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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

January 27, 2026

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.

We have launched translated versions of the online open house and survey. You may respond to the survey in your preferred language. With the launch of translated materials, we are extending the survey through March 31, 2026.

Select links below to access the open house in the following languages:

Survey work continues on the shoulder of East Lake Sammamish Parkway

The project team is continuing to survey utilities along East Lake Sammamish Parkway in Sammamish. Currently, this work is on the north end of the parkway. Most survey work will occur on the shoulder on Monday-Friday, between 7 a.m. and 3:30 p.m. This work involves no traffic impacts. Please look out for our survey crews and drive carefully in the area.

Learn more about what to expect in the project update, which we shared on January 16.

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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