Need for heavy panels was debated
The engineer who oversaw completion of the Interstate 90 connector said in an interview with the Globe yesterday that he questioned the need for heavy concrete panels in the tunnel's drop ceiling when he came on the job, but that he didn't press the issue with senior Big Dig officials, because the ceiling work was already well underway and he was persuaded it was being done safely.
Several of the 2 1/2- to 3-ton slabs crashed to the roadway Monday night, killing a 38-year-old mother of three and closing the tunnel indefinitely.
Officials of the Massachusetts Turnpike Authority said yesterday that the concrete panels were part of the tunnel's ventilation system and needed to be heavy to remain still when powerful fans operated at full power.
But some have questioned whether the slabs were needed at all, since their main purpose was to improve air circulation and fresh air was already entering at the entrance to the tunnel 200 feet away.
James Bruno, who served as project manager for Modern Continental on the $91 million contract to complete the connector tunnel, said that he and other construction managers suggested in meetings with Big Dig officials using lighter material for the ceiling, pointing out that the side walls of the tunnel are made of thin metal.
``You're just controlling air here; you don't need heavy concrete slabs," said Bruno, now a senior project manager at Beacon Consulting Group.
But he said senior Big Dig officials were not interested in using a lighter material, because doing so would have required many more supports to prevent the ceiling from vibrating. A lighter material is generally less sturdy and more likely to shift in the face of wind or vibration from traffic.
``When I came to the job, it was roughly 30 percent done," Bruno said. ``They were already doing it this way . . . So I stepped in and said OK. "
He said he dropped the issue after he saw that work crews were doing a careful job installing the ceiling, testing many of the bolts with a device that pulls on them to test their resistance.
Bruno stressed that he feels the tunnel was built safely, in spite of Monday's accident. ``It was excellent people doing excellent work," he said.
``We really tried to do the highest quality job and the safest job," said Bruno, adding that all the workers were well aware that the tunnel ceiling would be suspended over people's heads for decades to come. ``There were no shortcuts."
A number of government agencies are focusing on whether shoddy workmanship or design flaws in building the ceiling contributed to the accident. Much of the attention has focused on durability of the bolts-and-glue combination that hold up the steel frame on which the concrete ceiling panels rest.
The drop ceiling in the nearby Ted Williams Tunnel is affixed to the actual ceiling in a similar fashion, but Turnpike Authority officials said yesterday that panels in the connector tunnel ceiling were at least six times heavier than ones used in the Ted Williams Tunnel, which were a thin composite of metal and concrete that weighed about 800 pounds each.
But Michael P. Lewis, the state's Big Dig project manager, said during a press conference yesterday that the panels in the I-90 connector needed to be heavy for stability in the face of ``hurricane force winds" generated by fans near the roof of the tunnel. In an emergency, such as a tunnel fire, Lewis said, the fans would be turned up to maximum velocity to bring in fresh air, requiring a heavy drop ceiling that would not vibrate.
``We all know from watching the Weather Channel what happens to something like a piece of plywood or something light in hurricane force winds," Lewis explained.
The air flow is less forceful in the Ted Williams Tunnel, Lewis said, and its drop ceiling was primarily for aesthetics.
Now that the concrete panels are all being removed from the connector tunnel as part of the safety review, Turnpike Authority chairman Matthew J. Amorello has said he will consider reopening the tunnel without any drop ceiling at all. Some industry observers have said all along that the drop ceiling was mainly cosmetic, concealing the fans from the drivers below.
As project manager for the last phase of connector tunnel construction, Bruno was primarily responsible to keep the work running smoothly and as close to schedule as possible, rather than to change design of the project.
Ultimately, the tunnel opened to the public in 2003, and final construction work was completed in late 2004, more than a year behind schedule. However, Bruno said the time pressure didn't affect the quality of the work on the drop ceiling.
``We knew it was going to be hanging over the roadway," he said. ``We didn't fool around."
Scott Allen can be reached at allen@globe.com. 