Laserfiche WebLink
J <br /> Figure 2) will be advanced about 10 feet away from the location of the former tank. In the <br /> initial boring, continuous core samples will be collected from the approximate depth of the <br /> bottom elevation of the former tank to about 10 feet below the water table. These soil samples <br /> will allow characterization of the subsurface lithology and depth to groundwater at the tank <br /> site, and will provide target locations for collection of soil and groundwater samples in the <br /> 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 /> If the water table is sufficiently below the bottom elevation of the former tank, a boring will <br /> be advanced through the center of the former excavation. Soil samples will be collected at <br /> 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 (B4-3, 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 (B4-2 and B4-3, <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. <br /> Collected soil samples will be field-screened using procedures presented in Appendix C. Field j <br /> screening procedures include examination of soil for lithologic character, odor, unusual _! <br /> staining, and detection of organic vapors (using a photoionization detector). After completion <br /> 4 9E1171s4USTINV.V/M <br />