WORCESTER -- Specialists hired by the Massachusetts Turnpike Authority have discovered a second section of the Big Dig's Interstate 93 tunnel with a defect similar to the one that sent water gushing onto the road in September.
They also have discovered three additional panels in the tunnel with smaller defects that could cause leaks.
George Tamaro, the consultant hired by the Turnpike Authority, also said a repair job on the panel that caused the September leak could be more complicated and costly than initially anticipated. Officials want contractors to pay for the repairs.
The original plan was to cut away the faulty portion of the wall and replace it with concrete patches. The new plan calls for the contractor responsible for building that section, Modern Continental, to build a new section of wall on the outside of the tunnel in back of the existing one. The new wall would be 90 feet to 100 feet deep and 10 feet wide, squeezed between the flawed tunnel and the Federal Reserve Bank. Modern is still deciding which fix is the best, Tamaro said.
The second flawed wall panel could require a similar repair, he said. But since that the section is in the middle of a surface road, it might force the company to attack the problem from inside the tunnel.
Tamaro said the same defect that caused the September leak occurred in a portion of the wall when one contractor,
Modern failed to remove overflow concrete, and their new concrete compressed dirt and other debris against the dried concrete, which created a long narrow defect that sprang the leak.
Tamaro's investigation discovered Perini had hired a specialist in that type of wall construction, and Modern hadn't.
Modern has defended its work on the tunnel. So has Bechtel/Parsons Brinckerhoff, the private manager overseeing the project.