The Dominion Creek Tunnel and Trestle are located on an abandoned section of the Milwaukee Railroad near the top of Lookout Pass along the border of Montana and Idaho. The intent of this project was to rehabilitate the 650’ long bridge and the adjacent 450’ long tunnel in order to provide public pedestrian access to approximately 8 miles of the old railroad grade. All rehabilitation work had to retain historical accuracy, and preserve as much of the existing elements as possible. It is predicted that this will be the first leg of a continuous 30 mile long, mixed-use trail from the Montana/Idaho border to St. Regis, Montana. DJ&A, PC contracted with the US Forest Service to conduct a preliminary assessment of the trail, tunnel, and trestle, to prepare final plans and specifications for the construction of the preferred alternatives, and to assist in the construction observation of the project.
Based on the preliminary investigation, it was determined that the 100 year old steel bridge girders could remain in place on the trestle but it was necessary to remove the concrete ballast boxes as they had deteriorated extensively. Additionally, handrails needed to be installed over the entire length of the structure and repairs needed to be conducted on the concrete abutments on both ends of the trestle.
The tunnel rehabilitation involved patching two sections of the existing concrete lining and removing the ballast material to increase the drainage of the walls and floor of the tunnel. The trail itself was also improved by filling in low areas and sinkholes, and removing rock and debris from localized slides near the trail.
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Read about one of our projects for the USDA Forest Service in the Missoulian. Learn more
The Dominion Creek Tunnel and Trestle Repair Project was selected as a "case study" for the new Sustainable Infrastructure Rating System (envision™).
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