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.
Cynthia C. Dougherty 

Director 

Office of Ground Water and Drinking Water 

U. S. Environmental Protection Agency 

1200 Pennsylvania Ave., NW. 

Washington, DC 20460 

Mar 17, 2009

Proposed Rule on Geologic Sequestration of Carbon Dioxide 

Dear Director Dougherty, 

Now that the public comment period for EPA’s Proposed Rule on Geologic Sequestration 

of Carbon Dioxide (GS) has closed and the Agency is considering next steps, we are 

writing to summarize our views in relation to a few key points following our individual 

and joint comments of Dec24, 2008 and to bring them to the attention of the workgroup 

for its upcoming work and meetings. 

First we stress again the importance of promulgating adequate regulations for GS in a 

timely fashion. GS has an important role to play in reducing carbon dioxide emissions in 

the U.S. and, although projects can be permitted under existing rules, a dedicated set of 

regulations is needed both to increase certainty further but also adequately to safeguard 

human health and the environment. Therefore, in considering whether a Notice of Data 

Availability (NODA) is needed, we urge EPA to choose the most expeditious option that 

is accountable, transparent, legally robust and defensible, and also to ensure that 

whichever option is chosen does not delay the promulgation of the rule. 

Second, we highlight that the final rule needs to cater for GS in hydrocarbon reservoirs as 

well, and not just saline formations as proposed. Hydrocarbon reservoirs are likely to be 

among the first ones to be used for GS, and they need to be regulated appropriately. We 

do not believe that automatic delegation to Class II “as long as any production is 

occurring” is suitable. Under the economic driver of carbon constraints, additional risks 

might be posed in these reservoirs if operators inject larger volumes or at higher rates and 

pressures than they have been doing to date under Class II. Moreover, site 

characterization, operation, monitoring and closure requirements over and above the 

existing Class II will be needed to certify and assure “geologic sequestration” of injected 

carbon dioxide in hydrocarbon reservoirs. 

Third, we raise the issue of authority. The rulemaking to date has only cited authority 

under the Safe Drinking Water Act (SDWA). As we stated in our comments of Dec24, 

2008, an appropriate regulatory regime for GS must also be grounded on authority to 

prevent re-emissions of injected carbon dioxide to the atmosphere. The proposed rule 

defines GS solely for the purposes of protecting Underground Sources of Drinking Water 

(USDWs). Climate legislation is presently being drafted in Congress however, and will 

very likely rely on EPA’s injection classes to certify GS. Specifically, the legislation will 
very likely exempt carbon dioxide emissions from large facilities that are geologically 

sequestered according to regulations promulgated by EPA and/or other agencies. We 

stress the importance of EPA being ready and prepared to meet such requirements. 

Accounting protocols for carbon allowances is an issue that can be dealt with outside the 

scope of the current rulemaking, and is likely to have a far narrower remit than the 

current rule’s specific requirements for site screening, monitoring, and various plans. 

EPA, therefore, must define and regulate GS from the outset in a way that assures not 

only that USDWs are not endangered, but that GS for the purposes of climate protection 

is also taking place. 

To that effect, we make the following recommendations: 

• EPA must promulgate appropriate requirements for GS in hydrocarbon reservoirs 

in the current rulemaking. The mere continuation of hydrocarbon production in 

those fields is not a valid criterion for well classification; 

• “Geologic sequestration” should not be defined only for the purpose of protecting 

USDWs, but also for the purpose of preventing re-emissions of injected carbon 

dioxide to the atmosphere according to a defined permanence standard, as NRDC 

stated in its Dec24, 2008 comments; 

• Class II as it exists today should continue to apply to operations that inject carbon 

dioxide for the sole purpose of enhanced oil recovery as opposed to GS; 

• Class II as it exists today should not be associated with the definition or the 

purpose of GS; 

• A separate injection class or subclass with appropriate site characterization, 

operation, monitoring and closure provisions should govern all injection in 

hydrocarbon reservoirs for the (sole or concurrent) purpose of GS as defined 

above (which includes earning carbon credits) and injection that exceeds 

business-as-usual Class II volume, pressure or other key thresholds that result in 

greater risk; 

• The primacy delegation criteria for this class or subclass should be subject to the 

primacy delegation requirements that apply to Class VI as proposed, and not to 

the more general showing used for Class II; and 

• In order to be able to utilize existing wells in hydrocarbon reservoirs for GS, this 

class or subclass could allow for the transition of existing Class II wells into the 

class or subclass, provided that appropriate construction and mechanical integrity 

parameters are met, and provided that those wells begin compliance with the 

added site characterization, operation, monitoring, closure and other requirements 

in the new class or subclass. 

We thank you for your ongoing work and efforts on this rulemaking. 

