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1 lie 21 February 2001 AGE-NC Project No 95-0128 ' Page 3 of 4 ' 3 2 ANALYTICAL RESULTS FROM GROUND WATER SAMPLES TPH-g was detected in samples MW-4, MW-5 and VW-1 at concentrations of 15,000 Ag/1, 9,500 ' ,u9/1 and 370 ,4g/l, respectively Samples MW-2, MW-4, MW-5 and VW-1 also contained TPH-d at concentrations of 280,ug/l, 2,200 ,ug/l, 1,600 ,ug/1 and 150 ,ug/l, respectively TPH-g and TPH-d were not detected in the remaining samples ' Benzene was only detected in samples MW-4, MW-5 and VW-1 at 28 µg11, 180 µg/l and 9 µg11, respectively The remaining BTE&X compounds were only detected in samples MW-2, MW-4, ' MW-5, MW-6 and VW-1 at concentrations ranging from below detectable limits to 1,600 4g/1 of xylenes in MW-4 ' MTBE was detected by EPA Method 8020 in ground water samples MW-2, MW-3, MW-5, MW-8, MW-11A,MW IB, MW12A,MW-12B and VW-1 at concentrations ranging from 8 7/.cg/l in MW- 2 to 1,500µg11 in MW-5 MTBE was also quantified by EPA method 8260m and was detected in ' all ground water samples, excluding MW-10, at concentrations ranging from 1 1µg/1 in MW-1 to 1,400 µg11 in MW-5 � . Of the remaining fuel oxygenates, only TBA was detected in sample MW-2 at 7 3 ,ug/l The analytical results are summarized on Tables 2 and 3 The laboratory reports for the quarterly monitoring event (MAI Laboratory ID No 58930 to 58944), quality assurance and quality control (QA/QC) reports and the chain-of-custody form are included in Appendix B r 4.0. SUMMARY AND CONCLUSIONS The following conclusions were drawn from the results of monitoring this quarter • The highest concentration of dissolved hydrocarbons quantified as TPH-g, TPH-d and overall BTEX compounds occurs in the area surrounding the northern dispenser island Figures 5, 6 and 7 depict the benzene, TPH-g and MTBE isocontours - The highest concentration of MTBE detected in the ground grater occurs In monitoring -ell MW-5 which is situated in the northern corner of the property, down-gradient from the dispenser islands The high concentrations of MTBE in this well suggests that the MTBE is disassociating from the hydrocarbon plume The detection of MTBE in all monitoring wells, excluding MW-10, is the result of the high solubility of MTBE High concentrations of MTBE exist in the down-gradient wells an MTBE is not adequately defined to the north and . east Advanced GeoEnvironmental Inc