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Geologfca[Teckx(cs lnC Page 8 Site Conceptual Model Report Marci Property Project No 7012 August 23,2004 To determine the contaminant load for the cylinders, the analytical results for all the soil samples that fell into that zone were averaged Table 1 in Appendix D includes the soil data utilized in mass calculations ' 2.6.2 Groundwater Plume The water table wells were used to define the groundwater TPH-D plume ❑ Figure 9 illustrates the TPH-D concentration in the water table wells for the June 7, 2004 monitoring event The core of the plume is centered on well MW-5 which has consistently had the highest levels of TPH-D Figure 12 shows the groundwater plume in ' cross section ❑ CAD software was used to determine the volume within each contour line in Figure 9. This data was then used in the contaminant mass calculations ' 2.6.3 Soil Contaminant Mass Estimate Calculations The mass of contaminant in the soil was determined by calculating the volume of each soil ' zone The volume of each zone was multiplied by bulk density values from boring MW-4 samples (previous work by WJH) to obtain the pounds of soil in each zone The pounds of soil, in each zone, is then converted to kilograms and then multiplied by the contaminant load The average concentration in the zones was used as the contaminant load Table 1 in Appendix D contains the contaminant mass estimate calculations for the site The acalculations show that there are approximately 27,157 gallons (168,371 lbs) of TPH-D in the soil at the site The majority of the contamination is in the 30-65 foot zone beneath the former USTs 1 � 2.6.4 Groundwater Contaminant Mass Estimate Calculations The mass of contaminant in the groundwater was determined by calculating the volume of each groundwater contour The volume of each contour was multiplied by the porosity value of 43 5%, the porosity of the MW4 sample at 65 feet bgs, to obtain the volume of water (ft3) in within each contour The cubic feet of water, in each zone, is then converted to liters and ' then multiplied by the average contaminant load within the contour zone This produces the mass of contaminant in each zone ' The calculations in Table 1, Appendix D show that there are approximately 5 gallons (28 lbs) of TPH-D dissolved in the groundwater at the site as of the June 2004 monitoring event 2.7 Groundwater Beneficial Uses ` ' The Regional Water Quality Control Board-Central Valley Region's Basin Plan designates the beneficial uses of groundwater in the San Joaquin Valley as domestic, municipal, industrial and agricultural supply Documentation of uses of the area's groundwater was completed in January 2001 when GTI performed a well survey for a 2,000-foot radius around