$188M construction project on I-90 near Snoqualmie expected to delay traffic

One of the busiest traffic corridors in Western Washington needs to get worse before it can get better.

Starting this week, the Washington State Department of Transportation (WSDOT) moves into a new phase of its makeover of the SR-18 and I-90 exchange. That’s going to mean lane closures and even more congestion.  

This week’s construction activity will see work being done on both SR-18 and I-90, so drivers need to allow themselves extra time. This $188 million project will be one of WSDOT's largest for 2023.

"The one that is under construction this year is the 1-90, SR-18 interchange improvement and widening project, and we are creating diverging-diamond interchange, it’s going to keep traffic flowing through there and increase safety," said Adrienne Hatmaker, spokesperson for King County WSDOT.

The "diverging diamond design" will be the first in Western Washington. SR-18 will also need to be widened, but it means extensive prep work. Including taking down trees and taking soil samples to check for stability and other possible obstacles.

"It’s been a really busy interchange for a long time and SR 18 has had some frequent collisions up there, so everyone is really looking forward to having that widen," said Hatmaker.

Starting today through Feb. 4, the westbound SR-18 truck climbing lane will be closed from 8 a.m.–3 p.m. every day. Over on I-90 through Wednesday this week, look out for short duration lane closures in both directions just west of SR-18.

"But we won’t have to completely close anything off this year, so there maybe intermittent ramp closures here and there, but for the most part, people can still expect to drive that interchange," said Hatmaker.

Traffic at the interchange has exploded along with the local population, and a project like this puts more pressure on an already maxed-out infrastructure, but WSDOT is doing what it can to reduce overall wait-times and frustrations.

"Drivers just really need to know that, you know, it’s going to be a little bit tough the next couple of years, but it’s going to be worth it once we finish the interchange and the widening south," said Hatmaker.

PREVIOUS COVERAGE: State to begin work on diverging diamond interchange at I-90, SR 18

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The project is scheduled to be finished in 2025.

Affected drivers can sign up for email updates at the WSDOT project page to stay on top of upcoming changes and closures.