Groundwater modeling for an NPL risk assessment

Abstract

AbstractA risk assessment for this National Priority List (NPL) site evaluated the magnitude of the public health impact, assuming that no remediation had or would occur at a landfill. The purpose of the groundwater modeling effort was to predict future groundwater concentrations after liner failure at a residential well currently using the ground water. A two‐dimensional, transient, instantaneous‐release, multipoint‐source model was used to estimate the groundwater concentration at the residential well for 120 years after the release. A worst‐case concentration in ground water was calculated by assuming that no retardation or degradation (chemical or biological) would occur. A more realistic concentration was determined by developing a retardation factor. The modeled groundwater concentrations that were simulated did not exceed standards. If no remediation were to occur and worst‐case liner failure did occur, then the population would still not be at an unacceptable risk from consuming impacted ground water as a potable water supply. In reality, the predicted worst‐case exposure concentrations are unlikely to be reached, and the population (i.e., few individuals) might not be exposed.