...
Water quality standards (WQS) are provisions of state, territorial, authorized tribal, or federal law approved by the Environmental Protection Agency (EPA) that describe the ideal condition of a water body and how that condition will be protected or attained.
Scope
Each state, territory, and authorized tribe has its own legal and administrative procedures for adopting WQS. Standards are typically developed using a workgroup process or informal public meetings and are then proposed for public comment.
EPA must review and approve or disapprove each submission from a state, territorial, or authorized tribe. Proposed WQS must be approved by EPA before they can be used as the basis for actions under the Clean Water Act, such as establishing water quality-based effluent limitations or total maximum daily loads.
Regulatory citations
- 40 CFR Part 131 — Water quality standards
Key definitions
- Existing uses: Those uses attained in the water body on or after November 28, 1975, whether they are included in the water quality standards.
- Use attainability analysis: A structured scientific assessment of the factors affecting the attainment of the use, which may include physical, chemical, biological, and economic factors as described in 131.10(g).
- Water quality limited segment: Any segment where it is known that water quality does not meet applicable water quality standards and/or is not expected to meet applicable water quality standards, even after the application of the technology-based effluent limitations required by sections 301(b) and 306 of the Clean Water Act.
Summary of requirements
WQS consists of three core components. States, territories, and authorized tribes must specify the:
- Designated uses of a water body,
- Criteria to protect designated uses, and
- Antidegradation requirements to protect current uses and high-quality/high-value waters.
Designated uses. Common designated uses include:
- Protection and propagation of fish, shellfish, and wildlife;
- Recreation;
- Public drinking water supply; and
- Agricultural, industrial, navigational, and other purposes.
When designating uses, states should consider the extraterritorial effects of their standards. For example, once states revise or adopt standards, upstream jurisdictions will be required to provide for the attainment and maintenance of the downstream standards when revising their standards and issuing permits.
Criteria. Water quality criteria can be numeric, such as the maximum pollutant concentration levels permitted in a water body. Or they can be narrative, like a criterion that describes the desired conditions of a water body being “free from” certain negative conditions. Usually, both criteria are adopted.
When implementing WQS, if a water body has multiple designated uses with different criteria for the same pollutant, states and authorized tribes protect the most sensitive use, in accordance with 131.11(a).
Antidegradation requirements. Designated uses and water quality criteria are the main tools states and authorized tribes use to achieve the objectives and goals of the Clean Water Act. Antidegradation requirements complement these tools by:
- Supplying framework for upkeeping existing uses,
- Protecting waters that are higher quality and needed to support Clean Water Act goals, and
- Protecting waters identified as Outstanding National Resource Waters.
No activity is allowable under the antidegradation policy that would eliminate any existing use, whether that use is designated in a state’s WQS.