### 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.

# General Comment

Over 3 trillion standard cubic f eet (TCF) or 150 million metric tons of CO2 have been injected

for enhanced oil recovery (EOR) at the SACR OC oilfield in west Texas since 1972. Roughly

half of the injected CO2 has been produced and reinjected as part of a recycling effort; an

estimated 35 million tons is permanently sequeste red in the subsurface at SACROC. Clearly this

is a large scale CO2 injection site. As with the other four CO2 injection sites referenced in

Section II of this Notice, th ere has been no documented leakage of CO2 at SACROC.

The attached document (Smyth et al., 2009, Assessi ng risk to fresh water resources from long

term CO2 injection; Energy Procedia 1, p. 1957-1964) details some results of the DOE/NETLfunded (through SWP) field study of drinking water resources over SACROC. This study, which

has been conducted by researchers of the Bur eau of Economic Geology, Jackson School of

Geosciences and The University of Texas at Au stin, satisfies the LBNL suggestion that field

studies be conducted to assess impacts to dr inking water resources from CO2 injection.

Conclusions from this study are included in several comments being submitted by BEG

researchers.

In summary, based upon 114 samples from 60 wells and one spring of Dockum aquifer water

collected in an ~250 km2 area centered on SACROC , we fail to detect any impacts to drinking

water resources as a result of anthropogenic CO2 injection. Con centrations of As, Cd, F-, NO3-

N, Se, Al, Cl-, Mn, SO42-, and TDS do exceed dri nking water standards in some wells in Scurry

County; however, most of these wells are outside of and at some distance away from SACROC.

Results of the BEG study are consistent with the statement in the S upplemental Information

Section C Introduction that the o il and gas industry has been safe ly injecting CO2 for enhanced

oil and gas recovery for decades.

## This document is not availabl e 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 Read ing Room to view

or receive a copy of this docu ment. 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:

202-566-1744

Fax:

202-566- 9744

Email:

docket-customerservice@epa.govLetter ID: 0377

Commenter: Rebecca C. Smyth

Organization: University of Texas at Austin, Bureau of Economic Geology, Jackson School of Geosciences,

Gulf Coast Carbon Center

Letter ID: 0377 Comment ID: 28180 Letter Lines: 17 to 45

Comment Code: 2400 2.4. Other Research Offered by Commenters (seeking comment)

Comment: Over 3 trillion standard cubic feet (TCF) or 150 million metric tons of CO2 have

been injected for enhanced oil recovery (EOR) at the SACROC oilfield in west

Texas since 1972. Roughly half of the injected CO2 has been produced and

reinjected as part of a recycling effort; an estimated 35 million tons is

permanently sequestered in the subsurface at SACROC. Clearly this is a large

scale CO2 injection site. As with the other four CO2 injection sites referenced

in Section II of this Notice, there has been no documented leakage of CO2 at

SACROC.

The attached document (Smyth et al., 2009, Assessing risk to fresh water

resources from long term CO2 injection; Energy Procedia 1, p. 1957

‐ 1964) details

some results of the DOE/NETL

‐ funded (through SWP) field study of drinking water

resources over SACROC. This study, which has been conducted by researchers of

the Bureau of Economic Geology, Jackson School of Geosciences and The University

of Texas at Austin, satisfies the LBNL suggestion that field studies be

conducted to assess impacts to drinking water resources from CO2 injection.

Conclusions from this study are included in several comments being submitted by

BEG researchers.

In summary, based upon 114 samples from 60 wells and one spring of Dockum

aquifer water collected in an ~250 km2 area centered on SACROC, we fail to

detect any impacts to drinking water resources as a result of anthropogenic CO2

injection. Concentrations of As, Cd, F

‐ , NO3

‐ N, Se, Al, Cl

‐ , Mn, SO42

‐ , and TDS

do exceed drinking water standards in some wells in Scurry County; however, most

of these wells are outside of and at some distance away from SACROC.

Results of the BEG study are consistent with the statement in the Supplemental

Information Section C Introduction that the oil and gas industry has been safely

injecting CO2 for enhanced oil and gas recovery for decades.Individual Response: EPA has reviewed the paper “Assessing risk to fresh water resources from long

term CO2 injection

– laboratory and field studies.” EPA acknowledges the submittal and will continue to

review studies related to the evaluation of actual field results and the limitations of sampling and

analysis, as well as the limitations of modeling. EPA adds that is has been monitoring the progress at

SACROC, among other GS projects. EPA intends to continue to collect data on GS and to incorporate

such data and information as it implements its adaptive approach to the GS rulemaking to incorporate

new research, data, and information about GS. For more information on the adaptive approach, see the

responses to comments on the proposed rule in the rulemaking docket.