Project Overview
Montana Highway 86 (MT 86) is a scenic route winding through rural farmland and recreational areas, frequented by travelers journeying from Wilsall to Bozeman via Bridger Canyon. Along the way, they cross small creeks on timber bridges, many constructed in 1939 that have undergone regular maintenance over the years. However, no structure can be expected to last indefinitely, especially under the strain of increasingly heavier loads and growing traffic volumes.
The Montana Department of Transportation (MDT), in collaboration with the engineering firm Morrison-Maierle, is working to replace three of these timber bridges through the MT 86 Structures project. The three timber structures being replaced include the bridges over Cache Creek, Carrol Creek, and Flathead Creek. These bridges will be replaced with box culverts, tunnel-like concrete structures.
Bridge Replacement Timing
The project team is currently in the design phase, working on project plans and designing each culvert that will replace the existing timber structure. The project plans are expected to be completed by spring 2026, with construction tentatively scheduled for fall 2026 through summer 2027. The project timeline is dependent on the completion of the design phase and the availability of funding.
Temporary Bridges Installed on MT 86 at Flathead Creek and Cache Creek
Due to the deteriorating conditions of the timber structures spanning Flathead Creek and Cache Creek, MDT has issued new load postings or “Weight Limits.” Engineers recently evaluated these bridges and determined that weight restrictions are necessary due to their condition.
As a short-term solution to ease weight restrictions and restore capacity for highway-legal loads, MDT has installed single-lane, temporary bridges until the original structures are replaced.
The temporary single-lane bridges have a 12-foot width restriction. Vehicles exceeding this width will need to take an alternate route.
When traveling through these areas, drivers can expect reduced speed and new traffic patterns. Alternating single lane traffic across the structures is controlled by traffic lights.
The community is encouraged to stay informed about the project's progress and to reach out with questions, concerns, or feedback by emailing Sloane at
UPN 9805000