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Beginning in February 2025, the Washington State Department of Transportation will begin construction 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.
Old Highway 99 will be closed for six months in 2026 to construct the final fish-passablestructure. During this time, freight and local traffic will detour to I-5.
Project overview
The Washington State Department of Transportation and its contractor 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. The new culverts will be 68-feet wide and range from 50 to 70-feet long. Crews will also restore about 2,000 feet 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 up nearly 5 miles of potential habitat, benefiting salmon, steelhead, and other aquatic and wildlife species.
