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.
1 

COMMENTS ON THE U.S. ENVIRONMENTAL PROTECTION AGENCY’S 

PROPOSED RULE FOR FEDERAL REQUIREMENTS UNDER THE UNDERGROUND 

INJECTION CONTROL (UIC) PROGRAM FOR CARBON DIOXIDE (CO2) 

GEOLOGIC SEQUESTRATION (GS) WELLS 

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

Introduction 

The Energy & Environmental Research Center (EERC) at the University of North Dakota directs 

the Plains CO2 Reduction (PCOR) Partnership, which is one of seven regional partnerships 

funded by the U.S. Department of Energy’s Regional Carbon Sequestration Partnership Program 

and a broad range of project sponsors. The PCOR Partnership is a diverse group of public and 

private sector stakeholders working together to better understand the technical and economic 

feasibility of capturing and storing CO2 emissions from stationary sources of CO2 in the central 

interior of North America. Below, the PCOR Partnership provides a general overview of topics 

to be considered when rules are developed; in addition, more detailed comments on specific 

sections of the proposed rules are provided. 

General Overview 

Over the course of several decades, the enhanced oil recovery (EOR) industry has developed and 

successfully implemented operational practices to handle large volumes of CO2 safely and 

effectively. Since the 1970s, millions of tons of CO2 per year have been safely transported over 

thousands of miles of pipelines and injected into wells in a variety of geological settings 

throughout the world. The industry’s best practices can be extended into the field of CO2

sequestration with almost seamless ease. Tools of exploration, surface CO2 handling (including 

gas processing, compression, and transportation), well designs, injection practices, surveillance 

of emplaced CO2, and the science and experience to assess risks of site permanency are all 

directly applicable. For example, it is estimated that over 8 trillion cubic feet of CO2 has been 

stored in the Permian Basin. These volumes are indicative of an existing industry with an 

outstanding record of performance. This experience should not be discarded. Assurance of longterm storage is the key feature that needs to be demonstrated. 

Just as in nature with deep-sourced, natural CO2, there are low-risk sites that will 

permanently entrap CO2, and there are places where it may migrate, perhaps even to the surface. 

CO2 is a naturally occurring substance, and movement within the subsurface is very common. 

Rather than trying to fashion rules that protect against surface escape in all subsurface 

conditions, regulatory oversight needs to recognize the nearly ubiquitous presence of the 

molecule while identifying low-risk sites for entrapment and provide flexibility in regulation to 

accommodate the attendant risk level. 

In order to achieve statistically significant reductions of greenhouse gas emissions, largescale carbon capture and storage (CCS) will have to be implemented at numerous sites. One of 

the greatest potential barriers to widespread deployment of sequestration projects would be the 

specification of overly complex well design and monitoring of sites. Experience shows that 

exotic well designs add little benefit, while, on the other hand, judicious site selection adds 
2 

greatly to the security of emplacement. For example, subsurface sequestration formations 

overlain by bedded salts provide optimal conditions for long-term storage. The focus of 

regulation should be performance criteria, not design criteria. As long as CO2 sequestration sites 

can meet the standards required for permitting, injection of CO2 for sequestration is, to a large 

extent, similar to EOR operations. In turn, requirements for injection wells accessing judiciously 

selected zones for sequestration should be more closely aligned with those of Class II standards 

than the more stringent Class I hazardous waste well standards. As currently proposed, the Class 

VI requirements are more reflective of Class I hazardous waste well standards. 

It is important to be mindful that CO2, relative to other common and not-so-common 

injectates, is relatively innocuous. Increasing concentrations are easily detected in groundwater 

through simple monitoring of pH. Carbon dioxide in groundwater poses minimal acute or 

chronic threat to human health or the environment, especially when compared to other materials 

that have been classified as hazardous. As long as potential injection sites are appropriately 

characterized and judiciously selected and injection operations are designed and conducted 

according to longstanding engineering and regulatory standards, the leakage of CO2 into 

underground sources of drinking water (USDW) is likely to be a preventable and infrequent 

occurrence. In the rare event that CO2 should leak into USDWs, it is also important to note that 

its primary effect on groundwater will be to form a weak acid (carbonic acid) and lower pH, 

which can be relatively easily mitigated by a variety of commonly used, simple remediation 

practices. 

 A final comment has to do with any rules or policies that might marginalize EOR as a 

sequestration tool. The PCOR Partnership believes the early-captured CO2 will be injected in 

large volumes and stored during existing and new commercial (i.e., EOR) operations. The only 

reference to the use of EOR sites for sequestration is contained in proposed rule § 146.83(c) 

which discusses repermitting existing wells as Class VI storage wells. The emission reduction 

potential and sequestration associated with EOR are immense, and revenues from the oil 

produced will offset the cost to the economy and will, ultimately, accelerate more widespread 

deployment of CCS technologies. With the growing energy concerns in the United States, the 

contributions of CO2 EOR in the advancement of CCS need to be embraced. This reality needs to 

be further embraced when one contemplates a streamlined approach, such as “grandfathering” 

for Class II wells that may be useful for sequestration beyond the EOR project. 

Detailed Comments 

Page 43492. SUMMARY. Regarding the phrase “...help ensure consistency...”

Consistency does not necessarily mean that regulations are appropriate or effective. 

Geology is notoriously heterogeneous and, therefore, by definition inconsistent. 

Striving for consistency across geologic systems is difficult at best. One need only to 

look at the history of injection regulation across different states to see a lack of 

consistency is appropriate and primarily due to heterogeneity and inconsistency with 

respect to regional geologic characteristics. Guidelines must be flexible. Flexibility to 

ensure the safe maximization of CO2 storage must not be compromised by a desire to 

ensure consistency of rules across all geologic settings. 
3 

Page 43495. II. What Is EPA Proposing. “development of a key climate change mitigation 

technology”?

Will these rules really support the “development of a key climate change mitigation 

technology”? Is it really within the purview of protecting USDW? 

Page 43496. B. What Is EPA’s Authority under the Safe Drinking Water Act (SDWA) to 

Regulate Injection of CO2?Regarding the following quote from the document, 

referring to a key aspect of the Safe Drinking Water Act: 

“Section 1421 (b)(3)(A) of the Act also provides that EPA’s UIC regulations shall 

permit or provide for consideration of varying, geologic, hydrological, or historical 

conditions in different States and in different areas within a State.” 

It is important that this aspect of the SDWA is a guiding principle for the proposed 

regulations. Based on those words in the SDWA, flexibility is demanded by statute and 

must be built into any UIC regulations. Unfortunately, the regulations proposed for GS 

wells in this document are often anything but flexible, but rather are quite prescriptive 

and inflexible. 

Page 43498. The Weyburn Field is in Saskatchewan, Canada, not Alberta. 

Page 43498. The example cited here (Crystal Geyser, Utah) is not associated with an “injection 

activity.” It is naturally occurring CO2 that leaks via an improperly abandoned 

exploration well. 

Page 43498. This page includes a very good and reasonable description of the relative 

inapplicability of the Lake Nyos incident as an analog for possible negative 

consequences of a large CO2 leak from a geologic storage site. 

Page 43498. Regarding the statement, 

 

“the measures outlined in today’s proposed rulemaking to prevent endangerment of 

USDWs may also prevent migration of CO2 to the subsurface.” 

This statement is fine, as long as protecting leakage to the atmosphere does not lead to 

stricter measures than would be required to protect USDWs. For example, regulations 

should be driven by a desire to maintain a leakage rate below a certain percentage of 

the injected volume, unless that percentage can be demonstrated to adversely affect 

USDWs. Another way to state it is this: a 1% leakage rate may or may not adversely 

affect USDWs; therefore, a 1% rate should not necessarily be unacceptable. 

Page 43499. One would caution rule makers on putting too much faith into any one institution 

or any one method when studying potential impacts. Should not such information be 

provided by various technical sources? While the utility of models and laboratory data 

is recognized, their results should not supersede real-world experience, field-based data, 

and local knowledge. 
4 

Page 43500. Regarding the statement, 

“4-D seismic is a valuable tool for plume tracking” at Weyburn. 

 “Is” is a strong word. Based on personal conversations with those who have worked on 

Weyburn, it is suggested that “may be” is more accurate. 

Page 43500. Regarding the basis of some of the rules related to modeling 

 Much has happened in the world of modeling CO2 injection and long-term storage since 

2005. Many of the key messages from the workshop upon which some of the 

statements on this topic are based may be long out of date. 

Page 43502. G. How Would This Proposal Affect Existing Injection Wells under the UIC 

Program?

 The regulatory regime should readily accommodate the adoption of Class II wells into 

any new category. Unfortunately, this entire section gives the impression that storage is 

not occurring during EOR activities, which is not true. EOR provides partial storage 

capability until such time as the recovery of hydrocarbons ceases and all production 

activities are ended. 

Page 43502. H. What Are the Target Geologic Formations for GS of CO2? 

This section grossly misrepresents the types of geologic formations that are suitable for 

CO2 sequestration. It is irresponsible to discredit the meaningful role that depleting 

and/or depleted oil and gas reservoirs can play in sequestering CO2. While the document 

gives credit to the vast amount of geological information that is known about oil and gas 

reservoirs, it then implies that this knowledge does not overcome all of the perceived 

technical challenges associated with using oil and gas reservoirs for geologic storage. The 

techniques that would be used to alleviate the concerns listed in this section are less 

onerous than the proposed requirements to permit a Class VI injection well. Additionally, 

just as all deep saline formations may not be suitable for geologic storage, there may be 

oil and gas reservoirs that are not suitable as well. Prudent site selection should help 

determine suitable geologic settings, not broad statements declaring one geologic 

formation better than the other. 

CO2 storage in coal seams is an area of very active research. DOE Partnerships are 

conducting pilot-scale coal seam sequestration field tests. Utilizing coal seams at shallow 

depths would require less compression (gas phase vs. supercritical CO2), reduce drilling 

costs, may allow for greater concentrations of inert nitrogen (which could reduce capture 

costs), and be proximal to many minemouth operations. Ruling out such storage by 

administrative fiat is premature. The results of ongoing research need to be considered 

prior to such proposed actions. 
5 

Page 43503. H. Is Injected CO2 Considered a Hazardous Waste under RCRA? 

No. CO2 should not be considered a hazardous waste under RCRA. 

Page 43504. J. Is Injected CO2 Considered a Hazardous Waste under CERCLA? 

No. CO2 should not be considered a hazardous waste under CERCLA. 

Page 43505. 1. Proposed Geologic Siting Requirements

With regard to the need for data on all USDWs at a site: 

Wording here suggests that maps and cross sections must be generated of all USDWs 

near the proposed injection well. Submitting maps and cross sections of all of the 

USDWs, not just the lowermost USDW, seems unnecessarily burdensome to the 

owner/operator. Such maps will require significant additional work, and it is not clear 

how doing so will result in improved protection of USDWs since protective casing is 

already required from the surface all the way to the bottom of the lowermost USDW. 

Identifying and mapping the lowermost USDW should be sufficient to protect all 

overlying USDW zones. 

