Which category requires the greatest mixing and loading setback distance?

• A. Gravel Packed Public Well
• B. Non Gravel Packed Public Well
• C. All surface water
• D. All private water wells

Answer: (A)

Protecting drinking water sources by keeping mixing and loading activities away from them is keyed to how vulnerable the water source is. A gravel-packed public well is the most vulnerable among the options because the gravel-packed screen around the well can allow contaminants to move more readily into the aquifer, and the well serves a large number of people. Because of this higher vulnerability, the regulations require the largest setback distance from mixing and loading operations to reduce the risk of pesticide entry into the public water supply. Non-gravel-packed public wells are slightly less risky due to the protective effects of the well construction, private wells are typically less exposed to large-scale contamination, and surface water has its own protective considerations, but the gravel-packed public well demands the greatest separation.