15-4 Performance tests used to measure properties of synthetic geomembrane liners and typical values for these properties Test method Typical values ASTM D638, type IV: th at vie 2400|b/n2 Tensile strength at break Elongation at break Toughness Tear resistance initiation ASTM D1004 die C 45|b Puncture resistanc FTMS 101B. method 2031 Low temperature ASTM D746, procedure B 94°F ASTM D1603 Carbon black dispersion ASTM D3015 Accelerated heat aging ASTM D 573. D1349 egligible strength change after1 month at110°c Chemical resistance esistance to chemical EPA method 9090 change 120 days Resistance to pure ASTM D543 10% tensile strength change chemical reagents over 7 days Stress cracking resistance ASTM D1693 condition C 1500h "Adapted from Refs. 2, 52. In the liner system shown, two composite liners, commonly identified as the primary and secondary composite liners, are The primary composite liner is used for the collection of leachate, whereas the secondary composite liner serves as a teak-detection system and a backup for the primary composite liner. A modification of the liner system, involves replacing the sand drainage layer with a geonet drainage system. A manufactured product, the gCl is made from a high-quality bentonite clay(from Wyoming) and an appropriate binding material. The bentonite clay is essentially a sodium montmorillonite mineral that has the capacity to absorb as much as 10 times its weight in water. As the clay absorbs water, it becomes putty-like and very resistant to the movement of water Permeabilities aslow as 10-0 cm/s have been observed. Available in large sheets(12 to 14 by 100 ft), GCLs are overlapped in the construction of a liner system. In the two-layer composite layer landfill systems through f, leak-detection sensors are usually placed between the two liners Liner Systems for Monofills. Liner systems for monofils usually comprise two geomembranes, each provided with a drainage layer and a leachate collection system. A leachate detection system is placed between the first and second liners as well as below the lower liner. In many installations, a thick (3 to 5 ft )clay layer is used below the two geomembranes for added protection Construction of Clay Liners. Great care must be exercised in the construction of the clay layer. Perhaps the most serious problem with the use of clay is its tendency to form cracks due to desiccation. It is critical that the clay not be allowed to dry out as it is being placed. To insure that the clay liner performs as designed, the clay liner should be laid in 15- to 6-in layers with adequate compaction between the placement of succeeding layers. Laying the clay in thin layers avoids the possibility of leaks due to the alignment of clods that could occur if the clay layer is applied in a single pass. Another problem that has been encountered when clays of different types have been used is cracking due to differential swelling To avoid differential swelling only one type of clay must be used in the construction of the liner Leachate Collection Systems The design of a leachate collection system involves(1) the selection of the type of liner system to be used,(2)the development of the grading plan including the placement of the leachate collection and drainage channels and pipelines for the removal of leachate, and (3)the layout and design of the leachate removal, collection, and holding facilities13 In the liner system shown, two composite liners, commonly identified as the primary and secondary composite liners, are used. The primary composite liner is used for the collection of leachate, whereas the secondary composite liner serves as a teak-detection system and a backup for the primary composite liner. A modification of the liner system, involves replacing the sand drainage layer with a geonet drainage system. A manufactured product, the GCL is made from a high-quality bentonite clay (from Wyoming) and an appropriate binding material. The bentonite clay is essentially a sodium montmorillonite mineral that has the capacity to absorb as much as 10 times its weight in water. As the clay absorbs water, it becomes putty-like and very resistant to the movement of water. Permeabilities aslow as l0 -10 cm/s have been observed. Available in large sheets (12 to 14 by 100 ft), GCLs are overlapped in the construction of a liner system.. In the two-layer composite layer landfill systems through f, leak-detection sensors are usually placed between the two liners. Liner Systems for Monofills. Liner systems for monofills usually comprise two geomembranes, each provided with a drainage layer and a leachate collection system. A leachate detection system is placed between the first and second liners as well as below the lower liner. In many installations, a thick (3 to 5 ft) clay layer is used below the two geomembranes for added protection. Construction of Clay Liners. Great care must be exercised in the construction of the clay layer. Perhaps the most serious problem with the use of clay is its tendency to form cracks due to desiccation. It is critical that the clay not be allowed to dry out as it is being placed. To insure that the clay liner performs as designed, the clay liner should be laid in 15- to 6-in layers with adequate compaction between the placement of succeeding layers. Laying the clay in thin layers avoids the possibility of leaks due to the alignment of clods that could occur if the clay layer is applied in a single pass. Another problem that has been encountered when clays of different types have been used is cracking due to differential swelling. To avoid differential swelling only one type of clay must be used in the construction of the liner. Leachate Collection Systems The design of a leachate collection system involves (1) the selection of the type of liner system to be used, (2) the development of the grading plan including the placement of the leachate collection and drainage channels and pipelines for the removal of leachate, and (3) the layout and design of the leachate removal, collection, and holding facilities. 15-4