But the bridges are just one of a number of projects dealing with eye-popping increases in their estimated cost, including a major reworking of the Massachusetts Turnpike in Boston’s Allston neighborhood, a number of new high school projects and a planned soccer stadium in Pawtucket, R.I.

The increases come as construction costs—already posting sizable single-digit increases in the Boston area before the pandemic—have broken into the double digits, said James Kirby, president and CEO of Commercial Construction Consulting in Boston.

“They are making headlines,” Kirby said. “You are looking at 20% over two years. That is a staggering amount of money for any project, but when you are dealing with projects in the billions, that is a lot more zeroes.”

Plans to replace the Bourne and Sagamore bridges over the Cape Cod Canal have seen the biggest jump in estimated costs, with projections in 2019 pegging the price tag for the two spans at $1.4 billion to $1.65 billion. The state and the U.S. Army Corps of Engineers applied for $1 billion in federal funding for the project through the $1.2-trillion Infrastructure Investment and Jobs Act, according to a story in the Cape Cod Times.

The costs reflect the surge in construction inflation, State Transportation Secretary Jamey Tesler told State House News Service, noting his agency is “seeing inflation on a lot of our work and a lot of our bids” leading to a “significant increase in what we collectively thought the cost estimates would be for this project.”

State transportation officials have also upped their estimate on what it will cost to revamp the Allston portion of the Massachusetts Turnpike, boosting the projected amount to $2 billion, a $300-million increase.

After lengthy discussions and debate over various alternatives, state officials chose an at-grade option last fall that involves taking down the aging Turnpike viaduct in the Allston neighborhood of Boston and constructing eight Turnpike lanes, four tail tracks, four lanes of Soldiers Field Road and a pedestrian boardwalk over the Charles River, all at the same level.

The $300-million jump represents a 17.6% increase from the estimate unveiled last fall.

Local school officials across Massachusetts have also been forced to up their cost estimates on new projects, with the price tag to build new high schools in Lowell and Worcester having leaped during the past few months.

The cost to build a new Doherty Memorial High School in Worcester has increased by $23 million, with the total price tag now over $316 million. Bids for the electrical contract alone came in $10 million more than expected, with jumps in construction materials also contributing to the increase.

Officials in Lowell are dealing with a $38.5-million jump in the estimated cost of building a new high school in that city.

Also caught up in the whirlwind of construction price increases are plans for a $284-million soccer stadium that is part of a public-private partnership in Pawtucket, R.I.

Fortuitous Partners, the developer of the project, has halted plans to start work and is now asking for a $30-million increase in state assistance for the project, The Providence Journal reports. The $124-million stadium is part of a larger development called Tidewater Landing, which if built, would be the largest economic development project in Pawtucket's history. 

Overall, cost estimates on publicly funded projects are more difficult for a number of reasons, including not as many comparable projects to compare costs with, at least compared to the cost of putting up a new office building in New York, Kirby said.

There is also a tendency to underestimate the costs in the beginning, only to see the price tag revised upward, in part because the full scope of costs and challenges are not always understood at the start.

That is especially the case with huge projects, like the revamp of the Turnpike in Allston and replacing the Cape Cod bridges.

“There are no comparable projects to pick off the shelf and figure out what they cost,” Kirby said.

Richard Dimino, president and CEO of A Better City, said one factor in the rising price-tag for the now $2-billion revamp of the Allston Turnpike is that state officials began digging deeper into the plans.

“You have to give the state credit–they have been getting into more detail in the project’s design,” he said.

But construction inflation has not helped either.

“While the general inflation rate has been going up, the construction and transportation index inflation rates tend to go up faster and higher,” Dimino said. “That is a challenge for construction.”