The Environmental Protection Agency (EPA) and U.S. Army Corps of Engineers (USACE) are the agencies that conduct rulemaking to define WOTUS | Learn More >

Over the last decade, there have been multiple rulemakings regarding WOTUS, and ADEQ has historically commented on these revisions.

The Clean Water Rule (CWR) became law in August 2015, but a preliminary injunction issued by a Federal District Court halted the rule’s implementation in Arizona. Due to the legal stay, Arizona continued regulating per the pre-2015 guidance released by the EPA and USACE. Notably, the CWR was repealed in September 2019 | Read State Comment Letter >

The Navigable Waters Protection Rule (NWPR) became law in June 2020. Arizona began implementation of the NWPR until August 30, 2022, when the rule was vacated by a federal court. This vacatur resulted in Arizona returning to the pre-2015 guidance | Read State Comment Letter >

In December 2021, the EPA and USACE proposed WOTUS Rule 1 to put back into place the pre-2015 definition of WOTUS and included language reflective of previous Supreme Court decisions | Read State Comment Letter >

EPA and USACE then conducted a second rulemaking to create the Revised Definition of Waters of the United States, which went into effect March 20, 2023, and was amended on August 29, 2023, to incorporate the U.S. Supreme Court decision in the case of Sackett v. Environmental Protection Agency. ADEQ did not comment on the Revised Definition of Waters of the United States or the revision,

On March 24, 2025, EPA and USACE published the WOTUS Notice: the Final Response to SCOTUS in the federal register. The publication announced a series of listening sessions and solicited feedback on key aspects of the definition of WOTUS in anticipation of conducting rulemaking to revise the Conforming Rule | Read State Comment Letter >

EPA and USACE considered that feedback and on Nov. 20, 2025, published the Updated Definition of Waters of the United States in the federal register | Read State Comment Letter >