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.
Docket ID No. EPA–HQ–OW–2008–0390 

 December 24, 2008 

UNDERGROUND INJECTION TECHNOLOGY GROUP 

700 13th Street, N.W. 

Suite 700 

Washington, DC 20005-3960 

COMMENTS OF THE 

UNDERGROUND INJECTION TECHNOLOGY GROUP 

ON EPA’s PROPOSED GEOLOGIC SEQUESTRATION RULE

The Underground Injection Technology Group (UIT Group) submits these comments on the 

proposed rule for geologic sequestration of carbon dioxide under the Safe Drinking Water Act 

(SDWA), "Federal Requirements Under the Underground Injection Control (UIC) Program for 

Carbon Dioxide (CO2) Geologic Sequestration (GS) Wells", 73 Fed. Reg. 43491-541 (July 25, 

2008), Docket ID No. EPA–HQ–OW–2008–0390. The UIT Group is an association of 

underground injection well operators, and the members operate underground injection wells in a 

number of different UIC classes, including Class I. 

UIT Group members have no immediate plans to inject carbon dioxide for geologic sequestration 

purposes, but nevertheless have two significant issues with respect to the proposed rule. The 

first issue relates to the subject of aquifer exemptions, as discussed in the proposed rule at 73 

Fed. Reg. 43492 at 43512 (July 25, 2008). The second relates to the overall stringency of the 

rule, particularly with respect to monitoring requirements. These issues – and the UIT Group’s 

interest in them – are discussed in turn below. 

COMMENTS

A. Aquifer Exemptions

The Safe Drinking Water Act charged EPA with the responsibility to prevent underground 

injection that "endangers drinking water sources." 42 U.S.C. §300h. EPA has undertaken this 

mission with zeal and remarkable success. EPA’s aggressive regulatory scheme starts with a 

consciously overbroad definition of the range of aquifers to be protected. Indeed, EPA’s 

regulatory definition of "underground source of drinking water" (or "USDW") is not limited to 

aquifers that are or could reasonably be expected to serve as drinking water sources, but includes 

all aquifers capable of producing minimum amounts of water that contain less than 10,000 mg/l 

total dissolved solids. 40 C.F.R. §144.3. Recognizing the overbreadth of its basic "USDW" 

definition, EPA provided an "aquifer exemption" mechanism under which aquifers can be 

excluded from that definition on a case-by-case basis if they meet criteria designed to ensure that 

they are not and cannot reasonably be expected to serve as drinking water sources. 40 C.F.R. 

§§144.7, 146.4. The aquifer exemption mechanism thus provides the means by which aquifers 

that will not really be drinking water sources – and thus do not warrant protection from 

Underground Injection Technology Group 1 bdday@bryancave.com 
Docket ID No. EPA–HQ–OW–2008–0390 

 December 24, 2008 

"endangerment" under the Safe Drinking Water Act – can be excluded from EPA’s otherwise 

overbroad "USDW" definition. 

Unfortunately – as the preamble to the proposed rule notes – the aquifer exemption process has 

effectively been disabled in certain contexts. In particular, EPA – relying on "policies" that lack 

any basis in law or regulation – has generally refused to consider aquifer exemption requests for 

non-injection formations or for hazardous waste injection. 73 Fed. Reg. at 43512. Rather than 

preventing underground injection that "endangers drinking water sources" as the statute requires, 

this approach arbitrarily prevents injection that does not endanger any drinking water sources; in 

effect, it requires the protection of aquifers that are not worthy of protection – and that EPA may 

not even be authorized to protect – under the Safe Drinking Water Act. 

The "policy" banning aquifer exemptions for hazardous waste injection is inappropriate and 

lacks any reasonable basis. If a formation is not a drinking water source, it does not warrant 

protection under the Safe Drinking Water Act and should not be considered a "USDW." The fact 

that hazardous waste injection is involved has nothing to do with whether the aquifer is 

legitimately a drinking water source, and – far from being considered a determinative factor – it 

should not be considered in the aquifer exemption context at all. The fact that hazardous waste 

injection is involved certainly should not preclude any consideration of the technical merits of an 

aquifer exemption request, yet that is precisely the effect of EPA’s existing "policy" (which 

really amounts to an uncodified rule). 

