Arizona Underground Injection Control (UIC) Program; Class I-VI Primacy

<RULE> ENVIRONMENTAL PROTECTION AGENCY <CFR>40 CFR Part 147</CFR> <DEPDOC>[EPA-HQ-OW-2025-0087; FRL-11786-02-OW]</DEPDOC> <SUBJECT>Arizona Underground Injection Control (UIC) Program; Class I-VI Primacy</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Environmental Protection Agency (EPA). <HD SOURCE="HED">ACTION:</HD> Final rule. <SUM> <HD SOURCE="HED">SUMMARY:</HD> The U.S. Environmental Protection Agency (EPA) is approving an application from the State of Arizona (the State) that requests primary enforcement responsibility (primacy) for Class I-VI injection wells under the Safe Drinking Water Act (SDWA) section 1422. The EPA's approval of the State's UIC program primacy application will allow the Arizona Department of Environmental Quality (ADEQ) to authorize underground injection for all underground injection wells regulated under the SDWA within the State's jurisdiction and ensure compliance with UIC program requirements. The EPA will remain the permitting authority for all well classes on Indian lands within the State, except for Class II wells on Navajo Indian lands for which the EPA has granted the Navajo Nation primacy for the SDWA Class II UIC program. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> This final rule is effective on October 15, 2025. The incorporation by reference of certain material listed in this rule is approved by the Director of the Federal Register as of October 15, 2025. For judicial purposes, this final rule is promulgated as of October 15, 2025. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> The EPA has established a docket for this action under Docket ID No. EPA-HQ-OW-2025-0087. All documents in the docket are listed on the <E T="03">http://www.regulations.gov</E> website. Although listed in the index, some information is not publicly available, <E T="03">e.g.,</E> confidential business information (CBI) or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, is not placed on the internet and will be publicly available only in hard copy form. Publicly available docket materials are available electronically through <E T="03">http://www.regulations.gov.</E> <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Mary Hastings Puckett, Drinking Water Infrastructure Development Division, Office of Ground Water and Drinking Water (4606M), Environmental Protection Agency, 1200 Pennsylvania Ave. NW, Washington, DC 20460; telephone number: (202) 564-1525; or Kate Rao, Water Division, Groundwater Protection Section (WTR-4-2), Environmental Protection Agency, Region 9, 75 Hawthorne Street, San Francisco, CA 94105; telephone number: (415) 972-3533. Both can be reached by emailing <E T="03">UICprimacy@epa.gov.</E> </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> <HD SOURCE="HD1">Table of Contents</HD> <EXTRACT> <FP SOURCE="FP-2">I. Introduction</FP> <FP SOURCE="FP1-2">A. Federal UIC Program and Primary Enforcement Authority (Primacy)</FP> <FP SOURCE="FP1-2">B. Class I-VI Wells Under the UIC Program</FP> <FP SOURCE="FP-2">II. Legal Authorities</FP> <FP SOURCE="FP-2">III. Arizona's Application for UIC Primacy</FP> <FP SOURCE="FP1-2">A. Background</FP> <FP SOURCE="FP1-2">B. Public Participation Activities Conducted by Arizona</FP> <FP SOURCE="FP1-2">C. Summary of the EPA's Comprehensive Evaluation</FP> <FP SOURCE="FP1-2">D. Public Participation Activities Conducted by the EPA</FP> <FP SOURCE="FP-2">IV. Public Comments and the EPA's Response</FP> <FP SOURCE="FP1-2">A. Public Comments</FP> <FP SOURCE="FP1-2">B. The EPA's Response to Comments</FP> <FP SOURCE="FP-2">V. The EPA's Action</FP> <FP SOURCE="FP1-2">A. Incorporation by Reference</FP> <FP SOURCE="FP1-2">B. The EPA's Oversight</FP> <FP SOURCE="FP-2">VI. Statutory and Executive Order Reviews</FP> <FP SOURCE="FP1-2">A. Executive Order 12866: Regulatory Planning and Review</FP> <FP SOURCE="FP1-2">B. Executive Order 14192: Unleashing Prosperity Through Deregulation</FP> <FP SOURCE="FP1-2">C. Paperwork Reduction Act (PRA)</FP> <FP SOURCE="FP1-2">D. Regulatory Flexibility Act (RFA)</FP> <FP SOURCE="FP1-2">E. Unfunded Mandates Reform Act (UMRA)</FP> <FP SOURCE="FP1-2">F. Executive Order 13132: Federalism</FP> <FP SOURCE="FP1-2">G. Executive Order 13175: Consultation and Coordination With Indian Tribal Governments</FP> <FP SOURCE="FP1-2">H. Executive Order 13045: Protection of Children From Environmental Health and Safety Risks</FP> <FP SOURCE="FP1-2">I. Executive Order 13211: Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution, or Use</FP> <FP SOURCE="FP1-2">J. National Technology Transfer and Advancement Act (NTTAA)</FP> <FP SOURCE="FP1-2">K. Congressional Review Act (CRA)</FP> <FP SOURCE="FP-2">VII. References</FP> </EXTRACT> <HD SOURCE="HD1">I. Introduction</HD> <HD SOURCE="HD2">A. Federal UIC Program and Primary Enforcement Authority (Primacy)</HD> The SDWA protects public health by regulating the nation's public drinking water