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.
Page 1 of 7

October 15, 2009

U. S. Environmental Protection Agency

Docket ID No. EPA-HQ-OW-2008-0390

Office of Groundwater and Drinking Water (OGWDW)

Mail Code: 4101TT

1200 Pennsylvania Ave. NW

Washington, DC 20460

RE: Federal Requirements Under the Underground Injection Control (UIC) Program 

for Carbon Dioxide Geosequestration Wells, Notice of Data Availability

Dear Docket:

This letter details the comments of the American Water Works Association (AWWA) on the 

Notice of Data Availability (NODA) on the proposed requirements for carbon dioxide

geosequestration wells under the Underground Injection Control (UIC) Program as published in 

the August 31st Federal Register (73 FR 44802). As we have stated in our previous comments 

on the proposed rule, protection of underground sources of drinking water (USDWs) should be a 

key priority of any geologic carbon sequestration (GS) regulation developed as part of the 

Underground Injection Control (UIC) Program. AWWA appreciates the opportunity to comment 

on this NODA, and we would like to reiterate five central issues that we feel should be addressed 

in the final regulation:

 Protection of underground sources of drinking water (USDWs) should be the highest 

priority – water should trump everything;

 If USDW water quality is degraded by a GS project, the owner/operator of that project 

must be fully responsible for any costs born by drinking water utilities due to increased 

treatment or other mitigation requirements for that ground water or replacement of lost 

capacity in perpetuity;

 Prevention of unintended consequences is of utmost importance;

 Injection of carbon dioxide should not be permitted above and/or between USDWs;

 Injection of carbon dioxide and construction of injection wells should not be permitted in 

or near sole source aquifers, coal seams, earth-quake prone areas; and,

 Hydraulic fracturing should not be used at all for GS.

AWWA has reviewed the information provided in the NODA and this additional information is 

not sufficient for us to support the permitting or issuance of waivers for large-scale carbon 

Government Affairs Office

1300 Eye Street NW

Suite 701W

Washington, DC 20005

T 202.628.8303 

F 202.628.2846

www.awwa.org

Headquarters Office 

6666 W. Quincy Avenue

Denver CO 80235

T 303.794.7711 

F 303.347.0804

The Authoritative Resource on Safe Water SM
Page 2 of 7

sequestration projects. AWWA recommends that permitting of large-scale GS projects be 

delayed and no waivers allowed until information about Department of Energy (DOE) pilot 

projects and the effects of carbon sequestration on the subsurface and USDW can be collected 

and analyzed. We are concerned about the potential for GS projects to result in unintended, and 

possibly harmful, consequences to sources of drinking water. Much of the work on GS 

technology is still in pilot or pre-pilot phase at several magnitudes of scale smaller than the sort 

of projects envisioned under this proposal. 

AWWA recommends that theoretical and observational research be continued and that the 

research must be comprehensive. While the UIC program has a long history, the injection of 

large quantities of CO2 into the ground is a process that is not well understood. The substance is 

different than other UIC compounds and the behavior of the compound under severe pressures 

and temperatures is not well known. We strongly recommend that EPA and DOE perform both 

modeling (theoretical) and observational research to better understand the carbon sequestration 

process and the effects of CO2 injection on saline aquifers and the subsurface geology. The 

results of this research must be made available to permit writers and stakeholders in a timely 

manner so that improvements to the technology and permitting process can be realized

AWWA would also like to reiterate our concern of the current classification of a USDW as the 

best sources of drinking water are already being used by utilities. With the potential impacts 

from climate change, drinking water utilities are facing an even more limited supply of fresh 

drinking water. As a result, many utilities are turning to more challenging groundwater sources 

such as those that are very deep or have high salinity concentrations. Some of these new sources 

could fall outside of the current definition of a USDW, in that the aquifer has a TDS 

concentration higher than 10,000 ppm. The definition of a USDW was written at a time when 

many advanced water treatment technologies were generally cost prohibitive, and the general 

thinking that the high-salinity aquifers would never be utilized as drinking water sources.

Recognizing that it is difficult to extend protection to these aquifers due to the restrictions of the 

SDWA, AWWA recommends that during the project planning process or the injection depth 

waiver process (as identified in this NODA), the owner/operators should include state 

environmental departments as they can provide insight into what aquifers not currently classified 

as USDWs might be considered as future drinking water sources. The stakeholder process 

should also involve both regional and local planning boards, as well as the local water utilities. 

This process will allow for protection to be extended to the non-traditional aquifers, which will 

be necessary given the pressures on water resources that the country will be facing in the 

upcoming century. In addition, this process will prevent waivers from being issued for injection 

into saline aquifers that could be considered as future sources of drinking water.

DATA AND RESEARCH ON GS AND THE IMPACTS ON GROUNDWATER

The NODA provides a summary of Lawrence Berkeley National Laboratory (LBNL) theoretical 

studies on the interactions between groundwater, CO2 and the surrounding geology. Simulations 

of the potential for GS to cause changes in groundwater quality and the subsequent mobilization 

of trace elements (including arsenic and lead) as a result of CO2 leakage were developed. The 

modeling studies also addressed basin-scale hydrological impacts of large-volume injections of 

CO2 on groundwater aquifers (in particular, pressure front impacts caused by GS). 
Page 3 of 7

Results from the model simulations suggest that mobilization of lead and arsenic would occur 

with leaking of CO2 into shallow aquifers. This is unacceptable to drinking water utilities and to 

millions of consumers of groundwater in the United States. Model projections note that the 

Maximum Contaminant Levels (MCL) for arsenic would be exceeded in only a few cases. 

However, this does not address the fact that water utilities do not want their USDWs 

contaminated by arsenic or other contaminants in any quantity as a result of GS projectsr. In the 

case of lead, the model analysis incorrectly assumes that the Action Level for lead in the Lead 

and Copper Rule is a health based limit, whereas it is simply an indicator of effective corrosion 

control. In regard to acceptable lead concentrations, the model should address the Maximum 

Contaminant Level Goal (MCLG) which for lead is zero. Given that small concentrations of 

lead are detrimental to the mental development of children, any possible increase in lead in water 

either by mobilization in the source or corrosion of plumbing is unacceptable. Injected carbon 

dioxide that reaches USDWs is likely to make the groundwater water more corrosive with 

respect to lead and copper in distribution systems. This would increase the probability of 

elevated lead levels in homes and schools due to corrosion of plumbing fixtures. Any increase in 

raw water lead concentration constrains the utility in compliance with its optimized corrosion 

control treatment. 

EPA should be mindful of not only the health risks to drinking water, but also of other potential 

secondary standard and aesthetic degradation risks from exposure to other constituents such as 

pH, copper, iron, hardness, silica and boron. These are compounds for which either no MCLs 

have been developed or have secondary MCLs. Further, in states like California, water utilities 

must report Public Health Goals (PHGs) well below federal MCLs to the public. 

