Seasonal correlation of well contamination and septic tank distance

Approximately 40,000 residents in Palm Bay, Florida, rely on septic tanks as a means of sewage disposal and on weds as a drinking water source. High levels of precipitation (> 63 cm) during the months of July to September and the presence of porous sandy soils result in high water tables and septic tank overflows. The inability of septic tank leachate to percolate through the soil during the wet season results in ground water contamination, thus posing a health risk to those who drink from local wells. Sixty residential wells in Palm Bay were tested for fecal coliforms, nitrates, and phosphates to determine if season has a significant effect on the correlation between these parameters and the proximity of wells to septic tanks. Ground water samples collected at all distances from septic tanks during the wet season contained twice as many fecal coliforms and higher concentrations of nitrates and phosphates compared with samples collected during the dry season. Results showed a statistically significant correlation between increasing fecal coliform, nitrate, and phosphate concentrations and decreasing distance between wells and septic tanks.