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Project update

June 2018

Now posted: Project overview fact sheet , June 2018

Construction in full swing! Questions? Join us this summer at community events.

Construction continues for the wet weather treatment station at the corner of Fourth Avenue South and South Michigan Street in Georgetown. 

This summer, work on a new outfall structure on South River Street under the First Avenue South Bridge will begin. 

Beyond the project sites, King County remains committed to working with the Georgetown neighborhood. This summer, King County will be out in the community to share information and have conversations with community members. 

King County staff out in the community to share information about the project
Come see us at these upcoming meetings and events!

  • Georgetown Carnival: June 9, 12 – 10 p.m. 
  • Georgetown Garden Walk: July 8, 10 a.m. – 5 p.m.

More activities begin on site; Crews building Secant Pile Wall 

Starting in mid-April 2018, crews will begin building the wall of the facility’s underground Influent Pump Station. Work will include drilling holes about 90 feet into the ground and installing four-foot wide concrete cylinders. The cylinders are called secant piles.

Secant piles lock together to create a structurally stable ring. This ring will be nearly 100 feet wide and is part of the Influent Pump Station’s structural wall.

Read the latest project update for more information and view the video below to learn more about secant pile walls (ring).

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


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.

Project location


Back to the capital projects overview map .