The US Environmental Protection Agency (EPA) Federal Regulations and the European Council Directive on the Landfill of Waste describe prescriptive cross sections for hazardous and non-hazardous waste landfill cover systems. These systems are designed to prevent the intrusion of precipitation into the waste or the release of landfill gas from the waste.
Multidirectional shear strength transmitting Bentofix® needle-punched GCLs can replace difficult to build compacted clay liners (CCLs) in non-hazardous as well as in hazardous landfill cover systems. Due to their excellent multi-axial strain behaviour, Bentofix® needle-punched GCLs retain their sealing capability under high elongation, differential settlement conditions. Steep slope applications up to 2h:1v are possible with needle-punched nonwovens as the carrier and cover components of Bentofix®.
The physical requirements and chemical resistance of geomembranes for landfills are comparable to those needed in landfill basal linings. Carbofol® HDPE geomembranes are considered suitable for landfill sealing systems in covers and caps.
Structured or textured Carbofol® geomembranes are used to increase shear force transmission between the adjacent components under more challenging conditions to ensure long-term stability.
Protection
Geomembranes must be protected from mechanical damage from the cover material or any underlying source.
When using a mineral drainage layer the mechanically bonded Secutex® PP nonwovens are often installed rather than a sand protection layer. To avoid significant geomembrane deformation during installation and to ensure long-term protection, Secutex® nonwoven geotextiles with a minimum mass per unit area of 800 g/m2 are recommended.
Drainage
In landfill caps, Secudrain® drainage systems can effectively transmit and direct the perculated rainwater or gas to a collection or drainage point. Proper drainage minimises the standing water build-up on the sealing element, increases liner efficiency and improves the capping system stability.
Secudrain® geosynthetic drainage systems consist of three individual layers made of the following components:
1. filter nonwoven - protects the drainage layer from clogging,
2. drainage layer - collects and drains the water,
3. filter/protection nonwoven - serves as filter or separation layer to the mineral component or the protection layer for the geomembrane.
The composite welding of the three layers into one ensures the uniform shear force transmission within the drainage system. Due to of the uniform bonding, Secudrain® is also suitable for the use in steep slopes.
Filtration and separation Needle-punched bonded nonwoven filter geotextiles prevent the passage of soil particles from the vegetation layer into the drainage layer. Above all, the long-term permittivity of the geotextile filtration layer must be ensured to prevent the pressure build-up above the drainage layer that could compromise the liner system stability. With hydraulic and mechanical filter properties defined by the Guideline of the Research Association for Roads and Traffic and by using a geotextile of at least robustness class 3, the long-term efficiency of the geotextile filter is ensured.
Reinforcement
Secugrid® is a geogrid made of flat extruded monolithic bars welded at their junctions. It can withstand high installation loads or support large forces when low deformation is required. On steep or long slopes, Secugrid® geogrids can be used to improve the stability of soil veneers or entire lining systems. Secugrid® geogrids also allow steeper walls and slopes to be constructed.
Covering during operation
Temporary covers, which are installed during landfill operations, can minimise precipitation infiltration and reduce gas emissions, when applied prior to the final or temporary seal. 1.5 mm thick Carbofol® HDPE geomembranes are ideal for this application. They show excellent chemical as well as UV resistance and can withstand the robust weathering conditions of these areas.
Conclusion:
Carbofol® geomembranes and Bentofix® geosynthetic clay liners in combination with Secudrain® drainage systems, Secugrid® geogrids as well as Secutex® protection layers, permit high quality and cost-efficient solutions to the most demanding landfill applications.
Landfills
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