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' - - - Geolagwa_(T_eckracs7nc - - -- - - V - - - — - — - - - Page 5 - - - - - - Groundwater Monitoring Report Project No 425 2 June 9,2000 The results from the latest rounds of sampling are comparable with the results from the previous monitoring events The following observations are made • Concentrations in MW-1 continue to fluctuate from event to event See Figure 3 for graph of Benzene and TPH-G versus time in MW-1 • Concentrations in MW-2 showed an increase for the March event but the increase was below the historical maximum level observed in this well during the September, 1999 event See Figure 4 for graph of Benzene and TPH-G versus time in MW-2 Concentrations in MW-4 were non-detect for the March event Well MW-4 historically ' contains contaminants and this is the first non-detect event for the investigation e MW-5 contaminant concentrations continue to fluctuate with a notable increase in Benzene ' a MW-102 was non-detect for the third consecutive event • MW-202 contained a low level of Benzene during the September, 1999 event, but was non-detect for the second consecutive event ' o All of the domestic wells were non-detect for the event ' 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 flows in a northern direction at about 0 002 ft/ft However, over the past year and a half, the gradient has shifted towards the ' east The cause for this is not known at this time 2 Vertical groundwater gradients have been found to be flowing upward during early spring and downward during late spring and summer This may be due to the annual cycle of groundwater pumping needs of the community The upward flow of groundwater during certain portions of the year may be responsible for preventing these contaminants from significantly impacting the deeper aquifer zones ' 3 The concentrations of these petroleum compounds in the groundwater appear to be stable and not decreasing at a significant rate at all ' 4 The shallow water table groundwater plume is laterally defined except to the west 5 Free-floating gasoline was not present in MW-2 in September and only droplets in December 1999, but typically is present in late fall and winter months ' 6 Petroleum hydrocarbon concentrations in the groundwater at the site appear to fluctuate with each monitoring event 7 It appears that the deeper groundwater gradient is defined vertically since MW-102 and MW-202 are now non-detect . 8 The domestic wells associated with this site remain non-detect 1