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4L <br /> Page 4 <br /> was estimated by ESI to be about 13 feet below ground surface. According to an ESI <br /> report of April, 1991,groundwater flow direction was estimated to be to the northeast. <br /> On June 18 and 19, 1991, Artesian Environmental Consultants,Inc. (Artesian)conducted a <br /> Phase 11 subsurface investigation at Exxon Service Station 7-3330 at 3128 West Ben Holt <br /> Drive in Stockton,California. The purpose of this Phase 1I Site Investigation was to evaluate <br /> the vertical and lateral extent of the soil hydrocarbons detected in the previous investigation <br /> and the lateral extent of hydrocarbons detected in the groundwater. This investigation only <br /> evaluated on-site soil and groundwater conditions. No off-site sampling was performed <br /> ducting this investigation. <br /> Pour soil borings, B-4 through B-7, were drilled on June 18, 1991 to a depth of 20 feet <br /> below ground surface(Appendix B). Groundwater samples were collected from B-4 <br /> through B-7 using hydropunch sampling equipment. On June 19, 1991, three soil borings, <br /> B-1 through B-3,were drilled on the northern and downgradient boundary of the site, near <br /> the sidewalk on West Ben Holt Drive. Soil borings B-1 through B-3 were subsequently <br /> converted into monitor wells,MW-4 through MW-6,respectively. <br /> Soil samples were collected every five feet during the drilling of the soil borings. Total <br /> petroleum hydrocarbons as gasoline(TPH-g),were detected in soil samples collected from <br /> borings B-4 through B-6 at concentrations of up to 1,100 parts-per-million (ppm)in the <br /> sample from boring B-4 collected at 16 feet below ground surface(Table 1, Figures 3A and <br /> - 3B). This soil sample also contained the maximum concentrations of benzene,toluene, <br /> ethylbenzene and xylenes (BTEX). Hydrocarbons were not detected in soil samples <br /> collected from B-I through B-3 and B-7. <br /> TPH-g concentrations at 120,000 parts-per-billion (ppb) were highest in the hydropunch <br /> groundwater sample from soil boring B-4,located northeast and downgradient from the <br /> underground storage tank area(Table 2 and Figure 4). Concentrations of BTEX were also <br /> highest in hydropunch groundwater sample from boring B-4 (Figure 5). <br />