2023 Colorado Revised Statutes › Title 25 - PUBLIC HEALTH AND ENVIRONMENT (§§ 25-1-101 — 25-59-106) › ENVIRONMENTAL CONTROL (§§ 25-6.5-101 — 25-18.9-105) › Article 8 - WATER QUALITY CONTROL (§§ 25-8-101 — 25-8-1008) › Part 2 - WATER QUALITY CONTROL COMMISSION (§§ 25-8-201 — 25-8-210) › Section 25-8-204 - Water quality standards

(1)
Water quality standards shall be promulgated by the commission by regulations which describe water characteristics or the extent of specifically identified pollutants for state waters.
(2)
Water quality standards may be promulgated with respect to any measurable characteristic of water, including, but not limited to:
(a)
Toxic substances;
(b)
Suspended solids, colloids, and combinations of solids with other suspended substances;
(c)
Bacteria, fecal coliform, fungi, viruses, and other biological constituents and characteristics;
(d)
Dissolved oxygen, and the extent of oxygen demanding substances;
(e)
Phosphates, nitrates, and other dissolved nutrients;
(f)
pH and hydrogen compounds;
(g)
Chlorine, heavy metals, and other chemical constituents;
(h)
Salinity, acidity, and alkalinity;
(i)
Trash, refuse, oil and grease, and other foreign material;
(j)
Taste, odor, color, and turbidity;
(k)
Temperature.
(3)
Water quality standards may be promulgated for use in connection with any one or more of the classes of state waters established by the commission pursuant to section
25-8-203
and may be made applicable with respect to any designated portion of state water or to all state waters.
(4)
In promulgating water quality standards, the commission shall consider:
(a)
The need for standards which regulate specified pollutants;
(b)
Such information as may be available to the commission as to the degree to which any particular type of pollutant is subject to treatment; the availability, practicality, and technical and economic feasibility of treatment techniques; the impact of treatment requirements upon water quantity; and the extent to which the discharge to be controlled is significant;
(c)
The continuous, intermittent, or seasonal nature of the pollutant to be controlled;
(d)
The existing extent of pollution or the maximum extent of pollution to be tolerated as a goal;
(e)
Whether the pollutant arises from natural sources;
(f)
Beneficial uses of water; and
(g)
Such information as may be available to the commission regarding the risk associated with the pollutants including its persistence, degradability, the usual or potential presence of the affected organism in any waters, the importance of the affected organisms, and the nature and extent of the effect of the pollutant on such organisms.
(5)
In establishing water quality standards using statistical methodologies or in requiring the use of statistical methodologies for permit or enforcement purposes, statistical methodologies used must be based on assumptions that are compatible with the water quality data.
(6)
For the purpose of implementing section 303(c)(2)(B) of the federal act, the commission may adopt numerical water quality standards for toxic pollutants listed pursuant to section 307(a)(1) of the federal act for which criteria have been published under section 304(a) of the federal act, and these standards may be applied in accordance with this article to discharges of pollutants to specified portions or segments of surface waters where such pollutants may be discharged or are present in the affected surface waters and could reasonably be expected to interfere with classified uses. Monitoring requirements for discharges of such pollutants shall be reasonably related to the potential for the presence of such pollutants in the discharge at levels inconsistent with water quality standards and shall be imposed to the maximum extent practical on those responsible for the presence of the pollutants. This subsection (6) does not in any way limit the commission's authority to adopt water quality standards in order to comply with provisions of the federal act.
(7)
If, after full application of publicly owned treatment work authority pursuant to section 307(b)(1) of the federal act, stream standards or effluent limitations established pursuant to subsection (6) of this section are exceeded as a result of a discharge from a publicly owned treatment work, the commission, upon request of a publicly owned treatment work, shall conduct a public hearing to investigate the source of pollution causing such exceedance.
L. 81: Entire article R&RE, p. 1317, § 1, effective July 1. L. 85: (3) amended, p. 907, § 4, effective June 4. L. 89: (6) and (7) added, p. 1174, § 3, effective June 8. L. 96: (7) amended, p. 1260, § 162, effective August 7.
(1) For circumstances that will result in the repeal of this section, see § 25-8-507. (2) For the legislative declaration contained in the 1996 act amending this section, see section 1 of chapter 237, Session Laws of Colorado 1996.