There is also text in this section that can be interpreted as requiring the owner/operator to 

submit core, outcrop, seismic survey, cross sections, well logs, and other unspecified 

data. Some later passages on this subject suggest that they are not all necessarily required, 

but rather are examples of types of data that could be used to demonstrate and quantify 

various key characteristics of a formation. With respect to the need for various types of 

geological data, the document is at times vague, inconsistent and, occasionally, even 

contradictory. It is critical that geologic heterogeneity and regional differences in data 

availability be acknowledged and state or regional directors be given the flexibility to 

make decisions based on data sets that reflect the geologic and regional differences. For 

instance, seismic survey data are limited in coverage, are expensive to acquire, can be 

inconclusive with respect to interpretation, and should not be universally required as a 

precondition for site consideration. The regulations must be performance-based and 

reinforce the need to technically and efficiently achieve specific goals, such as proving 

that an adequate and competent seal exists or that a target formation has sufficient 

injectivity. The regulations should not prescribe precisely how such proof is obtained, but 

should only dictate that sufficient proof be presented to the director. The regulations 

should give the director a significant degree of flexibility to determine whether the body 

of evidence presented by the owner/operator constitutes sufficient proof that USDWs will 

be protected. The regulations may include a list of useful data types, but EPA should 

clearly state that the list is one of available tools from which to choose the most 

applicable to a specific site, not a list of required applications and data that must be 

acquired and presented. 

Following is a series of comments with regard to the quote on page 43505: 
6 

“...require owners or operators to submit geochemical data on (a) the injection zone, (b) 

the confining zones, (c) containment zones above the confining zones in which any 

potentially migrating CO2 could be trapped, (d) all USDWs, and (e) any other geologic 

zone or formation that is important to the proposed monitoring program.” 

The EPA should recognize that it is essentially saying that the entire rock column from 

the injection zone to the surface must be geochemically characterized. Such 

characterization goes far above and beyond that which is necessary to protect the 

USDWs. It is essentially forcing owners/operators to pay for potentially unnecessary 

research activities. For instance, in the Williston Basin, a vast majority of the 

hydrocarbon production is historically from Paleozoic formations. One result of this is 

that there is a wealth of readily available data on the nature of Paleozoic formations in the 

Williston Basin. Likewise, the Cenozoic formations are fairly well characterized because 

of the presence of coal and potable aquifers. However, the Mesozoic formations that lie 

between those two groups are relatively poorly understood. This is because there is little 

economic incentive to characterize most of the Mesozoic rocks beyond the fact that they 

are dominated by low permeability shales and evaporites. There are 15 named rock units 

in the Mesozoic section of the Williston Basin. The regulations as proposed indicate that 

they must all be geochemically characterized. To geochemically characterize all of these 

Mesozoic units as part of a GS project in which the primary sinks and seals are in the 

deeper Paleozoic would be very expensive and of dubious value to anyone. Once again, 

there must be flexibility and discretionary powers given to directors with respect to what 

formations must be geochemically characterized. Indeed, this concept of flexibility must 

apply for all types of characterization that are considered necessary to prove that a GS 

well application can be approved. 

Page 43507. Regarding the use of proprietary models: 

 

The use of proprietary models absolutely should be allowable. In many cases, such 

software packages are the only reliable models that can be applied with any real 

confidence in their results. That being said, the use of such models should not be required 

because, in some cases, especially those where adequate data exist, nonproprietary 

models can serve the purpose in a more cost-effective manner. 

Page 43507. Corrective Action. Regarding the use of specific cements in GS wells: 

The document states that the EPA proposal does not prescribe the specific cements to be 

used to plug abandoned wells, but in the next paragraph states that corrosion-resistant 

cements would be required. This is contradictory. EPA must clarify this issue. 

Pages 43509 to 43510. Well Component Degradation. Regarding cements: 

It is frustrating that the EPA discounts real-world, field-based data in favor of laboratorygenerated data and models. In this case, it describes laboratory work that had somewhat 

contradictory results and acknowledge that “... field studies show clear evidence of 

reactions between CO2 and well cement, but do not show such severe corrosion.” EPA 
7 

then goes on to mention two instances of field-based research that show only limited 

effects of CO2 on cements. But as they historically have been known to do (EPA rulings 

on air quality issues in southwestern North Dakota being just one example), EPA chooses 

to ignore the real-world data and make decisions based on the dire results of tests 

conducted on small samples under laboratory conditions that can be applied only to a 

very narrow set of subsurface conditions, if at all. The result of this is that the proposal 

can be interpreted to require the use of relatively new and expensive corrosion-resistant 

cements rather than cements that have already been used successfully at large-scale CO2

injection sites, in some cases for decades. One potential unintended consequence of this 

requirement is that the mechanical integrity of these new cements under deeper reservoir 

pressure and temperature conditions may not be completely understood, especially over 

time. Again, flexibility should be allowed with respect to the selection of cements. 

Page 43512. Injection Depth in Relation to USDWs. 

The requirement to be below the lowest USDW is not needed and should be evaluated on 

a site-specific basis. Furthermore, minimum depths should not be required. Again, this 

should be site-specific. 

Page 43515. Regarding monitoring wells in the Area of Review (AoR). 

Text in this section implies that monitoring wells in the injection zone within the AoR are 

desirable, which could be interpreted by some as being required. The first comment with 

respect to this issue is that it is important to note that monitoring wells that penetrate the 

plume have potential to serve as a leakage pathway and, therefore, their use should be 

minimized. Secondly, one of the reasons given for the placing of monitoring wells in the 

AoR is that studying the interactions between brine and CO2 may allow for the 

determination of whether precipitation and/or dissolution of minerals is occurring. It is 

important to note that such interactions are currently not well understood and are the 

topic of great debate and controversy within the published literature. There is no 

consensus in the technical community as to how such data evaluated in the context of a 

single site, as site-specific permitting and monitoring must be, can be applied to ensuring 

the protection of USDWs at that site. While such data would surely be interesting and 

possibly useful from a scientific standpoint when taken in the context of many sites, it is 

not clear how it could be applied to prove or disprove that USDWs at a given location are 

being protected or are in danger of contamination. This requirement comes across as a 

regulatory-mandated means of gathering data for researchers, an activity that is outside 

the scope of USDW protection and should not be forcibly paid for by owners/operators of 

GS wells. 

Page 43515 to 43516. Regarding monitoring. 

In general, this section is overly prescriptive with respect to the selection and application 

of monitoring techniques. One of the things that is lost in this discussion is that if the 

geometry of the trapping structure is well understood and the overlying seal has been 

demonstrated to be competent and thick, then plume monitoring should be relatively 
8 

straightforward and less complicated. Consider, for example, injection into a thoroughly 

characterized high-relief structure, such as an anticline or pinnacle reef encased in 

impermeable anhydrite. Migration of the CO2 would be minimal, and plume stabilization 

would be relatively rapid. A few carefully instrumented and placed monitoring wells, 

some above the seal and others just outside and below the structure, would be enough to 

ensure the plume does not leak through the seal or slip beneath the spill point at the 

bottom of the structure. With this in mind, it can be reasonably argued that seismic 

surveys (which may or may not provide useful insight regarding the plume, depending on 

the lithology) would not offer any additional data that would further ensure the protection 

of USDWs. If there is no significant structural element to the trap, then plume 

stabilization could very well take many decades, and in such a case, a more robust and 

comprehensive suite of monitoring tools may have to be applied. Many examples of both 

types of sites, and many more that fall in between, have been identified throughout the 

United States, and it is because of this variety that it is critical that UIC regulations for 

GS allow flexibility in choosing plume-tracking methods. The EPA acknowledges the 

need for flexibility in a paragraph in the middle of page 43516, but many of the 

requirements laid out in the document do not reflect that need. 

Page 43519. Combination of Fixed Time Frame and Performance Standard (monitoring). 

The EPA is proposing a postinjection monitoring period of 50 years, with the director 

having some discretion to either shorten or lengthen that time period. Based on the 

proposed text, 50 years is the default time period for postinjection monitoring until data 

on pressure, fluid movement, mineralization, and/or dissolution reactions support a 

determination that the plume has stabilized and does not pose a risk to USDWs. Referring 

to this as the “default” time period and requiring the acquisition of described data sets to 

modify the time period for monitoring indicate that a significant amount of 

characterization effort would have to be conducted during the postinjection period, 

perhaps over several years, to get such a change. The EPA acknowledges that modeling 

results indicate that CO2 plume stabilization likely occurs on the time frame of 10 to 

100 years after injection stops. One example of a GS site where plume stabilization could 

very well take 50 years or more is a site where there is no significant structural trapping 

element to the reservoir. A plume at such a location may behave in a less predictable 

manner and expand or migrate a significant distance before it stabilizes. However, CO2

injected into a thoroughly confined high-relief structure (e.g., pinnacle reef, carbonate 

mound, anticline, etc.) would likely stabilize relatively quickly. Barring a seismic event 

that breaches the seal, the movement of such a plume would be nil because it would 

literally have nowhere to go. In those cases, requiring the continued collection of several 

types of data for several years in order to prove what was probably obvious years before 

injection ceased would serve no real purpose other than to satisfy an arbitrary regulation. 

The nature of structural characteristics at each site under consideration for GS will be 

identified almost immediately, defined in detail during the earliest stages of site 

evaluation, and the understanding of their geometry will likely be further refined over the 

course of monitoring during the injection phase of the project. It is also important to keep 

in mind that the injection phase of GS projects, and the monitoring that goes with them, 

will, in most cases, be conducted for decades. Over those years, knowledge of the 
9 

reservoir system will increase, and by the time the injection phase comes to an end, there 

will be ample data to make informed decisions regarding an appropriate postinjection 

monitoring period. All of this leads to a logical conclusion that the establishment of 

postinjection monitoring periods should be site-specific and flexible. The 50-year site 

monitoring statement appears to have no rational basis and might effectively eliminate 

commercial activity. 

 

In summary, the proposed default monitoring time frame should be eliminated and 

replaced with a solely performance-based standard that reflects the specifics of a project 

and the knowledge of that project gained through the procedures and processes that are 

already required. The proposed rule gives the program director discretion to extend or 

shorten the postinjection site care period based on project-specific considerations; 

therefore, it seems unnecessary to, by rule, establish a lengthy default period. 

Page 43520. Proposed Financial Responsibility and Long-Term Care Requirements 

The requirements for financial assurance may discourage commercialization of CCS. As 

currently proposed, the rules would place greater financial assurance requirements on 

Class VI wells than are currently placed on Class I hazardous waste wells. The more 

rigorous requirement may result in a needless negative public perception of CCS. The 

chemical and physical properties of carbon dioxide injected for storage purposes are not 

uniquely distinctive to garner such attention under the UIC Program. 

Furthermore, in order for CCS projects to come to fruition, financial assurance 

obligations need to be consistently and reasonably achievable. If not, considerable 

uncertainties will be introduced into the economics and finances of proposed projects. 

The currently proposed rule assumes reliable cost estimates will be available at the time 

of permitting for a broad range of long-term activities lasting more than 50 years into the 

future. EPA should carefully consider the implications of the proposed financial 

assurance provisions so as to not discourage CCS activities. 

Pages 43525 to 43526. Regarding cost of compliance. 

EPA compares the costs associated with standard Class I wells and the proposed Class VI 

wells and estimates that the proposed rules would increase the costs of complying with 

UIC regulations by 46%. The EPA also states that it they “believe[s] the proposed rule 

will not impede CO2 GS from happening....” First, a 46% increase in costs is significant. 

Second, to profess that such a large increase in costs will not impede the implementation 

of GS projects seems rather naïve. 

Page 43535. § 146.5 Classification of injection wells.

