BELLOWS FALLS, Vt. – Back in August of 2019, it was officially decided by the Rockingham Selectboard to support the Vermont Agency of Transportation in reconstructing the rapidly deteriorating Depot Street Bridge in Bellows Falls. The concrete bridge is one of two bridges – the other is considered structurally deficient – that accesses the Island Street area where the Bellows Falls Waypoint Welcome Center and bus and train station is located.
The existing bridge was built in 1909 and crosses over the Bellows Falls Canal, which is owned by the Great River Hydro facility. It spans 96-feet and is 32-feet wide, has a poor culvert rating of four, and the concrete arch has spalling concrete and exposed rebar. There is also extensive spalling and exposed reinforcing along the waterline at the arch foundation, and the extent of the deterioration at the base of the arch – submerged in the river – is also in question.
Additionally, there is a definite contaminated soil issue, and existing utilities may also need to be relocated. The reconstruction project will also include the replacement of the existing historic arch with a new, reinforced concrete arch.
“The basic issue with the arch-type construction, however, is the cost of constructability due to the loss of power generation and flow to excavate and place new abutments on the canal,” Bellows Falls Town Manager Scott Pickup said in a recent interview.
When the Vermont Agency of Transportation had originally presented a full bridge replacement on-alignment with a new arch, they had also offered an alternative option in which the replacement would take place in the same location as the current bridge with similar dimensions.
The projected cost of the on-alignment option would be $3.4 million with a town share of $172,000; however, those figures did not include the hazardous waste remediation that would add an estimated $140,000 to be funded by the town. The construction would take approximately six months with a bridge closure of 120 days.
The second option presented is a new steel beam truss bridge and off-alignment by 450 feet, which would avoid relocating utilities and the hazardous waste impacts. However, it would also cause a loss of parking on the island. The existing bridge would be closed to traffic but would remain available to pedestrians. Additionally, the existing bridge would not be eligible for future town highway bridge funding.
The projected cost for the second option would be $3.5 million with a town share of $352,000 but would save the town from the added costs of hazardous waste remediation. This construction option would also take six months, but traffic could continue to use the current bridge to access the island until the new bridge was complete.
However, in a recent Bellows Falls Selectboard meeting, it was learned that because of previously unanticipated “underwater construction” engineering challenges – as well as a possible eight-month shutdown of the nearby hydroelectric plant during construction that would require a revenue loss reimbursement to the plant – the overall costs of the project would be driven well above what was originally estimated.
The loss of power revenue during the shutdown could add up to as much as $600,000 a month, which could ultimately add nearly $5 million in additional costs to the project.
With the second option presented, the steel beam truss-designed bridge, would not require underwater construction and would only require the hydroelectric plant to be shut down for a month. Although the overall design would not replicate the historic concrete arch of the existing bridge, it is believed that it would blend well the railroad history of the town.
A final decision has not been made, as VTrans is currently preparing updated cost estimates for both bridge options including the original plan but with a steel truss design, as well as the new, off-alignment proposal.