REALISTIC EXPOSURE SCENARIOS: THE KEY TO SAVING TIME AND MONEY ON RISK-BASED CORRECTIVE ACTIONS

The primary objective of risk-based corrective action is to establish a direct relationship between the extent of a corrective action and the level of risk (potential harm from contaminant exposure) associated with no corrective action. In reaching this objective, one is attempting to ensure that remediation resources are expended efficiently to reduce contamination that poses the most risk. To determine if corrective action is necessary, a risk assessment is performed. The goal of risk assessment is to calculate (as close to reality as possible) the potential for harm to a given receptor from exposure to contamination. The results of risk assessment are often accompanied by uncertainty in almost every parameter used to produce a risk estimate. This uncertainty varies with exposure scenarios that risk assessors must consider during their work.

Controlling uncertainty is critical to establishing the primary objective of risk-based corrective actions, that is, not wasting remediation resources on minor risks. Avoidance of this can only be accomplished by developing realistic exposure scenarios based on established facts or defensible trends supported by accepted evidence. More often than not, exposure scenarios used in risk assessments are “presumed” or prescribed by conservative regulations. The use of presumed or prescribed exposure scenarios defeats the primary objective of risk-based corrective actions by forcing remediation to protect improbable receptors.