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Geologic Sequestration of Carbon Dioxide

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Geologic sequestration (GS) is the process of injecting carbon dioxide (CO2) from a source, such as a coal-fired electric generating power plant, through a well into the deep subsurface. With proper site selection and management, geologic sequestration could play a major role in reducing emissions of CO2.

This page provides information on the EPA Office of Groundwater and Drinking Water’s work to ensure the protection of underground sources of drinking water (USDWs).


Geologic sequestration of CO2 through well injection meets the definition of “underground injection” in section 1421(d)(1) of the Safe Drinking Water Act (SDWA). EPA has authority for underground injection of under the SDWA Underground Injection Control (UIC) program.EPA and states, territories, and tribes that have primacy for UIC programs (“Primacy States”) act as co-regulators to protect USDWs from any potential endangerment from underground injection of CO2.

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.

Research efforts to evaluate the technical aspects of CO2 geologic sequestration are underway.EPA Regions and Primacy States currently permit injection wells associated with these research and development projects as Class V wells. Permit applications are evaluated on a case-by-case basis to ensure the protection of USDWs. EPA released Class V Experimental Technology Well Guidance for Pilot Geologic Sequestration Projects in March, 2007. This guidance is intended to address only the experimental pilot projects anticipated to be brought online in advance of full-scale operations over the next several years. Regulations now in development will address future full-scale projects.

EPA announced in October 2007 that the Agency plannned to propose regulations to ensure consistency in permitting full-scale geologic sequestration projects in the summer of 2008. Several public stakeholder workshops were held to inform the regulatory development process.

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Regulatory Development

Proposed rule for Federal Requirements Under the Underground Injection Control (UIC) Program for Carbon Dioxide (CO2) Geologic Sequestration (GS) Wells

In July 2008, EPA published the Federal Requirements Under the Underground Injection Control (UIC) Program for Carbon Dioxide (CO2) Geologic Sequestration (GS) Wells Proposed Rule for public review and comment. 

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Public Hearings, Webcasts, and Workshops

Public Hearings

Webcasts on Financial Responsibility Instruments for Geologic Sequestration (GS) Wells

In April and May 2009, EPA sponsored a series of public webinars on financial responsibility for carbon dioxide geologic sequestration (GS) wells. The goal of the series was to encourage information sharing on potential financial mechanisms that well owners and operators could use to meet the financial responsibility requirements for GS projects. EPA plans to use the information gathered through the webinar series to inform its decisions as it develops guidance related to financial responsibility for GS wells. The webinars addressed the following topics:

Collectively, about 100 people attended the webinars. The participants represented a range of organizations with interest in and unique perspectives on financial responsibility for GS, including staff members of EPA regions, corporations, consulting, and financial services, state/municipal governments, energy/environmental nonprofits, electricity providers (e.g., energy companies and utilities), and academia.

Stakeholder workshops

Technical workshops on Geological Sequestration

Since 2005 EPA has been sponsoring or co-sponsoring workshops to explore the technical aspects of CO2 geologic sequestration and to share ideas with stakeholders and experts.

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Class V Experimental Technology Well Guidance for Pilot Geologic Sequestration Projects

Pilot geologic sequestration projects around the country are assessing the efficacy of CO2 injection for the purpose of geologic sequestration. They will provide information about how CO2 behaves in the sub-surface and proper well construction and operational procedures.

EPA has provided UIC Program Guidance to assist state and EPA regional UIC programs in processing permit applications for these projects.  This Guidance applies only to near-term geologic sequestration pilot projects prior to full-scale deployment.  Regulations now in development will address full-scale projects.

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

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