The situation is no different with respect to the "policy" against aquifer exemptions for noninjection formations. Because several categories of injection (hazardous waste injection being 

but one) must occur below the lowermost USDW, aquifer exemptions for non-injection 

formations can be necessary in order for injection into overlying injection zones to occur. In this 

situation, there is no reason to foreclose any merits-based consideration of whether the noninjection formation is legitimately a source of drinking water. Either the formation is 

legitimately a source of drinking water or it is not; the fact that the formation is or is not intended 

for use as an injection zone – far from being the determinative factor EPA’s "policy" makes it – 

has no proper relevance at all. 

The existing regulations for aquifer exemptions are specific and detailed. See 40 C.F.R. §§144.7 

and 146.4. These regulations do not include any rules precluding aquifer exemptions for noninjection formations or for hazardous waste injection, nor do they provide any basis for EPA to 

impose such rules in the guise of "policy." In the proposed rule, EPA has requested comment on 

whether and how it should apply its aquifer exemption rules in the context of geologic 

sequestration, asking in particular whether it should effectively overturn its policy against aquifer 

exemptions for non-injection formations. 73 Fed. Reg. at 43512. The UIT Group urges EPA to 

recognize the critical role aquifer exemptions should play in harmonizing the regulatory 

definition of "USDW" with the Safe Drinking Water Act’s directive that EPA develop 

regulations preventing injection that endangers drinking water sources. EPA’s policies disabling 

the aquifer exemption process for hazardous waste injection and non-injection formations are 

arbitrary, and by definition they are unnecessary for the protection of drinking water sources. 

Accordingly, they should be abandoned so that the aquifer exemption rules can be applied as 

Underground Injection Technology Group 2 bdday@bryancave.com 
Docket ID No. EPA–HQ–OW–2008–0390 

 December 24, 2008 

written. This approach would be appropriate for all classes of injection wells, including wells 

used for geologic sequestration of carbon dioxide. Without this change, it is entirely illusory to 

suggest that the aquifer exemption process could provide any means for ameliorating EPA's 

unnecessary limitation of geological sequestration to formations below the lowermost USDW. 

B. Stringency of the Proposed Rule

The UIT Group is concerned by the overall level of stringency of the proposed requirements for 

Class VI injection wells. Carbon dioxide is among the most innocuous materials injected under 

the UIC program, and yet the proposed rules for carbon dioxide injection would be among the 

most elaborate and burdensome in the entire UIC program. This approach is incongruous at best, 

and certainly seems ill-suited to the goal of encouraging responsible development of geologic 

sequestration projects. However, the UIT Group’s specific concern is that the proposed Class VI 

regulations are so excessive in some respects that they could effectively undermine public 

confidence in the UIC program for other classes of injection wells, including Class I injection 

wells. 

The UIT Group is particularly concerned with the proposed Class VI monitoring requirements, 

which are based upon the premise that it is necessary to track the physical location of injected 

fluids and observationally “verify” that USDWs are not being endangered. These requirements 

would appear to make elaborate monitoring through the use of monitor wells or indirect 

geophysical “plume tracking” techniques mandatory for all geologic sequestration projects. In 

general, it simply isn’t true that this kind of monitoring is necessary, and – again as a general 

rule – such monitoring would be burdensome, costly, and of limited utility. 

Any discussion of monitor well requirements must start with an understanding of how the UIC 

program works: injection can’t even commence unless there has been an adequate demonstration 

that the injection zone is separated from USDWs by a confining zone sufficient to prevent the 

movement of fluids from the injection zone into a USDW. Operators of hazardous waste 

injection wells must go a step further: they must demonstrate – to a reasonable degree of 

certainty – that there will be no migration of hazardous constituents from the injection zone for 

as long as the waste remains hazardous. 

