Which type of well is least likely to become contaminated?

Drilled wells are constructed to reach deeper underground water sources, typically penetrating into consolidated rock formations or deeper aquifers that are less susceptible to surface contamination. This depth is crucial because it acts as a natural barrier, making it more difficult for pollutants and pathogens to reach the water supply.

In comparison, shallow wells or hand-dug wells are closer to the ground surface where they can easily be affected by surface runoff, agricultural runoff, and other environmental contaminants. These types of wells are more prone to issues from nearby septic systems, pesticides, and other pollutants that can leach into groundwater.

Artisan wells are also less common and typically rely on natural pressure to bring groundwater to the surface. While they can be less contaminated than shallow wells, their susceptibility is still higher compared to drilled wells because they may not always tap into much deeper aquifers.

Overall, the construction and depth of drilled wells provide more protection against contamination, which is why they are considered the type of well least likely to become contaminated.