Class VI wells should not be limited to injections beneath the lowermost formation 

containing a USDW. This is too restrictive in some areas. For instance, consider as an 

example the Lower Cretaceous Dakota Group in the North Dakota portion of the Williston 

Basin. On the eastern margin of the Williston Basin in North Dakota, the water within the 
10 

Dakota Group contains total dissolved solid (TDS) concentrations well below 10,000 parts 

per million (ppm), and the formation therefore qualifies as a USDW. However, hundreds 

of miles to the west and southwest, near the center and southwestern flanks of the Williston 

Basin, the Dakota Group has TDS concentrations well above 10,000 ppm, and it is used 

extensively as an injection disposal zone for oil field produced waters. The demonstrated 

injectivity of the Dakota Group and its unsuitability as a potential USDW in western North 

Dakota make it an attractive target for industries seeking to geologically store large 

volumes of CO2. A strict, literal interpretation of the proposed rule could unreasonably 

preclude the Dakota Group from being considered as a potential target zone for CO2 

storage. It is likely that similar examples of this scenario could be found in many other 

sedimentary basins. 

Page 43536. § 146.82 Required Class VI permit information. 

There are numerous requirements for information on formations overlying the proposed 

storage site. Requirements should be flexible and site-specific. The required information 

should be limited to relevant primary and/or secondary seals and be used to document the 

vulnerability or lack thereof of any USDWs in the area. 

Page 43536. § 146.82 Required Class VI permit information. 

The requirement of baseline geochemical data on subsurface formations should be 

flexible and site-specific. The required information should be limited to relevant primary 

and/or secondary seals and be used to document the vulnerability or lack thereof of any 

USDWs in the area. 

Page 43536. § 146.82 Required Class VI permit information. 

Well-plugging requirements can change throughout the life of a well. Therefore, 

requiring a well-plugging plan with the permit application is excessive and unnecessary. 

Page 43536. § 146.83 Minimum criteria for siting. 

Requiring the injection zone to have the ability to receive the “total anticipated volume of 

the carbon dioxide stream” seems unreasonable. Linking CO2 source potential with CO2 

injection potential is not recommended, and flexibility is required. For example, if the 

stream is coming from a power generating facility, it can be difficult to estimate the 

longevity of the plant given changes in technology that may allow for increased energy 

output. Multiple storage sites may be required for one source, or conversely, multiple 

sources may utilize a single storage site. 
11 

Page 43538. § 146.86 Injection well construction requirements. 

Requiring surface casing to extend below the base of the lowermost USDW precludes 

potential sequestration zones. 

Page 43538. § 146.87 Logging, sampling, and testing prior to injection well operation.

“...the owner or operator must run appropriate logs, surveys and tests to determine or 

verify the depth, thickness, porosity, permeability, and lithology of, and the salinity of any 

formation fluids in, all relevant geologic formations.” Relevant geologic formations 

needs to be defined. 

Page 43538. § 146.87 Logging, sampling, and testing prior to injection well operation.

The coring requirements are too burdensome if applicable cores are already available in 

the vicinity of the project. 

Page 43538. § 146.87 Logging, sampling, and testing prior to injection well operation.

Given the complexity of scheduling various service companies and activities at a project 

location requiring a schedule of all logging and testing 30 days prior to the first test and 

submission of any changes to the schedule 30 days prior to the next scheduled test are 

pointless and oftentimes impractical. 

Comments with regard to operating requirements, testing and monitoring, plugging, 

postinjection site care and site closure. 

Many comments that could be directed at the specific requirements were addressed previously in 

this document. Therefore, they will not be repeated here. 
Letter ID: 0220 

Commenter: Edward Steadman 

Organization: The Energy and Environmental Research Center at the University of North Dakota 

Letter ID: 0220 Comment ID: 21573 Letter Lines: 53 to 77 

Comment Code: 1250 1.1.1.4 Flexibility is needed (performance-based standards) 

Comment: Just as in nature with deep-sourced, natural CO2, there are low-risk sites that 

will permanently entrap CO2, and there are places where it may migrate, perhaps 

even to the surface. CO2 is a naturally occurring substance, and movement within 

the subsurface is very common. Rather than trying to fashion rules that protect 

against surface escape in all subsurface conditions, regulatory oversight needs 

to recognize the nearly ubiquitous presence of the molecule while identifying 

low-risk sites for entrapment and provide flexibility in regulation to 

accommodate the attendant risk level. 

In order to achieve statistically significant reductions of greenhouse gas 

emissions, large-scale carbon capture and storage (CCS) will have to be 

implemented at numerous sites. One of the greatest potential barriers to 

widespread deployment of sequestration projects would be the specification of 

overly complex well design and monitoring of sites. Experience shows that exotic 

well designs add little benefit, while, on the other hand, judicious site 

selection adds greatly to the security of emplacement. For example, subsurface 

sequestration formations overlain by bedded salts provide optimal conditions for 

long-term storage. The focus of regulation should be performance criteria, not 

design criteria. As long as CO2 sequestration sites can meet the standards 

required for permitting, injection of CO2 for sequestration is, to a large 

extent, similar to EOR operations. In turn, requirements for injection wells 

accessing judiciously selected zones for sequestration should be more closely 

aligned with those of Class II standards than the more stringent Class I 

hazardous waste well standards. As currently proposed, the Class VI requirements 

are more reflective of Class I hazardous waste well standards. 

Individual Response: The Agency believes that the Class VI requirements balance site-specific 

flexibility with USDW protection. Rather than setting performance or technology-based 

standards for GS projects, EPA is adopting a flexible approach, where operators of GS projects 

would develop and implement site-specific plans for delineating the AoR, testing and monitoring 

the site, performing corrective action, and post-injection site care. EPA believes that the plans—

which would be reviewed and approved by the Director and periodically updated throughout the 

life of the project—promote an ongoing dialogue between the operator and the Director that will 

encourage use of the most appropriate technologies for a particular project. 

EPA clarifies that the Class VI GS requirements are designed to ensure that, where deployed, GS 

1
is conducted in a manner that protects USDWs from endangerment. Encouraging investment in 

CCS projects and facilitating deployment are outside the scope of the GS rulemaking. 

Letter ID: 0220 Comment ID: 21574 Letter Lines: 79 to 92 

Comment Code: 1480 1.2.2.2.2 CO2 is not a pollutant 

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

Comment: It is important to be mindful that CO2, relative to other common and not-socommon injectates, is relatively innocuous. Increasing concentrations are easily 

detected in groundwater through simple monitoring of pH. Carbon dioxide in 

groundwater poses minimal acute or chronic threat to human health or the 

environment, especially when compared to other materials that have been 

classified as hazardous. As long as potential injection sites are appropriately 

characterized and judiciously selected and injection operations are designed and 

conducted according to longstanding engineering and regulatory standards, the 

leakage of CO2 into underground sources of drinking water (USDW) is likely to be 

a preventable and infrequent occurrence. In the rare event that CO2 should leak 

into USDWs, it is also important to note that its primary effect on groundwater 

will be to form a weak acid (carbonic acid) and lower pH, which can be 

relatively easily mitigated by a variety of commonly used, simple remediation 

practices. 

Individual Response: In response to the comment that CO2 is relatively innocuous and that the 

primary effect of a leak to groundwater will be to form a weak acid and lower pH, EPA clarifies 

that the mission of the UIC Program is to protect USDWs from injection activity that may 

endanger USDWs. Reduction in pH may also lead to mobilization of contaminants (e.g., arsenic, 

lead, and organic compounds), which can degrade water quality. In addition, the migration of 

formation fluids containing mobilized contaminants could cause endangerment of USDWs 

(Birkholzer et al., 2008a). 

EPA believes that the creation of a new injection well class (VI) under the existing UIC Program 

is necessary to enable deployment of GS as a climate change mitigation technology in a manner 

that protects USDWs from endangerment. EPA agrees that the UIC Program, under the authority 

of the SDWA, provides a strong framework for regulating injection of CO2 for GS and adds that 

the GS regulation tailors the UIC requirements to address the unique issues associated with 

large-scale GS including large injection volumes, the relative buoyancy of CO2, its corrosivity in 

the presence of water, the potential presence of impurities in captured CO2, and its mobility 

within subsurface geologic formations. 

EPA disagrees that the GS regulation overstates the risk of CO2 injection. 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, 

2
monitoring, and post-injection site care requirements in the GS rule to prevent leakage from 

injection formations and protect USDWs. 

EPA adds that the requirements of the GS rule are tailored to the nature of the CO2 itself and 

risks associated with the injection of CO2, and do not address the status of CO2 as either a 

pollutant, commodity, or waste. 

Letter ID: 0220 Comment ID: 21575 Letter Lines: 94 to 104 

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: A final comment has to do with any rules or policies that might marginalize EOR 

as a sequestration tool. The PCOR Partnership believes the early-captured CO2 

will be injected in large volumes and stored during existing and new commercial 

(i.e., EOR) operations. The only reference to the use of EOR sites for 

sequestration is contained in proposed rule § 146.83(c) which discusses 

repermitting existing wells as Class VI storage wells. The emission reduction 

potential and sequestration associated with EOR are immense, and revenues from 

the oil produced will offset the cost to the economy and will, ultimately, 

accelerate more widespread deployment of CCS technologies. With the growing 

energy concerns in the United States, the contributions of CO2 EOR in the 

advancement of CCS need to be embraced. This reality needs to be further 

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

injecting CO2 for the purpose of ER, and that sites used for ER may be suitable for GS and may 

be among the first GS sites. However, EPA believes that injection for the primary purpose of 

long term storage is sufficiently different from Class II ER operations and warrants tailored 

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

significantly greater than for Class II wells. Reservoir pressure conditions will also be different, 

with Class VI injection operations involving large volumes of CO2 and likely having higher 

pressures within their storage formations than Class II ER projects. 

EPA clarifies that the purpose of the GS rule is to ensure protection of USDWs from 

endangerment and not to promote or incentivize GS deployment. However, the Agency believes 

that establishing a regulatory framework for the future development and deployment of CCS 

technology can provide the regulatory and jurisdictional certainty needed to foster development 

and deployment of CCS while ensuring USDW protection. 

Letter ID: 0220 Comment ID: 21576 Letter Lines: 104 to 106 

Comment Code: 2064 1.5.3.2 Grandfathering construction of Class II wells (seeking comment) 

Comment: advancement of CCS need to be embraced. This reality needs to be further 

embraced when one contemplates a streamlined approach, such as "grandfathering" 

3
for Class II wells that may be useful for sequestration beyond the EOR project. 

Individual Response: EPA agrees that many Class II wells are designed and constructed to 

withstand exposure to CO2. The final GS rule provides for the construction of these 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, in lieu of requirements at §146.86(b) and §146.87(a). 

EPA adds that promotion of CCS is not within the scope of the GS rulemaking. The purpose of 

the rulemaking is to ensure that, where GS is deployed, it is conducted in a manner that protects 

USDWs from endangerment. 

Letter ID: 0220 Comment ID: 21577 Letter Lines: 108 to 120 

Comment Code: 1250 1.1.1.4 Flexibility is needed (performance-based standards) 

Comment: Detailed Comments 

Page 43492. SUMMARY. Regarding the phrase "...help ensure consistency..." 

Consistency does not necessarily mean that regulations are appropriate or 

effective. Geology is notoriously heterogeneous and, therefore, by definition 

inconsistent. Striving for consistency across geologic systems is difficult at 

best. One need only to look at the history of injection regulation across 

different states to see a lack of consistency is appropriate and primarily due 

to heterogeneity and inconsistency with respect to regional geologic 

characteristics. Guidelines must be flexible. Flexibility to ensure the safe 

maximization of CO2 storage must not be compromised by a desire to ensure 

consistency of rules across all geologic settings. 

