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A third round of verification soil samples was collected on November 17, 1993 Analysis of <br /> these samples revealed no detectable diesel concentrations at 20 feet below grade at the <br /> southern extent of the overexcavated area Analysis of samples collected from the northern <br /> extent of the overexcavated area revealed detectable diesel concentrations at 20 feet below <br /> grade (I 10 ppm and 2800 ppm) which decreased to non detectable levels between 23 and <br /> 27 5 feet below grade <br /> A final round of verification sampling was conducted on November 18, 1993 Analysis of <br /> these soil samples revealed the presence of diesel fuel to a depth of 26 feet below grade <br /> which extends laterally up to five feet north of the former middle tanks west end A copy of <br /> the Riedel Environmental Services Inc. Tank Removal report, with tables and figures <br /> depicting venfication sample analytical results, is attached in Appendix D for reference <br /> Recent dnlling efforts were positioned so as to examine current soil quality in the area <br /> previously observed to contain detectable petroleum hydrocarbons (near the west end of the <br /> former middle UST). The new borings VW-A and VW-B were drilled in positions adjacent <br /> to the locations where the greatest diesel concentrations were previously encountered Soil <br /> samples were collected every 2.5 feet through the diesel impacted zone (15 to 30 feet below <br /> grade) Analysis of these samples revealed no detectable BTEX concentrations No <br /> detectable diesel concentrations were encountered in the samples collected from borehole <br /> VW-A Diesel was encountered in the samples collected from borehole VW-B at 22 5 and <br /> 25 0 feet below grade only (1 10 ppm and 2 1 ppm respectively) <br /> One sample from each borehole was analyzed to determine the soluble threshold limit <br /> concentration of diesel Analysis of these samples revealed no detectable leachable (mobile) <br /> concentrations of diesel. <br /> One sample from borehole VW-A was additionally analyzed for total organic matter <br /> Analysis revealed the sample contained 0 19 % organic material Current analytical results <br /> are depicted on Figure 4 with current analytical reports included in Appendix C and listed in <br /> Table 1 <br /> MZ/09-O8_94/UST/94-0142 nbr <br />