Mystery Item That Stopped Drilling Under Seattle Identified

Mystery solved. I blogged last week about a mystery buried object  that had stopped Bertha, the world's largest tunnel-boring machine that is drilling a tunnel under Seattle. That object turned out to be nothing more than a metal pipe. So how could such a minor item stop such a mighty machine? And are there more obstacles in Bertha's way? Plus, how much will the delay caused by the pipe add to the project? The New York Times has the answers.