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Geologccal rechAtcs Inc Page 5 <br /> Groundwater Monitonng Report <br /> Project No 425 2 <br /> November 12,2001 <br /> ' 2.0 FINDINGS AND DISCUSSION <br /> ' The laboratory analytical data generated during the event indicate that TPH-G & BTEX <br /> compounds have been detected in the following monitoring wells MW-1, MW-2, MW-4 <br /> and MW-5 <br /> The results from the latest rounds of sampling are comparable with the results from the <br /> previous monitoring events The following observations are made <br /> • The horizontal groundwater gradient is currently towards the north <br /> ® Shallow vertical groundwater gradients are typically downward in the month of <br /> ' September <br /> e Groundwater levels have exhibited a trend of decreasing elevation This situation may <br /> have tapered off in the last quarter <br /> m TPH-G concentrations in MW-1 and MW-2 continue to fluctuate See Figures 4 & 5 <br /> for graph of Benzene and TPH-G versus time and Figure 6 for the distribution of TPH- <br /> ' G <br /> o Figure 7 demonstrates a general trend of increasing TPH-G concentration with <br /> decreasing groundwater elevation <br /> o Wells MW-4 and MW-5 contaminant concentrations exhibit a stable trend <br /> a Wells MW-102 and MW-202 did not contain contaminant concentrations above the <br /> laboratory reporting limits for the fourth consecutive event <br /> C All three of the domestic wells were non-detect for the event <br /> c Oxidation-Reduction Potential (ORP) was measured (Table 6 & Figure 9) The results <br /> suggest that well MW-2 is in the core of the contamination plume or is immediately <br /> down gradient of the plume Negative ORP values indicate that the wells are within the <br /> halo of reaction depleted water caused by biodegradation of the contaminants For the <br /> ' September 7, 2001 event, five water table wells had negative ORP values <br /> 3.0 CONCLUSIONS AND RECOMMENDATIONS <br /> The following conclusions have been drawn regarding the status of the groundwater at this <br /> ' site and recommendations for future work <br /> ' Conclusions <br /> 1 The water table groundwater gradient historically flowed in a northern direction at about <br /> 0 002 ft/ft prior to May 1998 However, since that time, the gradient has fluctuated <br /> from north to northeast <br /> 2 The intermediate depth groundwater flows easterly, with two shifts to southeast during <br /> September 2000 & September 2001 <br />