A Mammoet representative says crews will lift Bertha's entire front end as a single hoist, rotate it a quarter-turn in the air and set it on preconstructed repair supports so as not to crush the ground. The crane will then disassemble the drive and replace the front end with a reverse single hoist. By June, crews should be reconnecting the pieces inside, leaving July for testing and TBM recommissioning.

"It's a very aggressive schedule, but one that's laid out in great detail," Dixon says. "It's really going to take however long it's going to take."

But unknowns remain. "We know the damage is pretty much internal," Dixon says. "So we won't really see that damage until we get the pieces to the surface and do the disassembly."

Matt Preedy, Washington State Dept. of Transportation deputy program administrator, says as the owner of the project WsDOT stands by its assertion that it is up to STP and its subcontractor Hitachi Zosen to get Bertha tunneling again.

The original $3.1-billion project deadline was December 2015, but work is more than two years behind schedule.