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

During environmental investigations at a communications manufacturing facil ity in South West England, polychlorinated biphenyl (PCB) and chlorinated s olvent contamination was identified in soil at a number of locations across the site. The presence of the PCB contamination is known to have been caus ed during capacitor manufacture and general storage of PCBs on the site dur ing 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 s mall area was identified under a roadway in which the PCB contamination exc eeded the figure governing disposal to landfill. As a result, an alternativ e treatment/disposal technique was required for this more heavily contamina ted material. The contaminated soil contained a high clay fraction which ma de treatment more difficult. A number of remediation technologies/disposal routes were investigated incl uding bioremediation, solvent washing and incineration. However, research w ork and laboratory bench scale studies into soil washing and bioremediation indicated that these techniques would not be viable/effective. Also, solve nt washing trials indicated that the time required to complete the trials a nd the relatively high associated development costs made this option unattr active. The most effective and commercially attractive solution to the prob lem 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 characteri stics so that the treated material can be re-used. There were other areas o f 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 associa ted with any remediation works required. (C) 1999 Elsevier Science B.V. All rights reserved.