Sensitivity Analysis of Risk Assessment at a Petroleum-Hydrocarbon Contaminated Site

Abstract

In this study, sensitivity analysis was performed to evaluate the effectiveness of input parameters on the calculated risks at a petroleum-hydrocarbon contaminated site. Under a risk-based corrective action (RBCA) approach, the risks to human health and the environment associated with this site were evaluated. In addition, risk management strategies and corrective measures were developed to reduce risks to acceptable levels. Results from the sensitivity analysis of all input parameters for risk calculation indicate that the top five factors that play important roles in the risk calculation included emission area of contaminated air, average time for vapor flux, length of emission source, distance of pollutant transport, and width of contamination source. Results from the case study show that the major pollutant exposure pathway at this site was groundwater ingestion. Therefore, the top five most sensitive parameters among the groundwater exposure routes that affect risk calculation included daily water ingestion rate (using groundwater as source water), infiltration rate of water through soil, groundwater flow velocity, groundwater mixing-zone thickness, and distance of pollutant transport. On the basis of risk assessment results and sensitivity analysis, decision makers are required to incorporate remedial activities, including institutional and engineering controls and remediation programs (e.g., natural attenuation, source zone remediation, land-use control, and long-term monitoring) in risk management strategies to meet the minimum target risk levels (cancer risk of