The cover technique actually uses to its advantage the high water storage capacity of fine grained soils to retain water in the soil above the waste and refuse. The water is "stored" in that layer until it is released back into the atmosphere either through evaporation from the soil or transpiration from the native vegetation that is planted on the surface (EPA 2). One of the only limitations of the evapotranspiration cover is its inability to function adequately outside of arid and semi-arid environments. Only there can the refuse be covered in a reasonable amount of soil with a storage capacity great enough to manage and store the water that will enter the soil at the landfill site. In humid climates, or ones with higher annual rainfalls, evapotranspiration is not as functional as a landfill cover (Albright et al. 75).
Whereas evapotranspiration covers have not been as effective in wetter climates, geomembranes are nearly as effective as evapotranspiration covers, but can function in essentially any climate (Albright et al. 75). This is an important feature in a landfill cover, because obviously many landfills in the United States will be built in the humid Southeast or the rainy Northwest. Landfill cover systems must be developed for those regions as well in order to protect the environment from contamination and human health from pollutants. In those places that evapotranspiration covers would be ineffective, geomembranes offer a useful alternative. They consist, basically, of a layer of synthetic material -- generally a plastic of some kind -- that diverts water around and away from the refuse site. In combination with compacted clay and, sometimes, surface vegetation, geomembranes are functional alternatives to conventional landfill covers.
But, of course, these are not the only alternatives available. Research is being conducted into more exotic and unexpected landfill cover systems, whose effectiveness is less certain though nonetheless promising. Research into the use of anaerobically digested lime-stabilized wastewater sludge and soil as a cover for landfills produced surprisingly positive results. The researchers found that, in fact, the cover method had no negative effect on the landfill and produced no leached contaminants more significant than those produced from a clay compacted, conventional cover. The true potential of this cover type is in its extreme cost effectiveness, the fact that it could serve as an outlet for lime waste, and the sludge actually enhances and hastens natural decomposition of the landfill waste (Rhew and Barlaz 499). While it might seem a bit unconventional, perhaps too alternative, to simply dump sludge on top of a landfill as a cover method, there is every indication that it could be a successful remediation strategy as an alternative cover.
Another promising, albeit equally alternative method, is the use of cellulose material as a cover. Though actually forbidden by regulation in some places, there is research to suggest that cellulose covers could provide reasonable protection and sequestration of landfill contaminants. In the case of a recent study, researchers examined the effects of covering a landfill with waste cellulose material produced during the paper recycling process (Panarotto et al. 123). The researchers found, amazingly, that this cover method had no negative effects on the hydraulic or geomechanical requirements of a basic landfill cover. In other words, a cellulose cover of waste paper product performed as well as a landfill...
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