Seattle & King County to expand wastewater treatment in new agreement with EPA, DOJ, Ecology | US EPA (2024)

SEATTLE (June 26, 2024) – The U.S. Department of Justice, the U.S. Environmental Protection Agency, and the Washington Department of Ecology announced today that they have reached an agreement in principle with King County and the City of Seattle that commits the local governments to significant expansion of the work they agreed to perform in 2013 to reduce discharges of untreated combined sewage and stormwater into Lake Washington, Lake Union, the Duwamish River, and Puget Sound.

In 2013, Ecology and EPA found that the city and county’s interconnected combined sewer system regularly violated the state and federal clean water laws by sending hundreds of millions of gallons of untreated or undertreated wastewater into local waterways each year, and allowing sewage to back up into homes in some low-lying communities such as the Duwamish Valley. At that time, both the city and county signed consent decrees with Ecology and the United States committing to major infrastructure investments to reduce the wastewater entering local waterways and people’s homes.

Citing increasing rainfall intensity and other impacts of climate change, supply-chain disruptions, and the increased costs of construction in the Seattle area, in 2019 the city and county requested modifications to the 2013 consent decrees to allow for more time to control combined sewer overflows. The new agreements extend the completion date for some of the projects from 2030 to 2037 and commit the city and county to significant increases in wastewater storage and treatment capacity.

The additional time also enables closer coordination between the city and county, projects to reduce stormwater volumes, and additional planning and design work to ensure that new wet-weather control facilities are more resilient to a changing climate. Generally, this means that these facilities will be capable of handling larger volumes of combined sewage that will result from changing rainfall patterns in the Seattle area.

The agreed-to modifications include significant improvements to major projects including:

  • King County’s Mouth of the Duwamish Wet Weather Treatment Facility
    • The facility may now include outfalls owned by the City of Seattle.
    • Options include treatment of overflows (would increase treatment capacity by more than 25% to 190 million gallons per day), storage of overflows (would increase storage to 150 million gallons), or a combination of treatment and storage.
    • Original projected completion 2030, new projected completion 2034.
  • West Duwamish/Terminal 115 CSO Control Project
    • This project will store nearly one million gallons more than originally planned.
    • Delays in completion related to construction in a contaminated site.
    • Original projected completion 2025, new projected completion 2029.
  • Ship Canal Water Quality Project
    • The project will reduce combined-sewer discharges to the Lake Washington Ship Canal from six separate outfalls, reducing polluted discharges to the Ship Canal by an average of 84% per year.
    • EPA provided loans under the Water Infrastructure Finance and Innovation Act to the City of Seattle for $192.2 million and King County for $96.8 million for this project.
    • Delays in completion are related to Covid-19, supply chain issues, and unanticipated obstructions found during tunneling.
    • Original projected completion 2025, new projected completion 2027.
  • Montlake and University
    • These storage projects may be combined or remain separate facilities. Overall, stored volumes of wastewater will increase from 7.87 million to 11 million gallons for Montlake and from 5.23 million to 16.1 million gallons for University.
    • Original projected completion 2028, new projected completion 2037.

The agreement provides the city and county with a certain amount of flexibility to reviseprojects as long as they meet or exceed the original performance criteria.

This agreement underscores what’s possible when all parties come together to advance shared values and goals,” said Casey Sixkiller, Regional Administrator for EPA’s Region 10 office in Seattle. "From improving water quality in Lake Washington, the Ship Canal and Puget Sound, protecting treaty resources, and making the region’s water infrastructure more climate resilient, this agreementis a win from every angle.”

"Climate resilience is one of our greatest environmental priorities,” said Laura Watson, director of the Washington Department of Ecology. “We want to see improvements that are future-proofed for intensifying storms. By extending the overall timeframe for this work, it means the infrastructure can better protect water quality and vulnerable neighborhoods for a lot longer.”

Investments by Washington Department of Ecology and EPA

In December 2022, King County completed its Georgetown Wet Weather Treatment Station which can treat up to 70 million gallons per day of combined untreated sewage and stormwater that would have otherwise flowed directly into the Duwamish River and Puget Sound. The EPA provided King County with a $134.5 million Water Infrastructure Finance and Innovation Act loan for this project.

Since 2015, Ecology has awarded low-interest loans from its Clean Water State Revolving Fund totaling $266.5 million to Seattle and $395.3 million to King County for combined sewer overflow control projects.

In 2024, EPA also awarded a $194 million Water Infrastructure Finance and Innovation Act loan to King County, the majority of which will go toward various clean-water investments at West Point Treatment Plant, which cleans wastewater and stormwater. This project makes several improvements at the wastewater treatment plant, including removing corroded pipes, upgrading raw sewage pumps, and implementing structural upgrades to the administrative building to protect against future seismic events.Ecology has also committed $24.4 million in loan funding for this suite of projects.

What’s next

The new agreements must be approved by both the King County Council and the Seattle City Council. If the councils approve the modifications, they will be lodged with the U.S. District Court for the Western District of Washington and made available for comment for 30 days. The parties could then seek approval of the modifications by the court.

Seattle & King County to expand wastewater treatment in new agreement with EPA, DOJ, Ecology | US EPA (2024)


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