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.
COMMENTS OF THE UTAH DIVISION OF OIL, GAS AND MINING 

JOHN R. BAZA, DIRECTOR 

1594 W. NORTH TEMPLE, SUITE 1210 

PO BOX 145801 

SALT LAKE CITY, UT 84114 

PH: 801-538-5340 

ON THE 

U.S. ENVIRONMENTAL PROTECTION AGENCY’S 

PROPOSED FEDERAL REQUIREMENTS UNDER THE UNDERGROUND 

INJECTION CONTROL PROGRAM FOR CARBON DIOXIDE GEOLOGIC 

SEQUESTRATION WELLS 

DOCKET ID NO. EPA-HQ-OW-2008-0390 

December 23, 2008 

The Utah Division of Oil, Gas and Mining (“the Division”) appreciates the opportunity to 

comment on the referenced docket, related to the United States Environmental Protection 

Agency (“EPA”) proposal for Federal Requirements Under the Underground 

Injection Control (“UIC”) Program for Carbon Dioxide (“CO2”) Geologic Sequestration 

(“GS”) 

Wells. 

The Division has primacy over Class II injection wells in Utah, except for those on Indian 

Lands. The Division has been regulating injection wells since the 1950’s, and it obtained 

primacy for regulating injection wells under the UIC Program in 1982. 

The Division offers the following comments in regards to the proposed rules. 

Funding 

The Division has been administering a Class II UIC Program for many years while 

receiving less than adequate funding from EPA. This deficit in funding has been 

compensated by the state’s Oil and Gas Conservation Fee paid by operators based on oil 

and gas production volumes. It will be important for EPA to address adequate funding for 

the new Class VI Well program because states will not be able to simply take on such a 

new responsibility without a mechanism to adequately fund it. 

Protection of Underground Sources of Drinking Water (“USDW”) 

As with all underground injection, protection of USDWs should be the major focus of the 

rules. Protection is accomplished through containment of the CO2 stream through proper 

site selection and characterization of the geologic formation that is to be used for 
injection, along with sound construction of the injection wells and adequate monitoring 

practices. 

Enhanced Oil Recovery (“EOR”) and EOR Crossover 

Injection into reservoirs for EOR should remain unchanged and regulated under the Class 

II program. In the case where an operator of an EOR would also choose to use their wells 

for the purpose of GS the wells should still be regulated under the Class II program. 

Additionally injection into non-producing oil and gas reservoirs should also remain under 

the Class II program. Injection into non-oil and non-gas reservoirs should appropriately 

fall into the newly proposed Class VI well category for GS as proposed. 

The proposed rule allows the director of the program the discretion to “grandfather” the 

construction requirements of existing Class II wells to Class VI wells as long as a 

determination is made that these wells would not endanger a USDW. The Division agrees 

with this proposal considering that an existing Class II well for EOR would not be 

allowed to endanger a USDW. 

Injection Zones for Gas Sequestration 

EPA has proposed that all injection of CO2 for sequestration should be below the 

lowermost USDW. This proposal is too restrictive and could eliminate many areas of 

potential injection throughout the State of Utah that might otherwise be considered for 

sequestration. There should be no prohibition against injection into any zone even if 

above the lowermost USDW as long as it can be determined that geologic conditions 

would prevent endangerment to a USDW. 

Area of Review (“AOR”) Determination, Monitoring and Verification 

The EPA seeks comment on the use of modeling for AOR delineation, the use of 

proprietary models for GS sites, and the frequency of AOR reevaluation. By letter dated 

December 23, 2008, the Interstate Oil and Gas Compact Commission (“IOGCC”) has 

submitted several comments to the EPA on these issues with respect to the proposed rule. 

As a regulatory agency within a member state of IOGCC, the Division concurs with the 

IOGCC comments and recommendations related to AOR.

Proposed Well Construction Requirements 

EPA proposed that construction of GS wells be tailored to the construction requirements 

of a Class IH well. The Division agrees that USDWs need to be protected; however, these 

construction requirements may be too stringent for existing Class II EOR wells. To 

require remedial work on existing wells to achieve the proposed standards may in fact 

compromise the established mechanical integrity of an existing Class II well. 

