Which type of well has the lowest likelihood of contamination?

Drilled wells have the lowest likelihood of contamination due to their construction method and the depth at which they are typically installed. These wells are created by using a rotary drill to penetrate deep into the ground, reaching aquifers that are protected from surface contaminants.

The drilling process allows for precise placement of the well casing, which is lined with a protective material that helps to prevent surface water and contaminants from entering the well. Being deeper than many other types of wells, drilled wells often tap into purer water sources that are less susceptible to pollution from agricultural runoff, septic systems, or other environmental threats.

In contrast, bored and dug wells are typically shallower and may penetrate less protected areas of the aquifer, making them more vulnerable to surface contamination. Driven wells can also be at risk due to their shallowness and the environment in which they are installed. Thus, the construction and depth of a drilled well contribute significantly to its durability and resistance to contamination compared to other well types.