A case study of the management and remediation of soil contaminated with polychlorinated biphenyls

During environmental investigations at a communications manufacturing facility in South West England, polychlorinated biphenyl (PCB) and chlorinated solvent contamination was identified in soil at a number of locations across the site. The presence of the PCB contamination is known to have been caused during capacitor manufacture and general storage of PCBs on the site during the sixties and seventies. In general, the PCB contamination was relatively low and the affected soil was excavated and disposed of directly to a licensed landfill. However, a small area was identified under a roadway in which the PCB contamination exceeded the figure governing disposal to landfill. As a result, an alternative treatment/disposal technique was required for this more heavily contaminated material. The contaminated soil contained a high clay fraction which made treatment more difficult. A number of remediation technologies/disposal routes were investigated including bioremediation, solvent washing and incineration. However, research work and laboratory bench scale studies into soil washing and bioremediation indicated that these techniques would not be viable/effective. Also, solvent washing trials indicated that the time required to complete the trials and the relatively high associated development costs made this option unattractive. The most effective and commercially attractive solution to the problem was found to be low temperature thermal desorption (LTTD). An advantage of LTTD is that it not only removes the organic contaminants, including PCBs, but also allows the soil to retain its essential characteristics so that the treated material can be re-used. There were other areas of the site where access for investigation was difficult. These areas were evaluated using detailed probabilistic risk assessments to evaluate both any potential risk to humans and the potential costs associated with any remediation works required. (C) 1999 Elsevier Science B.V. All rights reserved.