An abandoned well is a well that has not been properly decommissioned. "Decommissioning" means the act of filling, sealing and plugging water well by a licensed water well driller or pump installer in accordance with the Rules and Regulations of the Nebraska Health and Human Services.

Old water wells not properly sealed may provide a direct link for contamination from surface water to groundwater. Agricultural and yard and lawn care chemicals, livestock waste, and other contaminants can filter through an abandoned well and contaminate groundwater supplies.

If a well is not properly sealed it may also pose a physical hazard to children or animals that could fall into larger wells.