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Project update

October 30, 2018

Tree survey work beginning November 5

As early as November 5, King County Wastewater Treatment Division will be surveying trees in the Enatai neighborhood and Mercer Slough. This work will help identify tree species and proximity to areas within the North Mercer Island/Enatai Sewer Upgrade Project working limits.

map of tree survey area 

What you can expect for tree survey work:

  • Work hours typically 8 a.m. to 4 p.m. on weekdays.
  • Work expected to take up to three days.
  • Up to two crew members in high visibility vests using measuring tapes and notebooks to survey trees and record data.
  • During tree survey, some trees will receive tree tags, aluminum nails with a tag that the tree will grow over.
  • King County has notified property owners ahead of any work on private property.

View project update .

If you or someone in your community would like to learn more about the project, please contact Kristine Cramer, or 206-477-5415 to schedule a briefing.

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.


Contact us

Contact Kristine Cramer, community services lead at:


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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.

1701_NME-final-pipeline-route_700View larger version. July 2017


Project design began in 2016 and will be complete in early 2020. Construction is expected to begin in 2020 and extend until 2024.

project timeline Click to view larger version .

Project location


Back to the capital projects overview map .

Related information

Regional Wastewater Services Plan

Local municipalities: