Landfill

While landfills may outwardly appear simple, they need to operate carefully and follow specific guidelines that include where to start filling, wind direction, the type of equipment used, method of filling, roadways to and within the landfill, the angle of slope of each daily cell, controlling contact of the waste with groundwater, and the handling of equipment at the landfill site.

Considerations have to be made regarding the soil that is used as a daily cover, which is usually 6 in (15.2 cm) thick, an intermediate cover of 1 ft (30.5 cm), and a final cover of 2 ft (61 cm). The compacting of the solid waste and soil has to be considered as well, so that the biological processes of decomposition can take place properly.

Shredding of solid wastes is one method of saving space at landfills. Another method is baling of wastes. The advantages to shredding are twofold. The material can be compacted to a greater density, thereby extending the life of the landfill, and it can be compacted more quickly as well. Less cover is required and there is also less danger of spontaneous fire. Landfills using shredded materials produce more organic decomposition than those disposing of unshredded solid wastes. The advantages of baling are an increase in landfill life because of an increase in waste density. Hauling times are reduced, as are litter, dust, odor, fires, traffic, noise, earth moving, and land settling. Less heavy equipment is needed for the cover operation and the amount of time it takes for the land to stabilize is reduced. Using biodegradable materials also helps save space in landfills because microorganisms can break down these materials more quickly. Trash bags made of biodegradable materials are of particular use because microorganisms cause holes to form in the bags, allowing the material inside to break down more quickly as well.

When the secure landfill reaches capacity, it is capped by a cover of clay, plastic, and soil, much like the bottom layers. Vegetation is planted to stabilize the surface and make the site more attractive. Sump pumps collect any fluids that filter through the landfill either from rainwater or from waste leakage. This liquid is purified before it is released. Monitoring wells around the site ensure that the groundwater does not become contaminated. In some areas where the water table is particularly high, above-ground storage may be constructed using similar techniques. Although such facilities are more conspicuous, they have the advantage of being easier to monitor for leakage.

The uses to which closed landfills have been put are varied. Efforts to limit what goes into the landfill reflect particular concerns of different communities across the country. They include industrial parks, airport runways, recreational parks, ski slopes, ball fields, golf courses, playgrounds, and many others. When it has been determined that the bearing capacity of the landfill surface is adequate, buildings can also be erected. The antiquated view of landfills as "garbage dumps" has given way to a science to engineer the establishment, maintenance, closure, and re-use of the area for the community.