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Apr
23

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 Sammamish Plateau Diversion Project will create new infrastructure to manage some wastewater flows from the East Lake Sammamish area. Currently, wastewater flows from the Sammamish Plateau travel to South Treatment Plant in Renton. When the project is finished, a portion of those flows will travel north to King County’s Brightwater Treatment Plant.

This project will add capacity to serve current and future populations in a busy, growing area.

Project update

April 11, 2025

Survey work happening in April

Currently, the Sammamish Plateau Diversion Project is in the exploration phase. Our project team is continuing to gather data through both desktop research and field surveys to help inform this project.

Starting in April, you may see crews surveying the right-of-way (ROW) on Northeast Inglewood Hill Road between East Lake Sammamish Parkway and 212th Avenue Northeast. During this work, surveyors will be in the public ROW marking utilities with paint and surveying locations. Additionally, crews will be accessing maintenance holes and catch basins in the roadway. We do not anticipate any traffic impacts during this work.

The work is scheduled to begin as soon as the week of April 14 and is expected to take up to 5 weeks to complete.

What to expect

  • Survey work taking place along the ROW on Northeast Inglewood Road between East Lake Sammamish Parkway and 212th Avenue Northeast.  
  • Work hours between 7 a.m. and 3 p.m., Monday-Friday.
  • Work will take place up to 5 weeks.  
  • Roads and sidewalks will remain open, and no traffic impacts are expected.

The map on the left below shows the entire project area in blue hatching with a blue inset box that shows the location of the survey work along the ROW. The map on the right shows a zoomed-in view of survey work within the blue inset box. This work is along the ROW on Northeast Inglewood Hill Road between East Lake Sammamish Parkway and 212th Avenue Northeast. 

The map on the left below shows the entire project area in blue hatching with a blue inset box that shows the location of the survey work along the ROW. The map on the right shows a zoomed-in view of survey work within the blue inset box.

We want to hear from you - please take our short survey!

King County’s project team wants to get to know you and your community better. By understanding your needs, we can serve you more effectively during the design and construction phases of this project. Please share your feedback with us by completing this survey. We expect that this survey will take about 10 minutes to complete.

We have two different surveys: one for community members and one for local businesses. If you are both a community member and a local business owner in the project area along East Lake Sammamish Parkway Northeast (see map below), please fill out both surveys.

If you prefer to provide the information in the survey over the phone or by other means, please contact Monica Van der Vieren at 206-477-5502 or monica.vandervieren@kingcounty.gov.

Learn about the latest project update.

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We welcome you to contact us at any time during the project to talk, ask questions, express concerns, and give feedback and input.

Project timeline

2023 - 2025 2026-2028 2028-2030
Alternatives Analysis Design Construction

Project timelines may change due to a number of factors. The Sammamish Plateau Diversion Project is in an early phase. We will provide updates as our work progresses and any schedule changes are needed.

Project location

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