§ 131.3 Definitions.

(a) The Act means the Clean Water Act (Pub. L. 92–500, as amended (33 U.S.C. 1251 et seq.)).

(b) Criteria are elements of State water quality standards, expressed as constituent concentrations, levels, or narrative statements, representing a quality of water that supports a particular use. When criteria are met, water quality will generally protect the designated use.

(c) Section 304(a) criteria are developed by EPA under authority of section 304(a) of the Act based on the latest scientific information on the relationship that the effect of a constituent concentration has on particular aquatic species and/or human health. This information is issued periodically to the States as guidance for use in developing criteria.

(d) Toxic pollutants are those pollutants listed by the Administrator under section 307(a) of the Act.

(e) Existing uses are those uses actually attained in the water body on or after November 28, 1975, whether or not they are included in the water quality standards.