Drinking Water

This report provides information on the (1) quality of drinking water drawn from community water systems and private wells and (2) factors that affect the quality of this drinking water. GAO found that much more is known about the quality of drinking water from community water systems than from private wells. To meet the Safe Drinking Water Act's requirements, community water systems must periodically monitor their water for contaminants, such as total coliform bacteria, pesticides, naturally occurring elements, and industrial solvents. In the six states that GAO reviewed, compliance data from fiscal years 1993 through 1996 showed that violations of the standard for total coliform bacteria were the most common, being reported by 3 to 6 percent of the more than 17,000 community water systems. A sizeable number of systems (although a small percentage of the total) violated standards for radiological contaminants, nitrate, and the herbicide atrazine. Violations of other standards were few. For private wells, available data are generally limited to total coliform bacteria and nitrate. Although these data are not always representative or unbiased, those that are have shown rates of bacterial contamination as high as 42 percent and rates of excessive nitrate as high as 18 percent. Less extensive data on two commonly used herbicides show much lower levels of contamination in private wells. Several factors influence the quality of drinking water from community systems or private wells, including the condition of the source of the water; the use of construction standards and other controls to protect water sources from contamination; and ongoing oversight and maintenance activities, such as testing and inspections, that help determine whether the water will remain safe.

GAO noted that: (1) much more is known about the quality of drinking water from community water systems than from private wells; (2) to meet the Safe Drinking Water Act's requirements, community water systems must periodically monitor their water for contaminants, such as total coliform bacteria, pesticides, naturally occurring elements, and industrial solvents; (3) in the six states that GAO reviewed, compliance data for fiscal years 1993 through 1996 show that violations of the standard for total coliform bacteria were the most common, being reported by 3 to 6 percent of the more than 17,000 community water systems; (4) a sizable number of systems, although a small percentage of the total, violated standards for radiological contaminants, nitrate, and the herbicide atrazine; (5) violations of other standards were few; (6) for private wells, the available data on water quality are, for the most part, limited to data on total coliform bacteria and nitrate; (7) these data have been collected for special studies, in response to state and local testing requirements for new wells, and through voluntary testing requested by well owners; (8) while these data are not always representative or unbiased, those that are have shown rates of bacterial contamination as high as 42 percent and rates of excessive nitrate as high as 18 percent; (9) less extensive data on two commonly used herbicides show much lower levels of contamination in private wells; (10) several factors influence the quality of drinking water obtained from community water systems and private wells; and (11) these factors include the condition of the source from which the drinking water is extracted, the use of construction standards and other controls designed to ensure that new water systems and private wells are properly constructed and protected from potential sources of contamination, and ongoing oversight and maintenance activities, such as periodic testing and inspections, that help determine whether the water will continue to be safe.

Recommendations

Our recommendations from this work are listed below with a Contact for more information. Status will change from "In process" to "Open," "Closed - implemented," or "Closed - not implemented" based on our follow up work.

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