Landfill caps can be used to:

* Reduce exposure on the surface of the rubbish landfill.
* Inhibit vertical penetration of water into wastes that would create contaminated leachate.
* Contain waste whilst treatment is being applied.
* Manage gas emissions from underlying rubbish.
* Generate a soil surface so as to sustain plant life and/or exist for other purposes.

Landfill Capping is the most common form of remediation because it is normally less expensive than other technologies and effectively manages the human being and ecological risks allied with a remediation site.

The design of landfill caps is location specific plus depends on the proposed functions of the system. Landfill Caps can range from a one-layer system of vegetated soil to a multifaceted multi-deposit technique of soils and geosynthetics. In general, less complex systems are necessary in waterless climates and more complicated systems are essential in damp climates. The material used during the building of landfill caps involve low-permeability and high-permeability soils and low-permeability geosynthetic products. The low-permeability materials redirect water and prevent its passageway into the rubbish. The high permeability materials convey water away that percolates into the cap. Added supplies may possibly be used to augment slope stability.

The most critical components of a landfill cap are the barrier layer and the drainage layer. The barrier layer can be low-permeability soil (clay) and/or geosynthetic clay liners (GCLs). A flexible geomembrane liner is placed on top of the barrier layer. Geomembranes are usually supplied in large rolls and are available in several thickness (20 to 140 mil), widths (15 to 100 ft), and lengths (180 to 840 ft). The candidate list of polymers commonly used is lengthy, which includes polyvinyl chloride (PVC), polyethylenes of various densities, reinforced chlorosulfonated polyethylene (CSPE-R), polypropylene, ethylene interpolymer alloy (EIA), and many newcomers. Soils used as barrier materials generally are clays that are compacted to a hydraulic conductivity no greater than 1 x 10-6 cm/sec. Compacted soil barriers are generally installed in 6-inch minimum lifts to achieve a thickness of 2 feet or more. A composite barrier uses both soil and a geomembrane, taking benefit of the properties of each one. The geomembrane is really impermeable, nevertheless, if it develops a escape, the soil component prevents major escape into the underlying garbage.

For amenities lying on putrescible wastes, the gathering and control of methane and carbon dioxide, strong greenhouse gases, must be part of facility design and operation.