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. 15 September 2005 , 'AGE-NC Project No 98-0465 ' Page 7 of 8 Y , ' Figure 6 depicts the lateral extent of MTBE-Impact to ground water, Figure 7 depicts the vertical extent of MTBE-Impact to ground water ' Based on AGE's Interpretation of the available data, the release(s) of petroleum hydrocarbons occurred at the former UST area during the removal activities during 1999 The only ground water samples collected with TPH and BTEX were "grab" mix matrix water samples from the UST I excavations No significant concentrations of TPH or BTEX were detected at monitoring wells within and down-gradient of the former UST area and only MTBE was detected from the site, at decreasing concentrations ' Once released to the subsurface, the contaminants migrated directly Into sandy material (UST backfill) to a vertical depth of approximately 10 feet bsg, at which point the contaminants ' encountered saturated sandy soil and began to migrate laterally There does not appear to be significant adsorbed contamination beyond the tank pit The lateral migration of dissolved contaminates was dominantly towards the north, in the direction of ground water flow(Figure 5) 1 5.0. SUMMARY AND CONCLUSIONS ' Based on data collected at the site AGE concludes • The ground water elevations on-site ranged from 5 66 to 5 87 feet below MSL Ground water flow at the UST location was inferred to be towards the northwest under a gradient of 0 005 ft/ft or less [ y+ • BTEX compounds were not detected in the ground water samples collected and analyzed during the Second Quarter 2005 • TPH-g was detected In the ground water sample collected from well MW-1 at a concentration of 570 µg/1 Historically, TPH-g has not been detected above,laboratory reporting limits in monitoring wells MW-2 through MW-4 • MTBE was detected in samples collected from MW-1 and MW-3 at concentrations of ` 27 µg/1 and 16µg/l,respectively The concentrations of MTBE exceed the Primary State and IFederal established maximum containment level (MCL) of 13 µg/1 for MTBE In drinking water • There was one isolated detection of MTBE in the ground water collected from boring B 1-W- 42-46'at a concentration of 6 4 /l The concentration of MTBE is well below the Primary arY State and Federal established maximum containment level (MCL) of 13 µg/1 for MTBE in drinking water • The lateral and vertical extent of MTBE-impacted ground water'has been defined in all Advanced GeoEnvironmental,Inc 1 ' I F