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APPENDIX B PRE-REMEDIATION ADSORBED MASS & VOLUME CALCULATIONS Super Center Mart 701 East Charter Way, Stockton, California Impacted Soil Mass/Volume Assumptions: • Utilizing Figures 3 and 4 the pre-remediation mass distribution of total petroleum hydrocarbons quantified as gasoline (TPH-g) can be estimated for impacted soils at the site. To estimate the mass, the adsorbed plume has been split into three contoured zones: 1,000 mg/kg, 100 mg/kg and 1 mg/kg. • Figures 3 and 4 were was generated using computer assisted design software.The software has a specific function to calculate the area of a selected object, such as each area between the above referenced TPH-g isoconcentration intervals. • The area and volume of each contoured zone can be estimated utilizing the computer-assisted design software and the program can be used to determine the area between the above referenced 1,000, 100 and 1 mg/kg contoured zone intervals (Figures 3 and 4), and then multiplying the area by the maximum height as determined through cross-sectional view. • The volume can be calculated by the formula: V = AREA-h, where "area" is determined through the design software (Figures 3 and 4) and "h" is the height as by splitting the adsorbed plume into two discrete intervals (based on contaminant distribution) of 10 to 40 feet below surface grade (bsg) and 40 to 60 feet bsg. • The average TPH-g concentration in the each depth discrete zone was estimated by summing the contour isoconcentration lines and the soil sample concentrations within the selected area and dividing by the total number of samples. ADSORBED SOIL PLUME MASS CALCULATIONS: TPH-g - 10 to 40 FEET BSG • >1,000 mg/kg (inner zone): The sum of 132-40(1,000 mg/kg),MW1-20(4,200 mg/kg), MW1- 35(11,000 mg/kg),MW3-20(1,400 mg/kg),MW9-30(1,600 mg/kg),MW9-35(3,000 mg/kg),MW9-40 (3,000 mg/kg)and the 1,000 mg/kg contour line; average=3,275 mg/kg (equivalent to 0.003275) • 100-1,000 mg/kg (second inner zone): The sum of B2-30 (460 mg/kg), MW3-35 (370 mg/kg), the 1,000 mg/kg contour line and the 100 mg/kg contour line; average = 482 mg/kg (equivalent to 0.000482). • 1-100 mg/kg (outer zone): The sum of 135-25(2.9 mg/kg),MW2-20(1.9 mg/kg),MW8-30 (1.6 mg/kg), MW8-35 (2.4 mg/kg),the 100 mg/kg contour line and the 1 mg/kg contour line; 18 average = 18 mg/kg (equivalent to 0.000018). Advanced GeoEnvironmental,Inc.