supply, including both surface and groundwater sources. Among other things the SDWA requires the EPA to develop minimum requirements for effective State and Tribal UIC programs to prevent underground injection of fluids (such as water, wastewater, brines from oil and gas production, and carbon dioxide) from endangering underground sources of drinking water (USDWs). In general, USDWs are aquifers or parts of aquifers that supply a public water system or contain enough groundwater of sufficient quality to supply a public water system. See 40 CFR 144.3 (defining USDW). The EPA's UIC program regulates various aspects of injection. These include technical aspects throughout the lifetime of the project from site characterization, construction, operation, and testing and monitoring through site closure, as well as permitting, site inspections, and reporting to ensure well owners and operators comply with UIC permits and regulations. SDWA section 1421 directs the EPA to establish requirements that States, territories, and authorized Tribes must meet to be granted primary enforcement responsibility or “primacy” for a UIC program. 42 U.S.C. 300h. SDWA section 1422 provides that an applicant seeking primacy for a UIC program must demonstrate to the EPA that the applicant's proposed UIC program meets the applicable requirements promulgated by the EPA pursuant to section 1421 for protecting USDWs. 42 U.S.C. 300h-300h-1. An applicant must demonstrate, among other things, jurisdiction over underground injection and that it possesses the administrative, civil, and criminal enforcement authorities required by the EPA's implementing regulations. See 40 CFR part 145, subpart B. After the EPA approves a State for UIC program primacy, the State's UIC program may be revised with EPA approval. See 40 CFR 145.32. The EPA evaluates each primacy application in accordance with SDWA section 1422 and the EPA's implementing regulations to determine whether the State has satisfactorily demonstrated that, after reasonable notice and public hearings, it has adopted and will implement a UIC program that meets the requirements of the SDWA regulations at 40 CFR parts 144, 145, and 146. In this final rule, the EPA is approving Arizona's primacy application to administer the UIC program for six classes of wells (Classes I-VI) in the state. EPA's approval is based on the Agency's determination that the application meets all applicable requirements for approval under SDWA section 1422 and the EPA's implementing regulations and that the State is capable of administering a UIC program in a manner consistent with the SDWA and applicable UIC regulations. The EPA will remain the permitting authority for all UIC well classes on Indian land within the State, except for Class II wells on Navajo Indian lands for which EPA has granted the Navajo Nation primacy for the SDWA Class II UIC program. The EPA will oversee Arizona's administration of the State's UIC program as authorized under the SDWA. <HD SOURCE="HD2">B. Class I-VI Wells Under the UIC Program</HD> The UIC program consists of six classes of injection wells. Each well class is based on the type and depth of the injection activity and the potential for that injection activity to result in the endangerment of a USDW. Class I wells are used to inject wastes into deep isolated rock formations. Class II wells are used to inject fluids related to oil and natural gas production, primarily to enhance recovery of oil and gas or to dispose into rock formations wastewater associated with oil or gas production. Class III wells are used to inject fluids to dissolve and extract minerals. Class IV wells are used to inject hazardous and radioactive wastes into or above USDWs and are only allowed as part of an EPA- or State-authorized groundwater clean-up action. Class V wells are used to inject non-hazardous fluids underground, typically into or above a USDW, and range from simple shallow wells to complex experimental injection technologies. Most Class V wells are “low-tech”, depending on gravity to drain fluids directly below the land surface and include dry wells, cesspools, and septic system leach fields. Class VI wells are used to inject carbon dioxide into deep rock formations for the purpose of long-term underground storage, also known as geologic sequestration. 40 CFR 144.6. The UIC program provides multiple safeguards that work together to protect USDWs and human health from injection activities. To operate an injection well, operators must receive authorization by permit, or by rule in certain circumstances, through the UIC program. Operators must obtain a permit that authorizes injection in accordance with specific statutory and regulatory conditions. A draft of each permit is made available for public comment before the decision is made whether to issue a final permit. Qualifying C ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 42k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━