Same question I have been asking. Something pointed them to that exact site prior to CW confession, which LE isn't divulging. The affidavit states that he went to check on a work site near Hudson by his own admission (I've no idea if that is the near or the exact location of the tanks. If it is, then CW truly is a moron because he led them straight to the bodies...which may have been what forced his confession once LE confronted him with drone evidence.
In the previous thread, I posted that I was interested in knowing what piqued LE interest in CW having an affair, after doing a welfare check. Perhaps because in my area, I'm pretty sure LE would show up, shrug and say, "Let's see if they return home, call us tomorrow if they don't," and then go about their business that day. They definitely would not begin investigating for infidelity nor inquiring about neighbor's surveillance cameras. But, I'm in a big city where LE have plenty other priorities. For CW, that 2-day investigation would have began the day they did the welfare check, and up to the day CW was arrested. The fact that her shoes, purse, suitcase, keys, car, etc remained is suspicion enough for foul play, but not for a cheating husband....MOO.