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.
p. 1 

STATE, Or MICHIGAN 

DEPARTMENT OF ENVIRONMENTAL QUALITY 

LANSING D Fm WE 4z` 13- 

JENNIFER M. GRANHOLM STEVEN E. CHESTER 

GOVERNOR DIRECTOR 

December 5, 2008 

Water Docket 

Environmental Protection Agency 

Mailcode: 2822T 

1200 Pennsylvania Ave., NW 

Washington, DC 20460 

Dear EPA Administrator: 

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

DEC 17 2008 

In response to the Environmental Protection Agency's (EPA's) request for comments on 

its proposed Federal Requirements under the Underground Injection Control (UIC) 

Program for Carbon Dioxide (C02) Geologic Sequestration (GS) Wells, the Michigan 

Department of Environmental Quality (MDEQ), through its Office of Geological Survey 

(Staff) hereby submits the following comments : 

EPA (II . G.) proposes that the Director have discretion to carry over or "grandfather" the 

construction requirements for existing Class I, 11, and V wells when they are converted 

to GS wells. 

" Staff believes that, before allowing the wells to be "grandfathered," the existing 

well construction must be evaluated with respect to potential migration of injected 

C02 upward via the well bore and remedial action required if the existing 

construction does not conform with construction requirements for new GS wells. 

EPA (III .) proposes adopting Regulatory Alternative 3, the Tailored Requirements 

Approach, for managing C02 injection for GS . 

" Staff believes that Regulatory Alternative 2, the General Requirements 

Approach, is the proper management approach because it gives the permitting 

authorities the necessary flexibility and discretion to properly manage C02 GS . 

EPA (III . A. 2 .) proposes periodic re-evaluation of the Area of Review (AoR), with a 10-

year minimum fixed frequency. 

" Staff believes that the frequency of re-evaluation should be based on the results 

of the initial modeling and subsequent monitoring and that a fixed 10-year 

minimum should not be mandated . 

DEC p 12008 

CONSTITUTION HALL " 525 WEST ALLEGAN STREET " PO, BOX 30473 " LANSING, MICHIGAN 48909-7973 

www.michigan.gov " (800) 882-9278 . 
EPA Administrator 

Page 2 

December 5, 2008 

EPA (I II . A. 2.) proposes phased corrective action for wells in the AoR. 

" Staff believes phased corrective action should not be allowed, since there is 

much uncertainty in the modeled results--specifically in the times at which the 

plume will reach various wells--due to typically sparse or non-existent geologic 

data in the AoR. 

EPA (III . A. 3.) proposes a surface casing and long-string casing for a GS well. 

" Staff believes an intermediate casing string should be mandated for those areas 

where such casing is appropriate; for example, where high-pressure gas is 

known or suspected to exist between the surface casing and the sequestration 

interval . Such casings should be required to be cemented to surface. 

EPA (III . A. 4.) proposes allowing hydraulic fracturing in GS wells. 

" Staff believes hydraulic fracturing should be allowed to improve wellbore 

injectivity when necessary so long as fracturing of the confining zone(s) is 

prohibited at all times. 

EPA (III . A. 4.) proposes allowing injection for sequestration above the lowermost 

USDW (Underground Source of Drinking Water) . 

" Staff believes injection should be allowed when the EPA Director determines that 

geologic conditions exist that will prevent fluid movement into adjacent USDWs. 

EPA (III . A. 4.) proposes establishing a minimum injection depth rather than requiring 

injection below the lowermost USDW. 

" Staff believes minimum injection depths may be appropriate if sufficient 

information is available regarding the depths of wells that may have been drilled 

into an AoR prior to state or federal regulation . 

EPA (III . A. 4.) proposes the use of tracers in the injected C02 to serve as warning of 

leakage. 

9 Staff is opposed to allowing tracers. 
EPA Administrator 

Page 3 

December 5, 2008 

EPA (III . A. 4.) proposes "continuous monitoring" of various injection parameters. 

