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CAP Addendum:Former Fue Station, 7500 West Eleventh Street, Tracy, C Page 5 <br /> 2.2.1 Existing Mass of Liquid, Dissolved and Sorbed Contaminants <br /> The mass of contaminants in the subsurface is composed of the LNAPL, the <br /> contaminants sorbed onto the soil and the dissolved contaminants in the groundwater. To <br /> develop an estimate of the total contaminant mass, we will consider each component <br /> separately. <br /> 2.2.1.1 Mass of LNAPL <br /> As was described in Section 2.1.4 above, the total volume of LNAPL in the subsurface is <br /> estimated to be 1,050 gallons, which is 3,975 liters. That LNAPL is composed of a <br /> mixture of gasoline and diesel fuel. <br /> The specific gravities of diesel and gasoline are 0.84 and 0.74, respectively. 1f we assume <br /> that the relative proportions of diesel and gasoline in the floating product in Monitoring <br /> Well MW-7 are in the same ratio as the concentrations of diesel and gasoline in the <br /> sample of groundwater recovered from that well on July 31, 2007, which were, <br /> respectively, 49,000 µg/L and 40,000 µg/L (see Table 2), then the estimated specific <br /> gravity of the mixture is 0.80. From that estimate and the estimated volume of LNAPL in <br /> the subsurface of 3,975 liters: <br /> ESTIMATED MASS OF LNAPL=3,179,746 GRAMS. <br /> 2.2.1.2 Mass of Contaminants in Soil <br /> Because the petroleum hydrocarbons that affect the soil beneath the Navarra Site consist <br /> of both gasoline and diesel, the total contaminants in that material is the sum of the <br /> concentrations of diesel and gasoline. <br /> As was discussed in Section 2.1.3, the area of the subsurface affected by LNAPL is <br /> conservatively assumed to extend from Monitoring Wells MW-13 to MWFP-3, which is <br /> a distance of 115 ft. and is estimated to be 80 ft. in width. As was discussed above, this <br /> will be the area within which the mass of contaminants will be considered. An estimate of <br /> the mean concentrations of diesel and gasoline within that area can be made based on the <br /> average of the sum of the concentrations in the upper 20 ft. of soil at the locations of <br /> Monitoring Wells MW-13, MW-7 and MWFP73. The concentrations of diesel and <br /> gasoline in those soils are presented in Table 3 and the mean of their sums computed for <br /> each boring. Those calculations yield the following: <br /> Boring Mean Concentration of <br /> Contaminants in Soil <br /> MW-13 8.17 mg/Kg <br /> MW-7 529.43 mg/Kg -?,9V <br /> MWFP-3 0.00 mg/Kg <br />