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.




Letter ID: 0131 

Commenter: Carl Carlsson 

Organization: SUEZ Energy Generation NA, LLC 

Letter ID: 0131 Comment ID: 21524 Letter Lines: 49 to 52 

Comment Code: 1330 1.1.3.1 Support use of GS in general 

Comment: As the owner of power generation facilities, SEGNA respectfully submits the 

following comments for consideration by EPA. SEGNA supports efforts to curb 

greenhouse gas emissions, including research and investment in carbon capture 

and sequestration (CCS) technology. 

Individual Response: EPA acknowledges the comment. Please see the remainder of EPA’s 

responses to this comment for further details. For additional information on EPA’s final 

regulatory approach, please see the final rule and preamble as well as the rulemaking docket. 

Letter ID: 0131 Comment ID: 21525 Letter Lines: 54 to 64 

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

Comment: General Comments 

Effort should be made, to the extent practicable, to keep provisions for 

Underground Injection Control (UIC) of CO2 consistent with already known and 

understood UIC principles and regulations. Care should be taken to avoid 

overestimating the risks associated with GS, in order to ensure that the final rules 

are not excessively burdensome or complex. Of course, the rules must 

simultaneously ensure adequate protection of human health and the environment. 

However, excessive, complex regulatory requirements have the potential to limit 

development of a technology that will be critical to our efforts to address climate 

change effectively, adding significantly to costs for a program that will already 

result in significant additional costs to the energy sector, industry and consumers. 

Individual Response: EPA disagrees that the requirements in the GS rule overstate the risk 

associated with GS. The UIC Program, under the authority of the SDWA, provides a strong 

framework for regulating injection of CO2 for GS; 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 recognizes the importance of providing clear, flexible, scalable, and appropriate 

regulations. EPA believes that the GS regulation will provide certainty to industry and the public 

by providing consistency in requirements across the U.S. and transparency about what 

requirements apply to owners or operators. 

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EPA clarifies that the Class VI GS requirements are designed to ensure that, where deployed, GS 

is conducted in a manner that protects USDWs from endangerment. Encouraging investment in 

CCS projects and facilitating deployment are outside the scope of the GS rulemaking. 

Letter ID: 0131 Comment ID: 21526 Letter Lines: 66 to 75 

Comment Code: 1655 1.3.5.1 Concerns about Lake Nyos and Mammoth Mountain-type events 

Comment Code: 1680 1.3.8 Don't overstate risk, don't stigmatize CO2 

Comment: Risks Associated with CO2 GS 

SEGNA agrees that all potential risks associated with geological sequestration of 

CO2 should be addressed, and that the public must be adequately informed. 

However, references to the large and rapid releases of CO2 from volcanic lakes, 

as occurred in Cameroon in the 1980's, must be presented carefully to more 

clearly demonstrate that geological sequestration--deep underground and under 

confining strata--is a completely different process and does not represent a risk 

to human health and the environment comparable to the referenced incident in 

Cameroon. The language in any subsequent documents issued by EPA should 

make this point more forcefully to avoid public confusion regarding the actual risk. 

Individual Response: The Agency believes it appropriately characterized the limnic eruption at 

Lake Nyos as a rare and naturally-occurring lake turnover event that is characteristic of stratified 

lakes in warm climates. The event at Lake Nyos, during which naturally-occurring CO2 trapped 

at the bottom of the Lake was released to the atmosphere, is not a valid analogue for GS. The 

preamble highlighted differences between the lithologic reservoirs that may serve as storage 

formations for CO2 and the processes occurring at Lake Nyos and other stratified tropical lakes 

(73 FR 43498). 

Letter ID: 0131 Comment ID: 21527 Letter Lines: 77 to 82 

Comment Code: 1630 1.3.3 RCRA/hazardous waste issues (seeking comment) 

Comment: CO2 as a Hazardous Waste 

Regarding the question of characterizing CO2 streams to determine if they need 

to be regulated as a hazardous waste, SEGNA feels that it is desirable to provide 

regulatory clarity on this issue, and therefore it is appropriate to consider, either 

as part of the rule or as a separate rulemaking, a categorical exemption for CO2 

streams. 

