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.
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Document ID: EPA-HQ-OW-2008-0390-0234

Last Name: Corneli

First Name: Steven B.

Title: Vice President, Market and Climate Policy

Organization: NRG Energy, Inc.

City: Princeton

State: NJ

Zip Code: 8540

Phone Number: 609.524.4500

Fax Number: 609.524.4501

Country Code: 

Email Address: 

Current Category Code: 255

Comment: 

Water Docket

Environmental Protection Agency

Mailcode: 2822T

1200 Pennsylvania Ave., NW

Washington, DC 20460

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

RE: COMMENTS ON THE PROPOSED FEDERAL REQUIREMENTS 

UNDER THE UNDERGROUND INJECTION CONTROL (UIC) PROGRAM FOR 

CARBON DIOXIDE (CO2) GEOLOGIC SEQUESTRATION (GS) WELLS.

Dear Sir or Madam:

Attached please find the comments of NRG Energy, Inc. in the above referenced

matter.

Sincerely,

Steven B. Corneli

Vice President

Market and Climate Policy

Comments of NRG Energy, Inc.

Proposed UIC Program for Carbon Sequestration

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

NRG Energy Inc. (NRG) submits the following comments concerning the

Environmental Protection Agency’s (EPA’s) proposed "Federal Requirements under

the Underground Injection Control (UIC) Program for Carbon Dioxide (CO2)

Geologic Sequestration (GS) Wells," as published in the Federal Register on July

25, 2008 at pages 43491-43541. NRG Energy, Inc., a Fortune 500 company, owns and

operates one of the country’s largest and most diverse power generation

portfolios. NRG’s 48 plants provide approximately 24,000 megawatts of generation

capacity--enough to power nearly 20 million homes. NRG believes that emissions

of GHGs from power generation and other sectors must be reduced, both

domestically and internationally, to successfully address climate change, and
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that commercially attractive, safe and environmentally secure carbon capture and

sequestration will be critical for that success. Headquartered in Princeton, NJ,

NRG is a member of the U.S. Climate Action Partnership (USCAP), a group of

business and environmental organizations calling for mandatory legislation to

reduce greenhouse gas emissions.

NRG appreciates the substantial efforts which have been part of this proposal

development governing CO2 injection for the purpose of GS. As a company, NRG is

committed to effectively addressing climate change, and believes that GS is a

critical component for the reduction of CO2 emissions. In general, NRG supports

and commends the efforts of the EPA to develop a rational approach that would

(1) create a new category of injection wells (i.e., Class VI) under the

Underground Injection Control (UIC) Program and (2) establishes Federal

regulations that are specifically tailored to CO2 injection for GS. However, we

are concerned about several technical requirements of the proposed rules that

would substantially increase the cost of GS without environmental benefits. It

is essential that EPA develop a regulatory framework that encourages the

commercial deployment of GS, otherwise efforts and investments to develop carbon

capture technology will be discouraged.

NRG is a member of the Carbon Sequestration Council (CCS Contact Group), and we

support the more extensive comments filed by this organization. NRG offers the

following comments on the proposed rule:

Injection Zones for Geologic Sequestration (GS)

The proposed rule limits GS to only those geologic formations that are below the

lowermost underground source of drinking water (USDW). Prohibiting injection

between and/or above the lowermost USDW would exclude GS in many potential

storage reservoirs throughout the US that could be utilized for injection while

still ensuring protection of USDWs. The petroleum industry has demonstrated that

they can operate CO2 injection wells for EOR/EGR while preventing USDW

endangerment. We believe protection of valuable drinking water sources could be

accomplished through proper site selection and characterization. NRG recommends

using science based techniques to demonstrate that geologic conditions exist

that will prevent CO2 migration to USDWs. Under these circumstances, the

lowermost USDW restriction would be unnecessary.

Area of Review and Corrective Action Requirements

1. Use of Computational Models for Area of Review

The EPA requested comment on the proposed rule regarding the use of modeling for

area of review (AoR). NRG supports the use of computational models for

determination of the AoR for geologic sequestration projects. The use of such

models is already being used in the UIC program for "no-migration" petitions for

Class I injection wells. We believe the use of modeling for determining the

pressure effects associated with the underground injection process is an

appropriate confirming process for safe site selection and corrective action to

address potential risk presented by GS.

2. AoR Reevaluation

The proposed rule requires a re-evaluation of the AoR determination on a
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frequency not to exceed once every ten years. NRG agrees with the Carbon

Sequestration Council’s recommended alternative approach to re-evaluate the AoR

only when site specific operation and monitoring data suggest that there is a

need for a new evaluation of the AoR. Periodic AoR re-evaluation will most

likely be necessary given the enormous volumes of CO2 that would be injected

into the subsurface, the lengthy timeframes likely for GS operations, and the

potential uncertainty of the original model prediction. We believe that it is

impractical and cost prohibitive to require re-evaluation of the AoR on a fixed

schedule. Re-evaluation of the AoR should only be conducted when monitoring and

testing data are determined to be inconsistent with the modeling results.

