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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 26, 2026

Survey work on East Lake Sammamish Parkway on Saturday morning, March 28

On Saturday, March 28, crews will survey the East Lake Sammamish Parkway between Sammamish Landing Park and the entrance of Weber Point (map below). Work hours are from 6 to 9 a.m.

What to expect:

  • Temporary single-lane closures for short durations.
  • Traffic signs, flaggers, and a truck with flashing lights.
  • Minor delays.
  • People on bikes will need to merge with traffic.

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

Learn more about this and other ongoing survey work in our latest project update.

A map shows a section of East Lake Sammamish Parkway bordered by a black box, calling out the survey area. The survey area, Sammamish Landing Park, East Lake Sammamish Parkway, and the entrance of Weber Point are labeled on the map.
Crews will conduct survey work on a section of East Lake Sammamish Parkway between Sammamish Landing Park and the entrance of Weber Point. The section is shown in the black rectangle on the map above.

An aerial view of Lake Sammamish with the

The Online Open House is winding down 

After almost three months and over 8,000 views, it’s time to wind down the Online Open House. After March 31, you will be able to continue viewing this product as a resource and fill out the survey on our Public Engagement page. Later this spring, we will share a summary of what we heard.

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 during the project’s design and construction phases.

If you haven’t already, we invite you to take our survey to share your thoughts with us. 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