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L <br /> L <br /> Two samples (SB5-15' and SB5-15'Dup) were collected from approximately the same location <br /> L as previous sample#4 which showed a TPH-D concentration of 2100 mg/Kg during the August <br /> 1990 sampling (Figure 3). Analytical results from both samples SB5-15' and SB5-15'Dup did <br /> L not show detectable concentrations of TPH-D. This decrease in TPH-D concentration from 2100 <br /> mg/Kg in 1990 to the current non-detectable concentration may also be attributed to localized <br /> variability due to differential adsorption of hydrocarbons to the clay and to natural biodegrada- <br /> tion of the hydrocarbons in place by native populations of hydrocarbon-consuming bacteria. <br /> 5.0 CONCLUSIONS AND RECOMMENDATIONS <br /> LAnalytical results from the Phase H soil sampling at the site indicated that there is no detectable <br /> petroleum impact to the soil in the area sampled. One sample (SB3-5'Dup) initially showed a <br /> concentration of 310 mg/Kg TPH-D however, the sample was re-analyzed and the second set <br /> of results indicated a non-detectable concentration. <br /> Based on the analytical results and the fact that depth to ground water in the vicinity of the site <br /> is greater than 170 feet bgs, WESTON recommends that no further action be taken at this site. <br /> L <br /> L <br /> L <br /> L <br /> L <br />