3. Corrective Action

EPA proposes to allow a phased approach to corrective action for GS wells. NRG

agrees that this approach is prudent and practical given the enormous volumes of

CO2 that would be injected for a geologic sequestration project. Implementation

of a phased corrective action to address risk associated with artificial

penetrations such as plugged well borings would reduce project costs and also

reduce the regulatory burdens of the permitting process.

Proposed Class VI Well Standards

The proposed Class VI well construction requirements are as stringent as those

for hazardous waste injection (Class I). NRG believes that this is not a logical

or appropriate regulatory approach to ensure protection of USDWs. The injection

of CO2 does not warrant the same level of regulations as hazardous waste

injection.

The primary issues associated with CO2 injection for GS are related to the

enormous volumes and the mobility of CO2 in the subsurface. However, the Class

VI requirements do not address these issues. These stringent well construction

requirements will only increase the costs of operation resulting in no

additional protection of USDWs. NRG agrees with the Carbon Sequestration

Council’s recommendation to use the Class II regulations as a starting point for

the development of the Class VI regulations. The oil and gas industry has

several decades of CO2 injection experience with the Class II UIC program and

has demonstrated that the construction requirements for Class II injections

wells are sufficient to protect human health and the environment.

Injection Well Operating Requirements

1. Injection Pressure Limitations

The proposed rule does not allow injection pressures that exceed 90% of the

fracture pressure of the receiving formation. NRG believes that this rule of

thumb would be an over protective requirement and would not be necessary for

ensuring containment of CO2 in the receiving formation. The existing requirement

under the UIC regulations for Class II wells allows injection pressure limits

that are based on site-specific conditions (i.e., well tests and geomechanical

studies) that have been proven to be effective in protecting the confining zone.

We believe a standard similar to Class II injection wells would be appropriate

for GS.

2. Continuous Monitoring
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NRG supports continuous monitoring of the annular and injection pressure for

well integrity purposes. However, the proposed requirement for continuous

monitoring of the annular fluid volume is impractical and unnecessary. We

recommend continuous measurement of the annular pressure as a means of leak

detection instead of the annual fluid volume.

3. Tracers

NRG opposes any requirement to use tracers for leak detection because leaks from

properly permitted injection wells are not likely to occur. The use of tracers

will not be effective in the detection of CO2 releases in the subsurface and

will not ensure the protection of USDWs. Tracers are more likely to cause "false

positives" by accidental leaks from the equipment on the surface. The Class VI

regulations are designed to prevent the kind of leakage that the tracers are

intended to detect.

Monitoring Requirements

The preamble of the proposed rule states that the "monitoring of subsurface

geochemistry and the position of the CO2 plume and pressure front are necessary

to verify predictions of plume movement, provide inputs for modeling, identify

needed corrective actions, and target geochemical and surface monitoring

activities." 73 Fed. Reg. at 43514. NRG believes that the proposed monitoring

requirements are excessive and unjustified. The use of monitor wells or seismic

data would be needed to verify the model predictions. In particular, it is

impractical and cost prohibitive to measure the exact location of the CO2 plume

and pressure front using monitor wells. The monitor wells would be very

expensive to install and may create a potential pathway for migration of CO2. In

addition, plume or pressure front monitoring have never been necessary or

required under the Class I hazardous waste injection well program because

experience has shown that it is not necessary to verify the model predictions.

Financial Assurance

NRG commends the EPA for allowing flexibility on financial assurance for GS

wells. Allowing flexibility will enable operators to use a combination of

approaches and instruments to meet the financial requirements over the life of

the injection well operation. We believe that it would be a mistake to impose

any restrictions on the types of financial assurance or instruments that can be

used for GS wells. We recommend that this approach be retained in the final

rule.

RCRA Applicability

The preamble of the proposed rule suggests that CO2 injected for GS projects may

be considered hazardous waste for RCRA purposes. 73 Fed. Reg. at 43503. EPA’s

brief discussion of the potential for injected CO2 streams to be characterized

as hazardous waste are causing concern among the electric power industry and

could have an effect on the future development of carbon capture and

sequestration projects. The premise that CO2 could be characterized as a

hazardous waste would likely prove detrimental to project development. The RCRA

definition of "solid waste" is limited to "solid, liquid, semi-solid, or

contained gaseous material." RCRA 1004(27). Because the gas and liquid
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(supercritical) phases involved in GS do not meet this definition, reading of

federal law would suggests that the CO2 stream for GS should not be considered

a "solid waste". EPA should clarify that the gas and liquid phases of the CO2

stream is not a solid or hazardous waste for RCRA purposes and therefore not

subject to RCRA waste determination requirements.

CERCLA Applicability

The preamble of the proposed rule suggests that CERCLA liability may arise out

of CO2 GS projects due to "potential USDW impacts", presence of impurities in

the stream, and the potential for reaction products to migrate from the

injection zone. 73 Fed. Reg. 43492, 43497 (July 25, 2008). EPA also states that

(CERCLA exempts from liability certain "federally permitted releases" including

releases in compliance with a UIC permit under SDWA. Therefore, 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.) 73 Fed. Reg. at 43504.

EPA’s suggestion that CERCLA liability may apply to CO2 GS projects raises

concern among the electric power industry. Because EPA raised this as a

potential issue, businesses and investors may be reluctant to support GS

projects faced with a potential for CERCLA liability hanging over their heads.

