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Elliott West Wet Weather Treatment Station upgrade

King County is planning to upgrade the Elliott West Wet Weather Treatment Station (EWWTS). The upgrade will ensure compliance with stricter environmental regulations, meet the demands of a growing population, and handle a changing climate.

Project description

Aerial view of the facility

Elliott West has been in service since 2005 acting as a wet weather treatment station when Combined Sewer Overflows (CSOs) occur. The station provides partial treatment of combined stormwater and wastewater by removing solids and chemically treating the combined wastewater. After this treatment, the wastewater is discharged through an outfall pipe into Elliott Bay.

To meet stricter environmental standards and handle a growing population with climate change impacts, EWWTS must be upgraded.

More information will be available about the chosen alternative and upgrade plans soon.

Project update

August 2023

Elliott West Wet Weather Treatment Station is getting an upgrade!

We want to know what matters most to you and how we can better provide you with project information and updates. Please take a few moments (3 to 5 minutes) to complete a brief survey.

Take our survey here

This project has been selected to pursue a collaborative delivery method known as General Contractor/Construction Manager or GC/CM. The GC/CM Request for Proposals (RFP) is expected to be advertised between January and March 2024, pending CPARB Project Review Committee approval. Learn more.

Project schedule

Construction is several years away. Currently, the project team is gathering information for a draft Engineering Report that will be submitted to the Washington State Department of Ecology for review. This draft report will be submitted to Ecology by summer 2024.

A more detailed project schedule will be made available soon.

Project location