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ENVIRONMENTAL INVESTIGATION REPORT Unocal Service Station No 5886 2701 West March Lane Stockton, California Delta Project No D095.066 ' Page 9 Benzene concentrations above the Iaboratory's limits of detection (0 005 mg/kg) was detected in soil sample GP-3-9 at a concentration of 0 0093 mg/kg The sample was collected from GP-3 at nine feet bsg Only two of the fifty soil samples (GP-3-9 and GP-11-14) contained detectable concentrations of toluene, ethylbenzene, total xylenes and TPH as gasoline Several soil samples contained concentrations ' of TPH as diesel ranging from 1 1 mg/kg to 15 mg/kg A tabulation of the analytical results from soil samples collected from the Geoprobes are presented in Table 4, Geoprobe Soil Sample Analytical Results Copies of the laboratory analytical reports are presented in Appendix C 4 4 2 Geoombe Ground Water Sampling Analytical Results One ground water sample was collected from the base of each Geoprobe and submitted for chemical analyses of TPH as gasoline and TPH as diesel using EPA Method 8015 Modified Each sample was ' also analyzed for BTEX using EPA Method 8020 Twenty-one ground water samples were submitted for chemical analyses, one from each soil boring The method used to collect the ground water samples is presented in Appendix B ' Benzene was detected in ground water sample GP-17W above the laboratory's limits of detection (0 5 micrograms per liter (14g/L)) This ground water sample reported benzene at 3 2 ;.g/L Figure 6 ' (Benzene Concentrations in Ground Water) shows the location of each Geoprobe sampling point and the associated benzene concentration reported in each ground water sample Isolated detectable concentrations of toluene (0 63 µg/L to 0 73 pg/L), ethylbenzene (0 66 gg/L to ' 1 9 deg/L), total xylenes (0 70 µg/L), and TPH as gasoline (190 µg/L to 260 Ag/L) were detected in four of the samples Figure 7 (TPH (Gasoline) Concentrations in Ground Water) shows the location of each Geoprobe sampling point and the associated TPH as gasoline concentration detected in each ground water sample RPT 160 SIS