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Estimation of mtial mass of'IPK as gasoline Moore Petroleum, 1399 E Yosemite Ave,Manteca,CA ' The volume contained within the 500 and 1,000 mg/kg contour lines is 125 cubic feet and the volume contained between the 1,000 mg/kg contour lie and MW-1B is 100 cubic feet This ' process may be applied to all of the contour intervals in Figures 5A through 5E These values are compiled in Table AH 1 The next step is to estimate the soil types present at each contour layer depth and the soil density associated with these soils A review of the ongmal drill logs revealed silty sand is present at the subject site from ground surface to approximately 20 feet bs, at which point a layer of clay was ' encountered Interviews were performed with several geologists and excavation specialists in order to estimate the approximate soil density for silty sand and clay It was generally agreed upon that a good estimate for the soil density of silty sand is 1.40 tons per cubic yard and 155 tons per cubic yard for clay The values for soil density must be converted to useable units of kg per cubic foot This conversion is as follows Soil Density (Silty Sand) = 140 tons x 907 18 kg X 1 yd 3 = 47 04 kg Yd 1 1 t ton 27 ft .f. ' Soil Density (Clay) - = 155 tons X 907 18 kg X 1 yd = 52 08 kg yd 3 1 ton 27 ft 3 ft 3 MNow that the soil density has been estimated, the mass of soil per contour interval volume may be calculated, in lalograms This is performed by multiplying the soil density, in kilograms per cubic ' foot, by the contour interval volume, in cubic feet This example will be focused on the contour interval depth of 15 feet, between the approximate zero line an the 500 mg/kg contour line The soil density for this volume is that of silty sand, 47 04 kilograms per cubic foot, and the volume t within this interval is approximately 1,300 cubic feet, the resulting soil mass per contour volume is as follows Soil mass per contour volume = 47 04kg X 1,300 ft3 = 61,152 kg ft ' for the contour interval between the approximate zero line and the 500 mg/kg contour line This number will be rounded to 61,000 kg, keeping significant digits in mid ' The next process is to estimate the mass of TPK as gasoline, per contour interval volume The first step in this process is to estimate an average concentration per contour interval It will be assumed that the average between the lower contour concentration and the]uglier contour concentration for a particular interval will be a good approximation for the average concentration of a particular contour interval volume For example, for the contours which exist at 15 feet bs, the average contour concentration between the approximate zero Tine (0 mg/kg) and the 500 mg/kg contour line is 250 mg/kg For the contour interval between 500 and 1,000 mg/kg, the average concentration will be 750 mg/kg and for the contour interval between 1,000 mg/kg and MW-1B (1,400 mg/kg), the average concentration will be 1,200 mg/kg The average 1