Mascoma Bridge Project Moves Forward
Lebanon — Calling all commuters on Routes 4 and 4A, and runners, walkers and bicyclists on the Northern Rail Trail: Expect to encounter preliminary work for the long-awaited new highway bridge over the Mascoma River by the middle of the summer, and an all-out construction project in the spring and summer of 2015.
“If the last few details fall into place, you’ll start to see ‘construction ahead’ signs this year,” said Jon Evans, the project environmental manager of the New Hampshire Department of Transportation.
Evans and project manager Victoria Chase unveiled the final design to the Lebanon City Council Wednesday and spoke about the plans for the new bridge following the meeting.
“I would expect that in late 2015, you’ll see the new bridge,” Chase said.
The new span, crossing the river just east of the existing bridge near the river’s outlet from Mascoma Lake, will be part of an $11-million project that will also realign Route 4’s adjacent intersection with Route 4A and Mill Road — an accident- prone intersection. Where plans several years ago called for a roundabout, or rotary, at the intersection, the current design brings Route 4A and Mill Road straight into the intersection, instead of at angles that create sight-line problems, and provides separate right-turn lanes off and onto Route 4.
If the project receives a state wetlands permit for its elaborate drainage system for road runoff on schedule, the NHDOT will start advertising for contract bids in April, Chase told the council.
The existing bridge, which the state estimates handles an average of 17,000 vehicles a day — 4 percent of them trucks — and would be taking on 29,000 vehicles a day by 2030, ranks fourth on NHDOT’s list of priorities, up from 17th barely four years ago. The present bridge has a pier on each bank and one in the middle of the river — all of them crumbling. The new bridge would be “a complete span of the river,” Evans said.
Preparation of the drainage system will take up much of the early work. In particular, planners hope the system will prevent the kinds of landslides and slope failure that running water now triggers off Route 4, particularly a slide that blocked part of Mill Road and a municipal trail that runs along the river roughly parallel to the Rail Trail.
“This is a tough site,” City Councilor Nicole Cormen said, pointing to the often-unstable soils and the long history of slides. “How certain are we that this is the best way?”
Chase said that while “nobody knows for sure … engineering judgment and experience” indicate that this plan, which would divert water into an underground system of pipes and culverts, “will lead to a more stable slope.”
Evans added that the drainage system, which includes catchment areas where runoff from the road would undergo treatment before entering the groundwater system, would improve the water quality of the Mascoma River.
Susan Almy, a member of the city Conservation Commission, said that “I feel a lot better about this” plan than she had about earlier designs.
In addition to delays and detours for commuters on the roads themselves, users of the Northern Rail Trail will run into closures and detours at the height of construction, particularly Monday through Friday during non-snowmobile seasons, the planners said. They added that ample notice, possibly on the city’s website, will go out before any closings.
Chase added that while the current plan calls for car-travel lanes on the bridge of 12 feet each in width, and marked shoulders of 4 feet each in width, the NHDOT is still considering the proposal from bicycle advocates to narrow the car lanes to 11 feet and widen the shoulders to 5 feet.
David Corriveau can be reached at firstname.lastname@example.org and 603-727-3304.