### 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.·co

. 5i

.0 o .<2 o

o 2 December 12, 2008

Water Docket Environmental Protection Agency Mailcode 2822T 1200 Pennsylvania Avenue, NW Washington, DC. 20460

RE: Docket EPA-HQ-OW-2008-0390, Federal Requirements lmder the

Underground Injection Control Program for Carbon' Dioxide Geologic

Sequestration Wells Proposed Rule

- 73 FR 43492, July 25, 2008

Dear Sir/Madam:

In response to the U.S. EPA proposed rule on geologic sequestration (73FR43492), the National Ground Water Association submits the attached general and specific comments.

NGWA i(l a not-for-profit professional society and trade association for the ground water industry. Our 14,000 members include some of the country's .Ieading public and private sector ground water scientists, engineers, water well contractors, manufacturers and suppliers of ground water related products and services. The Associ>ttion's visio'n is to be the leading community of ground water professionals that promotes the responsible development, use and management of ground water resources.

If you have questions about NGWA or these comments, please don't hesitate to contact me at 800.551.7379, ext. 560 or creimer@ngwa.org.

Sincerely,

Christine Reimer Government Affairs Director



# national

. 

# Clrf>L.lrH1 vvater .J 

# aSSOclatlon®

Address/ 601 Dempsey Road' Westerville, Ohio 43031**~8978** USA

Phone/ TolI·Free 800 551.7379/614 898.7791 Fax/614 898.778G

E-mail! ngwJ@ng\'lJ.org \'11'11'1/ ngwJ,org and l'iellowner.orgNational Ground Water Association Comments on Geological Sequestration Proposed Rule



## Comments

on Federal Requirements under the Underground Injection Control Program for Carbon Dioxide Geologic Sequestration Wells Proposed Rule

- 73 FR 43492, July 25, 2008 Docket

- EPA-HQ-OW-2008-0390

Submitted December 12, 2008

By National Ground Water Association 601 Dempsey Road Westerville, OH 43081 800.551.7379 Contact: Christine Reimer

1National Ground Water Association Comments 011 Geological Sequestration Proposed Rule



### Comments on Federal Requirements Under the Underground Injection Control Program for Carbon Dioxide Geologic Sequestration Wells Proposed Rule

- 73 FR 43492, JUly 25, 2008 Docket

- EPA-HQ-OW-2008-0390

The National Ground Water Association (NGWA) is a not-for-profit professional society and trade association for the ground water industry. Our 14,000 members include some of the country's leading public and private sector ground water scientists, engineers, water well contractors, manufacturers and suppliers of ground water related products and services. The Association's vision is to be the leading community of ground water professionals that promotes the responsible development, use and management of ground water resources.

In response to the U.S. EPA proposed rule on geologic sequestration (73FR43492), NGWA submits the following general and specific comments:

Definition of Underground Sources of Drinking Water

NGWA recommends that US. EPA reevaluate the appropriateness of the definition of an underground source of drinking water (USDW) as one containing less than 10,000 ppm total dissolved solids prior to large-scale licensing of carbon capture and storage (CCS) sites to ensure future drinking water supplies are not unintentionally degraded. For example, a recent article reported that deep brackish ground water, approximately 12,000 TDS, is under consideration as a water source for a development in Sandoval County, New Mexico. The article notes that the cost of water treatment is expected to be less than obtaining existing water rights (Sengebush, 2008) In 2003, water managers in 36 states anticipated shortages in localities, regions, or statewide in the next ten years (U.S. General Accounting Office, 2003). The potential for the increased use of brackish ground water for water supplies must be anticipated and considered.

Classification of Injection Wells for Carbon Sequestration, Class II Injection Well Transition, and Grandfathering

The EPA published a guidance document in March of 2007 recommending that the geologic sequestration experimental projects during this period of research use the Class V experimental category for classification of the injection wells (Using the Class V Experimental Technology Well Classification for Pilot Geologic Sequestration Projects

- EPA 2007). These projects are currently underway at the Department of Energy's (DOE's) National Energy Technology Laboratory Regional Partnership test sites. Thus, there will be a need in the future for a regulatory mechanism for transition of these Class V experimental wells to Class VI operational status. There are also a number of Class II enhanced oil recovery (EOR) wells that have been used for testing of the sequestration process. These wells, too, may need a mechanism for transition to Class VI for operational use.



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The NGWA Carbon Sequestration Task Force recommends that the experimental phase extend beyond the regional partnerships to each site proposed for productionscale injection of carbon dioxide. It is recommended that at least one well at each site be constructed under the Class V experimental category, and that testing of the adequacy of the geologic environment for geologic sequestration of carbon dioxide be conducted prior to permilling any well in the Class VI category at the site.

The transition of carbon dioxide injection wells from Class II (Enhanced Oil Recovery wells) to Class VI (carbon sequestration wells) will presumably be requested when production of the petroleum has ceased. Liquid carbon dioxide from a distant source, such as a power plant, can be stored in the depleted petroleum reservoir even after production has ceased, necessitating a change in classification of the injection well. The new use of the wells involves much longer storage time, and raises concerns about mechanical integrity and long term effects, including geochemical changes, on underground source of drinking water (USDWs). The reclassification should depend on
a positive outcome from a Class V experimental program conducted in the depleted reservoir, as described below.

The "grandfathering" of Class V carbon sequestration wells would mean allowing experimental wells to be permitted for operation after the testing period is over. The NGWA Carbon Sequestration Task Force recommends that each carbon sequestration system or wellfield have an experimental phase, and not rely on results from distant experimental locations. Thus, nearly every operational well would start as a Class V experimental well, or would go through a Class VI testing phase, before being permitted for long-term operation. The transition to Class VI operational status would require demonstrating that the minimum requirements are met at that location. Most wells would go through the following permitting phases:

• Class V experimental well construction permit: This permit would allow geologic and geophysical testing, aquifer testing, laboratory work, etc, but would not include injection of CO 2 (only potable water injection testing would be allowed).

• Class VI experimental well operational testing permit: At this stage, the full monitoring facilities would need to be constructed. This permit would allow test injection of liquid CO 2 at rates high enough to demonstrate that the location meets the minimum requirements for operation, for a period of up to two years.

• Class VI operation permit: After demonstrating that the location and the well meet all the minimum requirements for injection of CO 2 , the operation permit

can be issued.

The goals of the experimental well Class V construction permit would be to make the following demonstrations:

• A receiving zone of sufficient depth, area extent, thickness, porosity, and permeability is present;



### 3National Ground Water Association Comments on Geological Sequestration Proposed Rule

• Lithologic description, geological name, thickness and depth of each confining unit above the storage aquifer, and of each USDW. • A trapping mechanism that is free of pathways for migration of injected fluids into a USDW. These pathways may include major non-sealing faults, porous beds within the confining unit, changes of facies trending toward

more porous units and man-made structures such as wells or mine shafts. A trapping mechanism is defined as a geologic environment that prevents vertical and horizontal movement of fluids into a USDW; The volume of the trap shall exceed the proposed total volume of injected carbon dioxide for the life of the proposed facility

• Identification of all confining units between the primary injection/storage

zone and the lowermost USDW, and their adequacy to contain the injected fluid. Unless the only feasible injection zone has only one confining unit separating it from the lowermost USDW, this demonstration includes adequacy of confinement for both the primary confining unit and a secondary containment system that extends to the base of the lowermost USDW and is completely redundant of the primary confining system and could confine the injected CO 2 should the primary system fail. In locations where the secondary containment system is not possible, the applicant shall propose an alternative system of early warning of failure of the primary confining unit in order to avoid impacting any USDW should that confinement fail. This demonstration applies in the horizontal sense as well, demonstrating one or more mechanisms containing the fluid from horizontal movement into a USDW in the storage aquifer at a distant location.

• The construction of an operational monitoring system meeting all the requirements described in this document's MMV section, and demonstration of the adequacy of this system to meet those requirements.

• Demonstration of mechanical integrity

Having made the foregoing demonstrations, a Class VI operational testing permit can be issued for a period of up to two years. The goals of the experimental well Class VI operational testing permit would be to make the following demonstrations:

• A hydraulic demonstration of the adequacy (depth, area extent, thickness, porosity, and permeability) of the storage zone, using monitoring data and 4-D seismic monitoring of the extent of the CO 2 plume.

• Demonstration of the adequacy of the trap for 5/10 years of injection at the proposed rate. The volume of the trap shall exceed the proposed total volume of injected carbon dioxide for the 5/10 years of the first operation permit.

• Demonstration of the adequacy of confinement under operational conditions using monitoring data and a method of detecting the extent of the CO 2 plume in the storage aquifer, such as 4-D seismic monitoring or direct sampling.

• Re-evaluation of the Area of Review and extent of the zone of endangering influence.

• Re-evaluation of mechanical integrity, using the buoyancy of the injected CO 2 to better measure external mechanical integrity. The re-evaluation 

### 4

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shall include the testing required during the initial MIT, as well as evaluation of the cement for carbonation, or chemical weathering by CO 2

Under this permitting scenario, the vast majority of Class V experimental wells would be constructed after the Class VI standards had been published. The "grandfathering" of Class V wells that do not meet the Class VI construction standards would only be needed for DOE test sites established before rulemaking was complete. If these wells include the ongoing mechanical integrity monitoring of annular fluid pressure and composition, and they pass periodic mechanical integrity testing, they should be able to follow the same permitting procedures to become operational Class VI wells.

Geologic Characterization

The UIC program is required under the Safe Drinking Water Act to protect USDWs from contamination from fluids injected into the subsurface. Part of this requirement is the demonstration that the injected fluids will not migrate, through buoyancy, ground-water flow or injection pressure, into USDWs. This demonstration is based on the characteristics of the geological environment where injection is to take place. The current UIC regulations require investigation of waste disposal sites through an application-phase data summary (Area of Review study) and geologic testing while drilling the pilot hole of the injection well. In general, the critical attributes of the injection and confining units are measured during pilot hole drilling, and the integrity and extent of those units are addressed in the literature review and Area of Review study at the application phase. Because of the large volumes of carbon dioxide that are expected to be injected, and the vast extent of the storage zones, it is expected that more detailed information will be needed over a larger area for carbon sequestration than has been historically needed for injection of other wastes.

The NGWA recommends that the adequacy and safety of injection of liquid carbon dioxide at each site be evaluated by multi-phase, variable density ground-water modeling, supported by extensive field investigations (see section General Comments

on the Use of Modeling for Ground-Water Protection Related to CO 2 Sequestration, below) These models should be included at the experimental well permit application phase as conceptual models, and progressively refined as data are collected during well construction and testing, and monitoring of operations.

The test injection wellfoperational testing permit application for a carbon sequestration injection well must address the geological characteristics of the site. The data presented at this stage should be adequate to make and calibrate an appropriate ground-water model. The necessary elements of the geologic system for carbon sequestration include:

• A receiving zone of sufficient depth that the injected carbon dioxide can be maintained in a supercritical state

• Of sufficient areal extent that it includes the entire zone of endangering influence

• Of sufficient thickness and porosity to contain the volume of carbon dioxide injected

over the life of the proposed system



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• Of sufficient permeability to accept the peak daily flow of injected carbon dioxide from the facility • A trapping mechanism (consisting of either impermeable barriers or geochemical/mixing barriers) that is free of vertical or horizontal pathways for migration of injected fluids into a USDW. The volume of the trap shall exceed the proposed total volume of injected carbon dioxide for the life of the proposed facility • A primary confining system of sufficient areal extent, thickness and competency to contain the injected fluid at proposed rates and volumes without initiating or propagating fractures in the confining zone

• Unless the only feasible injection zone has only one confining unit separating it from the lowermost USDW, a secondary containment system that is completely redundant of the primary confining system and could confine the injected CO 2 should the primary system fail.

• The identification of a monitoring zone between the primary and secondary confining units. In locations where the secondary containment system is not possible, the applicant shall propose a monitoring formation to provide early warning of failure of the primary confining unit in order to avoid impacting any USDW should that confinement fail.

• Provide depth and completion information of all USDWs that may be affected by the injection if fluid movement does occur.

• Provide geochemical information on subsurface aquifers, including all USDWs: Baseline geochemical data on water-rock- CO 2 geochemistry and mineral reactions, maps and cross sections.

These elements should be identified in existing well records, in geologic literature, and by using the results of the exploratory program. The critical storage and confining units should be shown to exist over the entire area of review, or zone of endangering influence

The operation permit application should also include a preliminary multi-phase numerical transport model for CO 2 and formation fluid, including all of the elements listed above. This model should include at least one calibration scenario and will be used to provide a preliminary evaluation of the adequacy and safety of injection of carbon dioxide at the site, as well as a preliminary calculation of the potential storage volume of the geologic structure.

Each permit application for a carbon sequestration injection well must include an Area of Review study, which addresses the entire zone of endangering influence of the carbon sequestration operation, including the area impacted after cessation of injection due to buoyancy transport. The zone of endangering influence shall be determined by the ground-water model described above and illustrated with maps and cross sections.

Provide information on the geologic structure of the proposed site, including:

• Maps and cross sections of local geologic structure. Each cross section should include the location and depth of relevant data sources, including geophysical logs, that were used in developing the cross section

• Geologicai name and lithologic description of each injection zone, primary and/or secondary confining unit, and USDW


### 6

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• Data on the receiving formation and the confining systems: 1. Size of the storage reservoir, and extent of the confining units in comparison to the area of endangering influence 

### 2. Presence or absence of a secondary confining unit 3. Porosity, and permeability of the storage zone and confining units, including any geology/facies changes, based on field data which may include geologic cores, outcrop data, 3-dimensional seismic surveys, and well logs 

### 4. Capacity of the storage zone in comparison to the proposed total volume of carbon dioxide to be stored, 

### 5. Evaluation of the long-term effectiveness of the storage structure, including expected pathways of migration of injected carbon dioxide, and the horizontal barriers to fluid movement

• Geomechanical information on fractures, stress, rock strength, and in situ fluid pressures within the primary and secondary containment units and confining systems

• Identification of potential pathways for migration of injected fluids and determination that they would not conduct a volume of fluid that would cause a violation of the prohibition of fluid movement as it applies to the class of well that is to be constructed

• Identification of potential risks within the zone of endangering influence, including degradation of water quality in USDWs, gas buildup in USDWs, reduction of porosity through geochemical changes in USDWs, and popUlation that could be affected by gas releases.

• List of penetrations into the injection zone and secondary containment system.

• Information on seismic history and the presence/depth of seismic sources

During drilling and construction of the injection well, important, site-specific data must be collected to verify the facts included in the application, provide quantitative data for refinement of the ground-water model, and test the injectivity of the proposed injection

zone. The testing currently recommended in the regulations during construction of Class I wells includes geophysical logs run during drilling, deviation checks to ensure that reamed holes do not deviate from pilot holes, leaving conduits in the formation, and logs to measure the integrity of the completed wells. The NGWA recommends the following testing during construction:

A. Identification of the lowermost USDW should be confirmed during drilling, using tests such as the following:



### 1. Sampling discharge from packer tests (straddle packers or single-packer bottomhole test). 

### 2. Cross plots of induction or resistivity with sonic/neutron/density porosity measurements and deduction of fluid resistivity using Archies Law (verification of porosity with core samples) 3. Bottom-hole water sampling during pilot hole drilling (with mud) 

### 4. Depth sampling in pilot hole while pumping 

### 5. Collection, logging, and archiving, of rock cores through the sealing and target formations.

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### 7National Ground Water Association Comments on Geological Sequestration Proposed Rule



### B. The demonstration of confinement is the most critical task in construction of the well. Some information can be collected only prior to the installation of casing so careful consideration should be given to formation sampling before the well is completed. We recommend that borehole geophysical methods, such as, but not limited to, resistivity, neutron, gamma, and density logs, be combined with formation imaging such as, but not limited to, digital video and acoustic televiewer logging to specify lithologic units, geologic properties, and faults or fractures. Hydraulic testing such as straddle packer injection can be completed prior to completion of the well. After completion, long-term pumping tests should be conducted over a sufficient time period to assure near-pseudo-steady state head conditions in the vicinity of the well. Interpretation of these data and tests should be used to refine the ground-water flow and transport model.

General Comments on the Use of Modeling for Ground-Water Protection Related to CO 2 

### Sequestration

Quantitative modeling must play an important role in the assessment of ground-water protection related to CO 2 

### sequestration projects. A 'quantitative model' is defined here

as a quantitative mathematical analog of the real subsurface system.

Three overall purposes for quantitative modeling are generally recognized:

1. Generic: Model used in a hypothetical sense 2. Interpretive: Model used to understand system dynamics 3. Predictive: Model used to predict future behavior of the subsurface system.

All three purposes are generally needed for a CO 2 

### sequestration project. For example, generic models are used to determine the important physical or geochemical mechanisms that dominate transport or trapping of CO 2 • 

### An interpretive model is applied to test specific hypotheses regarding these behaviors. Predictive modeling provides the basis for design of the final injection scheme and establishment of potential risk to drinking water.

Quantitative models may range from simple anaIvtic 

### calculations to complex multicomponent multi-phase coupled three-dimensional numerical 

### simulations. The choice of quantitative model (analytic or numerical) depends in large part on the ultimate objective of the modeling study, and on practical constraints including availability of data and computational limitations. Which type of model or combination of models is most appropriate for a specific situation depends on many factors. In general, using a combination of modeling and analysis techniques is recommended, because different levels of complexity are needed at various stages of a project and for different objectives, and application of multiple modeling techniques can be used for "crosschecking" and overall quality assurance.

Numerical models are widely available and usually represent a relatively wide range of physical and chemical processes, spatial heterogeneity of material properties, and nonlinear interactions among different processes. While these kinds of models allow for substantial flexibility and can provide detailed predictions of system behavior, they also



### 8National Ground Water Association Comments on Geological Sequestration Proposed Rule

require large amounts of data, much of which may be difficult to obtain or estimate. As such, specific choices of models must be made with care, and some situations may most effectively be addressed by a combination of different kinds of models.

Quantitative modeling, whether conducted with analytical or numerical modeling tools, provides significant insights into system behavior. The advantages of such models are that they:

1. provide a framework for data collection centered about a specific set of transport and geochemical behaviors. 2. allow communication and the interpretation of these data in the context of scientific principles and facilitate collaboration among engineers, scientists, and regulators. 3. may be extended far into the future using multiple design scenarios 4. can be compared to measured data which allow hydraulic and geochemical parameters to be estimated. 5. Can be used to access the performance of the system in a long performance period for which field and laboratory data are not available.

It is important to recognize that all quantitative mathematical models are based upon a "conceptual model" which defines the important fluid and chemical interactions as well

as the spatial and temporal extent of the model. Because the conceptualization is a critical part of the modeling activity, it is important to explore multiple conceptual models during the modeling process to assure that important scenarios are not excluded from the analysis.

The selection of which quantitative model to use relies on the identification of the physical/chemical parameters and functions that must be represented. Because the injection and migration of CO 2 into the subsurface is hydraulically and chemically complex, comprehensive quantitative modeling would have to include many parameters and factors

-- including the flow of miscible and immiscible phases in all potential states

as well as chemical reactions among fluids and with the geologic media and necessary heat transfer. The geologic medium may also deform or be chemically altered in response to the presence of CO 2

. The complexity of these coupled processes, in the presence of complex hydrostratigraphy, lead to models that are at the limit of the current capabilities of available computer hardware and software. It is likely, therefore, that multiple models may be required to provide the necessary insights into the important physical and chemical processes. Ultimately, sound scientific and engineering judgments should be applied to determine which physical or chemical processes are most important for a given analysis, and to make assumptions that are consistent with those judgments. For example, during the injection phase of a CO 2 operation, multiphase flow physics tend to dominate other processes such as interphase mass transfer and geochemical reactions. This separation of time scales can lead to important simplifications for the purpose of risk assessment. Similar analysis of spatial scales can provide additional simplifications, leading to practical modeling tools for the purpose of risk assessment. It is, therefore. imperative that modeling experts participate and manage all phases of the modeling process, in concert and constant communication with the project team and the appropriate regulatory reviewers, to ensure that appropriate and comprehensive quantitative modeling tools are applied successfully."



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The process of comparing simulated and measured predictions for the purpose of developing a more accurate depiction of a subsurface flow system is generally referred to as "model calibration" in the ground-water literature. (This same process is referred to

as "inverse modeling" in exploration geophysics and "history matching" in petroleum reservoir simulation.) Model calibration involves varying the parameters of the quantitative model to achieve the minimum difference between measured and predicted responses. This is usually achieved through an automated process using non-linear regression or a heuristic algorithm to optimize the problem (e.g. as implemented in the PEST or UCODE software). In the case of ground-water modeling, the predicted and measured data are usually pressures, discharge rates, or concentrations of fluids or dissolved species. These data may not be available during the design stage of a CO 2 project unless wells already exist in the target formation. As wells are drilled and geologic and fluid information are collected, however, the model should be refined and calibrated. Most automated calibration procedures allow for statistical estimation of confidence in the estimated parameters, providing a basis for quantifying the sensitivity of the model to changes in its parameters, and for performing quality control of model predictions.

The design, construction, and calibration of analytic or numerical models should follow a quality assurance and quality control procedure. These procedures should include benchmarking of the mathematical predictions against known results, a method for assuring input data quality and lineage, and a statistical analysis of the predictive results against available data and/or sensitivity analyses. ASTM guides are available for ground-water modeling and code benchmarking (e.g. Guides D 6025, D 5447, D 5490, D 5611, D 5609, D 5610, and D 5718).

Use of commercial proprietary codes should be authorized. Proprietary doesn't mean secret. A proprietary code largely vetted by the industry can be the best application in many circumstances. To promote peer review and benchmarking, the assumptions and theories for all numerical models should be publicly available and the solution of any analytic equations used in the predictive process should be fully elaborated.

Area of Review and Corrective Action

In the context of carbon storage, NGWA thinks it is important to distinguish between the CO 2 plume footprint and the zone of elevated pressure. The rationale is given in the next section, but the following conditions should be met:

No fixed radius can be used, a zone of endangering influence (ZEI) must be determined through modeling (but cannot be smaller than 

### Y.i mile in its smallest horizontal dimension) In the volume generated by the CO 2 plume footprint (plus appropriate buffer) (this volume is defined as the "primary AOR"): all penetrations between the base of the injection formation and the base of the USDW should be reviewed and any necessary corrective action should be taken before start of project.



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### 10National Ground Water Association Comments on Geological Seqllestration Proposed Rule



### In the elevated pressure area but outside of the CO 2 

### plume footprint (defined as the "secondary AOR"), all current penetrations through the primary seal and the injection formation should be reviewed. However the applicant should be allowed to perform corrective action in a pseudo-concentric phased manner ahead of and according to the development of the pressure plume.

Secondary AORlzone of elevated pressure cannot be computed independently of other injection projects in the vicinity. The impact of other sequestration projects must be included in determining injection rate / period of injection.

Primary and secondary AOR must be periodically reviewed to ensure that modeling predictions are met. If they are not, the primary and secondary AOR should be revisited. The operator should keep track of any new penetration in the primary AOR volume and secondary AOR (for example, for oil and gas industry).

"Primary AOR"

- Why "Volume of Review"

Because CO 2 

### is strongly buoyant, it is not sufficient only to investigate penetrations in the injection formation and primary seal. The whole volume potentially contacted by the CO 2 

### plume should be reviewed. The review and corrective actions should be performed before the start of injection because there is no stopping the CO 2 

### migration once started. The greatest degree of effort should be on the deeper wells in the injection zone and primary containment then on the secondary containment and seal (if any) and then on shallower wells but as many as possible of the shallower wells should be compiled too.

Delayed Corrective Action for "Secondary AOR"

A simple time-dependent secondary AOR that expands as the volume of injection increases and the CO 2 

### migrates is not acceptable. The secondary AOR should be agreed upon and reviewed before injection starts but corrective action can be somewhat delayed. The secondary AOR consists of only the injection formation and seal as used in the current rules because only brine/formation water leakage is an issue in the elevated pressure area. The likely presence of a large elevated pressure area does not make realistic imposing corrective action on all wells before the start of a project. There is no need to provide corrective action to wells before the pressure significantly rises. If another problem (e.g., CO 2 

### leakage) occurs earlier at another location and injection stops, pressure will not keep rising and will drop. In addition, delaying corrective action will allow taking advantage of technical improvements that will undoubtedly occur in the next decades.

Modeling is Needed: When considering tens of miles, trying to use conservatively the analytical solution as provided in 40 CFR §146.06 will likely generate unrealistically large AORs. Parameters such as formation thickness and heterogeneity, storativity and permeability values will likely vary in the zone of elevated pressure suggesting that model results should be accepted as valid.

How to define the edge of the AOR? If the CO 2 

### plume is relatively easy to define in terms of modeling, this is much less true for the pressure plume. Limits to the secondary AOR can be defined more or less as it is currently done by the contour line of the

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additional pressure that would push the injection formation brine beyond some elevation threshold (for example, 100 ft below the base of the USDW). Time-varying area where corrective action needs to take place as injection progresses can be defined in a similar fashion.

AORs can be initially defined solely on the basis of modeling. However, NGWA strongly supports that a satisfactory match between prediction and actual field measurements needs to be assessed as the project progresses.

Fluid Movement

The UIC regulations have, from the beginning, included two standards of prohibition of fluid movement that may be appropriate for geological sequestration of carbon dioxide. The fluid movement requirement for Class I injection wells states:

The well must be constructed, operated, maintained, and plugged such that injection activities will not cause movement of any contaminant into a USDW

The fluid movement requirement for Class V injection wells states:

No owner or operator shall construct, operate, maintain, convert, plug, abandon,

or conduct any other injection activity in a manner that allows the movement of fluid containing any contaminant into underground sources of drinking water, if the presence of that contaminant may cause a violation of any primary drinking water regulation under 40 CFR part 142 or may otherwise adversely affect the health of persons. The applicant for a permit shall have the burden of showing that the requirements of this paragraph are met.

The NGWA recommendation for carbon sequestration well permitting includes an experimental phase for each location that will be used for geological sequestration of carbon dioxide. Wells constructed during the experimental phase at each location will have extensive testing requirements and exploratory objectives that will not be needed during the operational phase. It will not be necessary or practical to apply the same standard of fluid movement to both the experimental phase and the operational phase of carbon sequestration.

The NGWA recommendations also include early warning monitoring to detect movement of fluids containing carbon dioxide or contaminants before the fluids reach a USDW. The advantage of early warning monitoring is in the ability to detect fluid movement before a drinking water supply is impacted. The identification of a geological unit that

can serve as secondary containment for the injected fluid is addressed in the NGWA recommendations for geologic characterization. It is recommended that early warning monitoring be included in the requirements for operation of Class V experimental carbon sequestration wells, as well as Class VI operational carbon sequestration wells. The requirement for early warning monitoring should include authorization for action by the regulatory agency when fluid movement is detected by the early warning monitoring system.



### 12

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### ¢£ ¢National Ground Water Association Comments on Geological Sequestration Proposed Rule

Class V Experimental Carbon Sequestration Well: During the experimental phase of injection, while the well is permitted as a Class V well, the following fluid movement criterion should apply:

No owner or operator shall construct, operate, maintain, convert, plug, abandon, or conduct any other injection activity in a manner that allows the movement of fluid containing carbon dioxide or any contaminant into underground sources of drinking water, if the presence of carbon dioxide or that contaminant may cause a violation of any primary drinking water regulation under 40 CFR part 142 or may otherwise adversely affect the health of persons. The applicant for a permit shall have the burden of showing that the requirements of this paragraph are met.

Class VI Operational Carbon Sequestration Well: During the operational phase of injection, while the well is permitted as a Class VI well, the following fluid movement criterion should apply:

No owner or operator shall construct, operate, maintain, convert, plug, abandon, or conduct any other injection activity in a manner that allows the movement of fluid containing carbon dioxide or any contaminant into underground sources of drinking water, if the presence of carbon dioxide or that contaminant may cause a violation of any primary drinking water regulation under 40 CFR part 142 or may otherwise adversely affect the health of persons. Additionally, no owner or operator shall construct, operate, maintain, convert, plug, abandon, or conduct any other injection activity in a manner that allows the movement of carbon dioxide in gaseous phase to land surface, nor limit the extraction of drinking water from a underground

sources of drinking water by reduction of porosity or changes in pH or water quality due to geochemical reactions, or by causing a buildup of gas in the underground

sources of drinking water. The applicant for a permit shall have the burden of showing that the requirements of this paragraph are met.

If any water quality monitoring of an underground source of drinking water indicates the movement of any contaminant into the underground source of drinking water, or a violation of any part of the preceding paragraph, except as authorized under part 146, the Director shall publish a notice in newspapers of general circulation in whose service area the fluid movement was detected. If a meritorious request is submitted by the public, the Director shall prescribe such additional requirements for construction, corrective action, operation, monitoring, or reporting (including closure of the injection well) as are necessary to prevent such movement.

Well Construction, Testing, and Closure

Wells will be an integral part of a CO 2 sequestration operation. Wells will be used to inject CO 2 into the target sequestration formation and monitor the sequestration and other formations that could be affected by the injection. Because wells represent a potential conduit for CO 2 or formation fluids to move out of formation and possibly to the surface great care must be taken to construct wells such that they will not leak, monitor them to ensure that they do not start leaking, and close them to ensure that they do not



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become a leakage risk later. Wells must demonstrate the ability to contain both injected and native fluids without allowing significant movement between formations or to the surface.

Construction

Regardless of the site specific component the new wells will need to be designed to meet the overarching goals for all projects. The goals for and injection well will be to inject CO 2 and to keep fluid from moving along the wellbore between formations or to the surface. The goals for a monitoring well are to monitor the injection or other formations and also to keep fluids from moving along the wellbore. To accomplish these goals the design of the well needs to address site-specific, objective-specific (monitoring or injection), and fluid-specific considerations. All injection wells should be cased and cemented to stop fluid movement between formations. A surface casing should be installed and set below the lowermost USDW above the injection zone and cemented along its entire length. It is important when considering the height of the cement sheath behind the long-string casing to consider the overall "design" of the injection and monitoring zones. Because, it is ideal to have a secondary caprock it will be imperative to cement the well, at a minimum, from the injection zone to a level above the secondary confining unit. If the borehole through the secondary caprock is left uncemented the effectiveness of the secondary caprock will be greatly reduced. Furthermore, it may be advisable to cement the casing along the entire length to protect the casing from degradation due to anodic dissolution [Anstice et aI., 2005] or exposure to corrosive formation fluids. If the casing is not cemented along its entire length it may be necessary to use cathodic protection, depending on the site, to keep the casing from degrading. Watson and Bachu, [2007] found that about 81 

### % of wells in their study area that had surface casing vent flows (leaks) had them above the top cemented section.

The materials used for construction need to be compatible with the injected fluid and compatible with the formation fluids. Both injection and monitoring wells should be constructed to the same material standard unless there is an objective-specific reason not to, because they may both be subjected to similar aggressive down-hole conditions. In order to insure that proper wellbore construction materials are always selected a standard should be adopted that specifies wellbore materials should resist the expected downhole conditions to a sufficient degree such that degradation will not lead to leakage. The thicknesses of the casing and tubing must be sufficient to handle the pressure associated with the injected CO 2

. Although materials are an important aspect in well construction centralization of the casing is also important for insuring the cement job is successful. It is very important that the casing is centralized over the entire cemented section. This will provide the best condition to achieve full radial coverage of the cement between the casing and the formation.

For both types of wells, it is important that regulations require that internal safety

measures are installed in the well. This will help ensure that wells do not allow leakage out of the well through the wellbore in the case of an accident or other event. Down-hole shutoff equipment needs to be required. The shutoff equipment needs to be downhole to avoid leakage if the surface components of the well are damaged.



### 14

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In some areas it is likely that existing wells will be converted into both injection wells and monitoring wells. It seems unlikely that such wells will have been constructed to the

same standard as wells purpose-built for sequestration applications. This, however, is probably not reason enough to rule them out from being used as long as they meet the

same standards for protection as new wells do. This said, there should be a cutoff date

so that all wells used for CO 2 injection or monitoring constructed after the date are constructed to the same standard.

Injection wells should be designed to inject through tubing. Tubing and packer allow for monitoring pressure in the annulus between the tubing and casing to help identify any leaks. Furthermore the tUbing can be replaced relatively easily in the case any damage to the tubing is identified or to change the diameter of the tubing.

Wellbore Integrity Monitoring and Measurement

The integrity of monitoring and injection wells must be established and monitored. However, the type of integrity measurement(s) should be decided upon based on the construction of the well, the well materials, and the effectiveness of the monitoring techniques. Wells that are not cemented from total depth (TO) to the surface should be subject to more integrity monitoring than those that are cemented from TO to surface because the path behind the uncemented section of casing could act as a fast path for fluids to move between formations. No single specific monitoring technique should be required and it is expected that multiple techniques will be needed. The deviation of all wells should be measured to ensure that the geometry of the well is understood to identify areas that may require special attention, like poorly centralized sections, to

ensure that they are carefully characterized.

A requirement will be needed to ensure that the integrity and quality of the casing and cement job are initially and remain sufficient to prevent flUid movement along the wellbore. Because the cement is behind the casing, it will be necessary to use some type of logging tool to make the measurement. The selection of logging tools should be based on proven performance. The prescription of a particular tool may force the use of

a technology in the future that is not the best available for the job. This said, the standard for selection of the tool can be specified and should take into account the geometry of a wellbore. Because wells are cylindrical, the integrity and location of the cement must be verified using technology capable of radially evaluating and mapping the cement, identifying the location of channels or contaminated cement, and validating the casing-cement and cement-formation bonds, thus providing a 360 0 map of the cement and any potential defects for the entire length of the cemented casing.

Another method of ensuring the mechanical integrity of the well is the use of mechanical integrity tests, MITs. MITs, that raise the pressure in the well, like the standard annulus pressure test, are often used to measure the internal integrity. It is possible that the increase in pressure in the wellbore associated with some MITs could damage the interface between the casing and the cement possibly creating a leakage pathway. The

use of these MITs on CO 2 injection wells should be studied before it is made a requirement. MITs such as radioactive tracer surveys, RATS, or other alternative methods with comparable results, may be more appropriate for measuring internal



### 15

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integrity. Furthermore, RATS and temperature logging may also be an effective technique for identifying external wellbore leakage pathways.

The integrity of the well should be measured on a regular basis such that time-lapse comparisons are possible to see if there are changes within the wellbore over time that could lead to leakage situations.

Closure

When all injection operations are finished the site will be closed and the post closure period will begin. At this juncture the injection wells will be plugged and abandoned. The plugging needs to be done such that the CO 2 and formation fluids cannot use the wellbore as a conduit when it is complete. No wells should be abandoned until there has been a final round of measurements to verify the integrity of the well in case remedial action is needed prior to plugging. Wells plugged prior to the site closure phase should be plugged and abandoned following the same procedures as those in the closure phase. Any requirements need to ensure that all wells are properly plugged and abandoned using material and methods that will allow the well to remain safe and not become an avenue for leakage.

Monitoring, Measurement, and Verification

Measurement, monitoring, and verification (MMV) will be a key task for all geologic carbon sequestration operations. MMV should be looked at as a continuation of the measurements that were collected during the characterization and construction phases

as described in the sections on well construction, testing, and closure and geologic characterization. Characterization and construction measurements will provide the baseline for comparison during the injection and post injection phases of the sequestration project. The data collected during the MMV will be used to insure the site is not leaking or for the identification and remediation of leaks. The data will also be used to calibrate and reduce uncertainty in models of the site.

During the operational injection phase of a CCS project, MMV can be broken into operational monitoring, which is the monitoring of the injected CO 2 , and environmental monitoring, which is the monitoring of the subsurface including the sequestered CO 2 and the associated pressure front.

Operational MMV includes; monitoring the volume, flow rate, and composition of CO 2 that is injected. The injection pressure must be low enough that injection does not propagate new fractures and does not open existing faults or fractures for flow through the caprock or damage the containment properties of the injection well. The operational monitoring will also have to monitor the injection and monitoring wells to ensure they are functioning properly and not allowing any leakage. The integrity of the injection well must be monitored internally and externally to ensure that there is no degradation that could allow CO 2 to leave the target formation. Well integrity monitoring through the use of logs, annulus pressure monitoring, and mechanical integrity tests is covered in detail in the section on well construction, monitoring and abandonment.

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### 16National Ground Water Association Comments on Geological Sequestration Proposed Rule

Environmental MMV needs to be implemented to collect data from the four or more geologic formations that comprise the subsurface site: the storage formation, the primary cap rock, the monitoring formation, and the secondary cap rock. MMV must also provide information on shallow formations, including the lowermost USDW, that contain drinking water, the surface and, any potential leakage pathways between the storage formation

or monitoring formation and any drinking water formations or the surface (this may include additional monitoring of wells above what is required for operational monitoring).

