Southbound I-5 traffic shifts onto a bypass road starting Thursday, May 28, south of Bellingham

(BELLINGHAM)– Both lanes of southbound Interstate 5 will move onto a temporary two-lane bypass road through summer 2026 beginning at 8 p.m. Thursday, May 28, along Chuckanut Creek south of Bellingham.

During the traffic shift, contractor crews working for the Washington State Department of Transportation will install a new fish-passable structure beneath the southbound lanes as part of a project correcting 17 barriers near Lake Samish, according to a news release from WSDOT.

Beginning at 8 p.m. Thursday, May 28, both southbound I-5 lanes will shift onto a temporary two-lane bypass south of the existing lanes near Chuckanut Creek (milepost 247). People traveling through the area between 11:59 p.m. Thursday, May 28, and 5 a.m. Friday, May 29, should expect rolling slowdowns to allow crews to shift lanes. The temporary bypass will be in use until September.

The speed limit temporarily will reduce to 50 mph in the work area while the bypass is being used. With traffic off southbound I-5, crews will excavate the roadbed, remove the old culvert, install a new fish-passable structure and rebuild the permanent southbound I-5 lanes.

The bypass route will use a section of Old Samish Road, which has been closed to through traffic in both directions since April 27.

After southbound work is complete, Old Samish Road will remain closed to through traffic through the end of the year while a new fish passage structure is installed beneath the county road.

In the coming weeks, northbound I-5 traffic also will move onto a temporary two-lane bypass.

People can find more project information about the I-5 Tributaries to Friday, Lake and Chuckanut Creeks Fish passage project by visiting an online open house.

Real-time travel information is available via the WSDOT mobile app, the WSDOT travel map or by signing up for WSDOT's email updates.