B National water quality standards

Water quality standards are legally enforceable and set maximum allowable limits of concentration for various pollutant constituents or minimum limits of favorable constituents. Typically, standards relate to water quality in a receiving stream, for example, concentration of Biochemical Oxygen Demand (BOD). However, technology-based standards are established for use of the most effective control or treatment technologies available to prevent water pollution.

The early water quality standards, which related to health, were aimed at improving domestic drinking water supplies. If a particular water source was used for drinking, it had to meet the quality standards or be treated in some fashion so that it would meet those standards. Responsibility for meeting the standards has typically been assigned to the user. In general, the burden of meeting standards is now moving from the water user to the potential water polluter. Water quality standards are now aimed at control of potential pollutants at the source. This change in focus, in part, has resulted in the use of standards for point sources based not only on pollutant concentrations in water, but also on the best available technologies for control of water pollution.

Standards for confinement feedlots and agricultural NPS of pollution are technology-based and specify particular design or procedural practices. For example, NPDES permits required for confinement feedlots specify design and operation standards.

Design standards are also necessary in the definition of NPS water pollution control practices, particularly if they are structural. Procedural standards for pollution control may, for example, include such management practices as proper manure spreading or fertilizer management.

The provisions of section 303 of the 1972 Federal Water Pollution Control Act Amendments require that the State agency designated responsibility for water pollution control adopt water quality standards that have been submitted to EPA for approval.

State water quality standards are established for water uses for specific watercourses. The identification of specific water uses for watercourses is often referred to as stream classification. Stream classification is carried out by the States following State-defined procedures. The procedures generally consider:

• Needs and desires of the public

• Present and future demands on the watercourse

• Cost of maintaining different stream qualities

• Benefits expected under different control alternatives

Not all streams are classified, and those that are may not be classified in a straightforward manner. Wide variations in classification can occur along the same stream. Classification is done not only for streams, but for all natural watercourses.

Table 1-3 gives an example of a designated area classification system. Classification systems vary from State to State.

Table 1-3 Example of a designated area classification system

Class Water uses

I Sources of water supply for drinking or food processing purposes, requiring principally disinfection. Any other usage requiring water of lower quality.

II Sources of water supply for drinking or food processing purposes, requiring treatment in addition to disinfection. Any other usage requiring water of lower quality.

III Sources not used for drinking or food processing purposes, but used for swimming or other body contact recreation. Any other usage requiring water of lower quality.

IV Sources not used for drinking or food processing purposes or body contact recreation, but used for fishing or other nonbody contact recreation. Any other usage requiring water of lower quality.

V Sources used only for agriculture or industrial supplies, fish survival, or navigation.

Each water use classification requires a specific quality of water. Therefore, once a designated area is classified for specific uses by the State agency responsible for water pollution control, water quality standards are defined for that area. In some cases the pollutant assimilative capacity, water quality requirements, and other stream characteristics are not directly used in determining standards. In such cases, technology-based effluent standards are used. An example of these is the NPDES permits required of feedlot operations.

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