National Driller reported last month that Bertha, the tunnel boring machine working deep beneath downtown Seattle, has stopped cold. A mysterious object blocked its path. At the time, the Internet was going wild with theories. Was it a glacial boulder? How about the spaceship of ancient aliens?
Turns out it was an old steel well casing left behind by an earlier work crew in the same area, reports the Seattle Times. A research crew investigating the subsurface conditions for the Highway 99 project—the project that put Bertha to work—had left the 8-inch diameter casing behind in 2002.
Crews last month were drilling 5-foot diameter shafts from the surface down to the front of Bertha’s cutting face 60-feet down in hopes of finding, breaking up and removing all of the old casing to get the borer under way again. Bertha is part of a $1.09 billion project to drill an underground passage for a replacement for the Alaskan Way Viaduct strip of State Road 99.
It seems like the 57-foot tall Bertha, touted as the “world’s largest” borer, would chew up and spit out just about anything in its way. Turns out it can go through earth, concrete, rock and just about everything but … you guessed it … steel.
Maybe they should have called Miss Dig?