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Site Background Information: Vanco Truck &Auto Plaza <br /> Page 6 of 6 <br /> (110 mg/kg TPH-d)was detected adjacent to the fo mer piping sample location P13; at 16 <br /> feet bsg in soil probe boring ,B3. Petroleum by Jrocarbons were also detected at-a <br /> concentration of 12 mg/kg in the soil sample colt cted from boring B7 at 30 feet bsg; <br /> adjacent to piping-sample P7.Soil samples collecte J at 60 feet and 90 feet bsg from boring <br /> CPT-1 were impacted by petroleum hydrocarbons: PH-g was detected at-concentrations <br /> of 2.1 mg/kg(CPT1-60)and 6.3 mglkg(CPT1-90);TPH-d was detected at a concentration <br /> of 110 mg/kg (CPT1-90). <br /> Site assessment activities to date defined an area m here groundwater is impacted by high <br /> concentrations of- petroleum hydrocarbons. 1 he highest petroleum=hydrocarbon <br /> concentrations, up to 2,200,000 pgll TPH-d, were c elected in grab ground water samples <br /> adjacent to the former piping sample-location P13. F letroleum hydrocarbon concentrations <br /> as high as 190,000 pg/1 were detected in grab ground water samples just-north 'of <br /> dispenser D1. MTBE was detected in minor concentrations just north of dispenser-sample. <br /> D7. Ground water,was not-impacted below 35 feet bsg: Ground water samples collected-. <br /> from the ground water monitoring-wells defined the dissolved plume at the northern edge. <br /> of the dispenser islands; monitoring well MW-1 defines the eastern extent of the dissolved <br /> petroleum hydrocarbon plume. <br /> Based on AGE'S interpretation of the available d ta, the initial release(s) of petroleum <br /> hydrocarbons occurred from the former dispense s and associated piping prior to their <br /> removal in 2003. Once released to the subsurfac , the contaminants migrated through <br /> and/or adhered to the clayey silt material to a verb I depth of approximately 30 feet•bsg, <br /> at which point the contaminants encountered permeable silty sand to fine-grained material <br /> (HU1)and began to migrate laterally; lateral migration was dominantly toward the north to <br /> northeast, in the direction of-ground water flow. <br /> Advanced C'"Envfronumntak Inc. <br />