In order to prevent any discouragement of development in CO2 GS projects, EPA

should provide confirmation in the final regulations that injection of CO2 into

a permitted injection zone does not constitute a "release" for purposes of RCRA

or CERCLA. EPA should also take the opportunity to dispel the CERCLA liability

concerns by developing appropriate language to provide the clarity and assurance

needed to promote continued research, development and deployment of CO2 GS

projects.
Letter ID: 0234 

Commenter: Steven B. Corneli 

Organization: NRG Energy, Inc. 

Letter ID: 0234 Comment ID: 23158 Letter Lines: 51 to 58 

Comment Code: 1330 1.1.3.1 Support use of GS in general 

Comment: capacity--enough to power nearly 20 million homes. NRG believes that emissions 

of GHGs from power generation and other sectors must be reduced, both 

domestically and internationally, to successfully address climate change, and 

that commercially attractive, safe and environmentally secure carbon capture and 

sequestration will be critical for that success. Headquartered in Princeton, NJ, 

NRG is a member of the U.S. Climate Action Partnership (USCAP), a group of 

business and environmental organizations calling for mandatory legislation to 

reduce greenhouse gas emissions. 

Individual Response: EPA acknowledges the comment. 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: 0234 Comment ID: 23159 Letter Lines: 60 to 67 

Comment Code: 1420 1.2.1.1 Support the GS rulemaking 

Comment Code: 2020 1.5.1 Support Class VI designation 

Comment: NRG appreciates the substantial efforts which have been part of this proposal 

development governing CO2 injection for the purpose of GS. As a company, NRG is 

committed to effectively addressing climate change, and believes that GS is a 

critical component for the reduction of CO2 emissions. In general, NRG supports 

and commends the efforts of the EPA to develop a rational approach that would 

(1) create a new category of injection wells (i.e., Class VI) under the 

Underground Injection Control (UIC) Program and (2) establishes Federal 

regulations that are specifically tailored to CO2 injection for GS. However, we 

Individual Response: EPA agrees that tailored requirements for Class VI wells are necessary to 

address the unique nature of injecting large volumes of CO2 and to ensure that USDWs are 

protected from endangerment. The GS rule contains tailored requirements for the permitting, 

geologic site characterization, AoR and corrective action, well construction, operation, 

mechanical integrity testing, monitoring, well plugging, post-injection site care, and site closure 

of GS wells that directly address issues unique to the nature of large-scale CO2 injection for GS. 

The EPA believes the final rulemaking falls within EPA’s authority under the SDWA. EPA 

clarifies that the SDWA provides EPA with the authority to develop federal minimum 

requirements for underground injection, such as GS, that are directly related to protecting 

1
USDWs from endangerment. Thus, EPA does not have authority under the SDWA to address 

other issues related to CCS, such as capture and transportation. 

Letter ID: 0234 Comment ID: 23160 Letter Lines: 67 to 72 

Comment Code: 6000 3. Cost of the Proposed Rule 

Comment: regulations that are specifically tailored to CO2 injection for GS. However, we 

are concerned about several technical requirements of the proposed rules that 

would substantially increase the cost of GS without environmental benefits. It 

is essential that EPA develop a regulatory framework that encourages the 

commercial deployment of GS, otherwise efforts and investments to develop carbon 

capture technology will be discouraged. 

Individual Response: EPA believes that the GS rule requirements are necessary and appropriate 

to address the unique challenges posed by large-scale GS including large injection volumes, the 

relative buoyancy of CO2, its corrosivity in the presence of water, the potential presence of 

impurities in captured CO2, and its mobility within subsurface geologic formations. EPA 

acknowledges that the Class VI requirements have associated costs beyond baseline (Class I 

industrial wells) costs, and believes these costs are necessary and appropriate to address the 

unique challenges posed by large-scale GS including large injection volumes, the relative 

buoyancy of CO2, its corrosivity in the presence of water, the potential presence of impurities in 

captured CO2, and its mobility within subsurface geologic formations. 

The Agency clarifies that sequestration costs are expected to be a small component of total CCS 

project costs. EPA estimates that the GS rule requirements amount to approximately 2 percent of 

the total CCS project costs, according to the cost analysis for the final GS rule, which is in the 

rulemaking docket. 

EPA also disagrees that the GS rule does not provide benefits of protecting USDWs. The GS rule 

contains tailored requirements to ensure that wells are appropriately permitted, sited, constructed, 

operated, monitored, and closed in a manner that protects USDWs from endangerment. 

Letter ID: 0234 Comment ID: 23161 Letter Lines: 78 to 90 

Comment Code: 4410 2.4.4.3.1 Comments in favor of allowing injection above/between 

USDWs in certain circumstances 

Comment: Injection Zones for Geologic Sequestration (GS) 

The proposed rule limits GS to only those geologic formations that are below the 

lowermost underground source of drinking water (USDW). Prohibiting injection 

between and/or above the lowermost USDW would exclude GS in many potential 

storage reservoirs throughout the US that could be utilized for injection while 

still ensuring protection of USDWs. The petroleum industry has demonstrated that 

2
they can operate CO2 injection wells for EOR/EGR while preventing USDW 

endangerment. We believe protection of valuable drinking water sources could be 

accomplished through proper site selection and characterization. NRG recommends 

using science based techniques to demonstrate that geologic conditions exist 

that will prevent CO2 migration to USDWs. Under these circumstances, the 

lowermost USDW restriction would be unnecessary. 

