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.
December 24, 2008

U. S. Environmental Protection Agency

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

Office of Groundwater and Drinking Water (OGWDW)

Mail Code: 2822T

1200 Pennsylvania Ave. NW

Washington, DC 20460

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

for Carbon Dioxide Geosequestration Wells, Proposed Rule 

Dear Docket:

Enclosed are the comments of the American Water Works Association (AWWA) on the 

proposed requirements for carbon dioxide geosequestration wells under the Underground 

Injection Control (UIC) Program as published in the July 25st Federal Register (73 FR 43491). 

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

geologic carbon sequestration regulation developed as part of the Underground Injection Control 

(UIC) Program. AWWA appreciates the opportunity to comment on this proposed regulation, 

and we have several significant comments that we feel should be addressed in the final 

regulation. 

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

in our Washington Office. 

Yours Sincerely,

Chapter 5.

Thomas W. Curtis

Deputy Executive Director 

cc: Ben Grumbles – USEPA OW

Cynthia Dougherty – USEPA OGWDW

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 60

EXECUTIVE SUMMARY OF COMMENTS BY THE 

AMERICAN WATER WORKS ASSOCIATION 

ON THE PROPOSED FEDERAL REQUIREMENTS FOR 

CARBON DIXOIDE GEOLOGIC SEQUESTRATION (GS) WELLS

The American Water Works Association (AWWA) is providing detailed comments on the proposed 

requirements for GS wells as published in the July 25th, 2008 Federal Register (73 FR 43491). The 

following six central issues are addressed in more detail in our comments:

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

water should trump everything!

 Prevention of unintended consequences is of utmost importance;

 Injection of carbon dioxide and construction of injection wells should not be allowed in or near 

sole source aquifers, coal seams, earth-quake prone areas, or above the lowermost USDWs; 

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

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

responsible for any costs born by drinking water utilities due to increased treatment 

requirements for that ground water or replacement of lost capacity; and,

 The 10,000 mg/l TDS limit for classifying USDWs for the siting of Class VI wells needs to be 

revised upward. 

In its comments, AWWA makes several recommendations for the following specific items to be 

included in the final regulation:

 Requirement to consult with the state environmental department and affected water utilities to 

determine which aquifers currently not classified as USDWs might be considered as future 

drinking water sources;

 Definition of “endangerment” that includes water quality impacts beyond those contaminants 

with MCLs;

 Addressing liability, treatment costs for remediation, and financial recourse for a water utility if 

a USDW is degraded due to a GS project;

 Requirement for owner/operators of grandfathered wells to certify that the wells were 

constructed and cemented with materials appropriate for GS wells;

 Development of a standard computation flow model to delineate the area of review;

 Reevaluation of the area of review annually for the first ten years, and then every five years for 

the remaining life of the project;

 A permit process for geologic sequestration (separate from the coal plant), with required 

monthly reporting similar to the NPDES permit/reporting process;

 Inclusion of detailed monitoring requirements in the final regulation;

 Requirement for formal technical, managerial, and financial plans for GS owners/operators; and 

 Requirement for mandatory public notification and public hearings for any new permit and any 

permit revision or renewal, and for a 90-day public comment period

Several issues need more research by EPA and DOE, and the following research needs to be 

completed prior to issuance of the final regulation:

 Criteria for the determination that the carbon dioxide plume has stabilized;

 The potential for seismic shifts due to subsurface pressure changes;

 The minimum concentration of carbon dioxide in the injection stream; and

 The types of tracers that would be acceptable for GS.
Page 3 of 60

INTRODUCTION

The American Water Works Association (AWWA) is an international, nonprofit, scientific and 

educational society dedicated to the improvement of drinking water quality and supply. Founded

in 1881, the Association is the largest organization of water supply professionals in the world. 

Our 60,000 plus members represent the full spectrum of the drinking water community: 

treatment plant operators and managers, environmental advocates, engineers, scientists,

academicians, and others who hold a genuine interest in water supply and public health. Our

membership includes more than 4,700 utilities that supply roughly 80 percent of the nation's

drinking water.

AWWA appreciates the opportunity to comment on the proposed requirements for geologic 

sequestration wells as published in the July 25th, 2008 Federal Register (73 FR 43491). 

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

geologic carbon sequestration regulation developed as part of the Underground Injection Control 

(UIC) Program. 

AWWA has developed detailed comments on the proposed regulation. These comments 

presented in the following document, and are organized into the following four sections:

 Section 1: General comments on the proposed geologic sequestration regulation

 Section 2: Responses to EPA’s specific requests for comments as provided in the 

preamble to the proposed regulation

 Section 3: Monitoring guidelines for geologic carbon sequestration projects 

 Section 4: Comments on specific parts of the proposed regulation text
Page 4 of 60

I. GENERAL COMMENTS

In 2007, approximately 78% of 52,000 community water systems in the United States were 

supplied by groundwater and these systems served 90.5 million people. In addition, many 

surface water utilities are currently looking at conjunctive use and/or groundwater development 

as adaptation measures (supply portfolio diversification/new storage) to combat climate change. 

Each of these utilities could potentially be impacted by geologic carbon sequestration, simply by 

the fact that these utilities utilize groundwater resources. 

The proposed regulation is a good technical starting point given the evolving state of geologic 

sequestration; however, the proposed rule has many limitations that could allow for the 

endangerment of underground sources of drinking water (USDWs). Many of the requirements 

are based on faith, and not a lot of data, and the drinking water community is being asked trust 

that geologic sequestration technology will work even though there is very little experience with 

this technology on 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. 

There is the possibility for unintended consequences to occur with geologic sequestration is very 

real, 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. Prevention is the key word here. AWWA will address 

these issues, as well as some other important concerns, in this section of general comments. 

USDW Classification: The best sources of drinking water are already being used by utilities. 

In many areas, population growth is forcing utilities to look further or to look at more 

challenging sources. 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. Additionally, the pumping costs for these deep wells are no longer 

prohibitive given the lack of sufficient water sources. 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 proposed rule promises protection of USDWs from endangerment, in that 

the activity does not cause a primary drinking water Maximum Contaminant Level (MCL) to be 

exceeded in an USDW or affect human health. There are no anti-degradation provisions in the 

proposed regulation to protect other groundwater supplies, such as those aquifers that are not 

classified as a USDW but have been, or may be, identified as a future drinking water source. 

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.
Page 5 of 60

Technological advances in the area of desalination have reduced many of the treatment costs,

making it more and more accessible. Many utilities have no other choice for new water sources. 

Ever increasing population and water demands have utilities using non-traditional and poorer 

water sources (see Table 1-1 for examples; note that this is not meant to be a comprehensive list 

of all desalination plants in the United States).

Table 1-1: 

Water Utilities with More Challenging Water Sources

Utility Name Water Source Usage TDS Concentrations

El Paso Water Utilities and Ft. 

Bliss, Texas Hueco Bolson Basin 27.5 mgd 600 to 4,900 mg/l

Tampa Bay Water, Florida Seawater 25 mgd 18,000 – 32,000 mg/L

Yuma Desalting Plant, 

Arizona Drainage water 22 mgd 3,200 mg/L

Miami-Dade County, Florida Florida Aquifer 17.5 mgd (currently 

under design) 1,000 – 5,000 mg/L

Temescal Desalter Project, 

California Temescal Basin 15 mgd 700 mg/L

City of Abilene, Texas Surface water 8.0 mgd 1,200 mg/L

City of Sherman, Texas Surface water 7.5 mgd 900 – 1500 mg/L

Southmost Regional Water 

Authority, Texas Groundwater 6.75 mgd 3,500 mg/L

Lake Granbury SWATS, 

Texas Surface water 6.0 mgd 1,800 mg/L

City of Fort Stockton, Texas Groundwater 6.0 mgd 1485 mg/L

Newport News WTP, Virginia Lower and Middle Potomac 

Aquifers 5.7 mgd 3600 mg/L

Alameda County Water 

District, California

Niles Cone Groundwater 

Basin

5.0 mgd with 

expansion to 10 mgd 1,100 – 2,400 mg/L

Pascagoula, Mississippi Groundwater 4.5 mgd 1,000 mg/L

Dare County North WTP, 

North Carolina Groundwater 3.0 mgd 4,300 mg/L

Port Hueneme Brackish Water 

Facility, California Groundwater 3.0 mgd 1,300 mg/L

James City Service Authority, 

Virginia

Middle and Lower Potomac

Aquifers 2.5 mgd 1,000 – 2,400 mg/L

Buxton, North Carolina Groundwater 2.0 mgd 13,200 mg/L

Cape May, New Jersey Groundwater 2.0 mgd 2,100 mg/L

Dare County Cape Hatteras

WP, North Carolina Groundwater 2.0 mgd 11,200 mg/L

Las Animas, Colorado Groundwater 1.18 mgd 3,500 mg/L

VA Medical Center, Ft. Lyon, 

Colorado Groundwater 0.24 mgd 800 mg/L

The use of very deep and/or high salinity groundwater becoming more commonplace is only a 

matter of time. Therefore, we believe the 10,000 mg/L TDS USDW definition is no longer 

appropriate. Given that this regulation does not currently extend protection to non-traditional 

and poorer water sources, AWWA believes that these aquifers may be adversely impacted by 

this rulemaking. These aquifers, which have not been previously used as a drinking water 

source, may be in the future, and it is important to make sure that they are adequately protected. 

AWWA recommends that EPA consider the “green-effect” and that, in many cases, the overall 
Page 6 of 60

least cost alternative may be to treat brackish groundwater using desalination technology instead 

of trying to obtain surface water as the drinking water source. While the surface water may be 

less expensive to treat, if the utility is located in a dry environment, such as Arizona or New 

Mexico, the pumping costs to transport that water over a large distance may be much larger than 

the cost to treat a brackish groundwater. EPA should also consider that as technology evolves, 

utilities will be able to treat a much different set of waters than is currently being treated. 

Several utilities are using sea water or brackish water as drinking water sources, which would not 

have been even remotely considered as a viable option 20 years ago, when the TDS limit was 

originally developed.

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

SDWA, AWWA recommends that the regulation be revised to mandate that, during the project 

planning process, the owner/operators should include state environmental departments as they 

can provide insight into what aquifers currently (not 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 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.

USDW Endangerment: AWWA recommends revision to the definition of “endangerment” in 

the proposed rule. The current definition of endangerment is limited to SDWA UIC definition of 

10,000 TDS and to primary MCL contamination. Certain health-effects can be related to 

concentrations in water of compounds that do not exceed the primary MCL. However, under the 

current language, these potential contaminants would not be covered with the protections 

afforded by the SDWA. 

EPA should also consider the risk associated with the potential exposure of any contaminants 

that are released to the surface. While we recognize that a gradual leak may have little impact, 

the potential of a catastrophic leak is always present. EPA should be mindful during the rulemaking process of not only the risk to drinking water, but also of other potential risks from 

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

These are compound for which no MCLs have been developed but still impact drinking water 

quality and increase the necessary treatment costs. There could be potential health impacts due 

to long-term exposure to contaminant levels below the established MCLs. Also, beneficial uses 

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

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

by contaminating it with compounds for which MCLs do not exist. 

Assignment of Liability: Most importantly, the regulation does not seem to address the liability 

that would be realized by owners/operators of the geologic sequestration projects if water quality 

of USDWs is degraded by the operation of their project (even if the impacts are limited to 

MCLs). AWWA recommends that this issue be addressed in the final regulation, as drinking 

water utilities may have little financial recourse if the water quality one of their aquifers is 

degraded due to the operation of a geologic sequestration process. Provisions need to be 

included in the final rule that would allow the drinking water utility to recoup any costs that are 

realized due to increased treatment requirements for contaminated ground water or to replace lost 
Page 7 of 60

capacity. In some cases, utilities may need to install different types of treatment to remove 

compounds that might not have been present in the water prior to the geologic sequestration 

project. In other instances, treatment may consist of the addition of more chemicals to facilitate 

precipitation of the inorganic compounds or the utility may have to backwash membranes more 

often, resulting in higher energy and other operation and maintenance costs. In any of these 

cases, the owner/operator of the geologic sequestration project should be required to reimburse 

the drinking water utility for these incurred costs, and they should also be required to continue 

such payments for as long as the ground water source remains degraded.

Water utilities should not be penalized for having to develop local sites contaminated by 

sequestration activities for water supply. In fact they should be encouraged to do so, under the 

appropriate conditions, as there is no more critical public health issue than the need to provide 

potable water. In order to meet increasing demands imposed on them by a growing service 

population, water utilities will need to develop marginal water supplies. However, increased 

treatment costs due to contamination resulting from sequestration activities should not be borne 

by the local utility or their customers when national environmental objectives have been met 

without significant benefit to the local economy. 

Should a water utility “lose” an existing or future source of supply due to contamination or 

inaccessibility resulting from a sequestration project, there will be the issue of financial 

compensation (for treatment or development of an alternative source). As water resources 

become scarce, financial compensation for a lost source of supply may not suffice, as local 

alternatives may not be available. Hence, it will be critical that contingency planning to identify 

alternatives to the current groundwater supply be a part of the planning activities for the 

sequestration project, along with a commitment to provide an alternative source of water, should 

the need arise. 

AWWA also recommends that the company generating the carbon dioxide must maintain sole 

ownership of the carbon dioxide they generate. This would ensure that liability remains with the 

original generator in perpetuity; even if the carbon dioxide is commingled with some generated 

from another facility or if its disposal is managed by another company.

Trespass and Aquifer Displacement: AWWA recommends that the potential for trespass be 

addressed in the final rule. Carbon dioxide plumes may migrate into a location that a drinking 

water utility was planning to utilize, possibly for aquifer storage and recovery. What recourse is

provided by the proposed regulation in the event that trespass occurs, and damages are realized 

by the drinking water utility? Also, movement of the pressure front associated with a carbon 

dioxide plume may cause aquifers to shift in location, potentially moving them out of the 

jurisdiction of their original utility “owner.” This can be a serious problem in certain portions of 

the country where ground water resources are limited or conflict, and utilities face intense 

competition for water rights. AWWA questions if an appropriate recourse will be provided by 

the sequestration project owner/operator in the event that these water rights issues become a 

reality for the drinking water utility. 

Safe Drinking Water Act Authority: In its February 2008 stakeholders meeting, EPA seemed 

to imply that it was restricted in what it could regulate and/or require under the SDWA for UIC 
Page 8 of 60

projects to preventing “endangerment of USDW.” AWWA recognizes that EPA’s regulatory 

authority is limited by the requirements of the SDWA and will be advocating that several 

portions of the SDWA be amended to better protect the nation’s groundwater resources. Issues 

that we will be addressing include:

1. The definition of a USDW is provided within the SDWA, which may require 

amendment if the quality and accessibility groundwater sources is to be protected. 

We recognize that the 10,000 mg/L TDS limit is very outdated, and that a new 

upper limit should be established and applied when siting Class VI wells. We 

hesitate to recommend any specific number at this point in time, given that some 

drinking water utilities are so stressed for water resources that they are 

investigating extremely non-traditional water sources with high TDS levels.

2. Endangerment is defined by the SDWA and may need to be redefined to protect 

beneficial uses. The proposed rule seems to be focused on preventing brine from 

the carbon dioxide storage formations from reaching USDWs and/or preventing 

carbon dioxide from contaminating USDWs and causing exceedences of primary 

MCLs. The protective measures of the proposed rule may not be adequate from a 

source water and beneficial use protection standpoint as other changes are likely 

to occur besides exceeding primary MCLs (e.g., increased Fe/Mn, TDS, and 

lowered pH – all of which have secondary MCLs and possible increase in silica 

and boron, which do not have MCLs, but have water quality significance). EPA 

needs to be provided with the regulatory authority to protect against these other 

types of endangerment, and the SDWA should be modified to allow for these 

protective measures to be developed.

AWWA recommends that EPA not ignore the potential impacts outside of the scope of the 

SDWA such as those to air and human health if there is a massive leak. Could there be any 

conflicts or overlaps with the Clean Air Act or the Clean Water Act? Are other Program Offices 

within EPA planning on looking at this proposal? This review by other EPA Program Offices 

would seem to be necessary given the potential impacts that could arise if there is a failure of the 

confining layer.

Sole Source Aquifers: Several areas of the country rely on sole source aquifers as their drinking 

water resource. Given the special protective measures already afforded to these aquifers by 

EPA, AWWA strongly recommends that the final geologic sequestration regulation should

restrict project activities in the vicinity of these aquifers. Table 1-2 below presents a list of some 

of the sole-source aquifers that are located in potential geologic sequestration areas. (Note that 

this is not meant to be a comprehensive list of all of the sole source aquifers in the United 

States.)
Page 9 of 60

Table 1-2: 

Sole-Source Aquifers in Potential Geologic Sequestration Areas

Aquifer Name Location Potentially Impacted Characteristics

Upper Santa Cruz & Avra Basin 

Aquifer Arizona Tucson, Green Valley, Catalina Discharges 376,000 

acre-feet per year

Fresno County Aquifer California Fresno, Clovis Contains 5.8 million 

acre feet of water

Volusia Sole Source Aquifer Florida Ormond Beach, Daytona Beach, New 

Smyrna Beach and Deland Covers 1,450 sq. mi.

Biscayne Sole Source Aquifer Florida All of Dade County; parts of Broward, 

Monroe and Palm Beach Counties Covers 4,000 sq. mi.

Eastern Snake River Plain 

Aquifer Idaho 300,000 residents of Eastern Idaho Contains 200 to 300 

million acre-feet

Spokane Valley-Rathdrum 

Prairie Aquifer

Idaho, 

Washington

700,000 residents of Idaho and 

Washington Covers 325 sq. mi.

Chicot Aquifer System Louisiana Lafayette, Lake Charles, Crowley Supplies 800 mgd, 

most for irrigation

Southern Hills Aquifer System Louisiana, 

Mississippi Baton Rouge, Natchez, McComb Supplies 290 million 

gallons per day

New Jersey Coastal Plain 

Aquifer System New Jersey Over 3,000,000 residents Over 350 million gal. withdrawn per day

Northwest New Jersey Fifteen 

Basin Aquifer

New Jersey, 

New York Over 500,000 residents Covers 1,735 square 

mile area

Espanola Basin Aquifer System New Mexico Sante Fe, Los Alamos, and Española Covers 3,000 sq. mi.

Clinton Street Ballpark Aquifer 

System New York Broome and Tioga Counties 16.25 mgd withdrawn 

for drinking water 

Miami Valley Buried Aquifer Ohio Serves over 1,600,000 residents Provides 200 mgd for 

drinking water

Edwards Aquifer Texas San Antonia, San Marcos, New 

Branfels

Discharges 900,000 

acre-feet per year

Columbia and YorktownEastover Multiaquifer Virginia Exmore, Olney, Chincoteague Covers 695 sq. mi.

AWWA recommends that EPA prohibit owner/operators from constructing carbon dioxide

injection wells in sole source aquifers. Owner/operators should also be prohibited from ever 

injecting carbon dioxide into a formation that would result in the migration of the carbon dioxide 

to a point that is under a sole source aquifer. EPA should establish a minimum distance that 

needs to be provided between the closest geologic sequestration project and the location of any 

sole source aquifers. AWWA would recommend a 50 mile minimum; however, not being 

experts on the details of plume migration, AWWA recommends that EPA and DOE perform 

research on this topic to better assess what the regulatory requirement should be. Including these 

restrictions in the final geologic sequestration regulation would allow for the protection of 

drinking water aquifers that, if contaminated by carbon dioxide, could result in very significant 

and expensive issues for the drinking water utilities. 

Water versus Energy: AWWA questions how will geologic sequestration projects will be 

permitted if there is potential competition for a specific geologic basin between an energy 

company and a drinking water utility. Water should trump everything. The water sector should 

be given priority, especially if a drinking water utility has limited or no other options, as they 

have very limited water and storage resources. It may also be possible that there may not be a
Page 10 of 60

single federal and/or state oversight agency that could provide guidance in this arena as the 

agency would need to have oversight for air, water, environmental, energy, and other sectors. 

The NEPA process and the state equivalent, such as CEQA in California, will need to be well 

fleshed out at the outset of the permitting process.

Seismicity: The seismicity requirements in the Area of Review requirements are not very 

prescriptive. AWWA believes there is too much latitude for interpretation and that the 

regulation could be applied inconsistently by Directors of different states. AWWA recommends

making the language stronger to clarify exactly what is meant by the following requirement 

(§146.82(d)(3)): “...information on seismic history including the presence and depth of seismic 

sources and a determination that the seismicity would not interfere with containment.” A 

geologic sequestration project should be evaluated on the entire risk spectrum using different 

ranges of seismic activity and distance requirements from active faults to determine if the 

proposed site is acceptable. EPA should develop guidance that will assist owner/operators in 

making the appropriate determinations regarding seismic risk for a geologic sequestration 

project. For example, is there a minimum distance that should be provided between the potential 

plume footprint and an area of seismic activity? This information is critical as different 

owner/operators could decide to take on a different level of risk due to their comfort with the 

financial implications. AWWA does not want to see USDW protection compromised due to 

faulty assumptions about seismic activity in and around a potential project site.

AWWA recommends that EPA also investigate the need for modeling the potential for seismic

shifts due to the changes in subsurface pressures associated with the carbon dioxide injection 

process. A literature search should be performed to see if either Laurence Berkley National 

Laboratory or the National Energy Technology Laboratory has developed any information on 

this topic.

Project Security: AWWA recommends that EPA work with the Department of Transportation 

and the Department of Homeland Security to ensure the safety and security of geologic 

sequestration projects. We have concerns about the unintentional or intentional release of stored 

carbon dioxide and the related control and monitoring systems required, as well as security 

measures. A requirement for strict monitoring systems during project construction and operation 

is necessary to ensure that the project is not intentionally sabotaged, as this could result in a 

massive leak of carbon dioxide out of the confinement zone and into the environment. EPA 

should mandate strict monitoring systems be included as part of any geologic sequestration 

project, not only to ensure the safety of USDWs, but also the safety of those living in the 

footprint of the project. 

Data and Research Needs: AWWA believes that stakeholder access to the necessary data is 

lacking and will inhibit making informed/transparent decisions on geologic carbon sequestration 

projects. Stakeholders need better and more accessible data and data reduction tools (i.e., GIS 

maps). EPA should consider creating an interactive web based data warehouse that would store 

data and GIS layers on large carbon dioxide emitters, drinking water groundwater basins, 

seismic/volcanic/geothermal zones, proposed carbon dioxide saline injection basins, etc. and 

provide the ability to overlay layers. Stakeholders would then have improved abilities to 
Page 11 of 60

evaluate a proposed geologic sequestration project to determine if they would be impacted by the 

carbon dioxide plume and/or associated pressure front. 

AWWA also recommends that EPA review the following reports that address the potential costs 

of treating source water that has lowered pH levels and/or increased concentrations of iron, 

minerals and other potential contaminants.

 AWWA projects:

o Managing Change and Unintended Consequences: Lead and Copper Rule Corrosion 

Control Treatment (WITAF)

o Regulatory Risk Assessment for Arsenic in Water (WITAF)

o Technology and Cost Review of the Proposed Arsenic Regulation (WITAF)

 AwwaRF projects:

o Adsorbent Treatment Technologies for Arsenic Removal (#2731)

o Demonstration of Emerging Technologies for Arsenic Removal (#2661)

o Implementation of Arsenic Treatment Systems Part 2: Design Considerations, 

Operation, and Maintenance (#2665)

o Arsenic Removal by Iron-Modified Activated Carbon (#3158)

o Subsurface Treatment For Arsenic Removal--Phases I and II (#3082)

o Characterization and Performance of Filter Media for Manganese Control (#2951)

o Occurrence of Manganese in Drinking Water and Manganese Control (#2863)

o Advanced Processes for Simultaneous Arsenic and Manganese Removal (#2748)

o Occurrence Survey of Boron and Hexavalent Chromium (#2759)

o Integrated Water Treatment: Softening and Ultrafiltration (#2647)

o Enhanced Reverse Osmosis Systems: Intermediate Treatment to Improve Recovery 

(#4061)

o Membrane Treatment Of Impaired Irrigation Return (#4069)

o Zero Liquid Discharge Desalination of Waters with High Organic Content (#4163)

o Zero Liquid Discharge for Inland Desalination (#3010)

o Comparison of Zinc vs Non-Zinc Corrosion Control for Lead and Copper (#4103)

o Effect of Nitrification on Corrosion in the Distribution System (#4015

The lack of good background data and inappropriate oil and gas well closures reflect inadequate 

regulatory oversight that can only get worse as regulatory agencies are asked to take on more 

activities related to climate change. Climate change adaptation and mitigation measures, such as 

geologic sequestration, may be delayed due to inadequate regulatory agency resources (e.g., 

number of staff and expertise). EPA needs to support significant research to reduce the 

uncertainties associated with climate change and afford better long-term planning decisions as 

water utilities and their customers are likely to feel a disproportionate impact due to anticipated 

adaptation and mitigation activities. EPA should also work in concert with other federal 

agencies to spur research into technologies that can convert carbon dioxide into inert or 

innocuous products.
Page 12 of 60

II. RESPONSES TO EPA’S SPECIFIC REQUESTS FOR COMMENT

In this section, we have grouped all of the specific requests for comment provided in the 

preamble of the proposed regulation into different categories. This allows for AWWA to 

provide to certain groupings in whole, instead of addressing each request for comment 

individually. 

Category: USDW Location

EPA Request for Comment: EPA is proposing to preclude the injection of CO2 for long-term 

storage into coal seams where they are above the lowermost USDW. EPA requests comment on 

this proposed prohibition. EPA Notice 43503.

AWWA Response: AWWA recommends that EPA preclude the injection of carbon dioxide into 

coal seams located above the lowermost USDWs. First and foremost, AWWA is adamantly 

opposed to the injection of carbon dioxide into any storage formation not located beneath the 

lowermost USDW. If a utility ever desired to use the USDW as a water resource, they would 

have to drill through the carbon dioxide plume, thus creating a pathway for carbon dioxide to 

potentially migrate out of the confining layer and into nearby aquifers. This could cause 

contamination of USDWs located above the coal seam, and result in significant remediation 

activities for a water utility. Second, little research has been conducted to determine the specific 

impacts that storage of carbon dioxide would have on coal seams. Much of the research that has 

been performed to date has been on either carbon dioxide storage in saline reservoirs or in 

depleted oil/gas fields. AWWA recommends that at this point in time, EPA preclude the 

injection of carbon dioxide into all coal seams, no matter where they are located in the 

subsurface. This regulation was not designed for coal seams to be used as carbon dioxide 

storage reservoirs. Therefore, AWWA recommends that any wells constructed for the injection 

of carbon dioxide into coal seams wells be permitted under the Class V experimental wells until 

the potential impacts of coal seam carbon dioxide sequestration on USDWs are better 

understood.

EPA Request for Comment: EPA is soliciting comment on whether CO2 injection should be 

allowed into an injection zone above the lowermost USDW, when the Director determines that 

geologic conditions (e.g., thousands of feet of intervening formations between the injection zone 

and the overlying and/or underlying USDWs) exist that will prevent fluid movement into 

adjacent USDWs. EPA Notice 43512.

AWWA Response: As previously stated, AWWA is adamantly opposed to the injection of 

carbon dioxide into any storage formation not located beneath the lowermost USDW. If a utility 

ever desired to use the lowermost USDW as a water resource, they would have to drill through 

the carbon dioxide plume, thus creating a pathway for carbon dioxide to potentially migrate out 

of the confining layer and into nearby aquifers. This could cause contamination of USDWs 

located above the storage aquifer, and result in significant remediation activities for a water 

utility. AWWA recommends that EPA include a section in the final regulation prohibiting the 

injection of carbon dioxide into any formation located above the lowermost USDW.
Page 13 of 60

EPA Request for Comment: EPA specifically seeks comment on the merits of requiring the 

identification of additional confining and containment zones above the primary (i.e., lowermost) 

confining zone that could further impede vertical fluid movement and allow for pressure 

dissipation. EPA Notice 43506.

AWWA Response: AWWA recommends that EPA require owner/operators to identify these 

additional confining and containment zones as part of the site characterization process. This 

identification is important to understand the project as a whole, and failing to identify these 

additional zones results in a very large knowledge gap in the identification of potential mitigation 

options in the event that a leak occurs from the primary confining layer. Having this information 

available to regulators and stakeholders would allow for a better understanding of the project as a 

whole, and would provide for a more informed and comprehensive review process. If certain 

stakeholders, such as drinking water utilities, were provided with this information, utilities would 

have a better understanding of a geologic sequestration project with the knowledge that multiple 

confining layers separated the carbon dioxide injection zone from their USDWs. 

EPA Request for Comment: EPA is also requesting comments on whether aquifer exemptions 

should be allowed for the purpose of Class VI injection, and under what conditions should such 

aquifer exemptions be approved. EPA Notice 43512.

AWWA Response: AWWA does not support aquifer exemptions for the purposes of Class VI

injection projects. Water resources are becoming extremely limited in many parts of the country 

and many drinking water utilities will be turning to alternative supply sources, including brackish 

and saline groundwater, as well as deeper USDWs. 40 CFR 146.4 states that:

“An aquifer or a portion thereof which meets the criteria for an underground source of drinking 

water...may be determined...to be an exempted aquifer if it meets the following criteria: (a) It 

does not currently serve as a source of drinking water; and (b) It cannot now and will not in the 

future serve as a source of drinking water because: (1) It is mineral, hydrocarbon or geothermal 

energy producing, or can be demonstrated by a permit applicant as part of a permit application 

for a Class II or III operation to contain minerals or hydrocarbons that considering their quantity 

and location are expected to be commercially producible, (2) It is situated at a depth or location 

which makes recovery of water for drinking water purposes economically or technologically 

impractical; (3) It is so contaminated that it would be economically or technologically 

impractical to render that water fit for human consumption; or (4) It is located over a Class III 

well mining area subject to subsidence or catastrophic collapse; or (c) The total dissolved solids 

content of the ground water is more than 3,000 and less than 10,000 mg/l and it is not reasonably 

expected to supply a public water system.”

As previously stated, many drinking water utilities are exploring ground water resources that 

might not have been previously feasible to access or treat. The underlined portions of the aquifer 

exemption regulations are problematic as ground water resources that fit these definitions are 

now being tapped, given that much of the easily accessible and/or treatable ground water has 

already been utilized or allocated. By allowing for aquifer exemptions in these cases, EPA is 

precluding their use as a future USDW at a time when the country’s remaining ground water 
Page 14 of 60

resources should be aggressively protected. Therefore, AWWA recommends that EPA not allow 

aquifer exemptions for the purposes of Class VI injection.

EPA Request for Comment: EPA seeks comment on whether the Agency should set a minimum 

injection depth requirement for CO2 GS, rather than require that such injection take place below 

the lowermost USDW. EPA Notice 43512.

AWWA Response: EPA should consider setting a minimum injection depth for geologic carbon 

sequestration as well as requiring that the injection take place below either the lowermost USDW 

or the lowermost aquifer that would be used as a drinking water source. AWWA believes this is 

necessary to ensure that carbon dioxide injected in the supercritical phase remains as such. The 

IPCC Special Report on Carbon Dioxide Capture and Storage suggested that carbon dioxide 

should be sequestered depths of at least 800 to 1,000 meters because at these depths, supercritical 

carbon dioxide has a liquid-like density that provides the potential for efficient utilization of 

underground storage space in the pores of sedimentary rocks. Providing for a minimum depth 

for carbon dioxide injection would strengthen the protective measures for USDWs. However, it 

is important to note that the minimum injection depth should be coupled with the provision that 

carbon dioxide must be injected below either the lowermost USDW or the lowermost aquifer that 

could be used as a drinking water source. 

Category: Grandfathering Wells/ Enhanced Oil Recovery Wells

EPA Request for Comment: Injection of CO2 for the purposes of enhanced oil and gas recovery 

(EOR/EGR), as long as any production is occurring, will continue to be permitted under the 

Class II program. EPA seeks comment on the merits of this approach since owners or operators 

of some Class II EOR/EGR wells may wish to use wells for the purposes of production and GS 

prior to the field being completely depleted. EPA Notice 43502.

AWWA Response: AWWA agrees with this approach and supports the continued operation of 

Class II wells for EOR/EGR as long as they are still producing. However, AWWA recommends

that an economic test for oil and gas reservoir “depletion” be used to determine when the Class II 

well should be transitioned to Class VI, and then operated under the Class VI conditions. One 

suggestion for determining when the reservoir has been depleted is to determine what the lowest 

physical amount of production would be. When oil or gas production reaches this point, the 

owner or operator would be required to plug the production wells and begin the application 

process for converting the remaining injection wells to Class VI wells. EPA needs to monitor 

the operation of existing Class II wells to ensure that they are not being operated as carbon 

sequestration projects, as there are significant differences in the permitting and operation of these 

two classes. Companies will try to bypass some of the Class VI construction requirements by 

designing and operating the system as an EOR/EGR project for a few years, and then converting 

it to a geologic sequestration system. 

EPA Request for Comment: EPA seeks comment on the approach to grandfather construction 

requirements at the Director’s discretion for existing Class I, Class II, and Class V wells seeking 

to convert to Class VI wells, and whether additional construction requirements would be 

necessary to prevent endangerment to USDWs from the GS of CO2. EPA Notice 43502.
Page 15 of 60

AWWA Response: The construction requirements for the other well classes may not be as 

stringent as the requirements for Class VI wells. AWWA recommends that in order for wells 

from the other classes to be used for the injection of carbon dioxide, the wells must have been 

constructed using methods that are at least or more stringent than the Class VI requirements. 

Otherwise, as stated previously, it may encourage companies to construct an EOR well under the 

less strict Class II rules, with the goal of running the operation for a few years and then 

converting to a carbon sequestration operation. 

Certain operating methods for Class II wells may result in conditions that would be unacceptable 

for geologic sequestration. For example, EOR wells that used saltwater may be deteriorated to a 

point that would not be acceptable for the injection of carbon dioxide for geologic sequestration. 

In this case, these wells may have been constructed using different methods and materials that 

are not compatible with carbon dioxide. AWWA recommends that the owner/operators are 

required to prove that the grandfathered wells were constructed using corrosion resistant 

materials, and were cemented along the casing in accordance with the Class VI requirements. 

The well should be inspected to determine if any interior or exterior corrosion had occurred, and 

if so, there should be a determination that the well is not acceptable for use as a Class VI well. 

The review process should also include long-term demonstration by the owner/operator of the

performance of the well as a Class II well. This review could provide an indication of continued 

prevention of USDW contamination. While these are fairly strict requirements, following this 

process is essential to prevent the contamination of USDWs or other source water aquifers. This 

should be the ultimate goal of the grandfathering process, not the prevention of additional 

construction costs for the owner/operator.

EPA Request for Comment: Additionally, EPA seeks comment on how the grandfathering 

approach for existing wells may affect compliance with the other requirements in its proposal. 

EPA Notice 43502.

AWWA Response: Grandfathered wells may not have some of the protective measures that are 

required in the proposed regulation, such as the down-hole shut-off valve. This valve is an 

important safety mechanism and AWWA believes that a Class VI well should not be permitted 

for carbon sequestration unless it is constructed with this appurtenance. Also, some of the

potentially grandfathered wells may not be constructed in a way that would allow for the 

mechanical integrity testing requirements that are part of the regulation. AWWA believes that

some of the very prescriptive testing and monitoring requirements are necessary, as the 

grandfathered wells may not have been constructed in a way that would allow for these tests to 

be carried out. AWWA recommends that EPA include in the final regulation a requirement that 

the owners/operators of the wells conclusively prove that the grandfathered wells can be 

operated in compliance with all the other requirements of the proposed regulation or the wells 

will not be permitted for Class VI operation.

Category: Injection Stream 

EPA Request for Comment: By defining “carbon dioxide stream” to exclude hazardous wastes 

(146.81(d)), EPA’s rule, if finalized, assures that it would apply only to CO2 streams that are not 
Page 16 of 60

hazardous wastes as defined in 40 CFR Part 261. As a result, EPA’s proposed rule would 

preclude the injection of hazardous wastes in Class VI injection wells. EPA seeks comment on 

this approach and other considerations associated with the presence of “impurities” in the CO2 

stream. EPA Notice 43503.

AWWA Response: AWWA agrees with EPA’s approach in defining the “carbon dioxide 

stream” to exclude hazardous wastes. However, AWWA recommends that the final regulation 

include more specifics on the definition of the required quality of the injection stream and 

establishing a minimum concentration of carbon dioxide present in the injection stream. This 

requirement for the injection stream will ensure that the injection of other harmful or undesirable 

gases is limited. Our initial thoughts on this topic would be that 100% of the injectate must 

come from a carbon dioxide capture process and the injectate must be at least 98% carbon 

dioxide. Owner/operators must ensure that the remaining 2% of the injectate is not made up of 

compounds that would result in the injectate being classified as a hazardous waste. Also, 100% 

of the injection stream should be required to come from the carbon capture process as to preclude 

the co-mingling of wastes from other industrial processes in the injection stream as this is not an 

appropriate use of the Class VI injection wells. As AWWA is not a technical expert on this 

topic, AWWA recommends that EPA pursue research in association with DOE to develop a 

standard for the minimum concentration of carbon dioxide in the injection stream. 

EPA Request for Comment: Class VI requirements and permits will need to be carefully 

structured to ensure that they do not “authorize” inappropriate hazardous releases. This would 

include clarifying if there are potential releases from the well which are outside the scope of the 

Class VI permit. EPA requests comment on particular situations where this might occur. EPA 

notice 43504.

AWWA Response: AWWA agrees with EPA’s assertion that the permits and well requirements 

need to be carefully structured to prevent “authorized” releases of hazardous substances into 

subsurface geologic formations. We are not aware of any situations where this might occur, as 

long as the injectate is properly characterized and is not classified as a hazardous substance. 

There may be a situation where a release of carbon dioxide from the confining layer might cause 

the formation of a hazardous substance due to reactions with the surrounding geologic strata. To 

prevent this problem from occurring, the geologic characteristics of the geologic formations 

should be evaluated prior to injection for potential interactions with the injectate stream. If there 

are indications that hazardous substances could be formed, the site should not be considered 

acceptable for carbon sequestration.

EPA Request for Comment: EPA’s proposal allows Directors’ discretion on whether to require 

the use of tracers, and if so, what types of tracers. EPA seeks comment on the use of tracers in 

CO2 GS operations, and any potential impact of tracers on human health or ecosystems as they 

relate to USDWs. EPA Notice 43513.

AWWA Response: AWWA recommends that EPA require tracers to be injected along with the 

carbon dioxide stream to provide for a better mechanism of tracking the movement of the carbon 

dioxide plume. Certain tracers could provide for a better understanding of the plume behavior 

using non-traditional indicators, such as those that are conservative, easy to measure, non-toxic, 
Page 17 of 60

and do not degrade into contaminants of concern. These tracers could be easily identified in 

USDWs, as well as in the vadose zone, where they could be used as an indicator when carbon 

dioxide soil-gas monitoring proves difficult to interpret. Unfortunately, AWWA can not provide 

recommendations on specific tracers that could be utilized, and recommends that EPA perform

research, in association with DOE, on the types of tracers that would be acceptable for use in 

carbon sequestration.

Category: Modeling

EPA Request for Comment: EPA proposes that the owners or operators of GS wells be required 

to delineate the AoR for CO2 GS sites using computational fluid flow models designed for the 

specific site conditions and injection regime. EPA seeks comment on the use of modeling for 

AoR delineation. EPA Notice 43506.

When using a proprietary model, owners or operators should clearly disclose the code 

assumptions, relevant equations, and scientific basis. EPA seeks comment on allowing the use of 

proprietary models for GS sites. EPA Notice 43507.

AWWA Response: The proposed rule depends heavily on computer modeling to track the 

carbon dioxide plume and demonstrate that it is contained within the confining zone. As stated 

by EPA, some of these models are proprietary and the rule is unclear how or if confirmation of 

the model results will be provided. Additionally, each of the individual proprietary models can 

show a different answer to the problem. Owner/operators need to ensure that their basis for the 

model is static, and that the basis does not change once more details are known about the 

movement of the plume. For example, the operation of the geologic sequestration system should 

be adjusted based on modeling results, and the model shouldn’t be revised because the plume is 

moving in a direction not originally predicted.

AWWA recommends that EPA standardize on one specific model that is transparent and 

available for outside stakeholders to review, including the public. The other option is for EPA to 

develop a standard model that would be used for all geologic sequestration projects. If EPA 

were to develop a standard model, a pilot program should be part of the model development so

that the modeling results could be validated with real-life monitoring data. In either case, clearly 

stating the model assumptions made during model set-up is critical, and these assumptions must 

be made available to stakeholders when they are reviewing the model results.

Category: Area of Review (AoR)

EPA Request for Comment: EPA seeks comment on requiring the reevaluation of the site AoR 

on a periodic basis, under what conditions the AoR should be reevaluated, and the 

appropriateness of a 10-year minimum fixed frequency for AoR reevaluation. EPA Notice 

43507.

EPA proposes to allow a phased approach to corrective action but says this may not be 

appropriate in all situations; therefore EPA is proposing that the Director have the discretion to 

decide to allow this approach, based on the understanding of relevant geologic and site 
Page 18 of 60

conditions. EPA invites public comment on the merits and frequency of reevaluation of the AoR 

as well as the phased corrective action approach for GS wells. EPA Notice 43508.

AWWA Response: AWWA recommends that the area of review be reevaluated more frequently 

than suggested by EPA in the proposed regulation. AWWA recommends that the AoR be 

reevaluated annually for the first ten years of the project, and then every five years for the 

remaining operating period of the project. However, criteria should be established to trigger a 

shorter review period (based on a risk management approach) any time during the five-year time 

periods. For example, reevaluation of the AoR could be triggered by a shift in plume direction 

or sudden change in plume size or pressure. The local drinking water utilities, commissions, and 

planning boards need to be included in the AoR review process in the event that one of their 

drinking water sources becomes threatened due to a change in plume direction or behavior. 

Public involvement also needs to be a mandatory part of the AoR reevaluation process

AWWA recommends that a phased corrective action plan be developed as a result of the AoR 

reevaluation. This would prevent owner/operators from performing unnecessary work in the 

event that the plume migrates in a different direction than originally predicted. However, 

AWWA recommends that the required corrective actions be completed at least two years before 

the plume is expected to reach the specific location. Corrective actions should include reentering and replugging old or abandoned wells that have not been certified to be closed in 

accordance with the sequestration requirements. Also, in the case where old wells were plugged 

with cement that is not compatible with carbon dioxide, these wells should be re-entered and 

replugged. Finally, old wells for which no records exist should be re-entered and replugged to 

ensure that a pathway for carbon dioxide to escape is not provided. 

One issue that EPA needs to consider in the final regulation is the potential cost differential for 

either performing all of the necessary corrective actions immediately or by phasing them in over 

time. If the corrective actions are phased in, EPA needs to require that the owner/operator 

provide financial assurance that the corrective action measures will still be performed even if the 

company goes out of business and the carbon dioxide plume continues to migrate.

Category: Permit Life

EPA Request for Comment: EPA proposes that Class VI injection well permits would be issued 

for the operating life of the GS project including the post-injection site care period. EPA seeks 

comment on the merits of this approach. EPA Notice 43523.

AWWA Response: AWWA does not support issuing an operating permit for the life of the 

sequestration site. AWWA recommends issuing a lifetime operating permit for the coal plant, 

but with a separate and renewable permit for the operation of the geologic sequestration process. 

Much like the wastewater treatment plants and NPDES permits go through a permit review 

process every five years, AWWA recommends that this same process be used for operating 

permits for geologic sequestration processes. For water and wastewater treatment plants, the 

operating permit is issued at the start of operation and the plant must renew it every five years. 

This allows for the expansion of plant flow, and changes in required effluent criteria due to 

regulation modifications. Much as water and wastewater plants are required to keep up with 
Page 19 of 60

available technology, carbon sequestration systems should be required to apply BACT when it is 

feasible to incorporate it into the treatment process. Owner/operators should also be required to 

periodically re-evaluate their injectate stream for any emerging contaminants, and remove them 

if required. If wastewater treatment plants can be constructed and operating using this type of 

process, then a sequestration operation should be permitted in the same manner. Process changes 

are part of standard business operation in that regulations become more stringent, and processes 

become more efficient, and the owner/operators should be required to adapt to these changes

through the permit renewal process. 

AWWA recommends that the application process include a review of the site operations to see if 

any instances of unsafe operation or changes in regulation would require a change in the plant 

operation. If a problem were detected, the permit wouldn’t be immediately revoked, but the 

operator would be given the chance to rectify the situation so that the permit could be reissued. 

An owner/operator should consider the financial implications of this requirement and plan 

accordingly as the process will require a certain level of effort every five years to execute. 

AWWA recommends that the permit review process be aligned with the process used for review 

and renewal of NPDES permits. This would allow for all of the permit activities to be 

consolidated into one reapplication effort every five years.

The capacity of the various state agencies to deal with the five year permit review process is an 

issue that needs to be recognized. Some states that are already stressed for resources could be 

overwhelmed with this additional task. However, AWWA believes that this permit requirement 

should not be sacrificed because the states might be resource stressed. Therefore, the federal 

government should consider allocating enough money to the state programs to adequate staff 

their sequestration permit division

Group: Well Construction

EPA Request for Comment: EPA seeks comment regarding requirements for degradationresistant well construction materials, such as acid-resistant cements and corrosion resistant 

casing. EPA Notice 43510.

EPA seeks comment on the merits of requiring down-hole shut-off valves in GS wells. EPA 

Notice 43511.

