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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

An aerial view of the Elliott West Wet Weather Treatment Facility.

The Elliott West Wet Weather Treatment Station (EWWTS) is a combined sewer overflow (CSO) facility that was first completed in 2005. Since then, it has stored and treated sewage and stormwater during periods of heavy rain. EWWTS now needs to be upgraded to meet stricter environmental standards and to adapt to changing climate.

This project will ensure that the upgraded facility meets its permit requirements. This is a major investment to ensure King County continues to protect public health and the environment for years to come.

More information about the upgrade plans will be available this summer and fall. To stay updated, subscribe to our email list.

Project update

May 2, 2025

We want to hear from you!

Online Community Briefings May 29 and June 12, both at 7:00 p.m.

We are in the process of creating and sharing design proposals while gathering community feedback. We just finished the 30% design phase in early 2025. This meant we created over 1,000 drawings that show the future site's potential layout and configuration. These early drawings give details about the design and size of the wastewater treatment equipment, electrical facilities, building architecture, landscaping, and structural elements.

Our team is interested in your input on the proposed station design. We want to hear your preferences, opinions, and concerns before we proceed to the next phase of design. We are offering online briefings for nearby residents, businesses, and local organizations or councils that would like to learn more about the 30% project phase.

Upcoming online briefing dates are:

If you or your organization are unable to attend one of these dates, please contact Ryan Harlow at rharlow@kingcounty.gov or 206-848-0814 to schedule a time to meet with us. 
After completing the briefings, our project team will share the collected feedback with the design team for consideration. We will present the updated design concepts in an online open house in early fall, where we’ll collect more feedback from you to inform the 60% design expected to be complete in March of 2026. 

For project updates, join our email list.

Project schedule

The project schedule spans from 2023 to 2032. Design 2023-2027, and Construction 2027-2032. Community Outreach occurs the entire duration.

Our team is in the early stages of designing the needed upgrades to EWWTS. Project timelines may change due to a number of factors. We will provide updates as our work progresses and any schedule changes are needed.

Project location

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