness among the residents of the various watersheds in Renton. This program could be coordinated with programs sponsored by the Adopt-a-Stream Foundation (described below) and the Washington Department of Fish and Wildlife. Voluntary Ditch Maintenance Voluntary ditch maintenance programs could be instituted in appropriate locations of the city with preparation of informational materials and training workshops. Topics would include minimum maintenance requirements, safety precautions, and Public Works staff maintenance responsibilities. An adopt-a-ditch program could be f6iined to prevent destruction of ditch and swale vegetation required for biofiltration, reduce sediment and other contaminant loading, and increase public understanding of water quality issues. In the North Renton and West Hill basins, work could focus on cooperating with property owners adjacent to roadside ditches. 255C\LWTASK3 105 Herrera Environmental Consultants Storm Drain Stenciling The message Dump no waste, drains to stream can be painted on all visible public and private storm drain inlets in the city to raise awareness of water quality issues. Volunteers and even school children can help with a stenciling program. It may be necessary to provide volunteers with a city permit in case they are questioned while stenciling. Program coordination would require part-time involvement of a utility staff member. Stenciling is recommended twice annually, in spring and fall. Students and Young People Students from sixth grade through high school could receive training in watershed management, ecology, and water quality, then participate in stream monitoring programs as an element of water quality education. With agency oversigh,,, high school students receiving chemistry training could organize teams to perform scienti.1c investigations of water quality in Renton rivers and streams, producing data that could ultimately be used by regulatory agencies. (Two of the science teachers at Renton High School already incorporate water quality issues in their curricula.) The Green River Community College has developed a similar program with elementary and high schools in Kent, Auburn, and Enumclaw. If pursued, this option should be coordinated with the city aquifer education program and the local hazardous waste management program curriculum for kindergarten through grade 12. There are numerous curriculum resources available, including the Washington State Office of Environmental Education's Catalogue of Environmental Education Resources, and the Washington Superintendent of Public Instruction's 1993 publication, The Overwhelmed Educator's Guide to Environmental Education. Citizen Advocate Training A program similar to Bellevue's Stream Team (see below) could be developed in Renton to train volunteers to conduct many water quality monitoring and educational activities, including coordinating with school programs. Field trips to examine fish habitat and losses associated with unmanaged watersheds, as well as monitoring efforts, could be included in the training. Training should include an overview of governmental processes and responsibilities, including enforcement of regulations. Slide Show or Video for Schools and Organizations A slide show or video on watershed management could be developed for use in schools, community groups and clubs, business organizations, and city events. The content could include material from news broadcasts (e.g., from a local spill response or other watershed incident). The show or video should be widely advertised and made available on request to groups or individuals. Production could be managed either by a high school class, Renton Vocational Technical Institute, or a local volunteer. 255C\LWTASK3 106 Herrera Environmental Consultants Septic Tank Maintenance Brochure A special publication for Renton citizens could be developed to provide information on maintaining septic tanks and identifying signs of failure. The brochure should also list septic tank cleaning services in the area and the many resources available to answer questions, including a city telephone number or hotline. The Seattle/King County Department of Public Health has pertinent information (contact Sid Forman at 206/296-9736). Resources in Other Organizations Many other public agencies and organizations have developed water quality educational resources (including teacher training programs and curricula) that are available to Renton to use or adapt for use. Some of these are described below. King County Master Gardener Program—This program is sponsored by the Washington State University/Cooperative Extension - King County (contact Mary Robson at 206/296-4466). Local clinics or booths at local garden centers could be set up to answer questions about the proper use of pesticides and fertilizers to minimize surface water and ground water contamination. City of Bellevue Stream Team Program—This program involves citizens in caring for their neighborhood streams in individual watersheds and provides data on those streams to regulatory agencies. Participants attend a training workshop and receive a guide book, in addition to receiving a newsletter, videos, T-shirts, and brochures. Volunteers monitor water quality, participate in stream cleanup projects, learn about native plantings to control stream bank erosion, and stencil storm drains, among other activities (contact Nancy Hansen, education program manager for Bellevue Storm and Surface Water Utility at 206/451-4476). Adopt-a-Stream Foundation—This nonprofit organization promotes stream awareness around Puget Sound by providing educational materials for people interested in caring for streams and by teaching classes in "streamkeeping." The foundation has produced a video and sponsors activities such as river tours and whale watches. The group is currently developing an environmental education and interpretive center in Snohomish County, and plans to expand a workshop for teachers on the salmon life cycle that to date has been presented only in Snohomish County. The foundation also publishes a quarterly newsletter, Streamlines. The Renton School District is not currently involved with the Adopt-A-Stream Foundation, although individual teachers may have completed the training class. The foundation is open to working with the city of Renton upon request (contact Tom Murdoch or Martha Cheo at 206/388-3487). Metro Educational Materials—As part of its community salmon enhancement project, Metro has developed separate manuals for students, teachers, and community groups on raising salmon in the classroom. City of Seattle—The Seattle Aquarium's Puget Sound on Wheels program is designed for school groups of up to 200 students. The 45-minute presentation consists of an assembly and visits to 255C\LWTASK3 107 Herrera Environmental Consultants the traveling exhibit, which includes live animals. The numerous program topics include the state of the sound, marine wetlands, people and Puget Sound, marine plastic debris, and life cycle of the salmon. The Seattle Department of Parks and Recreation, in cooperation with the Marine Science Center in Poulsbo and Puget Sound Bank, distributes the Puget Soundbook and offers classes for kindergarten through grade 12 students. This program has been a part of Renton River Days in the past. More information for teachers is available from Cherie Williams (206/386-4353). Washington Department of Fish and Wildlife—The agency trains teachers and local volunteers about wildlife and aquatic habitats. Four workshops have been developed: Discover Wild Wetlands, Landscaping for Wildlife, Backyard Wildlife, and Project Wild. Workshops can also be tailored to the needs of a specific audience. Flyers are mailed from this office statewide, and the Math-Science Bulletin lists curricula from all over Washington (contact Margaret Tudor at 206/753-1702). Washington Office of Environmental Education—This agency operates under the state Superintendent of Public Instruction and provides teacher training, curriculum development, curriculum dissemination, and community environmental training. The agency sponsors the Teaching Resources for Environmental Education fair and publishes a catalog of its curriculum and audiovisual materials (contact Tony Angell at 206/365-3893). Options for Businesses Best Management Practices Brochure Either by mail or in person, locally generated or Metro/Independent Business Association (IBA) brochures about hazardous waste could be distributed to appropriate businesses in Renton. Targeted businesses should include automotive repair and body shops, aircraft service centers, small boat yards and repair shops, print shops, photo laboratories, and graphic arts firms (especially in the North Renton and West Hill basins). Workshop on Regulations and Best Management Practices Targeted workshops for businesses and industries on best management practices often are a helpful mechanism for two-way communication between business owners and public agencies. Businesses located within Renton's aquifer protection area already have been visited by city staff, Seattle/King County local hazardous waste management survey teams, or the Fire Department. Site audits or visits could be extended to other areas within the city, either using city staff or coordinating with the local hazardous waste management program(see water quality program discussion in Chapter 6). The annual Northwest Waste Information Expo, described in Chapter 6 under Existing Water Quality Efforts, provides valuable information to local businesses on waste management practices. The city should encourage local businesses to attend the exposition. 