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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 project includes new underground pipes in the East Lake Sammamish area and upgrades to the York Pump Station near Redmond.
This project will help WTD to expand its services and meet future wastewater needs.
Project update
January 7, 2026
The Sammamish Plateau Diversion Project reaches the first milestone
We are launching outreach in 2026 with an important update on the Sammamish Plateau Diversion Project. The project team has identified a corridor for a new wastewater pipe in the northeast Lake Sammamish area.
Visit our online open house
See the project corridor in detail and learn what the team considered in the project area. The online open house is live until the end of February 2026. Visit as often as you like and share your thoughts at kingcounty.gov/wtd/Sammamish-Plateau-Online-Open-House.
The online open house will be offered in multiple languages, and translated versions will be available soon!
¡La sesión virtual abierta al público se brindará en varios idiomas y estarán disponibles pronto!
本次线上开放日活动将提供多种语言版本，翻译版本即将上线！
本次線上開放日將提供多種語言版本，翻譯版本即將上線！
オンライン説明会は多言語で提供されており、翻訳版も近日中に公開予定です！
온라인 오픈 하우스는 다양한 언어로 사용하실 수 있게 되며, 빠른 시일 내에 번역본도 제공될 예정입니다!
Виртуальный день открытых дверей будет проводиться на нескольких языках и совсем скоро переведенные версии будут доступны для вашего ознакомления!
Upcoming survey work in East Lake Sammamish Parkway
The project team is continuing survey work in the right-of-way along East Lake Sammamish Parkway. Previous survey work in the City of Redmond was completed in 2025. Upcoming work is in the City of Sammamish.
Most survey work will occur on the shoulders of East Lake Sammamish Parkway Monday-Friday, between 7 a.m. and 3:30 p.m. This work involves no traffic impacts. Please watch for our survey crews and drive carefully in the area.
Crews will need to work in the roadway for some utility surveys. This work will take place at locations along East Lake Sammamish Parkway and at the Northeast Inglewood Hill Road intersection. Work in the roadway will occur on Saturdays from 6 a.m. to 9 a.m. to reduce traffic impacts. We will notify the community in advance of Saturday work and provide more detail on what to expect.
Previous project updates
- We had a splash seeing you at Salmon Days, October 2025
- Visit us at the Issaquah Salmon Days Festival!, September 2025
- Survey work on East Lake Sammamish Parkway Northeast in Redmond, May 2025
- Survey work winding down, and you can shape the future of clean water!, May 2025
- Survey work on Inglewood Hill Road and volunteer at CitySoil Farm, April 2025
- Updates from the Sammamish Plateau Diversion Project, March 2025
- 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 | 2025-2031 | 2031-2035 |
|---|---|---|
| Pre-design (including alternatives analysis) | Design (including environmental review and permitting) | Construction |
The Sammamish Plateau Diversion Project is in an early phase and project timeline may change during a project due to a number of factors. We will provide updates on our progress and any schedule changes.