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1� <br /> 3.0 FINDINGS <br /> 5 <br /> 3.1 Subsurface Conditions <br /> The site is underlain primarily by silts and clays with sand interbeds to the maximum <br /> depth explored of 27 feet. Surficial sands were observed in the locations of U-A, U-B, <br /> U-C, and U-4, at an approximate thickness of 5 to 8 feet (Figures 2, 3, 4). These <br /> a. F surficiai sands are gray to medium brown, and contain from 5 to 45 percent low <br /> j plasticity silt, with lesser amounts of coarse sand and fine gravel (Appendix A). An <br /> - orange-brown to dark-brown silty sand was encountered at a depth of 6 to 8-1/2 feet in <br /> Borings U-B and U-6. This sand is fine grained in the location of U-6 with a minimum 3 <br /> - thickness of 1 foot. In the vicinity of U-B, this sand has a maximinn thickness of 1 foot, <br /> and contains coarse sand and fine gravel. A lower sand horizon occurs in the vicinity of <br /> U-C, U-1, U-2, U-3, and U-4, at a depth ranging from approximately 16-1/2 to 20 feet <br /> below.grade. This horizon varies from fine silty sand in the vicinity of U-C and U-1, to <br /> well graded water-bearing sand and fine gravel in the locations of U-2, U-3 and U-4, <br /> ° and has a thickness ranging from 1-1/2 to at least 5 feet. These subsurface sands <br /> z appear to trend northwest-southeast, and cross the western portion of the site. <br /> Static :.groundwater occurred::at .a depth of, apprcximately. 8 feet:.`during the., 4 <br /> May 23; 1991,"same . g event 'with a northerly flow direction at a gradient of 0.006. <br /> (Figure 5). A north-northwesteriv flow direction was calculated..for: tile -vici ry,of <br /> Monitoring Wells U4 through U-3, which is consistent with that observed for those <br /> ' wells in previous sampling events. .The newly available data froth Wells U-4 through <br /> U-6 indicates that o oundsvaier flow on the broader scale of the site is toward the north. <br /> 3.2 Soil Analytical Results <br /> Selected soil samples collected during the Mav 9, 1991, drilling activities were <br /> submitted to a State-certified analytical laboratory, and analyzed for TPH-gasoline, <br /> TPH-diesel, and BTEX compounds (Table 2). TPH gasoline concentrations ranged <br /> from none-detected to a maximum of 1,700 ppm, in the 5 to 6-1/2 foot depth sample <br /> - <br /> from -U- <br /> _ BoringC_TPH <br /> om _-gas_o_Iwas also o <br /> _ine lbserLed in Borings U-.k U-C, and U-5, at _ <br /> --- - -- <br /> 420 ppm to 1,700 ppm. The maximum TPH-diesel concentration, 4,900 ppm, also <br /> yyf <br /> 3100101/REPORT;' .4 seprember 30, 1'9.1 <br /> ,- u <br />