119ft long steel pipe is Bertha’s mystery object

According to the Washington State Department of Transportation (WSDOT), crews on January 2 managed to remove enough soil from the cutter head and lower the water pressure, allowing for an inspection of the upper 15 feet of the chamber.

The inspection revealed an 8-inch-diameter, 119ft long steel pipe that was installed by WSDOT in 2002, in order to detect groundwater flow in the area, after the 2001 Nisqually earthquake. Some of the other objects that were also obstructing Bertha are believed to be parts of the same steel pipe. After the inspection, crews began injecting a low-strength blend of cement and sand into hollows that were created for purposes of the investigation. When the hollows were filled, shafts with a diameter of 5ft were drilled ahead of Bertha, in places where metal had been detected. Further investigation for additional factors of delay is required, while WSDOT still could not estimate how much time or money is required to get the machine back in operation.

See also: "Groundwater flow delays the unblocking of Bertha", "Mysterious object obstructs the world's largest TBM in Seattle"

Source: The Seattle Times, WSDOT