Bertha will sit idle for at least six more months before digging resumes on the new State Route 99 tunnel, the contractors for the tunnel announced Friday.
Seattle Tunnel Partners says the manufacturer has recommended three options to repair the world’s largest tunneling machine, which has been halted beneath the city since December because of mechanical problems.
Seattle Tunnel Partner’s project manager Chris Dixon says all of the options entail digging a shaft down in front of the machine. The width of the shaft of will be determined by which option is chosen.
All of the options call for disassembly of the massive cutting head, whose seals around the main bearing are broken and need to be repaired or replaced.
The first option calls for moving pieces of Bertha forward and then working on the machine vertically, which would require the narrowest shaft. Option two would entail bringing pieces up to the surface to work on them horizontally. The third option involves pulling the pieces and laying them horizontally at the bottom of the shaft, which would require the widest shaft to perform the work.
“Obviously, the smaller the shaft, the quicker the design, the quicker the construction, the less space it’s taking up at the surface,” Dixon says. “So that would be preferred. But we want to be completely satisfied.”
Dixon says September 1 is the current latest estimate for when Bertha might start digging again, but he can’t make any promises.
“We need to go step-by-step and make sure that the work is done safely, the conditions are safe and when it’s done, we have a machine that’s at 100 percent,” he says.