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.
Organization Name: Oklahoma Department of Environmental Quality

Submitter’s Representative: Saba Tahmassebi, Ph.D., P.E.

Government Agency Type: State

Government Agency: Oklahoma Department of Environmental Quality

General Comments:

Please consider the following comments:

1. Delay the proposed schedule for the implementation of the final rule.

With the current state of technology, there does not appear to exist enough data to determine whether 

geologic sequestration of carbon dioxide can be accomplished in a safe manner. In fact, in its preamble 

to the proposed rule, EPA states that conducting large volume carbon storage tests are necessary to 

demonstrate that large-scale CO2 injection and storage can be achieved safely and economically. The 

preamble also suggests that the DOE-sponsored “Deployment Phase” of research is likely to provide the 

necessary data to make this determination. The Deployment Phase is scheduled to be completed in 

2017. Therefore, EPA will not have enough data to adequately determine that large-scale 

implementation of the rule is safe until after 2017 when the data is gathered and analyzed.

Oklahoma DEQ recommends that EPA postpone finalizing the rule until after 2017 to include the results 

of the pilot studies. Without the benefit of considering the results of these studies, the safety of 

geologic sequestration activities will remain questionable.

In the meantime, EPA may modify the rule and consider proceeding with its implementation for 

depleted oil and gas reservoirs. Since these reservoirs have been extensively studied in the past, it is 

likely that enough data exists to ensure safe operations at some of the reservoirs under certain 

conditions. 

2. Reconsider shifting the burden to the States when not enough information is available.

It appears that much research is needed to ensure that geologic sequestration can be conducted in a 

safe manner. When research data is not available, or when EPA is uncertain of the best way to address 

a situation, the burden of addressing the issue is shifted to the states. Examples include corrective 

action methodology for abandoned wells, materials used in construction of the wells, and the use of 

tracers among other issues. 

Oklahoma DEQ recommends that EPA prepare guidance documents to address the above concerns.
3. Preclude aquifer exemptions.

It appears that EPA has struggled with balancing the perceived benefits of geologic sequestration with 

the need to protect USDWs. In much of the proposed rule, EPA sets a foundation for protecting the 

USDWs by including specific requirements. EPA then diverges from this foundation by suggesting that if 

it is not feasible to protect the USDWs, one may still proceed with sequestration activities by exempting 

the aquifers. In this instance, it appears that EPA considers the benefits of geologic sequestration to 

overweigh the need to protect USDWs.

Oklahoma DEQ recommends that EPA not consider aquifer exemptions for geologic sequestration.

4. Reexamine the standard for injection pressure.

The proposed rule sets a limit on injection pressure that is less than 90 percent of the fracture pressure 

of the injection zones. EPA may be aware that injection zones may also include sealed or closed 

fractures that are not permeable. These fractures may re-open at pressures below the 90 percent 

requirement providing a conduit for fluid migration. 

Oklahoma DEQ recommends that EPA consider the effect on the sealed and closed fractures and modify 

the maximum pressure requirement accordingly.

5. Clarify jurisdiction across state lines.

The proposed rule does not address injection issues across state lines. For example, if the pressure 

boundary and the CO2 plume traverse across state lines, will the permittee be required to obtain a UIC 

permit from the neighboring state? If so, what kind of permit? In addition to requiring monitoring and 

financial assurance, would the neighboring state also set limits on the injection rates? Etc.

Oklahoma DEQ recommends that EPA clarify jurisdiction across state lines.

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Contact information:

Saba Tahmassebi, Ph.D., P.E.

