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F - <br /> Former Beacon Station 494 October 8, 1996 <br /> Stockton, California Appendix B CIosure Report <br /> bsg, 217 to 221 feet bsg, and 224 to 232 feet bsg The depth to the first perforated interval <br /> and the fact that the well is over 250 feet from the site make it highly unprobable that the <br /> well would has ever been impacted by dissolved hydrocarbons from the shallow <br /> groundwater table at an approximate depth of 70 feet bsg <br /> DISTRIBUTION OF CONTAMINANTS <br /> Initial Distribution of Petroleum Constituents in Soil <br /> Based on the soil data collected during the assessment work and UST removal, it appears <br /> that the hydrocarbon impact in the soil was confined to the southern portion of the UST <br /> cavity and possibly a second impact to the north of and related to the dispenser islands <br /> Isoconcentration maps depicting the initial distribution of TPHg and benzene reported in the <br /> soil samples analyzed are included as Figure 3 and Figure 4 The highest concentrations of <br /> hydrocarbons reported were from soil samples collected from the soil boring for VW-1 <br /> (Table I Soil Sample Analytical Results within Appendix A) Well logs indicate the <br /> presence of silty clay beginning at approximately 30 to 35 feet bsg winch are underlain by <br /> sand bodies situated mostly beneath the southeastern portion of the site The sands contain <br /> the highest levels of hydrocarbons Silty clay is present again below the sand Apparently, <br /> the restricted permeability of the silty clay hindered the downward migration of <br /> hydrocarbons Soil types and the initial vertical distribution of TPHg are depicted on Cross <br /> Section A- A' (Figure 7) <br /> 1494 APB <br /> 7 HORIZON ENVIRONMENTAL INC <br />