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March 2026
Survey work continues and expands
The Sammamish Plateau Diversion Project continues to collect survey data along the project corridor. This information will inform the pipe location within the corridor and construction methods.
During this work, you can expect to see crews:
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Marking utilities along the shoulder of East Lake Sammamish Parkway. Currently, this work is taking place on the north end of the parkway in the City of Sammamish. Crews are working Monday-Friday, between 7 a.m. and 3:30 p.m. This work does not affect traffic.
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There will be occasional work in the roadway to locate underground utilities. This work will take place on Saturday morning to reduce traffic impacts. We will notify the community in advance of Saturday work and provide more detail on what to expect.
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Marking stream and wetlands in the project corridor. This work will begin this month and will occur along the project corridor along Northeast Inglewood Hill Road and East Lake Sammamish Parkway. Crews will also be on the northern part of the East Lake Sammamish Trail where the new pipe will eventually connect to King County’s existing pipes. To see this area on a map, visit our Online Open House. This work involves no traffic impacts.
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Surveying trees along the project area. Tree surveys will occur in spring 2026. People may see identification tags on some trees. A tag does not mean the tree will be affected by the project. Tree surveys will not cause traffic impacts.
Please look out for our survey crews and drive or bike carefully in the area.
 An example of an identification tag you might see on some trees in the project area during surveying in spring 2026.
Visit our online open house and share your thoughts – available in seven languages!
Thank you to the thousands of people who have viewed the Online Open House! 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 as we continue through design.
We’ve reached out to local businesses, homeowners associations, houses of worship, and community-based organizations to share information about the project. Who are we missing? Do you know an organization or group that should know about this work? We want to know!
Share with us any organizations or groups that should be in the loop. We want to hear from everyone!
The survey is open through March 2026. You can fill it out as many times as you like. It’s available in seven languages:
If you need accommodations to access this material or would like to share your thoughts with us directly, please contact:
Question: Can the project share traffic impacts? What traffic and trail impacts can you avoid?
King County’s response:
Yes, we will share proposed work hours, traffic control, detours, and more as we confirm details.
Our region and your community benefit from clean water projects. Construction impacts are a part of building and updating regional water systems like this one. We know construction can be disruptive for people living, working or passing through work areas.
The Community Services team will work with you every step of the way on the Sammamish Plateau Diversion Project. As design progresses, we will share information about potential community impacts. We are here to answer your questions and discuss the project.
Permitting and environmental review will identify impacts people may expect. You will have opportunities to comment during both processes.
This is a great time to help us understand what we need to track about roadway and trail use during design. Here are needs you have shared so far:
- Maintaining services and deliveries
- School bus pickups along East Lake Sammamish Parkway
- Managing vehicle and bike traffic, especially on garbage/recycling day
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Ensuring home access for residents and emergency services
- Identifying ways to avoid long backups on the roadway
WTD’s project teams work with you to support communities during construction. The project’s Community Services team provides advance notice of construction activities. We respond to community concerns and complaints. We work with WTD’s project managers to find reasonable solutions. We will give you progress updates and let you know when the new system is in operation.
We're here for you!
We know that large construction projects can be stressful for communities, and there are a lot of construction projects going on across the Eastside. Our project team is committed to being available and continuing to work with neighbors, businesses, visitors, and commuters every step of the way. We will be here for you all the way through design and construction and into operations. Feel free to contact us at any time!
Contact us
Community Services Project Team
Visit us at kingcounty.gov/SammamishPlateauDiversion
Please note that voicemails and emails are considered records and may be subject to public disclosure. The project phone number is operated by a third-party service called Grasshopper. Recordings on this service are considered records. If you prefer to discuss the project with us rather than commenting in voicemail or email, please leave a message and we'll call you back within one business day.
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