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' Mr Ron Rowe <br /> • 11/25/98 <br /> which was measured in April 1 93 to the current level f <br /> 196,000 µg/L, p 9 o <br /> 16,000 µg/L From 1992 to the present, TPH-G concentrations have decreased <br />' almost five-fold, and benzene concentrations by about seventeen times in samples <br /> collected from monitoring well MW-1 <br />' Previously collected biodegradation assessment data and other general trends <br /> suggest that the significant petroleum concentration decreases at this site are <br /> largely a result of initial source removal, and natural aerobic and anaerobic <br />' microbial activity The suggestion that higher groundwater conditions are <br /> responsible for the concentration decreases is disputed by the fact that the current <br /> low petroleum levels are from samples that were collected during a relatively <br /> large drop in the depth to groundwater <br />' Oxygenate parameters TBA, MTBE, ETBE, and TAME were not detected in site <br /> groundwater samples DIPE was detected in one groundwater sample at a <br />' concentration of 12 µg/L The relative magnitude of this concentration can not be <br /> evaluated because there is no currently established regulatory cleanup objective <br /> for DIPE The extent of DIPE impact appears to be limited to the site and in close <br /> proximity to the source of the petroleum release <br /> CLOSING <br /> Philip and Earthgrams will continue to provide requested information to the <br /> SJCEHD in an effort to assess the best method to ultimately attain case closure for <br /> this site Following the submittal of this report, we will be following up with a <br /> telephone call to the SJCEHD to determine future steps in our endeavor to close <br />' this UST case The next bi-annual groundwater monitoring event is tentatively <br /> scheduled for April 1999 If you have questions, or desire additional information, <br /> please call Mark Milward of Philip at(618) 281-7173, extension 1241 <br />' Sincerely yours, <br /> PHILIP SERVICES CORP <br />' Mark F Milward <br /> Hydrogeologist <br /> /mml3RDQTR98 <br />' Attachment 1 Figures <br /> 2 Tables <br /> 3 Groundwater Sampling and Analysis Procedures <br />' 4 Water Sample Field Data Sheets <br /> 5 Laboratory Reports and Chain-of-Custody Documentation <br /> 1 <br /> 1 <br /> 1 <br />