817F07008
Using the Class V Experimental Technology
stt WeN Classification for Pilot Geologic
Agencymental Protec'ion Sequestration Projects: UIC Program
Guidance #83
What is Geologic Sequestration?
Geologic sequestration (GS), the process of capturing carbon dioxide (CO2) from an
emission source (e.g., a power plant) and injecting it into deep subsurface rock
formations, is part of a portfolio of technologies and technical approaches (e.g. fuel
efficiency measures, use of biomass and alternative fuels, etc.) under consideration for
reducing Greenhouse Gas (GHG) emissions to the atmosphere. The U.S. Department
of Energy (DOE), through its Regional Carbon Sequestration Partnerships, is
sponsoring research at a number of projects that will test the effectiveness and safety of
CO2 GS in various geologic settings.
Why is EPA issuing guidance on CO2 injection?
The purpose of the Guidance is to assist State and EPA regional UIC Program
managers and permit writers in evaluating applications for GS projects and writing
appropriate and safe permit conditions for these projects. The Guidance also
encourages communication and data sharing to support a nationally consistent
management approach, increase understanding of technical issues related to GS, and
promote public confidence in an emerging technology with a potentially large-scale
application.
Why are Class V wells being used for GS?
Injection of fluids, including solids, semi-solids, and gases (e.g., CO2) into the
subsurface falls under EPA's authority under the Safe Drinking Water Act (SDWA) to
ensure that injection activities do not endanger underground sources of drinking water
(USDWs). The UIC regulations address the siting, construction, operation, and closure
of injection wells to protect human health and the environment.
The UIC regulations define five classes of injection wells. Of these five classes, EPA
has determined that the Class V experimental technology well subclass provides the
best mechanism for authorizing pilot GS projects. Class V experimental technology
wells are intended to demonstrate unproven but promising technologies. Wells that
inject CO2 for the purposes of enhanced oil recovery (EOR) and enhanced gas recovery
(EGR) are considered to be Class II injection wells. While there are similarities between
CO2 injection for the purposes of oil and gas extraction and for GS, there are important
differences as well. For example, CO2 injection for GS will eventually involve much
greater volumes of CO2 which will be stored in the subsurface for very long periods of
time. The Class V experimental technology well subclass is the best mechanism for
testing the efficacy of CO2 injection for GS, while ensuring an appropriate level of
groundwater and public health protection.
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What information does the Guidance contain?
The Guidance provides information for UIC Program managers and permit writers to
consider as they evaluate GS project applications and assess the appropriateness of
the proposed injection site, the area of review (AoR), and the well's design and
construction. It also provides information for permit writers to consider in writing permit
conditions related to mechanical integrity testing (MIT); measuring, monitoring, and
verification (MMV); and site closure.
Who should use the Guidance?
The Guidance will assist UIC Program managers and permit writers in State primacy
agencies and EPA Regional direct implementation programs that are responsible for
issuing permits for GS projects. GS project operators, including the Regional Carbon
Sequestration Partnerships, would find the information in the Guidance useful as they
consider injection sites and prepare permit applications.
The Guidance may also be of interest to operators of EOR and EGR wells, state oil and
gas boards, and the Interstate Oil and Gas Compact Commission. (Some EOR and
EGR operations may be converted for GS when the oil and gas reservoirs are
depleted.) The Guidance also provides information for environmental groups, the
public, and interested members of Congress.
Where can I get additional information?
The Guidance is available on EPA's website at
www.epa.gov/safewater/uic/wells sequestration.html. For further information, or
questions relating to the Guidance, please contact Lee Whitehurst, EPA Office of
Ground Water and Drinking Water, Drinking Water Protection Division, Prevention
Branch, at (202) 564-3896 or Whitehurst.Lee(o)epa.qov.
Office of Water (4606M)
EPA817-F-07-008
March 2007 www.epa.gov/safewater
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