What is the best well design to minimize the potential for contamination?

A properly sealed well with a sanitary seal and bentonite clay is the best design to minimize the potential for contamination. This design effectively creates barriers against surface contaminants. The sanitary seal prevents any surface water or contaminants from entering the well casing, which is crucial in protecting the groundwater from pollutants. Bentonite clay is used because of its excellent sealing properties; it expands when wet and fills any gaps surrounding the well casing. This ensures that there are no pathways for pathogens, chemicals, or other pollutants to infiltrate the well water supply.

In comparison, a well with a gravel pack does provide some filtration benefits, but it lacks the comprehensive sealing that a sanitary seal and bentonite clay offer. An unsealed well presents significant risks as it allows contaminants direct access to the groundwater. Leaving a well open to the environment exposes it to rain, surface runoff, and other environmental factors that can introduce a variety of pollutants, making it highly vulnerable to contamination. Therefore, the combination of a sanitary seal and bentonite clay provides the most effective protection against contamination.