Upon closure, landfills must be capped

The specific requirements for permanent sealing systems for Class I (inert waste), II (municipal solid, non­hazardous waste) and III (hazardous waste) landfills are typically outlined in the national regulations.

High safety requirements are imposed on all components of the sealing system. Each geosynthetic should typically be approved by the federal authority or a national agency. Part of the approval process should show, in testing data, that sealing system components can provide at least 100 years of service life.

Additionally, interest in potential redevelopment of a former landfill has grown substantially, making the closure controls even more important. Geosynthetic capping systems provide a safe, cost­effective, environmentally sound solution for repeatable, high­quality seals.

Surface sealing of Class I landfills typically needs only a single geosynthetic component, such as a geomembrane or geosynthetic clay liner. This underscores the performance quality of and trust in these materials.

According to several national and international landfill regulations, e.g. the European Landfill Directive, Class II designs must have two sealing components. These elements must check one another, so they must be of different compositions. The combination of a geosynthetic clay liner (GCL) with a geomembrane is a safe, qualifying, well established and recognized approach for successful, longterm designs.

To achieve a better ecological, economical and performance­related GCL for landfill applications a multi­component Bentofix® GCL with an impermeable polyethylene coating can be used in a landfill cap. It helps make GCL installations even more effective, safer and longer lasting as two barrier systems are installed in one step. The multi-component Bentofix GCL improves the overall performance and reduces the risks of a single lining system.

Landfill capping solutions

Carbofol® HDPE geomembranes are used with BAM approval or other national approvals in Class 1-rated landfills (inert waste) as the sole sealing element. In Class II (municipal solid waste; non-hazardous waste) and III landfills (hazardous waste), Carbofol® is used in combination with a mineral/clay layer (e.g. compacted clay liner). This geomembrane meets the stringent chemical and physical requirements that are necessary for a safe, long-life-designed landfill. The surface of Carbofol® is smooth (for slopes up to about 1:9) or homogeneously structured/textured (for steeper slopes). This solution provides a strong barrier against rainwater infiltration and methane migration.

Bentofix® geosynthetic clay liners (GCL) are composite materials made of two layers of geotextile that encapsulate a core of highly swellable powder sodium bentonite. The three layers are needle-punched together very densely and throughly, and the fibers are anchored (“Thermal Lock”) in the bottom geotextile. Needle-punching of the geotextile in manufacturing and a proprietary Thermal Lock process firmly bond the geotextile fibres across the entire surface of the materials. This prevents bentonite erosion and increases the durability of the material. Bentofix® GCLs replace thicker, more complex-to-construct, traditional mineral seals. The geosynthetic approach provides a barrier that is more resistant to desiccation and self-seals against installation damage. The internal shear strength and frictional characteristics of Bentofix® are also sufficient for steeper slopes.