This comment letter response contains two parts:   

(1) The original submittal from the commenter.

(2) A data base printout of EPA’s response to each point raised by the commenter.

Notes about the response letters:

• The response letters were generated by a data base used to track the content of all public

comment submittals and ensure that the Agency responds to each. Each comment letter

was assigned a Letter ID that corresponds to the last four digits of the docket number of the

original comment (as posted on www.regulations.gov).

• Each response letter includes: comment text; an EPA‐assigned comment code; and an

individual response. These are described and explained below.  

• The data base contains Comment text from the letters submitted by commenters.  

Many hard copy letters were scanned into electronic format for inclusion in the data

base. As a result, there may be some typographical errors attributable to optical

character recognition issues.  However, all original submittals were reviewed in the

process of drafting responses to ensure that the comment content was understood and

appropriately addressed.

• The content of each comment letter was divided into topic areas and assigned a unique

Comment ID.  Additionally, one or more Comment Codes (i.e., unique topic area ID) was

assigned to each discrete point raised by a commenter. This information was added to

the data base. To inform final rulemaking decisions, all comments and information

received on a given topic were reviewed by technical experts in each rule area (e.g., on

construction requirements).  

• Following decisions on the final rule requirements, Individual responses were drafted

by topic area to ensure completeness and consistency of the responses with the final

rule and other responses to similar comments.  Each discrete point made by a

commenter was given a unique response.

• Upon completion of comment responses, all information was entered into the data base.

Each letter response is a compilation of each comment and its individual response,

compiled in the order of the original comment letter.  As a result of this process, there is

repetition in the response text.  The Agency believes this approach ensures completeness

and attention to each comment letter that was submitted.   

• All comments in a topic area were reviewed, evaluated, and responded to concurrently.  

Responses on each topic area are compiled and are also available in the rulemaking docket.
Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402 

Richard L. Driggans 

Vice President 

Environmental Science, Technology & Policy 

December 17, 2008 

Water Docket 

Environmental Protection Agency 

Mailcode: 2822T 

1200 Pennsylvania Avenue, NW 

Washington, DC 20460 

Docket ID No. EPA-HQ-2008-0390 

RE: FEDERAL REQUIREMENTS UNDER THE UNDERGROUND INJECTION 

CONTROL (UIC) PROGRAM FOR CARBON DIOXIDE (CO2) GEOLOGIC 

SEQUESTRATION (GS) WELLS; PROPOSED RULE 

As the nation’s largest public power provider, the Tennessee Valley Authority (TVA) 

generates electricity at 29 hydroelectric dams, 11 coal-fired plants, 6 combustion turbine 

sites, 3 nuclear plants, a pumped-storage hydropower plant, and 17 green power sites 

that employ wind turbines, methane gas, and solar panels. These assets currently 

provide electrical power to 158 local distributors that serve 8.8 million people and 

650,000 businesses and industries in a seven-state service area. 

TVA’s coal-fired plants and combustion turbines (CO2-emitting facilities) provide about 

64 percent of this total generation of electrical energy to the Tennessee Valley Region of 

the Southeastern United States. As owner and operator of these facilities with 

responsibilities for meeting current and future power supply needs and as a Federal 

agency with resource stewardship responsibilities, TVA appreciates the opportunity to 

review and comment on this proposed rule that would (1) create a new category of 

injection wells (Category VI) under EPA’s Underground Injection Control (UIC) Program 

for protecting underground sources of drinking water (USDWs) and (2) establish Federal 

requirements for the underground injection of CO2 for the purpose of geologic 

sequestration (GS). See 73 Fed. Reg. 43492 (July 25, 2008). 

TVA offers the following comments on this proposed rule: 

General Comment

1. TVA acknowledges the challenge of developing a rule to provide regulatory 

certainty for the GS of CO in order to foster industry adoption of carbon capture 

and storage (CCS) in the face of considerable technological and experiential 

uncertainty about safely injecting and sequestering the huge volumes of 

supercritical CO that would be required to meet the goals of future climate change 

legislation. In the face of such uncertainty, this rule is justifiably stringent for 

2 

2
Water Docket - EPA 

Page 2 

December 17, 2008 

protecting USDWs, ecological resources, and the public. Because scale-up from 

experimental to fully operational wells will provide the experience necessary to 

have a rulemaking with the most appropriate protections, TVA requests that a 

provision be added to require periodic review (possibly every two years initially until 

sufficient operational experience is gained) and to revise the rule’s flexibility 

appropriately where justified. TVA agrees with EPA that the regulatory standard 

for permitting CO2 GS wells should be the protection of USDWs, which must take 

precedence over the need to sequester CO2 underground at any site. For this 

reason, TVA supports a stringent rule initially as long as a provision is made to 

revise the rule to incorporate operational experience as it is gained. 

