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Project update

August 2018

Shoring and more excavation activities begin at station site

Construction continues on the wet weather treatment station at the corner of Fourth Avenue South and South Michigan Street in Georgetown. While the underground Influent Pump Station wall is being completed (see our April 2018 update ), other pipes and supporting structures will be installed using sheet piles starting in August.

Steel sheet piles will hold back water and soil while crews dig and excavate soil to install pipes and supporting structures. The sheet piles will be installed using a large piece of equipment called a vibratory hammer. Increased noise and vibration levels are expected as the steel sheet piles are installed.

Crews will be monitoring noise and vibration levels to minimize disruption to the extent possible. Sheet piling is expected to begin in August and continue through fall 2018.  

Read the August project update for more information and view the video below to learn more and see a video example of this work.

Now posted: Project overview fact sheet , June 2018

Sheet pile driving
Secant pile construction

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.

Earlier this year, King County’s contractor Flatiron West Inc. started treatment station construction. This summer, construction on the new outfall structure will begin.

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 Treatment Station construction contract to Flatiron West Inc. Through an additional competitive process, Pacific Pile & Marine was awarded the contract to construct the new outfall structure. Major construction on the treatment station started in April, and outfall construction will begin this summer. Later this year, King County will select a contractor to build the new pipes to connect the station to the outfall structure.

Project timeline


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Contact Bibiana Ocheke-Ameh at:


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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.

Project location


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