Energy-Related Injection


Injection Well DiagramThe federal regulations for the Underground Injection Control (UIC) program are found in Title 40 of the Code of Federal Regulations under the regulation from the Environmental Protection Agency (EPA). The Safe Drinking Water Act (SDWA) establishes requirements and provisions for the UIC program. Congress passed the SDWA in 1974. In part, the SDWA requires EPA to develop minimum federal requirements for UIC programs and other safeguards to protect public health by preventing injection wells from contaminating underground source of drinking water (USDWs).

The UIC program consists of six classes of injection wells authorized under the SDWA. Each well class is based on the type and depth of the injection activity, and the potential for that injection activity to result in endangerment of an USDW.

  • Class I wells are used to inject hazardous and non-hazardous wastes into deep, isolated rock formations.
  • Class II wells are used exclusively to inject fluids associated with oil and natural gas production.
  • Class III wells are used to inject fluids to dissolve and extract minerals.
  • Class IV wells are shallow wells used to inject hazardous or radioactive wastes into or above a geologic formation that contains a USDW. This class of well is banned except when used as part of an environmental cleanup project
  • Class V wells are used to inject non-hazardous fluids underground. Most Class V wells are used to dispose of wastes into or above underground sources of drinking water.
  • Class VI wells are wells used for injection of carbon dioxide (CO2) into underground subsurface rock formations for long-term storage.

UIC regulations mandate the consideration of a variety of measures to assure that injection activities will not endanger USDWs. The concept of endangerment is defined in federal code of regulations (40 CFR 144.12).

Many UIC wells are regulated by states, tribes, and territories under delegation from the EPA.  For example, the Class II program is delegated to 40 states, two tribes, and three territories under Sections 1422 or 1425 of the SDWA.[1]


As oil and natural gas are brought to the surface, they generally are mixed with salt water. On a national average, approximately 10 barrels of salt water are produced with every barrel of crude oil[2]. Geologic formations are selected to receive the produced waters, which, in some cases, are reinjected through disposal wells.


Enhanced Oil Recovery (EOR) injection wells are used to increase production and prolong the life of oil-producing fields.  Fluids consisting of brine, freshwater, steam, polymers, or carbon dioxide are injected into oil-bearing formations to recover residual oil and in limited applications, natural gas.

The injected fluids thin (decrease the viscosity) or displace small amounts of extractable oil and gas. Oil and gas is then available for recovery. In a typical configuration, a single injection well is surrounded by multiple production wells that bring oil and gas to the surface.

The UIC program does not regulate wells that are solely used for production. However, EPA does have authority to regulate hydraulic fracturing when diesel fuels are used in fluids or propping agents. During hydraulic fracturing, another enhanced recovery process, a viscous fluid is injected under high pressure until the desired fracturing is achieved, the fractures are then propped open using materials (proppants) such as sand or ceramic beads.

Enhanced recovery wells are the most numerous types of Class II wells. They represent as much as 80 percent of the total number of Class II wells. Under the UIC program, the EPA establishes minimum standards to prohibit underground injection that would endanger USDWs, and applicable UIC program regulations are established for each state to be administered either by EPA (direct implementation) or by the state which can apply for and obtain “primacy” to administer all or portions of the UIC program within the state.  

Class II disposal fluids are primarily brines (salt water) that are brought to the surface while producing oil and gas (also known as produced water). Class II wells could also be used to inject fluids to enhance hydrocarbon production, such as CO2 in EOR projects. The number of active Class II wells varies from year to year based on fluctuations in oil and gas demand and production. There are approximately 180,000 Class II wells in the United States. 


Hydrocarbon storage wells are generally used for the underground storage of crude oil and other hydrocarbons that are liquid at standard temperature. These hydrocarbons are typically stored in depleted oil and gas formations and naturally occurring or mined caverns.. The wells are designed for both injection and removal of the stored hydrocarbons. The hydrocarbons are injected for storage and later pumped back out for processing and use. 

