Big Dig Ceiling Collapse 1 Anchor Bolt DiagramBoston Big Dig Area


Structure: Central Artery/Tunnel Project
Location: Boston, MA
Years of Construction: 1991-2006
Year of Failure: 2006
Type of Failure: Ceiling Collapse
Planner: Boston Transportation Planning Review
Construction Firm: Bechtel Corporation and Parsons Brinckerhoff

The Big Dig project refers to the Central Artery/Tunnel Project and is recognized as the largest, most complex and technologically challenging highway project in the history of the United States. The tunnel replaced Boston’s deteriorating six-lane elevated Central Artery with an eight to ten lane underground highway. [a] The project began in 1991 but was plagued by escalating costs, scheduling overruns, leaks, design flaws, charges of poor execution and use of substandard materials, criminal arrests, and one death. $2.8 billion dollars was the original estimated cost, but the project finished out at $14.6 billion dollars, 9 years behind schedule and $8.6 billion dollars over budget (adjusted for inflation).

On July 10, 2006, approximately 26 tons of concrete ceiling panels and suspension hardware collapsed onto the roadway of the Interstate 90 Connector Tunnel, killing one and injuring another. The cause of this collapse was later determined to be due to inappropriate use of the epoxy anchors that held up the concrete ceiling panels. [2] Fast set epoxy was substituted for the standard epoxy, allowing for similar strength during testing, but displaying very poor creep resistance over long term loading. [b] Power Fasteners Inc, was later indicted on one count of involuntary manslaughter. [c]

Two other failures associated with the Big Dig are related to flooding [d] and soil [e].