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C,eo6gicdl Techaws Inc Page 5 Groundwater Monitoring Report Project No 425 2 June 25,2003 i . BTEX & TPH- concentrations in MW-2 show a relatively static trend since December i 2001 See Figure 7 for graph of Benzene and TPH-G versus time (MW-2) and Figure 8 for the distnbution of TPH-G • Contaminant concentrations in well MW-4 exhibit a historically static trend i • Contaminant concentrations analyzed from monitonng well MW-5 fluctuates seasonally but exhibits an overall increasing trend • For the eleventh 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 ' • Dissolved Oxygen measurements were between 0 02 and 1 63 ppm • Oxidation-Reduction Potential (ORP) was measured (Table 5) The results for the June 2003 groundwater monitoring are inconclusive ORP values were negative in all tested ' monitonng wells with the exception of MW-6 DO measurements are low in most wells, corroborating with the negative ORP values i3.0 CONCLUSIONS AND RECOMMENDATIONS The following conclusions have been drawn regarding the status of the groundwater at this site and recommendations for future work iConclusions 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 N07°E at 0 0012 ft/ft 2 The intermediate depth groundwater has flowed easterly, with three shifts to southeast i during September 2000, September 2001 and December 2002 The northerly flow direction during the December 3, 2001 event was anomalous The gradient is currently N70°E at 0 0018 fl.lft ' 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 1plume may be spreading laterally toward the west 6 Petroleum hydrocarbon concentrations in the groundwater at the site fluctuate with each monitoring event The residual contarnination in soil, up gradient of MW-2, remains a ' significant source of impact to the groundwater plume