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G�lagccal Tecknccs lnc Page 6 Groundwater Monitoring Report Project No 724 2 February 7,2005 ' 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-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 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 • None of the shallow monitoring wells contained MTBE above the laboratory ' reporting limits, and therefore a contour diagram was not produced • Figure 8 illustrates the distribution of MTBE in the intermediate wells A localized high of 15 3 Itg/l 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 (59 ' µg11) 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 10 illustrates the distribution of Benzene in the intermediate wells Trace tconcentrations are present in wells MW-106 & MW-108 • Figure 11 illustrates the distribution of Benzene in the deep wells A node of elevated Benzene concentration (1 1 [ug/l) 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 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 plunge Dissolved oxygen values corroborate with the ORP values measured in these wells and suggest that the plume is relatively stable ' r 12 —MW-2 TPH-G vs GW Elevation with the exception of June 20, As indicated in Figure p ' 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