Individual Response: EPA acknowledges that there are limited circumstances where injection 

above the lowermost USDW can be performed in a manner that protects USDWs from 

endangerment, 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. 

Determinations about the appropriateness of a waiver would be made by the Director, based on 

evaluation of site-specific conditions. 

EPA believes that these requirements will ensure USDW protection while providing flexibility to 

UIC program Directors and owners or operators who undertake CO2 injection for GS. The 

Agency believes this approach: 1) responds to concerns about local and regional geologic storage 

capacity limitations imposed by the proposed injection depth requirements; 2) allows for a more 

site-specific assessment of injection depth for GS projects; 3) accommodates injection into 

different formation types; 4) allows for injection of CO2 for GS into non-USDWs above and/or 

between USDWs when appropriate and where it can be demonstrated that USDWs will be 

protected; and 5) responds to concerns about the use of aquifer exemptions for GS. Finally, 

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: 0234 Comment ID: 23162 Letter Lines: 94 to 103 

Comment Code: 3310 2.2.1.1 Comments in favor of requiring computational models to 

delineate the AoR (seeking comment) 

Comment: 1. Use of Computational Models for Area of Review 

The EPA requested comment on the proposed rule regarding the use of modeling for 

area of review (AoR). NRG supports the use of computational models for 

determination of the AoR for geologic sequestration projects. The use of such 

models is already being used in the UIC program for "no-migration" petitions for 

Class I injection wells. We believe the use of modeling for determining the 

pressure effects associated with the underground injection process is an 

appropriate confirming process for safe site selection and corrective action to 

address potential risk presented by GS. 

Individual Response: EPA acknowledges the commenter’s support and agrees that predicting 

3
the complex multiphase, buoyant flow of the CO2, co-injectates, and compounds that may be 

mobilized due to injection requires the sophistication of computational models, as required at 

§146.84(c)(1). Models can predict CO2 fate and transport, as well as changes in formation 

pressure, in three dimensions, as a function of time in order to delineate the subsurface storage 

site and the AoR. Models can account for site-specific and predicted operating conditions as well 

as geologic heterogeneities and potential migration through faults, fractures, and artificial 

penetrations. 

Letter ID: 0234 Comment ID: 23163 Letter Lines: 105 to 117 

Comment Code: 3530 2.2.3.1 AoR reevaluation frequency (seeking comment) 

Comment: 2. AoR Reevaluation 

The proposed rule requires a re-evaluation of the AoR determination on a 

frequency not to exceed once every ten years. NRG agrees with the Carbon 

Sequestration Council’s recommended alternative approach to re-evaluate the AoR 

only when site specific operation and monitoring data suggest that there is a 

need for a new evaluation of the AoR. Periodic AoR re-evaluation will most 

likely be necessary given the enormous volumes of CO2 that would be injected 

into the subsurface, the lengthy timeframes likely for GS operations, and the 

potential uncertainty of the original model prediction. We believe that it is 

impractical and cost prohibitive to require re-evaluation of the AoR on a fixed 

schedule. Re-evaluation of the AoR should only be conducted when monitoring and 

testing data are determined to be inconsistent with the modeling results. 

Individual Response: EPA agrees that site-specific factors should be considered in the 

reevaluation schedule, and notes that the AoR and corrective action plan must specify the sitespecific monitoring and operational conditions that warrant reevaluation, as specified in 

§146.84(b)(2)(ii). 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. However, EPA believes that 

setting a minimum reevaluation frequency is appropriate. In the final rule, 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. 

EPA believes that periodic AoR reevaluation at a set frequency is necessary to ensure protection 

of USDWs from endangerment and address the uncertainties inherent in predictive modeling. 

Periodic AoR reevaluations at §146.84(e) ensure that a deliberate effort is made to verify, based 

on monitoring and operational data, that the CO2 plume is moving within the subsurface as 

predicted. EPA believes that less frequent reevaluations may not be sufficient to appropriately 

model plume and pressure front movement, establish conditions for corrective action, and ensure 

protection of USDWs from endangerment. 

4
EPA clarifies that if site monitoring data agrees with the existing AoR delineation, a model 

recalibration may not be necessary, and the AoR reevaluation may consist of a demonstration 

that the current AoR delineation is adequate based on site monitoring data. 

Letter ID: 0234 Comment ID: 23164 Letter Lines: 119 to 126 

Comment Code: 3630 2.2.4.1 Comments in favor of allowing phased corrective action 

Comment: 3. Corrective Action 

EPA proposes to allow a phased approach to corrective action for GS wells. NRG 

agrees that this approach is prudent and practical given the enormous volumes of 

CO2 that would be injected for a geologic sequestration project. Implementation 

of a phased corrective action to address risk associated with artificial 

penetrations such as plugged well borings would reduce project costs and also 

reduce the regulatory burdens of the permitting process. 

