The March accident triggered a multi-day closure of the downtown subway tunnels underneath the garage, while also triggering an investigation by federal safety regulators.

The collapse sent 100 tons of rubble cascading onto the ground above the MBTA’s Green and Orange line tunnels, wreaking havoc with a key section of downtown Boston’s transportation system until inspections by the agency gave the tunnels a clean bill of health.

Compounding matters, HYM effectively triggered a second tunnel shutdown last month when it discovered serious water damage to one of the garage’s support columns.

John Moriarty & Associates, the contractor heading the demolition, will operate using new precautions and methods. No night work is now planned, while the contractor will now have “full- time resident engineers on site during any periods of demolition work,” according to a statement by the project’s development team.

The resumption of demolition work comes apparently after a green light was issued by city officials.

“A group of highly qualified inspectors and engineers have thoroughly inspected and examined the Government Center Garage site and the demolition plans,” HYM and National Real Estate Advisors said in a statement. “We are allowed to resume work and remain committed to ensuring the safety of our workers at all times.”

The developers, in their statement, also offered additional details on the emergency repairs made to the “severely deteriorated” column underneath the government center garage. The column was particularly critical given it also extends through the subway tunnels below.

The MBTA shut down the Green and Orange line tunnels underneath the garage from June 23 to June 26 after the agency was notified by HYM of the garage column's condition.

During the three-day shutdown, work crews descended into the tunnels beneath the garage, “refortifying” the water-damaged column with steel bracing, the developer said in a statement.

There is likely to be some financial fallout for HYM, its partners, and the Bulfinch Crossing megaproject from the shutdown of demolition work for three months—as well as the disruptions caused to downtown Boston’s subway system—but how much is not yet clear.

Led by former City Hall development chief Tom O’Brien, HYM has been taking down sections of the multi-acre, concrete behemoth over a period of years. Two new towers, an apartment high-rise that is now open, and an office tower slated for completion later this year, have taken shape on sites where parts of the garage once stood.

HYM had begun planning a 400,000-sq-ft-plus life sciences building as its next project when the fatal demolition accident occurred in late March. It’s not clear how the three-month delay in demolition will impact schedule of the life-sciences project.

HYM and its partners may also face a bill from the MBTA for the two closures.

"This service disruption as a result of HYM's project is unacceptable and the MBTA will seek to hold HYM Construction accountable for all costs associated with this event," MBTA General Manager Steve Poftak said in a statement after the June shutdown.

Responding to a question from ENR, a spokesperson said the agency is also tallying up the costs of earlier disruptions to downtown subway service from the March accident.

“The MBTA is in the process of determining the financial impact this will have and will hold HYM fully accountable,” the spokesperson wrote.