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' 18 February 2003 AGE-NC Project No 98-0448 ' Page 7 of 8 ' depth measurement was probably erroneous,possibly due to the formation of sedimcrit plug in the well at between 11 and 20 feet bsg Therefore, well MW-4A was not utilized to contour ground water elevations at the site ' The elevated concentrations of petroleum hydrocarbons detected in samples collected from wells MW-2 and MW-4A indicate that these wells are within the dissolved petroleum I hydrocarbon"core area"of the plume(Figures 4) In addition,previous and current analytical results from ground water samples suggest that there is a minor MTBE, DIPE and TBA- impact to ground water in the areas of wells MW-1, MW-2, MW-4, MW-6 and MW-8 ' (Table 2) • Laboratory results of ground water samples collected from MW-413 (screened 45 to 50 feet ' bsg) suggest that the dissolved petroleum hydrocarbon plume extends to at least 50 feet bsg, and is at least 30 feet thick Dissolved petroleum hydrocarbons continued to decline significantly in ground water samples MW-2,MW-4A and MW-413, which may be attributed to the air sparging activity at MW-413 Well MW-6 did not detect any petroleum hydrocarbon constituents of concern liefor two successive quarters Bascd on SVE remediation data collected between 11 September and 17 December 2002, AGE ' concludes • The volume of hydrocarbons extracted by the SVE system was calculated to be ' approximately 78 4 pounds, or approximately 12 5 gallons of petroleum hydrocarbons extracted (Appendix F) ' • The average SVE inlet flow rate was estimated to be 37 cubic feet per minute (cfm) at an average differential pressure of 0 45 inches of water (Table 5) ' • No general trends were evident from the PID field measurements over the September, October, November and December 2002 monitoring penods, however, laboratory analysis ofair samples generally reported increased petroleum concentrations between September and ' December 2002 I Advanced GeoEnvironmental,Inc