255C\LWTASK3 108 Herrera Environmental Consultants Resources in Other Organizations A number of other public agencies and business organizations have developed resources that pertain to businesses and have made them available for use in Renton. Many of these resources are described below. Independent Business Association—The IBA is a lobbying organization with 6,000 members in Washington. It provides reports and posters on hazardous waste disposal for businesses and conducts hazardous waste studies for automotive and marine repair and print shops. Its Small Business Center for Education has produced reports that outline waste problems and solutions for these industries. More information is available from Mardie Longstreth (206/453-8621). City of Bellevue—Bellevue received a state Centennial Clean Water Fund grant in 1990 to develop a program to train and certify businesses in water quality protection. This program, Business Partners for Clean Water, was intended to be a model for other jurisdictions. Four types of business are targeted: automotive, construction, building maintenance,and food service businesses (i.e., restaurants and food distributors and processors). Bellevue has developed a manual, a workshop, and a certification program for each industry. The businesses receive training in problem identification and applicable environmental regulations, and they are provided with information on sources for technical assistance. Bellevue has also developed extensive mailing lists, newsletters, press releases, and recruitment materials that Renton could use. The possibility exists that Bellevue could expand its program. The program manager is Julie Knott (206/637-5216). Automotive Service Association of Washington—The ASA has developed a waste management program aimed at auto shops that consists of workshops, a hazardous waste collection day at a local Pierce County facility, a poster campaign, and a 2-day trade fair demonstrating how to reduce the costs and liabilities of managing waste. In 1992, the ASA conducted eight statewide workshops on hazardous waste containment, stormwater quality control, and air quality. This program is available to any jurisdiction upon request. ASA also offers a stormwater workshop for automotive shops that focuses on such topics as where drainage water goes, how to find out how drains operate, how to test drains, and how to discharge legally. Beginning in March 1994, ASA is presenting a program that addresses solid waste, stormwater, hazardous waste, air quality, and site contamination issues. Workshops are arranged by Ted Slatten (206/581-2008). Recommended Public Education Program This section presents recommended public education activities that the city of Renton should conduct in the North Renton and West Hill drainage basins. These recommendations are based upon the findings of the monitoring and drainage basin characterization efforts completed as part of this study. Study results reveal that the two study basins, like other urban areas, experience a number of water quality problems, most of which are caused by diffuse sources associated with the intense level of human activity in the basin. 255C\LWTASK3 109 Herrera Environmental Consultants I Individual sources that could be easily controlled have not been identified. Although the water quality problems (e.g., exceedance of state standards for metals and fecal coliform bacteria, presence of oil sheens in runoff at select locations, and elevated phosphorus concentrations in stormwater) are not considered severe, it is important that the city develop a program for addressing these problems. Such programs, which include a public education component, are required under the Puget Sound Water Quality Management Plan and Ecology's Puget Sound stormwater management program (Ecology 1992a,b). Many of the recommendations presented below are directed at increasing public awareness of stormwater issues and providing information on best management practices for reducing stormwater pollution, as well as developing capabilities within city agencies to direct and manage these public education efforts. Public education efforts expected to be most effective for the city of Renton to pursue at this time are described in the following sections. As with all programs, it is critical that evaluation methods be developed to assess the effectiveness of any actions taken. Continual monitoring of the effectiveness of public education efforts will be an important part of future funding and proper coordination with other efforts. For this program, a survey of West Hill and North Renton businesses and residents could be taken, both before and after implementation (for example after 5 years). The survey would ask questions about people's awareness of water quality, proper household and business waste disposal practices, and city programs designed to reduce the amount of pollutants discharged to Lake Washington. The Renton Solid Waste Utility plans a telephone survey in 1995 to evaluate its education efforts. Stormwater topics could be included in that questionnaire to satisfy the needs of both programs. Other methods of evaluating effectiveness include tabulating the number and frequency of materials distributed, and the number of citizens and businesses reached. City staff s understanding of the public's general knowledge of program efforts would also be informative. Coordination with Comprehensive Storm and Surface Water Management Plan As the public education aspect of phase 2 of the comprehensive plan develops, activities should be coordinated with efforts in the West Hill and North Renton basins. It is expected that some of the public education activities recommended for the two Lake Washington study basins will begin before the comprehensive plan is completed. For example, the airport workshop is being conducted in June 1994 as part of this project. In addition, stenciling of catch basins and inlets in the North Renton and West Hill basins could be undertaken, if staff time is available to coordinate volunteer efforts. The results of these efforts should be provided to the comprehensive plan team for review and incorporation into the citywide plan. Many of the other recommendations should be adopted and implemented as part of the comprehensive plan. These other public education programs will require additional commitment of staff and funds. 255C\LWTASK3 110 Herrera Environmental Consultants Storm Drain Stenciling Program To raise public awareness and protect water quality, the city should pursue a storm drain stenciling program in the North Renton and West Hill basins as a pilot project for the entire city. If local residents are aware that catch basins discharge directly to local streams and Lake Washington, they may be less apt to dump waste materials into them or onto the ground adjacent to catch basins. Oily runoff and oily sheens were observed at several of the sites sampled in the North Renton and West Hill basins as part of this study. Catch basin stenciling may help alleviate some of these problems. Use of volunteers, which has been successful in other cities, is recommended. To avoid liability issues, volunteers should be required to sign a waiver. A sample waiver form used by the city of Seattle is presented in Appendix G. It may be necessary for volunteers to carry a city permit in case they are questioned while stenciling. Volunteers can be solicited by advertising in newspapers; in community catalogues and calendars; and with community councils and groups, chambers of commerce, Boy Scouts and Girl Scouts, and local schools (teachers can sign the waiver). The city could also require developers and contractors to apply the stencils on newly constructed catch basins or in areas near construction activity. Volunteers should be provided with a stencil, water-based paint, a safety jacket ($6 to $11), a safety staff and flag, disposable latex gloves ($6 to $7 per box), a steel-toothed brush and whisk broom to clean drains, plastic 50-gallon bags for garbage and for carrying the stencil from drain to drain, and a 5-gallon bucket to carry materials. The Public Works Department should provide maps showing locations of the drains to be stenciled. Ecology can provide free cardboard stencils that can be used for a single application. Reusable plastic stencils are available for about $11 each from Image Fabrication (contact Ann Scovil at 206/682-4467, 3931 First Avenue South, Seattle 98134). Stenciling should proceed during dry months, because the paint does not adhere well to cold or wet metal. The water-based, pump- spray paint (Seymour brand, 12 cans per case, good for 8 to 16 stencils per can) lasts about 6 months, so stenciling is recommended twice annually in both spring and fall. This program would require a utility staff person's part-time involvement to coordinate the volunteer effort and to keep track of areas requiring stenciling. Best Management Practices Workshop for Airport Tenants A workshop focusing an best management practices is recommended for tenants of the Renton Municipal Airport. As described earlier, runoff from the airport discharges to Lake Washington via the Black River culvert. Catch basins along the runway and tarmac, which are plumbed directly to the culvert, are not equipped with spill containment capability. Consequently, there is little opportunity to prevent spills that may occur at the airport from reaching Lake Washington. Because of the types of activities associated with normal airport operations, the potential for spills and or accidents to release pollutants into the nearby drainage system is relatively high. Potential sources include operator refueling of private airplanes, aircraft maintenance, aircraft washing, and aircraft deicing operations. 