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Underground Injection Control (UIC)

Background Information about Geologic Sequestration


Geologic Sequestration (GS) is the process of injecting carbon dioxide (CO2), captured from an industrial (e.g., steel and cement production) or energy-related source (e.g., a power plant or natural gas processing facility), into deep subsurface rock formations for long-term storage. This is part of a process frequently referred to as “carbon capture and storage” or CCS. 

Underground injection of CO2 for purposes such as enhanced oil recovery (EOR) and enhanced gas recovery (EGR) is a long-standing practice. CO2 injection specifically for geologic sequestration involves different technical issues and potentially much larger volumes of CO2 and larger scale projects than in the past.

EPA has finalized requirements for geologic sequestration, including the development of a new class of wells, Class VI, under the authority of the Safe Drinking Water Act’s Underground Injection Control (UIC) Program. These requirements, also known as the Class VI rule, are designed to protect underground sources of drinking water. The Class VI rule builds on existing UIC Program requirements, with extensive tailored requirements that address carbon dioxide injection for long-term storage to ensure that wells used for geologic sequestration are appropriately:

The rule also affords owners or operators injection depth flexibility to address injection in various geologic settings in the United States in which geologic sequestration may occur, including very deep formations and oil and gas fields that are transitioned for use as carbon dioxide storage sites.

In a separate, yet complimentary, rulemaking under authority of the Clean Air Act, EPA has finalized reporting requirements under the Greenhouse Gas Reporting Program for facilities that inject CO2 underground for geologic sequestration and all other facilities that inject CO2 underground. Information obtained under the Greenhouse Gas Reporting Program will enable EPA to track the amount of carbon dioxide received by these facilities. For more information about the Greenhouse Gas Reporting Program and geologic sequestration, please see link below.


Additional information on climate change and sequestration can be found at EPA’s Global Warming and the Department of Energy websites:

Additional information on supporting documents relating to the development of the GS rule can be found at