By Dustin Luca
---- — The accelerated construction technology that received praise for quickly replacing 14 bridges over Interstate-93 in Medford will be used to replace the North Main Street bridge near downtown Andover.
Built in 1929, the railroad overpass is one of the town’s busiest bridges. Carrying Route 28 traffic over the Andover commuter railroad tracks, the bridge connects downtown Andover to Shawsheen Square. The bridge is just north of the Public Safety Center and south of McDonald’s on Route 28.
Work could begin in the spring of 2014 and be completed by the end of 2014.
Officials with the state’s Department of Transportation last week presented their plan to replace the bridge at a public hearing last week, following six years of discussion and development.
The project will replace the bridge’s entire superstructure — the steel and concrete that cars drive over, according to John Watters, an engineer on the project. It will also replace parts of the bridge’s substructure — the walls underneath the bridge that support it.
The latest estimates put the project at around $3.4 million, which will be paid for by the state, according to Watters. Construction will start sometime in 2014 after it goes out to bid. With work beginning next March, an aggressive schedule could have it completed by the end of the 2014 calendar year, Watters said.
To do the work, the road will be reduced to two 10-foot lanes, one in each direction of travel, with one 4-foot-wide sidewalk, according to Matt Hopkinson, DOT project manager. One half of the bridge will be replaced at a time, with traffic travelling on the side of the bridge not being replaced.
To do this as quickly as possible, the state will put the steel and concrete together off-site and then fit the pieces together in Andover like “really big Legos,” according to Watters.
“When (the pieces) show up to the job site on a flatbed truck or trailer, we can pick them up like really big Legos and put them in place really quickly,” he said. “You almost have an instant bridge.”
The same technique was used in the state’s “Fast 14” bridge replacement project during the summer of 2011. The state replaced 14 bridges over Interstate 93 in Medford in just 10 weeks.
Complicating things in Andover, however, is the fact that freight and passenger trains move under the North Main Street bridge.
For cars, “we can usually create detours, temporary roads. Cars can make turns and traverses. Trains can’t,” Watters said. “Trains don’t like when we’re picking up steel beams over their head and they’re running at the same time. So this steel beam work that I’m talking about is going to have to work either at night when there’s shutdowns in the train service or on some weekends.”
While there will be impacts to traffic with the shifting and merging of lanes during construction, emergency vehicles will still be able to travel north from downtown Andover during the project, according to Hopkinson.
“You’re putting a fire truck on a 10-foot lane. They may have to stop traffic or slow traffic down in order to safely travel through there,” he said. “We looked at that and the folks at the safety complex seem to think they can work with that. We’ve addressed the safety issue. There should be none.”
To help emergency vehicles cross the bridge during construction, emergency workers will control area traffic lights to let traffic move through the bridge without interference, Public Safety Officer Chuck Edgerly said.
Sweeney Court, a small neighborhood with a driveway feeding right onto the southern end of the bridge, will also be impacted by the construction. When the northbound side of the bridge is being replaced, a new, temporary entrance will be created for those residents to access their property, according to Watters.
Selectman Alex Vispoli said the bridge is one “that’s been well overdue to get replaced.”
For the time being, however, the project doesn’t address a southbound safety issue that Vispoli said needs to be corrected.
“When you’re coming south from Shawsheen and coming up towards the library, you’ve got two lanes going to one (lane) pretty much at the bridge,” he said. “It’s a little bit of chicken, of ‘Who’s going to get the right-of-way there?’ It’s not really an ideal solution.”
Watters said the bridge is as wide on its north end as it is on its south end, and that the way the road is painted merges the lanes on the bridge. As planning continues, how to handle the merge is being considered.
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