Individual Response: EPA agrees that any requirements for the CO2 stream should be clearly 

identified. EPA received many comments regarding the applicability of the RCRA regulations 

and statute to CO2 streams that are geologically sequestered under the final Class VI UIC well 

requirements. As a result, EPA has decided to initiate a separate proposed rulemaking 

specifically to examine the issue of RCRA applicability to CO2 streams being geologically 

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sequestered, including the possible option of a conditional exemption from the RCRA 

requirements for CO2 GS in Class VI wells. EPA will consider these comments as part of its 

development of that proposal. The Agency will consider issues particular to RCRA in the context 

of that separate rulemaking, and recommends that the commenter read that proposed rule when it 

is published. The Agency notes that commenters who wish to submit comments on the RCRA 

proposal will need to do so during the comment period for that rule. Finally, EPA also notes that 

the final GS rule, which adds new regulations for Class VI wells under the Safe Drinking Water 

Act (SDWA), is not making any changes to the RCRA regulations. 

EPA clarifies that the GS rule requires owner or operators of Class VI wells to characterize their 

injection stream prior to injection, and throughout the operational life of the injection facility. 

Since the GS rule, at §146.81(d), prohibits CO2 streams that meet the definition of a hazardous 

waste under 40 CFR part 261, owners or operators will need to characterize their CO2 stream as 

part of their permit application to determine if the injectate is a RCRA hazardous waste. If so, 

injection may only occur in a Class I hazardous waste injection well. 

Letter ID: 0131 Comment ID: 21528 Letter Lines: 84 to 91 

Comment Code: 2300 1.7 Comments on the Alternatives Considered 

Comment: Proposed Regulatory Alternatives 

SEGNA agrees that options 1 and 4 ("Non-Specific Requirements Approach" 

and "Highly Specific Requirements Approach", respectively) are not appropriate for 

the reasons stated by EPA. Alternative 3, "Tailored Requirements Approach" 

suggested by EPA might be the best alternative since it builds on the existing UIC 

regulatory framework, though flexibility regarding specific program elements 

should be considered on a case-by-case basis, as appropriate, pursuant to 

the "General Requirements Approach" under Alternative 2. 

Individual Response: EPA agrees with the commenters that Regulatory Alternative 3 is 

appropriate. The technical requirements in Alternative 3 (and the final GS rule) build upon the 

long-standing UIC regulatory framework for deep wells and are appropriately tailored to address 

the unique nature of full-scale CO2 GS, including the volumes of CO2 to be injected, the 

buoyant and mobile nature of the injectate, and its corrosivity in the presence of water. 

Even though the Agency did not choose Alternatives 1 or 2, EPA agrees that flexibility is 

important to accommodate the varied conditions that may be encountered at GS sites while 

ensuring the protection of USDWs. The regulation provides flexibility for selection of 

appropriate sites and target formations (under §146.82), well construction specifics (under 

§146.86), and testing and monitoring regimes (under §146.90), provided the owner or operator 

can demonstrate that the injection and storage will not endanger USDWs and that minimum 

requirements for the site are met. 

Letter ID: 0131 Comment ID: 21529 Letter Lines: 93 to 98 

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Comment Code: 3350 2.2.1.5 Use of proprietary models for GS sites (seeking comment) 

Comment: Use of Proprietary Models to Delineate the Area of Review 

SEGNA agrees with EPA that models used for GS analysis should be based on 

accepted science and should be validated. In addition to requiring operators to 

disclose code assumptions, relevant equations and the scientific basis for 

proprietary models, SEGNA suggests that EPA consider establishing a validation 

process for such models using empirical data to ensure such models are sound. 

