Federal Requirements Under the Underground Injection Control (UIC) Program for Carbon Dioxide (CO2, 44802-44813 [E9-20920]

Agencies

• ENVIRONMENTAL PROTECTION AGENCY

[Federal Register Volume 74, Number 167 (Monday, August 31, 2009)]
[Proposed Rules]
[Pages 44802-44813]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E9-20920]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 146

[EPA-HQ-OW-2008-0390; FRL-8951-3]
RIN 2040-AE98


Federal Requirements Under the Underground Injection Control 
(UIC) Program for Carbon Dioxide (CO2) Geologic 
Sequestration (GS) Wells; Notice of Data Availability and Request for 
Comment

AGENCY: Environmental Protection Agency (EPA).

ACTION: Data availability; request for comment.

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SUMMARY: Today's Notice supplements the proposed ``Federal Requirements 
Under the Underground Injection Control (UIC) Program for Carbon 
Dioxide (CO2) Geologic Sequestration (GS) Wells'' of July 
25, 2008, presents new data and information, and requests public 
comment on related issues that have evolved in response to comments on 
the original proposal. This Notice contains preliminary field data from 
the Department of Energy-sponsored Regional Carbon Sequestration 
Partnership projects, the results of GS-related studies conducted by 
the Lawrence Berkeley National Laboratory, and additional GS-related 
research. Today's Notice also discusses comments and presents an 
alternative the Agency is considering related to the proposed injection 
depth requirements for Class VI wells.

DATES: Comments on the contents of this NODA must be received on or 
before October 15, 2009. EPA does not plan to extend the comment period 
for this Notice. EPA will hold a public hearing from 9 a.m. to 12 p.m. 
and 1 p.m. to 4 p.m., CDT, September 17, 2009 in Chicago, IL.

ADDRESSES: The public hearing will be held at the Ralph H. Metcalfe 
Federal Building, 77 W. Jackson Boulevard, Chicago, IL 60604. Due to 
capacity limitations, we encourage you to indicate your intent to 
participate through pre-registration. To pre-register, for directions, 
and for site specific information, please visit the following Web site: 
https://gshearing.cadmusweb.com/.
    Submit your comments, identified by Docket ID No. EPA-HQ-OW-2008-
0390, by one of the following methods:
     https://www.regulations.gov: Follow the on-line 
instructions for submitting comments.
     Mail: Water Docket, Environmental Protection Agency, 
Mailcode: 4101T, 1200 Pennsylvania Ave., NW., Washington, DC 20460.
     Hand Delivery: Water Docket, EPA Docket Center (EPA/DC), 
Public Reading Room, Room 3334, EPA West, 1301 Constitution Ave., NW., 
Washington, DC. Such deliveries are only accepted during the Docket's 
normal hours of operation which are 8:30 a.m. to 4:30 p.m., and special 
arrangements should be made for deliveries of boxed information.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OW-2008-
0390. EPA's policy is that all comments received will be included in 
the public docket without change and may be made available online at 
https://www.regulations.gov, including any personal information 
provided, unless the comment includes information claimed to be 
Confidential Business Information (CBI) or other information whose 
disclosure is restricted by statute. Do not submit information that you 
consider to be CBI or otherwise protected through https://www.regulations.gov or e-mail. Contact EPA directly (see the FOR 
FURTHER INFORMATION CONTACT section) prior to submitting CBI. The 
https://www.regulations.gov Web site is an ``anonymous access'' system, 
which means EPA will not know your identity or contact information 
unless you provide it in the body of your comment. If you send an e-
mail comment directly to EPA without going through https://www.regulations.gov your e-mail address will be automatically captured 
and included as part of the comment that is placed in the public docket 
and made available on the Internet. If you submit an electronic 
comment, EPA recommends that you include your name and other contact 
information in the body of your comment and with any disk or CD-ROM you 
submit. If EPA cannot read your comment due to technical difficulties 
and cannot contact you for clarification, EPA may not be able to 
consider your comment. Electronic files should avoid the use of special 
characters, any form of encryption, and be free of any defects or 
viruses.
    Docket: All documents in the docket are listed in the https://www.regulations.gov index. Although listed in the index, some 
information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, will be publicly available only in hard copy. 
Publicly available docket materials are available either electronically 
in https://www.regulations.gov or in hard copy at

[[Page 44803]]

the Water Docket, EPA Docket Center (EPA/DC), Public Reading Room, Room 
3334, EPA West, 1301 Constitution Ave., NW., Washington, DC. The Public 
Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through 
Friday, excluding legal holidays. The telephone number for the Public 
Reading Room is (202) 566-1744, and the telephone number for the EPA 
Docket Center is (202) 566-2426.

FOR FURTHER INFORMATION CONTACT: Mary Rose Bayer, Underground Injection 
Control Program, Drinking Water Protection Division, Office of Ground 
Water and Drinking Water (MC-4606M), Environmental Protection Agency, 
1200 Pennsylvania Ave., NW., Washington, DC 20460; telephone number: 
(202) 564-1981; e-mail address: bayer.maryrose@epa.gov. For general 
information, contact the Safe Drinking Water Hotline, telephone number: 
(800) 426-4791. The Safe Drinking Water Hotline is open Monday through 
Friday, excluding legal holidays, from 10 a.m. to 4 p.m. Eastern time. 
For general information about the public hearing, please contact Sean 
Porse by phone (202) 564-5990, by e-mail at porse.sean@epa.gov, or by 
mail at: US Environmental Protection Agency, Mail Code 4606M, 1200 
Pennsylvania Ave., NW., Washington, DC 20460.

SUPPLEMENTARY INFORMATION: 

I. General Information

    This Notice of Data Availability (NODA) presents new information 
and data related to geologic sequestration (GS) of CO2 
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 proposal is available online at https://www.epa.gov/fedrgstr/EPA-WATER/2008/July/Day-25/w16626.htm. 
Availability of this new information could change EPA's approach to the 
final rulemaking.
    The purpose of this NODA is to request public comment on new data 
and on related issues that have evolved in response to comments on the 
original proposal. This Notice provides additional information and data 
on the topic of injection depth as described in the July 25, 2008, 
proposal (73 FR 43492) and presents an alternative that responds to 
comments received on this issue. Therefore, EPA is providing the 
opportunity for notice and comment on the information provided in this 
Notice as a supplement to the proposed rule. The Agency seeks further 
public comment on any and all aspects of the specific data and 
alternatives it has identified in this Notice. EPA continues to review 
the comments received on the proposed rule and will address those 
comments and the comments submitted in response to this Notice in the 
final action.
    Persons interested in recent research related to GS and proposed 
injection depth requirements are encouraged to read and respond to this 
NODA. Additionally, owners and operators, States, Tribes, and State co-
regulators involved in GS activities may wish to comment on this 
publication.

