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3 CONTAMINANT MASS ESTIMATES <br />' Based on the groundwater sample analytical results from the June 2004 sampling <br /> event and iso-concentration contour interpretations, contaminant mass estimates have <br /> ' been assembled as requested in SJCEHD correspondence dated September 24, 2004 <br /> The contaminant mass calculation summary table has been presented in Tabled <br /> 4�,ryL <br /> 3.1 Contaminant Mass Calculations <br /> ' The calculations were performed by using the most recent vertical extent <br /> values as determined from the data collected during the June 2004 CPT boring <br /> of CPT-A as reported in the June 2004 Site Investigation Report The <br />' calculation also used the contoured concentration values from the October <br /> 2004 event <br /> ' Contaminant masses can be estimated based on a number of other estimated <br /> parameters using the following equation <br /> Contaminant mass in kilograms = Area(sq ft) x porosity x thickness (ft) x <br /> concentration (ug/kg) x (7 5 gal/cu ft x 3 81/gal x l E-9kg/ug) <br /> 3.2 Contaminant Mass Estimates <br /> The contaminant mass estimate calculations indicate that the total mass is 70 7 <br /> Kg for dissolved gasoline and 1 8 Kg for benzene'this represents a decrease <br /> in contaminant mass from the previous calculation as reported in the April <br /> 2003 Remedial Action Completion Report The calculated values differ in <br /> part, because the previous values were calculated using a vertical extent value <br /> of 50', where this current calculation is based on a vertical extent value of 90' <br />' Therefore, the previous thickness values were normalized to the current values <br /> (using 90') so that the comparison can be determined based solely on a <br /> concentration trend Upon normalizing the equation, the contaminant mass <br />' again appears to have decreased significantly <br /> ll <br />' Quarterly Groundwater Monitoring Report <br /> October 2004 <br /> The Earthgrams Company Facility <br /> 2651 South Airport Way-Stockton,California <br /> Prepared for SARA LEE BAKERY GROUP Prepared by Philip Services Corp <br /> tf 1EW624001321121382EGIStockton Airport Way\lnvestigatwn and Quarterly Reports\Quarterly Report 10_2004 doc December 09,2004 <br />