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I 5 RESULTS OF INVESTIGATION ' 5.1 Site Geology Sediments underlying the site consist primarily of sandy to clayey silt and silty clay with fine- to coarse-grained sand lenses The sedimentary units are generally laterally continuous From the ground surface to approximately 23 feet bgs in borings B-1 and B-2, ' and to 37 feet in boring B-3, sediments consist of sandy to clayey silt Pea gravel, believed to be tank fill, was encountered in boring B-1 from the ground surface to a depth of 7 feet bgs Laterally continuous, fine- to coarse-grained sand lenses (ranging in thickness from 2 to 4 feet) were encountered in boring B-1 from 22 feet to 26 feet bgs, and in bonng B-2 from 23 feet to 34 feet bgs Silty clay was encountered in borings B-2 and B-3 at depths of 34 feet and 37 feet bgs, respectively, to total depths explored (38 5 and 40 feet bgs, respectively) A geologic cross section is shown on Figure 4 Surface trace of the cross section is shown on Figure 2 Based on geotec.hrucal data obtained from the 11-foot soil sample collected from boring B-2, the soil beneath the site has a value for permeability of approximately 4 6 x 10-6 ' centimeters per second, a moisture content of approximately 22 percent and a dry density of approximately 98 pounds per cubic feet Analytical results for permeability, moisture content, and bulk density are presented in Table 2 ' 5.2 Distribution of Hydrocarbons in Soil ' Based on analytical results of soil samples collected from the borings, hydrocarbons were detected beneath the site The highest residual hydrocarbon concentrations were located in ' the vicinity of the former UST Hydrocarbons were not detected in samples collected from the vadose zone within the groundwater monitoring well borings, however, hydrocarbons were detected within the saturated zone in the groundwater monitoring well borings Analytical results of soil samples are presented in Table 3 Copies of the laboratory t analysis reports are presented in Appendix C TPHG was detected in the 25-foot soil sample collected from baring B-1 at a concentration of 1,080 ppm BTEX and MTBE were also detected in the soil sample from boring B-1 at concentrations of 9 5 ppm, 35 1 ppm, 16 8 ppm, 76 3 ppm, and 2 9 ppm, respectively (see Table 3) While no other soil samples collected from boring B-1 were I i SAON TJ2\2605\26051010 1 BS-9TcJb 2 EmCon 22605-101 001 5'1 Rev 0 8/4/97 1'