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DISCUSSION <br /> Petroleum hydrocarbons were not detected in samples collected from monitoring well MW-1, MW-3, <br /> MWA MW-6, or MW-7, consistent with the previous sampling event Benzene (1 5 ug/L) and xylenes <br /> 0 7 µg/L)were detected in the sample collected from monitoring well MW-2 Xylenes were also detected <br /> In sample collected from monitoring well MW-5 (3 3µg/L) MTBE was detected in the samples collected <br /> from monitoring wells MW-2 (2 6 µg/L) and MW-5 (7 8 µg/L) Groundwater analytical results for samples <br /> collected during the second quarter 2002 are generally consistent with the results of previous sampling <br /> events <br /> The groundwater flow direction was calculated to be toward the east-northeast at an average gradient of <br /> 0 0010 ft/ft Groundwater elevations in the monitoring wells decreased by more than 2 feet since the <br /> previous sampling event (March 2002) <br /> Stratus is currently infecting ambient air at low flow rates through sparge wells AS-1, AS-2, and AS-3 <br /> During the second quarter of 2002, site visits were conducted on April 8, 2002 and June 18, 2002, to <br /> monitor and optimize the performance of the air bubbling system A Stratus technician recorded down- <br /> well DO data and air bubbling flow rates during the site visits The DO readings observed in the vapor <br /> extraction wells were significantly higher than previous quarters Changes in DO concentrations in these <br /> wells will be closely monitored during the third quarter to evaluate if this data set is an anomaly Table 3 <br /> presents dissolved oxygen concentrations in select wells <br /> ATTACHMENTS <br /> • • Table 1 Groundwater Monitoring Data <br /> • Table 2 Groundwater Analytical Results for Oxygenates <br /> • Table 3 Dissolved Oxygen Concentrations <br /> • Figure 1 Site Location Map <br /> • Figure 2 Groundwater Elevation Contours (Second Quarter 2002) <br /> • Figure 3 Groundwater Analytical Summary(Second Quarter 2002) <br /> • Appendix A Field Data Sheets <br /> • Appendix B Sampling and Analysis Procedures <br /> • Appendix C Certified Analytical Reports and Chain-of-Custody Records <br /> P 1Bp Arco for URS121301Quarterly120021Arco_2130_2Q62 doe <br />