Abbreviations and Acronyms

AL: Action Level
AoR: Area of Review
CBI: Confidential Business Information
CFR: Code of Federal Regulations
CCS: Carbon Capture and Storage
CO2: Carbon Dioxide
DOE: Department of Energy
EGR: Enhanced Gas Recovery
EPA: Environmental Protection Agency
EOR: Enhanced Oil Recovery
GS: Geologic Sequestration
GHG: Greenhouse Gas
IPCC: Intergovernmental Panel on Climate Change
km: kilometer
LBNL: Lawrence Berkeley National Lab
m: meter
mg/l: milligrams per liter
Mt: Megaton
MCL: Maximum Contaminant Level
NETL: National Energy Technology Laboratory
NWIS: National Water Information System
NODA: Notice of Data Availability
ORD: Office of Research and Development
PWS: Public Water System
PWSS: Public Water Supply Supervision
RCSPs: Regional Carbon Sequestration Partnerships
SDWA: Safe Drinking Water Act
SECARB: Southeast Regional Carbon Sequestration Partnership
STAR: Science to Achieve Results
SWP: Southwest Regional Partnership on Carbon Sequestration
TDS: Total Dissolved Solids
UIC: Underground Injection Control
US: United States
USDW: Underground Source of Drinking Water
USGS: United States Geological Survey

Definitions

    Action Level (AL): The concentration of lead or copper in water 
specified in 40 CFR 141.80(c) which determines, in some cases, the 
treatment requirements contained in subpart I of this part that a water 
system is required to complete.
    Area of review (AoR): The region surrounding the geologic 
sequestration project that may be impacted by the injection activity. 
The area of review is based on computational modeling that accounts for 
the physical and chemical properties of all phases of the injected 
carbon dioxide stream.
    Buoyancy: Upward force on one phase (e.g., a fluid) produced by the 
surrounding fluid (e.g., a liquid or a gas) in which it is fully or 
partially immersed, caused by differences in pressure or density.
    Capillary force: Adhesive force that holds a fluid in a capillary 
or a pore space. Capillary force is a function of the properties of the 
fluid, and surface and dimensions of the space. If the attraction 
between the fluid and surface is greater than the interaction of fluid 
molecules, the fluid will be held in place.
    Carbon Capture and Storage (CCS): The process of capturing 
CO2 from an emission source, (typically) converting it to a 
supercritical state, transporting it to an injection site, and 
injecting it into deep subsurface rock formations for long-term 
storage.
    Carbon dioxide plume: The extent underground, in three dimensions, 
of an injected carbon dioxide stream.
    Carbon dioxide (CO2) stream: Carbon dioxide that has been captured 
from an emission source (e.g., a power plant), plus incidental 
associated substances derived from the source materials and the capture 
process, and any substances added to the stream to enable or improve 
the injection process. This subpart does not apply to any carbon 
dioxide stream that meets the definition of a hazardous waste under 40 
CFR part 261.
    Class VI wells: Wells used for geologic sequestration of carbon 
dioxide beneath the lowermost formation containing a USDW.
    Confining zone: A geologic formation, group of formations, or part 
of a formation stratigraphically overlying the injection zone that acts 
as a barrier to fluid movement.
    Corrective action: The use of Director approved methods to assure 
that wells within the area of review do not serve as conduits for the 
movement of fluids into underground sources of drinking water (USDWs).
    Director: The person responsible for permitting, implementation, 
and compliance of the UIC program. For UIC programs administered by 
EPA, the Director is the EPA Regional Administrator; for UIC programs 
in Primacy States, the Director is the person responsible for 
permitting, implementation, and compliance of the State, Territorial, 
or Tribal UIC program.
    Enhanced Oil or Gas Recovery (EOR/EGR): Typically, the process of 
injecting a fluid (e.g., water, brine, or CO2) into an oil 
or gas bearing formation to

[[Page 44804]]

recover residual oil or natural gas. The injected fluid thins 
(decreases the viscosity) or displaces small amounts of extractable oil 
and gas, which is then available for recovery. This is also known as 
secondary or tertiary recovery.
    Formation or geological formation: A layer of rock that is made up 
of a certain type of rock or a combination of types.
    Geologic sequestration (GS): The long-term containment of a 
gaseous, liquid or supercritical carbon dioxide stream in subsurface 
geologic formations. This term does not apply to its capture or 
transport.
    Geologic sequestration project: An injection well or wells used to 
emplace a CO2 stream beneath the lowermost formation 
containing a USDW. It includes the subsurface three-dimensional extent 
of the carbon dioxide plume, associated pressure front, and displaced 
brine, as well as the surface area above that delineated region.
    Injectate: The fluids injected. For the purposes of this rule, this 
is also known as the CO2 stream.
    Injection zone: A geologic formation, group of formations, or part 
of a formation that is of sufficient areal extent, thickness, porosity, 
and permeability to receive carbon dioxide through a well or wells 
associated with a geologic sequestration project.
    Maximum Contaminant Level (MCL): The maximum permissible level of a 
contaminant in water which is delivered to any user of a public water 
system.
    Model: A representation or simulation of a phenomenon or process 
that is difficult to observe directly or that occurs over long time 
frames. Models that support GS can predict the flow of CO2 
within the subsurface, accounting for the properties and fluid content 
of the subsurface formations and the effects of injection parameters.
    Pore space: Open spaces in rock or soil. These are filled with 
water or other fluids such as brine (i.e., salty fluid). CO2 
injected into the subsurface can displace pre-existing fluids to occupy 
some of the pore spaces of the rocks in the injection zone.
    Public Water System (PWS): A system for the provision to the public 
of water for human consumption through pipes or, after August 5, 1998, 
other constructed conveyances, if such system has at least fifteen 
service connections or regularly serves an average of at least twenty-
five individuals daily at least 60 days out of the year. Such term 
includes: any collection, treatment, storage, and distribution 
facilities under control of the operator of such system and used 
primarily in connection with such system; and any collection or 
pretreatment storage facilities not under such control which are used 
primarily in connection with such system. Such term does not include 
any ``special irrigation district.'' A public water system is either a 
``community water system'' or a ``noncommunity water system.''
    Pressure front: The zone of elevated pressure that is created by 
the injection of carbon dioxide into the subsurface. For GS projects, 
the pressure front of a CO2 plume refers to the zone where 
there is a pressure differential sufficient to cause the movement of 
injected fluids or formation fluids into a USDW.
    Saline formations: Deep and geographically extensive sedimentary 
rock layers saturated with waters or brines that have a high total 
dissolved solids (TDS) content (i.e., over 10,000 mg/l TDS). Saline 
formations offer great potential for CO2 storage capacity.
    Stratigraphic zone (unit): A layer of rock (or stratum) that is 
recognized as a unit based on lithology, fossil content, age or other 
properties.
    Total Dissolved Solids (TDS): The measurement, usually in mg/l, for 
the amount of all inorganic and organic substances suspended in liquid 
as molecules, ions, or granules. For injection operations, TDS 
typically refers to the saline (i.e., salt) content of water-saturated 
underground formations.
    Transmissive fault or fracture: A fault or fracture that has 
sufficient permeability and vertical extent to allow fluids to move 
between formations.
    Trapping: The physical and geochemical processes by which injected 
CO2 is sequestered in the subsurface. Physical trapping 
occurs when buoyant CO2 rises in the formation until it 
reaches a layer that inhibits further upward migration or is 
immobilized in pore spaces due to capillary forces. Geochemical 
trapping occurs when chemical reactions between dissolved 
CO2 and minerals in the formation lead to the precipitation 
of solid carbonate minerals.
    Underground Source of Drinking Water (USDW): as defined under 40 
CFR part 144.3, an aquifer or portion of an aquifer that supplies any 
public water system or that contains a sufficient quantity of ground 
water to supply a public water system, and currently supplies drinking 
water for human consumption, or that contains fewer than 10,000 mg/l 
total dissolved solids and is not an exempted aquifer.
    Special Accommodations: For information on access or accommodations 
for individuals with disabilities, please contact Sean Porse at (202) 
564-5990 or by e-mail at porse.sean@epa.gov. Please allow at least 10 
days prior to the meeting, to give EPA time to process your request.

