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Mass-Volume.Calculation of Dis olved MTBE,-Impact-. MANTECA CITY CORPORATION YARD :210 East Wetmore Street,Manteca, California= Assurnptions: • _ TH6 distribution of-dissolved MTBE concentrations on the site can be approximated by two ca-centric elliptical columns; .with the -'inndt column containing the, higher MTBE concentrations; The effective porosity.of soil at the site is 35%. " robably.'overestimated); • MTBE concentrations from data collected from sampling events performed between.April' 2001 and November 2003 at the site were averaged and used .to calculate the amount of dissolved MTBE in the ground water at the.site (Figure 3). Ground water sampling data from CPT borings dvanced at the site were used to determine the thickness'.or width of impacted grpund.water. MTBE was not detected in CPT ground water samples collected from 41-feet bsg,Using the average depth to-ground water at the site (21 feet) a. thickness of-20 feet of MTBE-impacted ground water..will be used for the. calculation. . The area of an ellipsoid can be calculated bythe_formu a: A,`='Tuab, where a is the long radius oft e ellipsoid and b-is the short radius. For the estimated inner ellipsoid;a= 79.;fl;b 40 ft; d thickness c z.20 ft For the estimated outer ellipsoid, a= 1:20.ft.b =69'ft, and c M 20' The average MTBE concentration for the-inner ellips6i is estimated to be 1,000 micrograms per liter_(µg/L),.and the average concentrationof the outer elli soidd-is estimated at 100 gg/L . These concentrations are equivalent to 0:000001 fVb and 0000001 ml. As a ml. is very. nearly equivalent to a cubic centimeter of water,w rdefy tion equals.one gram,these concentrations are nearly unitless numbers relative fomasscalculation .` s The-area of the inner ellipticalcolumn is given by: �:=7cab =Tc(70 ft)(40:ft) = 8,7.96 ft2 The volume of the inner elliptical column is given by; Vel =Ae7,x.C.= 8,796 ftz x 20 ft_=175,9 9 ft' Advaitced.GeoEnvironmeutal,Inc.