Reports reveal frantic effort to keep Bertha tunneling

The Seattle TimesMarch 5, 2014 

Workers with the Washington State Department of Transportation drill 5-foot-diameter metal shafts in front of the Bertha, the machine being used to dig a tunnel for the new State Route 99 in Seattle, Jan. 5, 2014.


Seattle Tunnel Partners spent three work shifts trying in vain -- as temperatures spiked, motors shut down and mud flooded in -- to budge its giant boring machine after stalls Dec. 6 and 7, newly released records show.

Daily reports by state inspectors explain how the contractors discussed probing the soil from above to look for an obstruction.

But before doing so, they pushed the $80 million drill near its limits, in hopes of breaking through a mysterious clog in the watery soil.

“Unable to move machine forward efficiently all shift. Thrust force and torque are running very high,” says a Washington State Department of Transportation (WSDOT) wrap-up from the day shift Dec. 6.

Two of the 24 huge electric motors that turn the round cutterhead automatically tripped off, and were reset.

“High temperatures in the main drive are causing shutdowns of machine as well,” the inspector wrote. Two more attempts during the swing shift also failed.


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