Fatal Big Dig Ceiling Failure Blamed on ‘Epoxy Creep’

Federal investigators said Tuesday that “epoxy creep” was a major factor in the Big Dig accident one year ago that killed a Boston woman when concrete tunnel ceiling panels fell and crushed her car, federal investigators said Tuesday.

Investigators with the National Transportation Safety Board said if any of the agencies involved in the tunnels’ construction and design had considered the possibility of epoxy slowly pulling away from the ceiling, the accident could have been avoided.

Bruce Magladry, director of the NTSB’s Office of Highway Safety, described “epoxy creep” as the tendency of some epoxies to slowly give way over time under constant applied pressure. Magladry compared the creep of the epoxy used in the collapsed ceiling to adhesive used on a mailing label, which would yield to pressure over a longer period of time.

“Although the epoxy used in the tunnel had acceptable short term strength, it was incapable of supporting much lower loads over an extended period of time,” Magladry said. “If any of the entities involved in the ceiling design and installation had considered creep as a possibility, a different epoxy or a different anchoring system would have been used.”

Milena Del Valle, 39, was crushed to death on July 10, 2006, when 12 tons of concrete ceiling panels fell from the Interstate 90 connector tunnel as she and her husband drove toward Boston’s Logan Airport.

On the one-year anniversary of the accident, the NTSB met to review and approve a final report on the probable cause of the ceiling collapse. The board was also expected to issue a series of recommendations.

The $14.798 billion Big Dig, the costliest highway project in U.S. history, has been plagued by construction problems and cost overruns during the two decades it has taken to design and build it.

Last summer’s accident spawned tunnel shutdowns, extensive ceiling repairs, a wrongful death lawsuit and a wave of federal, state and criminal investigations, including the NTSB probe.

Massachusetts Attorney General Martha Coakley is expected to announce soon whether she’ll press criminal charges in connection with the accident.

Also pending is a wrongful death lawsuit filed by Del Valle’s family against the Massachusetts Turnpike Authority, the agency overseeing the Big Dig, and several companies associated with design and construction of the project. The companies have said they stand behind their work.