ARCHIVED REPORTS XR0009983 - Laserfiche WebLink

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DISCUSSION Results of this monitoring event indicate that concentrations of dissolved gasoline hydrocarbons in wells MW-1 through MW-7 and MW-10 are generally consistent with results from previous sampling events with the exception that levels of TPHG have fallen below laboratory detection limits in the samples collected from monitoring wells MW-1, MW-2 and MW-3 BTEX levels have fallen below laboratory detection limits in the sample collected from monitoring well MW-2 Oxygenates TBA, MTBE, DIPE, ETBE, and TAME were analyzed in samples collected using USEPA Method 8260 MTBE was detected only in the sample collected from monitoring well MW-5 at a concentration of 614 µg/L. MTBE was not detected in MW-2 after being detected the previous quarter No other oxygenates were detected in the wells The groundwater flow direction (southeast) and gradient (0 0012 ft/ft) are generally consistent with previous quarters Groundwater elevation increased an average of approximately 4 0 feet from the previous sampling event(September 2000) The soil vapor extraction system has not been operational since November 1997 The majority of the vapor extraction well screens remain submerged The air bubbling system was not operated during fourth quarter 2000 as the compressor previously failed and warrants replacement Delta is in the process of replacing the compressor and restarting the air bubbling system ATTACHMENTS • Table 1 Groundwater Monitoring Data • Table 2 Groundwater Analytical Results for Oxygenates • Figure 1 Site Topographic Map • Figure 2 Groundwater Elevation Contours (Fourth Quarter 2000) • Figure 3 Groundwater Analytical Summary(Fourth Quarter 2000) • Appendix A Field Data Sheets • Appendix B Sampling and Analysis Procedures • Appendix C Certified Analytical Reports and Chain-of-Custody Records C\ARC0121301QTRLY\2000\2130Q400 Delta 1130101