<p>A buried steel pipe is at least partly to blame for stopping the giant tunnel-boring machine Bertha, which has been stuck since Dec. 6 along the Seattle waterfront near South Main Street. The long pipe was a “well casing” used to measure groundwater during studies in 2002 on the Alaskan Way Viaduct replacement project, state DOT spokesman Lars Erickson said this afternoon. The well site was listed in reference materials that were provided to bidders as part of the contract specifications, he said. “I don’t want people to say WSDOT didn’t know where its own pipe was, because it did,” Erickson said. It’s unclear for now why the pipe was left in the ground by the team that did those soil investigations, or why Seattle Tunnel Partners would not have removed it prior to drilling. A modern tunnel machine can chew through dirt and concrete, but not steel. Even fiberglass rods caused a snag that delayed work several days this summer. A steel pipe can become tangled in the spokes of the rotary cutting head, and in a conveyor screw that pushes dirt from the cutter face onto a belt that moves out the rear of the machine. Downtown Seattle contains some of the most frequently poked and studied ground on earth, which makes the blockage all the more confounding. Five-foot diameter holes were drilled alongside the tunnel path to install concrete pilings that protect the old viaduct; the contractors have used ground-penetrating radar; and geotechnical experts drilled test holes, which didn’t hit this particular object. The state Department of Transportation is holding a news conference this afternoon, during which state engineers and contractors will provide more details about the next steps, and about resuming drilling. An inspection was conducted at the front of the machine Thursday night.</p>