II. What Did EPA Propose?

    On July 25, 2008, EPA published the proposed ``Federal Requirements 
Under the Underground Injection Control (UIC) Program for Carbon 
Dioxide (CO2) Geologic Sequestration (GS) Wells.'' (73 FR 
43492) The Agency proposed a new class of injection well (Class VI) 
along with technical criteria for permitting GS wells, including 
criteria for geologic site characterization, area of review (AoR) and 
corrective action, well construction, operation, mechanical integrity 
testing, monitoring, well plugging, post-injection site care, and site 
closure. These standards, if finalized, would protect underground 
sources of drinking water (USDWs) under the Safe Drinking Water Act 
(SDWA). The technical criteria in the proposed rule are based on the 
existing UIC regulatory framework under the SDWA for deep injection 
wells, with modifications to address the unique nature of 
CO2 injection for GS.
    Existing GS project experience, natural and industrial analogs, 
research, and current regulatory experience with underground injection 
were considered in the development of the proposed rule. Ongoing 
research builds upon the existing foundation of substantial literature 
on CO2 injection and storage, some of which is available in 
the docket for this rulemaking. While CO2 injection to 
extract oil and gas has taken place for many years, the use of UIC 
wells to inject large quantities of CO2 for long-term 
storage is a relatively new practice. There are current projects and 
research underway that examine and demonstrate the effectiveness of 
underground injection as a tool for sequestering CO2.
    For example, there are four commercial projects in operation today:
     Sleipner (Norwegian North Sea)--1 Mt CO2/yr 
injected since 1996;
     Weyburn (Canada)--1 Mt CO2/yr injected since 
2000;
     In Salah (Algeria)--1.2 Mt CO2/yr injected 
since 2004;
     Snohvit (Norway)--0.7 Mt CO2/yr injected since 
2008.
    Many additional large-scale projects are funded and under 
development worldwide.
    The purpose of this NODA is to provide an update on newly available 
information and data related to research focused specifically on GS for 
long-term storage--with particular emphasis on data, research, and 
information that has become available since the July proposal 
publication.

[[Page 44805]]

    In addition, the proposed rule contains a discussion of injection 
depth. In the July 2008 FR Notice, EPA proposed that the injection of 
CO2 be confined to areas below the lowermost USDW (in the 
absence of an aquifer exemption). This approach is consistent with the 
approach used for other deep UIC wells; however, circumstances in a few 
States may warrant an alternative approach. Today's Notice provides 
additional discussion on an alternative the Agency is considering 
related to injection depth for GS wells.
    EPA received a number of comments indicating that the Agency should 
further explore environmental and regulatory issues beyond the scope of 
the proposed SDWA requirements for underground injection of 
CO2 for GS. EPA recognizes that a more comprehensive 
framework may be needed and that some stakeholders remain uncertain 
with respect to the potential applicability of other Federal 
environmental statutes such as the Clean Air Act, the Resource 
Conservation and Recovery Act, and the Comprehensive Environmental 
Response, Compensation, and Liability Act to various aspects of 
geologic sequestration of CO2. The Agency is currently 
evaluating the need for a more comprehensive regulatory framework to 
provide legal guidance regarding this emerging technology. If the 
Agency chooses to pursue a more comprehensive regulatory approach to 
this subject, it will seek public comment on any proposal it develops 
for this framework and will also endeavor to issue a more comprehensive 
rule in the same time frame as it has planned for the stand-alone UIC 
GS rulemaking.

