SEATTLE — Bertha, Seattle’s troubled tunnel machine, is on the move after being stalled for more than a year.
The giant boring device that is trying to dig a new State Route 99 beneath the city started drilling late Tuesday and had moved 6 feet by Wednesday afternoon, Lynn Peterson, secretary of the Washington State Department of Transportation, told a legislative committee.
Bertha must travel another 14 feet through unreinforced concrete to reach an access pit, so workers can remove its front section for repairs.
The machine started digging the tunnel — the key element in the Alaskan Way Viaduct Replacement Project — in 2013, but only made it about 1,000 feet of its 2-mile trip.
Peterson said they’re monitoring the machine’s temperature “to make sure she does not overheat.” They’re also monitoring the viaduct, she said, and have seen no movement during the drilling process.
It overheated and stopped working in December 2013, and workers spent most of last year digging the 120-foot-deep access pit. That work was stalled in December, however, when ground sinking was detected in the area.
The project is two years behind schedule.
Seattle Tunnel Partners officials said they don’t know how long it will take for Bertha to reach the pit. They anticipate the machine may overheat during the process, which would prompt them to shut it down to cool before resuming.
Workers prepared the inside of the pit by cutting away a Bertha-sized circle where the contraption will, hopefully, emerge.
“The machine must be partially disassembled before it can be lifted to the surface, a process that STP has said will likely take significant time and effort,” Laura Newborn, project spokeswoman, said in a statement.
Elsewhere on the project, crews have been building the north and south entrances to the tunnel.
The $3 billion project was designed to replace the SR99 viaduct, which was damaged in a magnitude-6.8 earthquake that struck Seattle in 2001.
