The world’s largest tunnel-boring machine named Bertha resumed tunneling on the $3.1 billion Alaskan Way Viaduct in Seattle this week. Bertha was ordered to stop digging underneath Seattle by the Washington Department of Transportation (WSDOT) when a massive sinkhole opened up at the jobsite in January.
Contractor Seattle Tunnel Partners was given conditional permission to restart the drill and resume digging on Tuesday so long as it adhered to a series of new safety protocol for ground control and worker safety, WSDOT officials said.
Bertha’s original purpose was to dig an underground expressway to replace the dilapidated Alaskan Way Viaduct that was damaged in a 2001 earthquake. However, the $80 million drill has a number of setbacks including repairs that lasted two years.
The highway project was originally supposed to cost $2 billion and be completed by 2015. It's now not expected to be finished until April 2018.