Don’t get too cozy with the announcement of a possible Sept. 1 restart to tunneling for Bertha, the tunnel-boring machine now idle underground in Seattle. That date remains a slightly optimistic goal, according to Chris Dixon, project director for Seattle Tunnel Partners.
While Dixon on Friday announced during a news conference the hopes for the Sept. 1 restart, which, if it comes to pass, would amount to approximately nine months of no digging for Bertha’s 1.7-mile-long tunnel for a new State Route 99 under downtown Seattle to replace the Alaskan Way Viaduct, he also said for the first time that it isn’t only the rubberized bearing seals that likely need replacing. The main bearing may be damaged after all.
Bertha, as we all should know by now, quit tunneling in early December 2013 when operators thought it had hit a major boulder. It hit no such thing and a restart to the machine in late January offered up the likely real reason for the high temperature readings: broken bearing seals allowing sand and grit into the bearing grease.
All seven of the seals must get replaced.
Along the way, though, Seattle Tunnel Partners—a joint venture of Dragados USA and Tutor Perini Corporation—has maintained they didn’t see any damage to the main bearing. The main bearing is known for breaking down in TBM projects, so the Washington State Dept. of Transportation contract required a second of these parts, a $5 million 35-ft-dia piece, be constructed by Bertha manufacturer Hitachi Zosen and be on the ready. That backup, now located in Hitachi Zosen’s home of Osaka, Japan, will get shipped to Seattle to be ready for installation.
The main bearing drives the machine’s cutter head.
To get to the seals—and the main bearing, if needed—crews will now spend months digging a 120-ft-deep pit in front of the machine, which is just over 1,000 ft into its route, to access the parts from the front instead of the time-consuming method of dismantling the machine from the rear. The pit will feature a concrete-lined wall.
While representatives from bearing manufacturer Rothe Erde of Germany say there’s potential sand and/or saltwater has made it into the bearing, they won’t know until they get all the way inside the machine.
A state review last week said the tunneled highway won’t finish by the last day of 2015 as planned, but Seattle Tunnel Partners says they haven’t revised their schedule yet and increased shifts could allow them to still meet their projected finish dates.
Of course, without Hitachi Zosen finding a root cause for the seal and bearing issue, there’s no reason to believe any timelines.
Tim Newcomb is Engineering News-Record’s Pacific Northwest contributor. He also writes for TIME, Popular Mechanics, Sports Illustrated and more. You can follow him on Twitter at @tdnewcomb or visit his website here.