Two major projects will affect westbound I

Dec 22, 2023

ISSAQUAH – The start of fall will bring several major closures on westbound Interstate 90 during the second half of September, including two east of Issaquah and two on the west end of Mercer Island.

During the closures, contractor crews working for the Washington State Department of Transportation will repave a rough section of the interstate where water is seeping onto the roadway. The closures on the west side of Mercer Island will allow crews to replace an expansion joint on the westbound I-90 Homer Hadley Bridge.

The closures east of Issaquah on westbound I-90 will take place:

The Mercer Island closures on westbound I-90 will be:

"We understand all of these closures are going to create a lot of challenges for people who rely on I-90," said WSDOT Project Engineer Shawn Wendt. "However, we need to replace the worn-out pavement and expansion joint before we get to another winter. We are doing this now because it took time to get contractors and materials in place."

Water dribbling underneath Interstate 90 from an old coal mine has led to cracked pavement, with the water seeping to the surface of the interstate about a mile west of the High Point interchange.

"This coal mine was sealed off before we built this section of I-90, but over the years water collected in it," Wendt said. "Now that water is leaking out and seeping underneath the highway. That, combined with freezing in the winter and extreme heat in the summer, eventually cracked the concrete."

To repair this, crews need to close the freeway for four full days and five nights the first week to remove the concrete, create a drainage system under the roadway, and repave it with asphalt. The second week will require three full days and four nights. Crews are working during the week because this section of I-90 sees high traffic use on weekends. About 29,000 vehicles a day use this portion of westbound I-90.

Crews will replace an expansion joint on the east approach to westbound I-90. This joint is more than 30 years old and is worn out.

The weekend of Sept. 16-19, crews will replace the right side of the joint, which includes the I-90 bike path and West Mercer Way on-ramp. The following weekend, crews will reduce westbound I-90 on Mercer Island to one lane beginning the afternoon of Sept. 22, with the full closure starting after the morning commute on Sept. 23. Work will finish by early Sept. 26.

With the lanes reduced, people traveling will need to plan ahead near Issaquah and on Mercer Island. The Issaquah lane reduction will limit the capacity on westbound I-90, which could cause delays at certain times of the day.

During the closure on Mercer Island, people on the Eastside who plan to travel to the west side of Lake Washington will need to use either I-405 to go around the lake or the SR 520 floating bridge, which has a toll.

People who are traveling can get real-time traffic information on mobile phones with the WSDOT traffic app and by following the WSDOT traffic Twitter feed.