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• and liquids from the waste prism to prevent migration of contaminants to the vadose zone <br /> or groundwater. Examples for passive source controls include landfill cover systems, lateral <br /> barriers, surface water drainage structures, and erosion controls devices. These passive <br /> controls generally act to minimize the amount of surface water that could enter the waste <br /> prism and stimulate the generation of leachate or landfill gas. <br /> 3.2.1 Landfill Cover System <br /> The CHSL is presently fitted with a Title-27-compliant final cover system, a robust LFG <br /> extraction and destruction system, and adequate surface water and erosion controls. <br /> However, as described in Section 2.1.3, a small (about 1.3 acres) segment of waste outside <br /> of the final closure footprint was discovered at the north end of the site. Additional source <br /> controls considered in this evaluation address this portion of the landfill. <br /> Construction of a prescriptive final cover system was completed in 1995, covering the extent <br /> of refuse as it was known at that time. As previously stated, approximately 1.3-acres of <br /> waste was not included in the site closure. Closure of this segment of waste is planned to <br /> begin in May 2013. The expanded final cover system will minimize the amount of <br /> precipitation that infiltrates into this segment of the waste prism. The decrease in moisture <br /> to the waste may result in a decrease in landfill gas generation over time. Enclosure of the <br /> refuse with impermeable geomembrane may create anaerobic conditions at locations that <br /> are now aerobic, which could result in an increase in landfill gas production. <br /> Geosynthetic and geosynthetic-monolithic hybrid final cover systems work well in a wide <br /> variety of climates, with slope stability being the most significant limiting factor on the use of <br /> these types of final cover systems. <br /> The proposed design for the final cover extension will include the following elements: <br /> • A two-foot thick foundation layer; <br /> • A 60-mil linear low density polyethylene (LLDPE) geomembrane; <br /> • A geocomposite drainage fabric; and <br /> • A two-foot thick select soil cover layer. <br /> 3.2.2 Landfill Gas Control <br /> The present active control system will be expanded as part of the closure project. Two <br /> additional landfill gas wells are planned for the geomembrane-covered refuse. <br /> Engineering Feasibility Study Geo-Lo <br /> January <br /> Page ■ 9 <br /> Corral Hollow Sanitary Landfill <br /> January 25,2013 ASSOCIATES <br />