Chief Engineer, Land Protection Division

Oklahoma department of Environmental Quality

P. O. Box 1677

Oklahoma City, OK 73101-1677

Phone: (405) 702-5142

Fax: (405) 702-5101

Email: Saba.Tahmassebi@deq.ok.gov
Letter ID: 0218 

Commenter: Saba Tahmassebi 

Organization: Oklahoma Department of Environmental Quality (DEQ) 

Letter ID: 0218 Comment ID: 21561 Letter Lines: 19 to 33 

Comment Code: 1510 1.2.2.3 Need for additional study 

Comment Code: 1850 1.4.2 CO2 GS Field Research 

Comment: 1. Delay the proposed schedule for the implementation of the final rule. With 

the current state of technology, there does not appear to exist enough data to 

determine whether geologic sequestration of carbon dioxide can be accomplished 

in a safe manner. In fact, in its preamble to the proposed rule, EPA states 

that conducting large volume carbon storage tests are necessary to demonstrate 

that large-scale CO2 injection and storage can be achieved safely and 

economically. The preamble also suggests that the DOE-sponsored "Deployment 

Phase" of research is likely to provide the necessary data to make this 

determination. The Deployment Phase is scheduled to be completed in 2017. 

Therefore, EPA will not have enough data to adequately determine that largescale implementation of the rule is safe until after 2017 when the data is 

gathered and analyzed. Oklahoma DEQ recommends that EPA postpone finalizing the 

rule until after 2017 to include the results of the pilot studies. Without the 

benefit of considering the results of these studies, the safety of geologic 

sequestration activities will remain questionable. In the meantime, EPA may 

Individual Response: EPA agrees that continued research will be integral to development of GS 

technology, but disagrees that the Agency should wait for the DOE pilot studies to be complete 

before finalizing the GS rule. EPA believes that establishing a regulatory framework for the 

future development and deployment of CCS technology protects USDWs from endangerment 

and will not impede industry adoption of CCS. 

EPA believes that sufficient research has been conducted and sufficient data gathered to proceed 

with rule promulgation. 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 

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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 maximum contaminant 

level (MCL) for safe drinking water. 

ORD's National Center for Environmental Research (NCER) 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. 

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 

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

necessary. 

Letter ID: 0218 Comment ID: 21562 Letter Lines: 33 to 37 

Comment Code: 1380 1.1.3.6 Deployment of GS 

Comment: sequestration activities will remain questionable. In the meantime, EPA may 

modify the rule and consider proceeding with its implementation for depleted oil 

and gas reservoirs. Since these reservoirs have been extensively studied in the 

past, it is likely that enough data exists to ensure safe operations at some of 

the reservoirs under certain conditions. 

Individual Response: EPA clarifies that the Class VI GS rule applies to all injection of CO2 

into the subsurface for the purpose of long-term storage regardless of the type of injection 

formation. The Class VI GS siting requirements allow GS projects to be permitted if the owner 

or operator can demonstrate, to the Director that a proposed site has geologic formations suitable 

to receive and confine the injected fluids in order to ensure protection of USDWs from 

endangerment. EPA acknowledges that depleted oil and gas reservoirs associated with ER 

operations may be used for CO2 storage and that these sites may be some of the first sites where 

commercial-scale GS is deployed. However, these wells can only be permitted if owners or 

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operators can demonstrate that injection into other formations meet the Class VI GS 

requirements. 

Letter ID: 0218 Comment ID: 21563 Letter Lines: 39 to 47 

Comment Code: 1200 1.1 General comments about the rulemaking 

Comment Code: 1435 1.2.1.3 EPA should develop guidance 

Comment: 2. Reconsider shifting the burden to the States when not enough information is 

available. It appears that much research is needed to ensure that geologic 

sequestration can be conducted in a safe manner. When research data is not 

available, or when EPA is uncertain of the best way to address a situation, the 

burden of addressing the issue is shifted to the states. Examples include 

corrective action methodology for abandoned wells, materials used in 

construction of the wells, and the use of tracers among other issues. Oklahoma 

DEQ recommends that EPA prepare guidance documents to address the above 

concerns. 

