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+«. Gealagkaf Tecluucs Ina Page 6 Groundwater Monitoring Report Project No.724.2 May 16,2005 1. TPH-G • Only MW-2 (63 Vg/L TPH-G) was the only well found detected for TPH-g contaminants above the laboratory reporting limits. A contour diagram was not plotted because of the limited data. • 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-107 &MW-108. • Figure 7 illustrates the distribution of TPH-G in the deep wells. Only MW-208 shows the elevated TPH-g concentration. MW-202, MW-209 and MW-210 were non-detect above the laboratory detection limits for TPH-g. 2. MTBE +-� • Figure 8 illustrates the distribution of MTBE in the intermediate wells. A localized high of 19 µg/1 is present in well MW--106 that attenuates west to the location of MW- 107. `" • Figure 9 illustrates the distribution of MTBE in the deep wells. A node of MTBE (15 [tg/l) is present in well MW-208 that attenuates to the southeast to the location of MW-209. 3. Benzene • Figure 10 illustrates the distribution of Benzene in the intermediate wells. Trace concentration is present in MW-106 and MW-108. • Figure 11 illustrates the distribution of Benzene in the deep wells. A node of elevated Benzene concentration (6.1 [,g/l) is present in well MW-208 that attenuates to non- 4.6 detectable levels in the southeast, south and southwest locations of MW-209, MW- 210 &MW-202, respectively. 4, Oxidation/Reduction Potential (ORP) and dissolved oxygen (DO) measurements (Table 6) show that all of the sampled wells have a mixture of a couple of positive and mostly negative ORP values and low DO readings. The negative ORP values observed in the wells show that 4� 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 generally corroborate with the ORP values measured in these wells and suggest that the plume is relatively stable. V As indicated in Figure 12—MW-2: TPH-G vs. GW Elevation, with the exception of rune 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 & RECOMMENDATIONS Based on our interpretation of the data collected over the course of this subsurface Lam.- investigation, GTI has reached several conclusions. These conclusions assume that the