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Rig <br /> Work Plan September 5, 1990 <br /> ARCO Station 548, Stockton, California AGS 30004-1 <br /> ala <br /> intervals produce PID readings of less than 50 ppmv, (2) until we encounter ground water, <br /> or(3) auger refusal. Any additional subjective evidence of ga3oline hydrocarbons such as <br /> soil discoloration or obvious odor will be noted. <br /> If the first boring is terminated above 30 feet below grade,three additional soil borings will <br /> be drilled approximately 2-102 feet from the edge of the tank area, equally spaced around <br /> the tank perimeter. If the first boring is drilled deeper than 30 feet,two more borings will <br /> be drilled ars ?nd the existing tank cavity using the above criteria until two consecutive <br /> samples collected at 54bot intervals produce PID readings of less than 50 ppmv. A boring <br /> will not be drilled on the opposite end from the fill port. <br /> Two Iocations for the proposed tank cavity area are shown on Plate P-2. One additional soil <br /> ® . borings will be drilled in the center of each location (Plate P-2) to approximately 20 feet <br /> below grade to evaluate the soil for hydrocarbons. ARCO will then evaluate the potential <br /> of each location for the new tank cavity. The new tanks will be installed in the proposed <br /> tank cavity with the approval of the SJPHS. If the laboratory analyses of soil samples from <br /> these two soil borings indicate gasoline hydrocarbon levels above acceptable levels, <br /> ® conductor casing may be installed from the tank bottom to the surface, between the new <br /> underground tanks if warranted. The conductor casing will allow soil borings to be drilled. <br /> 8 <br /> 4,ap/sed Geosystams <br />