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Site Background Information: West Clay Properties Page 9 of 10 MW-2, MW-3 and MW-5. The ground water plume appears to be somewhat symetrical, extending approximately 80 feet east to west and 80 feet north to south, surrounding UST No. 3 area. • Maximum concentrations detected were in the UST No. 3 area are: TPH-g at 47,000 µg/1; TPH-d at 30,000 µg/1; and benzene at 5,100 gg/1 (MW-2). Significant concentrations of TPH-g, TPH-d and BTEX have been consistently reported in samples collected from well MW-1,located east of the former UST No. 3 area. The new wells installed(MW-16 through MW-24)to define the vertical extent of dissolved hydrocarbon contamination demonstrated limited impact at the southern edge of the UST No. 3 area at a depth of 75 feet bsg, and not greater than 100 feet across the entire UST No. 3 area. Off-site grab ground water samples were"non-detect'for hydrocarbon contamination at all depths sampled.A minor release of 1,2-DCA mostly likely occurred with the TPH; the 1,2-DCA plume appears to be stable in samples collected from the monitoring well network. The maximum concentration of 1,2-DCA at the site is currently 41 µg/1 (MW-1). • The lateral and vertical extent of TPH and BTEX has been defined by the sample set. Northern UST Cluster Area • A release of TPH-g,BTEX and MTBE occurred from dispenser lines at the northern portion of the tank area. Samples collected from beneath the southern ends of each tank (upon removal) were "non-detect" for chemicals of concern. TPH-g was reported in a samples collected from the north end of the tank excavation at 988 mg/kg of TPH-g; TPH-g was reported in the 15-foot soil sample collected from boring B9 at 7,000 mg/kg TPH-g • Chemicals of concern were not detected in shallow soil samples collected near wells MW-2 and MW-7. The highest TPH-g and BTEX impact to soil in the upper vadose zone was removed through excavation in December 2003. Currently, no residual vadose zone hydrocarbon contamination is present at the site. The aerial extent of the soil contamination in soil appears defined to the near the former northern cluster area. Available data is suggestive of a release was most severe at the northern edge of the former northern cluster UST area.After the release,TPH/BTEX and MTBE migrated only slightly north in the area of well EW-1 and vertically to a depth of approximately 35 feet bsg near boring B9. The "deep"migration of hydrocarbons indicates a historically depressed water table depth of near 30 feet bsg. • Based on six-years of ground water monitoring, the impacted ground water appears stable between wells MW-10, MW-12, MW-13, MW-14 and MW-15. The plume appears to be laterally less than than 40 feet east to west and approximately 40 feet north to south, surrounding the former UST area at well EW-1. The maximum concentrations detected were: TPH-g at 11,000 µg/l; TPH-d at 110,000 µg/l; and benzene at 640 µg/l (MW-10). • Significant concentrations of TPH-g,TPH-d and BTEX compounds were detected in ground Advanced CeoEnvironmental,Inc.