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subsequent two borings at this site. If the core sampling indicates that the water table is <br /> sufficiently below the bottom elevation of the former tank, soil samples for PHC analysis will <br /> be obtained' from the cores at 5-foot intervals starting at 2 feet below the bottom elevation of <br /> the former tank and ending 2 feet above the water table. In addition, a groundwater sample <br /> will be collected from the first transmissive zone below the water table. <br /> : I <br /> If the water table is sufficiently below the bottom elevation of the former tank, a second boring `1 <br /> will be advanced through the center of the former excavation. Soil samples will be collected <br /> at 5-foot intervals starting at 2 feet below the bottom elevation of the tank and ending 2 feet <br /> above the water table. At a minimum, the two lowermost soil samples will be analyzed for <br /> PHCs. A third boring (Bl-3, Figure 2) will be advanced outside the tank excavation limits. <br /> Soil and groundwater samples for PHC analysis will be collected as for the initial boring. <br /> If the water table is within 5 feet of the bottom elevation of the former tank, no boring will <br /> be advanced within the former excavation. Instead, two additional borings (131-2 and BI-3, <br /> Figure 2) will be advanced in a radial pattern around the former excavation and within 10 feet <br /> of the former tank. Groundwater samples will be collected in these borings from the first <br /> transmissive zone below the water table. Soil samples for PHC analysis will be collected as <br /> for the initial boring. <br /> 3.1.2 Methodology <br /> The field investigation will be carried out in general accordance with Tri-Regional Board Staff <br /> Recommendations for Preliminary Investigation and Evaluation of Underground Storage Tanks <br /> (North Coast Regional Water Quality Control Board, et al, 1990). Soil borings will be <br /> advanced, sampled, and backfilled according to the procedures given in Appendix B, utilizing <br /> the Geoprobe direct-push method. Soil,samples will be collected for PHC analysis according <br /> to procedures given in Appendix C. Groundwater samples will be collected for PHC analysis <br /> according to procedures given in Appendix D. 1 <br /> Collected soil samples will be field-screened using procedures presented in Appendix C. Field <br /> screening procedures include examination of soil for lithologic character, odor, unusual <br /> staining, and detection of organic vapors (using photoionization detector). After completion <br /> of soil sampling, the borehole will be backfilled using a sand-cement slurry containing five <br /> percent bentonite as described in Appendix B. <br /> Unused soil samples from the boring and rinsate from decontamination of probe equipment will <br /> be containerized in U. S. Department of Transportation approved 55-gallon drums. These <br /> drums will be properly sealed and labeled, and will be secured within a fenced area of the <br /> 4 981 Mst usrRvv.wPN <br />