Volume 3, Issue 7 (July 2006)
Chromite Ore Processing Residue (COPR): Hazardous Contaminated Soil or Solid Waste?
Chromite ore processing residue (COPR), which contains hexavalent chromium (Cr6+) at concentrations typically in the range of thousands of milligrams/kilograms, was deposited over a timeframe of 50 years as fill at a site referred to as SA7 in New Jersey. Significant surface heaving associated with COPR weathering-induced mineralogical expansion has been observed at the site over time. The current site owner is being required to remediate the site to mitigate both human health risks associated with the Cr6+ and site redevelopment problems associated with COPR heave. The owner is presently required to remediate the COPR by excavation and off-site disposal at a licensed hazardous waste landfill. This is a very expensive remediation option, one that may not be financially sustainable at other COPR impacted sites. The owner has undertaken a major investigation to better characterize the nature of COPR and to develop on-site treatment technologies to reduce Cr6+ concentrations and mitigate COPR heave potential. As one part of the investigation, the characteristics of COPR were evaluated with respect to the definitions of hazardous contaminated soil and hazardous solid waste under the toxicity characteristic waste provisions of the U.S. Resource Conservation and Recovery Act (RCRA). Remediation clean-up standards, and thus the potential costs and applicable methods associated with site remediation, under these two definitions are significantly different. This paper explains these differences and evaluates the COPR for conformance with each definition. This evaluation includes comparison of sampling, logging, and laboratory testing techniques for COPR compared to soil, geotechnical parameter comparisons, and mineralogical and total metals comparisons. Based on these comparisons, the authors conclude that COPR should classify as a hazardous contaminated soil from both regulatory and scientific perspectives. The bases for this conclusion are provided in the paper. The methodology presented herein to evaluate COPR classification may have applicability to other contaminated soil-like media from industrial processes that are potentially subject to the requirements of RCRA hazardous waste regulations or similar regulations in other countries.