Massive fish passage project under I-90 in Factoria nearing its end

Eastbound I-90 drivers are close to getting their HOV lane back in Factoria. The fish passage project under the freeway is in its final months.

The lane has been closed for several years as the Washington State Department of Transportation (WSDOT) undertook one of its most complex fish passage projects to date. The state was tasked with replacing an old concrete culvert that was more than 50 feet below the freeway. It was greatly restricting fish passage in Sunset Creek.

Nearly all the work above the creek is done, and the eastbound I-90 HOV lane should reopen before the end of the year.

“Electrical and ITS work in the median, guardrail striping, final cleanup, and we have a lot of final planting to go through as well,” project engineer Seth Belknap said. “As of right now, the goal is to have the eastbound HOV lane opened up and return to the original configuration by the end of the year.”

So we’re almost there.

Work in the creek will last a few more months. The project might actually wrap up a few months ahead of schedule.

“We’ll have final — what we call punch list work — that is being worked on now and will take us through potentially January or February, but we anticipate being done in Quarter 1 of 2027,” Belknap said.

An image taken about a month ago shows the new streambed stretching about 975 feet beneath four new bridges for the I-90 fish passage project. (Photo courtesy of WSDOT)

Fish passage project adds 4 bridges and nearly 1,000 feet of streambed

The original schedule had work going through the summer of next year.

The contractor has really accomplished a lot in the three-plus years of construction.

“We’ve constructed four new bridges: two across the eastbound and westbound I-90, and SE 36th St. and E Gateway as well,” Belknap said.

A fish spotted in the stream in summer 2025, before bridge work began on Eastgate Way. The project team counted 59 juvenile coho salmon and cutthroat trout at the location. (Photo courtesy of WSDOT)

The project also created nearly 1,000 feet of streambed to replace the culvert.

“Underneath the bridges, we’ve constructed retaining walls that allowed us to delineate the path for removing the old concrete culvert and constructing a new streambed with habitat features down below,” Belknap said.

Workers had to dig down over 50 feet to excavate the streambed. Now we will wait and see if any fish return to the creek.

The project price tag is over $100 million.

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

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