• Project

I-90 – SR 18 Interchange Improvements

From 4 a.m. to 5 p.m. Mondays through Thursdays, travelers can expect intermittent single-lane and shoulder reductions on eastbound and westbound I-90 near the interchange, as crews conduct a variety of construction activities.

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 will require three construction stages lasting six to nine months each. 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.

Two full weekend closures of SR 18 between I-90 ramp intersections will occur in summer 2024 when traffic shifts into the new diverging diamond configuration.

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