I-5 – Secret Creek Fish Passage Project

Welcome to our online open house!

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 14 months on southbound I-5 and seven months on northbound I-5 with construction expected to be complete in 2026.

Old Highway 99 is anticipated to be closed for an extended duration in 2026 to construct the final fish-passable structure. 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.

Fish barriers will be removed at two locations along I-5 between Arlington and Sunday Lake

What to expect in 2025 and 2026

Construction is scheduled for February 2025 to December 2026.

Construction of both northbound and southbound I-5 will begin in early 2025. During this time, traffic will be shifted onto a temporary two-lane bypass roadway for 14 months on southbound I-5 and seven months on northbound I-5 while excavation and culvert installation occur. Northbound and southbound I-5 road construction is anticipated to be complete in early 2026.

Old Highway 99 is anticipated to be closed for an extended duration in 2026 to construct the final fish-passable structure. During this time, freight and local traffic will detour to I-5.

Key milestones

• February 2025
  Construction on I-5 NB and SB begins. Traffic will be reduced to two lanes.
• May 2025
  I-5 SB traffic will be shifted to a temporary two-lane bypass roadway on I-5.
• July 2025
  I-5 NB traffic will be shifted to a temporary two-lane bypass roadway on I-5.
• January 2026
  I-5 NB will return to existing three-lane configuration.
• March 2026
  I-5 SB will return to existing three-lane configuration. Old Highway 99 closure begins.
• December 2026
  Project will 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 Old Highway 99. 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

Madison Sehlke
WSDOT Communicator
madison.sehlke@wsdot.wa.gov

Megan Mosebar
WSDOT Project Engineer
megan.mosebar@wsdot.wa.gov