Interstate 90 will be fully closed for brief evening stretches near Snoqualmie Pass from Thursday through early October. Crews will be blasting rock during those times as they prepare to add new lanes.
Closures will occur during non-peak hours every Monday and Thursday, beginning at 8 p.m. and lasting roughly an hour, according to the Washington State Department of Transportation (WSDOT).
Crews may conduct a trial blast around 8 p.m. on June 14.
Road blocks will be in place at mileposts 54 and 61, roughly from Hyak to the Price Creek Sno-Park.
“We’re expecting a two- or three-mile backup at most,” said project spokesman Bob Hooker. “It’ll flush out fairly quickly once we open up the road again.”
All four lanes of the interstate will remain open in both directions during weekends.
The rock blasting is part of a $571-million plan to widen the interstate from four to six lanes along a five-mile stretch near Snoqualmie Pass.
The project includes replacing six bridges that are roughly 150 feet long with extended overpasses, each around 1,100 feet long. The idea is to turn the narrow streams below into wider flood plains that provide shallow animal crossings and better fish habitats – thus the need for longer bridges.
Crews will also remove fill material on the bridge approaches, stabilize slopes, straighten sharp curves to improve visibility, build a new snow shed to minimize avalanche-related closures, replace deteriorated pavement, and extend the chain-up areas.
As part of the blasting efforts, crews will carry away 12,000 cubic yards of rock debris, clearing an area 120 feet long and 24 feet deep. Very little if any rock debris is expected to land on the freeway itself, Hooker said.
During the blasting, WSDOT will close down I-90 much like it does for wintertime avalanche work.
“The difference is that this is planned, so people have notice,” Hooker said. “You could leave an hour early or an hour late and completely miss it.”
Hooker said it is probably better to wait out the delays rather than trying to use an alternate route.
“It might take an hour to get around if you use another highway,” he said.
Around 27,000 vehicles travel over Snoqualmie Pass on an average day, according to WSDOT. Volumes on weekends and holidays can exceed 50,000, the agency said.
Traffic is expected to increase 2 percent every year, reaching an average of over 41,000 vehicles per day by 2030, according to WSDOT.
The new lanes near Snoqualmie Pass will increase capacity by 50 percent in each direction. They will also allow at least two lanes to stay open in each direction during future road projects.
