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

I am commenting on Document ID EPA-HQ-OW-2008-0390-0297

III. Research, Data Analysis, and Findings

C. Lawrence Berkeley National Laboratory (LBNL) Studies

1. Ground Water Quality Changes Related to the Mobilization of Trace Elements

Gulf Coast Carbon Center at Bureau of Econo mic Geology, University of Texas at Austin,

conducted a laboratory-batch expe riment to investigate the ra nge of CO2-leakage impact on

groundwater quality of seven representative aquife rs in the Gulf Coast re gion, USA, starting with

representative sandstone aquifer rock samples.

Experiment results suggest that carbonate minerals are the domina nt contributor of changes in

groundwater quality as a result of addition of CO2. Dissolution of dolomite and calcite, when

they exist, caused the largest increase in con centrations of Ca, Mg, M n, Ba and Sr. The latter

three cations exist as trace elemen ts in the carbonate minerals.

Following CO2 input in the experiment, cations show different concentration trends, according

to which, cations can be grouped in to two categories. Type I cati ons?Ca, Mg, Si, K, Sr, Mn, Ba,

Co, B, Zn?rapidly increased following initial CO2 flux and reached stable concentrations before

the end of the experiment. T ype II cations?Fe, Al, Mo, U, V, As, Cr, Cs, Rb, Ni and

Cu?increased at the start of CO2 flux, but declined, in most cases , to levels lower than pre-CO2

concentrations.

Potential risks to drinking water quality are mostly related to Type I heavy metals such as Mn,

Ba, Sr, Co, and Zn, which are associated with ca rbonate minerals. Type II cations, which appear

to be related to desorption/adsorption, show limited impact on ground water quality. Anions

showed no significant increases after introduction of CO2. Although rocks from high arsenic

aquifers were included in the study, no risks rela ted to increased sulfur, lead, or arsenic were

observed in the study.

The paper attached is in press w ith Environmental Earth Science.

## 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: 0387

Commenter: Jiemin Lu

Organization: University of Texas at Austin, Bureau of Economic Geology (BEG), Gulf Coast

Carbon Center (GCCC)

Letter ID: 0387 Comment ID: 28185 Letter Lines: 17 to 52

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

Comment: I am commenting on Document ID EPA

‐ HQ

‐ OW

‐ 2008

‐ 0390

‐ 0297

III. Research, Data Analysis, and Findings

C. Lawrence Berkeley National Laboratory (LBNL) Studies

1. Grou nd Water Quality Changes Related to the Mobilization of Trace Elements

Gulf Coast Carbon Center at Bureau of Economic Geology, University of Texas at

Austin, conducted a laboratory

‐ batch experiment to investigate the range of CO2

‐

leakage impact on groundwater quality of seven representative aquifers in the

Gulf Coast region, USA, starting with represent ative sandstone aquifer rock

samples.

Experiment results suggest that carbonate minerals are the dominant contributor

of changes in groundwater quality as a result of addition of CO2. Dissolution of

dolomite and calcite, when they exist, caused the largest increase in

concentrations of Ca, Mg, Mn, Ba and Sr. The latter three cat ions exist as trace

elements in the carbonate minerals.

Following CO2 input in the experiment, cations show different concentration

trends, according to which, cations can be grouped into two categories. Type I

cations?Ca, Mg, Si, K, Sr, Mn, Ba, Co, B, Zn?rapidly increased following initial

CO2 flux and reach ed stable concentrations before the end of the experiment.

Type II cations?Fe, Al, Mo, U, V, As, Cr, Cs, Rb, Ni and Cu?increased at the

start of CO2 flux, but declined, in most cases, to levels lower than pre

‐ CO2

concentrations.

Potential risks to drinking water quality are mostly relat ed to Type I heavy

metals such as Mn, Ba, Sr, Co, and Zn, which are associated with carbonateminerals. Type II cations, which appear to be related to desorption/adsorption,

show limited impact on ground water quality. Anions showed no significant

increases after introduction of CO2. Although rocks from high arsenic aquifers

were included in the study, no risks related to increased sulfur, lead, or

arsenic were observed in the study.

Individual Response: EP A has reviewed the summary of research by the Bureau of Economic

Geology on CO2

‐ leakage impact on ground water quality of Gulf Coast aquifers. EPA

acknowledges the submittal and will continue to review studies and field results and the

limitations of sampling and analysis, as well as the limitations of modeling. 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.