Another thing you may want to consider is they were taking core samples. You can tell a whole bunch of history from those things. I doubt they were checking for a leak
I repectfully disagree. I have seen them do the same thing in an earthen dam of a 700 acre reservoir near me which was having issues due to it's construction over several springs. Perhaps core samples but stiil checking for leakage.
Maybe someone else here knows more about the technique?
What kind of history are you referring to?
