Expect lane closures during Interstate 90 fish passage project

June 12, 2012

By Staff

Motorists should prepare for closures along westbound Interstate 90 as crews improve a passage beneath the highway for salmon and other fish.

Crews started construction last month on a fish passage east of Highlands Drive Northeast and the Sunset Interchange between Issaquah and Preston in unincorporated King County. The $2.8 million project is meant to replace a narrow culvert on the East Fork of Issaquah Creek.

The stream is home to chinook, coho and sockeye salmon, as well as steelhead, sea-run cutthroat trout and resident trout.

Officials identified the 12-foot-wide culvert as a barrier to fish in January 2006. The state Department of Transportation planned a wider replacement to better accommodate the 25-foot-wide stream bed in the area near the culvert.

The project contractor is Bellevue-based Tri-State Construction. Officials awarded the contract late last year.

The narrow culvert impedes salmon and trout headed to historic rearing and spawning grounds. The structure also restricts the creek’s flow, increasing water velocity and creating tougher conditions for fish.

The area also includes a 1.8-foot drop in the stream — too steep for fish to jump. So, crews plan to regrade the stream to a more natural profile.

Plans call for crews to build a bridge as a replacement for the culvert. The replacement is meant to allow fish to migrate upstream to spawning grounds.

Construction is expected to continue until November. Motorists should expect closures of up to two left lanes on the westbound interstate on weekdays during construction.

Crews installed barriers and environmental fencing around the construction site.

State law requires the Department of Transportation to install and maintain culverts to assist fish passage. The agency and the state Department of Fish and Wildlife identify and prioritize culverts for replacement.

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