Individual Response: EPA agrees with commenters that available proprietary models may meet 

the complex needs for calculating the AoRs of GS sites, and shares their concern about the need 

to evaluate the inputs and assumptions used. EPA plans to allow the use of proprietary models in 

meeting the requirements for the GS regulation, as long as GS well operators using a proprietary 

model clearly disclose, to the Director's satisfaction, the code assumptions, relevant equations, 

and scientific basis. EPA adds that its Confidential Business Information requirements at 40 CFR 

144.5 will apply to the use of proprietary models. 

In response to comments suggesting that history matching or validation of these models is 

needed, EPA believes this is true for any model. EPA notes that the GS rule requires at 

§146.84(e) that the AoR be reevaluated to verify that the CO2 plume is moving as predicted and 

to allow for necessary revisions to the AoR and corrective action, testing and monitoring, 

injection well plugging, post-injection site care and site closure, and emergency and remedial 

response plans. EPA clarifies, however, that the Agency will not perform independent validation 

of individual modeling products. 

The Agency 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. 

Letter ID: 0131 Comment ID: 21530 Letter Lines: 100 to 103 

Comment Code: 3840 2.3.2 Horizontal well drilling techniques (seeking comment) 

Comment: Horizontal Well Construction 

SEGNA supports the allowance of horizontal drilling for well construction, provided 

that the construction and operation requirements are consistent with those applied 

to vertical wells. 

Individual Response: In the final rule, EPA allows the use of horizontal wells at GS projects. In 

the proposed rule, EPA sought comment on the appropriateness of horizontal drilling techniques 

for Class VI wells, and commenters representing energy companies, electric utilities, the oil and 

gas industry, CCS associations, states, and the public, unanimously supported the concept and 

provided many reasons why horizontal wells could be beneficial at GS sites. Based on an 

evaluation of these comments and additional research by EPA, the Agency has concluded that 

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horizontal wells that are properly constructed, logged, and tested for mechanical integrity (i.e., to 

meet the requirements of the GS rule) can ensure the protection of USDWs from endangerment. 

EPA clarifies that horizontal wells will be subject to the same tailored requirements as vertical 

wells. 

Letter ID: 0131 Comment ID: 21531 Letter Lines: 105 to 111 

Comment Code: 3820 2.3.1 Well construction procedures 

Comment: Specification of Well Construction Materials 

SEGNA agrees with EPA's position that the proposed rules should not specify 

materials that may be used, but rather should allow the owner or operator 

flexibility to choose, provided that the materials used are corrosion-resistant and 

meet appropriate standards. Well casing materials should be appropriate to the 

application, taking into account the chemical nature of the injected fluids and any 

additives, as well as the subsurface environment. 

Individual Response: EPA acknowledges the comment and agrees that, given the continuing 

evolution of material design and the numerous variables possible in a long-term GS project, 

listing specific requirements for casing and cement would not be appropriate. Rather, requiring 

that materials have sufficient structural strength and be compatible with fluids with which they 

may come in contact, in §146.86(b)(1), allows the owner or operator to determine the best casing 

and cementing design for each project based on information about the site and the planned 

injection and allows the Director to approve that design. 

See the discussion of Class VI well construction requirements in the preamble to the final GS 

rule for additional information. Additionally, EPA is developing guidance on the construction of 

Class VI wells. This guidance will be available on EPA’s website at 

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

Letter ID: 0131 Comment ID: 21532 Letter Lines: 113 to 119 

Comment Code: 4340 2.4.4.2 Minimum injection depth (seeking comment) 

Comment: Minimum Injection Depths 

EPA is not prescribing a minimum injection depth to keep CO2 in a supercritical 

state since some operators may inject CO2 in a gaseous state, but describes the 

potential deleterious effects of a change in state (for supercritical CO2) and the 

expansion of gaseous CO2. SEGNA believes it would be reasonable to stipulate 

a minimum injection / storage depth for supercritical CO2, but allow a 

discretionary lower depth for injection of gaseous CO2. 

