Roux Associates was retained by a large PRP group to conduct a supplemental pre-design investigation at the Pollution Abatement Services Superfund site, which was ranked No. 7 on the original NPL. The scope of work for the investigation included evaluating the practicability of pumping bedrock groundwater to address an off-site volatile organic compounds (VOC) plume, determining the source of PCBs in sediment in the streams and wetlands surrounding the site, and evaluating engineering "enhancements" suggested by the agencies in a 1993 ROD. Through effective agency negotiation, and with only a minimum of additional data collection, Roux Associates was able to first demonstrate the non-necessity (based on risk) and technical impracticability of the groundwater extraction and treatment remedy selected in the ROD for groundwater in bedrock. Based on the findings of the investigation, USEPA issued an Explanation of Significant Differences that revised the ROD to a natural attenuation remedy, thereby saving the client approximately $16 million.