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5 RESULTS OF INVESTIGATION <br />' 5.1 Site Geology <br /> Sediments underlying the site consist primarily of silt and fine- to medium-grained sand <br /> with a trace of fine- to medium gravel. The sedimentary units are generally laterally <br /> continuous. From the ground surface to approximately 23 to 28 feet bgs, sediments <br /> ' consist of silt, clayey silt and sandy silt. From approximately 23 to 35 feet bgs, sediments <br /> consist of sand and silty sand. Sediments from approximately 35 to 53 feet bgs consist of <br /> silt and sandy silt. From approximately 53 to 64 feet bgs, sediments consist of sand and <br /> ' silty sand at the northern portion of the site and laterally grades to silt and sandy silt <br /> toward the southern portion of the site. Sediments from approximately 67 feet bgs to the <br /> total depth explored (75.6 feet bgs) consist of sand. Geologic cross sections are shown on <br /> Figures 3 and 4. Surface trace of the cross section is shown on Figure 2. <br /> 5.2 Evaluation of Soil Conditions <br /> TPHG was detected in borings B-1, B-3, and B-7 at concentrations ranging from 1.1 parts <br /> ' per million (ppm) in B-1 (56.5 feet) and B-3 (56.5 feet) to 3.3 ppm in B-3 (41.5 feet). <br /> Benzene was detected in borings B-1 and B-3 at concentrations of 0.015 ppm in B-3 <br /> (56.5 feet) to 0.019 ppm in B-1 (56.5 feet). TPHG and BTEX concentrations were below <br /> ' laboratory detection limits for the other samples analyzed. The results of analyses are <br /> summarized in Table 2. Copies of the laboratory analysis reports are presented in <br /> ' Appendix C. <br /> Composite soil sample SP-1 was below detection limits for TPHG and BTEX. Total lead <br /> ' was detected at a concentration of 6.2 ppm. <br /> 5.3 Evaluation of Groundwater Conditions <br /> 1 <br /> TPHG was detected in the groundwater sample collected from monitoring well MW-1 at a <br /> concentration of 20,000 parts per billion (ppb). BTEX compounds were also detected in <br /> the sample from monitoring well MW-1 at concentrations of 780, 2,000, 690, and <br /> 4,100 ppb, respectively. However, the sample contained air bubbles, which may have <br /> effected the actual analyte concentration; therefore, well MW-1 was resampled on <br /> SAC\N-\P70\0805\08051470,I BS-95\pas:1 Rev.0,2!61'96 <br /> 0805-147.01 5-1 <br />