Seattle’s Big Bertha is back in business. Can she tunnel all the way?

After an expensive rescue, the giant drill is going back to work “Do we know we won’t have this problem 1,000 feet from now?”

About 750 days after she first broke down, Bertha, the massive drill long stuck under Seattle’s waterfront, is back on the job. Five stories tall and the biggest of her kind, Bertha overheated in December 2013, about a ninth of the way into digging a tunnel for an underground expressway. The contractor on the dig staged a painstaking rescue, and Bertha is slowly drilling again.

Bertha’s troubles are yet another twist in Washington’s effort to replace an elevated highway that was damaged in the 2001 Nisqually earthquake. Five years ago the state awarded a $1.35 billion contract to a joint venture named Seattle Tunnel Partners. After the drill overheated, STP decided it couldn’t repair Bertha underground, so it dug a rescue pit 120 feet deep. Over several days last March, workers used a 240-foot crane to haul out Bertha’s cutter face and drive mechanisms, which weigh 2,000 tons.

Since then, Hitachi Zosen, the Japanese company that manufactured Bertha, has redesigned, replaced, or repaired much of the drill, including her outer and inner seals, bearing, center pipe, and gears. It also added 86 tons of steel as reinforcement. STP lowered the repaired pieces into the pit, where it took several months to reconnect them to the machine and ensure everything was aligned. In December, STP began slowly refilling the rescue

pit with sand. Right before Christmas, Bertha drilled 8 feet in a test.

Why Bertha broke down isn’t a matter of public record yet, probably because the information is crucial to determine who foots the bill for repairs and delays. STP in the spring filed paperwork asking the state to reimburse it $125 million for the cost of digging the rescue pit and subsequent repairs, which the state contests. The final tab will likely be much higher. Already there are lawsuits aplenty: In June, STP sued its insurers, which two months later turned around and sued STP. The state sued STP in the fall.

In early December, the Seattle City Council asked STP’s project manager, Chris Dixon, why local authorities should be confident about repairs when they don’t know what went wrong. “How do we know we won’t have this problem 1,000 feet from now?” said council member Tim Burgess. Dixon’s response: “When someone tells you what they think caused the damage, you are only hearing one of six or seven causation theories that are out there.” He said STP has its own theories, but he couldn’t divulge them. “We believe we have addressed everything that we think might have caused the problem.”

If Bertha stalls again, a second rescue may be more difficult. When the drill broke, the contractors were able to dig the rescue pit without seriously disturbing city traffic. Once Bertha dives under the core of downtown, reaching her from above would be far more disruptive. In the meantime, Seattle drivers will continue to traverse the existing elevated highway, which according to the state scores a 9 out of 100 on a federal safety scale.

STP says that if all goes well, Bertha will be done drilling in January 2017, with the full tunnel opening in spring 2018—more than two years later than initially predicted. On Reddit’s Seattle board, people are betting on how far Bertha will make it. The user Neoitvaluocsol guessed she’ll go only 1 foot, and Double-dog-doctor figured Bertha will dig out 9,268 of her 9,270foot mission, saying, “She’ll make it most of the way, but that last two feet is going to be a bitch.”

The bottom line The state of Washington, contractors, and insurers are suing one another over who will pay for the cost of repairing Bertha.