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

This section includes project updates. For more details, read our latest project email. You can view previous project updates below. Sign up for our listserv to stay up to date.

Summer 2026

Read our latest project newsletter!

As the project moves into the early design phase, we have a newsletter with information about:

What we are doing during early design
What we’re hearing from the community
What you can expect during this phase
How you can stay connected

Check it out by clicking the links below!

English

Español (Spanish)

中文 (Chinese, Simplified)

正體字 (Chinese, Traditional)

日本語 (Japanese)

한국어 (Korean)

Русский (Russian)

Meet us at an upcoming community event

We will be at events in Redmond, Sammamish, and Issaquah this summer and fall to answer your questions and collect your comments and feedback.

Upcoming events:

GoGreen Movie Night in Marymoor Park
- Date: Wednesday, July 22
- Time: 7 to 9:20 p.m.
- Location: Marymoor Park in Redmond (Athletic Fields 7, 8, 9)
Sammamish Farmer’s Market
- Date: Wednesday, August 5
- Time: 4 to 8 p.m.
- Location: Sammamish Commons, 801 228th Ave. Southeast
Issaquah Salmon Days
- Date: Saturday, October 3, and Sunday, October 4
- Time: 10 a.m. to 6 p.m.
- Location: Downtown Issaquah

We hope to talk with you soon!

Previous project updates

Saturday morning survey work on June 27, June 2026
Saturday morning survey work June 13 and new Community Questions webpage!, June 2026
Come talk with us at Bike Everyday Day on May 13!, May 2026
Survey work this Saturday on East Lake Sammamish Parkway, March 2026
Saturday work coming up, and still time to share your thoughts about the project!, March 2026
More surveying coming up! And we’re still listening, March 2026
We’re still listening! Share your thoughts and questions with us at our online open house, February 2026
Survey work on East Lake Sammamish Parkway on Saturday morning, February 2026
Translations for the online open house and survey are available! Deadline to participate extended through March, January 2026
Update on what we’re hearing and how you can share comments and questions, January 2026
Visit our online open house and watch for upcoming survey work, January 2026
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	2026-2031	2031-2035
Pre-design	Design	Construction

Project schedules may change due to a number of factors. We will provide updates on our progress and schedule throughout the project.