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I Soil Data Soil sampling depths and analytical results are summarized in Table 4 Laboratory analytical data sheets and chain-of-custody forms are presented in Appendix III As shown in Table 4, toluene, xylenes , and ethylbenzene were detected in soils from MW-1, SB-2, SB-4, and SB-5 No other VOAs were detected in soil samples Concentrations of toluene and xylenes in soil were all considerably below designated levels to protect groundwater (100 ppm and 620 ppm, respectively) as established by the Central Valley Regional Water Quality Control Board in the October 1986 "Designated Level Methodology" staff report Ethylbenzene, however, was detected in concentrations above the 29 ppm "designated level" in a single soil sample taken at a depth of 17 to 17 5 feet from SB-2 Concentrations of total petroleum hydrocarbons as gasoline above 100 ppm were detected in soils from MW-1, SB-1, SB-2 It should be noted, however, that the laboratory detection limit used in the TPH-G analyses of the 40 5 to 41 0-foot soil samples from MW-1 and MW-2 was set at 250 ppm Analytical results for these samples were not available until after sample holding times had been exceeded and so the samples could not be resubmitted for analysis at a lower detection limit Soil samrles from MW-7, -8, -9, and -10 were archived pending results of groundwater sampling Since no contaminants were detected in water samples taken from those wells, the soil samples were not submitted for laboratory analysis t Figures 8, 9, and 10 show the estimated lateral and vertical extent of chemical occurrence in soils and groundwater at the site The extent of soil contamination has been depicted based on levels of TPH-G greater than 100 ppm The extent of groundwater contamination has been depicted based on the presence of chemicals in concentrations above drinking water j standards As shown in Figure 8 , soils containing elevated concentrations of petroleum hydrocarbons extend from the former tank location at a depth of 7 feet below ground surface, a lateral distance of up to 35 feet Petroleum hydrocarbon contamination extends vertically down to groundwater in the vicinity of the former tank site Groundwater Data Results of groundwater analyses are presented in Table 5 Laboratory analytical data sheets and chain-of-custody forms are included in Appendix IV As shown in Table 5, TPH-G, benzene, toluene, xylenes , ethylbenzene, and dichloromethane were detected in groundwater samples No other compounds were detected Concentrations of benzene above State DHS Maximum Contaminant Levels (MCLS) for drinking water were detected in monitor wells MW-1, -3, and -6 All other VOCs which were detected in groundwater were reported in concentrations well below established drinking water standards The lateral extent of groundwater contamination at this site, as shown in Figure 8, terminates a maximum of 100 feet downgradient of the former tank site The vertical extent of groundwater 1 19