255C\LWTASK3 l l l Herrera Environmental Consultants The workshop, to be conducted as part of this study, will emphasize best management practices to minimize the potential for stormwater pollution. Topics to be presented include regulatory requirements; best management practices for waste handling, storage, and disposal; spill response and reporting procedures; and opportunities for structural controls. The workshop is scheduled for June 1994. All tenants and their sublessees will be invited. The workshop will be coordinated with the airport manager and the Surface Water Utility. After the workshop, the utility should continue to encourage the airport tenants to implement best management practices. Follow-up discussions with the tenants should be conducted as part of the routine meetings between the tenants and the airport manager. Interdepartmental Briefing on Program Coordination It is recommended that an interdepartmental meeting be held at least once each year to coordinate the efforts of the various Renton city agencies that are involved in some form of environmental education, inspection, or other related programs. This meeting would provide an opportunity for city staff members to brief each other on their programs, results, and plans for the future. It is expected that coordination will improve the efficiency of city public education efforts by reducing the amount of overlap between programs and by sharing information on the types of programs that prove to be most effective. Environmental Education Coordinator It is recommended that the city evaluate the feasibility of devoting a full-time staff position to environmental education. This position would coordinate efforts of all the city agencies involved in environmental education (see above). In particular, coordination between Surface Water Utility projects dealing with stormwater quality and the Water Utility aquifer protection program will be needed to ensure that these two programs are consistent. In addition, the coordinator should also serve as a clearinghouse for information on environmental issues, using the extensive resources of environmental publications and programs that have already been developed by many local agencies (e.g., Ecology, Metro, and King County). The position would be responsible for specific city public education projects, such as developing and producing informational brochures, coordinating preparation of environmental articles and notices for a city newsletter and bill inserts, conducting workshops and special events, and coordinating environmental education projects with the Renton school district. School Curriculum Programs Education efforts directed toward children can be very effective in developing environmentally conscious attitudes throughout the community. It is recommended that the Surface Water Utility work with local schools to incorporate water quality and stormwater pollution topics into science programs. Renton High School is the ;losest school to the North Renton and West Hill basins. 255C\LWTASK3 112 Herrera Environmental Consultants Two of the science instructors (Ava Holm-Anderson and Bill Gaines, at 235-2294) already present water quality issues as part of the curriculum. One option would be to have a representative from the utility present information on the utility and stormwater issues to science classes once each quarter. Another option would be to coordinate efforts with Metro to present both stormwater and hazardous waste issues. Metro has a public education program (part of the local hazardous waste management program) that includes educational presentations on household hazardous waste, and the agency could assist Renton in developing a stormwater program. Metro also conducts classroom presentations on request and may be willing to work with Renton to incorporate stormwater issues into the presentation. If possible, the city should take advantage of this existing program. Public Informational Media The public education program should be directed toward the local community, to increase public awareness of stormwater issues. Brochures, newsletters, or utility bill inserts should be used to disseminate information about the Surface Water Utility stormwater program, to advise customers about upcoming activities, and to inform residents about stormwater issues and encourage them to implement best management practices. Production and distribution of a brochure describing the Surface Water Utility program and expected projects that will be undertaken in the future to improve stormwater quality would be appropriate as a first step in a public education campaign. Future topics could then target specific stormwater issues and solutions. A questionnaire dealing with environmental issues (including stormwater concerns) has been distributed to the community as part of the comprehensive plan development process. The intent of the questionnaire was to identify the level of understanding and concern within the community and to develop a mailing list of interested residents and business. This list could be used to distribute Surface Water Utility publications. However, to reach a larger audience, it is recommended that the utility explore the possibility of using the existing city newsletter to support future informational exchanges. The utility could thereby take advantage of mailing and distribution mechanisms that are in place and possibly could share the cost of mailing. Because there is limited space available on utility bills, this vehicle may be most effective for short messages, such as announcements of upcoming events like household hazardous waste collection days. For example, a reminder to recycle used motor oil that includes a list of local oil recycling centers (or a telephone number to contact for further information) could be included with an autumn utility bill, when many people are preparing to winterize their vehicles. STRUCTURAL CONTROLS FOR STORMWATER TREATMENT A number of structural controls have been developed to treat urban stormwater runoff. Most treatment systems rely primarily on physical processes such as sedimentation and filtration and are therefore more effective in removing particulates and particulate-bound pollutants than 255C\LWTASK3 113 Herrera Environmental Consultants dissolved pollutants. Some treatment systems can incorporate chemical and biological processes to achieve soluble pollutant removal. However, these mechanisms are typically more difficult to control than physical processes. As a result, removal of soluble pollutants is generally harder to achieve and requires significantly more complex and expensive treatment systems. Many new stormwater treatment technologies are emerging as research efforts provide better information on pollutant removal mechanisms and yield improved design criteria. A list of available structural controls for treating urban runoff is provided below: ■ Biofiltration swales and strips ■ Wet vaults and tanks ■ Infiltration basins and trenches ■ Constructed wetlands ■ Compost filters ■ Catch basin inserts ■ Peat and sand filters ■ Sediment traps ■ Wet ponds ■ Oil/water separators. Selection of the appropriate treatment technique for a given situation is contingent on the types of pollutants to be removed, available space, cost, and maintenance concerns. Under the Renton Storm and Surface Water Drainage Ordinance, most new development and redevelopment projects in the North Renton and West Hill basins are required to incorporate stormwater controls. The ordinance specifically adopts the King County Surface Water Design Manual, which specifies requirements and design criteria for stormwater treatment facilities. Any project that results in more than 5,000 square feet of new impervious surface subject to vehicular use or chemical storage is required to provide biofilters for stormwater treatment. In certain instances, projects with greater than one acre of impervious surface must also install wet ponds. Because structural controls are specifically required only for new and redevelopment projects, this section focuses on options for retrofitting existing drainage structures to improve stormwater quality. A discussion of structural control alternatives must consider the types of pollutants to be targeted for removal. Based on the results of stormwater and sediment sampling efforts, the following pollutants of concern have been identified in the North Renton and West Hill basins (see Chapter 2). North Renton West Hill Metals (antimony,'cadmium,a copper, Metals (antimony,a cadmium,a copper, lead, lead, mercury,a nickel,a silver,a mercury,a nickel,'silver,'and zinc) and zinc Fecal coliform bacteria Fecal coliform bacteria Total phosphorus Total phosphorus pH Total petroleum hydrocarbons Chrysene Chrysene PAHa PAHa Phthalatesa Phthalatesa PCBsa PCBsa Elevated in offshore sediment samples. 255C\LWTASK3 114 Herrera Environmental Consultants Structural controls implemented in the North Renton and West Hill basins should be capable of effectively removing these contaminants. In most cases, options for retrofitting existing drainage structures are limited because of site constraints such as grading requirements and land availability. Therefore, the discussion of stormwater treatment technologies for the Renton/Lake Washington drainage basins focuses on the following technologies, which can be incorporated into existing drainage facilities: ■ Biofilter ■ Compost filter ■ Oil/water separator ■ Sediment trap ■ Catch basin insert ■ Wet pond. The following sections provide brief descriptions of each of these stormwater treatment methods, their expected pollutant removal performance, and possible applications in the North Renton and West Hill basins. Biofilter Two types of biofilters are commonly used in stormwater treatment applications: biofiltration swales and vegetated filter strips. Both are land treatment systems that rely on both the capability of vegetation to filter pollutants from shallow overland flow, and the hydraulic characteristics of the swale or filter strip which retard the velocity of runoff, thus promoting sedimentation and infiltration. The primary difference between swales and filter strips is that swales receive concentrated stormwater flows such as discharges from storm drains or conveyance ditches, while filter strips receive unconcentrated sheet flow such as runoff from the edge of a parking lot. Biofilters typically serve both conveyance and treatment functions. However, for biofilters to be effective, it is important that they be designed so that the plant height is always greater than the depth of flow, and so that the velocity of stormwater as it moves though the system is low enough to prevent vegetation from bending over and becoming submerged below the flow surface. Swales are broad channels that are designed to spread stormwater flows over a wide, flat cross- section to reduce the velocity and promote contact with the vegetation. The longitudinal slope of a swale should be greater than 1 percent to convey flows, but not overly steep, to prevent erosion damage and to provide for adequate contact time between runoff and vegetation. Slopes of 2 to 4 percent are generally recommended (Metro 1992). If the slope is too great, check dams can be installed in swales to retard water flow rate, thereby increasing swale performance. Filter strips are broad vegetated surfaces over which stormwater runoff drains in sheet flow. One disadvantage of filter strips is the difficulty in maintaining sheet flow due to the tendency for rills and channels to form, as a result both of unevenly distributed stormwater and of excessive flows that stimulate erosion. Like swales, filter strips should not be