The Washington State Department of Transportation is replacing the earthquake-damaged Alaskan Way Viaduct with a new State Route 99, a multi-phase project which involves tunneling underground.
To get the job done, transportation experts have enlisted the help of the world’s largest tunneling machine, which is nicknamed Bertha.
Bertha’s entry into Seattle was met with much fanfare and she was making great progress in her dig until an unknown obstruction caused Bertha to stop tunneling on Dec. 7.
A Job for Trained Divers?
Professional divers, who are accustomed to underground-pressurized work, might be called to go down to the bottom of Bertha’s tunnel and help figure out what is causing the blockage, according to CDiver.net. The bottom portion of Bertha is currently 110 feet underground. While the job wouldn’t involve going underwater, it would involve working in greater-than-atmospheric pressure, the Seattle Times explained.
Chris Dixon, the project director for Seattle Tunnel Partners, thinks the divers could break the obstruction apart with pneumatic drills and jackhammers. The diving team who is subcontracted to be on call for the SR 99 project is Ballard Diving, a Seattle-based company with experience doing tunnel work. However, it was uncertain last week whether the project director would go with that method or an above-ground method for clearing the obstruction.
What’s Going on with the Project Now?
Seattle Tunnel Partners, the contractor in charge of the SR 99 project, has begun drilling wells to pump water out of the ground near Bertha, and has removed more than 300,000 gallons as of Friday, according to WSDOT. Early visual inspections revealed no sign of the obstruction, so crews are still at work lowering the water pressure around Bertha so that the team can get a better look at what is causing the hold-up. WSDOT doesn’t think crews will learn what’s blocking Bertha until 2014.
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(Photo via WSDOT)
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