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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 The highest levels of TPHG and benzene were detected in MW-2 at concentrations of 165 µg/l and 3 62 µg/I, respectively, which is below historic levels As in previous quarters, no constituents were detected in wells MW-3, MW-4, and MW-7 Oxygenates TBA, MTBE, DIPE, ETRE, and TAME were analyzed in samples collected using USEPA Method 8260 MTBE was detected only in MW-2 at a concentration of 3 62 gg/l, within the range of previous sampling results MTBE was not detected in MW-5 after being detected the previous eight quarters No other oxygenates were detected in the wells The groundwater gradient (0 0011 ft/ft) and direction of groundwater flow (northeast) were generally consistent with previous data Groundwater elevation increased an average of approximately 4 26 feet from the previous sampling event(June 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 third quarter 2000 as the compressor faded and warrants replacement Delta will replace the compressor and restart 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 (Third Quarter 2000) • Figure 3 Groundwater Analytical Summary(Third Quarter 2000) • Appendix A Field Data Sheets • Appendix B Sampling and Analysis Procedures • Appendix C Certified Analytical Reports and Chain-of-Custody Records PAVILION\MyDocumentslARCO121301QTRLY1200012I30Q300 Delta 11/22/00