Decades of experience with Class I injection has demonstrated that this regulatory approach is 

effective: under current regulatory standards, injection-related contamination of USDWs is 

virtually unknown, and EPA itself has concluded – after reviewing a broad range of studies – 

that properly-permitted Class I injection wells “provide an extremely low-risk” waste 

management option. See Class I Underground Injection Control Program: Study of the Risks 

Associated with Class I Underground Injection Wells (EPA, March 2001) at p. 42. In the face of 

such well-documented success it is difficult to see why there should be any crisis of confidence 

sufficient to justify the suggestion that the required “up-front” technical evaluation and controls 

on injection activity are somehow so unreliable that elaborate monitoring to track injected fluids 

and “verify” non-endangerment is necessary and should be required in every case. 

Underground Injection Technology Group 3 bdday@bryancave.com 
Docket ID No. EPA–HQ–OW–2008–0390 

 December 24, 2008 

Underground Injection Technology Group 4 bdday@bryancave.com 

It would be one thing if the kind of monitoring at issue were relatively easy and cost-effective, 

but it is not. In the deep subsurface, such monitoring is difficult, costly, and generally yields 

relatively limited information. Accordingly, while there may be specific circumstances under 

which the use of monitor wells or indirect geophysical methods can make sense, it is important 

to consider both the potential utility of such monitoring and the burdens and technical challenges 

involved, as the regulations for Class I hazardous waste injection wells reflect. To suggest that 

elaborate monitoring efforts should be mandatory at every site, as the proposed Class VI 

regulations appear to suggest, is unjustified and does disservice to the demonstrated effectiveness 

and success of the detailed site selection, characterization and pre-injection technical evaluation 

the UIC program requires. 

CONCLUSION

For the reasons presented herein, the UIT Group urges EPA to revise its purported “policies” 

with respect to aquifer exemptions to eliminate all existing restrictions on the availability of 

aquifer exemptions that the regulations themselves do not impose. The UIT Group also urges 

EPA to: (1) acknowledge the demonstrated and well-documented success of the existing UIC 

program regulations for Class I hazardous waste injection wells; and (2) avoid regulatory 

excesses in the proposed rule that could potentially undermine public confidence in the 

established effectiveness of the Class I regulations and the requirements for other UIC classes of 

wells. 

Respectfully submitted, 

Robert F. Van Voorhees 

Barton D. Day 

Counsel to the Underground Injection Technology Group 

Bryan Cave LLP 

700 Thirteenth Street, N.W. 

Suite 700 

Washington, D.C. 20005-3960 

Phone: 202.508.6014 

Fax: 202.220.7314 

rfvanvoorhees@bryancave.com 

bdday@bryancave.com 
Letter ID: 0243 

Commenter: Robert F. Voorhees 

Organization: Underground Injection Technology Group (UIT Group) 

Letter ID: 0243 Comment ID: 23338 Letter Lines: 43 to 118 

Comment Code: 4460 2.4.4.4.1 Comments in favor of allowing aquifer exemptions in certain 

circumstances 

Comment: A. Aquifer Exemptions 

The Safe Drinking Water Act charged EPA with the responsibility to prevent 

underground injection that "endangers drinking water sources." 42 U.S.C. §300h. 

EPA has undertaken this mission with zeal and remarkable success. EPA’s 

aggressive regulatory scheme starts with a consciously overbroad definition of 

the range of aquifers to be protected. Indeed, EPA’s regulatory definition of 

"underground source of drinking water" (or "USDW") is not limited to aquifers 

that are or could reasonably be expected to serve as drinking water sources, but 

includes all aquifers capable of producing minimum amounts of water that contain 

less than 10,000 mg/l total dissolved solids. 40 C.F.R. §144.3. Recognizing 

the overbreadth of its basic "USDW" definition, EPA provided an "aquifer 

exemption" mechanism under which aquifers can be excluded from that definition 

on a case-by-case basis if they meet criteria designed to ensure that they are 

not and cannot reasonably be expected to serve as drinking water sources. 40 

C.F.R. §§144.7, 146.4. The aquifer exemption mechanism thus provides the means 

by which aquifers that will not really be drinking water sources - and thus do 

not warrant protection from "endangerment" under the Safe Drinking Water Act - 

can be excluded from EPA’s otherwise overbroad "USDW" definition. 

