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u4 T 26 May 1998 AGE-NC Project No 95-0142 Page 3 of 4 3 2 ANALYTICAL RESULTS OF GROUND WATER SAMPLES TPH-g was detected in samples collected from wells VW-I through VW-4 at concentrations ranging from 1,400 to 130,000 parts per billion(ppb,reported as micrograms per liter) BTE&X compounds were detected in samples from each vapor well at concentrations as high as 29,000 ppb (toluene, VW-1) Benzene was detected in VW-1 at a concentration of 20,000 ppb TPH-g was detected in the sample collected from well MW-5 at concentrations of 960 ppb Each BTE&X compound was detected in the samples collected from well MW-5 at concentrations of 210 ppb benzene, 4 7 ppb toluene, 15 ppb ethyl benzene and 28 ppb TPH-g and BTE&X compounds were not detected this quarter in the sample collected from well MWA MTBE was the only oxygenated compound detected in water samples collected from the site MTBE was detected in the ground water samples collected from vapor wells VW-1, V W-2, VW-3 and VW- 4 at concentrations of 510 ppb, 18 ppb, 77 ppb and 26 ppb, respectively Analytical results for the ground water samples analyzed by EPA Methods 8015 and 8020 are • summarized in Table 2 Analytical results for the ground water samples as analyzed by EPA Method 8260 are summarized in Table 3 The laboratory report(MAI Laboratory I D Nos 871360 through 87136), chain-of-custody and QA/QC report are included in Appendix C 4.0. SUMMARY / CONCLUSIONS Based upon data collected from the site, AGE concludes • Ground water flow direction varies from northeast to southeast, but is generally eastward in the vicinity of the hydrocarbon release (TKI-90), well MW-4 represents the down-gradient well at the site • With ground water well above the slotted intervals of ground water monitoring wells MW-I through MW-3, these wells may not have been adequate to characterize the dissolved-phase hydrocarbon plume The well-placed screen intervals of wells MW-4, MW-5 and vapor wells VW-1 through WV-4 were adequate to characterize the dissolved-phase hydrocarbon plume • Detectable concentrations of hydrocarbons were present in both down gradient wells MW-4 and MW-5 The concentration of TPH-g and benzene in MW-5 appears to be declining slightly over the last four monitoring quarters, while the concentrations in MW-4 appear to be fluctuating between low concentrations and undetectable concentrations, suggesting that • the latter well is near the margin of the dissolved hydrocarbon plume • The highest concentration of dissolved petroleum hydrocarbons remains to the area of the Advanced GeoEnvironmental.Inc