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Geological Technics Inc Page 5 ' Groundwater Monitoring Report . Project No 662 2 July 7,2005 1 • Well MW-3 contained the gasoline oxygenate MTBE at 1510 µg/1 and for the first time in ' the investigation- 362 ug/l TPH-G • Extraction well EW-2 contained 3770 µg/1 MTBE and 446 µg11 TPH-G Deep Aquifer ' • Well MW-5 contained 2 5 µg11 MTBE • Well MW-6 contained 55 4 µg/l TPH-G • Well MW-104 contained 27 4 µg/l MTBE The distribution of groundwater contaminants is summarized as follows Note The Isoconcentration contours are generated utilizing the SURFER® computer ( g z g p modeling program We recognize that computer generated contour maps do not provide the ' most accurate representation of what is taking place to the field However, even hand- contoured map 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 (3770 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 ' (446 ug/1) is present in well EW-2 The plume is limited in lateral extent and as with the MTBE it attenuates to the north, northwest and west locations of well MW-1, MW-2 and MW-3 ' • Figure 6 Deep Well MTBE Concentrations shows that the highest level of MTBE (27 4 ug/l) 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 down gradient well MW-6 contained the only detection of TPH-G (55 4 ug/1) Wells MW-104 and MW-5 did not contain TPH-G concentrations above the laboratory reporting limit ' • 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 an 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 activity The DO values are low for all of the sampled wells indicating that the wells are within the halo of reaction depleted water caused by biodegradation