Wednesday, January 8, 2014

Bertha: Craw in Her Teeth? Updated.

"A 57-foot-long section of steel pipe lies in the SR 99 tunnel construction yard. This section of the pipe was pulled from the ground after it was struck by Bertha, the SR 99 tunneling machine, in early December 2013. On Jan. 2, 2014, crews found what is believed to be another section of pipe protruding through an opening in the machine’s cutterhead." [Statement from WSDOT.]

"Bertha," the world's largest Earth Pressure Balance Tunnel Boring Machine, featuring a 57.5 ft (17.48m ) cutterhead, weighing 887 st, driven by a 25,000 hp (18,388 kW) motor, ground to a halt on December 6th , having bored a mere 1,000 feet beneath Seattle.

According to a report on KPLU 88.5 FM,  "A steel pipe that the state Department of Transportation itself had installed back in 2002 may be the cause of the weeks-long work stoppage.

"An inspection on January 2nd revealed an 8 inch diameter (.20 meter) steel pipe protruding through one of the many openings in the cutterhead.

"The Washington State Department of Transportation (WSDOT) installed a well casing, following the 2001 Nisqually quake to better understand groundwater flow [in the vicinity of the Alaska Way Viaduct.]

"Whose Oversight?

"The location of this pipe was included in reference materials in the contract," said WSDOT.

 "However, contractor Seattle Tunnel Partners said the pipe's location came as "a surprise." The contractor claimed Department of Ecology rules require that such pipes be removed upon decommission of wells.

"But a spokesperson for the department said rules only require that casings for decommissioned wells are properly perforated and filled.

“There is no rule that [says] all well casings have to be removed.

"Both WSDOT officials and the contractor declined to elaborate."

In addition to the pipe, test borings suggest other objects, not yet within view, may be contributing to the blockage.  Crews have only examined the top 15 feet of a hole nearly 60 feet deep.

Click "Bertha" in the Index below for all SR99 Tunnel Project postings.

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