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.
1

                                                           

JJ Dooley, Senior Staff Scientist

Joint Global Change Research Institute, Pacific Northwest National Laboratory

October 8, 2009

PNNL Technical Report: PNNL‐18862

Comments on USEPA NODA for Proposed Class VI UIC Wells for Geologic CO2 Storage as Published in

the Federal Register / Vol. 74, No. 167 / Monday, August 31, 2009, pp. 44802‐448131

It is appropriate and commendable to continue to make efforts to factor the best science into the

proposed Class VI rule. The USEPA should be commended for their continued efforts – as evidenced by

this NODA – to make sure that the proposed Class VI CO2 Injection Well regulation is based on the most

up‐to‐date and comprehensive science with respect to geologic storage of anthropogenic CO2 in the

deep subsurface.

Completion of the proposed Class VI well rule should not be tied to the resolution of future US climate

policy. The USEPA should also be commended for moving forward with the standalone proposed Class

VI UIC rule even though there is a strong desire (and indeed a need) from many stakeholders to

understand how this proposed Class VI rule would fit into a larger national climate change mitigation

policy.  While it is undoubtedly true that in a perfect world, it would be best if the nation’s future

climate policy was fully articulated before the final Class VI rule were promulgated, we do not live in

such a perfect world.  And just as it is clear that the Class VI rule will need to be changed and revised

over time as we learn more about commercial scale geologic CO2 storage, it is also clear that the same

kind of “adaptive regulatory approach” will be needed for the larger national climate policy as we learn

more about the potential of various mitigation options as well as the extent and pace of negative

climatic impacts.  Therefore, it is wise to proceed with this rule as discussed in “Section II. What Did EPA

Propose?” of the NODA (p. 44805).

1 40 CFR Part 146 [EPA–HQ–OW–2008–0390; FRL–8951–3] RIN 2040–AE98 Federal Requirements Under the

Underground Injection Control (UIC) Program for Carbon Dioxide (CO2) Geologic Sequestration (GS) Wells; Notice

of Data Availability and Request for Comment.
2

                                                           

Affording all states the opportunity to deploy CCS should not be the motivation for allowing or

disallowing CO2 injection above a USDW in the final rule. In “Section II. What Did EPA Propose?” as well

as in other parts of the NODA, the USEPA notes that “a few States” were concerned that an outright ban

on injecting anthropogenic CO2 above a USDW may constrain the deployment of carbon dioxide capture

and storage (CCS) technologies within those states.  While the USEPA might well have a statutory

responsibility to examine impacts of the proposed rule on a state‐by‐state basis, the ability to deploy

CCS in every state is not a precondition for CCS being an important aspect of the nation’s portfolio of

options to address climate change.  It is already clear from our published research2 as well as research

from other groups3 that CCS is unlikely to deploy in some states for a variety of reasons, including a

fundamental lack of suitable deep storage formations or the presence of more cost effective emissions

abatement options.  In those cases, it is well accepted that the impacted states would be able to draw

upon other aspects of the nation’s greenhouse gas emissions mitigation portfolio to reduce their

emissions (e.g., renewable energy, nuclear power).  While the proposed rule never explicitly frames the

question of whether to allow CO2 to be stored above a USDW in terms of ensuring that all states have

the same set of greenhouse gas emissions mitigation options (which would be impossible given the

heterogeneous distribution of deep geologic CO2 storage resources), it appears that some of the

commenters on the July 2008 rule framed their comments and concerns in that manner.  The USEPA’s

focus should be on fulfilling its existing responsibilities under the SDWA as well as any future

responsibilities related to reducing greenhouse gas emissions in the most effective and efficient manner

possible for the nation.

The Discussion of the Modeling Conducted by LBNL Lacks Critical Context Needed for these Results to

Be Directly Relevant to the Proposed Class VI CO2 Storage Rule. “Section III. Research, Data Analysis,

and Findings. C. Lawrence Berkeley National Laboratory (LBNL) Studies” of the NODA is devoted to

summarizing key findings of state‐of‐the‐art research underway at LBNL (pp. 44807‐44804).  While much

of the substance of the research described here is important and germane to the NODA, the way in

which key aspects of this research is presented is problematic and does not further the USEPA’s goal of

communicating to potential CCS stakeholders that the USEPA is committed to crafting a proposed Class

VI rule that will allow it to fulfill its responsibilities under SDWA and other statues and that is built upon

a solid foundation of the best available scientific and engineering research.

2 For example, it is clear that the adoption of CCS technologies across the U.S. will be quite heterogeneous because

of differing endowments of geologic storage reservoirs as well as the relative cost effectiveness of other ways of

reducing greenhouse gases will vary across the nation.  See for example, Wise MA, JJ Dooley, RT Dahowski, and CL

Davidson (2007).  “Modeling the impacts of climate policy on the deployment of carbon dioxide capture and

geologic storage across electric power regions in the United States."  International Journal of Greenhouse Gas

Control. Volume 1, Issue 2, April 2007, Pages 261‐270. doi:10.1016/S1750‐5836(07)00017‐5

3 For example, the NATCARB.org database lists the geologic storage potential for a number of states as being

essentially zero.
3

                                                           

Climate change will affect USDWs even if CCS is not available as an emissions reduction technology.