Sincerely, 

George Peridas, Natural Resources Defense Council
Letter ID: 0291 

Commenter: George Peridas 

Organization: Natural Resources Defense Council 

Letter ID: 0291 Comment ID: 25285 Letter Lines: 35 to 43 

Comment Code: 1200 1.1 General comments about the rulemaking 

Comment: First we stress again the importance of promulgating adequate regulations for GS 

in a timely fashion. GS has an important role to play in reducing carbon dioxide 

emissions in the U.S. and, although projects can be permitted under existing 

rules, a dedicated set of regulations is needed both to increase certainty 

further but also adequately to safeguard human health and the environment. 

Therefore, in considering whether a Notice of Data Availability (NODA) is 

needed, we urge EPA to choose the most expeditious option that is accountable, 

transparent, legally robust and defensible, and also to ensure that whichever 

option is chosen does not delay the promulgation of the rule. 

Individual Response: EPA clarifies that the GS rule does not promote or encourage the use of 

GS; rather it is designed to ensure consistency in permitting underground injection of CO2 at GS 

operations across the United States and provide requirements to prevent endangerment of 

USDWs in anticipation of the eventual use of GS to reduce CO2 emissions. EPA believes that 

the GS regulation will provide regulatory certainty and oversight that operators have requested, 

and allow for the deployment of this key climate change mitigation technology that could be 

deployed to reduce CO2 emissions. 

Please see the remainder of EPA's responses to this comment letter 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: 0291 Comment ID: 25286 Letter Lines: 45 to 55 

Comment Code: 2046 1.5.2.3 Continuing to classify CO2 injection for EOR/EGR as Class II/ 

dividing line between Class II and Class VI (seeking comment) 

Comment Code: 2146 1.6.2.2 Comments opposing injection into depleted reservoirs 

Comment: Second, we highlight that the final rule needs to cater for GS in hydrocarbon 

reservoirs as well, and not just saline formations as proposed. Hydrocarbon 

reservoirs are likely to be among the first ones to be used for GS, and they 

need to be regulated appropriately. We do not believe that automatic delegation 

to Class II "as long as any production is occurring" is suitable. Under the 

economic driver of carbon constraints, additional risks might be posed in these 

reservoirs if operators inject larger volumes or at higher rates and pressures 

than they have been doing to date under Class II. Moreover, site 

characterization, operation, monitoring and closure requirements over and above 

1
the existing Class II will be needed to certify and assure "geologic 

sequestration" of injected carbon dioxide in hydrocarbon reservoirs. 

Individual Response: EPA clarifies that the final rule is designed to address all types of 

formations in which GS could take place. All applicants for GS wells must demonstrate that the 

proposed injection zone is suitable for receiving carbon dioxide and that the confining zone can 

contain the injected carbon dioxide and any displaced formation fluids. 

EPA believes that large-scale GS presents unique technical challenges, 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. 

For this reason, EPA has finalized the tailored requirements in the GS rule. 

EPA further clarifies that the GS rule is not intended to promote a preference for GS in any 

particular formation type, to address use of resources, or to reduce costs associated with GS into 

various formations. The focus of the GS rule is to ensure that, where GS is deployed, it is 

conducted in a manner that protects USDWs from endangerment. 

EPA clarifies that owners and operators of traditional EOR projects are subject to limits on 

injection established under their Class II permits. If they exceed those limits, they will be 

considered to be in violation of their Class II permit. EPA further clarifies that wells injecting 

into oil and gas formations for the primary purpose of long-term containment of carbon dioxide 

are subject to the site characterization, operation, monitoring, and closure requirements for Class 

VI wells in Subpart H of 40 CFR 146. For more information, please see the discussion on 

transition of Class II wells in the preamble to the final GS rule. 

Letter ID: 0291 Comment ID: 25287 Letter Lines: 57 to 73 

Comment Code: 1310 1.1.2.4 Comments on other "out of scope" issues, e.g., pore space 

ownership 

Comment Code: 1400 1.2 Comments on EPA's Authority to Regulate Injection of CO2 

Comment: Third, we raise the issue of authority. The rulemaking to date has only cited 

authority under the Safe Drinking Water Act (SDWA). As we stated in our comments 

of Dec24, 2008, an appropriate regulatory regime for GS must also be grounded on 

authority to prevent re-emissions of injected carbon dioxide to the atmosphere. 

The proposed rule defines GS solely for the purposes of protecting Underground 

Sources of Drinking Water (USDWs). Climate legislation is presently being 

drafted in Congress however, and will very likely rely on EPA’s injection 

classes to certify GS. Specifically, the legislation will very likely exempt 

carbon dioxide emissions from large facilities that are geologically sequestered 

according to regulations promulgated by EPA and/or other agencies. We stress the 

importance of EPA being ready and prepared to meet such requirements. Accounting 

protocols for carbon allowances is an issue that can be dealt with outside the 

scope of the current rulemaking, and is likely to have a far narrower remit than 

the current rule’s specific requirements for site screening, monitoring, and 

2
various plans. EPA, therefore, must define and regulate GS from the outset in a 

way that assures not only that USDWs are not endangered, but that GS for the 

purposes of climate protection is also taking place. 

