Now what? Crews hope drill can clear path for Berthaon December 9, 2013 @ 11:01 am (Updated: 4:43 pm - 12/10/13 )
The massive drilling machine has been stopped since hitting some obstruction last Friday about 60 feet deep, between South Jackson Street and South Main Street. Bertha had just passed the 1,000 foot mark and was close to crossing under the existing Alaskan Way Viaduct when it ran into resistance.
"The contractor is considering the shallow depth of the tunnel boring machine, the high groundwater table and the challenging nature of the historic fill soils at this location as they assess the strategies," said Program Administrator Todd Trepanier in a statement late Tuesday. "Together, WSDOT and Seattle Tunnel Partners are taking the necessary steps to ensure that the chosen strategy can be implemented safely."
Seattle Tunnel Partners says it doesn't expect to have more information until Friday.
"We don't know what the obstruction is, we don't know if it's man made or natural or how large it is," says Kadeena Yerkan, a project spokesperson.
"You can't really back up the machine and it's really difficult to determine what something is 60 feet down," Yerkan says. "It's a very important machine that has a big job ahead of it and you don't want to damage it anyway so the team is being very cautious in moving forward and weighing all the options."
The vertical drilling equipment is similar to drills used to dig deep columns and install concrete pilings for Bertha's launch pit in Sodo, the Seattle Times reports.
Even when crews identify the obstruction, It's unknown how long the drill will be stuck. The tunnel boring project has been marred by delays. Digging was halted for weeks this fall by a labor dispute.
Bertha, the world's largest drilling machine, will ultimately dig a 1.7 mile tunnel beneath downtown from adjacent to Safeco Field north to Battery Street.
The replacement for the Alaska Way Viaduct is slated to open late in 2015.
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