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' Cieologccal T@C{uucs int Page 6 Groundwater Monitoring Report Project No 724 2 May 17,2004 ' contoured map at best provide a shadow of reality Both need to be looked at as interpretation, not reality) ' 1 TPH-G • None- of the shallow monitoring wells contained TPH-G above the laboratory ' reporting limits, and therefore a contour diagram was not produced • Figure 6 illustrates the distribution of TPH-G in the intermediate wells A localized high is centered in well MW-108 and the concentrations attenuate to the southwest ' locations of MW-106 & MW-107 • 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, MW-209 & MW-210 2 MTBE • Figure 8 illustrates the distribution of MTBE in the water table wells A node of MTBE (3 8 ug/1) is present in well MW-7 that attenuates to non-detectable levels in the northwest, northeast and east locations of MW-4, MW-5 & MW-6, respectively • Figure 9 illustrates the distribution of MTBE in the intermediate wells A localized high of 10 9 ug/l is present in well MW-106 that attenuates radially from the well • Figure 10 illustrates the distribution of MTBE in the deep wells A node of MTBE (8 1 ug/1) is present in well MW-209 that attenuates to non-detectable levels in the northwest, west and southwest locations of MW-208, MW-202 & MW-210, ' respectively 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 A localized high is centered in well MW-108 and the concentrations attenuate to the ' west, southwest and south • Figure 12 illustrates the distribution of Benzene in the deep wells A node of elevated Benzene concentration (6 9 ug/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 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 ' 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 1