Vapor Intrusion Risk Assessment for Varying Subsurface Scenarios

SRS employees were challenged with performing a vapor intrusion analysis for an off-site residence with a basement directly adjacent to a former retail gasoline service station with limited information regarding the subsurface conditions of the off-site residential property.  Multiple attempts were made to gain access to the off-site residential property in order to complete investigative borings to gain a better understanding of the type of lithology and depth to bedrock on the property; however, access to this property was never granted.  Therefore, SRS employees conceptualized several plausible subsurface conditions scenarios for the off-site residence based on extrapolation from investigative borings along the on-site property boundary.  A variety of scenarios were evaluated ranging in soil types from sand to silt at varying thickness as well as varying depth to bedrock ranging from 2 to 6 feet below the basement floor.  A Johnson & Ettinger (J&E) model was completed for each scenario to present a range of risk and hazard results to assess the potential exposure for the off-site resident.