Unfortunately - as the preamble to the proposed rule notes - the aquifer 

exemption process has effectively been disabled in certain contexts. In 

particular, EPA - relying on "policies" that lack any basis in law or regulation 

- has generally refused to consider aquifer exemption requests for non-injection 

formations or for hazardous waste injection. 73 Fed. Reg. at 43512. Rather 

than preventing underground injection that "endangers drinking water sources" as 

the statute requires, this approach arbitrarily prevents injection that does not 

endanger any drinking water sources; in effect, it requires the protection of 

aquifers that are not worthy of protection - and that EPA may not even be 

authorized to protect - under the Safe Drinking Water Act. 

The "policy" banning aquifer exemptions for hazardous waste injection is 

inappropriate and lacks any reasonable basis. If a formation is not a drinking 

water source, it does not warrant protection under the Safe Drinking Water Act 

and should not be considered a "USDW." The fact that hazardous waste injection 

is involved has nothing to do with whether the aquifer is legitimately a 

1
drinking water source, and - far from being considered a determinative factor - 

it should not be considered in the aquifer exemption context at all. The fact 

that hazardous waste injection is involved certainly should not preclude any 

consideration of the technical merits of an aquifer exemption request, yet that 

is precisely the effect of EPA’s existing "policy" (which really amounts to an 

uncodified rule). 

The situation is no different with respect to the "policy" against aquifer 

exemptions for non-injection formations. Because several categories of 

injection (hazardous waste injection being but one) must occur below the 

lowermost USDW, aquifer exemptions for non-injection formations can be necessary 

in order for injection into overlying injection zones to occur. In this 

situation, there is no reason to foreclose any merits-based consideration of 

whether the non-injection formation is legitimately a source of drinking water. 

Either the formation is legitimately a source of drinking water or it is not; 

the fact that the formation is or is not intended for use as an injection zone - 

far from being the determinative factor EPA’s "policy" makes it - has no proper 

relevance at all. 

The existing regulations for aquifer exemptions are specific and detailed. See 

40 C.F.R. §§144.7 and 146.4. These regulations do not include any rules 

precluding aquifer exemptions for non-injection formations or for hazardous 

waste injection, nor do they provide any basis for EPA to impose such rules in 

the guise of "policy." In the proposed rule, EPA has requested comment on 

whether and how it should apply its aquifer exemption rules in the context of 

geologic sequestration, asking in particular whether it should effectively 

overturn its policy against aquifer exemptions for non-injection formations. 73 

Fed. Reg. at 43512. The UIT Group urges EPA to recognize the critical role 

aquifer exemptions should play in harmonizing the regulatory definition of 

"USDW" with the Safe Drinking Water Act’s directive that EPA develop regulations 

preventing injection that endangers drinking water sources. EPA’s policies 

disabling the aquifer exemption process for hazardous waste injection and noninjection formations are arbitrary, and by definition they are unnecessary for 

the protection of drinking water sources. Accordingly, they should be abandoned 

so that the aquifer exemption rules can be applied as written. This approach 

would be appropriate for all classes of injection wells, including wells used 

for geologic sequestration of carbon dioxide. Without this change, it is 

entirely illusory to suggest that the aquifer exemption process could provide 

any means for ameliorating EPA's unnecessary limitation of geological 

sequestration to formations below the lowermost USDW. 

