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attached in Appendix B Hydrocarbons were not reported for samples collected from the <br /> remaining five wells <br /> Review of historical TPH-D data indicates that the maximum TPH concentration reported <br /> since 1987 was for the sampling event conducted in September 1999 (780 ug/L, DM-6) <br /> Prior to the installation of DMW-6 and DMW-7 in December 1998, the only other reported <br /> TPH concentration was 180,ug/l at DMW-4 in May 1995 <br /> The weathered diesel reported as unknown hydrocarbon has been consistently detected <br /> during the seven sampling events conducted at DMW-6 and DMW-7 since December <br /> 1998 These wells are constructed so that representative water samples can be collected <br /> directly at the groundwater surface, where a surficial TPH-film would be expected, if <br /> present DMW-6 and DMW-7 were installed near the centers of the two zones of residual <br /> TPH soil impacts associated with the former USTs Therefore, the concentrations detected <br /> at these two wells should be representative of the worst-case scenario for TPH-D <br /> concentrations in groundwater at the Site From December 1998 to February 2000, the <br /> reported concentrations ranged from 53 ugIL to 780 ug/L in samples collected at DMW-6, <br /> and 74 ug/L to 660 ug/L in samples collected at DMW-7 The weathered diesel observed at <br /> MW-6 and DMW-7 does not appear to be present in samples collected from wells DMW-1 <br /> through DMW-5, with the exception of the sample collected during February 2000 at <br /> DMW-3 (53 ug/L) <br /> 40 FUTURE ACTIVITIES <br /> Quarterly groundwater monitoring at wells DMW-1 through DMW-7 will be continued <br /> during the fourth quarter of 2000 in order to monitor trends in water level elevations and <br /> the reported unknown hydrocarbon concentrations <br /> Dames & Moore 5 11AMREPORTIQ2-2000 DOC <br />