" Staff believes "continuous monitoring" is appropriate but that the precise 

definition of "continuous monitoring" may be contentious. 

EPA (III . A. 5.) proposes eliminating periodic internal mechanical integrity tests (MIT) in 

favor of continuous monitoring and to require external MITs on an annual basis. 

" Staff believes that continuous internal monitoring of injection wells is appropriate . 

Staff believes that external MITs should be conducted once every five years . 

EPA (III . A. 6.) seeks comment on the amount and types of monitoring to be conducted 

at GS sites. 

" Staff is not certain that the monitoring parameters listed will yield any information 

that relates to endangerment of USDW by leakage from the sequestration zone 

with the exception of the determination of the position of the C02 plume and area 

of elevated pressure. Staff believes, however, that the surface casing and tubing 

pressures, injection rates, and volumes should be measured daily and reported 

on a monthly basis. It is not clear that surface monitoring will provide 

unambiguous information regarding the position of the injected C02 plume, 

particularly in view of the uncertainty associated with the movement of the plume . It is also not clear that wells in the confining zone will be of any value since there 

may be no fluid movement into any particular well, and there is much uncertainty 

as to appropriate or optimum placement of confining zone monitoring wells. 

EPA (III . A. 8 .) proposes a 50-year post-closure monitoring period . 

" Staff believes that the 50-year time period is probably too long as there is no 

certainty that the entity that originated the sequestration project will be in 

existence for such a long period . 

EPA (III . A. 9 .) proposes corporate self-assurance for well plugging. 

" Staff is opposed to the use of corporate self-assurance . It has been the Office of 

Geological Survey's experience that the mere net worth of an owner or operator at any given time is not adequate to insure that funds for plugging are actually 

available or that the owner or operator will be viable and financially able to plug the wells. If a governmental entity assumes responsibility for plugging if the 

owner is unable to do so, requiring actual surety/conformance bonds or 

insurance allows the wells to be plugged without spending public monies. 
EPA Administrator 

Page 4 

December 5, 2008 

EPA (V.) proposes allowing state regulatory agencies to assume primacy for Class VI 

GS wells only. 

" Staff is in favor of this proposal. 

Please contact Mr. Harold R. Fitch, Director, Office of Geological Survey, at 

517-241-1548, if you have any questions with regard to these comments . 

Sincerely, 

SteGen E: C 

Director 

517-373-7917 

cc: Mr. Jim Sygo, Deputy Director, MDEQ 

Mr. Harold Fitch, MDEQ 

Mr. Mike Bricker, MDEQ 

Mr. Ray Vugrinovich, MDEQ 
Letter ID: 0264 

Commenter: Steven Chester 

Organization: Michigan Department of Environmental Quality (MDEQ) 

Letter ID: 0264 Comment ID: 22833 Letter Lines: 42 to 50 

Comment Code: 2060 1.5.3 Comments on grandfathering of existing wells (seeking comment) 

Comment: EPA (II. G.) proposes that the Director have discretion to carry over or 

"grandfather" the construction requirements for existing Class I, II, and V wells 

when they are converted to GS wells. 

- Staff believes that, before allowing the wells to be "grandfathered," 

the existing well construction must be evaluated with respect to potential 

migration of injected CO2 upward via the well bore and remedial action required 

if the existing construction does not conform with construction requirements for 

new GS wells. 

Individual Response: EPA agrees that a cautious approach to grandfathering is appropriate, 

particularly given that the converted well will be used for a substantially different process, which 

involves increased reservoir pressures associated with large volumes of stored CO2 and the 

corrosivity of CO2 in the presence of water. The final GS rule provides for the construction of 

these wells to be grandfathered (per 146.81(c)). EPA has included a requirement in the final 

Class VI rule that owners or operators seeking to convert existing wells for long term storage 

must demonstrate to the Director that the grandfathered 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). This demonstration must address the potential for upward migration 

of injected CO2. 

