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F Mass Balance for Remaining TPHg • Colberg Boat Works,401 North Stockton Street, Stockton, CA Page 3 Concentratronso,r = (5 2 + 1 0) mg/kg/2 = 3 1 mg/kg One important assumption to note is that for the lower boundaries labeled "non-detectable," the laboratory detection limit is used as the'Iower boundary value For hydrocarbon impacts in the ' water, this lower boundary is 50 pg/L and for hydrocarbon impacts to the soil, the lower boundary value is 1 0 mg/kg In order to calculate the mass of TPHg in each contour interval, it is necessary to multiply the volume of water and soil in each contour by the average TPHg concentration within each contour The volume of water needs to be converted from cubic feet into liters to ensure ' consistency with units The volume of soil needs to be converted into mass by using the assumed density of the soil For clay type soils, an average soil density of 52 08 kg/ft3 Is assumed The conversion for water is one cubic foot is equal to 28 3 liters Sample calculations for the mass of TPHg contained within the 100 ltg/L contour for groundwater and within the nondetectable contour for soil are given Mass,,,,,= 600 µg/L *28 3 L/1 ft3 *1910 ft3 = 32,431,800 ,ug Massso,l= 3 1 mg/kg * 52 08 kgjt3 * 10604f?= 1,711,995 mg '• Converting these numbers into kilograms is a simple mathematical conversion of dividing by one billion (1 x 109) for the groundwater and one million (1 x106) for the soil This gives a mass of 0 032 kilograms of TPHg inside the 100 µg/L contour for groundwater and a mass of 1 71 kilograms of TPHg inside the nondetectable contour for soil In order to calculate the total mass of TPHg, it is necessary to follow the same equations above for each of the contour areas The mass between 100 µg/L contour and the nondetectable contour for groundwater is 0 065 kilograms Adding the masses from each contour area gives a 1 total mass of TPHg remaining in the groundwater The total mass is 0 1 kilogra (0 21 pounds) of TPHg in groundwater The total mass of TPHg remaining in the soil is 1 7 kg (3 77 pounds) CONCLUSIONS AND RECOMMENDATIONS Based on the analytical data presented and the mass of TPHg present in soil and groundwater, Apex recommends proceeding with the magnesium peroxide pilot study b REPORT DISTRIBUTION Ms Lynn Swanson • Colberg Boat Works, LLC P O Box 1288 Stockton, CA 95201 SB C 1_PROJECnCOL01 001-Colberg Boat Workslmassbalance doc