Individual Response: EPA acknowledges the commenter’s support of phased corrective action 

and agrees 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 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. 

Letter ID: 0234 Comment ID: 23165 Letter Lines: 128 to 145 

Comment Code: 3820 2.3.1 Well construction procedures 

Comment: Proposed Class VI Well Standards 

The proposed Class VI well construction requirements are as stringent as those 

for hazardous waste injection (Class I). NRG believes that this is not a logical 

or appropriate regulatory approach to ensure protection of USDWs. The injection 

of CO2 does not warrant the same level of regulations as hazardous waste 

injection. 

The primary issues associated with CO2 injection for GS are related to the 

enormous volumes and the mobility of CO2 in the subsurface. However, the Class 

VI requirements do not address these issues. These stringent well construction 

requirements will only increase the costs of operation resulting in no 

additional protection of USDWs. NRG agrees with the Carbon Sequestration 

Council’s recommendation to use the Class II regulations as a starting point for 

the development of the Class VI regulations. The oil and gas industry has 

several decades of CO2 injection experience with the Class II UIC program and 

5
has demonstrated that the construction requirements for Class II injections 

wells are sufficient to protect human health and the environment. 

Individual Response: EPA recognizes that the oil and gas industry has decades of experience 

injecting CO2 for the purpose of enhanced recovery and that many of the wells used for ER may 

be suitable for GS. However, EPA believes that GS is sufficiently different from Class II ER 

operations to warrant the tailored requirements for Class VI wells. EPA believes that the 

construction requirements for Class VI wells, along with other requirements, e.g., site 

characterization, are tailored to address the unique issues associated with large-scale GS and are 

necessary to protect USDWs from endangerment and that lesser standards could potentially 

endanger USDWs. EPA believes that the construction requirements most directly address 

corrosivity concerns, while the large volumes and the mobility of CO2 in the subsurface are 

addressed by the siting requirements at §146.83. 

For example, the volume of CO2 anticipated to be injected in Class VI wells is significantly 

greater than for Class II wells, and reservoir pressure conditions will be different, with Class VI 

injection operations involving large volumes of CO2 and likely having higher pressures within 

their storage formations than Class II ER projects. Therefore, Class VI GS reservoir pressures 

will increase more in comparison to Class II ER during the injection phase of the GS project. 

EPA acknowledges that the Class VI requirements have associated costs beyond baseline costs 

assumed in the cost analysis for this rule (based on an assumption that Class I industrial wells are 

the baseline). EPA believes that the requirements for Class VI wells provide multiple layers of 

USDW protection from endangerment that justify the cost of meeting the requirements. The 

Agency clarifies that the purpose of the 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. 

Letter ID: 0234 Comment ID: 23166 Letter Lines: 149 to 159 

Comment Code: 4110 2.4.1.1 Injection pressure limitations 

Comment: 1. Injection Pressure Limitations 

The proposed rule does not allow injection pressures that exceed 90% of the 

fracture pressure of the receiving formation. NRG believes that this rule of 

thumb would be an over protective requirement and would not be necessary for 

ensuring containment of CO2 in the receiving formation. The existing requirement 

under the UIC regulations for Class II wells allows injection pressure limits 

that are based on site-specific conditions (i.e., well tests and geomechanical 

studies) that have been proven to be effective in protecting the confining zone. 

We believe a standard similar to Class II injection wells would be appropriate 

for GS. 

Individual Response: EPA believes the operating requirements for Class VI wells, including the 

pressure limitation, are necessary to protect USDWs from endangerment by providing multiple 

6
safeguards to ensure that well integrity, containment of fluids within the injection zone, and the 

integrity of the confining zone. 

EPA emphasizes that injection pressure limits are important to protect against fracturing of the 

confining zone, and that the requirement at §146.88(a) that the pressure in the injection zone not 

exceed 90 percent of the fracture pressure provides a margin of safety in the well operation and 

protects USDWs from endangerment. 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. 

EPA notes that the pressure limitation at §146.88(a) accounts for site-specific conditions. 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. 

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: 0234 Comment ID: 23167 Letter Lines: 161 to 167 

Comment Code: 4520 2.5.1 Continuous internal mechanical integrity monitoring (seeking 

comment) 

Comment: 2. Continuous Monitoring 

NRG supports continuous monitoring of the annular and injection pressure for 

well integrity purposes. However, the proposed requirement for continuous 

monitoring of the annular fluid volume is impractical and unnecessary. We 

recommend continuous measurement of the annular pressure as a means of leak 

detection instead of the annual fluid volume. 

Individual Response: EPA believes that monitoring of annulus fluid volume is an important 

method for verifying that the well system is intact, and knowing the annulus fluid volume is 

necessary for monitoring annulus pressure. While this requirement has until now been limited to 

Class I hazardous waste injection wells, the high volumes and supercritical nature of the 

injectate, the potential geomechanical stresses in the wellbore, and the potential for movement of 

the buoyant CO2 in the event of a MI loss make it an important safety consideration for GS 

7
projects. Continuous pressure monitoring allows immediate identification of corrosion-related 

well integrity loss. EPA agrees with the commenter that recording annulus fluid volume may not 

be appropriate. However, EPA believes that knowing annulus fluid volume as required at 

§146.88(e) is a necessary component of monitoring well mechanical integrity, but believes that 

knowing the annulus fluid volume added is sufficient to meet the intent of the requirement. The 

final GS rule requires that owners or operators use continuous recording devices to monitor 

injection pressure, rate and volume; as well as the pressure on the annulus between the tubing 

and the long string casing. It also modifies the requirement in the proposed rule to continuously 

monitor annulus fluid volume; it now requires recording of annulus fluid volume added. See 

§§146.88(e); 146.89(b); and 146.90(b). 

