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3.3 I.i hologic Study <br /> Three borings (EB-1, EB-2,and EB-3)were drilled at the site and logged in accordance with the <br /> Unified Soil Classification System to aid in evaluating subsurface lithology at the site. Boring logs <br /> are included in Appendix B. <br /> 4.0 GROUND WATER INVESTIGATION <br /> On September 21 and 22, 1995,Harza collected ground water samples from site monitoring wells <br /> MW-1 through MW-9, and from the Stockton Channel bordering Banner Island. <br /> 4.1 Sampling and Analysis <br /> Sampling procedures are described in Appendix A. Before sampling, all wells were purged of at <br /> least three casing volumes of water,until the physical parameters pH, electrical conductivity(EC), <br /> and temperature had stabilized. Purging was accomplished using a bailer, peristaltic pump, or <br /> Grundfos pump. After purging each well, a ground water sample was collected using a Teflon <br /> bailer. A surface water sample from the Stockton Channel was collected approximately 6 feet from <br /> shore at a depth of 6 inches using a dipper. Samples were analyzed for dissolved priority pollutant <br /> metals using EPA Method 6010 and 7000 series, TPHg/BTEX using EPA Method <br /> 5030/8015M/8020, TEPH including kerosene, diesel, and motor oil; and general water quality <br /> parameters including minerals and anions. As discussed in Section 2.0,a ground water grab sample <br /> was also collected from boring HB8 and analyzed for TEPH and dissolved lead. Well locations are <br /> shown on Figure 2. Water sample data sheets are presented in Appendix C. <br /> 4.2 Analytical Results <br /> Analyses were performed by ChromaLab. Analytical results are shown on Tables 2 and 3 and <br /> laboratory analytical reports are included as Appendix D. The results of the grab sample collected <br /> from boring HB8 are shown on Table 1. <br /> Concentrations of dissolved priority pollutant metals were significantly lower than had been reported <br /> in previous investigations. Only two metals were detected, and concentrations were at or slightly <br /> above the respective method reporting limits(IvIRLs). Arsenic was detected in samples from wells <br /> MW-2 and MW-4 at the MRL of 0.01 ppm,and selenium was detected in wells MW-1 (0.01 ppm), <br /> MW-7(0.01 ppm),MW-8(0.02 ppm),and MW-9(0.02 ppm);the MRL for selenium is 0.01 ppm. <br /> No metals were detected in the sample from the Channel. <br /> IMMUU7.030 3 <br /> i i-z�-9s <br /> WARZA <br />