2.6

– Responses to Public Comments on Testing and Monitoring

This file contains responses to public comments on testing and monitoring (comment

codes 4600 to 4670). This section i ncludes comments on testing and monitoring plans,
well testing, ground water quality monitoring, carbon dioxide plume tracking, and air
and soil monitoring

.

The table below presents all of the EPA

-assigned comment codes that are included in

this section of the comment and response summary. Use the bookmarks in the PDF to
move among the comment codes

.

Topics included in this summary and associated comment codes

Topic Code

2.6 Proposed Plume and Pressure Front Monitoring Requirements (40 CFR 146.90) 4600

2.6.1 Testing and monitoring plan requirement 4610

2.6.2 Injectate monitoring 4620

2.6.3 Corrosion monitoring 4630

2.6.4 Pressure fall

-off testing 4640

2.6.5 CO2 plume and pressure front tracking 4650
2.6.5.1 Plume tracking techniques/geophysical methods 4655

2.6.6 Geochemical monitoring 4660
2.6.7 Surface air monitoring and/or soil gas monitoring 4670

Every comment on these topic areas and the associated response is included in this
summary; there is some repetition where multiple commenters made the same

comment.

Responses to letters from individual commenters or organizations are also available in

the rulemaking docket.Comment Code: 4600 2.6 Proposed Plume and Pressure Front Monitoring Requirements (40 CFR 146.90)



### Individual Comments

Commenter Name: Iain Wright Letter ID: 0118 Commenter Organization: BP Alternative Energy Comment ID: 22067 Other EPA Comment Codes and Descriptions: 4655 2.6.5.1 Plume tracking techniques/geophysical methods (seeking comment)

Comment: MONITORING

Moving on to my second point: Monitoring. Monitoring is important, but there is a common mis-perception that if you want secure storage, you need to do lots of monitoring. Well, the UN says that "the proportion of CO2 retained by appropriately selected and managed sites is likely to exceed 99% over 1,000 years". SO THE KEY TO SECURE STORAGE IS THE APPROPRIATE SELECTION AND

MANAGEMENT OF THE SITE. If that is done properly, the site will be very secure and the need for monitoring can be appropriately reduced. Monitoring is like the speedometer on your car. It does contribute to your safety, but more important is the design of the car, the road and how you drive the car.

Having said that, at In Salah, we are doing a big research project into monitoring, so the program is much more extensive than would be appropriate for a commercial project. We are trying out new technologies (such as satellite imagery, micro-seismic), so that we can see how they perform against conventional oilfield monitoring technologies (such as tracers and conventional seismic).

But as you can probably hear from my accent, I’m a Scotsman, and Scotsmen don’t like to waste money, so every technology that we use at in Salah has been carefully chosen to represent good value for money. Before we started injection at In Salah, we did a site-specific assessment of leakage risk and then we tailored the monitoring program to address those risks. Mandating any specific monitoring technology could waste a great deal of money and resources without contributing to the protection of USDWs. SO WE WOULD CAUTION AGAINST A UNIVERSAL

MANDATE FOR ANY SPECIFIC MONITORING TECHNOLOGY.

Many of you will have heard of the other two monitored, industrial-scale CO2 injection projects in the world, at Sleipner and Weyburn. If you compare the monitoring activities at these sites, you can see that something which works well in one location, may not work at all in another location. WE ENCOURAGE EPA
TO USE RISK-ASSESSED, PERFORMANCE-BASED CRITERIA TO DETERMINE SITESPECIFIC

MONITORING PROGRAMS.

Response: EPA agrees with commenters and believes that flexibility is important in developing and implementing a monitoring plan that is appropriately tailored for a specific GS site. The purpose ofthe requirement at §146.90 to develop site-specific testing and monitoring plans is to ensure that the monitoring performed at a site is appropriate for site operational conditions and the geologic setting. EPA believes that this is the best approach for addressing potential risks at GS sites. These flexible provisions in the monitoring requirements for Class VI wells enable the owner or operator to tailor monitoring programs to the specific needs of each project in consultation with the Director.

The final regulation provides for flexibility in: 1) methodologies used to collect these data, 2) the spatial resolution at which the data should be collected, and 3) how often the data should be collected. The number and placement of monitoring wells will be based on site-specific information such as the calculated AoR, injection rate and volume, site geology, baseline data, and the presence of artificial penetrations within the AoR. In some instances, there may be a limited number of options for complying with EPA's minimum requirements. For example, monitoring for geochemical changes will require use of monitoring wells and collection of groundwater samples for chemical analysis. Many options currently exist for complying with other requirements, such as tracking the position of the plume and pressure front within the injection zone.

Flexibility is also provided regarding how to monitor for the specific data required by the final rule. The testing and monitoring plan is developed by the owner or operator in consultation with the Director and is designed to ensure that a detailed, Director-approved document describing how monitoring will be conducted during the lifetime of the project exists.

EPA also agrees that good site selection and management are crucial elements of a successful GS project, but disagrees that this is an effective substitute for rigorous site monitoring.

EPA does not believe that prescribing specific technologies to be used in all cases for GS would be appropriate given the variability in sites. Rather EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the

docket for the final GS rule.

Commenter Name: Leslie Savage Letter ID: 0122 Commenter Organization: Railroad Commission of Texas (RRC) Comment ID: 24749

Comment: 6. EPA should provide more flexibility in the requirements for monitoring, testing and reporting. For example,

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

The final regulation provides for flexibility in: 1) methodologies used to collect these data, 2) the spatial resolution at which the data should be collected, and 3) how often the data should be collected. The number and placement of monitoring wells will be based on site-specific informationsuch as the calculated AoR, injection rate and volume, site geology, baseline data, and the presence of artificial penetrations within the AoR. In some instances, there may be a limited number of options for complying with EPA's minimum requirements. For example, monitoring for geochemical changes will require use of monitoring wells and collection of groundwater samples for chemical analysis. Many options currently exist for complying with other requirements, such as tracking the position of the plume and pressure front within the injection zone.

Flexibility is also provided regarding how to monitor for the specific data required by the final rule. The testing and monitoring plan is developed by the owner or operator in consultation with the Director and is designed to ensure that a detailed, Director-approved document describing how monitoring will be conducted during the lifetime of the project exists. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologiesand recommended approaches for implementing a testing and monitoring plan, including preoperational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects.

Commenter Name: John Stormon Letter ID: 0123 Commenter Organization: Washington State Dept. of Ecology Comment ID: 23002 Other EPA Comment Codes and Descriptions: 3310 2.2.1.1 Comments in favor of requiring computational models to delineate the AoR (seeking comment)

Comment: Area of Review: The proposed standards correctly require not just modeling, but tracking of the actual CO2 plume and pressure front, with periodic reevaluation of the modeled behavior as additional experience is gained at a sequestration project. Modeling is a good method of predicting the behavior of injected CO2 but should not be relied upon without monitoring to verify the accuracy of the modeled predictions. The model will be continually refined throughout the life a sequestration project.

Response: EPA acknowledges the commenter’s support of the modeling approach, and agrees that reevaluation of the AoR as required at 146.84(e) must incorporate monitoring and operational data gathered since the last model run.

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

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

Commenter Name: John Hanger Letter ID: 0130 Commenter Organization: Pennsylvania Dept. of Env. Protection Comment ID: 21509Comment: Proposed Plume and Pressure Front Monitoring Requirements

-EPA should specifically identify (by technology) what type of monitoring would be necessary and applicable to verify containment of the CO2 and any failures away from the injection wells themselves.

Response: EPA does not believe that prescribing specific technologies to be used in all cases for GS would be appropriate given the variability in sites. Rather EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the

docket for the final GS rule.

Commenter Name: John Hanger Letter ID: 0130 Commenter Organization: Pennsylvania Dept. of Env. Protection Comment ID: 25077

Comment: -Language is included in the proposed rule detailing how the injection well will be monitored during its operation, but there is no language included that regulates the monitoring of areas surrounding the injection well. There is also concern about how deep and how close to the capping (sealing) formation the surrounding monitoring wells and other wells should be allowed to approach the capping formation.

Response: EPA clarifies that the final GS regulation, at §146.90(g)(1), requires all GS project owners or operators to monitor for pressure changes in the injection zone. Specific monitoring locations will be identified by the owner and operator and approved by the Director in the monitoring and testing plan, but EPA expects that monitoring wells will be placed throughout the AoR. EPA believes that pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume and eliminates the need for monitoring in the locations mentioned by the commenter.

Pressure monitoring within the injection zone is also necessary because any such monitoring above the confining zone would not detect movement of the pressure front unless a breach of the confining zone occurs. EPA believes that monitoring using wells in the injection zone (i.e., that penetrate the confining zone) can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that the benefits of monitoring in the injection formation outweigh the manageable risk of those monitoring wells serving as conduits for fluid movement. EPA 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.

EPA adds that owners or operators may consider performing additional pressure monitoring in wellsthat are above the confining zone (e.g., in the same wells used to perform ground water quality monitoring required at §146.90(d)) to provide additional verification that no pressure changes are occurring above the confining zone due to CO2 leakage. Monitoring also identifies needed remedial actions, provides inputs for AoR reevaluation modeling, and targets additional geochemical and surface monitoring needs. Knowledge of the location of the CO2 plume and the associated pressure front will assure the public that GS projects are proceeding according to plan, provide sufficient information to the owner or operator and Director, or allow for appropriate actions to address any indication that USDWs may be endangered.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring, which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the

docket for the final GS rule.

Commenter Name: Christine Reimer Letter ID: 0142 Commenter Organization: National Ground Water Association Comment ID: 22553 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

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 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 geologicalsequestration 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.

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 ofshowing 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.

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 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.

The final rule at §146.90(g) requires owners or operators 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, provide inputs 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.

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 important part 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 help owners 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 USDWs. 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 construction, operation, monitoring, post-injection site care, and site closure. The GS rule accomplishes this through requirements tailored to address the unique nature of GS, including the large 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, corrective action, operation, monitoring, or reporting (including closure of the injection well) as are necessary to prevent such movement.

Commenter Name: Christine Reimer Letter ID: 0142 Commenter Organization: National Ground Water Association Comment ID: 22555 Other EPA Comment Codes and Descriptions: 3820 2.3.1 Well construction procedures

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 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 toaddress site-specific, objective-specific (monitoring or injection), and fluidspecific considerations. All injection wells should be cased and cemented to

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 well construction 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 injection zone (i.e., that penetrate the confining zone) can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. To mitigate the risk of fluid movement, EPA requires owners and operators to submit a testing and monitoring plan that describes how the owner or operator plans to site and construct monitoring wells.

EPA has developed a brief technical paper on construction of monitoring wells 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.

Commenter Name: Christine Reimer Letter ID: 0142 Commenter Organization: National Ground Water Association Comment ID: 22557Other EPA Comment Codes and Descriptions: 3820 2.3.1 Well construction procedures

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 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 CO2. 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.

Response: EPA agrees that well materials need to be compatible with injected fluids and formation fluids. The GS rule at §146.86(b)(1) requires 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, in determining 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 pressure and axial loading in §146.86(b)(1)(ii), corrosiveness of the CO2 stream and formation 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 wells will not need to be built to withstand CO2 injection, but, nonetheless, will need to be built with materials 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.

Commenter Name: Christine Reimer Letter ID: 0142 Commenter Organization: National Ground Water Association Comment ID: 22565

Comment: 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 theinjection 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 CO2, and environmental monitoring, which is the monitoring of the subsurface including the sequestered CO2 and the associated pressure front.

Operational MMV includes; monitoring the volume, flow rate, and composition of CO2 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 CO2 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.

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).

Response: EPA agrees that multi-faceted monitoring, as described by the commenter, is a key element of ensuring that USDWs 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 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 withthe commenter that data collected during site characterization (such as baseline geochemistry, preinjection reservoir pressure, etc.) are appropriate to ensure that baseline information 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 geochemistry that may indicate fluid

movement.

EPA agrees that the ground water geochemical monitoring 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 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 suchmonitoring 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 logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the

docket for the final GS rule.

Commenter Name: Patrick Nugent Letter ID: 0143 Commenter Organization: Texas Pipeline Association (TPA) Comment ID: 23135

Comment: 3. One-size-fits-all testing and monitoring requirements should not be established. The required level of testing and monitoring should be determined on a site-by-site basis. Imposition of an across-the-board requirement would be inappropriate given the variations in geologic formations, and such a requirement would inhibit the development and use of geologic sequestration with little or no corresponding environmental benefit in certain cases. Regulatory bodies and operators should be free to tailor monitoring techniques to the specific conditions at each particular site, upon a determination that the techniques would produce reliable data. In addition. there should be no blanket

Response: EPA agrees with commenters and believes that flexibility is important in developing and implementing a monitoring plan that is appropriately tailored for a specific GS site. The purpose of the requirement at §146.90 to develop site-specific testing and monitoring plans is to ensure that the monitoring performed at a site is appropriate for site operational conditions and the geologic setting. EPA believes that this is the best approach for addressing potential risks at GS sites. These flexible provisions in the monitoring requirements for Class VI wells enable the owner or operator to tailor monitoring programs to the specific needs of each project in consultation with the Director.

The final regulation provides for flexibility in: 1) methodologies used to collect these data, 2) the spatial resolution at which the data should be collected, and 3) how often the data should be collected. The number and placement of monitoring wells will be based on site-specific information such as the calculated AoR, injection rate and volume, site geology, baseline data, and the presence of artificial penetrations within the AoR. In some instances, there may be a limited number of options for complying with EPA's minimum requirements. For example, monitoring for geochemical changes will require use of monitoring wells and collection of groundwater samples for chemical analysis. Many options currently exist for complying with other requirements, such as tracking the position of the plume and pressure front within the injection zone.

Flexibility is also provided regarding how to monitor for the specific data required by the final rule. The testing and monitoring plan is developed by the owner or operator in consultation with the Director and is designed to ensure that a detailed, Director-approved document describing how monitoring will be conducted during the lifetime of the project exists. EPA is developing guidanceon testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologiesand recommended approaches for implementing a testing and monitoring plan, including preoperational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring, which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: James Devine Letter ID: 0166 Commenter Organization: United States Geological Survey (USGS) Comment ID: 21351 Other EPA Comment Codes and Descriptions: 4655 2.6.5.1 Plume tracking techniques/geophysical methods (seeking comment)

Comment: Section 146.90 (g), Testing and Monitoring Requirements, FR page 43540

This section requires the owneror operator "to track the extent ofthe carbon dioxide plume and the position ofthe pressure front" by direct or indirect monitoring. Indirect, geophysical techniques include, for example, seismic, electrical, gravity, or electromagnetic surveys.. ." It is unclear if surface deformation measurement techniques, such as repeat topographic surveys,satellite-based elevation measurements, and tiltmeters, are included as acceptable indirect monitoring techniques. Surface deformation techniques are in use, for example, at In Salah, Algeria (Onuma et al., 2008, abstract, Detection of surface deformation related with CO2 injection by DInSAR at In Salah, Algeria, Proceedings of 33rd International Geological Congress, Oslo, Norway). It is suggested that the proposed regulations allow for techniques beyond the realm of"traditional" geophysics and techniques not yet developed.

Response: The final rule, at §146.90(g), requires owners or operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are required unless the Director determines, based on site-specific geology that such methods are not appropriate. EPA is affording Director's discretion regarding the use of geophysical techniques at some sites because the Agency recognizes that geophysical methods are not appropriate in all geologic settings. EPA clarifies that this determination will be made by the Director based on the site-specific geologic information submitted by the owner or operator with the permit application.

EPA is not prescribing that deformation measurement techniques be used. However, if the owner or operator believes they would enhance the monitoring regime, they may be proposed in the testing and monitoring plan. Likewise, if the Director had reason to believe such methods are necessary to ensure protection of USDWs, he/she is afforded discretion to require the use of additional monitoring techniques at §146.90(i).

EPA believes that this approach provides flexibility to develop a site-specific monitoring plan, ensures that direct monitoring is available to track the movement of the CO2 and validate models, and recognizes that indirect techniques are not appropriate in all situations. The owner or operator's approved testing and monitoring plan will include the site-specific details, technologies, testing and monitoring frequencies, and other pertinent information.EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the

docket for the final GS rule.

Commenter Name: Michael Mudd Letter ID: 0167 Commenter Organization: FutureGen Alliance (FGIA) Comment ID: 22458 Other EPA Comment Codes and Descriptions: 3300 2.2.1 Delineating the AoR/Modeling CO2

movement
Comment: Area of Review (AoR) and Area of Monitoring (AoM)

p. 43493, c. 2 The Proposed Rule defines Area of Review (AoR) as "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 physical and chemical properties of all phases of the injected

carbon dioxide stream.

The proposed regulation uses the Area of Review (AoR) for defining both monitoring requirements and corrective actions:

p. 43499, c. 1 Area of Review (AoR) and Corrective Action: The Agency requires

examination of both the vertical and horizontal extent of the area that will potentially be influenced by injection and storage activities and identification of all artificial penetrations in the area that may act as conduits for fluid movement into USDWs (e.g., active and abandoned wells) and, as needed, perform corrective action to these open wells (i.e., artificial penetrations).

p. 43539, c. 3 (d)(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);

Comment:

- EPA should define two regulatory regions surrounding the geologic sequestration project and provide specific definitions for those regions; 1) Area of Monitoring (AoM) and 2) Area of Review; where the AoM is used to define the spatial distribution of monitoring wells and the AoR is used to define the

limit of Corrective Action:

- Area of Monitoring (AoM): The region surrounding the geologic sequestrationproject that contains 95% of the carbon dioxide mass. The area of monitoring is based on monitoring data and computational modeling that accounts for the physical and chemical properties of all phases of the injected carbon dioxide stream. In the absence of monitoring data, the area of monitoring is based on computational modeling.

- Area of Review (AoR): The region surrounding the geologic sequestration reservoir that has or is indicated to develop pressures that are greater than 10% different from the pre-injection formation fluid pressure, but no less than the Area of Monitoring. The area of review is based on monitoring data and computational modeling that accounts for the physical and chemical properties of all phases of the injected carbon dioxide stream. In the absence of monitoring data, the area of review is based on computational modeling.

• The proposed definitions of AoM and AoR have several important components:

- The AoM has a mass-based definition.

- The AoR has a pressure-differential-based definition.

- The AoR is never smaller than the AoM.

- The AoR and AoM may be asymmetrical around the injection well(s).

- The AoR and AoM may vary over time.

- The carbon dioxide mass should be determined using a combination of monitoring data and computational modeling.

- Pressure differentials are based on equilibrium hydrostatic conditions.

Relative to existing UIC regulations governing waste disposal, EPA is introducing fundamentally new concepts for defining the area of review (AoR) for CO2 injection. The newly proposed concept is flawed and will pose an unjustifiable barrier to CO2 injection projects unless the approach for defining the AoR is addressed in the regulation. It is neither possible, nor practical, to predict where every molecule of CO2 will migrate; therefore, a threshold levels are required. In the case of large-scale injection projects, changes in formation pressures could be expected dozens to hundreds of miles from the injection well. It would not be practical for the AoR to comprise the entire area experiencing changes in formation pressure. A reasonable threshold for establishing the AoM might be where pressure changes are greater than 10% of the standard formation pressure.

The proposed regulation defines the Area of Review (AoR) as being the region that may be impacted by the injection activity, without defining or quantifying impact. To be useful the bounding areas for corrective actions and monitoring activities must have specific definitions. Under deep geologic sequestration conditions the injected fluid (i.e., supercritical CO2) has low compressibility, the displaced fluid (i.e., brine) has low compressibility, and the reservoirformation (e.g., sandstone) generally has low compressibility, all of which suggest that the impact (i.e., pressure change) of the injection activity could be detected at great distances from the injection well(s).

Injection of CO2 into deep saline formations is driven by differences between the well injection pressure and formation pressure. To avoid inducing fractures or opening existing fractures in the formation and caprock, well injection pressure will be limited to some fraction below the fracturing pressure. As CO2 migrates into the formation the formation pressure increases around the injection well. The pressure distribution in the formation around the injection well depends on the formation properties, structure, and injection rate. Injection formations will be required to be confined vertically and/or horizontally to prevent the vertical migration of injected fluids and saline

reservoir fluids into USDWs.

Confined formations (e.g., a caprock overlying a horizontally extensive formation) allow the formation fluid to be displaced laterally by the injected fluid. Injecting CO2 will result in elevated pressures both inside and beyond the CO2 plume. Elevated pressures within the CO2 plume have the potential to force CO2 and formation fluid through permeable wells, fractures, or faults that penetrate the formation. Elevated pressures outside the CO2 plume have the potential to force formation fluid through permeable wells, fractures or faults that penetrate the formation. The higher the formation pressure is above the ambient formation pressure, the greater the potential for CO2 and formation fluid to leak through permeable wells, fractures, and faults. The lateral pressure distribution is a function of the injection rate and the lateral distribution of formation permeability. When CO2 injection is halted, elevated pressures decay over time as the injected and formation fluids migrate away from the injection well(s).

The proposed regulations define an AoR and Corrective Action as being an area within which artificial penetrations may act as conduits for fluid movement into USDWs (e.g., active and abandoned wells) and, as needed, require the applicant to perform corrective action to seal these open wells. The potential for fluid movement into USDWs from the injection of CO2 into the injection formation is correlated with the area of elevated formation pressure, which is usually larger than the area that contains the injected CO2 mass. For confined formations, this area is defined by the lateral pressure distribution around the injection well(s).

Response: EPA believes that, while the commenter offers different terminology for the AoR and the area to be monitored, the GS rule addresses the commenter's suggestions. Notably, the owner or operator is required (under 146.90) to develop and implement a testing and monitoring plan for each GS project that must consider the delineated AoR that includes both the CO2 plume and associated pressure front and incorporates many of the attributes suggested by the commenter. EPA clarifies that delineation of the AoR, as required at 146.84(c), must account for the physical and chemical properties of all phases of the injected CO2 stream, based on available site characterization, monitoring, and operational data.

