Transportation officials aren’t sugarcoating it: the Commonwealth Avenue bridge project is going to massively disrupt travel for tens of thousands of commuters when it begins in earnest this week.
The silver lining, they say, is the work should go quickly. Those Green Line disruptions, road closures, and Massachusetts Turnpike lane reductions that the state has long warned are coming will all be over by mid-August.
To some commuters, that sounds optimistic.
“I’m kind of skeptical. It seems too good to be true,” said Sara DiBari, who uses the Mass. Pike to commute from Hopkinton to Medford most days. “If they don’t get it done in time, that’s going to be a nightmare, because all the students will be coming back into town and people will be coming back from vacation.”
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But state officials have little doubt they’ll be able to pull it off using the type of modern construction techniques that have transformed bridge projects over the last decade. The key is building major components off-site and working around the clock to quickly assemble them in place.
For Commonwealth Avenue, the materials are ready, the traffic changes have been tested, and the construction schedule is carefully planned, said Jonathan Gulliver, the acting highway administrator for the Massachusetts Department of Transportation.
“Barring a natural disaster coming in here, I don’t see a scenario where we would blow our schedule,” Gulliver said. “It would take a hurricane.”
The $82 million project will affect nearly all forms of transportation as the state moves to replace the deteriorating bridge, in two stages: the eastbound side this summer, and the other half next year.
For commuters, the first major jolt will come Wednesday night, when the Green Line B branch will be shut a few blocks on either side of the construction zone, to allow crews to remove the track and overhead cables. Shuttle buses will be used to relay passengers through the work zone.
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The next day at 7 p.m., the bridge will close to cars, as will the Boston University Bridge that connects Commonwealth Avenue and Cambridge.
And underneath the bridge, starting Friday night at 9, the Turnpike will be reduced to a maximum of two lanes in each direction through much of Boston. During weekends and overnight, the highway will lose another lane, meaning one direction will only get a single lane during those periods.
The Mass. Pike will return to three lanes on Aug. 8, and four lanes on Aug. 28. Meanwhile, the Green Line, BU Bridge, and Commonwealth Avenue are expected to return to normal Aug. 14, after the road is resurfaced and new sidewalks and track are added.
The project will cause headaches for the 128,000 to 145,000 daily drivers who pass the area on the Mass. Pike, 30,000 drivers who cross the Commonwealth Avenue bridge each day, and the 26,000 daily riders who use that stretch of the Green Line.
Over the next two weekends, the MBTA’s Framingham-Worcester commuter rail line and Amtrak’s Lake Shore Limited line to Chicago will also be closed through Boston, with shuttle service in their place.
While the disruptions may seem relatively short to the public, the project has been in the works since 2011, and the start of construction was even delayed a year in 2016.
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Much of the bridge has already been built, in pieces off-site. General contractor Walsh Construction Co. will assemble the 267 concrete panels, Lego-style, along 44 new steel girders as portions of the bridge are demolished. Crews of up to 70 workers at a time will work around the clock. A 440-ton, 137-foot crane — shipped in 22 truckloads from Kentucky and reassembled in Boston — will operate along the Mass. Pike, with two other hydraulic cranes positioned on Commonwealth Avenue.
For precedence, Gulliver pointed to the “Fast 14” bridge repair effort in the summer of 2011, in which MassDOT replaced 14 bridges on I-93 through Medford, working only on weekends.
Massachusetts has replaced nearly 200 bridges since 2008 using accelerated construction tactics, which differ from traditional bridge projects because they divert more traffic to allow more work to be done in a compressed time frame. If the Commonwealth Avenue bridge were to be replaced using traditional methods, for example, it might take four to five years with near-constant traffic backups.
These techniques have been adopted by dozens of states as more contractors have learned to use them and construction technology has advanced, said Neil Pedersen, executive director of the Transportation Research Board at the National Academies of Sciences, Engineering, and Medicine.
Accelerated projects are often more expensive than traditional construction jobs, because they use larger crews for 24-hour periods, and because prefabricated bridge materials cost more. But especially in cities, Pedersen said, it usually makes sense to get the work done quickly because the alternative is to back up traffic for years on end. That’s only so much of a comfort to those caught in traffic in the meantime, he acknowledged.
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“Even two weeks is going to be stressful,” he said. “Unfortunately, we don’t have the technology to go in and do this overnight.
Adam Vaccaro can be reached at adam.vaccaro@globe.com. Follow him on Twitter @adamtvaccaro.