WSDOT breaks ground to fix one of worst chokepoints in WA

Jan 31, 2023, 5:03 AM | Updated: 10:25 am
I-90/SR 18 interchange...
The state is finally breaking ground on a project addressing one of the worst chokepoints in the region, the connection between Interstate 90 and Highway 18 in Snoqualmie. (Photo from Washington State Department of Transportation)
(Photo from Washington State Department of Transportation)

The state is finally breaking ground on a project addressing one of the worst chokepoints in the region, the connection between Interstate 90 and Highway 18 in Snoqualmie. Work on a new interchange is about to begin this week.

The congestion at this interchange has become unbearable. On some days, the backups can reach more than a mile. Trucks routinely roll over when making the turn onto Highway 18 too fast.

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The current interchange just can’t handle all the traffic that uses it every day.

“The intent of this project is to help traffic flow, which will also help increase safety,” project manager James Harper said.

This project will rebuild the entire interchange, using the existing footprint of the current one.

This will be a diverging diamond interchange, the second one in Washington. This is where drivers use the opposite lane of traffic, eliminating the need for left turn lanes against on-coming traffic. It will also include more turning room for trucks to make the transition. Harper said the project will also add lanes to Highway 18, along with three new bridges.

“A key part of this project is widening State Route 18 to two lanes in each direction for two miles south of I-90,” he said.

Some preliminary work is already underway, but Harper said the first thing drivers will notice will be on the shoulders.

“Drivers will see some tree clearing taking place soon,” he said. “There will be traffic shifts and temporary barriers.”

Some of the trees that will be removed will be used to create new fish habitats around the multiple culverts being replaced and expanded in this project, which should wrap up in 2025.

“We’re always asking the public to be patient through construction,” he said. “Two years of a little bit of pain for what we think will be a lot of benefit at the end.”

Now I know what you are thinking, ‘this project only widens Highway 18 for two miles, which will just create chokepoints closer to Tiger Mountain.’

But WSDOT has another project to widen those miles south to the Issaquah-Hobart Road.  That work could begin in 2025 when this diverging diamond and widening project is completed.

Contractors are out this week digging test holes along Highway 18. The truck climbing lane on westbound 18 will be closed from 8 a.m. to 3 p.m. daily this week.

Check out more of Chris’ Chokepoints.


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WSDOT breaks ground to fix one of worst chokepoints in WA