III. Research, Data Analysis, and Findings

A. Content of NODA and Summary of Comments

    In this Notice, EPA is providing a short summary of several ongoing 
GS studies and interim information on current GS projects relevant to 
topics within the proposed GS regulation. This information and data 
were provided or made available after publication of the proposal in 
July 2008. More detailed information on the GS research and projects 
discussed below is available for review online as part of the docket 
for this rulemaking. EPA is providing this data and associated project 
summaries because the Agency expects that there may be additional 
studies and data on other GS projects, the use of existing 
technologies, and GS-related research that may inform the Agency's 
regulatory development process for GS. Such data could contribute to 
the Agency's understanding of site characterization, well construction, 
operation, and monitoring requirements. The Agency requests comment on 
data and research discussed in today's Notice and how the Agency might 
use this data and research in developing the final rule. The Agency 
also requests submission of additional GS studies related to the data 
and research discussed in this Notice to inform the GS rulemaking.
    In the preamble of the proposed rule, EPA described an adaptive 
approach to developing regulations for GS. This approach would allow 
the Agency to establish regulations to protect USDWs and enable the 
Agency to make changes to regulations over time as information from 
demonstration projects and other studies becomes available. EPA 
received comments from stakeholders requesting that additional data be 
made available to the public before a final rulemaking (particularly 
related to specific areas of GS) and indicating that more research is 
needed to support GS in general. Many commenters suggested that 
supplementary research on GS is necessary prior to rule promulgation 
and that EPA should wait until the Department of Energy (DOE)-sponsored 
Phase II and Phase III pilot projects are complete before finalizing 
the GS rule. Others believed that a final rulemaking should proceed and 
that new information and data from ongoing GS research should be 
considered and incorporated over time as part of an adaptive rulemaking 
process. Comments on the proposal encouraged additional research and 
investigations on areas including (but not limited to): Confining zone 
characterization; modeling; CO2 plume movement; 
geochemistry; impacts of GS on saline formations; leakage from 
abandoned wells caused by material and cement degradation; potential 
pathways for contamination of USDWs; leak mitigation and remediation; 
and criteria for determining that the CO2 plume has 
stabilized.
    The Agency is actively tracking the progress of the Regional Carbon 
Sequestration Partnership (RCSP) GS and carbon capture and storage 
projects. The RCSPs have been compiling information related to their 
pilot and demonstration projects and have been developing research 
projects related to these efforts. A summary of several of these 
projects is available in today's Notice.
    In addition, EPA's Office of Research and Development is conducting 
intramural and extramural research activities to develop modeling and 
monitoring tools for protecting underground sources of drinking water. 
Laboratory, modeling, and field investigations are focusing on a 
variety of injection and storage scenarios and candidate injection 
sites. Analytic and semi-analytic models are being developed and 
evaluated for determining the area of review based on geologic and 
hydrologic conditions. Comprehensive laboratory tests are being applied 
to the development and field-testing of monitoring strategies that can 
detect migration of fluids into shallow aquifers and assess potential 
geochemical impacts. The ultimate goal of these research activities is 
to provide more robust tools for permitting, monitoring, and evaluating 
GS sites from injection through post-injection site care and site 
closure to prevent endangerment of USDWs. EPA is also funding six 
projects for the study of ground water and human health impacts of GS 
through the Science To Achieve Results (STAR) grant program. The awards 
will be announced this fall on EPA's Web site (https://es.epa.gov/ncer/
).
    Furthermore, EPA and DOE have jointly supported GS-related studies 
at Lawrence Berkeley National Lab (LBNL), described in Section II.B. 
These studies use modeling to predict the potential impacts on ground 
water from GS activities.

B. DOE-Sponsored Regional Carbon Sequestration Partnership Projects

    Currently, DOE's National Energy Technology Laboratory (NETL) is 
developing and/or operating approximately 30 GS projects, a number of 
which have either completed injection or are in the process of 
injecting CO2. The purpose of these projects is to ``help 
determine the best approaches for capturing and permanently storing 
gases that can contribute to global climate change'' and to determine 
``the most suitable technologies, regulations, and infrastructure needs 
for carbon capture, storage, and sequestration in different parts of 
the country'' (https://www.netl.doe.gov/technologies/carbon_seq/partnerships/partnerships.html). Through cooperation with DOE, EPA has 
obtained pilot project data from several of these GS projects. RCSPs 
are conducting pilot and demonstration projects to study: site 
characterization (including injection and confining formation 
information, core data and site selection information); well 
construction (well depth, construction materials, and proximity to 
USDWs); frequency and types of tests and monitoring conducted (on the 
well and on the project site); modeling and

[[Page 44806]]

monitoring results; and injection operation (injection rates, 
pressures, and volumes, CO2 source and co-injectates). In 
addition to information available in the docket for this NODA, 
information on some of these projects is available at https://www.netl.doe.gov/publications/proceedings/08/rcsp/. The following is a 
short summary of select project activities and data generated.
Escatawpa, Mississippi (MS); Southeast Regional Carbon Sequestration 
Partnership (SECARB)
    SECARB is conducting a CO2 injection test in Jackson 
County, MS into a deep saline reservoir along the Gulf Coast that had 
not previously been characterized for oil and gas exploration. The 
injection zone, 9,500 feet (2,896 meters) deep in the Lower Tuscaloosa 
Massive Sand Unit, is overlain by two confining layers. The site is 
near the Victor J. Daniel Power Plant, the source of the 
CO2, which was delivered to the injection site via truck.
    Characterization of the site is based on a wealth of geophysical 
and core-derived information, including well core samples, open-hole 
and cased-hole well logging, baseline vertical seismic profiling, and 
pressure transient testing. Baseline sampling and analysis of formation 
fluids and soil flux sampling were also performed. The SECARB team 
performed a 3-dimensional simulation to estimate injectivity, storage 
capacity, and long-term fate of the injected CO2. The model 
estimated that the plume would extend up to 350 feet (106.7 meters) at 
the end of the injection test.
    An injection well and a monitoring well were drilled at the site. 
The injection well is permitted by the Mississippi Department of 
Environmental Quality as a UIC Class V experimental well. Both the 
injection and monitoring well were constructed with surface and long-
string casing that was cemented from the injection zone to the surface. 
Pre-injection mechanical integrity tests of the injection and 
monitoring well (annulus pressure test, radioactive tracer survey, 
differential temperature survey, and pressure fall-off tests) met UIC 
Class I requirements.
    In October of 2008, 3,027 tons (2,746 tonnes) of CO2 
were injected into the well; injection rates averaged 170 to 180 tons/
day (154 to 163 tonnes/day). Continuous monitoring devices were used to 
record (at 30 second intervals): Injection pressure, annular pressure, 
temperature, and rate. The injection was complete on October 28, 2008.
    SECARB is continuing to monitor activities at the site through 
surface or near-surface monitoring for upward CO2 seepage 
via groundwater sampling, soil flux sampling and tracer detection. The 
purpose of this monitoring and sampling is to determine whether 
CO2 is migrating upward from the injection zone. To date, 
there has been no indication of the return of the injected 
CO2 in the shallow subsurface. SECARB also plans to employ 
time-lapse seismic and geophysical tools to determine the deep 
subsurface fate of the injectate.
    This SECARB project employs, demonstrates, and validates the EPA's 
proposed Class VI well construction, operational, and monitoring 
requirements. The use of surface and near-surface monitoring techniques 
provides the EPA with preliminary information regarding the efficacy 
and appropriateness of these technologies at certain sites; and 
supports the need for a site-specific monitoring plan that will allow 
use of a range of monitoring technologies suitable for each unique GS 
site. This information and public comments on this research will be 
used to inform the Agency's final rulemaking.
    For additional information about the Escatawpa Project, see the 
full report in the docket for today's publication.
Aneth Field, Paradox Basin, Southeast Utah (UT); Southwest Regional 
Partnership on Carbon Sequestration (SWP)
    The Aneth Field is the site of an experimental combined EOR-GS test 
by the Southwest Partnership. The primary CO2 injection 
target is the carbonate Paradox Formation, which is approximately 5,600 
to 5,800 feet (1,707 to 1,768 meters) deep, and is overlain by the low-
permeability Gothic Shale. Petrographic, geochemical and mechanical 
analyses of the Gothic Shale are underway or planned.
    CO2 injection began in August 2007, and approximately 
150,000 tons (136,077 tonnes) of CO2 have been injected to 
date. Extensive monitoring of the site is complete or underway. 
Monitoring activities at the site include time-lapse vertical seismic 
profiling, microseismic monitoring, geochemical and tracer tests, 
CO2 soil flux measurements, a surface fracture and banding 
study, and self-potential monitoring.
    Monitoring data are being used to establish parameters for state-
of-the-art mathematical reservoir models, which include coupling of 
multiphase CO2-ground water flow, rock deformation, and 
chemical reactions to evaluate residence times, migration patterns and 
rates, and effects of CO2 injection on fluid pressures and 
rock strain.
    The Aneth Field project confirms the need for a project design with 
a robust monitoring plan, and tests the importance of monitoring and 
modeling agreement in GS projects. In addition, the project 
demonstrates the utility of various monitoring technologies that may be 
used by owners and operators of Class VI wells. This information and 
public comments on this research will be used to inform the Agency's 
final rulemaking.
Pump Canyon Site, Near Archuleta, New Mexico (NM); Southwest Regional 
Partnership on Carbon Sequestration (SWP)
    The SWP is conducting a Phase II project of CO2 
injection into deep, unmineable coal seams at the Pump Canyon Site near 
Archuleta, NM. To support characterization of the site, the SWP is 
performing a ``seal analysis'' of the ability of the Kirtland Formation 
to act as a barrier to the movement of CO2 or other 
reservoir fluids. The Kirtland Formation is a major, regional aquitard 
and reservoir seal that directly overlies the geologic formation 
containing the coal seams.
    To characterize the Kirtland Formation, detailed studies of 
geological core samples, downhole geophysical logs, and outcrop studies 
were conducted. Complete and in-progress laboratory analyses include 
electron microscopic studies of petrographic and petrophysical 
properties; capillary pressure measurements; multiscale fracture 
characterization using well logs and core analysis; descriptions of 
stratigraphic columns and sedimentary structures based on cores; pore 
size distributions analysis using BET (Brunauer-Emmett-Teller), and 
geomechanical analyses of the caprock and overlying aquifer.
    Operators are actively monitoring potential surface deformation 
from injection through the use of tilt meters and radar-based 
Interferrometric Synthetic Aperture Radar (InSAR) in addition to 
monitoring the site's injection pressure. They are also tracking the 
CO2 plume through continuous sampling of immediate offset 
production wells and through perfluorocarbon gas tracers (PFT) and 
naphthalene sulfonate water tracers (NST) introduced into the 
CO2 injection stream. These tracers are used for 
identification in the unlikely event of reservoir leakage.
    The Agency sought comment on using unmineable coal seams for GS in 
the proposed rule. The investigation at Pump Canyon will inform a 
determination on whether CO2 can be effectively and safely 
sequestered in coal seams.

