Unit)
Environments! Protection
Agency
Supplemental
Information on the Proposed
Requirements for Geologic
Sequestration of Carbon Dioxide
The United States Environmental Protection Agency (EPA) is releasing supplemental
information through a Notice of Data Availability (NOD A) on proposed requirements
under the Safe Drinking Water Act (SDWA) for the underground injection of carbon
dioxide (CO2). EPA's proposed regulations under the SDWA would ensure protection of
underground sources of drinking water from CO2 injection activities.
Why is the NODA needed?
This Notice of Data Availability (NODA) presents new information and data related to
geologic sequestration (GS) of carbon dioxide, obtained after publication of the July 25,
2008 proposed rule "Federal Requirements Under the Underground Injection Control
(UIC) Program for Carbon Dioxide (CO2) Geologic Sequestration (GS) Wells" (73 FR
43492). The Agency sought comment on a range of topics and received comments, data,
and additional information that warrants release prior to finalization of the GS regulation.
What is Geologic Sequestration?
GS is the process of injecting CO2 captured from an emission source (e.g., a power plant
or industrial facility) into deep subsurface rock formations for long-term storage. It is
part of a process known as "carbon capture and storage," or CCS.
CO2 is captured from flue gas produced by fossil-fueled power plants and industrial
facilities, typically compressed to convert it from a gaseous state to a supercritical fluid,
and transported to the sequestration site, usually by pipeline. The CO2 is then injected
into deep subsurface rock formations through one or more wells, using technologies that
have been developed and refined over several decades. CO2 is expected to be injected at
depths greater than approximately 800 meters (2,625 feet), where the pressure and
temperature below the earth's surface are sufficient to keep the CO2 in a supercritical
state.
When injected in an appropriate receiving formation, CO2 is sequestered by a
combination of physical and geochemical trapping processes. Physical trapping occurs
when the relatively buoyant CO2 rises in the formation until it reaches a low-permeability
layer that inhibits further upward migration, or when residual CO2 is immobilized in
formation pore spaces. Geochemical trapping occurs when chemical reactions between
the dissolved CO2 and minerals in the formation lead to the precipitation of solid
carbonate minerals. Similarly, naturally-occurring CO2 deposits have been physically
and geochemically trapped in geologic formations for millions of years.
Office of Water (4606M) EPA 816-F-09-005 August 2009
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The United States has CC>2 storage potential in deep saline formations, depleted oil and
gas fields, and deep, unmineable coal seams. These formations are present across most
of the country and 95 percent of the largest stationary sources in the nation that emit CO2
are within 50 miles of a candidate CC>2 storage formation.
What information does the NODA contain?
EPA's NODA contains supplemental information previously not available during the
initial publishing of the proposed regulations on GS. The NODA expands upon
information described in the July 2008 proposed rule related to:
• New data and research received from the Department of Energy's (DOE) National
Energy Technology Laboratory (NETL) and Lawrence Berkeley National
Laboratory (LBNL) concerning both GS projects and modeling to predict the
potential impacts on ground water from GS activities
• Injection depth for GS wells and a discussion of a waiver process to address
comments about the proposed regulation's requirement that Class VI wells inject
below the lowermost USDW
Who should review and comment on the NODA?
The NODA is for informational purposes and does not require any facilities to capture,
sequester, or otherwise comply with requirements related to GS. Owners and operators,
states, tribes, and state and tribal co-regulators involved in GS activities may wish to
comment on this publication. Additionally, individuals interested in the two primary
subject areas of the NODA may wish to review and comment. The Agency seeks
comments on the supplemental NODA for 45 days and does not anticipate extending the
length of the comment period.
How Can I Get More Information?
The NODA, proposed rule, supporting information, and information on how to comment
on the NODA are available on EPA's Web site at
http://www.epa.gov/safewater/uic/wells_sequestration.html. For additional information,
contact the Safe Drinking Water Hotline toll free Monday through Friday, 10:00 am to
4:00 pm eastern time (except federal holidays) at 1-800-426-4791.
Office of Water (4606M) EPA 816-F-09-005 August 2009
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