Furthermore, any changes to the AoR would necessitate a review of and potential change in thetesting and monitoring plan, consistent with the commenter's assertion that the AoR may vary over time. The final GS regulation includes a requirement at 146.84(e) that the AoR be reevaluated at least every 5 years, and also requires that the owner or operator review the AoR and corrective action, testing and monitoring, and emergency and remedial response plans within one year of an AoR reevaluation (as well as following significant changes to the facility, or when required by the Director). The relationship between the AoR reevaluation and the testing and monitoring plan should allow for considerations suggested by the commenter.

EPA believes that by linking development and review of the testing and monitoring plan to the AoR evaluation and reevaluation process, the GS rule, in effect, incorporates and addresses many of the commenter's considerations for an area of monitoring.

Commenter Name: Theresa Pugh Letter ID: 0169 Commenter Organization: American Public Power Association Comment ID: 23373

Comment: Monitoring -- Pg. 46

APPA believes it makes common sense to place monitors close enough to detect the leak before it can negatively affect the USDW.

Response: Regarding monitoring locations, section §146.90(d) requires periodic monitoring of the ground water quality and geochemical changes above the confining zone(s). EPA clarifies that this monitoring requirement does not include the confining layer itself. Monitoring above the confining layer will provide an indication of upward movement of CO2 that might endanger a USDW. In addition, the final GS regulation, at §146.90(g)(1), requires all GS project owners or operators to monitor for pressure changes in the injection zone. Monitoring of pressure in the injection zone gives even greater advance warning of fluid movement that could potentially affect impact USDWs. Theexact number and location of monitoring locations to be tested will, however, be based on sitespecific characteristics and vulnerabilities and described in the Director-approved testing and monitoring plan.

The GS rule stipulates that the monitoring frequency and spatial distribution of monitoring wells must be based on baseline geochemical data that were collected during the initial site characterization and the area of review evaluation, at §146.90(d)(2). The details of the geochemical monitoring will be based on site-specific information and described in the Director-approved 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 logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring, which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Theresa Pugh Letter ID: 0169 Commenter Organization: American Public Power Association Comment ID: 23432

Comment: MonitoringAPPA does not have great expertise in monitoring in GS commercial settings. However, it makes common sense to place monitors close enough to detect the leak before it can negatively affect the USDW. APPA realizes that some local jurisdictions may require surface monitoring or that OSHA may require surface monitoring for safety purposes. However, we doubt that surface monitoring would do much to protect USDWs.

Response: Baseline characterization of the site, including the geochemical data and initial modeling, will be highly valuable in selection of monitoring well locations and in refining plans for monitoring frequency. The GS rule stipulates that the monitoring frequency and spatial distribution of monitoring wells must be based on baseline geochemical data that were collected during the initial site characterization and the area of review evaluation at §146.90(d)(2). The details of thegeochemical monitoring will be based on site-specific information and described in the Directorapproved testing and monitoring plan.

The Agency believes that surface air and soil gas monitoring, when coupled with subsurface monitoring, may be appropriate at some GS projects to ensure USDW protection. EPA also acknowledges that surface air and soil gas measurements are subject to variability and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believe that this should entirely preclude their use. 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.

Commenter Name: Kyle Isakower Letter ID: 0170 Commenter Organization: American Petroleum Institute Comment ID: 24188 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90(b)

API Comments: (b) Installation and use, except during well workovers as defined in §146.868(d), of continuous recordingMONITORING devices (INCLUDING DIGITAL DEVICES CAPTURING PERIODIC DATA) to monitor injection pressure, rate and volume; AND RECORD AT LEAST DAILY the pressure on the annulus between the tubing and the long string casing; and the annulus fluid volume;

Rationale: §146.86(d) does not exist; perhaps §146.88(d) is what was apparently

intended.

There is concern regarding what constitutes continuous monitoring. Industry agrees that regular monitoring of the parameters identified by EPA is appropriate. Our experience with CO2 EOR strongly shows that daily monitoring ofmost of these parameters is adequate (exceptions to this would be on a sitespecific basis). Recording should generally be done on a daily basis and reporting on a semi-annually basis.

Response: EPA believes that a monitoring regime that includes continuous pressure monitoring of GS wells, as required at §146.88(e), is important and appropriate because the potentially corrosive nature of CO2 streams in the presence of water makes it critical to immediately identify corrosion-related well mechanical integrity loss.

Regarding the question of what constitutes continuous monitoring, EPA expects that Class VI injection wells under §146.88(e) will be equipped with dedicated computer-based continuous pressure monitoring devices (in concert with the Director-approved shut-off systems required for GS wells), which typically take readings several times per second and record them electronically in a computer system. EPA did not specify the types of devices in the final rule, however.

EPA adds that the final GS rule references §146.88(e), as the commenter suggests.

Commenter Name: Kyle Isakower Letter ID: 0170 Commenter Organization: American Petroleum Institute Comment ID: 24193 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 149.90(e) - (f)

API Comments: (e) A demonstration of external mechanical integrity pursuant to §146.89(c) at least once per year UNTIL THE WELL IS PLUGGED; (f) IF CONDITIONS WARRANT, A pressure fall-off test OR OTHER EQUIVALENT TEST

THAT IDENTIFIES RESERVOIR CONDITIONS WITH RESPECT TO FLOW DYNAMICS at

least once every five years unless more frequent testing is required by the Director based on site specific information;

Rationale: Technical clarifications.

Response: Regarding pressure testing, EPA 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. Therefore, EPA is requiring that pressure fall-off testing be conducted every five years at a minimum, and the final GS regulation 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) to ensure safe and effective operations. EPA disagrees that the rule should provide specifics of the test at the degree suggested, however.

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.

Commenter Name: James Rower Letter ID: 0173 Commenter Organization: Utility Solid Waste Activities Group (USWAG) Comment ID: 23498

Comment: Plume and pressure front monitoring - USWAG appreciates the importance of accurate monitoring of the subsurface extent of the plume and pressure front. Id. at 43514. We believe, however, that over time constant monitoring may prove unnecessary as more information is gained regarding the accuracy of initial modeling. Any requirements for plume and pressure front modeling in the Final Rule should be flexible enough to adjust in the coming years as industry andregulators become more knowledgeable regarding the reliability of the modeling techniques initially used.

Response: EPA agrees that flexibility is appropriate, and clarifies that the specific plume and pressure front monitoring requirements will be established in the monitoring and testing plan submitted by the owner or operator along with the permit application. EPA believes that the monitoring requirements for GS sites at §146.90 provide an appropriate level of flexibility in structuring a testing and monitoring plan that protects USDWs from endangerment.

In addition, EPA is using an adaptive approach to regulating GS. EPA will collect and review project data on early GS projects to determine whether the appropriate amount and types of information and appropriate documentation are required and being collected. The Agency will evaluate the information and determine if modifications to the requirements are necessary.

EPA believes that this approach provides flexibility to develop a site-specific monitoring plan, ensures that direct monitoring is available to track movement of the CO2 and validate models, and recognizes that indirect techniques are not appropriate in all situations. The owner or operator's approved testing and monitoring plan will include the site-specific details, technologies, testing and monitoring frequencies, and other pertinent information.

Pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume. When combined with information on temperature, pressure data provide an indication of the phase (e.g., gas, supercritical) and distribution of the injected CO2 (73 FR 43515). Monitoring can also identify needed remedial actions, provide inputs for AoR reevaluation modeling, evaluate predictions of plume movement, and target additional geochemical and surface monitoring needs.

Commenter Name: Kenneth Nemeth Letter ID: 0176 Commenter Organization: Southern States Energy Board Comment ID: 23542

Comment: Regarding specific points, we concur with the establishment of a threshold of a seabed up to three miles offshore, but no farther, and we support a requirement that the project operator should be able to demonstrate that the CO2 is contained within the storage zone. We do not support the need to monitor the exact location with in-zone monitoring wells, the CO2 plume, or displace brine pressure front. CO2 monitoring should be fit for purpose. Air and soil gas

Response: EPA agrees that the owner or operator should be able to demonstrate that CO2 is contained within the injection zone. For this reason, the final rule, at §146.90(g) requires owners or operators to perform CO2 plume and pressure front tracking.

The final rule, at §146.90(g), requires owners or operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are required unless the Director determines, based on site-specific geology that such methods are not appropriate.

Pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume. When combined with information on temperature, pressure data provide an indication of the phase (e.g., gas, supercritical) and distribution of the injected CO2 (73FR 43515). Monitoring can also identify needed remedial actions, provide inputs for AoR reevaluation modeling, evaluate predictions of plume movement, and target additional geochemical and surface monitoring needs.

EPA disagrees that knowing the location of the plume and pressure front is unnecessary; plume tracking and pressure monitoring are key components of monitoring at GS sites. A rigorous plume tracking and pressure monitoring scheme, such as one that meets the requirements at §146.90(g), is imperative for ensuring that the CO2 plume is contained within the injection zone.

EPA clarifies that the limitation of the Class VI requirements not applying beyond the three-mile limit offshore reflects the UIC program's authority under SDWA. See the preamble for additional information about sub-seabed sequestration.

Commenter Name: Frederick R. Eames Letter ID: 0178 Commenter Organization: CCS Alliance Comment ID: 23871

Comment: F. PLUME AND PRESSURE FRONT MONITORING REQUIREMENT

EPA proposes monitoring sequestration sites to track the location of the CO2 plume and associated pressure front over time. Plume monitoring is important to the long-term stability of CCS sites. However, we submit that such a requirement should be flexible to accommodate growing knowledge about injection and CO2 plumes. Monitoring has limited usefulness in some settings (e.g., 4D seismic often does not have the resolution to detect CO2 in some deep or complex settings or where hydrocarbon gases are present). Moreover, data gathering requirements related to plume tracking and testing should not unduly burden owners or operators, either in time or cost, and should be essential to evaluation of the plume's stability and safety.

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

EPA agrees with commenters that flexibility is important in developing and implementing a monitoring plan that is appropriately tailored for a specific GS site. The purpose of the requirement at §146.90 to develop site-specific testing and monitoring plans is to ensure that the monitoring performed at a site is appropriate for site operational conditions and the geologic setting. EPA believes that this is the best approach for addressing potential risks at GS sites. These flexible provisions in the monitoring requirements for Class VI wells enable the owner or operator to tailor monitoring programs to the specific needs of each project in consultation with the Director.

EPA agrees that seismic monitoring is not applicable to all 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. 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 is affording Director's discretion regarding the use of geophysical techniques at some sitesbecause the Agency recognizes that geophysical methods are not appropriate in all geologic settings. For example, geophysical methods are difficult to execute in areas that are structurally and topographically complex or where lithologies have limited contrast in density, porosity, permeability, and other physical properties. EPA clarifies that this determination will be made by the Director based on the site-specific geologic information submitted by the owner or operator with their permit application.

Commenter Name: Thomas Curtis Letter ID: 0181 Commenter Organization: American Water Works Association (AWWA) Comment ID: 23655

Comment: In its comments, AWWA makes several recommendations for the following specific items to be included in the final regulation:

- Inclusion of detailed monitoring requirements in the final regulation;

Response: EPA disagrees that the rule should specify the monitoring techniques for all GS sites. EPA believes that flexibility is important in developing and implementing a monitoring plan that is appropriately tailored for a specific GS site. The purpose of the requirement at §146.90 to develop site-specific testing and monitoring plans is to ensure that the monitoring performed at a site is appropriate for site operational conditions and the geologic setting. EPA believes that this is the best approach for addressing potential risks at GS sites. These flexible provisions in the monitoring requirements for Class VI wells enable the owner or operator to tailor monitoring programs to the specific needs of each project in consultation with 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 logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the

docket for the final GS rule.

Commenter Name: Thomas Curtis Letter ID: 0181 Commenter Organization: American Water Works Association (AWWA) Comment ID: 23696 Other EPA Comment Codes and Descriptions: 4500 2.5 Proposed Mechanical Integrity Testing (MIT) Requirements (40 CFR 146.89)

Comment: Category: Monitoring

EPA Request for Comment: EPA’s proposal would require owners or operators of Class VI GS projects to monitor internal mechanical integrity of their injection wells by continuously monitoring injection pressure, flow rate, and injected volumes, as well as the annular pressure and fluid volume to assure that no anomalies occur that may indicate an internal leak. EPA requests comment on the practicability of this requirement. EPA Notice 43513.EPA seeks comment on the appropriate frequency of internal and external MITs for GS injection wells, the appropriate types of MITs, and how to optimize MIT

methods for GS. EPA Notice 43514.

EPA seeks comment on the requirement for monitoring of GS sites for the purpose of tracking the location of the CO2 plume and associated pressure front over

time. EPA Notice 43514

EPA’s proposal would require that owners or operators perform a pressure falloff test at least once every five years. EPA seeks comment on the use and frequency of pressure fall-off testing for GS wells. EPA Notice 43515.

Specifically, EPA seeks comment regarding the usefulness of indirect geophysical monitoring and surface air and soil gas monitoring. In addition, EPA seeks comment regarding the use of a Director-approved monitoring plan for GS sites.

EPA Notice 43517.

AWWA Response: Detailed monitoring guidelines were developed as part of a joint research project by AwwaRF and AWWA. These guidelines are provided in Section III of these comments and EPA should include the named tests and frequencies in the final regulation to ensure that protection of USDWs is consistent across all geologic sequestration projects. Based upon these requirements, owner/operators would develop testing and monitoring plans, which should be reviewed and updated

at the same time as the re-evaluation of the Area of Review. The costs associated with monitoring of a sequestration project should not be a major consideration when determining the types and frequency of required monitoring. The goal of the monitoring requirements should be on preventing degradation of USDWs, not minimizing the cost to the owner/operator.

AWWA strongly recommends both that both internal and external mechanical integrity testing should be required to prevent leakage of carbon dioxide from the injection well. Monitoring of the plume and pressure front over time is absolutely required as part of the system operation and a project shouldn't even be considered unless this monitoring is included. All of the monitoring

Response: EPA agrees with the commenter; the final rule requires both internal and external mechanical integrity testing. Mechanical integrity testing is one of the cornerstones of the existing EPA UIC program. MIT requirements at §146.89 ensure protection of USDWs from endangerment and provide an important early warning of potential problems in the injection well. Routine mechanical integrity testing of injection wells provides data that enables the identification and remediation of well integrity problems before they lead to leakage and/or endangerment of USDWs.

The GS rule's requirements for MITs encompass many of the same tests mentioned in the AwwaRF and AWWA monitoring guidelines, including an approved tracer log, or noise logs and temperature logs. EPA believes that the MITs described in the rule at §146.89(c) are effective methods to demonstrate external MI. They have been used successfully by injection well operators for decades and provide an important early warning of potential problems in the injection well system. While the oxygen activation log is not explicitly required in the rule, the regulations do provide flexibility at §146.89(e) to allow the Director to require additional test methods or, with the approval of the Administrator, to approve the use of alternative MIT methods. These additional methods couldinclude the annual pressure test recommended in the AwwaRF/AWWA guidelines. The specific MITs required prior to start-up of injection or at well workovers would be identified in the permit by the Director. For additional information, please see the discussion of MITs in the final rule preamble.

As stated above, EPA disagrees that the rule should specify the monitoring techniques for all GS

sites.

EPA agrees that tracking the plume and the position of the pressure front during injection operations and the post-injection site care period will provide important data for determining that the injectate is confined within the target formation, as well as for evaluating any risks within the AoR. 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 there is a baseline with which to compare GS operation and post-injection data.

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 guidancedescribes recommended approaches for implementing a testing and monitoring plan, including preoperational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the

docket for the final GS rule.

EPA also agrees that periodic updates to the plan are appropriate. EPA clarifies that the final GS regulation includes a requirement that the AoR be reevaluated every 5 years, and it specifies at §146.90(j) that the operator revise the testing and monitoring plan to incorporate the results of the most recent AoR reevaluation and recent operational and monitoring data.

EPA clarifies that cost-benefit analyses are not used to determine the most appropriate monitoring technologies, location, or frequency. Instead, the Agency believes that the flexibility afforded the owner or operator at §146.90 to develop a testing and monitoring plan tailored to site-specific characteristics is appropriate for GS.

Commenter Name: Thomas Curtis Letter ID: 0181 Commenter Organization: American Water Works Association (AWWA) Comment ID: 24339 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Part 146.90(d)(1) AWWA recommends revising this part to read:

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 natural discontinuities and artificial penetrations and other factors.

Response: Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment EPA has made many revisions to the GS rule. See the final ruleand preamble for further discussion on EPA's final approach.

EPA's guidance on testing and monitoring will provide guidance on monitoring well placement. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Wendy Jacobs Letter ID: 0183 Commenter Organization: Harvard Law School Environmental Law and Policy

Center Comment ID:

25140

Comment: impurities) that can compromise the structure of the well and result in leaks of stored CO2. ELPC and ETIP laud other precautionary measures required in the proposed regulation, including down-hole shut off valves, continuous and frequent monitoring of the integrity of the internal and external portions of the well, tracking the plume and pressure front, and detailed electronic record keeping. Id. at 43,511, 43,538-40 (proposed 40 C.F.R. §§ 146.88-.91). The

Response: EPA agrees with commenters on the importance of monitoring at GS sites, including continuous monitoring and MITs. EPA emphasizes that monitoring of injection activities will be an important component of every GS project. Monitoring (and related reporting and recordkeeping) associated with injection wells and the movement of the CO2 plume is necessary to verify that the injectate is confined in the target formations and does not endanger USDWs.

After evaluating the risks and benefits of down-hole shut-off systems and considering additional research, EPA will not require automatic down-hole shut-off devices for onshore Class VI wells. 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. EPA believes that requiring the installation of automatic surface shut-off devices for onshore wells (and affording Director's discretion to require down-hole devices where necessary) ensures that proper precautions are taken to prevent subsurface fluid movement and ensure protection of USDWs, human health, and

the environment.

Additionally, the GS rule, at §146.88(e)(3), requires the installation of down-hole shut-off devices for Class VI wells located in the offshore submerged lands within the jurisdiction of a State UIC program. The Agency believes that the unique construction and operational conditions for offshore Class VI wells, including isolation from shorelines and the need to construct wells through the water column and the subsurface, may delay response time in the event of well difficulties. These conditions merit requiring automatic down-hole shut-off devices for offshore wells in the submerged

lands of a State.

EPA believes that requiring the installation of automatic surface shut-off devices for onshore wells (and affording Director's discretion to require down-hole devices where necessary) ensures that proper precautions are taken to prevent subsurface fluid movement and ensure protection of USDWs, human health, and the environment.

Commenter Name: Bradley J. Field Letter ID: 0186 Commenter Organization: New York State Dept. of Environmental Conservation

Div. of Mineral Resources Comment ID:

25204Other EPA Comment Codes and Descriptions: 4760 2.7.6 Proposed reporting frequency (seeking comment)

Comment: FF. EPA seeks comment on the appropriate amount and types of monitoring that should

be conducted at a GS site.

NYSDEC-DMN Response: NYSDEC-DMN agrees with EPA’s proposal to require operators to report semi- annually on the characteristics of injection fluids, injection pressure, flow rate, temperature, volume and annular pressure, and on the results of MITs, ground water monitoring, and any required atmospheric/soil gas monitoring. However, the amount and types of monitoring to be required should be site specific.

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

The final regulation provides for flexibility in: 1) methodologies used to collect these data, 2) the spatial resolution at which the data should be collected, and 3) how often the data should be collected. The number and placement of monitoring wells will be based on site-specific information such as the calculated AoR, injection rate and volume, site geology, baseline data, and the presence of artificial penetrations within the AoR. In some instances, there may be a limited number of options for complying with EPA's minimum requirements. For example, monitoring for geochemical changes will require use of monitoring wells and collection of groundwater samples for chemical analysis. Many options currently exist for complying with other requirements, such as tracking the position of the plume and pressure front within the injection zone.

Flexibility is also provided regarding how to monitor for the specific data required by the final rule. The testing and monitoring plan is developed by the owner or operator in consultation with the Director and is designed to ensure that a detailed, Director-approved document describing how monitoring will be conducted during the lifetime of the project exists. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologiesand recommended approaches for implementing a testing and monitoring plan, including preoperational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects.

EPA is retaining the semi-annual reporting requirements as proposed at §146.91(a). These requirements ensure the Director has the information needed to take preventive action in a timely manner to protect USDWs from endangerment. EPA notes that operators who want to streamline their reporting schedules can negotiate with the permitting authority to establish a schedule that allows reporting on all wells in a GS project at the same time; however, data for each well must be reported separately and at least as frequently as required at §146.91. For additional information, please see the final rule and the preamble for a discussion of EPA's final approach to recordkeeping and reporting.

EPA agrees that some monitoring types and frequencies (e.g., associated with ground water monitoring and plume tracking) will be site-specific. These activities must be established in the approved testing and monitoring plan, which will be incorporated as a condition of the Class VI permit.Commenter Name: Daniel Plath Letter ID: 0188 Commenter Organization: NiSource, Inc. Comment ID: 25230

Comment: aspects. The following points summarize four primary lessons learned through operation of natural gas storage that would be applicable to GS:

2. NiSource's Columbia subsidiary has performed many of the pre-activation and monitoring, measuring and verification (MMV) activities EPA discusses. While these technologies are useful, a number are primarily applicable to the initial development of a new field or as niche diagnostic tools for specific problems. Applying a large number of MMV techniques is appropriate for pilot projects though it is rarely a best practice for an established commercial application where the historical risks are well known and where there are practical limits on staff's time, budgets and other resources. Ultimately, the cost of GS will be passed on to electric customers and government regulations need to provide a balanced perspective.

