Triennial Review Rulemaking

Arizona surface water

Triennial Review Rulemaking

The Clean Water Act requires that Arizona establish surface water quality standards and review them every three years. This review process is known as the triennial review. ADEQ has a duty to conduct the triennial review of surface water quality standards, and, as appropriate, adopt or modify the standards through a rulemaking process.1

Water Quality Standards

Water quality standards are one of the cornerstones of the Clean Water Act and play a central role in the successful implementation of Arizona’s water quality management programs. Water quality standards:

  • Define water quality goals for surface waters in Arizona
  • Designate uses to be protected in Arizona’s surface waters
  • Prescribe criteria that ADEQ determines necessary to maintain and protect water quality for the designated uses
  • Provide the measure by which ADEQ assesses the water quality status of Arizona’s rivers, streams and lakes
  • Provide the regulatory basis for establishing load allocations in total maximum daily load (TMDL) analyses
  • Provide the regulatory basis for establishing water quality-based discharge limitations and controls in Arizona Pollutant Discharge Elimination System (AZPDES) permits when technology-based effluent limitations are insufficient to protect water quality
  • Provide the regulatory basis for the implementation of best management practices (BMPs) to control nonpoint sources of pollution, and for measuring the effectiveness of BMPs


Per 40 CFR 131.6 "Minimum Requirements for Water Quality Standards Submission", ADEQ modified various water quality standards as part of the 2019 Triennial Review package, submitted to EPA on November 19, 2019. These modifications changed rules in Title 18, Chapter 11, Article 1, and are published as a Notice of Final Rulemaking (NFRM) in the Arizona Administrative Register. Under the Clean Water Act, the Environmental Protection Agency must review and approve new state water quality standards before they become effective for purposes of the Act.2

In January 2022, EPA partially approved ADEQ's 2019 Triennial Review submission | View Notes from EPA's Partial Approval Letter >

  • Revisions to the definitions, antidegradation, mixing zones, and variance regulations adopted in ADEQ’s 2019 Triennial Review have been approved
  • EPA is still reviewing water quality standards related to aquatic life protection and Designated Uses from the 2019 submittal

The approved standards take effect immediately for Clean Water Act purposes. The submittal also included formatting revisions and other corrections that are non-substantive and are not new or revised water quality standards and are therefore not subject to EPA review and approval.


Recorded meetings and other stakeholder engagement materials are available for download | View > 

A summary of ADEQ’s water quality NFRM, with links to the Arizona Administrative Code is available on the Water Quality Division Final Rules page | View >

Sign up to receive email updates about Triennial Review | Subscribe >

For questions and comments, please email the Triennial Review Team | Email >