The wait for one of the world's largest tunnel-boring machines to resume excavation under downtown Seattle should come to an end in late November, according to a new schedule released by contractor Seattle Tunnel Partners (STP).
Dubbed "Bertha," the TBM has sat idle since December 2013, when it overheated; then, it was shut down, so crews could search for a cause and a solution. Bertha stopped just 1,083 ft into a 9,270-ft (1.7-mile) course to create space for a new Highway 99, which will replace the aging and seismically vulnerable Alaskan Way Viaduct. With the 57.5-ft-dia machine’s cutterhead now under repair, the joint venture of New York-based Dragados USA, Spain-based ACS Group and California-based Tutor Perini Corp. believes it can have Bertha digging again in four months.