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.




Letter ID: 0123 

Commenter: John Stormon 

Organization: Washington State Dept. of Ecology 

Letter ID: 0123 Comment ID: 22996 Letter Lines: 39 to 53 

Comment Code: 1350 1.1.3.3 Comments on the need for GS technology 

Comment Code: 1420 1.2.1.1 Support the GS rulemaking 

Comment: federal UIC regulations for the Geologic Sequestration of Carbon Dioxide. It is 

good to see that EPA has proposed a well defined, environmentally protective 

program through these rules for the geologic sequestration of carbon dioxide. 

I'm sure that EPA will receive many comments targeted at weakening or removing 

key parts of the proposed regulatory program; contrary to the arguments of some 

industry voices, geologic sequestration of carbon dioxide is new, untested 

technology that, if poorly implemented, could have large and long lasting 

environmental impacts including potentially degrading the quality of our ground 

water resources (USDW). Please help to encourage the use of this important 

technology by keeping a strong, environmentally protective regulatory program. 

One early disaster could destroy geologic sequestration of carbon dioxide as a 

strategy we can use to respond to rising atmospheric CO2 levels. Caution is 

warranted in the first set of regulations. Once experience with geologic 

sequestration has been gained, the regulations may be streamlined where 

appropriate. 

Individual Response: EPA agrees that the implementation of the GS rule in a manner that 

ensures protection of USDWs from endangerment is important to establishing a foundation for 

further advances in the field of CO2 GS. EPA acknowledges the need for regulatory certainty: 

the final GS requirements provide a level of certainty by setting forth unique requirements for 

GS. These requirements include: the tailored AoR delineation process at §146.84, the types of 

monitoring appropriate to GS projects at §146.90 and the post-injection site care process at 

§146.93. For additional information on these requirements, please also see the discussion of 

EPA’s Final Regulatory Approach in the preamble to the final GS rule. 

To protect USDWs from endangerment and meet the potentially fast pace of GS deployment, 

EPA is using an adaptive approach to regulating CO2 injection for GS. The Agency plans to 

collect and review data every six years on GS projects to determine whether the appropriate 

amount and types of information and appropriate documentation are being collected, and to 

determine if modifications to the requirements are appropriate or necessary. An adaptive 

approach will allow regulatory development to proceed in time to meet the current and future 

demands for Class VI permits, while EPA continues to gather data from pilot projects and other 

research as it becomes available. 

While EPA agrees with commenters that a stable, predictable, nationally consistent, and 

workable regulatory framework is important, EPA stresses that the focus of the GS rule is to 

1
ensure that, where GS is deployed, it is conducted in a manner that protects USDWs from 

endangerment. 

Letter ID: 0123 Comment ID: 22997 Letter Lines: 57 to 68 

Comment Code: 1510 1.2.2.3 Need for additional study 

Comment: Pilot Studies: Consider specifically including a streamlined process to 

encourage Pilot Studies at potential geologic sequestration projects. Thorough 

site characterization is the most important requirement for most geologic 

sequestration projects. Site characterization will be extremely expensive. EPA 

should consider some method to encourage potential projects to start with pilot 

studies, designed to collect detailed site characterization information and test 

analytical models prior to full scale project construction. In Washington we 

have included a special consideration for pilot studies in our geologic 

sequestration rule [WAC 173-218-115(4)(b)]. Of course this is also a potential 

loop-hole, so it is also important that pilot study permits have limits intended 

to prevent them from being used as a by-pass of the permitting process for full 

scale sequestration projects. 

Individual Response: EPA clarifies that, with the promulgation of the GS rule, it no longer 

considers it appropriate to permit CO2 injection wells that are testing the injectivity or 

appropriateness of an individual formation (e.g., as a prelude to a commercial-scale operation) as 

Class V experimental technology wells. Such wells should be permitted as Class VI wells. EPA 

clarifies that Class V experimental technology wells may be used for experimental projects 

designed to test new technologies. 