EPA adds that, following re-permitting as Class VI wells, these projects must be subject to the 

MIT requirements in the final GS rule. See the discussion of EPA's final regulatory approach in 

the preamble to the GS rule for additional detail on these requirements. 

Letter ID: 0264 Comment ID: 22834 Letter Lines: 52 to 57 

Comment Code: 2300 1.7 Comments on the Alternatives Considered 

Comment: EPA (III .) proposes adopting Regulatory Alternative 3, the Tailored 

Requirements Approach, for managing CO2 injection for GS. 

- Staff believes that Regulatory Alternative 2, the General Requirements 

Approach, is the proper management approach because it gives the permitting 

authorities the necessary flexibility and discretion to properly manage CO2 GS. 

Individual Response: Although Alternative 2 (General Requirements Approach) provides 

1
standards for siting, construction, operation, and monitoring associated with basic deep well 

design and operation, EPA does not believe that this alternative is appropriate for GS because it 

does not contain requirements tailored to meet the unique challenges of long-term CO2 GS, 

including the potentially large injection volumes, buoyancy, corrosivity in the presence of water, 

and viscosity and therefore cannot ensure protection of USDWs. 

EPA believes that the GS rule offers states the flexibility and discretion desired by commenters 

preferring Alternative 2 while ensuring the protection of USDWs. The final GS regulation gives 

the Director discretion to set permit criteria that are appropriate to site-specific conditions. The 

regulation provides flexibility to select appropriate sites and target formations (under §146.82), 

well construction specifics (under §146.86), and testing and monitoring regimes (under §146.90), 

provided the owner or operator can demonstrate that the injection and storage will not endanger 

USDWs and that minimum requirements for the site are met. Commenters representing electric 

utilities, water associations, and states supported Alternative 3 and the flexibility it provides to 

permitting authorities to make case-by-case permitting decisions while ensuring the protection of 

USDWs. 

Letter ID: 0264 Comment ID: 22835 Letter Lines: 59 to 64 

Comment Code: 3530 2.2.3.1 AoR reevaluation frequency (seeking comment) 

Comment: EPA (III. A. 2.) proposes periodic re-evaluation of the Area of Review (AoR), 

with a 10year minimum fixed frequency. 

- Staff believes that the frequency of re-evaluation should be based on 

the results of the initial modeling and subsequent monitoring and that a fixed 

10-year minimum should not be mandated. 

Individual Response: EPA believes that periodic AoR reevaluation at a set frequency of at least 

every five years is necessary to ensure protection of USDWs from endangerment and address the 

uncertainties inherent in predictive modeling. Periodic AoR reevaluations at §146.84(e) ensure 

that a deliberate effort is made to verify, based on monitoring and operational data, that the CO2 

plume is moving within the subsurface as predicted. EPA believes that less frequent 

reevaluations may not be sufficient to appropriately model plume and pressure front movement, 

establish conditions for corrective action, and ensure protection of USDWs from endangerment. 

EPA clarifies that if site monitoring data agrees with the existing AoR delineation, a model 

recalibration may not be necessary, and the AoR reevaluation may consist of a demonstration 

that the current AoR delineation is adequate based on site monitoring data. 

Letter ID: 0264 Comment ID: 22836 Letter Lines: 66 to 71 

Comment Code: 3660 2.2.4.2 Comments opposed to allowing phased corrective action 

2
Comment: EPA (I II . A. 2.) proposes phased corrective action for wells in the AoR. 

- Staff believes phased corrective action should not be allowed, since 

there is much uncertainty in the modeled results--specifically in the times 

at which the plume will reach various wells--due to typically sparse or nonexistent geologic data in the AoR. 

Individual Response: EPA disagrees that phased corrective action is inappropriate for GS 

projects, and retains this provision in the final GS regulation. EPA acknowledges the concern 

regarding the uncertainty in AoR modeling, and notes that addressing this is the intent of the 

AoR reevaluation process. EPA adds that the final rule includes a requirement that the AoR be 

reevaluated every five years or when monitoring or operational conditions warrant a reevaluation 

as identified at §146.84(b)(2)(ii). 

