The Vermont Agency of Transportation (VTrans), in collaboration with the Town of Middlebury, is undertaking a project to replace two nearly 100 year old rail bridges in the center of Middlebury with a tunnel. The two bridges are about 300 feet apart, with one located on Main Street/VT 30 and the other on Merchants Row.
For over 25 years, VTrans bridge inspection reports documented the ongoing deterioration of both bridges. Concrete cracking, delamination, and spalling had occurred on all bridge components. Embedded steel reinforcement was rusted and exposed. There was leakage through the deck and full depth holes on the Merchants Row sidewalk had to be patched.
In the spring of 2017, VTrans became increasingly concerned about the deteriorated condition of the sidewalks and concrete that fell onto the railroad tracks. A sudden, unplanned emergency closure would result in road closures in downtown Middlebury for several months. The Agency decided to remove both bridges in the summer of 2017 and install temporary bridges until permanent structures are built. Both the Main Street and Merchants Row Bridges were demolished in July/August 2017 and travel was restored within four weeks.
The 360-foot tunnel that will replace the Main Street and Merchants Row bridges will address several deficiencies now facing the railroad. Currently, the bridges do not have enough vertical clearance for double-stack rail cars. By lowering the rail bed approximately four feet, clearance can be increased to 21 feet without impacting the grade of the road and sidewalks above.
The tunnel will also enable the alignment of the rail to change, softening the curve that currently exists, allowing better horizontal clearance for trains. Drainage improvements and covering the track will reduce the risk of icing problems that have been severe in some winters as well as ponding that occurs.
Many considerations have gone into planning and designing the project. The design team has had to balance community needs and character, local and regional mobility, construction feasibility – all while keeping the rail line active, except during the 10-week closure period, as communities along the line depend on rail for deliveries of various commodities.
Among (though not all!) the items the project team has focused on are:
- Placing utilities in the Printer’s Alley underground so that they do not interfere with the crane needed to construct the tunnel
- Acquiring Right-of-Way, both temporary and permanent
- Negotiating with Vermont Rail Systems about feasible work windows that enable construction to get done without interrupting rail service
- Monitoring walls, foundations and windows of nearby historic buildings during activities that may produce vibrations
- Monitoring noise during construction
- Designing the project to mitigate risk from the 100-year flood level of Otter Creek
- Supporting a design that considers community character and aesthetics
- Creating a safe working environment for workers, motorists, and the community
- Scheduling a construction sequence to minimize community disruption
- Developing a communication and outreach program to identify and respond to community concerns
Before proceeding with construction, VTrans conducted an Environmental Assessment in accordance with the National Environmental Policy Act. The Final Environmental Impact Statement concluded with a Finding of No Significant Impact.
Replacing the rail bridges with a tunnel received broad support at public meetings and was endorsed by the Middlebury Town Selectboard. The tunnel will change the town landscape by overlaying the depressed, walled rail bed that cuts through the town with green space that will link Triangle Park with the Village Green.