EPA is preparing an addendum to UICPG #83 that describes the use of the Class V experimental 

technology well classification to clarify permitting for Class V wells. This addendum will 

address shifting of Class V experimental projects to full-scale GS projects and the future use of 

the Class V experimental technology well subclass for research and testing of new GS 

technologies. For additional information, please see the section entitled, “How Does This Rule 

Affect Existing Injection Wells Under the UIC Program?” in the preamble to the final GS rule. 

Letter ID: 0123 Comment ID: 22998 Letter Lines: 70 to 84 

Comment Code: 1600 1.3 Risk Associated with CO2 GS 

Comment Code: 2046 1.5.2.3 Continuing to classify CO2 injection for EOR/EGR as Class II/ 

dividing line between Class II and Class VI (seeking comment) 

Comment: Risk: Geologic Sequestration is not the same as Enhanced Oil Recovery (EOR) and 

needs to have much high standards than EOR activities have had to date. 

Protecting USDW is the most important aspect of the UIC program for the geologic 

sequestration of carbon dioxide. Although limited experience has been gained by 

the oil and gas industry injecting CO2 into proven structural traps for EOR, 

2
this experience has limited carry over to broader strategies for geologic 

sequestration. Geologic sequestration, unlike EOR, is being considered in basins 

without proven oil and gas capture and holding reservoirs. Even where exhausted 

oil and gas reservoirs are being considered for geologic sequestration, the 

amount of carbon dioxide to be injected is far greater than used for EOR and the 

goals of the injection are different. There is an unknown, likely large, level 

of risk associated with large geologic sequestration projects. The regulatory 

standards for site selection, site characterization and ongoing monitoring 

should be kept high to help ensure that the worst case scenarios are never 

realized. 

Individual Response: EPA agrees that the nature and risks of CO2 injection for long-term 

storage are different from Class II CO2 injection for ER, and that tailored requirements for GS 

wells are necessary to protect USDWs from endangerment. For this reason, the Agency tailored 

UIC requirements for Class VI wells that address the general risks deep injection may pose to 

USDWs and specifically address the unique nature of CO2 GS (i.e., very large volumes, very 

long time-periods, and reservoir pressure conditions). 

EPA recognizes that injecting large volumes of CO2 for GS poses unique challenges that, if not 

properly managed, could endanger drinking water sources or have other adverse impacts. 

Although EPA believes that a lot can be learned from the EOR experience, EPA agrees that 

caution is warranted and has, as a result, developed a new well class with requirements tailored 

to address the unique challenges posed by GS and potential risks associated with long-term 

injection of CO2. For example, these requirements include the tailored AoR delineation process 

per §146.84, monitoring that is appropriate to GS projects per §146.90, and extended postinjection site care per §146.93. 

As part of its adaptive rulemaking approach, the Agency plans, every six years, to collect and 

review data on GS projects to determine whether the appropriate amount and types of 

information and appropriate documentation are being collected, and to determine if 

modifications to the requirements are appropriate or necessary. 

Letter ID: 0123 Comment ID: 22999 Letter Lines: 86 to 93 

Comment Code: 2046 1.5.2.3 Continuing to classify CO2 injection for EOR/EGR as Class II/ 

dividing line between Class II and Class VI (seeking comment) 

Comment: EOR: Keep a strong separation between the programs for EOR and geologic 

sequestration. EOR occurs in areas with oil reservoirs, with little 

contemplation to the site's long term storage and CO2 containment 

characteristics. Although some oil and gas reservoirs are likely to have very 

good potential as geologic sequestration sites, the determination of which 

reservoirs should be based upon excellent site characterization work that 

verifies that they will provide good long term geologic sequestration with few 

environmental risks. 

3
Individual Response: As described above, EPA agrees that the nature and risks of CO2 

injection for long-term storage is different from Class II CO2 injection for ER, and that tailored 

requirements for GS wells are appropriate and necessary to protect USDWs from endangerment. 

