Big Dig ceiling killed Milena Del Valle — $1,287 epoxy failed, cost $460M

The Big Dig was the most expensive highway project in US history, burying Boston's central artery underground at a cost of $14.8 billion. On July 10, 2006, a 26-ton concrete ceiling panel — 20 by 40 feet — fell from the roof of the Fort Point Channel Tunnel onto a passing car. The panel crushed the passenger side, killing Milena Del Valle instantly and injuring her husband who was driving. The panel weighed as much as a loaded delivery truck and fell without warning.

The cause was epoxy anchor bolts. The ceiling panels were held in place by bolts embedded in the tunnel roof with an epoxy adhesive. Investigators found that the epoxy had been improperly mixed and applied, and the bolts were shorter than required. Over time, the epoxy crept — slowly deforming under the sustained load of the concrete panels — until a group of anchors failed simultaneously, dropping the panel. The NTSB identified 'epoxy creep' as the primary cause. The total cost of the epoxy that held the failed panel: $1,287.60.

The aftermath was sweeping. Powers Fasteners, the epoxy manufacturer, was indicted for involuntary manslaughter — a rare criminal charge in a construction failure. Bechtel/Parsons Brinckerhoff paid $405 million; Modern Continental and subcontractors paid $51 million; Powers Fasteners paid $22 million. The state spent $54 million inspecting and repairing all 242 bolt fixtures. A $1,287 material failure in a $14.8 billion project cost a life and hundreds of millions in settlements.