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 GEOL OGIC SEQUESTRATION RULE

The Underground Injection Technology Group (UIT Group) submits these comments on the proposed rule for geologic seque stration of carbon dioxide under the Safe Drinking Water Act (SDWA), "Federal Requirements Under the Unde rground Injection Contro l (UIC) Program for Carbon Dioxide (CO2) Geologic Sequestrati on (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 operato rs, and the members operate unde rground injection wells in a

number of different UIC cl asses, including Class I.

UIT Group members have no immediate plans to inje ct carbon dioxide for ge ologic sequestration purposes, but nevertheless have two significant is sues with respect to the proposed rule. The

first issue relates to th e subject of aquifer exemptions, as discussed in the pr oposed 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. Th ese 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 dri nking 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 prot ected. Indeed, EPA’s regulatory definition of "undergr ound source of drinking water" (or "USDW") is not limited to aquifers that are or could reasona bly be expected to serve as dr inking water sources, but includes all aquifers capable of producing minimum amo unts of water that cont ain less than 10,000 mg/l

total dissolved solids. 40 C.F.R. §144.3. R ecognizing the overbreadth of its basic "USDW" definition, EPA provided an "aquifer exempti on" mechanism under which aquifers can be excluded from that definition on a case-by-case basis if they meet cr iteria 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 dri nking water sources – and thus do not warrant protection from

Underground Injection Technology Group 1 bdday@bryancave.comDocket 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 certa in 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 th at "endangers drinking water sour ces" 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 ha zardous waste injection is inappropriate and lacks any reasonable basis. If a formation is not a drinking water so urce, 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 consider ed a determinative factor – it should not be considered in the aquifer exemption context at all. The f act that hazardous waste injection is involved certainly shou ld not preclude any consideration of the technical merits of an aquifer exemption request, yet that is precisely the effect of EPA’s ex isting "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 categorie s of injection (hazardous waste injection being but one) must occur below the lowermost US DW, aquifer exemptions for non-injection formations can be necessary in order for injection into overlying injection zone s 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 wate r or it is not; the fact that the formation is or is not intended for use as an injection zone – far from being th e 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 inje ction, nor do they provide any basis for EPA to impose such rules in the guise of "policy." In the proposed ru le, 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 ove rturn 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 Drinki ng Water Act’s directive that EPA develop regulations preventing injection th at endangers drinking water sour ces. EPA’s policies disabling the aquifer exemption process for hazardous wast e injection and non-inje ction 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.comDocket 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 cha nge, it is entirely illusory to suggest that the aquifer exemption process c ould 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 am ong 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 co uld effectively undermine public confidence in the UIC program for other classes of injection wells, incl uding 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 necess ary to track the physical location of injected fluids and observationally “verify” that USDW s are not being endangered. These requirements would appear to make elaborate monitoring th rough 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 burde nsome, 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 unl ess 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 mu st demonstrate – to a reasonable degree of certainty – that there will be no migration of ha zardous 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 well s “provide an extremely low-risk” waste management option. See Class I Underground In jection Control Program: Study of the Risks Associated with Class I Undergr ound Injection Wells (EPA, March 2001) at p. 42. In the face of

such well-documented success it is difficult to se e why there should be any crisis of confidence sufficient to justify the suggesti on that the required “up-front” t echnical evaluation and controls on injection activity are somehow so unreliable that elaborate monito ring to track injected fluids and “verify” non-endangerment is necessary and should be requi red in every case.

Underground Injection Technology Group 3 bdday@bryancave.comDocket 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 ki nd of monitoring at issue were re latively easy and cost-effective, but it is not. In the deep subs urface, such monitoring is difficu lt, costly, and generally yields relatively limited information. Accordingly, while there may be specific circumstances under which the use of monitor wells or indirect geophy sical methods can make sense, it is important to consider both the potential ut ility of such monitoring and the burdens and technical challenges involved, as the regulations for Cl ass I hazardous waste injection we lls reflect. To suggest that elaborate monitoring efforts should be mandato ry at every site, as the proposed Class VI regulations appear to suggest, is unjustified and does di sservice to the demons trated effectiveness

and success of the detailed site selection, charact erization and pre-injec tion technical evaluation the UIC program requires.