constructed on 255C\LWTASK3 115 Herrera Environmental Consultants steep slopes where it is difficult to evenly distribute flows across the filter. It is generally recommended that filter strips be used only in locations with drainage areas of less than 5 acres and with slopes of less than 10 percent (Ecology 1992a). Pollutant Removal Mechanisms of Biofilters Biofilters are primarily successful in removing particulates and particulate-bound pollutants through filtration and sedimentation. To a lesser extent, biofilters can remove dissolved pollutants through biological and chemical mechanisms. Biological removal occurs through plant uptake and microbial degradation (Spangler et al. 1977; Howard-Williams 1985). Examples of biological removal include the assimilation of dissolved nutrients into vegetation to support plant growth, and microbial degradation of oil and grease particles that adhere to grass blades. Chemical pollutant removal processes in biofilters include adsorption, complexation, and precipitation of pollutants in the soil profile. Biological and chemical removal processes are believed to play a limited role in biofilter performance, because runoff travels through biofilters relatively quickly, resulting in inadequate detention time for these processes to occur (Schueler 1987). Biofilter Performance Pollutant removal efficiencies in biofilters are highly dependent upon hydraulic capacity and vegetative quality. A number of studies have been conducted to evaluate the effectiveness of biofiltration swales in removing pollutants from urban runoff. Although removal efficiencies can be quite variable, overall results indicate that swales and filter strips are effective in removing particulates and particulate-bound pollutants, as well as some soluble pollutants (Schueler 1987). Metro (1992) studied a swale receiving runoff from 14.7 acres of primarily single family residential development that was constructed according to King County standards. Removal efficiencies were high for most metals (63 to 72 percent for total aluminum, iron, lead, and zinc) and total suspended solids (83 percent) but were low for total phosphorus (29 percent) and dissolved metals (0 to 30 percent). In a similar study,Wang et al. (1982) found that swales were effective in reducing metals concentrations in highway runoff. Removal efficiencies for total copper, lead, and zinc were high, ranging from 53 to 71 percent, 81 to 87 percent, and 57 to 94 percent, respectively. The U.S. EPA (1993b) has compiled available information on pollutant removal efficiencies of various stormwater treatment control technologies from numerous studies conducted throughout the United States. Average removal rates for biofiltration swales and vegetated filter strips are shown in Table 29. These data are similar to those collected by Metro (1992) and Wang et al. (1982), suggesting that swales are effective in removing suspended solids and total metals but are of only moderate use in removing nutrients. 255C\LWTASK3 116 Herrera Environmental Consultants Applicability of Biofilters in North Renton and West Hill Basins Although it does not appear that the roadside ditches serving many of the residential areas in the North Renton and West Hill basins have been specifically designed as biofilters, it may be possible to modify some of these ditches to enhance biofiltration function. City maintenance crews should survey the two basins to identify sites where it is feasible to incorporate biofiltration features into the existing conveyance structures. The following factors should be considered: ■ Channel geometry. Ideally, for biofiltration to be effective, the ditch should be fairly broad with shallow side slopes (1:3 side slope) to evenly distribute the flow across a shallow depth. Narrow, steep-sided ditches are not suitable unless there is sufficient space to recontour and broaden the channel. In these cases, it may be more realistic to simply stabilize the ditch to prevent erosion during high flows rather than attempt to incorporate biofiltration. ■ Longitudinal slope. As described above, channel slope should be on the order of 2 to 4 percent to prevent erosive conditions from developing and to allow stormwater to gently flow through the swale, thus providing adequate contact time for biofiltration to occur. Many of the existing roadside ditches meet this requirement with little if any modification. Others would require that check dams be installed approximately every 50 feet along the length of the ditch to reduce channel gradient. If check dams are required, the utility should contact adjacent property owners to explain the purpose of these check dams and to enlist their support in maintaining the ditch. ■ Vegetation. Ditches should be seeded with fine, close-growing water- resistant grasses, or with emergent wetland plants where slopes are shallow, resulting in long periods of saturation. Recommended seed mixtures for various applications are provided in section 5.5.4 of the King County (1990) Surface Water Design Manual. Both capital costs and operation and maintenance costs are moderate to high for biofilters. Table 30 summarizes information on permitting, regulatory compliance, costs, and urban applicability of biofiltration swales. Opportunities for retrofitting other existing structures in the North Renton and West Hill basins are somewhat limited due to space restrictions. A brief summary is provided below of potential biofiltration retrofit options for Coulon Beach Park, the Greater Highlands Mall, and Renton Municipal Airport. Coulon Beach Park Currently, stormwater runoff from the entire North Renton basin is routed through a series of open ditches prior to discharge to Lake Washington. It may be possible to modify these conveyance channels, most of which are located in or near Coulon Beach Park, to enhance their 255C\LWTASK3 117 Herrera Environmental Consultants biofiltration capacity and thereby improve the quality of stormwater discharged to Lake Washington. Installing treatment facilities at the downstream end of a drainage system is not usually advisable because of the large flow rates that must be accommodated. However, in this case the channel modifications required for biofiltration would also improve the habitat value for fish and other aquatic organisms. The existing sections of open channel would need to be redesigned, regraded, and replanted with appropriate vegetation. Because the areas that could be modified are located at the downstream end of the system, the primary concern would be to enhance biofiltration capacity without reducing the existing hydraulic capacity. It may be possible to reconfigure the channel cross- section, incorporating a biofiltration swale at the base of the channel to treat smaller flows, with a broad overflow channel above the swale for conveyance of runoff from large storm events. In addition, a flow spreader would need to be constructed at the head of the swale where the culverts from the various subbasins in the North Renton basin converge, to assure even distribution of flow. Greater Highlands Mall This large retail shopping center is located on the north side of Sunset Boulevard near Kirkland Avenue NE in the North Renton basin (see Figure 2). Parking is provided in a large paved lot located immediately south of the mall, between the mall and Sunset Boulevard. The lot has been graded to drain to several evenly spaced catch basins located in the center of the parking lot. There appears to be adequate space along the catch basin corridor to replace the existing piped system with a grass-lined swale without reducing parking capacity. The swale would treat the runoff from the parking area before it enters the city storm drain system. Runoff from roadways and parking lots typically contains elevated concentrations of total suspended solids, metals, and petroleum hydrocarbons, which biofilters are effective in removing. Although this site was not specifically targeted as part of the sampling effort for this project, the stormwater sample collected from station NR5, which is located well downstream of this site, contained elevated concentrations of copper, lead, zinc, and total petroleum hydrocarbons. The mall and associated parking areas are privately owned. Therefore, negotiation with the property owners would be required before modifying the existing system. Renton Municipal Airport Open, grass-lined depressions are located along both sides of the runway, providing some treatment for airport runway runoff. Runoff from the runway passes through these areas before being collected in catch basins and piped to adjacent waterways (i.e., the Cedar River and Lake Washington). The Surface Water Utility should coordinate with the airport manager to assess the condition of these grass-lined areas, identify appropriate maintenance procedures, and determine whether the areas should be modified to improve performance. 