Coal Creek sewer upgrade
Project update
February 15, 2023
Winter 2023 newsletter: Protecting and restoring the Coal Creek project area
We know that people are interested in what we are doing to protect and restore the Coal Creek Natural Area during this project. Check out our winter 2023 newsletter to learn about what you can expect to see during and after construction.
Select the "Sign up here" button in the Contact us box to get updates, surveys, notices, and other information by email and/or text. You can unsubscribe anytime.
Project description
King County Wastewater Treatment Division (WTD) will upgrade a regional sewer line that serves Bellevue and Newcastle. The existing pipeline was built between 1966 and 1991 in an area that looked different from today, with a smaller population. The pipeline is nearing its maximum capacity and needs to be upgraded to carry more wastewater and meet the growing needs of your community.
Once installed, the new sewer pipe is designed to serve your community for another 50 years or more.
Schedule
Protecting the Coal Creek Natural Area
The existing Coal Creek Trunk is approximately 2.5 miles long and primarily follows the banks of Coal Creek in the Coal Creek Natural Area between Newcastle and I-405. The new pipeline alignment will move the active pipeline away from Coal Creek offering better protection to this sensitive environmental area.
The selected pipeline alignment also aims to decrease impacts to both the Natural Area and Coal Creek Parkway SE during construction.
Project Elements
This map shows the project work areas and the construction methods King County’s contractor will use in each area. The contractor will install about 10,800 feet of pipe to build the new Coal Creek Trunk Sewer and re-establish connections to the City of Bellevue’s sewer collection system.
King County’s designers work to reduce community impacts and inconveniences where possible. But on large projects like this one, inconveniences are unavoidable. People can expect up to 3-years closure at the Red Cedar trailhead, with a trail detour around the construction site. There will be traffic impacts during work close to the Parkway.
Keep up to date to make sure you have the latest news and information as final design continues.
Learn more
You can visit online resources to learn more:
Introduction to King County’s regional wastewater service and the history in Bellevue, along with early design. 
Recent updates on project design. 
Red Cedar Trailhead Restoration Options - StoryMap and Tour
Contact us
Contact Monica Van der Vieren at:
monica.vandervieren
@kingcounty.gov
206-477-5502
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