[2] Veil, John, U.S. Produced Water Volumes and Management Practices in 2017, GWPC, February, 2020

Additional Resources:

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Injection Wells: A Guide to Their Use, Operation, and Regulation (2021 Update)

The purpose of this guide is to provide introductory information about groundwater and the Underground Injection Control Program. The guide is intended for a broad audience and avoids the use of technical jargon to the extent possible in describing groundwater and UIC concepts. 


Potential Induced Seismicity Guide: A Resource of Technical and Regulatory Considerations Associated with Fluid Injection

The State Oil and Gas Regulatory Exchange (Exchange) released today a third edition of its report on induced seismicity,


Well Integrity Regulatory Elements for Consideration: 2021 Edition

These "Regulatory Elements for Well Integrity" are intended to provide regulators with a set of ideas to consider when improving oversight of the permitting, construction, operation and plugging of oil and gas wells. The Elements were developed by a group of state officials who met informally in conjunction with GWPC meetings in Nashville, Tennessee (2012); Sarasota, Florida (2012); and St. Louis (2013). The elements were updated by a small group of state officials in July 2020.


State of Kansas Class II UIC Program Peer Review

Published September 2020


State of California Class II UIC Program Peer Review

This report is a snapshot of the California Class II UIC program as it existed in June 2018. The review team performed an in-depth review of the California UIC Class II program via a review of California laws and regulations, responses to a questionnaire, and a two-day state interview of DOGGR, SWRCB and Regional Water Board staff and management involved in the UIC program.


New Mexico Class II UIC Program Peer Review

In September, 2019 the New Mexico Oil Conservation Division (OCD) requested that the Ground Water Protection Council (GWPC) conduct a focused Peer Review of their Class II UIC program. These reviews were reinitiated nearly 4 years ago as part of the State Oil and Gas Regulatory Exchange (a joint project of the GWPC and the Interstate Oil and Gas Compact Commission (IOGCC)). Reviews have been conducted in 5 states since 2015. They involve an evaluation of the effectiveness of a state’s Class II UIC program, which demonstrates the ability of the UIC program to protect USDWs and public health. Equal effectiveness with Section 1422 SDWA programs is the standard required of Section 1425 delegated programs. This report details the findings of the peer review team, provides feedback on positive aspects of the program and offers suggestions for enhancing the effectiveness of the Class II UIC program managed by the OCD


Produced Water Report: Regulations, Current Practices & Needs

The GWPC released a 'Produced Water Report' on June 24, 2019, that examines current regulations, practices, and research needed to expand the use of produced water, a byproduct of oil and gas production, as a resource.Led by its member states, the GWPC brought together a collaboration of scientists, regulatory officials, members of academia, the oil and gas industry, and environmental groups to explore roles produced water might play in developing greater water certainty. The report consists of three focused modules which include:Module 1: Current Legal, Regulatory & Operational FrameworksModule 2: Produced Water Reuse in Unconventional Oil & Gas OperationsModule 3: Produced Water Reuse & Research Needs Outside Oil & Gas OperationsFreshwater stress is driven by rising populations, regional droughts, declining groundwater levels and several other factors. When surface water is scarce, communities and industries typically turn to groundwater to meet their freshwater needs.  Produced water may become a resource that could reduce the use of freshwater for some of these needs in specific locations.  


State Oil And Natural Gas Regulations Designed To Protect Water Resources (3rd Edition)

The Ground Water Protection Council is pleased to announce the release of its report “State Oil and Natural Gas Regulations Designed to Protect Water Resources”, Third Edition.  This report provides a compiled list of regulatory elements such as permitting, well integrity, hydraulic fracturing, well plugging, pits, tanks and spill management.  These are presented in a graphical form which details the number of states that implement them.  In addition, the report describes the regulatory framework under which oil and natural gas field operations are managed and suggests a series of regulatory considerations for agencies to review and, as appropriate, implement.  The report covers regulations as of January, 2016.


