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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

November 24, 2020

Online open house and self-guided tour available until December 17!

King County's Coal Creek Sewer Upgrade Project team is extending our online open house and site tour at the Upper West Trailhead into December to give you more time to learn about the project, ask questions, and share your thoughts.

When construction starts in 2022, it will be noticeable to people driving nearby and visiting the natural area. We are inviting neighbors, cyclists, trail enthusiasts and park visitors to review proposed plans and offer feedback.

Participate in either option to learn more about:

  • Different construction techniques and work areas
  • Protections for the environment and people during construction
  • Restoration after construction
Click here to visit our online open house >>
Available October 26 – December 17, 2020

You can also view the Online Open House and Self-Guided Tour Signs as a PDF files:

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:

Coal Creek Project team honors and celebrates National Disability Awareness Month 

During the month of October, we celebrate Disability Awareness Month in King County and the many contributions people with disabilities make to our communities.

WTD’s Coal Creek team is committed to providing opportunities for engagement that welcome individuals of all abilities. In July 2020, our project team celebrated the 30th Anniversary of the signing the Americans with Disabilities Act into law by creating a video about how to remote meetings and virtual calls more accessible for everyone in your workplace, community and organization. We are committed to continuing to provide opportunities for engagement for all people in our community and strive to ensure equal engagement opportunities for people of all abilities.

Check out the video below and learn more about how to make video calls and remote meetings more accessible for everyone in your workplace, community and organization and learn more about how King County is celebrating Disability Awareness Month.

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Click to view Summer 2020 newsletter

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:


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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

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