In the injection zone, monitoring must identify the location of the injected e0 2 and the associated pressure front. MMV in the monitoring zone should be geared to ensure that any vertical migration across the cap rock is identified. Monitoring of USDWs should be set up to look for changes that would be associated with the presence of e0 2 or eo 2

- displaced brine. While some general monitoring points in all of these zones will be needed, it may be more practical to locate monitoring points or take measurements near locations identified during the characterization and potential fast-paths, such as abandoned wells, existing wells, or faults and fractures. One location that may provide the best use of monitoring resources is near the injection weil. This is the most likely location for upward fluid movement without specific knowledge of a potential leakage pathway. Leakage could occur either through mechanical integrity failure or defects, or failure or defects of the confining units. Monitoring, in the monitoring zone and lowest USDW in addition to the injection zone, provides a vertical pressure profile, measures stress on the confining units, and may detect water quality changes.

In the monitored zones, geochemical and fluid chemical information should be based on constituents identified in the characterization as likely indicators of leakage. These indicators will likely include the pH and also be identified in the major and minor chemical constituents of the formation and ionic constituents of the formation-fluid.

The methods used for monitoring on projects to date have included time-lapse seismic, passive seismic, pressure logging, temperature logging, neutron saturation logging, fluid sampling, air sampling [IPee, 2005]. While it is probably not appropriate to specify the suite of MMV tools to be used at every site, because not all tools will work at all sites, it is important to emphasize that multiple MMV technologies will be required at every site in order to completely monitor and collect the necessary data to verify that the site is operating within the bounds of its permit. Although it seems unreasonable to specify all MMV technologies, it does seem reasonable to specify that monitoring wells be installed to collect the necessary fluid samples, pH, resistivity, and pressure data. Also, although seismic monitoring may not work everywhere, in locations where it is expected to work it should be incorporated into the monitoring scheme. Seismic monitoring for e0 2 plume location has been successfully employed in early projects including Sliepner storage project, Weyburn storage project, and Frio brine project [IPee, 2005, Wilson and Monea, 2005, Daley et aI., 2007]. The data collected from monitoring should be used to update and verify the site's performance and risk models.

In addition, to aid in selecting other MMV technologies, the International Energy Agency has developed a comprehensive database that can be accessed at: http://www.c02captureandstorage.info/c02tool v2.1 beta/index.php



### 17

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Although surface monitoring may be needed from a community outreach and environmental safety point of view, it is important to note that by the time any leakage is detected at the surface it will have already passed by and possibly impacted underground drinking waters. Projects like the Frio brine project [McCallum et ai, 2005] have incorporated tracers as a way to identify CO 2 leakage. The use of non-isotopic tracers, tracers other than C13, C14, and 018 that occur naturally in CO 2 , should be studied very carefully for unintended environmental effects prior to implementation.

Once injection ceases permanently, the operational portion of MMV can also cease. This period, called the closure period, is the time in which the operator will plug and abandon all wells that will not be used for further monitoring. Environmental MMV operations should continue throughout this period using the same suite of techniques as in the operational phase.

MMV should be conducted hand-in-hand with modeling over the entire period that MMV is occurring, with each new round of measurements being incorporated into a new iteration of the appropriate site models. An iterative measurement-modeling approach will allow for the best understanding of the shape and size of the AoR. It will also help identify areas of uncertainty in the model that may be reduced with changes in the MMV plan. Changes identified in the size of the AoR and for risk of leakage will help ensure that MMV is carried out at the right frequency and in the right locations. The timing of the MMV operations should be flexible and adjustable based on the performance of the site and the site models. It is likely that the site data from early in the operation will probably be more valuable than data from later in the operation for assessing the performance of the site and identifying and reducing uncertainties. MMV operations that

are not continuous should be conducted more frequently at the start of the operational phase and then be allowed to become less frequent if the site is performing safely and in concert with the model predictions. The initial, more frequent monitoring should be specified in the permit as an experimental phase of the injection project. The continuation of injection should be contingent upon successful containment of the injected CO 2 during the experimental phase.

As the pressure in the injection zone starts to stabilize it may be possible to lengthen the period between measurements if the reservoir is performing as expected based on the calibrated site models. When the location of the CO 2 either stops changing or can be predicted and validated against measurements over multiple measurement cycles, the ownership of the site and the responsibility for future MMV, if deemed necessary, may be transferred from the operator to the government, starting the post-closure phase. If the site is not behaving as expected, an iterative MMV-modeling approach will help identify areas of uncertainty that can be reduced by changes in the MMV plan to collect

more or different data to determine the site's performance.

Regulations for the operational phase need to ensure that a licensed Carbon Capture and Storage (CCS) site is operated safely and should allow for flexibility in the monitoring schedule based on the performance of the site and site models. A site that is performing well probably reqUires less frequent monitoring than one that is not performing well. A long-term match between MMV data and site modeling results probably indicates a good understanding of the site and shouid be one of the criteria used to decide when the custodianship of the site should be transferred from the

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### 18National Ground Water Association Comments on Geological Sequestration Proposed Rule

operator to the government. It is possible that iterative MMV and modeling will show that the AoR changes over time. The idea of a variable AoR should be included and accepted in any regulations. The results of the MMV and modeling including the integrity of the wells, fluid properties and volumes, subsurface location of the plume, leakage monitoring, modeling, and size of the AoR should be reported at least annually

or upon a sudden significant change.

Overview of Financial Responsibility Issues

Introduction

Applying financial responsibility for the various operational and post-closure risks is central to widespread deployment of CCS as an effective climate-change mitigation strategy. The commonly perceived CCS categories of risks include toxicological effects, induced seismicity, subsurface trespass, and climate effects (de Figueiredo et aI., 2006). The mechanisms for these risks include CO 2 gas leakage from the injection wellhead; gas leakage from geologic reservoir; development of injection-related seismicity in existing seismically active areas; and, degradation of drinking water aquifers by mobilization of brines or by geochemical interaction of fugitive CO 2 with overlying aquifers.

These liabilities may be further categorized in terms of operational liability and postinjection liability (e.g., Figueiredo et aI., 2006). Operational liability includes the environmental, health and safety risks associated with capture, transportation and injection of CO 2 • Post-injection liability is related to storage of carbon dioxide in the geologic formation after it has been injected. According to Figueiredo et aI., postinjection liability can be further divided according to (1) in situ liability of harm to human health, the environment, and property, including degradation of aquifers, and (2) climate liability related to leakage of CO 2 from the geologic reservoirs and its long-term effect on climate change.

The long period and geographic scale over which these liabilities can occur pose unique challenges for assessing CCS liability, in comparison to conventional business liability models. For example, the operational phase of individual CCS projects is anticipated to be tens of years (Gerard and Wilson, 2008). Although the post-injection risks are inferred to decrease with time, the long period over which these risks may manifest themselves and the inherent geophysical uncertainties of geologic reservoirs are not amenable to a strictly private solution to liability. For example, several authors (e.g., Figueredo et aI., 2006; Edison Electric Institute, 2007; WRI, 2006; and Gerard and Wilson, 2008) have suggested that the unique liabilities associated with CCS should be assigned to the operators during the injection phase and for a short period after cessation of injection and closure of the injection wells, and the long-term post-closure liability should become

a public responsibility because of the perceived significant public benefit that CCS will have on iocal and global climate. Another reason to involve the public sector in the longterm liability may be to ensure that a responsible entity will be around (i.e., should the CCS operator or holding company become insolvent) to address post-closure CCS problems, should they arise (World Resources Institute, 2007).



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Applicable and Relevant Liability Models

Public health/environmental liability models currently exist in North America that may to offer some insights to help develop workable CCS liability policy to safeguard public interests yet remain attractive to private/corporate investors who will help fund development of the required CCS technology and large-scale CCS operations.

Alberta Acid Gas Re-lnjection. Acid gas streams, consisting primarily of hydrogen sulfide and carbon dioxide, are commonly generated as a by-product of the gas "sweetening" process used to bring produced natural gases and solution gases up to pipeline specifications for sales and transport. Prior to introduction of acid gas re-injection, treatment of acid gases included flaring. The province of Alberta has over 

### 38 acid gas re-injection wells in operation (Wong et aI., 

### 2003). In Alberta, the injection well operator is financially responsible (liable) for operation and closure of acid gas re-injection wells, but there is no responsibility for post-closure monitoring or mitigation of gas leaks, whether leakage is from the storage reservoir or from the closed injection well (Bachu, 

### 2007). In addition, there is no provision to ensure that "orphaned" (abandoned) reinjection wells are closed properly by a public or private entity, should the operator becoming insolvent.

Price-Anderson Act. The Price-Anderson Act was passed as federal law in the United States in 

### 1957 to partially indemnify the nuclear industry against liability claims for nuclear incidents while still protecting the general public. The Act established a no-fault insurance fund in which the first 

### $10 billion of an incident claim is funded by industry and the federal government covers the remainder over this amount. The federal government instituted this Act to provide an incentive for private investment In nuclear power; without this type of indemnification, investors were unwilling to accept the unquanilifed risks of nuclear energy. Although criticized by some groups!, the Act has been renewed several times and is currently set to expire in 

### 2025. The Act appears to focus primarily on liability for nuclear plant operation and not for post-closure incidents. Over the first 43 years of operation until 

### 2000, the secondary federal insurance has not been required. The nuclear industry has paid a total of 

### $151 million to cover claims, including 

### $70 million for the Three Mile Island incident. During the same period, the Department of Energy has paid about 

### $65 million to cover claims for its own nuclear operations.

Resource Conservation and Recovery Act (RCRA). Enacted by the U.S. Congress in 

### 1976, RCRA mandates that companies set aside funds for post-closure care of solid and hazardous waste sites, and establishes EPA's authority to control related wastes from "cradle-to-grave" (USEPA(a), downloaded 

### 2008). For example, solid waste landfill operators in most U.S. states bear financial responsibility for public health and safety, environmental health, environmental monitoring, landfill maintenance, and remediation/treatment of leachate and contaminated ground water during landfill operation and for a post-closure period. Financial assurance of ability to cover these costs is generally required as a condition of the operator's state permit for both the operating and post-closure period. Some states (e.g., Maine) require that the financial

assurance cost estimates be based on the entire expected time that the solid waste

1 Criticized as a form of subsidy for industry, for failing to hold industry fully accountable for commercial nuclear safety, and for industry/contractor indemnification even under situations of gross negligence.



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## 20National Ground Water Association Comments on Geological Sequestration Proposed Rule

facility is expected to be generating leachate, landfill gases and other contaminants that have a potential for creating an adverse environmental impact. Pennsylvania bases bonding estimates on a 30-year post-closure period, but final closure is performancebased and site specific; upon final closure determination, a 10-year bond liability period

commences. However, the operator and landowner are still liable beyond this period for adverse effects and other changes in site conditions. Other states require post-closure monitoring, remediation and financial assurance for a finite period (e.g., Ohio

- 30 years; Vermont

- 20 years).

In 1986, Congress created a Leaking Underground Storage Tank (LUST) Trust Fund by amending Subtitle I of RCRA. The LUST Trust Fund provides money for overseeing and enforcing corrective action by a responsible party, and for cleanup at UST sites where the owner is unknown, unable, or unwilling to respond (USEPA(b), downloaded 2008). The Trust Fund is financed by a 0.1 cent tax on each gallon of motor fuel. All 50 states have cooperative agreements with EPA to spend this money for LUST-related activities. In addition, 47 states have established state-run LUST Funds to help owners and operators with UST upgrades and LUST remediation problems (Tiemann, 1999). Reimbursements from the state LUST Funds have generally benefited most UST owners/operators who comply with the existing state and federal UST regulations, regardless of finanCial ability to cover these costs. Like the RCRA LUST Trust Fund, the state LUST Funds are generated through gas taxes and tank fees.

Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). CERCLA (also referred to as Superfund), enacted by the U.S. Congress in 1980, established a tax on the chemical and petroleum industries to finance a fund that addresses the liabilities arising from the clean up of hazardous waste sites. Over a period of five years, $1.6 billion was collected and the tax went into a trust fund for cleaning up abandoned or uncontrolled hazardous waste sites (USEPA(c), downloaded 2008). CERCLA was amended in 1986 by the Superfund Amendments and Reauthorization Act (SARA). SARA increased the size of the trust fund to $8.5 billion (USEPA(d), downloaded 2008). While RCRA was intended to be forward-looking, CERCLA is intended to be backward-looking, i.e., contamination that occurred prior to RCRA authorization.

Tiered Approach

A key tenet of environmental laws and regulations is that pollution costs should be borne by their creators. U.S. environmental laws and regulations give this principle form by making polluters liable for property, health, and natural resource damages and unperformed resource reclamation obligations (Boyd, 2001). However, the anticipated great public benefit from CCS implementation and reluctance of private investors to become involved in an enterprise that may have several hundred years of post-closure liability suggest that a shared private/public liability model may be appropriate for longterm post-closure phase of CCS.

Gerard and Wilson (2008) provide a temporally-tiered approach to managing liability for all phases of CCS. This approach relies on operator liability and use of operator-funded bonds to cover liability during the operational phase (Phase 1) of CCS. Gerard and Wilson report that this approach has been used effectively for many oil and gas wells



### 21National Ground Water Association Comments on Geological Sequestration Proposed Rule

and wells regulated under the UIC Program where the operational lifetime of the wells is tens of years. This surety mechanism and time frame may also encourage proper site management and well closure for CCS wells. Short-term post-closure liability (Phase 2) for unanticipated accidents would rest with the operator, but active bonding by the operator would cease. Monitoring and verification during Phase 2 would be financed by publicly run or pooled financial mechanisms that would be funded by operator/industry contributions during the active injection phase of the project. The third phase of liability and management (Phase 3) would be a public responsibility, ensuring that long-term standards of care are met.

According to Gerard and Wilson, demarcation of the Phase 2 to Phase 

### 3 transition could be performance-based (e.g., based on pressure levels in the CCS reservoir or on dissolved CO 2 in the formation fluid), or prescriptive (e.g., after a finite period [10 years, 25 years, etc.]). By Phase 3, project performance and success are more certain and public "liability" and management would be viewed as primarily administration and record-keeping.

USEPA's Proposed UIC CCS Rule

In the proposed UIC CCS Rule, USEPA is proposing a combination of fixed timeframe and a performance standard. Post-injection site care (monitoring) would occur for a period of 50 years. This period could be shortened or lengthened based on plume behavior. If monitoring data demonstrate that the plume/pressure front is stabilized and the CO 2 injectate does not pose risk to USDWs, the 50-year post-injection site care period could be shortened. Conversely, if the plume/pressure front has not stabilized after 50 years of post-injection monitoring, USEPA would extend the monitoring period until stabilization is achieved.

Conclusion

It is apparent that much work and public-private sector discussions are needed to develop a liability policy framework and details that are workable and acceptable to all parties. In recognition of this, USEPA is requesting public comments on their proposed 50-year monitoring period with a performance element. Developing effective performance-based criteria upon which to base transfer of post-closure liability to the public appears to be an area that warrants considerable technical research. This transition mechanism could become one of the key issues to gain public acceptance for CCS.

The Task Force recommends that federal and energy industry funding for CCS research be directed toward establishing performance-based indicators for CO 2 reservoir stability to facilitate liability transfer. This tiered approach may offer ample incentives to ensure that CCS operations are managed responsibly, yet not discourage investors from supporting CCS. Public assumption of Phase 

### 3 liability after the CCS reservoir stabilizes appears commensurate with the great public benefit that CCS offers.

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## 22National Ground Water Association Comments on Geological Sequestration Proposed Rule

Acknowledgement

NGWA acknowledges the Association's Geologic Sequestration Task Force for their work in developing comments on geologic sequestration and EPA's proposed rule. Task force members include:

Glenn Amey PPL Services Corp Allentown, PA

Andrew Duguid, PhD Schlumberger Carbon Services Pittsburgh, PA

Matthew W Becker PhD University of Buffalo Buffalo, NY

Michael Celia, PhD Princeton University Princeton, NJ

William Cocke Dept. of Natural Resources and Environmental Conservation Dover, DE Jean-Philippe Nicot, PhD Bureau of Economic Geology University of Texas Austin, TX

Steven R Pinette, Certified Geologist SW Cole Engineering Scarborough, ME

Robert P Schreiber, PE, BCEE, D.wRE CDM (Camp Dresser & McKee Inc.) Cambridge, MA

Chen Zhu, PhD Indiana University Dept of Geological Sciences Bloomington, IN

g'r'<i'8'h a 

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## ;::: rt 23National Ground Water Association Comments on Geological Sequestration Proposed Rule



### References

Anstice, D.J., Page, C.L., and Page, M.M., 2005, "The pore solution phase of carbonated cement pastes," Cement and Concrete Research, Vol. 35, pp. 377-383.

Bachu, S., 2007, Legal and Regulatory Aspects of CCS, in Workshop on Capacity Building for Emerging Economies. Carbon Sequestration Leadership Forum in Porto Alegre, Brazil.

Boyd, J., 2001, Financial Responsibility for Environmental Obligations: Are Bonding and Assurance Rules Fulfilling Their Promise? Discussion Paper 01-42, Resources for the Future.

Daley, T.M., Solbau, RD., Ajo-Franklin, J.B., and Benson, S.M., 2007, "Continuous activesource seismic monitoring of CO 2 

### in a brine aquifer," Geophysics, Vol. 72, No.5, pp. A57-A61.

Edison Electric Institute, 2007, Status and Outlook for Carbon Capture and Storage Technology
in the United States. Written statement for the U.S. House Select Committee on Energy
and Global Warming.

Figueiredo, M. de, D. Reiner, H. Herzog, and K. Oye, 2006 The Liability of Carbon Dioxide Storage. Presented at the Eight International Conference on Greenhouse Gas Control Technologies, Trondheim, Norway

Fernando, H. J. Venezia, C. Ridgon, and P.Verma, date??, Capturing King Coal: Deploying Carbon Capture and Storage Systems in the U.S. at Scale. World Resources Institute
and Goldman Sachs.

Gerard, D., and E.J. Wilson, 2008, Environmental Bonds and the Problem of Long-Term Carbon Sequestration. Source. Journal of Environmental Management, In Press. Available
online as of July 2008: http://www.epp.cmu.edu/csir/ContentiResearch/Carbon%20Capture%20and%20Seguestration/Gerard%20 Wilson%20Bonding.doc



### Intergovernmental Panel on Climate Change, 2005, IPCC special report on carbon capture and storage, United Nations Framework Convention on Climate Change, ISBN 92-9169-119- 

### 4.

Maine Dept. of Environmental Protection, rev. 2001, Maine Solid Waste Management Rules, Chapter 400: General Provisions.



## g'i'6'8'h"il water aSSOCiation'
;..... ¢ Pc"",,"**1~1,f,** ... Ku 5\1**]l7~** fj\4**~~l.]J-l'** fa>! fjl1 HH71>5 w •."

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....**u{t~** 01-,'0 430;31**,8'l)~** USA 

### 24National Ground Water Association Comments on Geological Sequestration Proposed Rule

McCallum, S.D., Riestenberg, D.E., Cole, D.R., Freifeld, B.M., Trautz, R.C., Havorka, S.D., and Phelps, T.J., 2005, "Monitoring geologically sequestered CO 2 during the Frio brine pilot test using perfluorocarbon tracers," Proceedings of the 4th Annual Conference on Carbon Capture and Sequestration, May 2-5, 2005, Monitor and Exchange Publications and Forum, Washington, D.C.

Sengebush, Robert M., INTERA, Inc. Deep Brackish Water Considered for New Mexico Development. Southwest Hydrology, March/April 2008, p. 8.

Tiemann, M., 1999, Leaking Underground Storage Tank Issues. CRS Report: 97-471.



### , USEPA(a), downloaded 6/29/08. Summary of the Resource Conservation and Recovery Act. http://www.epa.gov/lawregs/laws/rcra.htm

USEPA(b), downloaded 6/29/08. Leaking Underground Storage Tank (LUST) Trust Fund. http:www.epa.gov/oust/ltffacts.htm

USEPA(c), downloaded 6/29/08. CERCLA Overview. http://www.superfund/policy/cercla.htm

USEPA(d) download 10/28/08, SARA Overview http://www.epa.gov/superfund/policy/sara.htm

U.S. General Accounting Office. Freshwater Supply: States' Views of House Federal Agencies Could Help Them Meet the Challenges of Expected Shortages (GAO-03-514). July 2003, p. 1.

Watson, T.L. and Bachu, S., "Evaluation of the potential for gas and CO 2 leakage along wellbores," paper SPE 106817 presented at the 2007 E&P Environmental and Safety Conference, Galveston, TX, March 5-7, 2007.

Wilson, M. and Monea, M., 2005, lEA GHG Weyburn Monitoring and Storage Project, Summary Report, 2000-2004, Petroleum Technology Research Center, Regina SK, Canada, Proceedings of the 7th International Conference on Greenhouse Gas Control Technologies (GHGT-7), Vol. III, September 5-9, Vancouver, Canada

Wong, S., D. Keith, E. Wichert, W. Gunter1and T. McCann, 2003, Economics of Acid Gas Reinjection: An Innovative CO 2 Storage Opportunity. In Greenhouse Gas Control Technologies, J. Gale and Y. Kaya (Eds.) 

### © 2003 Elsevier Science Ltd. All rights
reserved

World Resources Institute, 2007, Workshop Summary: Addressing Long-Term Liability of
Carbon Dioxide Capture and Geologic Sequestration.

World Resources Institute, 2006, Executive Summary: WRI Workshop on CCS Liability.



### 25 

## g'fd'8\\'&**w~ter** aSSOCiation' ¢i 

### dDocket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081

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## _. Preamble Questions Injection of C02 for the purposes of enhanced oil and gas The transition of carbon dioxide injection wells from Class II (Enhanced Oil
recovery (EORlEGR), as long as any production is Recovery wells) to Class VI (carbon sequestration wells) will presumably be occurring, will continue to be permitted under the Class II requested when production of the petroleum has ceased. Liquid carbon dioxide program. EPA seeks comment on the merits of this from a distant source, such as a power plant, can be stored in the depleted approach since owners or operators of some Class II petroleum reservoir even after production has ceased, necessitating a change in EOR/EGR wells may wish to use wells for the purposes of classification of the injection well. The new use of the wells involves much longer production and GS prior to the field being completely storage time, and raises concerns about mechanical integrity and long tenm depleted. EPA Notice 48. effects, including geochemical changes, on underground source of drinking water (USDWs). The reclassification should depend on a positive outcome from a Class V experimental program conducted in the depleted reservoir. See NGWA Comment Document (word document) Section titled "Classification of Injection Wells for Carbon Sequestration, Class II Injection Well Transition, and Grandfathering" for further details.

EPA seeks comment on how the grandfathering approach See NGW Comment Document (word document) Section titled "Classification of for existing wells may affect compliance with the other Injection Wells for Carbon Sequestration, Class II Injection Well Transition, and requirements in its oroposal. EPA Notice 50. Grandfatherino" for further details. The location and proximity of other formations to USDWs NGWA supports the general prohibition against injections above the lowermost
may preclude their use for GS. EPA seeks comment on USDW. An exemption process should be available to review and consider those prohibiting injection into such formations if they are above specific situations where injection cannot be done, or is being proposed not to be the lowermost USDW. EPA Notice 54. done, below the lowermost USDW

December 12, 2008 1Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551,7379, ext. 560. creimer@lnqwa.orq EPA's proposal would provide the Director the discretion to While NGWA beiieves that a site with a single confining can provide storage require the owner or operator to identify and characterize integrity, NGWA recommends that if there are additional confining iayers at the additionai confining and containment zones above the site they should be characterized to get a better estimate of leakage risk to primary (I.e., iowermost) confining zone that could further USDWs and possibly identify additional monitoring zones. impede verticai fluid movement and allow for pressure dissipation. EPA says that these layers could provide additionai sites for monitoring, mitigation, and remediation. EPA's proposai would not require that these additional

zones be identified for all GS sites because their absence does not necessarily indicate inappropriateness of a GS site. However, if such zones are present, information about their characteristics can provide inputs for predictive models, identify appropriate monitoring iocations, and improve pubiic confidence in and acceptance of a proposed GS site. EPA specificaiiy seeks comment on the merits of requiring the identification of these additional zones. EPA Notice 64.

In some cases, owners or operators may choose to use proprietary models (I.e., not avaiiable for free to the generai pubiic). EPA says it is aware that the use of proprietary codes may prevent fuii evaluation of model results (e.g., NRC, 2007). Several popuiar codes in the petroieumreservoir engineering discipiine are proprietary and owners

or operators of particular sites may prefer to use these codes as they have previous experience with them, and they have been used in peer-reviewed studies to model C02 sequestration. When using a proprietary modei,

owners or operators should clearly disclose the code assumptions, relevant equations, and scientific basis. EPA seeks comment on allowing the use of proprietary models for GS sites. EPA Notice 68.

EPA seeks comment on the applicabiiity of computational fluid flow models for deiineating the AoR of GS sites. EPA Notice 69.

December 12,2008 Yes, use of commercial proprietary codes should be authorized. Proprietary doesn't mean secret. A proprietary code largely vetted by the industry can be the best appiication in many circumstances. To promote peer review and benchmarking, the assumptions and theories for all numerical models should be pubiicly available and the solution of any analytic equations used in the predictive process should be fUlly elaborated.

See NGWA General Comment Document Section titled "General Comments on Use of Modeiing for Ground-Water Protection Related to C02 Sequestration".



### 2Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water AssocIation, 601 Dempsey Rd, WestervIlle, OH 43081

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......... ' EPA seeks comment on requiring the reevaluation of the Yes, reevaluation is needed and at a higher frequency than 10 years, particularly site AoR on a periodic basis, under what conditions the AoR at the beginning. should be reevaluated, and the appropriateness of a 10- year minimum fixed frequency for AoR reevaluation. EPA Notice 72. EPA proposes to allow a phased approach to corrective Yes, phased corrective action is a good idea. It wIll allow targeting of those wells action but says this may not be appropriate in all situations; most in need of corrective action and optimize financIal resources as the therefore EPA is proposing that the Director have the pressure/C02 plume may deviate from the initial AoR. That's why it is important to discretion to decide to allow this approach, based on the review AoR more often than 10 years. understanding of relevant geologic and site conditions. EPA invites public comment on the merits and frequency of reevaluation of the AoR as well as the phased corrective action approach for GS wells. EPA Notice 74.

EPA is soliciting comment on whether C02 injection should NGWA supports the general prohibition against injections above the lowermost be allowed into an injection zone above the lowermost USDW. An exemption process should be available to review and consider those USDW, when the Director determines that geologic specific situations where injection cannot be done, or is being proposed not to be conditions (e.g., thousands of feet of intervening formations done, below the lowermost USDW between the injection zone and the overlying and/or underlying USDWs) exist that wIll prevent fluid movement into adjacent USDWs. EPA Notice 93.

December 12,2008 

### 3Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560.**creimer~** ilnawa.ora Proposed Rule Revision or Comment Rationale §144.1 Purpose and scope of part 144. (1)(1 )(viii) Subpart H of this part sets forth requirements for owners or operators of Class VI injection wells. (g) Scope of the permit or rule requirement. The UIC Permit Program regulates underground injections by six classes of wells (see definition of "well injection," §144.3). The six classes of wells are set forth in §144.6. All owners or operators of these injection wells must be authorized either by permit or rule by the Director.

§144.6 Classification of wells. (e) Class V. Injection wells not included in Class I, II, 111, IV, or VI. Specific types of Class V injection wells

are described in §144.81. (I) Class VI. Wells used for geologic sequestration of Comment: NGWA supports the general prohibition against NGWA understands that there may be carbon dioxide beneath the lowermost formation injections above the lowermost USDW. An exemption portions of the country that will not have containing a USDW. process should be made available to review and consider adequate storage zones below the those specific situations where injection cannot be done, or is lowermost USDW. In these areas, the being proposed not to be done, below the lowermost USDW. Association believes that storage above the lowermost USDW may be allowed on a site specific basis based on director discretion assuming that all other conditions are met.

Subpart B -General Program Requirements

§144.15 Prohibition of non-experimental Class V wells for QeoloQic sequestration. The construction, operation or maintenance of any non-experimental Class V geologic sequestration well is prohibited.
5. Adding Section 144.18 to read as follows.

§144.18 Requirements for Class VI wells.

December 12,2008 1Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 Nationa[ Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800,551,7379, ext 560, creimer ilnowa,oro
Pro Dosed Rule Revision or Comment Rationale Owners or operators of Class VI wells must obtain a permit Class VI wells are not authorized by rule to inject

Subpart D-Authorization by Permit §144.36 Duration of permits. (a) Permits for Class I and V wells shall be effective Comment: Would there be a scenario where a facility would for a fixed term not to exceed 10 years, UIC Permits stop and restart? Concern is to make sure temporarily for Class II, III and V[ wells shall be issued for a stopped injection activity does not allow party to wait a period period up to the operating life of the facility, of time and then walk away or alternatively cause closure if only a temporary stop,

7, Section 144.39 is amended by revising the second sentence in paragraph (a) introductory text and by revising the second sentence in paragraph (a)(3) introductory text to read as follows:

§144.39 Modification or revocation and reissuance of oermits. (a) For Class I hazardous waste injection wells, Class II, Class III or Class VI wells the following may be causes for revocation and reissuance as well as modification: and for all other wells the following may be cause for revocation or reissuance as well as modification when the permittee requests or agrees.

(3) Permits other than for Class I hazardous waste injection wells, Class II, Class [II or Class VI wells may be modified during their terms for this cause only as follows:

December 12, 2008 

### 2Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer ilnqwa.orq
ProDosed Rule Revision or Comment Rationale Subpart E-Permit Conditions Section 144.51 is amended by revising the first sentence in paragraph (q)(1) and the first sentence in paragraph (q)(2) to read as:

§144.51 Conditions applicable to all permits.

(q) (1) The owner or operator ofa Class I, II, III orVI well permitted under this part shall establish mechanical integrity prior to commencing injection or
on a schedule determined by the Director. Thereafter the owner or operator of Class I, II, and III wells must maintain mechanical integrity as defined in §146.8 and the owner or operator of Class VI wells must maintain mechanical integrity as defined in §146.89 of this chapter.

(2) When the Director determines that a Class I, II, III

or VI well lacks mechanical integrity pursuant to §146.8 or §146.89 for Class VI of this chapter, he/she shall give written notice of his/her determination to the owner or operator.
9. Section 144.52 is amended by revising paragraph (a)(8) to read as follows:

§144.52 Establishing permit conditions. (a)(8) Mechanical integrity. A permit for any Class I, II, III or VI well or injection project which lacks mechanical integrity shall include, and for any Class V well may include, a condition prohibiting injection operations until the permittee shows to the satisfaction of the Director under §146.08 or§146.89 for Class VI that the well has mechanical integrity.

10. Section 144.55 is amended by revising the first sentence in paragraph (a) to read as follows:

December 12, 2008 3Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800,551,7379, ext 560, creimer 'ilnawaora ProDosed Rule Revision or Comment Rationale §144.55 Corrective Action. (a) Coverage, Applicants for Class I, II, (other than Proposed Revision: (a) Coverage, Applicants for Class I, II, Concem about the use of the term known existing), III or VI injection well permits shall identify (other than existing), III or VI injection well permits shall wells, Public records search may not be the location of all known wells within the injection identify the location of all known wells within the injection adequate for older oil and gas wells, for well's area of review which penetrate the injection well's area of review which penetrate the injection zone, or in example, Some language should be added
zone, or in the case of Class II wells operating over the case of Class II wells operating over the fracture pressure so that A more proactive approach is used, the fracture pressure of the injection formation. all of the injection formation, all known wells within the area of e.g. physically walk site or do aerial review, known wells within the area of review penetrating review penetrating formations affected by the increase in formations affected by the increase in pressure, pressure, Applicants for Class VI shall perform mapping with Applicants for Class VI shall perform corrective sufficient resolution as to make a comprehensive effort to action as specified in §146,84, identify wells that are not in the public record using aerial photography, aerial survey, or other methods acceptable to the director corrective action as specified in §146,84 if needed

Subpart G-Requirements for Owners and Ooerators of Class V Iniection Wells 11. Section 144,80 is amended by revising the first sentence in paragraph (e) and by adding paragraph (1) to read as follows:

§144.80 What is a Class V injection well? (e) Class V, Injection wells not included in Class I, II, 1I1,IVorVL (1) Class VI, Wells used for geologic sequestration of carbon dioxide,

PART 146-UNDERGROUND INJECTION CONTROL PROGRAM: CRITERIA AND STANDARDS

§146,5 Classification of injection wells. (e) Class V, Injection wells not included in Class I, II, 1I1.IVorVL

December 12, 2008 4Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer 'Vnawa.ora
Pro Dosed Rule Revision or Comment Rationale (I) Class VI. Wells used for geologic sequestration of carbon dioxide beneath the lowermost formation containing an underground source of drinking water (USDW).

Subpart H-Criteria and Standards Applicable to Class VI Wells

§146.81 Applicability. (a) This subpart establishes criteria and standards for underground injection control programs to regulate Class VI carbon dioxide geologic sequestration injection wells.

(b) This SUbpart applies to wells used to inject Comment: NGWA supports the use of Class VI as carbon dioxide specifically for the purpose of "specifically for geologic carbon sequestration and believes geologic sequestration, i.e., the iong-term that EOR and GS shouid be sequential and not concurrent" containment of a gaseous, liquid or supercritical carbon dioxide stream in subsurface geologic formations.

(c) This subpart applies to owners and operators of permit or ruie-authorized Class I industrial, Class II.

or Ciass V experimental carbon dioxide injection projects who seek to apply for a Class VI geoiogic sequestration permit for their well or wells. If the Director determines that USDWs will not be endangered, such wells are exempt, at the Director's discretion, from the casing and cementing requirements at §§146.86(b) and 146.87(a)(1) through (3).

(d) Definitions. The following definitions apply to this subpart. To the extent that these definitions confiict with those in §146.3 these definitions govern:

December 12, 2008 

### 5Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact Christine Reimer, NGWA, 800.551.7379, ext. 560.**creimer~** i2nawa.ora ProDosed Rule Revision or Comment Rationale Area of review means the region surrounding the Proposed Revision: Area of review means the region The AOR needs to be based on both the geologic sequestration project that may be impacted surrounding the geologic sequestration project that may be C02 plume and the associated pressure by the injection activity. The area of review is based impacted by the injection activity. The area of review is based front in order to completely identify the areas

on computational modeling that accounts for the on computational modeling that accounts for the physical and that may be affected by the injection physical and chemical properties of all phases of the chemical properties of all phases of the injected carbon injected carbon dioxide stream. dioxide stream and the zone of increased pressure created by the injection.

Carbon dioxide plume means the underground extent, in three dimensions, of an injected carbon dioxide stream.

Carbon dioxide stream means carbon dioxide that has been captured from an emission source (e.g., a power plant), plus incidental associated substances derived from the source materials and the capture process, and any substances added to the stream to enable or improve the injection process. This subpart does not apply to any carbon dioxide stream that meets the definition of a hazardous waste under 40 CFR part 261.

Confining zone means a geologic formation, group of formations, or part of a formation stratigraphically overlying the injection zone that acts as a barrier to fluid movement.

Corrective action means the use of Director approved methods to assure that wells within the

area of review do not serve as conduits for the movement of fluids into underground sources of drinking water (USDW).

December 12, 2008 6Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer 'i2nowa.ora ProDosed Rule Revision or Comment Rationale Geologic sequestration means the long-term containment of a gaseous, liquid or supercritical carbon dioxide stream in subsurface geologic formations. This term does not apply to its capture or transport.

Geologic sequestration project means an injection Proposed Revision: Geologic sequestration project means an See Section 144.6(1). If an exemption is well or wells used to emplace a carbon dioxide injection well or wells used to emplace a carbon dioxide provided, USDWs below the C02 plume or stream beneath the lowermost formation containing stream. It includes the subsurface three-dimensional extent of pressure front should be included in the AOR

a USDW. It includes the subsurface three- the carbon dioxide plume, associated pressure front, and specifically. dimensional extent of the carbon dioxide plume, displaced brine, as well as all USDWs and the surface area associated pressure front, and displaced brine, as above that delineated region. well as the surface area above that delineated region.

Injection zone means a geologic formation, group of formations, or part of a formation that is of sufficient areal extent, thickness, porosity, and permeability to receive carbon dioxide through a well or wells associated with a geologic sequestration project.

Post-injection site care means appropriate monitoring and other actions (inclUding corrective action) needed following cessation of injection to

assure that USDWs are not endangered as required under §146.93.

Pressure front means the zone of elevated pressure that is created by the injection of carbon dioxide into the subsurface. For the purposes of this subpart, the pressure front of a carbon dioxide plume refers to a
zone where there is a pressure differential sufficient to cause the movement of injected fiuids or formation fiuids into a USDW.

December 12, 2008 7Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer j)nqwa.ora
ProDosed Rule Revision or Comment Rationale Site closure the pointftime, as determined by the Director following the requirements under §146.93, at which the owner or operator of a GS site is released from post-injection site care responsibilities.

