A risk/cost analysis to manage viral contamination of groundwater

Abstract

Under the proposed groundwater disinfection rule of the 1986 Safe Drinking Water Act, municipal water systems have four options to demonstrate that natural disinfection of viruses occurs between the virus source and the municipal well. One option is to demonstrate that the necessary set-back distance exists between these facilities. The objective of this research was to evaluate the risk that virus concentrations at a municipal well would exceed recommended levels even though the virus source was separated from the well by the set-back distance recommended by the EPA. Groundwater transport modeling was used to evaluate this risk and compute the necessary distance upgradient from each Nebraska municipal well for sufficient virus die-off to occur. The number of wells with computed die-off distances greater than the regulatory set-back distances were divided by the total number of wells. The results of this research show that the potential risk for virus concentrations will exceed recommended virus levels in municipal wells using EPA's set-back distances.