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n <br /> 6 CONCLUSIONS AND RECOMMENDATIONS <br /> The presence of gasoline and benzene in soil and ground-water samples <br /> indicates that impact has occurred due to a release associated with the <br /> underground gasoline storage tanks which were removed from the site. <br /> The objectives of this assessment were to evaluate the vertical extent of <br /> impacted soils and the magnitude of ground-water impact. Based on the <br /> verification soil sample analytical results, detectable concentrations of <br /> petroleum hydrocarbons within the tank excavation are generally limited to <br /> two areas (the northern and southwestern areas of the excavation). Ben- <br /> zene has migrated to a depth of at least 41 feet in the location of monitor- <br /> ing well MW-1. However, no other petroleum hydrocarbons appear to have <br /> migrated this deep in the location of well MW-1. <br /> Based on the ground-water analytical results, ground water has been <br /> impacted by petroleum hydrocarbons. Specifically, TPHG and benzene <br /> were detected. However, the benzene concentration was not substantially <br /> greater than the 0.001 micrograms per liter primary drinking water stan- <br /> dard. There is no similar standard for TPHG. EMCON's conclusions, <br /> • based on these results and previous experience with similar sites, are that <br /> (1) ground-water remediation is not warranted and (2) resurfacing of the <br /> tank excavation has likely reduced migration of petroleum hydrocarbons <br /> within the soil. <br /> a 719\9D519050101 d $ Rev. 0 July 2, 1991 <br /> Emcon Associates <br />