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0 <br /> �• TWeadw�e;118�Rolb <br /> ISoil sampling conducted around the former UST location has identified high TPHg <br /> concentrations in soil above the water table. These TPHg results range from 8,100 milligram per <br /> kilogram (mg/kg) in boring 16B-8 (Treadwell &Rollo, 2004)up to 14,000 mg/kg in VW5 <br /> (AGE, 1999) at a depth of 10 to 11 feet bgs. These results indicate that a continuing source of <br /> contamination was present in this area. Previous soil sampling results also indicate that high <br /> TPHg concentrations (9,000 mg/kg in VW5 at 25 feet bgs and 8,300 mg/kg in SW21 at 35 feet <br /> bgs) exist below the current groundwater table in this area(AGE, 1999). This is likely residual <br /> contamination from when the groundwater table was deeper than 25 feet bgs. <br /> As previously reported in the 2004 Workplan, boring logs indicate that separate phase product <br /> may be present in soil and groundwater within the former UST location extending to at least <br /> 16B-8 to the west and MW-3 to the east. Significant,but lower TPHg concentrations are present <br /> in soil (at the groundwater interface) and/or in groundwater in borings 16B-10 to the south, and <br /> Nin boring 16B-713 and well EW-4 to the north. TPHg and benzene concentrations in groundwater <br /> drop off beyond this area in borings 1613-9 and 1613-11, and appear to be related to the"smear <br /> ' zone"or the depth interval of groundwater table fluctuation. <br /> This data suggested that there has been a continuing source of gasoline contamination at the <br /> former Tank No.7 location, and that free product may have been present. This would account for <br /> why years of in-situ remediation work has not resulted in more significant decreases in <br /> groundwater concentrations at the Tank No.7 location and may indicate that continued in-situ <br /> -- ____ <br /> ' remediation may not effectively mitigate the groundwater contamination. <br /> ' 4.0 SITE REMEDIATION <br /> The Site excavation activities are described in Sections 4.1 to 4.7. Deviations from the 2004 <br /> Workplan are presented in Section 4.2. <br /> 25971021.DJS 4 18 November 2004 <br />