Response: EPA agrees with commenters and believes that flexibility is important in developing and implementing a monitoring plan that is appropriately tailored for a specific GS site. The purpose of the requirement at §146.90 to develop site-specific testing and monitoring plans is to ensure that the monitoring performed at a site is appropriate for site operational conditions and the geologic setting. EPA believes that this is the best approach for addressing potential risks at GS sites. These flexible provisions in the monitoring requirements for Class VI wells enable the owner or operator to tailor monitoring programs to the specific needs of each project in consultation with the Director.

The final regulation provides for flexibility in: 1) methodologies used to collect these data, 2) the spatial resolution at which the data should be collected, and 3) how often the data should be collected. The number and placement of monitoring wells will be based on site-specific information such as the calculated AoR, injection rate and volume, site geology, baseline data, and the presence of artificial penetrations within the AoR. In some instances, there may be a limited number of options for complying with EPA's minimum requirements. For example, monitoring for geochemical changes will require use of monitoring wells and collection of groundwater samples for chemical analysis. Many options currently exist for complying with other requirements, such as tracking the position of the plume and pressure front within the injection zone.

Flexibility is also provided regarding how to monitor for the specific data required by the final rule. The testing and monitoring plan is developed by the owner or operator in consultation with the Director and is designed to ensure that a detailed, Director-approved document describing how monitoring will be conducted during the lifetime of the project exists. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologiesand recommended approaches for implementing a testing and monitoring plan, including preoperational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects.

Commenter Name: Robert F. Van Voorhees Letter ID: 0190 Commenter Organization: Carbon Sequestration Council Comment ID: 24479 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rulelanguage

Comment: Rule Provision: 146.90(a) & (b)

Proposed CCS Group Recommendations: (B) THE TESTING AND MONITORING PLAN MUST,

AT A MINIMUM, INCLUDE:

(a)(1) analysis of the carbon dioxide stream with sufficient frequency to yield data representative of its chemical and physical characteristics;

(b)(2) Installation and use, except during well workovers as defined in section 146.88(d), of continuous monitoring devices (INCLUDING DIGITAL DEVICES CAPTURING PERIODIC DATA) to monitor injection pressure, rate and volume; AND RECORD AT LEAST DAILY the pressure on the annulus between the tubing and the long strong casing;

(3) A DEMONSTRATION OF EXTERNAL MECHANICAL INTEGRITY PURSUANT TO §146.89(C)
UNTIL THE WELL IS PLUGGED;

(4) MONITORING OF THE PRESSURE BUILDUP IN THE INJECTION ZONE ANNUALLY,

INCLUDING
AT A MINIMUM, A SHUT DOWN OF THE WELL FOR A TIME SUFFICIENT TO CONDUCT

A VALID

OBSERVATION OF THE PRESSURE FALL-OFF CURVE AT LEAST ONCE EVERY FIVE
YEARS; AND (5) A QUALITY ASSURANCE PLAN FOR ALL TESTING AND MONITORING REQUIREMENTS.

Basis for CCS Group Comments: There is concern regarding what constitutes continuous monitoring. Industry agrees that regular monitoring of the parameters identified by EPA is appropriate. Experience with CO2 EOR strongly shows that daily monitoring of most of these parameters is adequate (exceptions to this would be on a site-specific basis). Recording should generally be done on a daily basis and reporting on a semi-annual basis.

Response: EPA believes that continuous pressure monitoring of GS wells, as required at §146.88(e), is important and appropriate because the potentially corrosive nature of CO2 streams in the presence of water makes it critical to immediately identify corrosion-related well mechanical integrity loss. Class VI injection wells must be equipped with dedicated computer-based continuous pressure monitoring devices (in concert with the Director-approved shut-off systems required for GS wells), which typically take readings several times per second and record them electronically in a computer

system..

EPA believes that a frequency of five years, as specified at §146.90(f), is an appropriate interval for pressure fall-off testing (particularly given the suite of tests operators will perform on the well and the site). EPA clarifies that the Director may require more frequent pressure fall-off tests at a specific project if necessary, based on site-specific circumstances. Pressure fall-off tests may be conducted in conjunction with other well performance tests (i.e., mechanical integrity testing) to ensure safe and effective operations. All monitoring data collected, including information frompressure fall-off tests, will be incorporated in AoR reevaluations at least every five years. EPA disagrees that the rule should provide specifics of the testing to the degree suggested, however.

EPA clarifies that periodic MITs will not be required following plugging of the well.

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.

Commenter Name: Robert F. Van Voorhees Letter ID: 0190 Commenter Organization: Carbon Sequestration Council Comment ID: 24482 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90(e) & (f)

Proposed CCS Group Recommendations: (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;

(f) A pressure fall-off test at least once every five years unless more frequent testing is required by the Director based on site specific information;

Basis for CCS Group Comments: Redundant to section 146.89

These issues are addressed in recommended subsection (b)(3) and (4).

Response: Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment, EPA has made many revisions to the GS Rule. See the final rule and preamble for further discussion on EPA's final approach. EPA adds that the purpose of including all testing and monitoring requirements in §146.90 is to clarify and to specify the content of the required testing and monitoring plan.

Commenter Name: Jeff W. Sheets Letter ID: 0192 Commenter Organization: ConocoPhillips Comment ID: 23897

Comment: Monitoring

ConocoPhillips supports EPA's proposed rules to prepare, maintain, and comply with a testing and monitoring plan, including chemical analysis of CO2 streams and allowing for fit-for-purpose monitoring. We recommend some changes as described in detail in API's submittal. API's recommendations emphasize careful site selection and characterization, which create the strongest protection for USDWs while still handling well construction and monitoring with the most cost effective protective measures. Specific monitoring requirements detailed in API's recommendation maintain appropriate rigor to protect USDWs while allowing for site specific details. EPA's flexibility around operator developed plans is appropriate, and API acknowledges the directors discretion and ability to add prescriptive requirements as appropriate for specific sites. The recommendations provide balance, since too many prescriptive elements in the requirementsthemselves, would run the risk of becoming too broadly applied and add unnecessary cost. Preserving the environmental benefits of CCS relies on managing cost-effective protective solutions.

Response: EPA agrees and believes that flexibility is important in developing and implementing a monitoring plan that is appropriately tailored for a specific GS site. The purpose of the requirement at §146.90 to develop site-specific testing and monitoring plans is to ensure that the monitoring performed at a site is appropriate for site operational conditions and the geologic setting. EPA believes that this is the best approach for addressing potential risks at GS sites. These flexible provisions in the monitoring requirements for Class VI wells enable the owner or operator to tailor monitoring programs to the specific needs of each project in consultation with the Director. Please also see EPA's response to API's comment.

Commenter Name: John R. Baza Letter ID: 0193 Commenter Organization: Utah Division of Oil, Gas, and Mining Comment ID: 23915 Other EPA Comment Codes and Descriptions: 4700 2.7 Proposed Recordkeeping and Reporting Requirements (40 CFR 146.91)

Comment: Monitoring

EPA seeks comments on proposed pressure plume and pressure front monitoring including issues such as the amount and type of monitoring, the usefulness of geophysical, air and soil monitoring, post-injection site monitoring, and frequency of reporting requirements. The IOGCC comments of December 23, 2008 have addressed all of these issues in great detail, and the Division concurs

with their recommendations.

Response: Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment, EPA has made many revisions to the GS Rule. See the final rule and preamble for further discussion on EPA's final approach.

EPA agrees with commenters that developing and following testing and monitoring plans is an important part of assuring that a GS project is operating properly and is crucial for the early detection of potential endangerment to USDWs. EPA also agrees that periodic updates to the plan are appropriate. EPA clarifies that the final GS regulation includes a requirement that the AoR be reevaluated at least every five years, and it specifies at §146.90(j) that the operator revise the testing and monitoring plan to incorporate the results of the most recent AoR reevaluation and recent operational and monitoring data.

EPA acknowledges the comment and the final rule retains the text as proposed. Please see the final rule and the discussion of testing and monitoring in the preamble for additional information.

Commenter Name: Andy Horn Letter ID: 0196 Commenter Organization: Colorado Ground Water Association (CGWA) Comment ID: 23926

Comment: Issue 6. Buffer Zone monitoring wells need to be addressed in the regulation.

The regulations do not specifically identify the need for monitoring to verify performance of the repository. Monitoring wells to detect potential migration from the repository need to be incorporated into the proposed rule. Earlyimplementation of GS should incorporate the concept of multiple barrier zones. This allows implementation of monitoring in zones below a USDW that can serve as a guard zone. These are critical in a zone between the repository and USDWs to allow for the early detection of a problem while mitigation is still an option. Even highly effective monitoring of GS reservoirs for failure may only inform operators after "the horse has left the barn." In addition to buffer-zone monitoring, pressures in confining units should be monitored to provide allow

detection of failure of the GS reservoir.

Response: EPA clarifies that the final rule requires monitoring to ensure that CO2 or injection zone formation fluids remain in the injection zone. EPA believes that the ground water geochemical monitoring above the confining zone required 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 adds that the baseline geochemical data required at §146.82(a)(6) will provide a basis for comparison. EPA is not requiring monitoring in the confining zone itself. However, 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 geochemical monitoring above the confining zone should not be restricted to areas near the plume. Research, both EPA-funded and external, has shown that the zone of elevated pressure may be much larger than the plume (e.g., Birkholzer, et al. 2008). This area of elevated pressure may cause migration of native brines from the target formation into overlying formations. Careful placement of monitoring wells within the delineated AoR (which includes areas beyond the extent of the CO2 plume) would allow for detection of changes in water quality related to GS activities. EPA acknowledges that very thick confining zones would reduce the chance that CO2 orother fluids will move from the injection zone; however, to increase protectiveness, a multiplebarrier approach to protecting USDWs from endangerment that includes both proper site characterization and a detailed monitoring regime is warranted.

EPA believes that geochemical monitoring in and above the confining zone complements pressure monitoring in the injection zone. EPA believes that pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume. The final rule, at §146.90(g), requires owners or operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are required unless the Director determines, based on site-specific geology that such methods are not appropriate.

EPA believes that pressure monitoring within the injection zone is necessary because any such monitoring above the confining zone would not detect movement of the pressure front unless a breach of the confining zone occurs.

Commenter Name: Andy Horn Letter ID: 0196 Commenter Organization: Colorado Ground Water Association (CGWA) Comment ID: 23932

Comment: While detailed geologic modeling is planned, monitoring wells should be installed into the injection zone, and into buffer zones above the injection zone, including fluid bearing zones below any potential USDW zone. In addition, pressure sensors should be installed in the confining units above the GSreservoir. The data collected from the monitoring wells and pressure monitoring points can be used to confirm the accuracy of a model and to monitor the zone above the injection zone for CO2 leakage. Monitoring wells should be installed into the buffer zone to provide early detection in the event CO2 or the associated pressure front begins to migrate into zones above the proposed injection zone. All monitoring wells should be designed to similar standards as injection well and will need pressure shut-in equipment.

Clustered monitoring wells should be considered to allow a single borehole to be used to monitor several different vertically discrete zones. For example, there is a potential that the injection zone, one or more buffer zones, and the USDW zone could be monitored from clustered monitoring wells installed into a single borehole. In the event such technology is used, equipment should be installed, maintained, and tested on a designated frequency to prevent migration of fluids

between zones.

Response: EPA agrees that pressure monitoring in the injection zone is appropriate. The final GS regulation, at §146.90(g)(1), requires all GS project owners or operators to monitor for pressure changes in the injection zone. EPA believes that pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume. Pressure monitoring within the injection zone is necessary because any such monitoring above the confining zone would not detect movement of the pressure front unless a breach of the confining zone occurs.

EPA adds that, although it is not required in the GS rule, owners or operators may consider performing additional pressure monitoring in wells that are above the confining zone (e.g., in the same wells used to perform ground water quality monitoring required at §146.90(d)) to provide additional verification that no pressure changes are occurring above the confining zone. Monitoring also identifies needed remedial actions, provides inputs for AoR reevaluation modeling, and targets additional geochemical and surface monitoring needs. Knowledge of the location of the CO2 plume and the associated pressure front will assure the public that GS projects are proceeding according to plan, provide sufficient information to the owner or operator and Director, or allow for appropriate actions to address any indication that USDWs may be endangered.

EPA acknowledges that, at certain sites, there may be a need for more or different monitoring schemes (which may include monitoring in the confining or buffer zones), and adds that it is important to balance the need for adequate monitoring that ensures USDW protection from endangerment against too many artificial penetrations which could serve as conduits for fluid migration. EPA expects site-specific testing and monitoring plans to describe the proposed monitoring regime, which must be approved by the Director. EPA recognizes that wells with multiple completions (i.e., what the commenter refers to as "clustered monitoring wells") may offer benefits; nothing in the rule precludes their use.

EPA believes that monitoring using wells in the injection zone (e.g., for pressure monitoring as required at §146.90(g)(1)) can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that properly constructed monitoring wells will be a safe way to obtain the data that is essential to ensure that the injected CO2 remains confined in the injection zone and that pressure changes are not causing movement of formation or other fluids. To mitigate the risk of fluid movement, EPA requires owners and operators to submit a testing and monitoring plan that describes how the owneror operator plans to site and construct monitoring wells. 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.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can also be found on EPA’s website.

Commenter Name: Craig R. Walters Letter ID: 0200 Commenter Organization: Anadarko Petroleum Corporation Comment ID: 24701 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90(b)

Anadarko Petroleum Corporation (APC) Comments: (b) The testing and monitoring plan must, at a minimum, include:

(a 1) Analysis of the carbon dioxide stream with sufficient frequency to yield data representative of its chemical and physical characteristics; (b2) Installation and use, except during well workovers as defined in § 146.86(d), of continuous recordingMONITORING DEVICES (INCLUDING DIGITAL DEVICES CAPTURING PERIODIC DATA) to monitor injection pressure, rate and volume; AND TO RECORD AT LEAST DAILY the pressure on the annulus between the tubing and the long string casing; and the annulus fluid volume; (3) A DEMONSTRATION OF EXTERNAL MECHANICAL INTEGRITY PURSUANT TO §146.89(C)
UNTIL THE WELL IS PLUGGED; (4) MONITORING OF THE PRESSURE BUILDUP IN THE INJECTION ZONE ANNUALLY,

INCLUDING
AT A MINIMUM, A SHUTDOWN OF THE WELL FOR A TIME SUFFICIENT TO CONDUCT

A VALID

OBSERVATION OF THE PRESSURE FALLOFF CURVE AT LEAST ONCE EVERY FIVE
YEARS; AND (5) A QUALITY ASSURANCE PLAN FOR ALL TESTING AND MONITORING REQUIREMENTS.

(b) Installation and use, except during well workovers as defined in §146.88(d), of continuous monitoring devices (including digital devices capturing periodic data) to monitor injection pressure, rate and volume; and RECORD AT LEAST DAILY the pressure on the annulus between the tubing and the long string casing;

Rationale: §146.86(d) does not exist; perhaps §146.88(d) is what was apparently

intended.

There is concern regarding what constitutes continuous monitoring. Industryagrees that regular monitoring of the parameters identified by EPA is appropriate. Our experience with CO2 EOR strongly shows that daily monitoring ofmost of these parameters is adequate (exceptions to this would be on a sitespecific basis). Recording should generally be done on a daily basis and reporting on a semi-annually basis. As a guiding principle, the frequency of monitoring should be determined by the level of risk posed by the injection operation.

Response: EPA believes that continuous pressure monitoring of GS wells, as required at §146.88(e), is important and appropriate because the potentially corrosive nature of CO2 streams in the presence of water makes it critical to immediately identify corrosion-related well mechanical integrity loss. Class VI injection wells must be equipped with dedicated computer-based continuous pressure monitoring devices (in concert with the Director-approved shut-off systems required for GS wells), which typically take readings several times per second and record them electronically in a computer

system..

EPA believes that a frequency of at least once every five years, as specified at §146.90(f), is an appropriate interval for pressure fall-off testing (particularly given the suite of tests operators will perform on the well and the site). EPA clarifies that the Director may require more frequent pressure fall-off tests at a specific project, if necessary based on site-specific circumstances. Pressure fall-off tests may be conducted in conjunction with other well performance tests (i.e., mechanical integrity testing) to ensure safe and effective operations. All monitoring data collected, including information from pressure fall-off tests, will be incorporated in AoR reevaluations, at least every five years. EPA disagrees that the rule should provide specifics of the testing at the degree suggested, however.

EPA clarifies that periodic MITs are not be required following plugging of the well.

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.

Commenter Name: Craig R. Walters Letter ID: 0200 Commenter Organization: Anadarko Petroleum Corporation Comment ID: 24705 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90(e)

Anadarko Petroleum Corporation (APC) Comments: (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;

Rationale: See 146.90(b)(3)

Response: Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment, EPA has made many revisions to the GS rule. See the final rule and preamble for further discussion on EPA's final approach. EPA adds that the purpose of including all testing and monitoring requirements in §146.90 is to clarify and to specify the content of the required testing and monitoring plan.Commenter Name: Craig R. Walters Letter ID: 0200 Commenter Organization: Anadarko Petroleum Corporation Comment ID: 24706 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90(f)

Anadarko Petroleum Corporation (APC) Comments: (f) A pressure fall-off test at least once every five years unless more frequent testing is required by the Director based on site specific information;

Rationale: See 146.90(b)(4)

Response: Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment, EPA has made many revisions to the GS rule. See the final rule and preamble for further discussion on EPA's final approach. EPA adds that the purpose of including all testing and monitoring requirements in §146.90 is to clarify and to specify the content of the required testing and monitoring plan.

Commenter Name: Brad Castleberry Letter ID: 0203 Commenter Organization: Water Environment Association of Texas (WEAT)Comment ID: 22179 Other EPA Comment Codes and Descriptions: 3100 2.1 Proposed Geologic Siting Requirements (40 CFR 146.83)

Comment: groundwater quality as well as public drinking water sources. Careful consideration should he given to ensure an adequate assessment is made of each proposed injection well site. This consideration should come in the form of detailed site studies. sophisticated computer modeling, and other tools used to predict hydrogeology. Careful consideration should also he given to ensure that adequate ongoing monitoring and reporting is provided for any site ultimately permitted pursuant to the proposed rules. Given the unique circumstancessurrounding this type of pollutant, and the lack of a significant body of longterm evidence to support the proposed activity, we would encourage EPA to include significant monitoring and reporting provisions to ensure the long-term viability of any permitted site with respect to surrounding groundwater quality.

Response: EPA agrees with the commenter regarding the importance of site characterization, and believes that the extensive requirements for geologic site characterization (at §146.82), AoR evaluation (§146.84), and testing of the well during drilling (§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 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 believes that monitoring plans and methods need to be site-specific and that the monitoring requirements for GS sites at §146.90 provide an appropriate level of flexibility in structuring a testing and monitoring plan that protects USDWs 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 changesabove 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 is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Christopher Murray Letter ID: 0207 Commenter Organization: Pacific Northwest National Laboratory Comment ID: 22443 Other EPA Comment Codes and Descriptions: 3300 2.2.1 Delineating the AoR/Modeling CO2

movement
Comment: Injection of CO2 into deep saline formations is driven by differences between the well injection pressure and formation pressure. To avoid inducing fractures or opening existing fractures in the formation and caprock, well injection pressure will be limited to some fraction below the fracturing pressure. As CO2 migrates into the formation the formation pressure increases around the injection well. The pressure distribution in the formation around the injection well depends on the formation properties, structure, and injection rate. Injection formations will be required to be confined vertically and/or horizontally to prevent the vertical migration of injected fluids and saline

reservoir fluids into USDWs.

Confined formations (e.g., a caprock overlying a horizontally extensive formation) allow the formation fluid to be displaced laterally by the injected fluid. Injecting CO2 results in elevated pressures both inside and beyond the CO2 plume. Elevated pressures within the CO2 plume have the potential to force CO2 and formation fluid through permeable wells, fractures, or faults that penetrate the formation. Elevated pressures outside the CO2 plume have the potential to force formation fluid through permeable wells, fractures or faults that penetrate the formation. The higher the formation pressure is above the ambient formation pressure, the greater the potential for CO2 and formation fluid to leak through permeable wells, fractures, and faults. The lateral pressure distribution is a function of the injection rate and the lateral distribution of formation permeability. When CO2 injection is halted, elevated pressures decay over time as the injected and formation fluids migrate away from the injection well(s).

The proposed regulations define an AoR and Corrective Action as being an area within which artificial penetrations may act as conduits for fluid movement into USDWs (e.g., active and abandoned wells) and, as needed, require the applicant to perform corrective action to seal these open wells. The potential for fluid movement into USDWs from the injection of CO2 into the injection formation is correlated with the area of elevated formation pressure, which is usually largerthan the area that contains the injected CO2 mass. For confined formations, this area is defined by the lateral pressure distribution around the injection well(s).

PNNL RECOMMENDATION

EPA should define two regulatory regions surrounding the geologic sequestration project and provide specific definitions for those regions; 1) Area of Monitoring (AoM) and 2) Area of Review; where the AoM is used to define the spatial distribution of monitoring wells and the AoR is used to define the limit

of corrective actions:

Area of Monitoring (AoM): The region surrounding the geologic sequestration project that The area of monitoring is based on monitoring data contains 95% of the carbon dioxide mass. and computational modeling that accounts for the physical and chemical properties of all phases of the injected carbon dioxide stream. In the absence of monitoring data, the area of monitoring is based on computational modeling.

Area of Review (AoR): The region surrounding the geologic sequestration reservoir that has or is indicated to develop pressures that are greater than 10% different from the original hydrostatic formation fluid pressure, but no less than the Area of Monitoring. The area of review is based on monitoring data and computational modeling that accounts for the physical and chemical properties of all phases of the injected carbon dioxide stream. In the absence of monitoring data, the area of review is based on computational modeling.

