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Soil Vapor Contaminant Mass Calculations <br /> ARCO Station No 2130 <br /> Stockton, California <br /> Zone Zone Total Sod Bulk Average Contaminant <br /> Contaminant Zone Footprint Thickness Volume Density Concentration Mass <br /> ft^2 ft) (ftA3) (lbs/ft^3 m ib <br /> 15 -40 ft bgs <br /> 1 ppm iso contour 1,833 25 45,835 120 2 11 <br /> 100 ppm iso contour 991 25 24,772 120 2700 8,026 <br /> 40 -60 ft bgs <br /> 1 ppm iso contour 7,772 20 155,431 120 19 354 <br /> 100 ppm iso contour 1,521 20 30,426 120 655 2,391 <br /> Total TPHg contaminant massl 10,782 <br /> Assumptions <br /> 1 Contaminant zone has uniform footprint top to bottom <br /> 2 Contaminant zone has uniform contaminant distribution throughout zone <br /> 3 Soil bulk density is uniform throughout the entire Contaminant zone <br /> 4 Sod bulk density is typical for for the silty, sandy, &clayey mixture of soil types found at this site <br /> 5 Average concentrations obtained by averaging TPHg concentrations in soil vapor analyses from <br /> Source URS Site Conceptual Model Report,June 2003, <br /> ARCO Service Station No 2130, Stockton, California <br /> Figure 4 TPHg Distribution in Soil 15-40 Feet BGS <br /> Figure 5 TPHg Distribution in Soil 40-60 Feet BGS <br /> ' 6 Contaminant Masses equal the products of Total Volume, Soil Bulk Density, &Average Concentration <br /> 7 1 ppm iso contour area does not include 100 ppm iso contour area <br /> • <br /> lbp-arcolvern121301engineering\Arco 2130 NFA caics kjb XLS <br /> ' Contaminant Mass- SOIL Vern's 1 of 1 11/17/2003 <br />