On July 10, several tons of ceiling tiles fell from a connector tunnel of Boston's Big Dig project, fatally crushing a motorist. The following week, the eastbound lanes in a section of another tunnel, the Ted Williams Tunnel, were ordered closed after inspectors found that two bolts holding up a concrete ceiling panel had come loose, having slipped an inch and a half from their foundation.

Gov. Mitt Romney, later speaking at a Statehouse news conference and illustrating his points with charts and diagrams, dramatically raised the number of potential trouble spots identified by engineers and investigators in the eastbound connector tunnel where the ceiling collapsed. In fact, tests showed more than 1,100 bolt assemblies that used epoxy and more than 300 other areas in the connector tunnel complex are unreliable. All will have to be reinforced, he said.

The $14.6 billion Big Dig -- the most expensive highway project in U.S. history -- was intended to ease traffic congestion in Boston, Mass., by burying a highway network that used to slice through the city, replacing it with a series of tunnels. The old elevated Central Artery was eliminated and major highways were thus put underground.

In addition to cost overruns and delays, the project has been plagued by leaks, falling debris and other problems linked to its construction. The project plunged last month into the deepest crisis in its history when the 12-ton section of ceiling panels broke loose, crushing a car and killing a 38-year-old woman inside. A contractor stands indicted on charges of supplying shoddy concrete.

This latest problem brings to question the epoxy-and-bolt system used to fasten the concrete slabs overhead, a system experts say is "so commonly used that its failure seems unique to the Big Dig," according to The Christian Science Monitor.

The bolts are anchored by epoxy, a high-strength adhesive that often requires mixing on-site before installation, into the top of the tunnels. The concrete panels form a drop ceiling that helps ventilate the tunnel. The woman who was killed was crushed when a section of panels anchored by epoxy fell on her car. Thousands of other bolt assemblies in the tunnel complex were constructed differently and are not believed to pose a risk, according to The Associated Press.

The panels in the Ted Williams Tunnel are lighter than those that fell and crushed the woman in the Interstate 90 connector tunnel that links the highway to the Ted Williams Tunnel. According to Alexander Bardow, the state engineer overseeing Big Dig tunnel inspections, lighter ceiling panels were originally chosen for the I-90 connector tunnel. Bardow told The Boston Globe that part-way through tunnel construction, Big Dig managers switched to a design that called for a heavier concrete ceiling, as it was apparently less expensive and easier to install.

Inspectors said that the Ted Williams Tunnel was safe but that 25 "areas of concern" were being monitored. Because subsequent inspections found gaps up to an inch deep between the panels and the ceiling, Romney overruled engineers for the state's Turnpike Authority, who had decided that the slipped bolts were not an immediate concern, and he closed the tunnel.

Random pull tests to gauge the load capacity of bolts throughout the Ted Williams Tunnel began immediately. The governor said the pull tests showed the current suspension system that supports the three-ton ceiling panels in the tunnel does not hold as much weight as required. Similar tests in the connector tunnel showed the epoxy anchor system to be unreliable, causing officials to order the installation of reinforcement anchor bolts throughout the tunnel.

"In grabbing ahold of these bolts and pulling on them with excess force, they're letting go ... at lower pressures than they were designed to handle," Romney said. "This epoxy system is not working the way it had been designed and engineered to work, and for that reason we can't count on it."

Indeed, the Massachusetts Transportation Authority has now enlisted European construction firm Hilti Corp. to install a similar model of load-bearing bolt anchors -- but ones that will not rely on high-strength adhesives such as epoxy.

Some bolts from the ceiling wreckage have shown "indications of very little adhesive having been applied," says Marty Schofield, vice president of product safety at Hilti Corp. An accident caused by improper installation or errors in mixing the epoxy, Schofield says, would vindicate the tunnel's designers.

Engineers often add redundancies -- identical, extra supports capable of holding significantly more weight than the structure actually demands -- for designs such as the Big Dig's ceiling. According to Jerome Connor, a structural engineering professor at the Massachusetts Institute of Technology (MIT) in Cambridge, there should have been enough epoxy-and-bolt anchors to hold the ceiling panels in place even if a few failed.

The epoxy-and-bolt anchor system, experts say, has long been a tried-and-true method for securing panels to tunnel ceilings. "It's the fact that they only used a limited number of bolts -- there was a very low margin of safety," Connor told The Christian Science Monitor. Connor contends that the too-few anchors used to hedge against failure in the I-90 Connector tunnel lacked enough capacity to carry the load.

A new system to support concrete ceiling panels in the Big Dig's I-90 connector tunnel is working, Gov. Romney said on July 18. Crews tested the system designed to shore up the failing epoxy bolt anchors of the tunnel ceiling and were to begin installing the system immediately.

"We now have two systems for re-mediating the failed epoxy-based system," Romney said. "One system is the undercut anchor bolt, the other is locking right into steel from the unistrut system that was imbedded into the concrete, wherever that is available." The Big Dig has used enough concrete to build a sidewalk three feet wide from Boston to San Francisco and back three times, according to project statistics.

