Four new bridges are being built along the I-90 corridor in Bellevue, but they aren’t for cars or bikes. They are for a fish passage.
This is one of the most ambitious fish passage recovery projects to date. The state needs to replace the series of pipes and culverts that connect Sunset Creek, which runs behind the T-Mobile campus on the south side of the freeway to the Humane Society on the north side.
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Ryan Boyle is the environmental biologist on this project. What kind of fish use this creek?
“There’s documented Coho salmon in that stream,” Boyle said. “They have been seen spawning in there. We spotted a 10-inch trout, local resident trout — Cutthroat. A smaller chance at Steelhead or Rainbow trout, and a little bit of a chance of Chinook salmon.”
I bet you had no idea that salmon were trying to work their way through that creek under I-90 in the series of pipes and culverts.
Boyle said the current system just doesn’t give the fish a good chance to get upstream.
“It’s a very long, very steep pipe right now,” he said. “The best fish really couldn’t swim up it. It’s just too high. It’s just too steep. They just don’t have the physical power to get up there.”
To clear out enough space to return Sunset Creek to a more normal state, workers will need to dig down about 60 feet under two roads and all of I-90.
“To do this, we are constructing four bridges,” Washington Department of Transportation (WSDOT) project engineer Seth Belknap said. “One on westbound 90. One on eastbound 90, as well as one on Southeast 36th Street and Southeast Eastgate Way.”
These bridges are going to be dug out from above, down to the creek bed. Larry Smith is with Atkinson Construction, the contractor for the job. His team will build the bridges in stages, working from south to north across the roads and the freeway. They will need to close lanes on the freeway in stages over the next few years to get it done.
“We’ll dig down a little bit, enough room to get an abutment put in and some girders set,” Smith said. “We’ll build a deck that allows us to detour the traffic on top of it. So we’ll have shallow foundations, precast girders, and a cast in place [to] put traffic back on it. Then we flop to the other half and build the other half.”
Drivers have already seen the eastbound I-90 HOV lane blocked for while. This is in preparation for the project. The cranes and heavy machinery will arrive in June. The eastbound bridges over I-90 will be finished this year. The westbound work will begin in 2024.
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WSDOT’s Belknap said it’s a challenge to keep traffic moving during such a complex project.
“The main goal is to keep people moving on I-90, as well as the local streets. So we will be constructing the bridges in halves and shifting traffic around the work zone,” Belknap said.
Southeast 36th Street, which runs along eastbound I-90, will have one alternating lane of traffic for about 18 months.
When the work on Eastgate Way begins next year, it will have to be closed. That’s going to be a big issue getting to the park-and-ride and Bellevue College.
We’ll be keeping you up-to-date on the closures as they change.
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Four new bridges are being built along the I-90 corridor in Bellevue, but they aren't for cars or bikes. They are for a fish passage.
