Application of risk assessment in determination of soil remediation targets

One challenge for soil and groundwater contamination remediation is to identify and assess potential risk of a historically contaminated site to human health and environment. In this article, a decision-making management model, risk based corrective actions guidance, is applied to devise a remediation strategy for a contaminant site to effectively mitigate the potential risk to human health and the environment. The detailed on-site contaminant investigation was first conducted for heavy metals and hydrocarbons by collecting 72 soil and groundwater samples. Then a conceptual site model was developed based on the Source-Pathway-Receptor linkage. The analysis results of the soil and groundwater samples were used to determine the potential risk to human health as well as the environment. Among the contaminants, lead is a cumulative toxicant. Currently, there is no official reference dose or carcinogenic slope factor for lead. For lead contamination, an adult lead model was adopted to determine remediation objectives by assessing human exposure through the measurement of lead in blood. Population race/ethnicity in study area was considered in this model to address a reasonable remediation goal. The analysis results indicate that 970.73 mg/kg of lead is the Tier III remediation objective. This research simultaneously predicts risk and proposes cost-effective options for remediating contaminated soil to acceptable values by tailoring on site-specific conditions and hazards. Meanwhile, an approach is developed to quantify the remediation objective for lead in soil and groundwater based on factual knowledge and scientific evidence concerning the type, level and environmental behavior of identified pollutants. Results from this study provide a streamlined process for future risk assessment work at hydrocarbon or lead polluted sites.