While it is obviously a requirement that the USEPA examine potential impacts associated with CCS on

USDWs, the reader is left with the strong impression that CCS represents the only (or the principal)

danger to USDWs associated with climate change mitigation.  This is not the case.  The IPCC’s 2008

Climate Change and Water4 notes that the large scale deployment of geothermal energy, biomass

energy, and the continued increased reliance on unconventional oil resources all represent potential

pathways for contaminating underground (as well as surface) sources of potable water.  This same IPCC

report also notes that there is evidence that doing nothing to address climate change can also lead to a

degradation of ground water through slower recharge rates and increased salinity.  In presenting the

potential dangers associated with large scale CCS deployment, the USEPA must do a better job of

contextualizing these findings and must not leave the reader with the impression that not using CCS will

result in no harm to USDWs.

Potential damage to USDWs from scenarios that are not consistent with the draft Class VI CO2 storage

rule must be clearly identified as extreme cases. The scenario described in “Prediction of the Fate and

Transport of Trace Elements” should have been presented as an extreme example of what can happen if

virtually every aspect of the proposed Class VI rule is willfully ignored and/or not enforced.  While this

scenario might be useful in illustrating basin‐scale behavior of geochemical and geomechanical reactions

in aquifers, it is not helpful in terms of presenting how the USEPA intends to regulate the safe, effective

deployment of CCS.  The scenario posits that there is leakage of CO2 for 100 years via a preferential

pathway and under those circumstances “the MCL for arsenic was exceeded in only a few simulation

scenarios.”  The July 2008 proposed Class VI rule would require that actions be taken prior to injection

(e.g., identification and remediation of any artificial penetration  capable of transmitting CO2 out of the

storage formation), during injection (e.g., high resolution monitoring to identify anomalous geophysical

and injection findings that can serve as early warnings for leakage, groundwater, vadose zone and/or

atmospheric monitoring), and after injection (via similar techniques) to identify leakage in time to allow

mitigation efforts well in advance of any adverse impact such as the mobilization of arsenic into a

USDW. Moreover, this kind of leakage rate parameterization defies our current understanding of the

science and engineering of geologic CO2 storage.5

  Given the flawed assumptions behind this analysis,

the conclusion that “the MCL for arsenic was exceeded” seems quite a bit less robust.

Also, while the LBNL scenario described in “Sedimentary Basin Case Study” represents state of the art

modeling of large scale deployment of CCS in a basin, it is not at all clear how relevant this work is to the

proposed Class VI rule as the scenario envisioned seems to be precluded by the requirements to receive

and retain a Class VI injection permit spelled out in the July 2008 draft rule.

4 Intergovernmental Panel on Climate Change. Technical Paper on Climate Change and Water.  Bates, B.C., Z.W.

Kundzewicz, S. Wu and J.P. Palutikof, Eds.  IPCC Secretariat, Geneva, 210 pp. June 2008.  

5 See for example. Dooley JJ, C Trabucchi, and L Patton.  2009.  "Design Considerations for Financing a National

Trust to Advance the Deployment of Geologic CO2 Storage and Motivate Best Practices." In press, the International

Journal of Greenhouse Gas Control: GHGT9 Special Issue. October 2009.
The “Sedimentary Basin Case Study” scenario states that 20 facilities each of which inject 5MtCO2 per

year are located within this hypothetical basin (See figure below).  Assuming that all 20 sources are

power plants, they would each be the equivalent of a 1000 MW IGCC+CCS.  It is difficult to imagine a

scenario in which 20 GW of electrical generating capacity would come on line simultaneously6 in just

one relatively small region of the United States.7

“Figure 8 Boundary of the developed basin‐scale model (solid red line), and the thickness of the Mt Simon Sandstone (in m)

with deep boreholes (black squares) for characterizing the Mt Simon geology, as well as regional faults (black lines). Also shown

are the core‐injection area (blue line) that hosts 20 hypothetical injection sites (pink stars), the MGSC Phase III ADM site in

Decatur, Illinois (red square), and the Illinois Basin boundary (in gray).”  Taken from BIRKHOLZER, J.T., Q. ZHOU, K. ZHANG, P.

JORDAN, J. RUTQVIST, C.‐F. TSANG (2008): Research Project on CO2 Geological Storage and Groundwater Resources: Large‐

scale Hydrogeological Evaluation and Impact on Groundwater Systems, Annual Report October 1, 2007 to September 30, 2008,

Report, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.

                                                           

6 See for example, MA Wise and JJ Dooley. 2009. “The Value of Post‐Combustion Carbon Dioxide Capture and

Storage Technologies in a World with Uncertain Greenhouse Gas Emissions Constraints.” International Journal of

Greenhouse Gas Control. Volume 3, Issue 1. (2009), pp. 39‐48 DOI: 10.1016/j.ijggc.2008.06.012 which forecasts CCS

deployment at this scale but spread out across the entire ECAR region and spread out across nearly half of a

century.

7 It is important to stress how unrealistic this scenario is for the purpose of informing the draft Class VI proposal.  A

back of the envelope calculation involving line of sight limitations imposed by the curvature of the Earth suggests

that if the cooling towers at these 20 facilities were 100m tall or higher one could literally see some of the other

plants.  Therefore, it is extremely difficult to envision how these 20 units could all come on line simultaneously

without anyone recognizing how closely spaced they are and taking action (most likely via alterations to some of

the pending Class VI injection permits) to avoid the scenario modeled by LBNL from ever materializing.