AWWA Response: AWWA recommends that injection wells be constructed from degradationresistant materials to prevent carbon dioxide from escaping from a portion of the injection well 

that may have been compromised due to non-compatible materials. AWWA also recommends 

that down-hole shut-off valves be required for all injection wells. These valves can be a first line 

of defense against contamination of USDWs due to faulty injection practices. Further research is 

needed by both EPA and DOE to identify specific construction methods that would prevent 

degradation of the well and the carbon sequestration site. AWWA recommends the creation of a 

certification program that would be used to guarantee that existing or newly developed 

construction methods are approved for use with geologic sequestration.
Page 20 of 60

Category: Hydraulic Fracturing

EPA Request for Comment: EPA is requesting comment on the extent and scope to which 

hydraulic fracturing should be allowed during GS injection, and whether the use of fracturing for 

the purposes of well stimulation is appropriate. EPA Notice 43511.

AWWA Response: Hydraulic fracturing during carbon dioxide injection has the potential to 

serious compromise the confining layer and AWWA recommends that this practice should not be 

allowed as part of the injection process. The objective of characterizing the injection and 

confining zones is to find a location that is free from faults, penetrations or other physical 

methods by which carbon dioxide could escape. Hydraulic fracturing creates fractures in the 

injection zone, and possibly the confining layer, which would allow for a pathway by which 

carbon dioxide could migrate into USDWs. Therefore, AWWA recommends that this process 

not be utilized at all in geologic carbon sequestration.

Category: Monitoring

EPA Request for Comment: EPA’s proposal would require owners or operators of Class VI GS 

projects to monitor internal mechanical integrity of their injection wells by continuously 

monitoring injection pressure, flow rate, and injected volumes, as well as the annular pressure 

and fluid volume to assure that no anomalies occur that may indicate an internal leak. EPA 

requests comment on the practicability of this requirement. EPA Notice 43513. 

EPA seeks comment on the appropriate frequency of internal and external MITs for GS injection 

wells, the appropriate types of MITs, and how to optimize MIT methods for GS. EPA Notice 

43514.

EPA seeks comment on the requirement for monitoring of GS sites for the purpose of tracking 

the location of the CO2 plume and associated pressure front over time. EPA Notice 43514

EPA’s proposal would require that owners or operators perform a pressure fall-off test at least 

once every five years. EPA seeks comment on the use and frequency of pressure fall-off testing 

for GS wells. EPA Notice 43515.

Specifically, EPA seeks comment regarding the usefulness of indirect geophysical monitoring 

and surface air and soil gas monitoring. In addition, EPA seeks comment regarding the use of a 

Director-approved monitoring plan for GS sites. EPA Notice 43517.

AWWA Response: Detailed monitoring guidelines were developed as part of a joint research 

project by AwwaRF and AWWA. These guidelines are provided in Section III of these 

comments and EPA should include the named tests and frequencies in the final regulation to 

ensure that protection of USDWs is consistent across all geologic sequestration projects. Based 

upon these requirements, owner/operators would develop testing and monitoring plans, which 

should be reviewed and updated at the same time as the re-evaluation of the Area of Review. 

The costs associated with monitoring of a sequestration project should not be a major 

consideration when determining the types and frequency of required monitoring. The goal of the 
Page 21 of 60

monitoring requirements should be on preventing degradation of USDWs, not minimizing the 

cost to the owner/operator. 

AWWA strongly recommends both that both internal and external mechanical integrity testing

should be required to prevent leakage of carbon dioxide from the injection well. Monitoring of 

the plume and pressure front over time is absolutely required as part of the system operation and

a project shouldn’t even be considered unless this monitoring is included. All of the monitoring 

requirements should be put forth in a monitoring plan, which should be reviewed and approved 

by the Director prior to the start of the project. This plan should be re-evaluated every five years 

during the permit review, and should be updated by the owner/operator based on any changes in 

operation or performance of the carbon dioxide plume.

Pressure fall-off testing should definitely be required however the five year length between 

testing is too long. This should be performed on an annual basis as part of the annual reporting 

requirements

Surface air and soil gas monitoring should be required however, baseline soil carbon dioxide 

levels should be determined prior to the start of monitoring. Testing for other compounds such 

as tracers that may included as part of the carbon dioxide injectate stream should also be 

considered in the development of the monitoring plan. 

Category: Required Project Plans

EPA Request for Comment: EPA seeks comment on the merits of requiring plans for 

monitoring, AoR, and post-injection site care as part of a permit application. EPA Notice 43517.

AWWA Response: The requirement for the development of plans for monitoring, AoR, and 

post-injection site care is necessary and is a very important part of the permit process. The 

information will provide outside stakeholders with a much better idea of how the project will 

proceed and can help to assure them that the owner/operator has a clear vision for the life of the 

project. AWWA recommends that these plans be reviewed at the same time that the area of 

review is reevaluated. During this review, the plans should be updated based on any operational 

changes since the last project review period and submitted to the Director for approval. AWWA 

recommends that a review occur every year for the first ten years of the project, and then should 

be reviewed every five years until injection ceases. 

EPA Request for Comment: EPA seeks comment on the frequency of all proposed reporting 

requirements. EPA Notice 43517

AWWA Response: AWWA recommends that the owner/operators of a Class VI well provide a 

monthly operating report to the Director instead of the semi-annual report as proposed. The 

operating information for the geologic sequestration project is extremely important and needs to 

be reviewed at a frequency by the regulatory agency to ensure problems are identified and 

addressed in a timely manner. For example, based on the proposed regulation, data collected on 

July 1, 2008 would not be seen by the regulatory agency before January 15, 2009, if the operator 

is allowed 15 days to submit the report. This would allow for very little time to correct any 
Page 22 of 60

potential issues in the operation of the project. We have provided example monthly reporting 

sheets that were developed as part of the AwwaRF project in Section III of our comments, and 

these reports are similar to the monthly reporting sheets used by water and wastewater treatment 

plants. Given the potential scale of carbon sequestration and the need to protect groundwater 

resources, a requirement for monthly operating reports is reasonable. 

With respect to the requirement for recordkeeping, AWWA recommends that the one-year 

holding requirement for the plugging and abandonment report be extended. This is an extremely 

important report, and the owner/operator must be required to keep this report on file for a 

minimum of 10 years following the closure of the project site. 

EPA Request for Comment: EPA seeks comment on the requirement for electronic reporting in 

its proposed rule. EPA Notice 43518.

AWWA Response: AWWA agrees with the electronic reporting requirements include as part of 

the proposed regulation. Electronic reporting allows for easier tracking of the operating data to 

observe any trends that might indicate potential contamination of a USDW. EPA should 

consider the infrastructure that will be required to collect information prior to publishing the first 

report and develop a model reporting plan for owner/operators to use when submitting data to 

state agencies.

EPA Request for Comment: In addition to the above recordkeeping and reporting requirements, 

EPA considered a requirement for owners or operators of GS sites to provide an annual report 

during the lifetime of the project, including the post-injection period, regarding the GS operation. 

Although EPA has not included a requirement for this report in its proposal, EPA seeks comment 

regarding the necessity for such an annual report. EPA Notice 43518.

AWWA Response: AWWA recommends that an annual reporting requirement be included in 

the proposed regulation. This report should summarize the operation of the system including

standard operating criteria, information on well operation, details of plume movement, and any 

details on major changes in well operation. It should be similar to the Consumer Confidence 

Reports (CCR) that drinking water utilities must develop and it should be mailed or emailed to 

all relevant stakeholders. EPA should develop requirements for the report similar to those 

required for the CCR because the annual report should be developed by someone one of the team 

members involved in the operation of the geologic sequestration project. 

Category: Post-Injection 

EPA Request for Comment: EPA requests comment on the proposed use of a tentative 50-year 

fixed timeframe that could be modified at the Director’s discretion based on monitoring and 

modeling data. EPA Notice 43519.

EPA is requesting comments on the proposed requirements for well plugging, post-injection site 

care, and site closure, including the proposed requirements for the post-injection time period. 

EPA Notice 43520.
Page 23 of 60

AWWA Response: AWWA recommends that the time period for post-injection site care be set 

at a minimum of 50-years and that the Director not be given any discretion to shorten this time 

period. After this 50-year period, the operator must continue to monitor until such time as they 

can demonstrate that the plume has stabilized and that it does not present any potential danger to 

USDWs or other potential sources of drinking water. This requirement is not overly prescriptive 

or burdensome given the information available on the long-term behavior of carbon dioxide 

plumes. This time period is necessary to monitor the site for changes that may occur over a 

longer amount of time, such as gradual leakages, fault movement, or sudden seismic shifts. 

After this time period, the owner/operator may apply to the Director for a modification or 

termination of the monitoring requirements.

AWWA has observed that the proposed regulation is lacking in details on the requirements to 

demonstrate that the carbon dioxide plume has stabilized. For example, the proposal does not 

include requirements that the plume pressure must be constant for a certain number of years or 

that the plume has not migrated for a set period of time. Since AWWA does not claim to be 

experts on the behavior of carbon dioxide plumes and can not provide recommendations on this 

topic, AWWA recommends that EPA should engage in research on determining exactly what 

these criteria should be. For example, when referencing lack of plume movement, what should 

the trigger time period be (no movement of plume for 10, 15, 20 or more years??). AWWA 

recommends that EPA clarify what is an acceptable frequency for a lack of change in the plume 

characteristics and also needs to clarify plume stabilization as this issue could be interpreted 

differently by different states. Guidance should be prepared by EPA on this topic so that there is 

consistent application of this requirement across all sequestration projects. A performance 

based system could also be developed that would require the operator to meet certain criteria to 

prove that the plume has stabilized. This could be used to justify the closing of the site after the 

50-year period of post-injection site care has elapsed. This would allow for a process where 

long-term monitoring decisions are made in response to the specific characteristics of each 

project. 

AWWA believes that the proposed post-injection site care requirements have been established

to prevent endangerment to USDWs. Carbon dioxide can potentially leak from the confining 

layer into other aquifers that, while not classified as USDWs, may still be considered drinking 

water sources in some areas of the county. EPA should also consider including requirements in 

the regulation to address the potential for endangerment of these aquifers during the postinjection period. Monitoring requirements should be extended to cover these aquifers, and the 

post-injection site care plan should include provisions for the protection of aquifers that are not 

classified as USDWs, but are still considered a future drinking water source.

Category: Financial

EPA Request for Comment: Because of the possibility that the owner or operator may face 

financial distress prior to the trust being fully funded, EPA is considering a guidance approach 

that would recommend adopting a pay in period of three years for GS projects, consistent with 

other similar programs in the Agency. EPA Notice 43521.
Page 24 of 60

EPA is assessing whether to provide guidance on the use of insurance providers and, if so, 

whether to update eligibility requirements for insurers for GS wells consistent with other current 

Federal agency practices. EPA Notice 43521.

EPA is requesting comments on whether financial responsibility mechanisms to be 

recommended in EPA guidance should be adjusted in the manner described, whether additional 

instruments should be included, and whether other adjustments to the financial responsibility 

mechanisms should be considered, all subject to EPA’s authority under the SDWA. EPA Notice 

43522.

AWWA Response: AWWA has several major concerns regarding owner/operator financial 

assurance and liability. Our primary concern is that the liability mechanism that would be 

triggered when the confining zone fails and carbon dioxide escapes has not been identified. 

Would this incident trigger CERCLA requirements if groundwater is degraded? AWWA 

recommends that the liability requirements and financial mechanisms that were used to address 

MTBE contamination be applied to any USDW degradation from carbon sequestration activities. 

The definition of a “corrective action” does not provide any protection for aquifers that are 

contaminated by the carbon sequestration process. The definition as provided in the proposed 

rule states that corrective action is “...the use of Director approved methods to assure that wells 

within the area of review do not serve as conduits for the movement of fluids into underground 

sources of drinking water (USDW).” Note that this definition does not address “fixing” the 

impact to USDW. What is unclear to AWWA is if the geologic sequestration process does

endanger groundwater aquifers, whether the owners/operators have any financial liability in 

restoring water quality (e.g., paying for extra treatment costs incurred by water utilities or other 

groundwater users), as the corrective action seems to focus on fixing injection wells and/or the 

confining layer. 

The question remains regarding what an owner/operator’s total liability would be outside of the 

USDW contamination. The potential exists for contamination of other ground water aquifers, 

such as those that are not classified as USDWs but are used as a drinking water sources, and it is 

extremely important that the liability requirements are extended to these aquifers. The cost to 

remediate any degradation can be extremely high. Depending on the scope and location of the 

degradation, examples of potential costs that might be incurred by a drinking water utility

include the installation of advanced water treatment technologies and/or development of 

alternative water sources. The responsibility for these costs must be assumed by the 

owner/operator in the event of a failure of the geologic sequestration process.

AWWA believes that the time limit for financial responsibility in the proposed regulation may be 

too long for most insurance agencies, which may trigger the need for the development of a trust 

fund or for owner/operators to use a self-insurance mechanism. If the trust fund is the desired 

method, EPA should require that companies constantly add to the fund, even if it appears that the 

fund is fully funded. In addition to the initial pay in period of three years, owner/operators 

should be required to pay in any additional amount identified during the five-year reviews for the

area of review and corrective action plan, injection well plugging plan, the post-injection site 

care and site closure plan, and the emergency and remedial response plan. This additional pay in 

is required so that we don’t have a repeat of the funding stoppage with the Superfund program. 
Page 25 of 60

AWWA questions whether it would be acceptable for energy companies and owner/operators to 

bond projects as a way to demonstrate financial assurance. AWWA recommends that EPA

develop formal technical, managerial, and financial requirements for carbon sequestration projects

that owner/operators must meet and maintain. This should be tied to the permitting process as 

these requirements must be demonstrated prior to the operating permit being issued. 

Demonstrating ongoing technical, managerial, and financial capabilities would be an important 

component of the five-year permitting review process that AWWA is recommending.

With respect to the required financial mechanisms, AWWA would like to leave the door open for 

establishing financial mechanisms on a project by project basis. The rulemaking should not 

prescribe or preclude particular financial instruments as the issue of financial assurance is very 

complex. Other funding models could be developed, and it may be that Moodys or Standards 

and Poors will see this as a potential opportunity. Many significant financial details remain that 

must be addressed before any guidance or regulation is issued on this topic. As an example, the 

issue of long-term liability still has not been resolved. Who is ultimately responsible for

ownership of the injection wells and the carbon dioxide plume after the post-closure period has 

ended? Does the liability transfer to whoever manages the trust fund (in that particular financial 

assurance mechanism)? 

AWWA would also like to see the issue of long-term liability resolved. EPA’s proposed 

geologic carbon sequestration rule is not able to address financial responsibility of the 

sequestration site after the formal period of post-injection site care has ended (default of 50 year 

length). Recognizing that EPA does not have the power to assign responsibility after this period 

of time has expired, AWWA recommends that EPA work with the appropriate stakeholders to 

develop legislation that will address the issue of who has to assume financial responsibility of the 

sequestration site after the site closure requirements have been fulfilled. AWWA anticipates that 

this legislation would provide for a means by which drinking water utilities could recover any 

costs incurred as a result of USDW contamination by geologic carbon sequestration activities. 

AWWA also recommends that EPA work with the appropriate stakeholders to develop

comprehensive climate change legislation with the goal of protecting water systems, and their 

customers, from loss of water supply or unplanned major financial burdens. Everyone needs to 

apply the lessons learned from MTBE contamination to prevent unintended consequences from 

developing with geologic sequestration wells.

Category: State Capacity

EPA Request for Comment: EPA seeks comment on any aspects of the ongoing State efforts to 

regulate the GS of CO2 and how these efforts might be used to better inform a final Federal 

rulemaking. EPA Notice 43497.

AWWA Response: From our perspective, EPA’s proposed rule appears to be focused on 

preventing brine from formations where carbon dioxide was stored from reaching USDWs

and/or from preventing carbon dioxide that reaches USDWs from causing primary MCLs to be 

exceeded. This focus may not be adequate from the standpoint of protecting source water and

beneficial use aquifers from detrimental changes in water quality other than the exceedance of 
Page 26 of 60

primary MCLs. Other water quality impacts could be observed such as increased concentrations 

of iron, manganese and TDS, as well as lowered pH, all of which have secondary MCLs. 

Increases in the concentrations of silica and boron, which do not currently have MCLs but can 

significantly degrade water quality, are also likely to occur.

This past year, the State of Washington adopted carbon sequestration regulations which AWWA 

recommends that EPA review and incorporate some of the language into the final regulation. 

The Washington regulations require that the owner or operator must demonstrate that the “design 

and construction standards of all facility structures and wells are sufficient to prevent migration 

of carbon dioxide or nonpotable water that will degrade water quality or impact beneficial uses 

outside the geologic containment system.” The language in this regulation provides protection 

mechanisms for groundwater sources that may not be used as USDWs but have other beneficial 

uses, such use as industrial applications or agriculture. Given the stresses that the drinking water 

industry is facing with respect to water resources, AWWA recommends that the monitoring 

requirements in the final rule be extended to protect against aquifer contamination beyond that 

which is associated with compounds that have primary MCLs. 

EPA Request for Comment: EPA is seeking comment on the merits and possible disadvantages 

of allowing primacy approval for Class VI wells independent of other well classes. EPA Notice 

43523.

AWWA Response: AWWA recommends that a state be able to administer only Class VI well 

permits, if they so desire. The Class VI well program is a very specialized class, which has 

major differences from all the other well classes. A state that decides to apply for primacy of the 

Class VI wells only would be able to specialize in this well class, and could develop and execute 

a very detailed program. The state would have an advantage in that the state staff would be very 

familiar with the regional geology, water resources and business operations in the areas proposed 

for geologic sequestration. One disadvantage could be seen if the applying state had never held 

primacy for any of the other classes of wells. Since this is a fairly specialized class, there could 

be some logistical issues in the beginning stages of the state administering the program. 

However, AWWA believes that these issues could be addressed through consultation with either 

the federal EPA offices, or in discussions with other states that are administering the Class VI

program. In our opinion, the benefits associated with state primacy, such as a more in depth 

knowledge of the state geology, operations and politics far outweighs any minor implementation

issues that might be associated with a state having primacy approval for only Class VI wells.

Other AWWA Comments Related to State Primacy and Capacity: When EPA allows states to 

obtain primacy for the Class VI wells and develop their own regulations for geologic 

sequestration, these regulations must be developed in accordance with Section 1422 of the 

SDWA instead of Section 1425. The language in Section 1422 mandates that state requirements

for geologic sequestration be as stringent as federal requirements. By comparison, the language 

in Section 1425 mandates that the state requirements represent an “effective” program to prevent 

injection which endangers drinking water sources. The language in Section 1425 leaves too 

much room for interpretation, and could result in varying degrees of protection of USDWs across 

the country. Given the current strain on our groundwater resources in some areas of the United 
Page 27 of 60

States, AWWA recommends that EPA ensure state regulations provide at least the same level of 

protection as the federal regulations.

AWWA recognizes that the SDWA currently provides for a $16 million statuary limit for federal 

support to states to enact and enforce the Act. Given that state primacy agencies are already 

resource limited and are inadequately funded to cover existing oversight responsibilities, 

AWWA anticipates that this regulation could place an even larger burden on them. Geologic 

carbon sequestration will require new resources, and in addition, staff with very specialized 

expertise in areas such as groundwater, wells, geochemistry, and underground injection. 

Inadequate resources and staff capabilities will result in delayed permit reviews/approvals and/or 

rushed and poor decision making. AWWA recognizes the funding limitation for the state 

primacy programs and this is an issue that Congress would have address either through a 

modification of the SDWA or by a revenue set-aside as part of a future "cap and trade" program. 

As a result, AWWA recommends that EPA consider the potential burden on state programs 

when finalizing the regulation and look for ways to streamline the process without sacrificing the 

protective measures of the regulation. 

Category: Public Participation

EPA Request for Comment: EPA requests comment on adopting the existing requirements for 

public participation at 40 CFR Part 25 and 40 CFR Part 124 and whether additional requirements 

should be included to reflect the availability of new tools for disseminating and gathering 

information. Such tools include cable networks, the Internet, and other new technology. EPA 

Notice 43523.

AWWA Response: 40 CFR 124 does not include a requirement for public notification when a 

request is made to modify, revoke and/or reissue an operating permit for a geologic sequestration 

project. It also does not provide for mandatory public hearings, as the regulations states that it is 

up to the discretion of the Director unless a hearing is specifically requested by a stakeholder. 

AWWA disagrees the omission of with these requirements and recommends that both of these 

activities be recognized as mandatory during the permit development, review, and approval 

processes for geologic sequestration projects.

Most of the geologic sequestration projects will be located in rural areas where the local water 

utility is very small with limited staffing and funding resources. While these utilities may be 

impacted by the projects, they may not have the technical ability to adequately participate in a 

project review. Therefore, AWWA recommends that as part of the public participation 

requirements, owner/operators should be required to notify and involve national and state 

drinking water organizations as well as the local water utilities. This would allow the local 

utility to be supported technically by the staff of the national organization, which can provide 

technical expertise in drinking water issues related to carbon sequestration.

Each project should be required to establish public advisory groups, such as those created for 

some of the regional carbon sequestration partnership projects. Owner/operators need to ensure 

they identify stakeholders groups from water sector, such as rural water associations, 
Page 28 of 60

groundwater associations, and drinking water utility associations. These groups would be

involved in the project from the beginning and provide the stakeholder voice for the project.

AWWA recommends that the public comment period for the permit review process be extended 

in the final regulation. Due to the technical nature of the geologic sequestration process, 

AWWA recommends that the comment period be extended from 30 days to 90 days. A 30 day 

comment period does not provide enough time for outside groups to obtain the permit, perform a 

detailed technical review and generate comments. Extending the comment period for 90 days 

allows the stakeholders to perform a much more comprehensive review of the project.

The issue of environmental justice must be appropriately considered when involving the public 

in geologic sequestration projects. Consideration should be given to ensure that certain 

populations aren’t repeatedly subjected to the problems that may arise from the sequestration 

projects. It is also necessary to remember that not everyone has access to the same media 

outlets. When an owner/operator is advertising public hearings or comment periods, they should 

be required to utilize all forms of media, including the newspaper, radio, television and internet. 

The general public has a wide range of media-viewing habits, and many have moved away from

some of the more traditional communication methods.

Category: Cost Analysis

EPA Request for Comment: The Agency assumes three monitoring wells per injection well for 

the purpose of estimating national costs; however, the Agency recognizes that operators and 

primacy agency Directors may choose more or fewer monitoring wells depending on project site 

characteristics. Because the monitoring wells and associated costs represent a significant 

component of the Cost Analysis, the Agency acknowledges that this factor may be significant in 

the overall uncertainty of the Cost Analysis. EPA requests comment on whether three monitoring 

wells per injection well is an appropriate costing assumption. EPA Notice 43527.

AWWA Response: AWWA does not agree with the assumption to use three monitoring wells

per injection well as the standard for the cost analysis. This number seems very low given the 

amount of area that would be covered by one injection well. Requiring three monitoring wells 

for an injection well that might be associated with a carbon dioxide plume stretching for over a 

mile seems like a drastic underestimate of the necessary monitoring. AWWA recommends that 

the requirement be based more on the projected plume performance and the potential interactions 

with USDWs or other important geologic formations. 

Other cost estimates have indicated that, in the overall cost of the project, monitoring is a very 

small percentage of the total project cost as compared to those associated with the capture and 

transport processes. This conclusion is contrary to EPA’s cost estimate, and AWWA is

concerned that the EPA’s high cost numbers for monitoring may be used to attempt to reduce the 

monitoring requirements and lower the overall project cost. AWWA recommends that the cost 

estimate be revised at a later date based upon data that becomes available from the DOE pilot 

projects. These projects might identify additional well construction costs, as well as be able to 

provide a better understanding of how the cost of monitoring compares to the rest of the project. 
Page 29 of 60

III. MONITORING GUIDELINES FOR GEOLOGIC CARBON SEQUESTRATION 

PROJECTS

This monitoring guideline has been designed to aid in the development of project specific 

monitoring plans designed to reduce risk and uncertainty and demonstrate compliance

throughout the project life cycle including site characterization, operation and closure. 

This guideline was developed as part of the American Water Works Association Research 

Foundation Project No. 4203, which was partially funded by the American Water Works 

Association. Information included in this monitoring guideline was obtained from the combined 

experience of the consultants and these primary sources: 

1) EPA’s proposed requirements under the underground injection control program from 

carbon dioxide geologic sequestration (EPA, 2008);

2) EPA’s guidance on systematic planning using the data quality objective process (EPA, 

2006); and,

3) The International Panel on Climate Change special report on carbon dioxide capture and 

storage (IPCC, 2005). 

1.0 CHARACTERIZATION

During the characterization phase of a Geologic Carbon Sequestration (GCS) project, 

measurements should be collected to establish a baseline for comparison with monitoring 

measurements made during the injection and post-injection phases. The data collected about 

these background conditions should characterize not only the injection formation but also the 

confining unit(s), horizons above the injection zone and below the lowermost USDW above the 

injection zone, and other USDWs encountered. Data collected about each formation should 

include:

 Thickness

 Lateral extent

 Porosity

 Permeability

 Mineralogy 

 Geochemistry (including analyses for all EPA Primary and Secondary drinking water 

constituents, and other constituents of interest)

To anticipate potential leakage pathways from the injection formation into any USDWs, the 

following additional data should be collected about the confining unit(s):

 Existing faults and fractures

 Discontinuities and pinch-outs

 Existing manmade penetrations

 Potentially seismically active zones

 Rock stress

 Rock strength
Page 30 of 60

Furthermore, the vadose zone and surface gas compositions should be characterized sufficiently 

such that natural temporal changes in these compositions can be differentiated from any future 

changes due CO2 leakage.

Background water samples are to be obtained from all monitor zones and the injection zone. 

Prior to sampling, the horizons are to be fully and properly developed. After development, a 

minimum of three well volumes is to be purged before samples are collected. The samples are to 

be analyzed for a variety of constituents to establish the "natural" or background quality of the 

water. The analysis is to include USEPA Primary and Secondary drinking water Standards, 

Unregulated Organic Contaminants and other groundwater monitoring parameters (e.g., silica 

and boron). 

2.0 MONITORING PLAN

The owner/operator of a GCS project should prepare a monitoring plan prior to the start of 

injection. The plan should be created using the baseline characterization data in order to choose 

the most effective monitoring technologies and monitoring locations. The monitoring plan 

should:

 Be designed to minimize risk to USDWs

 Include both operational and environmental monitoring

 Describe the specific monitoring technologies to be used and how they will be effective

 Include the timing of sampling and monitoring

 Include sample data recording forms (examples attached)

 Include how the monitoring data will be used to update site models and how the updated 

models will be used to update the monitoring plan

 Be designed to demonstrate compliance with standards or “triggers”

The plan should be developed following EPA’s Guidance on Systematic Planning Using the 

Data Quality Objective (DQO) Process (EPA, 2006). Figure 2-1 illustrates that the DQO process 

is a series of logical steps that guides managers and staff to a plan for the resource-effective 

acquisition of environmental data. It is both flexible and iterative, and applies to both decisionmaking (e.g., compliance / non-compliance with a standard) and estimation (e.g., ascertaining the 

mean concentration level of a contaminant). Each step defines criteria that will be used to 

establish the final data collection design. The first five steps are primarily focused on identifying 

qualitative criteria, such as: 

 Nature of the problem that has initiated the project and a conceptual model of the 

environmental hazard to be investigated; 

 Decisions or estimates that need to be made and the order of priority for resolving them; 

 Yype of data needed; and

 Analytic approach or decision rule that defines the logic for how the data will be used to 

draw conclusions from the project findings. 
Page 31 of 60

The sixth step establishes acceptable quantitative criteria on the quality and quantity of the data 

to be collected, relative to the ultimate use of the data. These criteria are known as performance 

or acceptance criteria, or DQOs. In the seventh step of the DQO Process, a data collection 

design is developed that will generate data meeting the quantitative and qualitative criteria 

specified at the end of Step 6.

The site model and risk models should be updated as frequently as new data is collected about 

the plume. Based on these updated models and the performance of the site, the monitoring plan 

should also be updated and the monitoring operations should be adapted as necessary. 
Page 32 of 60

Figure 2-1: The Data Quality Objective Process

(EPA, 2006)
Page 33 of 60

3.0 MONITORING DATA

The following recommendations should be carried out conscientiously to ensure successful 

operation of the well:

 Monitor well pressure is to be continuously monitored

 Injection wellhead pressure is to be continuously monitored

 Flow to the injection well is to be continuously monitored

 Monitor well water quality is to be monitored weekly

 Injection well injectivity tests are to be performed monthly

 Injection stream parameters are to be monitored weekly

 A complete analysis of the injection stream is to be performed annually

 Injection well mechanical integrity tests are to be performed annually

When the injection well is operational, a variety of data will be collected during both the initial 

testing and long-term operation of the injection well system. It is essential that the performance 

data collection begin upon operational startup to establish baseline information that serves for 

future data comparison and performance analyses. 

3.1 Injection Formation Analysis

During site characterization and during startup testing, samples from the injection formation are 

be collected and analyzed for pH, alkalinity, TDS/EC, major cations and anions, trace metals, 

dissolved organic carbon, total organic carbon, silica and boron. The suggested water quality 

analyses are listed in Table 3.1-1.
Page 34 of 60

Table 3.1-1:

Suggested Annual Water Quality Analyses of the Injection Formation

General Constituents Trace Metals

pH Aluminum

Alkalinity Antimony

TDS/EC Arsenic

Calcium Asbestos

Magnesium Barium

Potassium Beryllium

Sodium Cadmium

Bicarbonate Chromium

Chloride Copper

Sulfate Copper

Other Constituents Cyanide

Nitrate Fluoride

Dissolved organic carbon Iron

Total organic carbon Lead

Silica Manganese

Boron Mercury

Sulfide Nickel

Selenium

Silver

Sulfate

Thallium

Zinc

3.2 Injection Well Data Collection

The owner/operator must provide operational monitoring during the injection period to ensure 

that the physical and chemical properties of the injected CO2 stream are measured and recorded. 

Beginning with the start of injection, injection records should be maintained to evaluate injection 

well performance.

The pressure at the injection wellheads is to be continuously monitored and recorded. Daily 

average, maximum and minimum pressures are to be reported monthly. The internal and 

external integrity of the well and the injection pressure must also be monitored to ensure that the 

confining properties of the well and the project are maintained.

The flow rate into the injection well is to be continuously monitored and recorded. Daily 

average, maximum, and minimum flow rates, as well as the total volume of fluid pumped into 

the well are to be reported on a monthly basis.
Page 35 of 60

All pressure gauges, flow meters, chart recorders and any other equipment associated with the 

injection well monitoring system are to be calibrated on a semiannual basis using standard 

engineering methods

The physical injection well performance characteristics to be recorded include:

Flow Rate Parameters

 average daily flow rate to injection well as measured from flow meter 

 daily maximum sustained (15 minutes minimum) flow rate to injection well

 daily minimum sustained (15 minutes minimum) flow rate to injection well

 monthly average of the daily flow rates to injection well 

 monthly maximum (peak hour) flow rate to injection well 

 monthly minimum flow rate to injection well 

Volumetric parameters

 total daily effluent to injection well from as measured from totalizer 

 total monthly flow volume to injection well 

 monthly average of the daily flow volumes to injection well 

 monthly maximum of the daily flow volumes to injection well 

 monthly minimum of the daily flow volumes to injection well 

Wellhead pressure parameters

 daily average injection pressure at injection well (psig)

 daily maximum sustained (15 minutes minimum) injection pressure at injection well 

(psig)

 daily minimum sustained (15 minutes minimum) injection pressure at injection well 

(psig)

 monthly average injection pressure at injection well (psig)

 monthly maximum sustained injection pressure at injection well (psig)

 monthly minimum sustained injection pressure at injection well (psig)

 monthly wellhead pressure with no flow (shut-in pressure, psig)

Annulus pressure parameters

 daily average annular pressure at injection well (psig)

 daily maximum annular pressure at injection well (psig)

 daily minimum annular pressure at injection well (psig)

 monthly average annular pressure at injection well (psig)

 monthly maximum annular pressure at injection well (psig)

 monthly minimum annular pressure at injection well (psig)

The monitoring equipment should be designed so that manual backup capability to monitor 

pressure will be provided for systems utilizing automatic and continuous recording devices.
Page 36 of 60

3.3 Monitor Well Data Collection

Water quality should be monitored in the first porous zone above the primary confining unit, 

within and near the base of the lowermost USDW above the injection zone, and in any other 

USDWs that may be affected by CO2 injection as determined during risk assessment. 

The purpose of monitor zone data collection is to detect changes in water quality attributable to 

the injection fluids into the nearby injection well. To collect the water quality samples, the 

monitor wells will be equipped with sampling pumps. Prior to collecting water samples for 

analysis, at least three well volumes have to be pumped from the monitor zones. In addition to 

collection of samples for analysis of constituents listed on Table 1, monitoring well water quality 

is to be monitored through weekly and monthly samples during system startup for a smaller suite 

of constituents. Once startup testing has been completed, it may be feasible to decrease the 

sampling frequency. Samples are to be collected and analyzed weekly, monthly, and annually

are shown in Table 3.3-1.

Table 3.3-1: 

Water Quality Monitoring

Parameters Reporting Frequency

Specific Conductivity (μmhos/cm) Weekly

Total Dissolved Solids (mg/L) Weekly

pH (std. units) Weekly

Chloride (mg/L) Weekly

Sulfate (mg/L) Weekly

Field Temperature (°C) Weekly

Ammonia (mg/l) Weekly

Total Kjeldahl Nitrogen (TKN) (mg/L) Weekly

Alkalinity (mg/L) Weekly

Sulfide (mg/L) Weekly

Mercury (mg/L) Monthly

Lead (mg/L) Monthly

Sodium (mg/L) Monthly

Calcium (mg/L) Monthly

Potassium (mg/L) Monthly

Magnesium (mg/L) Monthly

Iron (mg/L) Monthly

Bicarbonate (mg/L) Monthly

Silica Annually

Boron Annually

Gross Alpha Activity Annually

Once startup testing has been completed, it may be feasible to decrease the sampling frequency.
Page 37 of 60

These data should be presented on time-series plots so that temporal trends are easily observed. 

If increases in dissolved organic or total organic carbon are observed, more detailed sampling 

should be performed to characterize the nature and extent of contamination. 

The pressure in each monitor well is to be continuously monitored and recorded relative to feet 

NGVD or in psi. Pressures are to be reported as follows.

 daily maximum pressure or water level (as appropriate)

 daily minimum pressure or water level (as appropriate)

 daily average pressure or water level (as appropriate)

 monthly maximum pressure or water level (as appropriate)

 monthly minimum pressure or water level (as appropriate)

 monthly average pressure or water level (as appropriate)

3.4 Injectivity Testing

Periodic determination of the injectivity of a well is used as a measure of the efficiency of a well. 

An injectivity test involves injecting fluid into a well at three (or more) injection rates and 

recording the injection pressure for each rate. The shut-in pressure of the injection well is to be 

measured before each different injection rate. The injectivity is calculated by dividing the 

injection rate by the required injection pressure (wellhead injection pressure minus shut-in 

wellhead pressure). The result is expressed as gallons per minute per pounds per square inch 

(gpm/psi). Factors affecting the injection wellhead pressure are a function of:

 The density differential between the injected fluid and the formation water in the 

injection zone

 The friction loss in the casing

 The bottom hole pressure (injection zone transmissivity)

The density differential is fairly constant as long as the temperature and density of the injection 

and formation fluids remain constant. Friction loss in the casing and bottom hole pressure can 

vary as a result of changes in the flow rate, the physical condition of the injection zone and the 

physical condition of the pipe. In general, pressure builds up slowly with time (for a given 

pumping rate) as the casing "ages". Similarly, plugging of an injection zone can cause a gradual 

pressure build-up over time. Testing should be conducted quarterly for the life of the well. The 

testing rates for injectivity testing should be established as soon as the well is put into operation. 

The testing procedure should be chosen so that it is easily repeatable.
Page 38 of 60

4.0 WELL INTEGRITY MONITORING

The integrity of the injection well must be monitored to ensure that the well does not become a 

conduit for fluid movement that could endanger USDWs. An injection well has mechanical 

integrity when there is no leak in the casing and no fluid movement into the underground source 

of drinking water through channels adjacent to the well bore. Mechanical integrity testing 

includes a pressure test, a radioactive tracer survey, a high-resolution temperature log and a 

television survey. This testing will be used, along with the monitoring data of the monitor zones, 

to demonstrate the absence of fluid movement above the injection zone. The injection wells are 

to be tested for mechanical integrity annually. 

The internal mechanical integrity must be monitored to ensure that no fluids can move from the 

well into any formation other than the injection formation. The external mechanical integrity 

must be monitored to ensure that there is no significant movement of fluids between formations.

The owner/operator must perform an internal mechanical integrity test (e.g. an annular pressure 

test) prior to the start of injection. Such a test must also be performed prior to the restart of 

injection after removing the injection tubing for a workover or any other activity. Although the 

owner/operator must continuously monitor the pressure in the fluid- filled annulus between the 

long string casing and the injection tubing to ensure that there is no leak, an annual pressure test 

should also be conducted. A pressure gauge with a maximum of 1 psi increments that is accurate 

to one quarter of 1 percent of full-scale deflection will be mounted on the temporary wellhead. 

The gauge will have previously been calibrated. Calibration will have been conducted on the 

gauge within a period of three months prior to the date of use. The annular space will be 

pressurized to 150 percent of the design maximum injection pressure. Pressure readings will be 

recorded every 5 minutes for a 1-hour period. The pressure must not vary by more than 5 

percent during the 1-hour testing period.

The internal integrity of the well should also be verified by corrosion monitoring of the injection 

tubing. This can be accomplished by comparing a baseline measurement with subsequent annual 

monitoring measurements made using corrosion logging tools. If the components of the 

injection stream warrant, the owner/operator should perform quarterly monitoring of the internal 

well materials for corrosion, change in mass, and change in thickness. This may be done by 

placing representative samples of the material in contact with the injection stream. 

The external mechanical integrity of the well must be regularly monitored to ensure that it does 

not allow leakage of fluids between formations that could endanger USDWs. The external 

mechanical integrity of the well must be tested annually using logs or surveys capable of 

detecting fluid movement between the long string casing and the adjacent formation(s). Such 

logs and surveys include:

 Tracer surveys

 Oxygen activation logs

 Noise logs

 Temperature logs.
Page 39 of 60

Prior to the start of injection, and every 5 years after injection, the owner/operator must evaluate 

the quality of the cement around the long string casing. This can be done using a technology that 

is capable of radially mapping the cement and casing to look for changes in the cement quality 

and potential leakage pathways. 

As part of the testing report the data for the injection wells and monitor wells for the previous 12 

months will be summarized in tabular and graphical format and interpreted. 

4.1 Environmental Monitoring

The owner/operator must perform environmental monitoring during the injection phase of the 

project to delineate the AoR. Environmental monitoring should therefore provide information 

about the boundary of the CO2 plume and the associated pressure front created by injection. 

Resources within the AoR, like minerals and USDWs, must also be monitored to ensure that they 

are not endangered by leakage of the injected CO2 or migration of formation fluids. 

Plume and Pressure Front Monitoring

The separate-phase CO2 plume and associated zone of increased pressure must be monitored to 

determine its location throughout the injection and post-injection phases of the CCS project. The 

first measurements to delineate the CO2 plume and the extent of the pressure front should be 

conducted within one year after the start of injection. Following the first measurements, 

monitoring should occur on a timeframe determined to be appropriate based upon the initial 

characterization and modeling, with a minimum of every 3 months during operational injection. 

The technologies used to delineate both the CO2 plume and the pressure front must be of 

sufficient resolution to visualize the maximum extent of the plume in three dimensions. 

Soil Gas and Surface Air Monitoring

Monitoring of gases in the vadose zone and at the surface is not generally expected to be an 

effective method for determining potential endangerment of USDWs. However, a leak detected 

at the surface will provide a potential indication that a leak into a USDW has already occurred 

and may need to be remediated. In particular, gas monitoring should be implemented in highrisk zones where characterization and modeling data indicate that it could be useful. 

5.0 POST-INJECTION MONITORING

The owner/operator must sustain the environmental monitoring during the post-injection phase 

of the project. This monitoring should be a continuation of the environmental monitoring that 

occurred during the injection phase, and it should provide information about the boundary of the 

CO2 plume and the associated pressure front created by the injection. Resources within the 

AOR, like minerals and USDWs, must also continue to be monitored to ensure that they are not 

endangered by leakage of the injected CO2 or formation fluids. The post-injection monitoring 

should be performed on an annual basis.

The separate-phase CO2 plume and associated zone of increased pressure must continue to be 

monitored to determine its location throughout the post-injection phase of the CCS project. 

Measurements to delineate the CO2 plume and identify the extent of the pressure front should 
Page 40 of 60

continue to be conducted on a timeframe established based on the operational phase monitoring 

and modeling. 

Water quality should continue to be monitored in the first porous zone above the primary 

confining unit, in the lowermost USDW above the injection zone, and in any other USDWs that 

may be affected by CO2 injection. Monitoring of vadose zone and surface gases should continue 

and/or be implemented based on the locations where site characterization and modeling indicate 

it would be useful, particularly in high-risk areas.

5.1 Criteria for Cessation of Monitoring

The decision to halt monitoring should be based on the determination of an acceptably low risk 

of endangerment to USDWs. This determination may be made when site monitoring data and 

modeling indicate that the following have occurred:

 The pressure due to injection has dissipated

 The separate-phase CO2 plume has stabilized 

 The separate-phase CO2 plume is reasonably expected not to encounter a pathway that 

will create a significant risk of leakage.

Once the risk of endangering USDWs is determined to be acceptably low, the project director 

may approve the cessation of monitoring.

6.0 REFERENCES

Environmental Protection Agency, 2008. Proposed Requirements under the Underground 

Injection Control Program from Carbon Dioxide Geologic Sequestration. July, 2008. 

Environmental Protection Agency, 2005. Guidance on Systematic Planning using the Data 

Quality Objective Process. EPA QA/G-4. February, 2005. 

IPCC (International Panel on Climate Change), 2005. Special Report on Carbon Dioxide 

Capture and Storage. 
Page 41 of 60

ATTACHMENTS 

FOR 

SECTION III
Page 42 of 60

Example Sample Data Recording Form - Monthly Injection Well Report

Month/Year:

Daily

Injection Pressure Injection Flow Inj Vol Weekly Monthly

Day

Max 

PSI

Min 

PSI

Avg 

PSI

Max 

GPM

Min 

GPM

Avg 

GPM Gallons

Cl 

mg/L

NH3 

mg/L

TKN 

mg/L

Sulfide 

mg/L pH

Sulfate

mg/L

TDS 

mg/L

Cond 

mmhos

Temp

C

Alkalinity

Mg/L

Hg

Mg/L

Pb

Mg/L

Ca

mg/L

Mg 

mg/L

Fe

Mg/L

Bicarb

Mg/L

G 

Alpha 

pCi/L

C 13 

pCi/L

C 14 

pCi/L

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

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19

20

21

22

23

24

25

26

27

28

29

30

31

TOTAL

MIN

MAX

AVG
Page 43 of 60

Example Sample Data Recording Form - Monthly Monitor Well Report

Month: Year: 

Upper Zone Lower Zone

Max. Sustained psi Min. Sustained psi Avg. Sustained psi Max. Sustained psi Min. Sustained psi Avg. Sustained psi

Date Day

1

2

3

4

5

6

7

8

9

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12

13

14

15

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29

30

31

MAX

MIN

AVG
Page 44 of 60

Example Sample Data Recording Form - Standardized Monthly Operating Data Summary

MONTHLY REPORT DATE

FACILITY FACILITY GMS ID #

EFFLUENT POINT TEST SITE GMS ID #

TEST SITE PAID #

UIC PERMIT NUMBER LEAD OPERATOR

PERMIT DATE OF ISSUANCE #

EXPIRATION DATE DAY TIME PHONE #

CASING DEPTH FT.BLS

TOTAL DEPTH FT.BLS

ASSOCIATED INJECTION WELL

TEST PERIOD (MONTHLY) SAMPLING DATE

PARAMETER STORET CODE* VALUE UNITS

PRESSURE, MO AVG

SUSTAINED PRESSURE, MO MAX

SUSTAINED PRESSURE, MO MIN

BICARBONATE as HCO3

MAGESIUM, DISSOLVED

IRON

POTASSIUM DISSOLVED

SODIUM

SULFATE TOTAL as SO4

NITROGEN TOTAL KJELDAHL as N (TKN)

TEMPERATURE WATER
Page 45 of 60

Example Sample Data Recording Form - Monthly Injection Well Report

Month: Year:

Annulus Tank Injection Pressure Injection Flows Injection Volumes

Date Day

Avg. 

Level 

Inches

Avg. 

Pressure 

PSI

Max. 

Pressure 

PSI

Min. 

Pressure 

PSI

Avg. 

PSI

Max. 

Sustained 

PSI

Min. 

Sustained 

PSI

Avg. 

ShutIn PSI

Avg. 

GPM

Max. 

Sustained 

GPM

Min. 

Sustained

GPM

Peak 

Hour 

GPM

Injection 

Total 

MG

Conc. 

Total 

MG

Waste 

Plant 

Total 

MG

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

MIN

AVG

TOTAL
Page 46 of 60

Example Sample Data Recording Form - Monthly Monitoring Well Report

Month/Year:

 Monthly

Upper Zone Lower Zone

Day

Cl 

mg/L

NH3 

mg/L

TKN 

mg/L

NO3 

mg/L pH

TPO4 

mg/L

TDS 

mg/L

Cond 

mmhos

SO4 

mg/L

G 

Alpha 

pCi/L

Rs 

226 

pCi/l

Rs 

228 

pCi/l

Cl 

mg/L

NH3 

mg/L

TKN 

mg/L pH

TPO4 

mg/L

TDS 

mg/L

Concd 

mmhos

SO4 

mg/L

G 

Alpha 

pCi/L

Rs 

226 

pCi/L

Rs 

228 

pCi/L

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

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19

20

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26

27

28

29

30

31

MIN

MAX

AVG
Page 47 of 60

IV. COMMENTS ON RULE TEXT

Part 144.6(f): Would “lowermost USDW” include formations that are not USDW’s at 

the point of injection but become USDW’s within the extent of the 

expected area of influence of the injection plume? AWWA recommends

that these types of formations be included within the definition of USDW 

based on the ability of carbon dioxide to easily migrate within the confines 

of an aquifer.

