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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

February 4, 2026

Survey work on East Lake Sammamish Parkway on Saturday morning, February 7

On Saturday, February 7, crews will survey a section of East Lake Sammamish Parkway between Northeast 49th Place and Sammamish Landing Park. During this work, crews will assess utilities located in the roadway. Work is scheduled to take place between 6 and 9 am.

There will be temporary single-lane closures for short durations. You will see traffic signs, flaggers, and a truck with flashing lights. Please drive slowly in the work area. People on bikes will need to merge with traffic. You can expect minor delays during this time.

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 Northeast 49th Place are labeled on the map.
Crews will conduct survey work on a section of East Lake Sammamish Parkway between Northeast 49th Place and Sammamish Landing Park. The section is shown in the black rectangle in the map above.

Crews continue to survey utilities in the shoulder on East Lake Sammamish Parkway on weekdays from 7 a.m. to 3:30 pm.

An aerial view of Lake Sammamish with the "Online Open House" text superimposed.

Visit our online open house, and share your comments and questions. Now available in seven languages!

Thank you to everyone who has visited the Sammamish Plateau Diversion Project online open house! We’ve already received valuable feedback through our survey – read more about what we’re hearing in our latest project update. See below for more information on translated versions!

Please continue to review and share your thoughts as often as you like at kingcounty.gov/wtd/Sammamish-Plateau-Online-Open-House.

Our online open house and survey are now available in multiple languages. You may respond to the survey in your preferred language. The survey is open through March 2026.

Select links below to access the open house in the following 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

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