Bertha is on the move again.
The tunnel boring machine got stuck a little over two years ago, shortly after it hit a metal pipe. It’s taken until now to get the machine going again.
Engineers will closely watch Bertha’s performance as it approaches the Alaskan Way Viaduct. It’ll get a thorough inspection in February. Then in March, Bertha will plunge under the viaduct, like a diver swimming under a boat.
The state will close the viaduct to traffic as the drill passes through dense glacial till made of sand and clay. Engineers will monitor the ground for movement with fine instruments.
The drill will operate 24 hours a day, 7 days a week. Workers will be stretched thin, some sleeping only five or six hours a night.
Once Bertha reaches the other side of the viaduct, the machine will slow down and the viaduct will reopen to traffic. The completed tunnel should open to traffic in April 2018.