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• 4 SUMMARY OF FINDINGS Philipcontinues to monitor subsurface conditions and the plume of gasoline-impacted P g P groundwater at the Earthgrain's facility Philip's data from this current morutoring event, and from previous assessments indicates that the plume of groundwater Impacted with detectable hydrocarbons is approximately 100 feet wide, and some 550 ' feet long, elongated in the same east-northeast direction as groundwater flow The highest concentrations of petroleum hydrocarbon compounds are centered near the former gasoline USTs, and around wells MW-1 and SP-1 The lateral extent to the north, south, and west had been delineated by historic, non- detectable, petroleum concentrations measured in groundwater samples collected from wells in those directions To the east, a TPH-G concentration of 100 µg/1 was measured in a groundwater sample collected from CPT-3 during the May 1999 site Investigation This same sample did not contain benzene, and Acculabs had characterized the TPH-G analysis as being uncharacteristic of a typical gasoline, suggesting that the Impact was more characteristic of degraded gasoline The oxygenate compound DIPE has been detected in samples collected from wells in close proximity to the source Philip will continue to monitor oxygenate levels to assess site conditions Based on recent monitoring results, Philip concludes that rate of natural petroleum hydrocarbon degradation is not progressing as effectively as previously estimated ' Philip and Earthgrains are planning to install an air-sparging and soil venting remediation system to augment natural degradation and initiate petroleum hydrocarbon source removal in the vicinity of the former gasoline USTs 1 9 July' 2(1to Groundwater Monrtonng Repos The Farthgrams Company 265I South Airport Way Stockton,California Prepared for THE EARTHmAINs COMPANY Prepared by Philip Services Corp 14%ENV%6240013n121392Ectiswckmnvstocki�w7000on doc August 14,200