255C\LWTASK3 118 Herrera Environmental Consultants There may also be adequate space in several areas along the fence line on the western border of the airport property where grass filter strips or swales could be constructed to treat runoff before it discharges to the Black River culvert. Runoff from these areas, which are currently occupied by independent operators who repair, maintain, and refuel aircraft, is currently collected in a series of catch basins located near the fence line. It appears that some of the catch basins could be replaced with biofilters without disturbing the existing facilities. Compost Filter Leaf and vegetative waste compost filters are a relatively new, experimental technology for treating stormwater that has been developed and patented by W&H Pacific (1993). These systems treat stormwater by routing it across a swale (in a surface system) or through a filter (in a vault) containing composted leaf and vegetative waste. Pollutants present in the stormwater adsorb onto the composted vegetation media and are retained in the swale or filter. These systems are desirable not only because they treat stormwater but also because they create a practical use for recycled yard waste. The composting filter can be incorporated into an existing biofiltration swale either by lining the base of the swale with compost material or by inserting a compost filter into an existing vault or catch basin. Given the nature of the existing storm drain system in the North Renton and West Hill basins, the second option appears to be the most practical as a retrofit option. To prevent overflows, a bypass structure must be incorporated into the insert to allow runoff from larger storm events to bypass the filter. Annual maintenance of the compost system is required to maintain performance (Lenhart 1993 personal communication). Typically, the compost material is removed and replaced periodically as it becomes clogged with accumulations of fine-grained sediment and debris. In some instances only the top layer of fine sediments would need to be scraped off to restore effective filter permeability (W&H Pacific 1993). It is also important to prevent grass from growing in compost beds because it decays into a slime that clogs the filter (Lenhart 1993 personal communication). Pollutant Removal Mechanisms of Compost Filters Pollutants are removed by filtration, cation exchange, adsorption, and biodegradation (W&H Pacific 1993). Like biofilters, compost systems are capable of filtering out many of the particulates and particulate-bound pollutants present in urban runoff. Many pollutants, particularly metals and polar organic compounds, can be effectively removed by cation exchange. Cation exchange is a chemical process where negatively charged surfaces in the organically rich compost attract and bind the positively charged pollutant compounds. Soil cation exchange capacity generally increases with increasing organic matter content. Therefore, compost material that is composed primarily of leaf and vegetative material exhibits a large cation exchange capacity. 255C\LWTASK3 119 Herrera Environmental Consultants The relatively large surface area afforded by the compost material also provides effective treatment, because many urban pollutants tend adhere to particulates and become bound to the surface of the compost. Pollutants such as oil and grease and total petroleum hydrocarbons (PAH), which are trapped in the compost, are eventually degraded by microorganisms present in the compost material. Compost Filter Performance Leaf and vegetative waste compost systems are relatively new and have not been subjected to extensive field tests. Performance tests conducted on a prototype facility constructed in Portland, Oregon by W&H Pacific (1993) have shown favorable results for metals, oil, and grease (Table 29). The prototype facility consists of a 100-foot by 16-foot swale lined with composted vegetation in which several baffles have been constructed to allow stormwater to accumulate to depths of about 1 foot over the filter material. The facility receives runoff from a 27-acre basin and is designed for a peak hydraulic loading of 6.7 cfs. To evaluate filter performance, samples were collected upstream and downstream of the prototype facility during six storms that occurred between September 1992 and March 1993. The compost filter was effective in removing turbidity (73 percent), total suspended solids (85 percent), metals (88 percent for total copper, 85 percent for total lead, and 76 percent for total zinc), and oil and grease (86 percent). However, with the exception of ammonia, the filter was generally ineffective in removing nutrients. For example only 19 percent of the total phosphorus present in the stormwater was removed by the filter. Negative removals were observed for other nutrients, particularly those that were present as anions (i.e., soluble phosphorus and nitrate). To date, no tests have been conducted on a drop-in filter unit that can be inserted into a stormwater detention vault or possibly into an existing catch basin. Performance of a vault system should be comparable to the swale/pond system, provided the vault and filter are sized appropriately for the expected stormwater flows. W&H Pacific is currently developing drop-in vault units of various sizes, the largest about 8 feet by 18 feet (Lenhart 1993 personal communication). Applicability of Compost Filters in North Renton and West Hill Basins Information on permitting, regulatory compliance, costs, and urban applicability of leaf and vegetative waste compost filters is summarized in Table 30. Drop-in filters are particularly suited to retrofitting existing drainage structures that serve parking lots and commercial areas where available space to construct treatment facilities is limited. In addition, available performance data, while limited, indicate that compost filter systems would effectively remove the primary pollutants of concern associated with these areas (i.e., metals, oil, and grease). Drop-in filters must be small to fit inside most existing underground detention vaults and to facilitate access for maintenance operations. Most manholes are likely too small and would have to be replaced with a larger vault. Because of the hydraulic characteristics of the compost media, compost filter applications are limited to small catchment areas where the peak runoff rates are low. 255C\LWTASK3 120 Herrera Environmental Consultants As a retrofit option, a primary consideration is the possible reduction in hydraulic capacity caused by the filter insert. Filter insert design should evaluate the proportion of runoff that passes through the filter for treatment versus the percentage that is bypassed due to hydraulic characteristics of the compost material. W&H Pacific has developed inserts of various sizes for detention vaults. Design capacities for these package units are listed below(Lenhart 1993 personal communication): Design Capacity Insert Size (cfs) 6 feet by 12 feet 0.4 8 feet by 18 feet 0.6 For larger basins, it may be possible to install several filters. However, the feasibility of using these systems will likely be dictated by the amount of space available for construction and the added cost associated with installing multiple vaults. Compost filter inserts must be evaluated on a case-by-case basis, taking into consideration the characteristics of the contributing area and the hydraulic requirements of the drainage system. For largely impervious areas like parking lots, one of the compost filter inserts described above would be capable of treating runoff from about a 2-acre area, assuming that runoff from only the standard Ecology water quality design storm (i.e., the 6-month, 24-hour storm) is passed through the filter and that larger storms are allowed to overtop the filter without being treated. Areas where runoff commonly contains high concentrations of oil, grease, and metals should be evaluated to determine whether installation of a compost filter is feasible and appropriate. These experimental units require regular maintenance, and in urban areas like Renton they would be suitable only for relatively small catchment areas of less than 4 acres. For these reasons it is recommended that other abatement opportunities, particularly source control, be explored before considering compost filter inserts. In addition, it is suggested that Renton consider testing a small prototype installation to determine whether these units would be compatible with city storm drain maintenance operations. Based on land use characteristics and available data on stormwater quality, several potential areas that could be considered for use of compost filters in the North Renton and West Hill basins have been identified. The highest concentrations of petroleum hydrocarbons measured during this study were observed in the stormwater samples collected from subbasins N4 and N6 in the North Renton basin (see Figure 2). Runoff from these basins also exhibited elevated concentrations of metals (copper, lead, and zinc exceeded the acute toxicity criteria for aquatic life). Although this study did not identify the specific sources of these contaminants, shopping centers and other commercial properties that require large parking areas are likely contributors of these contaminants because of the high vehicular use associated with these sites. Two shopping centers, Sunset Plaza and the Highlands Shopping Center, are located along Sunset Boulevard in subbasin N6. A potential site that may be suitable for installation of a 255C\LWTASK3 121 Herrera Environmental Consultants compost filter has been indentified at the Sunset Plaza property, which is located on the north side of Sunset Boulevard between Kirkland Avenue NE and Monroe Avenue NE (subbasin N6, see Figure 2). Sunset Plaza contains numerous retail facilities including Pay Less Drug Store, Thriftway, and Sunset Video. Parking is provided in a large lot that extends along the entire east side of the shopping center, facing Sunset Boulevard. A smaller parking lot is located behind the buildings at the southwest corner of the property. The larger lot slopes to the west; runoff is collected in a series of catch basins and routed to the southwest corner of the property where it merges with runoff from the rear parking lot. From this point, the storm drain runs to the west along NE 13th Street where it discharges into a larger trunk line on Kirkland Avenue NE. There is a large catch basin in NE 13th Street just beyond the Sunset Plaza property where a drop-in compost system could be installed to treat runoff from the entire shopping center (approximately 5 acres). Capital costs to excavate the roadway and install a vault with a compost filter may be moderate to high. A similar unit could also be installed in the shopping center where runoff from the two parking lots merges, but this would entail construction on private property. The North Renton and West Hill basins also contain a variety of other commercial and multifamily developments that may be suitable for installation of a compost filter (see Figures 5 and 6). Commercial development in the North Renton basin is generally concentrated in a narrow strip along Sunset Boulevard. Commercial development in the West Hill basin is generally confined to the Rainier Avenue corridor. Residential apartment complexes are located throughout the subbasins. Storm drains serving apartment complexes experiencing oil and grease contamination are ideal sites for installation of compost filters or oil/water separators (described in the following section). Oil sheens were detected in the stormwater runoff from at least one apartment complex in the West Hill basin (located at the intersection of Taylor Avenue and Renton Avenue). Other areas where retrofitting existing drainage structures with compost filters may be warranted include the SR-405 corridor in the North Renton basin, and the Renton Municipal Airport in the West Hill basin. Highway runoff typically contains elevated levels of metals, suspended solids, and oil and grease, which the available data indicate can be effectively removed by compost filters. Currently, runoff,from SR-405 proceeds directly to Lake Washington with no treatment. Retrofitting drainage structures in the SR-405 system should be considered only if runoff from SR-405 can be isolated and treated before it discharges into the city drainage system and combines with runoff from other parts of the basin. Further evaluation of the SR-405 storm drain system is needed to determine the practicality of installing compost filters for treating highway runoff. The utility should coordinate with the Washington Department of Transportation to evaluate opportunities for retrofitting the SR-405 storm drains. Similarly, most of the runoff from the airport is routed without treatment to the Black River culvert and discharges directly to Lake Washington. Small catchment areas at the airport where aircraft are maintained or frequently refueled may be suitable for retrofitting. Further evaluation of airport operations is required to identify potential sites where installation of compost systems may be warranted. 