An inspection of Bertha, the SR 99 tunneling machine that has been halted since Dec. 6, showed an 8-inch-diameter steel pipe protruding through one of the many openings in the cutterhead.
The pipe is believed to be a well casing installed by WSDOT in 2002 after the Nisqually earthquake to monitor the Alaskan Way Viaduct.
The pipe was included in reference materials the contractor received, but the contractor, Seattle Tunnel Partners, told KIRO 7 Eyewitness News they thought the pipe had been removed by a WSDOT contractor doing the viaduct monitoring work.
WSDOT did not go into detail about whose responsibility it was to remove the pipe.
Earlier this week, the contractor drilled 17 small-diameter, exploratory holes near the front of the machine to see if they could identify an obstruction. They encountered obstructions in four of the holes.
On Thursday, the water pressure was low enough and enough soil was removed from the excavation chamber to inspect the top 15 feet of the chamber.
WSDOT said the inspection showed at least some of the obstructions found by the exploratory holes are pieces of the pipe. WSDOT would only say the pipe "could be a contributing factor in the delay of boring."
The 8-inch pipe is 119 feet long. Crews have pulled a 55-foot piece of it out of the ground and another 60 feet remain underground. The rest of the pipe is likely in pieces.
The contractor is looking at options to remove the steel pipe and identify other potential obstructions.
So far, the machine has tunneled 1,000 feet.