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1 <br /> c7eo4kal rechida lac. Page 6 <br /> Groundwater Monitoring Report <br /> Project No 425 2 <br /> August 6,2004 <br />' • All three of the domestic wells were non-detect for this monitoring event <br /> • Dissolved Oxygen measurements are all on the low end of the scale, ranging between <br />' 0 04 and 2 6 ppm <br /> • Oxidation-Reduction Potential (ORP) measurements are all negative (Table 4) and <br />' corroborating with the low DO values <br /> t4.0 CONCLUSIONS AND RECOMMENDATIONS <br /> The following conclusions have been drawn regarding the status of the plume at this site and <br />' recommendations for future work <br /> Conclusions <br />' 1 The water table groundwater gradient historically flowed in a northerly direction at about <br /> 0 0020 ft/ft prior to May 1998 <br /> 2 The intermediate depth groundwater has flowed easterly, with three shifts to southeast <br />' during September 2000, September 2001 and December 2002 The northerly flow <br /> direction during the December 3, 2001 event was anomalous The gradient is currently <br /> N890E at 0 0025 ft/ft <br /> 3 The dominance of upward vertical flow of groundwater may be the primary reason the <br /> contaminants have not impacted the drinking water aquifer <br /> 4 Increased TPH-G concentrations in MW-5 suggest the plume may be spreading laterally <br />' to the west <br /> 5 Petroleum hydrocarbon concentrations in the groundwater at the site fluctuate with each <br /> monitoring event The residual contamination in soil, up gradient of MW-2, remains a <br />' significant source of impact to the groundwater plume <br /> 6 The deeper groundwater plume is defined vertically since MW-102 and MW-202 remain <br />' non-detect for contaminants, indicating that the contamination is not moving deeper into <br /> the aquifer <br /> 7 The groundwater plume is not defined to the northeast or to the west It may not be <br />' feasible to perform further definition to the west, but the northeast direction is available <br /> for well installation <br /> 8 The three domestic wells sampled remain non-detect for all analyzed constituents, <br />' indicating that the drinking water aquifer has not been impacted <br /> Recommendations <br /> The following recommendations are made <br /> 1 Continue quarterly groundwater monitoring events <br /> 2 Prepare a work plan for the bench-scale test <br />' 3 Further define the down gradient extent of the groundwater plume northeast of the site <br /> Install one monitoring well near MW-8 as shown in Figure 9 The MW-108 will be in the <br /> second zone about 10' screen in the course grained unit <br />