What is one of the most common reasons for the contamination of wells drilled through rock, clay, or hardpan?

The contamination of wells drilled through rock, clay, or hardpan is often linked to issues related to the construction and maintenance of the well itself. The most prominent reason for this is the failure to seal well casings properly. When well casings are not adequately sealed, there's a significant risk that surface water and contaminants can flow into the well through gaps and unsealed areas. This can allow bacteria, chemicals, and other harmful elements present on the surface or in the soil directly into the drinking water source. Proper sealing is critical in preventing surface water intrusion and maintaining the integrity of the groundwater.

While seepage of pollutants through soil, porosity of the rock, and the use of inferior quality well casings can contribute to contamination risks, they are generally considered secondary factors in this context. For instance, heavy rainfall can lead to the movement of contaminants, but that typically occurs more readily when the well is not sealed adequately. Understanding the importance of proper sealing techniques emphasizes the crucial role that well construction plays in safeguarding water quality.