Unused wells can threaten the quality of drinking water from private wells and those servicing public water systems because they provide a pathway for contaminants to move from the surface into deeper aquifers. Deteriorated well casings, open uncased boreholes, and poor or absent annular seals can also allow water to move between previously separated aquifers, which can degrade water quality. In addition, abandoned wells are sometimes used for illegal waste dumping, further highlighting the need for wells to be properly decommissioned.

Decommissioning or permanently removing a well from service involves filling or plugging the well in accordance with Idaho's “Well Construction Standards Rules” (IDAPA 37.03.09), which are administered by the Idaho Department of Water Resources. Idaho law requires well abandonments to be performed by a licensed well driller and in compliance with administrative rules. A properly decommissioned well will not produce or accept fluids, serve as a conduit for contaminant movement inside or outside the well casing, or allow surface or ground water to move into unsaturated zones, into another aquifer, or between aquifers. If no records exist from the contractor who drilled the well, contact the local health department, or the Idaho Department of Water Resources to identify the location of the abandoned well, look for pipes sticking above ground; pipes sticking through walls or floors in the basement; electrical switch boxes in the yard; cement pits in or under sheds; windmills; old crock, brick, or stone structures; or old hand pumps. Metal detectors and informative neighbors can also be helpful.