Risk Assessment Eliminating Naturally Occurring Metal

A risk assessment was completed for a metal electro plating manufacturing facility in Pennsylvania under Act 2.  Constituents analyzed for included volatile organic compounds, semi-volatiles organic compounds, and metals.  An analysis of the analytical data was completed to determine constituents of interest (COI) that exceeded applicable screening criteria and would be carried through the quantitative risk assessment.  Arsenic was detected in soil and groundwater at concentrations that exceeded applicable screening criteria.  However, upon a thorough evaluation of historic site activities, hydrogeologic conditions, analytical trend analyses, and reference to publications on background arsenic soil concentrations, it was determined that although arsenic exceeded screening criteria in site samples, arsenic is a naturally occurring constituent and the observations of arsenic in site media indicate that arsenic is present at concentrations consistent with background levels.  Therefore, a definitive argument was made for excluding arsenic in the quantitative risk assessment that was supported by a multiple-lines-of-evidence approach.