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i <br /> DISCUSSION: <br /> Groundwater samples were analyzed for TPHG, BTEX, MTBE and the oxygenates, tertiary butanol, DIPE, <br /> ETBE, and TAME. Results of this monitoring event indicated that dissolved gasoline hydrocarbons were <br /> are generally consistent with previous monitoring events. In addition, groundwater samples were analyzed <br /> for MTBE using USEPA Method 8020. Analytical results for MTBE using USEPA 8020 were below <br /> laboratory detection limits for wells MW-1 through MW-3, and VW-3. MTBE was detected in wells MW-4 at a <br /> concentration of 16.2 micrograms per liter (µg/L), using USEPA 8020. The groundwater gradient and <br /> direction of groundwater flow (east) were generally consistent with the previous sampling events. <br /> Groundwater elevation increased 8.53 feet from the previous sampling event (February 1998). <br /> Groundwater samples were analyzed for the oxygenates tertiary butanol, MTBE, di-isopropyl ether, ethyl <br /> tertiary butyl ether, and tertiary amyl methyl ether using USEPA Method 8260. MTBE was detected in wells <br /> MW-1, MW-2, MW-3, and MW-4 at concentrations of 3.90 gg/L, 3.30 µg/L, 2.90 Vg/L, and 18.1 µg/L, <br /> respectively. MTBE by USEPA Method 8260 was below laboratory detection limits for well VW-3. All other <br /> oxygenates were below laboratory detection limits for all wells. Therefore, Pinnacle recommends no further <br /> oxygenate analysis, using USEPA Method 8260, for this site. <br /> ATTACHMENTS: <br /> • Table 1 Groundwater Monitoring Data <br /> • Table 2 Groundwater Analytical Results for Oxygenates <br /> • Figure 1 Site Location Map <br /> • Figure 2 Generalized Site Plan <br /> • Figure 3 Groundwater Elevation Contours (Third Quarter 1998) <br /> • Appendix A Sampling and Analysis Procedures <br /> • Appendix B Laboratory Analysis Reports and Chain-of-Custody Records <br /> Appendix C Field Data Sheets <br /> i <br /> CP1D:11-SGN2NDQTR--1\2186QM2.DOC-481???:1 f" <br /> Rev. 11/6/48 <br />