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Calculated Mass of TPH-g in Soil . Forme/ F1SCO WAREHOUSE 1648 Shaw Road, Stockton, California IESTIMATED MASS OF TPH-G REMATNING IN SOIL Calculation of the mass of TPH-g remaining in soli is based on assumptions of average Iconcentrations of analytical results for soil samples collected from underground storage tank(UST) hand samples and soil borings between 1986 and 2003 The estimated area of TPH-g-Impacted soil is Illustrated on Figures 2, 5 and 6 The assumptions for the mass calculations ai e based on analytical ' data, results and findings of site investigation reports, and field observation- Investigation findings indicate that the majority of TPH-g-impact to soil is located in the area beneath the former USTs, at an interval of approximately 10 to 55 feet bsg (Figures 5 and 6) The calculations are divided into two areas,one greater than 1,000 mg/kg and one greater than 1 0 mg/kg The calculation for an elliptic cylinder mass is as follows V,= (n a b h), where "a" is the long semi-axis of the ellipse, "b" is the mterrnediate semi- axis and "h" is the height of the cylinder Estimated Mass of TPH- P a Assum tions O Average area,thickness and concentration of TPH-g inside the greater than 1,000 mg/kg iso- concentration contour line are 242 ft', 22 5 feet and 4,368 mg/kg, respectively V Average area, thickness and concentration of TPH-g Inside the greater than 10 mg/kg iso- concentration contour line are 966 ft', 45 feet and 2 65 mg/kg (minus the inner area), respectively O Average weight of soil 100 lbs/f3 (per unit volume) Y Average weight of gasoline 6 16 lbs/gallon Calculations for the inner Y elliptic cylinder mass P I1) Ve= (nx11ftx7ftx225ft) = 5,443ft3 2) 5,443 ft' X 100 lbs/ft3 = 544,300 lbs soil I 3) 4,368 mg/kg (TPH-g) X lkg/1 OX 106 mg X 544,300 lbs =2,378 lbs gasoline IAdvanced GeoEaviromnental,Inc