Transmissive fault or fracture means a fault or fracture that has sufficient permeability and vertical extent to allow fluids to move between formations.

§146.82 Required Class VI permit information. This section sets forth the information which the Comment: NGWA raises the question of whether a

owner or operator must submit to the Director in requirement should be included that all applications for Class order to be permitted as a Class VI well. The VI construction permits include a certification that the facility application for a permit for construction and was designed by an appropriately qualified professional operation of a Class VI well must include the engineer with an option for an appropriate qualified following: professional geologist to certify the well design (taking into consideration confinement, injectivity, etc).

Proposed addition: (1) Class VI

- Test/Injection Well Construction and Testing Permit Proposed addition: (a) The Director shall deny a construction permit if construction of the well itself may endanger the health of persons or the environment Proposed addition: (b) For construction permit approval, reasonable assurance is required that the project will function in compliance with this chapter. The Director shall require an exploratory well for those projects located in an area where available information is lacking conceming geologic or hydraulic confinement or existing information indicates that geologic or hydraulic confinement may be poor or lacking.

Proposed addition: (c) For a Class VI well, issuance of a construction permit does not obligate the Director to authorize any operation of the well, unless reasonable assurance has been provided that the well can operate in compliance with this chapter.

December 12, 2008 8Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer 'ilnawa.ora
ProDosed Rule Revision or Comment Rationale Proposed addition: (d) Information required in 40 CFR 144.31 (e)(1) through (6) Proposed addition: (e) A map showing the injection well(s) for which a permit is sought and the applicable area of review. Within the area of review, the map must show the number, or

name and location of all injection wells, producing wells, abandoned wells, plugged wells or dry holes, deep stratigraphic boreholes, State or EPA approved subsurface cleanup sites, surface bodies of water, springs, mines (surface and subsurface), quarries, water wells and other pertinent surface features including structures intended for human occupancy and roads. The map should also show faults, if known or suspected. Only information of public record is required to be included on this map;

Proposed addition: (f) The area of review based on modeling, using data obtained during logging and testing of the well and the formation as required by paragraphs (I), (r), and (s) of this section; Proposed addition: (g) Information on the geologic structure and hydrogeologic properties of the proposed storage site and overlying formations, including Proposed addition: (1) Maps and cross sections of the area of review; Proposed addition: (2) Location, orientation, and properties of known or suspected faults and fractures that may transect the confining zone(s) in the area of review and a determination that they would not interfere with containment:

Proposed addition: (3) Information on seismic history including the presence and depth of seismic sources and a determination that the seismicity would not interfere with containment:

December 12, 2008 9Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer J>-nqwa.orq Prooosed Rule Revision or Comment Rationale Proposed addition: (4) Data on the depth, areal extent: thickness, mineralogy, porosity, permeability and capillary pressure of the injection and confining zone(s); including geology/facies changes based on field data which may inciude geologic cores, outcrop data, seismic surveys, well logs, and names and lithologic descriptions;

Proposed addition: (5) Geomechanical information on fractures, stress, ductility, rock strength, and in situ fiuid pressures within the confining zone; and Proposed addition: (6) Geologic and topographic maps and

cross sections illustrating regional geology, hydrogeology, and the geologic structure of the local area

Proposed addition: (h) All wells within the AOR and whose A substantive risk analysis can be total depth is greater than the depth to the bottom of the performed only if all the (known) wells within lowermost USDW should be compiled. However, preventive the AOR and between the injection formation corrective action should be undertaken only for those wells and the bottom of the USDW are described. that penetrate the injection and confining zone(s)

Proposed addition: (i) Maps and stratigraphic cross sections indicating the general vertical and laterai limits of all USDWs, water wells and springs within the area of review, their positions relative to the injection zone(s) and the direction of water movement, where known; Proposed addition: Q) Baseline geochemical data on subsurface formations, including all USDWs in the area of review; Proposed addition: (k) Proposed operating data: Proposed addition: (1) Average and maximum daily rate and voiume of the carbon dioxide stream; Proposed addition: (2) Average and maximum injection pressure; Proposed addition: (3) The source ofthe carbon dioxide stream; and Proposed addition: (4) An analysis of the chemicai and physical characteristics of the carbon dioxide stream;

December 12,2008 10Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Weiis, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer 'llnqwa.orq Proposed Rule Revision or Comment Rationale Proposed addition: (I) The compatibility ofthe carbon dioxide stream with fluids in the injection zone and minerals in both the injection and the confining zone(s), based on the results of the formation testing program, and with the materials used to construct the well; Proposed addition: (m) Proposed formation testing program to obtain an analysis of the chemical and physical characteristics of the injection zone and confining zone;

Proposed addition: (n) Proposed stimulation program and a determination that stimulation will not interfere with containment;
Proposed addition: (0) Proposed formation testing program to obtain an analysis of the chemical, physical and radiological characteristics of and other information on the injection zone.

Proposed addition: (p) Proposed procedure to outline steps necessary to conduct injection operation; Proposed addition: (q) Engineering drawings of the surface and subsurface construction details olthe system, including design features for surge control and water hammer protection: Proposed addition: (r) Injection well construction procedures that meet the requirements of Section 146.86;

Proposed addition: (s) Proposed area of review and corrective action plan that meets the requirements under Section 146.84; Proposed addition: (t) The status of corrective action on wells in the area of review; Proposed addition: (u) A demonstration, satisfactory to the Director, that the applicant has met the financial responsibility requirements under Section 146.85; Proposed addition: (v) Proposed testing and monitoring plan required by Section 146.90 Proposed addition: (w) Proposed injection well plugging plan required by Section 146.92(b)

December 12, 2008 11Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer ilnowa.ora
ProDosed Rule Revision or Comment Rationale Proposed addition; (x) Proposed post-injection site care and site closure plan required by Section 146.93(a) Proposed addition: (y) Proposed emergency and remedial response plan required by Section 146.94; and

Proposed addition; (z) Any other information requested by the Director.

Proposed addition; (2) Required Class VI operation permit information (a) Information required in 40 CFR 144.31 (e)(1) Renumber 2(a) through (6);

(b) A map showing the injection well(s) for which a Renumber 2(b) permit is sought and the applicable area of review. Within the area of review, the map must show the number, or name and location of all injection wells, producing wells, abandoned wells, plugged wells or dry holes, deep stratigraphic boreholes, State or EPA approved subsurface cleanup sites, surface bodies of water, springs, mines (surface and subsurface), quarries, water wells and other pertinent surface features including structures intended for human occupancy and roads. The map should also show faults, if known or suspected. Only information of public record is required to be included on this map;

December 12, 2008 12Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer 'ilnowa.ora ProDosed Rule Revision or Comment Rationale (c) The area of review based on modeling, using Proposed Revision: 2(c) Re-evaluation of Area of Review. data obtained during logging and testing of the well After completion of the operational testing period, the Area of and the formation as required by paragraphs (I), (r), Review shall be re-evaluated, using a calibrated, multi-phase and (s) of this section; fluid flow model. The data collection during operational testing must be adequate for calibration of the model. If a calibrated model cannot be prepared using data collected during operational testing, the owner or operator shall apply for a new period of operational testing of up to two years in order to collect the required data.

(d) Information on the geologic structure and Renumber 2(d) hydrogeologic properties of the proposed storage site and overlying formations, including:

(1) Maps and cross sections of the area of review;

(2) Location, orientation, and properties of known or suspected faults and fractures that may transect the confining zone(s) in the area of review and a determination that they would not interfere with containment; (3) Information on seismic history including the presence and depth of seismic sources and a determination that the seismicity would not interfere with containment; (4) Data on the depth, areal extent, thickness, mineralogy, porosity, permeability and capillary
pressure of the injection and confining zone(s); including geology/facies changes based on field data which may include geOlogic cores, outcrop data, seismic surveys, well logs, and names and lithologic descriptions; (5) Geomechanical information on fractures, stress, ductility, rock strength, and in situ fluid pressures within the confining zone; and

December 12, 2008 13Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer6 'Unowa.ora ProDosed Rule Revision or Comment Rationale (6) Geologic and topographic maps and cross sections illustrating regional geology, hydrogeology, and the geologic structure of the local area.

(e) A tabulation of all wells within the area of review Renumber 2(e) which penetrate the injection or confining zone(s). Such data must include a description of each well's type, construction, date drilled, location, depth, record of plugging andlor completion, and any additional information the Director may require;

(f) Maps and stratigraphic cross sections indicating Renumber 2(f) the general vertical and lateral limits of all USDWs, water wells and springs within the area of review, their positions relative to the injection zone(s) and the direction of water movement, where known;

(g) Baseline geochemical data on subsurface Renumber 2(g) formations, including all USDWs in the area of review;

(h) Proposed operating data: Renumber 2(h) (1) Average and maximum daily rate and volume of the carbon dioxide stream; (2) Average and maximum injection pressure; (3) The source of the carbon dioxide stream; and

(4) An analysis of the chemical and physical characteristics of the carbon dioxide stream; Proposed addition: (5) Contingency plans to cope with all shut ins or well failures, including emergency discharge provisions;

December 12, 2008 14Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer ilnawa.ora ProDosed Rule Revision or Comment Rationale (0 The compatibility of the carbon dioxide stream Renumber 2(0 with fluids in the injection zone and minerals in both the injection and the confining zone(s), based on the results of the fonmation testing program, and with the materials used to construct the well;

0) Proposed fonmation testing program to obtain an Proposed revision: 20) Results of the formation testing analysis of the chemical and physical characteristics program to obtain an analysis of the chemicai, physical and of the injection zone and confining zone; radioiogical characteristics of and other information on the injection zone.

(k) Proposed stimulation program and a Renumber 2(k) detenmination that stimulation will not interfere with containment;

(I) The resuits of the formation testing program as Renumber 2(i) required in paragraph 0) of this section;

(m) Proposed procedure to outline steps necessary Renumber 2(m) to conduct injection operation;

(n) Schematic or other appropriate drawings of the Proposed revision: 2 (n) Engineering drawings olthe surface surface and subsurface construction details of the and subsurface construction details of the system, including well; design features for surge controi and water hammer protection, including the following: Proposed addition: (1) Record drawings, based upon inspections by the engineer of record or persons under his direct supervision, with all deviations noted; Proposed addition: (2) Copies of the mill certificates of all casings used in the construction of the well; Proposed addition: (3) Certification of completion submitted by the engineer of record; Proposed addition: (4) An operation manual including emergency procedures; Proposed addition: (5) Proposed monitoring program and data to be SUbmitted;

December 12, 2008 15Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800,551,7379, ext. 560, creimer ilnqwa,orq Proposed Rule Revision or Comment Rationale Proposed addition: (6) Proof that the existence of the well and any associated monitoring wells have been recorded with the permanent warranty deed or other instrument of conveyance

as a two page proviso or addendum that contains certification of the locations of the wells (by metes and bounds) and a detailed sketch of the parcel that shows the location of the well. The location shall be measured by a certified land surveyor, and shall contain the surveyor's signature, registration number, official seal, and the following statement: "1 hereby certify that this survey was made under my responsible direction and supervision, and is a correct representation of the land surveyed,"

(0) Injection well construction procedures that meet Renumber 2(0) the requirements of §146,86;

(p) Proposed area of review and corrective action Renumber 2(p) plan that meets the requirements under §146,84;

(q) The status of corrective action on wells in the Renumber 2(q)

area of review;

(r) All available logging and testing program data on Renumber 2(r ) the well required by §146,87;

(s) A demonstration of mechanical integrity pursuant Renumber 2(s) to §146,89;

(t) A demonstration, satisfactory to the Director, that Renumber 2(t) the applicant has met the financial responsibility requirements under §146,85;

(u) Proposed testing and monitoring plan required by Renumber 2(u) §146,90:

December 12, 2008 16Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560.**creimer~** j)nqwa.ora
ProDosed Rule Revision or Comment Rationale (v) Proposed injection well plugging plan required by Renumber 2(v) §146.92(b);

(w) Proposed post-injection site care and site closure Renumber 2(w) plan required by §146.93(a);

(x) Proposed emergency and remedial response plan Renumber 2(x) required by §146.94; and

(y) Any other information requested by the Director. Renumber 2(y)

Proposed addition: (3) Operational Testing Proposed addition: (a) For Class VI wells, the construction permit includes a period of temporary injection operation for the purposes of long term testing. Prior to commencement of operational testing: Proposed addition: 1. Construction of the injection well shall be complete and the permittee shall submit a notice of completion of construction to the Director. Proposed addition: 2. Each well shall first be tested for integrity of construction, and shall be followed by a short term injection test of such duration to allow for the prediction of the operating pressure. Proposed addition: 3. The permittee shall submit the following information to the Director, as described in the permit.

Proposed addition: a. A copy of the borehole television survey(s) Proposed addition: b. Geophysical logs, Proposed addition: c. Mechanical integrity test data, Proposed addition: d. Data obtained during the short term injection testing conducted according to subparagraph 2. above. Proposed addition: e. Confining zone data, Proposed addition: f. Background water quality data for the injection and monitor zones; Proposed addition: g. Waste stream analysis,

December 12, 2008 17Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimerG ilnawa.ora ProDosed Rule Revision or Comment Rationale Proposed addition: h. As-built well construction specifications, and Proposed addition: i. Other data obtained during well construction which demonstrates that the well will operate in compliance with this chapter. Proposed addition: 4. Any corrective action required under Section 146.84, shall be completed. Proposed addition: 5. Prior to granting approvai for operationai testing of a Class VI well, the Director shall consider the fOllowing information: Proposed addition: a. All available logging and testing program data on the well: Proposed addition: b. A demonstration of mechanical integrity

Proposed addition: c. The anticipated maximum pressure and fiow rate at which the permittee wiil operate:

Proposed addition: d. The results of the formation testing program; Proposed addition: e. The actuai injection procedure; Proposed addition: f. The compatibility of injected waste with fiuids in the injection zone and minerals in both the injection

zone and the confining zone; Proposed addition: g. The status of corrective action on defective wells in the area of review; and Proposed addition: (b) Written authorization for operational testing shall be obtained from the Director. Authorization shall be for up to two years or the expiration date of the construction permit, whichever is less, and is only renewable

once as described in Section 146.91. The authorization shall specify the conditions under which operational testing is approved. The authorization shall include:

Proposed addition: 1. Injection pressure limitation, Proposed addition: 2. Injection fiow rate limitation, Proposed addition: 3. injection well monitoring requirements,

Proposed addition: 4. Effluent monitoring requirements,

December 12, 2008 18Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer ilnowa.ora Proposed Rule Revision or Comment Rationale Proposed addition: 5. Weekly ground water sampling of monitor wells, Proposed addition: 6. Monthly specific injectivity testing, Proposed addition: 7. Reporting requirements, and Proposed addition: 8. An expiration date for the operational testing period not to exceed two years. Proposed addition: (c) Before authorizing operational testing, the Director shall conduct an inspection of the facility to determine if the conditions of the permit have been met.

Proposed addition: (d) A sampling frequency and reporting of less than once per month shall not be allowed.

Proposed addition: (e) For Class VI wells, the duration of the operational testing period shall not exceed two years or the expiration date of the construction permit, whichever is less. If the Director has not issued an intent to issue an operation permit for the einjectionwell9s) by the end of the operational testing period, the permittee shall cease injection.

Proposed addition: (I) For a Class VI well, if an operation permit has not been obtained for the well within two years after the cessation of operational testing, the permittee shall submit an application to the Director to plug and abandon the well in accordance with Section 146.92.

Proposed addition: (4) The Director shall conduct periodic inspections during construction

§146.83 Minimum criteria for siting.

(a) Owners or operators of Class VI wells must demonstrate to the satisfaction of the Director that the wells will be sited in areas with a suitable geologic system. The geologic system must be comprised of:

December 12, 2008 19Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimerl< ilnowa.ora Pro Dosed Rule Revision or Comment Rationale (1) An injection zone of sufficient areal extent, thickness, porosity, and permeability to receive the total anticipated volume of the carbon dioxide stream; (2) A confining zone(s) that is free of transmissive faults or fractures and of sufficient areal extent and integrity to contain the injected carbon dioxide stream and dispiaced formation fluids and allow injection at proposed maximum pressures and volumes without initiating or propagating fractures in the confining zone(s); and

(b) At the Director's discretion, owners or operators Proposed revision: (b) Owners or operators of Class VI wells While NGWA believes that a site with a of Ciass VI wells must identify and characterize must identify and characterize additional zones, if they exist, singie confining can provide storage integrity additional zones that will impede vertical fluid that will impede vertical fluid movement, allow for pressure we feel that if there are additional confining movement, are free of faults and fractures that may dissipation, and provide additionai opportunities for iayers at the site they should be interfere with containment, allow for pressure monitoring, mitigation and remediation. Vertical faults and characterized to get a better estimate of dissipation, and provide addilionai opportunities for fractures that transect these zones must be identified. leakage risk to USDWs and possibly identify monitoring, mitigation and remediation. additional monitoring zones.

§146.84 Area of review and corrective action. (a) The area of review is the region surrounding the geologic sequestration project that may be impacted by the injection activity. The area of review is based

on computational modeling that accounts for the physicai and chemical properties of all phases of the injected carbon dioxide stream.

December 12, 2008 20Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, WesteNiIIe, OH 43081 Contact Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer 'i)nqwa.orq
ProDosed Rule Revision or Comment Rationale (b) The owner or operator of a Class VI well must prepare, maintain, and comply with a plan to delineate the area of review for a proposed geologic sequestration project, periodically reevaluate the delineation, and perform corrective action that meets the requirements of this section and is acceptable to the Director. As a part of the permit application for approval by the Director, the owner or operator must submit an area of review and corrective action plan that includes the following information:

(1) The method for delineating the area of review that meets the requirements of paragraph (c) of this section, including the model to be used, assumptions that will be made, and the site characterization data

on which the model will be based;

(2) A description of: (i) The minimum fixed frequency, not to exceed 10 Proposed revision: (i) The owner or operator will reevaluate NGWA believes that a frequency of every 10 years, the owner or operator proposes to reevaluate the AOR after two yearsof operational testing (prior to years is too long to identify early the area of review; issuance of the operating permit), and after 5 years and then discrepancies between the site performance

no less frequently than every 5 years for the life of the project; and the site model. Seeing early difference will allow for earlier model updating and provide additional reduction in leakage risk.

(Ii) The monitoring and operational conditions that would warrant a reevaluation of the area of review prior to the next scheduled reevaluation as determined by the minimum fixed frequency established in paragraph (b)(2)(Q of this section.

(iii) How monitoring and operational data (e.g., injection rate and pressure) will be used to inform an
area of review reevaluation; and

December 12, 2008 21Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492
National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer 2lnawa.ora ProDosed Rule Revision or Comment Rationale (iv) How corrective action will be conducted to meet the requirements of paragraph (d) of this section, including what corrective action wiil be performed prior to injection and what, if any, portions of the area of review will have corrective action addressed on a phased basis and how the phasing will be determined: how corrective action will be adjusted if there are changes in the area of review; and how site

access will be guaranteed for future corrective action.

(c) Owners or operators of Class VI wells must Comment: There should be somewhere in the rules a perform the following actions to delineate the area of requirement that "mutual interference effects" should trigger review, identify all wells that require corrective action, reevaluation and re-delineation of the AORs of ail projects that and perform corrective action on those wells: are interferring with each other. In essence, when a new project is submitted for permitting, there should be a systemwide, "regional" entity charged with ensuring that AORs for each project are appropriate, and perhaps that a "hybrid" or "combo AOR" be defined for the set of mutually-interferring projects.

(1) Predict, using computational modeling, the projected lateral and vertical migration of the carbon dioxide plume and formation fluids in the subsurface from the commencement of injection activities until the plume movement ceases, pressure differentials sufficient to cause the movement of injected fluids or formation fluids into a USDW are no longer present,

or after a fixed time period as determined by the Director. The model must:

(i) Be based on detailed geologic data coilected to Proposed revision: (i) Be based on detailed geologic data NGWA proposes that if there are secondary characterize the injection zone, confining zone and collected to characterize the injection zone, confining zone(s), conflning units that they should be included any additional zones; and anticipated operating data, transmissive monitoring zones and any additional zones; and in the site model along with any transmissive including injection pressures, rates and total volumes anticipated operating data, including injection pressures, rates zones between the primary and secondary

over the proposed life of the geological sequestration and total volumes over the proposed life of the geological confining units. project; sequestration project;

December 12, 2008 22Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800,551,7379, ext 560, creimer 1'il.nawa,or n Proposed Rule Revision or Comment Rationale (iO Take into account any geologic heterogeneities, data quality, and their possible impact on model predictions: and (iii) Consider potential migration through faults, fractures, and artificial penetrations, (2) Using methods approved by the Director, identify Proposed revision: (2) Using methods approved by the This makes this consistent with NGWA's all penetrations, including active and abandoned Director, identify all penetrations, inclUding active and proposed section 146(a)(8) wells and underground mines, in the area of review abandoned wells and underground mines, in the area whose that may penetrate the confining zone, Provide a total depth is greater than the depth to the bottom of the description of each well's type, construction, date lowermost USDW, including those penetrating the confining drilled, location, depth, record of plugging andlor zone, Provide a description of each well's type, construction, completion, and any additional information the date drilled, location, depth, record of plugging andlor Director may require; and completion, and any additional information the Director may require; and
(3) Determine which abandoned wells in the area of review have been plugged (as required by §146,92) in a manner that prevents the movement of carbon dioxide or associated fiuids that may endanger USDWs,

(d) Owners or operators of Ciass VI wells must , perform corrective action on all wells in the area of review that are determined to need corrective action using methods necessary to prevent the movement of fiuid into or between USDWs including use of corrosion resistant materials, where appropriate,

(e) If monitoring data indicate an endangerment to USDWs, the owner or operator must notify the Director and cease operations as required by §146,94,

December 12, 2008 23Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimeru llnqwa.orq Proposed Rule Revision or Comment Rationale (I) At the minimum fixed frequency, not to exceed 10 Proposed revision: (I) At the minimum fixed frequency, not to This makes this consistent with NGWA's
years, as specified in the area of review and exceed two years if under operational testing (prior to proposed revision to Section 146.84(b)(2)(i) corrective action plan, or when monitoring and issuance of the operating permit), or 5 years (if operating operational conditions warrant, owners or operators permit has been issued), as specified in the area of review
must: and corrective action plan or when monitoring and operational conditions warrant, owners or operators must:

(1) Reevaluate the area of review in the same
manner specified in paragraph (c)(1) of this section:

(2) Identify all wells in the reevaluated area of review that require corrective action in the same manner specified in paragraph (c)(2) of this section;

(3) Perform corrective action on wells requiring corrective action in the reevaluated area of review in the same manner specified in paragraph (c)(3) of this section; and

(4) Submit an amended area of review and corrective action plan or demonstrate to the Director through monitoring data and modeling results that no amendment to the area of review and corrective action plan is needed.

(g) The emergency and remedial response plan (as required by §146.94) and a demonstration of financial responsibility (as described by §146.85)
must account for the entire area of review, regardless of whether or not corrective action in the

area of review is phased.

§146.85 Financial responsibility.

December 12,2008 24Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Weiis, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerviiie, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer 'llnawa.ora Proposed Rule Revision or Comment Rationale (a) The owner or operator must demonstrate and Comment: A question was raised during discussions about maintain financial responsibility and resources for how the producer of the C02 is impacted and whether they corrective action (that meets the requirements of should maintain some liability. §146.84), injection well plugging (that meets the requirements of §146.92), post-injection site care and site closure (that meets the requirements of §146.93), and emergency and remedial response (that meets the requirements of §146.94) in a
manner prescribed by the Director until:

(1) The Director receives and approves the completed post-injection site care and site closure plan; and (2) The Director determines that the site has reached the end of the post injection site care period.

(b) The owner or operator must provide to the Proposed revision: (b) The owner or operator must provide to NGWA proposes that potential changes in Director, at a frequency determined by the Director, the Director, at the same frequency as the AOR reevaluation, the size of the AOR require that all site plans written updates of adjustments to the cost estimate written updates of adjustments to the cost estimate to account be reevaluated at the same frequency as the to account for any amendments to the area of review for any amendments to the area of review and corrective AOR. and corrective action plan (§146.84), the injection action plan (§146.84), the injection well plugging plan well plugging plan (§146.92), and the post-injection (§146.92), and the post-injection site care and site closure site care and site closure plan (§146.93). plan (§146.93).

(c) The owner or operator must notify the Director of adverse financial conditions such as bankruptcy, that may affect the ability to carry out injection well piugging and post-injection site care and site closure.

December 12, 2008 25Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer j)nqwa.orq Proposed Rule Revision or Comment Rationale (d) The operator must provide an adjustment of the cost estimate to the Director if the Director has

reason to believe that the original demonstration is

no longer adequate to cover the cost of injection well plugging (as required by §146.92) and post-injection site care and site closure (as required by §146.93).

§146.86 Injection well construction requirements.

(a) General. The owner or operator must ensure that all Class VI wells are constructed and completed to:

(1) Prevent the movement of fluids into or between USDWs or into any unauthorized zones:

(2) Permit the use of appropriate testing devices and work over tools; and (3) Permit continuous monitoring of the annulus Comment: NGWA supports this provision space between the injection tubing and long string casing.

(b) Casing and Cementing of Class VI Wells.

December 12, 2008 26Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer ilnawa.ora ProDosed Rule Revision or Comment Rationale (1) Casing and cement or other materials used in the Comment NGWA supports this provision construction of each Class VI well must have sufficient structural strength and be designed for the life of the geologic sequestration project. All well materials must be compatible with fluids with which the materiais may be expected to come into contact and meet or exceed standards developed for such materials by the American Petroleum Institute, ASTM International, or comparable standards acceptable to the Director. The casing and cementing program must be designed to prevent the movement of fluids into or between USDWs. In order to allow the Director to determine and specify casing and cementing requirements, the owner or operator must provide the following information:

(i) Depth to the injection zone; (ii) Injection pressure, external pressure, internal pressure and axial loading; (iii) Hole size; (iv) Size and grade of all casing strings (wall thickness, external diameter, nominal weight, length, joint specification and construction material);

(v) Corrosiveness of the carbon dioxide stream, and formation fluids; (vi) Down-hole temperatures; (vii) Lithology of injection and confining zones; (viii) Type or grade of cement; and (ix) Quantity, chemical composition, and temperature of the carbon dioxide stream. (2) Surface casing must extend through the base of the lowermost USDW and be cemented to the surface.

December 12,2008 27Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer ilnawa.ora ProDosed Rule Revision or Comment Rationale (3) At least one long siring casing, using a sufficient Comment: NGWA supports this provision number of centralizers, must extend to the injection

zone and must be cemented by circulating cement to the surface in one or more stages.

(4) Circulation of cement may be accomplished by staging. The Director may approve an alternative method of cementing in cases where the cement cannot be recirculated to the surface, provided the

owner or operator can demonstrate by using logs that the cement does not allow fluid movement behind the well bore.

(5) Cement and cement additives must be Comment: NGWA supports this provision and especially that compatible with the carbon dioxide stream and the assessment should include the radial integrity of the formation fluids and of sufficient quality and quantity cement. to maintain integrity over the design life the geologic sequestration project. The integrity and location of the cement shall be verifled using technology capable of evaiuating cement quality radially and identifying the location of channels to ensure that USDWs are not endangered.

(c) Tubing and packer. (1) All owner and operators of Class VI wells must inject fluids through tUbing with a packer set at a depth opposite a cemented interval at the location approved by the Director. (2) In order for the Director to determine and specify requirements for tubing and packer, the owner or operator must submit the following information:

(i) Depth of selling: 0i) Characteristics of the carbon dioxide stream (chemical content, corrosiveness, temperature, and density); (iii) Injection pressure;

December 12, 2008 28Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer6 llnawa.ora ProDosed Rule Revision or Comment Rationale (iv) Annular pressure; (v) Injection rate (intermittent or continuous) and volume of the carbon dioxide stream; (vi) Size of casing; and (vii) Tubing tensile, burst, and collapse strengths.

§146.87 Logging, sampling, and testing prior to iniection well oDeration. (a) During the drilling and construction of a Class VI injection well, 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 fonnation fluids in, all relevant geologic formations to assure confonnance with the injection well construction requirements under§146.86, and to establish accurate baseline data against which future measurements may be compared. The owner or operator must submit to the Director a descriptive report prepared by a knowledgeable log analyst that includes an interpretation of the results of such logs and tests. At a minimum, such logs and tests must include;

(1) Deviation checks during drilling on all holes constructed by drilling a pilot hole which are enlarged by reaming or another method. Such checks must be at sufficiently frequent intervals to determine the location of the borehole and to assure that vertical

avenues for fluid movement in the form of diverging holes are not created during drilling; and

(2) Before and upon installation of the surface casing: (i) Resistivity, spontaneous potential, and caliper logs before the casing is installed; and

December 12, 2008 29Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551,7379. ext. 560. creimer 'Vnawa.ora ProDosed Rule Revision or Comment Rationale (iO A cement bond and variable density log, and a temperature log after the casing is set and cemented. (3) Before and upon installation of the long string casing: (i) Resistivity, spontaneous potential, porosity, caliper, gamma ray, fracture finder logs, and any other iogs the Director requires for the given geology before the casing is installed: and

(iI) A cement bond and variable density log, and a Proposed revision: (ii) A cement bond, variable density log, NGWA supports inclusion of a radial cement temperature log after the casing is set and and radial cement evaluation log and a temperature log after evaluation log in addition. The addition of cemented. the casing is set and cemented. this test will help identify any potential channels in the cement out from casing

(4) A series of tests designed to demonstrate the Comment: NGWA supports the inclusion of this series of internal and external mechanical integrity of injection tests. wells, which may include: (i) A pressure test with liquid or gas; (ii) A tracer survey such as oxygen-activation logging; (iii) A temperature or noise log; (iv) A casing inspection log, if required by the Director; and (5) Any alternative methods that provide equivalent

or better information and that are required of and/or approved of by the Director.

December 12, 2008 30Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer ilnowa.oro Prooosed Rule Revision or Comment Rationale (b) The owner or operator must take and submit to the Director whole cores or sidewall cores of the injection zone and confining system and formation fiuid samples from the injection zone(s). The Director may accept cores from nearby wells if the owner or operator can demonstrate that core retrieval is not possible and that such cores are representative of conditions at the well. The Director may require the

owner or operator to core other formations in the borehole.

(c) The owner or operator must record the fluid temperature, pH, conductivity, reservoir pressure and the static fiuid level of the injection zone(s).

(d) At a minimum, the owner or operator must determine or calculate the following information concerning the injection and confining zone(s): (1) Fracture pressure; (2) Other physical and chemical characteristics of the injection and confining zones; and (3) Physical and chemical characteristics of the formation fluids in the injection zone. (e) Upon completion, but prior to operation, the

owner or operator must conduct the following tests to verify hydrogeologic characteristics of the injection

zone: (1) A pump test; or (2) Injectivity tests.

December 12, 2008 31Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551,7379, ext. 560. creimer 'ilnawa.ora ProDosed Rule Revision or Comment Rationale (I) The owner or operator must provide the Director with the opportunity to witness all logging and testing by this subpart. The owner or operator must submit a schedule of such activities to the Director 30 days prior to conducting the first test and submit any changes to the schedule 30 days prior to the next scheduled test.

§146.88 Injection well operating requirements.

(a) Except during stimulation, the owner or operator must ensure that injection pressure does not exceed 90 percent of the fracture pressure of the injection

zone so as to assure that the injection does not initiate new fractures or propagate existing fractures in the injection zone. in no case may injection pressure initiate fractures in the confining zone(s) or
cause the movement of injection or formation fiuids that endangers a USDW.

(b) Injection between the outermost casing protecting USDWs and the well bore is prohibited.

(c) The owner or operator must fill the annuius between the tubing and the long string casing with a non-corrosive fiuid approved by the Director. The

owner or operator must maintain on the annulus a pressure that exceeds the operating injection pressure, uniess the Director determines that such requirement might harm the integrity of the well.

December 12, 2008 32Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer ilnawa.ora Proposed RUle Revision or Comment Rationale (d) Other than during periods of well work over (maintenance) approved by the Director in which the seaied tubing-casing annulus is of necessity disassembled for maintenance or corrective procedures, the owner or operator must maintain mechanical integrity of the injection well at all times.

(e) The owner or operator must install and use continuous recording devices to monitor: the injection pressure; the rate, volume, and temperature of the carbon dioxide stream; and the pressure on the annulus between the tubing and the long string casing and annulus fluid volume; and must install and use alarms and automatic down-hole shut-off systems, designed to alert the operator and shut-in the well when operating parameters such as annulus pressure, injection rate or other parameters approved by the Director diverge beyond permitted ranges and/or gradients specified in the permit;

(f) If a down-hole automatic shutdown is triggered or
a loss of mechanical integrity is discovered, the

owner or operator must immediately investigate and identify as expeditiously as possible the cause of the shutoff. If, upon such investigation, the well appears to be lacking mechanical integrity, or if monitoring required under paragraph (e) of this section otherwise indicates that the well may be lacking mechanical integrity, the owner or operator must

(1) Immediately cease injection;

December 12,2008 33Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geo[ogic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer i)nqwa.orq
Pronosed Rule Revision or Comment Rationale (2) Take all steps reasonably necessary to determine whether there may have been a release ofthe injected carbon dioxide stream into any unauthorized
zone; (3) Notify the Director within 24 hours; (4) Restore and demonstrate mechanical integrity to the satisfaction of the Director prior to resuming injection; and (5) Notify the Director when injection can be expected to resume.

§146.89 Mechanical integrity. (a) A Class VI well has mechanical integrity if: (1) There is no significant leak in the casing, tubing

or packer; and (2) There is no significant fluid movement into a USDW through channels adjacent to the injection well bore.

(b) To evaluate the absence of significant leaks under paragraph (a)(1) of this section, owners or operators must, following an initial annulus pressure test, continuously monitor injection pressure, rate, injected volumes, and pressure on the annulus between tubing and long stem casing and annulus fluid volume as specified in §146.88 (e);

(c) At least once per year, the owner or operator Proposed revision: At least once per year, the owner or There was a question as to whether one of must use one of the following methods to determine operator must use one of the following methods, as approved these tests individually would suffice in all the absence of significant fluid movement under by the director, to determine the absence of significant fluid circumstances. The change proposed is to paragraph (a)(2) of this section: movement under paragraph (a)(2) of this section. allow the director to review the proposal.

(1) A tracer survey such as oxygen-activation logging; (2) A temperature or noise log; or (3) A casing inspection log, if required by the Director.

December 12, 2008 34Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer ilnawa.ora ProDosed Rule Revision or Comment Rationale

(d) The Director may require any other test to evaluate mechanical inte9rity under para9raph (a)(1)

or (a)(2) of this section. Also, the Director may allow the use of a test to demonstrate mechanical integrity other than those listed above with the written approval ofthe Administrator. To obtain approval, the Director must submit a written request to the Administrator, which must set forth the proposed test and all technical data supporting its use. The Administrator must approve the request if it will reliably demonstrate the mechanical integrity of wells for which its use is proposed. Any altemate method approved by the Administrator will be published in the Federal Register and may be used in all States in accordance with applicable State law unless its

use is restricted at the time of approval by the Administrator.

(e) In conducting and evaluating the tests enumerated in this section or others to be allowed by the Director, the owner or operator and the Director must apply methods and standards generally accepted in the industry. When the owner or operator reports the results of mechanical integrity tests to the Director, he/she shall include a description of the test(s) and the method(s) used. In making his/her evaiuation, the Director must review monitoring and other test data submitted since the previous evaluation.

December 12, 2008 35Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer ilnawa.ora
Pro Dosed Rule Revision or Comment Rationale (f) The Director may require additional or alternative tests if the results presented by the owner or operator under paragraph (d) of this section are not satisfactory to the Director to demonstrate that there is no significant leak in the casing, tubing or packer

or si9nificant movement of fluid into or between USDWs resulting from the Injection activity as stated in paragraphs (a)(1) and (2) of this section.

§146.90 Testing and monitoring requirements.

