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.

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docket-customerservice@epa.govLetter ID: 0124

Commenter: Jonathan Pershing

Organization: World Res ources 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 largel y consistent with th e content of the

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

Guidelines are more important than the di fferences because they demonstrate the

need for site specific monitoring plans a nd risk assessments. Both frameworks

also include monitoring and risk asse ssments 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 integr ated 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 regul atory approach that is

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

available in the docket for this rulemaking. Fo r 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 tec hnical differences

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

of faults that pose risk of leakag e, injection pressure limits, well

construction requirements and capacity estima tes, 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 e nvironment, rather th an using a default

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

time it may take the CO2 plume to stabili ze 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 esta blishment and operati on of a registry

for information about CCS sites.

12 Individual Response: EPA acknowledges that there will be circumstances where it can be

demonstrated in less than 50 years that the pl ume 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 appropria te if it ensures non- endangerment of USDWs

pursuant to requirements at §146.93(c).

EPA believes that a default post-injection site car e 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 ac commodate site-specific circumstances and various

geologic conditions, and addre sses commenters’ concerns, wh ile ensuring USDW protection.

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

impacts.

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

for post-injection site care is ne cessary. A 50 year post-injection s ite care timeframe represents a

reasonable and protective monitoring period base d on a review of research studies, industry

reports, and existing environmental program s, and evaluation of public comments.