[[Page 44807]]

    For further information on aspects of the Pump Canyon project, 
please refer to data available in the NODA docket.

C. Lawrence Berkeley National Laboratory (LBNL) Studies

    An improperly managed GS project has the potential to endanger 
USDWs. The factors that increase the risk of USDW contamination are 
complex and can include improper siting, construction, operation and 
monitoring of GS projects. The proposed GS requirements address 
endangerment to USDWs by establishing new Federal requirements for the 
proper management of CO2 injection and storage. Risks to 
USDWs from improperly managed GS projects can include CO2 
migration into USDWs, causing the leaching and mobilization of 
contaminants (e.g., arsenic, lead, and organic compounds), changes in 
regional groundwater flow, and the movement of greater salinity 
formation fluids into USDWs, causing degradation of water quality. As 
mentioned in Section II of this Notice and in the proposal, 
CO2 has been injected on large scales at four sites: at 
Sleipner in the North Sea, at In Salah in Algeria, at Snohvit in 
Norway, and in the Weyburn Field in Alberta, Canada. There have been no 
documented cases of leakage from these projects. Additionally, for 
decades, the oil and gas industry has been safely injecting 
CO2 for the purpose of enhanced oil and gas recovery.
    LBNL is studying the potential effects of CO2 injection 
on ground water and surrounding formations to determine the potential 
for impacts on USDWs and human health in the event that a GS project is 
not properly sited, operated, or managed. Specifically, LBNL is 
evaluating the potential for GS to cause changes in ground water 
quality as a result of CO2 leakage and subsequent 
mobilization of trace elements such as arsenic, barium, cadmium, 
mercury, lead, antimony, selenium, zinc, and uranium. In addition, LBNL 
is evaluating basin-scale hydrological impacts of large-volume 
injection of CO2 on groundwater aquifers and in particular, 
the pressure front impacts caused by GS. Summaries of the interim 
results for these research areas are discussed below. The full 
publications are available in the docket and on LBNL's Web site at 
https://esd.lbl.gov/GCS/projects/CO2/index_CO2.html.
1. Ground Water Quality Changes Related to the Mobilization of Trace 
Elements
Summary
    LBNL used a comprehensive computational model to evaluate the 
potential impact of CO2 leaking from deep geologic 
sequestration sites on the concentrations of trace elements in potable 
ground waters (Birkholzer et al., 2008a). LBNL estimated the amount of 
trace elements from native mineral species that could potentially be 
mobilized by the intrusion of CO2, and the potential ground 
water concentrations that could result. LBNL then compared these 
estimates to EPA's Maximum Contaminant Levels (MCLs) and Action Levels 
(ALs) for drinking water to determine the potential for drinking water 
standards to be exceeded. It is important to note that model results 
were dependent on several assumptions and parameter values with a large 
degree of uncertainty, such as dissolution and dissociation constants. 
LBNL recommended that further studies should be conducted, including 
laboratory or field experiments and evaluation of natural analogues.
    LBNL conducted multiple model runs to assess a variety of scenarios 
and aquifer conditions and, as discussed below, found that if injected 
CO2 comes into contact with shallow USDWs, some trace 
element concentrations such as arsenic could increase.
Identification of Trace Elements of Concern
    An important step in developing the model used to assess the 
different scenarios was the identification of naturally occurring 
minerals that could act as a source of trace elements in ground water 
if they were to come into contact with CO2. This 
identification was accomplished through an extensive review of the 
scientific literature, through which potential minerals of concern were 
identified. The presence of these minerals in aquifer rocks was 
indirectly substantiated through an evaluation of more than 38,000 
water-quality analyses from potable aquifers reported in the United 
States Geological Survey's (USGS) National Water Information System 
(NWIS). While the abundances of these host minerals are typically very 
small, all trace elements targeted for study occur frequently in soils, 
sediments, and aquifer rocks.
    A preliminary assessment of CO2-related water quality 
changes, including pH, was conducted by calculating the expected 
equilibrium concentrations of trace elements as a function of the 
amount of CO2 in a representative potable groundwater. 
Results of this modeling obtained for typical aquifers under reducing 
conditions indicate that arsenic could potentially exceed Federal 
drinking water standards at elevated CO2 concentrations (40 
CFR 141.62 (b)(16)). Other trace elements, such as barium, cadmium, 
lead, antimony, and zinc, may also be mobilized in certain 
circumstances, but the majority of results did not show mobilization at 
levels exceeding the MCL or AL.
    LBNL used reactive-transport modeling to further study the fate and 
transport of arsenic and lead in a representative potable aquifer as 
influenced by leakage of CO2. This study is described as 
follows:
Prediction of the Fate and Transport of Trace Elements
    LBNL used the reactive-transport model TOUGHREACT to 1) study and 
predict the transport of CO2 within a shallow aquifer, 2) 
estimate potential geochemical changes caused by the presence of 
CO2, and 3) estimate the fate and transport of mobilized 
trace elements. LBNL conducted sensitivity studies to account for a 
range of conditions found in potable aquifers throughout the US and to 
evaluate the uncertainty associated with geochemical processes and 
model parameters. Starting with a representative ground water under 
equilibrium conditions, the model was used to estimate the impact of 
CO2 leakage into the aquifer for 100 years. For this 
analysis, the investigators assumed a hypothetical release scenario 
based on CO2 escape from a deep geologic sequestration site 
via a preferential pathway, such as a fault zone, entering the shallow 
aquifer at a constant rate.
    Results from this model simulation suggest that if CO2 
were to leak into a shallow aquifer, the potential for mobilization of 
lead and arsenic could be enhanced, causing increases in the 
concentration of these trace elements in ground water. While LBNL 
studies did suggest that CO2 interaction could cause 
significant concentration increases compared to the initial water 
composition, the MCL for arsenic was exceeded in only a few simulation 
scenarios, while the lead concentrations remained below the AL under 
all scenarios. It is important to emphasize that these studies looked 
at potential consequences of CO2 leakage into the USDW, not 
the likelihood of such leakage occurring. The goal of the UIC program 
and these regulations is to ensure that injectate does not contaminate 
USDWs in the first place.

