Proposed Rulemaking: Arizona Underground Injection Control Primacy Program

Background

On February 16, 2024, Arizona submitted an application for primary enforcement responsibility (primacy) of the Underground Injection Control (UIC) program under the Safe Drinking Water Act section 1422. Arizona is seeking to administer the UIC program for Classes I -VI injection wells located within the State.

The purpose of the UIC program is to ensure the protection of underground sources of drinking water. The UIC program regulates the construction, operation, permitting, and closure of injection wells used to place fluids underground for storage, disposal, or mineral production.

The UIC program regulates six classes of injection wells.

• Class I - industrial, municipal, hazardous, and radioactive waste disposal wells.
• Class II - injection wells related to oil and gas production and storage.
• Class III - solution mining injection wells.
• Class IV - shallow hazardous and radioactive waste injection wells (banned).
• Class V - injection wells related to non-hazardous fluids, often into or above USDWs.
• Class VI - injection of carbon dioxide for geologic sequestration.

EPA’s approval would allow the Arizona Department of Environmental Quality to authorize underground injection in the State in accordance with UIC program requirements.

Public Comment

EPA is seeking public input on EPA’s intent to approve Arizona’s request for primacy for the UIC program under the Safe Drinking Water Act section 1422.

As a result of EPA’s comprehensive review of the state’s application, the Agency is proposing to approve Arizona’s primacy application because EPA has determined that the application meets all applicable requirements for primacy approval under SDWA section 1422 and because the State has demonstrated that it is prepared to implement a UIC program in a manner consistent with the terms and purposes of SDWA and all applicable UIC regulations. Upon approval, EPA would oversee Arizona’s administration of its UIC program.

EPA requests that written comments be submitted on or before July 3, 2025, via the Federal eRulemaking Portal for Docket ID No. EPA-HQ-OW-2025-0087 at www.regulations.gov. All material associated with this action can be found in the Docket.