Adhesive blamed in Boston Big Dig tunnel collapse

WASHINGTON (Reuters) - U.S. transportation investigators on Tuesday blamed the fatal collapse in Boston's Big Dig tunnel last year on a ceiling adhesive that was not strong enough, and determined contractors and authorities probably could have taken steps to avert the disaster.

The National Transportation Safety Board concluded the epoxy slowly deformed and fractured over years, causing anchors supporting 20 concrete ceiling panels to give way last July 10. Tons of concrete crashed onto the roadway of the Interstate 90 connector, crushing a car and killing a motorist.

The $15 billion Big Dig highway and tunnel project -- the costliest public works project in U.S. history -- has faced construction problems and other controversy over the past two decades.

Investigators found the construction industry had a "general lack of understanding" about how the ceiling adhesive would perform in the long term, and that the contractors on the tunnel project failed to identify problems when they arose.

"A different anchor adhesive could have been chosen and the accident might have been prevented," according to the safety board's final report on the accident.

Massachusetts transportation officials also failed to establish a timely tunnel inspection program that likely would have revealed the deficiencies before the collapse occurred, investigators said.

State officials are considering whether to file criminal charges in the case. The state and companies involved in the project are facing lawsuits.