4
5

More importantly, if the assumption is that these 20 facilities do not come on line simultaneously but

rather phase in over time, then the July 2008 draft Class VI CO2 Storage rule would seem to prevent this

situation from occurring as the rule requires that new injection well applicants take into account

projects that have already been permitted when preparing their permit application.  It is difficult to see

how a situation could be allowed to develop where 20 very large facilities could be permitted so near

each other to start at the same time, without raising flags to regulators to request additional

information from the applicants on CO2 plume movement and pressure build up, and request

subsequent potential re‐evaluation of initial project AORs, pressure effects and potential impacts to

drinking water.  While the value of understanding near‐ and far‐field pressure effects for projects

located so close together is undisputed, the potential for so many projects being inadvertently

permitted in the same area alone is so far‐fetched that the scenario clearly can’t be put forth as a real

possibility, and perhaps EPA could do a better job in communicating that this scenario is not intended to

represent future reality. As an academic exercise to educate the technical community and inform

requirements within the proposed rule to ensure that cumulative effects across multiple projects within

the same geographic area, however, this work is important.  

More importantly however, if the EPA promulgates the rules as drafted and has the resources to enforce

the rules, these basin scale concerns will be managed proactively, and pressures can be maintained

within acceptable ranges.    This is the point that should have been clearly communicated via the

presentation of this modeling work.

On the Appropriateness of Allowing CO2 Storage above a USDW and the related issue of who will

regulate production wells that could intersect stored CO2? The overriding principle should be does the

proposed Class VI rule help protect the wellbeing of humans and the health of the environment.  

Framing the issue in this way makes it clear that there is an explicit tradeoff being made about the use

of USDWs for CO2 storage or the use of water bearing bodies that have more than 10,000 TDS but are

shallower than another formation which has waters with less than 10,000 TDS.  This calls for a flexible

and site‐ or region‐specific approach that still includes mandatory criteria such as the presence of

adequate caprocks above and below the proposed storage formation to ensure the protection of both

shallower and deeper USDWs.

The USEPA should also explain in detail what authority it has (or needs to be given) to ensure that any

future wells (oil, gas, water, injection) that drill through a formation which is being used for CO2 storage

are built to withstand the higher pressures and acidity of these formations without becoming pathways

for the migration of previously stored CO2 out of the target storage formation.  If the USEPA has no way

of regulating the construction of production wells that penetrate a CO2 storage formation and if it

believes that it will not be granted this authority, then this needs to bear on decisions to allow storage in

formations that are shallower than formations that might in the future be host to future water, oil or gas
6

production wells that could penetrate the storage formation.  The NODA asserts without elaboration

“The management scheme will also ensure that there is a strategy developed to address future needs to

access formations below the injection zone.” (p. 44810)  Without further elaborating how this would be

done in practice, it would appear that the July 2008 proposed rule and the August 2009 NODA have yet

to meaningfully address a key aspect of how injection above a USDW could be implemented safely.  It is

hoped that before this rule is finalized some clarity and specificity will be brought to this critical issue.

Additional financial responsibility measures for projects involving waivers do not appear to be

consistent or well articulated.  The NODA states on page 44811 that “The owner/operator would also

demonstrate sufficient, additional financial responsibility to address any potential contamination of

USDWs above or below the injection zone.”  This is immediately proceeded by a passage that speaks to

the need to prepare a plan that considers “regional water resources issues and has explored alternative

water supplies or water treatment options.”  Later on this same page, the prospective CO2 storage

operator is asked for a plan “for securing alternative resources or treating USDW formation waters in

the event of contamination related to the Class VI injection activity.”  These seem to be describing wildly

different levels of responsibility and financial commitment.  The requirement to demonstrate existing

financial resources needed to provide clean water to all possible current and future users within an

undefined region seems like an activity that could cost millions, hundreds of millions, billions of dollars.  

On the other hand, a plan for how one might secure alternative sources of water if the need should ever

arise seems like something that could be satisfied via a $10,000 paper study.  The large gap between

these two endpoints will likely lead to confusion among CCS stakeholders.  The USEPA is encouraged to

better define what would be expected of applicants for wells that would need waivers so that CCS

stakeholders can more thoughtfully respond to the proposal.
Letter ID: 0334  

Commenter: James J. Dooley  

Organization: Joint Global Change Research Institute, Pacific Northwest National Laboratory  

Letter ID: 0334 Comment ID: 28203 Letter Lines: 32 to 37  

Comment Code: 1000 1. General Comments on the Notice of Data Availability  

Comment: It is appropriate and commendable to continue to make efforts to factor the best  

science into the proposed Class VI rule. The USEPA should be commended for their  

continued efforts ‐ as evidenced by this NODA ‐ to make sure that the proposed  

Class VI CO2 Injection Well regulation is based on the most up‐to‐date and  

comprehensive science with respect to geologic storage of anthropogenic CO2 in  

the deep subsurface.  

Individual Response: EPA believes that the final rule is based on the most recent GS‐related data,

information, and scientific research available. 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.  

