A risk/cost analysis to manage viral contamination of groundwater

Under the proposed groundwater disinfection rule of the 1986 Safe Drinking Water Act, municipal water systems have four options to demonstrate that na tural disinfection of viruses occurs between the virus source and the munic ipal well. One option is to demonstrate that the necessary set-back distanc e exists between these facilities. The objective of this research was to ev aluate 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 setback distance recommended by the EPA. Groundwater transport mode ling was used to evaluate this risk and compute the necessary distance upgr adient from each Nebraska municipal well for sufficient virus die-off to oc cur. The number of wells with computed die-off distances greater than the r egulatory set-back distances were divided by the total number of wells. The results of this research show that the potential risk for virus concentrat ions will exceed recommended virus levels in municipal wells using EPA's se t-back distances. (C) 1998 IAWQ published by Elsevier Science Ltd. All righ ts reserved.