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03 August 2000 <br /> AGE-NC Project No 98-0448 <br /> Page 3 of 4 <br /> • From the September 1999 monitoring event to the April 2000 monitoring event, a substantial <br /> decrease in concentrations of dissolved petroleum hydrocarbons was quantified in ground <br /> water samples collected from wells MW-1, MW-2, MW-4A and MW-4B (Table '2) <br /> Conversely, a slight decrease was recorded from well MW-6 which is suggestive of a slight <br /> shift in the dissolved petroleum hydrocarbon plume towards the south-southwest <br /> • Well MW-4B yields data representative of deeper ground water conditions <br /> • Ground water elevations increased at the site an average 1 75 feet between September 1999 <br /> and April 2000, a trend of increasing ground water elevations was observed at the site <br /> between October 1994 and June 1998 Since June 1998, ground water elevations have <br /> fluctuated between 7 and 10 feet below mean sea level <br /> • Between the September 1999 and the April 2000 sampling events, no substantial increases <br /> were observed of constituents of concern <br /> • TBA was detected in water samples collected from wells MW-6, MW-7 and MW-8 at <br /> concentrations as high as 20µg/l, due to abnormally high laboratory reporting limits, TBA <br /> may also be present at the site at concentrations below the laboratory determined detection <br /> limits <br /> O Current and historical laboratory results of ground water samples suggest that there is a <br /> minor dissolved DIPE impact in the area of wells MW-1, MW-4B, MW-6 and MW-8 <br /> The elevated petroleum hydrocarbon concentrations detected in water samples collected from <br /> wells MW-1 and MW-2 (screened between 20 and 40 feet bsg), MW-4A (screened between <br />' 8 and 33 feet bsg) feet and MW-4B (screened between 45 and 50 feet bsg) suggest that these <br /> wells may be screened within or near the dissolved petroleum hydrocarbon"core area"of the <br /> plume <br />' • Based on increased petroleum hydrocarbon concentrations quantified from well MW-4B <br /> (screened 45 to 50 feet bsg)_dunng the June 1999, September 1999 and April 2000 <br /> monitoring events, AGE suspects that well EW-1 (screened between 15 and 45 feet bsg) <br /> may be a vertical conduit between shallow depth ground water(approximately 15 to 30 feet <br /> bsg) and deeper depth ground water(approximately 45 to 50 feet bsg) <br />' • An air sparging pilot test performed at the site on 25 August 1999 may have contributed to <br /> the significant decrease in quantified dissolved petroleum hydrocarbons detected from wells <br /> MW-1 and MW-2 (screened 20 to 40 feet bsg) <br /> I • The dissolved petroleum hydrocarbon plume appears to be sufficiently contained within the <br /> current array of ground water monitoring wells <br /> Advanced GeoEnvironmental,Inc <br />