State Of West Virginia Class II UIC Peer Review

The Ground Water Protection Council (GWPC) conducts the Class II UIC Peer Review process under the joint GWPC and Interstate Oil and Gas Compact Commission (IOGCC) “StatesFirst” Initiative. The purpose of this process is to assess the effectiveness of Class II UIC programs that have been delegated to states under Sections 1422 or 1425 of the Safe Drinking Water Act (SDWA). The peer review of the Class II UIC program administered by the West Virginia Department of Environmental Protection, Office of Oil and Gas (OOG) was conducted by a review team made up of UIC managers and technical staff from state Class II agencies of states outside of the USEPA region in which West Virginia resides (Region 3). This included an in-state interview of OOG staff and management at the OOG office in Charleston, West Virginia on March 21, 2017. The in-state interview was based on responses to a comprehensive questionnaire completed by the state UIC staff and follow-up questions posed to the UIC staff during the interview. In addition, the interview team members reviewed the state’s statutes and rules governing the UIC program and other materials provided by the state.


Underground Gas Storage Regulatory Considerations

A national Natural Gas Storage Work Group released this report on underground gas storage that evaluates potential vulnerabilities at gas storage operations and identifies prospective regulatory responses for consideration by state and federal agencies. Most underground gas storage facilities have safe histories of operation and allow large supplies of gas to be stored during times of low demand, and withdrawn from storage when demand for natural gas is high; thereby reducing the need for larger transmission pipelines and allowing for continuous supply of gas in the event of supply interruptions. However, when an accident occurs it can have dramatic impacts to public health, safety and the environment. The work group, which was led by states from across the country and was organized by the Interstate Oil and Gas Compact Commission and Ground Water Protection Council, developed the report “Underground Gas Storage Regulatory Considerations” to serve as a resource for regulatory agencies and includes input from experts in academia, industry, non-profit organizations, and other state and federal agencies.


Ground Water Report to the Nation

Our groundwater resources are in serious need of attention. Abundant, high quality, low-cost groundwater resources are fundamental to the long-term growth and vitality of our nation, yet this most important resource is often overlooked, if not neglected. Attention to the protection and management of groundwater has consistently lagged behind that given to surface waters, meaning that historic and current water resource laws and policies deal primarily with the protection and management of our more visible lakes, rivers, and wetlands.The purpose of the Ground Water Report to the Nation is to highlight some of the more prevalent threats to groundwater, share sucess stories, and make recommendations for improved groundwater protection and awareness.  Note: Please visit the Ground Water Report to the Nation topics page for individual chapters of the report.


Ohio Class II Peer Review

This review of the State of Ohio was finalized in January 2017 by a team of Class II program managers from other state programs and overseen by the GWPC.  We would like to thank the State of Ohio for their assistance to the review team and we look forward to working with other states as we move forward with additional reviews.


State Of Nebraska Class II UIC Program Peer Review

This review of the State of Nebraska was finalized in April, 2016 by a team of Class II program managers from other state programs and overseen by the GWPC.  We would like to thank the State of Nebraska and the staff of the Nebraska Oil and Gas Conservation Commission for their assistance to the review team and we look forward to working with other states as we move forward with additional reviews.


State Of Utah Class II UIC Program Peer Review

GWPC announces the publication of the first Class II UIC program peer review conducted under the revamped peer review process. This process, a joint GWPC and States First initiative, is designed to assist states by evaluating their Class II UIC programs, recognizing the positive aspects of a program, and offering suggestions for improvement. This review of the State of Utah, which was conducted in November, 2015 by a team of Class II program managers from other state programs and overseen by the GWPC, is the first of what GWPC hopes will be a series of state reviews to be conducted in the future.  We would like to thank the State of Utah and the staff of the Division of Oil, Gas, and Mining for their assistance to the review team and we look forward to working with other states as we move forward into 2016 and beyond.


