Southbound I-5 set for return to three lanes Friday, March 6, near Stanwood after new culvert installed

STANWOOD – The Interstate 5/Secret Creek Fish Passage project near Stanwood is expected to reach its second major milestone in less than a month, weather permitting, on Friday, March 6. Southbound I-5 traffic will shift from a temporary two-lane bypass roadway in the median back to its usual three-lane configuration on the mainline freeway during an overnight rolling slowdown beginning Thursday night, March 5.

With this shift, both northbound and southbound I-5 will once again operate with three lanes through the project area between Stanwood and Arlington. Travelers should continue to watch for construction vehicles entering and exiting the roadway through the median, as contractors working for the Washington State Department of Transportation continue to restore natural habitat along Secret Creek.

Southbound I-5 transition

Beginning at 8 p.m. Thursday, March 5, crews will begin shifting southbound traffic from the bypass road onto the mainline, weather permitting. Overnight travelers should watch for work crews and be prepared for a rolling slowdown scheduled for about 11:30 p.m.

By noon Friday, March 6, all three lanes of southbound I-5 will reopen to traffic, provided the weather cooperates. Crews need dry conditions to complete the work.

Improving fish passage in Secret Creek

Both directions of I-5 used temporary bypass roads south of the State Route 532 interchange (milepost 212) while crews removed old, narrow culverts that blocked fish from traveling up and downstream, then built new culverts beneath I-5 at Secret Creek. Northbound I-5 shifted back onto mainline lanes in February, and returning southbound traffic represents a significant step toward completing work beneath I 5.

Removing the barrier to fish passage and building a new structure beneath southbound I-5 required extensive excavation. Crews removed more than 45,000 cubic yards of material and installed a steel arch culvert that is 70 feet long and 70 feet in diameter. They then constructed 14,000 square feet of retaining walls and placed nearly 20,000 cubic yards of backfill – enough to fill six Olympic-sized swimming pools – behind the walls. Similar work was completed for the northbound lanes as well.

Once both directions of I-5 are restored to their original three-lane configuration, crews will continue working on stream reconstruction, fully restoring fish passage and improving habitat along Secret Creek.

Part of this work includes installing a third new fish passage structure beneath Pacific Highway, just west of I-5. Pacific Highway will remain closed between Fourth Avenue Northwest and 236th Street Northeast until Oct. 31. Freight and local traffic should detour using I-5.

The new crossings in Secret Creek provide a potential habitat gain of nearly 5 miles for salmon and steelhead. In addition to WSDOT’s ongoing work to correct barriers statewide, a 2013 federal court injunction requires the state to correct barrier culverts to salmon and steelhead within the injunction area in western Washington.

The $57.5 million Secret Creek fish passage project is scheduled for completion by December 2026. More information about the work also can be found at the project’s online open house.

Travelers are encouraged to stay informed by checking WSDOT’s real-time travel map, mobile app, and real-time travel data before traveling through the area.