Building a massive barrier wall in Boston Harbor to protect the city from the increasing risk of flooding isn't worth a price tag that could reach $11 billion, according to a new study for a City Hall-led commission.
A research team at the University of Massachusetts Boston's Sustainable Solutions Lab said the city should instead focus on smaller, shore-based projects, estimating it would take at least 30 years to build a wall while the need for solutions is far more immediate.
The study was the first to look at the feasibility of a harbor barrier wall, and it analyzed construction costs, as well as the impact on the environment, waterfront neighborhoods, and the region's marine industry.
The concept of a wall, which under one design would stretch 3.8 miles from Winthrop to Hull and be the largest in the world, was considered a year ago to be a bold but possibly necessary solution to combat the effects of climate change.
But planners and environmental protection advocates said the UMass findings brought about a collective sigh of relief with its recommendation to instead dedicate $2 billion to neighborhood protection efforts. To some, the harbor wall would have been the aquatic version of the Big Dig — the massive, prolonged highway construction project that had billions in cost overruns.
"I think people know these big huge projects can become complicated and troublesome," said Bud Ris, a former CEO of the New England Aquarium and a member of the Boston Green Ribbon Commission, a group of government, business, and civic leaders who encourage strategies to combat climate change. The group, cochaired by Mayor Martin J. Walsh, sponsored the study with funding from the Barr Foundation.
"Let's get on with the things we know can work," Ris said.
The UMass analysis, called the "Feasibility of Harbor-wide Barrier Systems: Preliminary Analysis for Boston Harbor," had been recommended by a Climate Ready Boston report that warned in 2016 of the need to take flooding protection measures. But the message took on a new sense of urgency following two storms last winter that left several Boston neighborhoods under water.
Researchers in that 2016 study concluded that sea levels in Boston Harbor could rise another three feet over the next several decades, and climate change could increase the frequency and severity of storms, making flooding a regular occurrence.
The UMass report analyzed the technical and economic possibility of an outer harbor wall from Winthrop to Hull that could cost upward of $11 billion, as well as an inner harbor wall from Logan Airport to the Seaport District that could cost $8 billion.
Neither wall could be built until 2050, at the earliest. And while the report found no evidence that a wall would harm the environment or the city's marine-based economy, the resources used to build the walls, it said, would be far better spent in the short term on shore-based protection projects in flood-prone neighborhoods.
Moreover, the type of gated barrier needed to avoid any adverse maritime impact is designed to be opened only a few times a year.
Under the predicted change in weather and sea level conditions, the barrier would have to be opened far more frequently, possibly 50 times a year, leading to inevitable mechanical failures and costly repairs.
"It does not make sense for decades, if not ever, to consider a harbor-wide barrier system," said the report's lead author, Paul Kirshen, academic director of the Sustainable Solutions Lab.
He said it would be best to not "throw all of our eggs in one basket," and would be more efficient to tackle neighborhood projects that have already been identified and could be modified as the effects of climate change become clearer.
"There's too much uncertainty in that . . . we would either over-invest or under-invest, and we can't afford to do that now," Kirshen said. "With the shore-based systems, we can really improve the quality of life for people living on the shore, with the amenities those shore-based systems provide."
The projects that have been identified in city studies have ranged from a plan to elevate parts of Main Street in Charlestown to the construction of a deployable wall at the Greenway in East Boston. Those projects have been included in the city's capital spending plan. A similar report that examined possible projects in the Seaport is expected to be released in the coming months.
The city is also looking at creating an overlay zoning district that would spell out requirements for building and construction under a new master plan along the waterfront.
Austin Blackmon, the city's chief of environment, energy, and open space, said Tuesday that the report affirmed the city's plans to address shore-based projects.
The report, he said, recognized the scale of "the inner and outer harbor barriers that would make the Big Dig look small, and from the storms we saw this year, we recognize we are already at risk of flooding," he said. "We need to be really focusing on advancing our onshore solutions."
Blackmon and Ris, of the Green Ribbon Commission, said business, government, and civil leaders will still need to coordinate a regional strategy to plan short-term projects, as well as find funding. A similar study by UMass in April said local neighborhood projects could cost more than $2 billion in the coming years and recommended financing from sources, such as the collection of new taxes and fees.
Ris said that carrying out the shore-based strategy will still be a challenge, but that the winter storms highlighted the potential dangers of coastal flooding and served as a warning call to local leaders.
"There's no question . . . it's a big challenge to come up with that money, a billion to $2 billion, but that's certainly easier than coming up with $8 to $15 [billion]," Ris said.
A look at some previous proposals for a barrier in Boston Harbor:
Milton J. Valencia can be reached at email@example.com. Follow him on Twitter @miltonvalencia.