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Ciea/agtral rec via lne. Page 10 <br /> Valley Wholesale Drug Company <br /> Protect No 989 2 <br /> Ile November 8,2004 <br /> I • No attenuation is assumed in MtBE mass estimates <br /> I <br /> Groundwater Calculations <br /> Some basic assumptions were used to determine the size and extent of the TPH-G <br /> groundwater plume <br /> • Groundwater plume assumed to have twice the area and thickness of the soil plume <br /> • Assumed volume of the groundwater plume exceeds the prediction generated by <br /> Surfer® <br /> ' • The plume was divided into three areas <br /> o The core conservatively averaging 200 µg/L <br /> o Ring 1 conservatively averaging 100 µg/L <br /> o Ring 2 conservatively averaging 50 gg/L <br /> • The conversion factor of 1 gallon of gasoline equals 6 2 pounds was used <br /> ' Some basic assumptions were used to determine the size and extent of the MtBE groundwater <br /> plume <br /> • The groundwater plume was divided into three areas <br /> o The Core encompasses concentrations measured between 40 and 75 gg/L <br /> o Ring l encompasses concentrations measured between 20 and 40 gg/L <br /> Mo Ring 2 encompasses concentrations measured between ND<0 5 and 20 µg/L <br /> • The average concentrations in each of the three areas were used in the calculations <br /> • The groundwater plume is assumed to be 10 feet thick <br /> • The conversion factor of 1 gallon of MtBE equals 6 2 pounds was used <br /> ' 3.6.2 TPH-G Mass Estimate Calculations <br /> Figure 9 shows a contour map of TPH-G soil contamination as interpreted by soil collected <br /> during various drilling events Figure 10 is a contour map of TPH-G groundwater <br /> ' contamination based on the third quarter 2004 monitoring data and data gathered from the <br /> August 2004 GeoProbe investigation Figures 10 and 11 are cross sections showing the <br /> estimated boundaries of TPH-G contamination, in the subsurface, used to calculate the mass <br /> ' of contamination in the soil <br /> The mass estimate calculation, quantifying the amount TPH-G remaining at the site, is <br /> included as Table 8 Approximately 56 1 gallons of gasoline remain in the soil and <br /> approximately 0 1 gallons remain in groundwater at the site <br /> 3.6.3 MtBE Mass Estimate Calculations <br /> Figure 13 shows a contour map of MtBE soil contamination as interpreted by soil collected <br /> during various drilling events The contamination appears to cover an area of approximately <br /> 37,000 ft2 Figure 14 is a contour map of MtBE impacted groundwater as interpreted by <br /> analytical data from quarterly groundwater monitoring events and the GeoProbe investigation <br /> of August 2004 <br />