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1 a <br /> 1 23 September 1998 <br /> AGE-NC Project No 95-0111 <br />' Page 3 of 4 <br />' concentrations as high as 52 ppb Ethyl benzene was detected in MW-1 and MW-2 at concentrations <br /> as high as 4 9 ppb and xylenes were detected in samples from MW-1, MW-2 and MW-5 at <br /> concentrations as high as 5 3 ppm 1 <br />' MTBE was detected by EPA Method 8260 in samples collected from each well MW-1, MW-2, <br /> MW-3, MW-4, MW-5 and MW-6 had MTBE detected at concentrations of 280 ppb, 2 8 ppb, 5 2 <br />' ppb,' 11 ppb, 8 8 ppb and 2 9 ppb, respectively TBA was detected in well MW-4 at a concentration <br /> of 5 1 ppb TAME was detected at 15 ppb in the sample from well MW-6 The other oxygenated <br /> volatile organic compounds were not detected in any of the water samples MTBE was also detected <br />' by EPA Method 8020 in samples collected from wells MW-1, MW-4 and MW-5 at concentrations <br /> of 180 ppb, 8 1 ppb and 6 5 ppb, respectively <br />' Analytical results of ground water samples are summarized in Table 2 and Table 3 The laboratory <br /> report(MAI Laboratory No 90881 to 90886),quality assurance and quality control report and chain- <br /> of-custody are included in Appendix B <br />' 40. CONCLUSIONS AND RECOMMENDATIONS <br /> 41 CONCLUSIONS <br /> tBased upon data collected from the site, AGE concludes <br />' • During the June 1998 monitoring event, the inferred ground water flow direction at the site <br /> was generally toward the northeast at gradient of approximately 0 04 ft/ft ° <br />' • In general, the concentrations of TPH-g were below 200 ppb BTEX concentrations have <br /> declined to levels at or near 52 ppb TPH-d concentrations, both on and off-site, have <br /> remained high, locally at approximately 50,000 ppb <br />' • Lower detection limits for MTBE has demonstrated the presence of the compound in well f <br /> MW-6 It appears that monitoring well MW-6,with sporadic detections of TPH-d, is located <br />' near the down-gradient margin of the plume of dissolved hydrocarbons <br /> • MTBE concentrations increased in MW- 1, MW-2 and MW-3, but have declined in MW-4 <br />' and MW-5 TAME,detected in the sample collected from well MW-6,may not be associated <br /> with the petroleum release from the site, as suggested by the lack of detectable <br /> concentrations of TAME in the other wells associated with the site <br /> I • The plume of dissolved petroleum hydrocarbons does not appear to be migrating, although <br />' Advanced GeoEnviron mental Inc <br />