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' Mr Ron Rowe <br /> December 3, 1997 <br />' Soil samples collected from Philip boreholes MW-9 through MW-13 all contained <br /> petroleum hydrocarbon concentrations below the laboratory method detection limit, with <br /> the exception of the 60-foot depth sample from borehole MW-13 The MW-13 soil <br /> sample contained a benzene concentration of 10 micrograms per kilogram (pg/kg) This <br />' sample was collected at a depth just below the groundwater table, and was probably <br /> contaminated by petroleum-impacted groundwater at that location <br />' SUMMARY <br /> The extent of petroleum-impacted groundwater has been delineated, and is contained <br />' solely within the Earthgram's property boundary Current TPH-G and BTEX <br /> concentrations measured in samples collected during this quarterly monitoring event are <br /> consistent with a decreasing trend of petroleum impact observed at this site From 1992 to <br /> the present, TPH-G concentrations have decreased almost four-fold, and benzene <br /> concentrations by two to six times in samples collected from monitoring well MW-1 <br /> Some fluctuations in TPH-G and benzene concentrations in groundwater samples <br /> collected from monitoring well MW-12 for the last several quarters are evident <br /> Biodegradation assessment data previously collected and other general trends suggest that <br /> the significant petroleum concentration decreases at this site are a result of initial source <br /> removal, natural aerobic and anaerobic microbial activity, and possibly groundwater <br /> dilution <br /> USEPA Method 8260 parameters TBA, MTBE, ETBE, and TAME were not detected in <br /> site groundwater samples DIPE was detected in two groundwater samples at <br /> 1 concentrations of 7 9 µg/L and 12 µg/l, Philip understands that there is no currently <br /> established regulatory cleanup objective for DIPE <br />' CLOSING <br /> Philip and Earthgrains will continue to provide requested information to the SJCEHD in <br /> an effort to assess the best method to ultimately attain case closure for this site Following <br />' the submittal of this report,we will be following up with a telephone call to the SJCEHD <br /> to determine the next step in our continuing work to close this facility If you have <br /> questions, or desire additional information, please call Mark Milward of Philip at (618) <br />' 281-7173 <br /> 1 <br /> 1 <br /> 1 <br />