The owner or operator of a Class VI well must prepare, maintain, and comply with a testing and monitoring plan to verify that the geologic sequestration project is operating as permitted and is not endangering USDWs. The testing and monitoring plan must be submitted with the permit application, for Director approval, and must include a description of how the owner or operator will meet the requirements of this section. Testing and monitoring associated with geologic sequestration projects must, at a minimum, include:

(a) Analysis of the carbon dioxide stream with sufficient frequency to yield data representative of its chemical and physical characteristics:

(b) Installation and use, except during well walkovers

as defined in §146.86(d), of continuous recording devices to monitor injection pressure, rate and volume: the pressure on the annulus between the tubing and the long string casing; and the annulus fluid volume;

December 12, 2008 36Docket

- EPA-HQ-OW-2008-0390; Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560.**creimer~** ilnawa.ora ProDosed Rule Revision or Comment Rationale (c) Corrosion monitoring of the well materials for loss of mass, thickness, crackin9, pitting and other signs of corrosion must be performed on a quarterly basis to ensure that the well components meet the minimum standards for material strength and performance set forth in §146.86(b) by:

(1) Placing coupons of the well construction materials in contact with the carbon dioxide stream;

or (2) Routing the carbon dioxide stream through a loop constructed with the material used in the well; or

(3) Using an alternative method approved by the Director;

(d) Periodic monitoring of the ground water quality Comment The monitoring should be site specific and include and geochemical changes above the confining particular analytes at risk to the aquifer from the existing zone(s) that may be a result of carbon dioxide geologic environment.
movement through the confining zone or additional identified zones: (1) The location and number of monitoring wells must be based on specific information about the geologic sequestration project, including injection rate and volume, geology, the presence of artificial penetrations and other factors;

(2) The monitoring frequency and spatial distribution of monitoring wells must be based on baseline geochemical data that has been collected under §146.82(a)(6) and any modeling results in the area of review evaluation required by §146.84(b);

(e) A demonstration of external mechanical integrity pursuant to §146.89(c) at least once per year throughout the duration of the geologic sequestration project;

December 12, 2008 37Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer i/nQwa.ora ProDosed Rule Revision or Comment Rationale

(f) A pressure fall-off test at least once every five Comment: What additional information does this test provide years unless more frequent testing is required by the that is not available from other sources? The perception from Director based on site specific information; some of our reviewers is that there may not be much information that is gathered that is not already available from other sources. If there is no significant additional information provided, running the test may not be necessary.

(g) Testing and monitoring to track the extent of the carbon dioxide plume and the position of the pressure front by either monitoring for pressure changes in the first formation overlying the confining

zone or using indirect, geophysical techniques (e.g., seismic, electrical, gravity, or electromagnetic surveys andlor down-hole carbon dioxide detection tools):

(h) At the Director's discretion, surface air monitoring andlor soil gas monitoring to detect movement of carbon dioxide that could endanger a USDW.

(1) The testing and monitoring plan must be based Proposed revision: (1) The testing and monitoring plan must Risk is more generally accepted and

on potential vulnerabilities within the area of review: be based on potential risks within the area of review; understood.

December 12, 2008 38Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer 'v.nqwa.orq Proposed Rule Revision or Comment Rationale (2) The monitoring frequency and spatial distribution of surface air monitoring andlor soil gas monitoring must reflect baseline data and the monitoring plan must include how the proposed monitoring will yield useful information on the area of review delineation andlor compliance with standards under 40 CFR 144.12:

(0 Any additional monitoring, as required by the Director, necessary to support, upgrade, and improve computational modeling of the area of review evaluation required under §146.84(b) and to determine compliance with standards under 40 CFR 144.12: and 

### 0) A quality assurance and surveillance plan for all testing and monitoring requirements.

§146.91 Reporting requirements. Proposed addition: (1) Class VI Test/Injection Well Construction Permit Proposed addition: (a) The Director shall require periodic data reports and progress reports during construction that include:

Proposed addition: 1.**Drille~s** log Proposed addition: 2. Geophysical surveys Proposed addition: 3. Core analyses Proposed addition: 4. Lithologic logs Proposed addition: 5. Drill stem tests Proposed addition: 6. Pump tests Proposed addition: 7. Daily job (construction) reports Proposed addition: 8. Water quality analyses Proposed addition: (b) The frequency of reporting shall be specified in the individual pennit

December 12, 2008 39Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext 560. creimeru 'ilnawa.ora
Pro Dosed Rule Revision or Comment Rationale Proposed addition: (c) Interpretation of data is required in the data reports or pro9ress reports at the completion of each significant phase of construction, such as completion of test well construction and testing, completion of injection weli construction, and completion of injection weli testing.

Proposed addition: (d) The owner or operator shali submit final reports of ali data coliected from the test injection eli with interpretations to the Director with the application for a Class VI Test/Injection Weli Construction and Testing Pemnit and a Class VI Injection Weli Operation Permit shali include ali information and data coliected under Section 146.87, with appropriate interpretations

Proposed addition: (2) Class VI Operational Testing Pemnit

Proposed addition: (a) The owner or operator shali submit, as part of the permit application, the proposed methodology for coliection and reporting of operational data, to ensure that the data is coliected, correlated, and reported in a fashion that would enable the Director to evaluate weli performance.

Proposed addition: (b) Ali Class VI welis shali report monthly the foliowing: Proposed addition: 1. Operating reports to the Director on:

Proposed addition: a. The physical, chemical, and other relevant characteristics of injection fluids; Proposed addition: b. Daily reading of the pressure and flow for each well. For each Class VI sequestration weli, a specific injectivity test shali be perfomned quarterly; Proposed addition: c. Monthly average, maximum and minimum values for injection pressure, flow rate and volume, and annular pressure; and Proposed addition: d. The results of monitoring prescribed under Section 146.90 Proposed addition: 2. Reporting the results, wtthin three months after the completion of:

December 12,2008 40Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer j)nawa.ora
ProDosed Rule Revision or Comment Rationale Proposed addition: a. Annular monitoring tests of mechanical integrity; Proposed addition: b. Any other test of the injection ell conducted by the permittee if required by the Director; and

Proposed addition: c. Any well work over. Proposed addition: (c) Specific injectivity testing shall be performed while the pumping rate to the well(s) has been set at a predetermined level and reported as the specific injectivity index (gpm/specific pressure (psi9)). As part of this test, the well shall be shut-in for a period of time necessary to conduct a valid observation of pressure fall-off. The owner or operator shall propose which pumping rate will be used based

on the expected flow, the design of the pump station including the volume ofthe wet well and pump type(s), and the type of
pump controls used. The pumping rate(s) shall be included

as a condition of the operation permit

Proposed addition: (d) Re-evaluation of Area of Review. After completion of the operatonal testing period, the Area of Review shall be re-evaluated, using a calibrated, multi-phase fluid flow model. The data collection during operational testing must be adequate for calibration of the model. If a calibrated model cannot be prepared using data collected during operational testing, the owner or operator shall apply for a new period of operational testing of up to two years in order to collect the required data. No more than two operational testing permits can be issued for any Class VI well. If the recalculated Area of Review includes any relevant wells or penetrations through the confining zone that were not reported in the permit application, a new tabulation of penetrations as required in Section 146.84(c)(2) and (3) shall be provided. Owners or operators must perform corrective action as required in Section 146.84(d).

December 12, 2008 41Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer unawa.ora Proposed Rule Revision or Comment Rationale Proposed addition: (e) If physical or geochemical data such as water quality, pressure changes, or mechanical integrity test results indicate that fluid movement into or between underground sources of drinking water may be occurring, the permittee shall submit addttional data to provide reasonable

assurance that the injection operation is in compliance with the requirements of this chapter. This additional data shall be submitted with the periodic operations reports, the content and frequency of which are specified in the individual permit.

Proposed addition: (f) A Class VI well permit shall be written to require that if CFR Section 146.14(a) is applicable, progress reports shall be submitted no later than thirty days following each interim date and the flnal date of compliance.

Proposed addition: (3) Class VI Injection Well Operation Permit. Proposed addition: (a) The applicant shall submit, as part of the penmit application, the proposed methodology for collection and reporting of operational data, to ensure that the data is collected, correlated, and reported in a fashion that would enable the Director to evaluate well performance.

Proposed addition: (b) All Class VI wells shall report monthly the following: Proposed addition: 1. Operating reports to the Director on:

Proposed addition: a. The physical, chemical, and other relevant characteristics of injection fluids; Proposed addition: b. Daily readings of the pressure and flow for each well. For each Class VI well, a specific injectivity test shall be perfonmed quarterly; Proposed addition: c. Monthly average, maximum and minimum values for injection pressure, flow rate and volume, and annular pressure; and Proposed addition: d. The results of monitoring prescribed under Section 146.90 Proposed addition: 2. Reporting the results, within three months after the completion of:

December 12, 2008 42Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer ilnQwa.orQ ProDosed Rule Revision or Comment Rationale Proposed addition: a. Periodic tests of mechanical integrity:

Proposed addition: b. Any other test of the injection weli conducted by the penmittee if required by the Director: and

Proposed addition: c. Any weli work over. Proposed addition: (c) Specific injectivity testing shali be performed while the pumping rate to the weli(s) has been set at a predetermined ievei and reported as the specific injectivity index (gpm/specific pressure (psig)). As part of this test, the weli shali be shut-in for a period of time necessary to conduct a vaiid observation of pressure fali-off. The owner or operator shali propose which pumping rate will be used based

on the expected flow, the design of the pump stations including the volume of the wet weli and pump type(s), and the type of pump controls used. The pumping rate(s) shali be included as a condition of the operation penmit.

December 12, 2008 43Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer 'Vnowa.ora ProDosed Rule Revision or Comment Rationale (d) Re-evaluation of Area of Review. Every five years, the Area of Review shall be re-evaluated, using a calibrated, multi phase fluid flow model. The data collection during operation must be adequate for calibration of the model. If a calibrated model cannot be prepared using data collected during operation, the owner or operator shall, within 90 days, apply for a new operation permit with a revised monitoring and testing plan designed to collect the required data. The reissued Class VI operation permit shall be valid for a period of

no more than two years. After two years of operation under a re-issued operating permit, the applicant shall again reevaluate the Area of Review using a calibrated, multi-phase fluid flow model and re-apply for a five-year operating permit. If the recalculated Area of Review includes any relevant wells

or penetrations whose total depth is greater than the depth to the bottom of the lowermost USDW that were not reported in the permit application, a new tabulation of penetrations as required in Section 146.84(c)(2) and (3) shall be provided. Ow

CONT FROM ABOVE

... must perform corrective action as required in Section 146.84(d). The owner or operator must, at a minimum, provide Proposed for deletion Covered in proposed Section 146.91 (3) and the following reports to the Director, for each subsections permitted Class VI well:

(a) Semi-annual reports containing: Proposed for deletion Covered in proposed Section 146.91(3) and subsections (1) Any changes to the physical, chemical and other Proposed for deletion Covered in proposed Section 146.91(3) and relevant characteristics of the carbon dioxide stream subsections from the proposed operating data;

(2) Monthly average, maximum and minimum values Proposed for deletion Covered in proposed Section 146.91 (3) and for injection pressure, flow rate and volume, and subsections annular pressure;

December 12, 2008 44Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer ilnowa.oro Proposed Rule Revision or Comment Rationale (3) A description of any event that exceeds operating Proposed for deletion Covered in proposed Section 146.91 (3) and parameters for annulus pressure or injection subsections pressure as specified in the permit; (4) A description of any event which triggers a Proposed for deletion Covered in proposed Section 146.91(3) and shutdown device required pursuant to §146.88(e) subsections and the response taken; (5) The monthly volume of the carbon dioxide stream Renumber 3(e) injected over the reporting period and project cumulatively; (6) Monthly annulus fluid volume added; and Renumber 3(f); delete "and" Proposed addition: (g) If physical or geochemical data such as water quality, pressure changes, or mechanical integrity test results indicate that fluid movement into or between underground sources of drinking water may be occurring, the permittee shall submit additional data to provide reasonable

assurance that the injection operation is in compliance with the requirements ofthis chapter. This additional data shall be submitted with the periodic operations reports, the content and frequency of which are specified in the individual permit.

Proposed addition: (h) A Class VI well permit shall be written to require that if CFR Section 146.41 (a) is applicable, progress reports shall be submitted no later than thirty days following each interim date and the final date of compliance.

(7) The results of monitoring prescribed under Proposed for deletion Covered in proposed Section 146.91 (3) and §146.90. subsections Covered in proposed Section 146.91(3) and subsections (b) Report, within 30 days the results of: Proposed for deletion Covered in proposed Section 146.91(3) and subsections (1) Periodic tests of mechanical integrity; Proposed for deletion Covered in proposed Section 146.91 (3) and subsections (2) Any other test of the injection well conducted by Proposed for deletion Covered in proposed Section 146.91 (3) and the permittee if required by the Director; and subsections (3) Any well work over. Proposed for deletion Covered in proposed Section 146.91 (3) and subsections

December 12, 2008 45Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800,551,7379, ext 560, creimer 'Vnowa,ora
ProDosed Rule Revision or Comment Rationale

(c) Owners or operators must submit reports in an Renumber (4) electronic format acceptable to the Director. At the discretion of the Director, other formats may be accepted,

§146.92 Injection well plugging. (a) Prior to the well plugging, the owner or operator must flush each Class VI injection well with a buffer fluid, determine bottom hole reservoir pressure, and perform a final mechanical integrity test

(b) Well Plugging Plan. The owner or operator of a Proposed revision: (b) Well Plugging Plan, The owner or The Area of Review re-evaluation should Class VI well must prepare, maintain, and comply operator of a Class VI well must prepare; maintain; including trigger a review and updating of all the plans with a plan that is acceptable to the Director. The updating on the same schedule as the update to the Area of (MMV, financial, plugging, emergency requirement to maintain and implement an approved Review: and comply with a plan that is acceptable to the response

... ) on the same interval that the plan is directly enforceable regardless of whether the Director, The requirement to maintain and implement an AOR is updated, NGWA suggests EPA requirement is a condition of the permit The well approved plan is directly

... check all timelines and make them plugging plan must be submitted as part of the compatible, permit application and must include the following information:

(1) Appropriate test or measure to determine bottom hole reservoir pressure; (2) Appropriate testin9 methods to ensure mechanical integrity as specified in §146.89; (3) The type and number of plugs to be used: (4) The placement of each plug including the elevation of the top and bottom of each plug; (5) The type and grade and quantity of material to be used in plugging, The material must be compatible with the carbon dioxide stream; and (6) The method of placement of the plugs.

December 12, 2008 46Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer 'ilnqwa.orq Pro Dosed Rule Revision or Comment Rationale (c) Notice ofintent to plug. The owner or operator must notify the Director at least 60 days before plugging of a well. At this time, if any changes have been made to the original well plugging plan, the

owner or operator must also provide the revised well plugging plan. At the discretion of the Director, a shorter notice period may be allowed.

(d) Plugging report. Within 60 days after plugging or Proposed revision: (d) Plugging Reports for Class VI Wells. at the time of the next semi-annual report (whiChever Within 60 days after completion of plugging and abandonment

occurs earlier) the owner or operator must submit a of a well or well field the permittee shall submit to the Director plugging report to the Director. If the semi-annual a final report which includes: report is due less than 15 days after completion of plugging, then the report must be submitted within 60 days after plugging. The report must be certified as accurate by the owner or operator and by the person who performed the plugging operation (if other than the owner or operator.)

Proposed addition: (1) Certification of completion In Note: It is important that the engineer and/or accordance with approved plans and specifications by an geologist have expertise and training in appropriately qualified engineer of record or professional Injection well drilling technology, reservoir geologist. characterization and injection well construction and operation.

Proposed addition: (2) Evidence, such as a sealed copy or certification from the county clerk, that a surveyor's plot of the location of the abandoned well has been recorded in the county courthouse property records.

§146.93 Post-injection site care and site closure.

December 12, 2008 47Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimerQ ilnqwa.orq Pro Dosed Rule Revision or Comment Rationale (a) The owner or operator of a Class VI well must Proposed revision: (a) The owner or operator of a Class VI The Area of Review re-evaluation should prepare, maintain, and comply with a plan for post- well must prepare: maintain: including updating on the same trigger a review and updating of the well injection site care and site closure that meets the schedule as the update to the Area of Review: and comply plugging plan, and the post injection site care requirements of paragraph (a)(2) of this section and with a plan for post-injection site care and site closure that and closure plan. NGWA suggests EPA is acceptable to the Director. meets the requirements of paragraph (a)(2) of this section and check all timelines and make them is acceptable to the Director. compatible. (1) The owner or operator must submit the postinjection site care and site closure plan as a part of the permit application to be approved by the Director.

(2) The post-injection site care and site closure plan must include the following information: (i) The pressure differential between pre-injection and predicted post-injection pressures in the injection zone; (ii) The predicted position of the carbon dioxide plume and associated pressure front at site closure

as demonstrated in the area of review evaluation required under §146.84(b): (iii) A description of post-injection monitoring location, methods, and proposed frequency: and

(iv) A proposed schedule for submitting post-injection site care monitoring results to the Director.

(3) Upon cessation of injection, owners or operators of Class VI wells must either submit an amended post-injection site care and site closure plan or demonstrate to the Director through monitoring data and modeling results that no amendment to the plan is needed. (4) The owner or operator may modify and resubmit the post-injection site care and site closure pian for the Director's approval within 30 days of such change.

December 12,2008 48Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Welis, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer unawa.ora Pro Dosed Rule Revision or Comment Rationale (b) The owner or operator shali monitor the site foliowing the cessation of injection to show the position of the carbon dioxide plume and pressure front and demonstrate that USDWs are not being endangered. (1) The owner or operator shali continue to conduct Proposed revision: (1) The owner or operator shali continue to NGWA believes some number should be monitoring as specified in the Director-approved post conduct monitoring as specified in the Director-approved post- included. 30 years is a number used in other injection site care and site closure plan for at least injection site care and site closure plan for at least 30 years EPA programs. The next question was 50 years following the cessation of injection. At the following the cessation of injection. At the Director's whether the burden should be placed on the Director's discretion, the monitoring will continue until discretion, the monitoring will continue until the geologic director to justify the longer number or on the the geologic sequestration project no longer poses sequestration project no longer poses an endangerment to operator to prove the site is stabilizing. It is

an endangerment to USDWs. USDWs. suggested that the director be allowed to approve both a shorter or longer timeframe. With the next subsection, the burden is placed on the owner or operator to prove a shorter timeframe is acceptable, while allowing in this subsection the director to require monitoring beyond 30 years.

(2) If the owner or operator can demonstrate to the Proposed revision: (2) If the owner or operator can Makes this subsection compatible with 30 satisfaction of the Director before 50 years, based on demonstrate to the satisfaction of the Director that the year timeframe proposed by NGWA in monitoring and other site-specific data, that the geologic sequestration project no longer poses an 146.93(b)(1) geologic sequestration project no longer poses an endangerment to USDWs, the Director may approve an endangerment to USDWs, the Director may approve amendment to the post-injection site care and site closure

an amendment to the post-injection site care and site plan to reduce the frequency of monitoring or may authorize closure plan to reduce the frequency of monitoring or site closure before the end of the 30-year period.
may authorize site closure before the end of the 50-
year period.

(3) Prior to authorization for site closure, the owner

or operator must submit to the Director a demonstration, based on monitoring and other sitespecific data, that the carbon dioxide plume and pressure front have stabilized and that no additional monitoring is needed to assure that the geologic sequestration project does not pose an endangerment to USDWs.

December 12, 2008 49Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800,551,7379, ext. 560. creimer i)nawa,ora
Pro Dosed Rule Revision or Comment Rationale (4) If such a demonstration cannot be made (i.e., if Proposed revision: (4) If such a demonstration cannot be Makes this subsection compatible with 30 the carbon dioxide plume and pressure front have made (i.e. if the carbon dioxide plume and pressure front have year timeframe proposed by NGWA in
not stabilized) after the 50 year period, the owner or not stabilized) after the 30 year period, the owner or operator 146,93(b)(1) operator must submit to the Director a plan to must submit to the Director a plan to continue post-injection continue post-injection site care. site care.

(c) Notice of intent for site closure, The owner or operator must notify the Director at least 120 days before site closure. At this time, if any changes have been made to the original post-injection site care and site closure plan, the owner or operator must also provide the revised plan. At the discretion of the Director, a shorter notice period may be allowed,

(d) After the Director has authorized site closure, the

owner or operator must plug all monitoring wells in a

manner which will not allow movement of injection or formation fluids that endangers a USDW.

(e) Once the Director has authorized site closure, the

owner or operator must submit a site closure report within 90 days that must thereafter be retained at a location designated by the Director. The report must include:

December 12, 2008 50Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wens, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerviile, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer ilnQwa.orQ
Pro Dosed Rule Revision or Comment Rationale (1) Documentation of appropriate injection and monitoring wen plugging as specified in §146.92 and paragraph (c) of this section. The owner or operator must provide a copy of a survey plat which has been submitted to the local zoning authority designated by the Director. The plat must indicate the location of the injection wen relative to permanently surveyed benchmarks. The owner or operator must also submit a copy of the plat to the Regional Administrator ofthe appropriate EPA Regional Office;

(2) Documentation of appropriate notification and information to such State, local and tribal authorities

as have authority over drilling activities to enable such State and local authorities to impose appropriate conditions on subsequent drilling activities that may penetrate the injection and confining zone(s): and (3) Records reflecting the nature, composition and volume of the carbon dioxide stream.

(I) Each owner or operator of a Class VI injection well
must record a notation on the deed to the facility property or any other document that is normally examined during title search that wiil in perpetuity provide any potential purchaser of the property the following information:

(1) The fact that land has been used to sequester carbon dioxide; (2) The name of the State agency, local authority, and/or tribe with which the survey plat was filed, as well as the address of the Regional Environmental Protection Agency Office to which it was submitted; and (3) The volume of fluid injected, the injection zone or
zones into which it was injected, and the period over which injection occurred.

December 12, 2008 51Docket

- EPA-HQ-OW-2008-0390: Comments on VIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800,551,7379, ext 560, creimer**~nqwa.orq** Proposed Rule Revision or Comment Rationale

(g) The owner or operator must retain for three years following site closure, records collected during the**post~injection** site care period. The owner or operator must deliver the records to the Director at the conclusion of the retention period, and the records must thereafter be retained at a location designated by the Director for that purpose,

§146,94 Emergency and remedial response. (a) As part of the permit application, the owner or Proposed revision: (a) As part of the permit application, the Keep same update schedule as AOR operator must provide the Director with an owner or operator must provide the Director with an emergency and remedial response plan that emergency and remedial response plan that describes actions describes actions to be taken to address movement to be taken to address movement of the injection or formation of the injection or formation fluids that may cause an fluids that may cause an endangerment to a USDW during endangerment to a USDW during construction, construction, operation, closure and post-closure periods, operation, closure and post-Closure periods, The emergency and remedial response plan must be reviewed and updated, as necessary, on the same schedule

as the update to the Area of Review,

(b) If the owner or operator obtains evidence that the injected carbon dioxide stream and associated pressure front may cause an endangerment to a USDW, the owner or operator must:

(1) Immediately cease injection: (2) Take all steps reasonably necessary to identify and characterize any release: (3) Notify the Director within 24 hours; and (4) Implement the emergency and remedial response plan approved by the Director.

(c) The Director may allow the operator to resume injection prior to remediation if the owner or operator demonstrates that the injection operation will not endanger USDWs,

December 12, 2008 52Docket

- EPA-HQ-OW-2008-0390: Comments on UIC Requirements for Geologic Sequestration Wells, 73 FR 43492 National Ground Water Association, 601 Dempsey Rd, Westerville, OH 43081 Contact: Christine Reimer, NGWA, 800.551.7379, ext. 560. creimer vnawa.ora Proposed Rule Revision or Comment Rationale

(d) The owner or operator must notify the Director and obtain his approval prior to conducting any well work over.

December 12, 2008 53

### Letter ID: 0142 Commenter: Christine Reimer Organization: National Ground Water Association

Letter ID: 0142 Comment ID: 22544 Letter Lines: 99 to 113

Comment Code: 2064 1.5.3.2 Grandfathering construction of Class II wells (seeking comment) Comment Code: 2066 1.5.3.3 Grandfathering construction of Class V wells (seeking comment)

Comment: Classification of Injection Wells for Carbon Sequestration, Class II Injection Well Transition, and Grandfathering

The EPA published a guidance document inMarch of 2007 recommending that the geologic sequestration experimental projectsduring this period of research use the Class V experimental category for cl assification of the injection wells (Using the Class V Experimental Technology Well Classification for Pilot Geologic Sequestration Projects - EPA 2007). These projects are currently underway at the Department of Energy’s (DOE’s) National Energy Technology Laboratory Regional Partnership test sites. Thus, there will be a need in the future for a regulatory mechanism for transition of these Class V experimental wells to Class VI operational status. There are also a number of Class II enhanced oil recovery (EOR) wells that have been used for testing of the sequestration process. These wells, too, may need a mechanism for transition to Class VI for operational use.

Individual Response: EPA agrees that many Class II and Class V experimental technology wells are designed and constructed to withstand exposure to CO2. The final GS rule provides for the construction of these wells to be grandf athered 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 does not believe that other requirements (e.g., MITs, siting, monitoring, operational, and AoR requirements) should also be grandfathere d. Following re-permitting of the well as Class VI, many of the unique factors of GS sites (e.g., increased reservoir pressures associated with large volumes of stored CO2 and the corrosivity of CO2 in the presence of water) will result in an increased risk profile, warranting the specifi c requirements in the final GS rule. Therefore, following re-permitting as Class VI wells, these proj ects must be subject to the operational, MIT, monitoring, reporting, plugging, and post- injection site care and site closure 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: 0142 Comment ID: 22545 Letter Lines: 115 to 226

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

1

### Comment Code: 2066 1.5.3.3 Grandfathering construction of Class V wells (seeking comment) Comment Code: 3130 2.1.3 Comments that operators should submit more (or different) geologic data than proposed Comment Code: 4710 2.7.1 Proposed submissions required for permit applications (seeking comment)

Comment: The NGWA Carbon Sequestration Task Force recommends that the experimental phase extend beyond the regional partnerships to each site proposed for productionscale injection of carbon dioxide. It is recommended that at l east one well at each site be constructed under the Cla ss V experimental category, and that testing of the adequacy of the geologicenvironment for geologic sequestration of carbon dioxide be conducted prior topermitting any well in the Class VI category at the site.

The transition of carbon dioxide injecti on wells from Class II (Enhanced Oil Recovery wells) to Class VI (carbon seque stration wells) will presumably be requested when production of the petrol eum has ceased. Liquid carbon dioxide from a distant source, such as a power pl ant, can be stored in the depleted petroleum reservoir even after production has ceased, necessitating a change in classification of the injection well. The new use of the wells involves much longer storage time, and raises concernsabout mechanical integrity and long term effects, including geochemical changes, on underground source of drinking water (USDWs). The reclassification should depend on a positive outcome from a Class V experimental program conducted in the depleted reservoir, as described below.

The "grandfathering" of Class V carbon se questration wells would mean allowing experimental wells to be permitted for operation after the testing period is over. The NGWA Carbon Sequestration Task Force recommends that each carbon sequestration system or wellfield have an experimental phase, and not rely on results from distant experimental locations. Thus, nearly every operational well would start as a Class V experimentalwell, or would go through a Class VI testing phase, before being permitted for long-term operation. The transition to Class VI operational status would require demonstrating that the minimum requirements are met at that locati on. Most wells would go through the following permitting phases:

- Class V experimental well construction permit: This permit would allow geologic and geophysical testing, aquifer testing, laboratory work, etc, but would not include injection of CO2 (only potable water injection testing would be allowed).

- Class VI experimental well operational testing permit: At this stage, the full monitoring facilities would need to be constructed. This permit would allow test injection of liq uid CO2 at rates high enough todemonstrate that the

2

### location meets the minimum requirements for operation, for a period of up to two
years.
- Class VI operation permit: After demonstrating that the location and the well meet all the minimum requirement s for injection of CO2, the operation permit can be issued.

The goals of the experimental well Class V construction permit would be to make the following demonstrations:

- A receiving zone of sufficient dept h, area extent, thickness, porosity, and permeability is present;

- Lithologic description, geological name, thickness and depth of each confining unit above the storage aquifer, and of each USDW.

- A trapping mechanism that is free of pathways for migration of injected fluids into a USDW. These pathways may include major non-sealing faults, porous beds within the confining unit, changes of f acies trending toward more porous units and man-made structures such as wells or mine shafts. A trapping mechanism is defined as a geologic environment that prevents vertical and horizontal movement of fluids into a USDW; The volume of the trap shall exceed the proposed total volume of injected carbon dioxide for the life of the proposed facility

- Identification of all confining units between the primary injection/storage zone and the lowermost USDW, and their adequacy to contain the injected fluid. Unless the only feasible injection zonehas only one confining unit separating it from the lowermost USDW, this demonstration includes adequacyof confinement for both the primary confining unit and a secondary containment system that extends to the base of the lowermost US DW and is completely redundant of the primary confining system and could confine the injected CO2 should the primary system fail. In locations where the secondary containment system is not possible, the applicant shall propose an alternative system of early warning of failure of the primary confining unit in order to avoid impacting any USDW should that confinement fail. This demonstration applies inthe horizontal sense as well, demonstrating one or moremechanisms containing the fluid from horizontal movement into a USDW in the storage aquifer at a distant location.

- The construction of an operational monitoring system meeting all the requirements described in this document’s MMV section, and demonstration of the adequacy of this system to meet those requirements.

- Demonstration of mechanical integrity

Having made the foregoing demonstrations, a Class VI operational testing permit can be issued for a period of up to two years. The goals of the experimental

3

### well Class VI operational testing permit would be to make the following demonstrations:

- A hydraulic demonstration of the adequacy (depth, area extent, thickness, porosity, and permeability) of the storage zone, using monitoring data and 4-D seismic monitoring of the extent of the CO2 plume. - Demonstration of the adequacy of the trap for 5/10 years of injection at the proposed rate. The volume of the trap shall exceed the propose d total volume of injected carbon dioxide for the 5/10 years of the first operation permit. - Demonstration of the adequacy of c onfinement under operational conditions using monitoring data and a method of detecting the extent of the CO2 plume in the storage aquifer, such as 4-D se ismic monitoring or direct sampling. - Re- evaluation of the Area of Review a nd extent of the zone of endangering influence. - Re-evaluation of mechanical integrity, using the buoyancy of the injected CO2 to better measure external mechanical integrity. The re-evaluation shall include the testing required during the initial MIT, as well as evaluation of the cement for carbonation, or chemical weathering by CO2

Under this permitting scenario, the vast ma jority of Class V experimental wells would be constructed after the Class VIstandards had been published. The "grandfathering" of Class V wells that do not meet the Class VI construction standards would only be needed for DOE te st sites established before rulemaking was complete. If these wells include the ongoing mechanical integrity monitoring of annular fluid pressure and composition, and they pass periodic mechanical integrity testing, they should be able to follow the same permitting procedures to become operational Class VI wells.

Individual Response: EPA believes that submittal and reviewof monitoring data (as required at §146.90) and the AoR reevaluation process (§146.84(e)) will provi de an opportunity for an ongoing review of the site and a dialogue between the Director and the owner or operator to ensure that the project is being operated in a manner that protects USDWs from endangerment. EPA notes that changes to these plans require a permit modification under §144.39, the public must be notified according to the public comment procedures under 40 CFR 124.

Please see the final rule and the discussion of geologic site characterization in the preamble for additional information.

EPA disagrees that every GS well should initially be permitted as a Class V well. The Agency believes that the tailored Class VI requirements including extensive requirements for geologic site characterization at § 146.82, AoR evaluation at §146.84, and testing of the well during drilling at §146.87 are appropriate to ensure that permitting authorities have the necessary information to evaluate whether a specific site will allow safe injection of CO2. EPA adds that submittal and review of monitoring data (as required at §146.90) and the AoR reevaluation process (§146.84(e)) will provide an opportunity for an ongoing reviewof the site and a dialogue between the Director and the owner or operator to ensure that the project is being operated in a

4

### manner that protects USDWs from endangerment. Given this approach to permitting Class VI projects, EPA believes that the requirements for grandfathering of constr uction at §146.81(c) are necessary and appropriate.

Letter ID: 0142 Comment ID: 22546 Letter Lines: 229 to 345

Comment Code: 3130 2.1.3 Comments that operators should submit more (or different) geologic data than proposed Comment Code: 4710 2.7.1 Proposed submissions required for permit applications (seeking comment)

Comment: Geologic Characterization

The UIC program is required under the SafeDrinking Water Act to protect USDWs from contamination from fluids injected into the subsurface. Part of this requirement is the demonstration that the injected fluids will not migrate, through buoyancy, ground-water flow or injection pressure, into USDWs. This demonstration is based on the characteri stics of the geological environment where injection is to take place. The current UIC regulations require investigation of waste disposal sites through an applic ation-phase data summary (Area of Review study) and geologic testing while drilling the pilot hole of the injection well. In general, the critical attributes of the injection and confining units are measured during pilot hole drilling, and the integrity and extent of those units are addressed in the literature review and Area of Review study at the application phase. Because of the large volumes of carbon dioxide that are expected to be injected, and the vast extent of the storage zones, it is expected that more detailed informati on will be needed over a larger area for carbon sequestration than has been historic ally needed for in jection of other
wastes.

The NGWA recommends that the adequacy and safety of injection of liquid carbon dioxide at each site be evaluated by multi-phase, variable density ground-water modeling, supported by extensive field inve stigations (see section General Comments on the Use of Modeling for Ground-Water Protection Related to CO2 Sequestration, below) These models shoul d be included at the experimental well permit application phase as conceptualmodels, and progressively refined as data are collected during well constr uction and testing, and monitoring of operations.

The test injection well/operational te sting permit application for a carbon sequestration injection well must address the geological characteristics of the site. The data presented at this stage should be adequateto make and calibrate an appropriate ground-water model. The necessary elements of the geologic system for carbon sequestration include:

- A receiving zone of sufficient depth that the injected carbon dioxide

5

### can be maintained in a supercritical state - Of sufficient areal extent that it includes the entire z one of endangering influence - Of sufficient thickness and porosity tocontain the volume of carbon dioxide injected over the life of the proposed system - Of sufficient permeability to accept the peak daily flow of injected carbon dioxide from the facility - A trapping mechanism (consisting of either impermeable barriers or geochemical/mixing barriers) that is free of vertical or horizontal pathways for migration of injected fluids into a USDW . The volume of the trap shall exceed the proposed total volume of injected carbon dioxide for the life of the proposed facility - A primary confining system of suffi cient areal extent, thickness and competency to contain the injected flui d at proposed rates and volumes without initiating or propagating fractures in the confining zone - Unless the only feasible injection zonehas only one confining unit separating it from the lowermost USDW, a secondary c ontainment system that is completely redundant of the primary confining system and could confine the injected CO2 should the primary system fail. - The identification of a monitoring zone between the primary and secondary confining units. In locationswhere the secondary containment system is not possible, the applicant shall propose a monitoring formation to provide early warning of failure of the primary confining unit in order to avoid impacting any USDW should that confinement fail. - Provide depth and completion information of all USDWs that may be affected by the injection if fluid movement does occur. - Provide geochemical information on subsurface aquifers, including all USDWs: Baseline geochemical data on water-rock- CO 2 geochemistry and mineral reactions, maps and cross sections.

These elements should be identified inexisting well records, in geologic literature, and by using the results of the exploratory program. The critical storage and confining units should be shown to exist over the entire area of review, or zone of endangering influence

The operation permit application should also include a preliminary multi-phase numerical transport model for CO2 and formation fluid, including all of the elements listed above. This model shoul d include at least one calibration scenario and will be used to provide a preliminary evaluation of the adequacy and safety of injection of carbon dioxide at the site, as well as a preliminary calculation of the potential storage vo lume of the geologic structure.

Each permit application for a carbon seque stration injection well must include an Area of Review study, which addre sses the entire zone of endangering influence of the carbon sequestration operation, including the area impacted after cessation of injection due to buoyancy transport. The zone of endangering

6

### influence shall be determined by the ground-water model described above and illustrated with maps and cross sections.

Provide information on the geologic structure of the proposed site, including:

- Maps and cross sections of local ge ologic structure. Each cross section should include the location and depth of relevant data sources, including geophysical logs, that were used in developing the cross section - Geological name and lithologic descripti on of each injection zone, primary and/or secondary confining unit, and USDW - Data on the receiving formation and the confining systems : 1. Size of the storage reservoir, and extent of th e confining units in comparison to the area of endangering influence 2. Presence or absence of a secondary confining unit 3. Porosity, and permeability of the storage zone and confining units, including any geology/facies changes, based on field data which may include geologic cores, outcrop data, 3-dimensional seismic surveys, and well logs 4. Capacity of the storage zone incomparison to the proposed total volume of carbon dioxide to be stored, 5. Evaluation of the long-term effectiveness of the storage structure, including expected pathwaysof migration of injected carbon dioxide, and the horizontal barriers to fluid movement - Geomechanical information on fractures, stress, rock strength, and in situ fluid pressures within the primary and s econdary containment units and confining systems - Identification of potential pathways for migration of injected fluids and determination that they would not conduct a volume of fluid that would cause a violation of the prohibition of fluid movement as it applies to the class of well that is to be constructed - Identification of potentialrisks within the zone of endangering influence, including degradation of water quality in USDWs, gas buildup in USDWs, reduction of porosity through geochemical changes inUSDWs, and populati on that could be affected by gas releases. - List of penetrations into the injecti on zone and secondary containment system. - Information on seismic history and the presence/depth of seismic sources

Individual Response: EPA agrees that extensive geologicaldata collection and computational modeling, similar to what the commenter suggests, are important components of characterizing a potential GS site. For this reason, the GS regulation requires owners or op erators to collect and submit extensive geological data (specified at §146.82) on the proposed GS site, including the injection and confining zones. Operators must also delineate the AoR using computational modeling that accounts for the multiphase flow of CO2 and native fluids (§146.84(c)), based on the geological data collected and proposed injection operations.

