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1 ' MTBE was detected in the grab ground water sample collected at boring B8-55 and B9-55 at concentrations of 170 gg/1 and 4l µg/l,respectively,by EPA Method 8020. MTBE was not detected ' in the grab ground sample collected from boring 138-70 by EPA Method 8260. However, a low concentration of MTBE was detected in the grab ground water sample collected at boring B8-70 at concentrations of 1.6µg/l,by EPA Method 8260. There were no reported detections of any other fuel ' oxygenating compounds. ' GROUND WATER MONITORING Between June 1994 and the March 2002, ten ground water monitoring wells have been installed and ' sampled for petroleum hydrocarbons. Initial ground water samples were collected in June 1994. To date, a total of thirteen ground water monitoring events have been conducted at the site. i Depth to ground water has ranged between 7.04 and 14.01 feet bsg at the former USTs locations, ground water flow direction has been consistently northeast at a gradient of approximately 0.02 ft/ft. ' Petroleum hydrocarbon compounds was detected once during the monitoring events; TPH-g (55 µg11), BTEX compounds have been detected at the following maximum concentrations: benzene ' (7.7 gg/1), toluene (0.78 µg/1) xylenes (1.9µg1]). MTBE has been detected in wells MW-3 through MW-10 at concentrations ranging from 0.84 µg/l (MW-8 in September 2002) up to 1,100 gg/1 (MW-4 in November 1999). ' • MTBE was detected in the grab ground water samples collected from at 55 feet bsg, down gradient of the former UST approximately 100 feet. The lateral extent of the petroleum hydrocarbons is limited by well MW-7 and MW-8,down-gradient from the former UST area. While the vertical extent of the dissolved MTBE impact to ground water ' has not been defined by the current well network. 1 1 • Advanced GeoEnvironmental,Inc. 1 ,