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I 4 SUMMARY OF FINDINGS AND RECOMMENDATIONS A summary of current groundwater conditions and PSC's recommendations are contained in the following sections 4.1 Groundwater Conditions PSC's data from this current monitoring event and from previous assessments indicates that the highest concentrations of petroleum hydrocarbon compounds are centered in the vicinity of the former gasoline USTs near wells SP-1 and PZ-1 Since the installation of new air sparging well SP-A, petroleum hydrocarbon concentrations in most monitoring well groundwater samples have decreased significantly, typically by a factor of 10 The plume of groundwater impacted with detectable hydrocarbons appears to have decreased since the installation of sparging well SP-A This plume may be less than 200 feet wide and 350 feet long, elongated in the same east- northeast direction as groundwater flow The lateral extent to the north, south, and west has 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 CPT-3 sample did not contain benzene, and the laboratory described it as being uncharacteristic of a typical gasoline, suggesting that it was more characteristic of degraded petroleum Oxygenates concentrations have also displayed a reduction since the installation of sparging well SP-A DIPE has been detected in samples collected from wells in close to the source The oxygenate compound TBA, not observed this quarter, has only been detected sporadically PSC recommends continuation of routine groundwater monitoring to assess 1 evolving subsurface conditions at the Earthgrains facility 4.2 Remedial Recommendations Groundwater sample and air vapor analytical results suggest that the air sparging and venting remedial operations are proving successful in removing dissolved phase gasoline contaminants in soil and groundwater A total of 985 12 pounds of petroleum hydrocarbons have been removed since the inception of remedial activities PSC will continue remedial actions, including ' installing a new sparging compressor, in an effort to ultimately achieve case closure for this site .0 August 2002 Groundwater Monitonng And Remediation Status Report The Earthgrains Baking Company 2651 South Airport Way Stockton,California ro' Prepared for THE EARTHCRAINS BAKING COMPANY Prepared by Philip Services Corp H1ENV162600132\I21382EGGSiockton\SwcktonNO902mon doe September 2,2002