For this reason, the Agency tailored UIC requirements for Class VI wells that address the general 

risks deep injection may pose to USDWs and specifically address the unique nature of CO2 GS 

(i.e., very large volumes, very long time-periods, and reservoir pressure conditions). EPA adds 

that the decision to permit GS at a given site will be based on the suitability of that particular 

site, not on the type of geologic formation. Furthermore, EPA clarifies that injection of carbon 

dioxide for the purpose of enhanced recovery is regulated under Class II. Owners or operators 

may use depleted oil and gas reservoirs for GS provided the injection is intended for long-term 

storage and the well meets the standards in §146.86(a). EPA is allowing the construction of Class 

II EOR wells to be grandfathered per §146.81(c), provided the owner or operator can 

demonstrate to the Director that the wells were engineered and constructed to meet the 

requirements at §146.86(a) and ensure protection of USDWs from endangerment. 

Letter ID: 0123 Comment ID: 23000 Letter Lines: 95 to 100 

Comment Code: 4322 2.4.4.1.1 Comments in favor of requiring injection below the lowermost 

USDW 

Comment: Injection Zones: Geologic sequestration should only be allowed beneath the 

lowest USDW. Protecting USDW is the most important aspect of the UIC program for 

the geologic sequestration of carbon dioxide. As proposed in the federal rules 

for geologic sequestration these sites should all be kept beneath the lowest 

USDW, to prevent the degradation of future ground water resources that we are 

likely to need in the coming centuries. 

Individual Response: EPA agrees that protecting USDWs from endangerment must be a top 

priority. The Agency believes that there are limited circumstances where injection above the 

lowermost USDW can be performed in a manner that protects USDWs, as long as appropriate 

protections are in place. The final GS rule at §146.95 establishes a process by which owners or 

operators can seek a waiver of the Class VI injection depth requirements for injection into nonUSDW formations above and/or between USDWs. The waiver approach requires the submission 

of extensive, site-specific information (in conjunction with the permit application submission) to 

demonstrate that injection of CO2 into a non-USDW that is above or between USDWs can be 

done in a manner that is protective of USDWs. It establishes: 1) requirements specifying 

information that owners or operators must submit, and Directors must consider, in consultation 

with PWSS Directors; 2) procedures for public notice of a waiver application and for DirectorRegional Administrator communication; 3) the waiver issuance process; and, 4) additional 

requirements that apply to owners or operators of Class VI wells granted a waiver of the 

injection depth requirements to ensure USDW protection above and below the injection zone. 

The final rule also establishes limited circumstances under which expansions of the areal extent 

of aquifer exemptions may be granted for owners or operators of Class II EOR/EGR wells 

transitioning to Class VI injection for GS. Additionally, the rule does not categorically preclude 

or prohibit injection into any type of formation. 

4
EPA believes that the requirements at §146.95 will ensure USDW protection while providing 

flexibility to UIC Program Directors and owners or operators who undertake CO2 injection for 

GS. 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: 0123 Comment ID: 23001 Letter Lines: 102 to 106 

Comment Code: 3120 2.1.2 Need to identify additional confining and containment zones 

(seeking comment) 

Comment: Containment or a caprock are critical to prevent the migration of CO2 upward 

into shallower USDWs. Allowing the director to require additional confining 

zones will allow regulators to include additional protective standards where 

needed and could allow use of an otherwise marginal formation for geologic 

sequestration. 

Individual Response: EPA agrees with the commenter that, in some situations, the presence of 

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

can improve USDW protection from endangerment. The final regulation retains the requirement 

at §146.83(b) which affords the Director discretion to require owners or operators to identify and 

characterize additional zones. 

Letter ID: 0123 Comment ID: 23002 Letter Lines: 108 to 114 

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

delineate the AoR (seeking comment) 

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

CFR 146.90) 

Comment: Area of Review: The proposed standards correctly require not just modeling, but 

tracking of the actual CO2 plume and pressure front, with periodic reevaluation 

of the modeled behavior as additional experience is gained at a sequestration 

project. Modeling is a good method of predicting the behavior of injected CO2 

but should not be relied upon without monitoring to verify the accuracy of the 

modeled predictions. The model will be continually refined throughout the life a 

sequestration project. 

