Landfill cap functions

Typically, a drainage layer is required for all major landfill classes (I, II, and III). This layer sheds precipitation directly, to avoid the buildup of a hydraulic 

head on the capping system.  The drainage layer must be permanently protected against clogging from the cover layer’s soil particles.  

Drainage geocomposites with three­dimensional matrices and filter geotextile cover layers control seepage and properly designed fulfil 

design requirements in landfill caps.

Geosynthetic drainage systems of this nature are sufficiently protected against the damage risk posed by cover soil installation.  

This enables the geosynthetic system to ensure the requisite long­term drainage function.

When installing a mineral drainage layer over a geosynthetic seal, a needle­punched

nonwoven geotextile can replace the otherwise necessary sand protective layer atop a geomembrane.  In these situations, one should also evaluate whether 

a filter/separation geotextile would be an optimal solution between the drainage layer and cover soil.

In landfill closure projects, it is increasingly important to utilise steeper slopes to minimize the soil­disturbing footprint of the site.  The multi­layer nature of 

sealing systems, however, complicates this space­saving goal.  It represents a particular challenge to the shear strength between layers.  Here, textured 

geomembranes provide enhanced frictional characteristics for slope stability.  Additionally, geogrids can be used to enable cost­effective, safe engineering of 

steeper slopes.