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CLEARWATER G R O U P anv,.o,on<�ti s«v,«e contaminants in the groundwater on site. Since the groundwater is constantly flowing off site, by removing the COCs from the groundwater on site, the flow of COCs off site is likewise t diminished. While the iSOC system is off, residual COCs (sorbed onto the soil) are expected to continue to leach into groundwater on site, increasing the levels in the on site groundwater monitoring wells; as the COC concentrations in groundwater on site increase, so the levels of COCl being transported off site will also increase. Currently, the iSOC system is shut off. During the period before active remediation of the source area takes place, Clearwater recommends restarting the remediation system and continuing with a quarterly monitoring schedule in order to minimize the chance for further downgradient or off Site contaminant migration in the vicinity of the iSOCTM system; the next groundwater-monitoring event would be during the fourth quarter of 2009. iSOCT"' AND REMEDIATION SYSTEM OPERATIONS AND MAINTENANCE Due to the rebound test, iSOCTM and remediation system O&M activity was not performed during this event. When SJEHD requests that the iSOCTMS should be re-installed, the O&M will be resumed. PROJECT STATUS SUMMARY Activities performed on the subject site during the third quarter of 2009 included: • The third quarter groundwater-monitoring event, conducted on October 1 and 5, 2009, and • The finalization of the groundwater remediation rebound test, initiated on April 1 , 2009, in order to determine whether or not contaminant concentrations would increase or decrease in the absence of enhanced bioremediation (oxygen infusion via iSOC tools). CONCLUSIONS Based on the groundwater remediation rebound test, the iSOC system was shown to have been effective at suppressing the levels of continuously leaching contaminants in groundwater. RECOMMENDATIONS • The SJEHD recently requested that Clearwater perform semi-annual monitoring at the subject site in the first and third quarters, starting in September 2009. Clearwater is proposing that the groundwater remediation system be turned back on in order to prophylactically suppress hydrocarbon concentrations in groundwater while Clearwater develops a more effective soil and groundwater remediation strategy for on Site source area treatment. ZB 178N — Barnes Trucking Facility 6 November 2009 Third Quarter 2009 Quarterly Monitoring Report