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Safe Drinking Water Act

Safe Drinking Water Act

The Safe Drinking Water Act of 1974, amended in 1986 and 1996, is the legal basis for regulating public drinking water in the United States. Its passage was spurred largely by mounting public awareness about contaminants in the environment, and concern for the safety of drinking water. The U.S. Environmental Protection Agency has primary enforcement responsibility.

Evolution of the Law

The Safe Drinking Water Act (SDWA) of 1974 was the first federal law mandating drinking-water standards for all public water systems, from big cities to roadside campgrounds. It was enacted as a result of a federal survey of large and small public drinking-water systems that revealed poor water quality was endangering public health. The U.S. Public Health Service had set some drinking water quality standards in 1914, but these were merely voluntary for public systems.

Under the 1974 SDWA, public water systems were required to follow water quality standards for particular contaminants. Water systems must be tested for these contaminants and, if necessary, the water is treated to reduce contaminants to the maximum contaminant levels (MCLs) set for each contaminant.

The first standards for required monitoring by public water systems were set for some inorganic contaminants (e.g., metals, nitrates), microbial contaminants (e.g., bacteria), turbidity , and radionuclides (trace amounts of radioactivity emitters such as radium, uranium, and radon). Also, special protection was made available to communities with an aquifer that was the sole source of drinking water.

Private wells are not regulated under the Safe Drinking Water Act. The EPA encourages, but cannot force, private well owners to have their water tested at least annually for health-threatening contaminants.


Major amendments to the SDWA in 1986 set a goal of eighty-three contaminant standards to be established by 1989 and twenty-five more contaminants for every 3 years thereafter. The additional contaminants identified in the 1986 Amendments included organic contaminants (e.g., pesticides and volatile organic compounds ) and chlorine disinfection byproducts. Lead pipes and lead solder in new drinking-water systems were banned. Rules were to be written regarding monitoring injection wells injecting wastes below drinking-water sources. States were required by the amendments to develop a wellhead protection program for public wells. And all surface water systems (i.e., systems using lakes or streams) had to use disinfection techniques and filter their water sources to remove microbes, including bacteria, viruses, and protozoans that commonly occur in surface water. These microbes do not routinely occur in groundwater (unless it has been contaminated); therefore, groundwater-based water systems were not required to disinfect or filter their water unless a need exists.

The 1996 amendments created a state revolving loan program to provide loan money to communities needing system upgrades or source-water protection. The 1986 Amendment requiring EPA to develop standards for twenty-five new contaminants every 3 years was rescinded. The U.S. Environmental Protection Agency was to consider risk and costbenefits of implementing any particular standard. Community water systems were required to publish annual reports to inform citizens about contaminant levels in their water and their community water system's performance in meeting drinking-water standards.

A Source-Water Assessment Program was added. All states were to survey land uses around every source water area (surface or groundwater), delineate the source-area boundaries, identify potential contaminant sources within them, and estimate the susceptibility of the drinking-water source to those potential contaminant sources.

Drinking-Water Standards

Of the nation's 170,000 public drinking-water systems, the U.S. Environmental Protection Agency estimates that more than half (about 53 percent) use groundwater as their source; the remainder (47 percent) use surface water. Regardless of source, water for public supply must meet federal and state standards designed to protect public health. There are two types of drinking-water standards: National Primary Drinking Water Regulations (NPDWR) and National Secondary Drinking Water Regulations (NSDWR).

The NPDWR lists both a Maximum Contaminant Level Goal (MCLG) and a Maximum Contaminant Level (MCL) for each listed contaminant. The MCLG reflects the contaminant level below which there is no known or expected human health risk. It is not an enforceable standard. The MCL is set as close as possible to the MCLG based on best available treatment technology and cost. It is the maximum amount of a contaminant that may be delivered to users of a public water system and is a legally enforceable standard.

The NSDWR sets nonmandatory, nonenforceable standards for fifteen contaminants that may cause water to have an undesirable color or odor, but do not have potentially adverse health consequences. Examples include iron, total dissolved solids, and pH.