Part 144.36(a): The geologic sequestration of carbon dioxide is not a fully proven 

technology and much is unknown about the long-term impacts, and 

potential unintended consequences of such injection. As previously 

stated, AWWA believes it would be prudent to limit the life of the Class 

VI permit so that necessary adjustments to the permit can be made as 

needed, with the opportunity for public comment. This will also establish 

a process for obtaining updated information on the injection operation. We 

would recommend a permit life of no more than 5 years. Therefore, 

AWWA recommends revising this part to read:

Permits for Class I and V wells shall be effective for a fixed term not to 

exceed 10 years. UIC Permits for Class II and III shall be issued for a 

period up to the operating life of the facility. Permits for Class VI wells 

shall be effective for a fixed term not to exceed 5 years. 

Part 146.5(f): There is the possibility that some of the geologic sequestration activities 

will occur in areas where there are no USDWs located in the area of 

review. These wells should still be permitted as Class VI wells, and 

AWWA recommends revising the Class VI definition to:

(f) Class VI. Wells used for geologic sequestration of carbon dioxide in 

the following applications:

1. Where carbon dioxide is injected below the lowermost formation 

containing a USDW; and,

2. Where carbon dioxide is injected in formations where no USDWs 

exist within the zone of elevated pressure associated with the 

injection well. 

Wells used for the geologic storage of carbon dioxide in formations 

above the lowermost USDW are prohibited.

This definition would capture all wells associated with geologic carbon 

sequestration activities whether or not a USDW was present in the 

projected footprint of the project. 

Part 146.81 AWWA recommends defining the quality of the injection stream and 

establishing a minimum concentration of carbon dioxide. This 

requirement for the injection stream will ensure that the injection of other 
Page 48 of 60

harmful or undesirable gases is limited. Our initial thoughts on this topic 

would be that 100% of the injectate must come from a carbon dioxide 

capture process and the injectate must be at least 98% carbon dioxide. 

Owner/operators must ensure that the remaining 2% of the injectate is not 

made up of compounds that would result in the injectate being classified 

as a hazardous waste. As AWWA is not an expert on this topic, we would 

suggest that EPA pursue research in association with DOE to develop a 

standard for the minimum concentration of carbon dioxide in the injection 

stream. 

Part 146.81(c) Specific benchmarks should be established to demonstrate that USDWs 

will not be endangered if the well is exempted from the casing and 

cementing requirements provided in Parts 146.86(b) and 146.87(a)(1) 

through (3). This will provide for a consistent application of this 

requirement across each permitting agency. 

Part 146.81(d) AWWA recommends revising the definition of “pressure front” to read:

Pressure front means the zone of elevated pressure that is created by the 

injection of carbon dioxide into the subsurface. For the purposes of this 

subpart, the pressure front of a carbon dioxide plume refers to a zone 

where there is a pressure differential sufficient to cause the movement of 

injected fluids or formation fluids through an injection zone, and/or 

confining zone, and into a USDW.

Part 146.81(d) AWWA recommends revising the definition of “transmissive fault or 

fracture” to read:

Transmissive fault or fracture means a fault, fracture or other 

discontinuity that has sufficient permeability and vertical extent to allow 

fluids to move between formations.

Part 146.82(b) AWWA recommends revising the second to the last sentence to read:

The map should also show faults and other major geologic discontinuities, 

if known or suspected. 

Part 146.82(b) AWWA recommends that the last sentence be deleted from this part. 

Owner/operators should be required to go beyond the data available in the 

public record to identify some of the features listed in this requirement. 

For example, the owner/operator should be required to do its due diligence 

to identify all abandoned wells, plugged wells or old boreholes in the area 

of review. While public records may be a good starting point for the 

identification of these features, given the fact that some of the existing 

wells could be decades old, it is hard to believe that records would exist 

for every one of them. EPA should mandate that owner/operators use well 
Page 49 of 60

identification technology to locate any existing wells that are not listed in 

the public record. 

AWWA recommends revising this part to read:

A surface map showing the injection well(s) for which a permit is sought 

and the applicable area of review. Within the area of review, the map 

must show the number, or name and location of all injection wells, 

producing wells, abandoned wells, plugged wells or dry holes, deep 

stratigraphic boreholes, State or EPA approved subsurface cleanup sites, 

surface bodies of water, springs, mines (surface and subsurface), quarries, 

water wells and other pertinent surface features including structures 

intended for human occupancy and roads. The map should also show 

faults, if known or suspected. The owner or operator must include all 

information available in the public record, as well as conducting 

independent site investigations to locate any of the above features that 

may not be identified in the public record.

Part 146.82 (c) AWWA recommends revising this part to read:

A map delineating the area of review based upon modeling, using all 

available data including data obtained during geophysical logging and 

testing of the well and the formation as required by paragraphs (l), (r), and 

(s) of this section.

Part 146.82(d)(1) AWWA recommends revising this part to read:

Isopach maps of the area of review, including the proposed injection and 

confining zone(s), a structural contour map hung on the top of the 

proposed injection zone, and at least two geologic cross sections of the 

area of review showing the geologic formations from the surface to total 

depth. 

Part 146.82(d)(2) AWWA recommends revising this part to read:

Location, orientation, and properties of known or suspected subsurface

faults, fractures, and other discontinuities that may transect the confining 

zone(s) in the area of review and a determination that they would not 

interfere with containment.

Part 146.82(d)(3) AWWA recommends revising this part to read:

Information on the seismic history within the proposed area of review

including presence and depth of seismic sources, knowledge of previous 

seismic events and history of these events, and a determination that the 

seismicity would not interfere with containment. 
Page 50 of 60

Part 146.82(d)(4) AWWA recommends revising this part to read:

A spreadsheet with data on the depth, areal extent, thickness, mineralogy, 

porosity, permeability, capillary and reservoir pressure of the injection 

and confining zone(s) within the area of review; including any 

geologic/facies changes based upon field data which may include geologic 

cores, outcrop data, seismic surveys, well logs, and names and lithologic 

descriptions.

Part 146.82(d)(5) AWWA recommends revising this part to read:

Geomechanical information on fractures, stress, ductility, rock strength, 

and in situ fluid pressures on the injection and confining zones within the 

area of review.

Part 146.82(e) AWWA recommends revising the first sentence to read:

A spreadsheet of all wells and other artificial penetrations within the area 

of review which penetrate the injection or confining zone(s). 

Part 146.82(f) AWWA recommends revising this part to read:

Potentiometric (water level) surface maps and stratigraphic cross sections 

indicating the general vertical and lateral limits of all USDWs including 

existing aquifers not meeting the definition of a USDW that are either 

currently being utilized as private or public water supplies or are 

identified as a future water supply, water wells and springs within the area 

of review, their positions relative to the injection zone(s) and the direction 

and velocity of water movement. At least two geologic cross sections 

showing the thickness and general vertical and lateral limits of all USDWs 

within the area of review. 

Part 146.82(g) This part should provide a list of the formations for which baseline 

geochemical data should be obtained. AWWA recommends revising this 

part to read:

Collection of baseline geochemical data on the subsurface formations, 

including all USDWs in the area of review. At a minimum, geochemical 

data should be provided for the injection formation, the confining zone 

immediately above the injection zone, the nearest adjacent porous and 

permeable formation to the confining zone, all USDWs in the area of 

review including existing aquifers not meeting the definition of a USDW 

that are either currently being utilized as private or public water supplies

or are identified as a future water supply, as well as for any additional 

formations as required by the Director.
Page 51 of 60

Part 146.82(h)(1) AWWA recommends revising this part to read:

Average and maximum daily injection rate and volume of the carbon 

dioxide stream.

Part 146.82(h)(2) AWWA recommends revising this part to read:

Average and maximum surface injection pressure;

Part 146.82(k) AWWA recommends revising this part to read:

Proposed stimulation program and a determination that stimulation will 

not interfere with or breach the confining layer.

Part 146.82(n) AWWA recommends revising this part to read:

Engineering drawings of the surface and subsurface construction details of 

the system, including design features for surge control and water hammer 

protection, including the following:

(i) Record drawings, based upon inspections by the engineer of record 

or persons under his direct supervision, with al deviations noted;

(ii) Copies of the mill certificates of all casings used in the construction 

of the well;

(iii) Certification of completion submitted by the engineer of record;

(iv) An operation manual including emergency procedures;

(v) Proposed monitoring program and data to be submitted;

(vi) Proof that the existence of the well and any associated monitoring 

wells have been recorded with the permanent warranty deed or other 

instrument of conveyance as a two page proviso or addendum that 

contains certification of the locations of the wells (by metes and 

bounds) and a detailed sketch of the parcel that shows the location 

of the well. The location shall be measured by a certified land 

surveyor, and shall contain the surveyor's signature, registration 

number, official seal, and the following statement: "I hereby certify 

that this survey was made under my responsible direction and 

supervision, and is a correct representation of the land surveyed."

Part 146.82(q) As the Director should approve the corrective action plan prior to any 

activities taking place within the area of review, AWWA recommends

revising this part to read:

The plan for corrective action on artificial penetrations within the area of 

review and the status of any correction actions, if previously approved by 

the Director. 
Page 52 of 60

Part 146.82(s) As the well should not yet be constructed when the owner/operator applies 

for the permit, the demonstration of mechanical integrity should not have 

occurred yet. Therefore, AWWA recommends revising this part to read:

The proposed demonstration method for mechanical integrity pursuant to 

§146.89. 

Part 146.82(v) As monitoring wells may also have to be plugged, AWWA recommends

revising this part to read:

Proposed injection and monitoring well(s) plugging plan required by 

§146.92(b). 

Part 146.83(a)(1) AWWA recommends revising this part to read:

An injection zone of sufficient areal extent, thickness, porosity, and 

permeability to receive the total anticipated volume of the carbon dioxide 

stream, and at a depth with sufficient overburden pressure to keep the 

carbon dioxide stream as a supercritical fluid.

Part 146.83(a)(2) AWWA recommends revising this part to read:

A confining zone(s) that is free of transmissive faults or fractures and of 

sufficient areal extent and integrity to contain the injected carbon dioxide 

stream and displaced formation fluids and allow injection at proposed 

maximum pressures and volumes without initiating or propagating

fractures in the injection and confining zone(s).

Part 146.83(b) This part of the rule should a requirement, not an option that can be 

requested at the discretion of the Director. While it is possible that a site 

with a single confining can provide storage integrity, AWWA 

recommends that additional confining layers at the site be characterized to 

get a better estimate of leakage risk to USDWs and possibly identify 

additional monitoring zones. It is important to know if these zones exist, 

and to have adequately documented their characteristics, to evaluate and 

demonstrate the possibility of secondary containment. AWWA 

recommends revising this part to read:

Owners or operators of Class VI wells must identify and characterize 

additional zones that will impede vertical fluid movement, are free of 

faults, fractures or other discontinuities that may interfere with 

containment, allow for pressure dissipation, and provide additional 

opportunities for monitoring, mitigation and remediation.

Part 146.84 It is important to note that the carbon dioxide plume will never cease 

moving. Even deep formations have a natural flow gradient, and it is 
Page 53 of 60

likely that there will always be some movement due to changes in density 

gradients and diffusion. This should be considered when defining the 

AoR for each project.

Part 146.84(c)(1)(iii) AWWA recommends revising this part to read:

Consider potential migration through faults, fractures, other 

discontinuities and artificial penetrations.

Part 146.84(c)(2) AWWA recommends revising the first sentence to read:

Using methods approved by the Director, identify all penetrations, 

including active and abandoned wells and underground mines, in the area 

of review that may penetrate any portion of the confining zone.

Part 146.84(d) AWWA recommends revising this part to read:

Owners or operators of Class VI wells must perform corrective action on 

all wells and other artificial penetrations in the area of review that are 

determined to need corrective action using methods necessary to prevent 

the movement of fluid into or between USDWs and between the injection 

zones(s) and USDWs, including use of corrosion resistant materials, where 

appropriate.

Part 146.84(d) Based upon our comments in the previous section of this document, 

AWWA recommends revising this part to read:

At the minimum fixed frequency, not to exceed one (1) year for the first 

ten (10) years of the operation of the carbon sequestration project and not 

to exceed five (5) years after the first ten year time period, as specified in 

the approved area of review and corrective action plan, or when 

monitoring and operational conditions warrant, owners or operators must:

Part 146.85(b) AWWA believes that potential changes in the size of the area of review

require that all site plans be reevaluated at the same frequency as the area 

of review. Therefore, AWWA recommends revising this part to read:

The owner or operator must provide to the Director, at the same frequency 

as the AOR reevaluation, written updates of adjustments to the cost 

estimate to account for any amendments to the area of review and 

corrective action plan (§146.84), the testing and monitoring plan 

(§146.90), the injection well plugging plan (§146.92), the post-injection 

site care and site closure plan (§146.93), and the emergency and remedial 

response plan (§146.94).
Page 54 of 60

Part 146.86(b)(1) AWWA recommends revising the second to the last sentence to read:

The casing and cementing program must be designed to prevent the 

movement of fluids into or between USDWs and between the injection 

zone(s) and USDWs. 

Part 146.86(b)(1)(i) AWWA recommends revising this part to read:

Depth to the injection zone and overburden pressures in the injection 

zone.

Part 146.86(b)(1)(v) The corrosiveness evaluation should include the possible combining of the 

carbon dioxide stream and the injection zone water, which has a higher 

potential to corrode than the carbon dioxide alone. AWWA recommends

revising this part to read:

Corrosiveness, chemical compatibility and reactivity of the carbon dioxide 

stream and the formation fluids located within the injection zone.

Part 146.86(b)(1)(viii)AWWA recommends revising this part to read:

Type or grade of cement and chemical compatibility and reactivity of 

cement and formation fluids located within the injection zone.

Part 146.87(b) AWWA suggests that submittal of the cores to the Director 

is not very practical. The requirement should be rewritten to state that the 

Director should be provided with a summary report describing the cores 

and the test results. The operator should be required to first submit a 

coring plan to the Director listing the intervals to be cored, the coring 

procedures, the tests to be conducted and proposed storage of the core for 

review and consideration of approval by the Director. A core report, 

including the test results, geomechanical characteristics, and values 

calculated from the testing, such as fracture gradient, should be submitted 

to the Director. The owner/operator should make the cores available for 

inspection by the Director upon the request. AWWA recommends

revising this part to read:

The owner or operator must submit to the Director a report describing

whole cores or sidewall cores representative of the injection zone and 

confining system and formation fluid samples from the injection zone(s). 

The Director may accept data from cores and fluid samples from nearby 

wells if the owner or operator can demonstrate that such data are 

representative of conditions at the well. The Director may require the 

owner or operator to core other formations in the borehole to acquire more 

information on the subsurface geologic characteristics.
Page 55 of 60

Part 146.88(a) AWWA is concerned that the limitation on injection 

pressure to 90% of the fracture pressure is not stringent enough. We heard 

it stated at the public hearing in Denver that fracturing of the injection 

formation can occur when injection pressures are below 90% of the 

fracture pressure. It is important to consider that injection pressure 

limitations need to take account of the possibility that, under certain 

conditions, faults can be re-activated even if injection pressures are kept 

below the level necessary to create new fractures or propagate existing 

fractures. Therefore, the regulation should provide for the injection 

pressure to be calculated based on the site geology, hydrogeology and 

geomechanics, in combination with the injection pressure limitation. 

Injection pressures and rates should be determined by well tests and 

geomechancial studies, taking into account both formation fracture 

pressure and formation parting pressure. However, due to the amount of 

uncertainty associated with this topic, AWWA recommends that EPA 

research their proposed limitation in more detail to determine the best 

method for preventing possible contamination of USDWs. Therefore, we 

recommend revising this part to read:

The owner or operator must ensure that injection pressure and rates 

remain within limits established by permit. Such permit limitations shall 

be based on well tests and geomechanical studies, including assessments 

of both the fracture pressure of the confining zone and the parting 

pressure of the confining zone. In no case may injection pressure initiate 

or propagate fractures in the confining zone, cause otherwise nontransmissive faults transecting the confining zone to become transmissive, 

otherwise degrade the integrity of the confining zone, or cause the 

movement of injection or formation fluids that endangers a USDW.

Part 146.88(b) AWWA recommends revising this part to read:

Injection of the carbon dioxide stream between the outermost casing 

protecting USDWs and the well bore is prohibited.

Part 146.88(d) AWWA recommends that the final rule require mandatory implementation 

of a Supervisory Control and Data Acquisition (SCADA) system as part of 

the geologic carbon sequestration system. This system would allow for 

continuous monitoring and storage of the data associated with the 

operation of the injection well. Owner/operators would be able to review 

data trends and detect anomalies or potential problems before they occur. 

This SCADA system should also be tied to a carbon dioxide detector to 

alarm and shut off the well in the event that carbon dioxide is detected 

above a pre-set level.
Page 56 of 60

Part 146.89(f) AWWA recommends revising this part to read:

The Director may require additional or alternative tests if the results 

presented by the owner or operator under paragraph (d) of this section are 

not satisfactory to the Director to demonstrate that there is no significant 

leak in the casing, tubing or packer or significant movement of fluid into 

or between USDWs, or between the injection zone(s) and USDWs, 

resulting from the injection activity as stated in paragraphs (a)(1) and (2) 

of this section.

Part 146.90 AWWA recommends revising this part to read:

The owner or operator of a Class VI well must prepare, maintain, and 

comply with a testing and monitoring plan to verify that the geologic 

sequestration project is operating as permitted and is not endangering 

USDWs. The testing and monitoring plan must be submitted with the 

permit application, for Director approval, and must include a description 

of how the owner or operator will meet the requirements of this section. 

The testing and monitoring plan must be reviewed and updated, as 

necessary, on the same schedule as the update to the Area of Review.

Part 146.90(d) AWWA recommends revising this part to read:

Periodic monitoring of the ground water quality and geochemical changes 

within (if wells can be installed without adversely affecting the integrity of 

the confining zone) and above the confining zone(s) that may be a result of 

carbon dioxide movement through the confining zone or additional 

identified zones:

Part 146.90(d)(1) AWWA recommends revising this part to read:

The location and number of monitoring wells must be based on specific 

information about the geologic sequestration project, including injection 

rate and volume, geology, the presence of natural discontinuities and

artificial penetrations and other factors.

Part 146.90(g) AWWA recommends revising this part to read:

Testing and monitoring to track the extent of the carbon dioxide plume 

and the position of the pressure front by either monitoring for pressure 

changes in the confining zone, in the first formation overlying the 

confining zone or using indirect, geophysical techniques (e.g., seismic, 

electrical, gravity, or electromagnetic surveys and/or down-hole carbon 

dioxide detection tools);
Page 57 of 60

Part 146.90(h)(1) AWWA recommends revising this part to read:

 The testing and monitoring plan must be based on site-specific geologic 

factors, modeling, and a risk-assessment of potential vulnerabilities within 

the area of review;

Part 146.91(11)(a) AWWA believes that the reporting frequency should be on a monthly 

basis, similar to what water and wastewater treatment plants have to do. 

The operating information for the geologic sequestration project is 

extremely important and needs to be reviewed at a frequency by the 

regulatory agency to ensure problems are identified and addressed in a 

timely manner. For example, with the way the regulation is currently 

structured, data collected on July 1, 2008 would not be seen by the 

regulatory agency before January 15, 2009, if the operator is allowed 15

days to submit the report. This would allow for very little time to correct 

any potential issues in the operation of the project. As such, AWWA 

recommends revising this part to read:

Monthly reports, due on the 15th day of each month for the previous 

month’s activities, containing:

Part 146.92(b) As previously stated AWWA believes that potential changes in the size of 

the area of review require that all site plans be reevaluated at the same 

frequency as the area of review. Therefore, AWWA recommends revising 

this part to read:

Well Plugging Plan. The owner or operator of a Class VI well must 

prepare, maintain, and comply with a plan that is acceptable to the 

Director. The plan must be reviewed and revised by the owner or 

operator, and submitted to the Director for approval, at the same 

frequency and time as the AOR reevaluation. The requirement to maintain 

and implement an approved plan is directly enforceable regardless of 

whether the requirement is a condition of the permit. The well plugging 

plan must be submitted as part of the permit application and must include 

the following information:

Part 146.92(b)(5) AWWA recommends revising this part to read:

The type and grade and quantity of material to be used in plugging. The 

material must be compatible with the carbon dioxide stream and preinjection formation conditions; and
Page 58 of 60

Part 146.93(a) As previously stated AWWA believes that potential changes in the size of 

the area of review require that all site plans be reevaluated at the same 

frequency as the area of review. Therefore, AWWA recommends revising 

this part to read:

The owner or operator of a Class VI well must prepare, maintain, and 

comply with a plan for post-injection site care and site closure that meets 

the requirements of paragraph (a)(2) of this section and is acceptable to the 

Director. The plan must be reviewed and revised by the owner or 

operator, and submitted to the Director for approval, at the same 

frequency and time as the AOR reevaluation.

Part 146.93(b)(2) AWWA recommends that there should be a minimum 50 year postinjection monitoring period for all carbon sequestration projects. This 

time period is necessary to monitor the site for changes that may occur 

over a longer amount of time, such as gradual leakages, or sudden seismic 

shifts. After this time period, the owner/operator may apply to the 

Director for a modification or termination of the monitoring requirements.

AWWA recommends revising this part to read:

If, after the 50-year post-injection monitoring period, the owner or 

operator can demonstrate to the satisfaction of the Director, based on 

monitoring and other site-specific data, that the geologic sequestration 

project no longer poses an endangerment to USDWs, the Director may 

approve an amendment to the post-injection site care and site closure plan 

to reduce the frequency of monitoring or may authorize site closure before 

the end of the 50-year period.

Part 146.93(b)(3) When addressing plume stabilization in association with site closure, it is 

important to realize that the carbon dioxide plume will never be 

completely stable. The carbon dioxide plume will continue to move by a 

combination of methods including density differences, natural formation 

flow gradients and diffusion. AWWA recommends that EPA engage in 

research to provide specific criteria on what exactly it would mean for the 

plume to have stabilized. If left up to the discretion of the various 

Directors, stabilization could be defined in many different ways. In order 

to have a consistent application of this part of the regulation, EPA should 

define the specific situations in which the plume could be considered 

“stable.” AWWA recommends revising this part to read:

Prior to authorization for site closure, the owner or operator must 

demonstrate to the Director, based on monitoring and other site-specific 

data that no additional monitoring is needed to assure that the geologic 

sequestration project does not pose an endangerment to USDWs. The 

demonstration must demonstrate all of the following: 
Page 59 of 60

(i) the estimated magnitude and extent of the project footprint (CO2 

plume and the area of elevated pressure) based on measurements 

and modeling; 

(ii) that CO2 movement and pressure changes match model 

predictions, 

(iii) the estimated location of the detectable CO2 plume based on 

measurement and modeling (measuring magnitude of saturation 

within the plume or mapping the edge of it); 

(iv) that there is no evidence of significant leakage of either CO2 or 

displaced formation fluids that endanger USDWs; 

(v) that the CO2 plume and displaced formation fluid are not expected 

to migrate in the future in a manner that encounters a potential 

leakage pathway; 

(vi) that the injection wells at the site completed into or through the 

injection zone or confining zone are properly plugged and 

abandoned; and,

(vii) any remaining project monitoring wells at the site are being 

managed by a person and in a manner acceptable to the Director.

Part 146.93(c) AWWA recommends that this part of the rule needs to include a directive 

that the Director needs to provide approval for site closure prior to 

implementation of the site-closure plan. AWWA recommends revising 

this part to read:

Notice of intent for site closure. The owner or operator must notify the 

Director at least 120 days before site closure. At this time, if any changes 

have been made to the original post-injection site care and site closure 

plan, the owner or operator must also provide the revised plan. The 

Director must provide approval for site closure prior to the 

implementation of the site closure plan. At the discretion of the Director, 

a shorter notice period may be allowed.

Part 146.93(d) There may be cases where the Director would want some of the 

monitoring wells to remain in service after site closure. While this may 

not be the case for all projects, for some of the earlier sites, the Director 

may want to continue minimal monitoring to continue to verify that the 

plume characteristics have remained stable. 
Page 60 of 60

Part 146.94(a) It is important that the emergency and remedial response plan is reviewed 

and updated on the same schedule as the area of review update. Changes 

in the area of review could affect the actions that would need to be taken 

in the event of an emergency. AWWA recommends revising this part to 

read:

As part of the permit application, the owner or operator must provide the 

Director with an emergency and remedial response plan that describes 

actions to be taken to address movement of the injection or formation 

fluids that may cause an endangerment to a USDW during construction, 

operation, closure and post-closure periods. The emergency and remedial 

response plan must be reviewed and updated, as necessary, on the same 

schedule as the update to the Area of Review.
Letter ID: 0181 

Commenter: Thomas Curtis 

Organization: American Water Works Association (AWWA) 

Letter ID: 0181 Comment ID: 23643 Letter Lines: 81 to 83 

Comment Code: 1200 1.1 General comments about the rulemaking 

Comment: - Protection of underground sources of drinking water (USDWs) should be the 

highest priority - water should trump everything! 

- Prevention of unintended consequences is of utmost importance; 

Individual Response: EPA agrees that protecting USDWs is a high priority. The purpose of the 

GS regulation is to ensure consistency in permitting underground injection of CO2 at GS 

operations across the United States and provide requirements to prevent endangerment of 

USDWs in anticipation of the eventual use of GS to reduce CO2 emissions. Please see the 

remainder of EPA's responses to this comment for further details. For additional information on 

EPA's final regulatory approach, please see the final rule and preamble as well as the rulemaking 

docket. 

Letter ID: 0181 Comment ID: 23644 Letter Lines: 84 to 86 

Comment Code: 2100 1.6 Target Geologic Formations for GS 

Comment Code: 4322 2.4.4.1.1 Comments in favor of requiring injection below the lowermost 

USDW 

Comment: - Injection of carbon dioxide and construction of injection wells should not be 

allowed in or near sole source aquifers, coal seams, earth-quake prone areas, or 

above the lowermost USDWs; 

Individual Response: EPA clarifies that the GS rule does not preclude injection into any nonUSDWs non-USDW formations, provided the site-suitability requirements in the GS rule are 

met. The purpose of the GS rule is to ensure protection of USDWs from endangerment, and the 

rule requires that owners or operators demonstrate that wells are sited in suitable systems with 

geologic formations to receive and confine injected CO2, required at §146.83 of the GS rule. If 

an owner or operator can demonstrate to the Director's satisfaction that GS in coal seams, basalts, 

salt domes, or shales can be accomplished in a manner that protects USDWs and meets all of the 

requirements of the GS rule, the project may be permitted as a Class VI well. 

In response to the comment that GS should not be allowed in areas with high-risk for a seismic 

event, EPA clarifies that the GS rule does not allow GS to be performed in seismically active 

areas and requires that operators must submit information about the seismic history of and 

seismic sources near a proposed GS site, as required at §146.82(a)(3)(v). This information, along 

with other required submissions, will be evaluated by the Director, who will determine the 

suitability of a potential project site for GS. 

1
Additionally, the GS rule, at 146.82(a)(5) requires prospective owners or operators to submit 

information on all USDWs, which would include sole source aquifers within the AoR. Based on 

that information the Director must consider the potential impact of the GS project on all USDWs, 

including any sole source aquifers when determining whether GS is acceptable at a given site. 

EPA clarifies that a state’s Class VI primacy program may be more stringent then the federal 

requirements. For example, a state has the discretion to ban GS projects from taking place in 

formations or areas that affect sole source aquifers. EPA anticipates that state permitting 

authorities are in the best position to make determinations about the appropriateness of a 

particular site based on all available information, including drinking water supply needs. 

As described above, the Agency believes that there are limited circumstances where injection 

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 or operators can seek a waiver of the Class VI injection depth requirements for injection 

into non-USDW formations above and/or between USDWs. 

Letter ID: 0181 Comment ID: 23645 Letter Lines: 87 to 87 

Comment Code: 4120 2.4.1.2 Allowing hydraulic fracturing during GS (seeking comment) 

Comment: - Hydraulic fracturing should not be used at all for GS; 

Individual Response: EPA emphasizes that fracturing of the confining zone during injection 

and/or stimulation is prohibited, as specified at §146.88(a). However, EPA believes there are 

some circumstances where fracturing of the injection zone is acceptable, provided the integrity of 

the confining system remains unaffected. The final rule allows the use of hydraulic fracturing at 

GS sites, where approved by the Director. Hydraulic fracturing is one of several stimulation 

technologies available to improve wellbore and formation injectivity. 

EPA clarifies that all stimulation, including hydraulic fracturing, must be approved by the 

Director. Owners or operators must submit a proposed stimulation program as part of the permit 

application under §146.82(a)(9); the plan must demonstrate that any stimulation activities will 

not compromise the integrity of the confining zone. The Director will evaluate the owner or 

operator's proposed stimulation plan in the context of all information about the site, and the 

owner or operator must perform stimulation only as approved. 

The final rule at §146.91(d)(2) also requires that the owner or operator notify the Director 30 

days before performing stimulation during the operational phase of a GS project; this will 

provide an additional opportunity for the Director to review the owner or operator's plans for 

stimulation and add other requirements as needed. 

Letter ID: 0181 Comment ID: 23646 Letter Lines: 88 to 91 

2
Comment Code: 1200 1.1 General comments about the rulemaking 

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

projects is responsible for any costs born by drinking water utilities due to 

increased treatment requirements for that ground water or replacement of lost 

capacity; and, 

Individual Response: As described above, EPA clarifies that the purpose of the GS regulation is 

to ensure consistency in permitting underground injection of CO2 at GS operations across the 

United States and provide requirements to prevent endangerment of USDWs in anticipation of 

the eventual use of GS to reduce CO2 emissions. 

Letter ID: 0181 Comment ID: 23647 Letter Lines: 92 to 93 

Comment Code: 1220 1.1.1.1 Terminology and definitions 

Comment Code: 4400 2.4.4.3 Allowing injection above or between USDWs (seeking comment) 

Comment: - The 10,000 mg/l TDS limit for classifying USDWs for the siting of Class VI 

wells needs to be revised upward. 

Individual Response: EPA is not changing the USDW definition; changing the definition of a 

USDW is outside the scope of the GS rulemaking. The GS rule focuses on ensuring protection of 

USDWs, as required under the SDWA, by establishing regulations to ensure the safe injection of 

CO2 for long-term storage. 

Letter ID: 0181 Comment ID: 23648 Letter Lines: 95 to 100 

Comment Code: 1200 1.1 General comments about the rulemaking 

Comment: In its comments, AWWA makes several recommendations for the following specific 

items to be included in the final regulation: 

- Requirement to consult with the state environmental department and affected 

water utilities to determine which aquifers currently not classified as USDWs 

might be considered as future drinking water sources; 

Individual Response: As part of the UIC permit review process in 40 CFR §124, the UIC 

Program Director is required to notify certain stakeholders of any public hearings and the 

availability of the draft permit. 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 EPA's final regulatory approach, please see the final rule and preamble as well as 

the rulemaking docket. 

3
Letter ID: 0181 Comment ID: 23649 Letter Lines: 95 to 96 ; 101 to 102 

Comment Code: 1220 1.1.1.1 Terminology and definitions 

Comment: In its comments, AWWA makes several recommendations for the following specific 

items to be included in the final regulation: 

- Definition of "endangerment" that includes water quality impacts beyond those 

contaminants with MCLs; 

Individual Response: EPA disagrees that endangerment should be defined in the context of the 

Class VI GS rule. Rather, the Agency clarifies that the purpose of the Class VI GS regulation, 

promulgated under authority of the SDWA, is to ensure that, where GS is deployed, it is 

conducted in a manner that protects USDWs from endangerment. 

Based on its evaluation of all public comments and input on the proposed rule and the NODA 

and Request for Comment, EPA has made many revisions to the Class VI GS rule. Please see the 

final rule and preamble for additional information. 

Letter ID: 0181 Comment ID: 23650 Letter Lines: 95 to 96 ; 103 to 104 

Comment Code: 5400 2.9 Proposed Financial Responsibility and Long-Term Care 

Requirements 

Comment: In its comments, AWWA makes several recommendations for the following specific 

items to be included in the final regulation: 

- Addressing liability, treatment costs for remediation, and financial recourse 

for a water utility if a USDW is degraded due to a GS project; 

Individual Response: The goal of financial responsibility is to ensure that financial resources 

are available to prevent endangerment of USDWs from improper plugging, remediation, and 

management of wells in the event that the owner or operator experiences financial difficulties. 

As such, owners or operators must demonstrate financial responsibility for, among other things, 

any needed emergency and remedial response actions that are necessary to mitigate 

endangerment of USDWs. Furthermore, the financial responsibility provisions provided the final 

GS rule are intended to ensure the owner or operator will be held liable for remediating or 

correcting any endangerment of USDWs via their demonstrated financial instrument up through 

site closure. For example, if during the life of the GS project (up until site closure) a Class VI 

well leaks, which results in endangerment of a USDW, the primacy State of other 3rd party 

beneficiary can call upon that financial instrument to pay for remediation or corrective action. 

EPA wants to clarify that the Agency can never be the beneficiary of the financial instrument 

used to meet §146.95 due to limitations under the Miscellaneous Receipts Act. See the final rule 

and preamble for further discussion of EPA's final approach to financial responsibility for Class 

VI wells. 

4
Letter ID: 0181 Comment ID: 23651 Letter Lines: 95 to 96 ; 105 to 106 

Comment Code: 2060 1.5.3 Comments on grandfathering of existing wells (seeking comment) 

Comment: In its comments, AWWA makes several recommendations for the following specific 

items to be included in the final regulation: 

- Requirement for owner/operators of grandfathered wells to certify that the 

wells were constructed and cemented with materials appropriate for GS wells; 

Individual Response: EPA agrees that a cautious approach to grandfathering is appropriate, 

particularly given that the converted well will be used for a substantially different process, which 

involves increased reservoir pressures associated with large volumes of stored CO2 and the 

corrosivity of CO2 in the presence of water. The final GS rule provides for the construction of 

these wells to be grandfathered (per 146.81(c)). EPA has included a requirement in the final GS 

rule that owners or operators seeking to convert existing wells for long term storage must 

demonstrate to the Director that the grandfathered wells were engineered and constructed meet 

the requirements at §146.86(a) and ensure protection of USDWs, in lieu of requirements at 

§146.86(b) and §146.87(a). 

Letter ID: 0181 Comment ID: 23652 Letter Lines: 95 to 96 ; 107 to 108 

Comment Code: 3300 2.2.1 Delineating the AoR/Modeling CO2 movement 

Comment: In its comments, AWWA makes several recommendations for the following specific 

items to be included in the final regulation: 

- Development of a standard computation flow model to delineate the area of 

review; 

Individual Response: EPA believes that operators should have the flexibility to select models 

with which they are familiar and that are most appropriate to the site conditions and available 

data types and amounts. EPA also recognizes that a standardized model for AoR delineations 

could be effective as long as the model accounts for the expected variations in site conditions, 

and adds that a state or regional UIC Director has the discretion to select one standard model if it 

took site-specific variations into account. 

EPA does not envision that members of the public would evaluate the AoR delineation models 

themselves. The models and their inputs will, by necessity, entail an extensive amount of 

technical information that may not be easily understood by the public. EPA believes that it is the 

Director's responsibility, as a steward of public health and the environment, to review models, 

model inputs, and results and to determine whether the model is appropriate for predicting the 

AoR, and to distribute information that may be easily understood by the public (e.g., in the form 

of a fact sheet). However, the models must be made available to the public. 

5
Letter ID: 0181 Comment ID: 23653 Letter Lines: 95 to 96 ; 109 to 110 

Comment Code: 3530 2.2.3.1 AoR reevaluation frequency (seeking comment) 

Comment: In its comments, AWWA makes several recommendations for the following specific 

items to be included in the final regulation: 

- Reevaluation of the area of review annually for the first ten years, and then 

every five years for the remaining life of the project; 

Individual Response: EPA agrees with commenters that reevaluations of the AoR every ten 

years may not be sufficient to appropriately model plume and pressure front movement, establish 

conditions for corrective action, and ensure protection of USDWs from endangerment. For these 

reasons, the Agency changed the minimum frequency for the AoR reevaluation at §146.84(e) 

from 10 years to at least every 5 years in the final GS rule. EPA believes that this revised 

frequency addresses commenters' concerns about the inherent uncertainties in modeling CO2 

movement, the emerging nature of GS technology, risk-based targeting of monitoring activities, 

and the unique nature of CO2 GS. In addition, the Director has discretion to require more 

frequent AoR reevaluation if he or she has reason to believe, based on site-specific information, 

that a five-year reevaluation schedule is not sufficiently protective of USDWs. 

Letter ID: 0181 Comment ID: 23654 Letter Lines: 95 to 96 ; 111 to 112 

Comment Code: 3150 2.1.5 Comments on required permit information (40 CFR 146.82) 

Comment Code: 4710 2.7.1 Proposed submissions required for permit applications (seeking 

comment) 

Comment: In its comments, AWWA makes several recommendations for the following specific 

items to be included in the final regulation: 

- A permit process for geologic sequestration (separate from the coal plant), 

with required monthly reporting similar to the NPDES permit/reporting process; 

Individual Response: EPA believes that permitting under the UIC Program is an essential 

element for ensuring that GS projects are operated in a manner that protects USDWs from 

endangerment. The UIC Program establishes minimum federal requirements for owners or 

operators of GS wells; and, States may choose to develop requirements that are as stringent as or 

more stringent than the minimum federal requirements. This affords states the flexibility to 

implement the program while ensuring that USDWs are protected from endangerment. If a State 

does not develop UIC Program requirements for Class VI wells, EPA implements the program in 

those states. The Agency clarifies that all owners or operators of Class VI wells must comply 

with the requirements under Subpart H of 146 in order to inject CO2 for GS through a Class VI 

well. A UIC injection well permit application is separate from other permitting activities (i.e., 

coal plant permitting). 

6
EPA believes that the extensive requirements for geologic site characterization (at §146.82), 

AoR evaluation (§146.84), and testing of the well during drilling (§146.87) are appropriate to 

ensure that permitting authorities have the necessary information to evaluate whether a specific 

site will allow safe injection of CO2. EPA adds that submittal and review of monitoring data (as 

required at §146.90) and the AoR reevaluation process (§146.84(e)) will provide an opportunity 

for an ongoing review of the site and a dialogue between the Director and the owner or operator 

to ensure that the project is being operated in a manner that protects USDWs from 

endangerment. 

EPA is developing a number of technical guidances and implementation materials to assist 

owners or operators and Directors in the permitting process. These guidances will provide 

recommendations regarding performing many of the activities necessary for applying for a 

permit, including developing all required plans and conducting site characterizations that meet 

the requirements of §146.82. These guidances can be found on EPA’s website at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

EPA clarifies that owners or operators of Class VI GS wells must comply with UIC semi-annual 

reporting requirements at 146.91(a). EPA believes that semi-annual reporting is appropriate to 

ensure that permitting authorities can maintain proper oversight of GS projects, particularly in 

the early stages of rule implementation and deployment of GS technologies. The Agency also 

clarifies that permitting authorities may choose to require more frequent reporting, at the 

discretion of the Director. 

EPA clarifies that it does not have the authority under the SDWA (and associated UIC 

requirements) to alter permitting requirements issued under other environmental statutes for coal 

plants or any CO2 sources. The UIC program's authority is limited to the injection operation and 

ensuring that USDWs are protected from endangerment. 

Letter ID: 0181 Comment ID: 23655 Letter Lines: 95 to 96 ; 113 to 113 

Comment Code: 4600 2.6 Proposed Plume and Pressure Front Monitoring Requirements (40 

CFR 146.90) 

Comment: In its comments, AWWA makes several recommendations for the following specific 

items to be included in the final regulation: 

- Inclusion of detailed monitoring requirements in the final regulation; 

Individual Response: EPA disagrees that the rule should specify the monitoring techniques for 

all GS sites. EPA believes that flexibility is important in developing and implementing a 

monitoring plan that is appropriately tailored for a specific GS site. The purpose of the 

requirement at §146.90 to develop site-specific testing and monitoring plans is to ensure that the 

monitoring performed at a site is appropriate for site operational conditions and the geologic 

setting. EPA believes that this is the best approach for addressing potential risks at GS sites. 

These flexible provisions in the monitoring requirements for Class VI wells enable the owner or 

7
operator to tailor monitoring programs to the specific needs of each project in consultation with 

the Director. 

EPA is developing guidance on testing and monitoring to assist owners or operators and 

Directors in evaluating requirements under §146.90, including proposed monitoring plans. The 

guidance describes available technologies and recommended approaches for implementing a 

testing and monitoring plan, including pre-operational geophysical logging and testing of 

injection wells, MITs, injection well testing during operation, groundwater quality monitoring, 

tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may 

be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s 

website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in 

January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and 

Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this 

manual is included in the docket for the final GS rule. 

Letter ID: 0181 Comment ID: 23656 Letter Lines: 95 to 96 ; 114 to 115 

Comment Code: 3150 2.1.5 Comments on required permit information (40 CFR 146.82) 

Comment Code: 4710 2.7.1 Proposed submissions required for permit applications (seeking 

comment) 

Comment: In its comments, AWWA makes several recommendations for the following specific 

items to be included in the final regulation: 

- Requirement for formal technical, managerial, and financial plans for GS 

owners/operators; and 

Individual Response: EPA agrees that requiring project plans for GS wells is appropriate. The 

final GS rule requires owners and operators to develop, gain approval for, and implement a series 

of project-specific plans, including: an area of review (AoR) and corrective action plan, a testing 

and monitoring plan, an injection well plugging plan, a post-injection site care and site closure 

plan, and an emergency and remedial response plan. All of these plans must be submitted at the 

time of permit application (§146.82(a)), along with a demonstration that appropriate financial 

resources are available, pursuant to requirements at §146.85, to fund all required activities. EPA 

believes that the requirement for the plans associated with GS projects will promote an ongoing 

dialogue between the owner or operator and the Director to ensure that USDWs are protected 

from endangerment. EPA is developing guidances to assist owners or operators in describing 

how to prepare the project plans and how to meet the financial responsibility requirements for 

GS wells. The guidances can be found on EPA’s website at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

Letter ID: 0181 Comment ID: 23657 Letter Lines: 95 to 96 ; 116 to 118 

Comment Code: 5560 2.10.3 Enhancing the public participation process (seeking comment) 

8
Comment: In its comments, AWWA makes several recommendations for the following specific 

items to be included in the final regulation: 

- Requirement for mandatory public notification and public hearings for any new 

permit and any permit revision or renewal, and for a 90-day public comment 

period 

Individual Response: EPA disagrees that a 90-day comment period should be required for all 

GS projects. EPA believes that the existing public comment period requirements at §124.10, 

which require a minimum 30-day comment period for draft permits, and which require public 

notice for most permit modifications, are appropriate for GS projects. The Agency does not 

believe it is appropriate to impose longer time frames if they are unnecessary, but supports the 

Directors' discretion and authority under §124.10 to extend the public comment period if he or 

she determines that such an extension is warranted. Circumstances that may affect a Director's 

determination may include the level of public interest in a GS project, specific permit details, or 

project-specific considerations. 

EPA also disagrees that public hearings should be mandatory for all GS permits, in order to 

account for the possibility that, if the public does not express an interest in a hearing, holding one 

would not be useful. 40 CFR 124.12 requires the Director to hold public hearings if there is a 

significant degree of interest in a draft permit. EPA expects that public hearings will be requested 

and held for many GS projects, due to the expected level of public interest in GS projects. 

Letter ID: 0181 Comment ID: 23658 Letter Lines: 120 to 125 

Comment Code: 1510 1.2.2.3 Need for additional study 

Comment: Several issues need more research by EPA and DOE, and the following research 

needs to be completed prior to issuance of the final regulation: 

- Criteria for the determination that the carbon dioxide plume has stabilized; 

- The potential for seismic shifts due to subsurface pressure changes; 

- The minimum concentration of carbon dioxide in the injection stream; and 

- The types of tracers that would be acceptable for GS. 

Individual Response: EPA agrees that continued research will be integral to development of GS 

technology, but disagrees that the Agency should wait for all current field research to be 

complete before finalizing the GS rule. The Agency believes that establishing a regulatory 

framework for the future development and deployment of CCS technology provides a framework 

for injecting CO2 so that the activity does not result in endangerment of USDWs. 

To protect USDWs from endangerment and meet the potentially fast pace of GS deployment, 

EPA is using an adaptive approach to regulating CO2 injection for GS. 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. An adaptive 

9
approach will allow regulatory development to proceed in time to meet the current and future 

demands for Class VI permits, while EPA continues to gather data from pilot projects and other 

research as it becomes available. 

Letter ID: 0181 Comment ID: 23659 Letter Lines: 139 to 143 

Comment Code: 1200 1.1 General comments about the rulemaking 

Comment: AWWA appreciates the opportunity to comment on the proposed requirements for 

geologic sequestration wells as published in the July 25th, 2008 Federal 

Register (73 FR 43491). Protection of underground sources of drinking water 

(USDWs) should be a key priority of any geologic carbon sequestration regulation 

developed as part of the Underground Injection Control (UIC) Program. 

Individual Response: EPA agrees that protecting USDWs is a high priority. The purpose of the 

GS regulation is to ensure consistency in permitting underground injection of CO2 at GS 

operations across the United States and provide requirements to prevent endangerment of 

USDWs in anticipation of the eventual use of GS to reduce CO2 emissions. Please see the 

remainder of EPA's responses to this comment for further details. For additional information on 

EPA's final regulatory approach, please see the final rule and preamble as well as the rulemaking 

docket. 