Letter ID: 0334 Comment ID: 28204 Letter Lines: 39 to 53  

Comment Code: 1100 1.1 Comments on the Comprehensive Approach  

Comment Code: 5000 5. Comments on the Proposed Rule (out of NODA Scope)  

Comment: Completion of the proposed Class VI well rule should not be tied to the  

resolution of future US climate policy. The USEPA should also be commended for  

moving forward with the standalone proposed Class VI UIC rule even though there  

is a strong desire (and indeed a need) from many stakeholders to understand how  

this proposed Class VI rule would fit into a larger national climate change  

mitigation policy. While it is undoubtedly true that in a perfect world, it  

would be best if the nation’s future climate policy was fully articulated before  

the final Class VI rule were promulgated, we do not live in such a perfect  

world. And just as it is clear that the Class VI rule will need to be changed  

and revised over time as we learn more about commercial scale geologic CO2  

storage, it is also clear that the same kind of "adaptive regulatory approach"  

will be needed for the larger national climate policy as we learn more about the  
potential of various mitigation options as well as the extent and pace of  

negative climatic impacts. Therefore, it is wise to proceed with this rule as  

discussed in "Section II. What Did EPA Propose?" of the NODA (p. 44805).  

Individual Response: The Agency is using an adaptive approach to ensure USDW protection and meet

the potentially fast pace of GS deployment. EPA believes that an adaptive approach will allow regulatory

development to proceed in time to meet the current and future demand for Class VI permits while

recognizing the need to continue to gather data from pilot projects and other research as it becomes

available; as well as to enhance understanding of the technical and administrative aspects of GS

deployment, operation, and technology developments. The Agency plans to collect and review data

every six years on GS projects to determine whether the appropriate amount and types of information

and appropriate documentation are being collected, and to determine if modifications to the

requirements are appropriate or necessary.

The issue of climate policy is outside the scope of the Notice of Data Availability and the UIC Program’s

authority under the GS rulemaking. For more information on the GS requirements and the UIC program,

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

Letter ID: 0334 Comment ID: 28205 Letter Lines: 55 to 93  

Comment Code: 3110 3.1.1. National Storage Capacity  

Comment: Affording all states the opportunity to deploy CCS should not be the motivation  

for allowing or disallowing CO2 injection above a USDW in the final rule. In  

"Section II. What Did EPA Propose?" as well as in other parts of the NODA, the  

USEPA notes that "a few States" were concerned that an outright ban on injecting  

anthropogenic CO2 above a USDW may constrain the deployment of carbon dioxide  

capture and storage (CCS) technologies within those states. While the USEPA  

might well have a statutory responsibility to examine impacts of the proposed  

rule on a state‐by‐state basis, the ability to deploy CCS in every state is not  

a precondition for CCS being an important aspect of the nation’s portfolio of  

options to address climate change. It is already clear from our published  

research {FOOTNOTE 2} as well as research from other groups {FOOTNOTE 3} that  

CCS is unlikely to deploy in some states for a variety of reasons, including a  

fundamental lack of suitable deep storage formations or the presence of more  

cost effective emissions abatement options. In those cases, it is well accepted  

that the impacted states would be able to draw upon other aspects of the  

nation’s greenhouse gas emissions mitigation portfolio to reduce their emissions  

(e.g., renewable energy, nuclear power). While the proposed rule never  

explicitly frames the question of whether to allow CO2 to be stored above a USDW  
in terms of ensuring that all states have the same set of greenhouse gas  

missions mitigation options (which would be impossible given the heterogeneous  

distribution of deep geologic CO2 storage resources), it appears that some of  

the commenters on the July 2008 rule framed their comments and concerns in that  

manner. The USEPA’s focus should be on fulfilling its existing responsibilities  

under the SDWA as well as any future responsibilities related to reducing  

greenhouse gas emissions in the most effective and efficient manner possible for  

the nation.  

{FOOTNOTE 2} For example, it is clear that the adoption of CCS technologies  

across the U.S. will be quite heterogeneous because of differing endowments of  

geologic storage reservoirs as well as the relative cost effectiveness of other  

ways of reducing greenhouse gases will vary across the nation. See for example,  

Wise MA, JJ Dooley, RT Dahowski, and CL Davidson (2007). "Modeling the impacts  

of climate policy on the deployment of carbon dioxide capture and geologic  

storage across electric power regions in the United States." International  

Journal of Greenhouse Gas Control. Volume 1, Issue 2, April 2007, Pages 261‐270.  

doi:10.1016/S1750‐5836(07)00017‐5  

{FOOTNOTE 3} For example, the NATCARB.org database lists the geologic storage  

potential for a number of states as being essentially zero.  

Individual Response: EPA agrees that protection of USDWs is the most important element of

determining suitability of a site for GS. However, EPA believes that there are situations where injection

into non‐USDW formations 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 and operators can seek a waiver of the Class VI injection depth requirements.

The purpose of the injection depth waiver requirements is to ensure protection of USDWs while

allowing the use of GS capacity above and between USDWs if a site is suitable and all Class VI

requirements are met.  