The proposed definitions of AoM and AoR have several important components:

- The AoMhas a mass-based definition. - The AoR has a pressure-differential-based definition. - The AoR is never smaller than the AoM. - The AoR and AoM may be asymmetrical around the injection well(s). - The AoR and AoM may vary over time. - The carbon dioxide mass should be determined using a combination of monitoring data and computational modeling. - Pressure differentials are based on equilibrium hydrostatic conditions.

Response: EPA believes that, while the commenter offers different terminology for the AoR and the area to be monitored, the GS rule addresses the commenter's suggestions. Notably, the owner or operator is required (under 146.90) to develop and implement a testing and monitoring plan for each GS project that must consider the delineated AoR that includes both the CO2 plume and associated pressure front and incorporates many of the attributes suggested by the commenter. EPA clarifies that delineation of the AoR, as required at 146.84(c), must account for the physical and chemical properties of all phases of the injected CO2 stream, based on available site characterization, monitoring, and operational data.

Furthermore, any changes to the AoR would necessitate a review of and potential change in the testing and monitoring plan, consistent with the commenter's assertion that the AoR may vary over time. The final GS regulation includes a requirement at 146.84(e) that the AoR be reevaluated at least every 5 years, and also requires that the owner or operator periodically review the AoR and corrective action, testing and monitoring, and emergency and remedial response plans within oneyear of an AoR reevaluation (as well as following significant changes to the facility, or when required by the Director). The relationship between the AoR reevaluation and the testing and monitoring plan should allow for considerations suggested by the commenter.

EPA believes that by linking development and review of the testing and monitoring plan to the AoR evaluation and reevaluation process, the GS rule, in effect, incorporates many of the commenter's considerations for an area of monitoring.

Commenter Name: John King Letter ID: 0211 Commenter Organization: Shell Exploration and Production Company (SEPCo) Comment ID:

22776

Comment: F. Testing and Monitoring Requirements

The preamble to the proposed rule indicates, "EPA considers CO2 plume and associated pressure front monitoring to be necessary for verification of model predictions." 73 Fed. Reg. at 43514. This is difficult to understand because the regulatory regime for Class I hazardous waste injection wells do not require elaborate modeling, and plume or pressure front monitoring have never been considered necessary and are not required in that context. In fact, extensive experience with Class I hazardous waste injection demonstrates that plume and pressure front monitoring is not necessary, either to provide confidence in modeling results or otherwise. By suggesting otherwise, the proposed rule unnecessarily undermines confidence in the modeling demonstrations that can and should be relied upon to support determinations that injected CO2 will not endanger USDWs.

The suggestion that it makes sense to monitor the movement of injected CO2 in the subsurface also does not consider the nature and utility of modeling used to evaluate injection well projects and of the technical difficulties and uncertainties such monitoring would involve. The root of the problem relates to the fact that modeling provides a conservative assessment of the potential for movement of injected fluids in the subsurface, not a precise "prediction" of actual fate and transport that can or should be "verified" on the basis of elaborate, costly, and uncertain efforts to observe the actual movement of fluids in the subsurface. As experience with hazardous waste injection shows, injection well operational data and the results of pressure fall-off tests provide ample data to validate the results of modeling. The additional monitoring requirements proposed in the GS context are excessive and unjustified.

Response: EPA disagrees that plume and pressure front monitoring are not justified for Class VI wells. The Agency recognizes that while there are similarities between injection of wastes for disposal (Class I) and GS (Class VI), there are significant differences as well. Important unique considerations for GS include the buoyancy of CO2, its corrosivity when in contact with water, its low viscosity (i.e., high mobility), and the very large injection volumes that are anticipated. There is also a degree of uncertainty regarding the behavior of large volumes of CO2 in the subsurface after injection. Given these characteristics of anticipated GS projects, EPA believes that plume and pressure front monitoring at §146.90(g) are justified to provide early warning of any unforeseen fluid movement that might endanger USDWs.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, provide inputs 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.

The final rule, at §146.90(g)(2) requires owners or operators to track the position of the CO2 plumeusing indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or downhole CO2 detection tools), unless the Director determines based on site-specific geology, that such methods are not appropriate. For example, geophysical methods are difficult to execute in areas that are structurally and topographically complex or where lithologies have limited contrast in density, porosity, permeability, and other physical properties. EPA clarifies that this determination will be made by the Director based on the site-specific geologic information submitted by the owner or operator with the permit application.

EPA believes that this approach provides flexibility to develop a site-specific monitoring plan, ensures that direct monitoring is available to track the movement of the CO2 and validate models, and recognizes that indirect techniques are not appropriate in all situations. The owner or operator's approved testing and monitoring plan will include the site-specific details, technologies, testing and monitoring frequencies, and other pertinent information.

EPA agrees that good site selection, modeling, and management are crucial elements of a successful GS project, but disagrees that this is an effective substitute for rigorous site monitoring. EPA disagrees that pressure fall-off tests are an appropriate substitute for monitoring pressure changes in the injection zone. Pressure fall-off tests provide information only in the vicinity of the injection well(s) and measure pressure conditions within the injection zone only. Direct monitoring of pressure changes in the injection zone can provide advance warning of movement of CO2 or brine that might ultimately endanger a USDW.

Commenter Name: John King Letter ID: 0211 Commenter Organization: Shell Exploration and Production Company (SEPCo) Comment ID:

22779

Comment: a. Monitor Wells

Monitor wells reaching the deep subsurface are problematic in a variety of respects. They are expensive to install, create potential pathways for vertical fluid migration, and -- in the deep subsurface where natural fluid movement may be very slow or effectively non-existent -- they have little potential to provide more than an isolated "point measurement." If the object is to track injected fluid within an injection zone, a monitor well could be placed in the path of the waste front to detect the waste front when it goes by, but the exercise would amount to a very expensive way to generate a single data point. There would be less likelihood of any benefit from monitoring wells designed to detect potential leakage from an injection zone, because the ability to detect such leakage is at best a hit-or-miss (if not a needle in a haystack) proposition. Monitor wells also have built-in confounding factors that includeboth the potential for well construction to impact fluid quality in the target sampling interval and the fact that sampling may itself cause fluid movement that might not otherwise occur. Because pressure fronts extend much further than injected fluid plume fronts during injection, pressure monitoring is more likely to be useful than fluid sampling, but costs would till be very high and the ability to detect relevant changes would still be very much hit-or-miss. For these reasons, EPA chose not to impose monitor well requirements for Class I hazardous waste injection wells, though it did allow monitor wells to be required at the discretion of the Administrator to address particular circumstances at the site. See 52 Fed. Reg. 32446 at 32463-64 (August 27, 1987), 53 Fed. Reg. 28118 at 28141, 28144-45 (July 26, 1988). Experience with hazardous waste injection does not commend the use of monitor wells even in that context, and there is no justification to impose as stringent an approach -- let alone a more stringent approach -- for the injection of CO2.

Response: As described above, EPA believes that monitoring using wells in the injection zone, e.g., for pressure monitoring as required at §146.90(g)(1), can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that properly constructed monitoring wells will be a safe way to obtain the data that is essential to ensure that the injected CO2 remains confined in the injection zone and that pressure changes are not causing movement of formation or other fluids. To mitigate the risk of fluid movement, EPA requires owners and operators to submit a testing and monitoring plan that describes how the owner or operator plans to site and construct monitoring wells. 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.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

EPA also acknowledges that complete coverage of the potential plume area or leakage in the subsurface is not possible through the use of monitoring wells. However, data from an appropriate number of monitoring wells sited based on site-specific information will provide direct information that is not otherwise obtainable and, along with other monitoring data, will support a broader understanding of fluid behavior at the site.

EPA adds that the iterative process of monitoring, modeling, and AoR reevaluation is appropriate to verify that the CO2 plume and pressure front are moving through the subsurface as predicted, verify the accuracy of the delineation model (or identify needed changes), and refine testing and monitoring activities to ensure that USDWs are protected from endangerment and that there would be adequate warning of potential problems at the site before any endangerment could occur.

EPA acknowledges the commenters' concern about the cost of monitoring. However, EPA believesthat monitoring is essential for protection of USDWs at GS sites. Although a significant cost in absolute terms, monitoring costs are expected to be a small fraction of site operating costs, according to EPA's cost analysis for the GS rulemaking (which is available in the docket).

Commenter Name: Ronald Evans Letter ID: 0215 Commenter Organization: Denbury Resources, Inc. (DRI) Comment ID: 24311

Comment: 4. EPA Proposed §146.90(i) 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

This section effectively proposes a "catch all" to allow the Director undefined discretion to order unlimited and unspecified additional monitoring to improve modeling and ensure compliance. Vesting the Director with such additional undefined discretionary authority increases the regulatory risks of the Class VI permitting process and accordingly increases costs. In the event that experience implementing the proposed rule requires some future revisions to include additional monitoring requirements, such changes should be proposed and adopted through appropriate rulemaking procedures and based on an adequate factual and scientific record. However, adopting an open-ended power to require "any" additional monitoring, at this early stage, undermines the purpose of providing a defined set of rules that members of the public may evaluate prior to making the large investments that will be involved in Class VI projects. Such uncertainty can only tend to increase costs, creating a barrier to capital formation and discouraging geologic sequestration. Accordingly, Denbury recommends deleting this section.

Response: EPA does not believe that UIC Directors should have undefined discretion when ordering additional monitoring requirements. EPA believes that, given the variety of site-specific circumstances that may be encountered at GS sites, it is reasonable to afford the Director discretion only when additional testing and monitoring requirements are required to ensure the protection of

USDWs.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance will discuss how the Director may exercise any discretion. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Edward Steadman Letter ID: 0220 Commenter Organization: The Energy and Environmental Research Center at the University of North Dakota Comment ID:

21626

Comment: Page 43515 to 43516. Regarding monitoring. In general, this section is overly prescriptive with respect to the selection and application of monitoringtechniques. One of the things that is lost in this discussion is that if the geometry of the trapping structure is well understood and the overlying seal has been demonstrated to be competent and thick, then plume monitoring should be relatively straightforward and less complicated. Consider, for example, injection into a thoroughly characterized high-relief structure, such as an anticline or pinnacle reef encased in impermeable anhydrite. Migration of the CO2 would be minimal, and plume stabilization would be relatively rapid. A few carefully instrumented and placed monitoring wells, some above the seal and others just outside and below the structure, would be enough to ensure the plume does not leak through the seal or slip beneath the spill point at the bottom of the structure. With this in mind, it can be reasonably argued that seismic surveys (which may or may not provide useful insight regarding the plume, depending on the lithology) would not offer any additional data that would further ensure the protection of USDWs. If there is no significant structural element to the trap, then plume stabilization could very well take many decades, and in such a case, a more robust and comprehensive suite of monitoring tools may have to be applied. Many examples of both types of sites, and many more that fall in between, have been identified throughout the United States, and it is because of this variety that it is critical that UIC regulations for GS allow flexibility in choosing plume-tracking methods. The EPA acknowledges the need for flexibility in a paragraph in the middle of page 43516, but many of the requirements laid out in the document do not reflect that need.

Response: EPA agrees that flexibility is important in developing and implementing a monitoring plan that is appropriately tailored for a specific GS site, and believes that the final regulation provides for flexibility in: 1) methodologies used to collect these data, 2) the spatial resolution at which the data should be collected, and 3) how often the data should be collected. The number and placement of monitoring wells will be based on site-specific information such as the calculated AoR, injection rate and volume, site geology, baseline data, and the presence of artificial penetrations within the AoR. In some instances, there may be a limited number of options for complying with EPA's minimum requirements. For example, monitoring for geochemical changes will require use of monitoring wells and collection of groundwater samples for chemical analysis. Many options currently exist for complying with other requirements, such as tracking the position of the plume and pressure front within the injection zone.

Flexibility is also provided regarding how to monitor for the specific data required by the final rule. The testing and monitoring plan is developed by the owner or operator in consultation with the Director and is designed to ensure that a detailed, Director-approved document describing how monitoring will be conducted during the lifetime of the project exists. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologiesand recommended approaches for implementing a testing and monitoring plan, including preoperational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects.The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the

docket for the final GS rule.With specific regard to plume tracking and pressure monitoring, EPA maintains that they are key components of monitoring at GS sites. A rigorous plume tracking and pressure monitoring scheme, such as one that meets the requirements at §146.90(g), is imperative for ensuring that the CO2 plume is contained within the injection zone.

The final rule at §146.90(g) requires owners or operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are required unless the Director determines, based on site-specific geology that such methods are not appropriate

Pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume. When combined with information on temperature, pressure data provide an indication of the phase (e.g., gas, supercritical) and distribution of the injected CO2 (73 FR 43515). Monitoring can also identify needed remedial actions, provide inputs for AoR reevaluation modeling, evaluate predictions of plume movement, and target additional geochemical and surface monitoring needs.

Commenter Name: Edward Mehnert Letter ID: 0221 Commenter Organization: Illinois State Geological Survey Comment ID: 21637 Other EPA Comment Codes and Descriptions: 3300 2.2.1 Delineating the AoR/Modeling CO2

movement
Comment: p.43506, IIIA2 Proposed Area of Review: Does the area of review need to be one contiguous area? For a deep saline aquifer with no structural trap, it may be beneficial to have two separate areas of review--one for the CO2 plume and another for the pressure front at a distant USDW boundary. In this setting, the pressure front may move brine upgradient into a portion of the aquifer that contains fresher water (<10,000 mg/L TDS). The distance between the injection well and the "freshwater" section of the aquifer may be more than 100 miles.

Response: EPA clarifies that the requirements for AoR delineation incorporate both the CO2 plume and associated pressure front. EPA agrees that both of these should be taken into account in determining corrective action needs and developing 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.

Commenter Name: Edward Mehnert Letter ID: 0221 Commenter Organization: Illinois State Geological Survey Comment ID: 21639

Comment: p.43514, IIIA6 Monitoring Requirements: The complete list of monitoring procedures may not be necessary in all settings, such as deep saline aquifers (>5,000 ft below ground surface). I hope that these rules will remain flexible such that they can benefit from the research currently being conducted by the USDOE-funded partnerships. Their Phase III efforts should provide valuable information on the feasibility and value of various monitoring methods.

Response: EPA agrees with commenters and believes that flexibility is important in developing andimplementing a monitoring plan that is appropriately tailored for a specific GS site. The purpose of the requirement at §146.90 to develop site-specific testing and monitoring plans is to ensure that the monitoring performed at a site is appropriate for site operational conditions and the geologic setting. EPA believes that this is the best approach for addressing potential risks at GS sites. These flexible provisions in the monitoring requirements for Class VI wells enable the owner or operator to tailor monitoring programs to the specific needs of each project in consultation with the Director.

The final regulation provides for flexibility in: 1) methodologies used to collect these data, 2) the spatial resolution at which the data should be collected, and 3) how often the data should be collected. The number and placement of monitoring wells will be based on site-specific information such as the calculated AoR, injection rate and volume, site geology, baseline data, and the presence of artificial penetrations within the AoR. In some instances, there may be a limited number of options for complying with EPA's minimum requirements. For example, monitoring for geochemical changes will require use of monitoring wells and collection of groundwater samples for chemical analysis. Many options currently exist for complying with other requirements, such as tracking the position of the plume and pressure front within the injection zone.

EPA believes, however, that implementing a testing and monitoring plan that includes all of the required elements under §146.90 is essential to ensuring USDW protection. Please see the preamble to the final rule for a complete justification of the elements of a GS testing and monitoring regime.

Flexibility is also provided regarding how to monitor for the specific data required by the final rule. The testing and monitoring plan is developed by the owner or operator in consultation with the Director and is designed to ensure that a detailed, Director-approved document describing how monitoring will be conducted during the lifetime of the project exists. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologiesand recommended approaches for implementing a testing and monitoring plan, including preoperational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

EPA is using an adaptive approach to regulating GS. EPA will collect and review project data on early GS projects to determine whether the appropriate amount and types of information and appropriate documentation are required and being collected. The Agency will evaluate the information and determine if modifications to the requirements are necessary.

Commenter Name: Darrick Eugene Letter ID: 0223 Commenter Organization: Texas Carbon Capture and Storage Association Comment ID: 23991

Comment: EPA Proposed §146.90(i) 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

This section effectively proposes a "catch all" to allow the Director undefined discretion to order unlimited and unspecified additional monitoring to improve modeling and ensure compliance. Vesting the Director with such additionalundefined discretional authority increases the regulatory risks of the Class VI permitting process and accordingly increases costs. In the event that experience implementing the proposed rule requires some future revisions to include additional monitoring requirements, such changes should be proposed and adopted through appropriate rulemaking procedures and based on an adequate factual and scientific record. However, adopting an open- ended power to require "any" additional monitoring, at this early stage, undermines the purpose of providing a defined set of rules that members of the public may evaluate prior to making the large investments that will be involved in a Class VI projects. Such uncertainty can only tend to increase costs, creating a barrier to capital formation and discourage geologic sequestration. Accordingly, TxCCSA would recommend deleting this section:

§146.90(i) 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.

Response: EPA does not believe that Directors should have undefined discretion when ordering additional monitoring requirements. EPA believes that, given the variety of site-specific circumstances that may be encountered at GS sites, it is reasonable to afford the Director discretion only when additional testing and monitoring requirements are added to ensure the protection of USDWs. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance will discuss how the Director may exercise any discretion. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Tiffany Rau Letter ID: 0224 Commenter Organization: Hydrogen Energy International Comment ID: 21676 Other EPA Comment Codes and Descriptions: 1250 1.1.1.4 Flexibility is needed (performancebased standards)

Comment: With respect to monitoring requirements in general, EPA should adopt regulations that are performance and risk-based and will result in a site-specific monitoring program that is designed to understand the location, movement and stabilization of the CO2 plume in the subsurface as well as the early identification of any leakage for appropriate corrective action. HEI commends EPA for its efforts in this regard, but believes that further modification is necessary. HEI agrees with the proposal to allow a phased approach to conduct

Response: EPA agrees with commenters and believes that flexibility is important in developing and implementing a monitoring plan that is appropriately tailored for a specific GS site. The purpose of the requirement at §146.90 to develop site-specific testing and monitoring plans is to ensure that the monitoring performed at a site is appropriate for site operational conditions and the geologic setting. EPA believes that this is the best approach for addressing potential risks at GS sites. These flexibleprovisions in the monitoring requirements for Class VI wells enable the owner or operator to tailor monitoring programs to the specific needs of each project in consultation with the Director.

The final regulation provides for flexibility in: 1) methodologies used to collect these data, 2) the spatial resolution at which the data should be collected, and 3) how often the data should be collected. The number and placement of monitoring wells will be based on site-specific information such as the calculated AoR, injection rate and volume, site geology, baseline data, and the presence of artificial penetrations within the AoR. In some instances, there may be a limited number of options for complying with EPA's minimum requirements. For example, monitoring for geochemical changes will require use of monitoring wells and collection of groundwater samples for chemical analysis. Many options currently exist for complying with other requirements, such as tracking the position of the plume and pressure front within the injection zone.

Flexibility is also provided regarding how to monitor for the specific data required by the final rule. The testing and monitoring plan is developed by the owner or operator in consultation with the Director and is designed to ensure that a detailed, Director-approved document describing how monitoring will be conducted during the lifetime of the project exists. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologiesand recommended approaches for implementing a testing and monitoring plan, including preoperational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Brian Williams Letter ID: 0225 Commenter Organization: BP Alternative Energy North America, Inc. (BP) Comment ID: 21721 Other EPA Comment Codes and Descriptions: 1250 1.1.1.4 Flexibility is needed (performancebased standards)

Comment: With respect to monitoring requirements in general, EPA should adopt regulations that are performance and risk-based and will result in a site-specific monitoring program that is designed to understand the location, movement and stabilization of the CO2 plume in the subsurface as well as the early identification of any leakage for appropriate corrective action. BP commends EPA for its efforts in this regard, but believes that further modification is necessary. BP agrees with the proposal to allow a phased approach to conduct

Response: EPA agrees with commenters and believes that flexibility is important in developing and implementing a monitoring plan that is appropriately tailored for a specific GS site. The purpose of the requirement at §146.90 to develop site-specific testing and monitoring plans is to ensure that the monitoring performed at a site is appropriate for site operational conditions and the geologic setting. EPA believes that this is the best approach for addressing potential risks at GS sites. These flexible provisions in the monitoring requirements for Class VI wells enable the owner or operator to tailor monitoring programs to the specific needs of each project in consultation with the Director.

The final regulation provides for flexibility in: 1) methodologies used to collect these data, 2) the spatial resolution at which the data should be collected, and 3) how often the data should be collected. The number and placement of monitoring wells will be based on site-specific informationsuch as the calculated AoR, injection rate and volume, site geology, baseline data, and the presence of artificial penetrations within the AoR. In some instances, there may be a limited number of options for complying with EPA's minimum requirements. For example, monitoring for geochemical changes will require use of monitoring wells and collection of groundwater samples for chemical analysis. Many options currently exist for complying with other requirements, such as tracking the position of the plume and pressure front within the injection zone.

Flexibility is also provided regarding how to monitor for the specific data required by the final rule. The testing and monitoring plan is developed by the owner or operator in consultation with the Director and is designed to ensure that a detailed, Director-approved document describing how monitoring will be conducted during the lifetime of the project exists. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologiesand recommended approaches for implementing a testing and monitoring plan, including preoperational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Andrew Duguid Letter ID: 0226 Commenter Organization: Schlumberger Carbon Services Comment ID: 24053 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: §146.90 Testing and monitoring requirements.

Proposed Rule: (b) Installation and use, except during well workovers 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;

Schlumberger Suggested Revision: -

Schlumberger Rationale: 146.86(d) does not exist; perhaps 146.88(d) is what was

intended.

Response: EPA acknowledges the comment; the final rule contains the suggested revision.