Individual Response: EPA agrees that it is not appropriate to set a minimum injection depth for 

GS projects or require that the CO2 be injected in a supercritical state. EPA believes that a 

5
determination of site-suitability for GS (i.e., that subsurface formations will receive and confine 

injected CO2) should be made on a site-specific basis. The GS rule, at §146.82, requires the 

owner or operator to provide extensive site- and project-specific information to the Director to 

demonstrate that the site meets the minimum site criteria at §146.83, that the CO2 will be 

contained within the injection formation, and that USDWs will be protected from endangerment. 

EPA acknowledges 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 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. 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: 0131 Comment ID: 21533 Letter Lines: 121 to 124 

Comment Code: 4320 2.4.4.1 Injection beneath the lowermost formation containing a USDW 

Comment: Injection Well Operating Requirements 

SEGNA agrees with EPA's proposal to allow Directors to exempt Underground 

Sources of Drinking Water (USDWs) below the injection zone, and allow injection 

below the lowermost non-exempted USDW. SEGNA also supports the 

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

exemptions for GS may be warranted. The final rule allows for the expansion of the areal extent 

of existing aquifer exemptions for Class II EOR/EGR wells transitioning to Class VI injection 

for GS pursuant to requirements at §§146.4 and 144.7(d). Class VI owners or operators granted 

expansions of existing Class II EOR/EGR aquifer exemptions for GS projects must meet all of 

the tailored requirements for Class VI wells in the final GS rule. 

However, the final rule precludes the issuance of new aquifer exemptions for Class VI wells; that 

is, aquifer exemptions will only be granted for projects that are transitioning from Class II 

EOR/EGR wells to Class VI. For additional information on aquifer exemptions for Class VI 

wells, 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: 0131 Comment ID: 21534 Letter Lines: 124 to 128 

Comment Code: 4490 2.4.5 Use of tracers and potential impact on human health or ecosystems 

6
(seeking comment) 

Comment: below the lowermost non-exempted USDW. SEGNA also supports the 

development of guidelines for cost-effective use of tracers, but the decision to 

require their use should be made by the permitting authority. Of the technical 

options suggested in the proposed rule, unique suites of perfluorocarbons (PFCs) 

appeared to be the best option. 

Individual Response: EPA agrees that tracers can be useful tools for monitoring GS projects. 

However, EPA agrees that tracer use is not appropriate in all situations. For this reason, EPA 

does not require the use of tracers at all GS sites; however, the Director has discretion to require 

their use if he/she determines that the use of tracers could improve monitoring of the site and 

enhance USDW protection from endangerment. The rule will also allow their use if proposed by 

the owner or operator and approved by the Director. 

EPA will continue to track research related to tracer use, and plans to, every six years, 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. 

Letter ID: 0131 Comment ID: 21535 Letter Lines: 130 to 133 

Comment Code: 4520 2.5.1 Continuous internal mechanical integrity monitoring (seeking 

comment) 

Comment: Mechanical Integrity Testing 

SEGNA agrees with EPA's proposal to require continuous downhole monitoring, 

as the required technology is currently available and should not present an undue 

cost when required on new wells. However, SEGNA is opposed to requiring 

Individual Response: EPA acknowledges the comment and believes that continuous pressure 

monitoring to demonstrate internal mechanical integrity of Class VI wells required at §146.89(b), 

instead of periodic testing, which is required for most other types of deep injection wells is 

important given the potential corrosive impact of CO2 and impurities on well materials, the 

potential geomechanical impacts to well integrity due to CO2 phase changes, and the 

temperature and pressure effects associated with injecting supercritical CO2. For additional 

information, please see the discussion of MITs in the final rule preamble. 

