Water Quality Standards
New Mexico’s Water Quality Standards, codified at 20.6.4 NMAC, define water quality goals by designating uses for rivers, streams, lakes and other surface waters, setting criteria to protect those uses, and establishing antidegradation provisions to preserve water quality. The standards are adopted by the Water Quality Control Commission (“WQCC”) through a rulemaking process, making them effective for state purposes. Then the rule is submitted to the United States Environmental Protection Agency (U.S. EPA) for approval under the federal Clean Water Act. The process for developing and amending water quality standards is outlined in the State’s approved Water Quality Management Plan and Continuing Planning Process.
There are several types of water quality standards amendments. They are as follows:
- Removing or Replacing a Designated Use.
- Use Attainability Analysis (“UAA”) – Amends a Designated Use to one with less stringent criteria.
- Existing Use Analysis (or equivalent) – Amends a Designated Use to one with more stringent criteria.
- Site-Specific Criterion – A numeric criterion applicable to all or part of a surface water of the state based on relevant site-specific conditions, supporting the Designated Use.
- Temporary Standards – Time-limited criterion applicable to either a waterbody or a discharger for a particular parameter that is preventing attainment of the Designated Use. The Temporary Standard does not replace the Designated Use for purposes of assessment or impairment.
- Criteria (Narrative or Numeric) – These types of amendments are generally reviewed and amended during a Triennial Review.
- Outstanding National Resource Waters (“ONRWs”) – Enhances the protections afforded under the Antidegradation Policy and Implementation Plan.
- Regulations – Amendments to 20.6.4 NMAC that are not water quality standards (designated uses, criteria or the antidegradation policy and implementation plan). These are generally reviewed and amended during a Triennial Review.
Water quality standards can be amended at any time. However, in accordance with Section 303(c)(1) of the CWA and 20.6.4.10 New Mexico Administrative Code, states are required to hold a public hearing at least once every three years to review, amend, and adopt water quality standards, as applicable. This is referred to as a “Triennial Review.” Because of the logistics associated with the lengthy administrative process to amend regulations and make them effective for both state and Clean Water Act purposes, the Department petitions for a Triennial Review hearing date at least every three years from the date EPA makes the last Triennial Review amendments effective for Clean Water Act purposes.
Click here for the list of New Mexico’s Water Quality Standard amendments (20.6.4 NMAC)
Current Surface Water Quality Standards
- As approved by the New Mexico’s Water Quality Control Commission for purposes of state implementation, effective September 24, 2022
- As approved by EPA effective, for Clean Water Act Purposes, July 24, 2020*.
- EPA-Approved Tribal Water Quality Standards
*Due to delays on EPA’s website, please refer to the Water Quality Standard amendments page for more information on EPA approved Water Quality Standards.
