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- Analysis of soil samples collected from borings SB-1 through SB-6 revealed no <br /> detectable diesel or volatile hydrocarbon concentrations <br /> • Analysis of groundwater samples collected from borings SB-1 through SB-6 <br /> revealed no detectable diesel concentrations No detectable volatile <br /> hydrocarbons were encountered in the groundwater samples collected from <br /> borings SB-1 through SB-4 and SB-6, upon analysis. The water sample <br /> collected from SB-5 revealed 0.8 ppb toluene upon analysis <br /> 5.0 Summary and Recommendations <br /> A review of soil sample analytical results reveals impact to soil quality at the location of the <br />' 300 and 550 gallon abandoned diesel fuel tanks Although samples collected from a hand <br /> boring near the abandoned tanks indicated high diesel concentrations (12,000 and 13,000 <br /> ppm), analysis of soil samples collected from monitoring wells MW-1 through MW-3 and soil <br /> borings SB-1 through SB-6 do not indicate any lateral migration of diesel fuel. Only two soil <br /> samples collected during investigative efforts indicated the presence of petroleum <br /> hydrocarbons One of the samples collected from downgradient well MW-1, at forty feet <br /> below grade, revealed toluene and xylenes at method detection lmuts (0 005) These <br /> concentrations do not indicate significant impact to soils and may be associated with an off- <br /> site release migrating through the utility fill surrounding the well The second sample <br /> reflecting the presence of petroleum hydrocarbons was collected at twenty feet below grade, <br /> from upgradient well MW-3. This sample revealed the presence of gasoline ('14 ppm) <br /> ethylbenzene (0 006 ppm) and xylenes (0 013 ppm) As the sample was collected from an <br /> upgradient well and the hydrocarbons encountered appear to be gasoline, it is likely that the <br /> hydrocarbon concentrations are due to unproper decontamination of drilling equipment, an <br /> alternate off-site hydrocarbon source or a laboratory error. <br /> A review of groundwater analytical data indicates the initial presence of diesel fuel in samples <br /> collected from wells MW-1 and MW-2 (down and side-gradient of the abandoned tanks <br /> respectively) Four subsequent quarterly sampling events have revealed no detectable <br /> petroleum hydrocarbons in these wells. To assess the possible off-site migration of the diesel <br /> hydrocarbons, six boreholes were drilled to facilitate sample collection. Analysis of the <br /> borehole groundwater samples did not mdicate any diesel fuel migration One groundwater <br /> sample only, collected from borehole SB-5, revealed 0 8 ppb toluene upon analysis. It is <br /> likely that this concentration is due to laboratory contamination, as toluene was encountered <br /> MZ103-17-93/ENG/93-0034 if 8 <br />