Water Quality Standards - Authorities, Definitions and Considerations

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Authorities

Under section 303(a)-(c) of the Clean Water Act, states are required to establish water quality standards.
EPA is responsible for reviewing standards adopted by the states to ensure their consistency with the requirements of the Act.
- EPA’s regulations at 40 CFR Part 131 describe the minimum requirements for water quality standards.
- Any new or revised water quality standards adopted by states and submitted to EPA after May 30, 2000 must be approved by EPA in order for those standards to be effective (40 CFR §131.21(c)(2)).

What are Water Quality Standards?

Water quality standards (WQS) are legally binding norms that describe the desired ambient condition (i.e., level of protection) for a waterbody and consist of the following three principle elements:
1. the “designated uses” of the state’s waters, such as public water supply, recreation, propagation of aquatic life and wildlife, or navigation;
2. “criteria” specifying the amounts of various pollutants, in either numeric or narrative form, that may be present in those waters without impairing the designated uses (note - criteria include any one or more of three components: magnitude, duration, and frequency); and,
3. antidegradation requirements providing for protection of existing water uses and limitations on degradation of high quality waters.

Examples of Provisions that May be Considered Water Quality Standards.

Legally binding rules that define, change, or establish:

the designated use(s) of a waterbody
the magnitude (e.g., concentration), duration, or frequency that the State would use to determine whether a waterbody is attaining any applicable water quality criteria
assessment thresholds (for listing purposes) to implement narrative water quality criteria (i.e., “translators”)
antidegradation requirements
general policies relating to uses (e.g., variances), criteria (e.g., mixing zones, low flows), or antidegradation

Examples of Provisions that May Not be Considered Water Quality Standards are:

non-substantive provisions (provisions that are not integral to, and do not modify, protections afforded by the designated uses, criteria, and antidegration provisions)
provisions that merely describe the sufficiency or reliability of information/data necessary for the state to make an attainment decision and do not change a level of protection (e.g., minimum sample size and age of data requirements, sampling techniques, quality assurance/quality control procedures)
implementation provisions (point or nonpoint source)
enforcement provisions
listing policies