SITE INFORMATION AND CORRESPONDENCE FILE 1

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CLEARW___'�IATER %"0' G R O U P, I N C. E—iron—,.tat Ser ices technology, they also demonstrate the need for multiple extraction points. As you are aware, the greatest cost associated with remedial action falls into the categories of capital expense (for the actual treatment equipment) and time/labor costs for system operation and maintenance. There would likely be no increase in treatment equipment cost under a two well extraction scenario, as the water/vapor flow rates would fall within the tolerance (flow rates and contaminant concentrations) required for the equipment to be installed in a single well scenario. The savings associated with shortening the length of remedial action would be significant. Under best case conditions the length of remedial operations would be reduced by half. • Clearwater believes passive skimmers provide a limited response, given the concentration and extent of separate and dissolved phase contamination at this site and the larger-scale remedial attention necessary to address said contaminants. Skimmers would be useful if the PHS/EHD wanted to consider a non-aggressive approach that relies on natural forces for the attainment of project endpoints. The skimmers would then likely be the only device deployed at the site. Given the facts presented in the RAP, and reiterated above, Clearwater requests PHS/EHD reconsideration of the existing conceptual design. In accordance with USTCF guidelines, the next phase of project activity will be put to competitive bid. Clearwater recommends that Mrs. Ruiz and her attorney include the PHS/EHD May 23 letter and this response in the bidders package. It would be most helpful if the PHS/EHD specified more definitively specific ideas for an alternate remediation plan. Problem Assessment Report Several issues were raised by the PHS/EHD regarding the information presented in the Problem Assessment Report (PAR) section of the February 21 submittal. We have tried to address them in order of relative importance: • PHS/EHD staff recalculated the amount of hydrocarbon contamination using an oval footprint for the hydrocarbon plume and a maximum site hydrocarbon concentration of 28,000 ppm (detected in a sample apparently collected during underground tank removal in February, 1989). PHS/EHD calculations indicate that 137,200 lbs of hydrocarbons are present in the subsurface. Assuming that gasoline is 0.72 times the density of water, this equates to almost 30,000 gallons of gasoline. Given the chemical data collected during this project, we believe that this estimate is excessive. The estimation of the amount of product in the subsurface is difficult, at best. There is no dispute that significant levels of contaminant are present, as