EPA disagrees with the comment that all sites should be evaluated by multi-phase, variable

7

### density groundwater modeling; instead, EPA believesthat owners or operators should have the flexibility to select models that are most appropriate to site conditions and available data types and amounts. EPA is also requiring that the AoR bereevaluated at a frequency of every 5 years using monitoring and operating data to verifythat the CO2 plume and pressure front are behaving as predicted in AoR calculation models (§146.84(e)).

Letter ID: 0142 Comment ID: 22547 Letter Lines: 347 to 382

Comment Code: 3866 2.3.3.3 Logging and testing requirements (40 CFR 146.87)

Comment: During drilling and construction of the in jection well, important, site-specific data must be collected to verify the f acts included in the application, provide quantitative data for refinement of the ground-water model, and test the injectivity of the proposed injection zone. The testing currently recommended in the regulations during construction of Class I wells includes geophysical logs run during drilling, devi ation checks to ensure that reamed holes do not deviate from pilot holes, l eaving conduits in the formation, and logs to measure the integrity of the completed wells. The NGWA recommends the following testing during construction:

A. Identification of the lowermost USDW should be confirmed during drilling, using tests suchas the following:

1. Sampling discharge from packer tests (straddle packers or single-packer bottom-hole test). 2. Cross plots of induction or resistivity with sonic/neutron/density porosity measurements and deduction of fluid resistivity using Archies Law (verification of porosity with core samples) 3. Bottom-hole water sampling during pilot hole drilling (with mud) 4. Depth sampling in pilot hole while pumping 5. Collection, logging, and archiving, of rock cores through the sealing and target formations.

B. The demonstration of confinement is the most critical task in construction of the well. Some informati on can be collected only prior to the installation of casing so careful consideration should be given to formation sampling before the well is completed. We recommend that borehole geophysical methods, such as, but not limited to, re sistivity, neutron, gamma, and density logs, be combined with formation imaging such as, but not limited to, digital video and acoustic televiewer logging to specify lithologic units, geologic properties, and faults or fractures. Hydraulic testing such as straddle packer injection can be completed prior to completion of the well. After completion, long-term pumping tests should be conducted over a sufficient time period to assure near-pseudo-steady state head conditions in the vicinity of the well. Interpretation of these data and tests should be used to refine the ground-water flow and transport model.

8

### Individual Response: EPA agrees there are numerous tests av ailable to characterize subsurface formations, including identifying the lowermost US DW. The owner or operator must describe his or her proposed formation testing program aspart of the permit application, pursuant to §146.82(a)(8). The Director will evaluate the proposed formation testing plan, along with sitespecific geologic information, the AoR and corrective action plan, and proposed well construction procedures. If, based on a review of this information, the Director determines that additional logs and tests are necessary to provideassurance that USDWs will be protected from endangerment, he or she has authority at §146.87(a)(5) to require additional testing. EPA adds that during the permit application process, the owner or operator and the permitting authority will work together to determine which test s are appropriate, based on the site-specific circumstances.

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.

Letter ID: 0142 Comment ID: 22548 Letter Lines: 385 to 504

Comment Code: 3330 2.2.1.3 Applicability /adequacy of computational models (seeking comment)

Comment: General Comments on the Use of Modeling for Ground-Water Protection Related to CO2 Sequestration

Quantitative modeling must play an important role in the assessment of groundwater protection related to CO2 sequestration projects. A ‘quantitative model’ is defined here as a quantitative mathematical analog of the real subsurface system.

Three overall purposes for quantitative modeling are generally recognized:

1. Generic: Model used in a hypothetical sense 2. Interpretive: Model used to understand system dynamics 3. Predictive: Model used to predict future behavior of the subsurface system.

All three purposes are generally needed for a CO2 sequestration project. For example, generic models are used to determine the important physical or geochemical mechanisms that dominate transport or trapping of CO2. An interpretive model is app lied to test specific hypotheses regarding these behaviors. Predictive modeling provides the basis for design of the final injection scheme and establishment of potential risk to drinking water.

Quantitative models may range from simple analytic calculations to complex

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### multi-component multi-phase coupled three-dimensional numerical simulations. The choice of quantitative model (analytic or numerical) depends in large part on the ultimate objective of the modeling study, and on practical constraints including availability of data and computational limitations. Which type of model or combination of models is most appropriate for a specific situation depends on many factors. In general, using a combination of modeling and analysis techniques is recommended, because different levels of complexity are needed at various stages of a projectand for different objectives, and application of multiple modeling techniques can be used for "cross-checking" and overall quality assurance.

Numerical models are widelyavailable and usually represent a relatively wide range of physical and chemical processes, spatial heterogene ity of material properties, and nonlinear interactions among different processes. While these kinds of models allow for substantial flexibility and can provide detailed predictions of system behavior, they also require large amounts of data, much of which may be difficult to obtain or estimate. As such, specific choices of models must be made with care, and somesituations may most effectively be addressed by a combination of different kinds of models.

Quantitative modeling, whether conducted withanalytical or numerical modeling tools, provides significant insights into system behavior. The advantages of such models are that they:

1. provide a framework for data collec tion centered about a specific set of transport and geochemical behaviors. 2. allow communication and the interpretation of these data in the context of scientific principles and facilitate co llaboration among engineers, scientists, and regulators. 3. may be extended far into the future using multiple design scenarios 4. can be compared to measured data which allow hydraulic and geochemical parameters to be estimated. 5. Can be used to access the performance of the system in a long performance period for which fiel d and laboratory data are not available.

It is important to recognize that all quantitative mathematical models are based upon a "conceptual model" which defines the important fluid and chemical interactions as well as the spatial and temporal extent of the model. Because the conceptualization is a critical part of the modeling activity, it is important to explore multiple conceptual models during the modeling process to assure that important scenarios are not excluded from the analysis.

The selection of which quantitative model to use relieson the identification of the physical/chemical parameters and functi ons that must be represented. Because the injection and migration of CO2 into the subsurface is hydraulically and

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### chemically complex, comprehensive quantitative modeling would have to include many parameters and factors -- including the flow of miscible and immiscible phases in all potential states as well as chemical reactions among fluids and with the geologic media and necessary heat transfer. The geologic medium may also deform or be chemically altered in response to the presence of CO2. The complexity of these coupled proces ses, in the presence of complex hydrostratigraphy, lead to models that are at the limit of the current capabilities of available computer hardware and so ftware. It is likely, therefore, that multiple models may berequired to provide the necessary insights into the important physical and chemical processes. Ultimately, sound scientific and engineering judgments should be applied to determine which physical or chemical processes are most important for a given analysis, and to make assumptions that are consistent with those judgments. For example, during the injection phase of a CO2 operati on, multi-phase flow physics tend to dominate other processes such as interphase mass transfer and geochemical reactions. This separation of time scales can lead to important simplifications for the purpose of risk assessment. Similar analysis of spatial scales can provide additional simplifications, leading to practical modeling tools for the purpose of risk assessment. It is, therefore. imperative that modeling experts participate and manage all phases of the modeling process, in concert and constant communication with the project team and the appropriate regulatory reviewers, to ensure that appropriate and comprehensive quantitative modeling tools are applied successfully."

The process of comparing simulated and measured predictions for the purpose of developing a more accurate depiction of a subsurface flow system is generally referred to as "model calibration" in th e ground-water literature. (This same process is referred to as "inverse mo deling" in exploration geophysics and "history matching" in petroleum reservoir simulation.) Model calibration involves varying the parameters of the quantitative model to achieve the minimum difference between measured and predicted responses. This is usually achieved through an automated process using non- linear regression or a heuristic algorithm to optimize the problem (e.g. as implemented in the PEST or UCODE software). In the case of ground-water modeling, the predicted and measured data are usually pressures, discharge rate s, or concentrations of fluids or dissolved species. These data may not beavailable during the design stage of a CO2 project unless wells already exist in the target formation. As wells are drilled and geologic and fluid information are collected, however, the model should be refined and calibrated. Most automated calibration procedures allow for statistical estimation of confidence in the estimated parameters, providing a basis for quantifying the sensitivity of the model to changes in its parameters, and for performing quality control of model predictions.

The design, construction, and calibration of analytic or numerical models should follow a quality assurance and quality control procedure. These procedures should include benchmarking of the mathematical predictions against known

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### results, a method for assuring input data quality and lineage, and a statistical analysis of the predictive results against available data and/or sensitivity analyses. ASTM guides are available for ground-water modeling and code benchmarking (e.g. Guides D 6025, D 5447, D 5490, D 5611, D 5609, D 5610, and D 5718).

Individual Response: EPA agrees that complex modeling techniques are necessary to calculate the AoR while adequately accounting for the complexities of a GS site and all phases of a CO2 plume. EPA believes, based on the research thatsupported the modeling re quirements in the GS regulation (as described in the background document, "Computational Modeling of Underground Injection of Carbon Dioxide for Determinati on of Area-of-Review and Potential Risk to Underground Sources of Drinking Water" cited in the proposed rule preamble as USEPA, 2008d), that technology has advanced to the po int that a CO2 injection project can be appropriately modeled to predict and track a CO2 plume (and pressure front). Each AoR calculation will be reviewed based on site-spe cific geologic conditions, planned operating conditions, and available modeling and computational technology. EPA agrees that appropriate data quality review should be conducted during AoR modeling. Methods for assuring input data quality and lineage, as well as statistical analysis of predictive results may be used during evaluation of a permit application, at the discretion of the Director.

EPA anticipates 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.

EPA adds that, to address uncertainty in modeled results, particularly over the long term, it is requiring that the AoR be reevaluated (under 146.84( e)) to verify the CO2 plume is behaving as predicted and to allow for necessary revisions to corrective action or monitoring. The final GS regulation includes a requirement that the AoR be reevaluated at le ast every 5 years (an adjustment from the ten year interval in the proposal), which shoul d further address the commenters' concerns. This frequency will provide the Agency with information on AoR reevaluations to support subsequent regulatory evaluations that are part of the Agency's adaptive approach. The Agency plans, every six years, tocollect 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: 0142 Comment ID: 22549 Letter Lines: 83 to 96 ; 1259 to 1260 ; 1276 to 1278

Comment Code: 1220 1.1.1.1 Terminology and definitions Comment Code: 4400 2.4.4.3 Allowing injection above or between USDWs (seeking comment)

Comment: Definition of Underground S ources of Drinking Water

NGWA recommends that US. EPA reevaluate the appropriateness of the definition of an underground source of drinking water (U SDW) as one containing less than

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### 10,000 ppm total dissolved so lids prior to large-scale licensing of carbon capture and storage (CCS) sites to ensurefuture drinking water supplies are not unintentionally degraded. For example, a recent article reported that deep brackish ground water, approximately 12,000 TDS, is under consideration as a water source for a development in Sa ndoval County, New Mexico. The article notes that the cost of water treatment is expected to be less than obtaining existing water rights (Sengebush, 2008) In2003, water managers in 36 states anticipated shortages in localities, regions , or statewide in the next ten years (U.S. General Accounting Office, 2003). The potential for the increased use of brackish ground water for water supplies must be anticipated and considered.

Sengebush, Robert M., INTERA, Inc. Deep Brackish Water Considered for New Mexico Development. Southwest Hydrology, March/April 2008, p. 8.

U.S. General Accounting Office. Freshwater Supply: States’ Views of House Federal Agencies Could Help Them Meet the Challenges of Expected Shortages (GAO-03-514). July 2003, p. 1.

Individual Response: EPA is not changing the USDW definition; changing the definition of a USDW is outside the scope of the GS rulemaking. The GS rule focuses on ensuring protection of USDWs, as required under the SDWA, by establishing regulations to ensure the safe injection of CO2 for long-term storage.

EPA recognizes that there is increasing demand for water re sources and that technology improvements may make high TDS aquifers viabledrinking water sources. EPA believes these potential resources should be c onsidered when injection depth waivers are sought. Therefore, the final GS rule at §146.95(b) requiresthe Director to consider thes e issues in determining whether an injection depth waiver is appropriate. Spec ifically, the Director must consider whether alternative injection sites are available; community needs, demands, and supply from drinking water resources; planned needs, potential and/or future use of USDWs and non-USDWs in the area; and a plan for securing alternative resources or treating USDW formation waters in the event of contamination related to the Class VI injection activity.

Letter ID: 0142 Comment ID: 22550 Letter Lines: 506 to 511

Comment Code: 3350 2.2.1.5 Use of proprietary models for GS sites (seeking comment)

Comment: Use of commercial proprietary codes shoul d be authorized. Proprietary doesn't mean secret. A proprietary code largely ve tted by the industry can be the best application in many circumstances. To promote peer review and benchmarking, the assumptions and theories for all numericalmodels should be publicly available and the solution of any analytic equationsused in the predic tive process should be fully elaborated.

Individual Response: EPA agrees that available proprietary models may meet the complex needs for calculating the AoRs of GS sites, and shares their concern about the need to evaluate

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### the inputs and assumptions used. EPA will allow 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 satisfacti on, 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: 0142 Comment ID: 22551 Letter Lines: 514 to 570

Comment Code: 3300 2.2.1 Delineating the AoR/M odeling CO2 movement Comment Code: 3400 2.2.2 Corrective Action

Comment: Area of Review and Corrective Action

In the context of carbon storage, NGWA thinks it is important to distinguish between the CO2 plume footprint and the zone of elevated pressure. The rationale is given in the next section, but the following conditions should be met:

- No fixed radius can be used, a zone of endangering influence (ZEI) must be determined through modeling (but cannot be smaller than 1⁄4 mile in its smallest horizontal dimension) - In the volume generated by the CO2 plume footprint (plus appropriate buffer) (this volume is defined as the "primary AOR"): all penetrationsbetween the base of the injection formation and the base of the USDW should be reviewed and any necessary corrective acti on should be taken before start of project.

- In the elevated pressure area but outside of the CO2 plume f ootprint (defined as the "secondary AOR"), all current penetrations through the primary seal and the injection formation should be review ed. However the applicant should be allowed to perform corrective action in a pseudo-concentric phased manner ahead of and according to the development of the pressure plume.

- Secondary AOR/zone of elevated pressure cannot be computed independently of other injection projects in the vicinit y. The impact of other sequestration projects must be included in determining injection rate / period of injection.

- Primary and secondary AOR must be peri odically reviewed to ensure that modeling predictions are met. If they are not, the primary and secondary AOR should be revisited. The operator should keep track of any new penetration in the primary AOR volume and secondary AOR (for example, for oil and gas industry).

"Primary AOR" - Why "Volume of Review"

Because CO2 is strongly buoyant, it is not sufficient only to investigate penetrations in the injection formati on and primary seal. The whole volume potentially contacted by the CO2 plume should be reviewed. The review and

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### corrective actions should be performed be fore the start of injection because there is no stopping the CO2 migration once started. The greatest degree of effort should be on the deeper wells in the injection zone and primary containment then on the secondary containment and seal (if any) and then on shallower wells but as many as possibl e of the shallower wells should be compiled too.

Delayed Corrective Action for "Secondary AOR"

A simple time-dependent secondary AOR that expands as the volume of injection increases and the CO2 migrates is not acceptable. The secondary AOR should be agreed upon and reviewed before injecti on starts but corrective action can be somewhat delayed. The secondary AOR consis ts of only the injection formation and seal as used in the current rules becauseonly brine/formation water leakage is an issue in the elevated pressure area. The likely presence of a large elevated pressure area does not make realistic imposing corrective action on all wells before the start of a project. There is no need to provide corrective action to wells before the pressuresignificantly rises. If another problem (e.g., CO2 leakage) occurs earlier at another location and injection stops , pressure will not keep rising and will drop. In addition, delaying corrective action will allow taking advantage of technical improvements that will undoubtedly occur in the next decades.

Individual Response: EPA agrees that the AoR for a GS project should incorporate both the CO2 plume and the pressure front , and clarifies that the requirements for AoR delineation in the final rule incorporate both the CO2 plume and associated pressure front. This area would be modeled based on anticipated CO2 volumes to be injected and other site-specific information that would impact pressure changes in the subsu rface. EPA agrees that both of these should be taken into account in determining corrective action needs and deve loping a testing and monitoring plan, and that the requirement to delineate the AoR at §146.84(c) addresses the potential risks raised by the commenters. EPA believes that the final GS requirements for delineating the AoR provide sufficient protection to USDWs, without introducing an overly complex regulatory process.

EPA acknowledges the commenter’s support of phase d corrective action and agrees that phased corrective action may provide many benefits to a project including, but not limited to, spreading the burden of cost, avoiding delays in project start-up, allowing for use of future, improved corrective action techniques and addressing unanticipated changes in the movement of the CO2 plume or pressure front. EPA believes that the phased corrective action approach is appropriate for GS projects, and retained it at 146.84(b)(2)(iv) in the final GS regulation.

Letter ID: 0142 Comment ID: 22552 Letter Lines: 572 to 588

Comment Code: 3330 2.2.1.3 Applicability /adequacy of computational models (seeking comment)

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### Comment: Modeling is Needed: When considering tens of miles, trying to use conservatively the analyti cal solution as provided in 40 CFR §146.06 will likely generate unrealistically large AORs. Parameters such as formation thickness and heterogeneity, storativity and permeability values will likely vary in the zone of elevated pressure suggesting that model results should be accepted as valid.

How to define the edge of the AOR? If the CO2 plume is relatively easy to define in terms of modeling, this is much less true for the pressure plume. Limits to the secondary AOR can be defined more or less as it is currently done by the contour line of the additional pre ssure that would push the injection formation brine beyond some elevation thre shold (for example, 100 ft below the base of the USDW). Time-varying area where corrective action needs to take place as injection progresses can be defined in a similar fashion.

AORs can be initially defined solely on the basis of modeling. However, NGWA strongly supports that a satisfactory match between prediction and actual field measurements needs to be assessed as the project progresses.

Individual Response: EPA agrees that monitoring and operati onal data should be used to verify that the CO2 plume and pressure front are moving as predicted in AoR calculation models (146.84(e)). EPA believes that th e requirements for periodic Ao R reevaluation can also help address uncertainties inherent in predictive modeling and al low for refinement of model predictions based on monitoring, operational, and other site-specific data.

Letter ID: 0142 Comment ID: 22553 Letter Lines: 591 to 676

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language Comment Code: 4600 2.6 Proposed Plume and Pressure Front Monitoring Requirements (40 CFR 146.90)

Comment: Fluid Movement

The UIC regulations have, from the beginning, included two standards of prohibition of fluid movement that may be appropriate for geological sequestration of carbon dioxide. The flui d movement requirement for Class I injection wells states:

The well must be constructed, operate d, maintained, and plugged such that injection activities will not cau se movement of any contaminant into a USDW

The fluid movement requirement for Class V injection wells states:

No owner or operator shall construct, operate, maintain, convert, plug, abandon, or conduct any other injection activity in a manner that allows the movement of fluid containing any contaminant into underground

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### sources of drinking water, if the pres ence of that contaminant may cause a violation of any primary drinking water regulation under 40 CFR part 142 or may otherwise adversely aff ect the health of persons. The applicant for a permit shall have the burden of showing that the requirements of this paragraph are met.

The NGWA recommendation for carbon seque stration well permitting includes an experimental phase for each location that will be used for geological sequestration of carbon dioxide. Wells c onstructed during the experimental phase at each location will have extensive testing requirements and exploratory objectives that will not be needed during the operational phase. It will not be necessary or practical to apply the same standard of fluid movement to both the experimental phase and the operational phase of carbon sequestration.

The NGWA recommendations also include early warning monitoring to detect movement of fluids containing carbon dioxi de or contaminants before the fluids reach a USDW. The advantage of early warning monitoring is in the ability to detect fluid movement before a drinking water supply is impacted. The identification of a geologicalunit that can serve as s econdary containment for the injected fluid is addressed in the NGWA recommendations for geologic characterization. It is reco mmended that early warning monitoring be included in the requirements for operation of Cl ass V experimental carbon sequestration wells, as well as Class VI operati onal carbon sequestration wells. The requirement for early warning monitoring should include authorization for action by the regulatory agency when fluid movement is detected by the early warning monitoring system.

Class V Experimental Carbon Sequestrati on Well: During the experimental phase of injection, while the well is permitted as a Class V well, the following fluid movement criterion should apply:

No owner or operator shall construct, operate, maintain, convert, plug, abandon, or conduct any other injection activity in a manner that allows the movement of fluid containing car bon dioxide or any contaminant into underground sources of drinking water, if the presence of carbon dioxide or that contaminant may cause a viol ation of any primary drinking water regulation under 40 CFR part 142 or may otherwise adversely affect the health of persons. The applicant for a permit shall have the burden of showing that the requirements of this paragraph are met.

Class VI Operational Carbon Sequestration Well: During the operational phase of injection, while the well is permitted asa Class VI well, the following fluid movement criterion should apply:

No owner or operator shall construct, operate, maintain, convert, plug, abandon, or conduct any other injection activity in a manner that allows

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### the movement of fluid containing car bon dioxide or any contaminant into underground sources of drinking water, if the presence of carbon dioxide or that contaminant may cause a viol ation of any primary drinking water regulation under 40 CFR part 142 or may otherwise adversely affect the health of persons. Additionally, no owner or operator shall construct, operate, maintain, convert, plug, abandon, or conduct any other injection activity in a manner that allows the movement of carbon dioxide in gaseous phase to land surface, nor limit the extraction of drinking water from a underground sources of drinking water by reduction of porosity or changes in pH or water quality due to geochemical reactions, or by causing a buildup of ga s in the underground sources of drinking water. The applicant for a permit shall have the burden of showing that the requirements of this paragraph are met.

If any water quality monitoring of an underground source of drinking water indicates the movement of any contaminant into the underground source of drinking water, or a violation of any part of the preceding paragraph, except as authorized under part 146, the Director shall publish a notice in newspapers of general circulation in whose service area the fluid movement was detecte d. If a meritorious request is submitted by the public, the Director shall prescribe such additional requirements for construction, corrective action, operation, monitoring, or reporting (including closure of the injection well) as are necessary to prevent such movement.

Individual Response: EPA does not agree that each GS site must first be permitted as an experimental Class V well before being authorized to operate a full-scale Class VI well. Following the promulgation of the final rule, EPA will allow the use of Class V experimental technology permits only for experimental purposes; i.e., to test new, unproven technologies. EPA does not consider it appropriate to permit CO2 inj ection wells that are testing the injectivity or appropriateness of an individual formation (e.g., as a prelude to a commercial-scale operation) as Class V experimental technology wells. Such wellsshould be permitted as Class VI wells.

The final rule at §146.90(g) requires owners or op erators 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.

EPA believes that pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume. Monitoring can also identify needed remedial actions, provideinputs for AoR reevaluation modeling, evaluate predictions of plume movement, and target additional geochemical and surface monitoring needs. Knowledge of the location of the CO2 plume and the associated pressure front will also 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

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### may be endangered.

In addition to monitoring to track the movement of the CO2 plume and pressure front, EPA believes that monitoring above the confining layer is an importantpart of a rigorous monitoring program and can help detect potential breaches of the confining zone. Such monitoring can provide an early warning that the plume or other substances may be approaching a USDW. The final rule, at §146.90(d), requires periodic monitoring of the ground water quality and geochemical changes above the confining zone(s). Monitoring in additional formations, e.g., the injection zone, may also be necessary, and if the Director believes such monitoring is warranted he/she has the authority to require that it be included in the testing and monitoring plan. EPA adds that the baseline geochemical data required at §146.82(a)(6) will helpowners or operators interpret the results of this monitoring.

EPA acknowledges that there are potential risks associated with GS, including the potential for leakage of CO2 or other substances into USDW s. However, the purpose of the UIC regulations including the Class VI requirements is to protect USDWs from endangerment. In order to protect USDWs from endangerment §144.12 prohibits the movement of fluid into USDWs. Consistent with §144.12, EPA is finalizing the Class VI requirements in order to ensure that USDWs are protected by minimizing and mitigating potential/identified risks through proper site characterization, well constructi on, operation, monitoring, post-inje ction site care, and site closure. The GS rule accomplishes this through requirements tailored to address the unique nature of GS, including the larg e volumes of CO2 injected, its buoyancy and potential corrosivity in the presence of water, and impurities in the CO2 stream. Furthermore, if any water quality monitoring of a USDW indicates the movement of any contaminant into the underground source of drinking water, except as authorized under part §146, the Director shall prescribe such additional requirements for construction, corre ctive action, operation, monitoring, or reporting (including closure of the injection well) as are necessary to prevent such movement.

Letter ID: 0142 Comment ID: 22554 Letter Lines: 679 to 690

Comment Code: 3820 2.3.1 Well construction procedures

Comment: Well Construction, Testing, and Closure

Wells will be an integral part of a CO2 sequestration operation. Wells will be used to inject CO2 into the target sequestration formation and monitor the sequestration and other formations that could be affected by the injection. Because wells represent a potential conduit for CO2 or formation fluids to move out of formation and possibly to the surface great care must be taken to construct wells such that they will not l eak, monitor them to ensure that they do not start leaking, and close them to ensure that they do not become a leakage risk later. Wells must demonstrate the ability to c ontain both injected and native fluids without allowing significant movement between formations or to the surface.

Individual Response: EPA agrees and believes that appropriately designed and constructed

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### wells are necessary to prevent endangerment to USDWs and maintain integrity of the well throughout the lifetime of a GS project. Thisis the foundation of the requirements for construction and pre-operational testing of Class VI wells at §§146.86 and 146.87.

Letter ID: 0142 Comment ID: 22555 Letter Lines: 692 to 701

Comment Code: 3820 2.3.1 Well construction procedures Comment Code: 4600 2.6 Proposed Plume and Pressure Front Monitoring Requirements (40 CFR 146.90)

Comment: Construction

Regardless of the site specific component the new wells will need to be designed to meet the overarching goals for all projects. The goals for and injection well will be to inject CO2 and to keepfluid from moving along the wellbore between formations or to the surface. The goals for a monitoring well are to monitor the injection or other formations and also to keep fluids from moving along the wellbore. To accomplish these goals the design of the well needs to address site-specific, objective-specific(monitoring or injection), and fluidspecific considerations. All injection we lls should be cased and cemented to

Individual Response: EPA agrees that appropriate injection well construction will depend on site-specific factors. In determining whether to grant a Class VI permit, the Director will evaluate the appropriateness of the proposed injection wellconstruction based on site-specific information about the injection project, including injection pressures, injection and confining zone lithology, and information about the carbon dioxide stream as provided in §146.86(b)(1). In addition to the flexibility given to the owner and operator, Director's discretion is specifically provided in §146.86(b)(1) for casing and cementing and §146.86(c)(2 and 3) for tubing and packer location and type.

EPA believes that monitoring using wells in the in jection 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. To mitigate the risk of fluid movement, EPA requires owners and operators tosubmit a testing and monitoring plan that describes how the owner or operator plans tosite and construct monitoring wells.

EPA has developed a brief technical paper on construction of monitoring we lls that perforate the confining zone; this paper can be found in the rulemaking docket. EPA is developing guidance on well construction that will include recommendations for monitoring well construction. The guidance will be available on EPA’s website at http://water.epa.gov/type/groundwater /uic/wells_sequestration.cfm.

Letter ID: 0142 Comment ID: 22556 Letter Lines: 701 to 716 ; 1213 to 1214 ; 1280 to 1282

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

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

Comment: specific considerations. All injection we lls should be cased and cemented to stop fluid movement between formations . A surface casing should be installed and set below the lowermost USDW above the injection zone and cemented along its entire length. It is important when considering the he ight of the cement sheath behind the long-string casing toconsider the overall "des ign" of the injection and monitoring zones. Because, it is idealto have a secondary caprock it will be imperative to cement the well, at a minimum, from the injection zone to a level above the secondary confining unit. If the borehole through the secondary caprock is left uncemented the effectiveness of the secondary caprock will be greatly reduced. Furthermore, it may beadvisable to cement the casing along the entire length to protect the casing from degradation due to anodic dissolution [Anstice et al., 2005] or exposure to corrosive formation fluids. If the casing is not cemented along its entire length it may be necessary to use cathodic protection, depending on the site, tokeep the casing from degrading. Watson and Bachu, [2007] found that about 81% of wells in their study area that had surface casing vent flows (leaks) had them above the top cemented section.

Anstice, D.J., Page, C.L., and Page, M.M., 2005, "The pore solution phase of carbonated cement pastes," Cement and Concrete Research, Vol. 35, pp. 377-383.

Watson, T.L. and Bachu, S., "Evaluation of the potential for gas and CO2 leakage along wellbores," paper SPE 106817 presented at the 2007 E&P Environmental and Safety Conference, Galveston, TX, March 5-7, 2007.

Individual Response: EPA agrees that the casing should be cemented along its entire length. The final GS rule requires, at §146.86(b)(2), thatthe surface casing must extend through the base of the lowermost USDW and be cemented to the surface, and that at least one long string casing must be cemented to the surface in one or more stages at §146.86(b)(3). EPA believes that these requirements are an important component of construction that will protect USDWs from endangerment.

Cathodic protection can also be used to contro l corrosion, even when the long-string casing is fully cemented. Though not required for all wells,additional techniques like cathodic protection may be required by the Director if he/she determines they are necessary at a specific location to ensure protection of USDWs. EPA adds that the Director also has the authority to require a casing inspection log, as specifiedat §146.89(d), which can be used to determine the presence or absence of corrosion of the long-string casing and can give early warning of casing problems with corrosion.

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.

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### Letter ID: 0142 Comment ID: 22557 Letter Lines: 718 to 732

Comment Code: 3820 2.3.1 Well construction procedures Comment Code: 4600 2.6 Proposed Plume and Pressure Front Monitoring Requirements (40 CFR 146.90)

Comment: The materials used for construction need to be compatible with the injected fluid and compatible with the formation fluids. Both injection and monitoring wells should be constructed to the same material standard unless there is an objective-specific reason not to, because they may both be subjected to similar aggressive down-hole conditions. In order to insure thatproper wellbore construction materials are always selected a standard should be adopted that specifies wellbore materials should resist the expected downhol e conditions to a sufficient degree such that degradati on will not lead to leakage. The thicknesses of the casing and tubing must besufficient to handle the pressure associated with the injected CO2. Although materials are an important aspect in well construction centralization of the cas ing is also important for insuring the cement job is successful. It is very important that the casing is centralized over the entirecemented section. This will provide the best condition to achieve full radial coverage of the cement between the casing and the formation.

Individual Response: EPA agrees that well materials need to be compatible with injected fluids and formation fluids. The GS rule at §146.86(b)(1) re quires that all injection well materials be compatible with fluids with which the materials may be expected to come into contact. Further, the rule, at §146.82(a)(7), requires owners or operators to submit information on planned injection pressures, that the Director will use in evaluating the proposed casing, tubing, and packer design. EPA adds that, indetermining the suitability of well materials and the design of the well, the Director must consider various aspects of the injection project, including injection pressure, external pressure, internal pressureand axial loading in §146.86(b)(1)(ii), corrosiveness of the CO2 stream and formati on fluids in §146.86(b)(1)(v).

EPA requires under §146.90 that owners or operators submit proposed testing and monitoring plans to the Director at the time of the permit application. The operator will need to demonstrate that the monitoring wells will be constructed and operated in a manner that will be sufficiently protective of USDWs from endangerment. Monitoring wells will differ from injection wells in their purpose, casing sizes, and depth, although their casing and cementing will likely be similar. Unlike injection wells, monitoring we lls will not need to be built to withstand CO2 injection, but, nonetheless, will need to be built with material s and a design that ensure integrity of the well throughout its planned life so that the well does not serve as a conduit for movement of the CO2 stream or formation fluids. As described above, EPA is developing guidance on testing and monitoring at GS sites, which will discuss monitoring well construction. The guidance will be available on EPA's web site, at http://water.epa.gov/type/groundwater /uic/wells_sequestration.cfm.

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### Letter ID: 0142 Comment ID: 22558 Letter Lines: 734 to 739

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

Comment: For both types of wells, it is important that regulations require that internal safety measures are installed in the well. This will help ensure that wells do not allow leakage out of the well through the wellbore in the case of an accident or other event. Down-hole shuto ff equipment needs to be required. The shutoff equipment needs to be downhol e to avoid leakage if the surface components of the well are damaged.

Individual Response: After evaluating the risks and benefits of down-hole shut-off systems and considering additional research, EPA will not re quire automatic down-hole shut-off devices for onshore Class VI wells since it is not necessary inall cases to ensure protection of USDWs from endangerment. Instead, the final rule, at §146.88(e)(2 ), requires that owners or operators of onshore Class VI wells install automatic surface shut-off devices. The rule affords Director's discretion to mandate automatic down-hole shut -off devices in onshore situations that may warrant their use. However, the Agency believ es that offshore Class VI wells present unique construction and operational conditi ons, including isolation from shorelines and the need to construct wells through the water column and the subsurface, which may delay response time in the event of well difficulties. The rule requires, at §146.88(e)(3), that owners or operators of offshore wells within State territorial waters install automatic down-hole shut-off systems. EPA believes that these requirements at §146.88(e) ensure that proper precautions are taken to prevent subsurface fluid movement and ensure protection of USDWs.

Letter ID: 0142 Comment ID: 22559 Letter Lines: 741 to 748

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

Comment: In some areas it is likely that existing wells will be c onverted into both injection wells and monitoring wells. It seems unlikely that such wells will have been constructed to the same standard as wells purpose-built for sequestration applications. This, however, is probably not reason enough to rule them out from being used as long as they meet the same standards for protection as new wells do. This said, there should be a cutoff date so that all wells used for CO2 injection or monitoring constructed after the date are constructed to the same standard.

Individual Response: EPA agrees that converted wells should be subject to Class VI requirements. Following conversion of the project to GS, many of the unique factors of GS sites (e.g., increased reservoir pressures associated with large vo lumes of stored CO2 and the corrosivity of CO2 in the presence of water) will result in an increased risk profile and warrant the specific requirements in the final GS rule. Projects that inject CO2 for the primary purpose of long term storage will be permitted as Class VI wells and will be subject to the specific requirements in the final GS rule. The GS rule contains tailored requirements that directly address issues unique to larg e-scale CO2 injection for GS.

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### The final GS rule provides that the construction of these wells be grandfathered per §146.81(c), provided the owner or operator candemonstrate 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 clarifies that only the construction reuirements are grandfathered and that all other Class VI requirements (reporting, monitoring, mechnical integrity testing, etc.) must be met following a determination under §146.81(c).

EPA does not plan to institute a "cut off" date for this requirement since conversion is a sitespecific decision that may take place at different times then other conversions and it cannot be predicted with certainty when all eligible ER fiel ds in the US will have been transitioned for GS. EPA encourages owners or operators and Directors to coordinate on re-permitted wells to ensure that all wells used for GS are constructed and operated in a manner that protects USDWs from endangerment.

Letter ID: 0142 Comment ID: 22560 Letter Lines: 750 to 754

Comment Code: 3826 2.3.1.3 Packer requirements (seeking comment)

Comment: Injection wells should be designed to inject through tubing. Tubing and packer allow for monitoring pressure in the annulus between the tubing and casing to help identify any leaks. Furthermore the tubing can be replaced relatively easily in the case any damage to the t ubing is identified or to change the diameter of the tubing.

Individual Response: EPA acknowledges the comment and agrees that the use of tubing and packer in accordance with §146.86(c) will offer the best multiple-barrier protection of USDWs from endangerment. This requirement is retained inthe final GS rule. 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 constr uction 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: 0142 Comment ID: 22561 Letter Lines: 757 to 785

Comment Code: 4500 2.5 Proposed Mechanical Integrity Testing (MIT) Requirements (40 CFR 146.89)

Comment: Wellbore Integrity Monitoring and Measurement

The integrity of monitoring and injection wells must be established and monitored. However, the type of integrity measurement(s) should be decided upon based on the construction of the well, the well materials, and the effectiveness of the monitoring techniques. Wells that are not cemented from total depth (TD) to the surface should be subject to more inte grity monitoring than those that

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### are cemented from TD to surface because the path behind the uncemented section of casing could act as a fast path for fluids to move between formations. No single specific monitoring technique should be required and it is expected that multiple techniques will be needed. The deviation of all wells should be measured to ensure that the geometry of the well is understood to identify areas that may require special attention, like poorly centralized sections, to ensure that they are carefully characterized.

A requirement will be needed to ensure that the integrity and quality of the casing and cement job are initially and remain sufficient to prevent fluid movement along the wellbore. Because the cement is behind the casing, it will be necessary to use some type of logging tool to make the measurement. The selection of logging tools should be based on proven performance. The prescription of a particular tool may force the use of a technology in the future that is not the best available for the job. This said, the standard for selection of the tool can bespecified and should take into account the geometry of a wellbore. Because wells are cylindri cal, the integrity and location of the cement must be verified using technol ogy capable of radially evaluating and mapping the cement, identifying the location of channels or contaminated cement, and validating the casing-cement and cement-formation bonds, thus providing a 360° map of the cement and any potential de fects for the entire length of the cemented casing.

