• Project

I-90 – SR 18 Interchange Improvements

SR 18 overnight single lane, alternating traffic from 9 p.m. to 5 a.m. Monday nights to Friday mornings starting Jan. 31. Lane reduction to continue through March as construction crews begin work on new 4-lane bridge over Deep Creek. Expect up to 20-minute delays for pilot vehicle to escort eastbound and westbound traffic through the eastbound lane.

Project overview

Growth in Snoqualmie Valley has made the I-90/SR 18 interchange one of the busiest in the state, causing backups during peak times and busy travel weekends. To improve traffic flow, WSDOT is building a diverging diamond interchange and adding two lanes on SR 18 between the interchange and Deep Creek.

2022 - 2025
Project status
$188 million
Project hotline

What to expect

Building the diverging diamond interchange and widening SR 18 will be accomplished through several stages of construction during which travelers can expect traffic shifts, speed reductions and intermittent lane and ramp closures throughout the life of the project.

Congestion will increase during construction, so people should plan extra time for trips or find alternative routes.

Reconstructing the I-90/SR 18 interchange will improve safety performance and travel times on I-90, SR 18 and Snoqualmie Parkway.