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Mr. Robert McClellon <br />Supervisor R.E.H.S. <br />April 6, 2009 <br />Page 4 of 4 <br />samples collected on March 11, 2009. Of these constituents, four (arsenic, iron, manganese and TDS) <br />were above their established regulatory levels. Because three of the metal results and TDS were above <br />their established regulatory levels, URS plans to continue quarterly monitoring of these metals and TDS. <br />Prior to the installation of the passive soil vapor extraction trench, the methane concentration historically <br />exceeded 5 percent by volume within the following probes: VW -4, VW -5S, VW -5D, VW -6S, and <br />VW -6D. Since the passive soil vapor extraction trench installation in September 2006, the methane <br />concentration has decreased within these probes to be less than 5 percent by volume during the following <br />quarter and has continued to be less than 5 percent during the subsequent quarters. Methane <br />concentrations measured within all probes during the first quarter of 2009 were less than 5 percent by <br />volume. Based on the results during this quarter, compared to the results prior to the passive soil vapor <br />extraction installation, the passive soil vapor extraction trench appears to be effective at controlling <br />methane from leaving the site. URS, on behalf of RadioShack, plans to continue monitoring activities for <br />measuring landfill gas concentrations within the probes, extraction wells, and passive vents once a <br />quarter. <br />Should you have any questions regarding this report, please contact me at (916) 679-2081. <br />Very truly yours, <br />URS <br />VKamine <br />Engineer <br />Enclosures: Table 1 Summary of 2009 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 2009 <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\2009\1 Q09\041409.doc <br />