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Geological Technics Inc Page Groundwater Monitoring Report Project No 425 2 May 12,2003 t ' • BTEX & TPH-G concentrations in MW-2 show a decreasing trend since the June 20, 2001 monitoring event, however, this quarter there was a slight increase from the December 2002 monitoring event See Figure 7 for graph of Benzene and TPH-G versus time (MW-2) and Figure 8 for the distribution of IPH-G • Contaminant concentrations in wells MW-4 and MW-5 fluctuate seasonally but exhibit 1 an overall increasing trend MW-4 appears to maintain a relatively consistent concentiation of TPH-G • For the tenth consecutive event, wells 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 o Dissolved Oxygen measurements were between 0 34 and 3 23 ppm, which is conducive ' to biodegradation activity • Oxidation-Reduction Potential (ORP) was measured (Table 5) The results for the ' March 2003 groundwater monitoring are inconclusive ORP values were negative in all tested monitoring wells DO measurements are low in most wells, corroborating with the negative ORP values 3 0 CONCLUSIONS AND RECOMMENDATIONS rhe 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 However, since that time, the gradient has fluctuated from north to northeast, the gradient is currently N85'E at 0 0021 ft/ft 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 N3 80E at 0 0014 ft/ft 3 Vertical groundwater gradients have been found to be flowing upward, during winter and early spring, and downward during late spring and summer However, it continued in an upward direction during this past summer and fall Upward vertical gradients dominate over downward gradients by a 4 1 ratio 4 The dominance of upward vertical flow of groundwater may be the primary reason the contaminants has not impacted the drinking water aquifer 5 The shallow water table groundwater plume is laterally defined except to the west Increases in TPH-G concentration in the western monitoring wells indicate that the plume may be spreading laterally toward the west