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§eolvgccaC?echnrus Inc <br /> Groundwater Monitoring Report Page 5 <br /> Project No 770 2 <br /> May 14,2002 <br /> An examination of the contaminant distribution and groundwater flow direction data doesn't <br /> ' reveal any obvious trends A consistent factor previously noted in the investigation was the <br /> increase in diesel concentrations in well MW-5, see Figure 4- MW-5 TPH-D vs <br /> Groundwater Elevation The September 2001 event marked the first decrease in the TPH-D <br /> concentrations but they have displayed an increasing trend since The plot in Figure 4 <br /> suggests a predominant direct relationship between groundwater elevation and contaminant <br /> concentrations <br /> f , Well MW-4 lies adjacent to the fo <br /> J rmer UST field Figure 5- MW-4 TPH-D vs <br /> Groundwater Elevation suggests an inverse relationship between groundwater elevation and <br /> contaminant concentrations in well MW-4 It is noted that the groundwater elevation <br /> exceeded the screened interval of well MW-4 and dilution may be taking place <br /> Conversely, the water table lies within the screened interval of well MW-5 and this may <br /> represent a more accurate reflection of residual contamination leaching into groundwater <br /> ' Well MW-5 continues to contain the highest concentrations of detected contaminants (see <br /> Figure 6) but it has not been down gradient of the former UST location for the seven <br /> monitoring events completed by GTI to date The reason for this anomaly is not known, but <br /> could be related to geologic units that slope to the west <br /> A comparison of diesel concentrations in well pair MW-5/MW-105 versus groundwater <br /> ' elevation reveals a pattern consistent with the difference between MW-4 & MW-5 noted <br /> above In Figure 7 —MW-5 & MW-105 TPH-D versus Groundwater Elevation, well MW- <br /> 5 contaminant concentrations correlate with changes in the water table Well MW-105, <br /> screened below the water table, exhibits an inverse relationship between contaminant <br /> concentrations and groundwater elevation <br /> GTI makes the following recommendations <br /> • Continue quarterly groundwater monitoring for determining direction and contaminant <br /> ' trends <br /> • Perform monthly groundwater level measurements for one year <br /> • Incorporate the newly installed wells, installed in early May 2002, into the quarterly <br /> ' monitoring schedule <br /> 1 <br /> i <br />