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i <br /> Mr Harlin Knoll <br /> San Joaquin County Environmental Health Division N <br /> 24 October 2000 <br /> Page 4 <br /> Mass of TPHg in Impacted Soil <br /> The volume (VS) of impacted soil was calculated by the equation <br /> Vs = IIr'h <br /> where <br /> r is the estimated radius of impacted soil = 10 ft <br /> • h is the estimated height of impacted soil = 35 ft <br /> Volume of impacted soil = Ilr'h = II(10 ft)235ft = 11 ,000ft3 <br /> The mass (MS) of impacted soil was calculated using the equation <br /> MS = (concentration of impacted soil)(densrty of soil)(volume of soil) = Cs x PS x Vs <br /> where <br /> • CS = 0 1 mg/kg TPHg the detection limit from Orion soil boring MW-2 <br /> since al I samples had no detectable TPHg concentrations (Table #1) <br /> • ps = 1 10 lb/ft' as typical soil density <br /> • Vs = 10,990ft3 is the calculated soil volume <br /> • Mass of TPHg in impacted soil in pounds (lbs) <br /> M _ 0 1 mg TPHg lb TPHg 0 454 kg Soil 11 o Ib (11,000 ft 3)= 0 12 lbs <br /> s kg Soil 454x103 mg TPHg lb Soil ft3 <br /> Mass of TPHg in Impacted Groundwater <br /> I Orion assumed that groundwater concentrations would diminish with distance from <br /> MW-2 Figure 3 shows the extent of impacted groundwater used for the following <br /> calculations Two volumes of groundwater were used to calculate the mass of TPHg <br /> remaining in groundwater One volume was estimated for a TPHg concentration of 400 <br /> pg/I and another volume for a TPHg concentration of 100 µg/l <br />' The volume of impacted groundwater was calculated by the following two equations <br /> Vw400 = H(r o0 )d7t and Vw,w = n(r;oa -` r oo )d�l <br /> • <br /> S\SFS\STOCKTON\LTR\LTR005 DOC 70/24/00 <br />