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20 May 1999 <br /> • AGE-NC Protect No 95-0142, <br />' Page 3 of 4 e _ <br /> from wells MW-3, MW-4, MW-5 and MW-6 at concentrations of 460µg11, 730 µg11, 680µg/l and <br />' 53,000µg/l, respectively <br /> BTEX compounds were detected in all the samples collected from the monitoring wells BTEX <br />' compounds were detected in samples from each vapor well at concentrations as high as 41,000 ,ug/l <br /> (toluene, VW-1) Benzene concentrations ranged from 9 4µg/1 (MW-3) to 30,000 µg/l (VW-1) <br />' BTEX compounds were detected in the sample from MW-6 at concentrations of 4,400µg11 benzene, <br /> 9,900µg/1 toluene, 1,300µg11 ethylbenzene and 9,200µg/l xylene BTEX compounds were detected <br /> in the sample from MW-4 at concentrations of 29 µg/l benzene, 100 µg11 toluene, 25 µg/1 ethyl <br />' benzene and 120 µg/1 xylene <br />' MTBE was the only oxygenated compound detected in water samples collected from the site MTBE <br /> was detected by EPA method 8260 Modified in the ground water samples collected from wells VW- <br /> 1, VW-2, VW-3 and VW-4 at concentrations of 560 µg/1, 2 8 µg/l, 97 µg/l, 7 2 µg/l respectively <br />' Analytical results for the ground water samples analyzed by EPA Methods 8015 Modified and 8020 <br /> are summarized in Table 2 Analytical results for the ground water samples as analyzed by EPA <br /> Method 8260 Modified are summarized in Table 3 The laboratory report (MAI Laboratory I D <br /> Nos 05925 through 05932), quality assurance and quality control (QA/QC) report and chain-of- <br /> custody form are included in Appendix B <br />' 4.4. CONCLUSIONS <br /> Based on data collected from the site, AGE concludes <br />' Ground water flow direction was generally toward the east <br /> • Ground water levels were above the screened intervals of ground water monitoring wells <br />' MW-1, MW-2, MW-3 and MW-4, these wells may not be adequate to characterize the <br /> shallow dissolved-phase hydrocarbon plume The well screen intervals of monitoring well <br /> MW-5 and vapor wells VW-1 through WV-4 were adequate to characterize the shallow <br />' dissolved-phase hydrocarbon plume <br /> Detectable concentrations of hydrocarbons were present in samples collected from the down <br /> ' gradient wells MW-4 and MW-5 The concentration of TPH-g and benzene in wells MW-3, <br /> MW-4 and MW-5 and vapor wells VW-1 and VW-2 have increased over the last quarter, <br /> while the dissolved hydrocarbon concentrations remained about the same in VW-3 and <br /> ' decreased slightly in vapor well VW-4 I <br /> Advanced GeoEnvironmental,Inc <br />