Seattle Tunnel Machine Begins Drilling Under City Streets

SEATTLE (AP) — Seattle's tunnel-boring machine has moved past the concrete walls that make up a repair pit and has started digging into soil about 80 feet below street-level.

After being out of commission for about two years, the machine called Bertha has tunneled about 73 feet and installed 12 concrete tunnel rings since it started moving again on Dec. 22.

The Seattle tunnel was the preferred choice to replace the Alaskan Way Viaduct when it was damaged in a 2001 earthquake. But the machine broke down in late 2013.

The contractor hired to build the tunnel dug a concrete-ringed access pit so workers could reach and fix the front of the machine.

Once repairs were done, the first step was to mine into and out of the access pit. Bertha accomplished that late Wednesday and spent Thursday digging toward South Main Street near Pier 48.