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I w ' 21 May 2001 • AGE-NC Project No 95-0173 Page 6 of 7 2000, the total volume of hydrocarbons extracted to date Is approximately 729 gallons The ' mass/volume calculations for extracted hydrocarbons are included with Appendix F A plot of the cumulative volume (gallons) of hydrocarbons extracted to date is Included with Appendix E 5.0. CONCLUSIONS The Implications from the March 2001 ground water monitoring event are as follows - Ground water flow direction at the site was generally toward the east-northeast at a gradient of 0 003 ft/ft or less, 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 ground water flow direction - The increase of ground water elevation of approximately 0 70 feet between December 2000 and March 2001 is probably due to seasonal fluctuation - Ground water elevation data collected on 21 March 2001 does not suggest ground water mounding is occurring due to the air sparging activities at the site • . Ground water at the site is approximately five feet above (drowned) the screen intervals in wells MW-1, MW-2, MW-3 and MW-4 (i e screened below ground water elevation), and may not yield samples fully representative of shallowest ground water conditions, well MW-13 is approximately 70 feet "drowned" The ground water elevation appeared to be withing the screen intervals of wells MW-5 through MW-12 and should be representative ' of shallowest ground water conditions The elevated concentrations of petroleum hydrocarbons detected in samples collected from wells MW-2, MW-3, MW-4, MW-13, AW-1 and AW-2 Indicate that these wells are within ' the dissolved petroleum hydrocarbon "core area" of the plume (Figures 4 and 5) The highest dissolved petroleum hydrocarbons were detected in the area of wells AW-1, ' AW-2 and MW-3, with Increasing depth, the dissolved plume apparently grades from higher concentrations to lower concentrations a A moderate to substantial decrease in concentrations of dissolved TPH-g and BTEX have been quantified at least since September 2000 in ground water samples collected from wells MW-2, MW-3, MW-4, MW-6, MW-13, AW-2A and AW-2B (Table 2) The TPH-g and BTEX decreases may be due to air sparging activities - Previous and current laboratory results of ground water samples suggest that there is a minor MTBE-impact to ground water in the areas of wells MW-3 and MW-4 (Table 2) - Laboratory results of ground water samples collected from MW-13 (screened 95 to 100 feet bsg) suggest that the dissolved petroleum hydrocarbon plume extends to at least 100 feet bsg, Advanced GeoE nviron mental,Inc I