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INTERNATIONAL TECHNOLOGY CORPORATION <br /> Ms Mary Maeys 2 January 15, 1996 <br /> ' Response The diesel fuel concentrations used to develop an average are listed in Table 1, <br /> g <br /> "Summary of Basement Soil Sample Analytical Results in ppm," included in <br /> Attachment 10. As the table's title implies, all analytical data obtained from <br /> historical bonngs surrounding the abandoned USTs is summarized in this table <br /> Of the 15 samples collected and analyzed to date from this area, ten possessed <br /> detectable diesel fuel concentrations These ten detected quantities (ranging <br /> from 870 ppm to 22,000 ppm) were added together, with the total divided by <br /> ten to achieve an average concentration for the impacted area (see calculation <br />' sheet in Attachment 10). <br /> Issue C Identify soil sample concentrations used to generate the maximum residual <br />' diesel concentration modeled in Location 2 (beneath the Lindsay Street <br /> sidewalk) see Section 6.3.2 of the IT Site Closure Recommendation Report - <br />' April 1995 <br /> Response The diesel fuel concentrations used to calculate the maximum residual diesel <br />' concentration modeled in Location 2 are listed in Table 2. "Confirmatory <br /> Sidewalk Soil Sample Analytical Results to ppm," included in Attachment 2.0 <br /> of this report. The analytical data listed in this table were obtained from two <br /> recent soil borings (VW-A and VW-B) drilled through the areas previously <br /> oil noted (11/93) to possess the greatest diesel concentrations. The recent results <br /> were significantly lower than the original results obtained from the same area, <br /> apparently indicating natural degradation of the residual diesel over time Only <br /> the recent analytical results were considered when calculating the current <br /> maximum residual diesel concentration <br /> If we were to take a more conservative approach and assume that the diesel <br /> concentrations encountered in November 1993, while not confirmed by July <br />' 1994 soil sample analytical results, are still present, then an average diesel <br /> concentration similar to item "B" above can be calculated Of the 49 soil <br /> samples collected in this sidewalk area, 20 contained detectable diesel <br />' concentrations. These 20 detected quantities (ranging between 2.1 ppm and <br /> 16,000 ppm) can be added together, with the total divided by 20 to give an <br /> average diesel concentration for the impacted area This average concentration <br /> 1 (2,440 ppm) can then be installed in the calculation to determine the maximum <br /> residual diesel fuel volume (38 33 gallons) The calculation sheets and data <br /> used can be found in Attachment 3.0 <br /> It should be noted that this calculation is believed to reflect a value far greater <br /> than the actual volume of residual diesel fuel The V-Leach model was run <br /> again using all detected historical diesel concentrations. Results of the rerun <br /> V-Leach modeling for Location 2 indicate a maximum concentration of 96 ppb <br /> diesel in groundwater after a period of 50 years No MCL for diesel fuel <br />