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Project update

May 4, 2022

Surveying continues/utility locates beginning in May

Starting as early as May 16, crews will locate utilities in north Mercer Island and Bellevue to prepare for major construction activities beginning later this Spring. Surveying and utility location will take place in neighborhoods, public parks, and along the I-90 trail. Most work will take place in the public right of way. King County will notify property owners ahead of any work on private property. 

What to expect while crews are locating utilities: 

  • Permitted hours are 7 a.m. to 7 p.m. Monday to Friday and 9 a.m. to 6 p.m. on Saturday.
    • We will provide advance notice of any weekend or after-hours work.
  • Utility location is expected to take approximately one month to complete.
    • Please note, construction schedules often change due to weather, staffing, and other unforeseen things.
  • Flaggers will direct vehicle, pedestrian, and bicycle traffic around the work site, as necessary.
  • Expect intermittent loud noise during jackhammering and saw cutting.
  • Expect increased continuous noise while the vacuum truck is in use.

Learn more about utility location via our project update.

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.

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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: