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: 0135 

Commenter: Jill D. Jonas 

Organization: Wisconsin Dept. of Natural Resources (WDNR) 

Letter ID: 0135 Comment ID: 21666 Letter Lines: 40 to 61 

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

USDW 

Comment: Limiting CO2 Injection to Formations below the Lowermost USDW 

Protecting the quality of groundwater resources that may be used as sources of 

drinking water must continue to be the highest priority for all regulations 

promulgated under the authority of the UIC program and the federal Safe Drinking 

Water Act. WDNR supports limiting CO2 injection to geologic formations which lie 

beneath the lowermost USDW and, more specifically, only to those deep formations 

that have also been determined by means of a detailed geological assessment to 

pose the least potential for endangering drinking water supplies. 

There may be a number of other suitable geologic formations for GS that are 

situated above the lowermost USDW (e.g. basalts, salt domes, shales, coal seams, 

etc.); however, these formations tend to be more limited in their geographic 

distribution and the economic and technological viability of these formations as 

GS sites is still in question. Additional study of GS in these settings can be 

accomplished on a case-by-case basis using the UIC program's existing authority 

to approve experimental Class V injection wells. 

For the present, limiting large-scale CO2 injections to formations that lie 

beneath the lowermost USDW while continuing to investigate CO2 injection above 

the lowermost USDW using the existing rules for Class V experimental wells will 

not delay the deployment of this climate change mitigation technology. 

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 

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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. 

Regarding the suggestion to allow experimental GS wells to continue to operate under Class V, 

EPA anticipates that some owners or operators will apply for Class V experimental technology 

permits for injection into formations including shallow basalts, coal seams, salt caverns and 

shales. These formations may or may not be located above the lowermost USDW or between 

USDWs. To facilitate experimental injection for GS and to increase understanding of injection 

into these formation types, the Agency is amending the Class V experimental technology 

guidance. The guidance will be available on EPA's web site, at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. EPA acknowledges that the 

Class V experimental technology well sub-classification may be appropriate for these projects, 

provided they are experimental in nature. EPA expects that, following the final GS rule, a limited 

number of experimental injection projects testing GS technology will continue. EPA anticipates 

that these projects will be small-scale and involve limited CO2 volumes. However, if these 

projects become larger scale and are no longer experimental, they will need to be permitted as 

Class VI wells. The construction, operation or maintenance of any non-experimental Class V GS 

well is prohibited, at §144.15. 

Letter ID: 0135 Comment ID: 21667 Letter Lines: 63 to 74 

Comment Code: 2020 1.5.1 Support Class VI designation 

Comment: Class VI GS Wells 

The Department also supports creation of a sixth well class for managing GS 

injection. The physical and chemical characteristics of the carbon dioxide 

stream, long capture times required, volume to be injected, and various geologic 

settings proposed for injection suggest that an adaptive regulatory approach is 

most effective for managing GS wells. Creating a separate well classification 

will enable EPA and other permitting authorities to enact the necessary 

technical criteria for site characterization, area of review and corrective 

action, well construction and operation, compliance monitoring, and post2
injection site care with minimal impact on existing regulations for injection 

practices in the other established well classes. 

Individual Response: EPA acknowledges the comment and 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 Class VI requirements are 

appropriate because of the unique nature and risks of CO2 injection for long-term storage (e.g., 

large injection volumes, long project duration, and reservoir pressure conditions). 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: 0135 Comment ID: 21668 Letter Lines: 76 to 92 

Comment Code: 5610 2.11.1 Allowing partial primacy for Class VI wells (seeking comment) 

Comment: Primacy for Class VI Injection Wells 

As the state agency which currently regulates all injection well classes in the 

State of Wisconsin, WDNR urges EPA to allow primacy approval for Class VI wells 

independent of the other well classes. First, such an approach provides state 

permitting authorities the flexibility to implement a more comprehensive 

approach to managing the capture, transportation, and sequestration of CO2. 

Second, some states already have one agency responsible for a Class H program 

and have another agency managing the other four existing injection well classes. 

Independent approval enables each state to determine if it is more suitable and 

cost effective to have one of those agencies or an alternative state agency 

administer the CO2 GS program separately from the UIC programs established for 

other injection well classes. Third, independent approval of Class VI injection 

well program primacy more clearly defines the criteria and primacy application 

process for those states that seek primary enforcement authority for GS and 

makes the administrative review and approval of state primacy applications for 

GS more manageable for EPA. 

