BOSTON (AP) Boston's failed bid for the 2024 Summer Olympics underestimated costs for hosting the games, potentially leaving Massachusetts taxpayers on the hook for significant cost overruns, according to a state-funded report released Tuesday.
Boston 2024, the local group organizing the bid, had projected construction costs for the Olympic Stadium, athletes village and other key facilities would total about $918 million out of a proposed $4.6 billion plan.
But the Brattle Group, a Cambridge-based consultancy, concluded a ''more reasonable estimate'' for construction costs likely would have been more than $970 million higher, based on previous games.
The firm also cast doubt on Boston 2024's savings, revenues and other projections.
The report also said state transit officials believe Boston 2024 failed to take into account a number of variables in its transportation budget, which could have increased the costs by as much as $1.3 billion.
The report concluded the financial implications for the state could have been substantial but its economic impact modest.
''The State and Local governments, while having only limited ability to influence and shape the bid, would bear significant financial risks as the ultimate guarantors,'' the Brattle Group stated. ''The taxpayers of the Commonwealth of Massachusetts would be the ultimate risk bearers.''
Local Olympics organizers responded late Tuesday, accusing the consultancy of not fact-checking its findings and dismissing the report as a ''simple comparison'' between Boston's plan and those of past host cities.
Among Boston 2024's many complaints were that the Brattle Group assumed it would cost roughly $500 million to build a broadcast and media center for the games. Organizers estimated the facility would cost just $50.5 million because it proposed leasing and retrofitting existing space rather than building something from scratch.
''This is a critical, nearly half-billion dollar error on the part of the Brattle Group,'' Boston 2024 said in a statement. ''There was no effort to critique our venue by venue construction budgets which we provided, down to very specific costs of steel, concrete, plumbing, electrical and HVAC on a square foot basis.''
The much-anticipated Brattle Group report had been in development well before Boston's bid imploded last month, the victim of low public support and persistent questions about its finances.
Gov. Charlie Baker and legislative leaders commissioned the $250,000 analysis in June as they weighed throwing their political support behind the Olympics effort. But instead of being a game changer, the report became something of a post-mortem.
Boston 2024 and the U.S. Olympic Committee announced on July 27 that they would end efforts to develop an American bid to compete against Paris, Rome and other international cities. The USOC has since been working with leaders in Los Angeles on a new proposal.
Baker said Tuesday that he would not have signed off on the proposal given the report's findings. He acknowledged, though, that organizers could have found better ways to address the state's concerns, if given more time.
Other politicians and opponents of the Olympics bid said the report validated their skepticism.
Senate President Stan Rosenberg said the report shows ''real risks'' were associated with bringing the games to Massachusetts while a spokeswoman for Mayor Marty Walsh said many of the report's concerns mirrored the mayor's own.
The No Boston Olympics group declared: ''Massachusetts dodged a bullet.''
House Speaker Robert DeLeo suggested the Brattle Group report might still prove useful as Massachusetts seeks new ways to spur economic development and improve Boston's much-maligned transit system.
Evan Falchuk, a former gubernatorial candidate who led the push for a ballot referendum that would effectively prevent state taxpayer dollars from being used on the games, was less impressed.
''The Brattle Group report lays out in black and white that Boston 2024 and its enablers in our government were lying,'' he said. ''The bid is over, but the Olympic saga must be a wakeup call for voters.''
Associated Press writer Steve Leblanc contributed to this report.