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Investigators probing how pieces of concrete crashed from a Big Dig tunnel are trying to determine if the highway project's contractors ever addressed warning signs about problems with bolts in 1999.
The bolts have become central to the investigation of Monday's collapse, which killed a Boston woman and injured her husband.
Attorney General Tom Reilly said contractors were aware of problems in that section of the tunnel in the fall of 1999, when five bolts failed during testing.
"It was not only identified, but there was a plan to address that problem, and what we're trying to determine right now is, was that plan implemented," Reilly said Wednesday, declining to provide any other details.
Matthew Amorello, chairman of the Massachusetts Turnpike Authority, and Michael Lewis, project director of the Big Dig, said initial visual inspections since the collapse revealed at least 60 signs of loose bolts and other potential failures.
In some places, bolts had started to come out of concrete tunnel ceilings. In other locations, they said, gaps had developed between the ceilings and metal plates that are part of the bracing that has been used to hold the massive panels aloft.
A spokesman for project manager Bechtel/Parsons Brinckerhoff declined to comment on the attorney general's allegation. Contractor Modern Continental did not immediately respond to a phone call and e-mail.
John Christian, an engineer hired to investigate for the Turnpike Authority, said the bolts used a standard design: Holes were drilled into the tunnel's concrete ceiling and bolts were then inserted, along with pressure-injected epoxy.
Increased focus on the bolts came as inspectors began reviewing the city's entire highway system — even parts that are decades old and not part of the $14.6 billion Big Dig system, the nation's most expensive highway project.
Avi Mor, of Dr. Mor & Associates, a California-based consulting firm specializing in analysis of construction defects, said if concrete failure was to blame for the collapse of the panel, investigators would likely find pieces of concrete still epoxied to the tie rods.
Reilly said there was no concrete attached to the rod that failed.
U.S. Attorney Michael Sullivan said federal investigators were checking whether companies that worked in the area of the tunnel collapse fulfilled the obligations in their contracts.
"We obviously want to identify any public safety risks ... but also to ensure that what the government paid for — through tax dollars — is in fact what was delivered," Sullivan said.
Amorello said plans to reopen the eastbound connector tunnel, part of the main route to Boston's Logan Airport and the scene of the accident, were postponed indefinitely to ensure motorists' safety and to collect more evidence in a possible criminal investigation.
Meanwhile, some who use the highway are nervous.
Cab driver Steve Past, 45, said he drives to the airport four or five times a day.
"The drivers aren't so scared, but people sitting in the back seat are scared. Because who knows? Today one piece falls down, tomorrow another piece," he said.
Scott Brook, a 41-year-old information technology consultant who uses one of the system's main tunnels, said he's found himself watching the ceiling after Monday's accident.
"I used to say that the Big Dig was the best thing to happen because it made my commute shorter, but I can't say it's such a great thing now," he said.
Copyright 2006 The Associated Press. All rights reserved.
This program aired on July 13, 2006. The audio for this program is not available.
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