Individual Response: EPA disagrees that the Agency’s policy regarding aquifer exemptions is 

either arbitrary or lacking any basis in law or regulation. EPA acknowledges that there are 

limited circumstances where aquifer exemptions for GS may be warranted. The final 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). 

2
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. 

However, the final rule precludes the issuance of new aquifer exemptions for Class VI GS wells; 

that is, aquifer exemptions will only be granted for projects that are transitioning from Class II 

EOR/EGR wells to Class VI. 

EPA clarifies that the final GS rule is not changing existing Agency policy. Rather 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 and 

protecting 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 adds that 

comments related to aquifer exemptions for injection of hazardous waste are outside the scope of 

the GS rulemaking. 

This approach is designed to ensure that the differences between traditional Class II EOR/EGR 

operations and Class VI operations are considered during the aquifer exemption application 

process and the Class VI permitting process. These differences include the anticipated large CO2 

injection volumes associated with GS, the buoyant and mobile nature of the injectate, and its 

corrosivity in the presence of water. The Agency believes that this process will encourage 

owners or operators and Directors to consider the use of alternative formations for GS, including 

non-USDW formations through the waiver process, prior to applying for or approving aquifer 

exemption expansions for Class II EOR/EGR wells transitioning to Class VI GS operations. 

For additional information on 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: 0243 Comment ID: 23339 Letter Lines: 120 to 176 

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

CFR 146.90) 

Comment: B. Stringency of the Proposed Rule 

The UIT Group is concerned by the overall level of stringency of the proposed 

requirements for Class VI injection wells. Carbon dioxide is among the most 

innocuous materials injected under the UIC program, and yet the proposed rules 

for carbon dioxide injection would be among the most elaborate and burdensome in 

the entire UIC program. This approach is incongruous at best, and certainly 

seems ill-suited to the goal of encouraging responsible development of geologic 

sequestration projects. However, the UIT Group’s specific concern is that the 

3
proposed Class VI regulations are so excessive in some respects that they could 

effectively undermine public confidence in the UIC program for other classes of 

injection wells, including Class I injection wells. 

The UIT Group is particularly concerned with the proposed Class VI monitoring 

requirements, which are based upon the premise that it is necessary to track the 

physical location of injected fluids and observationally "verify" that USDWs are 

not being endangered. These requirements would appear to make elaborate 

monitoring through the use of monitor wells or indirect geophysical "plume 

tracking" techniques mandatory for all geologic sequestration projects. In 

general, it simply isn't true that this kind of monitoring is necessary, and - 

again as a general rule - such monitoring would be burdensome, costly, and of 

limited utility. 

Any discussion of monitor well requirements must start with an understanding of 

how the UIC program works: injection can't even commence unless there has been 

an adequate demonstration that the injection zone is separated from USDWs by a 

confining zone sufficient to prevent the movement of fluids from the injection 

zone into a USDW. Operators of hazardous waste injection wells must go a step 

further: they must demonstrate - to a reasonable degree of certainty - that 

there will be no migration of hazardous constituents from the injection zone for 

as long as the waste remains hazardous. 

Decades of experience with Class I injection has demonstrated that this 

regulatory approach is effective: under current regulatory standards, injectionrelated contamination of USDWs is virtually unknown, and EPA itself has 

concluded - after reviewing a broad range of studies - that properly-permitted 

Class I injection wells "provide an extremely low-risk" waste management option. 

See Class I Underground Injection Control Program: Study of the Risks Associated 

with Class I Underground Injection Wells (EPA, March 2001) at p. 42. In the 

face of such well-documented success it is difficult to see why there should be 

any crisis of confidence sufficient to justify the suggestion that the required 

"up-front" technical evaluation and controls on injection activity are somehow 

so unreliable that elaborate monitoring to track injected fluids and "verify" 

non-endangerment is necessary and should be required in every case. 

It would be one thing if the kind of monitoring at issue were relatively easy 

and cost-effective, but it is not. In the deep subsurface, such monitoring is 

difficult, costly, and generally yields relatively limited information. 

