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URS <br /> Mr. Robert McClellon <br /> May 4, 2005 <br /> Page 2 <br /> FIELD ACTIVITIES <br /> Monitoring activities at the site were completed on April 29, 2005. Each of the twelve probes(four <br /> single completion probes and four dual completion probes)was measured in the field for the presence of <br /> methane, oxygen, and carbon dioxide using a hand-held,portable GEM 2000 landfill gas monitor. These <br /> measurements were recorded in the field book. <br /> RESULTS <br /> The methane concentrations in VW-1, VW-2, VW-7S,VW-713, VW-8S, and VW-813 were 0 percent. <br /> The methane concentrations in VW-3,VW-4,VW-5S, VW-513,VW-6S,and VW-613 were 2.0%, 10.4%, <br /> 22.7%, 13.4%, 21.4%, and 12.8%,respectively. The oxygen concentration in all probes ranged from 0% <br /> to 18.2%. The carbon dioxide concentration in all probes ranged from 0.6% to 29.1%.The results for <br /> each probe are summarized in Table 1. <br /> CONCLUSIONS AND RECOMMENDATIONS <br /> Methane was measured above 5.0% in VW4,VW-5S,VW-513,VW-6S, and VW-613. Based on the <br /> most recent quarterly results,the western extent of the methane plume is not currently known along the <br /> northern boundary of the site. We recommend that additional probes be installed at the site. <br /> The field activities required to install the two additional gas-migration monitoring probes and two <br /> extraction wells at the site were scheduled for April 28, 2005. On April 27,2005,URS informed <br /> SJCEHD that,given weather conditions,URS would be unable to install the gas-migration monitoring <br /> probes and extraction wells as planned. URS has scheduled the drilling contractor for June 1,2005. If <br /> you have any questions,please give me a call at(916)679-2081. <br /> Sincerely, <br /> URS Corporation Americas <br /> jniaKamine <br /> Civil Engineer <br /> gng <br /> Enclosures: Table 1 —Summary of Results <br /> Figure 1 —Site Plan <br />