Seattle's tunnel builders say getting their world-record tunnel machine going again will take at least six more months.
The tunnel machine known as Bertha has sat largely motionless for nearly three months since it overheated in early December.
Chris Dixon with Seattle Tunnel Partners told reporters Friday that his estimate was "slightly optimistic."
"What we try to do in construction is drive towards a date, towards a target and get everybody focused on that," Dixon said. "You want everybody to be working towards an objective, and if it's an open-ended thing, people aren't as focused on a task as they need to be, and it doesn't move along as quickly as you'd like."
An expert panel convened by the Washington State Department of Transportation said on Thursday that it should be feasible to resume tunneling between June and October. The panel also said the project could find ways to shave time off the project — including tunneling 24 hours a day, seven days a week — but it would be unable to finish the tunnel on time in December 2015.
Dixon said tunnel-machine manufacturer Hitachi Zosen presented eight options on Thursday for repairing the damaged system of seals around Bertha's main bearing. The bearing allows the machine's five-story-tall cutter head to rotate and chew through the earth.
Dixon said his firm is choosing between three of the eight options, all of which involve digging a 120-foot-deep pit in front of Bertha, then moving Bertha forward just enough to break into the newly dug pit. The crews would then remove its cutter head to gain access to the bearing and seals.
Each of the three options involves a pit of different length. Dixon said a larger pit would take longer to dig but would allow crews to lay the large pieces flat on their side for easier repair work.
Dixon said Seattle Tunnel Partners expects to choose one of the three options within two weeks.
All of Bertha's main bearing seals have to be replaced, though Dixon said Hitachi Zosen still doesn't know whether the main bearing itself is damaged.
The project does have a replacement bearing for Bertha, but it's sitting in Osaka, Japan, where Bertha was assembled.