Given the basis for MCLs, there is the potential for health impacts due to long-term exposure to 

contaminant levels below the established MCLs. Technically, MCLs are not the proper limit on 

which to base degradation. Drinking water MCLs should not be a license to pollute or 

contaminate. Drinking water MCLs are established from a different reference point. Rather than 

starting with a pristine condition and adding a contaminant, MCLs are established from sources 

that contain a contaminant. The exposure assessment and risk assessment components of a risk 

management decision resulting in an MCL are developed on the basis of population exposure. If 

the population is not exposed at present, the economic and health benefits/costs are not included 

in the choice or selection of an MCL. If a new segment of the population or a greater segment of 

the existing population becomes exposed as a result of an activity, the economic impact and 

benefit on this new population will not have been included in the risk management decision. 

One can assume the impact would increase proportionally, but there are no data to justify such an 

assumption.

Owners/operators could be in compliance with the regulation, but could be degrading an aquifer 

by contaminating it with compounds for which MCLs may or may not exist. Beneficial uses of 

groundwater could also be impacted by increases of these compounds in the aquifers. Research 

is needed to address these topics as well, not just on the potential for the mobilization of lead and 

arsenic due to the leakage of CO2 into shallow aquifers.

In addition, drinking water standards are not static and can change as a result of new studies. 

Arsenic is a good example as the MCL was lowered from 50 ppb to 10 ppb in 2001. GS 

operations should not be immune from the new requirements and should not have their permits 
Page 4 of 7

grandfathered into compliance without adjusting the compliance objectives. Also, lead and 

copper action levels are not health based water quality standards and should not be used as an 

objective or yardstick with which to measure adequacy of remedial measures. 

Ground Water Quality Changes

The LBNL report on computer model simulations of changes in groundwater changes due to CO2

leakage supports AWWA’s position that more research is needed to develop a better 

understanding of the potential impacts of GS projects on USDW. In particular, AWWA supports 

the LBNL recommendation that field research be done with “shallow” groundwater sources 

being used for water supply. 

AWWA notes that the report apparently has not been peer reviewed. We recommend that EPA 

conduct a peer review of both the report and the modeling approach. The peer review should be

performed by a panel of experts of qualified practitioners familiar with groundwater chemistry, 

fate and transport modeling, and drinking water treatment and regulations. This could be 

accomplished using the EPA Science Advisory Board Drinking Water Committee or the 

National Academies of Science as the review panel. At a minimum, the following topics should 

be considered:

 The model simulations involve numerous assumptions that should be verified on site 

specific groundwater supplies. The panel should provide recommendations on specific 

research needs.

 Lead dissolution by CO2 is being compared to the action level for lead, which is actually 

applied to the customer tap rather than the source water. The fact that CO2 intrusion 

would make the source water more corrosive could cause non-compliance with the lead 

and copper rule, even if the lead is below the action level.

 LBNL did not evaluate impacts of CO2 leakage on copper mobilization, which could be 

affected by more corrosive water produced by CO2 intrusion. Copper also has an action 

level that applies at the customer tap.

 The LBNL report covers natural analogues of CO2 intrusion into groundwater. These 

analogues suggest that high levels of hardness, iron, manganese, and boron could be 

produced. While these adverse water quality changes would not currently come under 

the definition of endangerment (boron and manganese could be future exceptions), they 

would degrade groundwater quality and limit beneficial use of water resources. 

Basin-Scale Hydrologic Impacts of CO2 Storage

The recent LBNL modeling studies on basin-scale carbon dioxide storage cited in the NODA 

indicate that pressure changes could propagate as far away as 124 miles (200 kilometers) from 

the CO2 injection area. This suggests that the area of review must be extended over a much 

larger area than previously anticipated. AWWA supports the requirement that basin-scale 

hydrologic impacts of CO2 storage on reservoir pressure pressures and far-field pressures be 

addressed in the GS permitting process. 
Page 5 of 7

WAIVER PROCESS FOR INJECTION ABOVE AND/OR BETWEEN USDWs

AWWA is in strong opposition to the proposed waiver process for injection above and/or 

between USDWs as it presents too great a risk to USDWs. GS is still an emerging technology 

and EPA should employ caution at this time until more experience is gained with pilot studies of 

deep saline injection zones. Efforts to date have focused on containment of supercritical carbon 

dioxide rather than gaseous or liquid forms that might exist at shallower depths. It is unclear 

how owners/operators would be able to demonstrate containment of these plumes. Further 

research is necessary to define suitable management practices.

AWWA is concerned that a waiver process, as well as the proposed regulation, has many 

limitations that could allow for the degradation of USDWs. Many of the requirements are based 

on faith and not data, and the drinking water community and the citizens they serve are being 

asked to trust that geologic sequestration technology will work even though there is very little 

experience with this technology at a large scale. For example, the requirements for determining 

the direction of carbon dioxide plume migration, predicting confining layer containment 

potential, and identifying necessary geo-chemical monitoring are based on modeling exercises, 

with limited monitoring data to validate these models and limited real-life data to support the 

requirements. The possibility for unintended consequences to occur with geologic sequestration 

is very real and is similar to what was observed with the use of MTBE. MTBE is the fuel 

additive that was meant to solve an air pollution problem but its use resulted in unanticipated 

drinking water pollution problems. Carbon dioxide is an energy production/use byproduct that 

causes air pollution/climate problem but whose mitigation (using geologic sequestration) could 

cause drinking water contamination and other (supply) problems. EPA needs to draw on the 

lessons learned from the MTBE situation, and do everything possible to prevent a similar 

situation from occurring with geologic sequestration. Even though MTBE is an excellent 

example, the difference in scale between the possible unintended consequences of sequestration 

and MTBE are huge. Experience gained from deep injection wastewater wells in Florida should 

also be documented and considered. 

AWWA strongly recommends that EPA not move forward with the injection depth waiver 

process. If EPA decides to proceed down this road despite AWWA’s negative comments, there 

are several significant issues that EPA needs to consider: 

 EPA’s suggested criteria for approving a GS injection depth waiver includes a 

requirement that the owner/operator identify all artificial penetrations in the Area of 

Review that penetrate the injection zone, the upper and lower confining zones, and all 

USDWs in the area. The stated purpose of this demonstration would be to ensure that 

public water supplies, private wells, and potential future water resources are identified 

and the location of artificial penetrations into such formations are known and these 

artificial penetrations can be appropriately plugged during the permitting process. 

Because drinking water wells are artificial penetrations, it appears that they would be 

plugged, making them useless for supplying water. If not, it is unclear how the 

owner/operator can demonstrate that the construction of these wells is equivalent to Class 

VI well requirements and thus would not serve as conduits to contaminate USDWs.
Page 6 of 7

 It is unclear that technology has been developed for drilling through injection zones

containing stored carbon dioxide without releasing some of the stored gas. EPA should 

insist that demonstration of such technologies be performed before considering a waiver 

program.

 The risk of damaging water or mineral resources will be greatly increased, and there 

needs to be an adequate mechanism for compensating water utilities and other resource 

owners for remedial actions that must be taken to restore or replace beneficial uses.

