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UR.S i • <br />Mr. Robert McClellon <br />July 9, 2008 <br />Page 4 <br />TDS were above their established regulatory levels, URS plans to continue quarterly monitoring of these <br />metals and TDS. <br />Prior to the installation of the passive soil vapor extraction trench, the methane concentration has <br />historically exceeded 5 percent by volume within VW -4, VW -5S, VW -5D, VW -6S, and VW -6D. Since <br />the passive soil vapor extraction trench installation, the methane concentration has decreased within <br />these probes to be less than 5 percent by volume during the following quarter and has continued to be <br />less than 5 percent during the subsequent quarters. Methane concentrations measured within all probes <br />during the second quarter of 2008 were less than 5 percent by volume. Based on the results during this <br />quarter, compared to the results prior to the passive soil vapor extraction installation, the passive soil <br />vapor extraction trench appears to be effective at controlling methane from leaving the site. URS, on <br />behalf of RadioShack, plans to continue the monitoring activities for measuring the landfill gas <br />concentrations within the probes, extraction wells, and passive vents once a quarter. <br />Should you have any questions regarding this report, please contact me at (916) 679-2081. <br />Very truly yours, <br />URS <br />Enclosures: Table 1 Summary of 2008 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 — June 2008 <br />Attachment 1 Monitoring Well Sampling Data Logs <br />Attachment 2 Analytical Report <br />cc: Judy McCampbell (RadioShack) <br />John Macanas (CIWMB) <br />Ross Atkinson (RWQCB) <br />K:\Wprocess\25532\WorldEnterprise\Quarterly Rpt\2008\2Q08\070908.doc <br />