Hang in there, commuters: More I-90/SR 18 closures are coming, but the end is in sight

Construction began in 2023 to install three new bridges, reconfigure the I-90/State Route 18 (SR 18) interchange to a diverging diamond, and widen over two miles of SR 18 from two to four lanes. The project also adds new traffic cameras along SR 18 and I-90, along with safety, stormwater, fish passage, and habitat improvements throughout the corridor.

During the past couple of years, commuters have dealt with many closures and lane restrictions, with miles-long backups becoming routine. Soon, this will all come to an end with the finish line scheduled sometime this summer.

Before that final date, the Washington State Department of Transportation (WSDOT) has a few major projects that will close sections of SR 18 near the I-90 interchange.

Overview

Contractor crews working for WSDOT are planning at least three extended weekend closures for final paving and striping work.

Weather permitting, the first closure will take place overnight on March 31 to set up equipment and barriers. The paving will start the evening of April 9. At least one lane will reopen between weekend closures.

Directional and full closures

There will be two directional closures, one for each direction of SR 18 between I-90 and Issaquah-Hobart Road. There will also be a third full closure of SR 18 under I-90 at the I-90/SR 18 interchange.

These closures will begin with an overnight closure of eastbound SR 18 at 8 p.m. Tuesday, March 31, to install new overhead signs. Eastbound SR 18 will reopen at 5 a.m. Wednesday, April 1.

The right lane of eastbound SR 18 will close at 9 a.m. Tuesday, April 7, so crews can begin to remove 8,500 feet of guardrail before paving work begins as early as 9 p.m. Thursday, April 9.

At least one lane of SR 18 will reopen at 5 a.m. Monday, April 13, while crews continue to reinstall the guardrail.

Weekend closures

Each of the three extended weekend closures will begin at 9 p.m. Thursday, with the roadway reopening with at least one lane at 5 a.m. Monday. There will be around-the-clock single lane closures in the days leading up to and after each of these three closures of SR 18 to allow crews to prepare the roadway for paving and work on drainage after paving.

When crews finish paving SR 18, there will be an additional weekend-long closure to apply final striping to the highway and ramps. This will consist of a sequence of full directional closures and ramp closures of up to eight hours each, not occurring simultaneously.

Detour options

Drivers should follow all signed detours or use alternate routes during these closures and expect significant delays and traffic congestion in the area and near the SR 18 and I-90 interchange.

Freight haulers and truck drivers should avoid Issaquah-Hobart Road and Issaquah city streets, which are not suitable for freight traffic. Truck traffic should use SR 169, I-405, and/or I-90 for all detours.

All people traveling through the I-90/SR 18 interchange during these closures should expect delays and add time to their travel plans.

Closures for paving and striping depend on relatively warm, dry weather. Project engineers will watch the weather closely when determining the precise dates for these closures. This also means that planned closures may be postponed and rescheduled with short notice if precipitation or cold temperatures are in the forecast.

Nate Connors is a traffic reporter for KIRO Newsradio. Follow him on X. Read more of his stories here. Submit news tips here.

Follow @https://twitter.com/kirotraffic