Individual Response: EPA agrees with commenters that states should be allowed to obtain 

primacy for Class VI wells independently of other well classes, and will allow independent 

primacy for Class VI wells under §145.1(i) of the final GS rule. Given the potential for CCS 

(encompassing capture, transportation, and geologic sequestration) to be an important part of a 

national priority to address climate change, EPA believes that providing states the flexibility to 

obtain primacy for Class VI wells independently of other well classes can help foster effective 

management of CCS. EPA believes that allowing independent Class VI primacy may encourage 

states to take responsibility for implementation of Class VI regulations and provide for a more 

comprehensive approach to managing CCS projects by promoting the integration of GS activities 

under SDWA into a broader framework for managing CCS. Furthermore, GS operations involve 

ancillary activities (e.g., pipeline operations, pore space ownership, land use rights, and surface 

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access) for which states can call upon other authorities that exist at the state level (but outside 

UIC authority) to provide a more comprehensive CCS management approach. 

EPA also believes that allowing states to apply only for Class VI primacy will shorten the 

primacy approval process for states. EPA's willingness to accept independent primacy 

applications for Class VI wells represents a shift in its longstanding policy of discouraging 

"partial primacy." It is very important to note that this shift in policy allowing for Class VI 

primacy does not apply to any other well Class under Section 1422. EPA will continue to 

discourage applications for partial primacy for all other well types under Section 1422. 

EPA clarifies 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) in the final GS rule. EPA believes that existing programs can adapt their expertise 

to the new requirements for Class VI wells and will be able to develop a primacy application for 

Class VI wells under section 1422 of SDWA and ensure that their GS programs integrate into 

national climate change priorities and protect USDWs from endangerment. 

EPA also clarifies that primacy is granted to a state, not to any agency within that state, and 

states are free to choose which agency will implement the Class VI program—for instance, an 

environmental quality protection agency (non-Class II) or the state's traditional oil and gas 

regulatory agency (Class II)—as long as the program meets the minimum federal requirements 

for Class VI wells as required under section 1422 of SDWA. Some states administer their 

program for all injection well classes through a single agency, whereas other States elect to 

divide the program between agencies. For example, in most States, the Class II program is run by 

an oil and gas agency and other well classes are run by a State environmental agency (e.g., the 

Oklahoma Corporation Commission oversees Class II wells in the State, and the Oklahoma 

Department of Environmental Quality oversees other well classes). Additionally, several States 

allow their oil and gas agencies to administer their UIC program for specific well classes or 

subclasses provided they meet all Federal requirements (e.g., the Texas Railroad Commission 

oversees Class III brine-mining wells and Class V geothermal wells in Texas). EPA believes that 

retaining this flexibility for States to identify the appropriate agency to oversee Class VI wells 

will address commenters’ concerns that States should be afforded the opportunity to determine 

which agency should oversee Class VI wells, and recognizes the existing expertise of both State 

oil and gas agencies and environmental agencies. 

Letter ID: 0135 Comment ID: 21669 Letter Lines: 94 to 106 

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

Comment: Tailored Regulatory Requirements 

WDNR supports EPA's selection of a flexible regulatory approach which recognizes 

that full-scale projects involving long-term storage of CO2 are unique due to 

the volume of CO2 that is to be injected, the buoyancy and viscosity of the 

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proposed injectate, the corrosive nature of CO2 when mixed with water, and the 

many geologic formations that can potentially be used for CO2 storage. By 

building on the existing regulatory framework for other deep injection wells and 

providing flexibility and/or discretion to the permitting authority to address 

site specific variability, the requirements being proposed by the Agency 

appropriately balance the need to provide protection to the nation's underground 

sources of drinking water with the need to provide a degree of regulatory 

certainty and consistency to owners and operators of GS facilities, 

Individual Response: EPA acknowledges the comment, and agrees that permitting decisions for 

GS wells should be based on site-specific factors. The GS rule requires owners or operators to 

submit, and Directors to consider, extensive site-specific data, specified at §146.82, to 

demonstrate that a site is suitable for GS. Additionally, many of the permit requirements for GS 

wells are established through individualized site-specific plans for AoR and corrective action, 

testing and monitoring, and injection well plugging and post-injection site care and site closure. 

EPA adds that 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.