Despite Leak Problem, Void In Soil, State Insists Big Dig Tunnels Are Safe

BOSTON (CBS) – A day after the void underneath one section of Big Dig tunnel reported, WBZ is learning more about another leak between two sections of the tunnel under South Boston.

Officials say drivers are safe because all of that water is being pumped out, but it can be up to hundreds of gallons an hour.

So far none of the temporary repairs have worked, and they need a permanent fix.

The problem is around what’s called the “super plug”.  It was supposed to connect two tunnels by the Fort Point Channel, but there’s a gap, at times six inches wide with water rushing in.

WBZ-TV’s Karen Anderson reports.

Details about this problem come on the heels of the report that the Big Dig soil around the I-90 connector tunnel that was frozen during construction for stability, is now sinking twice as quickly as engineers expected.

There is now a hole under the tunnel that 50,000 driver use every day.

The state says there is no danger.

But even one official is shocked by the size and scope of the problem.

Professor Andrew Whittle is the head of MIT’s Department of Civil Engineering and Environment.

“I’m more surprised that I don’t know what’s causing the movement,” says Whittle.

Whittle is an expert in ground soil. He has been stumped by what’s going on below the ground around the I-90 connector as the Big Dig soil thaws.

“I don’t think it’s a safety issue,” says Whittle. “It’s an issue that certainly wasn’t predicted, and it’s already cost some money to mitigate the effects.”

Whittle, who’s on the MassDOT board, says the tunnel can act as a bridge over possible voids below.

“The concrete box that makes up the tunnel contains a huge amount of steel,” said Whittle. “It’s a very stiff box with a lot of steel reinforcement so it’s probably not going anywhere.”


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