Arizona is Peerless, Her Breezes are Soft, and Her Aquifer Water Quality Standards are Newly Updated

On June 4^, 2025, the Arizona Department of Environmental Quality (ADEQ) announced that the Governor’s Regulatory Review Council (GRRC) has approved updated Aquifer Water Quality Standards (AWQS). Four new AWQS have been added for bromate, chlorite, haloacetic acids (HAAs), and uranium, and three existing AWQS have been modified, those for arsenic, microbiological contaminants, and total trihalomethanes.

AWQS are intended to protect Arizona’s aquifers, the state’s largest source of drinking water. AWQS are enforced through Arizona’s Aquifer Protection Permits (APPs), which are required for any facility that discharges pollutants where there is a reasonable probability the pollutant will reach an aquifer. These new rules will go into effect on August 4, 2025. Mines, industrial facilities, and wastewater treatment plants were specifically identified as types of facilities that may be impacted.

Although APPs are valid for the life of the facility, a majority of the roughly 500 APP permit holders will be required to revise their permit with the newly updated AWQS. ADEQ has released an implementation schedule by which they plan to revise all permits affected by the new rule on or before August of 2029. APP permit holders should have received notice of this required amendment from ADEQ in June of 2025, including which phase of the implementation they will be included in.

Baseline Monitoring Requirements

Arizona Administrative Code (A.A.C.) R18-9-A215(C) requires holders of individual permits to begin Baseline Monitoring for new or updated AWQS by November 4, 2025, unless they meet one of the following conditions:

• The permit has no ongoing monitoring requirement;
• The permittee has not begun ongoing monitoring;
• The permittee has submitted an Alternative Baseline Modeling Request; or
• The permittee has submitted an “Unlikely to be Present in Discharge Demonstration”.

Baseline monitoring requirements will depend on the existing monitoring requirements in the current APP. Permits with only discharge monitoring will sample once a month for one year (12 samples total), while permits with only groundwater monitoring requirements will sample quarterly for two years. Permit holders with no discharge or groundwater monitoring requirements are asked to meet with ADEQ as a discharge characterization may be necessary. Sampling must be conducted using the Arizona Department of Health Services approved methods summarized in the following table:

What Are My Next Steps?

• Closely read all communications from ADEQ regarding the implementation schedule. You should receive both email and physical notifications about your assigned phase. Phase assignments are posted on the ADEQ website: https://azdeq.gov/rulemaking/awqs-update/resources
• Schedule a pre-application meeting with ADEQ, especially if your facility is included in phase 1. You can schedule a meeting by filling out the form located here: https:/a/azdeq.gov/aquifer-protection-permit-app-pre-application-meeting-request
• Assess whether your facility should submit an alternative baseline monitoring request. If you would like to conduct monitoring on an alternative timeframe, duration, or frequency, you must submit a request to do so within three months of the new AWQS effective date (November 4, 2025). It is best practice to schedule a meeting with ADEQ before submitting an alternative baseline monitoring request to ensure alignment with the agency.
• Assess whether your facility should complete an “Unlikely to be Present in Discharge Demonstration”. If one or more of the pollutants for which there is an AWQS is unlikely to be present in your facility’s discharge, you can remove it from your Baseline Monitoring requirements by doing this.
• Discuss the updated AWQS with your on-site or contract laboratory to ensure the detection limits of the methods are calibrated to provide meaningful data with the lower limits.

If you’d like assistance preparing a monitoring or permitting strategy, applying for an amendment, completing any work associated with these changes, or have any questions about this update or the actions your facility needs to take, please do not hesitate to reach out to me at kblackmon@all4inc.com, or to my colleague Andrew Kelley at akelley@all4inc.com.