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yeofo fTerluucslr� Page 6 Groundwater Monitoring Report Project No 724 2 November 12,2004 ' • Figure 7 illustrates the distribution of TPH-G in the deep wells A localized high is centered in well MW-208 and the concentrations attenuate to non-detectable levels in the southwest and south locations of MW-202, MM-209 &MW-210 2 MTBE • Figure 8 illustrates the distribution of MTBE in the water table wells A node of ' MTBE (2 9 µg/1) is present in well MW-7 that attenuates to non-detectable levels in the northwest and northeast locations of MW-4& MW-5, respectively • Figure 9 illustrates the distribution of MTBE in the intermediate wells A localized ' high of 15 9 40 is present in well MW-106 that attenuates west to the location of MW-107 • Figure 10 illustrates the distribution of MTBE in the deep wells A node of MTBE ' (7 0 µg/1) is present in well MW-209 that attenuates to the northwest to the location of MW-208 3 Benzene • None of the shallow monitoring wells contained Benzene above the laboratory reporting limits, and therefore a contour diagram was not produced • Figure 11 illustrates the distribution of Benzene in the intermediate wells Trace concentrations are present in wells MW-106 &MW-108 • Figure 12 illustrates the distribution of Benzene in the deep wells A node of elevated Benzene concentration (0 6 µg/1) is present in well MW-202 that attenuates to the northeast, east and southeast locations of MW-208, MW-209 & MW-210, respectively ' Oxidation/Reduction Potential (ORP) and dissolved oxygen (DO) measurements (Table 6) show that all of the sampled wells have a mixture of positive and negative ORP values and ' low DO readings The negative ORP values observed in the wells show that they are either within the core of the contamination plume or are in the reaction/depletion shadow down gradient of the plume Dissolved oxygen values corroborate with the ORP values measured in these wells and suggest that the plume is relatively stable As indicated in Figure 13 —MW-2 TPH-G vs GW Elevation, with the exception of June 20, ' 1997, contaminant concentrations have generally mimicked the pattern of groundwater elevation changes for the past 10 years in down gradient well MW-2 The well was non- detect for the second time in the investigation ' 3.0 CONCLUSIONS & RECOMAWNDATIONS Based on our interpretation of the data collected over the course of this subsurface ' investigation, GTI has reached several conclusions These conclusions are based on the premise that the data we considered, although incomplete, are representative of actual site 1