Commenter Name: Neeraj Gupta Letter ID: 0229 Commenter Organization: Battelle Energy Technology (BET) Comment ID: 21850 Other EPA Comment Codes and Descriptions: 4610 2.6.1 Testing and monitoring plan requirement (seeking comment)

Comment: Page 102, Pressure monitoring in overlying zones- Implicit in this monitoring requirement is that network of deep monitoring wells will be required with the injection well. We know of no other method to accurately measure deep pressures. As such, this requirement will be costly to implement and should be spelled out clearly for planning purposes. It may also be pertinent to make this optional depending on identified risks.Response: EPA acknowledges the commenters' concern about the cost of monitoring. However, EPA believes that monitoring is essential for protection of USDWs at GS sites. Although a significant cost in absolute terms, monitoring costs are expected to be a small fraction of site operating costs, according to EPA's cost analysis for the GS rulemaking (which is available in the docket).

EPA believes that monitoring using wells in the injection zone, e.g., for pressure monitoring as required at §146.90(g)(1), can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that properly constructed monitoring wells will be a safe way to obtain the data that is essential to ensure that the injected CO2 remains confined in the injection zone and that pressure changes are not causing movement of formation or other fluids. To mitigate the risk of fluid movement, EPA requires owners and operators to submit a testing and monitoring plan that describes how the owner or operator plans to site and construct monitoring wells. 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.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, and tracking the CO2 plume and pressure front. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the

docket for the final GS rule.

Commenter Name: Neeraj Gupta Letter ID: 0229 Commenter Organization: Battelle Energy Technology (BET) Comment ID: 21857

Comment: Page 103, Monitoring within the confining zone- In our experience it is very difficult to measure parameters in confining layers like pH, salinity, minerals, heavy metals, and organic contaminants on a routine basis. Confining zones typically consist of very low permeability carbonates that do not produce water or unstable shale not suitable for sampling due to borehole stability concerns.

Response: EPA recognizes that the collection of representative ground water samples from depth poses challenges and that special methods, such as U-tubes, will be needed to preserve the integrity of such samples. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.Regarding the comment about the difficulty of sampling within the confining zone, EPA clarifies that §146.90(d) requires owners and operators to monitor ground water quality and geochemical changes above the confining zone(s), rather than within the confining zone.

Commenter Name: Steven B. Corneli Letter ID: 0234 Commenter Organization: NRG Energy, Inc. Comment ID: 23169 Other EPA Comment Codes and Descriptions: 4660 2.6.6 Geochemical monitoring

Comment: Monitoring Requirements

The preamble of the proposed rule states that the "monitoring of subsurface geochemistry and the position of the CO2 plume and pressure front are necessary to verify predictions of plume movement, provide inputs for modeling, identify needed corrective actions, and target geochemical and surface monitoring activities." 73 Fed. Reg. at 43514. NRG believes that the proposed monitoring requirements are excessive and unjustified. The use of monitor wells or seismic data would be needed to verify the model predictions. In particular, it is

Response: EPA disagrees that the monitoring requirements in the GS rule are excessive or unjustified. 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 important part of a rigorous monitoring program. Such monitoring can provide an early warning that the plume 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). EPA also believes that geophysical (e.g., seismic) methods are useful for plume tracking at GS sites. For this reason, the final rule at §146.90(g) requires the use of indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) unless the Director determines, based on site-specific geology that such methods are not appropriate

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

EPA also acknowledges that complete coverage of the potential plume area or leakage in the subsurface is not possible through the use of monitoring wells. However, data from an appropriate number of monitoring wells sited based on site-specific information will provide direct information that is not otherwise obtainable and, along with other monitoring data, will support a broader understanding of fluid behavior at the site.

EPA adds that the iterative process of monitoring, modeling, and AoR reevaluation is appropriate to verify that the CO2 plume and pressure front are moving through the subsurface as predicted, verify the accuracy of the delineation model (or identify needed changes), and refine testing and monitoring activities to ensure that USDWs are protected from endangerment and that there would be adequate warning of potential problems at the site before any endangerment could occur.Commenter Name: Steven B. Corneli Letter ID: 0234 Commenter Organization: NRG Energy, Inc. Comment ID: 23171

Comment: The preamble of the proposed rule states that the "monitoring of subsurface geochemistry and the position of the CO2 plume and pressure front are necessary to verify predictions of plume movement, provide inputs for modeling, identify needed corrective actions, and target geochemical and surface monitoring activities." 73 Fed. Reg. at 43514. NRG believes that the proposed monitoring requirements are excessive and unjustified. The use of monitor wells or seismic data would be needed to verify the model predictions. In particular, it is impractical and cost prohibitive to measure the exact location of the CO2 plume and pressure front using monitor wells. The monitor wells would be very expensive to install and may create a potential pathway for migration of CO2. In addition, plume or pressure front monitoring have never been necessary or required under the Class I hazardous waste injection well program because experience has shown that it is not necessary to verify the model predictions.

Response: EPA disagrees that plume and pressure front monitoring are not justified for Class VI wells. The Agency recognizes that while there are similarities between injection of wastes for disposal (Class I) and GS, there are significant differences as well. Important unique considerations for GS include the buoyancy of CO2, its corrosivity when in contact with water, its low viscosity (i.e., high mobility), and the very large injection volumes that are anticipated. There is also a degree of uncertainty regarding the behavior of large volumes of CO2 in the subsurface. Given these characteristics of anticipated GS projects, EPA believes that plume and pressure front monitoring at §146.90(g) are justified to provide early warning of any unforeseen fluid movement that might endanger USDWs.

The final rule at §146.90(g) requires owners or operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are required unless the Director determines, based on site-specific geology that such methods are not appropriate.

EPA believes that pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume. 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 believes that monitoring using wells in the injection zone, e.g., for pressure monitoring as required at §146.90(g)(1), can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that properly constructed monitoring wells will be a safe way to obtain the data that is essential to ensure that the injected CO2 remains confined in the injection zone and that pressure changes are not causing movement of formation or other fluids.

§146.90(g)(2) requires owners or operators to track the position of the CO2 plume using indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools), unless the Director determines based on site-specific geology, that such methods are not appropriate. For example, geophysical methods are difficult to execute in areas that arestructurally and topographically complex or where lithologies have limited contrast in density, porosity, permeability, and other physical properties. EPA clarifies that this determination will be made by the Director based on the site-specific geologic information submitted by the owner or operator with the permit application.

EPA believes that this approach provides flexibility to develop a site-specific monitoring plan, ensures that direct monitoring is available to track the movement of the CO2 and validate models, and recognizes that indirect techniques are not appropriate in all situations. The owner or operator's approved testing and monitoring plan will include the site-specific details, technologies, testing and monitoring frequencies, and other pertinent information.

EPA also acknowledges that complete coverage of the potential plume area or leakage in the subsurface is not possible through the use of monitoring wells. However, data from an appropriate number of monitoring wells sited based on site-specific information will provide direct information that is not otherwise obtainable and, along with other monitoring data, will support a broader understanding of fluid behavior at the site.

Commenter Name: Robert F. Voorhees Letter ID: 0243 Commenter Organization: Underground Injection Technology Group (UIT Group) Comment ID:

23339

Comment: B. Stringency of the Proposed Rule

The UIT Group is concerned by the overall level of stringency of the proposed requirements for Class VI injection wells. Carbon dioxide is among the most innocuous materials injected under the UIC program, and yet the proposed rules for carbon dioxide injection would be among the most elaborate and burdensome in the entire UIC program. This approach is incongruous at best, and certainly seems ill-suited to the goal of encouraging responsible development of geologic sequestration projects. However, the UIT Group’s specific concern is that the proposed Class VI regulations are so excessive in some respects that they could effectively undermine public confidence in the UIC program for other classes of injection wells, including Class I injection wells.

The UIT Group is particularly concerned with the proposed Class VI monitoring requirements, which are based upon the premise that it is necessary to track the physical location of injected fluids and observationally "verify" that USDWs are not being endangered. These requirements would appear to make elaborate monitoring through the use of monitor wells or indirect geophysical "plume tracking" techniques mandatory for all geologic sequestration projects. In general, it simply isn't true that this kind of monitoring is necessary, and - again as a general rule - such monitoring would be burdensome, costly, and of limited utility.

Any discussion of monitor well requirements must start with an understanding of how the UIC program works: injection can't even commence unless there has been an adequate demonstration that the injection zone is separated from USDWs by a confining zone sufficient to prevent the movement of fluids from the injection zone into a USDW. Operators of hazardous waste injection wells must go a step further: they must demonstrate - to a reasonable degree of certainty - thatthere will be no migration of hazardous constituents from the injection zone for as long as the waste remains hazardous.

Decades of experience with Class I injection has demonstrated that thisregulatory approach is effective: under current regulatory standards, injectionrelated contamination of USDWs is virtually unknown, and EPA itself has concluded - after reviewing a broad range of studies - that properly-permitted Class I injection wells "provide an extremely low-risk" waste management option. See Class I Underground Injection Control Program: Study of the Risks Associated with Class I Underground Injection Wells (EPA, March 2001) at p. 42. In the face of such well-documented success it is difficult to see why there should be any crisis of confidence sufficient to justify the suggestion that the required "up-front" technical evaluation and controls on injection activity are somehow so unreliable that elaborate monitoring to track injected fluids and "verify" non-endangerment is necessary and should be required in every case.

It would be one thing if the kind of monitoring at issue were relatively easy and cost-effective, but it is not. In the deep subsurface, such monitoring is difficult, costly, and generally yields relatively limited information. Accordingly, while there may be specific circumstances under which the use of monitor wells or indirect geophysical methods can make sense, it is important to consider both the potential utility of such monitoring and the burdens and technical challenges involved, as the regulations for Class I hazardous waste injection wells reflect. To suggest that elaborate monitoring efforts should be mandatory at every site, as the proposed Class VI regulations appear to suggest, is unjustified and does disservice to the demonstrated effectiveness and success of the detailed site selection, characterization and pre-injection technical evaluation the UIC program requires.

Response: EPA disagrees that monitoring at GS sites will undermine public confidence in GS and the UIC Program. EPA believes that appropriately designed and implemented monitoring plans will increase public confidence in the safety of GS, helping to assure the public that any problems are detected early and that appropriate measures are taken to protect USDWs from endangerment. Knowledge of the location of the CO2 plume and the associated pressure front will enable EPA to 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 disagrees that plume and pressure front monitoring are not justified for Class VI wells. The Agency recognizes that while there are similarities between injection of wastes for disposal (Class I) and GS (Class VI), there are significant differences as well. Important unique considerations for GS include the buoyancy of CO2, its corrosivity when in contact with water, its low viscosity (i.e., high mobility), and the very large injection volumes that are anticipated. There is also a degree of uncertainty regarding the behavior of large volumes of CO2 in the subsurface after injection. Given these characteristics of anticipated GS projects, EPA believes that plume and pressure front monitoring at §146.90(g) are justified to provide early warning of any unforeseen fluid movement that might endanger USDWs.

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 forpressure 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, provide inputs for AoR reevaluation modeling, evaluate predictions of plume movement, and target additional geochemical and surface monitoring needs.

In addition, §146.90(g)(2) requires owners or operators to track the position of the CO2 plume using indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools), unless the Director determines, based on site-specific geology, that such methods are not appropriate. EPA is affording Director's discretion regarding the use of geophysical techniques at some sites because the Agency recognizes that geophysical methods are not appropriate in all geologic settings. EPA clarifies that this determination will be made by the Director based on the site-specific geologic information submitted by the owner or operator with the permit application.

EPA believes that this approach provides flexibility to develop a site-specific monitoring plan, ensures that direct monitoring is available to track movement of the CO2 and validate models, and recognizes that indirect techniques are not appropriate in all situations. The owner or operator's approved testing and monitoring plan will include the site-specific details, technologies, testing and monitoring frequencies, and other pertinent information.

EPA acknowledges the commenters' concern about the cost of monitoring. However, EPA believes that monitoring is essential for protection of USDWs at GS sites. Although a significant cost in absolute terms, monitoring costs are expected to be a small fraction of site operating costs, according to EPA's cost analysis for the GS rulemaking, which is available in the docket).

Commenter Name: Robert F. Voorhees Letter ID: 0243 Commenter Organization: Underground Injection Technology Group (UIT Group) Comment ID:

23342

Comment: regulations themselves do not impose. The UIT Group also urges EPA to: (1) acknowledge the demonstrated and well-documented success of the existing UIC program regulations for Class I hazardous waste injection wells; and (2) avoid regulatory excesses in the proposed rule that could potentially undermine public confidence in the established effectiveness of the Class I regulations and the requirements for other UIC classes of wells.

Response: As described above, EPA disagrees that monitoring at GS sites will undermine public confidence in GS and the UIC Program. EPA believes that appropriately designed and implemented monitoring plans will increase public confidence in the safety of GS, helping to assure the public that any problems are detected early and that appropriate measures are taken to protect USDWs from endangerment. Knowledge of the location of the CO2 plume and the associated pressure front will enable EPA to 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.

As described above, the Agency recognizes that while there are similarities between injection ofwastes for disposal (Class I) and GS (Class VI), there are significant differences as well. Important unique considerations for GS include the buoyancy of CO2, its corrosivity when in contact with water, its low viscosity (i.e., high mobility), and the very large injection volumes that are anticipated. There is also a degree of uncertainty regarding the behavior of large volumes of CO2 in the subsurface after injection. Given these characteristics of anticipated GS projects, EPA believes that plume and pressure front monitoring at §146.90(g) are justified to provide early warning of any unforeseen fluid movement that might endanger USDWs.

EPA believes that this approach provides flexibility to develop a site-specific monitoring plan, ensures that direct monitoring is available to track movement of the CO2 and validate models, and recognizes that indirect techniques are not appropriate in all situations. The owner or operator's approved testing and monitoring plan will include the site-specific details, technologies, testing and monitoring frequencies, and other pertinent information.

Commenter Name: Kurt Waltzer Letter ID: 0250 Commenter Organization: Clean Air Task Force Comment ID: 22318

Comment: The proposed rule outlines several different types of monitoring requirements: (a) analysis of the CO2 stream; (b) continuous monitoring of injection pressure, rate and volume as well as other quantities; (c) corrosion monitoring for the well materials; (d) groundwater and geochemistry monitoring above the confining zone; (e) mechanical integrity testing; (f) pressure fall-off tests;(g) CO2 plume and pressure front tracking; and (h) surface air monitoring.

We do not wish to comment on (c). We consider subpart (i), enabling the Director to require additional forms of monitoring, as well as subpart (j), calling for a quality assurance and surveillance plan, entirely appropriate. We consider (a), (b), (d), (e), and (f) and (g) to be essential elements of a sound monitoring

system.

Response: EPA acknowledges the commenter’s support. Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment EPA has made many revisions to the GS rule. See the final rule and preamble for further discussion on EPA's final approach.

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

Commenter Name: Kurt Waltzer Letter ID: 0250 Commenter Organization: Clean Air Task Force Comment ID: 22319 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: In particular, monitoring above the caprock, sometimes informally referred to as "above-zone monitoring, and covered in (d), is a tested monitoring method [FN23], and one that can be key to verifying the integrity and lateral extent of the caprock (or confining zone). We support its inclusion, but also recognize that it might not be necessary to employ this method every time. We would only consider itsomission acceptable only if another method capable of testing and verifying the integrity of the confining zone is being used. Subpart (d) would also cover groundwater monitoring near the surface, at a long distance from the caprock. It is our understanding that researchers from the Lawrence Livermore National Laboratory are already confident in the merits of this approach and its accuracy in detecting small amounts of CO2. We therefore recommend the following minor changes to §146.90(d):

[In the paragraph below the text in all CAPS denotes added text. See also EPA-HQ-OW-0390-0250.pdf to see the original formatting.]

"Periodic monitoring of the ground water quality and GEOPHYSICAL, geochemical OR OTHER changes above the confining zone(s) that may be a result of carbon dioxide OR OTHER INDUCED fluid movement through the confining zone or additional identified zones; provided however that the DIRECTOR MAY INSTEAD REQUIRE THE

INCLUSION OF OTHER METHODS THAT TEST AND/OR VERIFY THE INTEGRITY OF

THE CONFINING ZONE(S) WITH SIMILAR ACCURACY AND TO THE SAME OR LARGER

AREAL EXTENT.(1) [...]"

[FN23: Used successfully at the Frio pilot project, and already being considered for other projects.]

Response: EPA clarifies that direct monitoring of ground water quality above the confining zone is important, and the GS rule requires this at §146.90(d). EPA believes that the ground water geochemical monitoring outlined in §146.90(d) will maximize protection of USDWs from endangerment at GS sites. Additional monitoring above the confining zone, as well as 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 under §146.90(i) to require that it be included in the testing and monitoring plan.

EPA adds that the baseline geochemical data required with the permit application at §146.82(a)(6) will provide information on predicting potential interactions between rocks and CO2 as the commenter suggests, and also expects that this information will inform the development and approval of a site-specific testing and monitoring plan. EPA expects that the data will also help determine whether any changes are occurring above the confining zone and whether they might be associated with the CO2 plume or pressure front.

EPA further clarifies that the final rule at §146.90(g) requires indirect monitoring not above the confining zone but in the injection zone, unless the Director determines, based on site-specific geology, that indirect methods are not appropriate. Indirect methods can include geophysical

methods.

Commenter Name: Michel Paque Letter ID: 0259 Commenter Organization: Ground Water Protection Council Comment ID: 24829

Comment: There should not be a requirement for monitor wells into the injection zone, and monitor wells should not be required for the purpose of tracking the plume orpressure front.

Response: EPA maintains that plume tracking and pressure monitoring are key components of monitoring at GS sites. A rigorous plume tracking and pressure monitoring scheme, such as one that meets the requirements at §146.90(g), is imperative for ensuring that the CO2 plume is contained within the injection zone. The final GS rule, at §146.90(g)(1), requires GS well owners or operators to use direct methods to monitor for pressure changes in the injection zone. The purpose of monitoring in the injection zone is to track the development and movement of the pressure front and CO2 plume. This will support an understanding of site performance and verify predictive modeling. Pressure monitoring within the injection zone is necessary because any such monitoring above the confining zone would not detect movement of the pressure front unless a breach of the confining

zone occurs.

Commenter Name: Michel Paque Letter ID: 0259 Commenter Organization: Ground Water Protection Council Comment ID: 24923 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90

EPA Proposal: (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 workovers 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;

GWPC Recommendations: Support the proposed EPA language in (a)

(b) Installation and use, except during well workovers as defined in §146.88(d), of continuous monitoring devices (including digital devices capturing periodic data) to monitor injection pressure, rate and volume; and record at least daily the pressure on the annulus between the tubing and the long string casing;

Rationale: 146.86(d) does not exist; perhaps 146.88(d) is what was apparently

intended.

Response: EPA acknowledges the comment; the final rule retains the language in §146.90(a) as proposed. EPA adds that the final GS rule references §146.88(e), as the commenter suggests.

Regarding §146.90(b), 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.

Commenter Name: Michel Paque Letter ID: 0259 Commenter Organization: Ground Water Protection Council Comment ID: 24927 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rulelanguage

Comment: Rule Provision: 146.90

EPA Proposal: (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;

(f) A pressure fall-off test at least once every five years unless more frequent testing is required by the Director based on site specific information;

GWPC Recommendations: (e) A demonstration of external mechanical integrity pursuant to §146.89(c) at least once per year until the well is plugged;

(f) A pressure fall-off test or other equivalent test that identifies reservoir conditions with respect to flow dynamics at least once every five years unless more frequent testing is required by the Director based on site specific information;

Rationale: Redundant to section 146.89

Response: Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment EPA has made many revisions to the GS rule. See the final rule and preamble for further discussion on EPA's final approach.

EPA 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 is necessary every five years at a minimum, and the final GS regulation 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) to ensure safe and effective operations.

Commenter Name: Iain Wright Letter ID: 0508 Commenter Organization: BP Alternative Energy Comment ID: 21183

Comment: Moving on to my second point, monitoring. Monitoring is very important, because a common mis-perception that if you want secure storage you need to do lots of monitoring. Well, the U.N. says that a proportion of CO2 obtained by appropriately selected and managed sites is likely to exceed 99 percent over a thousand years.

So the key to secure storage is the appropriate selection and management of the site. If that's done properly the site will be very secure and the need for monitoring can be appropriately reduced.

Monitoring is kind of like the speedometer on your car. It does contribute to your safety, but more important is the design of the car, the road, and how you drive the car. Having said that, at In Salah we are doing a big research project into monitoring. And so the program is much more extensive than it would beappropriate for a commercial project.

We're trying out new technologies, such as satellite imagery, micro-seismic, so we can see how they perform against conventional oil fuel monitoring technology,

such as tracers and conventional seismic.

But as you can probably hear from my accent I'm a Scotsman, and Scotsmen don't like to waste money. So every technology that we use at In Salah has been carefully chosen to represent great value for money. Before we started the injection at In Salah we did a site-specific assessment of the risk of leakage, and then we tailored the monitoring program to address all of those risks.

So mandating any specific monitoring technology would waste a lot of money and resources without contributing to the protection of USDWs. So we would caution against the universal mandate for any specific monitoring technology.

Many of you will have heard of the other two monitored industrial scale CO2 injection projects in the world at Sleipner and Weyburn. If you compare the monitoring activities of these sites you'll see that something which works in one location may not work at all in another location. So we encourage the EPA to use risk-based performance criteria to determine the site-specific monitoring

programs.

Response: EPA agrees with commenters and believes that flexibility is important in developing and implementing a monitoring plan that is appropriately tailored for a specific GS site. The purpose of the requirement at §146.90 to develop site-specific testing and monitoring plans is to ensure that the monitoring performed at a site is appropriate for site operational conditions and the geologic setting. EPA believes that this is the best approach for addressing potential risks at GS sites. These flexible provisions in the monitoring requirements for Class VI wells enable the owner or operator to tailor monitoring programs to the specific needs of each project in consultation with the Director.