Specific Comments

1. Regulatory (“Director’s”) Discretion - TVA supports a flexible rule that vests in the 

Director the discretion to grant certain approvals. However, where the Director is 

provided such discretion (e.g., for imposing secondary containment, requesting 

additional testing, monitoring CO2 fluxes in surface air and soil gas, changing the 

50-year default post injection care requirement, shortening the notification period 

for plugging an injection well or approving site closure plans), the proposed rule 

should include factors that the Director must consider in exercising discretion. 

2. Siting - The proposed rule provides the Director the discretion to require the owner 

or operator to identify and characterize additional (secondary) confining and 

containment zones above the primary (i.e., lowermost) confining zone to further 

impede vertical fluid movement and allow for pressure dissipation. There are 

situations that must require secondary containment, e.g., CO2 GS well fields 

located in the vicinity of a designated sole-source aquifer or other aquifer widely 

used for water supply. Assurance of CO2 containment must be near-absolute in 

such cases, and regulators must have discretion to require cap rock redundancy. 

As a further precaution, potential GS sites near sole-source aquifers, as well as 

those sites in high risk seismic locations, should initially be eliminated from 

consideration until sufficient experience with operational scale GS is gained. 

As a related matter, at least for the near future, siting a fossil-fueled plant that 

utilizes GS near a sole-source aquifer should only be considered where the 

infrastructure is in place for transporting supercritical CO2 to a distant injection well 

location. Because a large portion of the Nation’s fleet of fossil-fueled generating 

facilities were sited and built without consideration of CCS, there are considerable 

space, water supply, geologic, seismic, and financial constraints for retrofitting 
Water Docket - EPA 

Page 3 

December 17, 2008 

many existing facilities with this technology. Although the proposed rule does not 

require facilities to capture and/or sequester CO2, promulgation of this rule should 

acknowledge that GS of CO2 will not be suitable at a large number of existing 

facilities and may be most applicable for new-generation facilities that are properly 

sited a priori for CCS. 

3. Area of Review (AoR) - The proposed rule requested comment on requiring reevaluation of the site AoR on a periodic basis and the appropriateness of a 10 year 

minimum fixed frequency for AoR re-evaluation. TVA supports a re-evaluation 

frequency not to exceed 10 years. Periodic AoR re-evaluation will be needed 

given the enormous volumes of CO2 that would be injected, the potentially high 

mobility of CO2 in the subsurface, the lengthy timeframes likely for CO2 GS 

operations, and the uncertainty of the original model-predicted AoR limits, 

especially where multiple injections might occur below the same aquifer (noncontiguous but merging CO2 pressure fronts). 

In practice, much of what is required in an AoR evaluation (e.g., well field 

monitoring, computational fluid dynamics model calibration/verification, and 

updated prediction of future limits of the CO2 plume) will be performed on an ongoing basis to support well-field operation and monitoring. If after 10 years, 

updated modeling shows no significant change in AoR limits, the AoR re-evaluation 

should merely require presenting the latest modeling results and possibly 

confirming that no new penetrations have been identified and therefore no new 

corrective actions are necessary. 

4. Injection Depth in Relation to USDWs - The proposed rule requested comment on 

alternative approaches that would allow injection between and/or above the 

lowermost USDW, and thus potentially allow for more areas to be available for GS 

while preventing USDW endangerment. Limiting CO2 GS to geologic units below 

the lowest USDW is prudent and reasonable. Prohibiting injection between and/or 

above the lowermost USDW is essential to protecting valuable drinking water 

sources by avoiding unnecessary siting and operational risks. Once experience is 

gained with the long-term behavior and geologic containment of CO2, injection 

depths above the lowermost USDW may be considered appropriate on a sitespecific basis (e.g., where storage depth would be sufficient for maintaining CO2 in 

a supercritical state and separate from USDWs). 

