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fie Page 4 <br /> Mr Michael Infurna Jr, Senior REHS <br /> January 20, 2004 <br /> • Oxygenate compounds TBA, MTBE and DIPE have been detected <br /> sporadically in groundwater samples <br /> EHD concurred with PESC's investigation findings and requested a work plan to <br /> remediate the site to "pre-release" conditions in their June 11, 2002 <br /> correspondence PESC submitted to EHD a July 23, 2002 Pilot Testing Work Plan <br /> that presented remedial alternatives and proposed performing an air sparging and <br /> soil venting pilot test to evaluate that method for full scale implementation EHD <br /> approved the work plan in correspondence dated August 6, 2002 <br /> The airs sparging and soil venting pilot test was performed in January 2003 and <br /> P <br /> results from that, submitted in PESC's March 6, 2003 Remedial Action Plan, <br /> indicated that this approach would be effective in remediating impacted soil and <br /> groundwater The EHD approved PESC's proposed remedial action approach in <br /> correspondence dated March 25, 2003 <br /> Remediation System Operation <br /> Under an approved San Joaquin Valley Air Pollution Control District (SJAPCD) <br /> permit, PESC installed the air sparging and soil venting system and began <br /> continuous operation on November 18, 2003 As part of that permit, PESC is <br /> required to monitor the system on a periodic basis to evaluate its effectiveness <br /> Air flow rates are measured in sparging.well SP-1 and in venting wells VW-1 and <br /> MW-2 Three air samples are collected one influent sample prior to treatment by <br /> the first granulated activated carbon vessel and two effluent samples following <br /> treatment Samples are shipped to GD Air Testing Inc in Richardson, Texas for <br /> BTEX and TPHg analysis Results are routinely reported to the SJAPCD <br /> As shown in Table 1, combined venting rates for VW-I and MW-2 range from 31 <br /> cubic feet per minute (cfm)to 90 cfm TPH-G concentrations ranged from 1,270 <br /> ppmv at the onset of operation to 38 3 ppmv Based on these values, PESC has <br /> calculated that 73 96 pounds of petroleum hydrocarbons have been removed from <br /> the subsurface PESC originally estimated that 281 pounds of TPH existed in <br /> subsurface soil and 61 pounds of TPH existed in groundwater Therefore, <br /> approximately 22 percent of the original mass of contaminant have been removed <br /> j since initiation <br />