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The Vashon Treatment Plant, located on Vashon Island, is part of King County's regional wastewater treatment system.

It treats wastewater from homes and businesses within the Vashon Sewer District. Approximately 180,000 gallons a day of wastewater is treated at this facility. A maximum of 1.4 million gallons per day can be treated during the rain/storm season.

View the Vashon Treatment Plant Spring 2022 newsletter .

Vashon Treatment PlantVashon Treatment Plant site—after construction

View more photos on our Flickr site  .

Contact us

24 hour emergency and odor reporting:   206-263-1760
Administration:  206-463-7318 

Address
9615 S.W. 171st St.
Vashon, WA 98070

Directions and map

Related content

Public treatment plant tours (available but limited)

Education resources for schools and community groups

View NPDES permit

Service area 

Overflows and emergencies

Odor reporting

Service area maps