KING COUNTY Combined Sewer Overflow Water Quality Assessment for the Duwamish River and Elliott Bay SUMMARY 1 The river was alive with salmon. They rolled and The Duwamish Estuary: Yesterday and Today products we use in our households and busi- splashed everywhere. I Why don’t we see a variety of fish and wildlife in nesses, and the crops we could hear them in the the Duwamish River and Elliott Bay in Seattle today? grow eventually find their The answer is complicated. Much is uncertain. But fog, and some I could way into our water bodies one thing we know for sure. Our activities have see, huge shadows that through sewers, leaky dramatically changed the water bodies in the area. septic tanks, and stormwater climbed the air and Over the past 100 years, we’ve changed the shape, runoff. slipped back into the the location, and the physical features of Elliott Bay The Duwamish River and water so close to the and the Duwamish River by filling in wetlands, Elliott Bay are considered an dredging the bottom of the water bodies for easier boat I could have estuary – a place where fresh- navigation, building houses and businesses along touched them. water and marine waters mingle. shorelines, and diverting or eliminating streams and Estuaries support an abundance Richard Hugo, rivers that flow into these waterbodies. And we’ve The Real West of life. Young salmon stay in the changed the quality of the water that remains in Marginal Way, 1986 Elliott Bay-Duwamish River these water bodies. Past industrial practices, which estuary for a while in order to eat are no longer in use, have left a legacy of pollution in and build up strength before moving into open the sediments. Today, human waste, animal waste, marine water; perch, rockfish, sole, shrimp, crab, and the chemicals from the cars we drive, the and mussels live there year round; spotted sand- TABLE OF CONTENTS The Duwamish Estuary: Yesterday and Today ..................... 2 Thank You King County would like to express its King County CSO Water Quality Assessment .................... 3 appreciation to staff and members of the Combined Sewer Overflow Water Quality Controlling CSOs ........................................................................ 4 Assessment Stakeholder Committee, the Water Environment Research Foundation Peer Conducting The Study ............................................................... 5 Review Panel, Boeing, the Washington State Study Team................................................................................ 5 Department of Fisheries, and the National Marine Fisheries Service for all their hard work Study Approach ....................................................................... 6 and help on this project. Key Findings ................................................................................. 8 Health Risks To Aquatic Life ................................................. 9 COVER PHOTOS Health Risks To Wildlife ......................................................... 9 Top: Elliott Bay Health Risks To People ........................................................ 10 Bottom: Duwamish River From Eating Seafood ........................................................ 10 From Activities ................................................................... 10 Produced by the King County Department of Natural Resources Stakeholder Committee Conclusions Writer: Kathryn White, And Recommendations........................................................11 King County Water Quality Planner Design: Betty Hageman Graphic Design What’s Next? ............................................................................ 11 AUGUST 1999 For More Information ............................................................. 11 2 piper, bald eagle, great blue heron, and river otters untreated sewage mixed with stormwater to the feed and live in the area; and people use the area estuary during heavy rainstorms. King County is for activities such as fishing, shipping, airplane responsible for planning to construction, boating, swimming, SCUBA diving, reduce these combined sewer In portions of Seattle, as bird watching, and windsurfing. overflows (CSOs) to meet the in many older cities, both sewage and stormwater Due to human activities, the amount of flow and limits required by state regula- travel to a treatment plant the quality of the water in this estuary have tions. As we were making these through the same pipes. diminished significantly since the mid-1800s. As a plans we still did not have a clear result, fish and wildlife populations and our ability understanding of the dynamics During heavy or to use and enjoy the area have also diminished. of this complex estuary. To gain prolonged rains, pipes For example, commercial harvesting of shellfish is a better understanding of the and treatment plants no longer allowed in Elliott Bay. Over the past 25 estuary and the impacts of CSOs simply can’t handle such years, King County, businesses, environmental relative to other pollutant large volumes. To protect groups, tribal governments, and other agencies sources, we undertook an the treatment plants and have started to address these concerns by under- extensive study: King County avoid sewer backups into taking numerous pollution control efforts to Combined Sewer Overflow Water homes and businesses, improve water quality. However, pollutants from a Quality Assessment for the the “combined” sewers variety of sources continue to degrade the estuary. Duwamish River and Elliott Bay discharge their contents (hereafter referred to as “the directly to the nearest study”). Some of the questions body of water. These we looked at included: King County CSO Water Quality Assessment discharges are called • What is the existing quality combined sewer In a recent survey, you told King County that of the water and sediment? overflows (CSOs). protecting and enhancing water quality in the region is a very high priority for you. We agree. • What are the flow patterns Among the many sources of pollution in the in the water and how are chemicals dispersed estuary, the region’s oldest sewers still discharge and/or ingested by aquatic life, wildlife, and humans? 1854 1908 1985 Duwamish Estuary – Changes Over Time Shallows and flats Tidal swamps Deep water Developed floodplain and shoreline Undeveloped floodplain and shoreline Mean low water 3 Denny Way Combined Sewer Outfall harmful to public health and aquatic life because they carry chemicals and disease-causing patho- gens. In order to protect water quality and human health, King County has been steadily working toward meeting the Washington State Department of Ecology (Ecology) standard that restricts combined sewer overflows to an average of one untreated Disease-causing discharge per year at each CSO pathogens such as location. bacteria and viruses We have made tremendous are in the estuary. progress in reducing CSOs. Over Sources include the past ten years, the volume of agricultural practices, King County’s CSO discharges has stormwater runoff, been reduced from 2.4 billion failing septic systems, gallons to approximately 1.6 billion illegal sewer • What are the health risks to humans and other gallons on average per year. So far, connections, and creatures that come in contact with the estuary 10 out of 37 CSO locations now CSOs. Removing CSOs with CSOs and without CSOs? meet the state standard. Completed will reduce some of CSO control projects have cost over the risk of infection The study found • Will the waters and sediment become cleaner and safer as a result of our $60 million; another $200 million is from human clear evidence of CSO control efforts? If so, to what slated for current projects. The pathogens, most potential health extent? King County comprehensive sewer noticeably near the risks to aquatic life, plan calls for bringing the remain- Denny Way CSO. wildlife, and people This study, along with other envi- ing CSO locations to within the as the estuary exists ronmental programs and projects state standard by the year 2030, at today. These risks undertaken by King County and other an additional cost of approximately $311 million. agencies (e.g., the Green/Duwamish come from a The Elliott Bay-Duwamish River estuary includes variety of sources. Watershed Forum and organizations developing fish recovery plans), 15 CSO locations, which discharge approximately 1.4 Removing CSOs provide more understanding of how billion gallons of combined flow in each year of will reduce some CSO control projects complement average rainfall. Considering that the entire King risks, but others other environmental control programs. County system discharges a total of 1.6 billion will remain. This added information will be reviewed to assess CSO projects and priorities. The following Roof pages summarize how we conducted the study, what Drain Storm Combined System Drain we found, and further actions recommended. Sanitary Drain Controlling CSOs Overflow CSOs are one contributor to the pollution in the COMBINED SEWER Elliott Bay-Duwamish River estuary. Even though the sewage being discharged is greatly diluted by stormwater, both CSOs and stormwater may be To Treatment Plant 4 Lake Union CSO WQA Study Area Magnolia LEGEND Denny Way King County CSO King County CSO – Limited to one event per year Sewage Conduit N Tunnel Section Elliott Bay Study Area King St SEATTLE Connecticut St Lander St MERCER “....It is true that today Chelan Ave Hanford # 2 Harbor Ave this area is ISLAND Lake industrialized, but it was Duwamish Washington