Individual Response: EPA agrees that permitting decisions for GS wells should be based on 

site-specific factors. The GS rule requires owners or operators to submit, and Directors to 

consider, extensive site-specific data, specified at §146.82, to demonstrate that a site is suitable 

for GS. Additionally, many of the permit requirements for GS wells are established through 

individualized site-specific plans for AoR and corrective action, testing and monitoring, and 

injection well plugging and post-injection site care and site closure. EPA adds that the final GS 

rule includes a balance of specific criteria to be met by the owner or operator and areas of 

Directorial discretion and considerations for how that discretion would be exercised. The Agency 

believes this balance allows for GS projects to be designed and permitted to address the unique, 

site-specific aspects of each project, while providing consistency in permitting across the U.S. 

As described above, encouraging investment in CCS projects and facilitating deployment are 

outside the scope of the GS rulemaking. 

4
Letter ID: 0220 Comment ID: 21584 Letter Lines: 122 to 125 

Comment Code: 1400 1.2 Comments on EPA's Authority to Regulate Injection of CO2 

Comment: Page 43495. II. What Is EPA Proposing. "development of a key climate change 

mitigation technology"? Will these rules really support the "development of a 

key climate change mitigation technology"? Is it really within the purview of 

protecting USDW? 

Individual Response: EPA is finalizing federal minimum requirements for geologic 

sequestration under the SDWA’s UIC program. EPA believes that GS is a key climate change 

mitigation technology that is part of a portfolio of options that could be deployed to reduce CO2 

emissions. The SDWA mandates EPA to establish federal minimum requirements for state 

programs in order to prevent underground injection that endangers USDWs. See 42 U.S.C. 

§300h et. seq. Under the SDWA, the underground injection of any "fluid" is subject to the 

requirements of the UIC program. "Fluid" is defined under 40 CFR 144.3 as any material or 

substance which flows or moves, whether in a semisolid, liquid, sludge, gas or other form or 

state, and includes liquids, gases, and semisolids (i.e., slurries) injected into the subsurface. CO2 

injected for the purpose of GS is subject to the SDWA. 

EPA clarifies that the scope of this GS regulation is limited to injection of CO2, and that all 

requirements in the GS rule are designed to protect USDWs from endangerment. 

EPA acknowledges that GS falls within the broader context of CCS and the need for regulatory 

clarity to ensure that USDWs are protected from endangerment. In developing the final GS rule, 

the Office of Water coordinated with other Agency program offices and across federal agencies 

(e.g., with the Department of Energy; United States Geological Survey; Bureau of Ocean Energy 

Management, Regulation, and Enforcement, formerly the Minerals Management Service; Bureau 

of Land Management). The Agency continues to evaluate areas of potential applicability of other 

Federal environmental statutes including, but not limited to: the Clean Air Act; the Resource 

Conservation and Recovery Act; the Comprehensive Environmental Response, Compensation, 

and Liability Act; and the Marine Protection, Research and Sanctuaries Act to various aspects of 

GS and CCS. The Agency will continue to coordinate on GS and CCS related issues to minimize 

redundancy and maximize efficiencies for owners or operators. For additional information, 

please see the discussion entitled "How Does This Rulemaking Relate to Other Federal 

Authorities and GS and CCS Activities?" in the preamble to the final GS rule. 

Letter ID: 0220 Comment ID: 21585 Letter Lines: 127 to 140 

Comment Code: 1250 1.1.1.4 Flexibility is needed (performance-based standards) 

Comment: Page 43496. B. What Is EPA’s Authority under the Safe Drinking Water Act 

(SDWA) 

to Regulate Injection of CO2?Regarding the following quote from the document, 

referring to a key aspect of the Safe Drinking Water Act: 

5
"Section 1421 (b)(3)(A) of the Act also provides that EPA’s UIC regulations 

shall permit or provide for consideration of varying, geologic, hydrological, or 

historical conditions in different States and in different areas within a 

State." 

It is important that this aspect of the SDWA is a guiding principle for the 

proposed regulations. Based on those words in the SDWA, flexibility is demanded 

by statute and must be built into any UIC regulations. Unfortunately, the 

regulations proposed for GS wells in this document are often anything but 

flexible, but rather are quite prescriptive and inflexible. 

Individual Response: As described above, EPA believes that the Class VI requirements balance 

site-specific flexibility with USDW protection. The final GS rule affords flexibility to owners or 

operators. Many of the permit requirements will be established through site-specific plans 

developed by the owner or operator and approved by the Director. 

Letter ID: 0220 Comment ID: 21586 Letter Lines: 142 to 142 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment: Page 43498. The Weyburn Field is in Saskatchewan, Canada, not Alberta. 

Individual Response: EPA acknowledges the comment and agrees. 

Letter ID: 0220 Comment ID: 21587 Letter Lines: 144 to 146 

Comment Code: 1230 1.1.1.2 General comments on the regulatory text 

Comment: Page 43498. The example cited here (Crystal Geyser, Utah) is not associated with 

an "injection activity." It is naturally occurring CO2 that leaks via an 

improperly abandoned exploration well. 

Individual Response: EPA agrees with the commenter that the Crystal Geyser site is not 

associated with injection. However, this incident demonstrates that abandoned or improperly 

plugged boreholes can serve as conduits for migration of fluids to USDWs. It is for this reason 

that the final rule includes requirements related to performing corrective action on all deficient 

wells within the AoR at §146.84, and proper injection well construction that meets the goals of 

§146.86. 

Letter ID: 0220 Comment ID: 21588 Letter Lines: 148 to 150 

Comment Code: 1655 1.3.5.1 Concerns about Lake Nyos and Mammoth Mountain-type events 

Comment: Page 43498. This page includes a very good and reasonable description of the 

6
relative inapplicability of the Lake Nyos incident as an analog for possible 

negative consequences of a large CO2 leak from a geologic storage site. 

Individual Response: EPA acknowledges the comment. 

Letter ID: 0220 Comment ID: 21589 Letter Lines: 152 to 162 

Comment Code: 1670 1.3.7 Other/miscellaneous risks 

Comment Code: 5280 2.8.2.4 USDW non-endangerment demonstrations 

Comment: Page 43498. Regarding the statement, "the measures outlined in today’s proposed 

rulemaking to prevent endangerment of USDWs may also prevent migration of CO2 to 

the subsurface." 

This statement is fine, as long as protecting leakage to the atmosphere does not 

lead to stricter measures than would be required to protect USDWs. For example, 

regulations should be driven by a desire to maintain a leakage rate below a 

certain percentage of the injected volume, unless that percentage can be 

demonstrated to adversely affect USDWs. Another way to state it is this: a 1% 

leakage rate may or may not adversely affect USDWs; therefore, a 1% rate should 

not necessarily be unacceptable. 

Individual Response: EPA clarifies that all requirements in the GS rule are for the purpose of 

preventing endangerment to USDWs, and that the tailored permitting, siting, construction, 

operation, monitoring, and post-injection site care requirements in the GS rule are intended to 

prevent leakage from injection formations and protect USDWs. 

EPA acknowledges that there are potential risks associated with GS. The purpose of the Class VI 

requirements is to minimize and mitigate potential/identified risks through proper site 

characterization, well construction, operation, monitoring, post-injection site care, and site 

closure and to ensure protection of USDWs. The Agency clarifies that, under SDWA, EPA does 

not have the authority to directly regulate air emissions via CO2 leakage to the surface. 

However, the GS rule requires that CO2 injected for GS remain confined in the injection zone. 

Leakage outside of the injection zone as defined in a Class VI permit, which may be evidenced 

by leakage to the surface, would be a permit violation if a USDW is endangered. 

Letter ID: 0220 Comment ID: 21590 Letter Lines: 164 to 168 

Comment Code: 1810 1.4.1 Research on identifying risks to USDWs 

Comment Code: 3300 2.2.1 Delineating the AoR/Modeling CO2 movement 

Comment: Page 43499. One would caution rule makers on putting too much faith into any one 

institution or any one method when studying potential impacts. Should not such 

information be provided by various technical sources? While the utility of 

models and laboratory data is recognized, their results should not supersede 

7
real-world experience, field-based data, and local knowledge. 

Individual Response: EPA considered a wide range of information from laboratory, modeling, 

and field research as it developed the requirements for GS wells. In addition to laboratory studies 

and modeling research that provide relevant information on GS, the Agency is also involved in 

collecting and analyzing GS project data and permit information from a variety of sources. Most 

notably, EPA has evaluated UIC permits and reviewed operational data and information 

associated with the seven regional carbon sequestration partnerships funded by the U.S. 

Department of Energy and coordinated through the National Energy Technology Laboratory 

(NETL), and several international projects. In addition to the information cited in the preamble to 

the proposed rule, EPA published a Notice of Data Availability and Request for Comment 

(NODA) on August 31, 2009 (74 FR 44802), in which the Agency described the preliminary 

results of research at three DOE partnership sites: the Escatawpa, Mississippi project; the Aneth 

Field project in Paradox Basin, Southeast Utah; and the Pump Canyon Site, New Mexico. 

Regarding the suggestion that EPA give more weight to field data and experiential knowledge, 

EPA notes that it continues to track ongoing field and laboratory research into all aspects of GS. 

For example, EPA is tracking the operations and technical developments of more than three 

dozen small- and large-scale GS injection projects in the US and abroad. Also, since field 

experience and well construction, injection, and monitoring information relevant to GS comes 

from operations that inject acid gas or inject CO2 for ER, the Agency has conducted evaluations 

regarding these commercial field operations and continues to track GS-relevant developments in 

these commercial operations. 

The Agency will continue to track GS project developments and evaluate new and ongoing 

research and information to ensure USDW protection. EPA is using an adaptive approach to 

regulating GS under the UIC Program. Even after finalization of the GS regulation, the Agency 

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

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

and to determine if modifications to the finalized requirements are appropriate or necessary. 

EPA agrees that AoR modeling should be based on actual data collected on the site, including 

detailed geologic data collected to characterize the injection zone, confining zone and any 

additional zones, as required at 146.84(c)(1)(i). The Agency believes that the integration of site 

specific information into a predictive multiphase computational model will ensure the best 

possible AoR delineation. EPA also recognizes that modeling technology will continue to 

improve, and encourages and expects owners or operators to use the best available multiphase 

computational models to determine the AoR. Reliance on improved models will likely increase 

the accuracy and quality of the AoR characterization, resulting in increased protection of 

USDWs from endangerment. 

Letter ID: 0220 Comment ID: 21591 Letter Lines: 170 to 173 

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language 

Comment: Page 43500. Regarding the statement, "4-D seismic is a valuable tool for plume 

8
tracking" at Weyburn. "Is" is a strong word. Based on personal conversations 

with those who have worked on Weyburn, it is suggested that "may be" is more 

accurate. 

Individual Response: EPA acknowledges the comment; this paragraph is not included in the 

preamble to the final rule. 

Letter ID: 0220 Comment ID: 21592 Letter Lines: 175 to 178 

Comment Code: 1810 1.4.1 Research on identifying risks to USDWs 

Comment Code: 3300 2.2.1 Delineating the AoR/Modeling CO2 movement 

Comment: Page 43500. Regarding the basis of some of the rules related to modeling Much 

has happened in the world of modeling CO2 injection and long-term storage since 

2005. Many of the key messages from the workshop upon which some of the 

statements on this topic are based may be long out of date. 

