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February 14, 1992 <br /> l ARCO Service Station No. 2130, Stockton, California <br /> Excavation of Former Tank Cavity and Product bines <br /> A geologist from RESNA will l;e onsite to observe excavation of the soil from the former <br /> ® tank cavity. Immediately following the removal of the existing underground-storage tanks, <br /> the tank cavity will be excavated approximately 2 feet below the former tanks <br /> (approximately 12 feet below grade). During excavation, the geologist will use a PID is <br /> ® characterize the relative levels of hydrocarbons in the soil and note any subjective evidence <br /> of hydrocarbons such as obvious product odor and discoloration. We will collect soil <br /> samples within 2 feet of base of the former product 1-nes at 20-foot intervals. Soil samples <br /> will be submitted to a State-licensed laboratory and analyzed for appropriate compounds <br /> according to the SJCPHS-EHD guidelines. Details of our sampling procedures are in <br /> Appendix A. <br /> Estimate of Excavated Soil <br /> We estimate 920 cubic yards of soil may be excavated from the existing tank cavity and <br /> product-line trenches. The estimate of the volume of soil is based on (1) the dimensions <br /> of the existing tank cavity (75 feet by 30 feet by 12 feet) and the volume occupied by the <br /> existing tanks(3,170 cubic feet)and(2)the anticipated dimensions of the trenches excavated <br /> during the removal of the product and vapor piping (170 feet by 2 feet by 3 feet). The <br /> ® actual volume will vary depending on the final depths of the excavations. <br /> Excavated soil will be stockpiled onsite. The stockpiled soil will be placed on and covered <br /> with plastic sheeting to restrict vapor emissions and control dust. Soil samples will be <br /> ® collected from the stockpiles, composited, and analyzed for hydrocarbons to evaluate <br /> whether the soil can be classified as nonhazardous. <br /> �J r <br /> 30003-aw 9 <br /> .® <br />