 EPA indicates that the “Public Water Supply Supervision (PWSS) Director,” in 

conjunction with the UIC Program Director, must review and approve waivers for 

injection depths above the lowest USDW formation. However, EPA does not define who 

the PWSS Director is, but presumably it is the head of the State, Territorial, or Tribal 

Drinking Water Primacy Agency, which may be the EPA Regional Administrator (who 

can also be the UIC Program Director). EPA needs to define the position of DWSS 

Director and determine whether an EPA Regional Administrator can fill both roles 

without a conflict of interest.

If, after reviewing these significant issues, EPA remains committed to further developing the 

waiver process, the following requirements should be mandatory for the siting and operation of 

GS projects that inject CO2 above the lowermost USDW:

1. A GS owner/operator can only apply for the waiver for injection into a formation above the 

lowermost USDW if there is no other option available for sequestering CO2. The waiver 

process should not be available if there are other viable formations located below the 

lowermost USDW. It is not a process for GS owner/operators to use to try and reduce project 

costs by injecting into a shallower aquifer. In addition, the GS owner/operator will collect

baseline water quality data for the potentially impacted USDWs to allow for any degradation 

in water quality to be measured from the baseline conditions that exist prior to the injection 

of carbon dioxide.

2. The carbon dioxide injection well shall be located such that a buffer zone is provided 

between the injection activities and any active or planned drinking water wells. The buffer 

zone shall be large enough as to provide for a minimum of ten (10) years of travel time for

carbon dioxide, as modeled from the point of injection to the drinking water well. In the 

event of a leakage and/or USDW contamination event, this will allow for spatial separation 

that will provide the project owner/operator with enough time to appropriately remediate the 

contamination without adverse impact to the drinking water system. 

3. If injection activities result in the leakage of carbon dioxide into a USDW, the GS project 

owner/operator shall immediately notify operators of drinking water wells using that USDW 

to discontinue using the well if it no longer produces safe, wholesome, potable water. 

Notification shall also be provided to the appropriate state and local water and/or public 

health agencies. The GS project owner/operator shall immediately provide an alternative 

safe drinking water supply as approved by the appropriate water and/or public health 

agencies. 

4. Injection above the lower-most USDW should only be allowed if the full extent of the carbon 

dioxide plume does not completely cover the lateral extents of the lower-most USDW. The 

GS project, and resulting carbon dioxide plume, should be sited in such a way that provides 

for a minimum of four (4) separate points of access (via new drinking water wells) to the 

USDW without drilling through the plume of sequestered CO2. These four points should be 
Page 7 of 7

equally spaced around the project footprint to allow drinking water utilities unrestricted 

access to those USDWs without worry of leakage of CO2during well construction.

Despite providing the above-mentioned requirements, it is important to note that AWWA 

remains in strong opposition to the injection depth waiver process and our suggestion of these 

requirements in no way means that AWWA endorses the injection depth waiver process. 

However, we recognize that if EPA does decide to move forward on this issue, providing 

comment in response to the waiver question in the NODA is our only opportunity to shape the 

final regulation for GS using Class VI injection wells. 

SUMMARY

In summary, both the LBNL studies on groundwater quality changes and basin-scale hydrologic 

impacts suggest that additional research is needed to better understand the potential effects on 

USDWs. More research, including experimental work with actual groundwater above potential 

GS sites, is needed to ensure that arsenic, lead, and other constituents are not released as the 

result of the final GS rule. The section on lead needs to be re-evaluated based on the MCLG not 

on the Action Levels. The use of MCLs as the basis for a policy of permissible degradation 

needs to be reexamined. Additionally, AWWA suggests that EPA conduct a peer review of the 

LBNL reports and the modeling approach using the Science Advisory Board Drinking Water 

Committee or the National Academy of Science as the review panel. AWWA also supports the 

requirement that basin-scale hydrologic impacts of CO2 storage on reservoir pressure and farfield pressures be addressed in the GS permitting process. 

Most importantly, AWWA stands by our previously stated positions that injection should only be 

carried out at the pilot phase and only allowed below USDWs. If USDW water quality is 

degraded by a GS project, the owner/operator of that project is responsible for any costs borne by 

drinking water utilities due to increased treatment requirements for that ground water or 

replacement of lost capacity in perpetuity. The key words are “in perpetuity and without limit”, 

as remediation of that contaminated groundwater would continue in perpetuity. 

If you have any questions about these comments, please feel free to contact me or Cynthia Lane

in our Washington Office. 

Yours Sincerely,

Thomas W. Curtis

Deputy Executive Director 

cc: Pete Silva – USEPA OW

Cynthia Dougherty – USEPA OGWDW

Steve Heare – USEPA OGWDW
Letter ID: 0369  

Commenter: Thomas Curtis  

Organization: American Water Works Association (AWWA)  

Letter ID: 0369 Comment ID: 27933 Letter Lines: 31 to 58  

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

Comment: This letter details the comments of the American Water Works Association (AWWA)  

on the Notice of Data Availability (NODA) on the proposed requirements for  

carbon dioxide geosequestration wells under the Underground Injection Control  

(UIC) Program as published in the August 31st Federal Register (73 FR 44802).  

As we have stated in our previous comments on the proposed rule, protection of  

underground sources of drinking water (USDWs) should be a key priority of any  

geologic carbon sequestration (GS) regulation developed as part of the  

Underground Injection Control (UIC) Program. AWWA appreciates the opportunity  

to comment on this NODA, and we would like to reiterate five central issues that  

we feel should be addressed in the final regulation:  

‐ Protection of underground sources of drinking water (USDWs) should be the  

highest priority ‐ water should trump everything;  

‐ If USDW water quality is degraded by a GS project, the owner/operator of that  

project must be fully responsible for any costs born by drinking water utilities  

due to increased treatment or other mitigation requirements for that ground  

water or replacement of lost capacity in perpetuity;  

‐ Prevention of unintended consequences is of utmost importance;  

‐ Injection of carbon dioxide should not be permitted above and/or between USDWs;  

‐ Injection of carbon dioxide and construction of injection wells should not be  

permitted in or near sole source aquifers, coal seams, earth‐quake prone areas;  

and,  

‐ Hydraulic fracturing should not be used at all for GS.  

Individual Response: This comment pertains to EPA’s proposed GS rule (73 FR 43492) and is outside the

scope of the Notice of Data Availability. Please see responses to comments on the proposed rule for
EPA’s response to similar comments.  

Please see the remainder of EPA's response to this comment for additional responses and on the

injection depth waiver approach at §146.95.  

Letter ID: 0369 Comment ID: 27934 Letter Lines: 60 to 69  

Comment Code: 2000 2. Comments on Research, Data Analysis, and Findings presented in the NODA

(seeking comment)  

Comment: AWWA has reviewed the information provided in the NODA and this additional  

information is not sufficient for us to support the permitting or issuance of  

waivers for large‐ scale carbon sequestration projects. AWWA recommends that  

permitting of large‐scale GS projects be delayed and no waivers allowed until  

information about Department of Energy (DOE) pilot projects and the effects of  

carbon sequestration on the subsurface and USDW can be collected and analyzed.  

We are concerned about the potential for GS projects to result in unintended,  

and possibly harmful, consequences to sources of drinking water. Much of the  

work on GS technology is still in pilot or pre‐pilot phase at several magnitudes  

of scale smaller than the sort of projects envisioned under this proposal.  

