Sammamish Plateau Diversion

Project update

April 15, 2026

Survey work continues in the project corridor

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.

Project crews continue collecting survey data along the project corridor. This information will help inform the pipe location within the corridor and construction methods. To learn more about the project corridor, visit our Online Open House and click on the “Project Corridor” tab.

This spring, you can expect to see crews doing the following activities:

Marking utilities along East Lake Sammamish Parkway Northeast

Crews are working in the shoulder, which does not affect traffic. During this work, crews are working Monday through Friday, between 7 a.m. and 3:30 p.m. 

There will be occasional survey work in the roadway to locate underground utilities. This work will take place on specific Saturday mornings between 6 a.m. and 9 a.m. to reduce traffic impacts. We will notify the community in advance of Saturday work and provide more detail on what to expect. Sign up for project emails to stay up to date.

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

Surveying trees

Crews will be surveying and assessing larger trees along the project corridor. You may see numbered tags on some trees. Tags help in assessment and do not mean future impacts to the trees. The project team will work with public or private property owners if trees will be affected. Tree surveys will not impact traffic.

An example of an identification tag you might see on some trees in the project area during surveying in spring 2026.

Thank you for visiting our Online Open House and sharing your thoughts!

After three months and over 8,000 views, we’ve wrapped up the Online Open House. You will still 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.