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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

Local sewer agencies

service area map
King County wastewater treatment service area maps


King County's wastewater treatment process
King County's wastewater treatment process

King County provides wholesale wastewater treatment services to 17 cities and 17 local sewer utilities in King, Snohomish and Pierce counties. These local agencies own and operate independent collection systems, which include pipelines and pump stations to collect and carry wastewater flows in their service area to King County's regional system for treatment and disposal. The local agencies have 30-year agreements with King County for this service. King County owns and operates the regional treatment plants, pipelines, pump stations and other related facilities.

The county does not bill individual property owners for sewer service. Instead, it charges the local agencies an amount that is based on the county's monthly rate and the number of customers the agency serves. In turn, the local agencies bill their customers to recover the county charge plus the amount needed to operate and maintain their collection systems.

Local sewer agencies served by King County Wastewater Treatment Division

Alderwood Water & Wastewater District
City of Algona, Public Works
City of Auburn, Utilities
City of Bellevue, Utility Services
City of Black DiamondPublic Works 
City of Bothell, Public Works
City of Brier, Public Works
City of Carnation, Public Works
Cedar River Water & Sewer District
Coal Creek Utility District
Cross Valley Water District 
Highlands Sewer District  
City of Issaquah, Public Works
City of Kent, Public Works
City of Kirkland, Public Works
City of Lake Forest Park, Public Works
Lakehaven Utility District
City of Mercer Island, Sanitary Sewer Utility 
Muckleshoot Indian Tribe
Northeast Sammamish Sewer & Water District
Northshore Utility District
Olympic View Water and Sewer District
City of Pacific, Public Utilities
City of Redmond, Public Works
City of Renton, Public Works
Ronald Wastewater District
Sammamish Plateau Water & Sewer District
City of Seattle, Public Utilities
Skyway Water and Sewer District
Soos Creek Water & Sewer District
City of Tukwila, Public Works
Valley View Sewer District (formerly Val Vue Sewer District)
Vashon Sewer District
Woodinville Water District

Related committees

Logo for MWPAAC, Metropolitan Water Pollution Abatement Advisory Committee
Metropolitan Water Pollution Abatement Advisory Committee

The Metropolitan Water Pollution Abatement Advisory Committee, or MWPAAC, advises the King County Council and Executive on matters related to reducing water pollution. It was created by state law (RCW 35.58.210) and consists of representatives from cities and local sewer utilities that operate sewer systems in King County. Most of these cities and sewer utilities deliver their sewage to King County for treatment and disposal. View MWPAAC meeting schedule.

Regional Water Quality Committee

The King County Council's Regional Water Quality Committee develops, reviews, and recommends countywide policies and plans for water quality and sewer service issues, long-range capital facilities plans, rate policies and facilities siting to guide regional water quality responsibilities considered by the council.