Letter ID: 0181 Comment ID: 23660 Letter Lines: 156 to 187 

Comment Code: 1200 1.1 General comments about the rulemaking 

Comment: I. GENERAL COMMENTS 

In 2007, approximately 78% of 52,000 community water systems in the United 

States were supplied by groundwater and these systems served 90.5 million 

people. In addition, many surface water utilities are currently looking at 

conjunctive use and/or groundwater development as adaptation measures (supply 

portfolio diversification/new storage) to combat climate change. Each of these 

utilities could potentially be impacted by geologic carbon sequestration, simply 

by the fact that these utilities utilize groundwater resources. 

The proposed regulation is a good technical starting point given the evolving 

state of geologic sequestration; however, the proposed rule has many limitations 

that could allow for the endangerment of underground sources of drinking water 

(USDWs). Many of the requirements are based on faith, and not a lot of data, and 

the drinking water community is being asked trust that geologic sequestration 

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

technology on 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 

10
based on modeling exercises, with limited monitoring data to validate these 

models and limited real-life data to support the requirements. There is the 

possibility for unintended consequences to occur with geologic sequestration is 

very real, 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. Prevention is the key word 

here. AWWA will address these issues, as well as some other important concerns, 

in this section of general comments. 

Individual Response: EPA disagrees that GS is analogous to the MTBE situation. EPA believes 

that large scale GS can be done safely. 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 as it implements its adaptive approach to GS rulemaking to incorporate 

new research, data, and information about GS. An adaptive approach provides Class VI owners 

or operators the flexibility to use and apply newly developed technologies for GS as they become 

available in the future. 

The GS regulation builds upon the long-standing, protective regulatory framework of the UIC 

program, which has been regulating the injection of fluids for decades. The GS regulation 

enhances this existing framework with tailored requirements for Class VI GS wells to address the 

unique nature of large scale GS of CO2. These protective requirements include extensive 

geologic testing, detailed computational modeling of the AoR and periodic re-evaluations, 

detailed requirements for monitoring and tracking the CO2 plume and pressure front, and 

extended post-injection monitoring and site care. 

Letter ID: 0181 Comment ID: 23661 Letter Lines: 189 to 357 

Comment Code: 1220 1.1.1.1 Terminology and definitions 

Comment Code: 4400 2.4.4.3 Allowing injection above or between USDWs (seeking comment) 

Comment: USDW Classification: The best sources of drinking water are already being used 

by utilities. In many areas, population growth is forcing utilities to look 

further or to look at more challenging sources. 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. Additionally, the pumping costs for these deep wells 

are no longer prohibitive given the lack of sufficient water sources. 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 proposed 

rule promises protection of USDWs from endangerment, in that the activity does 

11
not cause a primary drinking water Maximum Contaminant Level (MCL) to be 

exceeded in an USDW or affect human health. There are no anti-degradation 

provisions in the proposed regulation to protect other groundwater supplies, 

such as those aquifers that are not classified as a USDW but have been, or may 

be, identified as a future drinking water source. 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. 

Technological advances in the area of desalination have reduced many of the 

treatment costs, making it more and more accessible. Many utilities have no 

other choice for new water sources. Ever increasing population and water demands 

have utilities using non-traditional and poorer water sources (see Table 1-1 for 

examples; note that this is not meant to be a comprehensive list of all 

desalination plants in the United States). 

Table 1-1: Water Utilities with More Challenging Water Sources 

[The information below was originally presented as a table. See Docket PDF EPAHQ-OW-2008-0390-0181 to see a copy of the original table.] 

Utility Name: El Paso Water Utilities and Ft.Bliss, Texas 

Water Source: Hueco Bolson Basin 

Usage: 27.5 mgd 

TDS Concentrations: 600 to 4,900 mg/l 

Utility Name: Tampa Bay Water, Florida 

Water Source: Seawater 

Usage: 25 mgd 

TDS Concentrations: 18,000 - 32,000 mg/L 

Utility Name: Yuma Desalting Plant, Arizona 

Water Source: Drainage water 

Usage: 22 mgd 

TDS Concentrations: 3,200 mg/L 

Utility Name: Miami-Dade County, Florida 

Water Source: Florida Aquifer 

Usage: 17.5 mgd (currently under design) 

TDS Concentrations: 1,000 - 5,000 mg/L 

Utility Name: Temescal Desalter Project, California 

Water Source: Temescal Basin 

Usage: 15 mgd 

TDS Concentrations: 700 mg/L 

12
Utility Name: City of Abilene, Texas 

Water Source: Surface water 

Usage: 8.0 mgd 

TDS Concentrations: 1,200 mg/L 

Utility Name: City of Sherman, Texas 

Water Source: Surface water 

Usage: 7.5 mgd 

TDS Concentrations: 900 - 1500 mg/L 

Utility Name: Southmost Regional Water Authority, Texas 

Water Source: Groundwater 

Usage: 6.75 mgd 

TDS Concentrations: 3,500 mg/L 

Utility Name: Lake Granbury SWATS,Texas 

Water Source: Surface water 

Usage: 6.0 mgd 

TDS Concentrations: 1,800 mg/L 

Utility Name: City of Fort Stockton, Texas 

Water Source: Groundwater 

Usage: 6.0 mgd 

TDS Concentrations: 1485 mg/L 

Utility Name: Newport News WTP, Virginia 

Water Source: Lower and Middle Potomac Aquifers 

Usage: 5.7 mgd 

TDS Concentrations: 3600 mg/L 

Utility Name: Alameda County Water District, California 

Water Source: Niles Cone Groundwater Basin 

Usage: 5.0 mgd with expansion to 10 mgd 

TDS Concentrations: 1,100 - 2,400 mg/L 

Utility Name: Pascagoula, Mississippi 

Water Source: Groundwater 

Usage: 4.5 mgd 

TDS Concentrations: 1,000 mg/L 

Utility Name: Dare County North WTP, North Carolina 

Water Source: Groundwater 

Usage: 3.0 mgd 

TDS Concentrations: 4,300 mg/L 

13
Utility Name: Port Hueneme Brackish Water Facility, California 

Water Source: Groundwater 

Usage: 3.0 mgd 

TDS Concentrations: 1,300 mg/L 

Utility Name: James City Service Authority, Virginia 

Water Source: Middle and Lower Potomac Aquifers 

Usage: 2.5 mgd 

TDS Concentrations: 1,000 - 2,400 mg/L 

Utility Name: Buxton, North Carolina 

Water Source: Groundwater 

Usage: 2.0 mgd 

TDS Concentrations: 13,200 mg/L 

Utility Name: Cape May, New Jersey 

Water Source: Groundwater 

Usage: 2.0 mgd 

TDS Concentrations: 2,100 mg/L 

Utility Name: Dare County Cape Hatteras WP, North Carolina 

Water Source: Groundwater 

Usage: 2.0 mgd 

TDS Concentrations: 11,200 mg/L 

Utility Name: Las Animas, Colorado 

Water Source: Groundwater 

Usage: 1.18 mgd 

TDS Concentrations: 3,500 mg/L 

Utility Name: VA Medical Center, Ft. Lyon, Colorado 

Water Source: Groundwater 

Usage: 0.24 mgd 

TDS Concentrations: 800 mg/L 

The use of very deep and/or high salinity groundwater becoming more commonplace 

is only a matter of time. Therefore, we believe the 10,000 mg/L TDS USDW 

definition is no longer appropriate. Given that this regulation does not 

currently extend protection to non-traditional and poorer water sources, AWWA 

believes that these aquifers may be adversely impacted by this rulemaking. These 

aquifers, which have not been previously used as a drinking water source, may be 

in the future, and it is important to make sure that they are adequately 

protected. AWWA recommends that EPA consider the "green-effect" and that, in 

many cases, the overall least cost alternative may be to treat brackish 

groundwater using desalination technology instead of trying to obtain surface 

14
water as the drinking water source. While the surface water may be less 

expensive to treat, if the utility is located in a dry environment, such as 

Arizona or New Mexico, the pumping costs to transport that water over a large 

distance may be much larger than the cost to treat a brackish groundwater. EPA 

should also consider that as technology evolves, utilities will be able to treat 

a much different set of waters than is currently being treated. Several 

utilities are using sea water or brackish water as drinking water sources, which 

would not have been even remotely considered as a viable option 20 years ago, 

when the TDS limit was originally developed. 

Recognizing that it is difficult to extend protection to these aquifers due to 

the restrictions of the SDWA, AWWA recommends that the regulation be revised to 

mandate that, during the project planning process, the owner/operators should 

include state environmental departments as they can provide insight into what 

aquifers currently (not 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 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. 

Individual Response: As described above, EPA is not changing the USDW definition; changing 

the definition of a USDW is outside the scope of the GS rulemaking. The GS rule focuses on 

ensuring protection of USDWs, as required under the SDWA, by establishing regulations to 

ensure the safe injection of CO2 for long-term storage. 

Letter ID: 0181 Comment ID: 23662 Letter Lines: 359 to 364 

Comment Code: 1220 1.1.1.1 Terminology and definitions 

Comment Code: 1610 1.3.1 Risks to USDWs 

Comment Code: 4400 2.4.4.3 Allowing injection above or between USDWs (seeking comment) 

Comment: USDW Endangerment: AWWA recommends revision to the definition of 

"endangerment" 

in the proposed rule. The current definition of endangerment is limited to SDWA 

UIC definition of 10,000 TDS and to primary MCL contamination. Certain healtheffects can be related to concentrations in water of compounds that do not 

exceed the primary MCL. However, under the current language, these potential 

contaminants would not be covered with the protections afforded by the SDWA. 

Individual Response: The Agency acknowledges commenter concerns about water resources 

and future water resource availability. However, modifying the definition of a USDW or 

“endangerment” is outside the scope of the GS rulemaking. USDWs are defined as aquifers 

currently being used as sources of drinking water or those capable of supplying a public water 

system and they have a total dissolved solids (TDS) content of 10,000 milligrams per liter or less 

as specified in §144.3. EPA adds that concerns about contaminants with health effects even at 

15
concentrations below the maximum contaminant level should be addressed as part of the review 

process for the national primary drinking water regulations; such concerns are outside the scope 

of this rulemaking. Please note that the definition of “endangerment” has been defined by 

Congress at SDWA §1421(d)(1)(2). 

The primary goal of the UIC Program under the SDWA is to protect USDWs from 

endangerment in order to ensure a reliable supply of drinking water for the American public. The 

GS rule, as part of the UIC program regulations, continues the program’s mandate of ensuring 

the protection of USDWs. EPA expects the tailored permitting, siting, construction, operation, 

monitoring, and post-injection site care requirements in the GS rule to prevent leakage from 

injection formations and protect USDWs. 

Letter ID: 0181 Comment ID: 23663 Letter Lines: 366 to 378 

Comment Code: 1610 1.3.1 Risks to USDWs 

Comment Code: 1650 1.3.5 Human health impacts 

Comment: EPA should also consider the risk associated with the potential exposure of any 

contaminants that are released to the surface. While we recognize that a gradual 

leak may have little impact, the potential of a catastrophic leak is always 

present. EPA should be mindful during the rulemaking process of not only the 

risk to drinking water, but also of other potential risks from exposure to other 

constituents such as pH, lead and copper, iron, hardness, silica and boron. 

These are compound for which no MCLs have been developed but still impact 

drinking water quality and increase the necessary treatment costs. There could 

be potential health impacts due to long-term exposure to contaminant levels 

below the established MCLs. Also, beneficial uses of groundwater could also be 

impacted by increases of these compounds in the aquifers. Owners/operators could 

be in compliance with the regulation, but could be degrading an aquifer by 

contaminating it with compounds for which MCLs do not exist. 

Individual Response: EPA acknowledges that there are potential risks associated with GS, 

including the potential for leakage of CO2 into USDWs, which could result in the mobilization 

of substances that could pose threats to USDWs or human health or could increase treatment 

costs. The purpose of the Class VI requirements is to minimize and mitigate potential/identified 

risks through proper site characterization, well construction, operation, monitoring, postinjection site care, and site closure. The mandate of the UIC Program, and the GS rule, is to 

protect USDWs from endangerment that may be caused by underground injection. The GS rule 

accomplishes this through requirements tailored to address the unique nature of GS, including 

the large volumes of CO2 injected, its buoyancy and potential corrosivity in the presence of 

water, and impurities in the CO2 stream. Many of these requirements specifically address the 

potential for mobilized substances to affect USDWs. The GS rule is concerned with the 

migration of CO2 and displacement of native fluids that may result in endangerment of USDWs. 

16
For example, the owner or operator must submit data about the site, including information on the 

porosity, permeability, mineralogy, and geochemistry of the targeted injection and confining 

zones. Operators must also present information on the compatibility of the CO2 stream with 

fluids in the injection zone and minerals in both the injection and confining zones as specified in 

§146.82(c)(3). The data will help identify potential geochemical reactions between the injected 

CO2 and the host geologic formations, which could result in the plugging of pore spaces or the 

dissolution of formation minerals. During injection operations, operators must extensively 

monitor ground water quality to provide early detection of any unacceptable movement of fluids 

or impurities in the subsurface as specified in §146.90. Operators must develop and follow an 

emergency and remedial response plan to address any adverse effects associated with the GS 

operation as specified in §146.94 and provide financial responsibility to address contamination 

as specified in §146.85. 

Recent research has focused on addressing this concern. EPA is funding research at the 

Lawrence Berkeley National Laboratory (LBNL) on potential USDW impacts associated with 

mobilization of trace elements. In the August 31, 2009, Notice of Data Availability and Request 

for Comment (74 FR 44802), EPA published the results of the study, which evaluated the 

potential for GS to cause changes in ground water quality as a result of CO2 leakage and 

subsequent mobilization of trace elements such as arsenic, barium, cadmium, mercury, lead, 

antimony, selenium, zinc, and uranium (Birkholzer et al., 2008a). In the study, LBNL estimated 

the amount of trace elements from native mineral species that could potentially be mobilized by 

the intrusion of CO2 and the potential ground water concentrations that could result, to 

determine the potential for drinking water standards to be exceeded. Results from this model 

simulation suggest that if CO2 were to leak into a shallow aquifer, the potential for mobilization 

of lead and arsenic could be enhanced, causing increases in the concentration of these trace 

elements in ground water. The Agency continues to monitor research related to CO2 

confinement, potential for CO2 leakage, and mobilization of trace elements. 

EPA adds that concerns about contaminants that cause health effects but do not have maximum 

contaminant levels should be addressed as part of the review process for the national primary 

drinking water regulations; such concerns are outside the scope of this rulemaking. EPA has also 

examined potential methods for conducting treatment of water affected by a CO2 leak; this study 

is presented in the final rulemaking docket. 

Letter ID: 0181 Comment ID: 23664 Letter Lines: 380 to 420 

Comment Code: 1310 1.1.2.4 Comments on other "out of scope" issues, e.g., pore space 

ownership 

Comment Code: 1610 1.3.1 Risks to USDWs 

Comment: Assignment of Liability: Most importantly, the regulation does not seem to 

address the liability that would be realized by owners/operators of the geologic 

sequestration projects if water quality of USDWs is degraded by the operation of 

their project (even if the impacts are limited to MCLs). AWWA recommends that 

this issue be addressed in the final regulation, as drinking water utilities may 

have little financial recourse if the water quality one of their aquifers is 

17
degraded due to the operation of a geologic sequestration process. Provisions 

need to be included in the final rule that would allow the drinking water 

utility to recoup any costs that are realized due to increased treatment 

requirements for contaminated ground water or to replace lost capacity. In some 

cases, utilities may need to install different types of treatment to remove 

compounds that might not have been present in the water prior to the geologic 

sequestration project. In other instances, treatment may consist of the addition 

of more chemicals to facilitate precipitation of the inorganic compounds or the 

utility may have to backwash membranes more often, resulting in higher energy 

and other operation and maintenance costs. In any of these cases, the 

owner/operator of the geologic sequestration project should be required to 

reimburse the drinking water utility for these incurred costs, and they should 

also be required to continue such payments for as long as the ground water 

source remains degraded. 

Water utilities should not be penalized for having to develop local sites 

contaminated by sequestration activities for water supply. In fact they should 

be encouraged to do so, under the appropriate conditions, as there is no more 

critical public health issue than the need to provide potable water. In order to 

meet increasing demands imposed on them by a growing service population, water 

utilities will need to develop marginal water supplies. However, increased 

treatment costs due to contamination resulting from sequestration activities 

should not be borne by the local utility or their customers when national 

environmental objectives have been met without significant benefit to the local 

economy. 

Should a water utility "lose" an existing or future source of supply due to 

contamination or inaccessibility resulting from a sequestration project, there 

will be the issue of financial compensation (for treatment or development of an 

alternative source). As water resources become scarce, financial compensation 

for a lost source of supply may not suffice, as local alternatives may not be 

available. Hence, it will be critical that contingency planning to identify 

alternatives to the current groundwater supply be a part of the planning 

activities for the sequestration project, along with a commitment to provide an 

alternative source of water, should the need arise. 

Individual Response: EPA agrees that owners or operators of Class VI wells must ensure that 

resources are available to prevent endangerment of USDWs from improper plugging, 

remediation, and management of wells. For this reason, the GS rule requires that owners or 

operators demonstrate and maintain financial responsibility for corrective action on wells in the 

AoR, injection well plugging, post-injection site care and site closure, and emergency and 

remedial response at GS sites as specified in §146.85. In the event of contamination or other 

adverse event to the USDW during the life of the project, the financial instrument(s), such as 

insurance, bonds, etc., rather than public monies, would cover necessary response actions. EPA 

clarifies that it is the owner or operator of the well who will be required to demonstrate financial 

responsibility, not the generator of the CO2, consistent with EPA’s authority under SDWA. 

18
Furthermore, EPA notes that tort and other remedies will continue to be available after site 

closure. Other Federal environmental statutes, e.g. Clean Air Act, 42 U.S.C. §§7401-7671; 

CERCLA, 42 U.S.C. §9601-9675; and RCRA, 42 U.S.C. §6901-6992, potentially apply as well 

to the risks created by the long-term storage of CO2. EPA has also examined potential methods 

for conducting treatment of water affected by a CO2 leak; this study is presented in the final 

rulemaking docket. 

EPA clarifies that long-term liability beyond the life of the project (after site closure) is beyond 

the scope of the GS rulemaking. Please see the final rule and the discussion of financial 

responsibility and long-term liability in the preamble for additional information. 

EPA adds that Class VI well owners and operators must site, construct, operate, monitor, and 

close their wells in a manner that protects USDWs, and Class VI permits will set forth rigorous 

technical requirements to ensure careful planning, operation, and closure of GS projects. Failure 

to meet these requirements would be considered a violation of the permit and would be subject to 

applicable civil, criminal, or administrative penalties under SDWA §1423. 

Letter ID: 0181 Comment ID: 23665 Letter Lines: 422 to 426 

Comment Code: 1310 1.1.2.4 Comments on other "out of scope" issues, e.g., pore space 

ownership 

Comment: AWWA also recommends that the company generating the carbon dioxide must 

maintain sole ownership of the carbon dioxide they generate. This would ensure 

that liability remains with the original generator in perpetuity; even if the 

carbon dioxide is commingled with some generated from another facility or if its 

disposal is managed by another company. 

Individual Response: EPA clarifies that the final Class VI GS rule applies to owners or 

operators of wells that will be used to inject CO2 into the subsurface for the purpose of longterm storage, and not the generator of the CO2. Any issues related to "ownership" of generated 

CO2 are outside the scope of the Class VI GS rulemaking. Rather, the purpose of the Class VI 

GS rule is to ensure consistency in permitting underground injection of CO2 at GS operations 

across the United States and provide requirements to prevent endangerment of USDWs in 

anticipation of the eventual use of GS to reduce CO2 emissions. 

Letter ID: 0181 Comment ID: 23666 Letter Lines: 428 to 440 

Comment Code: 1610 1.3.1 Risks to USDWs 

Comment Code: 1616 1.3.1.3 Fluid movement 

Comment: Trespass and Aquifer Displacement: AWWA recommends that the potential for 

trespass be addressed in the final rule. Carbon dioxide plumes may migrate into 

a location that a drinking water utility was planning to utilize, possibly for 

aquifer storage and recovery. What recourse is provided by the proposed 

19
regulation in the event that trespass occurs, and damages are realized by the 

drinking water utility? Also, movement of the pressure front associated with a 

carbon dioxide plume may cause aquifers to shift in location, potentially moving 

them out of the jurisdiction of their original utility "owner." This can be a 

serious problem in certain portions of the country where ground water resources 

are limited or conflict, and utilities face intense competition for water 

rights. AWWA questions if an appropriate recourse will be provided by the 

sequestration project owner/operator in the event that these water rights issues 

become a reality for the drinking water utility. 

Individual Response: EPA clarifies that owners and operators must perform extensive site 

characterization and modeling of the AoR to determine the extent of the CO2 plume prior to 

approving a GS project. The financial responsibility requirements at§146.84 require owners and 

operators to demonstrate and maintain resources to address emergency and remedial response to 

adverse events that may occur associated with GS. This would include impacts to drinking water 

utilities associated with fluid displacement. 

Letter ID: 0181 Comment ID: 23667 Letter Lines: 442 to 469 

Comment Code: 1220 1.1.1.1 Terminology and definitions 

Comment Code: 4400 2.4.4.3 Allowing injection above or between USDWs (seeking comment) 

Comment: Safe Drinking Water Act Authority: In its February 2008 stakeholders meeting, 

EPA seemed to imply that it was restricted in what it could regulate and/or 

require under the SDWA for UIC projects to preventing "endangerment of USDW." 

AWWA recognizes that EPA’s regulatory authority is limited by the requirements 

of the SDWA and will be advocating that several portions of the SDWA be amended 

to better protect the nation’s groundwater resources. Issues that we will be 

addressing include: 

1. The definition of a USDW is provided within the SDWA, which may require 

amendment if the quality and accessibility groundwater sources is to be 

protected. We recognize that the 10,000 mg/L TDS limit is very outdated, and 

that a new upper limit should be established and applied when siting Class VI 

wells. We hesitate to recommend any specific number at this point in time, given 

that some drinking water utilities are so stressed for water resources that they 

are investigating extremely non-traditional water sources with high TDS levels. 

2. Endangerment is defined by the SDWA and may need to be redefined to protect 

beneficial uses. The proposed rule seems to be focused on preventing brine from 

the carbon dioxide storage formations from reaching USDWs and/or preventing 

carbon dioxide from contaminating USDWs and causing exceedences of primary MCLs. 

The protective measures of the proposed rule may not be adequate from a source 

water and beneficial use protection standpoint as other changes are likely to 

occur besides exceeding primary MCLs (e.g., increased Fe/Mn, TDS, and lowered pH 

- all of which have secondary MCLs and possible increase in silica and boron, 

20
which do not have MCLs, but have water quality significance). EPA needs to be 

provided with the regulatory authority to protect against these other types of 

endangerment, and the SDWA should be modified to allow for these protective 

measures to be developed. 

Individual Response: As described above, EPA is not changing the USDW definition; changing 

the definition of a USDW is outside the scope of the GS rulemaking. The GS rule focuses on 

ensuring protection of USDWs, as required under the SDWA, by establishing regulations to 

ensure the safe injection of CO2 for long-term storage. 

Letter ID: 0181 Comment ID: 23668 Letter Lines: 471 to 477 

Comment Code: 1660 1.3.6 Ecosystem impacts (soil, air, surface water) 

Comment: AWWA recommends that EPA not ignore the potential impacts outside of the scope 

of the SDWA such as those to air and human health if there is a massive leak. 

Could there be any conflicts or overlaps with the Clean Air Act or the Clean 

Water Act? Are other Program Offices within EPA planning on looking at this 

proposal? This review by other EPA Program Offices would seem to be necessary 

given the potential impacts that could arise if there is a failure of the 

confining layer. 

Individual Response: EPA acknowledges that there are potential risks associated with GS. The 

purpose of the Class VI requirements is to minimize and mitigate potential/identified risks 

through proper site characterization, well construction, operation, monitoring, post-injection site 

care, and site closure and to ensure protection of USDWs. EPA believes that the measures in the 

GS rule that directly mitigate the possibility of CO2 leakage out of the injection zone will also 

indirectly mitigate the risks to receptors mentioned by the commenters, including fresh water, 

wildlife, ecosystems, and agriculture. 

EPA acknowledges that GS falls within the broader context of CCS and acknowledges that 

regulatory clarity is essential for enabling GS to move forward in a manner that protects human 

health and the environment. The Agency is working to identify areas related to GS that could be 

addressed under other statutes to ensure that GS is conducted in a manner that is protective of 

human health and the environment. Additionally, the Agency is and will continue to coordinate 

internally and with other Federal agencies involved in GS and CCS, including the Minerals 

Management Service, Bureau of Land Management, and the United States Geological Survey, to 

promote consistency in existing and future GS initiatives. 

Letter ID: 0181 Comment ID: 23669 Letter Lines: 479 to 567 

Comment Code: 1610 1.3.1 Risks to USDWs 

Comment: Sole Source Aquifers: Several areas of the country rely on sole source aquifers 

as their drinking water resource. Given the special protective measures already 

21
afforded to these aquifers by EPA, AWWA strongly recommends that the final 

geologic sequestration regulation should restrict project activities in the 

vicinity of these aquifers. Table 1-2 below presents a list of some of the solesource aquifers that are located in potential geologic sequestration areas. 

(Note that this is not meant to be a comprehensive list of all of the sole 

source aquifers in the United States.) 

Table 1-2: Sole-Source Aquifers in Potential Geologic Sequestration Areas 

[The information below was originally presented as a table. See Docket PDF EPAHQ-OW-2008-0390-0181 to see a copy of the original table.] 

Aquifer Name: Upper Santa Cruz & Avra Basin Aquifer 

Location: Arizona 

Potentially Impacted: Tucson, Green Valley, Catalina 

Characteristics: Discharges 376,000 acre-feet per year 

Aquifer Name: Fresno County Aquifer 

Location: California 

Potentially Impacted: Fresno, Clovis 

Characteristics: Contains 5.8 million acre feet of water 

Aquifer Name: Volusia Sole Source Aquifer 

Location: Florida 

Potentially Impacted: Ormond Beach, Daytona Beach, New Smyrna Beach and Deland 

Characteristics: Covers 1,450 sq. mi. 

Aquifer Name: Biscayne Sole Source Aquifer 

Location: Florida 

Potentially Impacted: All of Dade County; parts of Broward, Monroe and Palm 

Beach Counties 

Characteristics: Covers 4,000 sq. mi. 

Aquifer Name: Eastern Snake River Plain Aquifer 

Location: Idaho 

Potentially Impacted: 300,000 residents of Eastern Idaho 

Characteristics: Contains 200 to 300 million acre-feet 

Aquifer Name: Spokane Valley-Rathdrum Prairie Aquifer 

Location: Idaho, Washington 

Potentially Impacted: 700,000 residents of Idaho and Washington 

Characteristics: Covers 325 sq. mi. 

Aquifer Name: Chicot Aquifer System 

Location: Louisiana 

Potentially Impacted: Lafayette, Lake Charles, Crowley 

22
Characteristics: Supplies 800 mgd, most for irrigation 

Aquifer Name: Southern Hills Aquifer System 

Location: Louisiana, Mississippi 

Potentially Impacted: Baton Rouge, Natchez, McComb 

Characteristics: Supplies 290 million gallons per day 

Aquifer Name: New Jersey Coastal Plain Aquifer System 

Location: New Jersey 

Potentially Impacted: Over 3,000,000 residents 

Characteristics: Over 350 million gal. withdrawn per day 

Aquifer Name: Northwest New Jersey Fifteen Basin Aquifer 

Location: New Jersey, New York 

Potentially Impacted: Over 500,000 residents 

Characteristics: Covers 1,735 square mile area 

Aquifer Name: Espanola Basin Aquifer System 

Location: New Mexico 

Potentially Impacted: Sante Fe, Los Alamos, and Española 

Characteristics: Covers 3,000 sq. mi. 

Aquifer Name: Clinton Street Ballpark Aquifer System 

Location: New York 

Potentially Impacted: Broome and Tioga Counties 

Characteristics: 16.25 mgd withdrawn for drinking water 

Aquifer Name: Miami Valley Buried Aquifer 

Location: Ohio 

Potentially Impacted: Serves over 1,600,000 residents 

Characteristics: Provides 200 mgd for drinking water 

Aquifer Name: Edwards Aquifer 

Location: Texas 

Potentially Impacted: San Antonia, San Marcos, New Branfels 

Characteristics: Discharges 900,000 acre-feet per year 

Aquifer Name: Columbia and Yorktown- Eastover Multiaquifer 

Location: Virginia 

Potentially Impacted: Exmore, Olney, Chincoteague 

Characteristics: Covers 695 sq. mi. 

Individual Response: The GS rule, at §146.82(a)(5) requires prospective owners or operators to 

submit information on all USDWs (which would include sole source aquifers) within the AoR. 

The GS rule also requires operators to submit extensive information about the site, including the 

geologic characteristics of the injection and confining zones, to demonstrate that the injected 

23
CO2 will remain within the target formation. The Director must consider this information when 

determining whether GS is acceptable at a given site. EPA expects that this determination will 

include consideration of potential impacts of the GS project on any sole source aquifers. 

EPA agrees that, in many cases, UIC Directors will have extensive knowledge of which areas are 

suitable for GS, but clarifies that it is the responsibility of Class VI permit applicants to 

demonstrate the suitability of a particular site or formation. It is the responsibility of the Director 

to evaluate the information collected and submitted by the owner or operator to determine 

whether a permit for GS at the site is appropriate. 

Letter ID: 0181 Comment ID: 23670 Letter Lines: 570 to 582 

Comment Code: 1610 1.3.1 Risks to USDWs 

Comment Code: 1810 1.4.1 Research on identifying risks to USDWs 

Comment: AWWA recommends that EPA prohibit owner/operators from constructing carbon 

dioxide injection wells in sole source aquifers. Owner/operators should also be 

prohibited from ever injecting carbon dioxide into a formation that would result 

in the migration of the carbon dioxide to a point that is under a sole source 

aquifer. EPA should establish a minimum distance that needs to be provided 

between the closest geologic sequestration project and the location of any sole 

source aquifers. AWWA would recommend a 50 mile minimum; however, not being 

experts on the details of plume migration, AWWA recommends that EPA and DOE 

perform research on this topic to better assess what the regulatory requirement 

should be. Including these restrictions in the final geologic sequestration 

regulation would allow for the protection of drinking water aquifers that, if 

contaminated by carbon dioxide, could result in very significant and expensive 

issues for the drinking water utilities. 

Individual Response: EPA believes that the extensive site characterization requirements for GS 

projects in the final rule are protective of USDWs, including sole source aquifers. The GS rule, 

at §146.82(a)(5) requires prospective owners or operators to submit information on all USDWs, 

which would include sole source aquifers within the AoR. The GS rule also requires operators to 

submit extensive information about the site, including the geologic characteristics of the 

injection and confining zones, to demonstrate that the injected CO2 will remain within the target 

formation. The Director must consider this information and the potential impact of the GS 

project on any sole source aquifers when determining whether GS is acceptable at a given site. 

EPA agrees that, in many cases, UIC Directors will have extensive knowledge of which areas are 

suitable for GS, but clarifies that it is the responsibility of Class VI permit applicants to 

demonstrate the suitability of a particular site or formation. It is the responsibility of the Director 

to evaluate the information collected and submitted by the owner or operator to determine 

whether a permit for GS at the site is appropriate. 

EPA is tracking other recent research on GS and USDW protection including the following 

studies (which are available in the docket for the rulemaking): 

24
• Smyth et al. (2008) reviewed modeling and laboratory experiments and field results from 

groundwater studies conducted at SACROC, an ER site in west Texas where tens of millions of 

tons of CO2 have been injected for over 30 years. 

• Zheng et al. (2008) used more than 38,000 groundwater quality analyses from aquifers 

throughout the US to perform reactive transport modeling of groundwater quality after the 

intrusion of CO2. The model simulations indicate that aquifers containing more carbonate and 

clay minerals are less vulnerable to CO2 intrusion, and that, while under certain conditions CO2 

can potentially mobilize metals present in the aquifer, mobilized amounts of the metals are 

always below health-based limits. 

• Kharaka et al. (2009) conducted CO2 injection field tests in Montana and reported that 

shallowly injected CO2 can affect the chemistry of shallow groundwater by decreasing pH and 

mobilizing rock and soil ions. 

• Nicot (2008) modeled an injection roughly equivalent to 50 Mt CO2/year for 50 years in an 

area that is hydrologically similar to the Gulf Coast Basin. Model results indicate an average 

water table rise of approximately 1 meter with a minor increase in stream baseflow and a larger 

increase in ground water evapotranspiration. 

ORD's National Center for Environmental Research awarded six Science To Achieve Results 

(STAR) grants in the Fall of 2009 to recipients from major universities and institutions within 

the scope of the "Integrated Design, Modeling and Monitoring of Geologic Sequestration of 

Anthropogenic Carbon Dioxide to Safeguard Sources of Drinking Water" research area. These 

projects, which started in late 2009, include these lead institutions with specific topics of 

investigation: Clemson University will study potential impacts to drinking water aquifers of 

CO2-rich dissolved brines; 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 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. 

Letter ID: 0181 Comment ID: 23671 Letter Lines: 584 to 594 

Comment Code: 1610 1.3.1 Risks to USDWs 

Comment: Water versus Energy: AWWA questions how will geologic sequestration projects 

will be permitted if there is potential competition for a specific geologic 

basin between an energy company and a drinking water utility. Water should trump 

everything. The water sector should be given priority, especially if a drinking 

water utility has limited or no other options, as they have very limited water 

and storage resources. It may also be possible that there may not be a single 

federal and/or state oversight agency that could provide guidance in this arena 

25
as the agency would need to have oversight for air, water, environmental, 

energy, and other sectors. The NEPA process and the state equivalent, such as 

CEQA in California, will need to be well fleshed out at the outset of the 

permitting process. 

Individual Response: The Agency agrees that drinking water is an important resource that 

needs protection. The primary goal of the UIC Program under the SDWA is to protect USDWs 

from endangerment. It is outside the scope of this rulemaking or EPA’s authority to provide the 

water sector any type of priority over storage areas. Consistent with SDWA §1422, the UIC 

program provides that no underground injection shall be authorized if it results in the movement 

of fluid containing any contaminant into USDWs, if the presence of that contaminant may cause 

a violation of any primary drinking water regulation or may adversely affect the health of 

persons as specified in §144.12. 

EPA has added a requirement at 40 CFR 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. 

Letter ID: 0181 Comment ID: 23672 Letter Lines: 596 to 619 

Comment Code: 1620 1.3.2 Induced seismicity 

Comment: Seismicity: The seismicity requirements in the Area of Review requirements are 

not very prescriptive. AWWA believes there is too much latitude for 

interpretation and that the regulation could be applied inconsistently by 

Directors of different states. AWWA recommends making the language stronger to 

clarify exactly what is meant by the following requirement (§146.82(d)(3)): 

"...information on seismic history including the presence and depth of seismic 

sources and a determination that the seismicity would not interfere with 

containment." A geologic sequestration project should be evaluated on the entire 

risk spectrum using different ranges of seismic activity and distance 

requirements from active faults to determine if the proposed site is acceptable. 

EPA should develop guidance that will assist owner/operators in making the 

appropriate determinations regarding seismic risk for a geologic sequestration 

project. For example, is there a minimum distance that should be provided 

between the potential plume footprint and an area of seismic activity? This 

information is critical as different owner/operators could decide to take on a 

different level of risk due to their comfort with the financial implications. 

AWWA does not want to see USDW protection compromised due to faulty assumptions 

about seismic activity in and around a potential project site. 

AWWA recommends that EPA also investigate the need for modeling the potential 

for seismic shifts due to the changes in subsurface pressures associated with 

the carbon dioxide injection process. A literature search should be performed to 

see if either Laurence Berkley National Laboratory or the National Energy 

26
Technology Laboratory has developed any information on this topic. 

Individual Response: EPA believes that decisions about seismic risk should be made on a sitespecific basis. The Class VI requirements are designed to ensure that, where GS is employed, it 

is done in a manner that protects USDWs from endangerment. These requirements include site 

characterization during which owners or operators must submit information about the seismic 

history of and seismic sources near a proposed GS site, as well as data on known or suspected 

faults in the AoR, geomechanical information on fractures, stress, ductility, rock strength, and in 

situ fluid pressures within the confining zone as specified in §146.82(a)(3). This information is 

evaluated by the Director in conjunction with information about well construction, operation, 

monitoring, post-injection site care, and other site-specific information. The Director determines 

the suitability of a potential project site for GS. Sites with the potential for reopening or 

reactivation of faults or unacceptable seismic risk that could otherwise interfere with 

containment would not be suitable for GS sites–as owners or operators seeking to inject CO2 for 

GS at such sites would not be able to demonstrate USDW protection from endangerment. 

The final rule also contains operational requirements to ensure USDW protection including 

injection pressure limitations. During injection, the pressure in the injection zone must not 

exceed 90 percent of fracture pressure of the injection zone as specified in §146.88(a). This 

requirement is intended to prevent the opening of fractures or faults through over pressurization 

of the injection zone. EPA adds that these requirements are based on extensive study and review 

of scientific literature and laboratory and field experience. 

EPA clarifies that the rule does not contain any specific requirements describing "seismically 

appropriate" areas, and does not believe this is appropriate for all sites. EPA believes such 

determinations should be made on a site-specific basis. If such information is available, and the 

Director determines it to be relevant to the site characterization, it is in their authority to require 

detailed evaluations. However, EPA disagrees that this should be a requirement for all GS 

projects. In many cases, UIC Directors will have extensive knowledge of which areas are 

suitable for GS, but clarifies that it is the responsibility of Class VI permit applicants to 

demonstrate the suitability of a particular site or formation. It is the responsibility of the Director 

to evaluate the information collected and submitted by the owner or operator to determine 

whether a permit for GS at the site is appropriate. 

To support consistent interpretation and application of the safeguards related to induced 

seismicity in the GS rule, EPA is developing guidance on site characterization for GS projects to 

assist owners or operators and Directors in evaluating permit requirements and applications 

under §146.82. The guidance provides recommendations to owners or operators regarding 

information to support characterizing the regional geology and hydrogeology of a proposed GS 

site as well as how to perform the necessary geochemical, geomechanical, and geophysical 

analyses of the injection and confining zone. EPA expects that this guidance will assist permit 

writers/UIC Directors in making an objective decision about requiring additional confining 

layers. The guidance can be found on EPA’s website at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

27
Letter ID: 0181 Comment ID: 23674 Letter Lines: 621 to 632 

Comment Code: 1310 1.1.2.4 Comments on other "out of scope" issues, e.g., pore space 

ownership 

Comment: Project Security: AWWA recommends that EPA work with the Department of 

Transportation and the Department of Homeland Security to ensure the safety and 

security of geologic sequestration projects. We have concerns about the 

unintentional or intentional release of stored carbon dioxide and the related 

control and monitoring systems required, as well as security measures. A 

requirement for strict monitoring systems during project construction and 

operation is necessary to ensure that the project is not intentionally 

sabotaged, as this could result in a massive leak of carbon dioxide out of the 

confinement zone and into the environment. EPA should mandate strict monitoring 

systems be included as part of any geologic sequestration project, not only to 

ensure the safety of USDWs, but also the safety of those living in the footprint 

of the project. 

Individual Response: EPA clarifies that pipelines and CO2 transport are outside the scope of 

the Class VI GS rulemaking. The Class VI GS regulation is being promulgated under authority 

of the Safe Drinking Water Act. The purpose of the Class VI GS rule is to ensure consistency in 

permitting underground injection of CO2 at GS operations across the United States and provide 

requirements to prevent endangerment of USDWs in anticipation of the eventual use of GS to 

reduce CO2 emissions. 

Regarding the comment on ensuring the safety and security of GS projects related to 

unintentional or intentional release of stored CO2, EPA clarifies that the purpose of the Class VI 

GS rule is to ensure that where GS technologies are deployed, GS is performed in a manner that 

protects USDWs from endangerment. EPA agrees that testing and monitoring are important 

aspects of ensuring USDW protection, and the Class VI GS rule requires that owners or 

operators develop and implement a testing and monitoring plan. See the final rule and preamble 

discussion of testing and monitoring requirements for additional information. 

Letter ID: 0181 Comment ID: 23675 Letter Lines: 634 to 644 

Comment Code: 1910 1.4.4 Stakeholder outreach 

Comment Code: 5560 2.10.3 Enhancing the public participation process (seeking comment) 

Comment: Data and Research Needs: AWWA believes that stakeholder access to the necessary 

data is lacking and will inhibit making informed/transparent decisions on 

geologic carbon sequestration projects. Stakeholders need better and more 

accessible data and data reduction tools (i.e., GIS maps). EPA should consider 

creating an interactive web based data warehouse that would store data and GIS 

layers on large carbon dioxide emitters, drinking water groundwater basins, 

seismic/volcanic/geothermal zones, proposed carbon dioxide saline injection 

basins, etc. and provide the ability to overlay layers. Stakeholders would then 

28
have improved abilities to evaluate a proposed geologic sequestration project to 

determine if they would be impacted by the carbon dioxide plume and/or 

associated pressure front. 

Individual Response: EPA notes that the full results of the regional carbon sequestration 

partnership pilot projects will be available to the public once the projects are complete (the 

results of Phase II of these projects are currently available). Results of other research sponsored 

by EPA and DOE are available in the GS rulemaking docket as it is complete. 

EPA agrees that all information presented to the public must be clear, understandable, and 

available. In addition to requiring public notice of all draft permits under §124.10(a)(1)(ii), 

stakeholders may request copies of the draft permit and the permit application during the draft 

permit comment period; the application includes data on the geology of the injection and 

confining zones which are likely to be used as inputs for modeling. However, it is likely that 

information submitted in support of a permit in its original form (e.g., modeling inputs) may be 

extremely technical and not easily understood by a lay audience. Permitting authorities are 

required under §124.8 to produce a fact sheet which typically summarizes relevant information 

for the public in a much more understandable format than the supporting data in a permit 

application. The fact sheet describes the draft permit conditions, procedures to determine the 

final decision on the permit, any procedures to request a hearing, and procedures that may be 

available for additional public participation in the final permitting decision. EPA will encourage 

permitting authorities and operators to present all modeling data to the public. 

EPA has no plans to create a web-based GIS database, due to the sheer volume of information 

required and variety in GIS software products available by potential users. 

Information about specific GS projects would be available from permitting authorities as part of 

the administrative record associated with each permit. EPA will encourage (but not require) that 

this information be available online. 

Letter ID: 0181 Comment ID: 23676 Letter Lines: 646 to 674 

Comment Code: 1840 1.4.1.3 Other research 

Comment: AWWA also recommends that EPA review the following reports that address the 

potential costs of treating source water that has lowered pH levels and/or 

increased concentrations of iron, minerals and other potential contaminants. 

- AWWA projects: 

o Managing Change and Unintended Consequences: Lead and Copper Rule Corrosion 

Control Treatment (WITAF) 

o Regulatory Risk Assessment for Arsenic in Water (WITAF) 

o Technology and Cost Review of the Proposed Arsenic Regulation (WITAF) 

- AwwaRF projects: 

29
o Adsorbent Treatment Technologies for Arsenic Removal (#2731) 

o Demonstration of Emerging Technologies for Arsenic Removal (#2661) 

o Implementation of Arsenic Treatment Systems Part 2: Design Considerations, 

Operation, and Maintenance (#2665) 

o Arsenic Removal by Iron-Modified Activated Carbon (#3158) 

o Subsurface Treatment For Arsenic Removal--Phases I and II (#3082) 

o Characterization and Performance of Filter Media for Manganese Control (#2951) 

o Occurrence of Manganese in Drinking Water and Manganese Control (#2863) 

o Advanced Processes for Simultaneous Arsenic and Manganese Removal (#2748) 

o Occurrence Survey of Boron and Hexavalent Chromium (#2759) 

o Integrated Water Treatment: Softening and Ultrafiltration (#2647) 

o Enhanced Reverse Osmosis Systems: Intermediate Treatment to Improve Recovery 

(#4061) 

o Membrane Treatment Of Impaired Irrigation Return (#4069) 

o Zero Liquid Discharge Desalination of Waters with High Organic Content (#4163) 

o Zero Liquid Discharge for Inland Desalination (#3010) 

o Comparison of Zinc vs Non-Zinc Corrosion Control for Lead and Copper (#4103) 

o Effect of Nitrification on Corrosion in the Distribution System (#4015 

Individual Response: EPA acknowledges that there are potential risks associated with GS 

including the potential for leakage of CO2 into USDWs which may result in the mobilization of 

substances that could endanger USDWs or affect drinking water supplies and increase treatment 

costs. 

Recent research has focused on addressing this concern. EPA is funding research at the 

Lawrence Berkeley National Laboratory (LBNL) on potential USDW impacts associated with 

mobilization of trace elements. In the August 31, 2009, Notice of Data Availability and Request 

for Comment (74 FR 44802), EPA published the results of the study, which evaluated the 

potential for GS to cause changes in ground water quality as a result of CO2 leakage and 

subsequent mobilization of trace elements such as arsenic, barium, cadmium, mercury, lead, 

antimony, selenium, zinc, and uranium (Birkholzer et al., 2008a). In the study, LBNL estimated 

the amount of trace elements from native mineral species that could potentially be mobilized by 

the intrusion of CO2 and the potential ground water concentrations that could result, to 

determine the potential for drinking water standards to be exceeded. Results from this model 

simulation suggest that if CO2 were to leak into a shallow aquifer, the potential for mobilization 

of lead and arsenic could be enhanced, causing increases in the concentration of these trace 

elements in ground water. The Agency continues to monitor research related to CO2 

confinement, potential for CO2 leakage, and mobilization of trace elements. EPA also examined 

potential methods for conducting treatment of water affected by a CO2 leak; this study is 

presented in the final rulemaking docket. 

