Report: Temporary Bigfork pedestrian bridge unworkable
Apr. 4—A suite of options for a temporary pedestrian crossing to replace the shuttered Bridge Street Bridge in Bigfork has been deemed impractical in an analysis by Flathead County.
The report released Wednesday ruled out seven alternatives that ranged from erecting a suspension bridge over the Swan River, to installing a rental kit bridge or prefabricated steel truss span. The analysis found that each of the options presented sizable constraints involving utility relocation, right-of-ways and permitting. Modifying the existing span for pedestrian use was determined to be unsafe due to its deteriorated condition.
The report ultimately determined that the only feasible solution is to replace the historic structure. Construction on the new steel truss span is currently planned to happen in 2026.
However, in a press release, officials with Flathead County and the Montana Department of Transportation said they were searching for ways to expedite the project, "including innovative contracting methods and advance coordination with utility companies, landowners, and environmental resource entities."
The more than 100-year-old Bridge Street Bridge was closed to vehicles and pedestrians at the end of January due to structural concerns, including extensive corrosion issues. The bridge spans the Swan River and connects downtown Bigfork to Montana 35.
The Bigfork business community had asked the state Department of Transportation and Flathead County to explore alternatives for an interim pedestrian bridge until the new span is built.
Challenges surfaced with each alternative the county assessed, mainly due to site constraints and utilities.
The current span holds a gas line beneath the structure, while overhead power lines run adjacent to the bridge.
"Until these utilities are moved outside the anticipated construction limits, the existing truss cannot be removed, and cranes and other large equipment cannot be used on-site due to safety requirements," the report found.
Other site limitations include a lack of space to accommodate a parallel structure due to nearby buildings and retaining walls.
The most feasible site was determined to be upstream of the existing truss, which would require a single 120-foot span. However, that would require the construction of a pedestrian path to the location.
"An upstream crossing is expected to increase project costs and require additional right-of-way easements to be secured during the preconstruction phase; and therefore, has not been further considered in this analysis," the report states.
The analysis looked at the potential for a "superstructure" within the existing bridge, but was ruled out due to space limitations.
The report also cited permitting challenges, with any work likely requiring approval from the Montana Department of Natural Resources and Conservation and a floodplain development permit.
Based on the county's investigation, a temporary pedestrian crossing would have cost between $400,000 and $800,000.