Allowing phased corrective action is at the discretion of the Director. Any state, in developing a 

primacy package that is concerned that phased corrective action cannot be safely implemented 

based on the geologic or other conditions, can prohibit Director's discretion to allow phased 

corrective action. 

Letter ID: 0264 Comment ID: 22837 Letter Lines: 73 to 79 

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

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

Comment: EPA (III. A. 3.) proposes a surface casing and long-string casing for a GS well. 

- Staff believes an intermediate casing string should be mandated for 

those areas where such casing is appropriate; for example, where high-pressure 

gas is known or suspected to exist between the surface casing and the 

sequestration interval. Such casings should be required to be cemented to 

surface. 

Individual Response: EPA disagrees that specific requirements for intermediate casing strings 

should be included for all Class VI wells. The rule allows for more than one long-string casing to 

the injection zone in §146.86(b)(3), in essence permitting intermediate casings. 

EPA acknowledges that circumstances such as the presence of high-pressure gas could dictate 

the use of more than one long-string casing and in this case, each would be required to be 

cemented from the bottom of the hole to the surface resulting in multiple barriers of cement and 

casing between formations above the injection zone and the fluids being injected. With their 

permit applications, owners or operators must submit well construction procedures, as specified 

in §146.82 (a)(12), that demonstrate that the well, as constructed, will prevent unacceptable fluid 

movement, as specified in §146.86(a). The Director will evaluate the procedures in the context of 

other data about the site and may require intermediate casing if it is warranted to protect USDWs 

3
from endangerment. 

See the discussion of Class VI well construction requirements in the preamble to the final GS 

rule for additional information. Additionally, EPA is developing guidance on the construction of 

Class VI wells. This guidance will be available on EPA’s website at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

Letter ID: 0264 Comment ID: 22838 Letter Lines: 81 to 85 

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

Comment: EPA (III. A. 4.) proposes allowing hydraulic fracturing in GS wells. 

- Staff believes hydraulic fracturing should be allowed to improve 

well bore injectivity when necessary so long as fracturing of the confining 

zone(s) is prohibited at all times. 

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 fracturing is permitted 

during stimulation, but not during injection. During injection, the injection pressure must not 

exceed 90 percent of the fracture pressure, as specified in §146.88(a). 

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. 

Letter ID: 0264 Comment ID: 22839 Letter Lines: 87 to 92 

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

USDW 

Comment: EPA (III . A. 4.) proposes allowing injection for sequestration above the 

lowermost USDW (Underground Source of Drinking Water). 

- Staff believes injection should be allowed when the EPA Director 

4
determines that geologic conditions exist that will prevent fluid movement into 

adjacent USDWs. 

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. 

Additionally, the final GS rule does not categorically preclude or prohibit injection into any type 

of formation. 

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: 0264 Comment ID: 22840 Letter Lines: 94 to 99 

Comment Code: 4342 2.4.4.2.1 Comments in favor of setting a minimum injection depth 

Comment: EPA (III . A. 4.) proposes establishing a minimum injection depth rather than 

requiring injection below the lowermost USDW. 

- Staff believes minimum injection depths may be appropriate if sufficient 

information is available regarding the depths of wells that may have been drilled 

into an AoR prior to state or federal regulation. 

Individual Response: EPA disagrees that it is necessary 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 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 

5
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: 0264 Comment ID: 22841 Letter Lines: 101 to 104 

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

(seeking comment) 

Comment: EPA (III . A. 4.) proposes the use of tracers in the injected CO2 to serve as 

warning of leakage. 

-Staff is opposed to allowing tracers. 

Individual Response: EPA agrees that tracer use is not appropriate in all situations. For this 

reason, EPA does not require the use of tracers at all GS sites; rather, 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: 0264 Comment ID: 22842 Letter Lines: 106 to 110 

Comment Code: 1220 1.1.1.1 Terminology and definitions 

Comment Code: 4520 2.5.1 Continuous internal mechanical integrity monitoring (seeking 

comment) 

Comment: EPA (III. A. 4.) proposes "continuous monitoring" of various injection 

parameters. 

