Department of Ecology News Release - November 30, 2023

Seattle and King County penalized for sewer overflow violations


The Washington Department of Ecology and the U.S. Environmental Protection Agency (EPA) are jointly issuing penalties to Seattle and King County for violating conditions of their federal consent decrees and state water quality permits that regulate combined sewer overflows from Seattle’s sanitary sewer system.  

The penalties are for violations that occurred between July 1, 2021 and December 31, 2022. Seattle’s penalty is a total of $102,500: $95,000 for 38 sanitary sewer overflow events and $7,500 for one dry weather overflow from a combined sewer overflow discharge pipe (outfall). King County’s penalty totals $141,000: $126,000 for exceeding pollutant limits at its wet weather treatment stations that treat combined sewer overflow discharges, $7,500 for three sanitary sewer overflows, and $7,500 for one dry weather discharge from an outfall. 

Untreated or insufficiently treated discharges of sewage contain bacteria and other pollutants that can make conditions unsafe for people and animals. Combined sewers carry both stormwater and sewage. The city and county own and operate different parts of the combined sewer infrastructure within Seattle city limits. Combined sewers were originally built with overflow points intended to discharge during large storms. State and federal law requires communities to minimize untreated sewage reaching rivers, lakes, and Puget Sound by eliminating these overflows except in extreme weather circumstances.

Seattle discharges

Ecology and EPA are penalizing the City of Seattle $95,000 for 38 sanitary sewer overflow events. Sanitary sewer overflows are not allowed by the city’s discharge permit regardless of the type of weather. Several of the events reached Puget Sound, Lake Union, or the Duwamish River. A number of events resulted in sewage backing up into homes or other buildings. 

Ecology and EPA are also penalizing the city $7,500 for one dry weather overflow from a combined sewer overflow discharge pipe (outfall). The city’s water quality permit strictly prohibits discharges from combined sewer outfalls during dry weather periods.

King County discharges

Ecology and EPA are penalizing King County $126,000 for polluted discharges from its Elliott West, Carkeek, Alki, and MLK/Henderson combined sewer overflow treatment facilities. 


Pollutant Alki Carkeek Elliott West MLK/Henderson
Solids that carry pollutants into water (penalties totaling $50,000) X   X  
Chlorine (penalties totaling $34,000)   X X X
pH (penalties totaling $21,000)     X  
Disinfection failures (penalties totaling $15,000)   X X  
Fecal coliform (penalties totaling $6,000)     X  

Ecology and EPA are also penalizing the county $7,500 for three sewer overflows. The most significant event released 20.7 million gallons of combined sewer flows into the Ship Canal, due to a failure of a CSO outfall gate.

These violations do not involve King County’s main wastewater treatment plants—Brightwater, South Plant, and West Point. 

Combined sewer overflow consent decrees

These penalties are required under separate legal agreements called consent decrees that Ecology and EPA negotiated with the City of Seattle and King County in 2013 to settle past violations related to combined sewer overflow discharges. The consent decrees reinforce requirements for the city and county to comply with the state’s combined sewer overflow regulations

The city and county are continuing their work to improve water quality and reduce combined sewer overflows through major infrastructure investments and adjusting maintenance when issues are identified. 

Each consent decree identifies specific fines for certain types of unpermitted discharges. The city and county may invoke dispute resolution procedures if either party believes Ecology and EPA have assessed the consent decree penalties incorrectly. 

Ecology and EPA each will receive half of the penalty payments. Water quality penalty payments to Ecology are placed into the state’s Coastal Protection Fund, which provides grants to public agencies and Tribes for water quality restoration projects. 

Under the consent decrees, Seattle and King County have committed to controlling combined sewer overflows according to state regulations by 2030. While they have completed projects to reduce combined sewer overflow discharges over the last several years, additional work is needed to fully meet state requirements. 

Contact information

Scarlet Tang
Twitter: ecyseattle