Potential Injection-Induced Seismicity Associated with Oil & Gas Development: A Primer on Technical and Regulatory Considerations Informing Risk Management and Mitigation

Thirteen states partnered through a multi-state initiative called StatesFirst in 2015 to share and summarize current knowledge related to earthquakes potentially caused by human activity, otherwise referred to as induced seismicity.The work group comprised of members of state oil and natural gas and geological agencies and other advisory experts from academia, industry, non-profit organizations and federal agencies released a Primer to provide a guide for regulatory agencies to evaluate and develop strategies to mitigate and manage risks of injection induced seismicity. The Primer also outlines how states can best provide information to the public in a transparent and effective manner.


State Oil And Gas Regulations Designed To Protect Water Resources

In step with dramatic industry growth over the past five years, states have substantially improved ground water protection laws and regulations governing oil and natural gas production. State regulatory strategies differ in response to unique local circumstances and characteristics; over time, they evolve to address public concerns about the safety and environmental impact of oil and gas development, as well as rapidly changing technologies, new field discoveries, revised leading operational practices, internal and external reviews, and regulatory experience.


Overview Of Groundwater Protection Regulations In Oil And Gas States

This report is part of an update to the Ground Water Protection Council’s 2009 Report, State Oil and Gas Regulations Designed to Protect Water Resources.1 The purpose is to document and outline the range of definitions and requirements for protecting groundwater, based on the regulations of oil and gas agencies and water quality protection agencies in 27 oil and gas producing states. The report is divided into two parts, the first documents the groundwater protection standards for oil and gas agencies and the second part addresses the standards for the water quality protection agencies within the same states. The scope is limited to an overview of regulations that address groundwater quality protection standards through policy statements, definitions, technical requirements such as well casing and cementing depths, groundwater classification and groundwater protection standards. 


State Oil & Gas Regulations Designed To Protect Water Resources

The role of state oil and gas agencies in protecting groundwater through investigation and regulatory reform.

Work Groups

No workgroups were found.


No resolutions were found.



Comments on EPA Applying the Supreme Court’s County of Maui v. Hawaii Wildlife Fund Decision in the Clean Water Act Section 402 National Pollutant Discharge Elimination System Permit Program

The Ground Water Protection Council (GWPC) provided comments and feedback to the Environmental Protection Agency (EPA) regarding their draft memorandum which will provide guidance to the regulated community and permitting authorities on applying the recent decision of the United States Supreme Court in County of Maui v. Hawaii Wildlife Fund, 140 S. Ct. 1462 (2020), in the Clean Water Act Section 402 National Pollutant Discharge Elimination System (NPDES) permit program for point source discharges that travel through groundwater before reaching waters of the United States.GWPC recognizes that groundwater is not and has never been a jurisdictional water under the definition of waters of the United States. States have full authority over their groundwater resources. Many of our member agencies protect groundwater quality and resources utilizing both federal and state authorities that are outside the regulatory jurisdiction of the CWA.


Comments on EPA’s Draft National Water Program Guidance 2018-2019, Publication Number 800D17001

The Ground Water Protection Council (GWPC) provided comments on the draft National Water Program Guidance for 2018-2019.


Comments on Proposed USDA Forest Service Directive on Groundwater Resource Management

GWPC recognizes the emphasis in this document on working with states. We feel that collaboration and cooperation with the States is necessary for US Forest Service (USFS) to achieve the vision, goals, strategies, and actions set out within the Groundwater Directive for UIC activities. Recognizing that USFS is not authorized to implement the UIC program under the Safe Drinking Water Act and thus does not have the regulatory authority necessary to carry out some of the provision of the directive, our specific comments provide information on how and when USFS can work within the existing UIC regulatory framework administered by US Environment Protection Agency (USEPA) and the delegated states to ensure all applicable UIC authorizations and permits have been issued by the appropriate regulatory authority.