EPA clarifies that the purpose of the Class VI requirements is to minimize and mitigate 

potential/identified risks through proper site characterization, well construction, operation, 

monitoring, post-injection site care, and site closure. The rule at §146.82 requires owners or 

operators to submit extensive data about a proposed GS site in order to eliminate sites with 

potential for unacceptable fluid movement that could endanger USDWs. Operators must also 

develop and follow an emergency and remedial response plan to address any adverse effects 

associated with the GS operation at §146.94) and maintain financial responsibility to address 

30
contamination under §146.85. 

Letter ID: 0181 Comment ID: 23677 Letter Lines: 676 to 687 

Comment Code: 1840 1.4.1.3 Other research 

Comment: The lack of good background data and inappropriate oil and gas well closures 

reflect inadequate regulatory oversight that can only get worse as regulatory 

agencies are asked to take on more activities related to climate change. Climate 

change adaptation and mitigation measures, such as geologic sequestration, may 

be delayed due to inadequate regulatory agency resources (e.g., number of staff 

and expertise). EPA needs to support significant research to reduce the 

uncertainties associated with climate change and afford better long-term 

planning decisions as water utilities and their customers are likely to feel a 

disproportionate impact due to anticipated adaptation and mitigation activities. 

EPA should also work in concert with other federal agencies to spur research 

into technologies that can convert carbon dioxide into inert or innocuous 

products. 

Individual Response: EPA acknowledges that there may be technical and administrative 

challenges including resource concerns, and will work closely with the states to assist them in 

resolving funding issues or acquiring the resources, personnel, and training needed to address the 

unique technical challenges associated with GS. Please see EPA's guidance for primacy agencies 

on implementing the GS rule, which will be available on EPA’s website at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

While developing the GS regulation, EPA evaluated relevant GS research, including projects 

conducted by the seven regional carbon sequestration partnerships funded by the U.S. 

Department of Energy (DOE) and coordinated through the National Energy Technology 

Laboratory (NETL), and several international projects. Additionally, EPA's Office of Water 

continues to fund research at the Lawrence Berkeley National Laboratory examining the effects 

of CO2 interaction on ground water aquifers and any potential mobilization of trace elements 

that may occur. EPA is communicating with other research organizations and academic 

institutions including, among others, Princeton University, Massachusetts Institute of 

Technology, and Montana State University, where specific research on geologic sequestration, 

injection well materials, and CO2 monitoring techniques is in progress. EPA is also working 

with DOE, USGS, and others to identify tools and training techniques that will provide GS 

permitting assistance and technical expertise as appropriate. Additionally, EPA's Office of 

Research and Development (ORD) is undertaking multiple research efforts on GS. Topics of 

research include bolstering different default thermodynamic databases to include more 

comprehensive information on aqueous complexes and solid-phases that contain 

carbonate/bicarbonate and toxic elements for which EPA has a listed MCL (maximum 

concentration level) for safe drinking water. 

ORD's National Center for Environmental Research (NCER) awarded six Science To Achieve 

31
Results (STAR) grants in the Fall of 2009 to recipients from major universities and institutions 

within the scope of the "Integrated Design, Modeling and Monitoring of Geologic Sequestration 

of Anthropogenic Carbon Dioxide to Safeguard Sources of Drinking Water" research area. These 

projects, which started in late 2009, include these lead institutions with specific topics of 

investigation: Clemson University will study potential impacts to drinking water aquifers of 

CO2-rich dissolved brines; 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 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 is using an adaptive approach to regulating GS under the UIC Program. Even after 

finalization of the GS regulation, 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. 

Letter ID: 0181 Comment ID: 23678 Letter Lines: 697 to 721 

Comment Code: 2166 1.6.3.2 Comments opposing injection into unmineable coal seams 

Comment Code: 4322 2.4.4.1.1 Comments in favor of requiring injection below the lowermost 

USDW 

Comment: Category: USDW Location 

EPA Request for Comment: EPA is proposing to preclude the injection of CO2 for 

long-term storage into coal seams where they are above the lowermost USDW. EPA 

requests comment on this proposed prohibition. EPA Notice 43503. 

AWWA Response: AWWA recommends that EPA preclude the injection of carbon dioxide 

into coal seams located above the lowermost USDWs. First and foremost, AWWA is 

adamantly opposed to the injection of carbon dioxide into any storage formation 

not located beneath the lowermost USDW. If a utility ever desired to use the 

USDW as a water resource, they would have to drill through the carbon dioxide 

plume, thus creating a pathway for carbon dioxide to potentially migrate out of 

the confining layer and into nearby aquifers. This could cause contamination of 

USDWs located above the coal seam, and result in significant remediation 

activities for a water utility. Second, little research has been conducted to 

determine the specific impacts that storage of carbon dioxide would have on coal 

seams. Much of the research that has been performed to date has been on either 

carbon dioxide storage in saline reservoirs or in depleted oil/gas fields. AWWA 

32
recommends that at this point in time, EPA preclude the injection of carbon 

dioxide into all coal seams, no matter where they are located in the subsurface. 

This regulation was not designed for coal seams to be used as carbon dioxide 

storage reservoirs. Therefore, AWWA recommends that any wells constructed for 

the injection of carbon dioxide into coal seams wells be permitted under the 

Class V experimental wells until the potential impacts of coal seam carbon 

dioxide sequestration on USDWs are better understood. 

Individual Response: The final GS rule does not preclude injection into unmineable coal seams 

(or any non-USDW formation type) provided owners or operators can demonstrate that GS can 

be performed in a manner that protects USDWs from endangerment as required under today’s 

final rule. 

EPA recognizes that GS in unmineable coal seams has been the subject of less research than 

saline formations or depleted oil and gas reservoirs. However, EPA has examined select field 

projects involving injection into unmineable coal seams, including the Pump Canyon Site, near 

Archuleta, New Mexico. In the Notice of Data Availability and Request for Comment, EPA 

described research at the Pump Canyon site where the Southwest Partnership is studying CO2 

injection into deep, unmineable coal seams and performing a "seal analysis" of the ability of the 

Kirtland Formation to act as a barrier to the movement of CO2 or other reservoir fluids. EPA 

continues to follow this project, recently completed projects, and ongoing GS projects injecting 

into unmineable coal seams. Other coal seam injection projects are underway through the RCSPs 

in the Illinois Basin, Black Warrior Basin, and Central Appalachian Basin. 

EPA acknowledges that there may be risks associated with GS into coal seams. For this reason, 

the Agency is using an adaptive approach to regulate GS injection. The Agency anticipates that 

in the near-term, most GS in unmineable coal seams will continue to be experimental. Such 

projects may be permitted as Class V experimental technology wells if they are of an 

experimental nature (i.e., to test GS technologies and collect data).EPA will collect and review 

project data on early GS projects, including those that inject into various formation types, to 

determine whether the appropriate amount and types of information and documentation are being 

collected. 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. 

EPA clarifies that the final rule requires that injection for GS be into non-USDWs below the 

lowermost USDW; however, owners or operators may apply for a waiver from this requirement, 

as described in §146.95. For more information, see the discussion of waivers in the preamble to 

the final rule. 

Letter ID: 0181 Comment ID: 23679 Letter Lines: 723 to 739 

Comment Code: 4322 2.4.4.1.1 Comments in favor of requiring injection below the lowermost 

USDW 

33
Comment: EPA Request for Comment: EPA is soliciting comment on whether CO2 injection 

should be allowed into an injection zone above the lowermost USDW, when the 

Director determines that geologic conditions (e.g., thousands of feet of 

intervening formations between the injection zone and the overlying and/or 

underlying USDWs) exist that will prevent fluid movement into adjacent USDWs. 

EPA Notice 43512. 

AWWA Response: As previously stated, AWWA is adamantly opposed to the injection 

of carbon dioxide into any storage formation not located beneath the lowermost 

USDW. If a utility ever desired to use the lowermost USDW as a water resource, 

they would have to drill through the carbon dioxide plume, thus creating a 

pathway for carbon dioxide to potentially migrate out of the confining layer and 

into nearby aquifers. This could cause contamination of USDWs located above the 

storage aquifer, and result in significant remediation activities for a water 

utility. AWWA recommends that EPA include a section in the final regulation 

prohibiting the injection of carbon dioxide into any formation located above the 

lowermost USDW. 

Individual Response: As described above, EPA agrees that protecting USDWs from 

endangerment must be a top priority. The Agency believes that there are limited circumstances 

where injection 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 or operators can seek a waiver of the Class VI injection depth 

requirements for injection into non-USDW formations above and/or between USDWs. 

EPA believes that the requirements at §146.95 will ensure USDW protection while providing 

flexibility to UIC Program Directors and owners or operators who undertake CO2 injection for 

GS. EPA’s approach to addressing injection depth variability through a waiver process responds 

to concerns about future drinking water resource availability and the need to ensure that high 

quality water remains available in sufficient quantities to supply drinking water needs. For 

additional information on the waiver approach, please see the final rule and preamble, as well as 

EPA's responses to comments on the Notice of Data Availability and Request for Comment. 

Letter ID: 0181 Comment ID: 23680 Letter Lines: 741 to 758 

Comment Code: 3120 2.1.2 Need to identify additional confining and containment zones 

(seeking comment) 

Comment: EPA Request for Comment: EPA specifically seeks comment on the merits of 

requiring the identification of additional confining and containment zones above 

the primary (i.e., lowermost) confining zone that could further impede vertical 

fluid movement and allow for pressure dissipation. EPA Notice 43506. 

AWWA Response: AWWA recommends that EPA require owner/operators to identify 

these additional confining and containment zones as part of the site 

34
characterization process. This identification is important to understand the 

project as a whole, and failing to identify these additional zones results in a 

very large knowledge gap in the identification of potential mitigation options 

in the event that a leak occurs from the primary confining layer. Having this 

information available to regulators and stakeholders would allow for a better 

understanding of the project as a whole, and would provide for a more informed 

and comprehensive review process. If certain stakeholders, such as drinking 

water utilities, were provided with this information, utilities would have a 

better understanding of a geologic sequestration project with the knowledge that 

multiple confining layers separated the carbon dioxide injection zone from their 

USDWs. 

Individual Response: EPA agrees with the commenter that, in some situations, the presence of 

additional confining and containment zones above the primary (i.e., lowermost) confining zone 

can improve USDW protection from endangerment. EPA disagrees that secondary confining 

zones are required at all sites, e.g., where a primary confining zone that free of transmissive 

faults or fractures and of sufficient areal extent and integrity to contain the injected carbon 

dioxide stream and displaced formation fluids and allow injection at proposed maximum 

pressures and volumes without initiating or propagating fractures in the confining zone(s) (per 

§146.83(a)) is demonstrated to be present. The final regulation retains the requirement at 

§146.83(b) which affords the Director discretion to require owners or operators to identify and 

characterize additional zones. 

Letter ID: 0181 Comment ID: 23681 Letter Lines: 760 to 796 

Comment Code: 4470 2.4.4.4.2 Comments opposing aquifer exemptions in all cases 

Comment: EPA Request for Comment: EPA is also requesting comments on whether aquifer 

exemptions should be allowed for the purpose of Class VI injection, and under 

what conditions should such aquifer exemptions be approved. EPA Notice 43512. 

AWWA Response: AWWA does not support aquifer exemptions for the purposes of 

Class VI injection projects. Water resources are becoming extremely limited in 

many parts of the country and many drinking water utilities will be turning to 

alternative supply sources, including brackish and saline groundwater, as well 

as deeper USDWs. 40 CFR 146.4 states that: 

"An aquifer or a portion thereof which meets the criteria for an underground 

source of drinking water...may be determined...to be an exempted aquifer if it 

meets the following criteria: (a) It does not currently serve as a source of 

drinking water; and (b) It cannot now and will not in the future serve as a 

source of drinking water because: (1) It is mineral, hydrocarbon or geothermal 

energy producing, or can be demonstrated by a permit applicant as part of a 

permit application for a Class II or III operation to contain minerals or 

hydrocarbons that considering their quantity and location are expected to be 

commercially producible, (2) It is situated at a depth or location which makes 

35
recovery of water for drinking water purposes economically or technologically 

impractical; (3) It is so contaminated that it would be economically or 

technologically impractical to render that water fit for human consumption; or 

(4) It is located over a Class III well mining area subject to subsidence or 

catastrophic collapse; or (c) The total dissolved solids content of the ground 

water is more than 3,000 and less than 10,000 mg/l and it is not reasonably 

expected to supply a public water system." 

As previously stated, many drinking water utilities are exploring ground water 

resources that might not have been previously feasible to access or treat. The 

underlined portions of the aquifer exemption regulations are problematic as 

ground water resources that fit these definitions are now being tapped, given 

that much of the easily accessible and/or treatable ground water has already 

been utilized or allocated. By allowing for aquifer exemptions in these cases, 

EPA is precluding their use as a future USDW at a time when the country’s 

remaining ground water resources should be aggressively protected. Therefore, 

AWWA recommends that EPA not allow aquifer exemptions for the purposes of Class 

VI injection. 

Individual Response: EPA believes that there are limited circumstances where aquifer 

exemptions for GS may be warranted, and the final GS rule allows for the expansion of the areal 

extent of existing aquifer exemptions for Class II EOR/EGR wells transitioning to Class VI 

injection for GS pursuant to requirements at §§146.4 and 144.7(d). Class VI owners or operators 

granted expansions of existing Class II EOR/EGR aquifer exemptions for GS projects must meet 

all of the tailored requirements for GS wells in the final GS rule. 

If an owner or operator applies for a Class VI permit to inject CO2 into a previously exempted 

aquifer (non-USDW) that is located above and/or between USDWs, the permit applicant must 

also apply for a waiver of the injection depth requirements pursuant to §146.95 to ensure that if a 

waiver is granted, USDWs above and below the injection zone are protected from endangerment. 

The Agency developed the waiver process to address comments and concerns about current and 

future drinking water resources and the use of climate mitigation technology at appropriate sites. 

The aquifer exemption requirements in the final rule provide flexibility and afford owners or 

operators an opportunity to assess and select a suitable GS site while also preserving USDWs 

(i.e., formations/aquifers afforded SDWA protection). Class VI owners or operators granted 

expansions of existing Class II EOR/EGR aquifer exemptions for GS projects must meet all of 

the tailored requirements for GS wells in the final GS rule. EPA agrees with the commenter's 

concerns about USDW preservation and protection and believes that, in most cases, the injection 

depth waiver is a more appropriate option than aquifer exemptions for Class VI injection, and 

that aquifer exemption expansions for GS should be granted in limited circumstances. 

EPA agrees that future water resources needs are an important consideration, and believes that 

the injection depth waiver process at §146.95 responds to concerns about future drinking water 

resource availability and the need to ensure high quality water remains available in sufficient 

quantities to supply drinking water supply needs. For additional information on the waiver 

36
approach and aquifer exemptions for Class VI wells, please see the final rule and preamble, as 

well as EPA's responses to comments on the Notice of Data Availability and Request for 

Comment. 

Letter ID: 0181 Comment ID: 23682 Letter Lines: 798 to 815 

Comment Code: 4342 2.4.4.2.1 Comments in favor of setting a minimum injection depth 

Comment: EPA Request for Comment: EPA seeks comment on whether the Agency should set 

a 

minimum injection depth requirement for CO2 GS, rather than require that such 

injection take place below the lowermost USDW. EPA Notice 43512. 

AWWA Response: EPA should consider setting a minimum injection depth for 

geologic carbon sequestration as well as requiring that the injection take place 

below either the lowermost USDW or the lowermost aquifer that would be used as a 

drinking water source. AWWA believes this is necessary to ensure that carbon 

dioxide injected in the supercritical phase remains as such. The IPCC Special 

Report on Carbon Dioxide Capture and Storage suggested that carbon dioxide 

should be sequestered depths of at least 800 to 1,000 meters because at these 

depths, supercritical carbon dioxide has a liquid-like density that provides the 

potential for efficient utilization of underground storage space in the pores of 

sedimentary rocks. Providing for a minimum depth for carbon dioxide injection 

would strengthen the protective measures for USDWs. However, it is important to 

note that the minimum injection depth should be coupled with the provision that 

carbon dioxide must be injected below either the lowermost USDW or the lowermost 

aquifer that could be used as a drinking water source. 

Individual Response: EPA disagrees that it is necessary to set a minimum injection depth for 

GS projects and the Agency believes that a determination of site-suitability for GS (i.e., that 

subsurface formations will receive and confine injected CO2) should be made on a site-specific 

basis. The GS rule, at §146.82, requires the owner or operator to provide extensive site- and 

project-specific information to the Director to demonstrate that the site meets the minimum site 

criteria at §146.83, that the CO2 will be contained within the injection formation, and that 

USDWs will be protected from endangerment. 

EPA agrees that protecting USDWs from endangerment must be a top priority. The Agency 

believes that there are limited circumstances where injection 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 or operators can seek a waiver of 

the Class VI injection depth requirements for injection into non-USDW formations above and/or 

between USDWs. The waiver approach requires the submission of extensive, site-specific 

information (in conjunction with the permit application submission) to demonstrate that injection 

of CO2 into a non-USDW that is above or between USDWs can be done in a manner that is 

protective of USDWs. It establishes: 1) requirements specifying information that owners or 

operators must submit, and Directors must consider, in consultation with PWSS Directors; 2) 

37
procedures for public notice of a waiver application and for Director-Regional Administrator 

communication; 3) the waiver issuance process; and, 4) additional requirements that apply to 

owners or operators of Class VI wells granted a waiver of the injection depth requirements to 

ensure USDW protection above and below the injection zone. 

Letter ID: 0181 Comment ID: 23683 Letter Lines: 817 to 840 

Comment Code: 2046 1.5.2.3 Continuing to classify CO2 injection for EOR/EGR as Class II/ 

dividing line between Class II and Class VI (seeking comment) 

Comment: Category: Grandfathering Wells/ Enhanced Oil Recovery Wells 

EPA Request for Comment: Injection of CO2 for the purposes of enhanced oil and 

gas recovery (EOR/EGR), as long as any production is occurring, will continue to 

be permitted under the Class II program. EPA seeks comment on the merits of this 

approach since owners or operators of some Class II EOR/EGR wells may wish to 

use wells for the purposes of production and GS prior to the field being 

completely depleted. EPA Notice 43502. 

AWWA Response: AWWA agrees with this approach and supports the continued 

operation of Class II wells for EOR/EGR as long as they are still producing. 

However, AWWA recommends that an economic test for oil and gas reservoir 

"depletion" be used to determine when the Class II well should be transitioned 

to Class VI, and then operated under the Class VI conditions. One suggestion for 

determining when the reservoir has been depleted is to determine what the lowest 

physical amount of production would be. When oil or gas production reaches this 

point, the owner or operator would be required to plug the production wells and 

begin the application process for converting the remaining injection wells to 

Class VI wells. EPA needs to monitor the operation of existing Class II wells to 

ensure that they are not being operated as carbon sequestration projects, as 

there are significant differences in the permitting and operation of these two 

classes. Companies will try to bypass some of the Class VI construction 

requirements by designing and operating the system as an EOR/EGR project for a 

few years, and then converting it to a geologic sequestration system. 

Individual Response: EPA agrees that the nature and risks of CO2 injection for long term 

storage is different from Class II CO2 injection for EOR, and that tailored requirements for GS 

wells are appropriate and necessary to protect USDWs from endangerment. For this reason, the 

Agency tailored UIC requirements for Class VI wells that address the general risks deep 

injection may pose to USDWs and specifically address the unique nature of CO2 GS (i.e., very 

large volumes, very long time-periods, and reservoir pressure conditions). 

The Director has the authority to determine at what point a Class VI permit is required for those 

projects that are transitioning from the primary purpose of EOR to long term storage of CO2. 

The final regulation provides a set of technical factors for the Director to evaluate in making this 

determination, at §144.19. EPA believes that this approach provides sufficient protection of 

38
USDWs when there is an increased risk to USDWs as compared to traditional Class II operations 

while allowing for site-specific flexibility. 

EPA is developing guidance on transitioning permits from Class II to Class VI. The guidance 

will assist Directors in determining whether an injection project should be transitioned from 

Class II where the primary purpose is oil and gas production to Class VI where the primary 

purpose is long-term storage of large volumes of CO2. The guidance describes the recommended 

methods the Director may use to evaluate changes in risk to USDWs from projects, and how the 

Director may determine whether a project should be regulated within the Class II or Class VI 

UIC program. This guidance will be available on EPA’s website at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. For more information, please 

see the discussion on transition of Class II wells in the preamble to the final GS rule. 

Letter ID: 0181 Comment ID: 23684 Letter Lines: 842 to 874 

Comment Code: 2060 1.5.3 Comments on grandfathering of existing wells (seeking comment) 

Comment: EPA Request for Comment: EPA seeks comment on the approach to grandfather 

construction requirements at the Director’s discretion for existing Class I, 

Class II, and Class V wells seeking to convert to Class VI wells, and whether 

additional construction requirements would be necessary to prevent endangerment 

to USDWs from the GS of CO2. EPA Notice 43502. 

AWWA Response: The construction requirements for the other well classes may not 

be as stringent as the requirements for Class VI wells. AWWA recommends that in 

order for wells from the other classes to be used for the injection of carbon 

dioxide, the wells must have been constructed using methods that are at least or 

more stringent than the Class VI requirements. Otherwise, as stated previously, 

it may encourage companies to construct an EOR well under the less strict Class 

II rules, with the goal of running the operation for a few years and then 

converting to a carbon sequestration operation. 

Certain operating methods for Class II wells may result in conditions that would 

be unacceptable for geologic sequestration. For example, EOR wells that used 

saltwater may be deteriorated to a point that would not be acceptable for the 

injection of carbon dioxide for geologic sequestration. In this case, these 

wells may have been constructed using different methods and materials that are 

not compatible with carbon dioxide. AWWA recommends that the owner/operators are 

required to prove that the grandfathered wells were constructed using corrosion 

resistant materials, and were cemented along the casing in accordance with the 

Class VI requirements. The well should be inspected to determine if any interior 

or exterior corrosion had occurred, and if so, there should be a determination 

that the well is not acceptable for use as a Class VI well. The review process 

should also include long-term demonstration by the owner/operator of the 

performance of the well as a Class II well. This review could provide an 

indication of continued prevention of USDW contamination. While these are fairly 

39
strict requirements, following this process is essential to prevent the 

contamination of USDWs or other source water aquifers. This should be the 

ultimate goal of the grandfathering process, not the prevention of additional 

construction costs for the owner/operator. 

Individual Response: As described above, EPA agrees that a cautious approach to 

grandfathering is appropriate, particularly given that the converted well will be used for a 

substantially different process, which involves increased reservoir pressures associated with 

large volumes of stored CO2 and the corrosivity of CO2 in the presence of water. The final GS 

rule provides for the construction of these wells to be grandfathered (per 146.81(c)). EPA has 

included a requirement in the final GS rule that owners or operators seeking to convert existing 

wells for long term storage must demonstrate to the Director that the grandfathered wells were 

engineered and constructed meet the requirements at §146.86(a) and ensure protection of 

USDWs, in lieu of requirements at §146.86(b) and §146.87(a). EPA clarifies that only the 

construction requirements are grandfathered and that all other Class VI requirements (reporting, 

monitoring, mechnical integrity testing, etc.) must be met following a determination under 

§146.81(c). 

Letter ID: 0181 Comment ID: 23685 Letter Lines: 880 to 884 

Comment Code: 2060 1.5.3 Comments on grandfathering of existing wells (seeking comment) 

Comment Code: 4200 2.4.2 Down-hole shut-off valves in GS wells (seeking comment) 

Comment: AWWA Response: Grandfathered wells may not have some of the protective 

measures 

that are required in the proposed regulation, such as the down-hole shut-off 

valve. This valve is an important safety mechanism and AWWA believes that a 

Class VI well should not be permitted for carbon sequestration unless it is 

constructed with this appurtenance. Also, some of the potentially grandfathered 

Individual Response: EPA believes that some wells can be re-permitted for use as Class VI 

wells and safely operated, even if down-hole shut-off systems cannot be installed. EPA will not 

require automatic down-hole shut-off devices for onshore Class VI wells since it is not necessary 

in all cases to ensure protection of USDWs from endangerment. Instead, the final rule, at 

§146.88(e)(2), requires that owners or operators of onshore Class VI wells install automatic 

surface shut-off devices. The rule affords Director's discretion to mandate automatic down-hole 

shut-off devices in onshore situations that may warrant their use. However, the Agency believes 

that offshore Class VI wells present unique construction and operational conditions, including 

isolation from shorelines and the need to construct wells through the water column and the 

subsurface, which may delay response time in the event of well difficulties. The rule requires, at 

§146.88(e)(3), that owners or operators of offshore wells within State territorial waters install 

automatic down-hole shut-off systems. EPA believes that these requirements at §146.88(e) 

ensure that proper precautions are taken to prevent subsurface fluid movement and ensure 

protection of USDWs. 

The final GS regulation requires at §146.81(c) that owners or operators seeking to grandfather 

40
existing Class I, II, or V wells for GS demonstrate that grandfathered wells were engineered and 

constructed to meet the requirements at §146.86(a) and ensure protection of USDWs, in lieu of 

requirements at §§146.86(b) and 146.87(a). In addition, these grandfathered wells would still be 

required to meet the other requirements of the GS regulation (e.g., operating, monitoring, MIT, 

well plugging, and post-injection site care and site closure requirements). 

Letter ID: 0181 Comment ID: 23686 Letter Lines: 884 to 893 

Comment Code: 2060 1.5.3 Comments on grandfathering of existing wells (seeking comment) 

Comment Code: 4500 2.5 Proposed Mechanical Integrity Testing (MIT) Requirements (40 CFR 

146.89) 

Comment: constructed with this appurtenance. Also, some of the potentially grandfathered 

wells may not be constructed in a way that would allow for the mechanical 

integrity testing requirements that are part of the regulation. AWWA believes 

that some of the very prescriptive testing and monitoring requirements are 

necessary, as the grandfathered wells may not have been constructed in a way 

that would allow for these tests to be carried out. AWWA recommends that EPA 

include in the final regulation a requirement that the owners/operators of the 

wells conclusively prove that the grandfathered wells can be operated in 

compliance with all the other requirements of the proposed regulation or the 

wells will not be permitted for Class VI operation. 

Individual Response: EPA agrees with the commenter regarding the need for MITs; the final 

rule requires both internal and external mechanical integrity testing. Mechanical integrity testing 

is one of the cornerstones of the existing EPA UIC program. MIT requirements at §146.89 

ensure protection of USDWs from endangerment and provide an important early warning of 

potential problems in the injection well. Routine mechanical integrity testing of injection wells 

provides data that enables the identification and remediation of well integrity problems before 

they lead to leakage and/or endangerment of USDWs. 

EPA agrees that a cautious approach to grandfathering is appropriate, particularly given that the 

converted well will be used for a substantially different process. The final GS rule provides for 

the construction of these wells to be grandfathered (per 146.81(c)). EPA has included a 

requirement in the final GS rule that owners or operators seeking to convert existing wells for 

long term storage must demonstrate to the Director that the grandfathered wells were engineered 

and constructed meet the requirements at §146.86(a) and ensure protection of USDWs, in lieu of 

requirements at §146.86(b) and §146.87(a). EPA clarifies that only the construction requirements 

are grandfathered and that all other Class VI requirements (reporting, monitoring, mechanical 

integrity testing, etc.) must be met following a determination under §146.81(c). 

EPA adds that following re-permitting as Class VI wells, these projects would be subject to the 

requirements of the final GS rule, including MIT, monitoring, operational, reporting, plugging, 

and post-injection site care and site closure requirements. See the discussion of EPA's final 

regulatory approach in the preamble to the GS rule for additional detail on these requirements. 

41
Letter ID: 0181 Comment ID: 23687 Letter Lines: 895 to 921 

Comment Code: 1614 1.3.1.2 Impurities in captured CO2; purity standards for CO2 

Comment: Category: Injection Stream 

EPA Request for Comment: By defining "carbon dioxide stream" to exclude 

hazardous wastes (146.81(d)), EPA’s rule, if finalized, assures that it would 

apply only to CO2 streams that are not hazardous wastes as defined in 40 CFR 

Part 261. As a result, EPA’s proposed rule would preclude the injection of 

hazardous wastes in Class VI injection wells. EPA seeks comment on this approach 

and other considerations associated with the presence of "impurities" in the CO2 

stream. EPA Notice 43503. 

AWWA Response: AWWA agrees with EPA’s approach in defining the "carbon dioxide 

stream" to exclude hazardous wastes. However, AWWA recommends that the final 

regulation include more specifics on the definition of the required quality of 

the injection stream and establishing a minimum concentration of carbon dioxide 

present in the injection stream. This requirement for the injection stream will 

ensure that the injection of other harmful or undesirable gases is limited. Our 

initial thoughts on this topic would be that 100% of the injectate must come 

from a carbon dioxide capture process and the injectate must be at least 98% 

carbon dioxide. Owner/operators must ensure that the remaining 2% of the 

injectate is not made up of compounds that would result in the injectate being 

classified as a hazardous waste. Also, 100% of the injection stream should be 

required to come from the carbon capture process as to preclude the co-mingling 

of wastes from other industrial processes in the injection stream as this is not 

an appropriate use of the Class VI injection wells. As AWWA is not a technical 

expert on this topic, AWWA recommends that EPA pursue research in association 

with DOE to develop a standard for the minimum concentration of carbon dioxide 

in the injection stream. 

Individual Response: EPA understands that many CO2 streams may be relatively pure, and 

research indicates that the estimated amounts of impurities in a CO2 stream are likely to be low. 

However, these estimates are based on limited information, and uncertainties remain about the 

expected concentrations of impurities from the various types of CO2 streams. The concentrations 

of minor and trace elements in CO2 streams for GS projects are likely to vary by facility, coal 

composition, plant operating conditions, and pollution removal technologies. 

The GS rule does not set generic purity standards for CO2 injectate streams (e.g., a percent 

CO2). Instead, the GS rule addresses the quality and quantity of impurities by requiring owners 

or operators to submit information on the source of the CO2 and its physical and chemical 

properties. Specifically, the GS rule requires the owner or operator to submit data about the site, 

including an analysis of the chemical and physical characteristics of the CO2 stream, as required 

at §146.82(a)(7)(iv), and information on the compatibility of the CO2 stream with fluids in the 

42
injection zone and minerals in both the injection and the confining zones and the materials used 

to construct the well, per §146.82(c)(3). This information can help the Director determine the 

potential for geochemical reactions between the injectate (CO2) and the host geologic 

formations, which could result in the plugging of pore spaces or the dissolution of formation 

minerals. 

Letter ID: 0181 Comment ID: 23688 Letter Lines: 923 to 941 

Comment Code: 1630 1.3.3 RCRA/hazardous waste issues (seeking comment) 

Comment: EPA Request for Comment: Class VI requirements and permits will need to be 

carefully structured to ensure that they do not "authorize" inappropriate 

hazardous releases. This would include clarifying if there are potential 

releases from the well which are outside the scope of the Class VI permit. EPA 

requests comment on particular situations where this might occur. EPA notice 

43504. 

AWWA Response: AWWA agrees with EPA’s assertion that the permits and well 

requirements need to be carefully structured to prevent "authorized" releases of 

hazardous substances into subsurface geologic formations. We are not aware of 

any situations where this might occur, as long as the injectate is properly 

characterized and is not classified as a hazardous substance. There may be a 

situation where a release of carbon dioxide from the confining layer might cause 

the formation of a hazardous substance due to reactions with the surrounding 

geologic strata. To prevent this problem from occurring, the geologic 

characteristics of the geologic formations should be evaluated prior to 

injection for potential interactions with the injectate stream. If there are 

indications that hazardous substances could be formed, the site should not be 

considered acceptable for carbon sequestration. 

Individual Response: EPA agrees that proper siting, operation, and monitoring are important for 

protecting USDWs from endangerment. In addition, the UIC program Director has authority 

under SDWA §1423 to address potential compliance issues (e.g., potential releases that may 

endanger USDWs) resulting from injection violations in the unlikely event that a remedial 

response is necessary. Although EPA anticipates that the need for emergency or remedial actions 

at GS sites will be rare, the GS rule requires, at §146.94, that emergency and remedial response 

plans be developed and updated to address such events and that owners or operators demonstrate 

that financial resources are set aside to implement the plans if necessary, per §146.85. 

EPA clarifies that, while the Administrator reserves the right to promulgate regulations 

designating additional substances as hazardous under §102 of CERCLA, EPA intends to avoid 

any potential overlap of SDWA and CERCLA authority through its comprehensive Class VI 

requirements. 

CO2 itself is not listed as a hazardous substance under CERCLA; however, the CO2 stream may 

contain a listed hazardous substance (such as mercury) or may mobilize substances in the 

43
subsurface that could react with ground water to produce listed hazardous substances (such as 

sulfuric acid). Whether such substances may result in CERCLA liability from a sequestration 

facility depends entirely on the composition of the specific CO2 stream and the environmental 

media in which it is stored (e.g., soil or ground water). CERCLA exempts from liability, under 

CERCLA section 107, 42 U.S.C. 9607, certain “federally permitted releases” (FPR) as defined in 

CERCLA, 42 U.S.C. 9601(10). Class VI permits will need to be carefully structured to ensure 

that they prevent potential releases from the well which are outside the scope of the Class VI 

permit. 

Letter ID: 0181 Comment ID: 23689 Letter Lines: 943 to 958 

Comment Code: 4490 2.4.5 Use of tracers and potential impact on human health or ecosystems 

(seeking comment) 

Comment: EPA Request for Comment: EPA’s proposal allows Directors’ discretion on whether 

to require the use of tracers, and if so, what types of tracers. EPA seeks 

comment on the use of tracers in CO2 GS operations, and any potential impact of 

tracers on human health or ecosystems as they relate to USDWs. EPA Notice 43513. 

AWWA Response: AWWA recommends that EPA require tracers to be injected along 

with the carbon dioxide stream to provide for a better mechanism of tracking the 

movement of the carbon dioxide plume. Certain tracers could provide for a better 

understanding of the plume behavior using non-traditional indicators, such as 

those that are conservative, easy to measure, non-toxic, and do not degrade into 

contaminants of concern. These tracers could be easily identified in USDWs, as 

well as in the vadose zone, where they could be used as an indicator when carbon 

dioxide soil-gas monitoring proves difficult to interpret. Unfortunately, AWWA 

can not provide recommendations on specific tracers that could be utilized, and 

recommends that EPA perform research, in association with DOE, on the types of 

tracers that would be acceptable for use in carbon sequestration. 

Individual Response: EPA agrees that tracers can be useful tools for monitoring GS projects. 

EPA also acknowledges that tracers can also be used to identify (i.e., tag) injections by time, 

producer, or location, but clarifies that any requirement for the use of tracers at GS sites would 

be for the purpose of identifying potential endangerment to USDWs as a result of CO2 

movement from the injection zone. 

However, EPA does not believe that tracer use is appropriate in all situations. For this reason, 

EPA does not require the use of tracers at all GS sites; however, the Director has discretion to 

require their use if he/she determines that the use of tracers could improve monitoring of the site 

and enhance USDW protection from endangerment. The rule will also allow their use if 

proposed by the owner or operator and approved by the Director. 

EPA adds that the other aspects of the extensive monitoring required at GS sites, including 

monitoring of the well system, tracking of the CO2 plume and pressure front, and geochemical 

monitoring, will also detect leaks and track the CO2 plume. 

44
EPA will continue to track research related to tracer use, and plans to, every six years, 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: 0181 Comment ID: 23690 Letter Lines: 960 to 991 

Comment Code: 3300 2.2.1 Delineating the AoR/Modeling CO2 movement 

Comment Code: 3350 2.2.1.5 Use of proprietary models for GS sites (seeking comment) 

Comment: Category: Modeling 

EPA Request for Comment: EPA proposes that the owners or operators of GS wells 

be required to delineate the AoR for CO2 GS sites using computational fluid flow 

models designed for the specific site conditions and injection regime. EPA seeks 

comment on the use of modeling for AoR delineation. EPA Notice 43506. 

When using a proprietary model, owners or operators should clearly disclose the 

code assumptions, relevant equations, and scientific basis. EPA seeks comment on 

allowing the use of proprietary models for GS sites. EPA Notice 43507. 

AWWA Response: The proposed rule depends heavily on computer modeling to track 

the carbon dioxide plume and demonstrate that it is contained within the 

confining zone. As stated by EPA, some of these models are proprietary and the 

rule is unclear how or if confirmation of the model results will be provided. 

Additionally, each of the individual proprietary models can show a different 

answer to the problem. Owner/operators need to ensure that their basis for the 

model is static, and that the basis does not change once more details are known 

about the movement of the plume. For example, the operation of the geologic 

sequestration system should be adjusted based on modeling results, and the model 

shouldn't be revised because the plume is moving in a direction not originally 

predicted. 

AWWA recommends that EPA standardize on one specific model that is transparent 

and available for outside stakeholders to review, including the public. The 

other option is for EPA to develop a standard model that would be used for all 

geologic sequestration projects. If EPA were to develop a standard model, a 

pilot program should be part of the model development so that the modeling 

results could be validated with real-life monitoring data. In either case, 

clearly stating the model assumptions made during model set-up is critical, and 

these assumptions must be made available to stakeholders when they are reviewing 

the model results. 

Individual Response: The final rule does not require use of a standardized model. As described 

above, EPA believes that operators should have the flexibility to select models with which they 

45
are familiar and that are most appropriate to the site conditions and available data types and 

amounts. EPA also recognizes that a standardized model for AoR delineations could be effective 

as long as the model accounts for the expected variations in site conditions, and adds that a state 

or regional UIC Director could select one standard model if it took site-specific variations into 

account. 

EPA does not envision that members of the public will evaluate the AoR delineation models 

themselves. The models and their inputs will, by necessity, entail an extensive amount of 

technical information that may not be easily understood by the public. EPA believes that it is the 

Director's responsibility, as a steward of public health and the environment, to review models, 

model inputs, and results and to determine whether the model is appropriate for predicting the 

AoR, and to distribute information that may be easily understood by the public (e.g., in the form 

of a fact sheet). EPA adds that its Confidential Business Information requirements at 40 CFR 

144.5 will apply to the use of proprietary models. 

Letter ID: 0181 Comment ID: 23691 Letter Lines: 993 to 1018 

Comment Code: 3530 2.2.3.1 AoR reevaluation frequency (seeking comment) 

Comment: Category: Area of Review (AoR) 

EPA Request for Comment: EPA seeks comment on requiring the reevaluation of the 

site AoR on a periodic basis, under what conditions the AoR should be 

reevaluated, and the appropriateness of a 10-year minimum fixed frequency for 

AoR reevaluation. EPA Notice 43507. 

EPA proposes to allow a phased approach to corrective action but says this may 

not be appropriate in all situations; therefore EPA is proposing that the 

Director have the discretion to decide to allow this approach, based on the 

understanding of relevant geologic and site conditions. EPA invites public 

comment on the merits and frequency of reevaluation of the AoR as well as the 

phased corrective action approach for GS wells. EPA Notice 43508. 

AWWA Response: AWWA recommends that the area of review be reevaluated more 

frequently than suggested by EPA in the proposed regulation. AWWA recommends 

that the AoR be reevaluated annually for the first ten years of the project, and 

then every five years for the remaining operating period of the project. 

However, criteria should be established to trigger a shorter review period 

(based on a risk management approach) any time during the five-year time 

periods. For example, reevaluation of the AoR could be triggered by a shift in 

plume direction or sudden change in plume size or pressure. The local drinking 

water utilities, commissions, and planning boards need to be included in the AoR 

review process in the event that one of their drinking water sources becomes 

threatened due to a change in plume direction or behavior. Public involvement 

also needs to be a mandatory part of the AoR reevaluation process 

46
Individual Response: EPA agrees with commenters that reevaluations of the AoR every ten 

years may not be sufficient to appropriately model plume and pressure front movement, establish 

conditions for corrective action, and ensure protection of USDWs from endangerment. For these 

reasons, the Agency changed the minimum frequency for the AoR reevaluation at §146.84(e) 

from 10 years to at least every 5 years in the final GS rule. EPA believes that this revised 

frequency addresses commenters' concerns about the inherent uncertainties in modeling CO2 

movement, the emerging nature of GS technology, risk-based targeting of monitoring activities, 

and the unique nature of CO2 GS. In addition, the Director has discretion to require more 

frequent AoR reevaluation if he or she has reason to believe, based on site-specific information, 

that a five-year reevaluation schedule is not sufficiently protective of USDWs. 

Letter ID: 0181 Comment ID: 23692 Letter Lines: 1020 to 1039 

Comment Code: 3630 2.2.4.1 Comments in favor of allowing phased corrective action 

Comment: AWWA recommends that a phased corrective action plan be developed as a result of 

the AoR reevaluation. This would prevent owner/operators from performing 

unnecessary work in the event that the plume migrates in a different direction 

than originally predicted. However, AWWA recommends that the required corrective 

actions be completed at least two years before the plume is expected to reach 

the specific location. Corrective actions should include reentering and 

replugging old or abandoned wells that have not been certified to be closed in 

accordance with the sequestration requirements. Also, in the case where old 

wells were plugged with cement that is not compatible with carbon dioxide, these 

wells should be re-entered and replugged. Finally, old wells for which no 

records exist should be re-entered and replugged to ensure that a pathway for 

carbon dioxide to escape is not provided. 

One issue that EPA needs to consider in the final regulation is the potential 

cost differential for either performing all of the necessary corrective actions 

immediately or by phasing them in over time. If the corrective actions are 

phased in, EPA needs to require that the owner/operator provide financial 

assurance that the corrective action measures will still be performed even if 

the company goes out of business and the carbon dioxide plume continues to 

migrate. 

Individual Response: EPA believes that the phased corrective action approach is appropriate for 

GS projects, and retained it at §146.84(b)(2)(iv) in the final GS regulation. EPA believes that 

phased corrective action may provide many benefits to a project including, but not limited to, 

spreading the burden of cost, avoiding delays in project start-up, allowing for use of future, 

improved corrective action techniques and addressing unanticipated changes in the movement of 

the CO2 plume or pressure front. 

EPA agrees with the commenter that phased corrective action must account for any changes in 

the AoR, as demonstrated through a reevaluation or other site-specific data. For this reason, the 

47
final rule includes provisions that owners or operators review and update the AoR and corrective 

action plan throughout the life of the project, as specified in §146.84(c). These reviews must be 

performed within one year of an AoR reevaluation, following any significant changes to the 

facility (e.g., the addition of monitoring or injection wells), or when required by the Director. 

EPA also agrees that corrective action techniques must be appropriate for CO2 GS. All 

corrective action performed under §146.84(d) must be appropriate to the GS site and the 

injectate/formation fluid chemistry to ensure that the well does not allow CO2 or other fluids to 

move into or endanger USDWs. 

Regarding financial responsibility for corrective action, EPA clarifies that the owner or operator 

must demonstrate and maintain financial responsibility for all needed corrective action, 

regardless of whether it is to be phased. EPA is developing guidance on financial responsibility 

that will discuss approaches to how best to estimate appropriate costs for all required activities. 

The guidance will be available on EPA's web site, at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

Letter ID: 0181 Comment ID: 23693 Letter Lines: 1041 to 1087 

Comment Code: 5700 2.12 Comments on the proposed duration of Class VI permits (seeking 

comment) 

Comment: Category: Permit Life 

EPA Request for Comment: EPA proposes that Class VI injection well permits would 

be issued for the operating life of the GS project including the post-injection 

site care period. EPA seeks comment on the merits of this approach. EPA Notice 

43523. 

AWWA Response: AWWA does not support issuing an operating permit for the life of 

the sequestration site. AWWA recommends issuing a lifetime operating permit for 

the coal plant, but with a separate and renewable permit for the operation of 

the geologic sequestration process. Much like the wastewater treatment plants 

and NPDES permits go through a permit review process every five years, AWWA 

recommends that this same process be used for operating permits for geologic 

sequestration processes. For water and wastewater treatment plants, the 

operating permit is issued at the start of operation and the plant must renew it 

every five years. This allows for the expansion of plant flow, and changes in 

required effluent criteria due to regulation modifications. Much as water and 

wastewater plants are required to keep up with available technology, carbon 

sequestration systems should be required to apply BACT when it is feasible to 

incorporate it into the treatment process. Owner/operators should also be 

required to periodically re-evaluate their injectate stream for any emerging 

contaminants, and remove them if required. If wastewater treatment plants can be 

constructed and operating using this type of process, then a sequestration 

48
operation should be permitted in the same manner. Process changes are part of 

standard business operation in that regulations become more stringent, and 

processes become more efficient, and the owner/operators should be required to 

adapt to these changes through the permit renewal process. 

AWWA recommends that the application process include a review of the site 

operations to see if any instances of unsafe operation or changes in regulation 

would require a change in the plant operation. If a problem were detected, the 

permit wouldn't be immediately revoked, but the operator would be given the 

chance to rectify the situation so that the permit could be reissued. An 

owner/operator should consider the financial implications of this requirement 

and plan accordingly as the process will require a certain level of effort every 

five years to execute. AWWA recommends that the permit review process be aligned 

with the process used for review and renewal of NPDES permits. This would allow 

for all of the permit activities to be consolidated into one reapplication 

effort every five years. 

The capacity of the various state agencies to deal with the five year permit 

review process is an issue that needs to be recognized. Some states that are 

already stressed for resources could be overwhelmed with this additional task. 