Individual Response: EPA believes that the MITs describe d in the rule at §146.89 are effective methods and have been used successfully by injection well operators for decades and provide an important early warning of potential problems in the injection we ll system. EPA agrees with the commenter that flexibility to choos e appropriate MITs is important, and the GS rule affords this flexibility by requiring the owner or operator to prepare and gain approval for a project-specific testing and monitoring plan that includes MITs, per §146.90. Owners or operators should develop a plan that is appropriate to the well’s design and construction; the Director will evaluate the plan based on construction plans submitted with the permit application.

EPA clarifies that the regulations allow the Dire ctor to require additional methods or, with the Administrator's approval, to approve the use of alternative MIT methods based on specific information about the site or the well at §146.89(e). For additional information, please see the discussion of MITs in the final rule preamble.

EPA agrees with the commenter that the integrity and location of the cement must be verified using technology capable of radially evaluating and mapping the cement. For this reason, owners or operators must, during construction, perform a cement bond and variable density log to evaluate cement quality radially, and a temperature log after the casing is set and cemented (146.87(a)(2)(ii)).

In addition, EPA is using an adaptive approach to regulating GS. The Ag ency plans to collect and review data every six years on GS projects to determine whether the appropriate amount and

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### types of information and appropriate documentation are being collected, and to determine if modifications to the requirements are appropriate or necessary.

Letter ID: 0142 Comment ID: 22562 Letter Lines: 787 to 797

Comment Code: 4543 2.5.2.1 MIT procedures and methodsfor GS (seeking comment)

Comment: Another method of ensuring the mechanical integrity of the well is the use of mechanical integrity tests, MITs. MITs, that raise the pressure in the well, like the standard annulus pre ssure test, are often used to measure the internal integrity. It is possible that the increase in pressure in the wellbore associated with some MITs could damage the interface between the casing and the cement possibly creating a leakage pathway. The use of these MITs on CO2 injection wells should be studied before itis made a requirement. MITs such as radioactive tracer surveys, RATS, or other alternative methods with comparable results, may be more appropriate for measuring internal integrity. Furthermore, RATS and temperature logging may also be an effective technique for identifying external wellbore leakage pathways.

Individual Response: EPA believes that the MITs describe d in §146.89(c) of the rule (e.g., an approved tracer log or temperature or noise logs) are effective methods to demonstrate external MI to detect leakage along the wellbore, provide an important early warning of potential problems in the injection well system, and represent standard techniques that have been used successfully by the drilling industry and the UIC program for many years.

EPA disagrees that MITs would damage an in jection well. Routine MITs are designed to measure the sufficiency of the construction of an injection well and to detect subsequent well construction, material, and operati onal problems within the well sy stem before leaks occur. They are currently used effectively within the UIC program to ensure MI in other classes of injection wells. Damage to a well as a result of a routine, required MIT is unlikely and would be an indication of a sub-standard well or a well withsome type of construction and/or operational defect. Regarding the use of RATS, EPA adds that these are used only in specific circumstances, such as in the immediate vicinity of the we ll perforations/ injecti on zone. The regulations provide the Director flexibilityat §146.89(e) to approve the us e of alternative MIT methods. MITs are a means of measuring the adequacy of the construction of an injection well and a way to detect problems within the well system beforeleaks occur. For additional information, please see the discussion of MITs in the final rule preamble.

Regarding the commenter's recommendation that EPA study MITs on GS wells, EPA clarifies that it plans to collect and revi ew data every six years on early 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.

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### Letter ID: 0142 Comment ID: 22563 Letter Lines: 799 to 801

Comment Code: 4546 2.5.2.2 MIT frequency (seeking comment)

Comment: The integrity of the well should be measured on a regular basis such that timelapse comparisons are possible to see if there are changes within the wellbore over time that could lead to leakage situations.

Individual Response: EPA agrees that periodic external mechanical integrity testing is justifiable for the protection of USDWs from endangerment, given the unique nature of CO2 GS relative to other injection operations, including the potential for corrosion of the injection well components (steel casing and cement) and the buoyant nature of the injected CO2 and is finalizing regulations that require annual external MITs at §146.89(c).

Letter ID: 0142 Comment ID: 22564 Letter Lines: 803 to 815

Comment Code: 5200 2.8.2 Post injection site care (seeking comment) (40 CFR 146.93)

Comment: Closure

When all injection operations are finished the site will be closed and the post closure period will begin. At this juncturethe injection wells will be plugged and abandoned. The plugging needs to be done such that the CO2 and formation fluids cannot use the wellbore as a conduit when it is complete. No wells should be abandoned until there has been a final round of measurements to verify the integrity of the well in case remedialaction is needed prior to plugging. Wells plugged prior to the site closure phase should be plugged and abandoned following the same procedures as those in the closure phase. Any requirements need to ensure that all wells are properly plugged and abandone d using material and methods that will allow the well to remain safe and not become an avenue for leakage.

Individual Response: EPA agrees that Class VI injection wells must be plugged in a manner that protects USDWs from endangerment, and be lieves that the final rule requirements address the commenter’s concerns. EPA requires that, to protect human health as it relates to endangered USDWs, injection wells be plugged in a manner toensure that the well will not serve as a conduit for future fluid movement into USDWs. In the case of GS wells , the plugging materials must be compatible with CO2, as specified at 146 .92(b). EPA clarifies that the final GS rule at 146.92(a) requires owners or operatorsto perform a final external mechanical integrity test prior to the well plugging. These requirements apply whether the well is plugged upon cessation of injection or at the time of site closure.

Letter ID: 0142 Comment ID: 22565 Letter Lines: 818 to 856

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

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### CFR 146.90)

Comment: Monitoring, Measurement, and Verification

Measurement, monitoring, and verificati on (MMV) will be a key task for all geologic carbon sequestration operations. MMV should be looked at as a continuation of the measurements that were collected during the characterization and construction phases as described inthe sections on well construction, testing, and closure and geologic characterization. Characterization and construction measurements will provide the baseline for comparison during the injection and post injection phases of the sequestration project. The data collected during the MMV will be used to in sure the site is not leaking or for the identification and remedi ation of leaks. The data will also be used to calibrate and reduce uncertainty in models of the site.

During the operational injection phase of a CCS project, MMV can be broken into operational monitoring, which is the monitoring of the injected CO2, and environmental monitoring, which is the monitoring of the subsurface including the sequestered CO2 and the a ssociated pressure front.

Operational MMV includes; monitoring the volume, flow rate, and composition of CO2 that is injected. The injection pre ssure must be low enough that injection does not propagate new fractures and does not open existing faults or fractures for flow through the caprock or damagethe containment properties of the injection well. The operational monitoring will also have to monitor the injection and monitoring wells to ensurethey are functioning properly and not allowing any leakage. The integrity of the injection well must be monitored internally and externally to ensure that there is no degradation that could allow CO2 to leave the target formati on. Well integrity monitoring through the use of logs, annulus pressure monitoring, and mechanical integrity tests is covered in detail in the section on well construction, monitoring and abandonment.

Environmental MMV needs to be implemented tocollect data from the four or more geologic formations that comprise the subsurface site: the storage formation, the primary cap rock, the monitoring formation, and the secondary cap rock. MMV must also provide information on shallow formations, including the lowermost USDW, that contain drinking water, the surface and, any potential leakage pathways between the storage formation or monitoring formation and any drinking water formations or the surface (this may include additional monitoring of wells above what is required for operational monitoring).

Individual Response: EPA agrees that multi-faceted monitoring, as described by the commenter, is a key element of ensuring that US DWs are protected from endangerment. The GS rule, at §146.90, requires injectate monitoring, mechanical integrity testing, corrosion monitoring, tracking the CO2 plume and area of elevated pressure, monitoring geochemical

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### changes above the confining zone, and, at the discretion of the Director, surface air and soil gas monitoring for CO2 fluctuations, and any additional tests necessary to ensure USDW protection from endangerment. EPA also agrees with the commenter that data collected during site characterization (such as baseline geochemistry, pre-injection reservoir pressure, etc.) are appropriate to ensure that baseline informati on is available to form the basis for comparison during GS operation and post-injection. For example, the baseline geochemical information will allow the owner or operator and permitting authority to evaluate monitoring data and identify any changes in subsurface geochemistrythat may indicate fluid movement.

EPA agrees that the ground water geochemicalmonitoring outlined in §146.90(d) will maximize protection of USDWs from endangerment at GS sites. Direct geochemical sampling is an important part of a monitoring program. EPA agrees that direct monitoring for ground water quality above the confining zoneis important, and the GS rule requires this at §146.90(d). Monitoring in additional formations, e.g., the inje ction zone, may also be necessary, and if the Director believes such monitoring is warranted he/she has the authority to require that it be included in the testing and monitoring plan.

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 l ogging and testing of injection wells, MITs, injecti on 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 Geol ogic Formations" (DOE/NETL-311/081508); this manual is included in the docket for the final GS rule.

Letter ID: 0142 Comment ID: 22566 Letter Lines: 858 to 873

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

Comment: In the injection zone, monitoring must identify the location of the injected CO2 and the associated pressure front. MMV inthe monitoring zone should be geared to ensure that any vertical migrati on across the cap rock is identified. Monitoring of USDWs should be set up tolook for changes that would be associated with the presence of CO2 or CO 2-displaced brine. While some general monitoring points in all of these zones will be needed, it may be more practical to locate monitoring points or take measurements near locations identified during the characterization and potential fast-paths, such as abandoned wells, existing wells, or faults and fractures. One location that may provide the best use of monitoring resources isnear the injection well. This is the most likely location for upward fluid movement without specific knowledgeof a potential leakage pathway. Leakage could occur either through mechanical integrity failure or defects, or failure or defects of the confining units. Monitoring, in the

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### monitoring zone and lowest USDW in addition to the injection zone, provides a vertical pressure profile, measures stress on the confining units, and may detect water quality changes.

Individual Response: EPA agrees that multi-faceted monitoring is appropriate at GS sites. 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. Indire ct methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also required unless the Director determines, based on site-specific ge ology, that such methodsare not appropriate.

EPA believes that pressure monitoring in th e injection zone is necessary to track the development and movement of the pressure front and CO2 plume. Monitoring can also identify needed remedial actions, provideinputs for AoR reevaluation modeling, evaluate predictions of plume movement, and target additional geochemical and surface monitoring needs. Knowledge of the location of the CO2 plume and the associated pressure front will also assure the public that GS projects are proceeding according to plan, provide sufficient information to the owner or operator and Director, or allow for appropriate actions to address any indication that USDWs may be endangered.

EPA also believes that direct monitoring for ground water quality above the confining zone is important, and the GS rule requires this at §146.90(d). Monitoring in additional formations, e.g., the injection zone, may also be necessary, and if the Director believes such monitoring is warranted he/she has the authority to require that it be included in the testing and monitoring plan.

EPA believes that monitoring plans and methods need to be site-specific and believes that the monitoring requirements for GS s ites at §146.90 provide an appropriate level of flexibility in structuring a testing and monitoring plan that protects USDWs from endangerment.

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 l ogging and testing of injection wells, MITs, injecti on 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_se questration.cfm.

Letter ID: 0142 Comment ID: 22567 Letter Lines: 875 to 879

Comment Code: 4660 2.6.6 Geochemical monitoring

Comment: In the monitored zones, geochemical and fluid chemical information should be based on constituents identified in the characterization as likely indicators of leakage. These indicators will likely include the pH and also be identified in

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### the major and minor chemical constituents of the formation and ionic constituents of the formation-fluid.

Individual Response: While each monitoring plan must be s ite-specific based on data collected during the initial site characterization and base line geochemical monitoring, it is likely that geochemical sampling might include basic water quality parameters such as pH, specific conductivity, temperature, CO2, alkalinity, major ions, and select heavy metals. Additional parameters may be monitored based on the potential for leaching of minerals or the geochemistry of native fluids.

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 l ogging and testing of injection wells, MITs, injecti on 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_se questration.cfm.

Letter ID: 0142 Comment ID: 22568 Letter Lines: 881 to 901 ; 1224 to 1226 ; 1246 to 1248 ; 1284 to 1287

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

Comment: The methods used for monitoring on projects to date have included time-lapse seismic, passive seismic, pressure logging, temperature logging, neutron saturation logging, fluid sampling, air sampling [IPCC, 2005]. While it is probably not appropriate to specify the suite of MMV tools to be used at every site, because not all tools will work at all sites, it is important to emphasize that multiple MMV technologies will be re quired at every site in order to completely monitor and collect the necessarydata to verify that the site is operating within the bounds of its permit. Although it seems unreasonable to specify all MMV technologies, it does seem reasonable to specify that monitoring wells be installed to collect the necessary fluid samples, pH, resistivity, and pressure data. Also, although seismic monitoring may not work everywhere, in locations where it is expected to work it should be incor porated into the monitoring scheme. Seismic monitoring for CO2 plume location has been successfully employed in early projects including Sliepner storage project, Weyburn storage project, and Frio brine project [IPCC, 2005, Wilson and Monea, 2005, Daley et al., 2007]. The data collected from monitoring should be used to update and verify the site’s performance and risk models.

In addition, to aid in selecting other MMV technologies, the International Energy Agency has developed a comprehensive database that can be accessed at: http://www.co2captureandstorage.info/co2tool_v2.1beta/index.php

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### Daley, T.M., Solbau, R.D., Ajo-Franklin, J.B., and Benson, S.M., 2007, "Continuous active-source se ismic monitoring of CO2 in a brine aquifer," Geophysics, Vol. 72, No. 5, pp. A57-A61.

Intergovernmental Panel on Climate Change, 2005, IPCC special report on carbon capture and storage, United Nations Framework Convention on Climate Change, ISBN 92-9169-119-4.

Wilson, M. and Monea, M., 2005, IEA GHG We yburn Monitoring and Storage Project, Summary Report, 2000-2004, Petroleum Techno logy Research Center, Regina SK, Canada, Proceedings of the 7th International Conference on Greenhouse Gas Control Technologies (GHGT-7), Vol. III, September 5-9, Vancouver, Canada

Individual Response: EPA clarifies that the specifics of monitoring, including the number of monitoring wells, must be described in the site-specific testing and monitoring plan, which must be approved by the Director. EP A 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 technologie s 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 pressurefront, 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: 0142 Comment ID: 22569 Letter Lines: 903 to 910 ; 1253 to 1257

Comment Code: 4490 2.4.5 Use of tracers and potential impact on human health or ecosystems (seeking comment) Comment Code: 4670 2.6.7 Surface air monitoring and/or soil gas monitoring (seeking comment)

Comment: Although surface monitoring may be needed from a community outreach and environmental safety point of view, it isimportant to note that by the time any leakage is detected at the surface it will have already passed by and possibly impacted underground drinking waters. Proj ects like the Frio brine project [McCallum et al, 2005] have incorporated tracers as a way to identify CO2 leakage. The use of non-isotopic tracers, tracers other than C13, C14, and O18 that occur naturally in CO2, should be studied very carefully for unintended environmental effects prior to implementation.

McCallum, S.D., Riestenberg, D.E., Cole, D.R., Freifeld, B.M ., Trautz, R.C., Havorka, S.D., and Phelps, T.J., 2005, "Monitoring geologically sequestered CO2 during the Frio brine pilot test using perfluorocarbon tracers," Proceedings of the 4th Annual Conference on Carbon Ca pture and Sequestration, May 2-5, 2005, Monitor and Exchange Publicationsand Forum, Washington, D.C.

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### Individual Response: EPA clarifies that subsurface geochemi cal and pressure monitoring in the subsurface formations are the first line of monitoring that would allow detection of potential endangerment to USDWs from GS activities (this is required at al l GS sites, as described at §146.90(d)). The Agency also believes that surf ace air and soil gas monitoring, when coupled with subsurface monitoring, may be appropriateat some GS projects to ensure USDW protection. EPA acknowledges that surface air and soil gas monitoring may not be suitable in all settings as a method to ensure USDW protec tion. However, EPA does not believe that this should entirely preclude their use. 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.

If surface monitoring were the only monitoring method employed to ensure USDW protection, direct correlation of CO2 at the surface with CO 2 in the subsurface might be difficult; however, when combined with information gathered through other monitoring techniques required of GS well owners and operators (e.g., monitoring wells , geophysical techniques ), air and soil gas monitoring may provide valuable data on the magnitude and location of a leak. The CO2 itself may serve as a tracer in the form of stable is otopes of carbon. For exam ple, anthropogenic CO2 is depleted in 13C compared to naturally occurring CO2.

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 identif ying 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 believes that, in some circumstances, tracers can be an important component of a multifaceted approach to monitoring GS projects. However, the Agency recognizes that tracers may not be appropriate in all GS projects. For this reason, EPA does not require the use of tracers at all GS sites; however, the Director has discretion to requiretheir use if he/she determines that the use of tracers could improve monitoring of the s ite and enhance USDW protection from endangerment.

Letter ID: 0142 Comment ID: 22570 Letter Lines: 912 to 916

Comment Code: 5100 2.8.1 Injection well plugging activities (seeking comment) (40 CFR 146.92)

Comment: Once injection ceases permanently, the operational portion of MMV can also cease. This period, called the closure period, is the time in which the operator will plug and abandon all wells that will not be used for further monitoring. Environmental MMV operations should continue throughout this period using the same suite of technique s as in the operational phase.

Individual Response: EPA clarifies that, following plugging of the injection well and until site closure is authorized, owners or operators of GS wells must perform monitoring and provide post-injection site care as specified in the post-injection site care and site cl osure plan for at least

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### 50 years or for the duration of the alternative timeframe approved by the Director pursuant to requirements in §146.93(c), unless the owner or operator can make a demonstration earlier that the geologic sequestration project no longer poses a risk of endangerment to USDWs.

Letter ID: 0142 Comment ID: 22571 Letter Lines: 918 to 935

Comment Code: 3530 2.2.3.1 AoR reevaluation fre quency (seeking comment) Comment Code: 4650 2.6.5 CO2 plume and pressure front tracking (seeking comment)

Comment: MMV should be conducted hand-in-hand with modeling over the entire period that MMV is occurring, with each new round of measurements being incorporated into a new iteration of the appropriate site models. An iterative measurement-modeling approach will allow for the best understanding of the shape and size of the AoR. It will also help identify areas of uncertainty in the model that may be reduced with changes in the MMV plan. Changes identified in the size of the AoR and for risk of leakage will help ensure that MMVis carried out at the right frequency and in the right locations. The timing of the MMV operations should be flexible and adjustable based on the performance of the site and the site models. It is likely that the site data from early in the operation will probably be more valuable than data from later in the op eration for assessing the performance of the site and identifying and reducing uncertainties. MMV operations that are not continuous should be conducted morefrequently at the start of the operational phase and then be allowed to become less frequent if the site is performing safely and in concert with the model predictions. The initial, more frequent monitoring should be specified inthe permit as an experimental phase of the injection project. The continuati on of injection should be contingent upon successful containment of the injected CO2 during the experimental phase.

Individual Response: EPA agrees with commenters on the im portance of monitoring at GS sites and emphasizes that monitoring of injection activities will be an important component of every GS project. Monitoring associated with injecti on wells and the movement of the CO2 plume is necessary to verify that the injectate is confined in the target formations and does not endanger USDWs.

EPA agrees that monitoring data should be used to review model assumptions, verify computational model projections, and, when nece ssary, provide input for model refinements. As data are collected at an injection site, model parameters can be adjusted to match observations (i.e., for model calibration), which in turn improve s the predictive capability of the model. As a GS project proceeds, both monitoring and modeling will evolve, with monitoring results supporting effective AoR reevaluations and leading to improved model predictions.

As described above, EPA does not agree that each GS site should have to be permitted as a Class V experimental technology well beforebeing authorized to operate as a full-scale Class VI well. EPA does not consider it appropriate to permit CO2 injection wells that are testing the injectivity or appropriateness of an individual formation (e.g., as a prelude to a commercial-scale operation) as Class V experimental technology wells. Such wells should be permitted as Class VI wells.

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### EPA clarifies that some monitoring frequenc ies are specified in §146.90; others will be established in the monitoring and testing plansubmitted with the permit application under §146.90. The Director may require changes in the frequencies when the plan is updated, as is required at least every 5 years (or when there are changes to the fac ility or at the request of the Director).

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 l ogging and testing of injection wells, MITs, injecti on 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_se questration.cfm.

Letter ID: 0142 Comment ID: 22572 Letter Lines: 937 to 958

Comment Code: 4650 2.6.5 CO2 plume and pressure front tracking (seeking comment) Comment Code: 5460 2.9.2 Comments on transfer of lia bility for long-term care

Comment: As the pressure in the injection zone starts to stabilize it may be possible to lengthen the period between measurements if the reservoir is performing as expected based on the calibrated site models. When the location of the CO2 either stops changing or can be predicte d and validated against measurements over multiple measurement cycles, the ownership of the site and the responsibility for future MMV, if deemed necessary, may be transferred from the operator to the government, starting the post-closure phase. If the site is not behaving as expected, an iterative MMV- modeling approach will help identify areas of uncertainty that canbe reduced by changes in the MMV plan to collect more or different data to determine the site’s performance.

Regulations for the operational phase need to ensure that a licensed Carbon Capture and Storage (CCS) site is op erated safely and should allow for flexibility in the monitoring schedule ba sed on the performance of the site and site models. A site that is performing well probably require s less frequent monitoring than one that is not performing well. A long-term match between MMV data and site modeling results probably indicates a good understanding of the site and should be one of the criteria us ed to decide when the custodianship of the site should be transferred from the operator to the government. It is possible that iterative MMV and modeling will show that the AoR changes over time. The idea of a variable AoR should be included and accepted in any regulations. The results of the MMV and modeling including the integrity of the

Individual Response: EPA clarifies that once injection is co mplete, the owner or operator must monitor as specified in the post-injection site care and site closure plan for at least 50 years (the

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### Director may require longer if necessary to ensure USDW protection) or for the duration of the alternative timeframe approved by the Director pursuant to the requirements at §146.93(b), unless the owner or operator can make a demonstration earlier that the geologic sequestration project no longer poses a risk of endangerment to USDWs.

As described above, EPA agrees that monitoring data should be used to review model assumptions, verify computational model projections, and, when necessary, provide input for model refinements. As data are collected at an in jection site, model parameters can be adjusted to match observations (i.e., for model calibration or), which in turn improves the predictive capability of the model. As a GS project proceeds, both monitoring and modeling will evolve, with monitoring results supporting effective AoR reevaluations and leading to improved model predictions.

EPA agrees with commenters and believes thatflexibility is important in developing and implementing a monitoring plan that is appropriately tailored for a specif ic GS site. The purpose of the requirement at §146.90 to develop site-speci fic testing and monitoring plans is to ensure that the monitoring performed at a site is appropriate for site operational conditions and the geologic setting.

Regarding transfer of responsibility following site closure, please note that EPA does not have authority to transfer SDWA or other legal liability for Class VI wells to the State or federal government or a third-party fund. Under the final GS rule, once an owner or operator has met all regulatory requirements under Part 146 for Class VI wells and th e Director has approved site closure pursuant to requirement s at §146.93, the owner or operator will generally no longer be subject to enforcement for regulatory noncompliance. Furthermore, the financial instrument required under §146.85 will be released if it was not used. However, even if a site closure is approved under §146.93, an owner or operator may be held liable for regulatory noncompliance (including violation of 40 CFR 144.12) in certain circumstances. For example, an owner or operator may be held liable for regulatory noncompliance even after site closure was approved if the Director relied on erroneous information (e.g., erroneous modeling data) provided by the owner or operator when approving site closure.

Separate from EPA’s authority to enforce regul atory compliance, an owner or operator may be subject to a §1431 response order even after proper site cl osure is approved under §146.93. Under §1431 the Administrator may require an owner or operator to take necessary response measures if he or she receives information that a contaminant is present or is likely to enter a public water system or an USDW, which may pres ent an imminent and substantial endangerment to the health of persons, and the appropriate State and local authorities have not acted to protect the health of such persons. The action may include issuing administrative orders or commencing a civil action for appropriate relief against the owner or operator of a Class VI well. If the owner or operator fails to comply with the order, they may be subject to a civil penalty for each day in which such violation occurs or failure to comply continues.

Furthermore, after site closure an owner or operator may remain liable under tort and other remedies, or under other federal statutes including, but not limited to, Clean Air Act, 42 U.S.C.

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### §§ 7401-7671; CERCLA, 42 U.S.C. § 9601-9675; and RCRA, 42 U.S.C. § 6901-6992. See the final rule preamble for further discussion of EPA's final approach.

Letter ID: 0142 Comment ID: 22573 Letter Lines: 958 to 961

Comment Code: 4760 2.7.6 Proposed reporting frequency (seeking comment)

Comment: regulations. The results of the MMV and modeling including the integrity of the wells, fluid properties and volumes, subsurface location of the plume, leakage monitoring, modeling, and size of the AoR should be reported at least annually or upon a sudden significant change.

Individual Response: EPA is retaining the requirement at §146.91(a) for semi-annual reporting of monitoring and operational data. External mechanical integrity testing, which must be conducted annually, must be reported within 30 days of the test. EPA clarifies that some monitoring frequencies (e.g., associated with ground water monitoring and plume tracking) will be established in the approved testing and monitoring plan, which will be incorporated as a condition of the Class VI permit. The frequency ofthese tests will be determined based on sitespecific information.

EPA clarifies the final rule includes a requirement at §146.91(c) that operators report within 24 hours of any event that may endanger USDWs; any leakage that endangers a USDW would be addressed in this requirement.

For additional information, please see the final rule and the preamble for a discussion of EPA's final approach to recordkeeping and reporting.

Letter ID: 0142 Comment ID: 22574 Letter Lines: 964 to 1006 ; 1228 to 1234 ; 1240 to 1244 ; 1294 to 1298

Comment Code: 5400 2.9 Proposed Financial Respons ibility and Long-Term Care Requirements

Comment: Overview of Financial Responsibility Issues

Introduction

Applying financial responsib ility for the various operational and post-closure risks is central to widespread deployment of CCS as an effective climate-change mitigation strategy. The commonly perceive d CCS categories of risks include toxicological effects, induced seismicity, subsurface trespass, and climate effects (de Figueiredo et al., 2006). The mechanisms for these risks include CO2 gas leakage from the injection wellhead; gas leakage from geologic reservoir; development of injection-related seismi city in existing seismically active areas; and, degradation of drinking water aquifers by mobilization of brines or

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### by geochemical interaction of fugitive CO2 with overlying aquifers.

These liabilities may be further categorized in terms of operational liability and post-injection liability (e.g., Figueiredo et al., 2006). Operational liability includes the environmental, health and safety risks associated with capture, transportation and injection of CO2. Post-injection liability is related to storage of carbon di oxide in the geologic formation after it has been injected. According to Figueiredo et al., post-injection lia bility can be further divided according to (1) in situ li ability of harm to human health, the environment, and property, including degradation of aquifers, and (2) climate liability related to leakage of CO2 from the geologic reservoirs and its longterm effect on climate change.

The long period and geographic scale over which these liabilities can occur pose unique challenges for assessing CCS liability, in comparison to conventional business liability models. For example, the operational phase of individual CCS projects is anticipated to be tens of years (Gerard and Wilson, 2008). Although the post-injection risks are inferred to decrease with time, the long period over which these risks may manifest them selves and the inherent geophysical uncertainties of geologic reservoirs are not amenable to a strictly private solution to liability. For example, several authors (e.g., Figueredo et al., 2006; Edison Electric Institute, 2007; WRI, 2006; and Gerard and Wilson, 2008) have suggested that the unique liabiliti es associated with CCS should be assigned to the operators during the in jection phase and for a short period after cessation of injection and closure ofthe injection wells, and the longterm post-closure liability should become a public responsibility because of the perceived significant public benefit that CCS will have on local and global climate. Another reason to involve the pub lic sector in the long-term liability may be to ensure that a responsible entity will be around (i.e., should the CCS operator or holding company become insolvent) to address post-closure CCS problems, should they arise (World Resources Institute, 2007).

Edison Electric Institute, 2007, Status and Outlook for Carbon Capture and Storage Technology in the United States. Written statement for the U.S. House Select Committee on Energy and Global Warming.

Figueiredo, M. de, D. Reiner, H. Herz og, and K. Oye, 2006 The Liability of Carbon Dioxide Storage. Presented at the Eight Internati onal Conference on Greenhouse Gas Control Technol ogies, Trondheim, Norway

Gerard, D., and E.J. Wilson, 2008, Environmental Bonds and the Problem of LongTerm Carbon Sequestration. Source. Journal of Environmental Management, In Press. Available online as of July 2008: http://www.epp.cmu.edu/csir/Content/Research/Carbon%20Capture%20and%20Sequestrat ion/Gerard%20Wilson%20Bonding.doc

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### World Resources Institute, 2007, Workshop Summary: Addressing Long-Term Liability of Carbon Dioxide Capture and Geologic Sequestration.

World Resources Institute, 2006, Executive Summary: WRI Workshop on CCS Liability.

Individual Response: EPA agrees that assuring financial responsibility throughout the lifetime of a GS project, i.e., for corrective action on well s in the AoR, injecti on well plugging, PISC and site closure, and emergency and remedial response, is an important component of ensuring that USDWs are protected. The goal of financial responsibility is to en sure that financial resources are available to prevent endangerment of USDWs from improper plugging, remediation, and management of wells in the event that the owner or operator experiences financial difficulties.

Please see the discussion of EPA's final regulatory approachin the preamble to the final GS rule for additional information on how the GS requirements address the unique risks associated with GS projects.

Under SDWA authority, owners or operators of injection well s must ensure protection of USDWs from endangerment and are subject to liability for enforcement under the Act.

The final rule requires that an owner or operator must conduct monitoring as specified in the Director-approved PISC and site closure plan following the cessation of injection until the owner or operator can demonstrate to the Director that the geologic sequestration project no longer poses an endangerment to USDWs. For additionalinformation about the PISC and site closure requirements, see the preamble to the final GS rule.

Once an owner or operator has met all regulator y requirements under Part 146 for Class VI wells and the Director has approved site closure pursuant to requirements at §146.93, the owner or operator will generally no longer be subject to enforcement for regulatory noncompliance. Furthermore, their financial instrument as re quired under §146.85 will be released if it was not used. However, even if a site closure is approved under §146.93, an owner or operator may be held liable for regulatory noncompliance (inc luding violation of 40 CFR 144.12) in certain circumstances. For example, an owner or operator may be held liable for regulatory noncompliance even after site closure was a pproved if the Director relied on erroneous information (e.g., erroneous modeling data) provi ded by the owner or operator when approving site closure.

Additionally, an owner or operator may always besubject to any action the Administrator deems necessary to protect the health of persons under §1431 of the SD WA after site closure if there is unanticipated migration towards or into a US DW that causes or threatens imminent and substantial endangerment to publichealth. The action may include issuing administrative orders or commencing a civil action for appropriate relief. If the owner or operator fails to comply with the order, they may be subject to a civil penalty for each day in which such violation occurs or failure to comply continues.

The Agency clarifies that Class VI well permits may be transferred to another owner or operator

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### pursuant to §144.38 whereby generally all other regulatory re sponsibilities are transferred to that new owner and operator, which includes all potential liabilities associated with meeting the requirements of that permit. Please see further clarification on the issue of long term liability in the preamble of the final rule.

Furthermore, after site closure an owner or operator may remain liable under tort and other remedies, or under other federal statutes including, but not limited to, Clean Air Act, 42 U.S.C. §§ 7401-7671; CERCLA, 42 U.S.C. § 9601-9675; and RCRA, 42 U.S.C. § 6901-6992. EPA does not have authority to transfer SDWA or other legal liability for Class VI wells to the State or federal government or a third-party fund. See the final rule preamble for further discussion of EPA's final approach.

Letter ID: 0142 Comment ID: 22575 Letter Lines: 1008 to 1158 ; 1216 to 1218 ; 1240 to 1244 ; 1262 to 1274 ; 1289 to 1292

Comment Code: 5460 2.9.2 Comments on transfer of lia bility for long-term care

Comment: Applicable and Relevant Liability Models

Public health/environmental liability mode ls currently exist in North America that may to offer some insights to help develop workable CCS liability policy to safeguard public interests yet remain attractive to private/corporate investors who will help fund development of the re quired CCS technology and large-scale CCS operations.

Alberta Acid Gas Re-Injection. Acid ga s streams, consisting primarily of hydrogen sulfide and carbon dioxide, are co mmonly generated as a by-product of the gas "sweetening" process used to bring produced natural gases and solution gases up to pipeline specifications for sales and transport. Prior to introduction of acid gas re-injection, treatment of acid gases included flaring. The province of Alberta has over 38 acid gas re-injection wells in operation (Wong et al., 2003). In Alberta, the inje ction well operator is financially responsible (liable) for operation and closure of acid gas re-injection wells, but there is no responsibility for post-closure monitoring or mitigation of gas leaks, whether leakage is from the storage reservoir or from the closed injection well (Bachu, 2007). In addition, there is no provision to ensure that "orphaned" (abandoned) re-injection wellsare closed properly by a public or private entity, should the operator becoming insolvent.

Price-Anderson Act. The Price-Anderson Ac t was passed as federal law in the United States in 1957 to partially indemnify the nuclear industry against liability claims for nuclear incidents while still protecting the general public. The Act established a no-fault insuranc e fund in which the first $10 billion of an incident claim is funde d by industry and the federal government covers the remainder over this amount. The federal government instituted this Act to provide an incentive for private investment in nuclear power; without

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### this type of indemnification, inve stors were unwilling to accept the unquanitifed risks of nuclear energy. Although criticized by some groups , the Act has been renewed several times and iscurrently set to expire in 2025. The Act appears to focus primarily on liabilityfor nuclear plant operation and not for post-closure incidents. Over the first 43 years of operation until 2000, the secondary federal insurance has not been required. The nuclear industry has paid a total of $151 million to cover claims , including $70 million for the Three Mile Island incident. During the same peri od, the Department of Energy has paid about $65 million to cover claims for its own nuclear operations.

Resource Conservation and Recovery Act (RCRA). Enacted by the U.S. Congress in 1976, RCRA mandates that companies set aside funds for post-clo sure care of solid and hazardous waste sites, and esta blishes EPA’s authority to control related wastes from "cradle-to-grave" (U SEPA(a), downloaded 2008). For example, solid waste landfill operators in most U.S. states bear financial responsibility for public health and safety, environmental health, environmental monitoring, landfill maintenance, and remediation/treatment of leachate and contaminated ground water during landfill operation and for a post-closure period. Financial assurance of ability to cover these costs is generally required as a condition of the operator’s state permit for both the operating and post-closure period. Some states (e.g., Maine) require that the financial assurance cost estimates be based on the entire expected time that the solid waste facility is expected to be generating leachate, landfill gases and other contaminants that have a potential for creating an adverse environmental impact. Pennsylvania bases bonding estimates on a 30-year post-closure period, but final closure is performance-based and site specific; upon final closure determination, a 10-year bond liability period commences. However, the operator and landowner are still liable beyond this period for adverse effects and other changes in site conditions. Other states require post-closure monitoring, remediation and financial assurance for a finite period (e.g., Ohio - 30 years; Vermont - 20 years).

In 1986, Congress created a Leaking Underground Storage Tank (LUST) Trust Fund by amending Subtitle I of RCRA. The LUST Trust Fund provides money for overseeing and enforcing corrective ac tion by a responsible party, and for cleanup at UST sites where the owner isunknown, unable, or unwilling to respond (USEPA(b), downloaded 2008). The Trust Fund is financed by a 0.1 cent tax on each gallon of motor fuel. All 50 states havecooperative agreements with EPA to spend this money for LUST-related activities. In addition, 47 states have established state-run LUST Funds to help owners and operators with UST upgrades and LUST remediation problems (Tiemann, 1999). Reimbursements from the state LUST Funds have generally benefited most UST owners/operators who comply with the existing state and federal UST regulati ons, regardless of financial ability to cover these costs. Like the RCRA LUSTTrust Fund, the state LUST Funds are generated through gas taxes and tank fees.

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### Comprehensive Environmental Response, Co mpensation, and Liability Act (CERCLA). CERCLA (also referred to as Superfund) , enacted by the U.S. Congress in 1980, established a tax on the chemical and petroleum industries to finance a fund that addresses the liabilities arising from the clean up of hazardous waste sites. Over a period of five years, $1.6 billion was collected and the tax went into a trust fund for cleaning up abandoned or uncontrolled hazardous waste sites (USEPA(c), downloaded 2008). CERCLAwas amended in 1986 by the Superfund Amendments and Reauthorization Act (SARA). SARA increased the size of the trust fund to $8.5 billion (USEPA(d), downloaded 2008). While RCRA was intended to be forward-looking, CERCLA is intended to be backward-looking, i.e., contamination that occurred prior toRCRA authorization.