Because USDW protection is the priority of the GS rule, owners or operators seeking waivers must

provide a supplemental report (the GS Class VI injection depth waiver application report) referenced at

§146.82(d) and outlined at §146.95(a) with additional, site‐specific information including: additional

information about the injection zone; identification of confining units above and below the injection

zone; tailored AoR modeling above and below the injection zone; a demonstration that well design is

appropriate and protective of USDWs, in lieu of specific requirements at §146.86; a description of how

monitoring will be tailored for injection above/between USDWs; and information about public water

supplies in the AoR.  
Letter ID: 0334 Comment ID: 28206 Letter Lines: 95 to 106  

Comment Code: 2200 2.2. LBNL Studies  

Comment: The Discussion of the Modeling  

Conducted by LBNL Lacks Critical Context Needed for these Results to Be Directly  

Relevant to the Proposed Class VI CO2 Storage Rule. "Section III. Research, Data  

Analysis, and Findings. C. Lawrence Berkeley National Laboratory (LBNL) Studies"  

of the NODA is devoted to summarizing key findings of state‐of‐the‐art research  

underway at LBNL (pp. 44807‐44804). While much of the substance of the research  

described here is important and germane to the NODA, the way in which key  

aspects of this research is presented is problematic and does not further the  

USEPA’s goal of communicating to potential CCS stakeholders that the USEPA is  

committed to crafting a proposed Class VI rule that will allow it to fulfill its  

responsibilities under SDWA and other statues and that is built upon a solid  

foundation of the best available scientific and engineering research.  

Individual Response: EPA believes it accurately explained the results of the LBNL studies and notes that

the studies themselves were available to stakeholders through the docket for the GS rule and NODA.

EPA believes that the studies presented, along with all other research presented as background for the

GS rulemaking, support its position that the GS rule is based on a solid UIC regulatory framework, with

requirements that are tailored to the unique aspects of GS of CO2. The Agency plans to use an adaptive

approach to ensure that USDWs are protected from endangerment while making it possible to meet the

potentially fast pace of GS deployment. EPA believes that an adaptive approach will allow regulatory

development to proceed in time to meet the current and future demand for Class VI permits while

recognizing the need to: continue to gather data from pilot projects and other research as it becomes

available; and to enhance understanding of the technical and administrative aspects of GS deployment,

operation, and technology developments. EPA plans, every six years, to collect and review data on GS

projects to determine whether the appropriate amount and types of information and appropriate

documentation are being collected, and to determine if modifications to the requirements are

appropriate or necessary.  

Letter ID: 0334 Comment ID: 28207 Letter Lines: 108 to 126  

Comment Code: 6000 6. Other Comments that are Out of Scope for the NODA  

Comment: Climate change will affect USDWs even if CCS is not available as an emissions  

reduction technology. While it is obviously a requirement that the USEPA examine  

potential impacts associated with CCS on USDWs, the reader is left with the  

strong impression that CCS represents the only (or the principal) danger to  
USDWs associated with climate change mitigation. This is not the case. The  

IPCC’s 2008 Climate Change and Water {FOOTNOTE 4} notes that the large scale  

deployment of geothermal energy, biomass energy, and the continued increased  

reliance on unconventional oil resources all represent potential pathways for  

contaminating underground (as well as surface) sources of potable water. This  

same IPCC report also notes that there is evidence that doing nothing to address  

climate change can also lead to a degradation of ground water through slower  

recharge rates and increased salinity. In presenting the potential dangers  

associated with large scale CCS deployment, the USEPA must do a better job of  

contextualizing these findings and must not leave the reader with the impression  

that not using CCS will result in no harm to USDWs.  

{FOOTNOTE 4} Intergovernmental Panel on Climate Change. Technical Paper on  

Climate Change and Water. Bates, B.C., Z.W. Kundzewicz, S. Wu and J.P.  

Palutikof, Eds. IPCC Secretariat, Geneva, 210 pp. June 2008.  

Individual Response: This comment is outside the scope of the Notice of Data Availability and the UIC

Program’s authority under the GS rulemaking.  

Letter ID: 0334 Comment ID: 28208 Letter Lines: 128 to 156  

Comment Code: 2210 2.2.1. Groundwater Quality and Mobilization of Trace Elements (seeking

comment)  

Comment: Potential damage to USDWs from scenarios that are not consistent with the draft  

Class VI CO2 storage rule must be clearly identified as extreme cases. The  

scenario described in "Prediction of the Fate and Transport of Trace Elements"  

should have been presented as an extreme example of what can happen if virtually  

every aspect of the proposed Class VI rule is willfully ignored and/or not  

enforced. While this scenario might be useful in illustrating basin‐scale  

behavior of geochemical and geomechanical reactions in aquifers, it is not  

helpful in terms of presenting how the USEPA intends to regulate the safe,  

effective deployment of CCS. The scenario posits that there is leakage of CO2  

for 100 years via a preferential pathway and under those circumstances "the MCL  

for arsenic was exceeded in only a few simulation scenarios." The July 2008  

proposed Class VI rule would require that actions be taken prior to injection  

(e.g., identification and remediation of any artificial penetration capable of  

transmitting CO2 out of the storage formation), during injection (e.g., high  

resolution monitoring to identify anomalous geophysical and injection findings  

that can serve as early warnings for leakage, groundwater, vadose zone and/or  
atmospheric monitoring), and after injection (via similar techniques) to  

identify leakage in time to allow mitigation efforts well in advance of any  

adverse impact such as the mobilization of arsenic into a USDW. Moreover, this  

kind of leakage rate parameterization defies our current understanding of the  

science and engineering of geologic CO2 storage {FOOTNOTE 5}. Given the flawed  

assumptions behind this analysis, the conclusion that "the MCL for arsenic was  

exceeded" seems quite a bit less robust.  

