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Combined Sewer Overflow Control

By reducing combined sewer overflows into local water bodies, King County is protecting public health and the environment.
For questions about the King County CSO Control Program, please contact Karen Huber.

Wastewater Treatment Division
King Street Center
201 S. Jackson St., Suite 505
Seattle, WA 98104-3855

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Real Time CSO Notification

CSO Control Program 2012 Plan Review

King County Executive's Recommended Combined Sewer Overflow Control Plan 

In addition to his recommended plan, the Executive is recommending completion of a water quality assessment and monitoring study.

During 2010 – 2012 the CSO Control Program has reviewed its Combined Sewer Overflow (CSO) Control Plan. King County completed the review and submitted it, in the form of a plan amendment, to the Washington State Department of Ecology by 2013. The CSO Control Plan was last updated in 2008 with no recommended changes from the 1999 Regional Wastewater Services Plan.

The main documents resulting from the 2010- 2012 review are:

  • King County Executive’s Recommended Combined Sewer Overflow Control Plan, issued June 2012. King County Executive Dow Constantine submitted his recommended combined sewer overflow (CSO) control plan to the King County Council and the Regional Water Quality Committee for review and approval. 
  • 2012 Long-term CSO Control Plan Amendment, October 2012. This plan amendment includes the 2012 CSO Control Program Review Report, as amended by the King County Council, along with the signed legislation approving the 2012 King County Long-term CSO Control Plan Amendment. This Plan has been submitted to the USEPA and the WA Dept of Ecology. The plan documents King County’s review of its CSO Control Program, which was conducted in accordance with policies and guidelines in the 1999 Regional Wastewater Services Plan (RWSP).
  • The 2012 CSO Control Program Review Report is supported by nine technical memorandums