- Staff believes "continuous monitoring" is appropriate but that the 

precise definition of "continuous monitoring" may be contentious. 

Individual Response: EPA agrees with the commenter regarding the importance of 

demonstrating internal mechanical integrity (MI) and believes that continuous pressure 

monitoring to demonstrate internal mechanical integrity of Class VI wells is important, given the 

potential corrosive impact of CO2 and impurities on well materials, the potential geomechanical 

impacts to well integrity due to CO2 phase changes, and the temperature and pressure effects 

6
associated with injecting supercritical CO2. See §146.89(b). EPA also believes that the 

technology for continuous monitoring is practicable, available, and is currently in fairly wide 

use. EPA anticipates that the owner or operator’s testing and monitoring plan will describe the 

proposed specific equipment and recording frequency. 

Letter ID: 0264 Comment ID: 22843 Letter Lines: 112 to 118 

Comment Code: 4520 2.5.1 Continuous internal mechanical integrity monitoring (seeking 

comment) 

Comment Code: 4540 2.5.2 Proposed external MIT requirements 

Comment Code: 4546 2.5.2.2 MIT frequency (seeking comment) 

Comment: EPA (III . A. 5.) proposes eliminating periodic internal mechanical integrity 

tests (MIT) in favor of continuous monitoring and to require external MITs on an 

annual basis. 

- Staff believes that continuous internal monitoring of injection wells is 

appropriate. Staff believes that external MITs should be conducted once every 

five years. 

Individual Response: EPA agrees with the commenter regarding the importance of 

demonstrating internal mechanical integrity (MI), and the final GS rule retains the requirement 

for continuous pressure monitoring of Class VI wells to enable the immediate identification of 

corrosion-related internal mechanical integrity problems that could lead to significant well 

problems and failure. 

EPA disagrees that a five-year external MIT is appropriate. The final GS regulation retains the 

requirement that owners or operators of Class VI wells must demonstrate injection well external 

mechanical integrity at least once annually under §146.89(c). EPA believes this is justifiable for 

the protection of USDWs from endangerment given the unique nature of CO2 GS relative to 

other injection operations, including the potential corrosive impact of CO2 in the presence of 

water and impurities on well materials, the potential geomechanical impacts to well integrity due 

to CO2 phase changes, the temperature and pressure effects associated with injecting 

supercritical CO2, and the buoyant nature of the injected CO2. Because of the unknown longterm effects of CO2 GS, EPA chose a more conservative initial approach in the early stages of 

deployment for GS. 

In addition, a comprehensive review conducted by EPA of MIT results from 1993 to 1998 found 

that Class I wells injecting corrosive fluids fail MITs at rates two to three times higher than those 

that inject non-corrosive fluids (USEPA, 1999). Given the potential for CO2 to be corrosive (i.e., 

in the presence of water or aqueous formation fluids), there is a potential risk factor for MIT 

failure and, for this reason, EPA believes that the tailored MIT requirements in the final GS rule 

are appropriate. For additional information, please see the discussion of MITs in the final rule 

preamble. 

EPA adds that it is using an adaptive approach to regulating GS. The Agency plans to collect and 

7
review data every six years on GS projects, including MIT data, 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: 0264 Comment ID: 22844 Letter Lines: 120 to 134 

Comment Code: 4660 2.6.6 Geochemical monitoring 

Comment Code: 4670 2.6.7 Surface air monitoring and/or soil gas monitoring (seeking 

comment) 

Comment: EPA (III . A. 6.) seeks comment on the amount and types of monitoring to be 

conducted at GS sites. 

