They Finally Found What's Blocking The World's Largest Tunneling Machine

By Sarah Zhang on at

Ever since the colossal machine tunnelling under Seattle, nicknamed Bertha, was stopped in its tracks, there's been a frenzied speculation about what mysterious "object" could possibly block such a powerful machine. The answer is, at least partially, a big steel pipe.

The pipe was the well casing for a 2002 groundwater study, preceding tunnel construction. While Bertha can easily chew through rock, it doesn't do so well with steel. Why the pipe was left in the ground and why officials didn't know it would be in Bertha's way is still its own mystery. Those speculating that some "piece of old Seattle" was blocking Bertha seem to be right, after all, even if the history is more recent than they would have liked. [The Seattle Times]

Photo courtesy of WSDOT