However, AWWA believes that this permit requirement should not be sacrificed 

because the states might be resource stressed. Therefore, the federal government 

should consider allocating enough money to the state programs to adequate staff 

their sequestration permit division 

Individual Response: The final rule maintains the lifetime permit provision and clarifies that the 

permit extends through the post-injection site care period (144.36(a)). However, it also adds a 

requirement that the Director review each Class VI permit at least every 5 years to determine 

whether it should be modified, revoked and reissued, terminated or a minor modification made as 

provided in §§144.39, 144.40, or 144.41. The Director’s review will be informed by the owners’ 

or operators’ iterative reevaluation of the project. Specifically, the final rule includes a 

requirement that the AoR be reevaluated at least every five years, and also requires owners or 

operators to review and update the AoR and corrective action plan, the testing and monitoring 

plan, and the emergency and remedial response plan throughout the life of the project (146.84(e), 

146.90(j), and 146.94(d)). They must identify necessary amendments or demonstrate to the 

Director that no amendment is needed. In no case can reviews occur less often than once every 

five years. The iterative process and subsequent plan reevaluations ensure that time and 

resources are committed to the most critical aspects of the permit in preventing endangerment to 

USDWs. 

EPA believes that the iterative process of developing and executing the various plans required of 

GS well operators in the final rule (e.g., for AoR and corrective action, testing and monitoring, 

well plugging, and post-injection site care, and emergency and remedial response) is tailored to 

the unique aspects of—and is more appropriate for–GS than establishing a finite permit duration 

(e.g., five years as suggested by some commenters). This is preferable to a periodic permit 

reapplication. 

49
EPA believes that these changes will address many comments in support of permit renewal. 

Additionally, the reevaluation process could be aligned with issuance of other environmental 

permits associated with the facility, provided the minimum reevaluation frequency requirements 

are met. EPA clarifies that it does not have the authority under the SDWA (and associated UIC 

requirements) to alter permitting requirements issued under other environmental statutes for coal 

plants or any CO2 sources. The UIC program's authority is limited to the injection operation and 

ensuring that USDWs are protected from endangerment. 

EPA adds that, in addition to the requirement that the Director review the permit at least every 5 

years, as part of existing requirements at 40 CFR 144.39, the Director has the authority to revise 

the permit if project operations change or if the director believes based on monitoring or 

operational data that the project may endanger USDWs. EPA also added text to 144.39(a)(5) that 

says permit modifications may be required if the Director determines that a modification is 

necessary based on an AoR reevaluation, amendments to any of the project plans, or a review of 

the testing and monitoring results. The Director may also choose to require minor permit 

modifications under 40 CFR 144.41, depending on the extent of the plan amendment. 

EPA acknowledges that states and other commenters are concerned about resource availability 

for GS. The Agency will work closely with states to assist them in acquiring the resources, 

personnel, and training needed to address the unique challenges associated with GS. The Agency 

is developing guidance materials and plans to conduct on-line and in-person training for States 

and Tribes to enhance national understanding of the specific requirements in the GS rule and to 

support primacy application development and eventual implementation of the GS rule. 

The Agency plans to collect and review data on GS projects every six years 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 to 

ensure the protection of USDWs from endangerment. 

Letter ID: 0181 Comment ID: 23694 Letter Lines: 1089 to 1108 

Comment Code: 3862 2.3.3.1 Use of corrosion-resistant construction materials (seeking 

comment) 

Comment Code: 4200 2.4.2 Down-hole shut-off valves in GS wells (seeking comment) 

Comment: Group: Well Construction 

EPA Request for Comment: EPA seeks comment regarding requirements for 

degradation-resistant well construction materials, such as acid-resistant 

cements and corrosion resistant casing. EPA Notice 43510. 

EPA seeks comment on the merits of requiring down-hole shut-off valves in GS 

wells. EPA Notice 43511. 

AWWA Response: AWWA recommends that injection wells be constructed from 

50
degradation-resistant materials to prevent carbon dioxide from escaping from a 

portion of the injection well that may have been compromised due to noncompatible materials. AWWA also recommends that down-hole shut-off valves be 

required for all injection wells. These valves can be a first line of defense 

against contamination of USDWs due to faulty injection practices. Further 

research is needed by both EPA and DOE to identify specific construction methods 

that would prevent degradation of the well and the carbon sequestration site. 

AWWA recommends the creation of a certification program that would be used to 

guarantee that existing or newly developed construction methods are approved for 

use with geologic sequestration. 

Individual Response: EPA agrees that the use of non-compatible materials can result in 

degradation and failure of the well and could ultimately endanger a USDW. Under 

§146.86(b)(1), casings and cement and other materials used must have sufficient strength and be 

designed for the life of the sequestration project. Further, materials must meet standards listed in 

the rule and be compatible with fluids with which the materials may be expected to come into 

contact. Therefore, some well materials may need to be acid-resistant and some may not if they 

do not come in contact with the CO2 stream or other corrosive fluids and if approved by the 

Director. 

EPA disagrees that the rule should contain a construction method certification program. EPA 

believes that the prescribed construction requirements for Class VI wells are sufficient to protect 

USDWs from endangerment. EPA adds that the requirement at §146.86(b)(1) that materials must 

meet or exceed standards developed by the American Petroleum Institute, ASTM International, 

or comparable standards acceptable to the Director invokes the expertise of these bodies without 

the added burden of a certification program. 

See the discussion of Class VI well construction requirements in the preamble to the final GS 

rule for additional information. Additionally, EPA is developing guidance on the construction of 

Class VI wells. This guidance will be available on EPA’s website at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

After evaluating the risks and benefits of down-hole shut-off systems and considering additional 

research, EPA will not require automatic down-hole shut-off devices for onshore Class VI wells 

since such devices are not necessary in all cases to ensure protection of USDWs from 

endangerment. Instead, the final rule, at §146.88(e)(2), requires that owners or operators of 

onshore Class VI wells install automatic surface shut-off devices. The rule affords Directors 

discretion to mandate automatic down-hole shut-off devices in onshore situations that may 

warrant their use. However, the Agency believes that offshore Class VI wells present unique 

construction and operational conditions, including isolation from shorelines and the need to 

construct wells through the water column and the subsurface, which may delay response time in 

the event of well difficulties. The rule requires, at §146.88(e)(3), that owners or operators of 

offshore wells within State territorial waters install automatic down-hole shut-off systems. EPA 

believes that these requirements at §146.88(e) ensure that proper precautions are taken to prevent 

subsurface fluid movement and ensure protection of USDWs. 

51
Letter ID: 0181 Comment ID: 23695 Letter Lines: 1110 to 1126 

Comment Code: 4120 2.4.1.2 Allowing hydraulic fracturing during GS (seeking comment) 

Comment Code: 4130 2.4.1.3 Appropriateness of using fracturing for well stimulation (seeking 

comment) 

Comment: Category: Hydraulic Fracturing 

EPA Request for Comment: EPA is requesting comment on the extent and scope to 

hich hydraulic fracturing should be allowed during GS injection, and whether 

the use of fracturing for the purposes of well stimulation is appropriate. EPA 

Notice 43511. 

AWWA Response: Hydraulic fracturing during carbon dioxide injection has the 

potential to serious compromise the confining layer and AWWA recommends that 

this practice should not be allowed as part of the injection process. The 

objective of characterizing the injection and confining zones is to find a 

location that is free from faults, penetrations or other physical methods by 

which carbon dioxide could escape. Hydraulic fracturing creates fractures in the 

injection zone, and possibly the confining layer, which would allow for a 

pathway by which carbon dioxide could migrate into USDWs. Therefore, AWWA 

recommends that this process not be utilized at all in geologic carbon 

sequestration. 

Individual Response: EPA emphasizes that fracturing of the confining zone during injection 

and/or stimulation is prohibited, as specified at §146.88(a). However, as described above, EPA 

believes there may be some circumstances where fracturing of the injection zone may be 

acceptable, provided the integrity of the confining system remains unaffected. The final rule 

allows the use of hydraulic fracturing at GS sites, where approved by the Director. Hydraulic 

fracturing is one of several stimulation technologies available to improve wellbore and formation 

injectivity. 

Letter ID: 0181 Comment ID: 23696 Letter Lines: 1128 to 1170 

Comment Code: 4500 2.5 Proposed Mechanical Integrity Testing (MIT) Requirements (40 CFR 

146.89) 

Comment Code: 4600 2.6 Proposed Plume and Pressure Front Monitoring Requirements (40 

CFR 146.90) 

Comment: Category: Monitoring 

EPA Request for Comment: EPA’s proposal would require owners or operators of 

Class VI GS projects to monitor internal mechanical integrity of their injection 

wells by continuously monitoring injection pressure, flow rate, and injected 

volumes, as well as the annular pressure and fluid volume to assure that no 

anomalies occur that may indicate an internal leak. EPA requests comment on the 

52
practicability of this requirement. EPA Notice 43513. 

EPA seeks comment on the appropriate frequency of internal and external MITs for 

GS injection wells, the appropriate types of MITs, and how to optimize MIT 

methods for GS. EPA Notice 43514. 

EPA seeks comment on the requirement for monitoring of GS sites for the purpose 

of tracking the location of the CO2 plume and associated pressure front over 

time. EPA Notice 43514 

EPA’s proposal would require that owners or operators perform a pressure falloff test at least once every five years. EPA seeks comment on the use and 

frequency of pressure fall-off testing for GS wells. EPA Notice 43515. 

Specifically, EPA seeks comment regarding the usefulness of indirect geophysical 

monitoring and surface air and soil gas monitoring. In addition, EPA seeks 

comment regarding the use of a Director-approved monitoring plan for GS sites. 

EPA Notice 43517. 

AWWA Response: Detailed monitoring guidelines were developed as part of a joint 

research project by AwwaRF and AWWA. These guidelines are provided in Section 

III of these comments and EPA should include the named tests and frequencies in 

the final regulation to ensure that protection of USDWs is consistent across all 

geologic sequestration projects. Based upon these requirements, owner/operators 

would develop testing and monitoring plans, which should be reviewed and updated 

at the same time as the re-evaluation of the Area of Review. The costs 

associated with monitoring of a sequestration project should not be a major 

consideration when determining the types and frequency of required monitoring. 

The goal of the monitoring requirements should be on preventing degradation of 

USDWs, not minimizing the cost to the owner/operator. 

AWWA strongly recommends both that both internal and external mechanical 

integrity testing should be required to prevent leakage of carbon dioxide from 

the injection well. Monitoring of the plume and pressure front over time is 

absolutely required as part of the system operation and a project shouldn't even 

be considered unless this monitoring is included. All of the monitoring 

Individual Response: EPA agrees with the commenter; the final rule requires both internal and 

external mechanical integrity testing. Mechanical integrity testing is one of the cornerstones of 

the existing EPA UIC program. MIT requirements at §146.89 ensure protection of USDWs from 

endangerment and provide an important early warning of potential problems in the injection 

well. Routine mechanical integrity testing of injection wells provides data that enables the 

identification and remediation of well integrity problems before they lead to leakage and/or 

endangerment of USDWs. 

The GS rule's requirements for MITs encompass many of the same tests mentioned in the 

53
AwwaRF and AWWA monitoring guidelines, including an approved tracer log, or noise logs and 

temperature logs. EPA believes that the MITs described in the rule at §146.89(c) are effective 

methods to demonstrate external MI. They have been used successfully by injection well 

operators for decades and provide an important early warning of potential problems in the 

injection well system. While the oxygen activation log is not explicitly required in the rule, the 

regulations do provide flexibility at §146.89(e) to allow the Director to require additional test 

methods or, with the approval of the Administrator, to approve the use of alternative MIT 

methods. These additional methods could include the annual pressure test recommended in the 

AwwaRF/AWWA guidelines. The specific MITs required prior to start-up of injection or at well 

workovers would be identified in the permit by the Director. For additional information, please 

see the discussion of MITs in the final rule preamble. 

As stated above, EPA disagrees that the rule should specify the monitoring techniques for all GS 

sites. 

EPA agrees that tracking the plume and the position of the pressure front during injection 

operations and the post-injection site care period will provide important data for determining that 

the injectate is confined within the target formation, as well as for evaluating any risks within the 

AoR. EPA also agrees with the commenter that data collected during site characterization (such 

as baseline geochemistry, pre-injection reservoir pressure, etc.) are appropriate to ensure that 

there is a baseline with which to compare GS operation and post-injection data. 

EPA is developing guidance on testing and monitoring to assist owners or operators and 

Directors in evaluating requirements under §146.90, including proposed monitoring plans. The 

guidance describes recommended approaches for implementing a testing and monitoring plan, 

including pre-operational geophysical logging and testing of injection wells, MITs, injection well 

testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure 

front, and soil gas and surface air monitoring which may be required by the UIC Director for 

specific GS projects. The guidance can be found on EPA’s website at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, 

DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of 

CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in 

the docket for the final GS rule. 

EPA also agrees that periodic updates to the plan are appropriate. EPA clarifies that the final GS 

regulation includes a requirement that the AoR be reevaluated every 5 years, and it specifies at 

§146.90(j) that the operator revise the testing and monitoring plan to incorporate the results of 

the most recent AoR reevaluation and recent operational and monitoring data. 

EPA clarifies that cost-benefit analyses are not used to determine the most appropriate 

monitoring technologies, location, or frequency. Instead, the Agency believes that the flexibility 

afforded the owner or operator at §146.90 to develop a testing and monitoring plan tailored to 

site-specific characteristics is appropriate for GS. 

Letter ID: 0181 Comment ID: 23697 Letter Lines: 1170 to 1175 

54
Comment Code: 4610 2.6.1 Testing and monitoring plan requirement (seeking comment) 

Comment: be considered unless this monitoring is included. All of the monitoring 

requirements should be put forth in a monitoring plan, which should be reviewed 

and approved by the Director prior to the start of the project. This plan should 

be re-evaluated every five years during the permit review, and should be updated 

by the owner/operator based on any changes in operation or performance of the 

carbon dioxide plume. 

Individual Response: EPA agrees with commenters that developing and following testing and 

monitoring plans is an important part of assuring that a GS project is operating properly and is 

crucial for the early detection of potential endangerment to USDWs. EPA also agrees that 

periodic updates to the plan are appropriate. EPA clarifies that the final GS regulation includes a 

requirement that the AoR be reevaluated at least every 5 years, and it specifies at §146.90(j) that 

the operator revise the testing and monitoring plan to incorporate the results of the most recent 

AoR reevaluation and recent operational and monitoring data. EPA is developing guidance on 

how best to develop the various required project plans, including the testing and monitoring plan. 

The guidance can be found on EPA’s website at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

Letter ID: 0181 Comment ID: 23698 Letter Lines: 1176 to 1179 

Comment Code: 4640 2.6.4 Pressure fall-off testing (seeking comment) 

Comment: 

Pressure fall-off testing should definitely be required however the five year 

length between testing is too long. This should be performed on an annual basis 

as part of the annual reporting requirements 

Individual Response: EPA believes that a frequency of at least once every five years, as 

specified at §146.90(f), is an appropriate interval for pressure fall-off testing (particularly given 

the suite of tests operators will perform on the well and the site). EPA clarifies that the Director 

may require more frequent pressure fall-off tests at a specific project, if necessary based on sitespecific circumstances. Pressure fall-off tests may be conducted in conjunction with other well 

performance tests (i.e., mechanical integrity testing) to ensure safe and effective operations. All 

monitoring data collected, including information from pressure fall-off tests, will be incorporated 

in AoR reevaluations conducted at least every five years. 

Letter ID: 0181 Comment ID: 23699 Letter Lines: 1181 to 1185 

Comment Code: 4670 2.6.7 Surface air monitoring and/or soil gas monitoring (seeking 

comment) 

Comment: Surface air and soil gas monitoring should be required however, baseline soil 

carbon dioxide levels should be determined prior to the start of monitoring. 

55
Testing for other compounds such as tracers that may included as part of the 

carbon dioxide injectate stream should also be considered in the development of 

the monitoring plan. 

Individual Response: EPA agrees that surface air and soil gas monitoring, when coupled with 

subsurface monitoring, may be appropriate at some GS projects to ensure USDW protection. In 

the final rule, at §146.90(h), the decision to require such monitoring rests with the Director as a 

means of identifying leaks that may pose a risk to USDWs and informing emergency notification 

of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, 

pursuant to requirements at §146.91(c). 

The Agency agrees with the commenter that, if air and soil gas monitoring is performed, baseline 

soil CO2 levels need to be determined before monitoring. This would be considered and 

described in the site-specific testing and monitoring plan. 

Letter ID: 0181 Comment ID: 23700 Letter Lines: 1187 to 1203 

Comment Code: 4610 2.6.1 Testing and monitoring plan requirement (seeking comment) 

Comment Code: 5200 2.8.2 Post injection site care (seeking comment) (40 CFR 146.93) 

Comment: Category: Required Project Plans 

EPA Request for Comment: EPA seeks comment on the merits of requiring plans for 

monitoring, AoR, and post-injection site care as part of a permit application. 

EPA Notice 43517. 

AWWA Response: The requirement for the development of plans for monitoring, AoR, 

and post-injection site care is necessary and is a very important part of the 

permit process. The information will provide outside stakeholders with a much 

better idea of how the project will proceed and can help to assure them that the 

owner/operator has a clear vision for the life of the project. AWWA recommends 

that these plans be reviewed at the same time that the area of review is 

reevaluated. During this review, the plans should be updated based on any 

operational changes since the last project review period and submitted to the 

Director for approval. AWWA recommends that a review occur every year for the 

first ten years of the project, and then should be reviewed every five years 

until injection ceases. 

Individual Response: EPA agrees with the commenter. Owners or operators are required to 

submit an AoR and corrective action plan, a testing and monitoring plan, and a post-injection site 

care and site closure plan as part of the permit application, as specified in §146.82(a), to outline 

how these activities will be performed and how non-endangerment of USDWs will be 

demonstrated throughout the operational and post-injection site care periods. EPA is developing 

guidance on how best to develop the various required project plans, including the testing and 

monitoring plan. The guidance can be found on EPA’s website at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

56
The GS rule also requires owners or operators to review and update the AoR and corrective 

action plan and the testing and monitoring plan throughout the life of the project, as described at 

§146.84(c) and §146.90(j). The rule requires at §146.90(j) that the operator revise the testing and 

monitoring plan to incorporate the results of the most recent AoR reevaluation and recent 

operational and monitoring data. Owners or operators must review each plan and identify 

necessary amendments to the plan or demonstrate to the Director that no amendment is needed. 

These reviews must be performed within one year of an AoR reevaluation, following any 

significant changes to the facility (e.g., the addition of monitoring or injection wells), or when 

required by the Director. In no case can reviews occur less often than once every five years. This 

review frequency is appropriate to ensure that reviews of the plans are conducted on a defined 

schedule or when there is a change in the AoR or significant change, while adding little burden if 

an AoR reevaluation confirms that the plans are appropriate as written. See the preamble sections 

on the plans for additional information. 

EPA is not requiring formal periodic review and updates to the PISC and site closure plan 

throughout the injection phase as with the AoR reevaluation that is required at least every 5 

years. EPA does not expect that changes to this plan would be implemented until injection 

operations cease. EPA is requiring that upon the cessation of injection, the owner or operator 

submit an amended post-injection site care and site closure plan or demonstrate to the Director 

that no changes to the original post-injection site care and site closure plan are necessary, as 

specified in §146.93(a)(3). EPA envisions that owners or operators would take into account 

similar considerations that guide updates to other project plans, e.g., monitoring and operational 

data and results of AoR reevaluations. 

EPA has also added a new provision at §144.39(a)(5) identifying the basis for a modification, 

revocation, or reissuance of a Class VI permit whenever the Director determines that a change in 

the permit is necessary based on an amended AoR and corrective action plan, testing and 

monitoring plan, injection well plugging plan, post-injection site care and site closure plan, or 

emergency and remedial response plan is necessary. 

Letter ID: 0181 Comment ID: 23701 Letter Lines: 1205 to 1222 

Comment Code: 4760 2.7.6 Proposed reporting frequency (seeking comment) 

Comment: EPA Request for Comment: EPA seeks comment on the frequency of all proposed 

reporting requirements. EPA Notice 43517 

AWWA Response: AWWA recommends that the owner/operators of a Class VI well 

provide a monthly operating report to the Director instead of the semi-annual 

report as proposed. The operating information for the geologic sequestration 

project is extremely important and needs to be reviewed at a frequency by the 

regulatory agency to ensure problems are identified and addressed in a timely 

manner. For example, based on the proposed regulation, data collected on July 1, 

2008 would not be seen by the regulatory agency before January 15, 2009, if the 

operator is allowed 15 days to submit the report. This would allow for very 

little time to correct any potential issues in the operation of the project. We 

57
have provided example monthly reporting sheets that were developed as part of 

the AwwaRF project in Section III of our comments, and these reports are similar 

to the monthly reporting sheets used by water and wastewater treatment plants. 

Given the potential scale of carbon sequestration and the need to protect 

groundwater resources, a requirement for monthly operating reports is 

reasonable. 

Individual Response: The final rule remains unchanged from the proposal and requires semiannual reporting of monthly average, maximum and minimum values for injection pressure, flow 

rate and volume, annular pressure, and monthly annulus fluid volume added at §146.91(a). EPA 

believes that monthly reporting of routine operational data and monitoring results would provide 

no additional protection of USDWs from endangerment. EPA adds, at §146.91(c), that it has 

included in the final rule a requirement that operators must report within 24 hours of any event 

that may endanger USDWs. EPA notes that states seeking primacy for Class VI wells are free to 

require more frequent reporting. 

EPA reviewed the sample reporting forms submitted by AWWA (EPA-HQ-OW-2008-0390-

0181). The Agency will refer to these as it prepares guidance for complying with the reporting 

requirements. However, EPA notes that most reporting will be done electronically. 

Letter ID: 0181 Comment ID: 23702 Letter Lines: 1224 to 1228 

Comment Code: 4730 2.7.3 Reporting associated with closure and post-injection site care 

Comment: With respect to the requirement for recordkeeping, AWWA recommends that the 

oneyear holding requirement for the plugging and abandonment report be extended. 

This is an extremely important report, and the owner/operator must be required 

to keep this report on file for a minimum of 10 years following the closure of 

the project site. 

Individual Response: EPA is requiring that data collected during the post-injection phase be 

retained throughout the post-injection site care timeframe and for ten years following site 

closure. EPA agrees that well plugging reports should be retained for longer than one year. EPA 

has clarified the recordkeeping requirements in the final GS rule, which includes requirements 

that well plugging reports, as required at §146.92(d), post-injection site care data, as required at 

§146.93(f), and site closure reports, as required at §146.93(h), be kept for ten years after site 

closure. 

EPA believes that longer record retention times for GS wells are appropriate for the postinjection and site closure period to ensure that data are available to support non-endangerment 

demonstrations and to address any concerns that may arise following site closure. This data will 

also support EPA's review of project data as part of the adaptive rulemaking approach. 

58
Letter ID: 0181 Comment ID: 23703 Letter Lines: 1230 to 1239 

Comment Code: 4740 2.7.4 Electronic reporting (seeking comment) 

Comment: EPA Request for Comment: EPA seeks comment on the requirement for electronic 

reporting in its proposed rule. EPA Notice 43518. 

AWWA Response: AWWA agrees with the electronic reporting requirements include as 

part of the proposed regulation. Electronic reporting allows for easier tracking 

of the operating data to observe any trends that might indicate potential 

contamination of a USDW. EPA should consider the infrastructure that will be 

required to collect information prior to publishing the first report and develop 

a model reporting plan for owner/operators to use when submitting data to state 

agencies. 

Individual Response: EPA believes that electronic formatting is the most appropriate format for 

submitting Class VI project information to the Director, and based on comments received on the 

proposed rule, the majority of Class VI well owners or operators will have the capability to 

report electronically, and requires this at §146.91(e). 

EPA is developing guidance for states that describes the recordkeeping, reporting, and additional 

data management needs associated with GS activities and provides recommended guidelines on 

the types of data to be collected for tracking GS projects, reporting to EPA for compliance 

tracking, and transfer of data to EPA's GS data system. The recordkeeping and reporting 

guidance will be available on EPA's web site, at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

Letter ID: 0181 Comment ID: 23704 Letter Lines: 1241 to 1257 

Comment Code: 4750 2.7.5 Comments on the merit of annual reports (seeking comment) 

Comment: EPA Request for Comment: In addition to the above recordkeeping and reporting 

requirements, EPA considered a requirement for owners or operators of GS sites 

to provide an annual report during the lifetime of the project, including the 

post-injection period, regarding the GS operation. Although EPA has not included 

a requirement for this report in its proposal, EPA seeks comment regarding the 

necessity for such an annual report. EPA Notice 43518. 

AWWA Response: AWWA recommends that an annual reporting requirement be included 

n the proposed regulation. This report should summarize the operation of the 

system including standard operating criteria, information on well operation, 

details of plume movement, and any details on major changes in well operation. 

It should be similar to the Consumer Confidence Reports (CCR) that drinking 

water utilities must develop and it should be mailed or emailed to all relevant 

stakeholders. EPA should develop requirements for the report similar to those 

required for the CCR because the annual report should be developed by someone 

59
one of the team members involved in the operation of the geologic sequestration 

project. 

Individual Response: Individual Response: The final GS regulation retains the semi-annual 

reporting requirements as proposed and does not include a requirement for an annual report. 

Instead, EPA believes that periodic reevaluation of the AoR, as required at §146.84(e), along 

with any revisions to the required plans that may be necessary based on the AoR reevaluation, 

will promote an ongoing relationship between the permitting authority and the owner or operator. 

The final GS rule, at §§146.84(c), 146.90(j), and 146.94(d), requires owners or operators to 

review and update the AoR and corrective action plan, the testing and monitoring plan, and the 

emergency and remedial response plan throughout the life of the project. Owners or operators 

must review each plan and identify necessary amendments to the plan or demonstrate to the 

Director that no amendment is needed. These reviews must be performed within one year of an 

AoR reevaluation, following any significant changes to the facility (e.g., the addition of 

monitoring or injection wells), or when required by the Director. In no case can reviews occur 

less often than once every five years. 

EPA also encourages and expects owners and operators to share monitoring and operating data 

with the public voluntarily (e.g., through the Internet. Providing the public with information 

throughout the GS project will help clear up and avoid public misperceptions about the nature 

and safety of GS. For additional information, please see the final rule and the preamble for a 

discussion of EPA's final approach to recordkeeping and reporting. 

Letter ID: 0181 Comment ID: 23705 Letter Lines: 1259 to 1280 

Comment Code: 5240 2.8.2.2 Post injection timeframe (seeking comment) 

Comment: Category: Post-Injection 

EPA Request for Comment: EPA requests comment on the proposed use of a tentative 

50-year fixed timeframe that could be modified at the Director’s discretion 

based on monitoring and modeling data. EPA Notice 43519. 

EPA is requesting comments on the proposed requirements for well plugging, postinjection site care, and site closure, including the proposed requirements for 

the post-injection time period. EPA Notice 43520. 

AWWA Response: AWWA recommends that the time period for post-injection site care 

be set at a minimum of 50-years and that the Director not be given any 

discretion to shorten this time period. After this 50-year period, the operator 

must continue to monitor until such time as they can demonstrate that the plume 

has stabilized and that it does not present any potential danger to USDWs or 

other potential sources of drinking water. This requirement is not overly 

prescriptive or burdensome given the information available on the long-term 

behavior of carbon dioxide plumes. This time period is necessary to monitor the 

site for changes that may occur over a longer amount of time, such as gradual 

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leakages, fault movement, or sudden seismic shifts. After this time period, the 

owner/operator may apply to the Director for a modification or termination of 

the monitoring requirements. 

Individual Response: EPA agrees that a 50 year post-injection site care timeframe represents a 

reasonable and protective post-injection site monitoring period for most GS projects and 

available data, including data submitted by commenters, do not support a different default 

timeframe. EPA bases this on a review of research studies, industry reports, and existing 

environmental programs, and evaluation of public comments. Furthermore, EPA believes that a 

50-year default post-injection site care timeframe is not overly burdensome, does not exaggerate 

the risks associated with GS, is consistent with other environmental programs, and sufficiently 

protects USDWs from endangerment. For this reason, the final GS regulation retains the 50 year 

post-injection site care timeframe, as specified in §146.93(b)(1). 

However, EPA disagrees that a 50 year post-injection site care timeframe should be an absolute 

minimum. Rather, EPA believes, as some commenters suggest, that there will be circumstances 

where it can be demonstrated in less than 50 years that the plume and pressure front no longer 

pose a risk of endangerment to USDWs. For this reason, the GS rule offers owners or operators 

flexibility regarding the duration of the PISC timeframe by: (1) allowing the Director discretion 

to shorten or lengthen the PISC timeframe during the post-injection period based on site-specific 

data, pursuant to requirements at §146.93(b); or (2) affording the Director discretion to allow a 

Class VI well owner or operator to demonstrate, during the permitting process based on 

substantial data, that an alternative PISC timeframe may be appropriate if it ensures nonendangerment of USDWs pursuant to requirements at §146.93(c). 

EPA believes that a default post-injection site care timeframe of 50 years, with flexibility to 

adjust the timeframe for a limited number of GS projects during the permitting process where 

substantial data exists to demonstrate that an alternative timeframe would be protective of 

USDWs, or based on data collected during the PISC period, is appropriate to address the range of 

sites where GS is anticipated to occur, to accommodate site-specific circumstances and various 

geologic conditions, and addresses commenters’ concerns, while ensuring USDW protection. 

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

impacts. 

Letter ID: 0181 Comment ID: 23706 Letter Lines: 1282 to 1312 

Comment Code: 5220 2.8.2.1 Post-injection monitoring activities 

Comment Code: 5280 2.8.2.4 USDW non-endangerment demonstrations 

Comment: AWWA has observed that the proposed regulation is lacking in details on the 

requirements to demonstrate that the carbon dioxide plume has stabilized. For 

example, the proposal does not include requirements that the plume pressure must 

be constant for a certain number of years or that the plume has not migrated for 

a set period of time. Since AWWA does not claim to be experts on the behavior of 

carbon dioxide plumes and can not provide recommendations on this topic, AWWA 

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recommends that EPA should engage in research on determining exactly what these 

criteria should be. For example, when referencing lack of plume movement, what 

should the trigger time period be (no movement of plume for 10, 15, 20 or more 

years??). AWWA recommends that EPA clarify what is an acceptable frequency for a 

lack of change in the plume characteristics and also needs to clarify plume 

stabilization as this issue could be interpreted differently by different 

states. Guidance should be prepared by EPA on this topic so that there is 

consistent application of this requirement across all sequestration projects. A 

performance based system could also be developed that would require the operator 

to meet certain criteria to prove that the plume has stabilized. This could be 

used to justify the closing of the site after the 50-year period of postinjection site care has elapsed. This would allow for a process where long-term 

monitoring decisions are made in response to the specific characteristics of 

each project. 

AWWA believes that the proposed post-injection site care requirements have been 

established to prevent endangerment to USDWs. Carbon dioxide can potentially 

leak from the confining layer into other aquifers that, while not classified as 

USDWs, may still be considered drinking water sources in some areas of the 

county. EPA should also consider including requirements in the regulation to 

address the potential for endangerment of these aquifers during the postinjection period. Monitoring requirements should be extended to cover these 

aquifers, and the post-injection site care plan should include provisions for 

the protection of aquifers that are not classified as USDWs, but are still 

considered a future drinking water source. 

Individual Response: EPA acknowledges that many site-specific factors will influence the 

determination of when the CO2 plume and pressure front no longer pose a risk of endangerment 

to USDWs. It is for this reason that EPA believes that individual UIC Directors, in consultation 

with operators, will be in the best position to determine whether additional post-injection site 

care is needed. EPA expects this decision to be made based on relevant site data and in 

consultation with all potentially impacted parties. 

EPA is developing guidance to assist owners or operators in evaluating well plugging, postinjection site care, and site closure requirements of §146.92 and §146.93. Additionally, the 

guidance will assist Directors in evaluating proposed well plugging plans and post-injection site 

care and site closure plans under §146.92 and §146.93. The guidance describes recommended 

approaches for how an owner or operator could plug injection and monitoring wells; perform 

post-injection monitoring; demonstrate the appropriateness of an alternative post-injection site 

care time frame; demonstrate non endangerment; and perform site closure activities. The 

guidance will be available at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

EPA has conducted research regarding stabilization timeframes. As described in the preamble to 

the proposed rule, in determining the post-injection site care-timeframe for the proposed 

regulation, EPA reviewed industry reports, existing environmental programs, and initial GS 

research studies. EPA provided a synthesis of pertinent results from GS modeling studies in the 

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preamble to the proposed regulation. Further explanation of this analysis was included in an 

EPA-prepared background document that is available in the federal docket, titled 

"Computational Modeling of Underground Injection of Carbon Dioxide for Determination of 

Area-of-Review and Potential Risk to Underground Sources of Drinking Water." Based on 

review of these studies, modeling results indicate that the CO2 plume stabilization may occur on 

the timeframe of 10-100 years after the cessation of injection. EPA believes that a 50-year 

default post-injection site care timeframe is a reasonable midpoint for most GS projects and 

available data, including data submitted by commenters, do not support a different default 

timeframe, and has retained this in the final regulation. EPA will continue research in this area 

and 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: 0181 Comment ID: 23707 Letter Lines: 1314 to 1375 

Comment Code: 1310 1.1.2.4 Comments on other "out of scope" issues, e.g., pore space 

ownership 

Comment Code: 5430 2.9.1 Comments on proposed financial responsibility requirements (40 

CFR 146.85) 

Comment: Category: Financial 

EPA Request for Comment: Because of the possibility that the owner or operator 

may face financial distress prior to the trust being fully funded, EPA is 

considering a guidance approach that would recommend adopting a pay in period of 

three years for GS projects, consistent with other similar programs in the 

Agency. EPA Notice 43521. 

EPA is assessing whether to provide guidance on the use of insurance providers 

and, if so, whether to update eligibility requirements for insurers for GS wells 

consistent with other current Federal agency practices. EPA Notice 43521. 

EPA is requesting comments on whether financial responsibility mechanisms to be 

recommended in EPA guidance should be adjusted in the manner described, whether 

additional instruments should be included, and whether other adjustments to the 

financial responsibility mechanisms should be considered, all subject to EPA’s 

authority under the SDWA. EPA Notice 43522. 

AWWA Response: AWWA has several major concerns regarding owner/operator 

financial assurance and liability. Our primary concern is that the liability 

mechanism that would be triggered when the confining zone fails and carbon 

dioxide escapes has not been identified. Would this incident trigger CERCLA 

requirements if groundwater is degraded? AWWA recommends that the liability 

requirements and financial mechanisms that were used to address MTBE 

contamination be applied to any USDW degradation from carbon sequestration 

63
activities. The definition of a "corrective action" does not provide any 

protection for aquifers that are contaminated by the carbon sequestration 

process. The definition as provided in the proposed rule states that corrective 

action is "...the use of Director approved methods to assure that wells within 

the area of review do not serve as conduits for the movement of fluids into 

underground sources of drinking water (USDW)." Note that this definition does 

not address "fixing" the impact to USDW. What is unclear to AWWA is if the 

geologic sequestration process does endanger groundwater aquifers, whether the 

owners/operators have any financial liability in restoring water quality (e.g., 

paying for extra treatment costs incurred by water utilities or other 

groundwater users), as the corrective action seems to focus on fixing injection 

wells and/or the confining layer. 

The question remains regarding what an owner/operator’s total liability would be 

outside of the USDW contamination. The potential exists for contamination of 

other ground water aquifers, such as those that are not classified as USDWs but 

are used as a drinking water sources, and it is extremely important that the 

liability requirements are extended to these aquifers. The cost to remediate any 

degradation can be extremely high. Depending on the scope and location of the 

degradation, examples of potential costs that might be incurred by a drinking 

water utility include the installation of advanced water treatment technologies 

and/or development of alternative water sources. The responsibility for these 

costs must be assumed by the owner/operator in the event of a failure of the 

geologic sequestration process. 

AWWA believes that the time limit for financial responsibility in the proposed 

regulation may be too long for most insurance agencies, which may trigger the 

need for the development of a trust fund or for owner/operators to use a selfinsurance mechanism. If the trust fund is the desired method, EPA should require 

that companies constantly add to the fund, even if it appears that the fund is 

fully funded. In addition to the initial pay in period of three years, 

owner/operators should be required to pay in any additional amount identified 

during the five-year reviews for the area of review and corrective action plan, 

injection well plugging plan, the post-injection site care and site closure 

plan, and the emergency and remedial response plan. This additional pay in is 

required so that we don't have a repeat of the funding stoppage with the 

Superfund program. 

Individual Response: The goal of financial responsibility is to ensure that financial resources 

are available to prevent endangerment of USDWs from improper plugging, remediation, and 

management of wells in the event that the owner or operator experiences financial difficulties. 

As such, owners or operators must demonstrate financial responsibility for, among other things, 

any needed emergency and remedial response actions that are necessary to mitigate 

endangerment or potential endangerment of USDWs. See the final rule and preamble for further 

discussion of EPA's final approach to financial responsibility. 

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EPA clarifies that, while the commenter accurately defines corrective action for wells in the 

AoR, this term does not refer to actions needed to address endangerment in the UIC program 

regulations. EPA clarifies that the intent of the emergency and remedial response requirements at 

§146.94 is that if the owner or operator obtains any evidence that USDWs may be endangered, 

he or she must cease injection, take all steps reasonably necessary to identify and characterize 

any release, notify the Director, and implement the approved emergency and remedial response 

plan, per §146.94(b). 

EPA disagrees that GS is analogous to the MTBE situation. EPA believes that large scale GS can 

be done safely. The GS regulation builds upon the long-standing, protective regulatory 

framework of the UIC program, which has been regulating the injection of fluids for decades. 

The GS regulation enhances this existing framework with tailored requirements for Class VI GS 

wells to address the unique nature of large scale GS of CO2. These protective requirements 

include extensive geologic testing, detailed computational modeling of the AoR and periodic reevaluations, detailed requirements for monitoring and tracking the CO2 plume and pressure 

front, and extended post-injection monitoring and site care. 

Letter ID: 0181 Comment ID: 23708 Letter Lines: 1377 to 1385 

Comment Code: 4710 2.7.1 Proposed submissions required for permit applications (seeking 

comment) 

Comment Code: 5430 2.9.1 Comments on proposed financial responsibility requirements (40 

CFR 146.85) 

Comment: AWWA questions whether it would be acceptable for energy companies and 

owner/operators to bond projects as a way to demonstrate financial assurance. 

AWWA recommends that EPA develop formal technical, managerial, and financial 

requirements for carbon sequestration projects that owner/operators must meet 

and maintain. This should be tied to the permitting process as these 

requirements must be demonstrated prior to the operating permit being issued. 

Demonstrating ongoing technical, managerial, and financial capabilities would be 

an important component of the five-year permitting review process that AWWA is 

recommending. 

Individual Response: EPA agrees that financial responsibility demonstrations should be part of 

the permitting process for Class VI wells. As a result, the rule requires owners or operators to 

demonstrate adequate financial responsibility for all required activities with their permit 

application, per §146.82(a)(14). 

EPA is developing guidance on financial responsibility for Class VI wells. The guidance will 

include a discussion on how best to estimate costs to assist GS well owners or operators, third 

party insurers or providers of financial instruments, and permitting authorities in developing 

estimates of the costs associated with various GS activities. This guidance will be available on 

EPA's website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

65
Letter ID: 0181 Comment ID: 23709 Letter Lines: 1387 to 1392 

Comment Code: 5434 2.9.1.2 Need for additional instruments (seeking comment) 

Comment: With respect to the required financial mechanisms, AWWA would like to leave the 

door open for establishing financial mechanisms on a project by project basis. 

The rulemaking should not prescribe or preclude particular financial instruments 

as the issue of financial assurance is very complex. Other funding models could 

be developed, and it may be that Moodys or Standards and Poors will see this as 

a potential opportunity. Many significant financial details remain that must be 

Individual Response: Owners or operators may choose from a variety of financial instruments 

to meet their financial responsibility obligations under the rule, provided the Director determines 

that the operator's proposed financial responsibility demonstration is adequate to protect USDWs 

from endangerment, which means the ability of the owner or operator to pay for each activity for 

which financial responsibility must be demonstrated, including corrective action on wells in the 

AoR, injection well plugging, PISC and site closure, and emergency and remedial response 

throughout the life of the project. The final GS rule specifies at §146.85(a)(1) the permitted types 

of financial responsibility instruments. See the final rule and preamble for further discussion of 

EPA's final approach to financial responsibility. 

Letter ID: 0181 Comment ID: 23710 Letter Lines: 1392 to 1398 

Comment Code: 5460 2.9.2 Comments on transfer of liability for long-term care 

Comment: a potential opportunity. Many significant financial details remain that must be 

addressed before any guidance or regulation is issued on this topic. As an 

example, the issue of long-term liability still has not been resolved. Who is 

ultimately responsible for ownership of the injection wells and the carbon 

dioxide plume after the post-closure period has ended? Does the liability 

transfer to whoever manages the trust fund (in that particular financial 

assurance mechanism)? 

Individual Response: Under the final GS rule, once an owner or operator has met all regulatory 

requirements under Part 146 for Class VI wells and the Director has approved site closure 

pursuant to requirements at §146.93, the owner or operator will generally no longer be subject to 

enforcement for regulatory noncompliance. Furthermore, their financial instrument as required 

under §146.85 will be released if it was not used. However, even if a site closure is approved 

under §146.93, an owner or operator may be held liable for regulatory noncompliance (including 

violation of 40 CFR 144.12) in certain circumstances. For example, an owner or operator may be 

held liable for regulatory noncompliance even after site closure was approved if the Director 

relied on erroneous information (e.g., erroneous modeling data) provided by the owner or 

operator when approving site closure. 

Separate from EPA’s authority to enforce regulatory compliance, an owner or operator may be 

subject to a §1431 response order even after proper site closure is approved under §146.93. 

66
Under §1431 the Administrator may require an owner or operator to take necessary response 

measures if he or she receives information that a contaminant is present or is likely to enter a 

public water system or an USDW, which may present an imminent and substantial endangerment 

to the health of persons, and the appropriate State and local authorities have not acted to protect 

the health of such persons. The action may include issuing administrative orders or commencing 

a civil action for appropriate relief against the owner or operator of a Class VI well. If the owner 

or operator fails to comply with the order, they may be subject to a civil penalty for each day in 

which such violation occurs or failure to comply continues. 

Furthermore, after site closure an owner or operator may remain liable under tort and other 

remedies, or under other federal statutes including, but not limited to, Clean Air Act, 42 U.S.C. 

§§ 7401-7671; CERCLA, 42 U.S.C. § 9601-9675; and RCRA, 42 U.S.C. § 6901-6992. EPA 

does not have authority to transfer SDWA or other legal liability for Class VI wells to the State 

or federal government or a third-party fund. See the final rule preamble for further discussion of 

EPA's final approach. 

Letter ID: 0181 Comment ID: 23711 Letter Lines: 1400 to 1416 

Comment Code: 5400 2.9 Proposed Financial Responsibility and Long-Term Care 

Requirements 

Comment Code: 5460 2.9.2 Comments on transfer of liability for long-term care 

Comment: AWWA would also like to see the issue of long-term liability resolved. EPA’s 

proposed geologic carbon sequestration rule is not able to address financial 

responsibility of the sequestration site after the formal period of postinjection site care has ended (default of 50 year length). Recognizing that EPA 

does not have the power to assign responsibility after this period of time has 

expired, AWWA recommends that EPA work with the appropriate stakeholders to 

develop legislation that will address the issue of who has to assume financial 

responsibility of the sequestration site after the site closure requirements 

have been fulfilled. AWWA anticipates that this legislation would provide for a 

means by which drinking water utilities could recover any costs incurred as a 

result of USDW contamination by geologic carbon sequestration activities. AWWA 

also recommends that EPA work with the appropriate stakeholders to develop 

comprehensive climate change legislation with the goal of protecting water 

systems, and their customers, from loss of water supply or unplanned major 

financial burdens. Everyone needs to apply the lessons learned from MTBE 

contamination to prevent unintended consequences from developing with geologic 

sequestration wells. 

Individual Response: EPA is working to create a nationally consistent financial responsibility 

regime for GS projects within its authority under the SDWA while providing permitting 

authorities an appropriate level of flexibility. The goal of financial responsibility is to ensure that 

financial resources are available to prevent endangerment of USDWs from improper plugging, 

remediation, and management of wells in the event that the owner or operator experiences 

financial difficulties, thereby preventing costs from spilling over to the public. EPA believes that 

67
the general authorities provided under SDWA include the authority to set federal minimum 

requirements for financial responsibility to ensure that resources are available to protect USDWs 

throughout the life of the GS project. However, this authority does not extend to release owners 

or operators from long-term responsibility of other environmental statutes, such as CERCLA, for 

potential impacts to USDWs after the PISC period has ended, or for the potential economic costs 

associated with activities with impacts unrelated to USDWs (e.g., risks to air, or ecosystems). 

Comments related to comprehensive climate change legislation is outside the scope of this 

rulemaking. 

Under the final GS rule, once an owner or operator has met all regulatory requirements under 

Part 146 for Class VI wells and the Director has approved site closure pursuant to requirements 

at §146.93, the owner or operator will generally no longer be subject to enforcement for 

regulatory noncompliance. Furthermore, their financial instrument as required under §146.85 

will be released if it was not used. However, even if a site closure is approved under §146.93, an 

owner or operator may be held liable for regulatory noncompliance (including violation of 40 

CFR 144.12) in certain circumstances. For example, an owner or operator may be held liable for 

regulatory noncompliance even after site closure was approved if the Director relied on 

erroneous information (e.g., erroneous modeling data) provided by the owner or operator when 

approving site closure. 

Separate from EPA’s authority to enforce regulatory compliance, an owner or operator may be 

subject to a §1431 response order even after proper site closure is approved under §146.93. 

