17.7 Single Clay Liner and Single Geomembrane Liner Systems ▶ Single clay liners - until about 1982, most landfill liners - thickness : 0.9m to 1.8m - hydraulic conductivity : ▶ Single geomembrane liners – Around 1982

17.7 Single Clay Liner and Single Geomembrane Liner Systems

17.8 Recent Advances in the Liner Systems for Land fills ▶ Since 1984, most landfills developed for solid and hazardous wastes have double liners. The two liners are an upper primary liner and a lower secondary liner. ▶ Between the primary and secondary liners is a system for leak detection, collection, and removal (LDCR) of leachates.

17.8 Recent Advances in the Liner Systems for Land fills   ▶The geomembranes used for landfill lining must have a minimum thickness of 0.76mm, however, all geomembranes that have a thickness of 0.76mm may not be suitable in all situations. In practice, most geomembranes used as liners have thicknesses ranging from 1.8 to 2.54mm

17.8 Recent Advances in the Liner Systems for Land fills ▶ General guidelines for the primary leachate collection system and LDCR system : It can be a granular drainage layer or a geosynthetic drainage material such as a geonet. If a granular drainage layer is used, it should have a minimum thickness of 12 in. (0.3 m) The granular drainage layer (or the geosynthetic) should have a hydraulic conductivity, k, greater than 10-2 cm/sec. If a granular drainage layer is used, it should have a granular filter or a layer of geotextile over it to prevent clogging. A layer of geotextile is also required over the geonet when it is used as the drainage layer. The granular drainage layer, when used, must be chemically resistance to the waste material and the leachate that are produced. It should also have a network of perforated pipes to collect the leachate effectively and efficiently.

17.9 Leachate Removal Systems ▶ The bottom of a landfill must be properly graded (2% or more) so that the leachate collected from the primary collection system and the LDCR system will flow to a low point by gravity. ▶ Leachate removal system for primary system. Low-volume sump High-volume sump ▶ Leachate removal system for LDCR system Pumping Gravity

17.9 Leachate Removal Systems

17.9 Leachate Removal Systems

17.9 Leachate Removal Systems

17.9 Leachate Removal Systems

17.10 Closure of Landfills ▶ Cap will reduce and ultimately eliminate leachate generation. ▶ A schematic diagram of the layering system recommended by the U.S. Environmental Protection Agency and Koerner for hazardous waste landfills is Fig 17.17 ▶ Layering system consists : compacted clay cap geomembrane liner drainage layer cover of topsoil ▶ EPA recommends this period to be about 30 years

17.10 Closure of Landfills

17.10 Closure of Landfills

17.11 Summary and General Comments Selection of material Stability of side slope liner Leak response action plan