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.


This document is not available in Regulations.gov since it 

contains copyrighted material that may not be reproduced 

without consent of the copyright holder. 

Contact the EPA Docket Center, Public Reading Room to view 

or receive a copy of this document. Requests for copies may be 

made as follows: 

In person/writing: 

Environmental Protection Agency, Docket Center 

1301 Constitution Ave NW, 2822T, Room 3334 

Washington, DC. 20004 

Telephone: 

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Fax: 

202-566- 9744 

Email: 

docket-customerservice@epa.gov
Letter ID: 0124 

Commenter: Jonathan Pershing 

Organization: World Resources Institute (WRI) 

Letter ID: 0124 Comment ID: 23042 Letter Lines: 51 to 59 

Comment Code: 1420 1.2.1.1 Support the GS rulemaking 

Comment: The draft EPA UIC Class VI rule is largely consistent with the content of the 

CCS Guidelines. In many ways the similarities between the EPA approach and CCS 

Guidelines are more important than the differences because they demonstrate the 

need for site specific monitoring plans and risk assessments. Both frameworks 

also include monitoring and risk assessments of both the CO2 plume and 

associated area of elevated pressure, which is essential. The draft rule 

requires periodic updates to submitted plans, which is consistent with the CCS 

Guidelines emphasis on integrated planning and operation. 

Individual Response: EPA acknowledges the comment and is aware of WRI's guidelines and 

notes that there are many similarities between WRI's guidelines and the GS regulation, including 

agreement regarding the relevant aspects of GS that warrant a tailored regulatory approach that is 

appropriate to the unique nature of GS. These documents are referenced in the final rule and are 

available in the docket for this rulemaking. For additional information, please also see the 

discussion of EPA’s Final Regulatory Approach in the preamble to the final GS rule. 

Letter ID: 0124 Comment ID: 23043 Letter Lines: 60 to 74 

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

Comment: Despite the many consistencies, there are a few important technical differences 

which are outlined in the GHGT-9 paper. These differences include the definition 

of faults that pose risk of leakage, injection pressure limits, well 

construction requirements and capacity estimates, as well as the differences in 

definition of the post-injection phases of a project. On this last item, EPA 

proposes a default 50- year monitoring time-frame, while the CCS Guidelines 

require an operator to demonstrate (via six criteria) that the site no longer 

poses a danger to human health or the environment, rather than using a default 

timeframe. This approach was taken because of the expected difference in the 

time it may take the CO2 plume to stabilize among sites. The CCS Guidelines also 

mention a more detailed framework for what happens after an operator is no 

longer responsible for a site. Specifically, the CCS Guidelines encourage 

stewardship of a site by an entity that would be responsible for any needed 

monitoring, maintenance of a site, and establishment and operation of a registry 

for information about CCS sites. 

1
2

Individual Response: EPA acknowledges that 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 final 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 PISC 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, based on substantial data during the permitting process, 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 is necessary. A 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.