Primary Enforcement Authority for the Underground Injection Control Program

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What is UIC primary enforcement responsibility (primacy)?

Primary enforcement responsibility, often called primacy, refers to state, territory, or Tribal responsibilities associated with implementing EPA approved UIC programs. A state, territory, or Tribe with UIC primacy, or primary enforcement responsibility, oversees the UIC program in that state, territory, or Tribe.

The Safe Drinking Water Act (SDWA) requires the EPA to develop UIC program requirements that protect underground sources of drinking water (USDWs) from endangerment. The EPA developed UIC program requirements that are designed to be adopted by states, territories, and Tribes.

Primacy programs are established under the SDWA sections 1422 and 1425. Section 1422 applies to all well classes and requires primacy applicants to meet the EPA’s minimum requirements for UIC programs. Section 1425 applies to Class II wells only and requires primacy applicants to demonstrate their standards are effective in preventing endangerment of USDWs.

SDWA Section 1422

SDWA Section 1425

Program Requirements

Meets minimum EPA requirements for UIC programs

Demonstrate standards are effective in preventing endangerment of USDWs

Demonstrate to the EPA that the state, territory, or Tribe has jurisdiction over underground injection and the necessary administrative, civil and criminal enforcement penalty remedies.

Well Class Applicability

·        All well classes

·        Classes I – V

·        Class VI

Class II

What states, territories, and Tribes have primacy?

The EPA has approved UIC primacy programs for multiple well classes in thirty-one states and three territories. If a state, territory, or Tribe does not obtain primacy for all or some UIC well classes, the EPA implements the program directly through one of its regional offices. Currently, the EPA implements the UIC program for all well classes in seven states and three territories. Apart from the Navajo Nation and Fort Peck Class II programs, the EPA directly implements the UIC program in Indian country.

Use your cursor and hover over the states, tribes and territories (all referred to collectively as “State”) in the map below, or refer directly to the table, for state-specific primacy information.

UIC Primacy Map

 
Tribes
  Navajo Nation
  Fort Peck Tribes
  All Other Indian Tribes.
Key
  EPA manages all well classes.
  State has primacy for Class II wells only.
  State has primacy for multiple well classes.
  State has primacy for all well classes (Classes I, II, III, IV, V and VI).
 
 

 

What is the process for states, territories and tribes to apply for primacy or implement a program revision?

States, territories and tribes applying for UIC program primacy must follow the UIC primacy application process requirements presented at 40 CFR part 145. Two EPA guidance documents describe the general procedures for the Agency's review and approval of primacy and program revision applications.

EPA Guidance

Download EPA primacy and program revisions regulatory checklist and crosswalk.

The information provided on this webpage is intended to clarify procedures and facilitate transparency and consistency in primacy and program revision evaluations and approvals.

Arrows moving from left to right to show the four phases of the underground injection control program primacy application process.

​Phase I: Pre-application Activities

Under this phase, the EPA may support a state, territory, or Tribe by:

  • Identifying available resources and the critical elements of a primacy application or program revision.
  • Meeting to outline the process, address preliminary questions, and determine which well classes may be included in the application.
  • Reviewing the applicants draft UIC statutes and regulations, or any other material in the application package. 
  • Encouraging a comparison with federal regulations using the comparison crosswalk template.

Phase II: Application Evaluation and Completeness Determination

Under this phase, the EPA and the state, territory, or Tribe conducts the following activities:

  • EPA receives and reviews complete or mostly complete drafts of applicable critical elements of the primacy application.
  • Evaluates each primacy application element and coordinates with applicants to clarify questions and confirm stringency or effectiveness.
  • EPA and a state, territory, or Tribe may engage in a continued dialogue to clarify questions.
  • A state, territory or Tribe may identify regulatory or statutory changes to implement by the end of this phase.
  • The EPA’s regional UIC program verifies the application is complete and transmits it to the National UIC program to initiate rulemaking.

Phase III: Proposed Rulemaking

Under this phase, the EPA conducts the following activities:

  • Publishes a proposed rule signed by the EPA Administrator which indicates the EPA’s intent to approve or disapprove of a primacy application or program revision.
  • Initiates a minimum 45-day public comment period and holds a public hearing, if requested.
  • The EPA may request additional information and/or coordinate with applicants to confirm stringency or effectiveness.