Individual Response: EPA disagrees that the ability to safely deploy CCS on a commercial‐scale has not

been proven or finalizing that the rule should be delayed. EPA is monitoring international GS efforts

currently operating on a commercial scale. These include the Sleipner Project in the Norwegian North

Sea (operating since 1996); the Weyburn ER project in Saskatchewan, Canada (since 2000); the In Salah

Gas Project in Algeria (since 2004); and Snohvit, also in offshore Norway in the Barents Sea (since 2008).

Other projects EPA is tracking include Gorgon and Otway (in Australia); Ketzin (in Germany); Lacq (in

France); and CarbFix, (in Iceland). These projects are designed to operate for decades and plan to

cumulatively inject over 200 MT of CO2. A paper summarizing EPA's research on international GS

projects and legislation is in the rulemaking docket.

EPA also believes that the DOE pilot projects, while not commercial‐scale projects, provide sufficient

data on all aspects of GS operations (from well construction and injection to long‐term plume fate and

transport and monitoring of containment) to inform the GS rule.  

Letter ID: 0369 Comment ID: 27935 Letter Lines: 71 to 81  

Comment Code: 2000 2. Comments on Research, Data Analysis, and Findings presented in the NODA

(seeking comment)  
Comment: AWWA recommends that theoretical and observational research be continued and  

that the research must be comprehensive. While the UIC program has a long  

history, the injection of large quantities of CO2 into the ground is a process  

that is not well understood. The substance is different than other UIC compounds  

and the behavior of the compound under severe pressures and temperatures is not  

well known. We strongly recommend that EPA and DOE perform both modeling  

(theoretical) and observational research to better understand the carbon  

sequestration process and the effects of CO2 injection on saline aquifers and  

the subsurface geology. The results of this research must be made available to  

permit writers and stakeholders in a timely manner so that improvements to the  

technology and permitting process can be realized  

Individual Response: As described above, EPA disagrees that the ability to safely deploy CCS on a

commercial‐scale has not been proven. In addition to monitoring international commercial scale GS

efforts, EPA continues to work with DOE, national laboratories (such as Lawrence Berkeley National

Laboratories), the USGS, and internal Agency Offices (e.g., Office of Research and Development) on

modeling and field research on various aspects of GS, including potential risks to USDWs.  

EPA intends to use an adaptive approach to the GS regulation. 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: 0369 Comment ID: 27936 Letter Lines: 83 to 106  

Comment Code: 3220 3.2.2. Comments in Opposition to the Approach  

Comment: AWWA would also like to reiterate our concern of the current classification of a  

USDW as the best sources of drinking water are already being used by utilities.  

With the potential impacts from climate change, drinking water utilities are  

facing an even more limited supply of fresh drinking water. As a result, many  

utilities are turning to more challenging groundwater sources such as those that  

are very deep or have high salinity concentrations. Some of these new sources  

could fall outside of the current definition of a USDW, in that the aquifer has  

a TDS concentration higher than 10,000 ppm. The definition of a USDW was  

written at a time when many advanced water treatment technologies were generally  

cost prohibitive, and the general thinking that the high‐salinity aquifers would  

never be utilized as drinking water sources.  
Recognizing that it is difficult to extend protection to these aquifers due to  

the restrictions of the SDWA, AWWA recommends that during the project planning  

process or the injection depth waiver process (as identified in this NODA), the  

owner/operators should include state environmental departments as they can  

provide insight into what aquifers not currently classified as USDWs might be  

considered as future drinking water sources. The stakeholder process should  

also involve both regional and local planning boards, as well as the local water  

utilities. This process will allow for protection to be extended to the non‐  

traditional aquifers, which will be necessary given the pressures on water  

resources that the country will be facing in the upcoming century. In addition,  

this process will prevent waivers from being issued for injection into saline  

aquifers that could be considered as future sources of drinking water.  

Individual Response: EPA agrees that USDW protection is the highest priority and clarifies that the

purpose of the GS regulation is to ensure that GS, where deployed, is conducted in a manner that

protects USDWs. Incentivizing the use of GS or other renewable energy resources and technologies is

outside the scope of this rulemaking and the UIC Program’s authority under the SDWA. EPA disagrees

that finalization of the GS rule is premature. For additional information regarding the data on which EPA

based the final GS rule, see the preamble to the final GS rule.

EPA acknowledges the commenter's concerns about USDW protection and clarifies that the mission of

the UIC Program is to protect USDWs from endangerment. The final GS rule includes a requirement at

§146.95(b)(2) that the UIC Program Director consult with the PWSS Directors of all States, Territories,

and Tribes having jurisdiction within the AoR of a well for which a waiver is sought. EPA believes this

process is necessary and appropriate to ensure that water system concerns are considered when

evaluating a waiver application. EPA requires this information be documented to ensure that this

consultation will enable transparent public disclosure of all information evaluated by the Directors and

their respective recommendations.

EPA agrees that a stakeholder process that includes environmental departments, regional and local

planning boards, and local water utilities is important. EPA has added a requirement at §124.10(c)(1)(xi)

that state and local oil and gas regulatory agencies and state agencies regulating mineral exploration

and recovery, the PWSS program director, and all agencies that oversee injection wells in the state must

be notified as part of the public notice process for a Class VI permit. For additional information on public

participation associated with GS projects, see the preamble to the final rule and the responses to

comments on the proposed GS rule.  

Letter ID: 0369 Comment ID: 27937 Letter Lines: 108 to 176  

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

Comment: DATA AND RESEARCH ON GS AND THE IMPACTS ON GROUNDWATER  

The NODA provides a summary of Lawrence Berkeley National Laboratory (LBNL)  

theoretical studies on the interactions between groundwater, CO2 and the  

surrounding geology. Simulations of the potential for GS to cause changes in  

groundwater quality and the subsequent mobilization of trace elements (including  

arsenic and lead) as a result of CO2 leakage were developed. The modeling  

studies also addressed basin‐scale hydrological impacts of large‐volume  

injections of CO2 on groundwater aquifers (in particular, pressure front  

impacts caused by GS).  

Results from the model simulations suggest that mobilization of lead and arsenic  

would occur with leaking of CO2 into shallow aquifers. This is unacceptable to  

drinking water utilities and to millions of consumers of groundwater in the  

United States. Model projections note that the Maximum Contaminant Levels (MCL)  

for arsenic would be exceeded in only a few cases. However, this does not  

address the fact that water utilities do not want their USDWs contaminated by  

arsenic or other contaminants in any quantity as a result of GS projectsr. In  

the case of lead, the model analysis incorrectly assumes that the Action Level  

for lead in the Lead and Copper Rule is a health based limit, whereas it is  

simply an indicator of effective corrosion control. In regard to acceptable  

lead concentrations, the model should address the Maximum Contaminant Level Goal  

(MCLG) which for lead is zero. Given that small concentrations of lead are  

detrimental to the mental development of children, any possible increase in lead  

in water either by mobilization in the source or corrosion of plumbing is  

unacceptable. Injected carbon dioxide that reaches USDWs is likely to make the  

groundwater water more corrosive with respect to lead and copper in distribution  

systems. This would increase the probability of elevated lead levels in homes  

and schools due to corrosion of plumbing fixtures. Any increase in raw water  

lead concentration constrains the utility in compliance with its optimized  

corrosion control treatment.  

