King County provides wholesale wastewater treatment services to 18 cities, 15 local sewer utilities and the Muckleshoot Indian Tribe 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 Diamond , Public 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 Water & Sewer District |
| City of Mercer Island , Sanitary Sewer Utility |
| Muckleshoot Indian Tribe , Public Works |
| 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 |
| Sammamish Plateau Water & Sewer District |
| City of Seattle , Public Utilities |
| City of Shoreline , Wastewater Utility |
| 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 |
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