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Underground Injection Control (UIC)

Primary Enforcement Authority for the Underground Injection Control Program

On this page:

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. 

North Dakota is the only state with primary enforcement authority for UIC Class VI wells. EPA directly  implements the Class VI program in all other states, territories, and tribes. 

US map showing state UIC primacy programs

EPA directly implements the Class II program in ten 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. Sixteen states and three territories have UIC Class II primacy under SDWA Section 1422.

US map showing class II primacy states.

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Recently proposed or approved primacy programs or revision

North Dakota

EPA is approving an application from the State of North Dakota under the SDWA to revise the State’s existing UIC program for Class I, III, IV, and V injection wells located within the State, except those in Indian country. North Dakota has revised its UIC Class I, III, IV, and V program regulations to
transfer primary enforcement responisbility from the North Dakota Department of Health to the North Dakota Department of Environmental Quality. This final rule is effective May 15, 2019. Learn more about North Dakota's program revision.

On April 10, 2018, EPA issued a final rule approving North Dakota’s application for primary enforcement responsibility for Class VI Wells located within the state. EPA will continue to directly implement the Class VI program within Indian lands. North Dakota is the first state to receive primacy for Class VI UIC wells. Review information on North Dakota's UIC program revision package at Docket ID EPA-HQ-OW-2013-0280


On July 30, 2018, EPA issued a final rule amending 40 CFR part 147, Subpart N, to reflect the voluntary transfer of Class II primacy from the state of Idaho to EPA. Idaho will retain primacy for Class I, III, IV, and V wells.


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.