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•i <br /> M ®II®A7 <br /> Working to Restore Nature <br /> from approximately 3 feet bsg to approximately 40 feet bsg. Concentrations of TPHg are <br /> highest and more widespread at a depth of 40 feet bsg. TPHg was detected from soil <br /> sample collected beneath the product line (S-6-PL1) at a concentration of 39,000 ppm. <br /> TPHg and benzene concentrations at different depth intervals are shown on Plates 10 <br /> through 12. Results of laboratory analyses are shown on Table 2 and Table 3. <br /> TOG was detected in soil samples collected from soil boring B-12 and beneath the clarifier <br /> (S131-0) at 74 ppm and 400 ppm, respectively (Appendix A). TOG concentrations in soil <br /> samples collected from soil borings B-16 and B-17 were below laboratory detection limits <br /> (Table 2). <br /> Site_Hydrogeology- <br /> Static groundwater has fluctuated between 43 feet to 50 feet bsg. Groundwater gradients <br /> and directions of groundwater flow at the site rorn previous dates are presented on Plates <br /> 13 and 14 (RESNA, June 26, 1992, Report 30004-4 and RESNA, January 11, 1993, Report <br /> 30004-6). <br /> Based on the potentiometric data, the groundwater flow direction has generally been toward <br /> the east to southeast with hydraulic gradients ranging from 0.01 to 0.004. The flow direction <br />•� and gradient may be subject to seasonal fluctuations. <br /> Free-Phase and Dissolved Hydrocarbons in Groundwater <br /> Results of subjective analyses of groundwater samples collected during the monitoring events <br /> indicate floating product has not been present at the site since monitoring began (Table 1). <br />• <br /> Analytical results of groundwater samples collected since monitoring began indicate <br /> dissolved gasoline hydrocarbons have been detected in samples from wells MW-1, MW-2 <br /> (low concentrations), MW-3, and MW-5 but were not detected in wells MW-4 and MW-6 <br /> (Table 1). TOG was not detected in the samples collected from well MW-1. <br />• <br /> REMEDIATION OPTIONS <br /> Soil Remediation <br /> Based upon the estimated limits of residual hydrocarbons in soil and the results of the VET, <br /> it is our opinion that the existing vapor extraction wells are adequate for soil remediation <br /> at the site. <br /> 1213ccar/30004-8 5 <br />