Under §1431 the Administrator may require an owner or operator to take necessary response 

measures if he or she receives information that a contaminant is present or is likely to enter a 

public water system or an USDW, which may present an imminent and substantial endangerment 

to the health of persons, and the appropriate State and local authorities have not acted to protect 

the health of such persons. The action may include issuing administrative orders or commencing 

a civil action for appropriate relief against the owner or operator of a Class VI well. If the owner 

or operator fails to comply with the order, they may be subject to a civil penalty for each day in 

which such violation occurs or failure to comply continues. 

Furthermore, after site closure an owner or operator may remain liable under tort and other 

remedies, or under other federal statutes including, but not limited to, Clean Air Act, 42 U.S.C. 

§§ 7401-7671; CERCLA, 42 U.S.C. § 9601-9675; and RCRA, 42 U.S.C. § 6901-6992. EPA 

does not have authority to transfer SDWA or other legal liability for Class VI wells to the State 

or federal government or a third-party fund. See the final rule preamble for further discussion of 

EPA's final approach to financial responsibility for Class VI wells. 

As described above, EPA disagrees that GS is analogous to the MTBE situation. 

Letter ID: 0181 Comment ID: 23712 Letter Lines: 1418 to 1448 

Comment Code: 1530 1.2.3.1 State regulatory efforts on GS (seeking comment) 

Comment Code: 1650 1.3.5 Human health impacts 

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Comment: Category: State Capacity 

EPA Request for Comment: EPA seeks comment on any aspects of the ongoing State 

efforts to regulate the GS of CO2 and how these efforts might be used to better 

inform a final Federal rulemaking. EPA Notice 43497. 

AWWA Response: From our perspective, EPA’s proposed rule appears to be focused 

on preventing brine from formations where carbon dioxide was stored from 

reaching USDWs and/or from preventing carbon dioxide that reaches USDWs from 

causing primary MCLs to be exceeded. This focus may not be adequate from the 

standpoint of protecting source water and beneficial use aquifers from 

detrimental changes in water quality other than the exceedance of primary MCLs. 

Other water quality impacts could be observed such as increased concentrations 

of iron, manganese and TDS, as well as lowered pH, all of which have secondary 

MCLs. Increases in the concentrations of silica and boron, which do not 

currently have MCLs but can significantly degrade water quality, are also likely 

to occur. 

This past year, the State of Washington adopted carbon sequestration regulations 

which AWWA recommends that EPA review and incorporate some of the language into 

the final regulation. The Washington regulations require that the owner or 

operator must demonstrate that the "design and construction standards of all 

facility structures and wells are sufficient to prevent migration of carbon 

dioxide or nonpotable water that will degrade water quality or impact beneficial 

uses outside the geologic containment system." The language in this regulation 

provides protection mechanisms for groundwater sources that may not be used as 

USDWs but have other beneficial uses, such use as industrial applications or 

agriculture. Given the stresses that the drinking water industry is facing with 

respect to water resources, AWWA recommends that the monitoring requirements in 

the final rule be extended to protect against aquifer contamination beyond that 

which is associated with compounds that have primary MCLs. 

Individual Response: EPA recognizes the complexity and importance of states' approaches to 

managing GS and is aware that states are currently in various stages of developing statutory 

frameworks, regulations, workgroups, technical guidance, and strategies for addressing CCS and 

GS. 

Throughout the regulatory development process for the Class VI regulation, EPA monitored 

states' regulatory and legislative development efforts and approaches. In EPA's August 31, 2009, 

Notice of Data Availability (NODA) and Request for Comment, the Agency described its 

ongoing monitoring of states' regulatory efforts and approaches and how the Agency is 

considering this information as it develops guidance on the primacy application and approval 

process for Class VI wells. Information about these state activities may be found in the docket 

for the GS rule. 

EPA clarifies that the UIC program’s authority applies to protection of USDWs from 

69
endangerment. SDWA §1421(d)(2) states that “underground injection endangers drinking water 

sources if such injection may result in the presence in underground water which supplies or can 

reasonably be expected to supply any public water system of any contaminant, and if the 

presence of such contaminant may result in such system’s not complying with any primary 

drinking water regulation or may otherwise adversely affect the health of person.” EPA disagrees 

that the GS rule is only focused on MCL contamination as it relates to endangerment; rather the 

rule also focuses on “adverse effects on the health of person[s].” This does not necessarily 

require a showing of non-compliance with an MCL. 

EPA clarifies that the UIC regulations apply only to underground injection wells and injection 

activities, and not to "facility structures” that are not considered to be wells under §144.3. 

Under §146.94, if the owner or operator obtains evidence that injection may cause endangerment 

to a USDW, he or she must stop injection and implement the emergency and remedial response 

plan for that well. With proper site selection, the final, tailored, Class VI requirements address 

the large volumes of CO2 injected, its buoyancy, potential corrosivity in the presence of water, 

and potential impurities in the CO2 stream. In addition, the tailored permitting, siting, 

construction, operation, monitoring, and post-injection site care requirements in the GS rule are 

intended to prevent leakage from injection formations and protect USDWs. 

Letter ID: 0181 Comment ID: 23713 Letter Lines: 1450 to 1470 

Comment Code: 5610 2.11.1 Allowing partial primacy for Class VI wells (seeking comment) 

Comment: EPA Request for Comment: EPA is seeking comment on the merits and possible 

disadvantages of allowing primacy approval for Class VI wells independent of 

other well classes. EPA Notice 43523. 

AWWA Response: AWWA recommends that a state be able to administer only Class VI 

well permits, if they so desire. The Class VI well program is a very specialized 

class, which has major differences from all the other well classes. A state that 

decides to apply for primacy of the Class VI wells only would be able to 

specialize in this well class, and could develop and execute a very detailed 

program. The state would have an advantage in that the state staff would be very 

familiar with the regional geology, water resources and business operations in 

the areas proposed for geologic sequestration. One disadvantage could be seen if 

the applying state had never held primacy for any of the other classes of wells. 

Since this is a fairly specialized class, there could be some logistical issues 

in the beginning stages of the state administering the program. However, AWWA 

believes that these issues could be addressed through consultation with either 

the federal EPA offices, or in discussions with other states that are 

administering the Class VI program. In our opinion, the benefits associated with 

state primacy, such as a more in depth knowledge of the state geology, 

operations and politics far outweighs any minor implementation issues that might 

be associated with a state having primacy approval for only Class VI wells. 

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Individual Response: EPA agrees that states should be allowed to obtain primacy for Class VI 

wells independently of other well classes, and will allow independent primacy for Class VI wells 

under §145.1(i) of the final GS rule. In the past, EPA has not accepted UIC primacy applications 

for individual well classes under Section 1422 of SDWA. In other words, if a State wanted 

primacy for Class I wells, the State would also need to accept responsibility for Class III, IV, and 

V wells. This policy has been in place since the initiation of the UIC Program in the early 1980s 

and was intended to encourage states to take full responsibility for UIC programs, avoid 

duplication of efforts, and provide for administrative efficiencies. 

However, given the potential for CCS (encompassing capture, transportation, and geologic 

sequestration) to be an important part of a national priority to address climate change, EPA 

believes that providing states the flexibility to obtain primacy for Class VI wells independently 

of other well classes can help foster effective management of CCS. EPA believes that allowing 

independent Class VI primacy may encourage states to take responsibility for implementation of 

Class VI regulations and provide for a more comprehensive approach to managing CCS projects 

by promoting the integration of GS activities under SDWA into a broader framework for 

managing CCS. Furthermore, GS operations involve ancillary activities (e.g., pipeline 

operations, pore space ownership, land use rights, and surface access) for which states can call 

upon other authorities that exist at the state level (but outside UIC authority) to provide a more 

comprehensive CCS management approach. 

EPA also believes that allowing states to apply only for Class VI primacy will shorten the 

primacy approval process for states. EPA's willingness to accept independent primacy 

applications for Class VI wells represents a shift in its longstanding policy of discouraging 

"partial primacy." It is very important to note that this shift in policy allowing for Class VI 

primacy does not apply to any other well Class under Section 1422. EPA will continue to 

discourage applications for partial primacy for all other well types under Section 1422. 

EPA clarifies that states should be able to obtain primacy for Class VI wells independent of other 

well classes provided they develop regulations that are at least as stringent as the minimum 

Federal requirements (e.g., permitting, inspection, operation, monitoring, and recordkeeping 

requirements) provided in the final GS rule. EPA believes that existing programs can adapt their 

expertise to the new requirements for Class VI wells and will be able to develop a primacy 

application for Class VI wells under section 1422 of SDWA and ensure that their GS programs 

integrate into national climate change priorities and protect USDWs from endangerment. 

EPA agrees that states without primacy for other injection well classes may encounter some 

logistical challenges while developing a new Class VI primacy program. EPA is developing 

guidance that describes, for States, the process of applying for and receiving primacy for GS 

Class VI wells under Section 1422 of SDWA. The manual will also provide tools designed to 

assist States with the development of their primacy application and UIC Directors with 

evaluating permit application information. The guidance will be available at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

EPA also encourages States, Tribes, and Territories to consult with their EPA Region or other 

States, Tribes, and Territories administering the Class VI program for guidance as they begin the 

71
primacy application process and develop a UIC program for Class VI wells. 

Letter ID: 0181 Comment ID: 23714 Letter Lines: 1472 to 1500 

Comment Code: 5600 2.11 Comments related to UIC Program primacy for Class VI wells 

Comment: Other AWWA Comments Related to State Primacy and Capacity: When EPA allows 

states to obtain primacy for the Class VI wells and develop their own 

regulations for geologic sequestration, these regulations must be developed in 

accordance with Section 1422 of the SDWA instead of Section 1425. The language 

in Section 1422 mandates that state requirements for geologic sequestration be 

as stringent as federal requirements. By comparison, the language in Section 

1425 mandates that the state requirements represent an "effective" program to 

prevent injection which endangers drinking water sources. The language in 

Section 1425 leaves too much room for interpretation, and could result in 

varying degrees of protection of USDWs across the country. Given the current 

strain on our groundwater resources in some areas of the United States, AWWA 

recommends that EPA ensure state regulations provide at least the same level of 

protection as the federal regulations. 

AWWA recognizes that the SDWA currently provides for a $16 million statuary 

limit for federal support to states to enact and enforce the Act. Given that 

state primacy agencies are already resource limited and are inadequately funded 

to cover existing oversight responsibilities, AWWA anticipates that this 

regulation could place an even larger burden on them. Geologic carbon 

sequestration will require new resources, and in addition, staff with very 

specialized expertise in areas such as groundwater, wells, geochemistry, and 

underground injection. Inadequate resources and staff capabilities will result 

in delayed permit reviews/approvals and/or rushed and poor decision making. AWWA 

recognizes the funding limitation for the state primacy programs and this is an 

issue that Congress would have address either through a modification of the SDWA 

or by a revenue set-aside as part of a future "cap and trade" program. As a 

result, AWWA recommends that EPA consider the potential burden on state programs 

when finalizing the regulation and look for ways to streamline the process 

without sacrificing the protective measures of the regulation. 

Individual Response: EPA clarifies that primacy for Class II and primacy for Class VI are 

different. While there are many similarities between CO2-ER injection and GS, CO2 injection 

for the purpose of GS is not explicitly authorized under section 1425 of the SDWA; therefore GS 

of CO2 is regulated under Section 1422. In order for States, Tribes, or Territories to obtain 

Primacy for Class VI wells (under Section 1422 of the SDWA) they must demonstrate that they 

have requirements that are at least as stringent as the federal Class VI requirements; have the 

authority to inspect and assess construction and operation of the wells as well as have the 

necessary legal authorities to take administrative, civil and criminal enforcement actions required 

by the SDWA under §1423, impose criminal, civil, and administrative penalties on owners and 

72
operators for non-compliance with regulatory requirements; and demonstrate 

sufficient/appropriate technical capacity (e.g., personnel, infrastructure, and technical expertise) 

to implement their Class VI program. 

However, EPA acknowledges the expertise of state oil and gas agencies, which have been 

regulating Class II wells for decades. These agencies already understand many of the issues 

pertaining to Class VI wells, which should facilitate the adoption of Class VI primacy programs 

in states with Class II wells. 

EPA acknowledges that there may be technical and administrative challenges including resource 

concerns, and will work closely with the states to assist them in resolving funding issues or 

acquiring the resources, personnel, and training needed to address the unique technical 

challenges associated with GS. 

EPA will also incorporate Class VI wells into the UIC Program's grant allocation process. The 

States/Tribes/Territories must also demonstrate that they have adequate resources to implement 

the program through matching resources against those allocated by the UIC Program's grant 

allocation formula. Currently, primacy programs are required to meet a minimum of 25 percent 

matching requirement. 

EPA adds that the GS rule does not address “cap and trade.” Cap and trade is outside the scope 

of this rulemaking; the purpose of the GS rule is to ensure that injection of CO2 for GS is 

conducted in a manner that is protective of USDWs. 

Letter ID: 0181 Comment ID: 23715 Letter Lines: 1502 to 1517 

Comment Code: 5520 2.10.1 Appropriateness of existing public participation requirements 

(Part 25 and Part 124) for GS (seeking comment) 

Comment: Category: Public Participation 

EPA Request for Comment: EPA requests comment on adopting the existing 

requirements for public participation at 40 CFR Part 25 and 40 CFR Part 124 and 

whether additional requirements should be included to reflect the availability 

of new tools for disseminating and gathering information. Such tools include 

cable networks, the Internet, and other new technology. EPA Notice 43523. 

AWWA Response: 40 CFR 124 does not include a requirement for public notification 

when a request is made to modify, revoke and/or reissue an operating permit for 

a geologic sequestration project. It also does not provide for mandatory public 

hearings, as the regulations states that it is up to the discretion of the 

Director unless a hearing is specifically requested by a stakeholder. AWWA 

disagrees the omission of with these requirements and recommends that both of 

these activities be recognized as mandatory during the permit development, 

review, and approval processes for geologic sequestration projects. 

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Individual Response: EPA disagrees that the requirements at 40 CFR Parts 25 and 124 are 

inadequate for GS projects. These public participation requirements have been effective for the 

other UIC well classes. EPA believes that these requirements can help avoid public 

misperceptions about the nature and safety of GS projects and address the public's concerns 

about the project. EPA notes that public notice is required when a draft permit is issued including 

when existing permits are modified (except for minor modifications). See §124.10(a) Public 

notice is also required when a permit is revoked or reissued. See §124.5(c)). Although public 

hearings are not mandatory, EPA expects that public hearings will be requested and necessary 

due to the expected level of public interest in GS projects. See §124.12. The commenter is 

correct that public notice is not required when a request for modification, revocation and 

reissuance and termination of a permit is made, however, EPA believes the public notice 

required when the draft is issued is appropriate for GS wells. 

EPA recognizes that the AoR reevaluation process may generate significant levels of public 

interest. EPA added text to §144.39(a)(5) that permit modifications would be required if the 

Director determines that a modification is necessary based on an AoR reevaluation, amendments 

to any of the project plans, or a review of the testing and monitoring results. EPA notes that any 

permit modifications, except for minor modifications under 40 CFR 144.41, would invoke the 

public notification procedures of 40 CFR Part 124. 

EPA disagrees that public hearings should be mandatory for all GS permits, in order to account 

for the possibility that, if the public does not express an interest in a hearing, holding one would 

not be useful. 40 CFR 124.12(a) requires the Director to hold public hearings if there is a 

significant degree of interest in a draft permit. EPA expects that public hearings will be requested 

and held for many GS projects, due to the expected level of public interest in GS projects. 

Letter ID: 0181 Comment ID: 23716 Letter Lines: 1519 to 1554 

Comment Code: 5560 2.10.3 Enhancing the public participation process (seeking comment) 

Comment: Most of the geologic sequestration projects will be located in rural areas where 

the local water utility is very small with limited staffing and funding 

resources. While these utilities may be impacted by the projects, they may not 

have the technical ability to adequately participate in a project review. 

Therefore, AWWA recommends that as part of the public participation 

requirements, owner/operators should be required to notify and involve national 

and state drinking water organizations as well as the local water utilities. 

This would allow the local utility to be supported technically by the staff of 

the national organization, which can provide technical expertise in drinking 

water issues related to carbon sequestration. 

Each project should be required to establish public advisory groups, such as 

those created for some of the regional carbon sequestration partnership 

projects. Owner/operators need to ensure they identify stakeholders groups from 

74
water sector, such as rural water associations, groundwater associations, and 

drinking water utility associations. These groups would be involved in the 

project from the beginning and provide the stakeholder voice for the project. 

AWWA recommends that the public comment period for the permit review process be 

extended in the final regulation. Due to the technical nature of the geologic 

sequestration process, AWWA recommends that the comment period be extended from 

30 days to 90 days. A 30 day comment period does not provide enough time for 

outside groups to obtain the permit, perform a detailed technical review and 

generate comments. Extending the comment period for 90 days allows the 

stakeholders to perform a much more comprehensive review of the project. 

The issue of environmental justice must be appropriately considered when 

involving the public in geologic sequestration projects. Consideration should be 

given to ensure that certain populations aren't repeatedly subjected to the 

problems that may arise from the sequestration projects. It is also necessary to 

remember that not everyone has access to the same media outlets. When an 

owner/operator is advertising public hearings or comment periods, they should be 

required to utilize all forms of media, including the newspaper, radio, 

television and internet. The general public has a wide range of media-viewing 

habits, and many have moved away from some of the more traditional communication 

methods. 

Individual Response: EPA recognizes that there may be local public interest in GS projects, and 

notes that the Director has the authority to include local governments in the public participation 

process as necessary. The existing public participation requirements for UIC permits at 

§124.10(c)(1)(x)(A) require notification "to any unit of local government having jurisdiction 

over the area where the facility is proposed to be located." In addition, the final rule adds a 

requirement that the director of the State Public Water System Supervision program be notified. 

See §124.10(c)(1)(xi). EPA anticipates that this state director will notify public water systems 

within the area of review and will make their own evaluation of the proposed project. 

EPA anticipates that drinking water associations and local water utilities will express interest in 

and be notified of draft permits and public hearings as required under §124.10(c)(1)(ix) and 40 

CFR Part 25.5 (where EPA is providing public information) which requires the permitting 

authority to notify all interested parties. 

EPA disagrees that a 90-day comment period should be required for all GS projects. EPA 

believes that the existing public comment period requirements at 40 CFR 124.10, which require a 

minimum 30-day comment period for draft permits, are appropriate for GS projects. The Agency 

does not believe it is appropriate to impose longer time frames if they are unnecessary, but 

supports the Directors' discretion and authority under §124.10 to extend the public comment 

period if he or she determines that such an extension is warranted. Circumstances that may affect 

a Director's determination may include the level of public interest in a GS project, specific 

permit details, or project-specific considerations. 

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Regarding the suggestion to form advisory groups, EPA clarifies that such advisory groups could 

participate in the public process associated with any GS project, although such groups are not 

necessary for the public to engage the agency about any GS project. 

EPA agrees that environmental justice is an important concern. The Agency has determined that 

the GS rule will not have disproportionately high and adverse human health or environmental 

effects on minority or low-income populations because it increases the level of environmental 

protection for all affected populations. Please see the discussion of Environmental Justice and 

Executive Order 12898 in the preamble to the final GS rule. The rule does not require that GS be 

undertaken; but does require that if it is undertaken, operators will conduct the activity in such a 

way as to protect USDWs from endangerment caused by CO2. Additionally, this rule will ensure 

that all areas of the United States are subject to the same minimum Federal requirements for 

protection of USDWs from endangerment from GS. EPA's primacy implementation materials for 

UIC Directors place emphasis on considering the potential impact of any GS permits on 

communities (such as minority and low income populations) when evaluating Class VI injection 

well permit applications, as well as provides suggestions and tools for targeted outreach to 

ensure more meaningful public input and participation from the most affected communities 

during the permit evaluation and approval process. 

Letter ID: 0181 Comment ID: 23717 Letter Lines: 1556 to 1586 

Comment Code: 6220 3.2.2 Assumptions about the number of monitoring wells (seeking 

comment) 

Comment: Category: Cost Analysis 

EPA Request for Comment: The Agency assumes three monitoring wells per injection 

well for the purpose of estimating national costs; however, the Agency 

recognizes that operators and primacy agency Directors may choose more or fewer 

monitoring wells depending on project site characteristics. Because the 

monitoring wells and associated costs represent a significant component of the 

Cost Analysis, the Agency acknowledges that this factor may be significant in 

the overall uncertainty of the Cost Analysis. EPA requests comment on whether 

three monitoring wells per injection well is an appropriate costing assumption. 

EPA Notice 43527. 

AWWA Response: AWWA does not agree with the assumption to use three monitoring 

wells per injection well as the standard for the cost analysis. This number 

seems very low given the amount of area that would be covered by one injection 

well. Requiring three monitoring wells for an injection well that might be 

associated with a carbon dioxide plume stretching for over a mile seems like a 

drastic underestimate of the necessary monitoring. AWWA recommends that the 

requirement be based more on the projected plume performance and the potential 

interactions with USDWs or other important geologic formations. 

76
Other cost estimates have indicated that, in the overall cost of the project, 

monitoring is a very small percentage of the total project cost as compared to 

those associated with the capture and transport processes. This conclusion is 

contrary to EPA’s cost estimate, and AWWA is concerned that the EPA’s high cost 

numbers for monitoring may be used to attempt to reduce the monitoring 

requirements and lower the overall project cost. AWWA recommends that the cost 

estimate be revised at a later date based upon data that becomes available from 

the DOE pilot projects. These projects might identify additional well 

construction costs, as well as be able to provide a better understanding of how 

the cost of monitoring compares to the rest of the project. 

Individual Response: EPA agrees that the number of monitoring wells associated with GS 

projects will be site-specific and vary based on many factors, including the local geologic 

characteristics, the presence of other injection wells, the size of the AoR, and volumes of CO2 

injected. The proposed rule Cost Analysis described the number of monitoring wells as a ratio to 

the number of injection wells; EPA clarifies that the number of injection wells was based on the 

size of the AoR and the type of project. Therefore, the number of monitoring wells was indirectly 

based on the size of the AoR. Because ER project sites have injection wells that are more 

clustered than those in saline formations, the AoR and the number of monitoring wells were 

anticipated to be smaller at an ER project site compared to a saline formation project. EPA 

retained this assumption regarding the density of injection wells for the final rule analysis, but it 

changed its assumption on the number of monitoring wells at each site. For the final rule, the 

Agency assumes one monitoring well above the injection zone per two square miles of AoR; for 

monitoring wells into the injection zone, the Agency assumes one monitoring well per four 

square miles. EPA assumes monitoring wells into the injection zone will also be used to sample 

above the injection zone. The number of monitoring wells assumed for each project type is 

presented in Exhibit 5.2 of the Cost Analysis. 

Because the actual number of monitoring wells that will be necessary for a given project site is 

uncertain, EPA tested the sensitivity of overall cost estimates to the number of monitoring wells 

by applying a 25 percent decrease and increase in monitoring wells per project type to the 

original assumptions. This change results in annualized incremental rule costs approximately 16 

percent less and 16 percent greater than costs estimated for the primary analysis (as shown in 

Exhibit 5.26 of the Cost Analysis). 

In response to the concern that EPA will change its monitoring requirements to save costs, EPA 

clarifies that the number of monitoring wells in the cost analysis is an assumption developed for 

the purpose of the cost analysis only. The Agency is not specifying in the GS Rule the number of 

monitoring wells required at a GS site and clarifies that the exact number of monitoring wells at 

a particular GS project will be determined based on site-specific information and will be 

appropriate to ensure protection of USDWs from endangerment. For additional information on 

EPA's final regulatory approach, including testing and monitoring requirements, please see the 

final rule and preamble. 

EPA is developing guidance on monitoring and testing to assist owners/operators and Directors 

in evaluating requirements under §146.90, including developing determining the appropriate 

77
number of monitoring wells for a GS site. This guidance will be available on EPA’s website at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

Letter ID: 0181 Comment ID: 23718 Letter Lines: 1594 to 1600 

Comment Code: 1220 1.1.1.1 Terminology and definitions 

Comment Code: 4400 2.4.4.3 Allowing injection above or between USDWs (seeking comment) 

Comment: IV. COMMENTS ON RULE TEXT 

Part 144.6(f): Would "lowermost USDW" include formations that are not USDW’s at 

the point of injection but become USDW’s within the extent of the expected area 

of influence of the injection plume? AWWA recommends that these types of 

formations be included within the definition of USDW based on the ability of 

carbon dioxide to easily migrate within the confines of an aquifer. 

Individual Response: EPA clarifies that the GS rule (and all of the UIC regulations) requires the 

protection of all USDWs in the AoR of an injection activity. As part of the site characterization 

process and during AoR delineation, owners or operators must identify all USDWs within the 

AoR, model the full extent of the CO2 plume, and demonstrate that all USDWs within the AoR 

are protected from endangerment. This would include USDWs that are laterally connected to 

non-USDWs, as suggested by the commenter. 

Letter ID: 0181 Comment ID: 23719 Letter Lines: 1602 to 1614 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 5700 2.12 Comments on the proposed duration of Class VI permits (seeking 

comment) 

Comment: Part 144.36(a): The geologic sequestration of carbon dioxide is not a fully 

proven technology and much is unknown about the long-term impacts, and potential 

unintended consequences of such injection. As previously stated, AWWA believes 

it would be prudent to limit the life of the Class VI permit so that necessary 

adjustments to the permit can be made as needed, with the opportunity for public 

comment. This will also establish a process for obtaining updated information on 

the injection operation. We would recommend a permit life of no more than 5 

years. Therefore, AWWA recommends revising this part to read: 

Permits for Class I and V wells shall be effective for a fixed term not to 

exceed 10 years. UIC Permits for Class II and III shall be issued for a period 

up to the operating life of the facility. Permits for Class VI wells shall be 

effective for a fixed term not to exceed 5 years. 

Individual Response: The final rule maintains the lifetime permit provision and clarifies that the 

permit extends through the post-injection site care period (144.36(a)). However, it also adds a 

78
requirement that the Director review each Class VI permit at least every 5 years to determine 

whether it should be modified, revoked and reissued, terminated or a minor modification made as 

provided in §§144.39, 144.40, or 144.41. The Director’s review will be informed by the owners’ 

or operators’ iterative reevaluation of the GS project. Specifically, the final rule includes a 

requirement that the AoR be reevaluated at least every five years, and also requires owners or 

operators to review and update the AoR and corrective action plan, the testing and monitoring 

plan, and the emergency and remedial response plan throughout the life of the project (146.84(e), 

146.90(j), and 146.94(d)). Owners or operators must review each plan and identify necessary 

amendments or demonstrate to the Director that no amendment is needed. In no case can reviews 

occur less often than once every five years. The iterative process and subsequent plan 

reevaluations ensure that time and resources are committed to the most critical aspects of the 

permit in preventing endangerment to USDWs. 

EPA believes that the iterative process of developing and executing the various plans required of 

GS well operators in the final rule (e.g., for AoR and corrective action, testing and monitoring, 

well plugging, and post-injection site care, and emergency and remedial response) is tailored to 

the unique aspects of—and is more appropriate for–GS than establishing a finite permit duration 

(e.g., five years as suggested by some commenters). This is preferable to a periodic permit 

reapplication. 

Letter ID: 0181 Comment ID: 23720 Letter Lines: 1616 to 1633 

Comment Code: 1220 1.1.1.1 Terminology and definitions 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 4400 2.4.4.3 Allowing injection above or between USDWs (seeking comment) 

Comment: Part 146.5(f): There is the possibility that some of the geologic sequestration 

activities will occur in areas where there are no USDWs located in the area of 

review. These wells should still be permitted as Class VI wells, and AWWA 

recommends revising the Class VI definition to: 

(f) Class VI. Wells used for geologic sequestration of carbon dioxide in the 

following applications: 

1. Where carbon dioxide is injected below the lowermost formation containing a 

USDW; and, 

2. Where carbon dioxide is injected in formations where no USDWs exist within 

the zone of elevated pressure associated with the injection well. 

Wells used for the geologic storage of carbon dioxide in formations above the 

lowermost USDW are prohibited. 

This definition would capture all wells associated with geologic carbon 

sequestration activities whether or not a USDW was present in the projected 

footprint of the project. 

Individual Response: In the final rule EPA will allow injection into non-USDWs above or 

79
between the lowermost USDW where owners or operators can demonstrate that such injection 

can be performed in a manner that protects USDWs from endangerment, as long as appropriate 

protections are in place. 

EPA adds that, in the final rule at §144.6 (f), Class VI wells are defined as wells that are not 

experimental in nature that are used for geologic sequestration of carbon dioxide beneath the 

lowermost formation containing a USDW; or, wells used for geologic sequestration of carbon 

dioxide that have been granted a waiver of the injection depth requirements pursuant to 

requirements at §146.95 of this chapter; or, wells used for geologic sequestration of carbon 

dioxide that have received an expansion to the areal extent of an existing Class II enhanced oil 

recovery or enhanced gas recovery aquifer exemption pursuant to §§146.4 of this chapter and 

144.7(d). 

Letter ID: 0181 Comment ID: 23721 Letter Lines: 1635 to 1645 

Comment Code: 1220 1.1.1.1 Terminology and definitions 

Comment Code: 1614 1.3.1.2 Impurities in captured CO2; purity standards for CO2 

Comment: Part 146.81 AWWA recommends defining the quality of the injection stream and 

establishing a minimum concentration of carbon dioxide. This requirement for the 

injection stream will ensure that the injection of other harmful or undesirable 

gases is limited. Our initial thoughts on this topic would be that 100% of the 

injectate must come from a carbon dioxide capture process and the injectate must 

be at least 98% carbon dioxide. Owner/operators must ensure that the remaining 

2% of the injectate is not made up of compounds that would result in the 

injectate being classified as a hazardous waste. As AWWA is not an expert on 

this topic, we would suggest that EPA pursue research in association with DOE to 

develop a standard for the minimum concentration of carbon dioxide in the 

injection stream. 

Individual Response: As described above, the GS rule does not set generic purity standards for 

CO2 injectate streams (e.g., a percent CO2). The final GS rule retains the definition of a CO2 

stream as proposed. 

Letter ID: 0181 Comment ID: 23722 Letter Lines: 1647 to 1651 

Comment Code: 3800 2.3 Proposed Injection Well Construction Requirements (40 CFR 

146.86) 

Comment Code: 3866 2.3.3.3 Logging and testing requirements (40 CFR 146.87) 

Comment: Part 146.81(c) Specific benchmarks should be established to demonstrate that 

USDWs will not be endangered if the well is exempted from the casing and 

cementing requirements provided in Parts 146.86(b) and 146.87(a)(1) through (3). 

This will provide for a consistent application of this requirement across each 

permitting agency. 

80
Individual Response: EPA believes that, given the range of types of existing wells that may be 

candidates for conversion, flexibility is appropriate regarding conversion of Class I, II, or V 

wells for GS, provided it can be demonstrated to the Director's satisfaction that the converted 

well can conduct Class VI operations in a manner that does not endanger USDWs. The final GS 

rule, at §146.81(c), allows the construction of these wells to be grandfathered, provided the 

owner or operator can demonstrate to the Director that the wells were engineered and constructed 

to meet the requirements at §146.86(a) and ensure protection of USDWs, in lieu of requirements 

at §146.86(b) and §146.87(a). 

EPA is developing guidance documents that will support UIC Directors in evaluating whether 

grandfathering specific wells is appropriate. For example, primacy guidance for primacy 

agencies will describe areas of Director’s discretion and recommended procedures and 

considerations for exercising that discretion. EPA is also developing guidance on construction of 

Class VI wells. The guidances will be available on EPA's web site at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

Letter ID: 0181 Comment ID: 23723 Letter Lines: 1653 to 1668 

Comment Code: 1220 1.1.1.1 Terminology and definitions 

Comment: Part 146.81(d) AWWA recommends revising the definition of "pressure front" to 

read: 

Pressure front means the zone of elevated pressure that is created by the 

injection of carbon dioxide into the subsurface. For the purposes of this 

subpart, the pressure front of a carbon dioxide plume refers to a zone where 

there is a pressure differential sufficient to cause the movement of injected 

fluids or formation fluids through an injection zone, and/or confining zone, and 

into a USDW. 

Part 146.81(d) AWWA recommends revising the definition of "transmissible fault or 

fracture" to read: 

transmissible fault or fracture means a fault, fracture or other discontinuity 

that has sufficient permeability and vertical extent to allow fluids to move 

between formations. 

Individual Response: EPA disagrees with the suggested edit. The final definition of pressure 

front at §146.81(d) is unchanged and reads as follows: “[T]he zone of elevated pressure that is 

created by the injection of carbon dioxide into the subsurface. For the purposes of this subpart, 

the pressure front of a carbon dioxide plume refers to a zone where there is a pressure differential 

sufficient to cause the movement of injected fluids or formation fluids into a USDW.” 

The final definition of transmissive fault or fracture at §146.81(d) is unchanged and reads as 

follows: “[A] fault or fracture that has sufficient permeability and vertical extent to allow fluids 

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to move between formations.” EPA adds that it changed the text at §146.84(c)(1)(ii) to include 

“other discontinuity” to address concern regarding the potential for migration of CO2 at GS sites. 

It reads as follows: "Take into account any geologic heterogeneities, other discontinuities, data 

quality, and their possible impact on model predictions." 

Based on its evaluation of all public comments and input on the proposed rule and the NODA 

and Request for Comment, EPA has made many revisions to the Class VI GS rule. Please see the 

final rule and preamble for additional information. 

Letter ID: 0181 Comment ID: 23724 Letter Lines: 1670 to 1673 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 3150 2.1.5 Comments on required permit information (40 CFR 146.82) 

Comment: Part 146.82(b) AWWA recommends revising the second to the last sentence to read: 

The map should also show faults and other major geologic discontinuities, if 

known or suspected. 

Individual Response: Based on its evaluation of all public comments and input on the proposed 

rule and the NODA and Request for Comment EPA has made many revisions to the GS rule. 

Please see the final rule and preamble for additional information. 

Letter ID: 0181 Comment ID: 23725 Letter Lines: 1675 to 1698 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 3150 2.1.5 Comments on required permit information (40 CFR 146.82) 

Comment: Part 146.82(b) AWWA recommends that the last sentence be deleted from this part. 

Owner/operators should be required to go beyond the data available in the public 

record to identify some of the features listed in this requirement. For example, 

the owner/operator should be required to do its due diligence to identify all 

abandoned wells, plugged wells or old boreholes in the area of review. While 

public records may be a good starting point for the identification of these 

features, given the fact that some of the existing wells could be decades old, 

it is hard to believe that records would exist for every one of them. EPA should 

mandate that owner/operators use well identification technology to locate any 

existing wells that are not listed in the public record. 

AWWA recommends revising this part to read: 

A surface map showing the injection well(s) for which a permit is sought and the 

applicable area of review. Within the area of review, the map must show the 

number, or name and location of all injection wells, producing wells, abandoned 

wells, plugged wells or dry holes, deep stratigraphic boreholes, State or EPA 

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approved subsurface cleanup sites, surface bodies of water, springs, mines 

(surface and subsurface), quarries, water wells and other pertinent surface 

features including structures intended for human occupancy and roads. The map 

should also show faults, if known or suspected. The owner or operator must 

include all information available in the public record, as well as conducting 

independent site investigations to locate any of the above features that may not 

be identified in the public record. 

Individual Response: EPA believes that a determination about whether data/information is 

outside or within the public record will be site-specific, and based on knowledge of the site, data 

availability, and data quality. For instance, in meeting the requirement to tabulate information on 

wells in the AoR, the Director has the discretion to require the owner or operator to supplement a 

data records search, including requiring ground or airborne surveys for wells, if there is reason to 

believe, based on knowledge of the site or of available data bases, that the incompleteness of 

available information could compromise USDW protection from endangerment. 

Letter ID: 0181 Comment ID: 23726 Letter Lines: 1700 to 1704 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 3150 2.1.5 Comments on required permit information (40 CFR 146.82) 

Comment: Part 146.82 (c) AWWA recommends revising this part to read: 

A map delineating the area of review based upon modeling, using all available 

data including data obtained during geophysical logging and testing of the well 

and the formation as required by paragraphs (l), (r), and (s) of this section. 

Individual Response: EPA clarifies that the map of the AoR must reflect the model inputs, 

including the extensive geologic information, data collected during the site characterization 

process (e.g., information about artificial penetrations), and anticipated operating parameters 

(e.g., injection rates) submitted with the permit application under 146.82. EPA adds that the final 

rule, at §146.82(c)(1), requires that the final area of review be “based on modeling, using data 

obtained during logging and testing of the well and the formation...” 

Letter ID: 0181 Comment ID: 23727 Letter Lines: 1706 to 1824 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 3150 2.1.5 Comments on required permit information (40 CFR 146.82) 

Comment: Part 146.82(d)(1) AWWA recommends revising this part to read: 

Isopach maps of the area of review, including the proposed injection and 

confining zone(s), a structural contour map hung on the top of the proposed 

injection zone, and at least two geologic cross sections of the area of review 

showing the geologic formations from the surface to total depth. 

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Part 146.82(d)(2) AWWA recommends revising this part to read: 

Location, orientation, and properties of known or suspected subsurface faults, 

fractures, and other discontinuities that may transect the confining zone(s) in 

the area of review and a determination that they would not interfere with 

containment. 

Part 146.82(d)(3) AWWA recommends revising this part to read: 

Information on the seismic history within the proposed area of review including 

presence and depth of seismic sources, knowledge of previous seismic events and 

history of these events, and a determination that the seismicity would not 

interfere with containment. 

Part 146.82(d)(4) AWWA recommends revising this part to read: 

A spreadsheet with data on the depth, areal extent, thickness, mineralogy, 

porosity, permeability, capillary and reservoir pressure of the injection and 

confining zone(s) within the area of review; including any geologic/facies 

changes based upon field data which may include geologic cores, outcrop data, 

seismic surveys, well logs, and names and lithologic descriptions. 

Part 146.82(d)(5) AWWA recommends revising this part to read: 

Geomechanical information on fractures, stress, ductility, rock strength, and in 

situ fluid pressures on the injection and confining zones within the area of 

review. 

Part 146.82(e) AWWA recommends revising the first sentence to read: 

A spreadsheet of all wells and other artificial penetrations within the area of 

review which penetrate the injection or confining zone(s). 

Part 146.82(f) AWWA recommends revising this part to read: 

Potentiometric (water level) surface maps and stratigraphic cross sections 

indicating the general vertical and lateral limits of all USDWs including 

existing aquifers not meeting the definition of a USDW that are either currently 

being utilized as private or public water supplies or are identified as a future 

water supply, water wells and springs within the area of review, their positions 

relative to the injection zone(s) and the direction and velocity of water 

movement. At least two geologic cross sections showing the thickness and general 

vertical and lateral limits of all USDWs within the area of review. 

Part 146.82(g) This part should provide a list of the formations for which 

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baseline geochemical data should be obtained. AWWA recommends revising this part 

to read: 

Collection of baseline geochemical data on the subsurface formations, including 

all USDWs in the area of review. At a minimum, geochemical data should be 

provided for the injection formation, the confining zone immediately above the 

injection zone, the nearest adjacent porous and permeable formation to the 

confining zone, all USDWs in the area of review including existing aquifers not 

meeting the definition of a USDW that are either currently being utilized as 

private or public water supplies or are identified as a future water supply, as 

well as for any additional formations as required by the Director. 

Part 146.82(h)(1) AWWA recommends revising this part to read: 

Average and maximum daily injection rate and volume of the carbon dioxide 

stream. 

Part 146.82(h)(2) AWWA recommends revising this part to read: 

Average and maximum surface injection pressure; 

Part 146.82(k) AWWA recommends revising this part to read: 

Proposed stimulation program and a determination that stimulation will not 

interfere with or breach the confining layer. 

Part 146.82(n) AWWA recommends revising this part to read: 

Engineering drawings of the surface and subsurface construction details of the 

system, including design features for surge control and water hammer protection, 

including the following: 

(i) Record drawings, based upon inspections by the engineer of record or persons 

under his direct supervision, with al deviations noted; 

(ii) Copies of the mill certificates of all casings used in the construction of 

the well; 

(iii) Certification of completion submitted by the engineer of record; 

(iv) An operation manual including emergency procedures; 

(v) Proposed monitoring program and data to be submitted; 

(vi) Proof that the existence of the well and any associated monitoring wells 

have been recorded with the permanent warranty deed or other instrument of 

conveyance as a two page proviso or addendum that contains certification of the 

locations of the wells (by metes and bounds) and a detailed sketch of the parcel 

that shows the location of the well. The location shall be measured by a 

certified land surveyor, and shall contain the surveyor's signature, 

registration number, official seal, and the following statement: "I hereby 

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certify that this survey was made under my responsible direction and 

supervision, and is a correct representation of the land surveyed." 

Part 146.82(q) As the Director should approve the corrective action plan prior 

to any activities taking place within the area of review, AWWA recommends 

revising this part to read: 

The plan for corrective action on artificial penetrations within the area of 

review and the status of any correction actions, if previously approved by the 

Director. 

Part 146.82(s) As the well should not yet be constructed when the owner/operator 

applies for the permit, the demonstration of mechanical integrity should not 

have occurred yet. Therefore, AWWA recommends revising this part to read: 

The proposed demonstration method for mechanical integrity pursuant to §146.89. 

Part 146.82(v) As monitoring wells may also have to be plugged, AWWA recommends 

revising this part to read: 

Proposed injection and monitoring well(s) plugging plan required by §146.92(b). 

Individual Response: EPA disagrees that the suggested revisions are necessary. While EPA 

acknowledges and agrees with the importance of many of the specific items the commenter 

suggests adding to the text, the Agency believes that it is important to allow some flexibility to 

address the varied and site-specific conditions at GS sites. EPA anticipates that the iterative 

process by which owners or operators submit and Directors review geologic and other 

information to support the permit application will promote the most effective approach to 

addressing USDW endangerment. EPA adds that if the Director believes that additional 

information is needed to support a determination about the suitability of a proposed site, it is 

within his/her authority to request it. 

EPA notes that the final rule does include reference to capillary pressure in §146.82(a)(3)(iii), 

“Data on the depth, areal extent, thickness, mineralogy, porosity, permeability, and capillary 

pressure of the injection and confining zone(s); including geology/facies changes based on field 

data which may include geologic cores, outcrop data, seismic surveys, well logs, and names and 

lithologic descriptions.” 

EPA agrees that not all of the information listed at §146.82 of the proposed regulation will be 

available at the time the owner or operator develops their initial permit application. In response 

to comments and based on an evaluation of the proposed requirements at §146.82, the Agency 

revised this subpart so that the final regulation specifies separate requirements for information to 

be submitted with the permit application and before well construction is approved (at §146.82(a)) 

and information to be submitted before operation of the well is authorized (at §146.82(c)). 

EPA is developing guidance on site characterization for GS projects to assist owners or operators 

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and Directors in evaluating permit requirements and applications under §146.82. The guidance 

provides recommendations regarding characterizing the regional geology and hydrogeology of a 

proposed GS site as well as performing the necessary geochemical, geomechanical, and 

geophysical analyses of the injection and confining zone. The guidance can be found on EPA’s 

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

Letter ID: 0181 Comment ID: 23728 Letter Lines: 1826 to 1831 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 3100 2.1 Proposed Geologic Siting Requirements (40 CFR 146.83) 

Comment: Part 146.83(a)(1) AWWA recommends revising this part to read: 

An injection zone of sufficient areal extent, thickness, porosity, and 

permeability to receive the total anticipated volume of the carbon dioxide 

stream, and at a depth with sufficient overburden pressure to keep the carbon 

dioxide stream as a supercritical fluid. 

Individual Response: EPA disagrees that the GS rule should require that the CO2 remain in a 

supercritical state. EPA believes that, in many cases CO2 will be injected at depths where it will 

remain supercritical. However, the final rule does not require that it remain in a supercritical 

state once it is injected; nor does the rule preclude the injection of gaseous CO2 into shallower 

non-USDWs provided that the owner or operator meets the Class VI requirements and ensures 

protection of USDWs from endangerment. 

Letter ID: 0181 Comment ID: 23729 Letter Lines: 1841 to 1854 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 3120 2.1.2 Need to identify additional confining and containment zones 

(seeking comment) 

Comment: Part 146.83(b) This part of the rule should a requirement, not an option that 

can be requested at the discretion of the Director. While it is possible that a 

site with a single confining can provide storage integrity, AWWA recommends that 

additional confining layers at the site be characterized to get a better 

estimate of leakage risk to USDWs and possibly identify additional monitoring 

zones. It is important to know if these zones exist, and to have adequately 

documented their characteristics, to evaluate and demonstrate the possibility of 

secondary containment. AWWA recommends revising this part to read: 

Owners or operators of Class VI wells must identify and characterize additional 

zones that will impede vertical fluid movement, are free of faults, fractures or 

other discontinuities that may interfere with containment, allow for pressure 

dissipation, and provide additional opportunities for monitoring, mitigation and 

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remediation. 

Individual Response: EPA agrees with the commenter that, in some situations, the presence of 

additional confining and containment zones above the primary (i.e., lowermost) confining zone 

can improve USDW protection from endangerment. EPA disagrees that secondary confining 

zones are required at all sites, e.g., where a primary confining zone that free of transmissive 

faults or fractures and of sufficient areal extent and integrity to contain the injected carbon 

dioxide stream and displaced formation fluids and allow injection at proposed maximum 

pressures and volumes without initiating or propagating fractures in the confining zone(s) (per 

§146.83(a)) is demonstrated to be present. The final regulation retains the requirement at 

§146.83(b) which affords the Director discretion to require owners or operators to identify and 

characterize additional zones. 

