Landfill | Research & Encyclopedia Articles

Surface water, oceans and landfills are traditionally the main repositories for society's solid and hazardous waste. Landfills are located in excavated areas such as sand and gravel pits or in valleys that are near waste generators. They have been cited as sources of surface and groundwater contamination and are believed to pose a significant health risk to humans, domestic animals, and wildlife. Despite these adverse effects and the attendant publicity, landfills are likely to remain a major waste disposal option for the immediate future.

Among the reasons that landfills remain a popular alternative are their simplicity and versatility. For example, they are not sensitive to the shape, size, or weight of a particular waste material. Since they are constructed of soil, they are rarely affected by the chemical composition of a particular waste component or by any collective incompatibility of co-mingled wastes. By comparison, composting and incineration require uniformity in the form and chemical properties of the waste for efficient operation. Landfills also have been a relatively inexpensive disposal option, but this situation is rapidly changing. Shipping costs, rising land prices, and new landfill construction and maintenance requirements contribute to increasing costs.

About 57% of the solid waste generated in the United States still is dumped in landfills. In a sanitary landfill, refuse is compacted each day and covered with a layer of dirt. This procedure minimizes odor and litter, and discourages insect and rodent populations that may spread disease. Although this method does help control some of the pollution generated by the landfill, the fill dirt also occupies up to 20 percent of the landfill space, reducing its waste-holding capacity. Sanitary landfills traditionally have not been enclosed in a waterproof lining to prevent leaching of chemicals into groundwater, and many cases of groundwater pollution have been traced to landfills.

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 the siting 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 siting of a landfill will reduce the necessity for future clean-up and site rehabilitation. 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 siting of a landfill within their boundaries. 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.

Although a number of significant environmental issues are associated with the disposal of solid waste in landfills, the disposal of hazardous waste in landfills raises even greater environmental concerns. A number of urban areas contain hazardous waste landfills. Love Canal is, perhaps, the most notorious example of the hazards associated with these landfills. This Niagara Falls, New York neighborhood was built over a dump containing 20,000 metric tons of toxic chemical waste. Increased levels of cancer, miscarriages, and birth defects among those living in Love Canal led to the eventual evacuation of many residents. The events at Love Canal were also a major impetus behind the passage of the Comprehensive Environmental Response, Compensation and Liability Act in 1980, designed to clean up such sites. The U.S. Environmental Protection Agency estimates that there may be as many as 2,000 hazardous waste disposal sites in this country that pose a significant threat to human health or the environment.

Love Canal is only one example of the environmental consequences that can result from disposing of hazardous waste in landfills. However, techniques now exist to create secure landfills that are an acceptable disposal option for hazardous waste in many cases. The bottom and sides of a secure landfill contain a cushion of recompacted clay that is flexible and resistant to cracking if the ground shifts. This clay layer is impermeable to groundwater and safely contains the waste. A layer of gravel containing a grid of perforated drain pipes is laid over the clay. These pipes collect any seepage that escapes from the waste stored in the landfill. Over the gravel bed a thick polyethylene liner is positioned. A layer of soil or sand covers and cushions this plastic liner, and the wastes, packed in drums, are placed on top of this layer.

When the secure landfill reaches capacity it is capped by a cover of clay, plastic and soil, much like the bottom layers. Vegetation in 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.

Although technical solutions have been found to many of the problems associated with secure landfills, several nontechnical issues remain. One of these issues concerns the transportation of hazardous waste to the site. Some states do not allow hazardous waste to be shipped across their territory because they are worried about the possibility of accidental spills. If hazardous waste disposal is concentrated in only a few sites, then a few major transportation routes will carry large volumes of this material. Citizen opposition to hazardous waste landfills is another issue. Given the past record of corporate and governmental irresponsibility in dealing with hazardous waste, it is not surprising that community residents greet proposals for new landfills with the NIMBY (Not In My BackYard) response. However, the waste must go somewhere. These and other issues must be resolved if secure landfills are to be a viable long-term solution to hazardous waste disposal.

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