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Project update

July 1, 2021

Take a tour of the future construction zone with us!

Lets Talk Mercer Island!

Construction is expected to start later this year on the Mercer Enatai Sewer Upgrade. 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 as it moves into construction.

We will provide monthly updates on Let’s Talk, and we will monitor the site for resident questions and comments. And of course, as always, don’t hesitate to reach out directly with any questions or concerns you might have.

Construction ahead 

Major construction is set to begin later this year across north Mercer Island and southwest Bellevue. The sewer upgrade is a big project that’s been years in the making and will involve years of construction. We expect construction to begin this fall and be complete in 2025. Some of the work will be in heavily used public spaces, and some will be in residential areas. The end product will provide great public benefit, but the work to get there will involve inconveniences to residents and park and trail users. We are committed to keeping you informed about what’s happening and why in order to minimize impacts wherever possible. View Spring Newsletter and Construction Reference Guide

Take a walk through the future construction area of the Mercer Enatai Sewer Upgrade project. See where we’ll be working and what it means for neighbors, commuters, and park and trail users.

Dé un paseo en la futura área de construcción del proyecto de mejora del alcantarillado de Mercer Enatai. La construcción comenzará a finales de 2021 y durará hasta 2025. Vea en dónde estaremos trabajando y lo que significa para los vecinos, transportistas y usuarios del parque y del sendero. 

View video with English captions.

If you are interested in a project update for your community group or neighborhood, please contact Kristine Cramer at 206-477-5415 or

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.

nme_construction_reference_guideConstruction Reference Guide.


Project design began in 2016 and will be complete in 2021. Construction is expected to begin in 2021 and extend until 2025.

project timelineView larger version .


Contact us

Contact Kristine Cramer, community services lead at:


Shai Malone at

 Feedback form

Sign up for email or text updates

To sign up for text alerts, text KING MERCERSEWER to 468-311 for Mercer Island, and KING ENATAISEWER to 468-311 for Enatai. To sign up for email updates, please visit the public involvement page.

Project location

Project pipeline alignment and service area

Back to the capital projects overview map .

Related information

Regional Wastewater Services Plan

Local municipalities: