huge underground drilling machine, has hit something and it can t get past it. stephanie elam has the story. reporter: no doubt, bertha is a beheem. she s the largest tunnelling machine in the world and she was put to work tunnelling in seattle for a planned highway, but bertha was oonl tenth of the way along her journey when she suddenly encountered something large enough and strong enough to stop her in her tracks. we re being really cautious. want to make sure we don t damage this $80 million machine. reporter: but what is it? g geologists point to how it was filled in by engineers. you find shoes, newspapers, there s a boat buried in downtown seattle. so, you name it. it could be down there. reporter: another theory,