Individual Response: EPA continues to review new and ongoing modeling studies, including 

those conducted at national research laboratories, such as Lawrence Berkeley National 

Laboratories as well as data from the DOE Partnership GS pilot projects where some of the most 

current models are being developed and/or used. EPA published a Notice of Data Availability 

and Request for Comment on August 31, 2009 (74 FR 44802), in which the Agency described 

two recent modeling studies by the Lawrence Berkeley National Laboratory on the potential 

effects of CO2 injection on USDWs and human health in the event that a GS project is not 

properly sited, operated, or managed. These studies are in the rulemaking docket and on LBNL's 

website at http://esd.lbl.gov/GCS/projects/CO2/index_CO2.html. Additionally, EPA continues to 

fund research on ground water that will integrate experimental and modeling efforts with the 

objective of evaluating the potential consequences of CO2 leaks from GS operations into ground 

water resources. 

EPA is using an adaptive approach to regulating GS under the UIC Program. Even after 

finalization of the GS regulation, EPA 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. 

As described above, EPA recognizes that modeling technology will continue to improve, and 

encourages and expects owners or operators to use the best available multiphase computational 

models to determine the AoR. Reliance on improved models will likely increase the accuracy 

and quality of the AoR characterization, resulting in increased protection of USDWs from 

endangerment. 

Letter ID: 0220 Comment ID: 21593 Letter Lines: 180 to 187 

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

9
dividing line between Class II and Class VI (seeking comment) 

Comment: Page 43502. G. How Would This Proposal Affect Existing Injection Wells under the 

UIC Program? 

The regulatory regime should readily accommodate the adoption of Class II wells 

into any new category. Unfortunately, this entire section gives the impression 

that storage is not occurring during EOR activities, which is not true. EOR 

provides partial storage capability until such time as the recovery of 

hydrocarbons ceases and all production activities are ended. 

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

injecting CO2 for the purpose of ER, and that sites used for ER may be suitable for GS and may 

be among the first GS sites. Furthermore, EPA recognizes that some CO2 is sequestered when 

injecting CO2 for purposes of EOR. However, the Agency believes that the nature and risks of 

CO2 injection for the primary purpose of long term storage poses different risks than injection 

for the primary purpose of EOR, and therefore has developed new Class VI regulations to 

address these unique risks. For example, the volume of CO2 anticipated to be injected for long 

term storage is significantly greater than for EOR operations. Reservoir pressure conditions will 

also be different, with Class VI injection operations involving large volumes of CO2 and likely 

having higher pressures within their storage formations than Class II EOR projects. 

Letter ID: 0220 Comment ID: 21594 Letter Lines: 189 to 204 

Comment Code: 2143 1.6.2.1 Comments in favor of injection into depleted reservoirs 

Comment: Page 43502. H. What Are the Target Geologic Formations for GS of CO2? 

This section grossly misrepresents the types of geologic formations that are 

suitable for CO2 sequestration. It is irresponsible to discredit the meaningful 

role that depleting and/or depleted oil and gas reservoirs can play in 

sequestering CO2. While the document gives credit to the vast amount of 

geological information that is known about oil and gas reservoirs, it then 

implies that this knowledge does not overcome all of the perceived technical 

challenges associated with using oil and gas reservoirs for geologic storage. 

The techniques that would be used to alleviate the concerns listed in this 

section are less onerous than the proposed requirements to permit a Class VI 

injection well. Additionally, just as all deep saline formations may not be 

suitable for geologic storage, there may be oil and gas reservoirs that are not 

suitable as well. Prudent site selection should help determine suitable geologic 

settings, not broad statements declaring one geologic formation better than the 

other. 

Individual Response: EPA agrees that depleted oil and gas fields are promising formations for 

GS. However, EPA also believes that large-scale GS presents unique technical challenges, 

including large injection volumes, the relative buoyancy of CO2, its corrosivity in the presence 

10
of water, the potential presence of impurities in captured CO2, and its mobility within subsurface 

geologic formations. For this reason, EPA has finalized the tailored requirements in the GS rule. 

The final GS rule does not preclude injection into any formation type, including oil and gas 

reservoirs, provided owners or operators can demonstrate that GS can be performed in a manner 

that protects USDWs from endangerment and that the Class VI siting, well construction and 

operation, monitoring and testing, and post-injection site care and site closure requirements are 

met. 

EPA further clarifies that the GS rule is not intended to promote a preference for GS in any 

particular formation type, to address use of resources, or to reduce costs associated with GS into 

various formations. The focus of the GS rule is to ensure that, where GS is deployed, it is 

conducted in a manner that protects USDWs from endangerment. 

Letter ID: 0220 Comment ID: 21595 Letter Lines: 206 to 213 

Comment Code: 2163 1.6.3.1 Comments in favor of injection into unmineable coal seams 

Comment: CO2 storage in coal seams is an area of very active research. DOE Partnerships 

are conducting pilot-scale coal seam sequestration field tests. Utilizing coal 

seams at shallow depths would require less compression (gas phase vs. 

supercritical CO2), reduce drilling costs, may allow for greater concentrations 

of inert nitrogen (which could reduce capture costs), and be proximal to many 

minemouth operations. Ruling out such storage by administrative fiat is 

premature. The results of ongoing research need to be considered prior to such 

proposed actions. 

Individual Response: The final GS rule does not preclude injection into unmineable coal seams 

(or any formation type) provided owners or operators can demonstrate that GS can be performed 

in a manner that protects USDWs from endangerment as required under the GS final rulemaking. 

The Agency anticipates that in the near-term, most GS in unmineable coal seams will continue to 

be experimental. Such projects may be permitted as Class V experimental technology wells if 

they are of an experimental nature (i.e., to test GS technologies and collect data). EPA will 

continue to review data on early GS projects, including those in unmineable coal seams, to 

determine whether the appropriate amount and types of information and documentation are 

required and being collected. EPA 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. 

EPA recognizes that GS in unmineable coal seams has been the subject of less research than 

saline formations or depleted oil and gas reservoirs. However, EPA has examined select field 

projects involving injection into unmineable coal seams, including the Pump Canyon Site, near 

Archuleta, New Mexico. In the Notice of Data Availability and Request for Comment, EPA 

described research at the Pump Canyon site where the Southwest Partnership is studying CO2 

injection into deep, unmineable coal seams and performing a "seal analysis" of the ability of the 

11
Kirtland Formation to act as a barrier to the movement of CO2 or other reservoir fluids. EPA 

continues to follow this project, recently completed projects, and ongoing GS projects injecting 

into unmineable coal seams. Other coal seam injection projects are underway through the RCSPs 

in the Illinois Basin, Black Warrior Basin, and Central Appalachian Basin. 

Letter ID: 0220 Comment ID: 21608 Letter Lines: 215 to 217 

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

Comment: Page 43503. H. Is Injected CO2 Considered a Hazardous Waste under RCRA? 

No. CO2 should not be considered a hazardous waste under RCRA. 

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

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

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

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

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

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

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

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

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

proposal will need to do so during the comment period for that rule. Finally, EPA also notes that 

the final GS rule, which adds new regulations for Class VI wells under the Safe Drinking Water 

Act (SDWA), is not making any changes to the RCRA regulations. 

Letter ID: 0220 Comment ID: 21609 Letter Lines: 219 to 221 

Comment Code: 1640 1.3.4 CERCLA issues (seeking comment) 

Comment: Page 43504. J. Is Injected CO2 Considered a Hazardous Waste under CERCLA? 

No. CO2 should not be considered a hazardous waste under CERCLA. 

Individual Response: CO2 itself is not listed as a hazardous substance under CERCLA 

however, the CO2 stream may contain a listed hazardous substance (such as mercury) or may 

mobilize substances in the subsurface that could react with ground water to produce listed 

hazardous substances (such as sulfuric acid). Whether such substances may result in CERCLA 

liability from a sequestration facility depends entirely on the composition of the specific CO2 

stream and the environmental media in which it is stored (e.g., soil or ground water). CERCLA 

exempts from liability, under CERCLA section 107, 42 U.S.C. 9607, certain “federally permitted 

releases” (FPR) as defined in CERCLA, 42 U.S.C. 9601(10). Class VI permits will need to be 

carefully structured to ensure that they prevent potential releases from the well which are outside 

the scope of the Class VI permit. 

12
EPA is promulgating this rule under SDWA. To the extent that commenter is seeking 

interpretations of CERCLA and its related provisions, such interpretations are outside the scope 

of this rulemaking. 

EPA clarifies that, while the Administrator reserves the right to promulgate regulations 

designating additional substances as hazardous under §102 of CERCLA, EPA intends to avoid 

any potential overlap of SDWA and CERCLA authority through its comprehensive Class VI 

requirements. 

Letter ID: 0220 Comment ID: 21610 Letter Lines: 223 to 234 

Comment Code: 3140 2.1.4 Comments that the proposed geologic data requirements are too 

stringent 

Comment: Page 43505. 1. Proposed Geologic Siting Requirements 

With regard to the need for data on all USDWs at a site: 

Wording here suggests that maps and cross sections must be generated of all 

USDWs near the proposed injection well. Submitting maps and cross sections of 

all of the USDWs, not just the lowermost USDW, seems unnecessarily burdensome to 

the owner/operator. Such maps will require significant additional work, and it 

is not clear how doing so will result in improved protection of USDWs since 

protective casing is already required from the surface all the way to the bottom 

of the lowermost USDW. Identifying and mapping the lowermost USDW should be 

sufficient to protect all overlying USDW zones. 

Individual Response: EPA believes that identifying and mapping all surrounding USDWs near 

an injection well, as specified at §146.82(a)(5), is necessary to ensure protection of all USDWs 

from endangerment. The purpose of the UIC requirements (including those for Class VI wells) is 

to ensure the protection of USDWs from endangerment, which are defined based on total 

dissolved solids (TDS) content, not their location or depth (§144.3). 

EPA adds that knowing the number, location and depth of USDWs near an injection well will 

generate baseline regional information, support development of an effective testing and 

monitoring plan, and enhance owner or operator and Director understanding of the site. This 

requirement is common to all injection well classes. 

Letter ID: 0220 Comment ID: 21611 Letter Lines: 236 to 260 

Comment Code: 1250 1.1.1.4 Flexibility is needed (performance-based standards) 

Comment Code: 3100 2.1 Proposed Geologic Siting Requirements (40 CFR 146.83) 

13
Comment: There is also text in this section that can be interpreted as requiring the 

owner/operator to submit core, outcrop, seismic survey, cross sections, well 

logs, and other unspecified data. Some later passages on this subject suggest 

that they are not all necessarily required, but rather are examples of types of 

data that could be used to demonstrate and quantify various key characteristics 

of a formation. With respect to the need for various types of geological data, 

the document is at times vague, inconsistent and, occasionally, even 

contradictory. It is critical that geologic heterogeneity and regional 

differences in data availability be acknowledged and state or regional directors 

be given the flexibility to make decisions based on data sets that reflect the 

geologic and regional differences. For instance, seismic survey data are limited 

in coverage, are expensive to acquire, can be inconclusive with respect to 

interpretation, and should not be universally required as a precondition for 

site consideration. The regulations must be performance-based and reinforce the 

need to technically and efficiently achieve specific goals, such as proving that 

an adequate and competent seal exists or that a target formation has sufficient 

injectivity. The regulations should not prescribe precisely how such proof is 

obtained, but should only dictate that sufficient proof be presented to the 

director. The regulations should give the director a significant degree of 

flexibility to determine whether the body of evidence presented by the 

owner/operator constitutes sufficient proof that USDWs will be protected. The 

regulations may include a list of useful data types, but EPA should clearly 

state that the list is one of available tools from which to choose the most 

applicable to a specific site, not a list of required applications and data that 

must be acquired and presented. 