Accordingly, while there may be specific circumstances under which the use of 

monitor wells or indirect geophysical methods can make sense, it is important to 

consider both the potential utility of such monitoring and the burdens and 

technical challenges involved, as the regulations for Class I hazardous waste 

injection wells reflect. To suggest that elaborate monitoring efforts should 

be mandatory at every site, as the proposed Class VI regulations appear to 

suggest, is unjustified and does disservice to the demonstrated effectiveness 

4
and success of the detailed site selection, characterization and pre-injection 

technical evaluation the UIC program requires. 

Individual Response: EPA disagrees that monitoring at GS sites will undermine public 

confidence in GS and the UIC Program. EPA believes that appropriately designed and 

implemented monitoring plans will increase public confidence in the safety of GS, helping to 

assure the public that any problems are detected early and that appropriate measures are taken to 

protect USDWs from endangerment. Knowledge of the location of the CO2 plume and the 

associated pressure front will enable EPA to 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 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 (Class VI), 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 after injection. 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. 

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. 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. 

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 is affording Director's discretion regarding the use of 

geophysical techniques at some sites because the Agency recognizes that geophysical methods 

are not appropriate in all geologic settings. 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 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, 

5
technologies, testing and monitoring frequencies, and other pertinent information. 

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: 0243 Comment ID: 23340 Letter Lines: 128 to 131 

Comment Code: 1680 1.3.8 Don't overstate risk, don't stigmatize CO2 

Comment: sequestration projects. However, the UIT Group’s specific concern is that the 

proposed Class VI regulations are so excessive in some respects that they could 

effectively undermine public confidence in the UIC program for other classes of 

injection wells, including Class I injection wells. 

Individual Response: EPA disagrees that the GS regulation overstates the risk of CO2 injection 

or that it is excessive. EPA recognizes that injecting large volumes of CO2 for GS poses unique 

challenges that, if not properly managed, could endanger drinking water sources and have other 

adverse impacts. However, 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, 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. 

EPA also disagrees that the tailored requirements will create a negative public perception of GS. 

The Agency believes that a demonstration to the public that GS projects are meeting the GS 

rule's tailored requirements would likely improve confidence in the project and help address 

public questions and concerns. 

Letter ID: 0243 Comment ID: 23341 Letter Lines: 180 to 183 

Comment Code: 4460 2.4.4.4.1 Comments in favor of allowing aquifer exemptions in certain 

circumstances 

Comment: For the reasons presented herein, the UIT Group urges EPA to revise its 

purported "policies" with respect to aquifer exemptions to eliminate all 

existing restrictions on the availability of aquifer exemptions that the 

regulations themselves do not impose. The UIT Group also urges EPA to: (1) 

Individual Response: As described above, EPA clarifies that the final GS rule is not changing 

existing Agency policy. Rather 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 

6
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. 

Letter ID: 0243 Comment ID: 23342 Letter Lines: 183 to 188 

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

CFR 146.90) 

Comment: regulations themselves do not impose. The UIT Group also urges EPA to: (1) 

acknowledge the demonstrated and well-documented success of the existing UIC 

program regulations for Class I hazardous waste injection wells; and (2) avoid 

regulatory excesses in the proposed rule that could potentially undermine public 

confidence in the established effectiveness of the Class I regulations and the 

requirements for other UIC classes of wells. 

Individual Response: As described above, EPA disagrees that monitoring at GS sites will 

undermine public confidence in GS and the UIC Program. EPA believes that appropriately 

designed and implemented monitoring plans will increase public confidence in the safety of GS, 

helping to assure the public that any problems are detected early and that appropriate measures 

are taken to protect USDWs from endangerment. Knowledge of the location of the CO2 plume 

and the associated pressure front will enable EPA to 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. 

As described above, the Agency recognizes that while there are similarities between injection of 

wastes for disposal (Class I) and GS (Class VI), 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 after injection. 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. 

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

ensures that direct monitoring is available to track 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. 

7