Additionally, the requirement to set surface casing and cement through the base of the 

lowermost aquifer would be too restrictive. The regulating agency should have the 
discretion to evaluate wells on a site-specific basis to insure that USDWs will be 

protected. 

Operating Requirements 

EPA seeks comments on hydraulic fracturing, minimum depth requirements, and the 

potential impact of tracer use on human health and the environment. The Division 

concurs with the IOGCC recommendations (included in their December 23, 2008 

comments) that while hydraulic fracturing may be necessary for well completion, 

measures should be taken to prevent any fracturing of the confining zone. No minimum 

depth for GS should be specified and once again should be done on a site-specific basis. 

Use of tracers should be at the discretion of the regulating agency. 

Monitoring 

EPA seeks comments on proposed pressure plume and pressure front monitoring 

including issues such as the amount and type of monitoring, the usefulness of 

geophysical, air and soil monitoring, post-injection site monitoring, and frequency of 

reporting requirements. The IOGCC comments of December 23, 2008 have addressed all 

of these issues in great detail, and the Division concurs with their recommendations. 

Waste Characterization 

Injected CO2 is not and should not be considered a hazardous waste or regulated under 

RCRA or CERCLA. It is assumed that RCRA or CERCLA wastes would be removed 

from the CO2 stream prior to injection. 

Post Site Care Responsibility 

EPAs proposed rule sets the post-injection care period at 50 years. This may be modified 

if it can be demonstrated that the plume has stabilized and the pressure has dissipated. 

Setting a 50-year period may be unnecessarily long. The Division’s recommendation is 

that a shorter period be prescribed and then the regulating agency may have the discretion 

to set a longer post-injection care period if the specifics of a project indicate such a need. 
Letter ID: 0193 

Commenter: John R. Baza 

Organization: Utah Division of Oil, Gas, and Mining 

Letter ID: 0193 Comment ID: 23907 Letter Lines: 46 to 52 

Comment Code: 5600 2.11 Comments related to UIC Program primacy for Class VI wells 

Comment: The Division has been administering a Class II UIC Program for many years while 

receiving less than adequate funding from EPA. This deficit in funding has been 

compensated by the state’s Oil and Gas Conservation Fee paid by operators based 

on oil and gas production volumes. It will be important for EPA to address 

adequate funding for the new Class VI Well program because states will not be 

able to simply take on such a new responsibility without a mechanism to 

adequately fund it. 

Individual Response: EPA acknowledges that there may be technical and administrative 

challenges including resource concerns, and will work closely with the states to assist them in 

resolving funding issues or acquiring the resources, personnel, and training needed to address the 

unique technical challenges associated with GS. 

EPA will also incorporate Class VI wells into the UIC Program's grant allocation process. The 

States/Tribes/Territories must also demonstrate that they have adequate resources to implement 

the program through matching resources against those allocated by the UIC Program's grant 

allocation formula. Currently, primacy programs are required to meet a minimum of 25 percent 

matching requirement. 

Letter ID: 0193 Comment ID: 23908 Letter Lines: 54 to 60 

Comment Code: 1610 1.3.1 Risks to USDWs 

Comment: Protection of Underground Sources of Drinking Water ("USDW") 

As with all underground injection, protection of USDWs should be the major focus 

of the rules. Protection is accomplished through containment of the CO2 stream 

through proper site selection and characterization of the geologic formation 

that is to be used for injection, along with sound construction of the injection 

wells and adequate monitoring practices. 

Individual Response: The Agency agrees that drinking water is an important resource that 

needs protection. The primary goal of the UIC Program under the SDWA is to protect USDWs 

from endangerment. Consistent with SDWA §1422 the UIC program provides that no 

underground injection shall be authorized if it results in the movement of fluid containing any 

contaminant into USDWs, if the presence of that contaminant may cause a violation of any 

1
primary drinking water regulation or may adversely affect the health of persons as specified in 

§144.12. 

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, 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. 

Letter ID: 0193 Comment ID: 23909 Letter Lines: 62 to 70 

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: Enhanced Oil Recovery ("EOR") and EOR Crossover 

Injection into reservoirs for EOR should remain unchanged and regulated under 

the Class II program. In the case where an operator of an EOR would also choose 

to use their wells for the purpose of GS the wells should still be regulated 

under the Class II program. Additionally injection into non-producing oil and 

gas reservoirs should also remain under the Class II program. Injection into 

non-oil and non-gas reservoirs should appropriately fall into the newly proposed 

Class VI well category for GS as proposed. 

