Since 11:00 p.m. on December 11, the Callahan Tunnel connecting Boston Proper to East Boston has been closed. Undergoing extensive renovations, the tunnel which allows travelers using Route 1A to make a direct line to Logan Airport isn’t expected to reopen until March. NorthEndWaterfront, a local publication out of the North End, was able to get inside the infrastructure project to see just what exactly the Massachusetts Department of Transportation (MassDOT) is doing underneath Boston Harbor.

In the video clip (see: below), Frank DePaola, Highway Administrator for the MassDOT, notes that among the construction happening in the tunnel is the reinforcement of steel beams, the restoration of reflective panels, the replacement of light bulbs, and the implementation of new concrete, which, when poured, will require the tunnel to be completely sealed while heat is pumped in to allow it to properly set.

Perhaps most interesting from the video, though, is that DePaola mentions in their contract is a stipulation that allows for a $70,000 bonus to be shared for each day the tunnel is completed ahead of its March 12 deadline for up to 30 days. Conversely, laborers can expect a deduction in pay for each day the project runs late.

Sounds fair, right? Especially given Boston’s track record for massive transportation ventures (cough, Big Dig, cough).

For more information on traffic and detours, check out our coverage here. In the meantime, go under the harbor and behind the scenes of the Boston Callahan Tunnel renovation.