By WBZ-TV Chief Correspondent Joe Shortsleeve

BOSTON (CBS) – WBZ-TV went inside the closed Callahan Tunnel Tuesday, to get the first look at construction in the major artery to Logan Airport.

The 52-year-old tunnel was shut down for renovations the last week of December.

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WBZ was the first TV camera allowed in the tunnel to see the ongoing construction work.

Inside sparks are flying and crews are working pulling out the old roadway.

It’s all part of a $35 million renovation for the tunnel which connects downtown to East Boston.

It was Christmas Eve 2012 when one of the wall panels fell onto the road.  The next few days MassDOT found 100 other defective panels. That is when they made the decision to renovate.

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High pressure hoses are removing all the loose roadway to make way for new blacktop.

“We are seeing the steel framing,” Highway Commissioner Frank DePaola told WBZ-TV. “We are seeing it exposed and it is in good shape which means we can tie the new floor into the existing frame of the tunnel.”

The tunnel also needs new walls and air exchange vents. But, the contractor stands to earn a bonus worth tens of thousands of dollars if the work is completed before the March 12th deadline.

“We think the contractor can finish on time and possibly ahead of schedule and get some of that bonus,” DePaola said.

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That means in eight weeks, the Callahan, which normally carries 30,000 cars a day, should be back in business.