Individual Response: EPA clarifies that the scope of the GS regulation is limited to injection of 

CO2, and that all requirements in the GS rule are designed for the purpose of protecting USDWs 

from endangerment. Consequently, this comment is outside the scope of the rulemaking. The 

SDWA does not provide the UIC Program with the authority to develop regulations for all areas 

related to GS, such as releases to the atmosphere. 

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. 

To protect USDWs from endangerment and meet the potentially fast pace of GS deployment, 

EPA is using an adaptive approach to regulating CO2 injection for GS. The Agency plans to 

collect and review data every six years 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. An adaptive 

approach will allow regulatory development to proceed in time to meet the current and future 

demands for Class VI permits while EPA continues to gather data from pilot projects and other 

research as it becomes available. 

Letter ID: 0291 Comment ID: 25288 Letter Lines: 77 to 79 

Comment Code: 2046 1.5.2.3 Continuing to classify CO2 injection for EOR/EGR as Class II/ 

dividing line between Class II and Class VI (seeking comment) 

Comment Code: 2146 1.6.2.2 Comments opposing injection into depleted reservoirs 

Comment: • EPA must promulgate appropriate requirements for GS in hydrocarbon reservoirs 

in the current rulemaking. The mere continuation of hydrocarbon production in 

those fields is not a valid criterion for well classification; 

Individual Response: As described above, the final GS rule does not preclude injection into any 

non-USDW formation type, including hydrocarbon reservoirs, provided owners or operators can 

demonstrate that GS can be performed in a manner that protects USDWs from endangerment. 

3
EPA agrees that tailored requirements for Class VI wells are necessary to address the unique 

nature of injecting large volumes of CO2 and to ensure that USDWs are protected from 

endangerment. The GS rule contains tailored requirements for the permitting, geologic site 

characterization, AoR and corrective action, well construction, operation, mechanical integrity 

testing, monitoring, well plugging, post-injection site care, and site closure of GS wells that 

directly address issues unique to the nature of large-scale CO2 injection for GS. 

Letter ID: 0291 Comment ID: 25289 Letter Lines: 81 to 84 

Comment Code: 1220 1.1.1.1 Terminology and definitions 

Comment: • "Geologic sequestration" should not be defined only for the purpose of 

protecting USDWs, but also for the purpose of preventing re-emissions of 

injected carbon dioxide to the atmosphere according to a defined permanence 

standard, as NRDC stated in its Dec24, 2008 comments; 

Individual Response: EPA clarifies that atmospheric emissions monitoring and quantification 

are outside the scope of the Class VI GS rulemaking. The UIC program’s authority under the 

SDWA focuses on ensuring that GS projects are permitted, sited, constructed, operated, 

monitored, and closed in a manner that protects USDWs from endangerment. 

In a separate rulemaking under authority of the Clean Air Act, EPA is amending the Greenhouse 

Gas Reporting Program at 40 CFR Part 98 to add reporting requirements for CO2 injection and 

geologic sequestration. The greenhouse gas reporting requirements build on the Class VI 

requirements outlined in the final rule with the additional goals of verifying the amount of CO2 

sequestered and collecting data on any CO2 emissions to the surface from Class VI GS facilities. 

Based on its evaluation of all public comments and input on the proposed rule and the NODA 

and Request for Comment, EPA has made many revisions to the Class VI GS rule. Please see the 

final rule and preamble for additional information. 

Letter ID: 0291 Comment ID: 25290 Letter Lines: 86 to 108 

Comment Code: 2046 1.5.2.3 Continuing to classify CO2 injection for EOR/EGR as Class II/ 

dividing line between Class II and Class VI (seeking comment) 

Comment: • Class II as it exists today should continue to apply to operations that inject 

carbon dioxide for the sole purpose of enhanced oil recovery as opposed to GS; 

• Class II as it exists today should not be associated with the definition or 

the purpose of GS; 

• A separate injection class or subclass with appropriate site characterization, 

operation, monitoring and closure provisions should govern all injection in 

4
hydrocarbon reservoirs for the (sole or concurrent) purpose of GS as defined 

above (which includes earning carbon credits) and injection that exceeds 

business-as-usual Class II volume, pressure or other key thresholds that result 

in greater risk; 

• The primacy delegation criteria for this class or subclass should be subject 

to the primacy delegation requirements that apply to Class VI as proposed, and 

not to the more general showing used for Class II; and 

• In order to be able to utilize existing wells in hydrocarbon reservoirs for 

GS, this class or subclass could allow for the transition of existing Class II 

wells into the class or subclass, provided that appropriate construction and 

mechanical integrity parameters are met, and provided that those wells begin 

compliance with the added site characterization, operation, monitoring, closure 

and other requirements in the new class or subclass. 

