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Projects
Find information about current and planned future Mouth of Duwamish Wet Weather Facilities projects.
March 2025
What’s happening now
We expect to wrap up the planning phase this spring. At that time, we will share our proposed solution to control overflows from the five combined sewer overflow (CSO) outfalls near the mouth of the Duwamish River. The proposed solution will meet federal and state regulatory requirements and may include a wet weather treatment station, a storage tank, an outfall to discharge treated water, and pipes and supporting facilities that connect flows along the way.
Once we propose a solution, we will begin a review under the State Environmental Policy Act (SEPA) to evaluate environmental impacts. We will also seek approval from the Washington State Department of Ecology.
We will have more to share in the coming months about these processes and how you can get involved.
Stay connected!
As we progress through planning, design, and construction, we will continue to provide opportunities for you to ask questions and share thoughts and concerns. For project updates, join our email list using the link in the “stay informed” section of this webpage or by scanning the QR code below.
Contact Bibiana Ocheke-Ameh at bibiana.ocheke-ameh@kingcounty.gov or 206-477-5604 with questions or to request a briefing for your organization.
Project description
King County is currently evaluating methods to reduce overflows from 5 combined sewer outfalls (shown on the map below) in accordance with Washington State law and the federal consent decree. These methods may include storage, treatment, or conveyance and will result in a variety of future projects.
During the planning phase, the project team will recommend an approach to control CSOs that considers a number of factors including regulatory, cost, environmental, and community priorities. King County’s regulators will review and approve plans before the projects move into design and construction.
We anticipate planning to end in fall 2025, with design and construction of projects associated with the Mouth of Duwamish Wet Weather Facilities to immediately follow.
King County is seeking to understand the feasible options to control pollution from these outfalls and meet regulatory and environmental requirements.
Community outreach
For information about community outreach, visit the Mouth of Duwamish Wet Weather Facilities public engagement webpage.