Landfills: How Do They Work?

Throughout history the landfill has been the bottom line of waste management: this is where the buck stops. Because of its fundamental importance, a thorough understanding of how a landfill is designed and operated is necessary. Municipal landfills are the most common; they accept our household garbage and often take some commercial and industrial waste as well. They are generally operated by local municipalities, although some are privately owned. We are all stakeholders in the landfill, however, contributing our share when we place our garbage by the curbside each week. Another type of landfill is that used by industries. These are generally situated near the industrial plants they serve and are usually dedicated to the specific process wastes produced at the factory. In terms of design, they do not differ significantly from municipal landfills. There are also “secure” landfills for hazardous waste, known in the United States as Subtitle C hazardous waste disposal sites. These different landfills do not differ greatly in design, and the following descriptions are largely applicable to all of them. A number of specific case histories are presented in chapter 11. Historically, it has been convenient to site landfills in depressions such as ravines, canyons, abandoned quarries, and open pits that could be easily filled up. These locations were selected largely on the basis of convenience, with proximity to the centers being served and price of land being key parameters. In the early 1900s, and even as late as the early 1970s, landfills were seen as an ideal way of “reclaiming” swamps and wetlands. With the loss of natural areas to urbanization and agriculture, and with the recognition that wetlands play an important role in the ecosystem, this practice is no longer condoned. It is now recognized that one of the most effective ways of protecting the environment is by carefully siting landfills at locations that provide natural security. In particular, the geological formation should contain or naturally attenuate contaminants to acceptable concentrations. If natural attenuation is not possible, then engineered barriers must be incorporated. Today, the trend is toward both incorporating extensive engineered barriers and seeking sites that offer geological containment.