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Annual report

These reports are required under the National Pollutant Discharge Elimination (NPDES) permit for King County’s West Point Treatment Plant in Seattle and WAC 173-245-090.1.

Additionally, King County has an agreement with the U.S. Environmental Protection Agency (EPA) and Ecology called a “consent decree,” which also requires an annual report. The consent decree outlines the planned actions to bring the County’s CSO program into compliance with the federal Clean Water Act (CWA).

The agreement with EPA and Ecology consolidates the two annual reports into one. This report meets the consent decree, state, and federal requirements.

 

2025 Annual CSO and Consent Decree Report

 

Report Contents Appendices
1.0 Introduction A Untreated CSO Events, January–December 2025
2.0 Programs to Meet EPA’s Nine Minimum Controls B Treated CSO Events, January–December 2025
3.0 Control Status of CSO Locations C Alki Wet Weather Treatment Station 2025 Annual Report
4.0 CSO Control Measures Currently Underway D Carkeek Wet Weather Treatment Station 2025 Annual Report
5.0 Summary of Rainfall and CSO Events E Elliott West Wet Weather Treatment Station 2025 Annual Report
6.0 Summary of Consent Decree and NPDES Violations in 2025 F Henderson/MLK Jr. Way Wet Weather Treatment Station 2025 Annual Report
7.0 Post-construction Monitoring G Georgetown Wet Weather Station 2025 Annual Report

CSO Annual Snapshot

View snapshot as Acrobat PDF file.

Infographic summarizing King County’s 2025 combined sewer overflow control efforts, including project locations, 38 outfalls, 98.6% of flow treated, and RainWise program accomplishments.

Annual reports for previous years

 

Year File size
2025 Annual CSO and Consent Decree Report 2.9MB 
2024 Annual CSO and Consent Decree Report 3.0MB
2023 Annual CSO and Consent Decree Report 2.0MB
2022 Annual CSO and Consent Decree Report 2.1MB
2021 Annual CSO and Consent Decree Report 2.1MB
2020 Annual CSO and Consent Decree Report 2.2MB
2019 Annual CSO and Consent Decree Report 2.7MB
2018 Annual CSO and Consent Decree Report 1.3MB
2017 Annual CSO and Consent Decree Report 3.3MB
2016 Annual CSO and Consent Decree Report 3.0MB
2015 Annual CSO and Consent Decree Report 2.3MB
2014 Annual CSO and Consent Decree Report 3.1MB
2013 Annual CSO and Consent Decree Report 3.2MB
2012 Annual CSO Report 1.5MB
2011 Annual CSO Report 1.5MB
2010 Annual CSO Report 2MB
2009 Annual CSO Report 720KB
2008 Annual CSO Report 662KB
2007-2008 Annual CSO Report 772KB
2006-2007 Annual CSO Report 1.1MB
2005-2006 Annual CSO Report 513KB
2004-2005 Annual CSO Report 381KB
2003-2004 Annual CSO Report 313KB
2002-2003 Annual CSO Report 264KB
2001-2002 Annual CSO Report 300KB
2000-2001 Annual CSO Report 255KB
1999-2000 Annual CSO Report 2.9MB
1998-1999 Annual CSO Report 3.7MB
1997-1998 Annual CSO Report 4.0MB
1996-1997 Annual CSO Report 3.3MB
1995-1996 Annual CSO Report 3.3MB
1994-1995 Annual CSO Report 4.2MB
1993-1994 Annual CSO Report 2.0MB
1992-1993 Annual CSO Report 1.3MB
1991-1992 Annual CSO Report 1.2MB
1990-1991 Annual CSO Report 1.2MB
1989-1990 Annual CSO Report 862KB
1988-1989 Annual CSO Report 739KB
1987-1988 Annual CSO Report 400KB