I-5 – Secret Creek Fish Passage Project

Welcome to our online open house!

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

Project overview

The Washington State Department of Transportation and its contractor will remove existing fish barriers under I-5 and Pacific Highway near Stanwood and replace them with three new steel arch structures to improve 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.

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 Pacific Highway, 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.

Fish barriers have been removed at two locations along I-5 between Arlington and Sunday Lake. A third fish barrier will be removed under Pacific Highway.

What to expect in 2026

Construction expected to finish by December 2026

During construction, both northbound and southbound I-5 traffic were shifted to two-lane temporary bypass roads. Northbound I-5 returned to its existing three-lane configuration in February 2026. Southbound I-5 was shifted back to three lanes in March 2026.

I-5 NB Completed Culvert Structure

I-5 SB Completed Structure

Pacific Highway closed in February 2026 between Fourth Avenue Northwest and 236th Street Northeast to construct the final fish passable structure. Freight and local traffic should detour using I-5. Local traffic also may use Fourth Avenue Northwest. This work is expected to finish by Oct. 31, weather permitting.

Key milestones

• February 2025
  Construction on I-5 NB & SB begins. Traffic reduced to two lanes.
• May 2025
  I-5 SB traffic shifted to a temporary two-lane bypass roadway on I-5.
• July 2025
  I-5 NB traffic shifted to a temporary two-lane bypass roadway on I-5.
• February 2026
  I-5 NB returned to existing three-lane configuration.
  Pacific Highway closure begins.
• March 2026
  I-5 SB returned to existing three-lane configuration.
• October 2026
  Pacific Highway expected to reopen.
• December 2026
  Project expected to be complete.

Project funding

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

Project benefits

Restores habitat for fish

As part of the project, we will remove two fish passage barriers and install three new fish passable crossings at Secret Creek. The new crossings will restore access to over five miles 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.

Creates wildlife habitat connectivity

The site’s location is part of a wildlife corridor home to several species of animals, including deer, coyotes, bobcats, and beavers. The project’s large 68-foot wide arch culverts promote safe wildlife connectivity across NB and SB I-5 and Pacific Highway. This not only protects valued wildlife resources, but also improves traveler safety by limiting the potential for vehicular conflicts with wildlife.

Updates aging infrastructure

The project upgrades existing and aging infrastructure along I-5 by removing existing fish barrier structures, installing new large steel-arch culverts, and providing roadway improvements. These benefits include improved safety of the traveling public, improved resiliency to natural disasters, and reduced long-term maintenance costs.

Visit the project website to see the latest project updates:
https://wsdot.wa.gov/construction-planning/search-projects/i-5-secret-creek-fish-passage

To stay up to date on traffic changes on state highways, check the WSDOT travel map:
https://bit.ly/WSDOTTravelMap

Stay connected

David Rasbach
WSDOT Communicator
david.rasbach@wsdot.wa.gov

Jared Bentley
Project Engineer
jared.bentley@wsdot.wa.gov