Big Dig Tunnel Ceiling Collapse Could Have Been Avoided

National Transportation Safety Board officials agreed today that the death of a 39-year-old woman in Boston’s I-90 Connector tunnel could have been avoided if routine inspections had taken place in this portion of Boston’s Big Dig Project.

The woman was killed one year ago today after 12 tons of cement ceiling panels fell on the car her husband was driving. 

NTSB members met today in a hearing to issue their final report on the findings and approved a report saying the likely cause of the accident was "use of an epoxy anchor adhesive with poor creep resistance, an epoxy formulation that was not capable of sustaining long-term loads. Over time, the epoxy deformed and fractured until several ceiling support anchors pulled free and allowed a portion of the ceiling to collapse." The board unanimously approved the report. 

Last year Design News reported that the faulty bolt and epoxy assemblies that led to more headlines about Boston’s Big Dig/Central Artery Tunnel Project was just the kind of engineering who-done-it engineers find irresistible. At the time Design News questioned whether or not the wrong epoxy was used? Was the design faulty? Or was poor installation the reason for the failure?

Now we know.

Discussion within the hearing focused on the epoxy’s strength and how impervious it is to the environment in which it was being used. Questions were also raised as to why there were no routine inspections on this tunnel although once inspections began, following the fatality, a large number of anchors were found to be displaced from the roof of the tunnel. The inspections also concluded that the integrity of the ceiling structure was compromised. 

While doubts about the infrastructure’s safety only came to light last year following the fatality  – a December 1998 Inspector General’s Report reviewing the project’s use of anchor bolts documents numerous problems with the bolts and glue used to secure the ceiling in the Ted Williams Tunnel which opened to traffic in 1995. The  I-90 connector connects the Mass Pike with the Ted Williams Tunnel.

The type of epoxy adhesives used in the D Street Portal was the same as what was used in larger tunnels in the city’s project, yet there have been no known problems with them. The big question now is why did the materials fail in a smaller-scale tunnel within the same project?

The family of the woman killed last year is seeking hundreds of million dollars in damages.