Letter ID: 0131 Comment ID: 21536 Letter Lines: 133 to 138 

Comment Code: 4546 2.5.2.2 MIT frequency (seeking comment) 

Comment: cost when required on new wells. However, SEGNA is opposed to requiring 

Mechanical Integrity (MI) testing more frequently than the 5 year frequency 

typically required for deep wells, particularly if such testing results in well 

7
downtime. Unnecessary testing and associated downtime will significantly add 

to costs, and may have additional upstream impacts on generation that may 

introduce expensive storage requirements. 

Individual Response: EPA disagrees that a five-year external MIT is appropriate. The final GS 

regulation retains the requirement that owners or operators of Class VI wells must demonstrate 

injection well external mechanical integrity at least once annually under §146.89(c). EPA 

believes this is justifiable for the protection of USDWs from endangerment given the unique 

nature of CO2 GS relative to other injection operations, including the potential corrosive impact 

of CO2 in the presence of water and impurities on well materials, the potential geomechanical 

impacts to well integrity due to CO2 phase changes, the temperature and pressure effects 

associated with injecting supercritical CO2, and the buoyant nature of the injected CO2. Because 

of the unknown long-term effects of CO2 GS, EPA chose a more conservative initial approach in 

the early stages of deployment for GS. EPA believes that the USDW protectiveness of MITs 

justifies their cost. Please see the Cost Analysis, which is available in the rulemaking docket, for 

additional information on the costs of MITs. 

EPA adds that it is using an adaptive approach to regulating GS. The Agency plans to collect and 

review data every six years on GS projects, including MIT data, 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. 

Letter ID: 0131 Comment ID: 21537 Letter Lines: 140 to 145 

Comment Code: 5240 2.8.2.2 Post injection timeframe (seeking comment) 

Comment: Post-injection Site Care 

SEGNA disagrees with EPA's proposal to lengthen the post-injection site 

monitoring period to 50 years versus the current 30 year standard. EPA has 

provided insufficient justification for such an extension, which will add significant 

costs and adversely impact sequestration projects and their ability to obtain 

financing. As it currently reads, the proposed rule has provisions for extending 

Individual Response: EPA disagrees that a post-injection site care timeframe of 50 years is 

excessive for most Class VI wells. EPA proposed a default post-injection site care timeframe of 

50 years based on a review of research studies, industry reports, and existing environmental 

programs. This analysis was included in an EPA-prepared background document that is available 

in the federal docket for the GS rule, titled "Computational Modeling of Underground Injection 

of Carbon Dioxide for Determination of Area-of-Review and Potential Risk to Underground 

Sources of Drinking Water." EPA assessed various default timeframes based on additional 

review of research studies and evaluation of public comments. While numerous commenters 

suggested that EPA shorten the monitoring timeframe, none of the commenters provided 

sufficient data or other evidence to warrant a change in the proposed timeframe. While the 10- or 

30-year timeframe suggested by some of these commenters may be within the timeframe 

suggested in some studies, EPA believes that the potential risks of endangering USDWs will 

8
likely not decline within these timeframes and available data, including data submitted by 

commenters, do not support a different default timeframe. However, EPA recognizes that 

alternative timeframes may be appropriate under limited, specific circumstances. 

For this reason, the GS rule offers owners or operators flexibility regarding the duration of the 

PISC timeframe by: (1) allowing the Director discretion to shorten or lengthen the PISC 

timeframe during the post-injection period based on site-specific data, pursuant to requirements 

at §146.93(b); or (2) affording the Director discretion to allow a Class VI well owner or operator 

to demonstrate, during the permitting process based on substantial data, that an alternative PISC 

timeframe may be appropriate if it ensures non-endangerment of USDWs pursuant to 

requirements at §146.93(c). 

EPA believes that a default post-injection site care timeframe of 50 years, with flexibility to 

adjust the timeframe for a limited number of GS projects during the permitting process where 

substantial data exists to demonstrate that an alternative timeframe would be protective of 

USDWs, or based on data collected during the PISC period, is appropriate to address the range of 

sites where GS is anticipated to occur, to accommodate site-specific circumstances and various 

geologic conditions, and addresses commenters’ concerns, while ensuring USDW protection. 

