The MTA threw its Second Avenue Subway contractor under the bus yesterday — citing two colossal blunders in the midday explosion that caused an eruption of debris to rain down on an Upper East Side intersection.
Workers blasting out a diagonal escalator shaft at about 1 p.m. Tuesday put too many explosives in one area — and failed to properly anchor an 1,800-pound steel deck covering the hole.
“What happened was completely unacceptable and should not have occurred,” Michael Horodniceanu, president of MTA Capital Construction, said yesterday.
“I’m not jumping on or blaming anyone, but the responsibility lies with the contractor.”
The power from the explosion knocked away the steel deck and sent a shower of boulders, dirt and debris at least eight stories into the air, according to the preliminary investigation.
“The force of the blast was concentrated in one area. And the deck above was not able to withstand that force because it was not anchored in,” said MTA spokesman Kevin Ortiz.
SSK, the contractor in charge of the $4.4 billion project, was placed on the city’s caution list after revealing that it had received several federal Occupational Safety and Health Administration violations in the past five years that resulted in penalties, city officials said.
That list does not preclude SSK — a joint venture of Schiavone, JF Shea and Kiewit — from doing business with city agencies.
Horodniceanu said the MTA has halted blasting below the intersection until SSK presents it with a plan to prevent similar mishaps.
The contractor has also been ordered to use a blasting consultant more frequently and expand the area where pedestrians are restricted from walking while work is under way.
Workers must also check to make sure there is sufficient steel decking anchored properly and surrounded with rubber mats when blasting is under way.
A source had told The Post that workers placed a protective cover on the wrong hole before blasting, though the MTA yesterday denied that account.
An agency spokesman said it’s unclear why the explosives were overloaded in one area beneath an improperly secured deck.
The explosion sent a 30-foot mushroom cloud of smoke and rubble over Second Avenue and 72nd Street.
“We don’t know why it happened. We don’t know if it was human error, we don’t know if it was mechanical error. We are trying to find out more about that,” MTA spokesman Adam Lisberg said.
Additional reporting by Kevin Fasick