Individual Response: EPA disagrees that any of these protective requirements are unnecessary. 

EPA believes that requiring appropriate site characterization by the owner or operator (under 

§146.82) and providing an appropriate degree of flexibility to the Director to evaluate sitespecific geologic data will afford the greatest protection of USDWs from endangerment. EPA 

believes that it is important for the Director to have as much site-specific information as possible 

in order to make an informed decision to permit injection for GS at a specific site. The GS 

regulation allows flexibility where appropriate. Certain requirements (e.g., the need to 

characterize additional confining layers) are at the Director's discretion (§146.83(b)), based on 

his or her understanding of a particular site. 

Additionally, EPA disagrees that consideration of local and regional seismicity is not important. 

The site characterization provisions in the GS rule, including a review of the local and regional 

geology, and detailed review of any known or potential seismically active terrain in the vicinity 

of a proposed GS site are necessary to minimize the potential for induced seismic events or the 

reactivation of faults, which are a known potential risk associated with injection and are 

addressed in all aspects of the UIC regulations. 

Letter ID: 0220 Comment ID: 21612 Letter Lines: 262 to 290 

14
Comment Code: 1250 1.1.1.4 Flexibility is needed (performance-based standards) 

Comment Code: 3140 2.1.4 Comments that the proposed geologic data requirements are too 

stringent 

Comment: Following is a series of comments with regard to the quote on page 43505: 

"...require owners or operators to submit geochemical data on (a) the injection 

zone, (b) the confining zones, (c) containment zones above the confining zones 

in which any potentially migrating CO2 could be trapped, (d) all USDWs, and (e) 

any other geologic zone or formation that is important to the proposed 

monitoring program." 

The EPA should recognize that it is essentially saying that the entire rock 

column from the injection zone to the surface must be geochemically 

characterized. Such characterization goes far above and beyond that which is 

necessary to protect the USDWs. It is essentially forcing owners/operators to 

pay for potentially unnecessary research activities. For instance, in the 

Williston Basin, a vast majority of the hydrocarbon production is historically 

from Paleozoic formations. One result of this is that there is a wealth of 

readily available data on the nature of Paleozoic formations in the Williston 

Basin. Likewise, the Cenozoic formations are fairly well characterized because 

of the presence of coal and potable aquifers. However, the Mesozoic formations 

that lie between those two groups are relatively poorly understood. This is 

because there is little economic incentive to characterize most of the Mesozoic 

rocks beyond the fact that they are dominated by low permeability shales and 

evaporites. There are 15 named rock units in the Mesozoic section of the 

Williston Basin. The regulations as proposed indicate that they must all be 

geochemically characterized. To geochemically characterize all of these Mesozoic 

units as part of a GS project in which the primary sinks and seals are in the 

deeper Paleozoic would be very expensive and of dubious value to anyone. Once 

again, there must be flexibility and discretionary powers given to directors 

with respect to what formations must be geochemically characterized. Indeed, 

this concept of flexibility must apply for all types of characterization that 

are considered necessary to prove that a GS well application can be approved. 

Individual Response: The Agency believes that the requirement at §146.82(a)(6) to submit 

baseline geochemical data on subsurface geologic formations, including all USDWs in the AoR 

is appropriate and protective of USDWs. EPA believes that this data will support monitoring 

plan development, inform injectate fate and transport model development (e.g., by providing 

appropriate input parameters), and provide information needed to respond to any unexpected and 

unpermitted leaks outside of the injection zone. The baseline geochemical information will allow 

the owner or operator and permitting authority to evaluate monitoring data and identify any 

changes in subsurface geochemistry that may indicate fluid movement. 

The rule requires geochemical analysis of, at a minimum, the injection zone, confining zone, and 

all USDWs (§146.82(a)(6)). These geochemical tests are necessary to ensure the adequacy of the 

confining system and to serve as a baseline for future monitoring. The Director has the discretion 

15
to require geochemical analysis of additional subsurface zones if in the Director's opinion they 

are necessary for the protection of USDWs from endangerment. 

EPA agrees that site characterization should be site-specific, particularly in light of the variety of 

geologic settings in which GS may be employed. EPA believes that, while there is a large 

amount of required information, the owner or operator is given flexibility in determining what 

methods are used to demonstrate the suitability of a potential site. EPA envisions an ongoing 

dialogue between the Director and the owner or operator during the permitting process (as well 

as throughout the operation of the site). 

Letter ID: 0220 Comment ID: 21613 Letter Lines: 292 to 297 

Comment Code: 3350 2.2.1.5 Use of proprietary models for GS sites (seeking comment) 

Comment: Page 43507. Regarding the use of proprietary models: The use of proprietary 

models absolutely should be allowable. In many cases, such software packages are 

the only reliable models that can be applied with any real confidence in their 

results. That being said, the use of such models should not be required because, 

in some cases, especially those where adequate data exist, nonproprietary models 

can serve the purpose in a more cost-effective manner. 

Individual Response: EPA agrees with commenters that available proprietary models may meet 

the complex needs for calculating the AoRs of GS sites. EPA will allow, but not require, the use 

of proprietary models in meeting the requirements for the GS regulation, as long as GS well 

operators using a proprietary model clearly disclose, to the Director's satisfaction, the code 

assumptions, relevant equations, and scientific basis. EPA adds that its Confidential Business 

Information requirements at 40 CFR 144.5 will apply to the use of proprietary models. 

Letter ID: 0220 Comment ID: 21622 Letter Lines: 299 to 324 

Comment Code: 3864 2.3.3.2 Use of corrosion-resistant cements (seeking comment) 

Comment: Page 43507. Corrective Action. Regarding the use of specific cements in GS 

wells: The document states that the EPA proposal does not prescribe the specific 

cements to be used to plug abandoned wells, but in the next paragraph states 

that corrosion-resistant cements would be required. This is contradictory. EPA 

must clarify this issue. 

Pages 43509 to 43510. Well Component Degradation. Regarding cements: 

It is frustrating that the EPA discounts real-world, field-based data in favor 

of laboratory-generated data and models. In this case, it describes laboratory 

work that had somewhat contradictory results and acknowledge that "... field 

studies show clear evidence of reactions between CO2 and well cement, but do not 

16
show such severe corrosion." EPA then goes on to mention two instances of fieldbased research that show only limited effects of CO2 on cements. But as they 

historically have been known to do (EPA rulings on air quality issues in 

southwestern North Dakota being just one example), EPA chooses to ignore the 

real-world data and make decisions based on the dire results of tests conducted 

on small samples under laboratory conditions that can be applied only to a very 

narrow set of subsurface conditions, if at all. The result of this is that the 

proposal can be interpreted to require the use of relatively new and expensive 

corrosion-resistant cements rather than cements that have already been used 

successfully at large-scale CO2 injection sites, in some cases for decades. One 

potential unintended consequence of this requirement is that the mechanical 

integrity of these new cements under deeper reservoir pressure and temperature 

conditions may not be completely understood, especially over time. Again, 

flexibility should be allowed with respect to the selection of cements. 

Individual Response: Regarding corrective action requirements, EPA clarifies that all corrective 

action performed under §146.84(d) must be appropriate to the GS site to ensure that the well 

does not allow CO2 or other fluids to move into or endanger USDWs. EPA is developing 

guidance on AoR and corrective action at GS Class VI sites to assist owners or operators and 

Directors in evaluating requirements and proposed AoR and corrective action plans under 

§146.84. This guidance will be available on EPA’s website at 

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

Regarding cementing requirements, EPA disagrees that the potential corrosion of well materials 

and cements when exposed to CO2 in the presence of water or other fluids is overstated. While 

some studies of cement performance have shown encouraging results, other information gathered 

through stakeholder workshops, research, and field data provide evidence of chemical alteration 

and suggest a potential for degradation to occur and potentially endanger USDWs. 

EPA clarifies that the requirement at §146.86(b)(5) is that cement and cement additives must be 

compatible with the CO2 stream and formation fluids and of sufficient quality and quantity to 

maintain integrity over the design life of the GS project. EPA believes that the use of acidresistant cements is one of several protective measures for meeting that Class VI well 

construction requirement, along with the requirements for surface casing and long-string casing 

and well tubulars that are compatible with the CO2 and formation fluids. See the discussion of 

Class VI well construction requirements in the preamble to the final GS rule for additional 

information. 

EPA clarifies that it has reviewed both laboratory and field-based research (Barlet-Gouedard et 

al., 2006; Kutchko et al., 2007, Carey et al., 2007, and Crow et al., 2008) that have shown 

Portland cement alteration (carbonation) when the cement is exposed to CO2. While research 

indicates that cement alteration occurs, the alteration appears not to significantly reduce the 

integrity or performance of the cement. However, under conditions simulating flowing CO2-

saturated brine, loss of structural integrity (more significant degradation) of cement was found in 

laboratory studies (Duguid et al. 2005), although it is uncertain whether wells in GS operations 

would be exposed to flowing CO2-saturated brine. The field-based studies that identified 

17
alteration reflect the results of relatively few samples from a very small number of wells, and the 

well material samples may have been exposed primarily to dry CO2. Cement degradation and 

corrosion are a possibility, so the cement and cement additives used may need to be acidresistant to meet the requirement that they are compatible with the CO2 stream, formation fluids, 

and the anticipated injection zone conditions. 

Although the laboratory and field studies suggest that corrosion problems may not be severe, 

such problems cannot be conclusively ruled out, and the amount of available data on this topic is 

still limited. Laboratory exploration of cement alteration and degradation is an ongoing research 

area, and field-based studies are very few. There also does not appear to be a clear consensus on 

the corrosion risks for the steel components of injection wells. Given the anticipated long 

lifespan of Class VI wells and the difficulties that would be associated with a corrosion-related 

well failure, EPA believes that the construction requirements at §146.86 are justified. 

The Agency plans to, every six years, collect and review data on GS projects to determine 

whether the appropriate amount and types of information and appropriate documentation are 

being collected, and to determine if modifications to the requirements are appropriate or 

necessary. 

Letter ID: 0220 Comment ID: 21623 Letter Lines: 326 to 329 

Comment Code: 4324 2.4.4.1.2 Comments opposed to requiring injection below the lowermost 

USDW 

Comment: Page 43512. Injection Depth in Relation to USDWs. 

The requirement to be below the lowest USDW is not needed and should be 

evaluated on a site-specific basis. Furthermore, minimum depths should not be 

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

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

endangerment, as long as appropriate protections are in place. The final GS rule at §146.95 

establishes a process by which owners or operators can seek a waiver of the Class VI injection 

depth requirements for injection into non-USDW formations above and/or between USDWs. 

Such determinations would be made on a site-specific basis. 

Letter ID: 0220 Comment ID: 21624 Letter Lines: 329 to 330 

Comment Code: 4344 2.4.4.2.2 Comments opposed to setting a minimum injection depth 

Comment: evaluated on a site-specific basis. Furthermore, minimum depths should not be 

required. Again, this should be site-specific. 

Individual Response: EPA agrees that it is not appropriate to set a minimum injection depth for 

GS projects and the Agency believes that a determination of site-suitability for GS (i.e., that 

18
subsurface formations will receive and confine injected CO2) should be made on a site-specific 

basis. The GS rule, at §146.82, requires the owner or operator to provide extensive site- and 

project-specific information to the Director to demonstrate that the site meets the minimum site 

criteria at §146.83, that the CO2 will be contained within the injection formation, and that 

USDWs will be protected from endangerment. 

