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Appendix E, Petroleum hydrocarbons were detected in all soil <br /> F borings except Borings 1, 2, and B. All detections were <br /> characterized as diesel. With only two exceptions (Borings 6 <br /> and 10) , soil contamination was confined to a zone around the <br /> bottom of the former excavation. A clean bottom-of-the-hale <br /> sample was obtained in all borings except Boring #6. in <br /> samples where oil was visible, detections were as high as <br /> 7400 ppm. <br /> DISCUSSION AND CONCLUSIONS <br /> The vertical extent of the contamination can be estimated <br /> from Figure 5. Although groundwater was not encountered, it <br /> is probably only a few feet below the deepest borings. Since <br /> the bottom-of-the-hole sample in Boring 6 was found to be <br /> contaminated, some oil may have impacted the groundwater. <br /> The oil may have moved through the soil by passing through <br /> cracks in the dry silty clay. <br /> The horizontal extent of the contamination can be roughly <br /> estimated from the analytical results if movement of the oil <br /> has been predominantly downward. Borings 1, 2, and 8 <br /> i encountered no contaminated soil on the north and west sides of <br /> the sampling site. These findings suggest that lateral <br /> movement of the oil has been limited. In addition, the deepest <br /> contaminated soil (Boring 6) was found directly below one of <br /> the tanks where the highest concentration of TFHs were found in <br /> Y the previous investigation. No evidence obtained during this <br /> investigation suggests that lateral movement of the oil would <br /> be greater in one direction than in any another. Thus, the <br /> lateral extent of the contaminant plume may not extend much <br /> beyond the other perimeter borings. These borings may have <br /> been closer to the leaks in the tanks, or the tanks may have <br /> been closer to the eastern most borings than previous drawings <br /> indicated. <br /> 11 <br />