{FOOTNOTE 5} See for example. Dooley JJ, C Trabucchi, and L Patton. 2009.  

"Design Considerations for Financing a National Trust to Advance the Deployment  

of Geologic CO2 Storage and Motivate Best Practices." In press, the  

International Journal of Greenhouse Gas Control: GHGT9 Special Issue. October  

2009.  

Individual Response: EPA clarifies that the LBNL study was conducted to study the potential

vulnerability of representative and relevant aquifer types in the case of CO2 intrusion, in order to

provide sound scientific information as a basis for further studies on groundwater quality concerns. EPA

understands (and mentioned in the NODA) that the risk of CO2 leaking from deep storage is low for

properly managed GS projects, but the leakage probability is not necessarily zero (i.e., pre‐injection site

characterization may fail to detect leakage pathway or monitoring during and after injection may miss

small‐scale signals of local leaks). Therefore, the potential consequences of unlikely leakage events need

to be understood and predictive capabilities need to be developed as a basis for risk and vulnerability

assessment (just like other scientific studies are being conducted evaluating the potential risks of CO2

leakage into the atmosphere).  

EPA agrees that the risk of leakage is highest during the injection period, and that leakage becomes less

likely thereafter because of pressure reduction and increasing effects from solubility, capillary trapping,

and carbonate mineralization. However, buoyancy forces causing upward migration of CO2 through

geologic formations will remain for hundreds if not thousands of years following injection, long after

over‐pressures due to injection have dissipated in the injection zone. Furthermore, some trapping

mechanisms such as solubility trapping and mineralization are very slow in relation to the 100‐year time

period specified. Finally, the specified leakage rate is low compared to the expected volume of CO2 in

geologic storage reservoirs, i.e., only about 2.4 tonnes CO2/yr. Thus, as a simulation test case studying

the potential water quality impacts of leakage, the 100‐year time period selected in the LBNL study is

reasonable. The time period was chosen to be able to evaluate both the short‐term and the long‐term

geochemical consequences.  

EPA clarifies that site‐specific data are necessary to understand the potential geochemical reactions at a

GS site. For this reason, all GS project owner or operators must submit detailed, site‐specific information

about a proposed GS site, including information on the porosity, permeability, mineralogy, and

geochemistry of the targeted injection and confining zones as well as all USDWs within the Area of

Review. Operators must also present information on the compatibility of the CO2 stream with fluids in
the injection zone and minerals in the injection and confining zones (§146.82(c)(3)). The data can help

the Director determine the potential for geochemical reactions between the injectate (CO2) and the

host geologic formations. For additional information on EPA’s approach to site characterization for GS

wells, see the responses to comments on the proposed rule in the rulemaking docket.  

Letter ID: 0334 Comment ID: 28209 Letter Lines: 158 to 222  

Comment Code: 2220 2.2.2. Basin‐Scale Hydrologic Impacts of CO2 Storage (seeking comment)  

Comment: Also, while the LBNL scenario described in "Sedimentary Basin Case Study"  

represents state of the art modeling of large scale deployment of CCS in a  

basin, it is not at all clear how relevant this work is to the proposed Class VI  

rule as the scenario envisioned seems to be precluded by the requirements to  

receive and retain a Class VI injection permit spelled out in the July 2008  

draft rule.  

The "Sedimentary Basin Case Study" scenario states that 20 facilities each of which  

inject 5MtCO2 per year are located within this hypothetical basin (FIGURE 8).  

Assuming that all 20 sources are power plants, they would each be the equivalent  

of a 1000 MW IGCC+CCS. It is difficult to imagine a scenario in which 20 GW of  

electrical generating capacity would come on line simultaneously {FOOTNOTE 6} in  

just one relatively small region of the United States {FOOTNOTE 7}.  

FIGURE 8: BOUNDARY OF THE DEVELOPED BASIN‐SCALE (Taken from BIRKHOLZER, J.T., Q.  

ZHOU, K. ZHANG, P. JORDAN, J. RUTQVIST, C.‐F. TSANG (2008): Research Project on  

CO2 Geological Storage and Groundwater Resources: Large‐scale Hydrogeological  

Evaluation and Impact on Groundwater Systems, Annual Report October 1, 2007 to  

September 30, 2008, Report, Lawrence Berkeley National Laboratory, Berkeley, CA,  

USA.)  

{SEE PG 4 OF EPA‐HQ‐OW‐2008‐0390‐0334.pdf for IMAGE OF FIGURE 8}  

{FOOTNOTE 6} See for example, MA Wise and JJ Dooley. 2009. "The Value of Post‐  

Combustion Carbon Dioxide Capture and Storage Technologies in a World with  

Uncertain Greenhouse Gas Emissions Constraints." International Journal of  

Greenhouse Gas Control. Volume 3, Issue 1. (2009), pp. 39‐48 DOI:  

10.1016/j.ijggc.2008.06.012 which forecasts CCS deployment at this scale but  

spread out across the entire ECAR region and spread out across nearly half of a  

century.  

