Wells that are no longer used must be properly plugged per state groundwater protection regulations. Plugging materials include bentonite clay and cement. An open or improperly plugged well, even one that is 'capped' provides a direct route for surface contamination to impact the ground water aquifer. The ground water in Michigan is a valuable resource.
Owners of abandoned wells leading to contamination of the groundwater have been found legally responsible for cleanup of the groundwater contamination. The groundwater at risk of contamination from an abandoned well maybe the same source for drinking water utilized by the abandoned well owner's family and neighbors.