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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.

Construction updates

November Update: Dewatering equipment installation starting November 13, 2017 

King County crews will install dewatering equipment at the Vashon Bunker Trail (BT) 1 and 2 (see map below) starting Monday, November 13. Equipment includes baker tanks to hold excess water, a diesel-powered pump and a generator that will run 24/7 while the work is being completed. No changes are expected to traffic, and one lane will remain closed between BT1 and BT3 along 103 Avenue SW.

1711_VBT-mapSee flier  for more information.

Other construction activities

For more information contact: Bibiana Ocheke-Ameh at 206-477-5604 or

Beulah Park and Cove Drip Field

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 

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

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