5. Unspecified Operational Consequences - In the unfortunate event operational 

experience at a GS site shows the permitted geologic storage was ill advised and 

that CO2 injection from a fossil-fueled power plant sited and operated at (or 

transporting supercritical CO2 to) that location must be terminated, TVA requests a 

provision be added to this rule to address what consequences, with regards to 

resumed emissions of CO2, discontinuation of CCS would have for such a facility. 
Water Docket - EPA 

Page 4 

December 17, 2008 

TVA believes that a Class VI permitting program is reasonable and necessary before GS 

can be implemented at the operational scale necessary for mitigating power plant CO2

emissions, and TVA applauds EPA for this initial effort to provide a regulatory framework 

and some degree of regulatory certainty for GS under the UIC program. TVA 

appreciates the opportunity to comment on EPA’s proposed rule and anticipates its 

comments will be useful in forging an effective and protective regulation. If you or other 

staff have comments or questions regarding these TVA comments, please call or email 

Michelle Cagley of my staff (865) 632-2072; amcagley@tva.gov. 

Sincerely, 

Richard L. Driggans 
Letter ID: 0145 

Commenter: Richard Driggans 

Organization: Tennessee Valley Authority 

Letter ID: 0145 Comment ID: 23147 Letter Lines: 59 to 77 

Comment Code: 1250 1.1.1.4 Flexibility is needed (performance-based standards) 

Comment Code: 2400 1.8 Comments on EPA's adaptive rulemaking process 

Comment: General Comment 

1. TVA acknowledges the challenge of developing a rule to provide regulatory 

certainty for the GS of CO2 in order to foster industry adoption of carbon capture 

and storage (CCS) in the face of considerable technological and experiential 

uncertainty about safely injecting and sequestering the huge volumes of 

supercritical CO that would be required to meet the goals of future climate 

change legislation. In the face of such uncertainty, this rule is justifiably 

stringent for protecting USDWs, ecological resources, and the public. Because 

scale-up from experimental to fully operational wells will provide the 

experience necessary to have a rulemaking with the most appropriate protections, 

TVA requests that a provision be added to require periodic review (possibly 

every two years initially until sufficient operational experience is gained) and 

to revise the rule’s flexibility appropriately where justified. TVA agrees with 

EPA that the regulatory standard for permitting CO2 GS wells should be the 

protection of USDWs, which must take precedence over the need to sequester CO2 

underground at any site. For this reason, TVA supports a stringent rule 

initially as long as a provision is made to revise the rule to incorporate 

operational experience as it is gained. 

Individual Response: EPA agrees that an adaptive approach to the UIC GS rulemaking is 

appropriate. The Agency plans to use such an approach to ensure that USDWs are protected from 

endangerment while making it possible to meet the potentially fast pace of GS deployment. EPA 

believes that an adaptive approach will allow regulatory development to proceed in time to meet 

the current and future demand for Class VI permits while recognizing the need to: continue to 

gather data from pilot projects and other research as it becomes available; and to enhance 

understanding of the technical and administrative aspects of GS deployment, operation, and 

technology developments. EPA plans, every six years, to collect and review data on GS projects 

to determine whether the appropriate amount and types of information and appropriate 

documentation are being collected, and to determine if modifications to the requirements are 

appropriate or necessary. 

However, the Agency cannot definitively predict that future requirements will be less stringent 

than those in the final GS rule. The Agency believes that the Class VI requirements appropriately 

address the unique challenges posed by large-scale GS–including large injection volumes, the 

1
relative buoyancy of CO2, its corrosivity in the presence of water, the potential presence of 

impurities in captured CO2, and its mobility within subsurface formations. Any changes 

implemented under the adaptive rulemaking would be based on technical information and data 

generated and collected during early GS projects or other research. 

EPA believes that reevaluating the GS requirements every six years is appropriate to allow 

sufficient time for projects to be permitted, for State and Tribal programs to apply for and 

receive primacy, and for sufficient project data to be collected. For example, once the first GS 

projects are permitted, injection commences, and monitoring data are generated and analyzed, 

EPA can begin to review this data to verify the applicability and appropriateness of the 

requirements including the usefulness of AoR calculation models, and the utility and design of 

monitoring plans and corrective action plans. As construction and operation of GS projects 

continue (e.g., as AoR reevaluations are conducted or when the first projects cease injecting), 

EPA will have additional opportunities to evaluate the requirements in the course of subsequent 

reviews. 

