Skip to main content
King County logo

Wastewater Treatment Division (WTD) operations and projects

WTD operations staff remain on the job 24/7 to ensure the region’s wastewater treatment service continues. More information on how to report a problem you believe may be related to the County’s wastewater treatment system is available here:

The King County Wastewater Treatment Division remains committed to sharing information and gathering feedback from community members about its work and projects. WTD staff remain available to answer questions via email and phone during regular business hours. Project information lines remain available and are being monitored for ongoing construction projects.

Project update

September 15, 2020

King County thanks Coal Creek Natural Area visitors for your patience as our contractors carried out a temporary project and completed field work in August and early September.

Watch this page and your mailbox for a newsletter, and stay tuned for opportunities to participate in an online open house and take a self-guided tour of the project when you visit the Natural Area.

If you sign up for email updates and text alerts, you will be the first to hear about these opportunities!

The Coal Creek Project team celebrates #ADA30 with a new video on accessibility for remote meetings

On July 26, our nation celebrated the 30th anniversary of the signing of the Americans with Disabilities Act into law. Learn what King County is doing to provide equal access to employment, transportation, housing, education, health care, recreation, and community life. 

WTD’s Coal Creek team will celebrate #ADA30 with some help for everyone in a challenging time, when virtual meetings help us to connect safely with others. Watch the video below to see how you can make video calls and remote meetings more accessible for everyone in your workplace, community, and organization!

Design update

King County's Coal Creek Sewer Upgrade Project is in final design. In this phase the team refines the project design, conducts environmental review, and acquires permits and property rights.

We will continue to keep the community up to date, answer questions, hear your input, and address concerns. The Coal Creek team is committed to continuing outreach during the next few months. We will be reaching out to the community to find the best way to keep in touch with you!

Sign up for email and text alerts to keep up to date!

You can fill in the box at right to get updates, surveys, notices, and other information by email and/or text. You can unsubscribe anytime.

Questions? Concerns? Contact us!

If you would like to discuss the project, ask questions, give input, or share concerns, call Monica Van der Vieren at 206-477-5502 or email:

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.


Timeline for the Coal Creek Sewer Upgrade Project

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.

Design Phase

Contact us

Contact Monica Van der Vieren at:


Sign up for email or text updates

To manage your preferences, enter your email or wireless number and select Confirm.

If you are new to the project, you can get up to speed by visiting this Story Map, which covers the project background and early design.

Storymap: Coal Creek Sewer Upgrade

Project location

1711_project-location_600Project location and service area

project area mapProject area map

Back to the capital projects overview map .