ARCHIVED REPORTS_XR0004597 - Laserfiche WebLink

Home Browse Search

y Geological Technics Inc. Page 5 Groundwater Monitoring Report Project No.662.2 -V' March 24,2005 y. * Well MW-3 contained the gasoline oxygenate MTBE at 180 µg/l. 9 Extraction well EW-2 contained: 2200 µg/1 MTBE, 890 [tg/l TPH-G, 0.9 [,g/1 benzene, 3.6 µg/1 ETBE, 2.9 µg/1 TAME and 130 µg/1 TBA. y Deep Aquifer • • Well MW-5 contained 12 [tg/l MTBE and 35 ug/l lead for this first sampling event. y' • Well MW-6 contained 2.2 pg/1 MTBE and 28 ug/1 lead for this first sampling event. 0 Well MW-104 contained 16 µg/1 MTBE. The distribution of groundwater contaminants is summarized as follows: y (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 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 (2200 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. • Figure 5: Shallow Well TPH-G Concentrations shows that the highest level of TPH-G (890 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. • Figure 6: Deep Well MTBE Concentrations shows that the highest level of MTBE (16 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 all three deep screened wells MW-5, MW-6 and MW-104 did not contain TPH-G above the laboratory reporting limits and hence a contour diagram was not produced. • 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 although a steep drop is noted since the December 2004 pilot test. • Table 4 includes Oxidation-Reduction Potential (ORP) and Dissolved Oxygen (DO) measurements for the site's wells. All seven wells sampled had moderately positive ORP values that are higher than in the past suggesting that the plume may be undergoing some w biological activity. The DO values are low for all of the sampled wells indicating that the i wells are within the halo of reaction depleted water caused by biodegradation. S.