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The County projects waste disposal assuming an average rate of approximately 3% per year; <br />however, disposal quantities are greatly affected by economic activity within the service area. <br />Disposal at the NCRC&SL in 2009 was nearly equal to disposal in 2008. Disposal decreased by <br />approximately 15% from 2007 to 2008. <br />2.3 WASTE DECOMPOSITION PROCESS AND WASTE BY-PRODUCTS <br />Municipal solids wastes placed in the NCRC&SL will undergo natural chemical and biological <br />decomposition. The products of biological decomposition of organic wastes are solids, liquids, <br />and gases. <br />Decomposition begins with organic waste products undergoing aerobic (in the presence of free <br />oxygen) decomposition during storage and transport, and for a limited period after placement in <br />the landfill. Aerobic decomposition continues until available oxygen is depleted, after which <br />anaerobic (lacking oxygen) decomposition becomes dominant and proceeds until the biological <br />material is decomposed. Anaerobic decomposition produces landfill gas (LFG) which is <br />approximately 50% methane and carbon dioxide with other trace components. <br />LFG production will continue for a few years to hundreds of years, depending on conditions. The <br />rate of gas production depends on a number of factors, including refuse composition, oxygen <br />present, moisture content, pH, alkalinity, and temperature. <br />At NCRC&SL, contributions of moisture from outside sources to the waste mass will be limited <br />because: <br />• Precipitation is low <br />• Surface water management consists of diverting surface water run-on away from active <br />areas of the landfill; <br />• Daily cover limits infiltration of precipitation that falls directly onto the landfill; <br />• A final cover will be constructed over all fill areas which will minimize infiltration into the <br />waste mass; and <br />• Landfill staff periodically inspects the cover on filled modules for low spots that could allow <br />0 ponding water. <br />North County RC&SL Page 7 of 69 Public Works/Solid Waste <br />Joint Technical Document County of San Joaquin — February 10, 2010 <br />