Coal Creek sewer upgrade

Project update

June, 2026

Tunneling begins this summer!

The Coal Creek Sewer Upgrade project will soon reach a big milestone. 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.

About one mile of the new Coal Creek sewer pipe will be installed by tunneling underground. Tunneling reduces impacts on nearby communities and natural areas compared to traditional construction methods. Learn more about tunneling at our online open house!

Come chat with us!

Stop by the drop-in sessions below to learn more about the project. We hope to see you there!

• Sunday, June 28, 9 am to 12 pm at Forest Drive Trailhead
• Friday, July 10, 9 am to 12 pm at Forest Drive Trailhead

Our team will also be at the following community events this summer.

• Saturday, July 11, 11 am to 2 pm at Eastgate Block Party at Newport Way Library
• Saturday, July 18, 10 am to 5 pm Newcastle Art Fair at Avalon Newcastle Commons

Construction monitoring devices during tunneling

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.

An example of a construction monitoring device

Traffic impacts on Coal Creek Parkway SE

Commuters on Coal Creek Parkway SE can expect ongoing single lane closures and traffic delays between the Red Cedar Trailhead and I-405. Southbound lane closures are permitted for weekdays, 6:00 am to 3:00 pm. Northbound lane closures are permitted for weekdays, 10:30 am to 7:30 pm. Flaggers will be present to direct traffic. Drivers and cyclists will share a lane when traveling through the work area and are advised to use caution.

Reminder: do not enter construction zones

The Red Cedar trailhead and other work areas are active construction zones and remain closed to all public use. Other trailheads in the area such as the Cinder Mine, Red Town, Coal Creek Family YMCA, and Forest Drive trailheads are available for trail users. Stay out of fenced areas and the creek bank for your safety and to protect the Coal Creek Natural Area and salmon habitat.

Sign up for the project email list to get updates, learn about construction, and find outreach activities that you can participate in!