So, an Old Pipe Blocked a 6-Story Tall Tunnel Borer?
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.