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21 Field Observations <br /> Based on visual observations conducted during the borehole installation and sample collection, the <br /> vadose zone soils encountered at the site consisted primarily of slightly moist to moist blackish-gray <br /> clay This clay was encountered in almost all boreholes starting beneath the surface cap (either <br /> concrete or asphalt) down to the maximum depth augered of 15 feet bgs Sands were encountered <br /> ' in boreholes RGS1, RGN1 and SGN2 instead of the characteristic site clay These sands are <br /> thought to be part of the sand backfill for the underground storage tanks <br /> No groundwater was encountered within any of the borehole locations sampled <br /> 3.0 SAMPLE ANALYTICAL RESULTS <br /> All of the samples kept for laboratory analysis were sent to Quality Assurance Laboratory in San <br /> Diego, California via Federal Express The samples were analyzed for the following parameters <br /> o Total Petroleum Hydrocarbons as Gasoline (TPHV) - DOHS method 8015 <br /> o Benzene, Toluene, Xylene and Ethylbenzene (BTX&E) - EPA method 8020 <br /> o Total Lead (Pb) - AA method <br /> The analytical results for the samples are presented in tabular form on Table 2 Appendix A <br /> ' contains the laboratory analytical reports Also included on Table 2 are the Recommended <br /> Maximum Allowable Concentrations in soil per the State of California Leaking Underground Fuel <br /> Tank Field Manual (LUFT) These maximum allowable concentrations are solely recommendations <br /> and should not be considered to be cleanup action levels No definitive regulatory action levels <br /> have been established for gasoline The action levels are determined by the local regulatory agency <br /> on a site and compound specific basis However, TreaTek's practical experience with the local <br />' regulatory agencies and knowledge of the site conditions indicate that the recommended levels <br /> listed in Table 2 may be applicable to this site The following sections discuss the analytical results <br /> for the sal samples <br />' 31 Total Petroleum Hydrocarbons <br /> Three of the six samples analyzed exhibited detectable concentrations of total petroleum <br />' hydrocarbons as gasoline (TPH-G) <br /> The three samples which exhibited detectable concentrations for TPH-G were SGS1, PL1 and FI1 <br /> All three of these samples exhibited TPH-G concentrations well in excess of the recommended <br /> maximum allowable concentration (RMAC) for TPH-G of 1 0 mg/kg <br />' Two of these three samples were collected from locations near the fuel distribution island and <br /> pipeline at a depth of 15 feet Only one sample collected and analyzed near the underground fuel <br /> storagn tan4e nvF�eh.+n.-1 .a..:....a..h�.. Tr%l i n <br /> ���..+ �^l11uracu UWL1M tauJG rrn-ta r ancentratlons (bGb1) However, location SGS1 is also <br /> in close proximity to the fuel distribution island and pipeline <br /> 32 Benzene Toluene Xylene and Eth lbenzene BTX&E <br /> BTX&E compounds were detected in four of the six samples analyzed (RGN1, SGS1, PL1 and F11) <br /> Only the xylene concentration in sample PL1 and all BTX&E compound concentrations within sample <br /> FI1 were detected at concentrations above the compound specific RMAC <br /> I <br />