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Wastewater Treatment

King County, Washington

For questions about the Wastewater Treatment Division website, please send an e-mail message or contact us at:

King Street Center
201 S. Jackson St., Suite 500
Seattle, WA 98104-3855
Phone: 206-477-5371
Fax: 206-684-1741
Telecommunication device for the deaf (TTY): 711

Get Directions to our office location in Seattle, Washington.

Staff Contacts

Regional Wastewater Services Plan

Since 1958, King County has protected water quality in the Puget Sound region by providing wastewater treatment services to King, Pierce, and Snohomish counties.

In the 1990s, flow estimates based on projected population growth estimates in King County's wastewater service area indicated that King County's regional wastewater treatment system would run out of capacity by 2010. To ensure the continuation of high quality wastewater treatment services in the future, King County carried out an intensive planning effort, involving numerous elected officials, representatives from local sewer agencies, organizations and individuals from around the region. The Regional Wastewater Services Plan (RWSP) resulted from these efforts, which was adopted by the King County Council in November 1999 via Ordinance 13680.

RWSP list of planned projects through 2030. Source: Ratepayer Report, April 2014
Oveview of planned projects through 2030

Learn more about the RWSP


News releases

Related information

1958 cover
Our first plan -- the Metropolitan Seattle Sewerage and Drainage Survey, March 1958

For more information