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cieologkAt Tecluucs Itm Page 6 Groundwater Monitoring Report ' Project No 724 2 February 13, 2006 ' 1 TPH-G • None of the shallow wells contained TPH-G above the laboratory reporting limits and ' therefore a contour diagram was not produced 0 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 -3, MW -107 & MW -108 • 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 the location of MW - 210 Wells MW -202 and MW -209 did not contain TPH-G above the laboratory detection limits 2 MTBE ' • Figure 8 illustrates the distribution of MTBE in the shallow (water table) wells Contours were not produced for the drawing because only well MW -7 contained MTBE (lust above the laboratory reporting limit of 2 ug/L) ' * Figure 9 illustrates the distribution of MTBE in the intermediate wells A localized high of 25 [xg/1 is present in well MW -106 that attenuates west and east locations of ' MW -107 and MW -109, respectively • Figure 10 illustrates the distribution of MTBE in the deep wells A node of MTBE (9 4 [,g/l) 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 o None of the shallow wells contained Benzene above the laboratory reporting limits ' and therefore a contour diagram was not produced C Figure 11 illustrates the distribution of Benzene in the intermediate wells Trace concentrations of benzene are present in MW -3, MW -106 and MW -108 ' * Figure 12 illustrates the distribution of Benzene in the deep wells A node of elevated Benzene concentration (6 2 µg/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 14 wells 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 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