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�! 08 October 1999 AGE-NC Project No. 95-0197 Page 4 of 5 MW-4 were approximately three to six feet below the tops of the well screens. TPH-d was detected in ground 'water samples collected from MW-1, MW-2 and MW-3 at I concentrations between 5.1 micrograms per liter (,ug/l) and 81 Mcg/l; the laboratory reported that the chromatograms for the samples did not have typical diesel characteristics. BTEX compounds were not detected in ground water samples collected from wells MW-1, MW-2, MW-3 and MW-4. MTBE was detected in ground water samples collected from wells MW-2 and MW-3 at I concentrations ranging as high as.53 µg/1. MTBE was confirmed'utilizing EPA Method 8260 Modified in ground water samples collected from MW-2 and MW-3 at concentrations ranging as high as 45 4g/l. From April 1999 to July 1999, a general decrease in dissolved petroleum hydrocarbon concentrations was quantified in samples collected from well MW-1 (Table 2). Conversely, general increases were observed in samples collected from wells MW-2 and MW-3. Based upon data collected during the July 1999 monitoring event, AGE concludes: a Ground water monitoring data collected in the area of wells MW-1, MW-2,MW-3 and MW= 4 indicated a ground water flow direction generally toward the north at a gradient of 0.002 ft/ft.(Figure 3). a Due to the low gradient at the. site, slight variations in ground water measurements or changes of recharge/discharge of the local ground water could greatly modify groundwater, flow direction. a MW-1, MW-2, MW-3 and MW-4 are "properly screened", and yield samples fully representative of shallow ground water conditions. a The'dissolved petroleum hydrocarbon plume appears to be sufficiently contained Within the current array of ground water monitoring wells.` 5.0. RECOMMENDATIONS IBased upon the results of this investigation, AGE recommends: a Continued quarterly ground water monitoring. The next quarterly monitoring and sampling. is scheduled for October 1999. a Preparation of a work plan for two additional soil probe borings at the site, northwest and I . Advanced GeoEnvironmental, Inc.