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Pilot Testing Report and Conceptual Corrective Action Plan July 15, 1994 <br /> Manna Pro, 4004 South EI Dorado, Stockton, CA 9 <br /> 4 0 ANALYTICAL CHARACTERIZATION <br />' The analytical characterization of the site involves evaluating the horizontal and vertical distribution of <br /> compounds of concern in the subsurface Because of the nature of the known source, the <br />' compounds of concern are BTEX, TPH-D, and TPH-G The analytical characterization of the site In <br /> conjunction with its physical characterization provides the basis for the design of corrective actions <br /> i41 Adsorbed-Phase Hydrocarbons <br />' Adsorbed-phase hydrocarbons are hydrocarbons suspended chemically or physically in the soil <br /> matrix Variables that significantly affect the mass (quantity) of adsorbed-phase hydrocarbons in the <br /> soil include mass of hydrocarbons released, sorptive/desorptive characteristics of soil, thickness of <br /> the unsaturated zone, hydrocarbon partitioning coefficients, and permeability of the subsurface <br /> strata <br /> 41 1 Distribution of Adsorbed-Phase Hydrocarbons <br /> The distribution of adsorbed-phase hydrocarbons in the soil was determined through analysis of soil <br />' samples collected and analyzed during monitoring well installation and tank excavation <br /> Isoconcentration maps of TPH-G and TPH-D concentrations are presented in Figures 6 through 9 <br /> The typical distribution of adsorbed-phase hydrocarbons follows a downward path from the point of <br /> release directed primarily by gravity and geologic permeability After liquid-phase hydrocarbons <br /> reach the water table, subsequent migration is controlled by groundwater gradient The <br /> adsorbed-phase TPH-G/TPH-D concentrations measured at the site generally appear to follow a <br /> typical distribution This is shown by the centralized adsorbed-phase TPH-G/TPH-D and <br /> concentrations near the source area Figures 6 through 9 illustrate a general downward migration of <br /> hydrocarbons around the source area, governed primarily by gravity and geologic permeability <br /> 4 1 2 Adsorbed-Phase Hydrocarbon Mass Estimate <br />' The TPH-G and TPH-D analytical results were used to estimate the total mass of dissolved and <br /> adsorbed hydrocarbons in the subsurface The mass estimates of adsorbed-phase hydrocarbons <br />' were performed by using the planimeter feature of Autocad" software to calculate the area within <br /> • <br /> 2819Ro34 opo El <br /> GROUNDWATER <br /> tHEM TECHNOLOGY, INC <br />