Contaminant Categories.

As of 2003, ninety-five water contaminants were regulated by the U.S. Environmental Protection Agency. Approximately seven hundred substances have been cataloged as potential contaminants. Contaminants include harmless constituents as well as harmful ones.

Low levels of trace metals, nutrients, minerals, and salts are found naturally in water. At low concentrations, these contaminants are harmless; some may even be desirablefor example, many people prefer the taste of slightly mineralized water. Other contaminants are manufactured, and are undesirable at any concentration. Similarly, any level of bacteria in drinking water is considered to be a violation of the MCL.

The EPA's contaminant categories as of 2002 included: microorganisms (Cryptosporidium, Giardia lamblia, Legionella, total coliforms, fecal coliforms and E. coli ), disinfectant and disinfection byproducts, inorganic chemicals, organic chemicals, and radionuclides. MCLs for the ninety contaminants regulated as of 2002, their probable source, and related health effects can be found online at <>.

Keeping Water Safe

To ensure compliance with safe drinking water standards, water systems are required to frequently sample and test the water being delivered. If contaminant levels exceed MCLs, the water system must discontinue the use of that source until the level is reduced to below the MCL by treatment, blending, or finding an alternative source. Customers must be advised immediately of actions necessary to prevent disease outbreaks, such as boiling water before drinking in the case of microorganisms, or by switching to bottled water.

Management trends and challenges to protect drinking water are numerous. Infrastructure maintenance and replacement is needed to fix leaks, prevent breaks, and ensure proper water treatment. New technology allows scientists to measure the presence of previously unstudied or undetected contaminants (e.g., pharmaceuticals and personal care products, or PPCPs), which then must be investigated to determine if they, too, pose a human health risk in drinking water.

Population growth increases demand and changing land-use practices threatens supply quality, particularly groundwater. An aging population means more elderly citizens, who are more at risk from drinking-water contaminants. The public needs to learn not only to conserve water, but also to realize what daily practices add to nonpoint-source pollution of groundwater and surface water so they can avoid or minimize those practices. Rural areas of the United States have a particular challenge, since small systems often cannot afford these costly mandates.

The Safe Drinking Water Act is important to water management in that it illuminates the interconnection of water resources and land resources, and how land use affects water quality. In addition, source-water quality affects drinking-water treatment costs, so monitoring and enforcement of the SDWA and the Clean Water Act go hand in hand.

see also Chemicals from Pharmaceuticals and Personal Care Products; Clean Water Act; Environmental Protection Agency, U.S.; Drinking Water and Society; Drinking-Water Treatment; Infrastructure, Water-Supply; Land Use and Water Quality; Legislation, Federal Water; Pollution Sources: Point and Nonpoint; Population and Water Resources; Security and Water; Supplies, Protecting Public Drinking-Water; Supplies, Public and Domestic Water; Utility Management.

Laurel E. Phoenix

and Edward F. Vitzthum


Kubasek, Nancy K., and Gary S. Silverman. Environmental Law, 4th ed. Upper Saddle River, NJ: Prentice Hall, 2002.

U.S. Environmental Protection Agency. 25 Years of the Safe Drinking Water Act: History and Trends. EPA-816-R-99-007, December. Washington, D.C.: U.S. Environmental Protection Agency, 1999. Available online at <>.

Internet Resources

Ground Water and Drinking Water. U.S. Environmental Protection Agency. <>.

National Drinking Water Clearinghouse. <>.

Water On Tap: A Consumer's Guide to the Nation's Drinking Water. U.S. Environmental Protection Agency. <>.


Although the U.S. drinking-water industry and the U.S. Environmental Protection Agency (EPA) have been working on projects to enhance security of drinking-water supplies since the 1990s, the terrorist attacks of September 11, 2001 in New York and Washington, D.C. catapulted water security to the forefront. In 2002, the U.S. Congress enacted the Public Health Security and Bioterrorism Preparedness and Response Act. With respect to water supplies, this legislation amended the Safe Drinking Water Act and specified actions that community water systems and the EPA must take to improve the security of the nation's drinking-water infrastructure.

