ABSTRACT
New municipal landfills have become very difficult to site because of public opposition. The lack of new landfills together with the diminishing capacity of landfills now in operation could lead to a major crisis in the United States in 10 years. A major reason for public opposition to new landfills is the fear of groundwater contamination from landfill leachate. However, a review of case studies revealed few serious incidents, particularly among more recent landfills. Also, new federal regulations on landfill operation and design are expected to result in more strictly controlled landfills. The US Environmental Protection Agency concluded that if properly located, designed, and operated, future municipal solid waste landfills will be protective of human health and the environment.
Groundwater contamination by municipal landfills has been an issue for decades. The inorganic and organic chemical composition of landfill leachate and gas is quite variable and is dependent on the age of the landfill, how it was operated, and on the type of wastes present. Pathogens in leachate are not thought to be a major problem. About half of the volatile organic compounds reported in leachate have either a medium or low mobility in groundwater and the other half are classified as highly or very highly mobile. Some of these compounds could readily volatilize from leachate in the unsaturated zone. Chemical oxidation and hydrolysis of volatile organic compounds in landfill leachate may not be significant. Many organic compounds may biodegrade, but a few appear to be resistant.
Although case histories were found where leachate from municipal landfills resulted in serious groundwater contamination, the majority of active landfills did not have any type of groundwater monitoring program. Most problem landfills in the past were located in geologically unsuitable areas, were constructed without an effective liner, or were poorly operated.
Proposed federal regulations mandate the use of soil liners, leachate collection systems, final covers, and other requirements. However, very little documentation is available from which to evaluate the efficacy of these requirements. Soil and plastic 412liners can potentially control leachate movement, but little research has been done on field-scale soil liners, and there is little actual experience with plastic liners.
In the future, leachate collection and recirculation, travel-time calculations in liner designs, and site impact assessments may be implemented. Short-term remedies to the landfill crisis include on-site expansions, landfill mining, and possibly large regional megafills.
