Suspension System Eyed in Tragedy
By Casey Ross, Michele McPhee and Marie Szaniszlo
Wednesday, July 12, 2006 - Updated: 07:17 AM EST

The shocking Big Dig tunnel collapse has focused investigators’ attention on the apparent failure of a ceiling suspension system that was supposed to be far stronger than necessary to avoid a catastrophe, officials said yesterday.

    Federal and state investigators are scrutinizing the strength of bolts used to secure the ceilings as well as the sturdiness of the concrete and whether adequate testing was done to ensure the tunnel’s ceiling would hold up under stress.

    “The fact that this actually failed is extremely troubling,” said U.S. Rep. Stephen Lynch, adding that federal guidelines require that such suspension systems be able to carry eight times the load being supported.

    “Obviously, there was a failure in either quality control, design or construction,” he added. “We cannot allow people to go back in these tunnels until we know they’re safe.”

    The collapse of the ceiling, which killed 38-year-old Milena Del Valle of Jamaica Plain, was caused when a 3-ton ceiling slab gave way and caused three adjacent slabs to buckle and crash to the roadway with it, officials said.

    Big Dig boss Matt Amorello said engineering consultants, along with state and federal inspectors, are reviewing the project’s entire infrastructure. He also said Massachusetts Turnpike officials are examining their own records to determine whether concrete ceiling panels and the steel tiebacks holding them in place were stress-tested before being installed.

    Amorello declined to discuss the extent of construction changes made while the ceiling was being installed, although a Herald review of documents found that $500,000 in changes were approved in 2004 to adjust ceiling supports in areas surrounding the section that collapsed Monday night. That contract change required the installation of “adhesive anchors for the ceiling struts.” Documents show the I-90 tunnel was plagued by adhesive anchor failure in 2001.

    Amorello said the support system was tested to ensure adequate strength in 1999 or 2000.

    A 42-year-old laborer for the Big Dig said yesterday that after watching the “nonexistent safety testing” on the metal fasteners connecting slabs of concrete to tunnel ceilings, he warned his wife against traveling through the city’s tunnels.

    The laborer, a Boston man who installed microsillica in the tunnels as the concrete slabs were installed, said that after the fasteners were welded overhead into the I-beams there were no tests done to determine if the steel was secure.

    “There were guys on a scissor lift banging the fasteners with a hammer. If it didn’t pop out, they were on to the next one. I asked one of the guys, ‘Is that it?’ He goes, ‘Yup, that’s it.’ ”

    The laborer’s version of safety checks was confirmed by an iron worker who also worked on the Big Dig. “They should have been using X-ray machines and pull tests. Most of the time, that was never done,” the iron worker said. Both workers requested anonymity because they continue to work for the contractors connected to the $14.6 billion project.

    Bechtel/Parsons Brinckerhoff, the firm responsible for oversight of the Big Dig, said in a statement, “We are working closely with (the Massachusetts Turnpike Authority) to help determine the cause of this tragic accident and prevent a recurrence.”

    Modern Continental, the contractor responsible for the portion of the tunnel that collapsed, said it is cooperating with the investigation. “We are confident that our work fully complied with the plans and specifications provided by the Central Artery Tunnel Project,” the company said in a statement.

    So far, the Authority has identified 20 areas for inspection, he said. Meanwhile, traffic will continue to be detoured around the tunnel, he said.