In short, every community water system serving at least 3,300 persons must prepare or revise an emergency response plan, and conduct an assessment of their vulnerability to terrorist attack or other intentional act intended to substantially disrupt a safe and reliable drinking-water supply. Among other duties, EPA must conduct studies regarding the intentional introduction of harmful contaminants; the methods by which drinking-water infrastructures could be disrupted; and the methods by which alternative supplies of drinking water could be provided in the event of destruction or impairment of public water systems.

For further information about the Safe Drinking Water Act and water infrastructure security, see <>. Selected links to industry and government websites are available through this EPA webpage.

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Safe Drinking Water Act (1974)

Safe Drinking Water Act (1974)

Kyle A. Loring

In 1974 Congress enacted the Safe Drinking Water Act (SDWA) (P.L. 93-523, 88 Stat. 1660) to protect the quality of both actual and potential drinking water in the United States. Congress had created the SDWA in response to a nationwide survey that revealed health risks from inadequate public water-supply facilities and operating procedures. To achieve its goal the SDWA provides water quality standards for drinking-water suppliers, protects underground drinking-water sources, and directs appropriate deep-well injection of wastes.

The SDWA requires the U.S. Environmental Protection Agency (EPA) to regulate all "public water systems," defined as systems that provide piped water for human consumption for at least sixty days a year to at least fifteen service connections or twenty-five people. The EPA does this through Primary Drinking Water Regulations, by which it first identifies contaminants that may pose a risk to human health and that occur in drinking water at potentially unsafe levels. Then the EPA specifies a Maximum Contaminant Level Goal (MCLG) for each contaminant, which is set at the level below which there is no predicted health risk. Finally the EPA creates a legally enforceable Maximum Contaminant Level (MCL), which is the greatest amount of contaminant that will be allowed in the public water supply. This MCL must be set as close as is feasible to the MCLG after taking into account the best technology, treatment techniques, and costs. Since the 1996 amendments discussed below, the EPA may instead require a Treatment Technique for removing the contaminant if there is neither an economically or technologically feasible MCL, nor an accurate way to measure the contaminant in water.

States generally obtain primary authority to implement the SDWA after proving to the EPA that they will adopt and enforce standards at least as stringent as the national standards. While the states may oversee the program, the public water systems themselves physically ensure the safety of the tap water through treatment, testing, and reporting. In addition to these "at the tap" protections, the SDWA requires states and public water suppliers to protect initial water sources from contamination. In particular, the SDWA provides for an Underground Injection Control (UIC) program to prevent contamination of underground water sources by underground injection of contaminated fluids.

Due to criticism that the original act was an inflexible, unfunded mandate with an unattainable regulatory schedule, the 104th Congress extensively amended the act in 1996 (P.L. 104-182, 110 Stat. 1613). These amendments included new pollution prevention approaches, public information requirements, added flexibility to the regulatory process, and a Drinking Water State Revolving Fund. Pollution prevention took the form primarily of source-water quality assessment programs to determine the current health of water supplies and delineate the area to be protected. In addition, public water suppliers were required to inform their year-round customers about the source and quality of their tap water with an annual consumer confidence report.

The most important element of the amendments was the critically necessary funding mechanism added to the SDWA's stringent water quality requirements. This fund provided federal monetary aid to public water systems to repair and upgrade their facilities, focusing particularly on assisting small and disadvantaged communities that might otherwise find these repairs too expensive. The fund also gave priority to programs using pollution prevention to safeguard their drinking water supply.

See also: Federal Water Pollutioin Control Act.


Plater, Zygmunt J. B., Robert H. Abrams, et al. Environmental Law and Policy: Nature, Law and Society, 2nd ed. St. Paul, MN: West Publishing, 1998.

U.S. Environmental Protection Agency. "Safe Drinking Water Act Amendments of 1996" and "Understanding the Safe Drinking Water Act." July 2003. <>.

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