Fluid level can be detected using acoustic techniques (Schubert, 1998). The Texas Class I well 

regulations for industrial wells currently require continuous monitoring of annulus pressure and 

volume, and the majority of injection wells in Ohio conduct continuous monitoring (GWPC, 

2006). At least one commenter indicated that the technology required for continuous monitoring 

is currently available and should not present an undue cost burden. Continuous annulus 

monitoring is also conducted at the commercial-scaled carbon capture and geologic sequestration 

operation at the In Salah, Algeria natural gas plant where more than 3 million tons of CO2 have 

been sequestered since 2004. The technology for continuous monitoring is available, is currently 

in fairly wide use, and the costs are not burdensome, especially given the operational and safety 

considerations addressed. 

Letter ID: 0234 Comment ID: 23168 Letter Lines: 169 to 177 

Comment Code: 4490 2.4.5 Use of tracers and potential impact on human health or ecosystems 

(seeking comment) 

Comment: 3. Tracers 

NRG opposes any requirement to use tracers for leak detection because leaks from 

properly permitted injection wells are not likely to occur. The use of tracers 

will not be effective in the detection of CO2 releases in the subsurface and 

will not ensure the protection of USDWs. Tracers are more likely to cause "false 

positives" by accidental leaks from the equipment on the surface. The Class VI 

regulations are designed to prevent the kind of leakage that the tracers are 

intended to detect. 

Individual Response: EPA believes that, in some circumstances, tracers can be an important 

component of a multifaceted approach to monitoring GS projects. However, the Agency 

recognizes that tracers may not be appropriate in all GS projects. 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. 

While the intent of the GS regulations is to prevent leaks of CO2 to USDWs, EPA clarifies that 

all of the protective components of the regulation, including a comprehensive monitoring 

8
program per §146.90 (which includes testing of the well, ground water quality monitoring, and 

tracking of the CO2 plume and pressure front) support a multi-barrier approach to protecting 

USDWs. Additionally, some studies (e.g., Phelps and Cole, 2008; Hovorka et al., 2004; 

McCallum et al., 2005) found that tracers can provide useful CO2 monitoring information at 

injection wells both at depth and at near-surface locations. At Frio, tracers enabled quantification 

of CO2 plume behavior and provided a technique for model validity testing (McCallum et al., 

2005). EPA will continue to track research related to tracer use. The Agency 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: 0234 Comment ID: 23169 Letter Lines: 179 to 187 

Comment Code: 4600 2.6 Proposed Plume and Pressure Front Monitoring Requirements (40 

CFR 146.90) 

Comment Code: 4660 2.6.6 Geochemical monitoring 

Comment: Monitoring Requirements 

The preamble of the proposed rule states that the "monitoring of subsurface 

geochemistry and the position of the CO2 plume and pressure front are necessary 

to verify predictions of plume movement, provide inputs for modeling, identify 

needed corrective actions, and target geochemical and surface monitoring 

activities." 73 Fed. Reg. at 43514. NRG believes that the proposed monitoring 

requirements are excessive and unjustified. The use of monitor wells or seismic 

data would be needed to verify the model predictions. In particular, it is 

Individual Response: EPA disagrees that the monitoring requirements in the GS rule are 

excessive or unjustified. In addition to monitoring to track the movement of the CO2 plume and 

pressure front, EPA believes that monitoring above the confining layer is an important part of a 

rigorous monitoring program. Such monitoring can provide an early warning that the plume may 

be approaching a USDW. The final rule, at §146.90(d), requires periodic monitoring of the 

ground water quality and geochemical changes above the confining zone(s). EPA also believes 

that geophysical (e.g., seismic) methods are useful for plume tracking at GS sites. For this 

reason, the final rule at §146.90(g) requires the use of 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 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. 

9
EPA also acknowledges that complete coverage of the potential plume area or leakage in the 

subsurface is not possible through the use of monitoring wells. However, data from an 

appropriate number of monitoring wells sited based on site-specific information will provide 

direct information that is not otherwise obtainable and, along with other monitoring data, will 

support a broader understanding of fluid behavior at the site. 

EPA adds that the iterative process of monitoring, modeling, and 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 warning of potential problems at the site before any 

endangerment could occur. 

Letter ID: 0234 Comment ID: 23170 Letter Lines: 187 to 193 

Comment Code: 4650 2.6.5 CO2 plume and pressure front tracking (seeking comment) 

Comment: data would be needed to verify the model predictions. In particular, it is 

impractical and cost prohibitive to measure the exact location of the CO2 plume 

and pressure front using monitor wells. The monitor wells would be very 

expensive to install and may create a potential pathway for migration of CO2. In 

addition, plume or pressure front monitoring have never been necessary or 

required under the Class I hazardous waste injection well program because 

experience has shown that it is not necessary to verify the model predictions. 

