Holiday closure Monday May 28: Most county offices will be closed in observance of Memorial Day.
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

Get Directions to our office location in Seattle, Washington.

Real Time CSO Notification

CSO control projects

The wastewater treatment utility operated by King County has completed several projects to reduce combined sewer overflows since the 1980s. Two projects completed in 2005 include the Henderson/Martin Luther King Jr./Norfolk CSO Control Project and the Denny Way CSO Control Project (a joint project with the City of Seattle).

 Beach CSO map
Learn more about the Puget Sound Beach CSO Control Projects.

King County expects to build about 20 CSO control projects during the next 30 years. These projects have been ranked to protect public health, beginning with construction of CSO control projects along Puget Sound beaches (2010-2011) and the east end of the Lake Washington Ship Canal (2015). The final phase of projects will be built along the Duwamish River (2017-2027) and the west end of the Ship Canal (2029-2030).

Refer to the CSO Control Annual Report for an overview of King County's completed, current and planned CSO control projects. Many early projects involved sewer separation, flow diversion, and new tunnels. Most current and future projects involve construction of storage tanks and treatment facilities.

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