255C\LWTASK3 122 Herrera Environmental Consultants Oil/Water Separator There are two types of oil/water separators: the conventional gravity separator and the coalescing plate separator. The conventional gravity separator consists of a large vault equipped with baffles that prevent oil and other floating debris from passing through the separator. The coalescing plate separator is similar to the conventional gravity separator except that a bank of closely spaced parallel plates is inserted in the separator chamber to improve removal efficiency. Oil and grease are retained within the separator and must be removed periodically. Pollutant Removal Mechanisms of OiUWater Separators Oil is less dense than water and tends to float to the surface. Oil/water separators are designed to provide quiescent flow conditions so that globules of free oil present in the stormwater can rise to the water surface and coalesce into a separate oil phase, which can then be removed. Separators can effectively remove free oil that is present in the form of discrete oil globules; emulsified and dissolved oils are not effectively removed in conventional or coalescing plate separators. Separators are designed to provide the necessary hydraulic retention time to allow oil globules to float to the surface and become trapped in the chamber before being flushed out of the separator. Conventional gravity separators are typically effective in removing oil globules with a diameter of 150 microns or larger (API 1990). Coalescing plate separators are generally designed to remove oil globules with a diameter of 60 microns or larger (API 1990). The plates increase the surface area of the separator and may also reduce short-circuiting and turbulence, thus improving efficiency. OiMater Separator Performance Oil/water separator performance is largely dependent on the size distribution of oil globules present in the stormwater runoff. Performance also depends on the size of the storm event, which affects the retention time of stormwater in the separator. Ecol•)gy (1992a) requires that oil/water separators be designed to treat runoff from the 6-month, 24-hour design storm. Few data are available to assess the performance of oil/water separators currently in operation for stormwater treatment. However, limited information on the size distribution of globules in runoff from oil refineries is available (RPA 1989) and can be used in conjunction with separator design criteria to estimate overall removal efficiency. A conventional gravity separator designed to remove 150-micron oil globules is capable of removing approximately 40 percent of the total volume of oil in the incoming stormwater, while a coalescing plate separator designed to remove 60-micron oil globules is capable of removing approximately 80 percent of the oil. The U.S. EPA (1993b) has compiled available information on pollutant removal efficiencies of various stormwater treatment control technologies from numerous studies conducted throughout the United States. Available data, although limited, indicate that oil/water separators are ineffective in removing most pollutants present in urban runoff. Removal efficiencies for suspended solids, metals, and nutrients are on the order of only 5 to 15 percent (see Table 29). 255C\LWTASK3 123 Herrera Environmental Consultants Capital costs and operation and maintenance costs of oil/water separators are low to moderate. Table 30 summarizes information on permitting, regulatory compliance, costs, and urban applicability of oil/water separators. Applicability of Oil/Water Separators in North Renton and West Hill Basins Oil/water separators are designed primarily to remove petroleum compounds and other floatable material. These systems are usually small and can be easily retrofitted into an existing stormwater drainage system. Likely locations for their installation in Renton are areas where levels of petroleum compounds or oil and grease in stormwater are known to be high (e.g., subbasins N4, N6, and W3) or suspected to be high (e.g., the municipal airport, commercial parking lots, and multifamily residential parking lots). Sites suitable for installation of oil/water separators are similar to those identified in the previous section for leaf and vegetative waste compost filters: ■ Commercial areas in subbasins N4 and N6 along Sunset Boulevard in the North Renton drainage basin where concentrations of petroleum compounds in stormwater samples were elevated (further investigation of these areas is needed to identify appropriate sites, e.g., large parking lots, automotive repair and maintenance facilities, and auto parts stores) ■ Apartment complexes in both the North Renton and West Hill basins where oil sheens or other evidence of illegal dumping of oil from home auto repair activities has been observed ■ Commercial areas along Rainier Avenue in the West Hill basin where businesses are involved in activities that may generate oily wastes (e.g., auto repair shops and junk yards) ■ Areas at the Renton Municipal Airport that are used for aircraft refueling and aircraft maintenance. Sediment Trap A sediment trap is a catch basin designed with a small reservoir or trap to retain sediments that settle out in the structure. Catch basins can be either off-line or on-line. Off-line catch basins contain small sumps, usually 2 to 3 feet wide and 2 to 4 feet deep, and receive runoff only from the immediate watershed prior to passing the water into the main storm drain. On-line catch basins are larger, usually 4 to 8 feet in diameter, with a sump approximately 2 to 4 feet deep below the invert of the outlet, to handle the main storm drain flow. 255C\LWTASK3 124 Herrera Environmental Consultants Sediment Trap Performance Sediment trap performance is shown in Table 29. Cleaning frequency appears to be the primary factor influencing sediment trap performance. Pollutants are effectively removed only when there is adequate dead storage in the sump to promote sedimentation and prevent previously accumulated sediments from being resuspended and transported out of the system. Sediment traps remove only the coarse-grained sediments (e.g., sand and gravel) and allow the smaller silt and clay fractions to pass through the system. Because of their larger surface area, fine-grained sediments usually contain a greater concentration of pollutant than coarse-grained sediments on a weight basis. Therefore, it is unlikely that catch basins are highly effective in removing many of the particulate-bound pollutants present in urban runoff(e.g., metals, organic contaminants, and phosphorus). Average removal rates for sediment traps are shown in Table 29. Capital costs and operation and maintenance costs are moderate. Table 30 summarizes information on permitting, regulatory compliance, costs, and urban applicability of sediment traps. Applicability of Sediment Traps in Renton Based on observations made during field-verification of city drainage system maps and surveying of possible illicit connections to the storm drain system, it appears that most catch basins and manholes in the Renton system are already equipped with sediment traps. However, because sediment traps are small structural control systems that can be easily retrofitted into existing systems, city crews conducting routine maintenance operations should take note of any structures that do not have sumps, particularly in privately owned systems that should be modified. Catch Basin Insert A catch basin insert is a filter that can be inserted into an existing catch basin to remove sediment and some particulate-bound pollutants from runoff. Local suppliers (e.g., Enviro- Drain in Kirkland and Stormwater Services Corporation in Lynnwood) manufacture inserts that are designed to fit into standard type I and type II catch basins. Typically, the insert consists of an upper tray or screen that serves as a sediment trap and a lower tray that is filled with a filter medium for removing particulates as well as some dissolved pollutants. The insert is equipped with a bypass structure to route runoff around the filter trays, both to prevent the catch basin from overflowing if the filter becomes clogged and to handle runoff from large storm events. Pollutant Removal Mechanisms of Catch Basin Inserts Catch basin inserts function by physically filtering and chemically adsorbing pollutants present in runoff. Filtration occurs as stormwater percolates through successive layers of filter material. The upper layer consists of either a screen or filter material (e.g., felt) designed to remove sediment and larger particles. An oil-absorbent material can also be used to remove oil, grease, and other floatables. Removal in the lower trays is dictated by the type of media used. Available media include cellulose fibers that selectively adsorb oil and other hydrophobic materials, and activated carbon for removing organic compounds. 