Hobnail Tom Trail Bridges
Located in the picturesque Lolo National Forest, the Hobnail Tom Trail Bridges provide access to the Scapegoat and Bob Marshall Wilderness areas. This trail connects to the trail system that serves the entire Bob Marshall Wilderness Complex (BMWC). It is heavily used for administrative purposes and for recreation by outfitters, guides, hunters, and backpackers.
There are many substantial trail bridges in the BMWC. The Hobnail Tom Trail, approximately 27 miles in length, crosses the North Fork of the Blackfoot River with two bridges—Smokes Bridge and the North Fork Bridge.
Morrison-Maierle completed bridge inspections on each structure in September 2013. Both bridges showed significant decay, settling, and crushing in the native log structures. If these conditions were not addressed, the bridges would have eventually collapsed.
Morrison-Maierle developed a feasibility study that examined various
types, configurations, and locations for replacement structures. The Forest Service settled on two, timber through truss bridge designs. The new structures were designed in 2017-18 and completed in 2020.
The new bridges were designed as single span structures with no intermediate piers to remove unnatural waterway obstructions. Morrison-Maierle and the Forest Service decided that using treated timber members fit in with the wilderness’ surroundings better than other materials and would provide long-lasting structures.
Wilderness area restrictions, heavy snow load demands, and access constraints complicated this project. The contractor only had three days to helicopter in building materials and was limited to a chainsaw, a battery powered drill, and a wheelbarrow to build the bridges. Morrison-Maierle also had to factor in weight when selecting materials due to helicopter weight restrictions.
With these new bridges, the Forest Service and backcountry users now have access to the Scapegoat Wilderness with for years to come.