Individual Response: EPA clarifies that such decisions would be made by the state, if the well 

is located in a state with Class VI primacy. Any state that wishes to obtain primacy for Class VI 

wells will need to describe in their program description the criteria that would be used to make 

determinations on topics the commenter mentions. See §145.23. EPA adds that it is developing 

guidance for states and tribes that describes the process of applying for and receiving primacy for 

GS Class VI wells under Section 1422 of SDWA, as well as the technical and administrative 

issues associated with developing GS regulations that are the equivalent of minimum federal 

criteria and requirements. These are available on EPA’s website at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

Letter ID: 0218 Comment ID: 21564 Letter Lines: 49 to 57 

Comment Code: 4470 2.4.4.4.2 Comments opposing aquifer exemptions in all cases 

Comment: 3. Preclude aquifer exemptions. It appears that EPA has struggled with balancing 

the perceived benefits of geologic sequestration with the need to protect USDWs. 

In much of the proposed rule, EPA sets a foundation for protecting the USDWs by 

including specific requirements. EPA then diverges from this foundation by 

suggesting that if it is not feasible to protect the USDWs, one may still 

proceed with sequestration activities by exempting the aquifers. In this 

instance, it appears that EPA considers the benefits of geologic sequestration 

to overweigh the need to protect USDWs. Oklahoma DEQ recommends that EPA not 

consider aquifer exemptions for geologic sequestration. 

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 

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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 adds that all decisions regarding aquifer exemptions for Class VI wells are at the Director's 

discretion. If a Director believes that injection depth waivers are not appropriate for a specific 

site or for a category of formations within their state, the Director has the authority to not permit 

such injections. 

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 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: 0218 Comment ID: 21565 Letter Lines: 59 to 65 

Comment Code: 4110 2.4.1.1 Injection pressure limitations 

Comment: 4. Reexamine the standard for injection pressure. The proposed rule sets a limit 

on injection pressure that is less than 90 percent of the fracture pressure of 

the injection zones. EPA may be aware that injection zones may also include 

sealed or closed fractures that are not permeable. These fractures may re-open 

at pressures below the 90 percent requirement providing a conduit for fluid 

migration. Oklahoma DEQ recommends that EPA consider the effect on the sealed 

and closed fractures and modify the maximum pressure requirement accordingly. 

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Individual Response: EPA notes that during the site characterization process, owners or 

operators must submit data about the geology of the site, as specified at §146.82(a), including 

data on known or suspected faults and fractures and geomechanical information on fractures, 

stress, ductility, rock strength, and in situ fluid pressures within the confining zone. The Director 

will use these data to determine appropriate limits on injection. If the Director determines, based 

on a review of the information collected as part of site characterization, that a lower injection 

pressure limitation is appropriate, the Director has the authority to set a lower limit in the 

operating permit than the limit established in the rule. 

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: 0218 Comment ID: 21566 Letter Lines: 67 to 73 

Comment Code: 1310 1.1.2.4 Comments on other "out of scope" issues, e.g., pore space 

ownership 

Comment: 5. Clarify jurisdiction across state lines. The proposed rule does not address 

injection issues across state lines. For example, if the pressure boundary and 

the CO2 plume traverse across state lines, will the permittee be required to 

obtain a UIC permit from the neighboring state? If so, what kind of permit? In 

addition to requiring monitoring and financial assurance, would the neighboring 

state also set limits on the injection rates? Etc. Oklahoma DEQ recommends that 

EPA clarify jurisdiction across state lines. 

Individual Response: EPA acknowledges that CO2 plumes may cross state or even international 

boundaries and encourages cooperation and coordination among permitting authorities. The final 

Class VI GS rule, at §146.82(a)(2), requires the owner or operator to identify all State, Tribal, 

and Territorial boundaries within the AoR. Based on this information, the Director must provide 

written notification to all States, Tribes, and Territories to inform them of the permit application 

and ensure that they are involved in any necessary processes; this new requirement was added to 

the final rule at §146.82(b). The Agency encourages transparency in the permitting process and 

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anticipates that State-State/State-Tribal communication on Class VI permitting will facilitate 

information sharing and encourage safe, protective projects. 

EPA clarifies that the Class VI permit would be issued by the permitting authority in the state 

where the wellhead is located.