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Coal Creek sewer upgrade
The Coal Creek Sewer Upgrade Project will increase wastewater capacity for Bellevue and Newcastle.
Help Wastewater Treatment improve our accessibility!
Please complete our 5 minute survey by September 30 to help make our system accessible to everyone.
Project description
The Coal Creek Sewer Upgrade Project will upgrade a regional sewer line that serves Bellevue and Newcastle. Built between 1966 and 1991, the existing pipeline is at its maximum capacity and needs to be upgraded to carry more wastewater from the growing areas. The new pipe is expected to provide sewer service for decades.
This project will build about 2 miles of new sewer pipe. It will also move the active pipeline away from Coal Creek's environmentally sensitive areas.
Online open house
Our construction phase online open house is now available! Learn more about how this project is being built and what to expect during tunneling
Project update
October 2026
Tunneling in action!
The contractor is continuing around-the-clock tunneling work at the Red Cedar Trailhead in Bellevue.
Check out the video of the tunneling machine working deep underground!
What to expect during tunneling work:
- Work activity at the Red Cedar Trailhead will continue around the clock during tunneling. The tunneling machine will operate 24/7 to ensure smooth and safe operation.
- Typical construction noise during work hours.
- Temporary lane closures and construction vehicle traffic on Coal Creek Parkway SE.
- The Red Cedar Trailhead is closed. Trail users can access the natural area via the Forest Drive, Red Town, Cinder mine, and other trailheads. Please follow trail detours and stay out of fenced construction areas.
Stay in touch!
Sign up for the project email list to get updates, learn about construction, and find outreach activities that you can participate in!
Call or email our construction hotline at 425-537-7195 or CoalCreekProject@kingcounty.gov.
Previous project updates
- Tunneling begins soon! Coal Creek construction update, July 16, 2026
- Tunneling begins soon! Coal Creek construction update, June 25, 2026
- Early morning closure of Coal Creek Parkway SE on April 9 and 10, April 2, 2026
- Northbound single-lane closure on Coal Creek Parkway SE as early as March 23, March 20, 2026
- Updated work hours for early morning Coal Creek Parkway SE closure on February 24, February 23, 2026
- Updated work hours for early morning Coal Creek Parkway SE closures on January 28 and 30, January 27, 2026
- Construction on Coal Creek Parkway SE starting this month, January 16, 2026
- Lane closure on Coal Creek Parkway SE, near I-405, starts December 9, December 9, 2025
- Lane closure on Coal Creek Parkway SE near Factoria Boulevard SE to begin as early as Dec. 1, November 26, 2025
- Early morning closure of Coal Creek Parkway SE on Nov. 19 and 20, November 12, 2025
- Southbound single-lane closures on Coal Creek Parkway SE begin as early as October 13, October 7, 2025
- Lane closure on Coal Creek Parkway SE near Red Cedar Trailhead, September 18, 2025
- Pre-construction survey closing soon!, August 29, 2025
- Red Cedar Trailhead closure beginning as early as June 17, June 16, 2025
- Red Cedar Trailhead closure and traffic impacts beginning as early as summer 2025, May 16, 2025
- Coal Creek project awarded Salmon-Safe Certification, April 17, 2025
- News release: King County’s major sewer upgrade in Bellevue is the first project of its kind to earn Salmon-Safe certification, simultaneously modernizing infrastructure and improving habitat, April 9, 2025
- King County's Coal Creek Sewer Upgrade Project is heading into construction in 2025!, April 2025
- Survey work in the Coal Creek Sewer Upgrade Project area beginning this month, March 11, 2025
- Heads up: Work in Coal Creek Natural Area beginning mid-July, July 9, 2024
- Crews will install equipment to monitor conditions in the Coal Creek Natural Area as early as April 24, April 26, 2024
- Construction starting this year!, March 3, 2025
- Protecting and restoring the Coal Creek project area, Winter 2023
- Protecting and restoring the Coal Creek project area, February 16, 2023
- Did you see the latest project updates? June 3, 2022
- Winter 2022 newsletter, March 2022
- Opportunities for input- one ends, another begins, January 6, 2022
- Bringing in the New Year with a project update, January 3, 2022
- Neighbor feedback needed on parking/transportation options on Forest Drive Southeast, August 16, 2021
- Tree surveys starting, and more time to add your input! August 9, 2021
- Reaching out to the community: Accessibility ideas for the Red Cedar Trailhead, July 27, 2021
- Crews will carry out surveys in the Coal Creek Natural Area beginning June 18, June 16, 2021
- Crews will carry out surveys in the Coal Creek Natural Area beginning April 14, April 8, 2021
- Upcoming geotechnical surveying near 130th Ave SE, March 1, 2021
- Field work continuing for the Coal Creek Sewer Upgrade Project, February 5, 2021
- Self-Guided Tour Signs, October 2020
- Project newsletter, September 2020
- Field work complete by Friday, August 28, trail impacts reduced on Thursday and Friday, August 26, 2020
- Field work making progress; expected to wrap up Friday, August 28, August 2020
- Field work underway in August- weekday trail closures beginning Monday August 3rd, July 2020
- Sewer upgrades in the works: Join us June 17 & 23 to learn more! June 2020
- Work coming up in Coal Creek Natural Area, May 2020
- Utility location with lane closure on Coal Creek Parkway starting as early as May 15, May 2020
- Final design is underway for the Coal Creek Sewer Upgrade Project! April 2020
- Roadwork with lane closures on Coal Creek Parkway starting as early as April 27, April 23, 2020
- Planned Coal Creek Natural Area surveying at the end of March and in early April, March 23, 2020
- Data gathering at pre-existing survey locations will start as early as February 26, February 19, 2020
- Minor maintenance activity in Coal Creek Parkway tomorrow, December 18, December 17, 2019
- Fall 2018 newsletter
- Field survey update: Work begins on Coal Creek Parkway Monday, July 15, July 12, 2019
- Field investigations coming up in Summer 2019, June 7, 2019
- Tree surveying for the Coal Creek Sewer Upgrade Project beginning May 7, May 2019
- Survey work in the Coal Creek Natural Area beginning March 11, February 2019
- A King County sewer upgrade project is coming to your area, December 2018.
(View online version.) - Tree surveying in Coal Creek Natural Area Wednesday-Thursday, September 5-6, August 2018
- Field work for a new sewer line in Coal Creek Area continues in July, July 2018
- Survey activity week of May 14, 2018, May 2018
- Geotechnical work in the Coal Creek Parkway area begins in January, updated January 9, 2018
- Geotechnical work in the Coal Creek Parkway area begins in January, December 2017