FK, When it comes to a 13' deep trench excavation, it it extremely unsafe (and illegal)
to enter the excavation without trench plate shoring
Similiar to this...
The chances of being buried alive are significant, especially if the ground is over saturated.
If you did not see shoring brought onsite, then any gold recovered would have to have been excavated with the bucket.
Your camera appears to be pointed directly at the spoils pile.
I would expect to see someone periodically scanning the spoils pile with a metal detector.
I'm envisioning when the first bar was discovered, everybody would scramble up on the spoils pile to see what was found.
Once something was found, the excavator operator would dump the excavated material on the other side of the excavation...so envision a large barren spoils pile on one side of the trench and a smaller spoils pile on the other, from which they would pick bars of gold from as the guy with the metal detector pointed them out.
Your camera looks to be positioned to capture all of this.
It would be much faster to dump the excavated material into a 4x4 dump truck and haul it off, but I assume the ground was too muddy or the site was inaccessible.
Any jack hammering would have to be done with a large attachment to the excavator.
Bucket is taken off and the chisel tip is attached. Rock is broken up, then the bucket is put back on to excavate the fractured rock.
Digging the gold bars up with an excavator would probably damage them significantly.
I would expect that gold shavings would be scratched off with the bucket teeth.
Depending on how they backfilled the trench, this "select" material may have been placed back into the bottom of the trench or smeared around on the top. I would expect there is solid evidence remaining in the backfill material that could be recovered if it was washed.
Of course that would be contingent on gold being found.