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1 <br /> Geologaal TCCAMICS Inc Page 6 <br />' Groundwater Mowtormg Report <br /> Project No 770 2 <br /> November 19,2003 <br /> 1 � <br /> • The vertical extent of the plume is intermittently defined by MW-104, 105 & 106 <br /> ' w Oxidation-Reduction Potential (ORP) measurements (Table 5 in Appendix A) show that <br /> all of the site's wells except MW-8 have negative values The negative ORP value <br /> observed in the rest of the wells show that they are either within the core of the <br /> ' contamination plume or are in the reaction/depiction shadow down gradient of the <br /> plume Well MW-8 lies in the up gradient direction and its positive value suggests that_ <br /> the water around this well is outside of the impacted halo <br /> An examination of the contaminant distribution and groundwater flow direction data doesn't <br /> reveal any obvious trends A consistent factor previously noted in the investigation was the <br /> ' increase in diesel concentrations in well MW-5, see Figure 6- MW-5 TPH-D vs <br /> Groundwater Elevation The concentrations had previously demonstrated an increasing <br /> trend until June 2002 when wide fluctuations began The plot in Figure 5 previously <br /> ' suggested a predominant direct relationship between groundwater elevation and <br /> contaminant concentrations This situation has been reversed since June 2002 <br /> Well MW-4 lies adjacent to the former UST field Figure 7- MW-4 TPH-D vs <br /> Groundwater Elevation suggests an inverse relationship between groundwater elevation and <br /> contaminant concentrations in well MW-4 <br /> Well MW-5 continues to contain the highest concentrations of detected contaminants (see <br /> Figure S) It has not been down gradient of the former UST location for the monitoring <br /> events completed by GTI to date The reason for this anomaly is not known, but could be <br /> related to geologic units that slope to the west <br /> The deep wells diesel concentrations are plotted in Figure 9 Well MW-105 contained 55 3 <br /> 4g/l diesel and the other deep wells did not contain contaminant concentrations above the <br /> ' laboratory reporting limits (<50 ug/1) <br /> In Figure 10— MW-5 & MW-105 TPH-D versus Groundwater Elevation, well MW-5 <br /> ' contaminant concentrations have generally correlated with changes in the water table Well <br /> MW-105, screened below the water table, exhibits a typically inverse relationship between <br /> contaminant concentrations and groundwater elevation <br /> 1 <br />