Associations between distance lags, groundwater velocities, and detection efficiencies in groundwater monitoring networks.

Effects of distance lags between landfills and monitoring wells on contaminant detection capability were quantified in several groundwater velocity settings. Detection efficiency calculations were made with and without imposing a time limit on contaminant travel. In general, longer distance lags yielded higher detection efficiencies. However, detection efficiencies decreased as monitoring wells approached a buffer zone boundary imposing a maximum permissible contaminant transport distance. Imposing a time limit on contaminant travel substantially reduced detection efficiency in low velocity settings, especially at longer distance lags. Time limits were less significant in high velocity settings where contaminants more quickly reached monitoring wells. Detection efficiencies also decreased as velocity increased, but decreases were minor once the velocity reached a threshold value.