• Project

I-90 – SR 18 Interchange Improvements

From 11 p.m. Saturday, Sept. 30 to 5 a.m. Sunday, Oct. 1, crews will conduct emergency repair to damaged guardrail between Raging River and Deep Creek. Expect lane reductions and flaggers alternating traffic through a single lane.

From 9 p.m. Monday, Oct. 2 to 5 a.m. Tuesday, Oct. 3, the eastbound I-90 off-ramp to SR 18/Snoqualmie Parkway will close while construction crews place concrete barrier to make room for work zones at the interchange.

From 9 p.m. to 5 a.m. each day, Mondays through Thursdays, expect lane reductions with flaggers alternating traffic on SR 18 between the interchange and Raging River.

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.