[[Page 44808]]

    The Agency will use these preliminary results and public comments 
on this research as well as potential site-specific analyses, to refine 
and inform site characterization, monitoring, and remediation 
requirements and guidance, if necessary, in the Agency's final 
rulemaking. The Agency seeks comment on this research and any 
additional studies related to a) mobilization of constituents and b) 
the likelihood or frequency of such leakage/risks.
2. Basin-Scale Hydrologic Impacts of CO2 Storage
Summary
    Pressure build-up from large volume CO2 sequestration 
has been researched since the early 1990s. Recent studies have focused 
on better understanding large-scale pressure responses for future 
geologic sequestration projects (Zhou et al., 2008; Van der Meer and 
Yavuz, 2008; Nicot, 2008; Birkholzer et al., 2009). LBNL studied a 
hypothetical, future scenario of GS in a sedimentary basin as an 
illustrative example to demonstrate the potential for basin-scale 
hydrologic impacts of CO2 storage (Birkholzer et al., 
2008b).
Sedimentary Basin Case Study
    The example basin considered in this case study contains deep 
saline formations that are potential targets for large-scale 
CO2 storage projects because they are geologically favorable 
for permanent CO2 storage and the region has many large 
stationary sources of CO2. The basin contains a thick, 
extensive, high porosity, high permeability sandstone that is the 
primary target for CO2 storage. A superior confining shale 
layer is also present, making it an ideal site for geologic 
sequestration projects.
    LBNL used a preliminary computational hydrogeologic model of the 
basin to simulate regional ground water flow patterns as influenced by 
large-scale deployment of GS in the region. The model assumed a 
scenario where 20 independent GS projects spaced throughout the center 
of a 570 kilometers (km) by 550 km (354 miles by 342 miles) model 
domain each injected 5 million tonnes (5.51 million tons) of 
CO2 per year over 50 years. (The largest injection today is 
on the order of a million/tons/per year). Modeling results for this 
simulation indicated that the maximum size of each CO2 plume 
was 6-8 km (3.7-5 miles) with lateral separation between each GS 
project of about 30 km (18.6 miles). These model results suggest that 
the basin is favorable for effective trapping of CO2.
    In addition, simulation runs indicated that injection pressures did 
not exceed fracture pressure or the maximum value used in the model for 
this basin. However, results also indicated that far-field pressure 
changes could propagate as far away as 200 km (124 miles) from the core 
injection area where the geologic sequestration projects are located. 
After CO2 injection ended in the simulation, pressure 
buildup in the injection zone began to dissipate while the far-field 
pressure response continued to increase and expand. For this simulation 
example, a pressure increase of 0.5 bar existed at an areal extent of 
nearly 400 km by 400 km (249 miles by 249 miles) after 50 years. These 
model results indicate that basin-wide pressure influences can be large 
and may have intersecting pressure perturbations in a multiple-site 
scenario. While simulated changes in salinity within the storage 
formation were relatively small, the predicted pressure changes could 
push saline water upward into overlying aquifers if localized pathways 
such as conductive faults existed. As these large scale simulations 
indicated, limitations on injection volumes related to basin-scale 
pressure build-up should be considered during CO2 capacity 
estimation.
    EPA believes that the example studied by LBNL illustrates the 
importance of basin-scale evaluation of reservoir pressures and far-
field pressures resulting from CO2 injection. EPA requests 
comment on this study and welcomes additional studies that provide 
information on the need for basin-scale evaluations for GS injection.

D. Additional GS Research

    There are international, consensus-based and peer-reviewed reports 
on CCS, including the Intergovernmental Panel on Climate Change (IPCC) 
Special Report on Carbon Dioxide Capture and Storage (IPCC, 2005), 
which specifically includes a chapter on GS drawn from published 
literature and research studies. Comprehensive reviews of the results 
from GS research are also available (e.g., Holloway, 2001; Friedman, 
2007; Tsang et al., 2008). EPA will continue to track research project 
development and literature published by DOE and international 
governments and organizations including the International Energy Agency 
(IEA), IEA Greenhouse Gas Programme, and other major international CCS 
initiatives.
    With respect to geologic and reservoir modeling, EPA has conducted 
one such synthesis and analysis of GS research to inform the rulemaking 
efforts. Schnaar and Digiulio (2009) present a research review of over 
forty GS modeling studies spanning from 1993-2008. This review found 
that GS models are based on pre-existing codes that have been developed 
for predicting the movement of water and solutes in soil, the behavior 
of groundwater contaminants at hazardous waste sites, and the recovery 
of oil and gas from petroleum-bearing formations. However, modeling the 
injection and sequestration of CO2 poses unique challenges, 
such as the need to properly characterize CO2 transport 
properties across a large range of temperatures and pressures, and the 
need to couple multiphase flow, reactive transport, and geomechanical 
processes. The authors reviewed studies that demonstrated the use of 
modeling in project design, site characterization, assessments of 
leakage, and site monitoring.
    The complete modeling review is available in the online public 
docket at https://www.regulations.gov. A list of recent publications 
addressing potential environmental risks and risk management approaches 
for GS sites is also available in the docket. The Agency may use 
information generated from these studies to identify implementation 
guidance needs and refine the proposed requirements. EPA seeks comment 
on these studies and requests other research on geologic and reservoir 
modeling as well as research associated with potential environmental 
risks and risk management approaches for GS.

