Papers and Reports

During removal of an industrial landfill in Folsom, California, fill material was excavated and processed through a mechanical screening plant to segregate soil from construction and demolition debris. The segregated soil was stockpiled and analyzed for a wide range of chemical groups to determine if the soil could be backfilled on-site. The analytical results indicated many of the stockpiles had concentrations of polycyclic aromatic hydrocarbons (PAHs) that exceeded US EPA Regional Screening Levels, and a large quantity of soil was initially classified as requiring off-site disposal at considerable cost. Because PAHs are ubiquitous in urban settings and the landfill did not contain a significant source of PAHs, development of a site-specific PAH cleanup goal was proposed to regulators. Cal/EPA guidance for using on-site data to develop a background threshold for metals was applied to the development of the PAH cleanup goal. The Cal/EPA approach involves demonstrating whether the data belong to a single population or multiple populations based on data distribution tests and probability plots. This article explains the statistical and graphical methods that were used to demonstrate that the Cal/EPA approach was valid for PAHs and that the calculated cleanup level was consistent with published anthropogenic background levels of PAHs in California and across the United States. The site-specific PAH cleanup goal enabled most of the soil to be backfilled on-site, saving about $227,000 in transportation and disposal costs, and regulators subsequently approved unrestricted future use of the property.