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k Mass-Volume Calculation of Dissolved TPH-g SIERRA LUMBER- 375 West Hazelton Avenue, Stockton, CA Assumptions • The distribution of dissolved hydrocarbon concentrations on the site can be approximated by two co-centric elliptical columns, with the Inner column containing the higher TPH-g concentrations (See Figure 10), • The effective porosity of soil at the site Is 35% (probably overestimated), and • Data collected from the September 1999 ground water sampling event are representative of existing site conditions The area of an ellipsoid can be calculated by the formula Ae = 7cab, where a Is the long radius of the ellipsoid and b Is the short radius For the estimated Inner ellipsoid, a= 25 ft, b = 12%z ft, and thickness c = 30 ft For the estimated outer ellipsoid, a= 45 ft, b =27!/2, ft, and c = 20' The average TPH-g concentration for the Inner ellipsoid is estimated to be 40,000 micrograms per liter (ppb), and the average concentration of the outer ellipsoid Is estimated at 5,000 ppb These concentrations are equivalent to 000040 g/ml and 000005 g/ml As a ml Is very nearly equivalent to a cubic centimeter of water, which by definition equals one gram, these concentrations are nearly unitless numbers relative to mass calculations The area of the inner elliptical column Is given by ACi=nab = 7s(25 ft)(12%2ft) = 981 8 ft2 The volume of the inner elliptical column Is given by Ve, =Ae1 x c = 981 8 ft' x 30 ft = 29,454 ft' Water occupies the porosity In the soil, which is estimated to be 35% of the soil volume, so the total volume of water in the saturated portion of the inner ellipsoid Is approximated by Ve! =( 35)(29,454 ft3) = 10,309 ft' One cubic foot of water contains 7 48 gallons, so the volume of the water in the inner ellipsoid Is given by ' VG1 = (10,309 ft)(7 48 gal ft) = 77,111 gallons Advanced GeoEnllronmental,Inc