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Project update

King County’s Georgetown Wet Weather Treatment Station celebrates Platinum Achievement Award for Sustainability

King County’s Georgetown Wet Weather Treatment Station earned the coveted “Platinum” rating from the Institute for Sustainable Infrastructure’s Envision rating system. This is the first Platinum-awarded Envision project in Washington and recognizes the County’s commitment to sustainable communities and the environment. View news release.

November 2018

King County’s Wastewater Treatment Division (WTD) is building a new wet weather treatment station in Georgetown at the corner of Fourth Avenue South and South Michigan Street. As part of the Wet Weather Treatment Station project, WTD is also building a new outfall structure under the First Avenue South Bridge and connecting pipes from the station to the outfall. Read the November Project Update for more information on all three project areas, highlights from the past month, and upcoming work.

What to expect during construction:

  • Excavation activities and pipe installation continue at treatment station, conveyance, and outfall sites through the end of the year.
  • Increased truck traffic going in and out of all construction sites.
  • Increased noise and vibration levels as sheet piles are installed.
  • Work is completed weekdays during the following hours:
    • Station and outfall: 7 a.m. to 6 p.m.
    • Conveyance pipes: 6 a.m. to 2:30 p.m.
  • Drills, pumps, excavators, cranes and trucks working on project sites.
  • Hotline staffed 24/7: 206-205-9286

Read the latest project update for more information.

Now posted: Project overview fact sheet , June 2018; Summer 2018 newsletter , August 2018

Project description

Rendering of Georgetown Wet Weather Treatment SystemSite of future Georgetown Wet Weather Treatment Station at the corner of 4th Avenue South and South Michigan Street.

The Georgetown Wet Weather Treatment Station Project includes the construction of a combined sewer overflow (CSO) wet weather treatment station between the Brandon Street and South Michigan Street Regulator Stations, related pipes and a new outfall structure to release the treated water into the Duwamish River. When constructed, the station can treat up to 70 million gallons of combined rain and wastewater a day that would otherwise have discharged directly to the Duwamish without treatment during storm events.

This project will help clean up the Duwamish River by treating stormwater runoff and sewage during heavy rains. Right now, heavy rains can fill up our sewer pipes, sending polluted runoff and sewage through a pipe into the river. King County began on-site work in April 2017 and expects to finish construction in 2022.

Wet Weather Treatment StationWet weather treatment stations clean overflows locally on-site during heavy rain storms.


Through a competitive process, King County awarded the construction contracts to three separate contractors.

In spring 2018, King County’s contractor Flatiron West, Inc. started treatment station construction. In the summer of 2018, Pacific Pile and Marine began the construction on the new outfall structure and in the fall of 2018, JW Fowler Company also began preparation work to construct the conveyance pipeline which will connect the treatment station to the outfall.

Project timeline


Contact us

Construction hotline:

Contact Bibiana Ocheke-Ameh at:


 Feedback form

Sign up for email or text updates on the public involvement page.

King County partnered with Nature Consortium and Seattle Public Schools to teach 5th graders at Maple Elementary about water conservation and create art for the construction fence. View more project videos in the Library.

Project location


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