A risk-based approach (RBA) can significantly reduce costs associated with site remediation (e.g. soil excavation). There are several elements involved in a RBA, one being a residual risk assessment. An iterative process is used to: 1) simulate removal of specific soil locations which contribute to excess risk, 2) recalculate exposure point concentrations, and 3) re-estimate site risks. The primary advantage is that exposures are evaluated on an average soil concentration not a single cleanup value, permitting some locations to remain which would have been removed under the single cleanup value method. This process was used at an MGP site in South Carolina. Original soil volume estimates (24,000 tons) were based on meeting a Region IX cleanup value for benzo(a)pyrene. However, several sample locations contributed to the excess risk. The process showed that if these few locations were removed, an acceptable risk level and lower soil excavation volume were achieved (6700 tons). Cost savings were approximately $1.1 Million.
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