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1 v } <br /> 4� <br /> yY <br /> A S S O C I A T E S I N C <br /> SBI from 42 to 50 feet bgs and 52 to 60 feet bgs was not classified because a soil sample was not <br /> recovered Soil in borings SB1 through SB4 generally consisted of inorganic clay and silty clay <br /> from 52 to 60 feet bgs to 62 feet bgs, the maximum depth explored, although soil in borings S133 <br /> and SB4 consisted of silty clay and silt, respectively <br />' Soil from borings MW9, MWIO, VW1, VW2, VW3, ASI, PZ1a, and PZlb generally consisted <br /> of inorganic and sandy silt from the surface to depths between 11 5 to 15 feet bgs, although soil <br /> 1 in borings V W 1 and ASI consisted of silty sand Soil consisted of gravelly clay and silty clay <br /> from depths between 11 5 to 15 feet bgs and 21 5 to 30 feet bgs, although soil in bonngs MW9, <br /> MWIO, and VW2 contained well graded sand and silty sand, soil in boring VW3 contained <br /> 1 clayey gravel, and soil in boring PZ1b contained inorganic silt Soil consisted of inorganic silt <br /> and sandy silt from depths between 21 5 to 30 feet bgs and 51 5 to 60 feet bgs, although soil in <br /> borings MW9 and MWIO contained of varying layers of sand and clay and soil in boring VW1 <br /> 1 contained layers of silty sand, and soil in boring PZ1a and PZ1b contained layers of clays Soil <br /> consisted of silty sand from depths between 51 5 to 60 feet bgs and 81 5 feet bgs, the maximum <br /> depth explored in these borings, although soil in borings MW9, MWIO, ASI, PZ i a, and PZ 1 b <br />' contained layers of silt Soil boring logs with a detailed description of soil types are contained in <br /> Appendix A <br /> } 3.2 Hydrogeology <br /> 3 2 1 Third Quarter 2001 Event <br /> Water level measurements were collected from wells MWI through MWIO on September 25 <br /> g p <br /> 2001 Water levels in shallow groundwater monitoring wells MWI through MW7, MW9, and <br /> MWIO ranged from 63 33 to 64 89 feet below the tops of the well casing elevations representing <br /> a decrease in the water elevation of 3 00 feet since June 2001 The water level data were used to <br /> develop the groundwater elevation contour map (Figure 4) Assuming that horizontal isotropic <br /> conditions prevail, groundwater in the uppermost aquifer beneath the site flowed towards the <br /> southeast The average hydraulic gradient on September 25, 2001 was calculated to be 0 006 ft/ft <br />' or approximately 33 ft/mile <br /> The average groundwater elevation of the on-site shallow wells MWI through MW3 on <br /> September 25, 2001 was approximately —35 39 feet above sea level This is 0 94 feet more than <br /> the groundwater elevation in the deep well, MW8, which means that the vertical gradient at the <br /> site was downward A summary of groundwater monitoring data is presented in Table 3 <br /> 1 3.2.2 FourthQ uarter 2001 Event <br /> Water level measurements were collected from wells MWI through MWIO on December 17, <br /> 2001 Water levels in shallow groundwater monitoring wells MWI through MW7, MW9, and <br /> MWIO ranged from 63 68 to 65 35 feet below the tops of the well casing elevations representing <br /> a decrease in the water elevation of 0 33 feet since September 2001 The water level data were <br /> w\I 63931reportslrifs doc 7 <br /> 1 <br />