Phase IV: Final Rulemaking and Codification

Under this phase, the EPA conducts the following activities:

  • Reviews all public comments provided through the EPA docket and the public hearing.
  • Depending on the comments, the EPA may request additional information and/or coordinate with applicants to confirm stringency or effectiveness. 
  • Drafts the final rule approving, or disapproving, the primacy application or program revision.
  • Prepares the final rule package for submission to the EPA Administrator. The final rule package includes: a summary of the public comments and the EPA’s responses; documentation of any changes from the state’s original application and the EPA’s rationale for finalizing the rule with such changes; and the regulatory text that will be codified in 40 CFR part 147 after the program is approved.
  • The EPA Administrator signs the final rule for publication in the federal register.

What are the core elements of a primacy application or program revision? 

Segmented wheel divided into six pieces, each piece representing one of the core elements of an underground injection control program primacy application or a substantial program revision application.

UIC Program regulations at 40 CFR part 145 identify six core elements of a UIC primacy application or substantial program revision.

Each of the six requirements are identified below. All documents are required for a new primacy application. For program revisions, depending on the nature of the UIC program changes, a state, territory, or tribe may need to revise one or more of the six core elements and submit a revised primacy application to the EPA.

Governor's Letter Program Description Attorney General's Statement Memorandum of Agreement Copy of Applicant's UIC Statutes and Regulations Public Participation Process Determination
  • A signed letter from the governor of the state requesting approval for UIC program primacy.
  • Must specify that approval is sought under sections 1422 or 1425 of the SDWA.
  • A document describing in narrative form the  scope, structure, coverage and  processes of the applicant’s program.
  • A certification by a qualified representative of the state, asserting that the state’s statutes, regulations and judicial decisions demonstrate adequate authority to administer the UIC program.
  • The central  agreement setting out the provisions and arrangements between the applicant and the EPA.
  • Describes the administration, implementation and enforcement of the applicant’s UIC program.
  • A copy of the applicable UIC statutes and regulations.  
  • SDWA  Section 1422: Applicants may incorporate the federal regulations by reference, adopt the federal language verbatim, or establish final provisions that are as stringent as the federal requirements.
  • SDWA Section 1425: Applicants must demonstrate that their Class II regulations are effective in preventing underground injection that endangers USDWs.
  • Documentation of the public participation process the applicant used to notify the public of its intent to apply for primacy.
Review an example letter from a recently approved program. Review and example from a recently approved program. Review and example from a recently approved program. Review an example from a recently approved program. Review an example from a recently approved program. Review an example from a recently approved program.

 

What states, territories, and tribes are currently in the primacy application or program revision process?

Status of state, territory, and tribal primacy and program revision applications

Flow chart for UIC primacy and program revision applications

Arizona

Summary of Action

On May 9, 2025, the U.S. Environmental Protection Agency’s Administrator Lee Zeldin signed the Proposed Rule to approve the State of Arizona’s request for primary enforcement responsibility of Class I-VI wells under the UIC program. After conducting a comprehensive review, the EPA is proposing to approve Arizona’s primacy application because the EPA has determined, subject to public comment, that the application meets all applicable requirements for primacy approval under the Safe Drinking Water Act section 1422. Upon approval, the State of Arizona will become the permitting authority for all UIC well classes in the state.

Review the Proposed Rule documenting the Agency's action. 

EPA will hold one virtual public hearing during the public comment period. Learn more about Arizona's primacy proposal and register to speak at the virtual hearing.  

What states, territories, and tribes have recently completed the primacy application or program revision process?

West Virginia

Summary of Action

On February 18, 2025, the U.S. Environmental Protection Agency's Administrator Lee Zeldin signed the final rule approving the State of West Virginia’s request for primary enforcement responsibility of Class VI wells under the UIC program. On May 1, 2024, the State of West Virginia submitted to the EPA a program revision application package to add Class VI injection wells to the state’s existing UIC program. On November 27, 2024, the EPA published a Proposed Rule in the Federal Register for public input. The public comment period for the Proposed Rule ended on December 30, 2024. After considering written comments and input from an all-day public hearing on December 30, 2024, the EPA determined that the State of West Virginia’s Class VI UIC program met all requirements for approval. This action allows the West Virginia Department of Environmental Protection (WVDEP) to issue UIC permits for geologic carbon sequestration facilities as Class VI wells and ensure compliance of Class VI wells under the UIC program within the State. 

Review the EPA’s responsiveness summary to public comments.

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Last updated on May 20, 2025