The final regulation provides for flexibility in: 1) methodologies used to collect these data, 2) the spatial resolution at which the data should be collected, and 3) how often the data should be collected. The number and placement of monitoring wells will be based on site-specific information such as the calculated AoR, injection rate and volume, site geology, baseline data, and the presence of artificial penetrations within the AoR. In some instances, there may be a limited number of options for complying with EPA's minimum requirements. For example, monitoring for geochemical changes will require use of monitoring wells and collection of groundwater samples for chemical analysis. Many options currently exist for complying with other requirements, such as tracking the position of the plume and pressure front within the injection zone.

Flexibility is also provided regarding how to monitor for the specific data required by the final rule. The testing and monitoring plan is developed by the owner or operator in consultation with the Director and is designed to ensure that a detailed, Director-approved document describing how monitoring will be conducted during the lifetime of the project exists. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologiesand recommended approaches for implementing a testing and monitoring plan, including preoperational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gasand surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the

docket for the final GS rule.

Commenter Name: Scott Anderson Letter ID: 0520 Commenter Organization: Environmental Defense Fund Comment ID: 21428

Comment: We like the fact that the rules place a lot of importance on monitoring. In several instances, the rules proposed using monitoring to modify the various aspects of the operations, but we think the rules can go further in this respect and we will spell that out in our final comments.

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

Commenter Name: Cynthia Lane Letter ID: 0528 Commenter Organization: American Water Works Association (AWWA) Comment ID: 21386 Other EPA Comment Codes and Descriptions: 1435 1.2.1.3 EPA should develop guidance

Comment: EPA should provide guidance on acceptable monitoring techniques and frequency, provide for a consistent application of the monitoring requirements. Another

Response: EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Mike Moore Letter ID: 0532 Commenter Organization: North American Carbon Capture and Storage Association (NACCSA) Comment ID:

21367 Other EPA Comment Codes and Descriptions: 4000 2.4 Proposed Injection Well Operating Requirements (40 CFR 146.88)

Comment: The second area of concern is the proposed rule's treatment of CCS operations and monitoring. The proposed rule would require CCS wells to meet or exceed the operating standards of industrial and hazardous waste wells in many cases. NACSA believes that such treatment is not justified by the attributes of carbon dioxide. Also the director would have discretion without any guidance to require

Response: The Agency recognizes that while there are similarities between injection of wastes for disposal (Class I) and GS (Class VI), there are significant differences as well. Important unique considerations for GS include the buoyancy of CO2, its corrosivity when in contact with water, itslow viscosity (i.e., high mobility), and the very large injection volumes that are anticipated. There is also a degree of uncertainty regarding the behavior of large volumes of CO2 in the subsurface after injection.

Given these characteristics of anticipated GS projects, EPA believes that the monitoring requirements at §146.90 are justified to provide early warning of any unforeseen fluid movement or problems with the injection well that might endanger USDWs. EPA emphasizes that monitoring of injection activities will be an important component of every GS project. Monitoring associated with injection wells and the movement of the CO2 plume is necessary to verify that the injectate is confined in the target formations and does not endanger USDWs.

EPA believes the operating requirements for Class VI wells are necessary and provide multiple safeguards to ensure that well integrity, containment of fluids within the injection zone, and that the integrity of the confining zone is not compromised. Some of the operating requirements in the GS regulation (e.g., pressure limitations or annulus pressure requirements) are consistent with those for other injection well types, while other requirements (e.g., use of automatic shut-off systems or tracers at the Director's discretion) are tailored to directly address the potential for large volumes of CO2 to be injected, among other factors.

The requirements for GS projects are tailored to address the unique issues associated with GS including large injection volumes, the relative buoyancy of CO2, its corrosivity in the presence of water, the potential presence of impurities in captured CO2, and its mobility within subsurface geologic formations. EPA also believes these requirements are appropriate for Class VI wells given the potential geomechanical stresses in the wellbore, and the potential for movement of the CO2 in the event of a mechanical integrity loss.

Commenter Name: George Peridas Letter ID: 0534 Commenter Organization: Natural Resources Defense Council (NRDC) Comment ID: 21462 Other EPA Comment Codes and Descriptions: 3700 2.2.5 Comments on the requirement for an AoR and corrective action plan

Comment: The requirements for extensive monitoring is another example. This architectural design nature of having to continue to update the proposed plans, operational parameters, closure plans, etcetera as modeling data comes in and that is monitoring comes in. I think it is a very sound one which should be maintained

Response: EPA acknowledges the commenter's support of the AoR and corrective action plan, and retains the requirement in the final regulation §146.84(b). EPA believes that the iterative process by which monitoring and operational data are used to validate the original AoR calculation, along with the combined knowledge and ongoing dialogue between the owner or operator and the Director on the local geologic conditions will be critical in developing and implementing plans that protect USDWs from endangerment.

EPA agrees that monitoring data should be used to review model assumptions, verify computational model projections, and, when necessary, provide input for model refinements. As data are collected at an injection site, model parameters can be adjusted to match observations (i.e., for model calibration 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 believes that developing and following testing and monitoring plans is an important part of assuring that a GS project is operating properly and is crucial for the early detection of potential endangerment to USDWs. EPA also believes that periodic updates to the plan are appropriate. EPA clarifies that the final GS regulation includes a requirement that the AoR be reevaluated at least every 5 years, and it specifies at §146.90(j) that the operator revise the testing and monitoring plan to incorporate the results of the most recent AoR reevaluation and recent operational and monitoring

data.

Comment Code: 4610 2.6.1 Testing and monitoring plan requirement (seeking comment)



### Individual Comments

Commenter Name: Christine Reimer Letter ID: 0142 Commenter Organization: National Ground Water Association Comment ID: 22609 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: [In the text below, text in CAPS 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.

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 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.

Commenter Name: Brianne Metzger Letter ID: 0151 Commenter Organization: Spectra Energy Corp Comment ID: 21841

Comment: EPA is also proposing "periodic monitoring of the ground water quality and geochemical changes above the confining zone(s)." § 146.90(d). It is unclear how many wells would be required, and whether EPA expects all zones would be monitored. Given the potential size of the CO2 plume and the number of confining zones, this could potentially require many monitoring wells, which could be extremely expensive and unlikely to produce useful data. It is our strong recommendation that EPA minimize the amount of monitoring to the zone immediately above the confining zone, and only to the extent that the CO2 plume is within close proximity. For example, there may be regional conditions where ground water is separated by hundred or thousands of feet of confining strata, and where such monitoring is unnecessary. We would recommend that the Director be given discretion to limit or tailor ground water monitoring, as appropriate, based on regional and site specific factors.

Response: The GS rule stipulates that the monitoring frequency and spatial distribution ofmonitoring wells must be based on baseline geochemical data that were collected during the initial site characterization and the area of review evaluation, as described in §146.90(d)(2). The details of the geochemical monitoring will be described in the Director-approved testing and monitoring plan.

Regarding monitoring locations, section §146.90(d) requires periodic monitoring of the ground water quality and geochemical changes above the confining zone(s). Monitoring above the confining layer will provide an indication of upward movement of CO2 that might endanger a USDW. The exact number of formations to be tested will, however, be based on site-specific characteristics and vulnerabilities and described in the Director-approved 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 logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

EPA also acknowledges that complete coverage of the potential plume area or leakage in the subsurface is not possible through the use of monitoring wells. However, data from an appropriate number of monitoring wells sited based on site-specific information will provide direct information that is not otherwise obtainable and, along with other monitoring data, will support a broader understanding of fluid behavior at the site.

EPA acknowledges the commenters' concern about the cost of monitoring. However, EPA believes that monitoring is essential for protection of USDWs at GS sites. Although a significant cost in absolute terms, monitoring costs are expected to be a small fraction of site operating costs, according to EPA's cost analysis for the GS rulemaking (which is available in the docket).

Commenter Name: Bonnie Lovelace Letter ID: 0152 Commenter Organization: Montana Department of Environmental Quality (MDEQ) Comment ID:

22118 Other EPA Comment Codes and Descriptions: 3700 2.2.5 Comments on the requirement for an AoR and corrective action plan; 4710 2.7.1 Proposed submissions required for permit applications (seeking comment)

Comment: 17. EPA seeks comment on the merits of requiring plans for monitoring, area of review and post-injection site care as part of a permit application. MDEQ agrees that this is necessary and appropriate. A"cradle-to-grave" approach is wise in this instance and allows for updating the permit application materials as new technologies are forthcoming.

Response: EPA acknowledges the commenter’s support of the GS project plans. EPA believes that the requirement for the plans associated with GS projects will promote an ongoing dialogue between the owner or operator and the Director to ensure that USDWs are protected from endangerment. EPA is developing guidances for owners or operators describing recommended approaches to prepare the project plans. The guidances will be available on EPA's web site, at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.On the topic of monitoring and plan revision: EPA agrees with commenters on the importance of monitoring at GS sites and emphasizes that monitoring of injection activities will be an important component of every GS project. EPA also believes that periodic updates to the plans are appropriate. EPA clarifies that the final GS regulation includes a requirement that the AoR be reevaluated at least every 5 years, and it specifies at §146.90(j) that the operator revise the testing and monitoring plan to incorporate the results of the most recent AoR reevaluation and recent operational and monitoring

data.

EPA agrees that incorporating the plans into the permit rather than establishing specific requirements for corrective action, monitoring, injection well plugging, and post-injection site care in the regulation provide the appropriate flexibility to address the variety of site-specific conditions that may be encountered at GS sites. This approach is retained in the final rule. Please see the final rule and the discussion of the required GS project plans in the preamble for additional information.

EPA also believes that it is appropriate to require owners and operators to submit all plans, including the injection well plugging and post-injection site care and site closure plans, at the time of permit application. EPA believes that the Director needs a satisfactory level of assurance that the owner or operator has planned for these events before injection commences and that the owner or operator has ensured that appropriate financial resources are available to fund all required activities, as required at §146.85. The final rule retains requirements for submitting these plans with the permit application at §146.82(a). EPA believes that the requirement for this and other plans associated with GS projects will promote an ongoing dialogue between the owner or operator and the Director to ensure USDWs are protected from endangerment. In addition, these plans will support a demonstration that owners and operators have adequate financial resources to meet well plugging and post-injection site care and site closure requirements.

Commenter Name: Michael Mudd Letter ID: 0167 Commenter Organization: FutureGen Alliance (FGIA) Comment ID: 22473 Other EPA Comment Codes and Descriptions: 3700 2.2.5 Comments on the requirement for an AoR and corrective action plan

Comment: A-7 Record Keeping and Reporting Requirements III-A-7 We support the requirement for 1) a monitoring and testing plan 2) an AoR and Correction Action Plan and 3) a Post-Injection Site Care and Site Closure plan.

Response: EPA acknowledges the commenter’s support of the GS project plans. EPA believes that the requirement for the plans associated with GS projects will promote an ongoing dialogue between the owner or operator and the Director to ensure that USDWs are protected from endangerment. EPA is developing guidance for owners or operators describing recommended approaches to prepare the project plans. The guidance will be available on EPA's web site, at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

EPA agrees that developing, implementing, and periodically reviewing the required GS project plans is an important part of assuring that a GS project is operating properly and is crucial for the early detection of potential endangerment to USDWs. EPA also believes that periodic updates to the plans are appropriate. EPA clarifies that the final GS regulation includes a requirement that the AoR be reevaluated at least every 5 years, and it specifies at §146.90(j) that the operator revise the testing and monitoring plan to incorporate the results of the most recent AoR reevaluation and recent operational and monitoring data. EPA also agrees that the site-specific plans required for GS projects will maximize protection of USDWs from endangerment.Commenter Name: Kyle Isakower Letter ID: 0170 Commenter Organization: American Petroleum Institute Comment ID: 24196 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90(h)(1)

API Comments: (1) The testing and monitoring plan must be based on potential

vulnerabilitiesSITE-SPECIFIC GEOLOGIC FACTORS, MODELING, AND RISK-ASSESSMENT

within the area of review;

Rationale: Technical clarification

Response: Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment, EPA has made many revisions to the GS rule. See the final rule and preamble for further discussion on EPA's final approach. EPA anticipates that the testing and monitoring plan will address site-specific geologic factors, modeling, and risk-assessment. EPA is developing guidance on how best to develop the various required project plans, including the testing and monitoring plan. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Kyle Isakower Letter ID: 0170 Commenter Organization: American Petroleum Institute Comment ID: 24197 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90(i)

API Comments: (i) Any additional monitoring, as required by the Director, BASED ON SITE-SPECIFIC CONDITIONS AND RISK-BASED FACTORS, 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

Rationale: Technical clarification

Response: Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment, EPA has made many revisions to the GS rule. See the final rule and preamble for further discussion on EPA's final approach. EPA agrees that any additionalmonitoring requirements would be based on site-specific geologic factors, modeling, and riskassessment. EPA is developing guidance for directors that provides recommended approaches when exercising discretion to require additional monitoring. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Kyle Isakower Letter ID: 0170 Commenter Organization: American Petroleum Institute Comment ID: 24251 Other EPA Comment Codes and Descriptions: 4710 2.7.1 Proposed submissions required for permit applications (seeking comment)Comment: Rule Provisions: 146.90, 146.93(a), 146.94(a) EPA Preamble Question: 34. EPA is proposing that permit applications for GS sites include several plans not currently required under existing UIC regulations. These plans include a monitoring and testing plan, an AoR and corrective action plan, and a post-injection site care and site closure plan. EPA seeks comment on the merits of requiring plans for monitoring, AoR, and Post-injection site care as part of a permit application. EPA Notice 43517.

API Response: The development of such plans is a good idea because it negates prescriptive regulation of the process. API is concerned that every modification of a plan may trigger a major permit modification. Although actual monitoring of injection formation is most effective, there is still the unintended consequence of penetrating the confining zone to gain that data. The number of monitoring wells should not be established in advance. It is unclear how monitoring well construction, operation, and closure will be regulated since these are not actual injection wells.

Timing of development of plans should be linked to the actual activity being addressed (i.e. staged). It should not be necessary to prepare and submit a site closure plan or the post-closure monitoring plan at the start of the project, particularly considering that these activities will not occur for many years after the project starts.

Response: EPA agrees with commenters that developing and following testing and monitoring plans is an important part of assuring that a GS project is operating properly and is crucial for the early detection of potential endangerment to USDWs. EPA expects that the number of monitoring wells needed will be determined based on site-specific information. EPA also agrees that periodic updates to the plan are appropriate. EPA clarifies that the final GS regulation includes a requirement that the AoR be reevaluated at least every five years, and it specifies at §146.90(j) that the operator revise the testing and monitoring plan to incorporate the results of the most recent AoR reevaluation and recent operational and monitoring data.

EPA believes that monitoring using wells in the injection zone, e.g., for pressure monitoring as required at §146.90(g)(1), can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. The testing and monitoring plan must describe how the owner or operator plans to site and construct monitoring wells. 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.

EPA clarifies that every revision to the testing and monitoring plan will not necessarily trigger a major permit modification. The existing regulation at 40 CFR 144.39(a) identifies causes for modification of permits that would invoke the public notification procedures at 40 CFR 124. In the final rule, EPA added text to §144.39(a)(5) that permit modifications would be required if the Director determines that a modification is necessary based on an AoR reevaluation, amendments to any of the project plans, or a review of the testing and monitoring results.

In addition, 40 CFR Part 144.41 identifies causes for minor modifications of permits (which do not require following the procedures of Part 124). In the final rule, EPA added a subparagraph (h) to§144.41 that would include minor amendments (e.g., to clarify, correct, or update) to the testing and monitoring plan, plugging plan, post-injection site care and site closure plan, or emergency and remedial response plan for a GS well (i.e., amendments that are not included under 144.39(a)(5) and that do not require additional permit requirements).

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the docket for the final GS rule. EPA notes that closure of monitoring wells should be addressed in the post-injection site care and site closure plan.

EPA also believes that it is appropriate to require owners and operators to submit all plans, including the injection well plugging and post-injection site care and site closure plans, at the time of permit application. EPA believes that the Director needs a satisfactory level of assurance that the owner or operator has planned for these events before injection commences and that the owner or operator has ensured that appropriate financial resources are available to fund all required activities, as required at §146.85. The final rule retains requirements for submitting these plans with the permit application at §146.82(a).

Commenter Name: Thomas Curtis Letter ID: 0181 Commenter Organization: American Water Works Association (AWWA) Comment ID: 23697

Comment: be considered unless this monitoring is included. All of the monitoring requirements should be put forth in a monitoring plan, which should be reviewed and approved by the Director prior to the start of the project. This plan should be re-evaluated every five years during the permit review, and should be updated by the owner/operator based on any changes in operation or performance of the carbon dioxide plume.

Response: EPA agrees with commenters that developing and following testing and monitoring plans is an important part of assuring that a GS project is operating properly and is crucial for the early detection of potential endangerment to USDWs. EPA also agrees that periodic updates to the plan are appropriate. EPA clarifies that the final GS regulation includes a requirement that the AoR be reevaluated at least every 5 years, and it specifies at §146.90(j) that the operator revise the testing and monitoring plan to incorporate the results of the most recent AoR reevaluation and recent operational and monitoring data. EPA is developing guidance on how best to develop the various required project plans, including the testing and monitoring plan. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Thomas Curtis Letter ID: 0181 Commenter Organization: American Water Works Association (AWWA) Comment ID: 23700 Other EPA Comment Codes and Descriptions: 5200 2.8.2 Post injection site care (seeking comment) (40 CFR 146.93)

Comment: Category: Required Project Plans

EPA Request for Comment: EPA seeks comment on the merits of requiring plans for monitoring, AoR, and post-injection site care as part of a permit application.EPA Notice 43517.

AWWA Response: The requirement for the development of plans for monitoring, AoR, and post-injection site care is necessary and is a very important part of the permit process. The information will provide outside stakeholders with a much better idea of how the project will proceed and can help to assure them that the owner/operator has a clear vision for the life of the project. AWWA recommends that these plans be reviewed at the same time that the area of review is reevaluated. During this review, the plans should be updated based on any operational changes since the last project review period and submitted to the Director for approval. AWWA recommends that a review occur every year for the first ten years of the project, and then should be reviewed every five years until injection ceases.

Response: EPA agrees with the commenter. Owners or operators are required to submit an AoR and corrective action plan, a testing and monitoring plan, and a post-injection site care and site closure plan as part of the permit application, as specified in §146.82(a), to outline how these activities will be performed and how non-endangerment of USDWs will be demonstrated throughout the operational and post-injection site care periods. EPA is developing guidance on how best to develop the various required project plans, including the testing and monitoring plan. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

The GS rule also requires owners or operators to review and update the AoR and corrective action plan and the testing and monitoring plan throughout the life of the project, as described at §146.84(c) and §146.90(j). The rule requires at §146.90(j) that the operator revise the testing and monitoring plan to incorporate the results of the most recent AoR reevaluation and recent operational and monitoring data. 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. This review frequency is appropriate to ensure that reviews of the plans are conducted on a defined schedule or when there is a change in the AoR or significant change, while adding little burden if an AoR reevaluation confirms that the plans are appropriate as written. See the preamble sections on the plans for additional information.

EPA is not requiring formal periodic review and updates to the PISC and site closure plan throughout the injection phase as with the AoR reevaluation that is required at least every 5 years. EPA does not expect that changes to this plan would be implemented until injection operations cease. 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 to the 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 envisions that owners or operators would take into account similar considerations 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) identifying the basis for 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 corrective action plan, testing and monitoring plan, injection well plugging plan, post-injection site care and site closure plan, or emergency and remedial response plan is necessary.Commenter Name: Thomas Curtis Letter ID: 0181 Commenter Organization: American Water Works Association (AWWA) Comment ID: 23743 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Part 146.90 AWWA recommends revising this part to read:

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. The testing and monitoring plan must be reviewed and updated, as necessary, on the same schedule as the update to the

Area of Review.

Response: EPA agrees that periodic updates to the plan are appropriate. EPA clarifies that the final GS regulation includes a requirement that the AoR be reevaluated at least every 5 years, and it specifies at §146.90(j) that the operator revise the testing and monitoring plan to incorporate the results of the most recent AoR reevaluation and recent operational and monitoring data. Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment EPA has made many revisions to the GS rule. See the final rule and preamble for further discussion on EPA's final approach.

EPA agrees with commenters that developing and following testing and monitoring plans is an important part of assuring that a GS project is operating properly and is crucial for the early detection of potential endangerment to USDWs.

Commenter Name: Thomas Curtis Letter ID: 0181 Commenter Organization: American Water Works Association (AWWA) Comment ID: 23745 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Part 146.90(h)(1) AWWA recommends revising this part to read:

The testing and monitoring plan must be based on site-specific geologic factors, modeling, and a risk-assessment of potential vulnerabilities within the area of review;

Response: As described above, EPA agrees that periodic updates to the plan are appropriate, and the final GS regulation includes a requirement that the AoR be reevaluated at least every 5 years, and it specifies at §146.90(j) that the operator revise the testing and monitoring plan to incorporate the results of the most recent AoR reevaluation and recent operational and monitoring data. 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.

Commenter Name: Bradley J. Field Letter ID: 0186 Commenter Organization: New York State Dept. of Environmental Conservation Comment ID:Div. of Mineral Resources 25206

Comment: HH. In addition, EPA seeks comment regarding the use of a Director-approved monitoring plan for GS sites.

NYSDEC-DMN Response: The Director should be given flexibility to approve sitespecific monitoring plans.

Response: EPA agrees with commenters that developing and following testing and monitoring plans and giving Directors flexibility to approve the plans based on site-specific criteria are important parts of assuring that a GS project is operating properly and is crucial for the early detection of potential endangerment to USDWs.

