Final cover system Bench(terrace) as required Final cel Fina 3: 1 typical slope 6 in intermediate variable andfill liner system Sectional view through a sanitary landfill a lifi is a complete laver of cells over the active area of the landfill(see Fig 15-1) ally. landfills are comprised of a series of lifts. A bench (or terrace) is co will exceed 50 to 75 ft. Benches are used to maintain the slope stability of the landfill. for of surface water drainage channels, and for the location of landfill gas recovery piping. The final lift includes the cover laver. The final cover laver is applied to the entire landfill surface after all landfilling materials designed to enhance surface drainage, intercept percolating water. and support surface The liquid that collects at the bottom of a landfill is known as leachate. In deep landfills, leachate is often collected at intermediate points. In general, leachate is a result of the percolation of precipitation. uncontrolled runoff. and irrigation water into the landfill leachate can also include water initially ell as infiltrating groundwater. Leachate contains a variety of chemical constituents derived from the solubilization of the materials deposited in the landfill and from the products of the chemical and biochemical reactions occurring within the landfill Landfill gas is the mixture of gases found within a landfill. The bulk of landfill gas consists of methane (CHa)and carbon dioxide (COz), the principal products of the anaerobic decomposition of the biodegradable organic fraction of the msw in the landfill. Other components of landfill gas include atmospheric nitrogen and oxygen, ammonia, and trace organic compounds Landfill liners are materials(both natural and manufactured) that are used to line the bottom area and below-grade sides of a landfill. Liners usually consist of layers of compacted clay and/or geomembrane material designed to prevent migration of landfill leachate and landfill gas. Landfill control facilities include liners, landfill leachate collection and extraction systems, landfill gas collection and extraction systems, and daily and final cover layers Environmental monitoring involves the activities, associated with collection and analysis of water and r samples, that are used to monitor the movement of landfill gases and leachate at the landfill site Landfill closure is the term used to describe the steps that must be taken to close and secure a landfill site once the filling operation has been completed. Postclosure care refers to the activities associated with the long-term monitoring and maintenance of the completed landfill (typically 30 to 50 years) Overview of Landfill Planning, Design, and Operation. The principal elements that must be considered in The planning design, and operation of landfills include(1) landfill layout and design; (2) landfill operations and management;(3) the reactions occurring in landfills; (4)the management of landfill gases; (5)the management of leachate;(6)environmental monitoring; and (7 landfill clo and postclosure care Preparation of the site for landfilling The first step in the process involves the preparation of the site for landfill construction Existing site drainage must be modified to route any runoff away from the intended landfill area. rerouting of2 A lift is a complete layer of cells over the active area of the landfill (see Fig. 15-1). Typically, landfills are comprised of a series of lifts. A bench (or terrace) is commonly used where the height of the landfill will exceed 50 to 75 ft. Benches are used to maintain the slope stability of the landfill, for the placement of surface water drainage channels, and for the location of landfill gas recovery piping. The final lift includes the cover layer. The final cover layer is applied to the entire landfill surface after all landfilling operations are complete. The final cover usually consists of multiple layers of soil and/or geomembrane materials designed to enhance surface drainage, intercept percolating water, and support surface vegetation. The liquid that collects at the bottom of a landfill is known as leachate. In deep landfills, leachate is often collected at intermediate points. In general, leachate is a result of the percolation of precipitation, uncontrolled runoff, and irrigation water into the landfill. Leachate can also include water initially contained in the waste as well as infiltrating groundwater. Leachate contains a variety of chemical constituents derived from the solubilization of the materials deposited in the landfill and from the products of the chemical and biochemical reactions occurring within the landfill. Landfill gas is the mixture of gases found within a landfill. The bulk of landfill gas consists of methane (CH4) and carbon dioxide (CO2), the principal products of the anaerobic decomposition of the biodegradable organic fraction of the MSW in the landfill. Other components of landfill gas include atmospheric nitrogen and oxygen, ammonia, and trace organic compounds. Landfill liners are materials (both natural and manufactured) that are used to line the bottom area and below-grade sides of a landfill. Liners usually consist of layers of compacted clay and/or geomembrane material designed to prevent migration of landfill leachate and landfill gas. Landfill control facilities include liners, landfill leachate collection and extraction systems, landfill gas collection and extraction systems, and daily and final cover layers. Environmental monitoring involves the activities, associated with collection and analysis of water and air samples, that are used to monitor the movement of landfill gases and leachate at the landfill site. Landfill closure is the term used to describe the steps that must be taken to close and secure a landfill site once the filling operation has been completed. Postclosure care refers to the activities associated with the long-term monitoring and maintenance of the completed landfill (typically 30 to 50 years). Overview of Landfill Planning, Design, and Operation. The principal elements that must be considered in The planning, design, and operation of landfills include (1) landfill layout and design; (2) landfill operations and management; (3) the reactions occurring in landfills; (4) the management of landfill gases; (5) the management of leachate; (6) environmental monitoring; and (7) landfill closure and postclosure care. Preparation of the site for landfilling. The first step in the process involves the preparation of the site for landfill construction. Existing site drainage must be modified to route any runoff away from the intended landfill area. Rerouting of Fig. 15-1 Sectional view through a sanitary landfill. Fig 15-1