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, a state-funded report released Tuesday concludes.
Boston 2024, the local group organizing the bid, had projected that 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, concludes 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, noting 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 concludes the financial implications for the state could have been substantial while 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."
Boston 2024 organizers had no immediate comment on the report.
The 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 independent analysis in June, capping costs at $250,000.
But Boston 2024 and the U.S. Olympic Committee announced on July 27 that they would to end the planning efforts after Baker declined to throw his support to the plan and Boston Mayor Marty Walsh refused to sign a guarantee committing taxpayer dollars to cover any overages.
Boston in January was named the USOC's pick to go up against Paris, Rome and other international cities, besting Los Angeles, San Francisco and Washington, D.C.
"Even though the bid was withdrawn, this report demonstrates that there were a series of real risks associated with bringing the games to Massachusetts," Senate President Stan Rosenberg said in a statement.
Some Olympics opponents agreed: "The healthy skepticism expressed by voters and leaders in the State House was warranted," the No Boston Olympics groups said in a statement. "Massachusetts dodged a bullet."
Others were unimpressed by the findings. 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, questioned why it took so long for the elected leaders to come to the conclusion.
"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."
Laura Oggeri, a spokeswoman for Walsh, said many of the Brattle Group's concerns mirrored questions the mayor had throughout the bidding process.
Going forward, House Speaker Robert DeLeo said, the report still could serve as a resource for the state as it seeks to spur economic development and improve Boston's much-maligned transit system.