Slashdot Mirror
Object Blocking Giant Tunnel Borer Was an 8" Diameter Pipe
An anonymous reader writes "A few weeks ago we discussed news that a tunnel boring machine measuring 57.5 feet in diameter was halted underneath Seattle after running into a mysterious object. Project engineers have now figured out what the object is: an 8-inch-diameter pipe. In 2002, researchers for another project — the replacement of the Alaskan Way viaduct — drilled down into the ground to take water samples. They used the 115-ft-long pipe as a well casing. As it turns out, this well site was listed in the contract specifications given to all bidders for the tunnel's construction. In addition, the crew manning the machine noticed that it was chewing up pieces of metal, and they removed part of the pipe and kept going. Only later did they realize that significant damage had been done to the machine's cutting face. Officials aren't sure how long repairs will take, or how much they will cost."
That happened at the hotel I used to work at. One of the tour buses entering hit and knocked over a gate, which hit an electric utility pole. I never got the next part of the story straight, and probably nobody knows for sure. But the underground piling holding the gate bent and burst an unmarked gas line as it shifted underground, and somehow a spark from it or the power pole lit the gas.
The ensuing fire required 2 fire trucks, 4 Gas Company trucks, and one Edison truck on-site as they tried to figure out what to do. The hotel was over 100 years old and the break was before the meter so in a section of pipe that was the Gas Company's responsibility. They couldn't find any records of where they had originally installed the gas lines, so they couldn't simply go upstream and turn a valve to shut off the gas, at least not without shutting off gas to the entire neighborhood. They had to bring in special equipment to trace the pipe underground several hundred feet upstream to the main pipe under the road. They determined no shutoff valve had been installed when the line was first constructed. So they picked a good spot between the fire and the road, dug down (with shovels so as not to cause another break), and spliced in a new shutoff valve. The fire burned for over 2 days while they did all this. The gate was ruined. The power pole was a write-off and Edison had to install a new one. I spoke with the Gas Company guy in charge of the whole thing and he said this was the biggest incident he'd ever been involved in in his 30 year career, and it was the main topic of discussion for several days among all the Gas Company branches in the entire Southwest U.S. We were just fortunate the fire was in a remote location and didn't spread.
Always document your work.