Landfill

Sanitary landfills involve well-designed engineering methods to protect the environment from contamination by solid or liquid wastes. A necessary condition in designing a sanitary landfill is the availability of vacant land that is accessible to the community being served and has the capacity to handle several years of waste material. In addition, cover soil must be available. Of course, the location must also be acceptable to the local community. Historically, landfills were placed in a particular location more for convenience of access than for any environmental or geological reason. Now more care is taken in determining the location of new landfills. For example, sites located on faulted or highly permeable rock are passed over in favor of sites with a less-permeable foundation. Rivers, lakes, floodplains, and groundwater recharge zones are also avoided. It is believed that the care taken in the initial location of a landfill will reduce the necessity for future clean-up and site rehabilitation. Locations near airports are avoided because the landfill usually attracts birds that can interfere with aircraft. Due to these and other factors, it is becoming increasingly difficult to find suitable locations for new landfills. Easily accessible open space is becoming scarce and many communities are unwilling to accept the building of a landfill within their boundaries. Since 1978, over 14,000 landfills have been filled up and shut down. Many major cities have already exhausted their landfill capacity and must export their trash, at significant expense, to other communities or even to other states and countries.

The three basic procedures that are carried out in sanitary landfills are: spreading the solid waste materials in layers; compacting the wastes as much as possible; and covering the material with dirt at the end of each day. This method reduces the breeding of rats and insects at the landfill, reduces the threat of spontaneous fires, prevents uncontrolled settling of the materials, and uses the available land efficiently. Although this method does help control some of the pollution generated by the landfill, the fill dirt also occupies up to 20% of the landfill space, reducing its waste-holding capacity. Another important consideration for landfill design is the use of the site after it is filled. Some sites have become parks, housing projects, or sites for agriculture. Under pressure from the government, environmentalists, and the public, and with diminishing natural and financial resources available to them, municipalities are now planning their landfills carefully to avoid some of the later costs of clean-up or containment.