Dec 17, 2007 3:13 pm US/Eastern
Report: Fewer Leaks In Big Dig Tunnels
BOSTON (AP) ―
The remaining 650 leaks found in Big Dig tunnels are on schedule to be repaired by next summer, state officials said Monday, potentially closing another troubled chapter of the most expensive highway construction project in U.S. history.
Nearly 3,000 leaks were discovered after a massive leak into the Thomas P. "Tip" O'Neill tunnel in Boston in September 2004 backed up traffic for miles and raised safety concerns about the $14.798 billion project. The leaks comprised one of the project's many problems, most recently a ceiling collapse that killed a woman.
Robert Rooney, the state's deputy secretary for Public Works, said major leak repairs in the tunnels could be done by the summer of 2008, based on a timetable from turnpike officials and project manager Bechtel/Parsons Brinckerhoff.
"They were projecting with our expected work resources that they would have those 650 pretty much resolved," Rooney said.
Rooney, who is heading a "stem to stern" safety review of the state's highway system, also presented an engineering report to the Massachusetts Turnpike Authority board, which oversees the Big Dig. The report, written two weeks ago, said there were 670 leaks remaining but officials estimate that has reduced to 650 since that time.
The report by the engineering firm of Wiss, Janney, Elstner Associates Inc. found the current leak rate in the 17 miles of Big Dig tunnels "is well below the generally accepted norm" nationally.
All tunnels have leaks, said Andrew Osborn, a Wiss, Janney engineer who wrote the report.
"You're basically injecting grouts through a crack, blindly, to the rear," he explained. "You're not going to get 100 percent of the leaks to stop permanently. There is going to be recurrence of some leakage but over time we are seeing a reduction in the total volume of water coming in through the walls."
Rooney said one or two repair crews are working every night, though progress can be slowed by logistics including coordinating lane closures.
There likely will be new leaks discovered, as well, he said.
"Some may occur that we don't have currently. We may find some that are currently there we just don't know about. It's an ongoing evolutionary kind of thing," he said.
The report said leaking was most pronounced from February through April, because the concrete walls contract in cold weather and create spots for water to flow through.
State Transportation Secretary Bernard Cohen, who is chairman of the turnpike board, said the leaks posed "significant risks" over time, including corrosion to structural steel and damage to electrical equipment.
"We're moving in the right direction. We are well below the volumes (of water) that you might expect to see from a structure like this," Cohen said.
The engineering firm plans to report back to the board next June with the results of further examination into the sources of the water, the accuracy of the infiltration volume measurements and the chemistry of the water to determine the corrosive effects.
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