CONCLUSION

For the reasons presented herei n, the UIT Group urges EPA to revi se its purported “policies” with respect to aquifer exemptions to eliminate all existing restrictions on the availability of aquifer exemptions that the regulations themse lves 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 wast e injection wells; and (2) avoid regulatory excesses in the proposed rule that could pot entially undermine public confidence in the established effectiveness of the Class I regulati ons 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.comLetter ID: 0243

Commenter: Robert F. Voorhees Organization: Undergro und 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 regulato ry definition of "underground source of drinking water" (o r "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 amount s 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 provide d an "aquifer exemption" mechanism under which aquifers can be excluded from that definition on a case-by-case basis if they meet criter ia 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 otherw ise 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 aqui fer 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 a pproach arbitrarily prevents injection that does not endanger any drinking water sources; in effect, it requires th e 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 wa rrant 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 whet her the aquifer is legitimately a

1drinking water source, and - far from bei ng considered a determinative factor - it should not be considered in the aquife r exemption context at all. The fact that hazardous waste injec tion is involved certainly should not preclude any

consideration of the technical merits of an aquifer ex emption 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 resp ect to the "policy" against aquifer exemptions for non-injection formati ons. 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 in jection zones to occur. In this situation, there is no reason to foreclose any merits-based consideration of whether the non-injection form ation is legitimately a s ource 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 exem ptions 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 aquife r exemption rules in the context of geologic sequestration, asking in partic ular whether it s hould 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 ha rmonizing the regulatory definition of "USDW" with the Safe Drinking Water Act’s directive that EPA develop regulations preventing injection that endangers dr inking 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 di oxide. Without this change, it is entirely illusory to suggest that the aq uifer exemption process could provide any means for ameliorating EPA's unn ecessary 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 la w or regulation. EPA acknowledges that there are limited circumstances where aquifer exemptions fo r GS may be warranted. The final rule allows for the expansion of the areal ex tent of existing aquifer exemp tions for Class II EOR/EGR wells transitioning to Class VI in jection for GS pursuant to requirements at §§146.4 and 144.7(d).

2Class 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 ch anging existing Agency policy. Rather the Agency developed the waiver process to address comm ents and concerns about current and future drinking water resources and the use of climate mitigation technology at a ppropriate sites. The aquifer exemption requirements in the final ru le provide flexibility and afford owners or operators an opportunity to asse ss and select a suitable GS si te while also preserving and protecting USDWs (i.e., formations/aquifers affo rded SDWA protection). Class VI owners or operators granted expansions of existing Class II EOR/EGR aquifer exem ptions 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 injec tion of hazardous waste are outside the scope of the GS rulemaking.

This approach is designed to ensure that th e differences between traditional Class II EOR/EGR operations and Class VI operati ons are considered during the aquifer exemption application process and the Class VI permitting process. Thes e 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 Agen cy believes that this process will encourage owners or operators and Directors to consider the use of alterna tive 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 Clas s 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 Da ta 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 th e most elaborate and burdensome in the entire UIC program. This approach is incongruous at be st, and certainly seems ill-suited to the goal of encouraging responsible development of geologic sequestration projects. However, the UIT Group’s specific con cern is that the

3proposed Class VI regulations are so excessi ve 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 premis e 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 sequestrati on projects. In general, it simply isn't true that this kind of monitoring is necessary, and - again as a general rule - such monitori ng 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 inject ion zone is separated from USDWs by a confining zone sufficient to prevent the m ovement 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 cons tituents from the injection zone for as long as the waste remains hazardous.