Individual Response: EPA agrees that injection of CO2 for the primary purpose of enhancing 

oil and gas recovery should remain under the Class II Program. The Agency also believes that 

the nature and risks of CO2 injection for the primary purpose of long term storage poses different 

risks than injection for the primary purpose of EOR, and therefore has developed new Class VI 

regulations to address these unique risks. For example, the volume of CO2 anticipated to be 

injected for long term storage is significantly greater than for EOR operations. Reservoir 

pressure conditions will also be different, with Class VI injection operations involving large 

volumes of CO2 and likely having higher pressures within their storage formations than Class II 

EOR projects. 

The final Class VI regulations require that any owner or operator injecting CO2 for the primary 

purpose of long term storage obtain a Class VI permit with some special consideration for the 

fact that they are transitioning from a well not originally designed to meet Class VI requirements. 

The Director has the authority to determine at what point a Class VI permit is required for those 

projects that are transitioning from the primary purpose of EOR to long term storage of CO2. 

The final regulation provides a set of technical factors for the Director to evaluate in making this 

determination, at §144.19. EPA believes that this approach provides sufficient protection of 

USDWs when there is an increased risk to USDWs as compared to traditional Class II operations 

while allowing for site-specific flexibility. 

EPA anticipates that there will be GS/ER projects that were formerly classified as Class II that 

will seek to be permitted as Class VI injection wells. EPA is allowing the construction of these 

wells to be grandfathered per §146.81(c), provided the owner or operator can demonstrate to the 

Director that the wells were engineered and constructed to meet the requirements at §146.86(a) 

and ensure protection of USDWs, in lieu of requirements at §146.86(b) and §146.87(a). EPA 

believes that allowing for grandfathering of select construction requirements, if approved by the 

Director, will ease the transition to Class VI from an existing ER project while protecting 

USDWs from endangerment. 

EPA is developing guidance on transitioning permits from Class II to Class VI. The guidance 

5
will assist Directors in determining whether an injection project should be transitioned from 

Class II where the primary purpose is oil and gas production to Class VI where the primary 

purpose is long-term storage of large volumes of CO2. The guidance describes recommended 

methods the Director may use to evaluate changes in risk to USDWs from projects, and how the 

Director may determine whether a project should be regulated within the Class II or Class VI 

UIC program. This guidance will be available on EPA’s website at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. For more information, please 

see the discussion on transition of Class II wells in the preamble to the final GS rule. 

Letter ID: 0291 Comment ID: 25291 Letter Lines: 92 to 101 

Comment Code: 5600 2.11 Comments related to UIC Program primacy for Class VI wells 

Comment: • A separate injection class or subclass with appropriate site characterization, 

operation, monitoring and closure provisions should govern all injection in 

hydrocarbon reservoirs for the (sole or concurrent) purpose of GS as defined 

above (which includes earning carbon credits) and injection that exceeds 

business-as-usual Class II volume, pressure or other key thresholds that result 

in greater risk; 

• The primacy delegation criteria for this class or subclass should be subject 

to the primacy delegation requirements that apply to Class VI as proposed, and 

not to the more general showing used for Class II; and 

Individual Response: EPA clarifies that Class VI wells are regulated under Section 1422 of 

SDWA, and adds that states should be able to obtain primacy for Class VI wells independent of 

other well classes provided they develop regulations that are at least as stringent as the minimum 

Federal requirements (e.g., permitting, inspection, operation, monitoring, and recordkeeping 

requirements) provided in the final GS rule. 

In order for States, Tribes, or Territories to obtain Primacy for Class VI wells (under Section 

1422 of the SDWA) they must demonstrate that they have requirements that are at least as 

stringent as the federal Class VI requirements; have the authority to inspect and assess 

construction and operation of the wells as well as have the necessary legal authorities to take 

administrative, civil and criminal enforcement actions required by the SDWA under §1423, 

impose criminal, civil, and administrative penalties on owners and operators for non-compliance 

with regulatory requirements; and demonstrate sufficient/appropriate technical capacity (e.g., 

personnel, infrastructure, and technical expertise) to implement their Class VI program. 

EPA agrees that a separate well classification is appropriate for GS and that tailored 

requirements for Class VI wells are necessary to address the unique nature of injecting large 

volumes of CO2 and to ensure that USDWs are protected from endangerment. The GS rule 

contains tailored requirements for the permitting, geologic site characterization, AoR and 

corrective action, well construction, operation, mechanical integrity testing, monitoring, well 

plugging, post-injection site care, and site closure of GS wells that directly address issues unique 

6
7

to the nature of large-scale CO2 injection for GS.