Compacted clay liner

The U.S. EPA guidance6 discusses three types of liners FMLs, compacted clay liners (CCLs), and composite liner systems (an FML overlying a compacted low-permeability soil layer). Material specifications in the guidance for FMLs and CCLs are briefly reviewed below, along with regulations regarding all three liner systems. 

In landfills, the presence of a compacted clay liner has been thought to be an adequate barrier for the transport of leachates out of the impounded area however, organic solvents and petroleum products, which are typical constituents of landfills that have accepted industrial and chemical processing wastes, have been shown to permeate clays at much faster rates than do aqueous solutions (Brown and Thomas,... 

Borrow source/quarry Compacted clay liner (CCL)... 

Compacted soil liners also are cormnonly referred to as compacted clay liners (CCLs) because only soils that contain a sufficient amormt of clay can provide the suitably low saturated hydrattlic conductivity typically required for contaimnent applications (e.g.,/ sat < 10 m/sec).The primary purposes of compacting a source clay for use as a liner material are to reduce the saturated hydraulic conductivity by densifying the clay (i.e., reducing the pore sizes) and to destroy any small secondary defects (e.g., fissures or cracks) that may act as conduits for flow in the natural soil formation. 

General requirement for clay liners The permeability of a re-molded clay is influenced by a number of factors, the key ones being plasticity, density, moisture content during compaction and method of compaction. Although the detailed requirements for compacted clay liners (CCLs) vary, the following parameters usually apply ... 

Compacted clay liner 0.1-3 Strongly varying with soil properties (Scherbeck and Jessberger 1992)... 

The aforementioned can be summed up as follows far larger settlements are permissible over the long term for the HDPE geomembranes than for nearly all other liners components, in particular for compacted clay liners or asphaltic concrete liners. Geomembranes must, however, be reliably protected from penetrative deformations with small radii of curvature, such as those due to pieces of gravel. Types, appropriate design and tests of protective layers will be dealt with in Chap. 8. 

Data about the imperviousness of a faultless liner system under defined boundary conditions for as large a number of pollutants and soil materials as possible form an important component of the characterisation of the efficacy of this liner for instance in comparison to equivalent alternative liner systems. Therefore, in the following, a parameterization will be discussed for the permeation rate (or the permeability) and the induction time for diffusive mass transport in the composite liner consisting of a geomembrane and a compacted clay liner (or more generally a porous mineral material). Quantities, which refer to the geomembranes, will be denoted with index 1, such as thickness d and diffusion coefficient D, and quantities referring to the mineral liner will have index 2 such as thickness d2 and effective diffusion coefficient D2. The porosity of the water-saturated mineral liner is denoted with 0 as above. 

For Landfill Class I (disposal of mineral or mineralised wastes with low contamination) and for conventional landfills for demolition waste, excavated soil etc. only a compacted clay liner is required. The system components for class I and II cappings, being the most common types nowadays installed in Germany, are listed in Table 9.1. Guidelines with strict requirements for materials selection and testing, construction technique and quality control were published for the standard systems (Muller 1996 Muller 2001 N.N. 1993). 

Fig. 11.3. A groove is milled into the surface of a compacted clay liner into which the sensor cable is laid. The extent of preparatory work on the subgrade of the geomembrane depends highly on the subgrade properties. In any case one has to meet the requirement, that indentations imprinted on the geomembrane by the cable and electrodes have to fall short of the acceptable limits (see Sect. 8.3.1)...

Jessberger, H. L. 1995. Waste containment with compacted clay liners. Proceedings of the International Conference on The Geoenvironment 2000. ASCE Special Publication, 46, 463-483. 

Compacted clay liners Bentonite clay liner Geosynthetic clay liners Composite clay liners... 

Fang, H. Y. Evans, J. C. 1988. Long term permeability tests using leachate on a compacted clay liner material. Ground Water Contamination Field Methods, ASTM STP 963, 397-404. 

Figure 19.1 Use of geotextiles in waste containment liner systems from bottom to top Compacted Clay Liner (CCL), Geosynthetic Clay Liner (GCL), Geogrid (GG), Geomembrane (GM), Geotextile-Geonet Geocomposite (GC), Geonet (GN), Geotextile (GT), Geopipe (GP). GSI Institute.

The base liner in modem waste containment facilities is typically a double-composite liner system. Double-composite liner systems are used to contain municipal solid waste and are required for waste containment facilities designed to contain hazardous waste. The primary liner system of a double-composite liner system typically includes a geomembrane and a geocomposite clay liner as the primary barrier layer and a geomembrane underlain by a compacted clay liner composite as the secondary barrier layer. 

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