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June 2026
 Crews prepare a work site for tunneling near Coal Creek Parkway SE
The Coal Creek Sewer Upgrade project will soon reach a big milestone! About one mile of the new Coal Creek sewer pipe will be installed by tunneling underground.
Starting as soon as July, tunneling is expected to begin at the Red Cedar Trailhead. Once it begins, tunneling will run 24/7 to ensure smooth and safe operation.
Here is what you can expect:
- Work activity at the Red Cedar Trailhead will continue around the clock during tunneling. The tunneling machine will operate 24/7. This is to reduce impacts to neighbors and ensure smooth and safe operation of the tunneling equipment.
- The tunneling machine will dig deep underground. You may feel small vibrations. King County will monitor vibration levels to ensure work continues safely.
- Tunneling is expected to be done by the end of the year.
- Noise typical to a construction site near work areas during work hours.
- Temporary lane closures and construction vehicle traffic on Coal Creek Parkway SE.
- The Red Cedar Trailhead will be 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.
Tunneling reduces impacts on nearby communities and natural areas compared to traditional construction methods. Visit our online open house to learn more tunneling and the Coal Creek project.
Come chat with us!
Stop by one of our upcoming drop-in sessions to learn more about tunneling and talk to the project team. We hope to see you there!
- Sunday, June 28, 9 am to 12 pm, Forest Drive Trailhead
- Friday, July 10, 9 am to 12 pm, Forest Drive Trailhead
Our team will also be at the following community events this summer:
- July 11, 11 am to 2 pm, Eastgate Block Party at Newport Way Library
- July 18, 10 am to 5 pm, Newcastle Art Fair at Avalon Newcastle Common
Construction monitoring devices during tunneling
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Several construction monitoring devices have been installed in right-of-way areas along the tunneling route. These devices collect data about underground conditions to track tunnelling progress. They will remain in place until tunneling is complete.
Please do not disturb the construction monitoring devices. Contact our team with any questions about the devices.
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Adding wastewater capacity for growing communities in Bellevue and Newcastle
Construction for King County Wastewater Treatment Division's (WTD) Coal Creek Sewer Upgrade Project began in 2025. It will add wastewater capacity and move the active pipeline away from Coal Creek's environmentally sensitive areas. This project was the first wastewater infrastructure project to earn a Salmon-Safe certification!
After construction, the contractor will restore the Coal Creek Natural Area, parking areas, and affected roadways to protect the creek, trails, and infrastructure. The rebuilt Red Cedar Trailhead will keep the same look-and-feel while enhancing accessibility for visitors of all abilities.
For more information
Visit the Coal Creek project website for the most up-to-date construction information:
Call or email our construction hotline at 425-537-7195 or CoalCreekProject@kingcounty.gov.
Note: This is the King County Coal Creek Sewer Upgrade Project hotline. If there is an emergency, please dial 911. This phone line is for incoming calls only. We will never call you by this number. If you receive a call claiming to be from this number, please be aware it may be a scam.
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