5
Individual Response: EPA acknowledges the commenter’s support of the modeling approach, 

and agrees that reevaluation of the AoR as required at 146.84(e) must incorporate monitoring 

and operational data gathered since the last model run. 

EPA agrees with commenters on the importance of monitoring at GS sites and emphasizes that 

monitoring of injection activities will be an important component of every GS project. 

Monitoring associated with injection wells and the movement of the CO2 plume is necessary to 

verify that the injectate is confined in the target formations and does not endanger USDWs. 

EPA agrees that monitoring data should be used to review model assumptions, verify 

computational model projections, and, when necessary, provide input for model refinements. As 

data are collected at an injection site, model parameters can be adjusted to match observations 

(i.e., for model calibration), which in turn improves the predictive capability of the model. As a 

GS project proceeds, both monitoring and modeling will evolve, with monitoring results 

supporting effective AoR reevaluations and leading to improved model predictions. 

Letter ID: 0123 Comment ID: 23003 Letter Lines: 116 to 127 

Comment Code: 3822 2.3.1.1 Depth of surface casing (seeking comment) 

Comment: Well Standards: The well construction standards may be difficult or impossible 

to meet in some geologic settings. The standards require a surface casing 

installed to the lowermost USDW and cemented to the surface. In geologic 

settings with bedrock and deep drinking water quality aquifers, it may be 

impossible to set the surface casings this deep. Washington's Columbia River 

basalts may be as deep as 10,000 ft, much of that depth with drinking water 

quality ground water. The multiple flows and fractures in these beds make for 

difficult drilling and frequently require setting intermediate casings. The 

standards should allow a protective casing program that can be reliably 

installed in all geologic settings. Deep aquifers may provide the most 

protective geologic settings for CO2 injection; the standards should not 

discourage their use. 

Individual Response: EPA disagrees that the surface casing requirements in the GS rule 

preclude injection below deep USDWs. The final GS rule at §146.86(b)(2) requires that surface 

casing extend through the base of the lowermost USDW and be cemented to the surface through 

the use of single or multiple strings of casing and cement. It does not, however, specify how 

cementing must be accomplished, and gives flexibility to the owner or operator to propose 

alternate methods to provide a sufficient amount of cement to meet the standard that USDWs are 

protected from endangerment. EPA notes that there are many potential ways to meet the 

requirement, such as the use of staged cementing. 

EPA recognizes concerns regarding construction of Class VI wells where the lowermost USDW 

is very deep. To further address comments on deep injection wells, the final GS rule at §146.95 

includes requirements for owners or operators that seek a waiver of the injection depth 

6
requirements. Owners or operators of Class VI wells operating under injection depth waivers 

must comply with additional construction requirements to ensure that wells used to inject above 

or between USDWs are protective. See the discussion of the waiver approach in the preamble to 

the final GS rule for additional information. 

Letter ID: 0123 Comment ID: 23004 Letter Lines: 129 to 132 

Comment Code: 4200 2.4.2 Down-hole shut-off valves in GS wells (seeking comment) 

Comment: Downhole valves and other required downhole equipment may impact or prevent 

certain monitoring techniques. It is important to require appropriate safeguards 

but establishing prescriptive safeguards may be counterproductive and are likely 

to prevent the use of cutting edge technologies as new methods are developed. 

