So Bertha got plugged by the very soil it is supposed to drill through?

I heard somewhere (2nd hand geek-out conversation) that the boring machine was sized by DOT, and an Equipment Specification was put out to the bidding world (i.e. diameter, horsepower, etc). No doubt there is risk in writing a performance specification (changing conditions), but it lets the experts, the actual people who own/build this kind of gear decide if they have the right stuff to do the job.

This machine is repeatedly getting stuck in material it is supposed to blow through. It seems like it is not getting the mechanical advantage it was supposed to, or the shape of the cutting head does not work for the soil it is being used in. Probably a combination of the cutter head and crowd.

No one would be surprised if WADOT made an engineering blunder in the bid document. Not after these last couple of years. It usually comes down to something very simple. Like spending two years scheming up the machine specs instead of saying: we need a hole this big to go from here to there.

I don't know I just heard that a while back, and now that it is plugged again it starts to look more plausible.