Individual Response: EPA believes that pressure monitoring in the injection zone is necessary 

to track the development and movement of the pressure front and CO2 plume. Monitoring can 

also identify needed remedial actions, provide inputs for AoR reevaluation modeling, evaluate 

predictions of plume movement, and target additional geochemical and surface monitoring 

needs. Knowledge of the location of the CO2 plume and the associated pressure front will also 

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. 

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. 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. 

10
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 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. 

EPA acknowledges the commenters' concern about the cost of monitoring. However, EPA 

believes that monitoring is essential for protection of USDWs at GS sites. Although a significant 

cost in absolute terms, monitoring costs are expected to be a small fraction of site operating 

costs, according to EPA's cost analysis for the GS rulemaking (which is available in the docket). 

Letter ID: 0234 Comment ID: 23171 Letter Lines: 181 to 193 

Comment Code: 4600 2.6 Proposed Plume and Pressure Front Monitoring Requirements (40 

CFR 146.90) 

Comment: The preamble of the proposed rule states that the "monitoring of subsurface 

geochemistry and the position of the CO2 plume and pressure front are necessary 

to verify predictions of plume movement, provide inputs for modeling, identify 

needed corrective actions, and target geochemical and surface monitoring 

activities." 73 Fed. Reg. at 43514. NRG believes that the proposed monitoring 

requirements are excessive and unjustified. The use of monitor wells or seismic 

data would be needed to verify the model predictions. In particular, it is 

impractical and cost prohibitive to measure the exact location of the CO2 plume 

and pressure front using monitor wells. The monitor wells would be very 

expensive to install and may create a potential pathway for migration of CO2. In 

addition, plume or pressure front monitoring have never been necessary or 

required under the Class I hazardous waste injection well program because 

experience has shown that it is not necessary to verify the model predictions. 

Individual Response: EPA disagrees that plume and pressure front monitoring are not justified 

for Class VI wells. The Agency recognizes that while there are similarities between injection of 

wastes for disposal (Class I) and GS, there are significant differences as well. Important unique 

considerations for GS include the buoyancy of CO2, its corrosivity when in contact with water, 

its low viscosity (i.e., high mobility), and the very large injection volumes that are anticipated. 

There is also a degree of uncertainty regarding the behavior of large volumes of CO2 in the 

subsurface. Given these characteristics of anticipated GS projects, EPA believes that plume and 

pressure front monitoring at §146.90(g) are justified to provide early warning of any unforeseen 

fluid movement that might endanger USDWs. 

11
The final rule at §146.90(g) requires owners or operators to perform monitoring to track the 

extent of the CO2 plume and pressure front. The owner or operator must use direct methods to 

monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, 

gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are required unless 

the Director determines, based on site-specific geology that such methods are not appropriate. 

EPA believes that pressure monitoring in the injection zone is necessary to track the 

development and movement of the pressure front and CO2 plume. Knowledge of the location of 

the CO2 plume and the associated pressure front will also 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. 

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. 

§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. For example, geophysical methods are difficult to execute in areas that are 

structurally and topographically complex or where lithologies have limited contrast in density, 

porosity, permeability, and other physical properties. EPA clarifies that this determination will 

be made by the Director based on the site-specific geologic information submitted by the owner 

or operator with the permit application. 

EPA believes that this approach provides flexibility to develop a site-specific monitoring plan, 

ensures that direct monitoring is available to track the movement of the CO2 and validate 

models, and recognizes that indirect techniques are not appropriate in all situations. The owner or 

operator's approved testing and monitoring plan will include the site-specific details, 

technologies, testing and monitoring frequencies, and other pertinent information. 

EPA also acknowledges that complete coverage of the potential plume area or leakage in the 

subsurface is not possible through the use of monitoring wells. However, data from an 

appropriate number of monitoring wells sited based on site-specific information will provide 

direct information that is not otherwise obtainable and, along with other monitoring data, will 

support a broader understanding of fluid behavior at the site. 

Letter ID: 0234 Comment ID: 23172 Letter Lines: 195 to 203 

Comment Code: 5430 2.9.1 Comments on proposed financial responsibility requirements (40 

12
CFR 146.85) 

Comment: Financial Assurance 

NRG commends the EPA for allowing flexibility on financial assurance for GS 

wells. Allowing flexibility will enable operators to use a combination of 

approaches and instruments to meet the financial requirements over the life of 

the injection well operation. We believe that it would be a mistake to impose 

any restrictions on the types of financial assurance or instruments that can be 

used for GS wells. We recommend that this approach be retained in the final 

rule. 

Individual Response: EPA agrees that it is appropriate to allow a flexible approach for financial 

responsibility, which is why owners or operators may choose from a variety of financial 

instruments to meet their financial responsibility obligations, provided the Director determines 

that the operator's proposed financial responsibility demonstration is adequate to prevent USDW 

endangerment by paying 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. The allowable instruments are identified at 

§146.85(a). 

