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i 1 2.2 Ground -Water Sampling and Laboratory Analysis AZURE . ENVIRONMENTAL ' Ground -water samples were collected from monitoring wells MW -1, MW -2 and MW -3 on February 15, 2006. Monitoring well MW -1 is located adjacent to fuel USTs at the Site; wells MW -2 and MW -3 are located adjacent to UST system underground piping and fuel dispensers ' (Figure 2). Ground -water samples were analyzed for total petroleum hydrocarbons as gasoline (TPHg); benzene, toluene, ethylbenzene, and xylenes (BTEX) compounds; fuel oxygenates, including methyl tertiary -butyl ether (MTBE); and lead scavengers, including 1,2-dichloroethane ' (1,2 -DCA). Laboratory analysis results are summarized in Table 2; laboratory certificates are included in Appendix A, field sampling data sheets in Appendix B and descriptions of field sampling methods and procedures in Appendix C. Most recent ground -water monitoring data for ' MTBE concentrations detected at the Site are illustrated in Figure 3. First quarter 2006 ground -water monitoring data indicate low concentrations of MTBE were ' detected only in wells MW -1 (5.8 ug/1) and MW -2 (1.2 ug/l). The February 2006 sampling result for MTBE at well MW -1 (5.8 ug/l) revealed a lower concentration than the previous quarter sampling results collected in October 2005 (i.e., 4.1 ug/1). Historical MTBE results indicate a ' consistent trend of decreasing MTBE concentrations at well MW -1 (Figure 4). The February 2006 sampling result for MTBE at well MW -2 (1.2 ug/l) is consistent with the historical range of MTBE concentrations detected at the well since it was first sampled in December 2003. TPHg, ' BTEX compounds, other fuel oxygenates and lead scavengers were not detected in the wells (Table 2). MTBE concentrations in ground water are expected to continue to decrease as a result of natural attenuation processes (i.e., dispersion, dilution, adsorption, and volatilization). These degradation processes should ultimately reduce the concentrations and mass of MTBE in Site ' ground water to meet remedial goals. Future monitoring data will be evaluated to further assess changes of MTBE concentrations in Site ground water and to assess criteria for case closure. ' 3.0 TECHNICAL STATUS REPORT ' Work completed during the first quarter 2006 and work expected to be completed during the second quarter 2006 includes continued performance of the ground -water monitoring program. ' Future recommended activities include completion of a sensitive receptor survey to identify and assess beneficial uses of ground water and potential exposure pathways at the Site. Previous recommendations to install an additional downgradient ground -water monitoring well at the Site should be re-evaluated and- may not be. necessary in the event. that_ future monitoring results _ confirm attenuation of MTBE concentrations to below ground -water remedial goals. 2 9