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1 _ <br /> 1 <br /> Mr James L Barton <br /> 1 December 2, 2004 <br /> Page 10 <br /> 1 Regulatory Compliance <br /> ENSR corresponds regularly with the lead agency the RWQCB The SVE system discharges <br />' under an Authority to Construct (ATC) issued from the San Joaquin County Air Quality Control <br /> District (SJCAQCD) <br /> Conclusions <br />' Based on the Comparative Analysis, the groundwater contaminant plume does not <br /> appear to be <br /> migrating further Some of the data is following a decreasing trend indicating that the <br /> remediation system is performing its intended function Plume plots (included in the <br /> Attachments) indicate that the central mass of the plume remains centered in an area around <br /> MW-11, MW-3 and MW-2 Plume plots and area, volume, and average concentrations will be <br /> updated with each new quarterly data set and Included with the quarterly monitoring reports <br /> Because the original estimated timeframe for cleanup was two years and the system has now <br /> been operating for five years, this RSE was undertaken to evaluate the system performance <br /> and areas for operational Improvement Unocal and the RWQCB are interested in accelerating <br /> the cleanup of this site, therefore, potential system enhancements and technology changes <br /> • were also considered In addition to continuing operation of the existing AS/SVE system, <br /> additional enhancements to the AS system were considered Including in situ chemical oxidation <br /> (ISCO) for ozone, Fenton's reagent, hydrogen peroxide, or nutrients as suggested In ENSR's <br /> Work Plan and Efforts to Cease Plume Movement dated June 14, 2004 Prior to committing to a <br /> major technology shift, ENSR recommends that additional performance data on the AS/SVE <br /> system be collected The SVE system was restarted in September 2004 and, therefore, there is <br /> Insufficient data to evaluate Its current performance If concentrations rebound or do not appear <br /> to be approaching acceptable levels quickly enough, ENSR will Investigate enhancing the AS <br /> system with ISCO <br /> Based on the plume analysis, the remediation system Is not currently affecting the central mass <br /> of the contaminant plume The central mass is located south of MW-11 to MW-3 and MW-2 and <br /> generally lies outside the zone of influence of the nearest sparge wells To address the central <br /> mass, additional sparge wells should be installed in the vicinity of MW-11 and MW-3 The most <br /> expeditious solution to address the mass in the vicinity of MW-11 would be to convert MW-23S <br /> into a sparge well This well is located less than 10 feet from MW-11 and is screened <br /> approximately 10 feet below the bottom of monitoring well MW-11 thus the zone of Influence <br /> would encompass the contaminant mass around MW-11 To address the area around MW-3, <br /> new sparge wells would need to be Installed <br /> SUMMARY <br /> FindincLs <br /> The system appears to be well maintained, and operating as intended However, the <br /> comparative analysis indicates that system enhancements are needed to address the central <br /> klDcsacramentolpro)ectslProiects10694015098-293lFinaAReports15098 RSE Results Report doc <br />