May 21, 2009

Landfill caps can be used to:

* Lessen exposure on the surface of the trash landfill.
* Inhibit vertical infiltration of water into wastes that would create contaminated leachate.
* Contain waste while treatment is being applied.
* Control gas emissions from underlying garbage.
* Generate a soil surface so as to support plants and/or exist for added purposes.

Landfill Capping is the most common manner of remediation as it is commonly less costly than other technologies and effectively manages the human and environmental risks coupled with a remediation place.

The strategy of landfill caps is location specific and depends on the intentional functions of the system. Landfill Caps can range from a one-layer system of vegetated top soil to a complicated multi-deposit technique of soils and geosynthetics. In general, less involved systems are necessary in dry climates and more intricate systems are required in wet weather climates. The fabric used during the assembly of landfill caps include low-permeability and high-permeability soils and low-permeability geosynthetic products. The low-permeability materials divert water and preclude its path into the garbage. The high permeability materials convey water away that percolates into the cap. Other materials could be used to enhance slope steadiness.

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 advantage of the properties of each. The geomembrane is in actual fact impermeable, however, if it develops a escape, the soil component prevents significant escape into the underlying trash.

For amenities on top of putrescible wastes, the gathering and manage of methane and carbon dioxide, potent greenhouse gases, must be part of facility design and operation.