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I <br /> A S S O C I A T E S I N C . <br /> rte. D <br /> ISCUSSION <br /> Former Diesel Tanks <br /> Based on analytical results and field observations, soil in the vicinity of the remote fill pipeline <br /> does not appear to be impacted by diesel hydrocarbon constituents. Although SB 1 and S132 soil <br /> samples contained concentrations of TPHd ranging from <1.0 to 7.5 ppm, the chromatogram <br /> pattern indicated the chromatogram pattern did not match that of a fresh diesel standard and the <br /> discrete peaks observed may or may not be naturally occurring organics in the soil. <br /> Soil beneath the location of the former diesel USTs, in the immediate vicinity of SB3, appears to <br /> be impacted by total petroleum hydrocarbons. However the impacted soil appears to be limited <br /> vertically to the upper 35 feet of the soil column and laterally to an area within approximately five <br /> to ten°feet (as exhibited by sample 597, collected during the UST removal, and subsequent <br />` borings S134, SB5, GPI, and GP2). Furthermore, no BTEX or MTBE were generally observed in <br /> the soil samples analyzed from borings SB3 through S135 and GPI and GP2. Of the 15 soil <br /> i samples collected from these borings, only total xylenes were detected at a concentration of F <br /> 0.0058:ppm (marginally above the detection limit of 0.005 ppm) in sample GP2-20. <br /> According to groundwater measurements recorded in the area by San Joaquin County Flood ! <br /> Control, groundwater is estimated to be approximately 55 feet bgs, with a historical low of 70 <br /> feet bgs in 1993 and a historical high of 40 feet bgs in 1985. <br /> Due to the low concentrations of the unidentified hydrocarbon, the absence of BTEX compounds, <br /> depth to groundwater, and the fact that the site is capped with asphalt, this area does not appear <br /> to warrant additional investigation. <br /> 1 , <br /> F <br /> i <br /> I <br /> w:1172921reportslSuppl Invest.doc 5 <br />