IV. Injection Depth for GS Projects

A. What did EPA propose for Class VI well injection depth relative to 
the location of USDWs?

    In the proposed rule, EPA defined Class VI injection wells as wells 
used for GS (injection) of CO2 beneath the lowermost 
formation containing a USDW. In Section III.A.4 of the preamble, EPA 
discussed Injection Depth in Relation to USDWs to further clarify the 
Agency's expectations regarding injection depth for Class VI wells. The 
proposed requirements would preclude injection of CO2 into 
zones in between and above USDWs. EPA is aware that confining Class VI 
CO2 injection to below the lowermost USDW may restrict the 
use of sequestration in areas of the country with deep USDWs where well 
construction would be technically impractical or infeasible. As 
proposed, the definition would also preclude injection of 
CO2 into shallow formations such as coal seams and basalts. 
The Agency requested comment on alternative approaches that would allow 
injection between and/or above the

[[Page 44809]]

lowermost USDW and thus potentially allow for more areas to be 
available for GS while continuing to prevent endangerment of USDWs.
    Approaches on which the Agency sought comment in the preamble, as 
alternatives to the proposed injection depth requirements included:
     Allowing Class VI CO2 injection above the 
lowermost USDW when the Director determines that geologic conditions 
exist that will prevent fluid movement into adjacent USDWs;
     Allowing the use of an aquifer exemption process for Class 
VI injection; and,
     Establishing, by regulation, a minimum injection depth for 
GS of CO2.

B. Why did EPA propose that Class VI wells inject below the lowermost 
USDW?

    EPA initiated the regulatory development process for GS and 
proposed new, tailored Federal requirements appropriate for the unique 
nature of injecting large volumes of CO2 for long-term 
storage to ensure that USDWs are not endangered. The proposed injection 
depth requirements for Class VI wells are consistent with the siting 
and operational requirements for deep, technically sophisticated Class 
I wells and are an important component of the UIC program.
    The basis of these requirements is the principle that placing 
distance between the injection formation and USDWs decreases risks to 
USDWs. In these deep-well injection scenarios, the added depth and 
distance between the injection zone and overlying formations serve both 
as a buffer allowing for pressure dissipation and as a zone for 
monitoring that may detect any excursions (of the injectate) out of the 
injection zone. Additional distance also allows trapping mechanisms, 
including dissolution of CO2 in native fluids and 
mineralization, to occur over time--thereby reducing risks that 
CO2 may migrate from the injection zone and endanger USDWs. 
Additionally, the depth and distance below the lowermost USDW allow the 
potential for the presence of additional confining layers (between the 
injection zone and overlying formations/USDWs).

C. Injection Depth Comments, Data, and Research

    EPA received a range of comments both in support of, and opposed 
to, the proposed injection depth requirements for Class VI wells.
Comments Supporting the Proposed Injection Depth Requirements
    Comments that supported the proposed requirements indicated that 
injection should be constrained to below the lowermost USDW (should not 
be allowed above and/or between USDWs) because:
     SDWA requires the UIC program to promulgate regulations 
(including injection depth requirements) that maximize USDW protection;
     Injection below the lowermost USDW is a long-standing 
principle of UIC deep well injection;
     In many cases, injection below the lowermost USDW ensures 
a greater distance between the injection zone and USDWs;
     GS is a new/unproven technology (at large scale) and, in 
the early years of deployment, injection depth limitations are prudent. 
These requirements could be relaxed in the future as information is 
learned about GS injection;
     Keeping injection below the lowermost USDW will reduce the 
likelihood of wells (e.g., water, mineral, and/or hydrocarbon 
production) being drilled through a CO2 plume in the future.
    These comments and concerns about injection depth are further 
supported by ongoing research, data, and activities related to water 
use, availability, and planning; some of this research and data were 
submitted to the proposed rule docket (e.g., EPA-HQ-OW-2008-0390-
0181.1). Water availability research in the United States indicates 
that water treatment of higher salinity waters (in excess of the USDW 
protectiveness threshold of 10,000 ppm TDS) may be more cost effective 
than the cost of obtaining water rights or surface water elsewhere in 
the area (Sengebush, 2008). Additionally, as technologies advance, 
treatment of increasingly deeper and/or higher salinity waters may 
become a common practice employed in many communities throughout the 
US. Other studies support the need to consider long-term drinking water 
protection and the confluence of population growth and constrained 
water resources in parts of the US when developing injection depth 
requirements (US Government Accountability Office, 2003; Davidson, et 
al., 2008).
Comments Opposed to the Proposed Injection Depth Requirements
    Those opposed to the proposed requirements supported allowing 
injection above and between USDWs. These commenters indicated that such 
injection should be allowed under the following conditions and based on 
the following arguments:
     At any depth without limitations;
     Based on site-specific information and in certain geologic 
settings, where there are adequate confining systems above and below 
the injection zone;
     Where formations have been exempted (for other injection 
purposes) and/or where the formations are greater than 10,000 ppm TDS;
     Based on geographically delineated exemptions (e.g., 
specifically delineated formations, basins, or regions where injection 
could occur at depths above/between USDW);
     Because many parts of the country will be excluded from GS 
activities and as a result CCS deployment may be restricted (if this 
requirement is maintained as written);
     Because Class II, Class III, and Class V operations are 
already injecting above the lowermost USDW without any potential for 
threats to underlying (or overlying) USDWs; and,
     Because there should not be a blanket prohibition for 
Class VI GS wells.
    Research, information, and comments that support allowing injection 
above and between USDWs have focused on climate change mitigation, 
CO2 geologic storage capacity assessments, and current UIC 
injection practices. Commenters interested in climate change mitigation 
emphasized the role that GS will play in reducing greenhouse gas (GHG) 
emissions while national GS capacity estimates focus on formations 
irrespective of depth (above/below the lowermost USDW). Furthermore, 
some specific research on CO2 injection for GS into various 
formations including shallow, volcanic rocks such as flood basalts 
(McGrail, et al., 2006) and coal seam injection (Dooley, et al., 2006; 
IPCC, 2005; MIT 2007; White et al., 2005) illustrates the potential for 
GS in these formations, but only if there is depth requirement 
flexibility. Certain States have indicated that where USDWs are very 
deep (e.g., 15,000 ft/4,572 meters and deeper) and layered (stratified) 
these regions would become unavailable for large-scale GS projects 
because injectors would not be able to comply with the current 
injection depth (and well construction) requirements. These States 
suggest that GS should be allowed in certain areas if a site-specific 
demonstration can be made that USDWs will be protected.
    Some comments support the suggestion that current Class II, Class 
III, and Class V injection activities occurring above and between USDWs 
may serve as a viable analogue for GS injection depth requirements. 
Class II and Class III owners and operators of sites where injection is 
taking place above and between USDWs must identify and demonstrate 
upper and lower impermeable confining units.

