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. Technically equivalent cost-efficient alternatives can be obtained with complete geosynthetic solutions from NAUE.

Sealing

Multi-directional 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 be haviour, Bentofix® needle-punched GCLs retain their sealing capability under the high elongation, differential settlement conditions of landfill capping systems. Steep slope applications up to 2.5h: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 base linings. Carbofol® HDPE geomembranes have been success fully tested for their resistance to many chemical environments and are considered suitable for landfill sealing systems in covers and caps.

Structured Carbofol® geomembranes are used to increase shear force transmission between the adjacent components under more challenging conditions to ensure long-term slope stability.

Protection

Geomembranes must be protected from mechanical damage caused by the cover material or any underlying source.

When using a mineral drainage layer the Secutex® PP nonwovens are often installed rather than a sand protection layer. To avoid significant geomembrane defor mation during the installation and to ensure long-term protection, Secutex® nonwoven geotextile with a minimum mass per unit area of 800 g/m² is recommended.

When used in combination with Carbofol® geomembrane, Secudrain® geosynthetic drainage systems not only fulfill the filter and drainage function, but also act as a protection layer for the geomembrane. The Secudrain® protection and drainage system also prevents deformation in the Carbofol® geomembrane.

Drainage

In landfill caps, Secudrain® drainage systems can effectively transmit and direct the perculated percolated rainwater to a collection or drainage pipe. 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 – synthetic core transmits the water

3. Filter/protection nonwoven – serves as a filter or separation layer to the mineral component or as a protection layer for the geomembrane

The composite bonding of the three layers into one product 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.

The stable structure of the core layer provides the long-term drainage performance of Secudrain®.

Secudrain® can also be used as the gas venting and protection layer beneath the liner in capping systems.

Design cross sections

Filtration and separation

Needle-punched bonded Secutex® nonwoven filter geotextiles prevent
the passage of soil particles from the vegetation layer into the
drainage layer.

The requirements on the filtration and separation layer are described
in the recommendations of the geotechnics of landfills and contaminated
sites working group (GDA).

Above all, the long-term permittivity of the geotextile fil tration
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 Guide
line of the German Re search Association for Roads and Traffic (FGSV)
and by using a geotextile of at least a Class 3 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 lengthy
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 (60 mil) Carbofol® HDPE geomembranes are ideal for this
application. They show excellent chemical as well asand UV resistance
and can withstand the robust challenging weathering conditions of these
areas.

Conclusion

Complete geosynthetic solutions from NAUE can be employed to address
the site-specific requirements of your project. The geosynthetic
products of NAUE are produced to the highest quality standards. Products
certified by government regulators are available for single-layered and
multi-layered liner systems.

Carbofol® geomembranes and Bentofix® geosynthetic clay liners in
combination with Secudrain® drainage systems, Secugrid® geo grids as
well as Secu tex® protection layers, provide high- quality and,
cost-efficient solutions to for the most demanding applications.