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Sammamish Plateau Diversion

The Sammamish Plateau Diversion Project will build new wastewater infrastructure to serve the growing East Lake Sammamish area.

Project description

The Sammamish Plateau Diversion Project will create new infrastructure to manage some wastewater flows from the East Lake Sammamish area. Currently, wastewater flows from the Sammamish Plateau travel to South Treatment Plant in Renton. When the project is finished, a portion of those flows will travel north to King County’s Brightwater Treatment Plant. 

This project will add capacity to serve current and future populations in a busy, growing area.

Project timeline

2023 - 2025 2026-2028 2028-2030
Alternatives Analysis Design Construction

Project timelines may change due to a number of factors. The Sammamish Plateau Diversion Project is in an early phase. We will provide updates as our work progresses and any schedule changes are needed.

Project update

February 2024

Right now, our project team is hard at work developing project options.

Project teams use all kinds of data to identify workable project options. The team evaluates those options considering a range of factors. Factors include constructability, permitting, community and environmental impacts, and more.

In the coming months, you may notice occasional site visits. Later this year, the project team will perform soil and groundwater surveys. A contractor will sample with drilling equipment. This work can create traffic delays and noise. We will let the community and commuters to know what to expect before these surveys begin.

Once the project team has identified project options, we will let you know. We will reach out online and in person.

Learn about the latest project update.

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We welcome you to contact us at any time during the project to talk, ask questions, express concerns, and give feedback and input.

Project location