Both approaches will utilize site-specific data, and be based on pressure monitoring and USDW 

impacts. 

EPA believes however, that to ensure USDW protection from endangerment, a default timeframe 

for post-injection site care will be necessary in all but a limited number of cases. This default 50 

year post-injection site care timeframe represents a reasonable and protective monitoring period 

based on a review of research studies, industry reports, and existing environmental programs, 

and evaluation of public comments. 

To the commenters who expressed concern about the cost of post-injection site care, EPA does 

not agree that post-injection site care timeframes longer than 30 years will be prohibitively 

expensive. In fact, EPA believes that post-injection site care monitoring will represent a 

relatively minor component of total project cost, and will provide an essential level of protection 

from endangerment for USDWs. A discussion of the costs attributed to monitoring technologies 

(used during injection and the post-injection site care timeframes) is available in the Technology 

and Cost Document for the GS rule, which is in the federal docket for this rulemaking. EPA 

believes that it is logical to make use of existing monitoring infrastructure at a GS site in order to 

ensure USDWs are not endangered. 

Letter ID: 0131 Comment ID: 21538 Letter Lines: 145 to 147 

Comment Code: 5260 2.8.2.3 Adjusting the post-injection timeframe (seeking comment) 

Comment: financing. As it currently reads, the proposed rule has provisions for extending 

this period in the event that performance standards are not met, so the standard 

would be adequately protective with a 30-year requirement. 

Individual Response: EPA disagrees that a post-injection site care timeframe of 50 years is 

9
excessive for most Class VI wells. While numerous commenters suggested that EPA shorten the 

monitoring timeframe, none of the commenters provided sufficient data or other evidence to 

warrant a change in the proposed timeframe. While the 10- or 30-year timeframe suggested by 

some of these commenters may be within the timeframe suggested in some studies, there are 

circumstances (e.g., little development of mineral trapping of CO2) under which the potential 

risks of endangering USDWs will likely not decline within these timeframes and available data, 

including data submitted by commenters, do not support a different default timeframe. 

EPA acknowledges there will be circumstances where it can be demonstrated in less than 50 

years that the plume and pressure front no longer pose a risk of endangerment to USDWs. For 

this reason, the GS rule offers owners or operators flexibility regarding the duration of the PISC 

timeframe by: (1) allowing the Director discretion to shorten or lengthen the PISC timeframe 

during the post-injection period based on site-specific data, pursuant to requirements at 

§146.93(b); or (2) affording the Director discretion to allow a Class VI well owner or operator to 

demonstrate, during the permitting process based on substantial data, that an alternative PISC 

timeframe may be appropriate if it ensures non-endangerment of USDWs pursuant to 

requirements at §146.93(c). 

EPA believes that a default post-injection site care timeframe of 50 years, with flexibility to 

adjust the timeframe for a limited number of GS projects during the permitting process where 

substantial data exists to demonstrate that an alternative timeframe would be protective of 

USDWs, or based on data collected during the PISC period, is appropriate to address the range of 

sites where GS is anticipated to occur, to accommodate site-specific circumstances and various 

geologic conditions, and addresses commenters’ concerns, while ensuring USDW protection. 

Both approaches will utilize site-specific data, and be based on pressure monitoring and USDW 

impacts. 

Letter ID: 0131 Comment ID: 21539 Letter Lines: 149 to 153 

Comment Code: 5430 2.9.1 Comments on proposed financial responsibility requirements (40 

CFR 146.85) 

Comment: Financial Responsibility and Long-term Care Requirements 

Generally, SEGNA supports efforts to minimize post-closure monitoring 

requirements and costs, and to increase options for demonstrating financial 

assurance, so as to not unnecessarily discourage entities from pursuing or 

financing carbon sequestration projects. 

