Do not dispose of waste into basement or garage floor drains. Never dump it on the ground. Yes, the oil may have initially come out of the ground, but it wasn't from a drinking water well. Be careful where you dispose of waste or where you wash equipment. Properly dispose of household chemicals and refuse.
Sinkholes are probably the worst place to put trash.
Usually, a sinkhole is a direct connector to ground water. Properly seal old abandoned wells. And remember, water drawn from a well most likely originated nearby as rainfall or snowmelt. Good land use practices can pay off with good water quality. Many thanks are given to the following individuals for their assistance in developing this publication.