EPA believes that shorter review intervals, e.g., 2 years, as the commenter suggests, would not 

provide sufficient time for projects to be permitted, State and Tribal programs to apply for and 

receive primacy, and sufficient data to be collected. EPA clarifies that, if early project data 

indicate before six years that revisions are appropriate, EPA will publish new requirements prior 

to then. 

Letter ID: 0145 Comment ID: 23148 Letter Lines: 81 to 88 

Comment Code: 1250 1.1.1.4 Flexibility is needed (performance-based standards) 

Comment: 1. Regulatory ("Director’s") Discretion - TVA supports a flexible rule that 

vests in the Director the discretion to grant certain approvals. However, where 

the Director is provided such discretion (e.g., for imposing secondary 

containment, requesting additional testing, monitoring CO2 fluxes in surface air 

and soil gas, changing the 50-year default post injection care requirement, 

shortening the notification period for plugging an injection well or approving 

site closure plans), the proposed rule should include factors that the Director 

must consider in exercising discretion. 

Individual Response: The final GS rule includes a balance of specific criteria to be met by the 

owner or operator and areas of Directorial discretion and considerations for how that discretion 

would be exercised. The Agency believes this balance allows for GS projects to be designed and 

permitted to address the unique, site-specific aspects of each project, while providing consistency 

in permitting across the U.S. 

EPA is developing guidances for States that describe the process of applying for and receiving 

primary enforcement authority (primacy) for GS Class VI wells under Section 1422 of SDWA, 

2
as well as the technical and administrative issues on developing GS regulations that are the 

equivalent of minimum federal criteria and requirements. The guidance will describe areas of 

Directorial discretion and considerations for how that discretion would be exercised. This 

guidance will be available on EPA’s website at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

Letter ID: 0145 Comment ID: 23149 Letter Lines: 90 to 98 

Comment Code: 3120 2.1.2 Need to identify additional confining and containment zones 

(seeking comment) 

Comment: 2. Siting - The proposed rule provides the Director the discretion to require 

the owner or operator to identify and characterize additional (secondary) 

confining and containment zones above the primary (i.e., lowermost) confining 

zone to further impede vertical fluid movement and allow for pressure 

dissipation. There are situations that must require secondary containment, 

e.g., CO2 GS well fields located in the vicinity of a designated sole-source 

aquifer or other aquifer widely used for water supply. Assurance of CO2 

containment must be near-absolute in such cases, and regulators must have 

discretion to require cap rock redundancy. As a further precaution, potential 

Individual Response: EPA retains the requirement to identify additional containment/confining 

zones, if required by the Director, as proposed (e.g., §146.83(b)). The Agency's decision is 

supported by commenters representing states, water associations, and an electric utility who 

assert that these requirements (at §146.83(b)) promote a flexible, risk-based, site-specific 

approach to characterizing and permitting a site for GS projects. 

The Agency believes that providing the Director discretion will allow consideration of a range of 

sites for GS, based on site-specific conditions and ensure USDW protection. EPA believes that 

requiring appropriate site characterization by the owner or operator (under §146.82) and 

providing an appropriate degree of flexibility to the Director to evaluate site-specific geologic 

data will afford the greatest protection of USDWs from endangerment. 

EPA is developing guidance on site characterization for GS projects to assist owners or operators 

and Directors in evaluating permit requirements and applications under §146.82. The guidance 

provides recommendations regarding characterizing the regional geology and hydrogeology of a 

proposed GS site as well as performing the necessary geochemical, geomechanical, and 

geophysical analyses of the injection and confining zone. EPA expects that this guidance will 

assist permit writers in making an objective decision about requiring additional confining layers. 

The guidance can be found on EPA’s website at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

Letter ID: 0145 Comment ID: 23150 Letter Lines: 98 to 114 

3
Comment Code: 3110 2.1.1 Proposed siting requirements (i.e., injection/confining zones, 

trapping mechanism) 

Comment: discretion to require cap rock redundancy. As a further precaution, potential 

GS sites near sole-source aquifers, as well as those sites in high risk seismic 

locations, should initially be eliminated from consideration until sufficient 

experience with operational scale GS is gained. 

