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, d <br /> 3.0 FINDINGS <br /> 3.1 Subsurface Conditions <br /> The site is underlain primarily by silts and clays with minor occurrences of sand to <br /> 16-1/2 feet, the maximum depth explored. Silty sands were encountered from the <br /> ground surface to approximately 6 feet of depth in the borings fon Wells U-1 through <br /> U-3 and Borings U-B and U-C during a previous phase of this investigation. A dark- <br /> brown to light-brown silt was encountered from grade to a depth of approximately 9 to <br /> 10-1/2 feet in the borings of Wells U-7 and U-8. This silt is underlain by a green to <br /> yellow-brown clayto the 16 foot depth in this location. At Wells U-9 and U-10 a dark- <br /> brown <br /> P , <br /> brown to light-brown silty clay occurs from grade to a depth of 16 feet. Underlying <br /> these predominantly fine-grained deposits, a sand horizon occurs at a depth of <br /> 15-1/2 feet below grade at Wells U-8 through U-10. This deposit is a light-brown sand <br /> containing 35-45% fines (Figures 3 and 4). Boring logs for the most recent well <br /> installations with more detailed geology and well construction information are <br /> presented in Attachment A. <br /> Static groundwater occurred at a depth of approximately 9 feet during the <br /> March 31, 1992, sampling event, with a northwesterly flow direction at a gradient of <br /> 0.005 (Table 1, Figure 5). The northwesterly flow direction is consistent with past <br /> monitoring events. <br /> 3.2 Soil Analytical Results <br /> Selected soil samples collected during the March 10 through March 12, 1992, drilling <br /> activities were submitted to a state-certified analytical laboratory'ry and analyzed for <br /> TPH-gasoline, TPH-diesel, and BTEX compounds (Table 2). ! The hydrocarbon <br /> concentrations of the soil samples from Wells U-7 and U-8 ranged from 2.0 ppm to <br /> 7.8 ppm TPH-diesel, none detected to 20 ppm TPH-oil, and no detectable <br /> concentrations of TPH-gasoline. All concentrations occurred at the 5 to 6-1/2 foot <br /> depth. No detectable concentrations of petroleum hydrocarbons were found in any of <br /> the soil samples collected from Wells-U-9 and U-10. Certified analytical reports are <br /> included in Appendix B. <br /> 3100103/REPORTS 5 June 11, 1992 <br /> ii <br />