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' Geological Teclraucsl Page 6 Groundwater Momtoring Report ' Project No 724 2 November 21,2005 i ' • Figure 6 illustrates the distribution of TPH-G in the intermediate wells A localized high is centered in well MW-106 and the concentrations attenuate to the locations of ' MW-2 & MW-108 • Figure 7 illustrates the distribution of TPH-G in the deep wells Only MW-208 contained elevated TPH-G concentrations (770 ug/L) Wells MW-202, MW-209 and ' MW-210 did not contain TPH-G above the laboratory detection limits 2 MTBE • A contour diagram was not produced for the shallow wells because only well MW-7 ' contained MTBE (at the laboratory reporting limit of 2 ug/L) • Figure 8 illustrates the distribution of MTBE in the intermediate wells A localized high of 20 µg/1 is present in well MW-106 that attenuates west and east locations of ' MW-107 and MW-109,respectively • Figure 9 illustrates the distribution of MTBE in the deep wells A node of MTBE (13 ttg/1) is present in well MW-209 that attenuates to the west, northwest and southwest locations of MW-202, MW-208 and MW-210 3 Benzene ' • Figure 10 illustrates the distribution of Benzene in the intermediate wells Trace concentrations of benzene are present in MW-2, MW-106 and MW-108 • Figure 11 illustrates the distribution of Benzene in the deep wells A node of elevated Benzene concentration (6 6 [tg/1) is present in well MW-208 that attenuates to non- detectable levels in the southeast, south and southwest locations of MW-209, MW- 210 &MW-202, respectively Oxidation/Reduction Potential (ORP) and dissolved oxygen (DO) measurements (Table 6) show that 16 of 17 wells sampled have low to highly 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 zone down gradient of the plume Dissolved oxygen values generally corroborate with the ORP values measured in ' these wells and suggest that the plume is relatively stable As indicated in Figure 12— 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 ' 3.0 CONCLUSIONS L SIONS & RECOMMENDATIONS ' Based on our interpretation of the data collected over the course of this subsurface investigation, GTI has reached several conclusions These conclusions assume that the ' premise that the data we considered, although incomplete, are representative of actual site conditions We acknowledge that there may be undiscovered conditions, which would upon their consideration, change our interpretation and thus our conclusions 1