Motorists traveling along Route 3 in Hanover and Norwell over the past three months might have wondered just what is happening on the median strip, where construction crews have been busy excavating, removing dirt and vegetation, installing drainage structures, and depositing gravel.
No, they are not expanding the busy state highway, the primary route between Boston and Cape Cod.
State transportation officials say the flurry of activity is the start of a $30 million project to replace four structurally deficient bridges that carry Route 3 over High Street in Norwell and Webster Street (Route 123) in Hanover.
The bridge reconstruction is not related to any previous discussions of widening Route 3 into three lanes in each direction, officials said.
“MassDOT continues to review all possibilities to improve travel on Route 3,” said Judith Riley, a spokeswoman for the Massachusetts Department of Transportation. “At this time, there are no active plans to widen Route 3.”
As part of the bridge project, which began in May and is scheduled for completion in October 2020, contractors are also realigning the highway to soften existing curves and make other safety upgrades.
One notable feature of the project is the planned use of the 1.9-mile-long stretch of the median strip separating the north and southbound sides of the highway.
“The presence of a wide median allows us the opportunity to not only realign Route 3 but to utilize it as a temporary bypass during construction, to maintain adequate traffic flow,” said Gerard Bernard, District 5 construction engineer for the Department of Transportation.
On an average day in 2015, 82,877 vehicles traveled along that stretch of Route 3, according to the agency.
Contractors are building two roads -- one in each direction -- within the 100- to 120-foot-wide median that will be used as temporary bypass routes for motorists during the project, 80 percent of whose costs are being funded by federal dollars and 20 percent by state funds.
State officials said that detouring traffic off the bridges to the median strip road will allow for construction of the new bridges to flow seamlessly and minimize disruption to Route 3 traffic. Throughout the project, two travel lanes will be maintained at all times in each direction and use by motorists of the breakdown lanes will continue during peak hours.
Other benefits to using the median strip are that all construction will take place outside of active roadways, creating a safer environment for contractors and the public, and no temporary bridges will be needed, saving on construction costs.
Two of the new bridges will be built in the median strip itself -- one at the south end and one at the north end -- during the time the bypass roads are constructed. Once that work is done, northbound traffic will be diverted over the new bridge at High Street, while southbound traffic will be diverted over the new bridge at Webster Street, state officials said.
The two offline bridges will then be demolished and the remaining two new bridges constructed in their place. Traffic will then be temporarily shifted off the first pair of bridges in the median to the second pair. The temporary roadways will then be converted to permanent realigned ones and traffic shifted off the two remaining existing bridges so they can be razed.
Once the work is complete, what had been the temporary median strip roads will become a permanent part of the realigned Route 3.
Officials said use of a median strip bypass road is a technique they have employed on many occasions, including currently for a project on Interstate 95 in Attleboro. But in the case of the I-95 project, the bypass road is temporary and will be removed at the end of the project.
The four multispan bridges being removed on Route 3 were constructed in 1960, and all are considered to have one or more major components -- the deck, superstructure, and substructure -- in poor condition. Officials said the four new single-span steel and concrete bridges will be constructed with more durable materials to minimize maintenance costs over their service life.
Hanover Town Administrator Troy Clarkson said the town welcomed the state addressing the bridges, calling it a complement to other major improvements in town.
“Hanover is in the midst of an exciting revitalization, with more than a quarter of a billion dollars in private investment occurring along the Route 53 corridor,” he said. The town “is investing as well, approving a [tax break] for the Hanover Mall, and making improvements to Route 53 with a turning lane near the University Sports Complex.”
“We realize the need for the repairs of the infrastructure,” said Norwell Town Administrator Peter Morin. “We appreciate the investment the state is making in it and appreciate the level of communication they’ve had to inform us of their progress and where it might be disruptive. Thus far it’s been minimally disruptive.”
The bridge replacements on Route 3 are among a number of major road projects south of Boston this summer.
Others include the replacement of the Atlantic Avenue bridge over Little Harbor Inlet in Cohasset; resurfacing of Route 3A in Marshfield and Route 3 in Plymouth; reconstruction of Route 14 in Pembroke; and two projects involving road reconstruction, traffic signal upgrades, and other improvements on Route 123 in Brockton.Globe correspondent John Laidler can be reached at email@example.com.