Determine, to the extent possible, the depth of the water table and the relative permeability of the geologic layers between the soil surface and the ground water. If sinkholes are present, surface water or runoff can quickly reach ground water with little natural soil filtering. Some pesticides readily move through soils that are well-drained, sandy, or low in organic matter. Wells should be properly cased, capped and grouted. Wells that are not protected act as conduits for surface contaminants to drain into the aquifer.
Open wells used near mixing-loading sites are particularly vulnerable to contamination.
Grade the area around the wellhead to keep runoff away from the well. Pesticide spills near wells can move directly and quickly into ground water. Avoid mixing, storing, or disposing of pesticides within 100 feet of a well. Some pesticide labels may recommend greater distances. Properly close all abandoned wells and never dispose of wastes in unused wells.