EPA should be mindful of not only the health risks to drinking water, but also  

of other potential secondary standard and aesthetic degradation risks from  

exposure to other constituents such as pH, copper, iron, hardness, silica and  

boron. These are compounds for which either no MCLs have been developed or have  

secondary MCLs. Further, in states like California, water utilities must report  

Public Health Goals (PHGs) well below federal MCLs to the public.  

Given the basis for MCLs, there is the potential for health impacts due to long‐  
term exposure to contaminant levels below the established MCLs. Technically,  

MCLs are not the proper limit on which to base degradation. Drinking water MCLs  

should not be a license to pollute or contaminate. Drinking water MCLs are  

established from a different reference point. Rather than starting with a  

pristine condition and adding a contaminant, MCLs are established from sources  

that contain a contaminant. The exposure assessment and risk assessment  

components of a risk management decision resulting in an MCL are developed on  

the basis of population exposure. If the population is not exposed at present,  

the economic and health benefits/costs are not included in the choice or  

selection of an MCL. If a new segment of the population or a greater segment of  

the existing population becomes exposed as a result of an activity, the economic  

impact and benefit on this new population will not have been included in the  

risk management decision. One can assume the impact would increase  

proportionally, but there are no data to justify such an assumption.  

Owners/operators could be in compliance with the regulation, but could be  

degrading an aquifer by contaminating it with compounds for which MCLs may or  

may not exist. Beneficial uses of groundwater could also be impacted by  

increases of these compounds in the aquifers. Research is needed to address  

these topics as well, not just on the potential for the mobilization of lead and  

arsenic due to the leakage of CO2 into shallow aquifers.  

In addition, drinking water standards are not static and can change as a result  

of new studies. Arsenic is a good example as the MCL was lowered from 50 ppb to  

10 ppb in 2001. GS operations should not be immune from the new requirements  

and should not have their permits grandfathered into compliance without  

adjusting the compliance objectives. Also, lead and copper action levels are  

not health based water quality standards and should not be used as an objective  

or yardstick with which to measure adequacy of remedial measures.  

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

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

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

LBNL’s work does not suggest that leakage of CO2 is likely; in fact it is mentioned in the NODA that the

risk of CO2 leaking from deep storage is low for properly managed GS projects.  

EPA clarifies that the MCLs, MCLGs, and ALs cited in the study were presented in LBNL’s work as a

reference point for comparison purposes. The LBNL study makes no assertion about drinking water

standards. EPA acknowledges that any increase in concentration of metals is undesirable to water

utilities and the final rule requirements were established to maximize protection of USDWs. EPA clarifies

that potential geochemical reactions that may cause mobilization or mineralization are an important

consideration in GS permitting decisions. 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)). 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.

EPA notes the LBNL study did not address the question of increased partial pressures of CO2 dissolved in

water causing corrosion in water distribution systems or plumbing fixtures. However, the dissolved CO2

would likely degas upon withdrawal from the aquifer, making corrosion in distribution systems unlikely.

As noted, other constituents such as iron, manganese, silica, copper, and boron could also be mobilized

and their concentrations in the aquifer water could increase, depending on aquifer mineralogy and

prevailing redox conditions. As with other species that were examined, the extent of mobilization, and

its significance in relation to drinking water quality, would have to be characterized on a site‐specific

basis.  

EPA agrees that temporary hardness could also become an issue in the unlikely case of CO2 intrusion.

However, degassing of the dissolved CO2 would induce the precipitation of carbonates with co‐

precipitation of many of the cited hazardous elements, and could actually decrease their concentrations

to levels lower than present in uncontaminated water. This phenomenon, while theorized, has neither

been modeled nor evaluated experimentally.  

Letter ID: 0369 Comment ID: 27938 Letter Lines: 178 to 214  

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

comment)  

Comment: Ground Water Quality Changes  

The LBNL report on computer model simulations of changes in groundwater changes  

due to CO2 leakage supports AWWA’s position that more research is needed to  

develop a better understanding of the potential impacts of GS projects on USDW.  

In particular, AWWA supports the LBNL recommendation that field research be done  

with "shallow" groundwater sources being used for water supply.  

AWWA notes that the report apparently has not been peer reviewed. We recommend  

that EPA conduct a peer review of both the report and the modeling approach.  

The peer review should be performed by a panel of experts of qualified  

practitioners familiar with groundwater chemistry, fate and transport modeling,  

and drinking water treatment and regulations. This could be accomplished using  
the EPA Science Advisory Board Drinking Water Committee or the National  

Academies of Science as the review panel. At a minimum, the following topics  

should be considered:  

‐ The model simulations involve numerous assumptions that should be verified on  

site specific groundwater supplies. The panel should provide recommendations on  

specific research needs.  

‐Lead dissolution by CO2 is being compared to the action level for lead, which  

is actually applied to the customer tap rather than the source water. The fact  

that CO2 intrusion would make the source water more corrosive could cause non‐  

compliance with the lead and copper rule, even if the lead is below the action  

level.  

‐ LBNL did not evaluate impacts of CO2 leakage on copper mobilization, which  

could be affected by more corrosive water produced by CO2 intrusion. Copper also  

has an action level that applies at the customer tap.  

‐ The LBNL report covers natural analogues of CO2 intrusion into groundwater.  

These analogues suggest that high levels of hardness, iron, manganese, and boron  

could be produced. While these adverse water quality changes would not currently  

come under the definition of endangerment (boron and manganese could be future  

exceptions), they would degrade groundwater quality and limit beneficial use of  

water resources.  

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

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

to provide a foundation for further studies on ground water quality concerns, such as site‐specific

studies including laboratory and field experiments and associated modeling. EPA notes that one field

study has been conducted, while other research work is ongoing or planned. For example, Kharaka et al.

(2009) reports on a field experiment with injection of CO2 into shallow groundwater and water quality

measurements. In addition, the Agency plans, every six years, to collect and review data on GS projects

and research 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.

EPA notes that two scientific manuscripts summarizing LBNL’s study have since been published, both of

which were peer‐reviewed (i.e., Apps et al., 2009; Zheng et al., 2009).  
Letter ID: 0369 Comment ID: 27939 Letter Lines: 216 to 224  

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

Comment: Basin‐Scale Hydrologic Impacts of CO2 Storage  

The recent LBNL modeling studies on basin‐scale carbon dioxide storage cited in  

the NODA indicate that pressure changes could propagate as far away as 124 miles  

(200 kilometers) from the CO2 injection area. This suggests that the area of  

review must be extended over a much larger area than previously anticipated.  

AWWA supports the requirement that basin‐scale hydrologic impacts of CO2 storage  

on reservoir pressure pressures and far‐field pressures be addressed in the GS  

permitting process.  