As a related matter, at least for the near future, siting a fossil-fueled plant 

that utilizes GS near a sole-source aquifer should only be considered where the 

infrastructure is in place for transporting supercritical CO2 to a distant 

injection well location. Because a large portion of the Nation’s fleet of 

fossil-fueled generating facilities were sited and built without consideration 

of CCS, there are considerable space, water supply, geologic, seismic, and 

financial constraints for retrofitting many existing facilities with this 

technology. Although the proposed rule does not require facilities to capture 

and/or sequester CO2, promulgation of this rule should acknowledge that GS of 

CO2 will not be suitable at a large number of existing facilities and may be 

most applicable for new-generation facilities that are properly sited a priori 

for CCS. 

Individual Response: The GS requirements are designed to ensure protection of USDWs from 

endangerment by requiring that injection wells are permitted, sited, constructed, operated, 

monitored, and plugged in a manner that does not endanger USDWs. GS in areas that may pose 

risks to USDWs, as assessed and identified by the owner or operator and the Director during the 

site selection process, would not be permitted. 

In response to the comment that GS should not be allowed in areas with high-risk for a seismic 

event, EPA clarifies that the GS rule does not allow GS to be performed in seismically active 

areas and requires that operators must submit information about the seismic history of and 

seismic sources near a proposed GS site (146.82(a)(3)(v)). This information, along with other 

required submissions, will be evaluated by the Director, who will determine the suitability of a 

potential project site for GS. 

EPA clarifies that 146.82(a)(5) requires prospective owners or operators to submit information 

on all USDWs (which would include sole source aquifers) within the AoR. The Director would 

consider this information and the potential impact of the GS project on any sole source aquifers 

in determining whether GS is acceptable. 

Letter ID: 0145 Comment ID: 23152 Letter Lines: 116 to 133 

Comment Code: 3530 2.2.3.1 AoR reevaluation frequency (seeking comment) 

4
Comment: 3. Area of Review (AoR) - The proposed rule requested comment on requiring reevaluation of the site AoR on a periodic basis and the appropriateness of a 10 

year minimum fixed frequency for AoR re-evaluation. TVA supports a reevaluation frequency not to exceed 10 years. Periodic AoR re-evaluation will be 

needed given the enormous volumes of CO2 that would be injected, the potentially 

high mobility of CO2 in the subsurface, the lengthy timeframes likely for CO2 GS 

operations, and the uncertainty of the original model-predicted AoR limits, 

especially where multiple injections might occur below the same aquifer (noncontiguous but merging CO2 pressure fronts). 

In practice, much of what is required in an AoR evaluation (e.g., well field 

monitoring, computational fluid dynamics model calibration/verification, and 

updated prediction of future limits of the CO2 plume) will be performed on an 

on-going basis to support well-field operation and monitoring. If after 10 

years, updated modeling shows no significant change in AoR limits, the AoR reevaluation should merely require presenting the latest modeling results and 

possibly confirming that no new penetrations have been identified and therefore 

no new corrective actions are necessary. 

Individual Response: EPA believes that reevaluations of the AoR every ten years may not be 

sufficient to appropriately model plume and pressure front movement, establish conditions for 

corrective action, and ensure protection of USDWs from endangerment. For these reasons, the 

Agency changed the minimum frequency for the AoR reevaluation at §146.84(e) from 10 years 

to at least every 5 years in the final GS rule. EPA believes that this revised frequency addresses 

commenters' concerns about the inherent uncertainties in modeling CO2 movement, the 

emerging nature of GS technology, risk-based targeting of monitoring activities, and the unique 

nature of CO2 GS. 

In addition, the Director has discretion to require more frequent AoR reevaluation if he or she 

has reason to believe, based on site-specific information, that a five-year reevaluation schedule is 

not sufficiently protective of USDWs. 

EPA adds that if site monitoring data agrees with the existing AoR delineation, a model 

recalibration may not be necessary, and the AoR reevaluation may consist of a demonstration 

that the current AoR delineation is adequate based on site monitoring data. 

