A construction project to ease congestion at one of Washington’s busiest highway interchanges is nearing the finish line, but drivers should expect several more months of disruptions.
The I-90/SR 18 interchange project has already delivered improvements since the opening of a diverging diamond interchange last summer.
Marcus Humberg with WSDOT said the redesign, along with newly added lanes, has reduced the backups that once stretched onto I-90 during peak travel times and busy weekends.
“So it actually really improves the flow of traffic, and we saw that almost immediately when we opened it,” Humberg said. “Traffic backups that used to extend well onto I-90 in both directions… it’s almost gone.”
Despite that progress, the final phase of the project will bring a new round of closures and delays as crews complete paving and striping work.
Closures Begin This Week
The next phase kicks off with an overnight closure of eastbound SR 18 beginning at 8 p.m. Tuesday, March 31, between I-90 and Issaquah-Hobart Road. The roadway is expected to reopen by 5 a.m. the following morning.
Additional work will follow in early April. The right lane of eastbound SR 18 will close to allow crews to remove thousands of feet of guardrail in preparation for paving. Weather permitting, paving work could begin as early as the evening of April 9.
From there, drivers should prepare for at least three extended weekend closures throughout the spring and summer. Each closure is scheduled to begin at 9 p.m. Thursday and last through 5 a.m. Monday, with at least one lane reopening in between closures.
“We’ve got basically three long extended weekend closures of the freeway that people are going to have to contend with,” Humberg said. “We expect there’s going to be a lot of traffic, backups, and extended wait times.”
Detours will be clearly marked, and drivers are encouraged to plan ahead, allow extra travel time, and consider alternate routes. Freight traffic is advised to avoid Issaquah city streets and instead use routes such as SR 169, I-405, or I-90.
Project Nearly Complete
Once paving and striping are finished, the diverging diamond interchange project itself will be complete. The broader SR 18 widening effort is expected to wrap up by late summer.
When all work is complete, transportation officials say the improvements should provide long-term relief for one of the region’s most congested travel corridors.
Until then, drivers should brace for delays.
“Add extra time to your trips,” WSDOT officials advise, “and expect congestion in and around the I-90/SR 18 interchange.”
To learn more about the project, click here.