Individual Response: The final GS rule focuses on permitting of individual GS wells and therefore does

not include requirements for basin‐scale evaluations. However, 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. 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 project. For

additional information regarding EPA’s requirements for AoR delineation and monitoring of GS projects,

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

Letter ID: 0369 Comment ID: 27940 Letter Lines: 226 to 286  

Comment Code: 3220 3.2.2. Comments in Opposition to the Approach  

Comment: WAIVER PROCESS FOR INJECTION ABOVE AND/OR BETWEEN USDWs  

AWWA is in strong opposition to the proposed waiver process for injection above  
and/or between USDWs as it presents too great a risk to USDWs. GS is still an  

emerging technology and EPA should employ caution at this time until more  

experience is gained with pilot studies of deep saline injection zones. Efforts  

to date have focused on containment of supercritical carbon dioxide rather than  

gaseous or liquid forms that might exist at shallower depths. It is unclear how  

owners/operators would be able to demonstrate containment of these plumes.  

Further research is necessary to define suitable management practices.  

AWWA is concerned that a waiver process, as well as the proposed regulation, has  

many limitations that could allow for the degradation of USDWs. Many of the  

requirements are based on faith and not data, and the drinking water community  

and the citizens they serve are being asked to trust that geologic sequestration  

technology will work even though there is very little experience with this  

technology at a large scale. For example, the requirements for determining the  

direction of carbon dioxide plume migration, predicting confining layer  

containment potential, and identifying necessary geo‐chemical monitoring are  

based on modeling exercises, with limited monitoring data to validate these  

models and limited real‐life data to support the requirements. The possibility  

for unintended consequences to occur with geologic sequestration is very real  

and is similar to what was observed with the use of MTBE. MTBE is the fuel  

additive that was meant to solve an air pollution problem but its use resulted  

in unanticipated drinking water pollution problems. Carbon dioxide is an energy  

production/use byproduct that causes air pollution/climate problem but whose  

mitigation (using geologic sequestration) could cause drinking water  

contamination and other (supply) problems. EPA needs to draw on the lessons  

learned from the MTBE situation, and do everything possible to prevent a similar  

situation from occurring with geologic sequestration. Even though MTBE is an  

excellent example, the difference in scale between the possible unintended  

consequences of sequestration and MTBE are huge. Experience gained from deep  

injection wastewater wells in Florida should also be documented and considered.  

AWWA strongly recommends that EPA not move forward with the injection depth  

waiver process. If EPA decides to proceed down this road despite AWWA’s  

negative comments, there are several significant issues that EPA needs to  

consider:  

‐ EPA’s suggested criteria for approving a GS injection depth waiver includes a  

requirement that the owner/operator identify all artificial penetrations in the  

Area of Review that penetrate the injection zone, the upper and lower confining  

zones, and all USDWs in the area. The stated purpose of this demonstration would  

be to ensure that public water supplies, private wells, and potential future  

water resources are identified and the location of artificial penetrations into  
such formations are known and these artificial penetrations can be appropriately  

plugged during the permitting process. Because drinking water wells are  

artificial penetrations, it appears that they would be plugged, making them  

useless for supplying water. If not, it is unclear how the owner/operator can  

demonstrate that the construction of these wells is equivalent to Class VI well  

requirements and thus would not serve as conduits to contaminate USDWs.  

‐ It is unclear that technology has been developed for drilling through  

injection zones containing stored carbon dioxide without releasing some of the  

stored gas. EPA should insist that demonstration of such technologies be  

performed before considering a waiver program.  

‐The risk of damaging water or mineral resources will be greatly increased, and  

there needs to be an adequate mechanism for compensating water utilities and  

other resource owners for remedial actions that must be taken to restore or  

replace beneficial uses.  

Individual Response: EPA agrees that USDW protection is the highest priority; the purpose of the GS

regulation is to ensure that GS, where deployed, is conducted in a manner that protects USDWs.

EPA clarifies that the mission of the UIC Program is to protect USDWs from endangerment. Based on an

evaluation of comments on the proposed injection depth requirements and the waiver process, EPA

believes that there are limited situations where injection into deep non‐USDW formations above the

lowermost USDW can be performed in a manner that protects USDWs. The final GS rule at §146.95

establishes a process by which owners or operators can seek a waiver of the Class VI injection depth

requirements. The rule establishes requirements for extensive site‐specific information that the owner

or operator must submit and the Director must consider, in consultation with PWSS Directors, to ensure

that all USDWs are protected. This information includes a modified AoR evaluation that addresses the

need for confinement above and below the injection formation, the additional impacts of artificial

penetrations, and the location of all the public water supplies affected, reasonably likely to be affected,

or served by USDWs in the AoR. The Agency anticipates that injection depth waivers will be issued in

limited circumstances.

Furthermore, owners or operators granted injection depth waivers are subject to additional

requirements at §146.95(f), including modified construction requirements and requirements to monitor

above and below the injection zone to ensure protection of USDWs underlying and overlying the

injection zone during both well operation and the post‐injection site care period. EPA adds that, for GS

projects where injection depth waivers are sought, the Director must also consider the proposed

emergency and remedial response plan and a demonstration of financial responsibility in making a

determination whether to grant a waiver §146.95(b)(1)(iv).

In an effort to ensure national consistency and application of the requirements, §146.95(d) requires the
Regional Administrator to make the final determination regarding waiver issuance following an

evaluation of all site‐specific information, public notice, and recommendations from the UIC Director.

EPA believes that UIC Program staff are in the appropriate position to evaluate the technical details of

the waiver application, in concert with the UIC permit application, to inform the Regional

Administrator's decision.

EPA disagrees that finalization of the GS rule is premature or is not based on data. EPA believes that the

tailored requirements for GS wells, which are built on a long‐protective UIC regulatory framework and

extensive data gathered from DOE pilot projects, international full‐scale GS projects, and decades of

Class II ER experience, provide appropriate USDW protection. The Agency believes that a proactive

approach is appropriate to ensure USDW protection from endangerment.

EPA notes that technologies exist to inject through over‐pressured formations while maintaining zonal

isolation (e.g., oil and gas industry experience in drilling through shallow pockets of gas or other zones

that have higher pressures). EPA has reviewed information on these types of projects and has

determined that, if properly constructed, wells can be drilled through pressurized zones without causing

fluid movement. However, 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 as specified in §146.95(b)(1)(vii).

For additional information regarding the data on which EPA based the final GS rule and the specific rule

requirements, see the preamble to the final GS rule and technical support documents in the docket for

this rulemaking.  

Letter ID: 0369 Comment ID: 27941 Letter Lines: 265 to 276  

Comment Code: 3320 3.3.2. AoR and Corrective Action  

Comment: ‐ EPA’s suggested criteria for approving a GS injection depth waiver includes a  

requirement that the owner/operator identify all artificial penetrations in the  

Area of Review that penetrate the injection zone, the upper and lower confining  

zones, and all USDWs in the area. The stated purpose of this demonstration would  

be to ensure that public water supplies, private wells, and potential future  

water resources are identified and the location of artificial penetrations into  

such formations are known and these artificial penetrations can be appropriately  

plugged during the permitting process. Because drinking water wells are  

artificial penetrations, it appears that they would be plugged, making them  

useless for supplying water. If not, it is unclear how the owner/operator can  

demonstrate that the construction of these wells is equivalent to Class VI well  
requirements and thus would not serve as conduits to contaminate USDWs.  