- Staff is not certain that the monitoring parameters listed will yield any 

information that relates to endangerment of USDW by leakage from the sequestration 

zone with the exception of the determination of the position of the CO2 plume and 

area of elevated pressure. Staff believes, however, that the surface casing and 

tubing pressures, injection rates, and volumes should be measured daily and 

reported on a monthly basis. It is not clear that surface monitoring will 

provide unambiguous information regarding the position of the injected CO2 

plume, particularly in view of the uncertainty associated with the movement of the 

plume. It is also not clear that wells in the confining zone will be of any value 

since there may be no fluid movement into any particular well, and there is much 

uncertainty as to appropriate or optimum placement of confining zone monitoring 

wells. 

Individual Response: EPA agrees that pressure monitoring in the confining zone may not 

provide the data needed to evaluate plume movement. Instead, the final GS regulation, at 

§146.90(g)(1), requires all GS project owners or operators to monitor for pressure changes in the 

injection zone. EPA believes that pressure monitoring in the injection zone is necessary to track 

the development and movement of the pressure front and CO2 plume which provides valuable 

information in determining whether there is a potential for USDW endangerment. 

Pressure monitoring within the injection zone is necessary because any such monitoring above 

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

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

penetrate the confining zone) can be safely performed if the wells are constructed to prevent flow 

between the injection zone and USDWs or other layers above the confining zone. Such 

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

EPA acknowledges that air and soil gas monitoring are subject to variability and may not be 

suitable in all settings as a method to ensure USDW protection. However, EPA does not believe 

that this should entirely preclude their use. For example, if a leak to the surface is suspected, 

surface monitoring could provide vital information on its location and magnitude to assist 

owners and operators in identifying what USDWs may have been impacted by a leak. EPA 

8
clarifies that the various air and soil gas monitoring methods (e.g., chambers, eddy covariance, 

hyperspectral imaging) all have different capabilities that may prove useful in specific GS 

projects (Miles, et al. 2005; Pickles and Cover, 2005; IPCC, 2005; Menzies, et al. 2001). The 

final rule at §146.90(h) retains the allowance for surface air and soil gas monitoring at the 

discretion of the Director as a means of identifying leaks that may pose a risk to USDWs and 

informing emergency notification of a Class VI owner or operator and UIC Director in the event 

of a USDW endangerment, pursuant to requirements at §146.91(c). EPA clarifies that the 

decision to use surface monitoring and the selection of monitoring methods will be site-specific 

(e.g., may be influenced by geology, injection depth, and operational conditions) and must be 

based on potential risks to USDWs within the AoR. 

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. 

Letter ID: 0264 Comment ID: 22845 Letter Lines: 136 to 140 

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

Comment: EPA (III . A. 8.) proposes a 50-year post-closure monitoring period . 

- Staff believes that the 50-year time period is probably too long as 

there is no certainty that the entity that originated the sequestration project 

will be in existence for such a long period. 

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

excessive for most GS sites. However, EPA recognizes that there may be sites where the 50 year 

post injection site care timeframe may be either not appropriate or more burdensome than 

necessary based on site-specific conditions. 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 nonendangerment 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 most cases. The 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. 

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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. 

To the comment that the entity that originated the project may not be in existence for such a long 

period, the Agency believes that in order to protect USDWs from endangerment under the 

SDWA, operators must demonstrate under §146.85 that financial resources are available to plug 

the injection well and provide post-injection site care at the point in time that the first CO2 is 

injected. EPA understands that changes in staff or ownership occur associated with all injection 

operations that operate over timeframes of several years or decades, and believes that owners and 

operators granted UIC permits have a responsibility to maintain continuity in expertise and data 

associated with the project. 

Letter ID: 0264 Comment ID: 22846 Letter Lines: 142 to 151 

Comment Code: 5432 2.9.1.1 Need to adjust financial responsibility mechanisms (seeking 

comment) 

Comment: EPA (III . A. 9.) proposes corporate self-assurance for well plugging. 

- Staff is opposed to the use of corporate self-assurance. It has been the 

Office of Geological Survey's experience that the mere net worth of an owner or 

operator at any given time is not adequate to insure that funds for plugging are 

actually available or that the owner or operator will be viable and financially 

able to plug the wells. If a governmental entity assumes responsibility for 

plugging if the owner is unable to do so, requiring actual surety/conformance 

bonds or insurance allows the wells to be plugged without spending public 

monies. 