Owners or operators may select and use multiple instruments for specific project activities. See 

the final rule and preamble for further discussion of EPA's final approach to financial 

responsibility. EPA also anticipates that the availability of third-party GS financial instruments 

will grow in response to demand for such instruments by Class VI well owners or operators. 

Letter ID: 0234 Comment ID: 23173 Letter Lines: 205 to 220 

Comment Code: 1630 1.3.3 RCRA/hazardous waste issues (seeking comment) 

Comment: RCRA Applicability 

The preamble of the proposed rule suggests that CO2 injected for GS projects may 

be considered hazardous waste for RCRA purposes. 73 Fed. Reg. at 43503. EPA’s 

brief discussion of the potential for injected CO2 streams to be characterized 

as hazardous waste are causing concern among the electric power industry and 

could have an effect on the future development of carbon capture and 

sequestration projects. The premise that CO2 could be characterized as a 

hazardous waste would likely prove detrimental to project development. The RCRA 

definition of "solid waste" is limited to "solid, liquid, semi-solid, or 

contained gaseous material." RCRA 1004(27). Because the gas and liquid 

(supercritical) phases involved in GS do not meet this definition, reading of 

federal law would suggests that the CO2 stream for GS should not be considered 

a "solid waste". EPA should clarify that the gas and liquid phases of the CO2 

stream is not a solid or hazardous waste for RCRA purposes and therefore not 

subject to RCRA waste determination requirements. 

13
Individual Response: EPA received many comments regarding the applicability of the RCRA 

regulations and statute to CO2 streams that are geologically sequestered under the final Class VI 

UIC well requirements. As a result, EPA has decided to initiate a separate proposed rulemaking 

specifically to examine the issue of RCRA applicability to CO2 streams being geologically 

sequestered, including the possible option of a conditional exemption from the RCRA 

requirements for CO2 GS in Class VI wells. EPA will consider these comments as part of its 

development of that proposal. The Agency will consider issues particular to RCRA in the context 

of that separate rulemaking, and recommends that the commenter read that proposed rule when it 

is published. The Agency notes that commenters who wish to submit comments on the RCRA 

proposal will need to do so during the comment period for that rule. 

Furthermore, EPA disagrees that the Class VI requirements themselves, necessarily have any 

implications for whether a particular material is a RCRA “solid waste” or implicates CERCLA 

liability, as EPA understands the comment to suggest. EPA notes that the GS rule is not 

promulgated under either of those statues, and further, the applicability of those statutes will not 

be determined under the SDW or the terms of the GS rule, but rather according to those statues 

themselves and any implementing regulations may apply. 

EPA adds that promoting the use of GS is outside the scope of the GS rule. Rather, the purpose 

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

USDWs from endangerment. 

Letter ID: 0234 Comment ID: 23174 Letter Lines: 222 to 245 

Comment Code: 1640 1.3.4 CERCLA issues (seeking comment) 

Comment: CERCLA Applicability 

The preamble of the proposed rule suggests that CERCLA liability may arise out 

of CO2 GS projects due to "potential USDW impacts", presence of impurities in 

the stream, and the potential for reaction products to migrate from the 

injection zone. 73 Fed. Reg. 43492, 43497 (July 25, 2008). EPA also states that 

(CERCLA exempts from liability certain "federally permitted releases" including 

releases in compliance with a UIC permit under SDWA. Therefore, 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.) 73 Fed. Reg. at 43504. 

EPA’s suggestion that CERCLA liability may apply to CO2 GS projects raises 

concern among the electric power industry. Because EPA raised this as a 

potential issue, businesses and investors may be reluctant to support GS 

projects faced with a potential for CERCLA liability hanging over their heads. 

In order to prevent any discouragement of development in CO2 GS projects, EPA 

14
15

should provide confirmation in the final regulations that injection of CO2 into 

a permitted injection zone does not constitute a "release" for purposes of RCRA 

or CERCLA. EPA should also take the opportunity to dispel the CERCLA liability 

concerns by developing appropriate language to provide the clarity and assurance 

needed to promote continued research, development and deployment of CO2 GS 

projects. 

Individual Response: EPA notes that the GS rule is not promulgated under the RCRA or 

CERCLA statutes, and further, the applicability of those statutes will not be determined under 

the SDWA or the terms of the GS rule, but rather according to those statutes themselves and any 

implementing regulations that may apply EPA received many comments regarding the 

applicability of the RCRA regulations and statute to CO2 streams that are geologically 

sequestered under the final Class VI UIC well requirements. As a result, EPA has decided to 

initiate a separate proposed rulemaking specifically to examine the issue of RCRA applicability 

to CO2 streams being geologically sequestered, including the possible option of a conditional 

exemption from the RCRA requirements for CO2 GS in Class VI wells. EPA will consider these 

comments as part of its development of that proposal. The Agency will consider issues particular 

to RCRA in the context of that separate rulemaking, and recommends that the commenter read 

that proposed rule when it is published. The Agency notes that commenters who wish to submit 

comments on the RCRA proposal will need to do so during the comment period for that rule. 

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 

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. 

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 adds that promoting the use of GS is outside the scope of the GS rule. Rather, the purpose 

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

USDWs from endangerment.