Individual Response: After evaluating the risks and benefits of down-hole shut-off systems and 

considering additional research, EPA will not require automatic down-hole shut-off devices for 

onshore Class VI wells since it is not necessary in all cases to ensure protection of USDWs from 

endangerment. Instead, the final rule, at §146.88(e)(2), requires that owners or operators of 

onshore Class VI wells install automatic surface shut-off devices. The rule affords Director's 

discretion to mandate automatic down-hole shut-off devices in onshore situations that may 

warrant their use. However, the Agency believes that offshore Class VI wells present unique 

construction and operational conditions, including isolation from shorelines and the need to 

construct wells through the water column and the subsurface, which may delay response time in 

the event of well difficulties. The rule requires, at §146.88(e)(3), that owners or operators of 

offshore wells within State territorial waters install automatic down-hole shut-off systems. EPA 

believes that these requirements at §146.88(e) ensure that proper precautions are taken to prevent 

subsurface fluid movement and ensure protection of USDWs. 

Letter ID: 0123 Comment ID: 23005 Letter Lines: 134 to 140 

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

Comment Code: 4655 2.6.5.1 Plume tracking techniques/geophysical methods (seeking 

comment) 

Comment: Monitoring: Direct monitoring of the formations immediately above the confining 

layer for a geologic sequestration injection zone is an important requirement 

for the early detection of unacceptable leakage. Monitoring wells installed into 

this monitoring zone will be quite expensive but should be required for all 

projects. Geophysical methods and other indirect monitoring, while useful, 

should not be allowed to substitute for all direct monitoring above the 

confining layer. 

Individual Response: EPA disagrees that pressure monitoring above the confining zone is 

appropriate. Instead, EPA believes that pressure monitoring in the injection zone is necessary to 

track the development and movement of the pressure front and CO2 plume. The final rule (at 

7
§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 also required unless the 

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

EPA believes that pressure monitoring within the injection zone is necessary because any such 

monitoring above the confining zone would not detect movement of the pressure front unless a 

breach of the confining zone occurs. EPA believes that monitoring using wells in the injection 

zone (i.e., that penetrate the confining zone) can be safely performed if the wells are constructed 

to prevent flow between the injection zone and USDWs or other layers above the confining zone. 

Such construction technologies exist and have been used in the oil and gas industry for years. 

EPA believes that the benefits of monitoring in the injection formation outweigh the manageable 

risk of those monitoring wells serving as conduits for fluid movement. EPA adds that owners or 

operators may consider performing additional pressure monitoring in wells that are above the 

confining zone (e.g., in the same wells used to perform ground water quality monitoring required 

at §146.90(d)) to provide additional verification that no pressure changes are occurring above the 

confining zone due to CO2 leakage and that the Director has the authority to require such 

monitoring under §146.90(i). Monitoring also identifies needed remedial actions, provides inputs 

for AoR reevaluation modeling, and targets additional geochemical and surface monitoring 

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

the public that GS projects are proceeding according to plan, provide sufficient information to 

the owner or operator and Director, or allow for appropriate actions to address any indication that 

USDWs may be endangered. 

EPA also agrees that direct monitoring for ground water quality above the confining zone is 

important, and the GS rule requires this at §146.90(d). Monitoring in additional formations, e.g., 

the injection zone, may also be necessary, and if the Director believes such monitoring is 

warranted he/she has the authority to require that it be included in the testing and monitoring 

plan. 

Letter ID: 0123 Comment ID: 23006 Letter Lines: 142 to 151 

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

Comment: The number of wells drilled through the confining layer into the injection zone 

should be minimized. Each well represents a risk of establishing a pathway for 

the migration of CO2 or in-situ fluids into shallower aquifers. Projects may be 

able to get sufficient monitoring data from injection wells to minimize the need 

for stand-alone injection zone monitoring wells. 

Decisions on the level of direct and indirect monitoring should be made on a 

site by site basis, based upon the geologic characteristics, but some direct 

monitoring must be required above the confining layer to confirm that indirect 

monitoring is accurate. 

8
Individual Response: As described above, EPA believes that direct pressure monitoring in the 

injection zone is necessary to track the development and movement of the pressure front and 

CO2 plume. 