Tiered Approach

A key tenet of environmental laws and re gulations is that pol lution costs should e borne by their creators. U.S. environmental laws and regulations give this principle form by making polluters liablefor property, health, and natural resource damages and unperformed resource reclamation obligations (Boyd, 2001). However, the anticipated great public benefit from CCS implementation and reluctance of private investors to become involved in an enterprise that may have several hundred years of post-closure liability suggest that a shared private/public liability model may be a ppropriate for long-term post-closure phase of CCS.

Gerard and Wilson (2008) provide a tem porally-tiered approach to managing liability for all phases of CCS. This approach relies on operator liability and use of operator-funded bonds to cover liability during the operational phase (Phase 1) of CCS. Gerard and Wilson report that this approach has been used effectively for many oil and gas wells and wells regulated under the UIC Program where the operational lifetime of the wellsis tens of years. This surety mechanism and time frame may also encourage proper site management and well closure for CCS wells. Short-term post- closure liability (Phase 2) for unanticipated accidents would rest with the operator, but active bonding by the operator would cease. Monitoring and verification during Phase 2 would be financed by publicly run or pooled financial mechanisms that would be funded by operator/industry contributions during the active injection phase of the project. The third phase of liability and management (Pha se 3) would be a public responsibility, ensuring that long-term standard s of care are met.

According to Gerard and Wilson, demarcati on of the Phase 2 to Phase 3 transition could be performance-based (e.g., based on pressure levels in the CCS reservoir or on dissolved CO2 in the formation fluid), or prescriptive (e.g., after a finite period [10 years, 25 years, etc.]). By Phase 3, project performance and success are more certain and public "liability" and management would be viewed as primarily administration and record-keeping.

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### USEPA’s Proposed UIC CCS Rule

In the proposed UIC CCS Rule, USEPA is proposing a combination of fixed timeframe and a performance standard. Po st-injection site care (monitoring) would occur for a period of 50 years. This period could beshortened or lengthened based on plume behavior. If monitoring data demonstrate that the plume/pressure front is st abilized and the CO2 injectate does not pose risk to USDWs, the 50-year post-in jection site care periodcould be shortened. Conversely, if the plume/pressure front has not stabilized after 50 years of post-injection monitoring, USEPA woul d extend the monitoring period until stabilization is achieved.

Conclusion

It is apparent that much work and public -private sector discussions are needed to develop a liability policy framework and details that are workable and acceptable to all parties. In recogniti on of this, USEPA is requesting public comments on their proposed 50-year monitoring period with a performance element. Developing effective performance-based criteria upon which to base transfer of post-closure liability to the public app ears to be an area that warrants considerable technical research. This transition mechanism could become one of the key issues to gain public acceptance for CCS.

The Task Force recommends that federal and energy industry funding for CCS research be directed toward establishing performance-based indicators for CO2 reservoir stability to facilitate liabilitytransfer. This tiered approach may offer ample incentives to ensure that CCS operations are managed responsibly, yet not discourage investors from supporting CCS. Public assumption of Phase 3 liability after the CCS reservoir stabilizesappears commensurate with the great public benefit that CCS offers.

Bachu, S., 2007, Legal and Regulatory Aspect s of CCS, in Workshop on Capacity Building for Emerging Economies. Carbon Seque stration Leadership Forum in Porto Alegre, Brazil.

Gerard, D., and E.J. Wilson, 2008, Environmental Bonds and the Problem of LongTerm Carbon Sequestration. Source. Journal of Environmental Management, In Press. Available online as of July 2008: http://www.epp.cmu.edu/csir/Content/Research/Carbon%20Capture%20and%20Sequestrat ion/Gerard%20Wilson%20Bonding.doc

Tiemann, M., 1999, Leaking Underground Storage Tank Issues. CRS Report: 97-471.

USEPA(a), downloaded 6/29/08. Summary of th e Resource Conservation and Recovery Act. http://www.epa.gov/lawregs/laws/rcra.htm

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### USEPA(b), downloaded 6/29/08. Leaking Underground Storage Tank (LUST) Trust Fund. http:www.epa.gov/oust/ltffacts.htm

USEPA(c), downloaded 6/29/08. CERCLA Overview. http://www.superfund/policy/cercla.htm

USEPA(d) download 10/28/08, SARA Overview http://www.epa.gov/superfund/policy/sara.htm

Wong, S., D. Keith, E. Wichert, W. Gunter 1and T. McCann, 2003, Economics of Acid Gas Reinjection: An Innovative CO2 Storage Opportunity. In Greenhouse Gas Control Technologies, J. Gale and Y. Kaya (Eds.) © 2003 Elsevier Science Ltd. All rights reserved

Individual Response: As described above, once an owner or operator has met all regulatory requirements under Part 146 for Class VI wells and the Director has approved site closure pursuant to requirements at §146.93, the owner or operator will generally no longer be subject to enforcement for regulatory noncompliance.

EPA does not have authority to transfer SDWA or other legal liab ility for Class VI wells to the State or federal government or a third-party fund. See the final rule preamble for further discussion of EPA's final approach.

Letter ID: 0142 Comment ID: 22576 Letter Lines: 1310 to 1329

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

Comment: Preamble Questions: Injection of CO2 for the purposes of enhanced oil and gas recovery (EOR/EGR), as long as any producti on is occurring, will continue to be permitted under the Class II program. EPA seeks comment on the merits of this approach since owners or operators of some Class II EOR/EGR wells may wish to use wells for the purposes of production and GS prior to the field being completely depleted. EPA Notice 48.

NGWA Response: The transition of carbon di oxide injection wells from Class II (Enhanced Oil Recovery wells) to Cla ss VI (carbon sequestration wells) will presumably be requested when producti on of the petroleum has ceased. Liquid carbon dioxide from a distant source, such as a power plant, can be stored in the depleted petroleum reservoir even after production has ceas ed, necessitating a change in classification of the inje ction well. The new use of the wells involves much longer storage time, and raises concerns about mechanical integrity and long term effects, including geochemical changes, on underground source of drinking water (USDWs). The reclassification should depend on a positive outcome from a Class V experimentalprogram conducted in the depleted reservoir. See NGWA Comment Document (word document) Section titled ""Classification of Injection Wells for Carbon Sequestration, Class II Injection

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### Well Transition, and Grandfathering"" for further details.

Individual Response: EPA agrees that a cautious approachto grandfathering is appropriate, particularly given that the converted well will be used for a substantially different process, which involves increased reservoir pre ssures 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 GS rule that owners or operators seeking to c onvert existing wells for long term storage must demonstrate to the Director that the grandfathered wells were engineeredand constructed 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, following re-permitting as Class VI wells, these projects must be subject to the operational, MIT, monitoring, reporting, plugging, and post-injection site care and site closure requirements in the final GS rule. See the discus sion of EPA's final regulatory approach in the preamble to the GS rule for additional detail on these requirements.

Letter ID: 0142 Comment ID: 22577 Letter Lines: 1331 to 1337

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

Comment: Preamble Questions: EPA seeks comment on how the grandfathering approach for existing wells may affect compliance with the other requirements in its proposal. EPA Notice 50.

NGWA Response: See NGW Co mment Document (word document) Section titled "Classification of Injection Wells for Carbon Sequestration, Class II Injection Well Transition, and Grandfathering" for further details.

Individual Response: EPA disagrees that every GS well should initially be permitted as a Class V well, as suggested by the commenter in the do cument on classification of injection wells for geologic sequestration. The Agency believes that the tailored Class VI requirements including extensive requirements for geol ogic site characterization at§146.82, AoR evaluation at §146.84, and testing of the well during drilling at §146.87 are appropriate to ensure that permitting authorities have the necessary information to evaluate whether a specific site will allow safe injection of CO2. EPA adds that submittal and review of monitoring data (as required at §146.90) and the AoR reevaluation process (§146.84(e)) will provi de an opportunity for an ongoing review of the site and a dialogue between the Director and the owner or operator to ensure that the project is being operated in a manner that protects USDWs from endangerment. Given this approach to permitting Class VI proj ects, EPA believes that the requirements for grandfathering of construction at §146.81( c) are necessary and appropriate.

Letter ID: 0142 Comment ID: 22578 Letter Lines: 1339 to 1346

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

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### USDW Comment Code: 4410 2.4.4.3.1 Comments in favor of allowing injection above/between USDWs in certain circumstances

Comment: Preamble Questions: The locati on and proximity of other formations to USDWs may preclude their use for GS. EPA seeks comment on prohibiting inje ction into such formations if they are above the lowermost USDW. EPA Notice 54.

NGWA Response: NGWA supports the general prohibition against in jections above the lowermost USDW. An exemption process should be available to review and consider those specific situations where injection cannot be done, or is being proposed not to be done, below the lowermost USDW

Individual Response: EPA agrees that protecting USDWs from endangerment must be a top priority. The Agency believes that there are limited circumstances where injection above the lowermost USDW can be performed in a manner that protects USDWs, as long as appropriate protections are in place. The final GS rule at §146.95 establishes a process by which owners or operators can seek a waiver of the Class VI in jection depth requirement s for injection into nonUSDW formations above and/or between USDWs.

The waiver approach requires the submission of extensive, site-specific information (in conjunction with the permit application submission) to demonstrate that injection of CO2 into a non-USDW that is above or between USDWs can be done in a manner that is protective of USDWs. It also establishes procedures for public notice of a waiver application and for DirectorRegional Administrator communication and requirements specifying information that owners or operators must submit, and Directors must consider, in consultation with PWSS Directors.

Letter ID: 0142 Comment ID: 22579 Letter Lines: 1348 to 1366

Comment Code: 3120 2.1.2 Need to identify additional confining and containment zones (seeking comment)

Comment: Preamble Questions: EPA’s proposal would provide the Director the discretion to require the owner or operator to identifyand characterize additional confining and containment zones above the primary (i .e., lowermost) confining zone that could further impede vertical fluid movement and allow for pressure dissipation. EPA says that these layers could provide additional site s for monitoring, mitigation, and remediation. EPA’s propos al would not require that these additional zones be identifie d for all GS sites because their absence does not necessarily indicate inappropriateness of a GS site. However, if such zones are present, information about their characteristics can provide inputs for predictive models, identify appropriate monitoring locations, and improve public confidence in and acceptance of a proposed GS site. EPA specifically seeks comment on the merits of requiring the identification of these additional zones. EPA Notice 64.

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### NGWA Response: While NGWA believes thata site with a single confining can provide storage integrity, NGWA recommends that if there are additional confining layers at the site they shoul d be characterized to get a better estimate of leakage risk to USDWs and possibly identify additional monitoring

zones.

Individual Response: EPA agrees with the commenter that, insome situations, the presence of additional confining and containment zones above the primary (i.e., lowermost) confining zone can improve USDW protection from endangerment. The final regulation retains the requirement at §146.83(b) which affords the Director discretion torequire owners or op erators to identify and characterize additional zones. Any additional confining zones would need to be included in the geologic site characterization process, which the owner or operator would submit and the Director would review in determining whether to grant a permit. EPA is developing guidance on site characterization for GS proj ects to assist owners or operators and Directors in evaluating permit requirements and applications under §146. 82. The guidance provides recommendations regarding characterizing the regi onal geology and hydrogeology of a proposed GS site as well as performing the necessary geochemical, geomechani cal, and geophysical analyses of the injection and confining zone. EPA expects that this gui dance will assist permit writers in making an objective decision about requiring additional c onfining layers. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Letter ID: 0142 Comment ID: 22580 Letter Lines: 1368 to 1385

Comment Code: 3350 2.2.1.5 Use of proprietary models for GS sites (seeking comment)

Comment: Preamble Questions: In some cases, owners or operators may choose to use proprietary models (i.e., not available for free to the general public). EPA says it is aware that the use of proprietary codes may prevent full evaluation of model results (e.g., NRC, 2007). Several popular codes in the petroleumreservoir engineering discipline are proprietary and owners or operators of particular sites may prefer to use these codes as they have previous experience with them, and they have been used inpeer-reviewed studies to model CO2 sequestration. When using a proprietary model, owners or operators should clearly disclose the code assumptions, relevant equations, and sc ientific basis. EPA seeks comment on allowing the use of proprietary models for GS sites. EPA Notice 68.

NGWA Response: Yes, use of commercial proprietary co des should be authorized. Proprietary doesn't mean secret. A proprietary code larg ely vetted by the industry can be the best application inmany circumstances. To promote peer review and benchmarking, the assumptions and theories for all numerical models should be publicly available and the solution of any analytic equations used in the predictive process shoul d be fully elaborated.

Individual Response: As described above, EPA agrees thatavailable proprietary models may meet the complex needs for calculating the AoRs of GS sites, and shares their concern about the

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### need to evaluate the inputs and assumptions used. EPA will allow the use of proprietary models in meeting the requirements for the GS regul ation, 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: 0142 Comment ID: 22581 Letter Lines: 1387 to 1392

Comment Code: 3330 2.2.1.3 Applicability /adequacy of computational models (seeking comment)

Comment: Preamble Questions: EPA seeks comment on the applicability of computational fluid flow models for delineating the AoR of GS sites. EPA Notice 69.

NGWA Response: See NGWA General Comment Document Section titled "General Comments on Use of Modeling for Ground-Water Protection Related to CO2 Sequestration".

Individual Response: As described above, EPA agrees that complex modeling techniques may be required to calculate the AoR while adequate ly accounting for the comp lexities of a GS site and all phases of a CO2 plume.

Letter ID: 0142 Comment ID: 22582 Letter Lines: 1394 to 1400

Comment Code: 3530 2.2.3.1 AoR reevaluation fre quency (seeking comment)

Comment: Preamble Questions: EPA seeks comment on re quiring the reevaluation of the site AoR on a periodic basis, under what conditions the AoR should be reevaluated, and the appropriateness of a 10-year minimum fixed frequency for AoR reevaluation. EPA Notice 72.

NGWA Response: Yes, reevaluation is needed and at a higher frequency than 10 years, particularlyat the beginning.

Individual Response: EPA agrees that reevaluations of the AoR every ten years may not be sufficient to appropriately model plume and pre ssure front movement, establish conditions for corrective action, and ensure protection of USDWs from endangerment. For these reasons, the Agency changed the minimum frequency for the AoR reevaluation at §146.84(e) from 10 years to at least every 5 years in the final GS rule. EPA believes that this revised frequency addresses commenters' concerns about the inherent uncertainties in modeling CO2 movement, the emerging nature of GS technology, risk-based targeting of monitoring activities, and the unique nature of CO2 GS.

In addition, the Director has discretion to require more frequent AoR reevaluation if he or she

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### has reason to believe, based on site-specific information, that a five-year reevaluation schedule is not sufficiently protective of USDWs.

Letter ID: 0142 Comment ID: 22583 Letter Lines: 1402 to 1413

Comment Code: 3530 2.2.3.1 AoR reevaluation fre quency (seeking comment) Comment Code: 3630 2.2.4.1 Comments in favor of allowing phased corrective action

Comment: Preamble Questions: EPA proposes to allow a phased approach to corrective action but says this may not be appropriate in all situations; therefore EPA is proposing that the Director have the discretion to decide to allow this approach, based on the understanding of relevant geol ogic and site conditions. EPA invites public comment on the merits and frequency of reevaluation of the AoR as well as the phased corrective acti on approach for GS wells. EPA Notice 74.

NGWA Response: Yes, phased corrective action is a good idea . It will allow targeting of those wells most in need of corrective action and optimize financial resources as the pressure/CO2 plume may deviate from the initial AoR. That's why it is important to reviewAoR more often than 10 years.

Individual Response: EPA acknowledges the commenter’s support of phased corrective action and agrees that phased corrective action may provide many benefits to a project including, but not limited to, spreading the burden of cost, avoi ding delays in project start-up, allowing for use of future, improved corrective action techniques and addressing unanticipated changes in the movement of the CO2 plume or pressure front . EPA believes that the phased corrective action approach is appropriate for GS projects, and retained it at §146.84(b)(2)(iv) in the final GS regulation.

Also, as described above, EPA changed the minimum frequency for the AoR reevaluation at §146.84(e) from 10 years to 5 years in the final GS rule.

Letter ID: 0142 Comment ID: 22585 Letter Lines: 1415 to 1438

Comment Code: 4322 2.4.4.1.1 Comments in favor of requiring injection below the lowermost USDW Comment Code: 4410 2.4.4.3.1 Comments in favor of allowing injection above/between USDWs in certain circumstances

Comment: Preamble Questions: EPA is soliciting comment on whether CO2 injection should be allowed into an injection zone above th e lowermost USDW, when the Director determines that geologic conditions (e .g., thousands of feet of intervening formations between the injection zone and the overlying and/or underlying USDWs) exist that will prevent fluid movement into adjacent USDWs. EPA Notice 93.

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### NGWA Response: NGWA supports the general prohibition against in jections above the lowermost USDW. An exemption process should be available to review and consider those specific situations where injection cannot be done, or is being proposed not to be done, below the lowermost USDW

Proposed Rule: 144.6(f)

Comment: NGWA supports the general prohibition against injections above the lowermost USDW. An exemption process should be made available to review and consider those specific situations where injection cannot be done, or is being proposed not to be done, below the lowermost USDW.

Rationale: NGWA understands that there may be portions of the c ountry that will not have adequate storage zones below the lowermost USDW. In these areas, the Association believes that storage above the lowermost USDW may be allowed on a site specific basis based on director discretion assuming that all other conditions are met.

Individual Response: As described above, the final GS ruleat §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 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.

Letter ID: 0142 Comment ID: 22586 Letter Lines: 1440 to 1445

Comment Code: 5700 2.12 Comments on the proposed durati on of Class VI permits (seeking comment)

Comment: Proposed Rule: 144.36(a)

Comment: Would there be a scenario where a facility would stop and restart? Concern is to make sure temporarily stopped injection activity does not allow party to wait a period of time and then walk away or alternatively cause closure if only a temporary stop.

Individual Response: EPA clarifies that the final regulati on at 144.51(o) statesthat temporary or intermittent cessation of injection operations isnot abandonment. Please see the requirements for approving plugging and abandonment pl ans pursuant to §§144.51(o)--(p), 146.10, and 146.92. See also the discussion of plugging and abandonment in the preamble to the final rule.

Letter ID: 0142 Comment ID: 22587 Letter Lines: 1449 to 1465

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### Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language Comment Code: 3440 2.2.2.2 Evaluation of wells in the AoR (e.g., types of data to be reviewed)

Comment: Proposed Rule: 144.55(a)

Proposed Revision: (a) Coverage. Applicants for Class I, II, (other than existing), III or VI injection well permits shall identify the location of all known wells within the injection well's area of review which penetrate the injection zone, or in th e case of Class II wells op erating over the fracture pressure of the injection formation, all known wells within the area of review penetrating formations affected by the increase in pressure. Applicants for Class VI shall perform mapping with sufficient resolution as to make a comprehensive effort to identify wells that are not in the publ ic record using aerial photography, aerial survey, or other methods acceptable to the director corrective action as specif ied in §146.84 if needed

Rationale: Concern about the use of the term known wells. Public records search may not be adequate for older oil and gas wells, for example. Some language should be added so that A moreproactive approach is used, e.g. physically walk site or do aerial review.

Individual Response: The final rule leaves §144.55 unchanged from the existing UIC requirements; i.e., Class VI wellsare not addressed in this provision. 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: 0142 Comment ID: 22588 Letter Lines: 1467 to 1473

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

Comment: Proposed Rule: 146.81(b)

Revision or Comment: Comment: NGWA supports the use of Cl ass VI as "specifically for geologic carbon sequestration and believes that EOR and GS should be sequential and not concurrent"

No rationale provided

Individual Response: EPA agrees that injection of CO2 for the primary purpose of enhancing oil and gas recovery should remain under the Cl ass II Program. The Agency believes that the nature and risks of CO2 injection for the primary purpose of l ong term storage poses different risks than injection for the primary purpose of ER, and therefore has developed new Class VI regulations to address these uniquerisks. For example, the volume of CO2 anticipated to be injected for long term storage is significantly greater than for ER operations. Reservoir pressure

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### conditions will also be different, with Class VI injection operations involving large volumes of CO2 and likely having higher pressure s within their storage formationsthan Class II ER projects.

Letter ID: 0142 Comment ID: 22589 Letter Lines: 1475 to 1496

Comment Code: 1220 1.1.1.1 Terminology and definitions

Comment: Proposed Rule: 146.81(d) [Definition - Area of review]

Proposed Revision: Area of review means the region surrounding the geologic sequestration project that may be imp acted by the injection activity. The area of review is based on computational modeling that accounts for the physical and chemical properties of all phases of the injected carbon dioxide stream and the zone of increased pressure created by the injection.

Rationale: The AOR needs to be based on both the CO2 plume and the associated pressure front in order to completely identify the areas that may be affected by the injection

Proposed Rule: 146.81(d) [Definition - Geologic sequestration project]

Proposed Revision: Geologic sequestration project means an injection well or wells used to emplace a carbon dioxide stre am. It includes the subsurface threedimensional extent of the carbon dioxide plume, associated pressure front, and displaced brine, as well as all USDWs and the surface area above that delineated region.

Rationale: See Section 144.6(f). If an exemption is provided, USDWs below the CO2 plume or pressure front should beincluded in the AOR specifically.

Individual Response: EPA agrees that the AoR definition should account for the impact of the CO2 plume on USDWs. The Agency has carefully considered all comments on the AoR definition at §146.84(a) and modi fied it to read as follows : “[T]he region surrounding the geologic sequestration project where USDWs may be endangered by the injection activity. The area of review is delineated us ing computational modeling that accounts for the physical and chemical properties of all phase s of the injected CO2 stream and is based on available site characterization, monitoring, and operational data.”

The Agency has also modified the final definition of geologic sequestrati on project to read as follows: “Geologic sequestration project means aninjection well or wells used to emplace a carbon dioxide stream beneath the lowermost formation containing a USDW; or, wells used for geologic sequestration of carbon dioxide that have been granted a waiver of the injection depth requirements pursuant to requirements at §146.95; or, wells used for geologic sequestration of carbon dioxide that have received an aquifer exemption expansion. It includes the subsurface three-dimensional extent of the carbon dioxide plume, associated pressure front, and displaced brine, as well as the surface area above that delineated region.”

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### Based on its evaluation of all public comments and input on the proposed rule and the NODA and Request for Comment, EPA has made many revisions to the Cla ss VI GS rule. Please see the final rule and preamble for additional information.

Letter ID: 0142 Comment ID: 22590 Letter Lines: 1498 to 1653 ; 1667 to 1819

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language Comment Code: 4710 2.7.1 Proposed submissions required for permit applications (seeking comment)

Comment: Proposed Rule: 146.82

Comment: NGWA raises the question of whether a requirement should be included that all applications for Class VI construction permits include a certification that the facility was designed by an appropriately qualif ied professional engineer with an option for an appropriate qualified professional geologist to certify the well design (taking into consideration confinement, injectivity, etc).

Proposed addition: (1) Class VI - Test/Injection Well Construction and Testing Permit

Proposed addition: (a) The Director shall deny a construction permit if construction of the well itself may endanger the health of persons or the environment

Proposed addition: (b) For construction permit approval, reasonable assurance is required that the project will function incompliance with this chapter. The Director shall require an exploratory well for those proj ects located in an area where available information is lacking concerning geologic or hydraulic confinement or existing information indicates that geologic or hydraulic confinement may be poor or lacking.

Proposed addition: (c ) For a Class VI well, issuance of a construction permit does not obligate the Director to authorize any operation of the well, unless reasonable assurance has been provided that the well can operate in compliance with this chapter.

Proposed addition: (d) Information required in 40 CFR 144.31 (e)(1) through (6)

Proposed addition: (e) A map showing the in jection well(s) for which a permit is sought and the applicable area of review. Within the area of review, the map must show the number, or name and lo cation of all injection wells, producing wells, abandoned wells, plugged wells or dry holes, deep stratigraphic boreholes, State or EPA approved subsurface cleanup sites, surface bodies of

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### water, springs, mines (surface and subsurface), quarries, water wells and other pertinent surface features including structures intended for human occupancy and roads. The map should also show faults, if known or suspected. Only information of public record is required tobe included on this map;

Proposed addition: (f) The area of review based on modeling, using data obtained during logging and testing of the well and the formation as required by paragraphs (l), (r ), and (s) of this section;

Proposed addition: (g) Information on the geologic structure and hydrogeologic properties of the proposed storage siteand overlying formations, including

Proposed addition: (1) Maps and cross sections of the area of review;

roposed addition: (2) Location, orientation, and properties of known or suspected faults and fractures that may transect the confining zone(s) in the area of review and a determination that they would not interfere with containment;

Proposed addition: (3) Information on seismic history including the presence and depth of seismic sources and a determination that the seismicity would not interfere with containment;

Proposed addition: (4) Data on the depth, areal extent, thickness, mineralogy, porosity, permeability and capillary pressure of the injection and confining zone(s); including geology/f acies changes based on field data which may include geologic cores, outcrop data, seismic surveys, well logs, and names and lithologic descriptions;

Proposed addition: (5) Geomechanical information on fractures, stress, ductility, rock strength, and in situ flui d pressures within the confining zone; and

Proposed addition: (6) Geologic and topographic maps and cross sections illustrating regional geology, hydrogeology, and the geologic structure of the local area

Proposed addition: (h) All wells within the AOR and whose total depth is greater than the depth to the bottom of the lowermost USDW should be compiled. However, preventive corrective action should be undertaken only for those wells that penetrate the injection and confining zone(s)

Rationale: A substantive risk analysis can be performed only if all the (known) wells within the AOR and between the injection formation and the bottom of the USDW are described.

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### Proposed addition: (i) Maps and stratigraphic cross sections indicating the general vertical and lateral limits of all USDWs, water wells and springs within the area of review, their positions relativ e to the injection zone(s) and the direction of water movement, where known;

Proposed addition: (j) Baseline geochemical data on subsurface formations, including all USDWs in the area of review;

Proposed addition: (k) Proposed operating data:

Proposed addition: (1) Average and maximum daily rate and volume of the carbon dioxide stream;

Proposed addition: (2) Average and maximum injection pressure;

Proposed addition: (3) The source of the carbon dioxide stream; and

Proposed addition: (4) An analysis of the chemical and physical characteristics of the carbon dioxide stream;

Proposed addition: (l) The compatibility of the carbon dioxide stream with fluids in the injection zone and minerals in both the injection and the confining zone(s), based on the results of the formation testing program, and with the materials used to construct the well;

Proposed addition: (m) Proposed formation te sting program to obtain an analysis of the chemical and physical characteristics of the inje ction zone and confining
zone;
Proposed addition: (n) Proposed stimulati on program and a determination that stimulation will not interfere with containment;

Proposed addition: (o) Proposed formation te sting program to obtain an analysis of the chemical, physical and radiolog ical characteristics of and other information on the injection zone.

Proposed addition: (p) Proposed procedure to outline steps necessary to conduct injection operation;

Proposed addition: (q) Engineering drawings of the surface and subsurface construction details of the system, including design features for surge control and water hammer protection;

Proposed addition: (r ) Injection well construction procedures that meet the requirements of Section 146.86;

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### Proposed addition: (s) Proposed area of review and corrective action plan that meets the requirements under Section 146.84;

Proposed addition: (t) The status of corre ctive action on wells in the area of review;

Proposed addition: (u) A demonstration, satisfactory to the Director, that the applicant has met the financial respon sibility requirements under Section 146.85;

Proposed addition: (v) Proposed testing and monitoring plan required by Section 146.90

Proposed addition: (w) Proposed injection well plugging plan re quired by Section 146.92(b)

Proposed addition: (x) Proposed post-injection site care and site closure plan required by Section 146.93(a)

Proposed addition: (y) Proposed emergency and remedial response plan required by Section 146.94; and

Proposed addition: (z) Any other information requested by the Director.

Proposed addition: (2) Required Class VI operation permit information

Proposed Rule: 146.82(a) & (b)

Revision or Comment: Renumber 2(a) & (b)

Proposed Rule: 146.82(d) - (h)

Revision or Comment: Renumber 2(d) - 2(h)

Proposed Rule: 146.82(h)

Proposed addition: (5) Contingency plans tocope with all shut-ins or well failures, including emergency discharge provisions;

No rationale provided

Proposed Rule: 146.82(i)

Revision or Comment: Renumber 2(i)

Proposed Rule: 146.82(j)

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### Proposed revision: 2(j) Results of the formation testing program to obtain an analysis of the chemical, physical and radiological characteristics of and other information on the injection zone.

No rationale provided

Proposed Rule: 146.82(k) - (m)

Revision or Comment: Renumber 2(k) - 2(m)

No rationale provided

Proposed Rule: 146.82(n)

Proposed revision: 2 (n) Engineering drawings of the surface and subsurface construction details of the system, including design features for surge control and water hammer protection, including the following:

Proposed addition: (1) Record drawings, based upon inspections by the engineer of record or persons under his direct supervision, withall deviations noted;

Proposed addition: (2) Copies of the mill certificates of all casings used in the construction of the well;

Proposed addition: (3) Certification of completion submitted by the engineer of record;

Proposed addition: (4) An operation manual including emergency procedures;

Proposed addition: (5) Proposed monitoring program and data to be submitted;

Proposed addition: (6) Proof that the exis tence of the well and any associated monitoring wells have been recorded with the permanent warranty deed or other instrument of conveyance as a two pageproviso or addendum that contains certification of the locations of the we lls (by metes and bounds) and a detailed sketch of the parcel that shows the location of the well. The location shall be measured by a certified land surveyor, and shall contain the surveyor's signature, registration number , official seal, and the following statement: "I hereby certify that this survey was made under my responsible direction and supervision, and is a correct repres entation of the land surveyed."

No rationale provided

Proposed Rule: 146.82(o) - (y)

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### Revision or Comment: Renumber 2(o) - (y)

Proposed Rule: 146.82

Proposed addition: (3) Operational Testing

Proposed addition: (a) For Class VI wells , the construction permit includes a period of temporary injecti on operation for the purposesof long term testing. Prior to commencement of operational testing:

Proposed addition: 1. Construction of the injection well shall be complete and the permittee shall submit a notice of completion of construction to the Director.

Proposed addition: 2. Each well shall first be tested for integrity of construction, and shall be followed by a short term injection test of such duration to allow for the prediction of the operating pressure.

Proposed addition: 3. The permittee shall submit the following information to the Director, as described in the permit.

Proposed addition: a. A copy of the borehole television survey(s) Proposed addition: b. Geophysical logs, Proposed addition: c. Mechanical integrity test data, Proposed addition: d. Data obtained during the short term injection testing conducted according to subparagraph 2. above. Proposed addition: e. Confining zone data, Proposed addition: f. Background water quality data for the injection and monitor zones; Proposed addition: g. Waste stream analysis, Proposed addition: h. As-built well construction specifications, and Proposed addition: i. Other data obtained during well construction which demonstrates that the well will operate in compliance with this chapter.

Proposed addition: 4. Any corrective action required under Section 146.84, shall be completed.

Proposed addition: 5. Prior to granting approval for operational testing of a Class VI well, the Director shall consider the following information:

Proposed addition: a. All available lo gging and testing program data on the well; Proposed addition: b. A demonstration of mechanical integrity Proposed addition: c. The anticipated maximum pressure and flow rate at which the permittee will operate; Proposed addition: d. The results of the formation testing program;

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### Proposed addition: e. The actual injection procedure; Proposed addition: f. The compatibility of injected waste with fluids in the injection zone and minerals in both the injection zone and the confining zone; Proposed addition: g. The status of corre ctive action on defective wells in the area of review; and

Proposed addition: (b) Written authorization for operational testing shall be obtained from the Director. Authorization shall be for up to two years or the expiration date of the construction permit, whichever is less, and is only renewable once as described in Secti on 146.91. The authorizati on shall specify the conditions under which operational testing is approved. The authorization shall include:

Proposed addition: 1. Injection pressure limitation, Proposed addition: 2. Injection flow rate limitation, Proposed addition: 3. Injection well monitoring requirements, Proposed addition: 4. Effluent monitoring requirements, Proposed addition: 5. Weekly ground water sampling of monitor wells, Proposed addition: 6. Monthly sp ecific injectivity testing, Proposed addition: 7. Reporting requirements, and Proposed addition: 8. An expiration date for the operational testing period not to exceed two years.

Proposed addition: (c ) Before authorizing operational testing, the Director shall conduct an inspection of the facility to determine if the conditions of the permit have been met.

Proposed addition: (d) A sampling frequency and reporting of less than once per month shall not be allowed.

Proposed addition: (e) For Class VI we lls, the duration of the operational testing period shall not exceed two years or the expirati on date of the construction permit, whichever is less. If the Director ha s not issued an intent to issue an operation permit for the einjectionwell9s) by the end of the operational testing period, the permittee shall cease injection.

Proposed addition: (f) For a Class VI well, if an operation permit has not been obtained for the well within two years after the cessation of operational testing, the permittee shall submit an app lication to the Dire ctor to plug and abandon the well in accordance with Section 146.92.

Proposed addition: (4) The Director shall conduct periodic inspections during construction

No rationale provided

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### Individual Response: Based on its evaluation of all publiccomments and input on the proposed rule and NODA and Request for Comment EPA has made many revisions to the GS Rule. Please see the final rule and the discussion of geol ogic site characterization in the preamble for additional information.

EPA clarifies that the final rule does not require anowner or operator to obtain a separate Class VI operational testing permit. However, EPA revised §146.82 so that the final regulation specifies separate requirements for information to be submitted with the permit application and before well construction is approved (at §146.82(a)) and information to be submitted before operation of the well is authorized (at §146.82(c)). Final information on injection zone pressures are required following drilling of the well, at §146.82(c)(4).

EPA disagrees that the rule needs to specify the qualifications of owner or operator staff creating the permit submittals. EPA is developing a number of technical guidances and implementation materials to assist owners or operators and Directors in the permitting process. These guidances will provide suggestions on how toperform many of the activitiesnecessary for applying for a permit, including developing all required plan s and conducting site ch aracterizations under §146.82. Technical guidances and implementation materials will be available on EPA's web site, at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Letter ID: 0142 Comment ID: 22591 Letter Lines: 1655 to 1665

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language Comment Code: 3560 2.2.3.2 Conditions that merit reevaluation of the AoR (seeking comment) Comment Code: 4710 2.7.1 Proposed submissions required for permit applications (seeking comment)

Comment: Proposed Rule: 146.82(c)

Revision or Comment: Proposed Revision: 2(c ) Re-evaluation of Area of Review. After completion of the operational testing period, the Area of Review shall be re-evaluated, using a calibrated, multi-phase fluid flow model. The data collection during operational testing must be adequate for calibration of the model. If a calibrated model cannot be prepared using data collected during operational testing, the owner or operator shall apply for a new period of operational testing of up to two years inorder to collect the required data.

No rationale provided

Individual Response: EPA agrees that AoR reevaluations should be based on the same type of modeling that is used to perform the initial delineation, but disagreesthat the suggested change is necessary. EPA clarifies that all AoR modeling (including that which supports reevaluations) should be based on accepted, verified, and validated scientific methods. Under requirements at §146.84(b), the owner or operator must demonstrate in the proposed AoR and corrective action plan, to the satisfaction of the Director that the modeled AoR (and all updates) will be based on

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### detailed geologic data collected on the site. EPA anticipates that any model that does this in a comprehensive and satisfactory manner would be approved by the Director.

Letter ID: 0142 Comment ID: 22592 Letter Lines: 1821 to 1832

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language Comment Code: 3120 2.1.2 Need to identify additional confining and containment zones (seeking comment)

Comment: Proposed Rule: 146.83(b)

Proposed revision: (b) Owners or operators of Class VI wells must identify and characterize additional zones, if they exist, that will impede vertical fluid movement, allow for pressure dissipati on, and provide additi onal opportunities for monitoring, mitigation and remediation. Vertical faults and fractures that transect these zones must be identified.

Rationale: While NGWA believes that a sitewith a single confining can provide storage integrity we feel that if there are additional confining layers at the site they should be characterized to get a better estimate of leakage risk to USDWs and possibly identify additional monitoring zones.

Individual Response: EPA agrees with the commenter that, insome situations, the presence of additional confining and containment zones above the primary (i.e., lowermost) confining zone can improve USDW protection from endangerment. The final regulation retains the requirement at §146.83(b) which affords the Director discretion torequire owners or operators to identify and characterize additional zones. Any additional confining zones would need to be included in the geologic site characterization process, which the owner or operator would submit and the Director would review in determining whether to grant a permit. EPA is developing guidance on site characterization for GS proj ects to assist owners or operators and Directors in evaluating permit requirements and applications under §146. 82. The guidance provides recommendations regarding characterizing the regi onal geology and hydrogeology of a proposed GS site as well as performing the necessary geochemical, geomechani cal, and geophysical analyses of the injection and confining zone. EPA expects that this gui dance will assist permit writers in making an objective decision about requiring additional c onfining layers. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Letter ID: 0142 Comment ID: 22593 Letter Lines: 1834 to 1844

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language Comment Code: 3530 2.2.3.1 AoR reevaluation fre quency (seeking comment)

Comment: Proposed Rule: 146.84(b)(2)(i)

Proposed revision: (i) The owner or operator will reevaluate the AOR after two

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### yearsof operational testing (prior to issuance of the operating permit), and after 5 years and then no less frequently than every 5 years for the life of the project;

Rationale: NGWA believes that a frequency of every 10 years is too long to identify early discrepancies between the site performance and the site model. Seeing early difference will allow for earlier model updating and provide additional reduction in leakage risk.

