A 1930s wooden bridge in Glacier National Park in Montana had deteriorated and needed to be replaced. But its structural rating was so low that heavy construction equipment or girders needed to build a new bridge could not be transported on it. Barnhart proposed erecting a temporary bridge to move equipment and structural elements to the far side.
Barnhart set up a 440-ton crawler crane on the approach side. The crew disassembled a small rough terrain (RT) crane and took it across the existing bridge to handle a tandem lift of the bridge structure. Temporary shoring was driven in on the bank and as center support. A 113' temporary bridge span was placed from the bank to the center support. The RT crane, in tandem with the crawler crane, then set the 113' far side span.
Barnhart’s bridge system had an unusually high capacity and required less shoring than traditional temporary bridge systems. This was necessary due to park service requirements to reduce environmental impact in the park and waterway. With the temporary bridge in place, heavy equipment, plus 220' single span girders weighing about 70 tons each, could be transported across the bridge.
Due to the harsh winters normally experienced in the area, the crew mobilized out last fall, shut down over the winter and will return in the spring to complete the project. Once the new structure is open for traffic, the temporary bridge will be disassembled and the old bridge will be demolished.