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Water: Basics

Overview of the Water Quality Standards-to-Permits Process

  1. The process begins when a state or Indian tribe establishes water quality standards for a water body within its jurisdiction, as required by the Clean Water Act.  Water quality standards include designated uses for a water body (e.g., public water supply, propagation of fish and wildlife, recreation); water quality criteria necessary to support the designated uses; and a policy for preventing degradation of the quality of water bodies. Water quality criteria include numeric criteria for specific parameters (e.g., copper, chlorine, temperature, pH); toxicity criteria to protect against the aggregate effects of toxic pollutants; and narrative criteria that describe the desired condition of the water body (e.g., free from visible oil sheen).

  2. States and tribes assess water bodies to determine whether they are attaining the established standards.

  3. After identifying potential water quality problems, the state or tribe sets priorities for which water bodies to target first for further evaluation.

  4. The state or tribe may then evaluate the appropriateness of the established water quality standards for specific waters and reaffirm or refine the standards as appropriate.

  5. Next, the state or tribe defines what controls on point and nonpoint sources are necessary either through an analysis of the entire water body or by assessing the impact of individual sources of pollution (e.g., a single industrial process wastewater discharge).  When assessing point source discharges to determine whether controls based on water quality standards are necessary, an NPDES permitting authority should conduct an analysis to determine whether the discharge causes, has the "reasonable potential" to cause, or contributes to an excursion of any water quality criteria in the receiving water.  Where effluent limits based on water quality standards are necessary, the permitting authority allocates responsibility for controls through wasteload allocations and then effluent limits in NPDES permits consistent with those wasteload allocations.

  6. Controls on individual sources are established through nonpoint source programs or NPDES permits.

  7. Point source effluent monitoring allows the NPDES authority to assess compliance with the required controls and take enforcement actions where necessary.

  8. Finally, the state or tribe uses the information gathered from monitoring sources of pollution and the quality of the water body itself to measure progress in attaining water quality standards.

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