Individual Response: EPA agrees that injection of CO2 for the primary purpose of enhancing 

oil and gas recovery should remain under the Class II Program. 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 believes that there are significant differences between how projects are operated, as well as 

the risks posed by these different injection activities. The new tailored approach of the GS rule 

was designed to address the general risks deep injection may pose to USDWs and was tailored 

specifically to address the risks posed by long-term storage of CO2 (i.e., very large volumes, 

very long time-periods, and reservoir pressure conditions). 

EPA is developing guidance on transitioning permits from Class II to Class VI. The guidance 

will assist Directors in determining whether an injection project should be transitioned from 

Class II, where the primary purpose is oil and gas production, to Class VI, where the primary 

purpose is long-term storage of large volumes of CO2. The guidance describes the recommended 

methods the Director may use to evaluate changes in risk to USDWs from projects, and how the 

Director may determine whether a project should be regulated within the Class II or Class VI 

UIC program. This guidance will be available on EPA’s website at 

2
http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. For more information, please 

see the discussion on transition of Class II wells in the preamble to the final GS rule. 

Letter ID: 0193 Comment ID: 23910 Letter Lines: 72 to 76 

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

Comment: The proposed rule allows the director of the program the discretion to 

"grandfather" the construction requirements of existing Class II wells to Class 

VI wells as long as a determination is made that these wells would not endanger 

a USDW. The Division agrees with this proposal considering that an existing 

Class II well for EOR would not be allowed to endanger a USDW. 

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). The final 

Class VI regulations require that any owner or operator injecting CO2 for the primary purpose of 

long term storage obtain a Class VI permit with some special consideration for the fact that they 

are transitioning from a well not originally designed to meet Class VI requirements. The Director 

has the authority to determine at what point a Class VI permit is required for those projects that 

are transitioning from the primary purpose of EOR to long term storage of CO2. The final 

regulation provides a set of technical factors for the Director to evaluate in making this 

determination, at §144.19. EPA believes that this approach provides sufficient protection of 

USDWs when there is an increased risk to USDWs as compared to traditional Class II operations 

while allowing for site-specific flexibility. EPA adds that, following re-permitting as Class VI 

wells, these projects would be subject to the operational, MIT, monitoring, reporting, plugging, 

and post-injection site care and site closure requirements in the final GS rule. 

Letter ID: 0193 Comment ID: 23911 Letter Lines: 78 to 85 

Comment Code: 4324 2.4.4.1.2 Comments opposed to requiring injection below the lowermost 

USDW 

Comment: Injection Zones for Gas Sequestration 

EPA has proposed that all injection of CO2 for sequestration should be below the 

lowermost USDW. This proposal is too restrictive and could eliminate many areas 

of potential injection throughout the State of Utah that might otherwise be 

considered for sequestration. There should be no prohibition against injection 

into any zone even if above the lowermost USDW as long as it can be determined 

that geologic conditions would prevent endangerment to a USDW. 

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

3
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. 

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 highquality 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: 0193 Comment ID: 23912 Letter Lines: 87 to 94 

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

Comment: Area of Review ("AOR") Determination, Monitoring and Verification 

The EPA seeks comment on the use of modeling for AOR delineation, the use of 

proprietary models for GS sites, and the frequency of AOR reevaluation. By 

letter dated December 23, 2008, the Interstate Oil and Gas Compact Commission 

("IOGCC") has submitted several comments to the EPA on these issues with respect 

to the proposed rule. As a regulatory agency within a member state of IOGCC, the 

Division concurs with the IOGCC comments and recommendations related to AOR. 

Individual Response: Based on its evaluation of all public comments and input on the proposed 

rule and NODA and Request for Comment, EPA has made many revisions to the GS Rule. See 

the final rule and preamble for further discussion on EPA’s final approach. 

