WSDOT waits on weather to finish key I-90, SR 18 project

Spring in the northwest can be beautiful, but it can also be wet and nasty. That’s why it’s so difficult to plan major construction projects this time of year.

The Washington State Department of Transportation (WSDOT) is hoping to finish up one of its biggest projects over the next few months, but contractors are working at the whim of the weather. Striping and final paving can be very difficult to get done this time of year. Contractors need warmer and drier weather to put the finishing touches on projects.

That’s why WSDOT is spending so much time with its meteorologists while trying to finish the new interchange at I-90 and SR 18 and the two miles of widening to the south.

“Weather is just a constantly shifting target, WSDOT’s Marcus Humberg said. “We’ve already had to shift the first weekend’s worth of work that was going to be on April 2. Now it’s looking at April 9, if the weather holds out.”

Interchange open but final paving layer still needed

The contractor opened the new interchange last summer. The widening finished a few months later. Now it’s time for the final work.

“Yes, we were able to open the DDI [diverging diamond interchange],” Humberg said. “Yes, we were able to open the widening. No, we don’t have that top layer of asphalt, that final driving wear surface that goes on top.”

The contractor needs several extended weekend closures to put a bow on the project.

“Three extended full weekend closures, one eastbound, one westbound, one full closure underneath I-90, and then we will have four weekend closures of a ramp each,” Humberg said. “Then we’ll come back with one more weekend closure to stripe the whole project.”

The first full weekend closure is expected to begin next Thursday, April 9. This closure will be in the eastbound direction, meaning drivers will not be able to go east on SR 18 from the Issaquah-Hobart Road to I-90.

The goal is to have all of the work finished before the end of the school year.

“We’re hoping, as long as the weather holds out, that we’ll have a good roadway ready to open up for the summer travel season,” Humberg said.

Next phase of SR 18 widening delayed until 2029-2030

As we look forward to this project wrapping up, we should be planning for the next phase of work on the corridor, but that’s not going to happen for a while.

WSDOT was expected to take about a year off and then start the SR 18 widening from where it ends now, across Tiger Mountain to the Issaquah-Hobart Road, but that work has been pushed by the legislature.

“They delayed the SR 18 widening, the funding for it until the 2029, 2030 biennium,” Humberg said. “That’s when we’re going to potentially see more work on the SR 18 corridor.”

We’ll be watching the weather with WSDOT as it tries to finish the current work. We’ll let you know when work is a go or when it’s postponed.

Chris Sullivan is a traffic reporter for KIRO Newsradio. Read more of his stories here. Follow KIRO Newsradio traffic on X.

Follow @https://twitter.com/newsguysully