EPA acknowledges 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 non-USDW 

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. The requirements are designed to ensure that the 

owner or operator, the Director, and the Regional Administrator consider, on a site specific basis, 

the implications, benefits, and challenges associated with GS and ensuring water availability and 

USDW protection. 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: 0220 Comment ID: 21625 Letter Lines: 332 to 353 

Comment Code: 4610 2.6.1 Testing and monitoring plan requirement (seeking comment) 

Comment Code: 4660 2.6.6 Geochemical monitoring 

Comment: Page 43515. Regarding monitoring wells in the Area of Review (AoR). 

Text in this section implies that monitoring wells in the injection zone within 

the AoR are desirable, which could be interpreted by some as being required. The 

first comment with respect to this issue is that it is important to note that 

monitoring wells that penetrate the plume have potential to serve as a leakage 

pathway and, therefore, their use should be minimized. Secondly, one of the 

reasons given for the placing of monitoring wells in the AoR is that studying 

the interactions between brine and CO2 may allow for the determination of 

whether precipitation and/or dissolution of minerals is occurring. It is 

important to note that such interactions are currently not well understood and 

are the topic of great debate and controversy within the published literature. 

There is no consensus in the technical community as to how such data evaluated 

in the context of a single site, as site-specific permitting and monitoring must 

be, can be applied to ensuring the protection of USDWs at that site. While such 

data would surely be interesting and possibly useful from a scientific 

standpoint when taken in the context of many sites, it is not clear how it could 

be applied to prove or disprove that USDWs at a given location are being 

protected or are in danger of contamination. This requirement comes across as a 

regulatory-mandated means of gathering data for researchers, an activity that is 

outside the scope of USDW protection and should not be forcibly paid for by 

19
owners/operators of GS wells. 

Individual Response: EPA disagrees that the monitoring requirements in the GS rule do not 

provide site-specific benefits for protection of USDWs or that monitoring is for the benefit of 

scientific research only. EPA believes that geochemical monitoring, when compared to baseline 

data, can provide direct evidence that USDWs may be endangered. 

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. 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 acknowledges that, at certain sites, there may be a need for more or different monitoring 

schemes (which may include monitoring in the confining zone), and adds that it is important to 

balance the need for adequate monitoring that ensures USDW protection from endangerment 

against too many artificial penetrations which could serve as conduits for fluid migration. Sitespecific testing and monitoring plans must describe the proposed monitoring regime, which must 

be approved by the Director. 

Letter ID: 0220 Comment ID: 21626 Letter Lines: 355 to 378 

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

CFR 146.90) 

Comment: Page 43515 to 43516. Regarding monitoring. In general, this section is overly 

prescriptive with respect to the selection and application of monitoring 

techniques. One of the things that is lost in this discussion is that if the 

geometry of the trapping structure is well understood and the overlying seal has 

been demonstrated to be competent and thick, then plume monitoring should be 

relatively straightforward and less complicated. Consider, for example, 

injection into a thoroughly characterized high-relief structure, such as an 

anticline or pinnacle reef encased in impermeable anhydrite. Migration of the 

CO2 would be minimal, and plume stabilization would be relatively rapid. A few 

carefully instrumented and placed monitoring wells, some above the seal and 

others just outside and below the structure, would be enough to ensure the plume 

20
does not leak through the seal or slip beneath the spill point at the bottom of 

the structure. With this in mind, it can be reasonably argued that seismic 

surveys (which may or may not provide useful insight regarding the plume, 

depending on the lithology) would not offer any additional data that would 

further ensure the protection of USDWs. If there is no significant structural 

element to the trap, then plume stabilization could very well take many decades, 

and in such a case, a more robust and comprehensive suite of monitoring tools 

may have to be applied. Many examples of both types of sites, and many more that 

fall in between, have been identified throughout the United States, and it is 

because of this variety that it is critical that UIC regulations for GS allow 

flexibility in choosing plume-tracking methods. The EPA acknowledges the need 

for flexibility in a paragraph in the middle of page 43516, but many of the 

requirements laid out in the document do not reflect that need. 

Individual Response: EPA agrees that flexibility is important in developing and implementing a 

monitoring plan that is appropriately tailored for a specific GS site, and believes that the final 

regulation provides for flexibility in: 1) methodologies used to collect these data, 2) the spatial 

resolution at which the data should be collected, and 3) how often the data should be collected. 

The number and placement of monitoring wells will be based on site-specific information such 

as the calculated AoR, injection rate and volume, site geology, baseline data, and the presence of 

artificial penetrations within the AoR. In some instances, there may be a limited number of 

options for complying with EPA's minimum requirements. For example, monitoring for 

geochemical changes will require use of monitoring wells and collection of groundwater samples 

for chemical analysis. Many options currently exist for complying with other requirements, such 

as tracking the position of the plume and pressure front within the injection zone. 

Flexibility is also provided regarding how to monitor for the specific data required by the final 

rule. The testing and monitoring plan is developed by the owner or operator in consultation with 

the Director and is designed to ensure that a detailed, Director-approved document describing 

how monitoring will be conducted during the lifetime of the project exists. 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. In addition, in January 2009, 

DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of 

CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in 

the docket for the final GS rule. 

With specific regard to plume tracking and pressure monitoring, EPA maintains that they are key 

components of monitoring at GS sites. A rigorous plume tracking and pressure monitoring 

scheme, such as one that meets the requirements at §146.90(g), is imperative for ensuring that 

the CO2 plume is contained within the injection zone. 

21
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 

Pressure monitoring in the injection zone is necessary to track the development and movement of 

the pressure front and CO2 plume. When combined with information on temperature, pressure 

data provide an indication of the phase (e.g., gas, supercritical) and distribution of the injected 

CO2 (73 FR 43515). 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. 

Letter ID: 0220 Comment ID: 21627 Letter Lines: 380 to 424 

Comment Code: 5240 2.8.2.2 Post injection timeframe (seeking comment) 

Comment: Page 43519. Combination of Fixed Time Frame and Performance Standard 

(monitoring). The EPA is proposing a postinjection monitoring period of 50 

years, with the director having some discretion to either shorten or lengthen 

that time period. Based on the proposed text, 50 years is the default time 

period for postinjection monitoring until data on pressure, fluid movement, 

mineralization, and/or dissolution reactions support a determination that the 

plume has stabilized and does not pose a risk to USDWs. Referring to this as the 

"default" time period and requiring the acquisition of described data sets to 

modify the time period for monitoring indicate that a significant amount of 

characterization effort would have to be conducted during the postinjection 

period, perhaps over several years, to get such a change. The EPA acknowledges 

that modeling results indicate that CO2 plume stabilization likely occurs on the 

time frame of 10 to 100 years after injection stops. One example of a GS site 

where plume stabilization could very well take 50 years or more is a site where 

there is no significant structural trapping element to the reservoir. A plume at 

such a location may behave in a less predictable manner and expand or migrate a 

significant distance before it stabilizes. However, CO2 injected into a 

thoroughly confined high-relief structure (e.g., pinnacle reef, carbonate mound, 

anticline, etc.) would likely stabilize relatively quickly. Barring a seismic 

event that breaches the seal, the movement of such a plume would be nil because 

it would literally have nowhere to go. In those cases, requiring the continued 

collection of several types of data for several years in order to prove what was 

probably obvious years before injection ceased would serve no real purpose other 

than to satisfy an arbitrary regulation. The nature of structural 

characteristics at each site under consideration for GS will be identified 

almost immediately, defined in detail during the earliest stages of site 

evaluation, and the understanding of their geometry will likely be further 

refined over the course of monitoring during the injection phase of the project. 

22
It is also important to keep in mind that the injection phase of GS projects, 

and the monitoring that goes with them, will, in most cases, be conducted for 

decades. Over those years, knowledge of the reservoir system will increase, and 

by the time the injection phase comes to an end, there will be ample data to 

make informed decisions regarding an appropriate postinjection monitoring 

period. All of this leads to a logical conclusion that the establishment of 

postinjection monitoring periods should be site-specific and flexible. The 50- 

year site monitoring statement appears to have no rational basis and might 

effectively eliminate commercial activity. 

In summary, the proposed default monitoring time frame should be eliminated and 

replaced with a solely performance-based standard that reflects the specifics of 

a project and the knowledge of that project gained through the procedures and 

processes that are already required. The proposed rule gives the program 

director discretion to extend or shorten the postinjection site care period 

based on project-specific considerations; therefore, it seems unnecessary to, by 

rule, establish a lengthy default period. 

Individual Response: EPA agrees that there will be circumstances where it can be demonstrated 

in less than 50 years that the plume and pressure front no longer pose a risk of endangerment to 

USDWs. For this reason, the final GS rule offers owners or operators flexibility regarding the 

duration of the PISC timeframe by: (1) allowing the Director discretion to shorten or lengthen 

the PISC timeframe during the post-injection period based on site-specific data, pursuant to 

requirements at §146.93(b); or (2) affording the Director discretion to allow a Class VI well 

owner or operator to demonstrate, during the permitting process based on substantial data, that an 

alternative PISC timeframe may be appropriate if it ensures non-endangerment of USDWs 

pursuant to requirements at §146.93(c). 

EPA believes however, that to ensure USDW protection from endangerment, a default timeframe 

for post-injection site care will be necessary in all but a limited number of cases. This default 50 

year post-injection site care timeframe represents a reasonable and protective monitoring period 

based on a review of research studies, industry reports, and existing environmental programs, 

and evaluation of public comments. 

EPA believes that a default post-injection site care timeframe of 50 years, with flexibility to 

adjust the timeframe for a limited number of GS projects during the permitting process where 

substantial data exists to demonstrate that an alternative timeframe would be protective of 

USDWs, or based on data collected during the PISC period, is appropriate to address the range of 

sites where GS is anticipated to occur, to accommodate site-specific circumstances and various 

geologic conditions, and addresses commenters’ concerns, while ensuring USDW protection. 

Both approaches will utilize site-specific data, and be based on pressure monitoring and USDW 

impacts. 

Letter ID: 0220 Comment ID: 21628 Letter Lines: 426 to 440 

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

23
Requirements 

Comment: Page 43520. Proposed Financial Responsibility and Long-Term Care Requirements 

The requirements for financial assurance may discourage commercialization of 

CCS. As currently proposed, the rules would place greater financial assurance 

requirements on Class VI wells than are currently placed on Class I hazardous 

waste wells. The more rigorous requirement may result in a needless negative 

public perception of CCS. The chemical and physical properties of carbon dioxide 

injected for storage purposes are not uniquely distinctive to garner such 

attention under the UIC Program. Furthermore, in order for CCS projects to come 

to fruition, financial assurance obligations need to be consistently and 

reasonably achievable. If not, considerable uncertainties will be introduced 

into the economics and finances of proposed projects. The currently proposed 

rule assumes reliable cost estimates will be available at the time of permitting 

for a broad range of long-term activities lasting more than 50 years into the 

future. EPA should carefully consider the implications of the proposed financial 

assurance provisions so as to not discourage CCS activities. 

Individual Response: The goal of financial responsibility is to ensure that 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 believes 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 GS sites 

is an important component of ensuring that USDWs are protected. See the final rule and 

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

EPA disagrees that the requirements on financial responsibility are overly stringent. The goal of 

financial responsibility is to ensure that resources are available to prevent the endangerment of 

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

owner or operator experiences financial difficulties. EPA disagrees that the requirements equate 

GS wells with Class I hazardous waste wells; rather, the financial responsibility requirements for 

GS wells are tailored to the unique nature of the long term GS of CO2. EPA does not agree that 

the financial assurance requirements will result in negative public perceptions of GS. EPA 

believes that the public will be reassured that any necessary activities will be covered despite the 

owner’s or operator’s financial difficulties. 

