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Project update

June 14, 2022

Tree removal in Mercer Island begins soon

As a part of this project, we will plant 600 new trees across Mercer Island to replace the nearly 400 trees we remove during the project. We are coordinating directly with the City of Mercer Island about tree protection, removal, and restoration. Tree removal will begin at the North Mercer Pump Station as early as Friday, June 17. Tree removal along the I-90 trail begins as early as next week. To learn more about what to expect, read our announcement here

Read our Plan for Trees  factsheet in our project library – to learn more.

Join us at the Mercer Island Farmers Market this Sunday! 

The project’s community relations team will set up a booth at the Mercer Island Farmers Market this upcoming Sunday, June 19. Staff will share project updates, have informational materials, and answer questions. We hope to see you there! 

The North Mercer Island/Enatai hotline is back in service.

Please call 206-263-1915 if you have a question about the project.

Thanks for your patience and understanding.

Recent notifications:

To learn more about what we are building, construction, and what to expect, click on the StoryMap below.

Aerial view of Lake Washington. Click Storymap: learn more about the North Mercer/Enatai Sewer Upgrade Project.

Sign up for email and text updates 

Sign up for general project updates in two geographic areas:

North Mercer Island project area

Enatai project area

Click on a project area number to learn more and sign up to receive email or text updates.

Project areas: 1 | 2 | 3 | 4 | 5| 6 | 7 | 8

The construction route has been divided into 8 areas. You can sign up to receive updates for one or all of these areas.

Project description

With over 400 miles of pipes moving wastewater to one of our award-winning treatment plants, King County WTD works hard to maintain our system. We inspect and monitor our regional system and update plans for needed upgrades.

King County WTD needs to replace sewer pipes that serve areas in North Mercer Island, the southwest portion of Bellevue near Enatai Beach, and the Town of Beaux Arts Village. This pipeline carries wastewater from the North Mercer Island Pump Station to the Sweyolocken Pump Station in Bellevue.

Learn more:


Project design began in 2016 and will be complete in 2021. Construction is expected to begin in 2022 and extend until 2025. View March 2022 project newsletter for latest schedule .


Contact us

Contact Kristine Cramer, community services lead at:

24-hour construction hotline: 206-263-1915

Project location

The project area spans from the North Mercer Pump Station to the Sweyolocken Pump Station (Mercer Slough)

Back to the capital projects overview map .

Lets Talk Mercer Island!

The City of Mercer Island and King County are collaborating to ensure Mercer Island residents get timely, accurate construction information. In addition to the County’s website, Let’s Talk Mercer Island will feature the project with monthly updates and will monitor for resident questions and comments. 

Related information

System planning

Local municipalities: