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City of Stockton A68104 02A <br /> June 6, 1996 Page 7 <br /> As shown in Drawing 7, some of the PPC impacted soil was removed by the excavation work <br /> performed on July 7, 1994 The volume of the remaining PPC impacted soil is estimated <br /> to be approximately 36 cubic yards This estimate was calculated from the inferred extent <br /> of PPC migration as shown in Drawings 6 and 7 using the Autocado program (release 12) <br /> with Sofdesk Earthworks® module <br /> The concentrations in the remaining volume of PPC impacted soil are assumed to be no <br /> more than the concentrations detected in the soil samples collected on July 7, 1994 from the <br /> north edge, south edge, and bottom of the excavation (i e , N12, S10 5, and B19 5) Using <br /> the greatest concentration of each selected PPC detected in the excavation boundary <br /> samples, the following calculations present an estimate of the mass and volume of PPCs <br /> remaining in the soil <br /> • Greatest concentrations of PPCs in parts per million (ppm) <br /> Benzene = 0 049 ppm, Toluene = 13 ppm, Eth lbenzene 10 ppm <br /> rXylenes 8 5 ppm, and TPH-G = 39 ppm <br /> • Volume of contaminated soil 36 cubic yards (yds3) <br /> • Mass of contaminated soil <br /> 36 yds3 * 15 tons � 54 tons = 108 X 105 pounds (lbs) <br /> yd S3 <br /> • Mass of remaining benzene <br /> (1 08 X 105) * (0 049 X 10-6) = 5 3 X 10-3 lbs <br /> 1 <br /> r <br />