Drinking Water Contamination by Dumps and Landfills

The U.S. Environmental Protection Agency (EPA) estimates that between 0.1% and 0.4% of usable surface aquifers are contaminated by industrial impoundments and landfills (1). Dumps and landfills are a threat to water supplies when water percolates through waste, picking up a variety of substances such as metals, minerals, organic chemicals, bacteria, viruses, explosives, flammables, and other toxic materials. This contaminated water is called leachate and is produced when the waste becomes saturated with water (2). Wastes with high moisture content or which receive artificial irrigation, rainwater, surface or groundwater infiltration produce leachate and methane gas. It has been shown that once a dump is saturated, annual precipitation of 36 inches per year can percolate 1 million gallons of contaminated water per acre (3). If the leachate is not contained and migrates from a site the chemical and physical properties of the substances and the soil, as well as the hydrogeological conditions around the site, will determine the extent of contamination. If a leachate reaches ground or surface water it could contaminate water supply wells.

Dumps and landfills are not entirely synonymous and a distinction should be made. A dump is defined as, " a site used to dispose of solid wastes without environmental controls." (4). The term 'landfill' is replacing 'dump' due to the modernization of our solid waste facilities. Landfill is defined as a "facility in which solid waste from municipal and/or industrial sources is disposed; sanitary landfills are those that are operated in accordance with environmental protection standards." (2) This distinction is very important because it allows us to distinguish between two different eras and practices. Even so, some modernized landfills are poorly engineered or located in an environmentally unsound areas. The upgrade of waste disposal sites from dumps to environmentally sound solid waste disposal systems was mandated by a set of hazardous waste amendments passed in 1986. Landfills are now regulated at one of three class levels depending on the nature of solid or hazardous waste accepted.

Well designed landfills should not cause water quality problems because leachate problems are anticipated and controlled.

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1. USEPA (1980b). Planning Workshop to develop recommendations for a Ground Water Protection Strategy. Appendixes. Washington DC. pp 171.

2. EPA Drinking Water Glossary: A Dictionary of Technical and Legal Terms Related to Drinking Water. USEPA Office of Water. June 1994. pp 17.

3. Salvato, JA., et al. 1971. Sanitary Landfill-Leaching Prevention and Control. Journal Water Pollution Control Federation, 43(10):2084-2100.

4. Environmental Glossary. 4th ed. 1986. Edited by G. William Frick and Thomas F.P. Sullivan. pub by Government Institutes, Inc., Rockville,MD. pp 99.

This page was prepared by T.L. Pedersen , June 1997. UCD EXTOXNET FAQ Team.
Revised by B.T. Johnson, November, 1997