Letter ID: 0181 Comment ID: 23730 Letter Lines: 1856 to 1860 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 3300 2.2.1 Delineating the AoR/Modeling CO2 movement 

Comment: Part 146.84 It is important to note that the carbon dioxide plume will never 

cease moving. Even deep formations have a natural flow gradient, and it is 

likely that there will always be some movement due to changes in density 

gradients and diffusion. This should be considered when defining the AoR for 

each project. 

Individual Response: EPA agrees with the commenter that there may be cases where movement 

of the CO2 plume will never cease due to gradient, diffusion, and density gradients, but disagrees 

that the AoR definition at 146.84(a) should describe a never-ending timeframe of CO2 plume 

movement. The GS regulation recognizes that plume movement may stabilize to a point where 

movement of the CO2 plume slows or pressures in the injection zone sufficiently decline to the 

point that they no longer pose an endangerment to USDWs, although movement does not 

completely cease. EPA believes that in all cases, these criteria will be met at some point after the 

cessation of injection. As discussed in the preamble to the proposed GS regulation and the 

associated background document "Computational Modeling of Underground Injection of Carbon 

Dioxide for Determination of Area-of-Review and Potential Risk to Underground Sources of 

Drinking Water" (cited in the proposed rule preamble as USEPA, 2008d), research has shown 

that CO2 may continue to migrate for a period of time after injection ceases. 

For this reason, the GS regulation does not specify a timeframe over which the AoR delineation 

model should run. Rather, the model should be used to predict the ultimate plume movement up 

to the point the plume movement ceases or pressures in the injection zone sufficiently decline to 

the point that they no longer pose an endangerment to USDWs. 

EPA believes that an iterative process of AoR reevaluation is appropriate to verify that the CO2 

plume and pressure front are moving through the subsurface as predicted, verify the accuracy of 

the delineation model (or identify needed changes), and refine testing and monitoring activities 

to ensure that USDWs are protected from endangerment and that there would be adequate 

88
warning of potential problems at the site before any endangerment could occur. EPA adds that 

the requirement at 146.93(b) for post-injection site care further ensures that any continued 

movement of the CO2 plume and pressure front will be addressed until it can be demonstrated 

that the GS operation no longer poses an endangerment risk to USDWs. 

Letter ID: 0181 Comment ID: 23731 Letter Lines: 1862 to 1865 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 3300 2.2.1 Delineating the AoR/Modeling CO2 movement 

Comment: Part 146.84(c)(1)(iii) AWWA recommends revising this part to read: 

Consider potential migration through faults, fractures, other discontinuities 

and artificial penetrations. 

Individual Response: EPA did not change 146.84(c)(1)(iii) but instead changed the text at 

146.84(c)(1)(ii) to read as follows: "Take into account any geologic heterogeneities, other 

discontinuities, data quality, and their possible impact on model predictions" to address the water 

association commenter's concern regarding the potential for migration of CO2 at GS sites. 

Letter ID: 0181 Comment ID: 23732 Letter Lines: 1867 to 1871 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 3200 2.2 Proposed Area of Review and Corrective Action Requirements (40 

CFR 146.84) 

Comment: Part 146.84(c)(2) AWWA recommends revising the first sentence to read: 

Using methods approved by the Director, identify all penetrations, including 

active and abandoned wells and underground mines, in the area of review that may 

penetrate any portion of the confining zone. 

Individual Response: EPA clarifies that the mapping and cross sections required to be 

submitted under 146.82(a)(3) will define the limits of the confining zone, which would be 

accounted for in the AoR delineation and corrective action evaluation required at 146.84(c). EPA 

adds that owners or operators must also, under 146.82(a)(2), submit a map of the AoR that shows 

all injection wells, producing wells, abandoned wells, plugged wells or dry holes, deep 

stratigraphic boreholes, State or EPA approved subsurface cleanup sites, surface bodies of water, 

springs, mines (surface and subsurface), quarries, water wells and other pertinent surface features 

including structures intended for human occupancy and roads. EPA believes that these 

requirements address the commenter's concerns. 

EPA adds that any well that penetrates the confining zone, even if it does not extend all the way 

through the confining formation, is to be included in the tabulation. EPA is issuing guidance on 

89
how to identify all wells that require corrective action. The guidance describes EPA's 

recommended approaches for the data to be considered in an initial AoR delineation, how to 

apply computational modeling to delineate the AoR, performing corrective action at GS sites, 

and, when appropriate, completing AoR reevaluations. The guidance will be available on EPA's 

web site, at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

Letter ID: 0181 Comment ID: 23733 Letter Lines: 1881 to 1888 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 3530 2.2.3.1 AoR reevaluation frequency (seeking comment) 

Comment: Part 146.84(d) Based upon our comments in the previous section of this document, 

AWWA recommends revising this part to read: 

At the minimum fixed frequency, not to exceed one (1) year for the first ten 

(10) years of the operation of the carbon sequestration project and not to 

exceed five (5) years after the first ten year time period, as specified in the 

approved area of review and corrective action plan, or when monitoring and 

operational conditions warrant, owners or operators must: 

Individual Response: EPA agrees with commenters that reevaluations of the AoR every ten 

years may not be sufficient to appropriately model plume and pressure front movement, establish 

conditions for corrective action, and ensure protection of USDWs from endangerment. For these 

reasons, the Agency changed the minimum frequency for the AoR reevaluation at §146.84(e) 

from 10 years to at least every 5 years in the final GS rule. EPA believes that this revised 

frequency addresses commenters' concerns about the inherent uncertainties in modeling CO2 

movement, the emerging nature of GS technology, risk-based targeting of monitoring activities, 

and the unique nature of CO2 GS. In addition, the Director has discretion to require more 

frequent AoR reevaluation if he or she has reason to believe, based on site-specific information, 

that a five-year reevaluation schedule is not sufficiently protective of USDWs. 

Letter ID: 0181 Comment ID: 23734 Letter Lines: 1890 to 1899 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 5430 2.9.1 Comments on proposed financial responsibility requirements (40 

CFR 146.85) 

Comment: Part 146.85(b) AWWA believes that potential changes in the size of the area of 

review require that all site plans be reevaluated at the same frequency as the 

area of review. Therefore, AWWA recommends revising this part to read: 

The owner or operator must provide to the Director, at the same frequency as the 

AOR reevaluation, written updates of adjustments to the cost estimate to account 

for any amendments to the area of review and corrective action plan (§146.84), 

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the testing and monitoring plan (§146.90), the injection well plugging plan 

(§146.92), the post-injection site care and site closure plan (§146.93), and the 

emergency and remedial response plan (§146.94). 

Individual Response: EPA agrees that it is important to periodically update cost estimates that 

support financial responsibility determinations. The final GS rule, at §146.85(c), requires the 

owner or operator to provide updates to the cost estimate within 60 days of any amendments to 

the AoR and corrective action plan, the injection well plugging plan, the PISC and site closure 

plan, and the emergency and remedial response plan. Owners or operators must also adjust the 

estimates for inflation annually under §146.85(c)(2). EPA adds that the Director can also require 

the owner or operator to provide an adjustment of the cost estimate if the Director determines 

that the original demonstration is no longer adequate, as specified at §146.85(e). 

Letter ID: 0181 Comment ID: 23735 Letter Lines: 1901 to 1905 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 3800 2.3 Proposed Injection Well Construction Requirements (40 CFR 

146.86) 

Comment: Part 146.86(b)(1) AWWA recommends revising the second to the last sentence to 

read: 

The casing and cementing program must be designed to prevent the movement of 

fluids into or between USDWs and between the injection zone(s) and USDWs. 

Individual Response: EPA believes that the existing language as written ensures the prohibition 

of fluid movement between the injection zone and any USDW and the suggested change is 

unnecessary. Based on its evaluation of all public comments and input on the proposed rule and 

NODA and Request for Comment EPA has made many revisions to the GS rule. Please see the 

final rule and preamble for additional information. 

Letter ID: 0181 Comment ID: 23736 Letter Lines: 1911 to 1917 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 3862 2.3.3.1 Use of corrosion-resistant construction materials (seeking 

comment) 

Comment: Part 146.86(b)(1)(v) The corrosiveness evaluation should include the possible 

combining of the carbon dioxide stream and the injection zone water, which has a 

higher potential to corrode than the carbon dioxide alone. AWWA recommends 

revising this part to read: 

Corrosiveness, chemical compatibility and reactivity of the carbon dioxide 

stream and the formation fluids located within the injection zone. 

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Individual Response: EPA clarifies that reference to corrosiveness of the CO2 stream in 

§146.86 refers to the potential for CO2 to be corrosive in the presence of water or formation 

fluids. EPA believes that the risk of creating acidic fluids that could come in contact with well 

materials and cements is addressed by the construction requirements in §146.86 to ensure 

protection of USDWs from endangerment. 

Letter ID: 0181 Comment ID: 23737 Letter Lines: 1919 to 1922 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 3864 2.3.3.2 Use of corrosion-resistant cements (seeking comment) 

Comment: Part 146.86(b)(1)(viii)AWWA recommends revising this part to read: 

Type or grade of cement and chemical compatibility and reactivity of cement and 

formation fluids located within the injection zone. 

Individual Response: Based on its evaluation of all public comments and input on the proposed 

rule and NODA and Request for Comment EPA has made many revisions to the GS rule. Please 

see the final rule and the discussion of financial responsibility in the preamble for additional 

information. 

Letter ID: 0181 Comment ID: 23738 Letter Lines: 1924 to 1943 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 3866 2.3.3.3 Logging and testing requirements (40 CFR 146.87) 

Comment: Part 146.87(b) AWWA suggests that submittal of the cores to the Director is not 

very practical. The requirement should be rewritten to state that the Director 

should be provided with a summary report describing the cores and the test 

results. The operator should be required to first submit a coring plan to the 

Director listing the intervals to be cored, the coring procedures, the tests to 

be conducted and proposed storage of the core for review and consideration of 

approval by the Director. A core report, including the test results, 

geomechanical characteristics, and values calculated from the testing, such as 

fracture gradient, should be submitted to the Director. The owner/operator 

should make the cores available for inspection by the Director upon the request. 

AWWA recommends revising this part to read: 

The owner or operator must submit to the Director a report describing whole 

cores or sidewall cores representative of the injection zone and confining 

system and formation fluid samples from the injection zone(s). The Director may 

accept data from cores and fluid samples from nearby wells if the owner or 

operator can demonstrate that such data are representative of conditions at the 

well. The Director may require the owner or operator to core other formations in 

the borehole to acquire more information on the subsurface geologic 

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characteristics. 

Individual Response: EPA clarifies that it is not the Agency's intent that physical cores be 

submitted to the Director. In the final GS rule, EPA has revised the first sentence of §146.87(b) 

to read as follows: "The owner or operator must take whole cores or sidewall cores of the 

injection zone and confining system and formation fluid samples from the injection zone(s), and 

must submit to the Director a detailed report prepared by a log analyst that includes: well log 

analyses (including well logs), core analyses, and formation fluid sample information...." 

Letter ID: 0181 Comment ID: 23739 Letter Lines: 1945 to 1970 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 4110 2.4.1.1 Injection pressure limitations 

Comment: Part 146.88(a) AWWA is concerned that the limitation on injection pressure to 

90% of the fracture pressure is not stringent enough. We heard it stated at the 

public hearing in Denver that fracturing of the injection formation can occur 

when injection pressures are below 90% of the fracture pressure. It is important 

to consider that injection pressure limitations need to take account of the 

possibility that, under certain conditions, faults can be re-activated even if 

injection pressures are kept below the level necessary to create new fractures 

or propagate existing fractures. Therefore, the regulation should provide for 

the injection pressure to be calculated based on the site geology, hydrogeology 

and geomechanics, in combination with the injection pressure limitation. 

Injection pressures and rates should be determined by well tests and 

geomechancial studies, taking into account both formation fracture pressure and 

formation parting pressure. However, due to the amount of uncertainty associated 

with this topic, AWWA recommends that EPA research their proposed limitation in 

more detail to determine the best method for preventing possible contamination 

of USDWs. Therefore, we recommend revising this part to read: 

The owner or operator must ensure that injection pressure and rates remain 

within limits established by permit. Such permit limitations shall be based on 

well tests and geomechanical studies, including assessments of both the fracture 

pressure of the confining zone and the parting pressure of the confining zone. 

In no case may injection pressure initiate or propagate fractures in the 

confining zone, cause otherwise non-transmissive faults transecting the 

confining zone to become transmissible, otherwise degrade the integrity of the 

confining zone, or cause the movement of injection or formation fluids that 

endangers a USDW. 

Individual Response: EPA agrees that the operator must remain within limits established by the 

Class VI permit. EPA clarifies that the owner or operator is required in §146.82(a)(7) to propose 

a maximum injection pressure as part of the permit application. The proposed injection pressure 

will be evaluated by the Director based on site-specific conditions, and be informed by data on 

the injection zone. During injection, the pressure in the injection zone must not exceed 90 

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percent of the fracture pressure of the injection zone, as specified at §146.88(a). The fracture 

pressure (and, therefore, the injection pressure) are based on site-specific geologic and 

geomechanical data collected during the site characterization process required at §146.82. If, 

based on this information, a lower pressure limitation is appropriate, the Director has the 

authority to set a lower limit in the operating permit. 

In response to the concern about reopening of faults at lower pressures than 90 percent of 

fracture pressure, EPA believes that the requirement for the owner or operator to submit data on 

known or suspected faults and fractures and information on the seismic history of the site will 

inform the determination of an appropriate pressure limitation in the permit. Any sites with the 

potential for reopening or reactivation of faults or unacceptable seismic risk that could otherwise 

interfere with containment will not be permitted as GS sites. 

EPA is developing guidance on site characterization for GS projects to assist owners or operators 

in meeting the requirements of §146.82 and to assist directors in evaluating permit applications. 

The guidance will describe recommended approaches for characterizing the regional geology and 

hydrogeology of a proposed site and performing the necessary geochemical, geomechanical, and 

geophysical analyses of the injection and confining zone. EPA is also developing guidance for 

primacy agencies that will include recommended approaches for evaluating owner or operatorsubmitted data in setting permit conditions. The guidance will be available on EPA's web site, at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

Letter ID: 0181 Comment ID: 23740 Letter Lines: 1972 to 1975 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 4000 2.4 Proposed Injection Well Operating Requirements (40 CFR 146.88) 

Comment: Part 146.88(b) AWWA recommends revising this part to read: 

Injection of the carbon dioxide stream between the outermost casing protecting 

USDWs and the well bore is prohibited. 

Individual Response: EPA retains the provision as proposed, and clarifies that injection 

between the casing and the well bore is prohibited. This is consistent with requirements for other 

injection well classes in the UIC program. 

Letter ID: 0181 Comment ID: 23741 Letter Lines: 1977 to 1984 

Comment Code: 4000 2.4 Proposed Injection Well Operating Requirements (40 CFR 146.88) 

Comment: Part 146.88(d) AWWA recommends that the final rule require mandatory 

implementation of a Supervisory Control and Data Acquisition (SCADA) system as 

part of the geologic carbon sequestration system. This system would allow for 

continuous monitoring and storage of the data associated with the operation of 

the injection well. Owner/operators would be able to review data trends and 

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detect anomalies or potential problems before they occur. This SCADA system 

should also be tied to a carbon dioxide detector to alarm and shut off the well 

in the event that carbon dioxide is detected above a pre-set level. 

Individual Response: To meet the requirements at §146.88(e), Class VI wells will be equipped 

with some type of continuous computer-based monitoring device that will be connected to 

alarms and the shut-off system. EPA does not believe it is necessary to specify what type of 

equipment is to be used to trigger the shut-off system. Instead, the regulation allows the owner or 

operator some flexibility in deciding what equipment and alarms should be installed to allow site 

specific flexibility and to make use of improvements in technology. EPA believes that the 

technology for continuous monitoring is available and is currently in fairly wide use. The 

combination of computer-driven continuous pressure monitoring linked to an automatic injection 

shut-off provides maximum protection of USDWs from endangerment and provides the earliest 

warning to owners or operators that well repairs need to be performed. 

Letter ID: 0181 Comment ID: 23742 Letter Lines: 1986 to 1993 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 4500 2.5 Proposed Mechanical Integrity Testing (MIT) Requirements (40 CFR 

146.89) 

Comment: Part 146.89(f) AWWA recommends revising this part to read: 

The Director may require additional or alternative tests if the results 

presented by the owner or operator under paragraph (d) of this section are not 

satisfactory to the Director to demonstrate that there is no significant leak in 

the casing, tubing or packer or significant movement of fluid into or between 

USDWs, or between the injection zone(s) and USDWs, resulting from the injection 

activity as stated in paragraphs (a)(1) and (2) of this section. 

Individual Response: EPA clarifies that the regulations at §146.89(e) allow the Director to 

require additional methods or, with the Administrator's approval, to approve the use of 

alternative MIT methods based on specific information about the site or the well. 

EPA believes that the MITs described in the rule at §146.89 are effective methods and have been 

used successfully by injection well operators for decades and provide an important early warning 

of potential problems in the injection well system. 

In addition, EPA is using an adaptive approach to regulating GS. 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. 

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Letter ID: 0181 Comment ID: 23743 Letter Lines: 1995 to 2004 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 4610 2.6.1 Testing and monitoring plan requirement (seeking comment) 

Comment: Part 146.90 AWWA recommends revising this part to read: 

The owner or operator of a Class VI well must prepare, maintain, and comply with 

a testing and monitoring plan to verify that the geologic sequestration project 

is operating as permitted and is not endangering USDWs. The testing and 

monitoring plan must be submitted with the permit application, for Director 

approval, and must include a description of how the owner or operator will meet 

the requirements of this section. The testing and monitoring plan must be 

reviewed and updated, as necessary, on the same schedule as the update to the 

Area of Review. 

Individual Response: EPA agrees that periodic updates to the plan are appropriate. EPA 

clarifies that the final GS regulation includes a requirement that the AoR be reevaluated at least 

every 5 years, and it specifies at §146.90(j) that the operator revise the testing and monitoring 

plan to incorporate the results of the most recent AoR reevaluation and recent operational and 

monitoring data. Based on its evaluation of all public comments and input on the proposed rule 

and NODA and Request for Comment EPA has made many revisions to the GS rule. See the 

final rule and preamble for further discussion on EPA's final approach. 

EPA agrees with commenters that developing and following testing and monitoring plans is an 

important part of assuring that a GS project is operating properly and is crucial for the early 

detection of potential endangerment to USDWs. 

Letter ID: 0181 Comment ID: 23744 Letter Lines: 2020 to 2026 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 4655 2.6.5.1 Plume tracking techniques/geophysical methods (seeking 

comment) 

Comment: Part 146.90(g) AWWA recommends revising this part to read: 

Testing and monitoring to track the extent of the carbon dioxide plume and the 

position of the pressure front by either monitoring for pressure changes in the 

confining zone, in the first formation overlying the confining zone or using 

indirect, geophysical techniques (e.g., seismic, electrical, gravity, or 

electromagnetic surveys and/or down-hole carbon dioxide detection tools); 

Individual Response: EPA has revised the final GS regulation, at §146.90(g)(1), to require all 

GS project owners or operators to monitor for pressure changes in the injection zone. EPA 

believes that pressure monitoring in the injection zone is necessary to track the development and 

movement of the pressure front and CO2 plume. Pressure monitoring within the injection zone is 

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necessary because any such monitoring above the confining zone would not detect movement of 

the pressure front unless a breach of the confining zone occurs. EPA believes that monitoring 

using wells in the injection zone (i.e., that penetrate the confining zone) can be safely performed 

if the wells are constructed to prevent flow between the injection zone and USDWs or other 

layers above the confining zone. Such construction technologies exist and have been used in the 

oil and gas industry for years. EPA believes that the benefits of monitoring in the injection 

formation outweigh the manageable risk of those monitoring wells serving as conduits for fluid 

movement. EPA adds that owners or operators may consider and Directors may require 

performing additional pressure monitoring in wells that are above the confining zone (e.g., in the 

same wells used to perform ground water quality monitoring required at §146.90(d)) to provide 

additional verification that no pressure changes are occurring above the confining zone due to 

CO2 leakage. Monitoring also identifies needed remedial actions, provides inputs for AoR 

reevaluation modeling, and targets additional geochemical and surface monitoring needs. 

Knowledge of the location of the CO2 plume and the associated pressure front will assure the 

public that GS projects are proceeding according to plan, provide sufficient information to the 

owner or operator and Director, or allow for appropriate actions to address any indication that 

USDWs may be endangered. 

In addition, §146.90(g)(2) requires owners or operators to track the position of the CO2 plume 

using indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or 

down-hole CO2 detection tools), unless the Director determines based on site-specific geology, 

that such methods are not appropriate. 

EPA acknowledges that, at certain sites, there may be a need for more or different monitoring 

schemes (which may include monitoring in the confining zone), and adds that it is important to 

balance the need for adequate monitoring that ensures USDW protection from endangerment 

against too many artificial penetrations which could serve as conduits for fluid migration. Sitespecific testing and monitoring plans must describe the proposed monitoring regime, which must 

be approved by the Director. 

Flexibility is also provided regarding how to monitor for the specific data required by the final 

rule. The testing and monitoring plan is developed by the owner or operator in consultation with 

the Director and is designed to ensure that a detailed, Director-approved document describing 

how monitoring will be conducted during the lifetime of the project exists. 

EPA is developing guidance on testing and monitoring to assist owners or operators and 

Directors in evaluating requirements under §146.90, including proposed monitoring plans. The 

guidance describes available technologies and recommended approaches for implementing a 

testing and monitoring plan, including pre-operational geophysical logging and testing of 

injection wells, MITs, injection well testing during operation, groundwater quality monitoring, 

tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may 

be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s 

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

Letter ID: 0181 Comment ID: 23745 Letter Lines: 2028 to 2032 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

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Comment Code: 4610 2.6.1 Testing and monitoring plan requirement (seeking comment) 

Comment: Part 146.90(h)(1) AWWA recommends revising this part to read: 

The testing and monitoring plan must be based on site-specific geologic factors, 

modeling, and a risk-assessment of potential vulnerabilities within the area of 

review; 

Individual Response: As described above, EPA agrees that periodic updates to the plan are 

appropriate, and the final GS regulation includes a requirement that the AoR be reevaluated at 

least every 5 years, and it specifies at §146.90(j) that the operator revise the testing and 

monitoring plan to incorporate the results of the most recent AoR reevaluation and recent 

operational and monitoring data. Based on its evaluation of all public comments and input on the 

proposed rule and NODA and Request for Comment EPA has made many revisions to the GS 

rule. See the final rule and preamble for further discussion on EPA's final approach. 

Letter ID: 0181 Comment ID: 23746 Letter Lines: 2034 to 2046 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 4760 2.7.6 Proposed reporting frequency (seeking comment) 

Comment: Part 146.91(11)(a) AWWA believes that the reporting frequency should be on a 

monthly basis, similar to what water and wastewater treatment plants have to do. 

The operating information for the geologic sequestration project is extremely 

important and needs to be reviewed at a frequency by the regulatory agency to 

ensure problems are identified and addressed in a timely manner. For example, 

with the way the regulation is currently structured, data collected on July 1, 

2008 would not be seen by the regulatory agency before January 15, 2009, if the 

operator is allowed 15 days to submit the report. This would allow for very 

little time to correct any potential issues in the operation of the project. As 

such, AWWA recommends revising this part to read: 

Monthly reports, due on the 15th day of each month for the previous month’s 

activities, containing: 

Individual Response: As described above, the final rule remains unchanged from the proposal 

and requires semi-annual reporting of monthly average, maximum and minimum values for 

injection pressure, flow rate and volume, annular pressure, and monthly annulus fluid volume 

added at §146.91(a). EPA believes that monthly reporting of routine operational data and 

monitoring results would provide no additional protection of USDWs from endangerment. 

For additional information, please see the final rule and the preamble for a discussion of EPA's 

final approach to recordkeeping and reporting. 

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Letter ID: 0181 Comment ID: 23747 Letter Lines: 2048 to 2060 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 5100 2.8.1 Injection well plugging activities (seeking comment) (40 CFR 

146.92) 

Comment: Part 146.92(b) As previously stated AWWA believes that potential changes in the 

size of the area of review require that all site plans be reevaluated at the 

same frequency as the area of review. Therefore, AWWA recommends revising this 

part to read: 

Well Plugging Plan. The owner or operator of a Class VI well must prepare, 

maintain, and comply with a plan that is acceptable to the Director. The plan 

must be reviewed and revised by the owner or operator, and submitted to the 

Director for approval, at the same frequency and time as the AOR reevaluation. 

The requirement to maintain and implement an approved plan is directly 

enforceable regardless of whether the requirement is a condition of the permit. 

The well plugging plan must be submitted as part of the permit application and 

must include the following information: 

Individual Response: EPA agrees that developing, maintaining, and implementing an injection 

well plugging plan is important to assuring that GS wells are plugged in a manner that will 

ensure that the well will not serve as a conduit for CO2 leakage preventing endangerment of 

USDWs. 

EPA disagrees with the suggested change, however. The final rule requirement at §146.92(c) for 

the owner or operator to notify the Director of any changes to the injection well plugging plan at 

least 60 days before plugging the well will allow the owner or operator (through communication 

with the Director) to address any issues associated with the initial well plugging plan submitted 

with the permit application. EPA is not requiring formal periodic review and updates to the 

injection well plugging plan throughout the injection phase. EPA does not expect that changes to 

this plan would be implemented until injection operations cease. EPA envisions that owners or 

operators will take into account similar considerations that guide updates to other project plans, 

e.g., monitoring and operational data and results of AoR reevaluations. 

EPA clarifies that the owner or operator's injection well plugging plan will be incorporated as a 

condition of their UIC permit and is therefore enforceable; failure to follow the approved plan 

would be considered a violation of the permit and would be subject to applicable civil, criminal, 

or administrative penalties under §1423 of the SDWA. 

Letter ID: 0181 Comment ID: 23748 Letter Lines: 2068 to 2077 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 5200 2.8.2 Post injection site care (seeking comment) (40 CFR 146.93) 

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Comment: Part 146.93(a) As previously stated AWWA believes that potential changes in the 

size of the area of review require that all site plans be reevaluated at the 

same frequency as the area of review. Therefore, AWWA recommends revising this 

part to read: 

The owner or operator of a Class VI well must prepare, maintain, and comply with 

a plan for post-injection site care and site closure that meets the requirements 

of paragraph (a)(2) of this section and is acceptable to the Director. The plan 

must be reviewed and revised by the owner or operator, and submitted to the 

Director for approval, at the same frequency and time as the AOR reevaluation. 

Individual Response: As described above, the final rule requires review and revision of the 

post-injection and site care closure plan when injection ceases, as described in §146.93(a)(3). 

EPA is not requiring formal periodic review and updates to the PISC and site closure plan 

throughout the injection phase. EPA does not expect that changes to this plan would be 

implemented until injection operations cease. See the final rule and preamble for further 

discussion on EPA's final approach. 

Letter ID: 0181 Comment ID: 23749 Letter Lines: 2094 to 2125 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 5300 2.8.3 Site closure activities (40 CFR 146.93) 

Comment: Part 146.93(b)(3) When addressing plume stabilization in association with site 

closure, it is important to realize that the carbon dioxide plume will never be 

completely stable. The carbon dioxide plume will continue to move by a 

combination of methods including density differences, natural formation flow 

gradients and diffusion. AWWA recommends that EPA engage in research to provide 

specific criteria on what exactly it would mean for the plume to have 

stabilized. If left up to the discretion of the various Directors, stabilization 

could be defined in many different ways. In order to have a consistent 

application of this part of the regulation, EPA should define the specific 

situations in which the plume could be considered "stable." AWWA recommends 

revising this part to read: 

Prior to authorization for site closure, the owner or operator must demonstrate 

to the Director, based on monitoring and other site-specific data that no 

additional monitoring is needed to assure that the geologic sequestration 

project does not pose an endangerment to USDWs. The demonstration must 

demonstrate all of the following: 

(i) the estimated magnitude and extent of the project footprint (CO2 plume and 

the area of elevated pressure) based on measurements and modeling; 

(ii) that CO2 movement and pressure changes match model predictions, 

(iii) the estimated location of the detectable CO2 plume based on measurement 

and modeling (measuring magnitude of saturation within the plume or mapping the 

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edge of it); 

(iv) that there is no evidence of significant leakage of either CO2 or displaced 

formation fluids that endanger USDWs; 

(v) that the CO2 plume and displaced formation fluid are not expected to migrate 

in the future in a manner that encounters a potential leakage pathway; 

(vi) that the injection wells at the site completed into or through the 

injection zone or confining zone are properly plugged and abandoned; and, 

(vii) any remaining project monitoring wells at the site are being managed by a 

person and in a manner acceptable to the Director. 

Individual Response: EPA acknowledges that many site-specific factors will influence the 

determination of when the CO2 plume and pressure front no longer pose a risk of endangerment 

to USDWs. It is for this reason that EPA believes that individual UIC Directors, in consultation 

with operators, will be in the best position to determine whether additional post-injection site 

care is needed. EPA expects this decision to be made based on relevant site data and in 

consultation with all potentially impacted parties. 

EPA agrees that a complete cessation of plume movement may not occur at some sites for long 

time periods due to density differences, natural formation flow gradients and diffusion. EPA 

clarifies that a complete cessation of plume movement is not required, only a demonstration that 

the plume and pressure front no longer pose a risk of endangerment to USDWs. 

EPA is developing guidance to assist owners or operators in evaluating well plugging, postinjection site care, and site closure requirements of §146.92 and §146.93. Additionally, the 

guidance will assist Directors in evaluating proposed well plugging plans and post-injection site 

care and site closure plans under §146.92 and §146.93. The guidance describes recommended 

approaches for how an owner or operator could plug injection and monitoring wells; perform 

post-injection monitoring; demonstrate non endangerment; and perform site closure activities. 

The guidance will be available at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

Letter ID: 0181 Comment ID: 23750 Letter Lines: 2140 to 2144 

Comment Code: 5200 2.8.2 Post injection site care (seeking comment) (40 CFR 146.93) 

Comment Code: 5300 2.8.3 Site closure activities (40 CFR 146.93) 

Comment: Part 146.93(d) There may be cases where the Director would want some of the 

monitoring wells to remain in service after site closure. While this may not be 

the case for all projects, for some of the earlier sites, the Director may want 

to continue minimal monitoring to continue to verify that the plume 

characteristics have remained stable. 

Individual Response: EPA clarifies that the owner or operator must conduct post-injection site 

care that is consistent with the approved PISC plan or for the duration of the alternative 

timeframe approved by the Director pursuant to requirements in §146.93(c), until a 

demonstration can be made to the satisfaction of the Director that the plume and pressure front 

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no longer pose a risk of endangerment to USDWs. After this determination is made, site closure 

is approved and the post-injection site care period would end, as specified in §146.93 (b)(1). 

If, however, there is reason to believe that additional minimal monitoring is necessary to verify 

that the plume characteristics have remained stable, this would be considered post-injection site 

care monitoring. If a reduction in monitoring frequency or methods is appropriate (i.e., an 

additional year or so of verification of the non-endangerment demonstration), the Director has 

discretion to authorize an amendment to the post-injection site care and site closure plan. This is 

consistent with the requirements at §146.93(b)(2). 

Letter ID: 0181 Comment ID: 23751 Letter Lines: 2146 to 2156 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 5800 2.13 Comments on emergency and remedial response (40 CFR 146.94) 

Comment: Part 146.94(a) It is important that the emergency and remedial response plan is 

reviewed and updated on the same schedule as the area of review update. Changes 

in the area of review could affect the actions that would need to be taken in 

the event of an emergency. AWWA recommends revising this part to read: 

As part of the permit application, the owner or operator must provide the 

Director with an emergency and remedial response plan that describes actions to 

be taken to address movement of the injection or formation fluids that may cause 

an endangerment to a USDW during construction, operation, closure and postclosure periods. The emergency and remedial response plan must be reviewed and 

updated, as necessary, on the same schedule as the update to the Area of Review. 

Individual Response: EPA has added a requirement at §146.94(d) that owners or operators must 

review their emergency and remedial response plan within one year of an AoR reevaluation 

required under §146.84 or following significant changes to the facility. Subsequently, owners or 

operators must submit an amended plan or demonstrate to the Director that no amendment to the 

plan is needed based on the AoR reevaluation or any significant changes made to the facility. 

Letter ID: 0181 Comment ID: 24332 Letter Lines: 2006 to 2011 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 4660 2.6.6 Geochemical monitoring 

Comment: Part 146.90(d) AWWA recommends revising this part to read: 

Periodic monitoring of the ground water quality and geochemical changes within 

(if wells can be installed without adversely affecting the integrity of the 

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confining zone) and above the confining zone(s) that may be a result of carbon 

dioxide movement through the confining zone or additional identified zones: 

Individual Response: EPA clarifies that §146.90(d) requires geochemical monitoring above the 

confining zone. To mitigate the risk of fluid movement, EPA requires owners and operators to 

submit a testing and monitoring plan that describes how the owner or operator plans to site and 

construct monitoring wells. 

EPA believes that monitoring using wells in the injection zone, e.g., for pressure monitoring as 

required at §146.90(g)(1), can be safely performed if the wells are constructed to prevent flow 

between the injection zone and USDWs or other layers above the confining zone. Such 

construction technologies exist and have been used in the oil and gas industry for years. EPA 

believes that properly constructed monitoring wells will be a safe way to obtain the data that is 

essential to ensure that the injected CO2 remains confined in the injection zone and that pressure 

changes are not causing movement of formation or other fluids. To mitigate the risk of fluid 

movement, EPA requires owners and operators to submit a testing and monitoring plan that 

describes how the owner or operator plans to site and construct monitoring wells. EPA is 

developing guidance on well construction that will include recommendations for monitoring well 

construction. The guidance will be available on EPA’s website at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

EPA is developing guidance on testing and monitoring to assist owners or operators and 

Directors in evaluating requirements under §146.90, including proposed monitoring plans. The 

guidance describes available technologies and recommended approaches for implementing a 

testing and monitoring plan, including pre-operational geophysical logging and testing of 

injection wells, MITs, injection well testing during operation, groundwater quality monitoring, 

tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may 

be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s 

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

Letter ID: 0181 Comment ID: 24339 Letter Lines: 2013 to 2018 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 4600 2.6 Proposed Plume and Pressure Front Monitoring Requirements (40 

CFR 146.90) 

Comment: Part 146.90(d)(1) AWWA recommends revising this part to read: 

The location and number of monitoring wells must be based on specific 

information about the geologic sequestration project, including injection rate 

and volume, geology, the presence of natural discontinuities and artificial 

penetrations and other factors. 

Individual Response: Based on its evaluation of all public comments and input on the proposed 

rule and NODA and Request for Comment EPA has made many revisions to the GS rule. See the 

final rule and preamble for further discussion on EPA's final approach. 

103
EPA's guidance on testing and monitoring will provide guidance on monitoring well placement. 

The guidance can be found on EPA’s website at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

Letter ID: 0181 Comment ID: 24371 Letter Lines: 2062 to 2066 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 5100 2.8.1 Injection well plugging activities (seeking comment) (40 CFR 

146.92) 

Comment: Part 146.92(b)(5) AWWA recommends revising this part to read: 

The type and grade and quantity of material to be used in plugging. The material 

must be compatible with the carbon dioxide stream and pre-injection formation 

conditions; and 

Individual Response: EPA believes, considering the potentially corrosive nature of CO2 when 

it is in contact with water, that the requirement that the material must be compatible with the 

CO2 stream is appropriate. The final rule retains this requirement. 

Letter ID: 0181 Comment ID: 24372 Letter Lines: 2079 to 2092 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 5240 2.8.2.2 Post injection timeframe (seeking comment) 

Comment: Part 146.93(b)(2) AWWA recommends that there should be a minimum 50 year 

postinjection monitoring period for all carbon sequestration projects. This time 

period is necessary to monitor the site for changes that may occur over a longer 

amount of time, such as gradual leakages, or sudden seismic shifts. After this 

time period, the owner/operator may apply to the Director for a modification or 

termination of the monitoring requirements. AWWA recommends revising this part 

to read: 

If, after the 50-year post-injection monitoring period, the owner or operator 

can demonstrate to the satisfaction of the Director, based on monitoring and 

other site-specific data, that the geologic sequestration project no longer 

poses an endangerment to USDWs, the Director may approve an amendment to the 

post-injection site care and site closure plan to reduce the frequency of 

monitoring or may authorize site closure before the end of the 50-year period. 

Individual Response: As described above, EPA agrees with commenters that a 50 year postinjection site care timeframe represents a reasonable and protective post-injection site monitoring 

period in most cases and available data, including data submitted by commenters, do not support 

a different default timeframe. EPA bases this on a review of research studies, industry reports, 

104
and existing environmental programs, and evaluation of public comments. Furthermore, EPA 

believes that a 50-year default post-injection site care timeframe is not overly burdensome, does 

not exaggerate the risks associated with GS, is consistent with other environmental programs, 

and sufficiently protects USDWs from endangerment. For this reason, the final GS regulation 

retains the 50 year post-injection site care timeframe, as specified in §146.93(b)(1). 

However, EPA disagrees that a 50 year post-injection site care timeframe should be an absolute 

minimum. Rather, EPA believes, as some commenters suggest, that there will be circumstances 

where it can be demonstrated in less than 50 years that the plume and pressure front no longer 

pose a risk of endangerment to USDWs. For this reason, the GS rule offers owners or operators 

flexibility regarding the duration of the PISC timeframe by: (1) allowing the Director discretion 

to shorten or lengthen the PISC timeframe during the post-injection period based on site-specific 

data, pursuant to requirements at §146.93(b); or (2) affording the Director discretion to allow a 

Class VI well owner or operator to demonstrate, during the permitting process based on 

substantial data, that an alternative PISC timeframe may be appropriate if it ensures nonendangerment of USDWs pursuant to requirements at §146.93(c). 

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

for post-injection site care will be necessary in most cases. The default 50 year post-injection site 

care timeframe represents a reasonable and protective monitoring period based on a review of 

research studies, industry reports, and existing environmental programs, and evaluation of public 

comments. 

EPA believes that a default post-injection site care timeframe of 50 years, with flexibility to 

adjust the timeframe for a limited number of GS projects during the permitting process where 

substantial data exists to demonstrate that an alternative timeframe would be protective of 

USDWs, or based on data collected during the PISC period, is appropriate to address the range of 

sites where GS is anticipated to occur, to accommodate site-specific circumstances and various 

geologic conditions, and addresses commenters’ concerns, while ensuring USDW protection. 

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

impacts. 

Letter ID: 0181 Comment ID: 24373 Letter Lines: 2127 to 2138 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 5300 2.8.3 Site closure activities (40 CFR 146.93) 

Comment: Part 146.93(c) AWWA recommends that this part of the rule needs to include a 

directive that the Director needs to provide approval for site closure prior to 

implementation of the site-closure plan. AWWA recommends revising this part to 

read: 

Notice of intent for site closure. The owner or operator must notify the 

Director at least 120 days before site closure. At this time, if any changes 

have been made to the original post-injection site care and site closure plan, 

105
the owner or operator must also provide the revised plan. The Director must 

provide approval for site closure prior to the implementation of the site 

closure plan. At the discretion of the Director, a shorter notice period may be 

allowed. 

Individual Response: EPA considers the combination of the Director's evaluation of the data 

submitted to support a demonstration of non-endangerment of USDWs, as specified in 

§146.93(b)(3), and the Director's receipt of and agreement with the notification of intent for site 

closure as confirmation that GS site closure can proceed. 

Letter ID: 0181 Comment ID: 24374 Letter Lines: 1720 to 1725 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 3150 2.1.5 Comments on required permit information (40 CFR 146.82) 

Comment: Part 146.82(d)(3) AWWA recommends revising this part to read: 

Information on the seismic history within the proposed area of review including 

presence and depth of seismic sources, knowledge of previous seismic events and 

history of these events, and a determination that the seismicity would not 

interfere with containment. 

Individual Response: EPA agrees that consideration of local and regional seismicity is 

important. This information is required for GS projects at §146.82(a)(3)(v). The site 

characterization provisions in the GS rule also require the owner or operator to submit data on 

known or suspected faults in the AoR (§146.82(a)(3)(ii)). Beyond the AoR (the specific project 

area) EPA notes that the site characterization requires a review of the local and regional geology, 

and detailed review of any known or potential seismically active terrain in the vicinity of a 

proposed GS site would certainly be required in a GS site characterization. 

Letter ID: 0181 Comment ID: 24375 Letter Lines: 1873 to 1879 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 3420 2.2.2.1 Scope of the inventory process (e.g., reliance on publicly 

available information, depth of wells) 

Comment: Part 146.84(d) AWWA recommends revising this part to read: 

Owners or operators of Class VI wells must perform corrective action on all 

wells and other artificial penetrations in the area of review that are 

determined to need corrective action using methods necessary to prevent the 

movement of fluid into or between USDWs and between the injection zones(s) and 

USDWs, including use of corrosion resistant materials, where appropriate. 

Individual Response: EPA revised the text at §146.84(d) to require the use of materials that are 

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"compatible with the carbon dioxide stream." EPA believes this language change addresses 

commenters' concerns and is also consistent with other language regarding materials 

requirements in the GS rule. EPA believes that meeting the requirement for preventing 

"movement of fluid into or between USDWs" will prevent movement between the injection zone 

and USDWs; therefore, it did not make the suggested change. 

Letter ID: 0181 Comment ID: 24376 Letter Lines: 1907 to 1909 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 3800 2.3 Proposed Injection Well Construction Requirements (40 CFR 

146.86) 

Comment: Part 146.86(b)(1)(i) AWWA recommends revising this part to read: 

Depth to the injection zone and overburden pressures in the injection zone. 

Individual Response: EPA believes that the requirement in 146.86(b)(ii) to report the external 

pressure provides the same information as the requested change. Based on its evaluation of all 

public comments and input on the proposed rule and NODA and Request for Comment EPA has 

made many revisions to the GS rule. Please see the final rule and preamble for additional 

information. 

Letter ID: 0181 Comment ID: 24377 Letter Lines: 1833 to 1839 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment Code: 3100 2.1 Proposed Geologic Siting Requirements (40 CFR 146.83) 

Comment: Part 146.83(a)(2) AWWA recommends revising this part to read: 

A confining zone(s) that is free of transmissible faults or fractures and of 

sufficient areal extent and integrity to contain the injected carbon dioxide 

stream and displaced formation fluids and allow injection at proposed maximum 

pressures and volumes without initiating or propagating fractures in the 

injection and confining zone(s). 

Individual Response: EPA acknowledges the importance of selecting GS sites with confining 

zones that are free of transmissive faults and fractures but disagrees that the rule should prohibit 

fracturing within the injection zone. EPA believes that, in some circumstances, fracturing is 

necessary (i.e., in association with an approved for stimulation program to improve wellbore and 

formation injectivity). EPA clarifies that all stimulation for GS must be approved by the Director 

pursuant to requirements at §146.91. 

Letter ID: 0181 Comment ID: 25061 Letter Lines: 1364 to 1375 

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Comment Code: 5432 2.9.1.1 Need to adjust financial responsibility mechanisms (seeking 

comment) 

Comment: AWWA believes that the time limit for financial responsibility in the proposed 

regulation may be too long for most insurance agencies, which may trigger the 

need for the development of a trust fund or for owner/operators to use a selfinsurance mechanism. If the trust fund is the desired method, EPA should require 

that companies constantly add to the fund, even if it appears that the fund is 

fully funded. In addition to the initial pay in period of three years, 

owner/operators should be required to pay in any additional amount identified 

during the five-year reviews for the area of review and corrective action plan, 

injection well plugging plan, the post-injection site care and site closure 

plan, and the emergency and remedial response plan. This additional pay in is 

required so that we don't have a repeat of the funding stoppage with the 

Superfund program. 

Individual Response: EPA acknowledges that there may be several possible approaches to 

setting pay-in periods for trust funds. However, EPA emphasizes that regardless of the use or 

duration of a pay-in period, the value of the trust must ultimately be equal to the cost estimate. 

The final rule requires that the Director approve the use and length of pay-in periods. EPA is 

developing guidance (available on EPA's website at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm) that describes the types of 

financial instruments that owners or operators can use to meet financial responsibility 

requirements for GS wells. Specifically, the guidance will discuss pay-in periods and provide 

guidance for Directors to use in determining an appropriate pay-in period. EPA adds that owners 

or operators may choose from a variety of financial instruments to meet their financial 

responsibility needs. 

The final GS rule, at §146.85(c), requires the owner or operator to provide adjustments to the 

cost estimate to account for any amendments to the AoR and corrective action plan, the injection 

well plugging plan, the PISC and site closure plan, and the emergency and remedial response 

plan. Owners or operators must also adjust the estimates for inflation annually under 

§146.85(c)(2). EPA adds that the Director can also require the owner or operator to provide an 

adjustment of the cost estimate if the Director determines that the original demonstration is no 

longer adequate, as specified at §146.85(e). Any adjustment to the cost estimate would require 

the owner or operator to adjust the funded amount of any financial responsibility instruments, as 

required at §146.85(c)(4). 

Under SDWA, EPA has the general authority to set financial responsibility requirements for 

injection well owners or operators to ensure that adequate resources are available to protect 

USDWs throughout the life of the GS project. However, this authority does not extend to 

allowing the Agency to create a financial instrument with EPA as the trustee, due to the 

restrictions of the Miscellaneous Receipts Act (MRA). The MRA requires that EPA deposit the 

funds it receives for the use of the Government into the Treasury, therefore funds would not 

necessarily be available for GS financial responsibility. 

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Additionally, EPA does not have authority under SDWA to establish a trust fund for purposes of 

financial responsibility for Class VI projects. The Agency clarifies that the trust funds that are 

addressed as financial responsibility instruments on the GS rule are set up by individual owners 

or operators and are different from a national-level trust described by the commenters that would 

cover large numbers of GS projects.