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CIC04fca[rechKICS W Page 8 Groundwater Monitoring Report Project No 723 2 March 21,2005 The results of the groundwater sample analysis show the following ' ❑ Review of the historic groundwater elevations show that groundwater levels experience seasonal fluctuations from the mid 1990s to spring 2000 but have been decreasing steadily with each seasonal cycle since spring 2000 ' ❑ The concentrations of BTEX and TPH-G continue to fluctuate in individual monitoring wells from one sampling event to the next However, there is a general trend of concentrations tracking the groundwater elevations ' ❑ The main mass of contaminants appears to have migrated to the depth of the intermediate well screen interval (43 to 70 ft bgs) ❑ On site deep well MW-101 intermittently contains contaminants and it contained low levels TPH-G for the event It is noted that the contaminant concentrations in MW-101 have continuously declined since it's installation in contrast to the shallow wells that do ' not show a similar contaminant decline ❑ Deep well MW-201 occasionally contains trace BTEX but was non-detect for this event The intermittent contamination is probably a drilling artifact created by the use of mud rotary drilling The contaminant concentration decline since the first monitoring event in December 2001 supports the conclusion that the initial high concentrations were from a drilling artifact ❑ Figure 10 illustrates TPH-G and Benzene concentrations versus elevation in well MW-3, which lies near the core of the plume There appears to be a fairly direct relationship r between the water table and the TPH-G concentrations (although a reverse condition was ' present for this latest event) Benzene concentrations have stabilized in the well ❑ Figure 11 illustrates TPH-G and Benzene concentrations versus elevation in well MW-4, which lies up gradient of the core of the plume The contaminant concentrations exhibit a decreasing trend in this well ❑ Figure 12 illustrates TPH-G and Benzene concentrations versus elevation in deep well MW-101, which lies near the core of the plume The TPH-G and benzene concentrations ' display a decreasing trend The steep decline in the initial concentrations suggests that the contaminants detected in the well were initially a drilling artifact ❑ Oxidation-Reduction Potential (ORP) and Dissolved Oxygen (DO) measurements (Table ' 7) show that twelve of fifteen wells monitored are screened in areas of the groundwater plume that are affected by the biodegradation reactions occurring within the plume The low to highly negative ORP values during the January 2005 event indicate that the wells are within the halo of reaction depleted water caused by biodegradation of the contaminants The low DO values of the wells also reflected this condition 1