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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.

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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

March 19, 2026

Survey work on the parkway continues and Saturday work planned for March 28

The project team continues to survey utilities along East Lake Sammamish Parkway in Sammamish. Currently, this work is taking place around the 3900 block of the parkway. Most survey work will occur on the shoulder on Monday through Friday, between 7 a.m. and 3:30 p.m. This work will not affect traffic.

On Saturday, March 28, crews will survey the East Lake Sammamish Parkway between Sammamish Landing Park and the entrance of Weber Point. Work is scheduled to take place between 6 a.m. and 9 a.m.

Please look out for our survey crews and drive or bike carefully in the area.

Learn more about this upcoming work in our latest project update.

An aerial view of Lake Sammamish with the

Visit our online open house and share your thoughts – available in seven languages!

Thank you to the thousands of people who have viewed the Online Open House! We appreciate everyone who has filled out a survey and shared questions, suggestions, and contacts for community groups. Your responses help us understand your concerns and serve the community better as we continue through design.

We’ve reached out to local businesses, homeowners associations, houses of worship, and community-based organizations to share information about the project. Who are we missing? Do you know an organization or group that should know about this work? We want to know!

Share with us any organizations or groups that should be in the loop. We want to hear from everyone!

The survey is open through March 2026. You can fill it out as many times as you like. It’s available in seven languages:

Previous project updates

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.

Project location