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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 update
March 10, 2025
Currently our project team is continuing to work on project options. This exploration phase takes longer when King County builds new sewer facilities than when we replace existing pipes, equipment, and facilities.
Finding the right location for new facilities presents unique challenges in areas like the Sammamish Plateau neighborhood. Teams need to consider residential and business development, the natural environment, roadways and traffic, utilities, and more. To consider all these unique needs, you may see our project team this spring and summer conducting more survey work.
We appreciate the community bearing with us during this time! We look forward to sharing what we have learned later this year.
We want to hear from you - please take our short survey!
King County’s project team wants to get to know you and your community better. By understanding your needs, we can serve you more effectively during the design and construction phases of this project. Please share your feedback with us by completing this survey. We expect that this survey will take about 10 minutes to complete.
We have two different surveys: one for community members and one for local businesses. If you are both a community member and a local business owner in the project area along East Lake Sammamish Parkway Northeast (see map below), please fill out both surveys.
- Community members: publicinput.com/kcwtdsammcomsurvey
- Businesses: publicinput.com/kcwtdsammbussurvey
If you prefer to provide the information in the survey over the phone or by other means, please contact Monica Van der Vieren at 206-477-5502 or monica.vandervieren@kingcounty.gov.
Learn about the latest project update.
We welcome you to contact us at any time during the project to talk, ask questions, express concerns, and give feedback and input.
Previous project updates
- Single lane closures on East Lake Sammamish Parkway scheduled for January 17, January 2025
- Traffic detours for monitoring equipment in East Lake Sammamish Parkway beginning the week of January 13th, January 2025
- Updates and holiday sewer tips from the Sammamish Plateau Diversion Project, December 2024
- Field work update and opportunity to provide input, October 2024
- Schedule update: East Lake Sammamish Parkway single-lane closures are scheduled to start October 10, October 2024
- Work along East Lake Sammamish Parkway starts October 9, October 2024
- Work along East Lake Sammamish Parkway starts next month, September 2024
- Permit approved for East Lake Sammamish Parkway single-lane closures, August 2024
- Upcoming work along East Lake Sammamish Parkway expected to begin later this summer, July 2024
- New schedule for upcoming work along East Lake Sammamish Parkway, July 2024
- East Lake Sammamish Parkway single-lane closures, July 2024
- Field Work coming up this summer on East Lake Sammamish Parkway, May 2024
- King County’s Sammamish Plateau Project looks forward to a busy year, February 2024
- Welcome to the Sammamish Plateau Diversion Project, December 2023
- King County launches the Sammamish Plateau Diversion Project, Fall 2023
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.