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URS 00 <br /> Mr. Robert McClellon <br /> January 20, 2005 <br /> Page 3 <br /> foot of bentonite was placed in the annulus. The remainder of the annulus was filled with neat cement. <br /> A stove pipe/monument was installed at the top of each probe.The construction details of the probes are <br /> provided in the boring log corresponding to the probe. Since discolored soil or odorous soil was not <br /> encountered during URS activities,the soil cuttings were placed on the ground surface of the site as <br /> specified in the approved work plan. <br /> After the four additional dual probes were constructed,each probe was measured for methane,carbon <br /> dioxide, oxygen,and volatile organic compounds (VOCs). A landfill gas monitor, GEM 2000,was used <br /> to measure the probes for methane, carbon dioxide,and oxygen. A photoionization meter,MiniRae <br /> 2000, was used to measure probes for VOCs. These results were logged in the field book. <br /> Quarterly Monitoring Activities <br /> On October 18 and 19,2004,the monitoring activities at the site were completed.Each probe was <br /> measured for methane,oxygen,and carbon dioxide using a hand-held,portable GEM 20001andfill gas <br /> monitor. These measurements were recorded in the field book. <br /> RESULTS <br /> The methane concentrations in VW-1,VW-2,VW-3,VW-7S,VW-71),VW-8S, and VW-81)were 0 <br /> percent. The methane concentrations in VW-4,VW-5S, VW-513,VW-6S,and VW-61)were 15.0%, <br /> 8.5%, 10.3%, 17.9%,and 18.7%,respectively. The oxygen concentration in the probes ranged from 0% <br /> to 21.6%. The carbon dioxide concentration in the probes ranged from 1.1 to 30.7 percent.The results <br /> for each probe are summarized in Table 1. <br /> CONCLUSIONS AND RECOMMENDATIONS <br /> Methane was measured in VW4,VW-5S,VW-513,VW-6S, and VW-61)above 5.0 percent. Based on <br /> the most recent quarterly results,the western extent of the methane plume is not currently known along <br /> the northern boundary of the site.We recommend that additional probes be installed at the site. If you <br /> have any questions,please give me a call at(916)679-2081. <br /> Sincerely, <br /> URS Corporation Americas <br /> Jay G. Kamine <br /> Senior Civil Engineer <br /> JGK/gng <br /> Enclosures: Table 1 —Summary of Results <br /> Figure 1 —Site Plan <br /> Boring Logs <br />