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Underground Injection Control (UIC)

Primary Enforcement Authority for the Underground Injection Control Program

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How primary enforcement authority is defined

The UIC program requirements were developed by EPA. They are designed to be adopted by states, territories, and tribes. 

Primary enforcement authority, 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 authority oversees the UIC program in that state, territory, or tribe.

How states, territories, and tribes apply for primacy

Primacy programs are established under two sections of the Safe Drinking Water Act (SDWA).   

Section 1422 requires primacy applicants meet EPA’s minimum requirements for UIC programs.  Programs authorized under this section, referred to as 1422 programs, have primacy for Class I, II, III, IV, V, and VI wells. Under Section 1422, applicants may submit primacy applications for:

  • All well classes
  • Classes I – V
  • Class VI

Section 1425 requires primacy applicants to demonstrate their standards are effective in preventing endangerment of USDWs. Section 1425 programs are not required to meet EPA’s minimum requirements as long as applicants can show their standards protect USDWs. Section 1425 applies to Class II wells only.

EPA may grant primacy for all or part of the UIC program.  This means that in some jurisdictions primary enforcement authority for certain well classes may be shared with EPA. 

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States, territories, and tribes with primacy

Thirty four states and three territories have EPA approved primacy programs for well classes I, II, III, IV and V.  Additionally, seven states and two tribes have applied for and received primacy approval for Class II wells only. 

No Class VI primacy applications have been approved by EPA.  EPA implements the Class VI program nationally. However, EPA has issued a proposed rulemaking to grant North Dakota primary enforcement responsibility. Read more.

US Map showing states, territories, and tribes with UIC Class II primacyStates, territories, and tribes with UIC Class II primacy

EPA directly implements the Class II program in nine states, three territories, the District of Columbia, and for all tribes except for the Navajo Nation and Fort Peck Tribes.  Twenty four states and two tribes have UIC Class II primacy under SDWA Section 1425. Seventeen states and three territories have UIC Class II primacy under SDWA Section 1422.

US Map showing states, territories, and tribes with UIC Class II primacy based on SDWA designations States, territories, and tribes with UIC Class II primacy

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Recently proposed or approved primacy programs or revisions


EPA is seeking public comment on a proposal to transfer authority of Idaho’s Underground Injection Control (UIC) program for Class II injection wells from Idaho to EPA, as requested by the state.

EPA is providing notice and concurrently issuing a proposed rule to amend the federal regulations to reflect this transfer. This rule is intended update 40 CFR part 147, Subpart N, which currently lists Idaho as having primacy for the Class II program. The proposed rule indicates that the EPA will  directly implement the Class II UIC program in Idaho. The public comment period for this proposal will be 45 days from the date of publication in the Federal Register.


EPA issued final approval, under the SDWA, granting the Commonwealth of Kentucky primary enforcement responsibility for UIC Class II injection wells located within the state. This action excludes Class II injection wells located on Indian lands. State of Kentucky Underground Injection Control (UIC) Class II Program; Primacy Approval Final Rule is effective March 21, 2017.

EPA's role in states, territories, and tribes without approved programs

If a state, territory, or tribe does not obtain primacy for all or some of the well classes, EPA implements the program directly through one of its regional offices. Currently, EPA implements the UIC program for all well classes in nine states and two territories.  Except for the Navajo Nation and Fort Peck Class II programs, EPA directly implements the UIC program in Indian country.

View a summary of state, territory, and tribal responsibilities for the UIC program.