Individual Response: EPA will retain self-insurance as an option for financial responsibility for 

Class VI wells. EPA believes that if properly used, the financial test can be an appropriate option 

for some owners or operators. EPA recognizes that it is important for self-insurers to be creditworthy, otherwise USDWs may not be adequately protected. Owners or operators who choose to 

self-insure and use the financial test must be able to demonstrate profitability, with a margin 

sufficient to cover contingencies and unknown obligations, and stability. If the owner or operator 

meets corporate financial test criteria, this is an indication that the owner or operator can 

guarantee its ability to satisfy financial obligations based solely on the strength of the company’s 

financial condition. If an operator or operator is not able to meet the corporate financial test 

criteria, it may arrange a corporate guarantee by demonstrating that its corporate parent meets the 

financial requirements on its behalf. 

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Additionally, EPA is developing guidance to assist Directors in evaluating the appropriateness of 

self-insurance in specific circumstances, such as how best to evaluate owners or operators' 

demonstrations of financial worthiness or whether certain owners or operators pose too great a 

financial risk to use self-insurance as a financial responsibility instrument. This guidance will be 

available on EPA's website at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. States have the discretion 

under the rule to prohibit the use of financial instruments they feel are inadequate. 

Letter ID: 0264 Comment ID: 22847 Letter Lines: 153 to 156 

Comment Code: 5610 2.11.1 Allowing partial primacy for Class VI wells (seeking comment) 

Comment: EPA (V.) proposes allowing state regulatory agencies to assume primacy for Class 

VI GS wells only. 

- Staff is in favor of this proposal. 

Individual Response: EPA agrees with commenters that states should be allowed to obtain 

primacy for Class VI wells independently of other well classes, and will allow independent 

primacy for Class VI wells under §145.1(i) of the final GS rule. Given the potential for CCS 

(encompassing capture, transportation, and geologic sequestration) to be an important part of a 

national priority to address climate change, EPA believes that providing states the flexibility to 

obtain primacy for Class VI wells independently of other well classes can help foster effective 

management of CCS. EPA believes that allowing independent Class VI primacy may encourage 

states to take responsibility for implementation of Class VI regulations and provide for a more 

comprehensive approach to managing CCS projects by promoting the integration of GS activities 

under SDWA into a broader framework for managing CCS. Furthermore, GS operations involve 

ancillary activities (e.g., pipeline operations, pore space ownership, land use rights, and surface 

access) for which states can call upon other authorities that exist at the state level (but outside 

UIC authority) to provide a more comprehensive CCS management approach. 

The Agency believes that it is important for states to use their unique efficiencies to promote 

adoption of this burgeoning and important technology, while assuring that USDWs are protected 

from endangerment through the UIC regulatory framework. EPA believes that, due to the 

importance of implementing an effective, comprehensive, and seamless CCS program, States 

should be provided the flexibility to obtain primacy for Class VI only. 

EPA also believes that allowing states to apply only for Class VI primacy will shorten the 

primacy approval process for states. EPA's willingness to accept independent primacy 

applications for Class VI wells represents a shift in its longstanding policy of discouraging 

"partial primacy." It is very important to note that this shift in policy allowing for Class VI 

primacy does not apply to any other well Class under Section 1422. EPA will continue to 

discourage applications for partial primacy for all other well types under Section 1422. 

EPA clarifies that states should be able to obtain primacy for Class VI wells independent of other 

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well classes provided they develop regulations that are at least as stringent as the minimum 

Federal requirements (e.g., permitting, inspection, operation, monitoring, and recordkeeping 

requirements) provided in the final GS rule. EPA believes that existing programs can adapt their 

expertise to the new requirements for Class VI wells and will be able to develop a primacy 

application for Class VI wells under section 1422 of SDWA and ensure that their GS programs 

integrate into national climate change priorities and protect USDWs from endangerment.