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.
Under the Safe Drinking Water Act (SDWA), the US EPA protects underground sources of drinking water from threats related to injection activities. 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 exercises authority over underground injection through 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 drinking water 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. As a result of these differences and the importance of considering geological sequestration, EPA began in 2007 to address injection of CO2 as part of certain pilot projects and then in October 2007 EPA announced that the Agency planned 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.
In July 2008, EPA published the requirements for Carbon Dioxide (CO2) Geologic Sequestration (GS) Wells as a proposed Rule that was subject to public review and comment. In August 2009, EPA published new requirements for Carbon Dioxide (CO2) Geologic Sequestration (GS) Wells; a Notice of Data Availability, and submitted the information for public review and comment.
The new information supplements the agency’s 2008 proposed rule that, if finalized, would create a new class of injection well and establish requirements under the authority of the SDWA to ensure that geologic sequestration activities do not endanger drinking water sources. The publication reviews research and data on geologic sequestration and presents an alternative the agency is considering related to the proposed injection depth requirements for carbon dioxide. In addition, the publication announces that EPA is evaluating the need for a more comprehensive regulatory framework to manage the geologic sequestration of CO2.
The public review and comment process is underway. For a full history of the legislative and regulatory background for this action, see: www.epa.gov/safewater/uic/wells_sequestration.html#Links