Epoxy Faulted in Big Dig Collapse

A criminal investigation in Boston is focusing on inappropriate use of quick-setting epoxy as the explanation for a ceiling collapse in a Big Dig connector tunnel that resulted in a fatality last summer. The information reported by the Boston Globe conflicts with prevailing opinion by outside experts interviewed on a background basis by Design News who feel the problem was due to a cascading series of engineering miscalculations.

According to an article in the Boston Globe, however: “Invoices from the 1999 ceiling construction job show that Modern Continental Construction Co. received and apparently used at least one case of a quick-drying epoxy to secure ceiling bolts to the tunnel roof rather than standard epoxy, which the ceiling designers had specified.”

Bolts fastened with standard epoxy can hold a load of 6,350 pounds as opposed to 4,285 pounds.

A criminal investigation into the problems causing the ceiling collapse was begun by Massachusetts Thomas F. Reilly who unsuccessfully ran for governor in 2006. He was replaced by Martha Coakley, who had strong reservations about pursuing a criminal case. The Big Dig was a highly charged political event in Boston, and is still in the spotlight as former governor Mitt Romney campaigns for the Republican presidential nomination.

Coakley’s office, however has been collecting evidence through a secret grand jury investigation. The Globe said that scuttlebutt outside the courtroom indicated that investigators are focusing on possible use of the quick-drying adhesive.

Interviews by Design News with outside experts over the past three months point to a cacophony of engineering areas that make the Big Dig project almost look like a Keystone Cops adventure applied to technology. One theory is that contractors inappropriately applied components in the two-component adhesive system. Another is that hangers were poorly designed, contributing to the failure. Another is that the number of bolts called for was reduced in a rush to met deadlines. Weigh limits used in safety tests have also been questioned.

Coakley’s office has not yet announced if it will ask the grand jury to bring charges in the Big Dig case.