Skip to main content

KingCounty.gov is an official government website.

Official government websites use .gov
Website addresses ending in .gov belong to official government organizations in the United States.
Secure .gov websites use HTTPS
A lock or https:// means you've safely connected to the .gov website. Only share sensitive information on official, secure websites.
King County Logo

Sammamish Plateau Diversion

The Sammamish Plateau Diversion Project will build new wastewater infrastructure to serve the growing East Lake Sammamish area.

Sign up for news and updates

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 13, 2026

Survey work continues on the shoulder of East Lake Sammamish Parkway

The project team continues 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 am and 3:30 pm. This work involves no traffic impacts. Please look out for our survey crews and drive carefully in the area.

Crews will need to work in the roadway for some utility surveys. This work will take place at locations along East Lake Sammamish Parkway and at the Northeast Inglewood Hill Road intersection. Work in the roadway will occur on Saturdays from 6 am to 9 am to reduce traffic impacts. We will notify the community in advance of Saturday work and provide more detail on what to expect.

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