***If there was no human underground activity whatsoever, would those cancer causing chimicals (CCC) still show up?****
My in-laws bought some property down in centeral Arkansas that had a gas well drilled on it years before. The well caught on fire when drilled and all those hillbillies thought they had drilled into HELL and the devil was coming out to get them! No one gave rights to drill there for decades.
Everyone used a hand dug shallow well but the well was later abandoned when someone bought the land accross the road and put in a septic tank which polluted all the shallow wells around.
The deep wells drilled after that had a sheen and smelled of oil yet their had been no fracking anywhere in the area.
As a side note, East of AZTEC, NM, which has thouands of gas wells, there was an attempt to use an underground nuclear blast to fracture the formations (Operation Gasbuggy). It worked, but all the gas was now radioactive and so they abandoned the project.
The devil came down to... Arkansas?
Something similar was done near Rifle Colorado (Nuke frac in oil shale up on the Book Cliffs). It was a boondoggle, too.