South Whatcom County drivers will need to find alternate routes starting Monday morning, when Old Samish Road closes to through traffic near Chuckanut Creek at 5 a.m. on April 27. The closure, announced Friday by Whatcom County Public Works, is expected to remain in place through the end of 2026, making it one of the longer single-road closures the area has seen in recent years.

The shutdown is tied to a significant infrastructure project: WSDOT's I-5 Tributaries Fish Passage Project, which is targeting 17 fish barrier removals near Lake Samish. Old Samish Road, which runs roughly parallel to I-5 between N. Lake Samish Drive at Exit 246 and connects to Chuckanut Drive (SR 11), sits directly in the construction zone where work will remove barriers blocking fish migration along Chuckanut Creek.

The project scope is broader than just a culvert swap. During the spring and summer, Old Samish Road itself will serve as a temporary two-lane bypass for southbound Interstate 5 traffic while contractor crews remove a fish barrier beneath southbound I-5. A separate temporary bypass will be used for northbound I-5 lanes. Once that portion of the work is complete, southbound I-5 returns to its original alignment, but Old Samish Road will remain closed while a new fish-passable structure is installed beneath the county road.

According to WSDOT, the new crossings near Chuckanut Creek and Old Samish Road could open more than a mile of habitat for coho salmon, trout, steelhead, and sea-run cutthroat trout. Fish passage restoration has become a major focus for state and county agencies in recent years as part of broader salmon recovery efforts across western Washington. Whatcom County contains dozens of streams that historically supported salmon runs, many of which have been blocked by aging culverts and undersized crossings installed decades ago.

Local access will be maintained from both the east and the west up to the closure points near Chuckanut Creek. Residents and property owners who live along Old Samish Road between the closure points and their respective ends will still be able to reach their homes and businesses; through traffic, however, will need to use alternate routes. Drivers are advised to plan ahead, as the closure will be in effect during the busy spring and summer seasons when recreational traffic to Lake Samish and Chuckanut Drive typically increases.

WSDOT's project engagement page notes that the work addresses one of the largest fish barrier correction efforts in this part of the state, encompassing multiple locations near Lake Samish. The effort is partly driven by a 2013 federal court ruling that required Washington State to accelerate fish passage corrections on state-owned roads.

Drivers accustomed to using Old Samish Road as a shortcut between the Lake Samish area and Chuckanut Drive will need to use I-5 or other local roads for the duration. The closure comes shortly after a separate reminder about work zone safety from Whatcom County, which is National Work Zone Awareness Week. County officials have asked drivers across the region to slow down, pay attention, and be prepared for changed conditions throughout the construction season.

For real-time traffic conditions and updates, WSDOT's travel map is the best resource during the closure period. The project page will also be updated as construction milestones are reached. Residents with specific concerns about access or timeline can contact Whatcom County Public Works directly through the county website.

The closure is scheduled to lift by the end of December 2026, though construction timelines can shift depending on weather, permitting, and project complexity. Drivers should watch for signage along Old Samish Road and both Chuckanut Drive and I-5 leading up to and following Monday's start date.