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' 22 May 1998 . AGE-NC Project No 95-0128 ' Page 3 of 4 ' constituents were also detected in each of these samples wells at concentrations as high as 350 ppb (benzene,MW-5) TPH-g,TPH-d and BTE&X were not detected in monitoring wells MW-1 through MW-3 ' The fuel additive MTBE was detected In the ground water samples from wells MW-4 through MW- 7 and vapor well VW-1 TBA was detected in the ground water samples from wells MW-4, MW-6 ' and MW-7 Analytical results for EPA Methods 8015 and 8020 for the ground water samples are summanzed ' on Table 2 The analytical results for EPA Methods 8260m are summarized on Table 3 The laboratory report(MAI Laboratory Sample TDs 86102 through 86109), QA/QC report and chain-of custody are included as Appendix B 1 4.0. CONCLUSIONS AND RECOMMENDATIONS 41 CONCLUSIONS The following conclusions were drawn from the results of monitoring this quarter I0 The highest concentration of dissolved hydrocarbons quantified as TPH-g and overall BTE&X compounds remain in the vicinity of vapor well VW-1, located at the western edge of the dispenser northern island I6 Concentrations of hydrocarbons (and MTBE)decreased in wells MW-5 and MW-6 over the last quarter • Well MW-7 delineates the apparent western edge of the dissolved TPH-g and BTE&X plume, however, it appears that MTBE has diffused beyond MW-7 • Hydrocarbons, BET&X and oxygenated compounds were not detected in wells MW-1 through MW-3, which sample water from depths of 50 feet and greater, indicating that deeper ground water has not been impacted by the fuel release(s) 42 RECOMMENDATIONS Based on the results of this investigation, AGE recommends the following • Installation of additional ground water monitoring wells to assess and monitor the lateral • extent of the off-site migration of dissolved hydrocarbons AGE has an approved work plan for the well installation and needs only to obtain PHS-EHD approval of specific site Advanced GeoEnvironmental Inc I �