Romney said tests on the new system showed it could support up to 14,000 pounds. The estimated load the supports would have to hold is about 2,000 pounds.

Despite the indication of effectiveness of the pull tests, the project remains in the eye of an extensive probe -- which includes criminal investigators -- focusing on construction errors rather than on flawed design. Massachusetts Attorney General Thomas Reilly has already subpoenaed construction documents to determine whether contractors flouted safety protocol. Reilly has said that some documents reflected a "substantial dispute" among engineers over whether the anchor system was adequate to hold the weight of the three-ton ceiling panels.

Yet according to officials, government documents and people who shaped the project over the years, the Big Dig has not gone awry because its flaws were unknown. It has gone awry in spite of repeated warnings about its cost and design.

Late last month, The Boston Globe reported that John J. Keaveney, the on-site safety officer for the Interstate 90 connector, sent a memo in 1999 that directly warned his superiors the tunnel ceiling could collapse because the bolts could not support the heavy concrete panels, and feared for his conscience if someone died as a result.

Keaveney, educated as an engineer and long experienced in construction, said that after he raised the concern, his superiors at Modern Continental, the company then building the tunnel, and representatives from Bechtel/Parsons Brinckerhoff, the private sector manager of the Big Dig, sought to reassure him by telling him that such a system had been tested and was proven to work.

Keaveney said he was not alone in his worries and thus wrote the memo to reflect what he called the collective concerns being voiced among ironworkers installing the ceiling and other Modern Continental employees on the scene that the ceiling wouldn't hold.

Keaveney wrote in the memo that the amount of weight being suspended from the ceiling appeared to be "excessive," given that the bolts were "only inserted into concrete with epoxy." He also observed water dripping from the holes that construction workers drilled before the epoxy and bolts were inserted. Given the water pressure on the tunnel ceiling, he questioned whether the epoxy would hold. In the memo, he outlined other major concerns about the soundness of the ceiling system, including that the bolts and tiebacks were "exposed to the elements" prior to their installation, sitting on pallets, and appeared to have signs of rust. He also wrote that the bolts "will be subject to horizontal and lateral movement...every time the Vent Building utilizes the Ventilation fans."

He said he really began to worry about the ceiling after a third-grade class from his hometown came to visit the Big Dig for a tour in spring 1999. He showed the class some concrete ceiling panels and pointed to the bolts protruding from the ceiling, explaining that the panels would one day hang from those bolts. A third-grade girl skeptically asked, "Will those things hold up the concrete?" Thereafter he began voicing his concerns. "It was like the [third-graders] had pointed out the emperor has no clothes," he said.

Many officials now acknowledge that all of the warnings (not only Keaveney's) were overshadowed by "zeal among politicians, business leaders, lobbyists and private contractors who had a stake in the project." Half a dozen state and federal investigations are looking into corruption, costs and construction methods.

Gov. Romney's recent grim assessment came in the wake of Matthew Amorello's resignation last week as chairman of the Massachusetts Turnpike Authority and Big Dig boss. Amorello, who resigned after intense criticism following the July 10 collapse, will officially step down August 15. His departure is something the governor has been pushing for since he took office in 2003. Amorello was tapped in 2001 by acting Gov. Jane Swift to head the Turnpike Authority and Big Dig.

Authorities have also begun an investigation to determine whether the woman's death should lead to criminal charges.

When excavation began in 1991, it was heralded as a jewel of engineering and vision, The Washington Post recently noted of the network of tunnels that would "burrow under Boston, eliminating traffic gridlock, reducing air pollution and ushering an economic rebirth into one of the nation's oldest cities."

Fifteen years and $14.6 billion later, the Big Dig is nearly complete. Its problems, however, continue -- tragically.

Earlier: 'Digging' Boston's Highway-Tunnel System

Image Credits

Michael Dwyer/Associated Press (via New York Times)

Chitose Suzuki/Associated Press (via Washington Post)

Resources

Bolt failure at Big Dig: An anomaly?
by Matt Bradley
The Christian Science Monitor, July 21, 2006

Governor: Big trouble with Big Dig bolts
by Brooke Donald
The Associated Press, July 17, 2006

Loose Bolts Lead to Closing of Section of Big Dig Tunnel
by Katie Zezima
The New York Times, July 21, 2006

Memo warned of ceiling collapse
by Sean P. Murphy
The Boston Globe, July 26, 2006

Big Dig Tunnel Is Opened for Buses
by John Holusha
The New York Times, July 21, 2006

Myriad Reports Pointed To Big Dig's Problems
by Amy Goldstein
The Washington Post, July 23, 2006

Romney foresees further Big Dig troubles: Says tunnel inspections keep revealing deeper woes
by Tom Benner
The Patriot Ledger, July 28, 2006