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5 RESULTS OF INVESTIGATION <br /> 5.1 Site Geology <br />' Sediments underlying the site consist primarily of clayey silt to fine- to coarse-grained <br /> sand The sedimentary units are generally laterally continuous From the ground surface to <br /> approximately 28 to 32 feet bgs, sediments consist of clayey silt to silty clay with laterally <br /> discontinuous sand lenses ranging in thickness from 4 to 7 feet From approximately 32 to <br /> 37 feet bgs, sediments consist of silty sand Sediments from approximately 37 to 53 feet <br /> bgs consist of fine grained sand, which grades to fine- to coarse-grained sand Geologic <br /> cross sections are shown on Figure 3 Surface trace of the cross section is shown on <br /> Figure 2 <br /> ' Based on geotechnical data obtained from soil samples, the soil beneath the site has <br /> permeability ranging from 7 65 x 10-7 to 2 79 x 10-6 centimeters per second, and a dry <br /> density ranging from 107 pounds per cubic feet (lbs/ft') to 109 lbs/ft3 Analytical results of <br /> soil samples analyzed for permeability, moisture content, and bulk density are presented in <br /> Table 3 <br /> ' 5.2 Distribution of Hydrocarbons in Soil <br /> ' Based on analytical results of soil samples collected from the borings, hydrocarbons were <br /> detected beneath the site The highest residual hydrocarbon concentrations were located in <br /> the vicinity of the former USTs and dispenser islands In addition, hydrocarbons were <br /> ' detected at shallow depths (above historical capillary fringe) <br /> Residual hydrocarbons were detected in soil samples collected from borings B-IR through <br /> B-5R, but were below laboratory detection limits in soil samples collected from bonng B- <br /> 6R TPHG concentrations ranged from below laboratory detection hnuts to 11,000 parts <br /> per million (ppm) Benzene concentrations ranged from below laboratory detection limits <br /> to 5 4 ppm TOG was detected in the soil sample collected at 10 5 feet bgs from soil <br /> boring B-2R at a concentration of 10,000 ppm, but was below laboratory detection limits <br /> ' from the same bonng (B-2R) sample collected at a depth of 25 5 feet bgs and from soil <br /> samples collected from boring B-6R TPHD, CLHC and PCBs were below laboratory <br /> detection limits for all soil samples MTBE was detected in soil samples collected from <br /> boring B-2R The results of analyses are summarized in Tables I and 2 TOC was detected <br /> ' SAC\N V']2\2613\26131000 11313-95\116 2 Rev 0 2/5/97 <br /> 22613 100 001 5-1 <br />