Contractors working for the state of Washington are planning a high-stakes operation to rescue Bertha — the world's largest tunneling machine.
Bertha is supposed to be boring a 2-mile highway tunnel under downtown Seattle, but it got stuck in December.
Bertha is on Seattle's waterfront, between South Main and South Jackson streets, about 60 feet straight down. At first, they thought the machine was being stymied by a big glacial rock. Then attention focused on the chewed-up remains of a metal pipe. But now it seems Bertha's ailment is mechanical.