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� Geolagiral T¢clueirsl�tc. Page 5 j Groundwater Monitoring Report Project No.425.2 November 17,2003 l The results of the September 2003 event are comparable with the results from previous monitoring events. The following observations are made: { • The horizontal groundwater gradient, calculated from the water table wells, is currently towards the north. . • The gradient calculated from the intermediate wells is to then ortheast. • Vertical groundwater gradients were negative in the shallow/intermediate well pairs and positive in the intermediate/deep well pairs. • TPH-G concentrations in MW-1 continue to fluctuate within levels usually observed for { the site. The concentration of TPH-G in MW-1 measured during e thSeptember 2003 p event were the lowest recorded at the site in three years. See Figure 7 for a graph of Benzene and TPH-G versus time (MW-1) and Figure 9 for a contour map showing the distribution of TPH-G at the site. • BT.EX & TPH-G concentrations in MW-2 show a relatively stable trend with seasonal fluctuations since December 2001. See Figure 8 for graph of Benzene and TPH-G versus time (MW-2). • Contaminant concentrations in well MW-4 exhibit a historically static trend. • Contaminant concentrations analyzed from monitoring well MW-5 fluctuates f seasonally but exhibits an overall increasing trend. This quarter shows the highest concentrations of TPH-G in MW-5 to date. "' • For the twelfth consecutive event, well MW-102 did' not contain contaminant concentrations above the'laboratory reporting limits. • All three of the domestic wells were non-detect for this monitoring event: • Dissolved Oxygen measurements are all on the low end of the scale, ranging between 0.02 and 1.93 ppm. • Oxidation-Reduction Potential (ORP) measurements are all negative (Table 5) and corroborating with the low DO values. I � 3.0 CONCLUSIONS AND RECOMMENDATIONS The following conclusions have been drawn regarding the status-of the groundwater at this site and recommendations for future work: Conclusions 1. The water table groundwater gradient historically flowed in a northerly direction. at about 0.0020 ft/ft prior to May 1998. 2. The intermediate depth groundwater has flowed easterly, with three shifts to southeast during September 2000, September 2001 and December 2002. The northerly flow direction during the December 3, 2001 event was anomalous. The gradient is currently N360E at 0.0018 ft/ft.