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• C Ms_ Christina Carbaial April 24, 2006 Page 2 The gases produced in a landfill will either vent vertically to the atmosphere or migrate horizontally through subsurface soil to locations on adjacent properties. If the soil surrounding a landfill. consists of permeable materials, there is a greater likelihood that the LFG will migrate to off-site locations. If the methane gas component of LFG is allowed to accumulate in a confined.area(i.e.,utility lines, irrigation valve boxes,vaults,basements,wall spaces, etc.) and is exposed to an ignition source, it can be explosive at concentrations between 5 and 15 percent by volume. At higher concentrations,rnethane gas is flammable. However,the presence of methane gas i.n site soil does not mean there is an immediate threat of explosion because flames cannot typically propagate through soil. ® eration Criteria. -- The most current'Permits to Construct/Operate dated July 22,2002 and October 8,2002, tissued by the San Joaquin:.Valley Unified Air Pollution Control District(SJVUAPCD) delineates several main operational,criteria for the subject system. This operational criteria states that flare exit gas temperature be maintained at a minimum of 1400 degrees Fahrenheit during system operation. In addition the systems are to be operated to maintain compliance with SJVUAPCD Title V and Rule 4642 requirements. State California.Code of Regulations (CCR Title 27)requires that solidwaste disposal. site ownersloperators implement LFG control or monitoring provisions to ensure that methane gas concentrations in soil at the property line do not exceed the lower explosive limit(LET.,, or 5 percent by volume) and that interiors of on-site structures do not exceed 1.25 percent methane by volume in air. Gas Testing Testing for methane gas (the combustible component of LFG), oxygen gas, carbon dioxide gas, pressure, and temperature was performed using a Landtec Gem-5010 Gas Analyzer or comparable unit. This instrument measures combustible gas concentrations in air directly on.either of two scales: the first as percent by volume of the lower explosive limit (.LEL)of methane gas in air(5 percent)- the second as percent by volume(0 to 100 percent) in the gas sampled. Instrument calibration forms are attached to this report. LFG Monitoring Probes Tn accordance with the approved testing schedule, LFG Monitoring Probes(GP) are to be tested quarterly or when methane gas concentrations detected exceed. 5 percent by volume_ During this reporting period, all perimeter LFG monitoring probes defined as Nos. l through 25 were tested. .for the presence of LFG. Results indicated that no methane gas concentrations. in excess of 5