Drinking water safety in Idaho and throughout the entire United States is regulated by the federal Safe Drinking Water Act (SDWA), first passed by the U.S. Congress in 1974. Amendments passed in 1986 and 1996 set national limits on contaminant levels in drinking water anywhere in the United States to ensure that the water is safe for human consumption. These limits are known as maximum contaminant levels (MCLs). In addition, the law establishes treatment techniques (TTs) in place of MCLs to control unacceptable levels of some contaminants in water.

The SDWA allows states to apply for authorization to administer and implement parts of the the law. To attain authorization or "primacy," states must adopt drinking water regulations that are at least as stringent as the federal regulations and show that they can enforce the program requirements. Idaho was awarded drinking water primacy in 1978. DEQ is the state agency delegated by the U.S. Environmental Protection Agency (EPA) to implement the safe drinking water program in Idaho. However, if you use a private well, you are responsible for the safety of your water.

Overall, Idaho's drinking water is quite safe, although local contamination has been discovered in some of the state's ground water resources. The best source of specific information about your drinking water is your water supplier. Each year, community water systems in Idaho are required to prepare annual Consumer Confidence Reports (CCR) for their customers telling them where their drinking water comes from and what's in it. (A community water system is a public water system that serves at least 15 service connections used by year-round residents or regularly serves at least 25 year-round residents, such as a municipality, subdivision, mobile home park, apartment complex, or nursing home.) Contact your water supplier to get a copy.

Under the SWDA, DEQ is required to submit an Annual Compliance Report (ACR) to EPA defining the quality and safety of drinking water in our state during the previous calendar year. The most recent report, covering calendar year 2006, shows a significant drop in the number of violations and the number of systems in violation. DEQ attributes this development to improved data reporting and tracking, increased system awareness of safe drinking compliance procedures, and a triennial monitoring cycle.

View 2006 Annual Compliance Report (DEQ Publication, September 2007: pdf 883 kb, 209 pages)

Under the Public Health Security and Bioterrorism Preparedness and Response Act of 2002, the SWDA was amended to require community water systems that serve populations greater than 3,300 to implement new security measures. The measures are designed to assure an uninterrupted supply of safe drinking water and maintain an adequate supply of water for fire fighting in the event of natural disasters such as earthquakes and drought and man-made disasters including vandalism and terrorist attacks.

The act requires these systems to conduct a vulnerability assessment (VA) to evaluate weaknesses to potential threats and identify steps that can reduce the risk of serious consequences from attack or acts of vandalism and to prepare an emergency response plan incorporating the results of the VA. In Idaho, 42 community water systems, representing two-thirds of the population served by public water systems, must complete a VA. Although smaller systems are not required to comply, DEQ has urged all water systems to prepare these security aids for their own protection.