The testing and monitoring plan is developed by the owner or operator in consultation with the Director and is designed to ensure that a detailed, Director-approved document describing how monitoring will be conducted during the lifetime of the project exists. The testing and monitoring plan must be approved by 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 logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Robert F. Van Voorhees Letter ID: 0190 Commenter Organization: Carbon Sequestration Council Comment ID: 24354

Comment: G. Testing and Monitoring Requirements

The preamble to the proposed rule indicates that "EPA considers CO2 plume and associated pressure front monitoring to be necessary for verification of model predictions." 73 Fed. Reg. at 43514. This proposal unnecessarily undermines confidence in the modeling demonstrations that can and should be relied upon to support determinations that injected CO2 will not endanger USDWs. Modeling provides a conservative assessment of the potential for movement of injected fluids in the subsurface, not a precise "prediction" of actual fate and transport that can or should be "verified" on the basis of elaborate, costly,

and uncertain efforts to observe the actual movement of fluids in the subsurface. As experience with hazardous waste injection shows, injection well operational data and the results of pressure fall-off tests provide ample data to validate the results of modeling. The additional monitoring requirements proposed in the GS context go beyond what is required for Class I hazardous waste injection wells; these requirements are excessive and unnecessary.

Response: EPA agrees that good site selection and modeling are crucial elements of a successful GS project, but disagrees that this is an effective substitute for rigorous site monitoring, including pressure monitoring. 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, provide inputs for AoR reevaluation modeling, evaluate predictions of plume movement, and target additional geochemical and surface monitoring needs. Knowledge ofthe 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 disagrees that plume and pressure front monitoring are not justified for Class VI wells. The Agency recognizes that while there are similarities between injection of wastes for disposal (Class I) and GS (Class VI), there are significant differences as well. Important unique considerations for GS include the buoyancy of CO2, its corrosivity when in contact with water, its low viscosity (i.e., high mobility), and the very large injection volumes that are anticipated. There is also a degree of uncertainty regarding the behavior of large volumes of CO2 in the subsurface after injection. Given these characteristics of anticipated GS projects, EPA believes that plume and pressure front monitoring at §146.90(g) are justified to provide early warning of any unforeseen fluid movement that might endanger USDWs.

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.

§146.90(g)(2) requires owners or operators to track the position of the CO2 plume using indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools), unless the Director determines based on site-specific geology that such methods are not appropriate. For example, geophysical methods are difficult to execute in areas that are structurally and topographically complex or where lithologies have limited contrast in density, porosity, permeability, and other physical properties. EPA clarifies that this determination will be made by the Director based on the site-specific geologic information submitted by the owner or operator with their permit application.

EPA disagrees that pressure fall-off tests are an appropriate substitute for monitoring pressure changes in the injection zone. Pressure fall-off tests provide information only in the vicinity of the injection well(s) and measure pressure conditions within the injection zone only. Direct monitoring of pressure changes in the injection zone can provide advance warning of movement of CO2 or brine that might ultimately endanger a USDW.

EPA acknowledges the commenters' concern about the cost of monitoring. However, EPA believes that monitoring is essential for protection of USDWs at GS sites. Although a significant cost in absolute terms, monitoring costs are expected to be a small fraction of site operating costs, according to EPA's cost analysis for the GS rulemaking (which is available in the docket).

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. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Robert F. Van Voorhees Letter ID: 0190 Commenter Organization: Carbon Sequestration Council Comment ID: 24478 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rulelanguage

Comment: Rule Provision: 146.90 [Introductory text]

Proposed CCS Group Recommendations: (A) BASED ON A SITE-SPECIFIC ASSESSMENT OF

THE POTENTIAL FOR FLUID MOVEMENT FROM THE INJECTION WELL OR INJECTION
ZONE, AND
ON THE POTENTIAL VALUE OF MONITORING WELLS TO DETECT SUCH MOVEMENT,

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 INCLUDE A DESCRIPTION OF HOW THE OWNER OR OPERATOR WILL

MEET THE REQUIREMENTS OF THIS SECTION;

Basis for CCS Group Comments: Drilling monitoring wells should be carefully considered since each well introduces a potential pathway for fluid movement. In addition the cost of adding multiple wells could create a barrier to CCS development, while providing limited information on actual movement of the CO2

stream.

Response: Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment, EPA has made many revisions to the GS rule. See the final rule and preamble for further discussion on EPA's final approach.

EPA anticipates that the testing and monitoring plan will address site-specific geologic factors, modeling, and risk-assessment. EPA is developing guidance on how best to develop the various required project plans, including the testing and monitoring plan. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm

EPA believes that monitoring using wells in the injection zone, e.g., for pressure monitoring as required at §146.90(g)(1), can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that properly constructed monitoring wells will be a safe way to obtain the data that is essential to ensure that the injected CO2 remains confined in the injection zone and that pressure changes are not causing movement of formation or other fluids. To mitigate the risk of fluid movement, EPA requires owners and operators to submit a testing and monitoring plan that describes how the owner or operator plans to site and construct monitoring wells. 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.

Commenter Name: Robert F. Van Voorhees Letter ID: 0190 Commenter Organization: Carbon Sequestration Council Comment ID: 24485 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90(i) & (j)Proposed CCS Group Recommendations: (i) 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

(j) A quality assurance and surveillance plan for all testing and monitoring requirements.

Basis for CCS Group Comments: These issues are addressed in subsection (c)(6) and (b)(5) respectively.

Response: Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment, EPA has made many revisions to the GS rule. See the final rule and preamble for further discussion on EPA's final approach.

Commenter Name: Robert F. Van Voorhees Letter ID: 0190 Commenter Organization: Carbon Sequestration Council Comment ID: 24543 Other EPA Comment Codes and Descriptions: 4710 2.7.1 Proposed submissions required for permit applications (seeking comment)

Comment: Rule Provisions or Federal Register Cite: 146.90, 146.93(a), 146.94(a) EPA Preamble Question: 34. EPA is proposing that permit applications for GS sites include several plans not currently required under existing UIC regulations. These plans include a monitoring and testing plan, an AoR and corrective action plan, and a post-injection site care and site closure plan. EPA seeks comment on the merits of requiring plans for monitoring, AoR, and post-injection site care as part of a permit application. EPA Notice 43517.

CSC Response: The development of such plans is a good idea because it negates prescriptive regulation of the process. CSC is concerned that every modification of a plan may trigger a major permit modification, although it does not appear that current regulations would require that result. If major permit modifications were required, EPA would lose the adaptability desired for responding to experience gained from GS projects.

It is unclear how the construction, operation, and closure of any monitor wells would be regulated, since these are not actual injection wells.

Timing of development of plans should be linked to the actual activity being addressed (i.e. staged). It should not be necessary to prepare and submit a site closure plan or the post-closure monitoring plan at the start of the project, particularly considering that these activities will not occur for many years after the project starts.

Response: EPA agrees with commenters that developing and following testing and monitoring plans is an important part of assuring that a GS project is operating properly and is crucial for the early detection of potential endangerment to USDWs. EPA expects that the number of monitoring wells needed will be determined based on site-specific information. EPA also agrees that periodic updates to the plan are appropriate. EPA clarifies that the final GS regulation includes a requirement that theAoR be reevaluated at least every five years, and it specifies at §146.90(j) that the operator revise the testing and monitoring plan to incorporate the results of the most recent AoR reevaluation and recent operational and monitoring data.

EPA clarifies that every revision to the testing and monitoring plan will not necessarily trigger a major permit modification. The existing regulation at 40 CFR 144.39(a) identifies causes for modification of permits that would invoke the public notification procedures at 40 CFR 124. In the final rule, EPA added text to §144.39(a)(5) that permit modifications would be required if the Director determines that a modification is necessary based on an AoR reevaluation, amendments to any of the project plans, or a review of the testing and monitoring results.

In addition, 40 CFR Part 144.41 identifies causes for minor modifications of permits (which do not require following the procedures of Part 124). In the final rule, EPA added a subparagraph (h) to §144.41 that would include minor amendments (e.g., to clarify, correct, or update) to the testing and monitoring plan, plugging plan, post-injection site care and site closure plan, or emergency and remedial response plan for a GS well (i.e., amendments that are not included under 144.39(a)(5) and that do not require additional permit requirements).

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the docket for the final GS rule. EPA notes that closure of monitoring wells should be addressed in the post-injection site care and site closure plan.

EPA also believes that it is appropriate to require owners and operators to submit all plans, including the injection well plugging and post-injection site care and site closure plans, at the time of permit application. EPA believes that the Director needs a satisfactory level of assurance that the owner or operator has planned for these events before injection commences and that the owner or operator has ensured that appropriate financial resources are available to fund all required activities, as required at §146.85. The final rule retains requirements for submitting these plans with the permit application at §146.82(a).

Commenter Name: Craig R. Walters Letter ID: 0200 Commenter Organization: Anadarko Petroleum Corporation Comment ID: 24604 Other EPA Comment Codes and Descriptions: 4710 2.7.1 Proposed submissions required for permit applications (seeking comment)

Comment: Rule Provisions: 146.90, 146.93(a), 146.94(a) EPA Rule Issue: 34. EPA is proposing that permit applications for GS sites include several plans not currently required under existing UIC regulations. These plans include a monitoring and testing plan, an AoR and corrective action plan, and a post-injection site care and site closure plan. EPA seeks comment on the merits of requiring plans for monitoring, AoR, and postinjection site care as part of a permit application. EPA Notice 43517.

Anadarko Petroleum Corporation (APC) Response: The development of plans is a good idea because it negates prescriptive regulation of the process. APC is concerned that every modification of a plan may trigger a major permitmodification. Although actual monitoring of injection formation is most effective, there is still the unintended consequence of penetrating the confining zone to gain that data. The number of monitoring wells should not be established in advance. It is unclear how monitoring well construction, operation, and closure will be regulated since these are not actual injection

wells.

Timing of development of plans should be linked to the actual activity being addressed. It should not be necessary to prepare and submit a site closure plan or the post-closure monitoring plan at the start of the project, particularly considering that these activities will not occur for many years after the project starts.

Response: EPA agrees with commenters that developing and following testing and monitoring plans is an important part of assuring that a GS project is operating properly and is crucial for the early detection of potential endangerment to USDWs. EPA expects that the number of monitoring wells needed will be determined based on site-specific information. EPA also agrees that periodic updates to the plan are appropriate. EPA clarifies that the final GS regulation includes a requirement that the AoR be reevaluated at least every five years, and it specifies at §146.90(j) that the operator revise the testing and monitoring plan to incorporate the results of the most recent AoR reevaluation and recent operational and monitoring data.

EPA believes that monitoring using wells in the injection zone, e.g., for pressure monitoring as required at §146.90(g)(1), can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. The testing and monitoring plan must describe how the owner or operator plans to site and construct monitoring wells. 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.

EPA clarifies that every revision to the testing and monitoring plan will not necessarily trigger a major permit modification. The existing regulation at 40 CFR 144.39(a) identifies causes for modification of permits that would invoke the public notification procedures at 40 CFR 124. In the final rule, EPA added text to §144.39(a)(5) that permit modifications would be required if the Director determines that a modification is necessary based on an AoR reevaluation, amendments to any of the project plans, or a review of the testing and monitoring results.

In addition, 40 CFR Part 144.41 identifies causes for minor modifications of permits (which do not require following the procedures of Part 124). In the final rule, EPA added a subparagraph (h) to §144.41 that would include minor amendments (e.g., to clarify, correct, or update) to the testing and monitoring plan, plugging plan, post-injection site care and site closure plan, or emergency and remedial response plan for a GS well (i.e., amendments that are not included under 144.39(a)(5) and that do not require additional permit requirements).

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in thedocket for the final GS rule. EPA notes that closure of monitoring wells should be addressed in the post-injection site care and site closure plan.

EPA also believes that it is appropriate to require owners and operators to submit all plans, including the injection well plugging and post-injection site care and site closure plans, at the time of permit application. EPA believes that the Director needs a satisfactory level of assurance that the owner or operator has planned for these events before injection commences and that the owner or operator has ensured that appropriate financial resources are available to fund all required activities, as required at §146.85. The final rule retains requirements for submitting these plans with the permit application at §146.82(a).

Commenter Name: Craig R. Walters Letter ID: 0200 Commenter Organization: Anadarko Petroleum Corporation Comment ID: 24700 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90 Anadarko Petroleum Corporation (APC) Comments: 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) BASED ON A SITE-SPECIFIC ASSESSMENT OF THE POTENTIAL FOR FLUID

MOVEMENT FROM
THE INJECTION WELL OR INJECTION ZONE, AND ON THE POTENTIAL VALUE OF

MONITORING
WELLS TO DETECT SUCH MOVEMENT, 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 INCLUDE A DESCRIPTION OF

HOW THE OWNER OR OPERATOR WILL MEET THE REQUIREMENTS OF THIS SECTION;

No rationale provided

Response: Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment, EPA has made many revisions to the GS rule. See the final rule and preamble for further discussion on EPA's final approach.

EPA anticipates that the testing and monitoring plan will address site-specific geologic factors, modeling, and risk-assessment. EPA is developing guidance on how best to develop the variousrequired project plans, including the testing and monitoring plan. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Craig R. Walters Letter ID: 0200 Commenter Organization: Anadarko Petroleum Corporation Comment ID: 24709 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90(i)

Anadarko Petroleum Corporation (APC) Comments: (i) 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

Rationale: See 146.90(c)(6)

Response: Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment, EPA has made many revisions to the GS rule. See the final rule and preamble for further discussion on EPA's final approach.

Commenter Name: Craig R. Walters Letter ID: 0200 Commenter Organization: Anadarko Petroleum Corporation Comment ID: 24710 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90(j)

Anadarko Petroleum Corporation (APC) Comments: (j) A quality assurance and surveillance plan for all testing and monitoring requirements.

Rationale: See 146.90(b)(5)

Response: Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment, EPA has made many revisions to the GS rule. See the final rule and preamble for further discussion on EPA's final approach.

Commenter Name: Chris M. Hobson Letter ID: 0201 Commenter Organization: Southern Company Comment ID: 22173

Comment: Finally, Southern Company urges EPA to focus operating and monitoring requirements on containment and preventive measures rather than to impose requirements that will not indicate C02 migration until potentially damaging migration has occurred. In particular, we encourage containment monitoring only, such as one or at most two above-zone monitoring wells that measure pressure to detect non-containment. ¡d. at 43514. The Final Rule should encourage Owners or Operators to invest monitoring resources towards detecting subsurface movement of CO2 or other substances at a point when action may be taken to address any potential problems and prevent further migration, whether below or to the

surface.Response: EPA disagrees that pressure monitoring above the confining zone is appropriate. Instead, the final GS regulation, at §146.90(g)(1), requires all GS project operators to monitor for pressure changes in the injection zone. EPA believes that pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume. Pressure monitoring within the injection zone is necessary because any such monitoring above the confining zone would not detect movement of the pressure front unless a breach of the confining zone occurs. EPA believes that monitoring using wells in the injection zone (i.e., that penetrate the confining zone) can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that the benefits of monitoring in the injection formation outweigh the manageable risk of those monitoring wells serving as conduits for fluid movement. EPA adds that owners or operators may consider performing additional pressure monitoring in wells that are above the confining zone (e.g., in the same wells used to perform ground water quality monitoring required at §146.90(d)) to provide additional verification that no pressure changes are occurring above the confining zone due to CO2 leakage.

In addition, EPA believes that shallow monitoring above the confining layer is an important part of a rigorous monitoring program. 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.

Commenter Name: John Corra Letter ID: 0205 Commenter Organization: Wyoming Department of Environmental Quality (DEQ) Comment ID:

22204 Other EPA Comment Codes and Descriptions: 4710 2.7.1 Proposed submissions required for permit applications (seeking comment)

Comment: 7. Permit application content:

a. We agree with the US EPA that permit applications for GS sites should include several plans not currently required under existing UIC regulations. These plans include a monitoring and testing plan, an AoR and corrective action plan, and a post-injection site care and site closure plan.

Response: EPA agrees with commenters that developing and following testing and monitoring plans is an important part of assuring that a GS project is operating properly and is crucial for the early detection of potential endangerment to USDWs. The final rule retains this requirement.

EPA agrees that incorporating the plans into the permit rather than establishing specific requirements for corrective action, monitoring, injection well plugging, and post-injection site care in the regulation provide the appropriate flexibility to address the variety of site-specific conditions that may be encountered at GS sites.

EPA believes that it is appropriate and necessary to require owners and operators to submit all plans, including the injection well plugging and post-injection site care and site closure plans, at the time of permit application for the Director to make a proper permit decision. EPA believes that the Director needs a satisfactory level of assurance that the owner or operator has planned for these events before injection commences and that the owner or operator has ensured that appropriate financial resourcesare available to fund all required activities, as required at §146.85. The final rule retains requirements for submitting these plans with the permit application at §146.82(a). EPA expects that the requirement for this and other plans associated with GS projects will promote an ongoing dialogue between the owner or operator and the Director to ensure USDWs are protected from endangerment. In addition, these plans will support a demonstration under §146.85 that owners and operators have adequate financial resources to meet well plugging and post-injection site care and site closure requirements. Please see the final rule and the discussion of the GS project plans for additional

information.

Commenter Name: Edward Steadman Letter ID: 0220 Commenter Organization: The Energy and Environmental Research Center at the University of North Dakota Comment ID:

21625 Other EPA Comment Codes and Descriptions: 4660 2.6.6 Geochemical monitoring

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

Text in this section implies that monitoring wells in the injection zone within the AoR are desirable, which could be interpreted by some as being required. The first comment with respect to this issue is that it is important to note that monitoring wells that penetrate the plume have potential to serve as a leakage pathway and, therefore, their use should be minimized. Secondly, one of the reasons given for the placing of monitoring wells in the AoR is that studying the interactions between brine and CO2 may allow for the determination of whether precipitation and/or dissolution of minerals is occurring. It is important to note that such interactions are currently not well understood and are the topic of great debate and controversy within the published literature. There is no consensus in the technical community as to how such data evaluated in the context of a single site, as site-specific permitting and monitoring must be, can be applied to ensuring the protection of USDWs at that site. While such data would surely be interesting and possibly useful from a scientific standpoint when taken in the context of many sites, it is not clear how it could be applied to prove or disprove that USDWs at a given location are being protected or are in danger of contamination. This requirement comes across as a regulatory-mandated means of gathering data for researchers, an activity that is outside the scope of USDW protection and should not be forcibly paid for by owners/operators of GS wells.

Response: EPA disagrees that the monitoring requirements in the GS rule do not provide sitespecific benefits for protection of USDWs or that monitoring is for the benefit of scientific research only. EPA believes that geochemical monitoring, when compared to baseline data, can provide direct evidence that USDWs may be endangered.

EPA believes that monitoring using wells in the injection zone (i.e., that penetrate the confining zone) can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that the benefits of monitoring in the injection formation outweigh the manageable risk of those monitoring wells serving as conduits for fluid movement. EPA adds that owners or operators may consider performing additional pressure monitoring in wells that are above the confining zone (e.g., in the same wells used to perform ground water quality monitoring required at §146.90(d)) to provide additional verification that nopressure changes are occurring above the confining zone due to CO2 leakage. Monitoring also identifies needed remedial actions, provides inputs for AoR reevaluation modeling, and targets additional geochemical and surface monitoring needs. Knowledge of the location of the CO2 plume and the associated pressure front will assure the public that GS projects are proceeding according to plan, provide sufficient information to the owner or operator and Director, or allow for appropriate actions to address any indication that USDWs may be endangered.

EPA acknowledges that, at certain sites, there may be a need for more or different monitoring schemes (which may include monitoring in the confining zone), and adds that it is important to balance the need for adequate monitoring that ensures USDW protection from endangerment against too many artificial penetrations which could serve as conduits for fluid migration. Site-specific testing and monitoring plans must describe the proposed monitoring regime, which must be approved by the Director.

Commenter Name: Tiffany Rau Letter ID: 0224 Commenter Organization: Hydrogen Energy International Comment ID: 21672

Comment: - A monitoring plan that measures the performance of the highest leakage risk parameters and validates or updates predictive performance models.

The appropriate implementation of these key areas will ensure the safe and secure operation of a geologic sequestration project.

Response: EPA agrees with commenters that developing and following testing and monitoring plans is an important part of assuring that a GS project is operating properly and is crucial for the early detection of potential endangerment to USDWs. The final rule retains this requirement.

Commenter Name: Tiffany Rau Letter ID: 0224 Commenter Organization: Hydrogen Energy International Comment ID: 21674

Comment: (2) Flexibility in Design of Monitoring Programs and Selection of Technologies

HEI agrees with EPA that monitoring is important. For example, once a site has been selected, appropriate baseline surveys should be conducted and analyzed prior to commencing operations. During operations and at site closure, appropriate monitoring technologies should be applied to confirm the integrity and effectiveness of the storage site. However, there is a common misperception that, in order to achieve secure storage, a large amount of monitoring is required. The United Nations states that "the proportion of CO2 retained by appropriately selected and managed sites is likely to exceed 99% over 1,000 years." Thus, the key to secure storage is the appropriate selection and management of the site and these activities should be the focus of any regulatory framework for CO2 geo-sequestration. If done properly, a selected site will be secure with a monitoring program that is designed and focused on the particular storage site.

Response: EPA agrees that good site selection, modeling, and management are crucial elements of a successful GS project, but disagrees that this is an effective substitute for rigorous site monitoring. EPA also agrees with commenters and believes that flexibility is important in developing and implementing a monitoring plan that is appropriately tailored for a specific GS site. The purpose ofthe requirement at §146.90 to develop site-specific testing and monitoring plans is to ensure that the monitoring performed at a site is appropriate for site operational conditions and the geologic setting. EPA believes that this is the best approach for addressing potential risks at GS sites. These flexible provisions in the monitoring requirements for Class VI wells enable the owner or operator to tailor monitoring programs to the specific needs of each project in consultation with 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 logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Tiffany Rau Letter ID: 0224 Commenter Organization: Hydrogen Energy International Comment ID: 21679

Comment: Furthermore, in various parts of the Proposed Rule, EPA has prescribed particular monitoring technologies. Mandating any specific technology(ies) would have the adverse effect of (1) promoting particular technologies to the exclusion of other developed - and to be developed - technology(ies), and (2) substantially increasing costs without necessarily contributing to the protection of USDWs. This would hinder the development and deployment of CCS at commercial scale. Moreover, it would discourage the development of other technologies. HEI therefore strongly discourages EPA from promulgating regulations that mandate the use of any specific monitoring technology.