255C\LWTASK3 125 Herrera Environmental Consultants Catch Basin Insert Performance Because catch basin inserts are a relatively new and experimental stormwater treatment technology, there has been little field experience to evaluate performance and maintenance requirements of these devices. The King County Surface Water Management Division recently installed an insert (obtained from a local supplier) in a catch basin at a gas station in south King County. This insert consisted of an upper coarse filter screen, followed by a lower tray containing a natural cellulose fiber to adsorb oil. Initial testing conducted during two storm events indicated that removal of metals (total copper, lead, and zinc) was fairly low (5 to 21 percent). No removal of dissolved metals was observed. However, during the field studies, it was observed that a large portion of the runoff was bypassed around the filter, indicating that the insert was undersized (Koon 1994 personal communication). To better understand the effectiveness of catch basin inserts, King County, Metro, the city of Seattle, the Port of Seattle, and Snohomish County are currently developing a large-scale program to field-test several commercially available inserts on a variety of land uses. Inserts will be installed in type I catch basins (18- by 24-inch size) at Metro park-and-ride facilities, gas stations, county maintenance facilities, and Port of Seattle work yards. Several filter media will be tested, including wood fiber pulp, cellulose fiber, polyester fibers, nonwoven filter fabric, and activated carbon, to evaluate their ability to remove total suspended solids, oil, grease, total and dissolved metals (copper, lead, and zinc), and total phosphorus. Results of the study are expected to be available by June 1994 (Koon 1994 personal communication). Applicability of Catch Basin Inserts in North Renton and West Hill Basins Information on urban applicability and costs of catch basin inserts is summarized in Table 30. Because field experience with catch basin inserts is limited, these systems should be considered only under the following circumstances: ■ Where source control efforts have been implemented in accordance with standard practices but have failed to significantly reduce stormwater pollutant loading ■ Where the contributing area is small, well defined, and under the control of a single business or ownership ■ Where qualified personnel are available and committed to monitoring and maintaining the inserts. The city should also consider installing and testing a commercially available insert on city property, possibly at the city maintenance yard, before making recommendations for use on private property. Even if additional tests indicate that catch basin inserts are effective and suitable for use on private storm drain systems, the city should implement an aggressive inspection program to document that these private installations are properly maintained. 255C\LWTASK3 126 Herrera Environmental Consultants Wet Pond and Wet Vault A wet pond or wet vault contains a large permanent pool (i.e., dead storage) that functions as an energy dissipater, slowing the velocity of incoming stormwater to allow suspended solids to settle. In addition, in wet ponds, and to a lesser extent in wet vaults, the dead storage provides a suitable environment and adequate hydraulic residence time to promote biological and chemical reactions. Removal Mechanisms of Wet Ponds and Vaults Wet ponds and wet vaults function primarily as sedimentation facilities, removing a high percentage of the suspended sediment and associated particulate-bound pollutants from stormwater runoff. Removal of soluble pollutants in wet ponds occurs via biological processes (e.g., microbial degradation or plant uptake) and chemical processes (e.g., adsorption, chemical complexation, or precipitation). Wet vaults are generally not effective in removing soluble pollutants because of the absence of plant biomass, soil adsorption sites, and sunlight, which are necessary for most of these biological and chemical processes to occur. In addition, some additional pollutant removal can occur in wet ponds in areas where underlying soils are permeable and at least some of the runoff can infiltrate into the soil. Wet Pond and Wet Vault Performance Pollutant removal efficiencies reported for stormwater treatment wet ponds and wet vaults are quite variable. However, data indicate that a well designed system can be effective in removing many particulate-bound pollutants. The U.S. EPA (1993b) has recently compiled available information on the performance of various stormwater treatment technologies from a number of studies conducted throughout the United States. The data indicate that wet ponds are highly effective in removing total suspended solids and metals (lead and zinc), and moderately effective in removing nutrients (total phosphorus and total nitrogen) (Table 29). Poor to moderate removal efficiencies are generally observed for the soluble forms of most pollutants (e.g., dissolved phosphorus and dissolved metals). Nutrient removal in wet ponds, which is affected by a variety of site-specific factors such as soil characteristics and vegetation as well as seasonal effects, is particularly complex and difficult to predict. Because wet vaults rely exclusively on sedimentation, they are effective only in removing suspended solids and particulate-bound pollutants. A comparably designed wet vault (i.e., same volume and surface area) should be as effective as a wet pond in removing pollutants that are present predominantly in particulate form (e.g., total suspended solids and lead) but would exhibit lower removal efficiencies for other more soluble pollutants such as nutrients, copper, and zinc. Applicability of Wet Ponds and Vaults in North Renton and West Hill Basins Information on urban applicability anu costs of wet pond systems is summarized in Table 30. Wet ponds are not usually suitable as retrofit options because they require a significant amount 255C\LWTASK3 127 Herrera Environmental Consultants of land to construct. They may however, be suitable for large redevelopment projects that can reserve tracts for stormwater treatment facilities. For example, a pond system was installed at the Paccar/Kenworth property in the North Renton basin, which recently was converted to a truck manufacturing facility. These ponds are designed to treat runoff from the northern half of the site, which was redeveloped. A wet pond stormwater treatment facility is also being proposed for the Houser Way road extension project currently under investigation in the North Renton basin. The project would extend Houser Way between North 8th Street and North 4th Street to provide access to properties in this area(see Figure 2). If approved, a wet pond would be installed to treat runoff from the new section of roadway. Because they are installed underground, wet vaults are more suitable for retrofitting. However, vaults are not as effective as wet ponds in removing many of the pollutants of concern identified in the North Renton and West Hill basins (i.e., phosphorus and metals). As a result, it is recommended that wet vaults be considered as an option only in situations where the drainage system is modified to provide added detention for flow control. In this case, incorporating dead storage along with the active storage required for detention would provide some water quality benefit without significantly increasing the cost of the vault. 255C\LWTASK3 128 Herrera Environmental Consultants 7. SUMMARY AND RECOMMENDATIONS Based upon the data gathered and presented here, it is clear that in general, stormwater pollution in the North Renton and West Hill drainage basins does not pose a serious threat to water quality or aquatic habitat within Lake Washington. However, the data also clearly show that stormwater pollutants are being generated in several subbasins at rates that warrant initiation of pollution abatement strategies. Most runoff from the North Renton and West Hill basins is collected and discharged directly to Lake Washington, without treatment. Because of the highly urbanized nature of these basins, little opportunity exists for providing end-of-pipe treatment systems. The North Renton and West Hill basins share many of the same stormwater pollution problems experienced by other urban areas in the Puget Sound region and across the country. The primary concerns identified during this investigation include frequent exceedences of state water quality standards for pollutants such as metals (copper, lead, and zinc), pH, and fecal coliform bacteria, particularly under storm flow conditions. Total phosphorus concentrations were also elevated in many of the stormwater and base flow samples. Contamination by petroleum compounds, although observed at several stations, particularly in the North Renton basin, was generally less prevalent than many of the other pollutants. These problems are typical in urban runoff and are likely caused by a number of diffuse sources, rather than a single source or even a few localized sources within these two basins. Therefore, of the three alternatives evaluated for abating stormwater pollution, the two nonstructural alternatives are most applicable to conditions in the Renton/Lake Washington drainage basins. These two options (i.e., development of a water quality program and implementation of a public education program within the Surface Water Utility) focus on eliminating stormwater pollution at its source by modifying public perceptions and practices that affect water quality. Structural controls such as the treatment technologies described in this report can be effective in reducing stormwater pollution. However, their costs can be significant, and in highly developed areas like the North Renton and West Hill basins, they are limited by the amount of undeveloped land available to construct these types of facilities. Furthermore, no stormwater treatment facilities are completely effective in removing pollutants present in urban runoff. At this time, no specific pollutant sources have been identified in either of these basins. Instead, the responsibility for the stormwater pollution problems that exist lies with all the residents of the basins who knowingly or unknowingly release pollutants that eventually reach nearby storm drains and are discharged to Lake Washington. The stormwater pollution abatement strategies recommended here for implementation by the Renton Surface Water Utility are presented and explained in detail in Chapter 6 of this report. These recommendations are prioritized and presented in summary form in the sections below. 