ROCKINGHAM — As crews put finishing touches on a $60 million bridge replacement in Brattleboro, state officials are embarking on another major project just a short drive up Interstate 91.
The $44.3 million replacement of two bridges near Exit 6 in Rockingham will start soon, though much of the preliminary work planned for the week of March 20 was delayed due to recent snowfall.
The new bridges will replace two steel spans that are in “poor condition,” according to the state Agency of Transportation. Replacing them is a three-year job that has been entrusted to a Maine-based contractor and a Nebraska-based design firm.
“Both companies are very well-respected and have extensive histories of successfully completing projects of this magnitude and much larger,” said Doug Bonneau, project manager for VTrans.
Taken together, the Brattleboro and Rockingham I-91 bridge projects represent an investment of more than $100 million and more than seven years of work. The bridges at both sites date to the early 1960s, with similar designs.
Both also have exhibited similar structural problems. In Rockingham, the 850-foot-long parallel bridges spanning the Williams River are supported by steel trusses that “are experiencing moderate deterioration,” Bonneau said.
Of greater concern for VTrans are the bridges' gusset plates - steel plates that tie the steel trusses together. Those plates are undersized by modern standards, and the trusses are considered “fracture critical,” Bonneau said.
“This means that the trusses don't have the redundancy of support elements that reroute the loads should one element fail,” he said. “This is what led to the failure of the I-35 bridge in Minnesota [in 2007].”
VTrans has noted additional problems at the site including deteriorated concrete decks that are too narrow by today's standards. The bridges' steel trusses couldn't support the heavier, wider concrete decks that are now required, Bonneau said.
The state tapped two companies to replace the Rockingham bridges: Woolwich, Maine-based Reed & Reed Inc. is the project contractor, while Omaha, Neb.-based HDR Engineering Inc. was the designer. Bonneau noted that HDR has a New England presence with offices in Manchester, N.H., and Boston.
The companies were chosen via a “design/build” process meant to reduce costs and encourage creativity. It allows contractors to “figure out the most efficient bridge that they could provide” within parameters set by the state, Bonneau said.
VTrans received several proposals for the Rockingham project and made a selection based on price and technical merits, he added.
The project, which is 90 percent federally funded, will start this spring. First up is construction of a crossover that will allow northbound traffic to be funneled onto one lane of the current southbound bridge.
That traffic switchover is expected to happen in May, officials said. Then, crews can begin demolishing the northbound bridge.
The project is scheduled to run through spring of 2020.
The Brattleboro I-91 bridge replacement started in 2013 and has been plagued by delays that eventually led to a financial settlement between the state and the contractor.
But Bonneau said each of the four teams that submitted proposals for the Rockingham project “agreed that we have allotted a reasonable time frame for the bridge replacements.”
The projected length is based on standard construction practices, Bonneau said. He also said the schedule “includes considerations for accessing the site; building and removing interstate median crossovers; as well as removing and replacing two very tall bridges over an active railroad and river.”