Project overview
Washington State Department of Transportation and contractor crews will replace existing fish barriers under I-5 and Pacific Highway near Stanwood with three new fish-passable arch structures to restore fish passage.
As of March 2026, crews have installed new culverts beneath northbound and southbound I-5. A third culvert is being installed beneath Pacific Highway. All three structures will be 68-foot-wide steel arch culverts, ranging from 50 feet to 70 feet long. Crews will rehabilitate approximately 2,000 feet of creek channel from the west side of Pacific Highway, through the I-5 median, and to the east side of Northbound I-5.
The new crossings will provide potential stream habitat gain of nearly 5 miles, which support the populations of salmon, steelhead, other aquatic species and wildlife.
What to expect
Construction is scheduled to finish December 2026.
Northbound I-5 and Southbound I-5
Construction on both northbound I-5 and southbound I-5 began early 2025, and stream construction and median work will continue into late 2026. People traveling through the area should expect occasional lane reductions and watch for equipment exiting and entering the highway from the median.
Pacific Highway
Pacific Highway closed Monday, Feb. 2, between Fourth Avenue Northwest and 236th Street Northeast to construct the final fish passable structure. During this time, freight and local traffic will be detoured to I-5. Local traffic also may use Fourth Avenue Northwest. This work is expected to be completed by Oct. 31, weather permitting.
This project is part of the WSDOT Fish Passage 2030 Delivery Plan for King, Snohomish and Island Counties (PDF 109KB). WSDOT has worked for many years to remove fish passage barriers. Twenty-one northwest Washington tribes asked the U.S. District Court to find that the State of Washington has a treaty-based duty to preserve fish runs.
