Washington State Department of Transportation photo

New steel culverts will upgrade the existing passages.

The Washington State Department of Transportation (WSDOT) began construction in February 2025 of new fish passable structures on both northbound and southbound Interstate 5 at Secret Creek north of Arlington in Snohomish County.

During construction, both northbound and southbound I-5 traffic will be shifted to a two-lane temporary bypass for nine months with construction expected to be complete in 2026. In 2026, construction will move to Old Highway 99 which will be closed for six months during which time traffic will be detoured onto I-5.

WSDOT and its contractor, Granite, will remove existing fish barriers under Interstate 5 and Old Highway 99 near Stanwood and replace them with three new steel arch structures to improve fish passage. Granite was awarded a $48 million contract in May 2024 for the project.

The new crossings will restore access to more than 5 mi. of stream habitat. When rivers and streams reconnect, fish can better access the habitat they need to reproduce, access food resources, escape predators and find refuge from high winter stream flows. Fish passage restoration efforts are key to rejuvenating ecosystems and bolstering climate resilience.

The location is part of a wildlife corridor home to several species of animals, including deer, coyotes, bobcats and beavers. The project's large culverts promote safe wildlife connectivity across NB and SB I-5 and Old Highway 99. This not only protects valued wildlife resources but also improves traveler safety by limiting the potential for vehicular conflicts with wildlife.

The new culverts will be 68 ft. wide and range from 50-70 ft. long. Crews will also restore about 2,000 ft. of creek channel, starting west of Old Highway 99, running through the I-5 median and extending to the east side of northbound I-5.

This project is estimated to open nearly 5 mi. of habitat, benefiting salmon, steelhead and other aquatic and wildlife species.

This $57.5 million project is funded by the Move Ahead Washington transportation funding package.

For more information, visit wsdot.wa.gov/construction-planning/search-projects/i-5-secret-creek-fish-passage.

(Photo courtesy of Washington State Department of Transportation.)

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