255C\LW'I'ASK3 129 Herrera Environmental Consultants WATER QUALITY PROGRAM It is recommended that the city first develop a water quality program within the Surface Water Utility to reduce the amount of pollutants released into stormwater from the various potential sources in the North Renton and West Hill basins. This program would target local businesses and residences to ensure that best management practices for controlling nonpoint sources of pollution are implemented. Until now, there has been no concerted effort within the city to - encourage and enforce source control efforts by the local community. Structural controls should be considered only if source control efforts fail to reduce the amount of pollutants entering the storm drain system, or in very specific applications where the contributing area is small and the types of pollutants present are readily removed by standard treatment processes (e.g., particulates and particulate-bound pollutants). It is recommended that the utility focus first on developing the necessary framework and establishing procedures for implementing a departmental stormwater quality program. Priorities for program development are described below: ■ Establish the regulatory authority within the utility to develop guidelines and enforce source control activities. This may require the city to pass an ordinance that specifically addresses surface water pollution problems. ■ Coordinate with other city departments to obtain technical assistance and to define each department's role in supporting pollution control efforts throughout the city (e.g., Water Utility, Fire Department, Maintenance Division, Parks and Recreation Department, Solid Waste Utility, Land Use Compliance Program). Water pollution issues are not unique to the Surface Water Utility; these problems affect a number of areas and services provided by the city. Consequently, cooperation among the various city departments is essential to the development of an effective water quality program. Currently, city departments are active to varying degrees in efforts to reduce pollution. To increase efficiency and. avoid overlap among the various departments, particularly in the areas of public education and inspection services, it is important to consolidate efforts in these areas wherever possible. ■ Develop a record-keeping system to track the progress of the utility's water quality program. Again, because the Surface Water Utility will likely rely on services and information collected by other city departments, it is important to establish procedures for retrieving and reporting this information. ■ Coordinate with other local and state agencies for technical assistance and to establish communications between the other agencies that provide pollution control services (e.g., Ecology spill response unit and urban bay program, Metro and King County local hazardous waste survey teams, and Metro trouble call program). ■ Develop a technical resource center within the utility, using resources available through other local agencies, to maintain up-to-date information on best management practices. 255C\LWTASK3 130 Herrera Environmental Consultants ■ Establish procedures for maintaining existing city storm drain facilities to enhance the performance of these systems in removing urban pollutants. The Maintenance Division should also investigate options for expanding its existing program to include inspections of privately owned stormwater control facilities. Once the initial development process is completed, the utility can begin to implement various phases of the program. Implementation will likely progress in stages as staffing and resources allow. It is recommended that the first efforts be directed toward providing technical assistance to local businesses, implementing a public education program that promotes the use of best management practices for controlling nonpoint pollution, and initiating routine inspections of both city and privately owned storm drain systems. A rough estimate of the resources needed to support a utility-based water quality program is provided in Table 31. At least one additional utility staff position will be required to develop and implement the program. It is assumed that the city has the computer hardware and software required to establish an effective record-keeping and tracking system. It is expected that the majority of the first year will be spent in establishing the necessary enforcement authority and interdepartmental coordination. Implementation of a technical assistance program for local businesses should begin in the North Renton and West Hill basins. Both basins contain diverse urban development that makes them ideal test cases for other areas in the city. The North Renton basin lies entirely within the city jurisdiction. However, portions of the West Hill basin are outside Renton, requiring coordination with King County. The following activities should be implemented: ■ Establish a business inspection program targeting high-priority businesses such as automotive operations (e.g., automotive repair, sales, and service, and auto parts stores) and airport tenants involved in repairing, washing, refueling, or operating aircraft. Coordinate with the local hazardous waste management program to schedule inspections of high-priority businesses, and develop a utility-based program to provide additional assistance and enforcement as needed. ■ Develop and implement workshops for these high-priority businesses, or coordinate with existing local programs to provide guidance and technical assistance in implementing best management practices. Coordinate with other programs in the region (e.g., Waste Information Network, Independent Business Association, and, local hazardous waste management program) to make use of existing resources. Depending on the availability of other city staff (e.g., land use compliance officer and Fire Department inspectors) and local agencies (e.g., Metro and King County local hazardous waste program survey and onsite consultation teams), it may be possible to expand the business program to include other areas of the city. However, it is expected that additional utility staff will be needed to implement a citywide technical assistance program. 255C\LWTASK3 131 Herrera Environmental Consultants The water quality program will require the Maintenance Division to expand its storm drain inspection and maintenance activities. Like the other program activities, this will likely require additional crews to provide citywide inspection coverage. However, initial coverage of the North Renton and West Hill basins should be possible with existing crews. Additional monitoring and illicit connection surveys should be targeted for the second phase of the program. Much of the work envisioned for the North Renton and West Hill basins can be performed by the existing crews (after training) with assistance from the utility program coordinator. Survey, sampling, and dye testing activities should be coordinated with the maintenance supervisor and scheduled as crew time is available. After the water quality program has been fully implemented and tested in the North Renton and West Hill basins, the utility should evaluate its effectiveness in reducing activities that contribute to stormwater pollution. Depending on the success of the pilot program, the city should consider expanding the program into other areas of the city. PUBLIC EDUCATION PROGRAM It is important that residents be made aware of local water quality issues and understand what they can do as individuals to help reduce stormwater pollution. The stormwater quality problems identified in the North Renton and West Hill basins are commonly caused by nonpoint pollution sources such as automotive use, fertilizer use, and waste disposal practices. Most of the pollutants present (i.e., metals, fecal coliform bacteria, petroleum hydrocarbons, and nutrients) are ubiquitous in an urban setting. Therefore, it is important that city residents understand that everyone living in the drainage basins contributes to the problem in one way or another, and that the cooperation of all residents is needed to reduce the amount of pollutants discharged to stormwater. It is recommended that initial efforts target the following activities: ■ Develop a network of volunteers to stencil catch basins and storm drain inlets, identifying these as draining to Lake Washington. Stenciling can begin in the North Renton and West Hill basins and then expand into other areas of the city as resources allow. The utility's program coordinator would be responsible for organizing and training volunteer groups. The city would provide the necessary equipment (i.e., maps showing the locations of catch basins and inlets to be marked, paint, stencils, and safety equipment). ■ Conduct a workshop at the airport to educate tenants about stormwater issues, regulatory requirements, and best management practices. ■ Assist local high school science teachers in educating students about nonpoint pollution and the utility's stormwater quality program. This effort involves visiting each science class each quarter to provide information about nonpoint pollution. The utility program coordinator would work with the teachers and the Metro public education program to develop necessary program materials 255C\LWTASK3 132 Herrera Environmental Consultants and to evaluate the potential for field trips or field assignments to be incorporated into the curriculum. ■ Develop a brochure to be distributed to the local community describing the Surface Water Utility water quality program. Investigate using the existing city newsletter to regularly publish articles that deal with stormwater issues. 255C\LWTASK3 133 Herrera Environmental Consultants 255C\LWTASK3 134 Herrera Environmental Consultants 8. REFERENCES Andrews, C. December 7, 1993. Personal communication (telephone conversation with Mark Ewbank, Herrera Environmental Consultants). Renton Fire Department, Renton, WA. API. 1990. Monographs on refinery environmental control—management of wastewater discharges, design, and operation of oil-water separators. API Publication 421. 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