Individual Response: As described above, EPA agrees that reevaluations of the AoR every ten years may not be sufficient to ensure protecti on of USDWs from endangerment, and has changed the minimum frequency for the AoR reevaluation at §146.84(e) from 10 years to at least every 5 years in the final GS rule.

In addition, the Director has discretion to require more frequent AoR reevaluation if he or she has reason to believe, based on site-specific information, that a five-year reevaluation schedule is not sufficiently protective of USDWs.

Letter ID: 0142 Comment ID: 22594 Letter Lines: 1846 to 1856

Comment Code: 3560 2.2.3.2 Conditions that merit reevaluation of the AoR (seeking comment) Comment Code: 5600 2.11 Comments related to UIC Program primacy for Class VI wells

Comment: Proposed Rule: 146.84(c)

Comment: There should be somewhere in th e rules a requirement that "mutual interference effects" should trigger reevaluation and re -delineation of the AORs of all projects that are interferring with each other. In essence, when a new project is submitted for permitting, there should be a system-wide, "regional" entity charged with ensuring that AORs for each project are appropriate, and perhaps that a "hybrid" or "combo AOR" be defined for the set of mutuallyinterferring projects.

No rationale provided

Individual Response: EPA anticipates that the impacts of multiple operators injecting into hydraulically connected formations will be accounted for in the initial AoR calculation. EPA adds that the owner or operator must demonstrate, in the proposed AoR and corrective action plan, to the satisfaction of the Director that the modeled AoR will be based on detailed geologic data collected on the site and includes consideration of existing conditions such as the presence of multiple operators. EPA adds that if any new GS projects are permitted within the AoR of a GS project between AoR evaluations, the AoR reev aluation would need to address such projects. EPA also expects that the permitting of the newer GS project would have considered the presence of an existing GS project.

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### EPA understands that the CO2 plumes for large GS projects may cross State, Tribal, Territorial, EPA Regional, or national boundaries . The final GS rule, at §146.82( a)(2), requires the owner or operator to identify all State, Tribal, and Territorial boundaries within the AoR. Based on this information, the Director must provide written notif ication to all States, Tribes, and Territories to inform them of the permit app lication, as specified in §146.82(b)and ensure that they are involved in any necessary processes (e.g., development of the emergency and remedial response plan, as specified in §146.94). The Agency enc ourages transparency in the permitting process and anticipates that State-State/State-Tribalcommunication on GS permitting will facilitate information sharing and encourag e safe, protective projects.

Because some GS projects will require coordination across State, Tribal and Territorial jurisdictions, the Agency will work with the appropriate entities to facilitate communication among States, Tribes, and Territori es interested in obtaining primacy during the implementation phase of the GS regulation. Such communication may involve other organizations such as the Sierra Club, NDWAC, associations, and other experts. However, the responsibility for addressing such subjects ultimately rests with the States, Tribes, and Territories with primacy. In addition, EPA is developing guidances for states that describe the proc ess of applying for and receiving primary enforcement responsibility (p rimacy) for GS Class VI wells under Section 1422 of SDWA, as well as the technical and administrative issueson developing GS regulations that are the equivalent of minimum Federal criteria and requirements. The guidance will be available at http://water.epa.gov/type/groundwater/uic/wells_s equestration.cfm.

Letter ID: 0142 Comment ID: 22595 Letter Lines: 1858 to 1868

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language Comment Code: 3300 2.2.1 Delineating the AoR/M odeling CO2 movement

Comment: Proposed Rule: 146.84(c)(1)(i)

Proposed revision: (i) Be based on detailed geologic data collected to characterize the injection zone, confining zone(s), transmissive monitoring zones and any additional zones; and anticipated operating data, including injection pressures, rate s and total volumes over the proposed life of the geological sequestration project;

Rationale: NGWA proposes that if there are secondary confining units that they should be included in the site model along with any transmissive zones between the primary and secondary confining units.

Individual Response: EPA agrees that additional confining and containment zones should be accounted for in the AoR delineation if site-specific circumstances indicate a need for this. 146.84 (c)(1)(i) specifies that computational modeling should be base d on detailed geologic data collected to characterize the inj ection zone and confining zone, aswell as any additional zones.

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### Letter ID: 0142 Comment ID: 22596 Letter Lines: 1870 to 1880

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language Comment Code: 3440 2.2.2.2 Evaluation of wells in the AoR (e.g., types of data to be reviewed)

Comment: Proposed Rule: 146.84(c)(2)

Proposed revision: (2) Using methods approved by the Director, identify all penetrations, including ac tive and abandoned wells and underground mines, in the area whose total depth is greater than the depth to the bottom of the lowermost USDW, including those penetrating the conf ining zone. Provide a description of each well’s type, construction, date drilled, location, depth, record of plugging and/or completion, and any additi onal information the Director may require; and

Rationale: This makes this consistent with NGWA's proposed section 146(a)(8)

Individual Response: EPA clarifies that any well that penetrates the confining zone, even if it does not extend all the way through the confining formation, is tobe included in the tabulation. EPA is issuing guidance on. The guidance describes EPA's recommended approaches for the data to be considered in an initial AoR de lineation, how to apply computational modeling to delineate the AoR, how to identify all wells that require corrective acti on, performing corrective action at GS sites, and, when appropriate, completing AoR reevaluations. The guidance will be available on EPA's web site, at http://water.epa.gov/type/groundwater/uic/wells_se questration.cfm.

The final rule retains the language in §146.84(c)(2 ) as proposed. EPA clarifies that the mapping and cross sections required to be submitted under §146.82(a)(3) will define the limits of the confining zone, which would be accounted for in the AoR delineation and corrective action evaluation required at §146.84(c). EPA adds that owners or operators must also, under §146.82(a)(2), submit a map of the AoR that shows all injection wells, producing wells, abandoned wells, plugged wells or dry holes, deep stratigraphic boreholes, State or EPA approved subsurface cleanup sites, surface bodiesof water, springs, mines (surface and subsurface), quarries, water wells and other pertinent surface features including structures intended for human occupancy and roads. EPA be lieves that these requirements address the commenter's concerns.

Letter ID: 0142 Comment ID: 22597 Letter Lines: 1882 to 1891

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language Comment Code: 3530 2.2.3.1 AoR reevaluation fre quency (seeking comment)

Comment: Proposed Rule: 146.84(f)

Proposed revision: (f) At the minimum fixed frequency, not to exceed two years

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### if under operational testing (prior to i ssuance of the operating permit), or 5 years (if operating permit has been issued), as specified in the area of review and corrective action plan or when monitoring and operational conditions warrant, owners or operators must:

Rationale: This makes this consistent with NGWA's proposed revision to Section 146.84(b)(2)(i)

Individual Response: EPA agrees that reevaluations of the AoR every ten years may not be sufficient to appropriately model plume and pre ssure front movement, establish conditions for corrective action, and ensure protection of USDWs from endangerment. For these reasons, the Agency changed the minimum frequency for the AoR reevaluation at §146.84(e) from 10 years to at least every 5 years in the final GS rule. EPA believes that this revised frequency addresses commenters' concerns about the inherent uncertainties in modeling CO2 movement, the emerging nature of GS technology, risk-based targeting of monitoring activities, and the unique nature of CO2 GS. In addition, the Director has discretion to requiremore frequent AoR reevaluation if he or she has reason to believe, based on site-speci fic information, that a five-year reevaluation schedule is not sufficiently protective of USDWs.

Letter ID: 0142 Comment ID: 22598 Letter Lines: 1893 to 1898

Comment Code: 5430 2.9.1 Comments on proposed financial responsibility requirements (40 CFR 146.85)

Comment: Proposed Rule: 146.85(a)

Comment: A question was raised during discus sions about how the producer of the CO2 is impacted and whether they should maintain some liability.

No rationale provided

Individual Response: Once an owner or operator has met all regulatory requirements under Part 146 for Class VI wells and the Director has approved site closure pursuant to requirements at §146.93, the owner or operator will generally no l onger be subject to enforcement for regulatory noncompliance. Furthermore, their financial instrument as required under §146.85 will be released if it was not used. However, even if a site closure is approved under §146.93, an owner or operator may be held liable for regulatory noncompliance (including violation of 40 CFR 144.12) in certain circumstances. For example, anowner or operator may be held liable for regulatory noncompliance even after site closure was approved if the Director relied on erroneous information (e.g., erroneous modeling data) provided by the owner or operator when approving site closure.

Additionally, an owner or operator may always besubject to any action the Administrator deems necessary to protect the health of persons under §1431 of the SD WA after site closure if there is unanticipated migration towards or into a US DW that causes or threatens imminent and substantial endangerment to publichealth. The action may include issuing administrative orders

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### or commencing a civil action for appropriate relief. If the owner or operator fails to comply with the order, they may be subject to a civil penalty for each day in which such violation occurs or failure to comply continues.

The Agency clarifies that Class VI well permits may be transferred to another owner or operator pursuant to §144.38 whereby generally all other regulatory re sponsibilities are transferred to that new owner and operator, which includes all potential liabilities associated with meeting the requirements of that permit. Please see further clarification on the issue of long term liability in the preamble of the final rule.

Furthermore, after site closure an owner or operator may remain liable under tort and other remedies, or under other federal statutes including, but not limited to, Clean Air Act, 42 U.S.C. §§ 7401-7671; CERCLA, 42 U.S.C. § 9601-9675; and RCRA, 42 U.S.C. § 6901-6992. EPA does not have authority to transfer SDWA or other legal liability for Class VI wells to the State or federal government or a third-party fund. See the final rule preamble for further discussion of EPA's final approach.

Letter ID: 0142 Comment ID: 22599 Letter Lines: 1900 to 1909

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language Comment Code: 5430 2.9.1 Comments on proposed financial responsibility requirements (40 CFR 146.85)

Comment: Proposed Rule: 146.85(b)

Proposed revision: (b) The owner or operator must provide to the Director, at the same frequency as the AOR reevaluation, written updates of adjustments to the cost estimate to account for any amendments to the area of review and corrective action plan (§ 146.84), the injection well plugging plan (§146.92), and the post-injection site care and site closure plan (§146.93).

Rationale: NGWA proposes that potential changes in the size of the AOR require that all site plans be reevaluated at the same frequency as the AOR.

Individual Response: EPA agrees that it is important to periodically update cost estimates that support financial responsibility determinations. EPA clarifies that the GS rule, at §146.85(c) requires the owner or operator to provide annual updates to the cost estimate to account for any amendments to the AoR and corrective action plan, the injection well plugging plan, the PISC and site closure plan, and the emergency and remedial response plan. See the final rule and preamble for further discussion of EPA's final a pproach to financial responsibility. EPA adds that the Director can also requirethe owner or operator to provide an adjustment of the cost estimate if the Director determines that the original demonstration is no longer adequate, as specified at §146.85(e). The owner or operator must also update the cost estimate annually to adjust for inflation under §146.85(c)(2).

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### Letter ID: 0142 Comment ID: 22600 Letter Lines: 1911 to 1913

Comment Code: 3820 2.3.1 Well construction procedures

Comment: Proposed Rule: 146.86(a)(3)

Comment: NGWA supports this provision

Individual Response: EPA acknowledges the comment and agrees that protection of USDWs from endangerment and prevention of fluid movement between formations is paramount. Appropriately designed and constructed wells are necessary to prevent endangerment to USDWs and maintain integrity of the well throughout the lifetime of a GS project . This is the foundation of the requirements for constructi on of Class VI wells at §146.86.

Letter ID: 0142 Comment ID: 22601 Letter Lines: 1915 to 1917

Comment Code: 3862 2.3.3.1 Use of corrosion-resistant construction materials (seeking comment) Comment Code: 3864 2.3.3.2 Use of corrosion-resistant cements (seeking comment)

Comment: Proposed Rule: 146.86(b)(1)

Comment: NGWA supports this provision

Individual Response: EPA agrees that cement that is co mpatible with the CO2 and formation fluids will enhance Class VI well integrity. EPA also agrees that developing technology in the field of acid-resistant cement will provide the industry with future benefits. In the interest of USDW protection, the Agency requires that the materials used in Class VI wells be compatible with fluids with which they may come in contact, as spec ified in §146.86(b)(1).

EPA adds that the requirements at §146.86(b)(1) state that materials must meet or exceed standards developed for such materials by the American Petroleum Institute, ASTM International, or comparable standards acceptable to the Director. This requirement invokes the expertise of these bodies and allows the use of technologies that are yet to be developed.

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: 0142 Comment ID: 22602 Letter Lines: 1919 to 1921

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)

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### Comment: Proposed Rule: 146.86(b)(3)

Comment: NGWA supports this provision

Individual Response: EPA disagrees that protecting deep USDWs underlying multiple, more shallow USDWs is "overkill." Protection of USDW s, regardless of their depth or stratigraphic location, is the primary mission and mandate of the UIC program—as specified by Congress in the SDWA—and the purpose of all requirements for injection wells. Any injection activity must be demonstrated to not endanger USDWs, regardle ss of their depth, and if such a demonstration cannot be made, then the activity will not beallowed under UIC requirements or the SDWA. Water agencies commenting on the proposed rule noted that diminishing water supplies are requiring water utilities to use deeper and more saline sources, and the SDWA mandates EPA to set regulations that protect USDWs from endangerment.

The final GS rule at §146.86(b)(2) requires that surface casing extend through the base of the lowermost USDW and be cemented to the surface through the use of a single string or multiple strings of casing and cement. It does not, however, specify how cementing must be accomplished, and it allows the owner or operator to propose alternate methods that provide a sufficient amount of cement to meet the standard that USDWs are protected from endangerment. EPA notes that there are many potential ways to meetthe requirement, such as the use of staged cementing.

EPA recognizes concerns regarding construction of Class VI wells where the lowermost USDW is very deep. To further address comments on deep injection wells, the final GS rule at §146.95 includes requirements for owners or operators that seek a waiver of the injection depth 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.

Letter ID: 0142 Comment ID: 22603 Letter Lines: 1923 to 1926

Comment Code: 3864 2.3.3.2 Use of corrosion-resistant cements (seeking comment)

Comment: Proposed Rule: 146.86(b)(5)

Comment: NGWA supports this provision and especially that the assessment should include the radial integrity of the cement.

Individual Response: EPA acknowledges the comment agrees that cement that is compatible with the CO2 and formation fluids will enhance Cl ass VI well integrity. The final rule retains this provision.

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

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### 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: 0142 Comment ID: 22604 Letter Lines: 1928 to 1935

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language Comment Code: 3866 2.3.3.3 Logging and testing requirements (40 CFR 146.87)

Comment: Proposed Rule: 146.87(a)(3)(ii)

Proposed revision: (ii) A cement bond, vari able density log, and radial cement evaluation log and a temperature log after the casing is set and cemented.

Rationale: NGWA supports inclusion of a radial cement evaluation log in addition. The addition of this test will help identify any potential channels in the cement out from casing

Individual Response: EPA clarifies at §146.87(a)(2)( ii) that owners or operators must perform a cement bond (i.e., cement evaluation) log af ter the casing is set and cemented.

Letter ID: 0142 Comment ID: 22605 Letter Lines: 1937 to 1939

Comment Code: 3866 2.3.3.3 Logging and testing requirements (40 CFR 146.87)

Comment: Proposed Rule: 146.87(a)(4)

Comment: NGWA supports the inclusi on of this series of tests.

Individual Response: EPA acknowledges the comment and agrees that logging and testing requirements are appropriate and necessary. The requirements at §146.87 stem from existing knowledge and practices in place for other injection well classe s and within the oil and gas industry, and are tailored to the sp ecial characteristics of CO2 injection for GS. The final rule retains the requirements for demonstration of internal and external mechanical integrity required at §146.87(a)(4).

Letter ID: 0142 Comment ID: 22606 Letter Lines: 1941 to 1949

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language Comment Code: 4543 2.5.2.1 MIT procedures and methodsfor GS (seeking comment)

Comment: Proposed Rule: 146.89(c)

Proposed revision: At least once per year, the owner or operator must use one of the following methods, as approved by the director, to determine the absence

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### of significant fluid movement under paragraph (a)(2) of this section.

Rationale: There was a question as to whether one of these tests individually would suffice in all circumstances. The change proposed is to allow the director to review the proposal.

Individual Response: EPA clarifies that all MI Ts the owner or operator proposes to use must be described in the proposed testing and monitoring plan, which must be approved by the Director. See §146.90. EPA believes that the MITs described in §146.89(c) of the rule (e.g., an approved tracer log or temperature or noise logs) are effective methodsto demonstrate external MI, provide an important early warning of potential problems in the injection well system, and represent standard techniques that have been used successfully by the drilling industry and for the UIC Program for decades. The Agency notes that the regulations do provide the Director flexibility at §146.89(e) to approve th e use of alternative MIT methods.

Letter ID: 0142 Comment ID: 22607 Letter Lines: 1951 to 1954

Comment Code: 4660 2.6.6 Geochemical monitoring

Comment: Proposed Rule: 146.90(d)

Comment: The monitoring should be site speci fic and include particular analytes at risk to the aquifer from the existing geologic environment.

Individual Response: While each monitoring plan must be s ite-specific based on data collected during the initial site characterization and base line geochemical monitoring, it is likely that geochemical sampling might include basic water quality parameters such as pH, specific conductivity, temperature, CO2, alkalinity, major ions, and select heavy metals. Additional parameters may be monitored based on the potential for leaching of minerals or the geochemistry of native fluids.

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 l ogging and testing of injection wells, MITs, injecti on 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_se questration.cfm.

Letter ID: 0142 Comment ID: 22608 Letter Lines: 1958 to 1964

Comment Code: 4640 2.6.4 Pressure fall-off testing (seeking comment)

Comment: Proposed Rule: 146.90(f)

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### Comment: What additional information does this test provide that is not available from other sources? The perception from some of our reviewers is that there may not be much information that is gathered that is not already available from other sources. If there is no significant additional information provided, running the test may not be necessary.

Individual Response: EPA disagrees and believes that pressure fall-off testing is necessary for GS wells. Pressure fall-off tests are designed to verify that modeled projections of reservoir pressure decline agree with measured pressure decline profiles. These tests can be useful in AoR calculations and reevaluations and may also indicate mischaracterization of site geology and the presence of leakage pathways. EPA therefore believes that pressure fall-off testing must be conducted at least once every five years, and the final GS regulati on includes this requirement at §146.90(f). Pressure fall-off tests may be conducted in conjunction with other well performance tests (i.e., mechanical integrity testing) toensure safe and effective operations.

Letter ID: 0142 Comment ID: 22609 Letter Lines: 1968 to 1975

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language Comment Code: 4610 2.6.1 Testing and monitoring plan requirement (seeking comment)

Comment: [In the text below, text inCAPS denotes added text.]

Proposed Rule: 146.90(h)(1)

Proposed revision: (1) The testing and monitoring plan must be based on potential RISKS within the area of review;

Rationale: Risk is more generally accepted and understood.

Individual Response: The final rule at §146.90(h)(1) incorporates the suggested revision. Based on its evaluation of all public comments and input on the propos ed rule and NODA and Request for Comment EPA has made many revisions to the GS rule. See th e final rule and preamble for further discussion on EPA's final approach.

Letter ID: 0142 Comment ID: 22610 Letter Lines: 1977 to 2177

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language Comment Code: 4710 2.7.1 Proposed submissions required for permit applications (seeking comment)

Comment: Proposed Rule: 146.91

Proposed addition: (1) Class VI Test/Injection Well Construction Permit

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### Proposed addition: (a) The Director shall require periodic data reports and progress reports during construction that include:

Proposed addition: 1. Driller's log Proposed addition: 2. Geophysical surveys Proposed addition: 3. Core analyses Proposed addition: 4. Lithologic logs Proposed addition: 5. Drill stem tests Proposed addition: 6. Pump tests Proposed addition: 7. Daily job (construction) reports Proposed addition: 8. Water quality analyses

Proposed addition: (b) The frequency of reporting shall be specified in the individual permit

Proposed addition: (c ) Interpretation of data is required in the data reports or progress reports at the completion of each significant phase of construction, such as completion of test well construction and testing, completion of injection well construction, and comp letion of injection well testing.

Proposed addition: (d) The owner or operator shall submit final reports of all data collected from the test injection ell with interpretations to the Director with the application for a Class VI Test/Injection Well Construction and Testing Permit and a Class VI Injection Well Operation Permit shall include all information and data collected under Section 146.87, with appropriate interpretations

Proposed addition: (2) Class VI Operational Testing Permit

Proposed addition: (a) The owner or operator shall submit, as part of the permit application, the proposed methodology for collection and reporting of operational data, to ensure that the datais collected, correlated, and reported in a fashion that would enable the Director to evaluate well performance.

Proposed addition: (b) All Class VI wellsshall report monthly the following:

Proposed addition: 1. Operating reports to the Director on:

Proposed addition: a. The physical, chemical, and other relevant characteristics of injection fluids;

Proposed addition: b. Daily reading of the pressure and flow for each well. For each Class VI sequestration well, a specific injectivity test shall be performed quarterly;

Proposed addition: c. Monthly average, maximum and minimum values for injection

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### pressure, flow rate and volume , and annular pressure; and

Proposed addition: d. The results of monitoring prescribed under Section 146.90

Proposed addition: 2. Reporting the results , within three months after the completion of:

Proposed addition: a. Annular monitoring tests of mechanical integrity;

Proposed addition: b. Any other test of the injection ell conducted by the permittee if required by the Director; and

Proposed addition: c. Any well work over.

Proposed addition: (c ) Specific injectivity testing shall be performed while the pumping rate to the well(s) has beenset at a predetermined level and reported as the specific injectivity index (gpm/specific pressure (psig)). As part of this test, the well shall be shut-in for a period of time necessary to conduct a valid observation of pressure fall-off. The owner or operator shall propose which pumping rate will be used ba sed on the expected flow, the design of the pump station including the volume of the wet well and pump type(s), and the type of pump controls used. The pumping rate(s) shall be included as a condition of the operation permit.

Proposed addition: (d) Re-evaluation of Area of Review. After completion of the operatonal testing period, the Area of Review shall be re-evaluated, using a calibrated, multi-phase fluid flow model. The data collection during operational testing must be adequate for calibration of the model. If a calibrated model cannot be prepared using data colle cted during operational testing, the owner or operator shall apply for a new period of operational testing of up to two years inorder to collect the required data. No more than two operational testing permits can be i ssued for any Class VI well. If the recalculated Area of Review includes any relevant wellsor penetrations through the confining zone that were not repo rted in the permit application, a new tabulation of penetrations as required in Section 146.84(c)(2) and (3) shall be provided. Owners or operators must perf orm corrective action as required in Section 146.84(d).

Proposed addition: (e) If physical or geochemical data such as water quality, pressure changes, or mechanical integrity test results indicate that fluid movement into or between underground sourcesof drinking water may be occurring, the permittee shall submit additional data toprovide reasonable assurance that the injection operation is in compliance with the requirements of this chapter. This additional data shall be submitted with the periodic operations reports, the content and frequency of which are specified in the individual permit.

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### Proposed addition: (f) A Class VI well permit shall be written to require that if CFR Section 146.14(a) is applicable, progress reports shall be submitted no later than thirty days following each interim date and the final date of compliance.

Proposed addition: (3) Class VI Injection Well Operation Permit.

Proposed addition: (a) The applicant shall submit, as part of the permit application, the proposed methodology for collection and reporting of operational data, to ensure that the datais collected, correlated, and reported in a fashion that would enable the Director to evaluate well performance.

Proposed addition: (b) All Class VI wellsshall report monthly the following:

Proposed addition: 1. Operating reports to the Director on:

Proposed addition: a. The physical, chemi cal, and other relevant characteristics of injection fluids;

Proposed addition: b. Daily readings of the pressure and flow for each well. For each Class VI well, a specific inje ctivity test shall be performed quarterly;

Proposed addition: c. Monthly average, maximum and minimum values for injection pressure, flow rate and volume , and annular pressure; and

Proposed addition: d. The results of monitoring prescribed under Section 146.90

Proposed addition: 2. Reporting the results , within three months after the completion of:

Proposed addition: a. Periodic tests of mechanical integrity;

Proposed addition: b. Any other test of the injection well conducted by the permittee if required by the Director; and

Proposed addition: c. Any well work over.

Proposed addition: (c ) Specific injectivity testing shall be performed while the pumping rate to the well(s) has beenset at a predetermined level and reported as the specific injectivity index (gpm/specific pressure (psig)). As part of this test, the well shall be shut-in for a period of time necessary to conduct a valid observation of pressure fall-off. The owner or operator shall propose which pumping rate will be used ba sed on the expected flow, the design of the pump stations including the volume of the wet well and pump type(s), and the type of pump controls used. The pumping rate(s) shall be included as a

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### condition of the operation permit.

(d) Re-evaluation of Area of Review. Every five years, the Area of Review shall be re-evaluated, using a calibrated, multi-phase fluid flow model. The data collection during operation must be adequatefor calibration of the model. If a calibrated model cannot be prepared using data collected during operation, the owner or operator shall, within 90 days, apply for a new operation permit with a revised monitoring and testing plan desi gned to collect the required data. The re-issued Class VI operation permit shall bevalid for a period of no more than two years. After two years of operation under a re-issued operating permit, the applicant shall again re- evaluate the Area of Review using a calibrated, multiphase fluid flow model and re-apply for a five-year operating permit. If the recalculated Area of Review includes any relevant wells or penetrations whose total depth is greater than the depth to the bottom of the lowermost USDW that were not reported in the permit applicati on, a new tabulation of penetrations as required in Section 146.84(c)(2) and (3) sh all be provided. Owners or operators must perform corrective action as required in Section 146.84(d) must perform corrective action as required in Section 146.84(d).

No rationale provided

Proposed Rule: Introductory text to 146.91 and 146.91(a)(1)-(4)

Revision or comment: Proposed for deletion

Rationale: Covered in proposed S ection 146.91(3) and subsections

Proposed Rule: 146.91(a)(5)

Revision or comment: Renumber 3(e)

Proposed Rule: 146.91(a)(6)

Revision or comment: Renumber 3(f); delete "and"

Proposed addition: (g) If physical or geochemical data such as water quality, pressure changes, or mechanical integrity test results indicate that fluid movement into or between underground sourcesof drinking water may be occurring, the permittee shall submit additional data toprovide reasonable assurance that the injection operation is in compliance with the requirements of this chapter. This additional data shall be submitted with the periodic operations reports, the content and frequency of which are specified in the individual permit.

Proposed addition: (h) A Class VI well permit shall be written to require that if CFR Section 146.41(a) is applicable, progress reports shall be submitted no later than thirty days following each interim date and the final date of

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### compliance.

No rationale provided

Proposed Rule: 146.91(a)(7); 146.91(b)(1)-(3)

Proposed for deletion

Rationale: Covered in proposed S ection 146.91(3) and subsections

Proposed Rule: 146.91(c)

Renumber (4)

Individual Response: Based on its evaluation of all publiccomments 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 discus sion on EPA's final approach. EPA is developing guidances on injection well construction and on monitoring and testing that wi ll assist owners or operators and Directors in performing the pre- operational logging and testing required at §146.86. This guidance will be available on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_se questration.cfm.

As described above, EPA clarifies that the final rule does not require an owner or operator to obtain a separate Class VI operational testing permit. However, EPA revised §146.82 so that the final regulation specifies separate requirements for information to be submitted with the permit application and before well construction is approved (at §146.82(a)) and information to be submitted before operation of the well is authorized (at §146.82(c)). Final information on injection zone pressures are required following drilling of the well, at §146.82(c)(4).

Letter ID: 0142 Comment ID: 22611 Letter Lines: 2179 to 2190

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language Comment Code: 4730 2.7.3 Reporting associated with closure and post-injection site care

Comment: Proposed Rule: 146.92(b)

Proposed revision: (b) Well Plugging Plan. The owner or operator of a Class VI well must prepare; maintain; including updating on the same schedule as the update to the Area of Review; and comply with a plan that is acceptable to the Director. The requirement to maintain and implement an approved plan is directly...

Rationale: The Area of Review re-evaluation should trigger a review and updating of all the plans (MMV, financial, plugging, emergency response...) on the same interval that the AOR is updated. NGWA suggests EPA check all timelines and make them compatible.

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### Individual Response: EPA agrees that the AoR reevaluations offer a good opportunity to promote a dialogue between the owner or operator and the permitting authority. Additionally, EPA recognizes that the AoR reevaluation has the potential to change or add important data to the other project plans and therefore the Agency agrees that the other Cl ass VI plans must be updated when an AoR reevaluation takes place. The final GS rule, at §§146.84(c), 146.90(j), and 146.94(d), requires owners or operators to reviewand update the AoR and corrective action plan, the testing and monitoring plan, and the emergency and remedial response plan throughout the life of the project. Owners or operators must review each plan and identify necessary amendments to the plan or demonstrate to the Director that no amendment is needed. These reviews must be performed within one year of an AoR reevaluation, following any significant changes to the facility (e.g., the addition of monitoring or injection wells) , or when required by the Director. In no case can reviews occur less often than once every five years. EPA is preparing guidance for owners or operators on developing and updating all of the required GS project plans. The guidance will be available on EPA's web site, at http://water.epa.gov/type/groundwater/uic/wells_seque stration.cfm. See the final rule and preamble for further discussion on EPA's final a pproach regarding the GS project plans.

Letter ID: 0142 Comment ID: 22612 Letter Lines: 2192 to 2208

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language Comment Code: 4730 2.7.3 Reporting associated with closure and post-injection site care Comment Code: 5100 2.8.1 Injection well plugging activities (seeking comment) (40 CFR 146.92)

Comment: Proposed Rule: 146.92(d)

Proposed revision: (d) Plugging Reports fo r Class VI Wells. Within 60 days after completion of plugging and abandonment of a well or well field the permittee shall submit to the Director a final report which includes:

Proposed addition: (1) Certification of completion in accordance with approved plans and specifications by anappropriately qualified engineer of record or professional geologist.

Note: It is important that the engineer and/or geologist have expertise and training in injection welldrilling technology, reservoir characterization and injection well constr uction and operation.

Proposed addition: (2) Evidence, such as a sealed copy or certification from the county clerk, that a surveyor's plot of the location of the abandoned well has been recorded in the county c ourthouse property records.

Individual Response: EPA agrees that appropriately qualified personnel (e.g., engineers and geologists) should be involved in all aspect s of the GS operation, including the well plugging process. When the owner or operator (and/or the person who performs the plugging operation)

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### signs the plugging report and certifie s it as accurate; they are attesting to the fact that all required activities were performed by qualified personnel. This is required under §146.92(d) and is a condition of the permit that is enforceable under §1423 of the SDWA. EPA clarifies that, in addition to requiring appropriate well plugging, the Director retain s the option of witnessing any plugging activity or testing at the well.

EPA clarifies that §146.93(g) requires the owner or operator, as part of the closure process, to record a notation on the deed stating that the property was used for GS. In addition, §146.93(f)(1) requires submissi on of a survey plat indicating the location of the well to the local zoning authority, as well as to the Director.

Letter ID: 0142 Comment ID: 22613 Letter Lines: 2212 to 2222

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language Comment Code: 4730 2.7.3 Reporting associated with closure and post-injection site care Comment Code: 5220 2.8.2.1 Post-injection monitoring activities

Comment: Proposed Rule: 146.93(a)

Proposed revision: (a) The owner or operator of a Class VI well must prepare; maintain; including updating on the same schedule as the update to the Area of Review; and comply with a plan for post- injection site care and site closure that meets the requirements of paragra ph (a)(2) of this section and is acceptable to the Director.

Rationale: The Area of Review re-evaluation should trigger a review and updating of the well plugging plan, and the post inj ection site care and closure plan. NGWA suggests EPA check all timelines and make them compatible.

Individual Response: EPA agrees with the commenter that, in some cases, the appropriate postinjection monitoring strategy may end up being different than initially projected at the time of permit application and there may be a need to amend the post-injection site care and site closure plan. EPA is requiring that upon the cessation of injection, the owner or operator submit an amended post-injection site care and site closure plan or demonstrate tothe Director that no changes to the original post-injection site care and site closure plan are necessary, as specified in §146.93(a)(3). EPA is not requiring formal periodic review and updates to the PISC and site closure plan throughout the injecti on phase. EPA does not expect that changes to this plan would be implemented until injection operations cease. EPA envisions that owners or operators will take into account similar cons iderations that guide updates to other project plans, e.g., monitoring and operational data and results of AoR reevaluations.

EPA has also added a new provision at §144.39(a)(5) requiring a modification, revocation, or reissuance of a Class VI permit whenever the Director determines that a change in the permit is necessary based on an amended AoR and correc tive action plan, testing and monitoring plan, injection well plugging plan, post- injection site care and site closure plan, or emergency and

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### remedial response plan is necessary. This would invoke the public notification procedures of 40 CFR Part 124 and the modification would be incorporated into the permit. EPA adds that, if any monitoring or other site data indicate a need for amending the post-injection site care plan, the owner or operator is expected to amend the plan accordingly.

Letter ID: 0142 Comment ID: 22614 Letter Lines: 2224 to 2250

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language Comment Code: 5240 2.8.2.2 Post injection timeframe (seeking comment)

Comment: Proposed Rule: 146.93(b)(1)

Proposed revision: (1) The owner or operator shall continue to conduct monitoring as specified in the Director-approved post- injection site care and site closure plan for at least 30 year s following the cessati on of injection. At the Director's discretion, the monitoring will continue until the geologic sequestration project no longer posesan endangerment to USDWs.

Rationale: NGWA believes some number should be included. 30 years is a number used in other EPA programs. The next que stion was whether the burden should be placed on the director to ju stify the longer number or on the operator to prove the site is stabilizing. It is suggestedthat the directorbe allowed to approve both a shorter or longer timeframe. With the next subsection, the burden is placed on the owner or operator to prove a shorter timeframe is acceptable, while allowing in this subsecti on the director to require monitoring beyond 30 years.

Proposed Rule: 146.93(b)(2)

Proposed revision: (2) If the owner or operator can demonstrate to the satisfaction of the Director that the ge ologic sequestration project no longer poses an endangerment to USDWs, the Director may approve an amendment to the post-injection site care and site closure plan to reduce the frequency of monitoring or may authorize site closure before the end of the 30-year period.

Rationale: Makes this subsection compatible with 30 year timeframe proposed by NGWA in 146.93(b)(1)

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 s ite 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

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### research studies and evaluation of public comments. While numerous commenters suggested that EPA shorten the monitoring timeframe, none of the commenters provided suffi cient data or other evidence to warrant a change inthe 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 recognizes that there may be site s where the 50 year post injection site care timeframe may be either not appropriate or more burdensome than necessary based on sitespecific conditions. For this reason, the GS rule o ffers 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-in jection 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 beappropriate if it ensures non-endangerment of USDWs pursuant to requirements at §146.93(c). 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 analternative timeframe would be protective of USDWs, or based on data collected during the PISCperiod, is appropriate to address the range of sites where GS is anticipated to occur, to ac commodate site-specific circumstances and various geologic conditions, and addre sses commenters’ concerns, while ensuring USDW protection. Both approaches will utilize site-specific data, and be based on pressure monitoring and USDW impacts, as the commenter suggests.

Letter ID: 0142 Comment ID: 22615 Letter Lines: 2252 to 2262

Comment Code: 1240 1.1.1.3 Suggested changes/edits to rule language Comment Code: 5800 2.13 Comments on emergency and remedial response (40 CFR 146.94)

Comment: Proposed Rule: 146.94(a)

Proposed revision: (a) As part of the permit application, the owner or operator must provide the Director with an emergency and remedial response plan that describes actions to be taken to address movement of the injection or formation fluids that may cause an endangerment toa USDW during construction, operation, closure and post-closure peri ods. The emergency and remedial response plan must be reviewed and updated, as necessary, on the same schedule as the update to the Area of Review.

Rationale: Keep same update schedule as AOR

Individual Response: In response to comments on the durati on of the emergency and remedial response plan, EPA clarifies that the plan will apply over the lif e of the GS project through the post-injection site care period (§146.94(a)). EPA has added a requirement at §146.94(d) that

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### 81 owners or operators must review their emergency and remedial response planwithin one year of an AoR reevaluation required under §146.84 or following significant changes to the facility. Subsequently, owners or operators must submit anamended plan or demonstrate to the Director that no amendment to the plan is needed base d on the AoR reevaluation or any significant changes made to the facility.