[[Page 44810]]

These confining units serve as barriers to fluid movement and pressure 
and must ensure continuous injectate isolation, confinement, and USDW 
protection. Identification of such units is conducted through analysis 
of sonic and resistivity logs, drill stem tests, and wire line tests.

D. Evaluation of Concerns About Injection Depth for Class VI GS Wells

Discussion
    Under Section 1421 of the Safe Drinking Water Act (SDWA), UIC 
regulations must prevent underground injection that endangers USDWs. 
While EPA has met this statutory requirement in the past by requiring 
injection below the lowermost USDW, for some of the injection 
activities that may pose increased risks, the Act allows other 
approaches as well (Kobelski, et al., 2005).
    In today's NODA, EPA is providing additional information on an 
alternative for addressing injection depth in limited circumstances 
where there are deep USDWs. EPA believes that a waiver process may 
respond to the range of comments, both for and against the proposed 
requirement that Class VI wells inject below the lowermost USDW. The 
goals of this approach are to: (1) Provide flexibility to UIC Program 
Directors and owner/operators that will undertake CO2 
injection for GS; (2) respond to concerns about local and regional 
geologic storage capacity limitations imposed by the proposed injection 
depth requirements; (3) allow for a more site-specific assessment; (4) 
accommodate injection into different formation types; and, (5) consider 
the concept that CO2 injection for GS above and/or between 
USDWs could be as safe and effective as injection below the lowermost 
USDW as evidenced by past experiences with some Class II, III and V 
injection wells. EPA believes this approach may additionally 
accommodate requests for geographic flexibility while placing such 
determinations at the State or Regional level. Lastly, the approach is 
designed to acknowledge and accommodate comments and concerns about 
drinking water resource availability and the potential/known future 
needs, and to afford such water resources protection.
    EPA is considering a number of topics and the implications of the 
various commenters' concerns related to this potential alternative as 
follows:
    There have been a number of national GS capacity estimates 
developed (e.g., by DOE's National laboratories, USGS, etc.). Some of 
these assessments have broadly identified porous, permeable formations 
that may receive and store CO2 at a range of depths beneath 
the ground surface (Burruss, R.C., et al, 2009; DOE, 2007; Davidson et 
al., 2008; MIT, 2007; Dooley, 2006). In developing injection depth 
requirements, EPA acknowledges that these capacity estimates do not 
directly address specific site suitability attributes that would be 
identified through the UIC permitting site-characterization process. 
Additionally, these formations (identified through capacity estimates) 
may be stratified, stacked, or layered and in combination, their 
cumulative capacity could be limited (i.e., less than assessed). In the 
absence of such site-specific information, it is currently difficult to 
identify what percentage of assessed national capacity is actually 
suitable for GS. In addition, very small geologic storage sites, even 
when aggregated within a given area, may not be conducive to/
appropriate for large-scale, commercial GS projects. However, the 
approach described in this Notice allows for such a determination to be 
made on a site-specific basis.
    Second, the alternative under consideration does not prohibit 
injection into any specific formation types (e.g., basalts and/or coal 
seams). It affords all formations equal treatment and allows specific 
regions of the country the regulatory flexibility to determine if any 
injection at a particular site and depth is the appropriate approach. 
It will also help to manage injection in areas where there may be 
multiple, stratified formations with significant assessed cumulative 
capacity.
    Third, because the Agency believes that it is necessary to address 
the specific, unique characteristics of Class VI injection (e.g., large 
injection volumes, viscosity, and buoyancy) and the Agency does not 
have information or data indicating that Class II operations are 
entirely analogous to Class VI, large-scale injection, this alternative 
allows Class VI injection depth considerations to be tailored for GS. A 
number of dominant differences between Class II and Class VI operations 
indicate that these well classes warrant different treatment. EPA 
received comment during the public comment period supporting the need 
for such a distinction. These differences include: the risk profiles 
for these operations; the greater total injection volumes (of 
CO2) for Class VI GS; and, differences in formation 
pressures (potentially higher for GS), greater opportunities for 
mobilization of constituents, and injection rates and operating 
conditions.
    The alternative EPA is considering relies on the principle of site-
suitability for GS: injection zones/formations that have suitable upper 
and lower confining units, appropriate lateral and vertical extent to 
receive and contain the injected CO2, and an appropriate 
management scheme to ensure that the water and other resources 
contained within the injection zone will not be needed in the future. 
The management scheme will also ensure that there is a strategy 
developed to address future needs to access formations below the 
injection zone.
    This approach would allow regulators and communities (e.g., States, 
etc.) to assess the most appropriate injection depth for a given 
project, in a given geographic or geologic area. It may also allow 
communities, local, and State authorities to plan resource use 
appropriately and, if necessary, circumvent the need to drill through a 
CO2 filled zone/formation/plume to exploit resources (both 
water and hydrocarbon) in or below the injection zone.
    Conversely, EPA is weighing the fact that this alternative would be 
a divergence from the existing UIC deep-well injection requirements for 
industrial and hazardous waste injection. It will result in greater 
injection depth variability throughout the United States and may result 
in emplacement of fluids by injection in closer proximity to USDWs than 
would occur under the proposed requirements. Additionally, adoption of 
this alternative could potentially add a new administrative burden to 
UIC programs pursuing the waiver approach.
Consideration of New Approach
    Based on new information and data from comments received on the 
proposed rule, the Agency is considering a waiver process to allow GS 
injection above and between USDWs under specific conditions in lieu of 
a blanket prohibition on injection above and between USDWs. The 
proposed Class VI GS injection depth requirements would remain 
unchanged but would allow an owner or operator seeking to inject above 
and/or between USDWs to apply for a waiver from t