Individual Response: EPA clarifies that, while all wells in the AoR must be identified, only improperly

plugged wells that penetrate the confining zone must be plugged per §146.84. EPA expects that most

active drinking water wells would not be completed at depths close to the injection zone for a GS

project. For additional information on corrective action for GS projects, see the preamble to the final

rule and the responses to comments on the proposed GS rule.

EPA adds that 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 corrective action, to ensure that the proposed site is evaluated in the context of the

presence of USDWs above and below the injection zone.  

Letter ID: 0369 Comment ID: 27942 Letter Lines: 278 to 286  

Comment Code: 3300 3.3. Comments on Specific Elements of the Waiver Approach  

Comment: ‐ It is unclear that technology has been developed for drilling through  

injection zones containing stored carbon dioxide without releasing some of the  

stored gas. EPA should insist that demonstration of such technologies be  

performed before considering a waiver program.  

‐The risk of damaging water or mineral resources will be greatly increased, and  

there needs to be an adequate mechanism for compensating water utilities and  

other resource owners for remedial actions that must be taken to restore or  

replace beneficial uses.  

Individual Response: EPA believes that technologies and past experience exist to inject through over‐

pressured formations while maintaining zonal isolation (e.g., oil and gas industry experience in drilling

through shallow pockets of gas or other zones that have higher pressures). EPA has reviewed

information on these types of projects and has determined that, if properly constructed, wells can be

drilled through pressurized zones without causing fluid movement. However, 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).

EPA clarifies that the financial responsibility and emergency and remedial response requirements in the

final GS rule, at §§146.85 and 146.94, are designed to ensure that actions can be taken expeditiously to
address impacts to drinking water supplies and that resources are available to fund those actions. EPA

adds that, for GS projects where injection depth waivers are sought, the Director must also consider the

proposed emergency and remedial response plan, as well as a demonstration of financial responsibility,

in making a determination on whether to grant a waiver per §146.95(b)(1)(iv).  

Letter ID: 0369 Comment ID: 27943 Letter Lines: 288 to 295  

Comment Code: 3350 3.3.5. Requirement to Submit Waiver Application to UIC and PWSS Program

Directors  

Comment: ‐EPA indicates that the "Public Water Supply Supervision (PWSS) Director," in  

conjunction with the UIC Program Director, must review and approve waivers for  

injection depths above the lowest USDW formation. However, EPA does not define  

who the PWSS Director is, but presumably it is the head of the State,  

Territorial, or Tribal Drinking Water Primacy Agency, which may be the EPA  

Regional Administrator (who can also be the UIC Program Director). EPA needs to  

define the position of DWSS Director and determine whether an EPA Regional  

Administrator can fill both roles without a conflict of interest.  

Individual Response: EPA clarifies that the PWSS Director is the person who has charge of the program

administering the PWSS portion of drinking water regulations in any states, Territories, or Tribes within

the AoR of the GS well. The final GS rule includes a requirement that the UIC Program Director consult

with the PWSS Directors of all states, Territories, and Tribes having jurisdiction within the AoR of a well

for which a waiver is sought as specified in §146.95(b)(2). EPA believes this process is necessary and

appropriate to ensure that water system concerns are considered when evaluating a waiver application.

EPA requires that this information be documented to ensure that this consultation will enable

transparent public disclosure of all information evaluated by the Directors and their respective

recommendations. EPA clarifies that the PWSS director does not have "veto power" over a UIC

permitting decision; instead, the role of the PWSS Director is to ensure consideration of water system

and water resource issues where injection into non‐USDW formations above the lowermost USDW is

being considered. EPA believes that UIC Program staff are in the appropriate position to evaluate the

technical details of the waiver application, in concert with the UIC permit application, and the final

requirements retain decision making authority with the UIC Program.  

While EPA disagrees that the EPA Regional Administrator will fill both of these roles, EPA clarifies that

the Regional Administrator will provide written concurrence or non‐concurrence regarding whether to

issue an injection depth waiver per §146.95(d). EPA adds that the final determination regarding waiver

issuance will be made by the Director, following evaluation of all site‐specific information, public notice,

and receipt of written concurrence or non‐concurrence from the Regional Administrator. EPA believes

Agency input is necessary in making injection depth waiver decisions and agrees with commenters who
expressed interest in ensuring that multi‐state boundary and water resource issues are addressed. The

Agency also believes that Agency involvement in the waiver decision process will contribute to national

consistency in waiver issuance.

EPA is 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, and additional considerations

that may apply to projects that have been issued waivers. This guidance will be available on EPA’s

website at water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.  

Letter ID: 0369 Comment ID: 27944 Letter Lines: 297 to 338  

Comment Code: 3230 3.2.3. Comments that Additional Submissions are Needed (seeking comment)  

Comment: If, after reviewing these significant issues, EPA remains committed to further  

developing the waiver process, the following requirements should be mandatory  

for the siting and operation of GS projects that inject CO2 above the lowermost  

USDW:  

1. A GS owner/operator can only apply for the waiver for injection into a  

formation above the lowermost USDW if there is no other option available for  

sequestering CO2. The waiver process should not be available if there are other  

viable formations located below the lowermost USDW. It is not a process for GS  

owner/operators to use to try and reduce project costs by injecting into a  

shallower aquifer. In addition, the GS owner/operator will collect baseline  

water quality data for the potentially impacted USDWs to allow for any  

degradation in water quality to be measured from the baseline conditions that  

exist prior to the injection  

of carbon dioxide.  

2. The carbon dioxide injection well shall be located such that a buffer zone is  

provided between the injection activities and any active or planned drinking  

water wells. The buffer zone shall be large enough as to provide for a minimum  

of ten (10) years of travel time for carbon dioxide, as modeled from the point  

of injection to the drinking water well. In the event of a leakage and/or USDW  

contamination event, this will allow for spatial separation that will provide  

the project owner/operator with enough time to appropriately remediate the  

contamination without adverse impact to the drinking water system.  

3. If injection activities result in the leakage of carbon dioxide into a USDW,  
the GS project owner/operator shall immediately notify operators of drinking  

water wells using that USDW to discontinue using the well if it no longer  

produces safe, wholesome, potable water. Notification shall also be provided to  

the appropriate state and local water and/or public health agencies. The GS  

project owner/operator shall immediately provide an alternative safe drinking  

water supply as approved by the appropriate water and/or public health  

agencies.  

4. Injection above the lower‐most USDW should only be allowed if the full extent  

of the carbon dioxide plume does not completely cover the lateral extents of the  

lower‐most USDW. The GS project, and resulting carbon dioxide plume, should be  

sited in such a way that provides for a minimum of four (4) separate points of  

access (via new drinking water wells) to the USDW without drilling through the  

plume of sequestered CO2 . These four points should be equally spaced around  

the project footprint to allow drinking water utilities unrestricted access to  

those USDWs without worry of leakage of CO2 during well construction.  