EPA believes that monitoring using wells in the injection zone (i.e., that penetrate the confining 

zone) can be safely performed if the wells are constructed to prevent flow between the injection 

zone and USDWs or other layers above the confining zone. Such construction technologies exist 

and have been used in the oil and gas industry for years. EPA believes that the benefits of 

monitoring in the injection formation outweigh the manageable risk of those monitoring wells 

serving as conduits for fluid movement. EPA adds that owners or operators may consider 

performing additional pressure monitoring in wells that are above the confining zone (e.g., in the 

same wells used to perform ground water quality monitoring required at §146.90(d)) to provide 

additional verification that no pressure changes are occurring above the confining zone due to 

CO2 leakage and that the Director has the authority to require such monitoring at §146.90(i). 

EPA adds that the final rule also requires geochemical monitoring above the confining zone, at 

§146.90(d). 

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 is also 

developing guidance, available on the same website, on well construction that will include 

recommendations for monitoring well construction. 

In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, 

Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL311/081508); this manual is included in the docket for the final GS rule. 

Letter ID: 0123 Comment ID: 23007 Letter Lines: 153 to 157 

Comment Code: 4500 2.5 Proposed Mechanical Integrity Testing (MIT) Requirements (40 CFR 

146.89) 

Comment Code: 4630 2.6.3 Corrosion monitoring 

Comment: Periodic corrosion and well integrity testing is important for all pollution 

prevention programs. This well testing will help operators to focus maintenance 

and repair activities on the wells that are degrading. It is far better to 

prevent leakage from a well breach than to fix the well after discovering that 

it has leaked. 

Individual Response: EPA agrees with the commenter; the final rule requires both internal and 

external mechanical integrity testing. Mechanical integrity testing is one of the cornerstones of 

9
the existing EPA UIC program. The MIT requirements at §146.89, along with the corrosion 

monitoring required at §146.90(c), ensure protection of USDWs from endangerment and provide 

an important early warning of potential problems in the injection well. Routine mechanical 

integrity testing of injection wells provides data that enables the identification and remediation of 

well integrity problems before they lead to leakage and/or endangerment of USDWs. For 

additional information, please see the discussion of MITs in the final rule preamble. 

EPA also agrees that corrosion monitoring is appropriate given the potentially corrosive nature 

of the CO2 stream. CO2 in the presence of water becomes acidic, potentially accelerating 

corrosion of well materials. The CO2 stream for a GS project may also contain small volumes of 

impurities that could contribute to corrosion. For these reasons, the final rule requires quarterly 

corrosion monitoring (at §146.90(c)). 

Letter ID: 0123 Comment ID: 23008 Letter Lines: 159 to 167 

Comment Code: 5800 2.13 Comments on emergency and remedial response (40 CFR 146.94) 

Comment: Remedial Action: Establish triggers for entering remedial action during the 

negotiation of the geologic sequestration permit. Identification of 

environmental impacts from monitoring at a permitted facility is frequently 

followed by a prolonged legal discussion of when these impacts become large 

enough to trigger remedial actions. EPA should consider moving this discussion 

to the initial permitting process so that the operator and regulatory agency 

agree before impacts are observed. This will help all to understand where the 

threshold is and will help to prevent legal efforts intended to delay beginning 

remedial actions when environmental impacts have been observed. 

Individual Response: EPA believes that the final rule takes a proactive approach to remedial 

actions by requiring, under §146.94, each permit application to include an emergency and 

remedial response plan so that both the owner or operator and the Director may immediately 

respond to any fluid movement that may endanger a USDW at GS sites. Furthermore, EPA 

believes that each response action will be site- and event- specific, and that setting specific 

environmental impact triggers outside of a showing of USDW endangerment in advance would 

not be practical or account for every potential scenario. For this reason, the emergency and 

remedial response requirements at §146.94 are designed to ensure that, in the unlikely event of 

endangerment, the owner or operator will immediately cease injection (i.e., take immediate 

action to avoid any further endangerment) and initiate a dialogue with the Director as soon as 

possible to identify appropriate next steps based on the circumstances. 

