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Project update

April 19, 2021

Local news: Massive sewer upgrade project on the way this fall , April 15, 2021 (Mercer Island Reporter)

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 .

map of the construction activitiesConstruction Reference Guide

King County’s North Mercer Island/Enatai Sewer Upgrade project starts construction later this year. This important project will provide great public benefit, but the work to get there will involve inconveniences to residents and users of public spaces. Find out more about the project in the video below, and how our work makes a difference every time you wash dishes or take a shower.

El proyecto de actualización del alcantarillado del norte de Mercer Island/Enatai en el condado de King comenzará a construirse durante este año. Este proyecto importante proporcionará un gran beneficio público, pero el trabajo para lograrlo implicará inconvenientes para los residentes y los usuarios de espacios públicos. Obtenga más información sobre el Proyecto en esto video y de qué manera nuestro trabajo marca la diferencia cada vez que lava los platos o se ducha.

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.

Project area mapView larger version . December 2018


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: