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i ' Mr Terry Tardlti December 17, 2001 . Page 3 Table 4. Comparison of Groundwater Analytical Results with Previous Sampling Event TPH-G Benzene MTBE 8260 B 3'd qtr,01 4e qtr,01 3m qtr,01 4h qtr,01 3rd tr,01 4th 9tr,01 Highest concentration,(µ L) 240 360 72 90 1,900 24,000 Well with!tt hest concentration MW-3 MW 3 MW 3 MW-3 MW-1 MW 1 Number of wells with detection 2/4 1/4 1/4 1/4 3/4 3/4 Discussion: Based on this quarter's data, groundwater flows northeast under a hydraulic gradient of approximately 0 0018, as shown in Figure 2 Benzene concentrations remained consistent with the previous quarter in wells MW-1, MW-2, and MW-4, and increased slightly in well MW-3 Toluene, ethybenzene, and total xylenes concentrations remained consistent with historical results in all four wells TPH-G concentrations were below laboratory reporting limit of 5,000 ug/L in MW-1, within historical results in MW-3, and were not detected in MW-2 and MW-4 • Due to the elevated concentrations of MTBE in the sample from MW-1, the method reporting limit for BTEX, TPH-G, and MTBE were increased due to l sample dilution The dilution is necessary because the MTBE concentration_ is out of the calibration range for the target analyte MTBE concentrations increased to a historical high result of 24,000 ug/L in MW-1 The sample was reanalyzed to verify this result MTBE was not detected in MW-2, and remained consistent with historical results in MW-3 and MW-4 The following documents are enclosed with this letter Figure 1 Site Map Figure 2 Groundwater Elevation Contour Map, October 31, 2001 Figure 3 Groundwater Constituent and Isoconcentration Map, October 31, 2001 Table 1 Historical Groundwater Elevation Data Table 2 Groundwater Flow Direction and Gradient Table 3 Groundwater Analytical Data Table 4 Comparison of Groundwater Analytical Results with Previous Sampling Events • Thu report was prepared to accordance with the standards of the environmental consulting industry at the time it was prepared It should not be relied upon by parties other than those for whom it was prepared,and then only to the extent of the scope of work which was authorized This report does not guarantee that no additional environmental contamination beyond that described in this report exists at the site P\21000\21417\Reports\4th-01 qtr doc