Individual Response: EPA agrees that flexibility is important. Owners or operators have the 

flexibility to choose from a variety of financial instruments to meet their financial responsibility 

obligations. Owners or operators may use one or multiple financial responsibility instruments for 

well plugging and PISC (§146.85(a)(6)). However EPA will not allow for a separate financial 

responsibility demonstration for well plugging and PISC (i.e., a demonstration submitted prior to 

well plugging and the beginning of the post-injection site care period rather than with the permit 

application). A demonstration of financial responsibility for all phases of the GS project will be 

required prior to the issuance of a Class VI permit (§146.85(a)(5)(i)). 

10
EPA is developing guidance on financial responsibility for Class VI wells to assist owners or 

operators in evaluating the financial responsibility requirements for Class VI wells. This 

guidance will be available on EPA's website at 

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

Letter ID: 0131 Comment ID: 21540 Letter Lines: 155 to 159 

Comment Code: 5700 2.12 Comments on the proposed duration of Class VI permits (seeking 

comment) 

Comment: Proposed Injection Permit Duration 

SEGNA agrees that with EPA's proposal that permits be issued for the operating 

life and post-closure care period of the injection well. The ongoing monitoring, 

reporting and regulatory review required by other provisions of this proposed rule 

are adequate to ensure that human health and the environment are protected. 

Individual Response: EPA agrees with commenters that Class VI permits should be issued for 

the operating life of the GS project. EPA believes that the iterative process of developing and 

executing the various plans required of GS well operators under the final rule (e.g., for AoR and 

corrective action, testing and monitoring, injection well plugging, post-injection site care, and 

emergency and remedial response) is tailored to the unique aspects of—and is more appropriate 

for–GS than establishing a finite permit duration (e.g., five years as suggested by some 

commenters). EPA adds that the required reviews of the AoR and corrective action plan, the 

testing and monitoring plan, and the emergency and remedial response plan at least every five 

years throughout the life of the project are preferable to a periodic permit reapplication. The 

iterative process and subsequent plan reevaluations ensure that time and resources are committed 

to the most critical aspects of the permit in preventing endangerment to USDWs. 

EPA clarifies that the final GS rule specifies that Class VI permits will be issued for the 

operating life of the facility and the post-injection site care period (144.36(a)). The rule also 

requires the Director to review Class VI permits at least every 5 years to determine whether they 

should be modified, revoked and reissued, terminated or a minor modification made as provided 

in §§144.39, 144.40, or 144.41. 

Letter ID: 0131 Comment ID: 21541 Letter Lines: 161 to 168 

Comment Code: 1420 1.2.1.1 Support the GS rulemaking 

Comment: Conclusion 

In summary, SEGNA is supportive of EPA's efforts to provide regulatory clarity for 

geologic sequestration of CO2. We encourage EPA to consider the above 

recommendations to ensure that geologic sequestration of CO2 is conducted in 

an environmentally safe and technically sound manner, while avoiding 

unnecessary technical and regulatory complexity. An appropriate balance 

11
12

between these considerations will maximize the potential for this technology to 

play a significant role in addressing the challenges of climate change. 

Individual Response: EPA acknowledges the comment and believes that the creation of a new 

injection well class (VI) under the existing UIC Program is necessary to enable deployment 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 agrees that the implementation of the GS rule in a manner that ensures protection of 

USDWs from endangerment is important to establishing a foundation for further advances in the 

field of CO2 GS. EPA acknowledges the need for regulatory certainty: the final GS requirements 

provide a level of certainty by setting forth unique requirements for GS. These requirements 

include: the tailored AoR delineation process at §146.84, the types of monitoring appropriate to 

GS projects at §146.90 and the post-injection site care process at §146.93. For additional 

information on these requirements, please also see the discussion of EPA’s Final Regulatory 

Approach in the preamble to the final GS rule.