Migration of PCBs through a Composite Liner System

In 2009, all Polychlorinated biphenyl (PCB) contaminated materials were excavated for permanent disposal from the Pottersburg PCB Storage Facility. The facility was comprised of four cells of PCB contaminated soil and waste constructed between 1984 and 1987. This exhumation presented a unique opportunity to evaluate the performance of the cells' barrier systems. The barrier systems of Cells 1 and 2 included a leachate collection system, leak detection system and compacted clay liner, whereas Cells 3 and 4 were comprised of a leachate collection system, leak detection system, geomembrane and compacted clay liner. Samples of the liner system were collected and depth profiles of PCB concentrations were determined through the leachate collection system, geomembrane (where present) and compacted clay liner for each of the four cells. These profiles provide insight into the contaminant migration pattern of PCBs over the 22 to 25 year storage period. This paper reports on the performance of the barrier system in Cell 3 in containing PCBs at the Pottersburg PCB Storage Facility. In addition, results from laboratory sorptive tests examining the migration of PCBs through the geomembrane samples taken from the base liner are presented. As well, the diffusion and sorptive properties of the excavated geomembranes with respect to BTEXs are presented. Pollute modeling software was used to established diffusion coefficients for BTEX with respect to geomembrane. These results were used to analyze the contaminant migration profile through the barrier system.