Letter ID: 0145 Comment ID: 23153 Letter Lines: 135 to 141 

Comment Code: 4322 2.4.4.1.1 Comments in favor of requiring injection below the lowermost 

USDW 

Comment: 4. Injection Depth in Relation to USDWs - The proposed rule requested comment on 

alternative approaches that would allow injection between and/or above the 

lowermost USDW, and thus potentially allow for more areas to be available for GS 

while preventing USDW endangerment. Limiting CO2 GS to geologic units below the 

5
lowest USDW is prudent and reasonable. Prohibiting injection between and/or 

above the lowermost USDW is essential to protecting valuable drinking water 

sources by avoiding unnecessary siting and operational risks. Once experience 

Individual Response: EPA agrees that protecting USDWs from endangerment must be a top 

priority. The Agency believes that there are limited circumstances where injection above the 

lowermost USDW can be performed in a manner that protects USDWs, as long as appropriate 

protections are in place. The final GS rule at §146.95 establishes a process by which owners or 

operators can seek a waiver of the Class VI injection depth requirements for injection into nonUSDW formations above and/or between USDWs. The waiver approach requires the submission 

of extensive, site-specific information (in conjunction with the permit application submission) to 

demonstrate that injection of CO2 into a non-USDW that is above or between USDWs can be 

done in a manner that is protective of USDWs. It establishes: 1) requirements specifying 

information that owners or operators must submit, and Directors must consider, in consultation 

with PWSS Directors; 2) procedures for public notice of a waiver application and for DirectorRegional Administrator communication; 3) the waiver issuance process; and, 4) additional 

requirements that apply to owners or operators of Class VI wells granted a waiver of the 

injection depth requirements to ensure USDW protection above and below the injection zone. 

EPA believes that the requirements at §146.95 will ensure USDW protection while providing 

flexibility to UIC Program Directors and owners or operators who undertake CO2 injection for 

GS. The Agency believes this approach: 1) responds to concerns about local and regional 

geologic storage capacity limitations imposed by the proposed injection depth requirements; 2) 

allows for a more site-specific assessment of injection depth for GS projects; 3) accommodates 

injection into different formation types; 4) allows for injection of CO2 for GS into non-USDWs 

above and/or between USDWs when appropriate and where it can be demonstrated that USDWs 

will be protected; and 5) responds to concerns about the use of aquifer exemptions for GS. 

Finally, EPA’s approach to addressing injection depth variability through a waiver process 

responds to concerns about future drinking water resource availability and the need to ensure that 

high quality water remains available in sufficient quantities to supply drinking water needs. For 

additional information on the waiver approach, please see the final rule and preamble, as well as 

EPA's responses to comments on the Notice of Data Availability and Request for Comment. 

Letter ID: 0145 Comment ID: 23155 Letter Lines: 147 to 153 

Comment Code: 5460 2.9.2 Comments on transfer of liability for long-term care 

Comment Code: 5800 2.13 Comments on emergency and remedial response (40 CFR 146.94) 

Comment: 5. Unspecified Operational Consequences - In the unfortunate event operational 

experience at a GS site shows the permitted geologic storage was ill advised and 

that CO2 injection from a fossil-fueled power plant sited and operated at (or 

transporting supercritical CO2 to) that location must be terminated, TVA 

requests a provision be added to this rule to address what consequences, with 

regards to resumed emissions of CO2, discontinuation of CCS would have for such 

a facility. 

6
Individual Response: EPA clarifies that EPA’s authority under the Safe Drinking Water Act is 

limited to and the focus of the GS regulation is on preventing USDW endangerment due to 

injection, and that any impacts to or procedures for fossil fuel power plants are outside the scope 

of the GS rule. EPA is, however, developing guidance on the development and implementation 

of emergency and remedial response plans for GS sites. To meet the requirements for developing 

an emergency and remedial response plan (specified at §146.94(a)), an owner or operator should 

identify people (in addition to the Director), such as first responders, who should be contacted in 

the event of an emergency associated with the well. EPA envisions that the party that transports 

the CO2 onsite should be notified as well. 

See the final rule preamble for further discussion of EPA's final approach. 