Letter ID: 0193 Comment ID: 23913 Letter Lines: 96 to 106 

Comment Code: 3820 2.3.1 Well construction procedures 

Comment Code: 3824 2.3.1.2 Cementing of long-string casing (seeking comment) 

Comment: Proposed Well Construction Requirements 

EPA proposed that construction of GS wells be tailored to the construction 

requirements of a Class IH well. The Division agrees that USDWs need to be 

4
protected; however, these construction requirements may be too stringent for 

existing Class II EOR wells. To require remedial work on existing wells to 

achieve the proposed standards may in fact compromise the established mechanical 

integrity of an existing Class II well. Additionally, the requirement to set 

surface casing and cement through the base of the lowermost aquifer would be too 

restrictive. The regulating agency should have the discretion to evaluate wells 

on a site-specific basis to insure that USDWs will be protected. 

Individual Response: EPA disagrees that the well construction standards for Class VI wells are 

too stringent. Rather, the construction requirements at §146.86 provide an appropriate level of 

protection from endangerment to USDWs that is based upon the existing UIC framework for 

deep wells. The new tailored approach was designed to address the general risks deep injection 

may pose to USDWs and was tailored specifically to address the unique nature of CO2 GS (i.e., 

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 adds that promoting GS or carbon management efforts is outside the 

scope of the GS rulemaking, which focuses on protecting USDWs from endangerment. 

Regarding the comment that remedial work will compromise the mechanical integrity of an 

existing Class II well, EPA clarifies that if a Class II well cannot be converted for GS injection 

and operated in a way that protects USDWs, including maintaining mechanical integrity and safe 

operation, conversion to Class VI will not be allowed. EPA believes that many Class II wells are 

constructed in a manner that would allow conversion for use as Class VI wells, but 

acknowledges that this may not be the case for all such wells. 

The final GS rule, at §146.81(c), allows the construction of ER wells to be grandfathered, 

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). Only the cemented-in-place construction 

requirements will be grandfathered under the final GS rule; following conversion, these wells 

will be permitted as Class VI wells and be subject to the operational, MIT, monitoring, reporting, 

plugging, and post-injection site care and site closure requirements in the final GS rule. 

EPA is developing guidance on transitioning from Class II to Class VI. The guidance will assist 

Directors and owner/operators in evaluating where a project may fit within a Class II to Class VI 

transition. The guidance describes the methods available for the Director to determine the risk 

posed to USDWs from a GS/ER project, and how the Director may determine if a project should 

be regulated by a Class II or Class VI UIC program. The guidance will be available on EPA's 

web site, at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

Letter ID: 0193 Comment ID: 23914 Letter Lines: 108 to 117 

Comment Code: 4120 2.4.1.2 Allowing hydraulic fracturing during GS (seeking comment) 

Comment Code: 4344 2.4.4.2.2 Comments opposed to setting a minimum injection depth 

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

(seeking comment) 

5
Comment: Operating Requirements 

EPA seeks comments on hydraulic fracturing, minimum depth requirements, and the 

potential impact of tracer use on human health and the environment. The Division 

concurs with the IOGCC recommendations (included in their December 23, 2008 

comments) that while hydraulic fracturing may be necessary for well completion, 

measures should be taken to prevent any fracturing of the confining zone. No 

minimum depth for GS should be specified and once again should be done on a 

site-specific basis. Use of tracers should be at the discretion of the 

regulating agency. 

Individual Response: The final rule allows the use of hydraulic fracturing at Class VI well sites, 

where approved by the Director. Hydraulic fracturing is one of several stimulation technologies 

available to improve wellbore and formation injectivity. 

EPA clarifies that all stimulation, including hydraulic fracturing, must be approved by the 

Director. Owners or operators must submit a proposed stimulation program as part of the permit 

application under §146.82(a)(9); the plan must demonstrate that any stimulation activities will 

not compromise the integrity of the confining zone. The Director will evaluate the owner or 

operator's proposed stimulation plan in the context of all information about the site, and the 

owner or operator must perform stimulation only as approved. 

The final rule at §146.91(d)(2) also requires that the owner or operator notify the Director 30 

days before performing stimulation during the operational phase of a GS project; this will 

provide an additional opportunity for the Director to review the owner or operator's plans for 

stimulation and add other requirements as needed. EPA clarifies that UIC regulations prohibit 

fracturing of the confining zone at any time during injection or stimulation. 

