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G¢olagical Takowi s W. Page 9 �. Additional Site Characterization And I"Quarter 2004 Groundwater Monitoring Project No.425.2 March 22,2004 • Alkalinity of the contaminated zone was enriched compared to background. This may be secondary evidence of aerobic biodegradation activity. + Nitrate of the contaminated zone was depleted compared to background. • Sulfate and total iron levels suggest that MW-2 is near the core of the plume. '" • Oxidation-reduction potential of the contaminated zone is lower compared to background. • Background dissolved oxygen levels suggest the site is conducive to aerobic biodegradation activity. • The measured pH in the water table wells is conducive to maintaining aerobic biodegradation activity. • Temperature is inconclusive. 3.2 Geology and Field Observations V The following section discusses the subjective field observations and geology documented during this investigation based on the interpretations of the field geologist. Figure 2 is a „r Site Map indicating a line of section for a cross sectional view, which is attached as Figure 3. • The lithology of the site is basically, alternating Iayers of clay-sand mixtures and sand- gravel mixtures. • The lithology between the surface,and 204ect bgs is predominately clays and sands. �. • The lithology between 20 and 4dfieet bgs is predominately sands and gravels. V. • The lithology between 40 and 80.-feet bgs is comprised of alternating layers of clay-sand mixtures and sand-gravel mixtures approximately 2 to 8 feet in thickness. 3.3 Hydrology of Site On January 3, 2004, the depth to groundwater was measured in the sixteen existing monitoring wells (Figure 2) prior to purging. A discussion of the hydrology of the site follows: Water Table Wells Depths to groundwater in the water table monitoring wells averaged 12.51 feet below the top of casing. The average groundwater elevation in the water table wells during the ,+ January 3, 2004 groundwater-monitoring event was 73.21 feet above mean sea level (AMSL). Site-specific groundwater bearing and slope were calculated using MW-3, MW-4 and MW- `' 7 and found to be N21°E @ 0.0010 ft/ft. These results are consistent with historical groundwater bearing and slope calculations at the site. +� Groundwater elevation, bearing and slope for the water table wells was calculated from data gathered during the January 2004, monitoring event and the results are summarized in Table 5 of Appendix A.