EPA clarifies that, if the owner or operator obtains evidence that USDWs may be endangered or 

that leakage is occurring, he or she must cease injection, take all steps reasonably necessary to 

identify and characterize any release, notify the Director, and implement the approved 

emergency and remedial response plan (§146.94(b)). 

10
Letter ID: 0123 Comment ID: 23009 Letter Lines: 169 to 174 

Comment Code: 5400 2.9 Proposed Financial Responsibility and Long-Term Care 

Requirements 

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

CFR 146.85) 

Comment: Financial Assurance: Financial assurance accounts, funded with real assets must 

be required. Financial tests and self insurance are of no value if a company 

becomes financially insolvent. As we have recently seen in the financial world, 

the collapse of a company can occur quite rapidly. Financial assurance is only 

of value if the assets remain in the account after the company's financial 

demise. 

Individual Response: EPA agrees that assuring financial responsibility for corrective action on 

wells in the AoR, injection well plugging, PISC and site closure, and emergency and remedial 

response at Class VI sites is an important component of ensuring that USDWs are protected. The 

goal of financial responsibility is to ensure that financial resources are available to prevent 

endangerment of USDWs from improper plugging, remediation, and management of wells in the 

event that the owner or operator experiences financial difficulties. 

EPA will retain self-insurance as an option to demonstrate financial responsibility for Class VI 

wells. EPA believes, based on input by commenters, that self-insurance, if properly used, can be 

an appropriate option for certain owners or operators. Self-insurance has been used successfully 

in the past (e.g., under the Class I and RCRA programs). EPA recognizes that there are some 

concerns about the use of self insurance, including those mentioned by the commenters, and is 

developing guidance (available on EPA’s website at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm) to assist Directors in 

evaluating the appropriateness of self-insurance in specific circumstances, such as how to 

evaluate owners or operators' demonstrations of financial worthiness or whether certain owners 

or operators pose too great a financial risk to use self-insurance as a financial responsibility 

instrument. EPA acknowledges that states may not be authorized under state law to allow for self 

insurance or other financial instruments. Therefore, states may prohibit the use of any financial 

instruments included in the rule, including self insurance, for Class VI wells. See the final rule 

and preamble for further discussion of EPA's final approach to financial responsibility. 

Letter ID: 0123 Comment ID: 23010 Letter Lines: 176 to 188 

Comment Code: 1614 1.3.1.2 Impurities in captured CO2; purity standards for CO2 

Comment: Non-CO2 Contaminants: The proposed standard will allow co-disposal of imported 

non-CO2 waste streams. One of the most disturbing aspects of the proposed 

standards would allow non-CO2 contaminants to be injected with the CO2 unless 

the contaminants would make the CO2 a hazardous waste. Injected gases may not 

qualify as a hazardous waste under current standards. It appears that the 

proposed rules would allow a facility to import waste materials to add to the 

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CO2 and be injected as a cheap disposal option; this should be prevented. 

Washington State prohibits the injection non-CO2 contaminants if technology is 

available for their removal; Washington also prohibits the use of underground 

injection for most waste disposal. An alternative option would be to allow nonCO2 contaminants only as specifically addressed in a facility's permit and a 

statement that the non-CO2 contaminants must be by-products of the CO2 stream 

and may not be imported for disposal by injection with the CO2. 

Individual Response: The GS rule does not set generic purity standards for CO2 injectate 

streams (e.g., a percent CO2). Instead, the GS rule addresses the quality and quantity of 

impurities by requiring owners or operators to submit information on the source of the CO2 and 

its physical and chemical properties. Specifically, the GS rule requires the owner or operator to 

submit data about the site, including an analysis of the chemical and physical characteristics of 

the CO2 stream, as required at §146.82(a)(7)(iv), and information on the compatibility of the 

CO2 stream with fluids in the injection zone and minerals in both the injection and the confining 

zones and the materials used to construct the well, per §146.82(c)(3). This information can help 

the Director determine the potential for geochemical reactions between the injectate (CO2) and 

the host geologic formations, which could result in the plugging of pore spaces or the dissolution 

of formation minerals.