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Groundwater Contamination in the United States The United States employs groundwater as a critical natural resource. In addition to agricultural and industrial uses, half of the U.S. population depends on groundwater for household drinking water. While the EPA estimates that less than 2 percent of the Nation’s groundwater is contaminated, this tends to be concentrated near heavily populated areas. As groundwater demand increases these areas are challenged to provide adequate drinking water. Residential Areas Groundwater is a storage area for freshwater. Contaminants in other parts of the hydrologic cycle, such as the atmosphere or bodies of surface water, can be transferred into groundwater supplies through movement and flow of this cycle. As residential communities grow, increasingly large paved areas funnel storm water directly into local streams and lakes. Runoff from streets, roofs, construction sites, and landscaped areas concentrate pollutants. Contaminants that would ordinarily percolate slowly into the soil now accumulate and run into storm drains and streams that cannot handle the volume and concentration. Household Hazardous Waste Fertilizers, herbicides, insecticides, fungicides, and pesticides applied to lawns and gardens contain hazardous chemicals that can flow into storm drains or travel through the soil to contaminate groundwater. Salt is used to melt snow for winter driving. Each year more than 11 million tons of salt are applied to roads in the United States. This salt is washed directly into the surrounding soil and water. Septic systems are designed to slowly drain away human waste underground at a slow, harmless rate. An improperly designed, located, constructed, or maintained septic system can leak bacteria, viruses, household chemicals, and other contaminants into the groundwater. Agriculture and Industry There are more than 65,000 synthetic organic contaminants (SOCs) commonly used in the U.S., the greatest quantities of which are generated during the normal course of business. Not surprisingly, EPA ground water surveys conducted over the last decade confirm the widespread occurrence of organic contaminants, mainly due to their extensive use. See our pages entitled Analytical Services for Drinking Water for information about SOC analysis.Hazardous waste is stored in containers that eventually degrade and leak, allowing waste to seep into soil, wash into streams, and make its way into groundwater. In the United States today there are estimated to be more than 20,000 abandoned and uncontrolled hazardous waste sites, with more added every year. Landfills have a protective barrier to prevent contaminants from leaching into the water. However, in old landfills, or if there is a damaged or absent barrier, contaminants can leach into the groundwater. Toxicity Corrosivity Leaching Procedure (TCLP) analysis is performed to determine the effects of time and environment on landfill samples. Read more in the Underground Storage Tanks (USTs) can corrode, crack and develop leaks, releasing petroleum products, acids, solvents or chemicals into the environment. When these liquids get into the groundwater, serious contamination can occur. There are estimated to be more than 10 million storage tanks buried in the United States. See our page on Underground Storage Tanks, for more information.Natural Contaminants Groundwater moving through sedimentary rocks and soils accumulates a range of compounds such as magnesium, calcium, and chlorides. Some aquifers have high natural concentration of dissolved elements such as arsenic, boron and selenium. See Common Contaminants for detailed list including sources and health effects of various compounds | |||||||||||||||||||||||||||
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