King County Sewerline Upgrade

Construction and Activity Starting on 90th Place Southeast

As early as August 1, King County crews will begin preparing 90th PL SE for construction as part of the North Mercer Island/Enatai Sewer Upgrade project. Construction will include parking revisions, temporary driveway impacts, and service interruptions for everyone who lives or travels on this street. See our email update for more information.

Sewer Line Construction Begins in North-Central Mercer Island

King County crews will install an upgraded sewer pipe on SE 22nd St, 78th Ave SE, and SE 24th in Mercer Island residential neighborhoods using an “open-cut” trenching construction technique. During open-cut construction, crews will saw cut the roadway’s surface, remove asphalt, and dig from the surface to the pipe depth. Expect increased noise, vibrations, and some driveway access interruptions on SE 22nd St, 78th Ave SE, and SE 24th.

Meet the Project Team at the Mercer Island Farmers Market

The County’s community relations team will set up a booth at the Mercer Island Farmers Market on the following dates: August 21 and Sept 18. Staff will share project updates, have informational materials, and answer your questions.

Please Follow Detour and Closure Signage

Construction crews have reported people ignoring posted closure and detour signage around active construction areas. While the coast may look clear, construction is complex - do not enter areas that are closed for your own safety, and follow detour signs to protect yourself and construction workers.

Learn more about this project on the County's website and view the latest newsletter mailed to homes on the Island.

Last week, King County shared plans to close the I-90 trail between Shorewood Drive and Southeast 35th Street as early as June 8. They are now planning to start the closure as early as June 17. Before the closure starts, crews will install a pedestrian detour and will maintain trail access during installation.

Here's what to expect:

Work to install new sewer pipes as part of the North Mercer / Enatai sewer upgrade project will impact everyone who lives near or travels on the I-90 trail. On Mercer Island, the County will close the I-90 trail in sections to complete the work. During each closure, crews will use a construction technique called “open-cut” trenching to bury the new pipe where it needs to go.

The County expects to close the trail in this section around the clock for about six months until the trail has been restored.

What to expect during trail closures:

• The I-90 trail will close 24/7 between Shorewood Drive and SE 35th St, starting as early as June 17.
• Permitted weekday work hours are from 7 a.m. to 7 p.m.
• Please note that construction schedules often change due to weather, staffing, and other unforeseen things.
• Bicycle and pedestrian traffic will detour off the I-90 trail (see maps on reverse).
• The detour will merge bicycles and cars along North Mercer Way.
• We will paint sharrows on the road to remind drivers to look for bicycles.
• Pedestrians will be directed to use a separate path on the north side of North Mercer Way.
• Speed limits on North Mercer Way will reduce to 20 MPH near the construction area.
• Trenches for open-cut construction will be covered with steel plates at the end of each workday.

King County will close the I-90 trail corridor between Shorewood Drive and Southeast 35th Street as part of the North Mercer Sewer Upgrade Project. This is the first section of the I-90 trail that will close for construction. Work will impact those who live near or travel on the trail. Learn more on the County's website.

Expect increased noise and vibration in neighborhoods, public parks, and along the I-90 trail.

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.

Utility location helps crews avoid service disruptions during construction work. To locate utilities, crews will use a jackhammer break-up pavement. Next, they use a vacuum excavation truck to remove dirt and locate buried utilities. Once the utilities have been located and documented, the roadway will be restored with asphalt.

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.
• The County 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.

King County will share additional information about impacts and schedule via the location-specific email lists, as needed. Learn how to sign up for targeted construction notifications here.

For your safety, and the safety of our crews, please drive slowly and obey signs near active work areas.

Construction is starting across north Mercer Island and southwest Bellevue. This project has been years in the making and will involve four years of construction - project work will be in heavily-used public spaces and residential areas. Check out King County's latest storymap below to learn about:

• What is being built
• What to expect
• Schedule and duration
• Detour routes
• What it will look like when the project is done
• How to reach King County about this project

Construction will begin this spring to upgrade four miles of sewer pipeline across north Mercer Island and southwest Bellevue. In addition to the new sewer pipeline, King County will upgrade the County’s North Mercer Pump Station and the City of Mercer Island’s Lift Station 11 at Fruitland Landing. The pipes, installed in the 1970s, are aging and reaching capacity. The sewer upgrade is a big project that will involve years of construction.

Before major construction starts, the crews will be surveying, setting up construction trailers, and preparing work areas for active construction. King County is committed to being a good neighbor and keeping you informed about what is happening to minimize impacts whenever possible - the City of Mercer Island will share their updates here on Let's Talk.

You can learn more by reading King County's latest newsletter on the project's website.

If you’d like to receive email or text updates, you can easily sign up online.

After years of planning and design, construction is now expected to begin early next year (2022) on the Mercer Enatai Sewer Upgrade project. A new interactive "StoryMap" virtual tour through the construction zone will help everyone find out how the work will impact Mercer Island and what King County and the City are doing to prepare for construction. The StoryMap will also guide viewers through the construction techniques that King County uses, how it works with communities during construction, the history of the project, and more.

King County’s North Mercer Island - Enatai Sewer Upgrade project starts construction very soon. This important project will provide great public benefit, but the work to get there will involve inconveniences to residents and users of public spaces along the north end of Mercer Island. This new 5-minute video takes you on a virtual tour of the construction areas to see where crews will be working over the next several years. Watch it here.

This spring and summer, King County will prepare for major construction activities, expected to begin in September 2021. That means it will finalize contract documents and job specifications, hire contractors to do the work, and get all the paperwork in place to get started.

View Spring 2021 Newsletter here.