{FOOTNOTE 7} It is important to stress how unrealistic this scenario is for the  
purpose of informing the draft Class VI proposal. A back of the envelope  

calculation involving line of sight limitations imposed by the curvature of the  

Earth suggests that if the cooling towers at these 20 facilities were 100m tall  

or higher one could literally see some of the other plants. Therefore, it is  

extremely difficult to envision how these 20 units could all come on line  

simultaneously without anyone recognizing how closely spaced they are and taking  

action (most likely via alterations to some of the pending Class VI injection  

permits) to avoid the scenario modeled by LBNL from ever materializing.  

More importantly, if the assumption is that these 20 facilities do not come on  

line simultaneously but rather phase in over time, then the July 2008 draft  

Class VI CO2 Storage rule would seem to prevent this situation from occurring as  

the rule requires that new injection well applicants take into account projects  

that have already been permitted when preparing their permit application. It is  

difficult to see how a situation could be allowed to develop where 20 very large  

facilities could be permitted so near each other to start at the same time,  

without raising flags to regulators to request additional information from the  

applicants on CO2 plume movement and pressure build up, and request subsequent  

potential re‐evaluation of initial project AORs, pressure effects and potential  

impacts to drinking water. While the value of understanding near‐ and far‐field  

pressure effects for projects located so close together is undisputed, the  

potential for so many projects being inadvertently permitted in the same area  

alone is so far‐fetched that the scenario clearly can’t be put forth as a real  

possibility, and perhaps EPA could do a better job in communicating that this  

scenario is not intended to represent future reality. As an academic exercise to  

educate the technical community and inform requirements within the proposed rule  

to ensure that cumulative effects across multiple projects within the same  

geographic area, however, this work is important.  

More importantly however, if the EPA promulgates the rules as drafted and has  

the resources to enforce the rules, these basin scale concerns will be managed  

proactively, and pressures can be maintained within acceptable ranges. This is  

the point that should have been clearly communicated via the presentation of  

this modeling work.  

Individual Response: EPA acknowledges that 20 projects coming online simultaneously is not a realistic

assumption, rather it is a modeling simplification. However, even if the 20 projects were phased over a

10‐year period (and assuming a 50‐year operational life time), there would still be a 40‐year period with

all 20 projects in operation, and the basic results obtained from the modeled scenario would not

significantly change if a phased scenario had been assumed. Considering the existing power plants and

other large stationary CO2 emitters in the example region, with a total annual emission of 300 Mt CO2,

EPA believes that the modeling scenario is reasonable.
The sedimentary basin case cited in Birkholzer et al. (2008b) assumes that one third of the current

annual emissions from large stationary sources in the example area are being captured and stored. LBNL

started with the assumption that in order to have GS make a contribution to climate change mitigation,

large volumes of CO2 would have to be injected, representing a significant fraction of the CO2 generated

from stationary sources within a given area.  

Given that large volumes from several facilities would need to be sequestered in a given area, it may be

unrealistic to assume that storage sites can be placed so far from each other that their pressure

envelopes would never overlap. The spatial pattern of GS projects used in LBNL’s work was developed

by placing the 20 storage sites into the center of the example basin where the geological conditions

were most favorable for CO2 storage (i.e., sufficient thickness and depth of storage reservoir, distance

from natural gas storage fields in operation, large distance to transmissive faults). In other words, the

assumption was made that CO2 would be pipelined from stationary emitters located in areas where

geologic conditions are less favorable (i.e., too shallow for injection of supercritical CO2, too deep for

economic injection and not permeable enough). Thus, the hypothetical GS scenario is not a scenario of

inadvertent permitting without recognizing close proximity of several GS sites, but rather close

proximity is assumed to be necessary in certain cases and potential impacts thereof are being evaluated.

Furthermore, while an average distance about 30 km is assumed in LBNL’s scenario, pressure

interference between individual storage projects could be expected even if this distance was doubled or

even tripled, while the far‐field pressure perturbation away from the basin center would be similar.

EPA agrees that proactive management of basin scale concerns to maintain pressures within acceptable

ranges is important, and encourages owners or operators and permitting authorities to communicate

planned GS activities to maximize coordination and minimize pressure interference. If a permit applicant

(or the permitting authority) is aware of pending GS projects near a proposed well, the AoR delineation

performed pursuant to §146.84 should account for the impacts of multiple owners and operators

injecting within a single basin. EPA anticipates that, where multiple operators are involved, the Director

would not approve modeling that does not account for changes that may result from all injection

operations. As the commenter points out, the proximity of injection sites to each other and the relative

timing of each injection operation might indicate a possible increase in risk for the containment of the

total CO2 and/or the effects of hydraulic perturbations and brine displacement.  

EPA adds that if any new GS projects are permitted within the AoR of a GS project between AoR

evaluations, the AoR reevaluation would need to address such projects. EPA also expects that the

permitting of the newer GS project would have considered the presence of an existing GS project. For

additional information regarding EPA’s requirements for AoR delineation for GS projects, see the

responses to comments on the proposed rule in the rulemaking docket.  
Letter ID: 0334 Comment ID: 28210 Letter Lines: 224 to 234  

Comment Code: 3420 3.4.2. Request for Information on Areas Where Injection Depth and USDWs Are a

Concern (seeking comment)  

Comment Code: 3430 3.4.3. Request for Information on Constructing Wells Through Existing CO2

Plumes (seeking comment)  

Comment: On the Appropriateness of Allowing CO2 Storage above a USDW and the related  

issue of who will regulate production wells that could intersect stored CO2? The  

overriding principle should be does the proposed Class VI rule help protect the  

wellbeing of humans and the health of the environment. Framing the issue in this  

way makes it clear that there is an explicit tradeoff being made about the use  

of USDWs for CO2 storage or the use of water bearing bodies that have more than  

10,000 TDS but are shallower than another formation which has waters with less  

than 10,000 TDS. This calls for a flexible and site‐ or region‐specific approach  

that still includes mandatory criteria such as the presence of adequate caprocks  

above and below the proposed storage formation to ensure the protection of both  

shallower and deeper USDWs.  