Decades of experience with Class I injection has de monstrated that this regulatory approach is effec tive: 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 "pr ovide an extremely low-risk " waste management option. See Class I Underground Inje ction Control Program: Study of the Risks Associated with Class I Underground Injection Wells (EPA, Marc h 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 su fficient to justify the sugge stion that the required "up-front" technical evaluation and controls on inject ion activity are somehow so unreliable that elaborate monitoring to track injected fluids and "verify" non-endangerment is necessary and s hould be required in every case.

It would be one thing if the kind of monitoring at i ssue were relatively easy and cost-effective, but it is not. In the deep subsurface, such monitoring is difficult, costly, and generally yiel ds 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 pro posed Class VI regula tions appear to suggest, is unjustified and does disservi ce to the demonstrated effectiveness

4and success of the detailed site selecti on, 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 appropr iately designed and implemented monitoring plans will increase public confidence in the safe ty 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 a ssure 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 i ndication that USDWs may be endangered.

EPA disagrees that plume and pressure front mon itoring are not justified for Class VI wells. The Agency recognizes that while there are similari ties between injection of wastes for disposal (Class I) and GS (Class VI), there are signifi cant 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 characteris tics of anticipated GS projects, EPA believes that plume and pressure front m onitoring at §146.90(g) are justifie d 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 met hods (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 th e injection zone is n ecessary 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 m odeling, evaluate predictions of plume movement, and target additional ge ochemical and surface monitoring needs.

In addition, §146.90(g)(2) requires owners or oper ators to track the position of the CO2 plume using indirect methods (e.g., seismic, electri cal, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools), un less the Director determines, based on site-specific geology, that such methods are not appropr iate. 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 geologi c settings. EPA clarifies that th is determination will be made by the Director based on the site-specific geologi c 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 no t appropriate in all s ituations. The owner or operator's approved testing and monitoring pl an will include the site-specific details,

5technologies, testing and monitoring freque ncies, and other pertinent information.

EPA acknowledges the commenters' concern abou t the cost of monitoring. However, EPA believes that monitoring is essential for protecti on of USDWs at GS site s. Although a significant cost in absolute terms, monito ring 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 ris k, don't stigmatize CO2

Comment: sequestration projects. However, the UIT Group’s specific conc ern is that the proposed Class VI regulations are so excessi ve 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 inje cting large volumes of CO2 for GS poses unique challenges that, if not properly managed, could endanger drinking water s ources and have other adverse impacts. However, with proper site sele ction, the final, tailored, Class VI requirements address the large volumes of CO2 injected, its bu oyancy, potential corrosivity in the presence of water, and potential impurities in the CO2 stream. In addition, EP A 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 th e 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 urge s EPA to revise its purported "policies" with respect to a quifer exemptions to eliminate all existing restrictions on th e availability of aquife r 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 deve loped the waiver process to address comments and concerns about current and future drinking wa ter resources and the use of climate mitigation technology at appropriate sites. The aquifer exemption requiremen ts in the final rule provide flexibility and afford owners or operators an oppor tunity to assess and select a suitable GS site

6while also preserving USDWs (i.e., formations/a quifers afforded SDWA protection). Class VI owners or operators granted expansions of ex isting Class II EOR/EGR aquifer exemptions for GS projects must meet all of th e 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-doc umented 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 effectivene ss 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 UI C Program. EPA believes that appropriately designed and implemented monitoring plans will in crease 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 sufficien t information to the owner or operator and Director, or allow for appropr iate actions to address any indication that USDWs may be endangered.

As described above, the Agency r ecognizes that while there are si milarities between injection of wastes for disposal (Class I) and GS (Class V I), 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 visc osity (i.e., high mobility), and th e very large injection volumes that are anticipated. There is also a degree of unc ertainty regarding the be havior of large volumes

of CO2 in the subsurface after injection. Given these characteristi cs of anticipated GS projects, EPA believes that plume and pressure front m onitoring at §146.90(g) are justified to provide early warning of any unforeseen fluid m ovement 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 no t appropriate in all s ituations. The owner or operator's approved testing and monitoring pl an will include the site-specific details, technologies, testing and monitoring freque ncies, and other pertinent information.

7