In addition, to maintain the integrity of the confining zone, the final rule requires that, except 

during stimulation, the injection pressure not exceed 90 percent of the fracture pressure of the 

injection zone. 

EPA also 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 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 siting criteria at 

§146.83 and 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 

6
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. 

Finally, EPA agrees that the use of tracers should not be required at all GS sites, but should be 

available as an option. For this reason, EPA does not require the use of tracers at all GS sites; 

however, the Director has discretion to require their use if he/she determines that the use of 

tracers could improve monitoring of the site and enhance USDW protection from endangerment. 

The rule will also allow their use if proposed by the owner or operator and approved by the 

Director. 

Letter ID: 0193 Comment ID: 23915 Letter Lines: 119 to 126 

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

CFR 146.90) 

Comment Code: 4700 2.7 Proposed Recordkeeping and Reporting Requirements (40 CFR 

146.91) 

Comment: Monitoring 

EPA seeks comments on proposed pressure plume and pressure front monitoring 

including issues such as the amount and type of monitoring, the usefulness of 

geophysical, air and soil monitoring, post-injection site monitoring, and 

frequency of reporting requirements. The IOGCC comments of December 23, 2008 

have addressed all of these issues in great detail, and the Division concurs 

with their recommendations. 

Individual Response: Based on its evaluation of all public comments and input on the proposed 

rule and NODA and Request for Comment, EPA has made many revisions to the GS Rule. See 

the final rule and preamble for further discussion on EPA's final approach. 

EPA agrees with commenters that developing and following testing and monitoring plans is an 

important part of assuring that a GS project is operating properly and is crucial for the early 

detection of potential endangerment to USDWs. EPA also agrees that periodic updates to the 

plan are appropriate. EPA clarifies that the final GS regulation includes a requirement that the 

AoR be reevaluated at least every five years, and it specifies at §146.90(j) that the operator revise 

the testing and monitoring plan to incorporate the results of the most recent AoR reevaluation 

and recent operational and monitoring data. 

EPA acknowledges the comment and the final rule retains the text as proposed. Please see the 

final rule and the discussion of testing and monitoring in the preamble for additional information. 

7
Letter ID: 0193 Comment ID: 23916 Letter Lines: 128 to 132 

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

Comment Code: 1640 1.3.4 CERCLA issues (seeking comment) 

Comment: Waste Characterization 

Injected CO2 is not and should not be considered a hazardous waste or regulated 

under RCRA or CERCLA. It is assumed that RCRA or CERCLA wastes would be removed 

from the CO2 stream prior to injection. 

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: 0193 Comment ID: 23917 Letter Lines: 134 to 141 

Comment Code: 5240 2.8.2.2 Post injection timeframe (seeking comment) 

Comment Code: 5260 2.8.2.3 Adjusting the post-injection timeframe (seeking comment) 

Comment: Post Site Care Responsibility 

EPAs proposed rule sets the post-injection care period at 50 years. This may be 

modified if it can be demonstrated that the plume has stabilized and the 

pressure has dissipated. Setting a 50-year period may be unnecessarily long. The 

Division’s recommendation is that a shorter period be prescribed and then the 

regulating agency may have the discretion to set a longer post-injection care 

period if the specifics of a project indicate such a need. 

Individual Response: EPA disagrees that a post-injection site care timeframe of 50 years is 

excessive for most Class VI wells. EPA proposed a default post-injection site care timeframe of 

50 years based on a review of research studies, industry reports, and existing environmental 

programs. This analysis was included in an EPA-prepared background document that is available 

in the federal docket, titled "Computational Modeling of Underground Injection of Carbon 

Dioxide for Determination of Area-of-Review and Potential Risk to Underground Sources of 

Drinking Water." EPA assessed various default timeframes based on additional review of 

8
9

research studies and evaluation of public comments. While numerous commenters suggested that 

EPA shorten the monitoring timeframe, none of the commenters provided sufficient data or other 

evidence to warrant a change in the proposed timeframe. While the 10- or 30-year timeframe 

suggested by some of these commenters may be within the timeframe suggested in some studies, 

EPA believes that the potential risks of endangering USDWs will likely not decline within these 

timeframes and available data, including data submitted by commenters, do not support a 

different default timeframe. 

However, EPA acknowledges 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 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.