Groundwater contamination occurs when natural phenomena or human activites add undesirable substances to the groundwater at a concentration that is toxic to the receptor, taking into account the rate of intake. Therefore groundwater stewardship and well water protection includes ensuring good land use practices; first on your property and secondly within the recharge area of the entire aquifer.

A contaminated water sample from a well most likely does not mean that the whole aquifer is contaminated. Localized contamination can result from a malfunctioning septic system or improper handling of chemicals near the well site. Older dug wells without properly installed casings are more susceptible to pollution than drilled well.

Common sources of contamination are: malfunctioning septic fields, animals, garbage, compost piles, storage tanks, and parking.

Other sources of contamination are: leaking fuel storage tanks, landfills, chemical spills, infiltration from land treated with pesticides, herbicides, fertilizers and livestock wastes, improper storage or disposal of garden chemicals, poison, household cleaners and detergents, batteries, automotive fluids, road salts, paint and solvents.