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4 . 1 Analysis of Soil and„Ground Water Samples Soil samples collected from ABM-1, AB-2 , and MW-10 through MW-12 and ground water samples collected from MW-7 . MW--8 , and MW-10 through MW-12 were analyzed for the following: © TPH--G using EPA Methods 5030 and 8015G o BTEX using EPA Methods 5030 and 8020 o TPH-D using EPA Methods 5030 and 8015D Results of laboratory analysis of soil and ground water samples are summarized in Tables 1 and 2 , respectively. Official laboratory reports and chain of custody documents are included in Appendix G. 5. 0 DISCUSSION OF RESULTS AND FINDINGS A brief description of site geology and hydrogeology based on field activities and results of laboratory analysis of the soil and ground water is discussed below. 5. 1 Site Geology Based on this and previous subsurface investigations, the stratigraphy beneath the site consists primarily of silty sand and poorly-graded sand with interbedded silty sand and silty clay units across the site (refer to Hydrogeologi.c Cross Sections A-A' and B-B' ; Figures 5 and 6) . 5. 2 Site Hydro_ ect ologv_ The average depth to ground water beneath the site is 66 fbg. Ground water elevations from MW-7 , MW-8, and MW-10 through MW-12 , as measured on April 7 , 1992 , were used to develop the ground water elevation map shown in Figure 3 . The average ground water gradient onsite is estimated to be 0. 002 foot per foot to the east. 5 . 3 Results of Soil Analysis Analytical results of soil samples collected and analyzed are summarized in Table 1, and revealed the following: o TPH-D and TPH-G were detected in samples collected from MW--10 (12 and 270 parts per million) (ppm) ) , at 46 fbg, respectively. • Benzene was detected in soil samples collected from MW-10 and MW-12 at depths ranging from 46 fbg to 71 fbg. 4