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Geological Techda lnc Page 5 Groundwater Monitoring Report Project No 662 2 . December 2,2005 ' • Well MW-2, which is upgradient of the former USTs, has not contained contaminant concentrations above the laboratory detection limits for all quarterly events completed ' thus far in the investigation • Well MW-3 contained the gasoline oxygenate MTBE at 1290 Fig/l and 311 ug/1 TPH-G • Extraction well EW-2 contained 1330 µg/1 MTBE and 303 [,g/1 TPH-G ' Deem Aquifer • Well MW-5 contained 16 µg11 MTBE ' • Well MW-6 did not contain contaminant concentrations above the laboratory detection limits ' • Well MW-104 contained 114 gg/l MTBE The distribution of groundwater contaminants is summarized as follows ' (Note The Isoconcentration contours are generated utilizing the SURFER® computer modeling program We recognize that computer generated contour maps do not provide the ' most accurate representation of what is taking place in the field However, even hand- contoured maps at best provide a shadow of reality Both need to be looked at as interpretation, not reality) • Figure 4 Shallow Well MTBE Concentrations shows that the highest level of MTBE (1330 ug/1) is present in well EW-2 The plume is limited in lateral extent and attenuates ' to the north, northwest and west locations of well MW-1, MW-2 and MW-3, respectively • Figure 5 Shallow Well TPH-G Concentrations shows that the highest level of TPH-G (330 ug/1) is present in well MW-1 The plume is limited in lateral extent and it ' attenuates to the west and south locations of well MW-2 and MW-3 a Figure 6 Deep Well MTBE Concentrations shows that the highest level of MTBE (11 4 ug/1) is present in well MW-104 The plume attenuates to the down gradient (east) locations of wells MW-5 and MW-6 Figure 7 Deep Well TPH-G Concentrations shows that none of the wells contained TPH- G concentrations above the laboratory detection limits A contour diagram was not ' produced due to this condition • Figure 8 MTBE vs Groundwater Elevation in MW-3 illustrates a fairly direct relationship between the concentration of MTBE in groundwater and the elevation of groundwater in well MW-3 A linear trend line has been added to the figure to show a general decline in both groundwater elevation and MTBE concentrations over time ' • Figure 9 MTBE vs Groundwater Elevation in MW-104 does not indicate a clear relationship between groundwater depth and MTBE concentrations The MTBE values appear to have a slight increasing trend ' * Table 4 includes Oxidation-Reduction Potential (ORP) and Dissolved Oxygen (DO) measurements for the site's wells The ORP values continue to fluctuate but the moderately positive values suggest that the plume may be undergoing some biological