This photo of the Veranda Street bridge shows the white geofoam blocks that will be used to support the foundation of the new structure. To the left of I-295 is the deck of the new bridge, which will be rolled into place once the old bridge is demolished and removed. Photo courtesy of Maine Department of Transportation

An ambitious highway construction project that will shut down Maine’s busiest stretch of state highway for more than three days starts this week.

The Maine Department of Transportation has spent years preparing motorists for the closure of Interstate 295 between Portland and Falmouth and of Veranda Street, which runs below the highway. Traffic will be prohibited on the roads while an aging highway overpass is demolished and replaced in a rapid-fire operation.

“This is certainly not something we do every day; it is unprecedented in terms of the type of work and nature of the interstate highway that carries this much traffic through our state’s largest city,” said Paul Merrill, communications director for the state transportation department.

Veranda Street will be closed for a week starting Monday. I-295 between exits 9 and 10 will close at 7 p.m. Friday and reopen by 11 a.m. Monday, April 25. Motorists should avoid the area entirely during the construction, the department said.

Even with multiple public meetings, regular news media coverage, paid TV, radio and print ads and direct mail to Portland and Falmouth residents, Merrill suspects some drivers haven’t gotten the news.

“I think no matter how robust our outreach efforts are, unfortunately, there are some people who didn’t get the message. But we want to minimize that number as much as possible,” Merrill said.

About 53,000 motor vehicles use the five-mile stretch of four-lane highway between Portland and Falmouth every day. Even though traffic is typically lower on the weekend the closure is planned, it will create major disruptions.

“So many people use that corridor. It is arguably one of the most important stretches of road in the state,” Merrill said.

Construction giant Cianbro has 64 hours to tear down and rebuild the I-295 bridge over Veranda Street. The 60-year-old bridge is past its useful life and deteriorating. It is classified as structurally deficient. The replacement costs $20.8 million.

Working on a razor-thin timeline, workers will destroy the existing bridge, remove the rubble, then use huge self-propelled transporters to lift a prefabricated bridge deck into the old span’s place.

Veranda Street will close to motor vehicle, pedestrian and bicycle traffic on Monday. The street has to close so the transporters, loaded with the new deck, can get into place and take practice runs, Merrill said.

Then Friday night, the real work begins. Shortly after the highway closes, multiple construction vehicles equipped with hoe rams – basically huge jackhammers – will start tearing the old bridge apart. “The demolition is going to be extremely loud and extremely disruptive,” Merrill said.

After the rubble is removed, the transporters will move two bridge sections – each 80 feet long, 47 feet wide and weighing 400 tons – into place. Transporters move up to 3 miles per hour fully loaded and need to lift the bridge plates 8 feet in the air to get into place. The entire operation is expected to take about six hours, Merrill said.

The replacement should be finished and the highway reopened to traffic by mid-morning on April 25. There is no indication the schedule will change, Merrill added. Cianbro’s contract has financial incentives to finish on time or faster and financial penalties if it misses the deadline.

“Per the contract, they have until 2 p.m. Monday to delay for one week because of the weather,” Merrill said. “At this point, severe weather like a hurricane would be the only reason to push this for another weekend.”

A wholesale redesign of Veranda Street will accompany the bridge replacement. A confusing and dangerous jumble of highway ramps and one-way travel lanes surrounding the bridge underpass will be replaced with two simple intersections and streets wide enough to accommodate sidewalks and bicycle lanes. Construction on the project is scheduled to finish in November.

During bridge construction, all through-traffic should detour onto the Maine Turnpike and get back onto I-295 using the Falmouth Spur.

Traffic heading north on I-295 and Route 1 will be detoured onto the Exit 9 off-ramp heading toward Falmouth. Vehicles can connect back to the highway and communities north via Route 1.

Southbound vehicle traffic will be detoured to Bucknam Road in Falmouth, then south on Middle Road to Ocean and Washington avenues for a connection to I-295 south.

State transportation engineers have informed Google and Waze of the detours and closure in an effort to make sure the GPS apps are accurate, Merrill said.

The transportation department wants the public to stay away from the construction zone but has a live feed of the project as well as detour maps available at its project website, verandaplan.org.