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V <br /> was the location of the only significant detection of PHCs beneath the USTs. Soil samples will <br /> �• be collected at 5-foot intervals starting at 2 feet.below the.bottom elevations of the tanks and <br /> ending 2 feet above the water table. At a minimum, the two lowermost soil samples will be <br /> analyzed for PHCs. A third boring (B5-3, Figure 2) will be advanced outside the tank <br /> excavation limits, northwest of Tank#4. Soil and groundwater samples for PHC analysis will <br /> be collected as for the initial boring. <br /> If the water table is within 5 feet of the bottom elevations of the former tanks, no boring will <br /> be advanced within the former excavation. Instead, the two additional borings (B5-2 and B5-3, <br /> �- Figure 2) will be advanced in a radial pattern around the former excavation and within 10 feet <br /> of the former tanks. 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 /> V <br /> for the initial boring. <br /> �. 3.1.1.2 Piping <br /> Samples from beneath the piping leading to the former dispensers indicated detectable <br /> `' concentrations of PHCs near the dispenser area. If the water table is sufficiently deep, as <br /> determined by the borings at the USTs, a boring will be advanced at the location of the former <br /> V dispensers. Soil samples will be collected at 5-foot intervals starting at 5 feet below ground <br /> surface, and ending 2 feet above the water table. At a minimum, the two lowermost soil <br /> samples will be analyzed for PHCs. A second boring (B5-5, Figure 2) will be advanced north <br /> �., of the dispenser, in the vicinity of piping sample P8 (Appendix A). Soil samples for PHC <br /> analysis will be collected as for the dispenser sample above. <br /> If the water table is within 10 feet of ground surface, no boring will be advanced at the former <br /> dispenser or along the pipeline. Instead, two borings (B5-4 and B5-5, Figure 2) will be. <br /> advanced within 10 feet of the dispenser to evaluate the lateral and vertical extent of PHCs in <br /> groundwater. One will be installed to the northwest and one to the southwest of the former <br /> dispenser (Figure 2). 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 in the vicinity of the USTs. <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, 1940). Soil borings will be <br /> LW 5 99117WUSTD4V.V&N <br /> IMtBOYAJIAN & ROSS, INC. <br /> Environmental Scientists & Engineers <br /> La <br />