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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 former piping sample location P13, at 15 <br /> feet bsg in soil probe boring 83. Petroleum hydrocarbons were also detected at-a <br /> concentration of,12 mg/kg in the soil sample collected 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 mglkg-(CPT1-60)and 6.3 mg/kg(CPT1-90); PH-d was detected ata concentration <br /> of 110 mg/kg:(CPT1-90). <br /> Site assessment activities to date defined an area m here ground water-is impacted by high <br /> concentrations of- petroleum hydrocarbons. I he highest petroleum-hydrocarbon <br /> concentrations, up to 21200,000 pg/I TPHA;were c etected-in grab ground water samples <br /> adjacent to the former-piping sample location P13. F lettoloum hydrocarbon concentrations <br /> as high as 190,000 pgll 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 awater samples collected <br /> from the ground,water monitoring wells defined the dissolved plume at-the northern edge <br /> of the dispenser islands; monitoring well MWA defines the eastern extent of-the dissolved <br /> petroleum hydrocarbon plume. <br /> Based on AGE'S interpretation of the available data, the initial release(s) of petroleum <br /> hydrocarbons occurred-from the former-dispenseis and associated piping prior to their <br /> removal in 2003. Once released to the subsurfa , the contaminants migrated through <br /> and/or,adhered to the clayey silt,material to a verti I depth of approximately 30 feet,bsg, <br /> at which point the contaminants encountered perm able silty•sand to fine-grained material <br /> (HU1)and began to migrate laterally; lateral rnigrati n was dominantly toward the north to <br /> northeast, in the direction of ground water flow. <br /> Advanced GeoEnviroomental,Inc. <br />