Bertha, the massive drill long stuck under Seattle’s waterfront, is back to work.

Bloomburg is reporting that after approximately 750 days after she first broke down, Bertha, the massive drill long stuck under Seattle's waterfront, is back to work. 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's slowly drilling again.

As Bloomberg Businessweek reported last March, 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. Just before Christmas, Bertha drilled eight feet in a test that signaled she's ready.

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