EPA adds that the purpose of the GS rule is not to encourage the use of GS; rather, the purpose 

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

USDWs from endangerment. 

Letter ID: 0220 Comment ID: 21629 Letter Lines: 442 to 448 

Comment Code: 6100 3.1 Comments on the cost estimates 

Comment: Pages 43525 to 43526. Regarding cost of compliance. EPA compares the costs 

associated with standard Class I wells and the proposed Class VI wells and 

24
estimates that the proposed rules would increase the costs of complying with UIC 

regulations by 46%. The EPA also states that it they "believe[s] the proposed 

rule will not impede CO2 GS from happening...." First, a 46% increase in costs 

is significant. Second, to profess that such a large increase in costs will not 

impede the implementation of GS projects seems rather naïve. 

Individual Response: EPA clarifies that the GS rule addresses costs associated with 

sequestration only, i.e., not capture or transportation. Sequestration costs are expected to be a 

small component of total CCS project costs. Increasing this small component of the total CCS 

costs by 48 percent (i.e., based on final GS Rule costs) amounts to approximately a 2 percent 

increase in total CCS project costs. 

EPA clarifies that the GS regulation does not promote or encourage the use of GS; rather it is 

designed to ensure consistency in permitting underground injection of CO2 at GS operations 

across the United States and provide requirements to prevent endangerment of USDWs in 

anticipation of the eventual use of GS to reduce CO2 emissions. 

Letter ID: 0220 Comment ID: 21630 Letter Lines: 450 to 466 

Comment Code: 4324 2.4.4.1.2 Comments opposed to requiring injection below the lowermost 

USDW 

Comment: Page 43535. § 146.5 Classification of injection wells. Class VI wells should not 

be limited to injections beneath the lowermost formation containing a USDW. This 

is too restrictive in some areas. For instance, consider as an example the Lower 

Cretaceous Dakota Group in the North Dakota portion of the Williston Basin. On 

the eastern margin of the Williston Basin in North Dakota, the water within the 

Dakota Group contains total dissolved solid (TDS) concentrations well below 

10,000 parts per million (ppm), and the formation therefore qualifies as a USDW. 

However, hundreds of miles to the west and southwest, near the center and 

southwestern flanks of the Williston Basin, the Dakota Group has TDS 

concentrations well above 10,000 ppm, and it is used extensively as an injection 

disposal zone for oil field produced waters. The demonstrated injectivity of the 

Dakota Group and its unsuitability as a potential USDW in western North Dakota 

make it an attractive target for industries seeking to geologically store large 

volumes of CO2. A strict, literal interpretation of the proposed rule could 

unreasonably preclude the Dakota Group from being considered as a potential 

target zone for CO2 storage. It is likely that similar examples of this scenario 

could be found in many other sedimentary basins. 

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

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

endangerment, as long as appropriate protections are in place. The final GS rule at §146.95 

establishes a process by which owners or operators can seek a waiver of the Class VI injection 

depth requirements for injection into non-USDW formations above and/or between USDWs. It 

establishes: 1) requirements specifying information that owners or operators must submit, and 

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Directors must consider, in consultation with PWSS Directors; 2) procedures for public notice of 

a waiver application and for Director-Regional 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. 

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

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

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

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

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

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

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

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

EPA’s approach to addressing injection depth variability through a waiver process responds to 

concerns about future drinking water resource availability and the need to ensure that high 

quality water remains available in sufficient quantities to supply drinking water needs. For 

additional information on the waiver approach, please see the final rule and preamble, as well as 

EPA's responses to comments on the Notice of Data Availability and Request for Comment. 

Letter ID: 0220 Comment ID: 21631 Letter Lines: 468 to 472 

Comment Code: 3140 2.1.4 Comments that the proposed geologic data requirements are too 

stringent 

Comment Code: 3150 2.1.5 Comments on required permit information (40 CFR 146.82) 

Comment: Page 43536. § 146.82 Required Class VI permit information. There are numerous 

requirements for information on formations overlying the proposed storage site. 

Requirements should be flexible and site-specific. The required information 

should be limited to relevant primary and/or secondary seals and be used to 

document the vulnerability or lack thereof of any USDWs in the area. 

Individual Response: EPA agrees that site characterization should be site-specific, particularly 

in light of the variety of geologic settings in which GS may be employed. EPA believes that, 

while there is a large amount of required information, the owner or operator is given flexibility in 

determining what methods are used to demonstrate the suitability of a potential site. EPA 

envisions an ongoing dialogue between the Director and the owner or operator during the 

permitting process (as well as throughout the operation of the site). 

Letter ID: 0220 Comment ID: 21632 Letter Lines: 474 to 482 

Comment Code: 3150 2.1.5 Comments on required permit information (40 CFR 146.82) 

Comment: Page 43536. § 146.82 Required Class VI permit information. The requirement of 

baseline geochemical data on subsurface formations should be flexible and site26
specific. The required information should be limited to relevant primary and/or 

secondary seals and be used to document the vulnerability or lack thereof of any 

USDWs in the area. 

Page 43536. § 146.82 Required Class VI permit information. Well-plugging 

requirements can change throughout the life of a well. Therefore, requiring a 

well-plugging plan with the permit application is excessive and unnecessary. 

Individual Response: The Agency believes that the requirement at §146.82(a)(6) to submit 

baseline geochemical data on subsurface geologic formations, including all USDWs in the AoR 

is appropriate and protective of USDWs. EPA believes that this data will support monitoring 

plan development, inform injectate fate and transport model development (e.g., by providing 

appropriate input parameters), and provide information needed to respond to any unexpected and 

unpermitted leaks outside of the injection zone. The baseline geochemical information will allow 

the owner or operator and permitting authority to evaluate monitoring data and identify any 

changes in subsurface geochemistry that may indicate fluid movement. 

The rule requires geochemical analysis of, at a minimum, the injection zone, confining zone, and 

all USDWs (§146.82(a)(6)). These geochemical tests are necessary to ensure the adequacy of the 

confining system and to serve as a baseline for future monitoring. The Director has the discretion 

to require geochemical analysis of additional subsurface zones if in the Director's opinion they 

are necessary for the protection of USDWs from endangerment. 

Letter ID: 0220 Comment ID: 21633 Letter Lines: 484 to 492 

Comment Code: 3100 2.1 Proposed Geologic Siting Requirements (40 CFR 146.83) 

Comment: Page 43536. § 146.83 Minimum criteria for siting. Requiring the injection zone 

to have the ability to receive the "total anticipated volume of the carbon 

dioxide stream" seems unreasonable. Linking CO2 source potential with CO2 

injection potential is not recommended, and flexibility is required. For 

example, if the stream is coming from a power generating facility, it can be 

difficult to estimate the longevity of the plant given changes in technology 

that may allow for increased energy output. Multiple storage sites may be 

required for one source, or conversely, multiple sources may utilize a single 

storage site. 

Individual Response: The Agency disagrees with the commenter that there should not be an 

absolute requirement that the injection zone be capable of receiving the total anticipated volume 

of CO2. The GS rule is designed to ensure that the total volume of CO2 anticipated to be injected 

can be safely stored within the target injection zone. This evaluation is based on site-specific 

characteristics including the local geology (e.g., data on formation thickness, porosity, and 

permeability and the presence of confining zones). The GS injection requirements, under SDWA 

authority, ensure protection of USDWs from endangerment through assessment of the suitability 

of an injection zone (§146.83), appropriate site characterization (§146.82), and area of review 

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evaluation (§146.84) among other requirements. 

The Agency believes that this comment may be based on an assumption that Class VI injection 

wells will be co-located with CO2 producing facilities. While this may, in some cases, be an 

accurate assumption, the specifications, design, and purpose of the CO2 source/facility are not 

addressed by the Class VI GS requirements. 

The productivity of the CO2 source (e.g., power plant, industrial facility, etc.) is not the driver of 

site suitability. Rather, the acceptability of a candidate site is determined, in part, by the amount 

of CO2 it can receive without allowing pressures in the injection formation to build up to levels 

that may fracture the confining zone or cause unacceptable fluid movement. If a CO2 source 

produces more than a formation can hold, then once the capacity of the receiving formation is 

reached, any additional CO2 produced would have to be injected elsewhere. 

Letter ID: 0220 Comment ID: 21634 Letter Lines: 494 to 496 

Comment Code: 3824 2.3.1.2 Cementing of long-string casing (seeking comment) 

Comment: Page 43538. § 146.86 Injection well construction requirements. Requiring surface 

casing to extend below the base of the lowermost USDW precludes potential 

sequestration zones. 

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

preclude injection below deep USDWs. 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 requirements. Owners or operators of 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. 

EPA stresses that protection of USDWs from endangerment, regardless of their depth or the 

number of USDWs in an area, is the primary mission and mandate of the UIC program and the 

purpose of all requirements for injection wells. Any injection activity must be demonstrated to 

not endanger USDWs, regardless of their depth, and if such non-endangerment cannot be shown, 

the activity will not be allowed under UIC requirements or the SDWA. 

Letter ID: 0220 Comment ID: 21635 Letter Lines: 498 to 512 

Comment Code: 3866 2.3.3.3 Logging and testing requirements (40 CFR 146.87) 

Comment: Page 43538. § 146.87 Logging, sampling, and testing prior to injection well 

operation. "...the owner or operator must run appropriate logs, surveys and 

tests to determine or verify the depth, thickness, porosity, permeability, and 

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29

lithology of, and the salinity of any formation fluids in, all relevant geologic 

formations." Relevant geologic formations needs to be defined. 

Page 43538. § 146.87 Logging, sampling, and testing prior to injection well 

operation. The coring requirements are too burdensome if applicable cores are 

already available in the vicinity of the project. 

Page 43538. § 146.87 Logging, sampling, and testing prior to injection well 

operation. Given the complexity of scheduling various service companies and 

activities at a project location requiring a schedule of all logging and testing 

30 days prior to the first test and submission of any changes to the schedule 30 

days prior to the next scheduled test are pointless and oftentimes impractical. 

Individual Response: Regarding clarification of the term "relevant geologic formations," EPA 

expects that during the permit application process, the owner or operator and the permitting 

authority will work together to determine which formations should be studied, based on the sitespecific circumstances. 

EPA disagrees that the requirements for logs, surveys and tests are excessive. All logs, surveys, 

and tests listed at §146.87(a) are necessary to verify information about the injection and 

confining zones and ensure that the well is being drilled and cased as approved and has 

mechanical integrity. Reliance on existing lithologic and geologic information may not provide 

adequate details for site-specific well design and geologic knowledge to support protection of 

USDWs from endangerment. EPA notes that the Director has the discretion at §146.87(a)(5) to 

approve alternative methods that provide equivalent or better information, and the Director may 

accept information on cores of the injection and confining zones from nearby wells if the owner 

or operator can demonstrate that such cores are representative of conditions at the well in 

question and core retrieval is not possible, as specified at §146.87(b). 

EPA disagrees that the 30-day notification requirement is unreasonable. Acknowledging the 

developing nature of CO2 GS, EPA believes that involvement by the permitting authority in each 

project will provide much needed field data for assurance of USDW protection from 

endangerment and will help update and refine the permitting process. Adequate timing of 

notification will ensure the Director's ability to be involved. 

EPA is developing guidance on monitoring and testing that will describe recommended tests and 

procedures to assist owners/operators and Directors in evaluating the requirements for preoperational logging and testing under §146.87. This guidance will be available on EPA’s website 

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