What's been blocking the world's largest tunnel boring machine beneath downtown Seattle for the past month isn't as historical or out-of-this-world as some hoped and speculated it to be. It's just a steel pipe.
"Bertha", the $80 million, five-story-tall boring machine was digging a new path when it got stuck 60 feet below Seattle's streets on Dec. 6. Much probing and speculating on what stopped it followed thereafter. Some thought it was a giant boulder while others hoped it was a piece of lost history from Seattle's shipbuilding boom and gold rush era. A local restaurant even promoted the idea that it was a 70-foot "clamosaurus" that escaped from the restaurant's founder in 1937.
On Friday, the Washington State Department of Transportation (WSDOT) finally issued a statement identifying the culprit: an 8-inch-diameter, 150 feet-plus long steel pipe. "A piece of an 8-inch-diameter steel pipe could be seen protruding through an opening in the machine's cutterhead. Probes from the surface also detected metal in front of the machine," the statement reads.
The steel pipe is a well casing the department installed in 2002 after the 6.8 magnitude Nisqually earthquake in 2001 for geologists to better understand groundwater flows in the area. The WSDOT also said in its statement that the location of the pipe was included in the materials provided to Seattle Tunnel Partners, the contractor of the 1.7-mile tunnel project. "I don't want people to say WSDOT didn't know where its own pipe was, because it did," said DOT spokesman Lars Erickson. The contractor, however, said, it didn't know that the pipe was there.
According to Matty Preedy, a deputy program administrator at the WSDOT, further investigation is needed to identify other potential obstructions. "This is just the first step in determining what's obstructing the machine," he said. "We need to investigate further to see if there are other factors that could have contributed to the blockage."
Preedy also said that it was too early to talk about any additional costs or delays. "It's still too early to know how this issue will affect the project's schedule and budget," he said. "Our focus right now is on resuming tunneling as quickly and safely as possible."
