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CLOSURE REQUEST Appendix C <br /> Former American Forest Products Company 07/19/01 <br /> 2801 West Lane C-1 <br /> Stockton,California <br /> APPENDIX C <br /> MASS BALANCE CALCULATIONS <br /> The results of a mass balance calculation of TPHd in sot] are presented in Table C-1, which originally <br /> presented in the Draft Amended Closure Report(Dames &Moore, 1994a) The mass of hydrocarbon <br /> dtscharged onto site soils was calculated by using soil concentration contour maps of TPHd in five-foot <br /> increments from 10 to 35 feet below ground surface (bgs) These contour maps, presented previously in <br /> the Feasibility Study/Remedial Action Plan(Dames &Moore, 1988) and updated for this closure request, <br /> were developed from analytical results for soil samples collected by Bechtel National (1985), J H <br /> Kleinfelder(1987), and Dames &Moore(1988, 1990, 1995, 1998) <br /> Concentrations of TPHd were contoured at intervals of 100, 1,000, 5,000, and 10,000 mg/kg For the <br /> purpose of the mass balance, the concentration applied to each interval, i e , 100 to 1,000, 1,000 to 5,000, <br /> 5,000 to 10,000,and greater than 10,000 mg/kg, was the geometric mean of the interval A summary of <br /> the concentrations, areas, volumes, and TPHd mass before and after excavation is presented in Table C-1 <br /> Figures 9 through 14 superimpose the excavated areas at depths of 10, 15, 20, 25, 30 and 35 feet bgs on <br /> the corresponding contours of lateral distribution of TPHd <br /> Soil volumes within each layer were based on a thickness of five feet The 25-foot layer was considered <br /> to be 3 5 feet thick from 22 5 to 26 feet bgs, which was the final depth of the east excavation <br /> Confirmation testing in the east excavation reported TPHd levels of 740 mg/kg at 26 feet bgs The 30- <br /> foot layer was considered to be 6 5 feet thick <br /> The mass of TPHd for each layer concentration interval was calculated as the product of the <br /> concentration, the soil volume, and the soil bulk density The bulk density was considered to be 87 <br /> pounds per cubic foot <br /> t <br /> 2 � <br /> G UOBIAFPIclosurelMass Balance- appendix doc 07/191012 05 PM <br />