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One sample was analyzed to determine the naturally occurring hydrocarbon content of the <br /> soil Results of this test appear to indicate that the hydrocarbon concentrations reported <br /> during the total petroleum hydrocarbon testing may be inflated due to naturally occurring <br /> hydrocarbon matter in the soil <br /> Groundwater, although not tested as part of this investigation, is examined on a quarterly <br /> basis at the site Analytical results obtained from wells MW-1 and MW-2 (located <br /> downgradient from the former tanks) have revealed no detectable petroleum hydrocarbon <br /> concentrations for five consecutive quarterly events <br /> The silt/clay layer noted between 25 and 32 feet below grade may be serving as a barrier to <br /> vertical diesel migration, preventing impact to groundwater while allowing the diesel to <br /> naturally attenuate in place <br /> 5.0 Summary and Recommendations <br /> A review of verification soil sample analytical data appears to indicate that diesel impact to <br /> soil is areally limited to approximately 78 yd of soil, located beneath the west end of the <br /> former middle UST (beginning at 17 5 feet below grade) Review of recent soil sample <br /> analytical data appears to indicate that diesel concentrations have decreased over the past <br /> year <br /> A review of groundwater analytical data collected from wells MW-1 and MW-2 reveals no <br /> detectable diesel concentrations for five consecutive sampling events The lack of diesel in <br /> groundwater may be attributed to a silt/clay confining layer which exists between 25 and 32 <br /> feet below grade <br /> Based on the fact that the extent of diesel impact to soil appears to be areally limited, the <br /> encountered diesel concentrations in soil appear to be decreasing and no impact to <br /> groundwater has been observed, it appears that no remedial actions are required at this time <br /> i <br /> IT recommends completing three additional quarterly groundwater monitoring events to <br /> confirm site conditions Upon completion of these events (October 1994, January 1995, and <br /> April 1995), the necessity of any further actions at the site will be evaluated. <br /> M7Jo9-08-94/UST/94-0142 nbr 10 <br />