Letter ID: 0145 Comment ID: 23156 Letter Lines: 155 to 159 

Comment Code: 1420 1.2.1.1 Support the GS rulemaking 

Comment: TVA believes that a Class VI permitting program is reasonable and necessary 

before GS can be implemented at the operational scale necessary for mitigating 

power plant CO2 emissions, and TVA applauds EPA for this initial effort to 

provide a regulatory framework and some degree of regulatory certainty for GS 

under the UIC program. TVA appreciates the opportunity to comment on EPA’s 

Individual Response: EPA agrees that the creation of a new injection well class (VI) under the 

existing UIC Program is necessary to enable the use of GS as a climate change mitigation 

technology in a manner that protects USDWs from endangerment. EPA agrees that the UIC 

Program, under the authority of the SDWA, provides a strong framework for regulating injection 

of CO2 for GS and adds that the GS regulation tailors the UIC requirements to address the 

unique issues associated with large-scale GS including large injection volumes, the relative 

buoyancy of CO2, its corrosivity in the presence of water, the potential presence of impurities in 

captured CO2, and its mobility within subsurface geologic formations. 

EPA acknowledges that GS falls within the broader context of CCS and the need for regulatory 

clarity to ensure that USDWs are protected from endangerment. In developing the final GS rule, 

the Office of Water coordinated with other Agency program offices and across federal agencies 

(e.g., with the Department of Energy; United States Geological Survey; Bureau of Ocean Energy 

Management, Regulation, and Enforcement, formerly the Minerals Management Service; Bureau 

of Land Management). The Agency continues to evaluate areas of potential applicability of other 

Federal environmental statutes including, but not limited to: the Clean Air Act; the Resource 

Conservation and Recovery Act; the Comprehensive Environmental Response, Compensation, 

and Liability Act; and the Marine Protection, Research and Sanctuaries Act to various aspects of 

GS and CCS. The Agency will continue to coordinate on GS and CCS related issues to minimize 

redundancy and maximize efficiencies for owners or operators. For additional information, 

please see the discussion entitled "How Does This Rulemaking Relate to Other Federal 

Authorities and GS and CCS Activities?" in the preamble to the final GS rule. 

7
8

Letter ID: 0145 Comment ID: 23157 Letter Lines: 141 to 145 

Comment Code: 4322 2.4.4.1.1 Comments in favor of requiring injection below the lowermost 

USDW 

Comment Code: 4410 2.4.4.3.1 Comments in favor of allowing injection above/between 

USDWs in certain circumstances 

Comment: sources by avoiding unnecessary siting and operational risks. Once experience 

is gained with the long-term behavior and geologic containment of CO2, injection 

depths above the lowermost USDW may be considered appropriate on a site-specific 

basis (e.g., where storage depth would be sufficient for maintaining CO2 in a 

supercritical state and separate from USDWs). 

Individual Response: EPA acknowledges that there are limited circumstances where injection 

above the lowermost USDW can be performed in a manner that protects USDWs from 

endangerment, as long as appropriate protections are in place. The final GS rule at §146.95 

establishes a process by which owners or operators can seek a waiver of the Class VI injection 

depth requirements for injection into non-USDW formations above and/or between USDWs. 

The waiver approach requires the submission of extensive, site-specific information (in 

conjunction with the permit application submission) to demonstrate that injection of CO2 into a 

non-USDW that is above or between USDWs can be done in a manner that is protective of 

USDWs. The requirements are designed to ensure that the owner or operator, the Director, and 

the Regional Administrator consider, on a site specific basis, the implications, benefits, and 

challenges associated with GS and ensuring water availability and USDW protection. 

It establishes: 1) requirements specifying information that owners or operators must submit, and 

Directors must consider, in consultation with PWSS Directors; 2) procedures for public notice of 

a waiver application and for Director-Regional Administrator communication; 3) the waiver 

issuance process; and, 4) additional requirements that apply to owners or operators of Class VI 

wells granted a waiver of the injection depth requirements to ensure USDW protection above and 

below the injection zone. EPA believes that these requirements will ensure USDW protection 

while providing flexibility to UIC program Directors and owners or operators who undertake 

CO2 injection for GS. 

For additional information on the waiver approach, please see the final rule and preamble, as 

well as EPA's responses to comments on the Notice of Data Availability and Request for 

Comment.