The proof should be boots on the ground photos, aerial photos, and the review of historical facts through the office of a forensic Archaeologist, to get the professional 'Opinion' for the permitting, and to be able to prove you can retrieve the items found safely if they turn out to be artifacts and not deposits.
The next phase I would go through there is the ground scanners......the drill seems too OLD and ARCANE.......once you have an object on screen with outlines of man made form, and have proven the existence on something of importance placed there, it should be no problem to clear the area with a large caisson to retrieve at that depth......
It seems they are concerned with their budget, as are the guys at the show, who are busy giving us the view of a few cores, when we both know that if they would just fork over the money to fund the show the right way they would have the artifacts, the 3d scans of ground pen radar systems, and other high tech gadgets that can detect those magnetic stones the Spanish are so fond of using ....LOL
So what is really going on is they are relying on the show to boost and fund the costs, and are in essence not paying enough to get it done right
I dont think that they are tight on money so to say, but they should step up and scan the whole area with something powerful and get some look at the underlaying tunnels and the rest of the maze.