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7.11. Landfill GasGAS- (LFG) Surface Emissions Control MANAGEMENT PLAN <br />Municipal solid wastes placed in the Foothill landfill will undergo natural chemical and biological <br />decomposition following disposal The products of biological decomposition of organic wastes <br />are solids, liquids, and gases. <br />The waste decomposition process begins with organic waste products undergoing aerobic <br />(presence of free oxygen) decomposition during storage and transport and for a limited period <br />after placement in the landfill. Aerobic decomposition continues until available oxygen is <br />depleted. When oxygen is depleted, anaerobic (lack of oxygen) decomposition becomes <br />dominant. <br />Typical byproducts of aerobic decomposition of MSW are carbon dioxide water, and nitrate <br />Typical primary products of anaerobic decomposition are methane carbon dioxide organic <br />acids, nitrogen, ammonia, iron sulfides, manganese, and hydrogen. These products are the <br />Primary factors controlling the quality and quantity of leachate and landfill gas produced <br />Methane in the gas may range from 50% to 60% and carbon dioxide may range from 30% to <br />50% (Boyle, 1977). <br />Methane production from MSW will continue from a few years to hundreds of years in certain <br />environments. The rate of gas production depends on a number of parameters: refuse <br />composition, oxygen present, moisture content pH alkalinity, and temperature <br />LFG Surface emissions are monitored by a "surface scan" in which the methane content of the <br />air immediately above the landfill is measure in accordance with Title V regulations and the <br />Permit to Operate (Appendix A). This measurement indicates that surface emissions are within <br />the regulatory limit. <br />Surface emissions are controlled by the LFG collection and treatment system Figure Xx15) <br />This system consists of nine vertical wells and four horizontal collectors each of which is <br />Foothill Sanitary Landfill Page 88 Public Works/Solid Waste <br />Joint Technical Document �_ County of San Joaquin — Revised 7/30/10 <br />