Individual Response: EPA clarifies that the GS rule sets requirements for siting of GS projects, including

the presence of adequate confining zones above (and where waivers are issued, below) the injection

zone for the purpose of protecting USDWs from endangerment. EPA adds that the GS rule does not

promote the use of any formations for GS over other uses.  

Finally, EPA clarifies that regulating production wells is outside the UIC program’s authority, but adds

that the presence of production wells in the AoR of a Class VI well must be considered in the AoR and

corrective action plan.  

Letter ID: 0334 Comment ID: 28211 Letter Lines: 236 to 253  

Comment Code: 3430 3.4.3. Request for Information on Constructing Wells Through Existing CO2

Plumes (seeking comment)  

Comment: The USEPA should also explain in detail what authority it has (or needs to be  

given) to ensure that any future wells (oil, gas, water, injection) that drill  

through a formation which is being used for CO2 storage are built to withstand  

the higher pressures and acidity of these formations without becoming pathways  

for the migration of previously stored CO2 out of the target storage formation.  

If the USEPA has no way of regulating the construction of production wells that  

penetrate a CO2 storage formation and if it believes that it will not be granted  
this authority, then this needs to bear on decisions to allow storage in  

formations that are shallower than formations that might in the future be host  

to future water, oil or gas production wells that could penetrate the storage  

formation. The NODA asserts without elaboration "The management scheme will also  

ensure that there is a strategy developed to address future needs to access  

formations below the injection zone." (p. 44810) Without further elaborating how  

this would be done in practice, it would appear that the July 2008 proposed rule  

and the August 2009 NODA have yet to meaningfully address a key aspect of how  

injection above a USDW could be implemented safely. It is hoped that before this  

rule is finalized some clarity and specificity will be brought to this critical  

issue.  

Individual Response: EPA believes that, as part of its mission to protect current and future drinking

water sources and to respond to public concerns about future drinking water resource availability it is

appropriate to consider planned water, hydrocarbon, or mineral resource exploitation potential as part

of a thorough site‐specific evaluation of a proposed GS site. Therefore, to provide additional USDW

protection and ensure that any planned drilling is conducted appropriately, the final GS rule requires the

Director to consider planned or permitted water, hydrocarbon, or mineral resource exploitation

potential of the proposed injection formation and other formations both above and below the injection

zone to determine if there are any plans to drill through the formation to access resources in or beneath

the proposed injection zone/formation as specified in §146.95(b)(1)(vii).  

Letter ID: 0334 Comment ID: 28212 Letter Lines: 255 to 275  

Comment Code: 3340 3.3.4. Financial Responsibility  

Comment: Additional financial responsibility measures for projects involving waivers do  

not appear to be consistent or well articulated. The NODA states on page 44811  

that "The owner/operator would also demonstrate sufficient, additional financial  

responsibility to address any potential contamination of USDWs above or below  

the injection zone." This is immediately proceeded by a passage that speaks to  

the need to prepare a plan that considers "regional water resources issues and  

has explored alternative water supplies or water treatment options." Later on  

this same page, the prospective CO2 storage operator is asked for a plan "for  

securing alternative resources or treating USDW formation waters in the event of  

contamination related to the Class VI injection activity." These seem to be  

describing wildly different levels of responsibility and financial commitment.  

The requirement to demonstrate existing financial resources needed to provide  

clean water to all possible current and future users within an undefined region  

seems like an activity that could cost millions, hundreds of millions, billions  
of dollars. On the other hand, a plan for how one might secure alternative  

sources of water if the need should ever arise seems like something that could  

be satisfied via a $10,000 paper study. The large gap between these two  

endpoints will likely lead to confusion among CCS stakeholders. The USEPA is  

encouraged to better define what would be expected of applicants for wells that  

would need waivers so that CCS stakeholders can more thoughtfully respond to the  

proposal.  

Individual Response: The requirements at §146.95 for owners and operators seeking injection depth

waivers are intended to add to and modify the requirements that all GS well owners or operators must

meet, including those for financial responsibility, to ensure that the proposed site is evaluated in the

context of the presence of USDWs above and below the injection zone. EPA anticipates that issuance of

waivers will be limited to circumstances where there are deep USDWs and/or where the lack of a waiver

of injection depth requirements would result in impractical or technically infeasible well construction,

and where USDW protection is demonstrated and maintained through the life of the GS project.  

EPA is developing guidance on financial responsibility to assist owners or operators in evaluating the

requirements of §146.85 and to assist Directors in evaluating financial responsibility demonstrations.

EPA is also developing guidance on the injection depth waiver process. The guidance describes the

recommended approach an owner or operator may follow when submitting a waiver application,

processing waiver applications by the UIC and PWSS Program Directors. These guidances will be

available on EPA’s website at water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.