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Mr. Robert McClellon <br /> April 29,2011 <br /> Page 4 <br /> Prior to the installation of the passive soil vapor extraction trench,the methane concentration historically <br /> exceeded 5% by volume within the following probes: VW-4, VW-5S, VW-5D,VW-6S, and VW-6D. <br /> Since the passive soil vapor extraction trench installation in September 2006,the methane concentration <br /> has decreased within these probes to less than 5% by volume during the following quarter and has <br /> continued to be less than 5% by volume during the subsequent quarters. Methane concentrations <br /> measured within all probes during 1Q11 were less than 5% by volume. <br /> Based on the results during this quarter,compared to the results prior to the passive soil vapor extraction <br /> installation,the passive soil vapor extraction trench appears to be effective at controlling methane from <br /> leaving the site. Because the results of the monitoring activities for measuring landfill gas concentrations <br /> within the probes have been less than 5%by volume since December 2006(following the installation of <br /> the passive soil vapor extract trench),we recommend that the monitoring activities continue on an annual <br /> basis. <br /> Should you have any questions regarding this report, please contact me at(916) 679-2081. <br /> Very truly yours, <br /> URS <br /> yJay . ine <br /> lEngineer <br /> : Table 1 Summary of 2011 Field Measurement Results <br /> Table 2 Dissolved Metals Results,Total Dissolved Solids Results, and Field <br /> Measurement Results Summary in Groundwater <br /> Figure 1 Site Plan <br /> Figure 2 Groundwater Elevation March 2011 <br /> Attachment 1 Monitoring Well Sampling Data Logs <br /> Attachment 2 Analytical Report <br /> cc: Jaime Caballero (RadioShack) <br /> Sabra Ambrose (CIWMB) <br /> Ross Atkinson(RWQCB) <br /> H.\Wprocess\25532\WorldEnterprise\Quarterly Rpt\2011\1Q11\043011.doc <br />