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Mr. Todd Del Frate -2- <br /> SECOND SEMESTER AND ANNUAL 2006 GROUNDWATER AND SURFACE WATER <br /> MONITORING REPORT; FOOTHILL SANITARY LANDFILL <br /> Methane was not found in soil gas wells except SG-11 (2.6%). <br /> As we discussed, it is surprising that the methane in the soil gas trench beneath Module 1 was <br /> significantly increased (23.1%) above past concentrations (not more than 5%). I suspect this is <br /> due to the placement of a gas-impermeable HDPE membrane over the side of Module 'T' <br /> adjacent to Module 1, thereby inhibiting the venting of landfill gas through that surface for the first <br /> time in the history of the landfill. As you may remember, we took much effort to ensure a gas- <br /> tight barrier above Module 'T'. With this new information, I suggest that we consider barriers that <br /> allow the upward movement of landfill gas from lower refuse strata in future separations between <br /> old and new refuse over Module "I". <br /> Surface water was not sampled this semester. <br /> I certify under penalty of law that I have personally examined and am familiar with the information <br /> submitted in this document and all attachments and that, based on my inquiry of those individuals <br /> immediately responsible for obtaining the information, I believe that the information is true, <br /> accurate, and complete. I am aware that there are significant penalties for submitting false <br /> information, including the possibility of fine and imprisonment. <br /> If you have any questions, please call me at (209) 468-8504. <br /> Sincerely, �9 <br /> W. MICHAEL CARROLL, PE <br /> Senior Civil Engineer <br /> WMC:kb <br /> CAAA SanJoaquin\FH2ndSem061etter.doc <br /> Enclosure <br /> Robert McClellon, Environmental Health Department <br /> LA 31610 <br />