Individual Response: EPA agrees that protecting drinking water resources is vital and is the purpose of

the UIC requirements. The waiver approach establishes extensive site‐specific information related to

injecting above or between USDWs that the owner or operator must submit and the Director must

consider, in consultation with PWSS Directors, to ensure that water supplies in the area and all USDWs

are protected. Furthermore, owners or operators granted injection depth waivers are subject to

additional requirements at §146.95(f) ensuring protection of USDWs above and below an injection zone.  

Many of these additional requirements specifically address water resources and the types of

information the commenter suggests. The rule, at §146.95(b) establishes considerations that the UIC

Director must assess when evaluating a waiver application to ensure that USDW protection, site‐specific

drinking water resource issues, and the use and impact of GS technologies are considered and

documented. Considerations that address water resources include: community needs, demands, and

supply from drinking water resources; planned needs, potential and/or future use of USDWs and non‐

USDWs in the area; 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; and a proposed plan for securing alternative resources or

treating USDW formation waters in the event of contamination related to the Class VI injection activity.

Other aspects of the final approach to waivers also address the commenter's concerns. For example,

owners or operators seeking a waiver must demonstrate that the injection zone is bounded by laterally

continuous, impermeable confining units above and below the injection zone adequate to prevent fluid

movement and pressure buildup outside of the injection zone; and, that the confining units are free of

transmissive faults and fractures as specified in §146.95(a)(2). Also, in making a determination whether

to grant a waiver, the Director must consider potential capacity of the geologic formation to sequester
CO2, accounting for the availability of alternative injection sites as specified in §146.95(b)(1)(iii) and all

other site characterization data, the proposed emergency and remedial response plan, and a

demonstration of financial responsibility as specified in §146.95(b)(1)(iv).  

Letter ID: 0369 Comment ID: 27945 Letter Lines: 350 to 362  

Comment Code: 2200 2.2. LBNL Studies  

Comment: In summary, both the LBNL studies on groundwater quality changes and basin‐scale  

hydrologic impacts suggest that additional research is needed to better  

understand the potential effects on USDWs. More research, including experimental  

work with actual groundwater above potential GS sites, is needed to ensure that  

arsenic, lead, and other constituents are not released as the result of the  

final GS rule. The section on lead needs to be re‐evaluated based on the MCLG  

not on the Action Levels. The use of MCLs as the basis for a policy of  

permissible degradation needs to be reexamined. Additionally, AWWA suggests  

that EPA conduct a peer review of the LBNL reports and the modeling approach  

using the Science Advisory Board Drinking Water Committee or the National  

Academy of Science as the review panel. AWWA also supports the requirement that  

basin‐scale hydrologic impacts of CO2 storage on reservoir pressure and far‐  

field pressures be addressed in the GS permitting process.  

Individual Response: EPA clarifies that the GS rule does not specifically require owners or operators to

address basin‐scale hydrologic impacts of CO2 storage on reservoir pressure and far‐field pressures.

However, 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 continues to fund research the effect of GS on USDWs. In December 2009, EPA awarded a STAR

grant to Clemson University to investigate the potential for GS to affect USDWs. The research will

involve laboratory experiments and modeling simulations to investigate the fate of dissolved CO2 in

underground geologic formations and to determine possible risks associated with the dissolution of CO2

in underground aquifers. Other projects funded by the STAR grants include the following: the University
of Illinois‐Urbana will conduct research related to reducing hydrologic and geochemical uncertainties

associated with CO2 sequestration in deep, saline reservoirs; the University of Texas at Austin will assess

appropriate monitoring approaches at geologic sequestration sites; the University of Utah will integrate

design, monitoring, and modeling of GS to assist in developing a practical methodology for

characterizing risks to USDWs; Columbia University will conduct laboratory experiments on shallow

aquifer systems to improve our understanding of geochemical and microbiological reactions under low

ph/high CO2 stress; and Princeton University will develop a set of computational tools to model CO2 and

brine movement associated with GS.

EPA notes that changing the criteria, such as maximum contaminant levels, used by the UIC program to

determine whether a USDW is endangered is outside the scope of this rulemaking.  

EPA also clarifies that it does not have the authority to ask the Science Advisory Board or the National

Academy of Sciences to review the LBNL studies because the studies were not performed by EPA but by

LBNL, a branch of the Department of Energy.  

Letter ID: 0369 Comment ID: 27946 Letter Lines: 364 to 370  

Comment Code: 3220 3.2.2. Comments in Opposition to the Approach  

Comment: Most importantly, AWWA stands by our previously stated positions that injection  

should only be carried out at the pilot phase and only allowed below USDWs. If  

USDW water quality is degraded by a GS project, the owner/operator of that  

project is responsible for any costs borne by drinking water utilities due to  

increased treatment requirements for that ground water or replacement of lost  

capacity in perpetuity. The key words are "in perpetuity and without limit", as  

remediation of that contaminated groundwater would continue in perpetuity.  

Individual Response: EPA acknowledges the commenter's concerns about the permanence of

contamination and the need to protect USDW from endangerment, and clarifies that the mission of the

UIC Program is to protect USDWs from endangerment. EPA clarifies that owners or operators of all GS

projects, regardless of whether they are operating under a waiver, must employ proper site

characterization, construction, operation, testing, monitoring, and post injection site care to ensure that

USDWs are protected. Owners or operators must also develop an emergency and remedial response

plan pursuant to the requirements at §146.94 to address potential USDW contamination and

demonstrate financial responsibility, as required at §146.85 as part of the permit application process.

The purpose of the emergency and remedial response plan and associated financial responsibility

requirements is to explain that an owner or operator has considered regional water resource issues, has

explored alternative water supplies or water treatment options to address unanticipated movement of
the injectate or formation fluids into any overlying or underlying USDWs, and has appropriate resources

to address the need for future response actions to protect USDWs from endangerment.  

Letter ID: 0369 Comment ID: 28578 Letter Lines: 340 to 346  

Comment Code: 3220 3.2.2. Comments in Opposition to the Approach  

Comment: Despite providing the above‐mentioned requirements, it is important to note that  

AWWA remains in strong opposition to the injection depth waiver process and our  

suggestion of these requirements in no way means that AWWA endorses the  

injection depth waiver process. However, we recognize that if EPA does decide to  

move forward on this issue, providing comment in response to the waiver question  

in the NODA is our only opportunity to shape the final regulation for GS using  

Class VI injection wells.  

Individual Response: EPA acknowledges the commenter's concerns about USDW protection and, as

described above, clarifies that the mission of the UIC Program is to protect USDWs from endangerment.

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.  

The waiver approach at §146.95 establishes requirements for extensive site‐specific information related

to injecting above or between USDWs that the owner or operator must submit and the Director must

consider, in consultation with PWSS Directors, to ensure that water supplies in the area and all USDWs

are protected.  

Furthermore, owners or operators granted injection depth waivers are subject to additional

requirements at §146.95(f), which include: modified construction requirements and requirements to

monitor above and below the injection zone in order to ensure protection of USDWs underlying and

overlying the injection zone during both well operation and the post‐injection site care period.