Response: EPA agrees that prescribing specific technologies to be used in all cases for GS would not be appropriate given the variability in sites, and believes that the rule provides flexibility to owners or operators to develop site-specific testing and monitoring plans that employ appropriate technologies provided they meet the requirements at §146.90. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the

docket for the for the final GS rule.

Commenter Name: Brian Williams Letter ID: 0225 Commenter Organization: BP Alternative Energy North America, Inc. (BP) Comment ID: 21717

Comment: - A monitoring plan that measures the performance of the highest leakage risk parameters and validates or updates predictive performance models.The appropriate implementation of these key areas will ensure the safe and secure operation of a geologic sequestration project.

Response: EPA agrees with commenters that developing and following testing and monitoring plans is an important part of assuring that a GS project is operating properly and is crucial for the early detection of potential endangerment to USDWs. The final rule retains this requirement.

Commenter Name: Brian Williams Letter ID: 0225 Commenter Organization: BP Alternative Energy North America, Inc. (BP) Comment ID: 21719

Comment: (2) Flexibility in Design of Monitoring Programs and Selection of Technologies

BP agrees with EPA that monitoring is important. For example, once a site has been selected, appropriate baseline surveys should be conducted and analyzed prior to commencing operations. During operations and at site closure, appropriate monitoring technologies should be applied to confirm the integrity and effectiveness of the storage site. However, there is a common misperception that, in order to achieve secure storage, a large amount of monitoring is required. The United Nations states that "the proportion of CO2 retained by appropriately selected and managed sites is likely to exceed 99% over 1,000 years." Thus, the key to secure storage is the appropriate selection and management of the site and these activities should be the focus of any regulatory framework for CO2 geo-sequestration. If done properly, a selected site will be secure with a monitoring program that is designed and focused on the particular storage site.

Response: EPA agrees that good site selection, modeling, and management are crucial elements of a successful GS project, but disagrees that this is an effective substitute for rigorous site monitoring. EPA also agrees with commenters and believes that flexibility is important in developing and implementing a monitoring plan that is appropriately tailored for a specific GS site. The purpose of the requirement at §146.90 to develop site-specific testing and monitoring plans is to ensure that the monitoring performed at a site is appropriate for site operational conditions and the geologic setting. EPA believes that this is the best approach for addressing potential risks at GS sites. These flexible provisions in the monitoring requirements for Class VI wells enable the owner or operator to tailor monitoring programs to the specific needs of each project in consultation with 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 logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Brian Williams Letter ID: 0225 Commenter Organization: BP Alternative Energy North America, Inc. (BP) Comment ID: 21729 Other EPA Comment Codes and Descriptions: 1250 1.1.1.4 Flexibility is needed (performancebased standards)Comment: Furthermore, in various parts of the Proposed Rule, EPA has prescribed particular monitoring technologies. Mandating any specific technology(ies) would have the adverse effect of (1) promoting particular technologies to the exclusion of other developed - and to be developed - technology(ies), and (2) substantially increasing costs without necessarily contributing to the protection of USDWs. This would hinder the development and deployment of CCS at commercial scale. Moreover, it would discourage the development of other technologies. BP therefore strongly discourages EPA from promulgating regulations that mandate the use of any specific monitoring technology.

Response: EPA agrees that prescribing specific technologies to be used in all cases for GS would not be appropriate given the variability in sites, and believes that the rule provides flexibility to owners or operators to develop site-specific testing and monitoring plans that employ appropriate technologies provided they meet the requirements at §146.90. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the

docket for the for the final GS rule.

Commenter Name: Andrew Duguid Letter ID: 0226 Commenter Organization: Schlumberger Carbon Services Comment ID: 24004

Comment: 3. In the preamble of the draft u-tube technology is specifically called out as a technology available for high pressure fluid sampling. Schlumberger wants point out to the epa there are other techniques for high pressure fluid sampling the use of wireline conveyed sample bottles. We want to ensure that no one particular technology is adopted or required for high pressure sampling. The selection of a single sampling technique (although not in the rule language) could cause the best available technology to be overlooked now or in the future. We propose that epa either delete the reference to the u-tube samples of clarify that it is not the only solution available for taking high pressure samples

Response: EPA recognizes that the collection of representative ground water samples from depth poses challenges and that special methods, such as U-tubes, will be needed to preserve the integrity of such samples. However, EPA is not requiring the use of U-tubes for sampling under the final rule. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Directorfor specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Andrew Duguid Letter ID: 0226 Commenter Organization: Schlumberger Carbon Services Comment ID: 24065 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Proposed Rule: (1) The testing and monitoring plan must be based on potential vulnerabilities within the area of review;

Schlumberger Suggested Revision: (1) The testing and monitoring plan must be based on site-specific geologic factors, modeling, and risk-assessment within the area of review;

Schlumberger Rationale: -

Response: EPA anticipates that the testing and monitoring plan will address site-specific geologic factors, modeling, and risk-assessment. EPA is developing guidance on how best to develop the various required project plans, including the testing and monitoring plan. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

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.

Commenter Name: Ben Yamagata Letter ID: 0227 Commenter Organization: Coal Utilization Research Council Comment ID: 21789 Other EPA Comment Codes and Descriptions: 1250 1.1.1.4 Flexibility is needed (performancebased standards)

Comment: Plume and Pressure Front Monitoring

EPA would require each Class VI well permit application to contain a monitoring plan to verify that a GS well is operating as intended and not endangering USDW. EPA should be aware that certain monitoring technology is currently under development and not available as a tool in the near term to meet the proposed EPA requirements. Further, the usefulness of available technology is a functionof site-specific characterizations. The EPA should not impose a one-size-fitsall approach. CURC recommends that the EPA permit well owners and operators to propose the use of available technology to meet the proposed requirements and then to amend their tailored monitoring plans as technology evolves.

Response: EPA agrees that prescribing specific technologies to be used in all cases for GS would not be appropriate given the variability in sites, and believes that the rule provides flexibility to owners or operators to develop site-specific testing and monitoring plans that employ appropriate technologies provided they meet the requirements at §146.90. 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-operationalgeophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the

docket for the for the final GS rule.

Commenter Name: Neeraj Gupta Letter ID: 0229 Commenter Organization: Battelle Energy Technology (BET) Comment ID: 21850 Other EPA Comment Codes and Descriptions: 4600 2.6 Proposed Plume and Pressure Front Monitoring Requirements (40 CFR 146.90)

Comment: Page 102, Pressure monitoring in overlying zones- Implicit in this monitoring requirement is that network of deep monitoring wells will be required with the injection well. We know of no other method to accurately measure deep pressures. As such, this requirement will be costly to implement and should be spelled out clearly for planning purposes. It may also be pertinent to make this optional depending on identified risks.

Response: EPA acknowledges the commenters' concern about the cost of monitoring. However, EPA believes that monitoring is essential for protection of USDWs at GS sites. Although a significant cost in absolute terms, monitoring costs are expected to be a small fraction of site operating costs, according to EPA's cost analysis for the GS rulemaking (which is available in the docket).

EPA believes that monitoring using wells in the injection zone, e.g., for pressure monitoring as required at §146.90(g)(1), can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that properly constructed monitoring wells will be a safe way to obtain the data that is essential to ensure that the injected CO2 remains confined in the injection zone and that pressure changes are not causing movement of formation or other fluids. To mitigate the risk of fluid movement, EPA requires owners and operators to submit a testing and monitoring plan that describes how the owner or operator plans to site and construct monitoring wells. 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.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, and tracking the CO2 plume and pressure front. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the

docket for the final GS rule.Commenter Name: Mark Bohrer Letter ID: 0241 Commenter Organization: North Dakota Industrial Commission Comment ID: 23256 Other EPA Comment Codes and Descriptions: 4710 2.7.1 Proposed submissions required for permit applications (seeking comment)

Comment: 34. EPA is proposing that permit applications for GS sites include several plans not currently required under existing UIC regulations. These plans include amonitoring and testing plan, an AoR and corrective action plan, and a postinjection site care and site closure plan. EPA seeks comment on the merits of requiring plans for monitoring, AoR, and post-injection site care as part of a permit application. EPA Notice 43517.

Allowing for different plans would be much more effective than prescriptive regulations; however, a plan modification should not be considered a major permit modification. Caution needs to be taken when monitoring the injection formation due to the artificial penetration of the confining zone to gain data. The number of monitoring wells should be decided on a case-by case basis. It is unclear how monitoring wells will be regulated since they are not injection wells. The timing of plan submittal should be linked to the activity being

Response: EPA agrees with commenters that developing and following testing and monitoring plans is an important part of assuring that a GS project is operating properly and is crucial for the early detection of potential endangerment to USDWs.

EPA expects that the number of monitoring wells needed will be determined based on site-specific information as the testing and monitoring plan is developed. EPA believes that monitoring using wells in the injection zone (i.e., that penetrate the confining zone) can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that the benefits of monitoring in the injection formation outweigh the manageable risk of those monitoring wells serving as conduits for fluid movement.

EPA also agrees that periodic updates to the plan are appropriate. EPA clarifies that the final GS regulation includes a requirement that the AoR be reevaluated at least every 5 years, and it specifies at §146.90(j) that the operator revise the testing and monitoring plan to incorporate the results of the most recent AoR reevaluation and recent operational and monitoring data. EPA clarifies that every revision to the testing and monitoring plan will not necessarily trigger a major permit modification. The existing regulation at 40 CFR 144.39(a) identifies causes for modification of permits that would invoke the public notification procedures at 40 CFR 124, including: alterations or additions to the facility; availability of additional information; new regulations; and compliance schedule modifications. In the final rule, EPA added text to §144.39(a)(5) that permit modifications would be required if the Director determines that a modification is necessary based on an AoR reevaluation, amendments to any of the project plans, or a review of the testing and monitoring results.

In addition, 40 CFR Part 144.41 identifies causes for minor modifications of permits (which do not require following the procedures of Part 124). These include correction of typographical errors; more frequent monitoring or reporting; changes in an interim compliance date; changes in ownership or control of a facility; changes in the quantities or types of fluids injected which are within the capacity of the facility; changes in construction requirements; or amendments to a plugging and abandonment plan. In the final rule, EPA added a subparagraph (h) to §144.41 that would include minor amendments (e.g., to clarify, correct, or update) the testing and monitoring plan, pluggingplan, post-injection site care and site closure plan, or emergency and remedial response plan for a GS well (i.e., amendments that are not included under 144.39(a)(5) and that do not require additional permit requirements).

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the docket for the final GS rule. EPA notes that closure of monitoring wells should be addressed in the post-injection site care and site closure plan.

Commenter Name: Kurt Waltzer Letter ID: 0250 Commenter Organization: Clean Air Task Force Comment ID: 22310

Comment: Perhaps inadvertently, the proposed rule does not explicitly require updating of several of the required plans. In most but not all cases, there is a rather ambiguous requirement to "maintain" a given plan. Explicit requirements to make updates as warranted appear to be missing from provisions relating to:

• the testing and monitoring plan required by §146.90 (the ambiguous word "maintain" is used and there appears to be no requirement that estimated plugging costs be kept current);

Response: EPA agrees that developing and following testing and monitoring plans is an important part of assuring that a GS project is operating properly and is crucial for the early detection of potential endangerment to USDWs. EPA also agrees that periodic updates to the plan are appropriate. EPA clarifies that the final GS regulation includes a requirement that the AoR be reevaluated at least every 5 years, and it specifies at §146.90(j) that the operator revise the testing and monitoring plan to incorporate the results of the most recent AoR reevaluation and recent operational and monitoring

data.

Commenter Name: Kurt Waltzer Letter ID: 0250 Commenter Organization: Clean Air Task Force Comment ID: 22317

Comment: Monitoring

In §146.90 the proposed rule outlines requirements for testing and monitoring. We strongly support the inclusion of such provisions. Monitoring is central to verifying and adapting the operational parameters of a GS project, while the concept of GS cannot be simply based on the premise of confinement without verification. We also support the provisions calling for a testing and monitoring plan, although we have suggested above that the requirements for updating this plan be strengthened. The collection of baseline data and information prior to the commencement of operations is also necessary for anumber of monitoring techniques to produce useful results, and should be preserved.

Response: EPA agrees with commenters that developing and following testing and monitoring plans is an important part of assuring that a GS project is operating properly and is crucial for the early detection of potential endangerment to USDWs. EPA also agrees that periodic updates to the plan are appropriate. EPA clarifies that the final GS regulation includes a requirement that the AoR be reevaluated at least every 5 years, and it specifies at §146.90(j) that the operator revise the testing and monitoring plan to incorporate the results of the most recent AoR reevaluation and recent operational and monitoring data. EPA adds that the final rule, at §146.82, retains the data collection requirements that are part of the permit application.

Commenter Name: Kurt Waltzer Letter ID: 0250 Commenter Organization: Clean Air Task Force Comment ID: 25257 Other EPA Comment Codes and Descriptions: 3500 2.2.3 Area of Review Reevaluation (seeking comment)

Comment: Perhaps inadvertently, the proposed rule does not explicitly require updating of several of the required plans. In most but not all cases, there is a rather ambiguous requirement to "maintain" a given plan. Explicit requirements to make updates as warranted appear to be missing from provisions relating to:

• the testing and monitoring plan required by §146.90 (the ambiguous word "maintain" is used and there appears to be no requirement that estimated plugging costs be kept current);

Response: The final rule includes provisions that owners or operators review and 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, as specified in §146.84(c), §146.90(j), and §146.94(d). 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.

Commenter Name: Michel Paque Letter ID: 0259 Commenter Organization: Ground Water Protection Council Comment ID: 24922 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90

EPA Proposal: 10. 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:GWPC Recommendations: Support the proposed EPA language.

Response: Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment EPA has made many revisions to the GS rule. See the final rule and preamble for further discussion on EPA's final approach.

EPA agrees with commenters that developing and following testing and monitoring plans is an important part of assuring that a GS project is operating properly and is crucial for the early detection of potential endangerment to USDWs.

Commenter Name: Michel Paque Letter ID: 0259 Commenter Organization: Ground Water Protection Council Comment ID: 24930 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90(h)

EPA Proposal: (1) The testing and monitoring plan must be based on potential vulnerabilities within the area of review;

(2) The monitoring frequency and spatial distribution of surface air monitoring and/or 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 and/or compliance with standards under 40 CFR 144.12;

GWPC Recommendations: (1) The testing and monitoring plan must be based on sitespecific geologic factors, modeling, and risk-assessment within the area of review;

(2) Agree with EPA language

Rationale: The GWPC feels that the term "potential vulnerabilities" is too nebulous. We suggest replacing this term with the term "site-specific geologic factors, modeling, and risk-assessment."

Response: Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment EPA has made many revisions to the GS rule. See the final rule and preamble for further discussion on EPA's final approach.

EPA anticipates that the testing and monitoring plan will address site-specific geologic factors, modeling, and risk-assessment. EPA is developing guidance on how best to develop the various required project plans, including the testing and monitoring plan. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Michel Paque Letter ID: 0259 Commenter Organization: Ground Water Protection Council Comment ID: 24931 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rulelanguage

Comment: Rule Provision: 146.90(i)

EPA Proposal: (i) 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

(j) A quality assurance and surveillance plan for all testing and monitoring requirements.

GWPC Recommendations: Support the proposed EPA language.

Rationale: Agree with EPA’s rationale.

Response: EPA acknowledges the comment. The final rule retains these provisions as proposed.

Letter ID: 0263 Commenter Organization: Interstate Oil & Gas Compact Commission Comment ID: 22820

Comment: III A. 6 Proposed Plume andPressure Front Monitoring Requirements

JJ. In addition, EPA seeks comment regarding the use of a Director-approved monitoring plan for GS sites.

IOGCC Response: The Director should be given flexibility to approve site specific monitoring plans as proposed in the IOGCC model regulations.

Response: EPA agrees with commenters that developing and following testing and monitoring plans and giving Directors flexibility to approve the plans based on site-specific criteria are important parts of assuring that a GS project is operating properly and is crucial for the early detection of potential endangerment to USDWs.

The testing and monitoring plan is developed by the owner or operator in consultation with the Director and is designed to ensure that a detailed, Director-approved document describing how monitoring will be conducted during the lifetime of the project exists. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologiesand recommended approaches for implementing a testing and monitoring plan, including preoperational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Scott Anderson Letter ID: 0510 Commenter Organization: Environmental Defense Fund Comment ID: 21226

Comment: We also think that further steps are needed in order to assure that monitoring includes all aspects of projects. But right now the rule in several places doesrequire monitoring to be used to drive adjustments in the project, but we feel strongly that we need to go further, and we also think that this was contemplated by the IPCC when they said that in a properly selected and managed site that 99 percent of this to be expected to be retained over a thousand

years.

Monitoring needs to be used in a reiterative process to improve site characterization, the definition, and the adjustment as necessary of the AoR. Adjustment in the risk analysis, adjustment in models, needs to be used to inform and create new input into the models. It needs to help determine, and revise, and improve the monitoring program itself. It needs to inform financial assurance requirements. And it needs to inform closure requirements. In short, monitoring is essential to an adaptive well-managed sequestration site. And then the rule that makes a good start at requiring that and needs to finish the job.

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

EPA agrees with commenters that developing and following testing and monitoring plans is an important part of assuring that a GS project is operating properly and is crucial for the early detection of potential endangerment to USDWs. EPA also agrees that periodic updates to the plan are appropriate. EPA clarifies that the final GS regulation includes a requirement that the AoR be reevaluated at least every 5 years, and it specifies at §146.90(j) that the operator revise the testing and monitoring plan to incorporate the results of the most recent AoR reevaluation and recent operational and monitoring data.

EPA agrees that monitoring data should be used to review model assumptions, verify computational model projections, and, when necessary, provide input for model refinements. As data are collected at an injection site, model parameters can be adjusted to match observations (i.e., for model calibration 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 that monitoring is a key element of ensuring that USDWs are protected from endangerment. Tracking the plume and the position of the pressure front during injection operations and the post-injection site care period will provide important data for determining that the injectate is confined within the target formation, as well as for evaluating any risks within the AoR and ensuring protection of USDWs 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 information 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 geochemistry that may indicate fluid movement.

Commenter Name: Cynthia Lane Letter ID: 0528 Commenter Organization: American Water Works Association (AWWA) Comment ID: 21385Comment: We need appropriate subsurface monitoring technology identified and developed to prevent or respond to potential contamination of USDW's, by these and other chemical compounds.

Response: EPA does not believe that prescribing specific technologies to be used in all cases for GS would be appropriate given the variability in sites. Rather EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the

docket for the final GS rule.

Comment Code: 4620 2.6.2 Injectate monitoring



### Individual Comments

Commenter Name: Herbert Skolnick, Ph.D. Letter ID: 0110 Commenter Organization: Group Against Smog and Pollution, Inc. (GASP) Comment ID: 22040

Comment: Conclusion

Regardless of what specific form the CO2 sequestration program ultimately takes, at a minimum, the program must ensure that:

1. the chemistry of the CO2 and its contaminants is ascertained prior to injection;

Response: EPA agrees that monitoring of the injectate prior to and during injection is important to allow for comparison of baseline data and operational-phase monitoring results to provide warning of potential USDW endangerment. For this reason owners or operators must perform an analysis of the chemical and physical characteristics of the CO2 stream, as required at §146.82 (a)(7)(iv). In addition, Section §146.90(a) requires owners or operators to perform analysis of the CO2 stream during injection operations with sufficient frequency to yield data representative of its chemical and physical characteristics.

Commenter Name: Herbert Skolnick, Ph.D. Letter ID: 0110 Commenter Organization: Group Against Smog and Pollution, Inc. (GASP) Comment ID: 22043 Other EPA Comment Codes and Descriptions: 4630 2.6.3 Corrosion monitoring; 4660 2.6.6 Geochemical monitoring

Comment: Regardless of what specific form the CO2 sequestration program ultimately takes, at a minimum, the program must ensure that:2. the sequestered material’s behavior in the chemical, geological, and hydrological environment where it is stored is anticipated and carefully monitored; and

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

Commenter Name: Dwight Lockwood, PE, QEP Letter ID: 0141 Commenter Organization: Global Energy, Inc. Comment ID: 23104 Other EPA Comment Codes and Descriptions: 1630 1.3.3 RCRA/hazardous waste issues (seeking comment); 1640 1.3.4 CERCLA issues (seeking comment)

Comment: CO2 as Hazardous Waste (RCRA or CERCLA)

1.We support the EPA view that injectate should be characterized relative to 40

CFR Part 261. We further believe that the stream can be treated to remove undesired contaminants to the levels that thresholds are not triggered.

2.Characterization and certification in the permit application should be a sufficient basis for assurance here. Periodic sampling and analysis on some reasonable frequency during injection is acceptable. On the other hand, we do not believe that this measurement and reporting needs to be more than perhaps quarterly, as the adverse impact of exceedances for relatively short periods is not likely to be geologically significant very fast. Corrective action to mitigate the effects of an incorrect injection fluid (but not to remedy an injection already accomplished) needs to be pragmatic and not onerous.

3.As with Class I well liability exemptions, Class VI wells, once their injectate is characterized and approved (as not triggering CERCLA or RCRA), and regular sampling of the stream for quality control is implemented then a similar exemption is warranted.

Response: EPA agrees that monitoring of the injectate prior to and during injection is important to allow for comparison of baseline data and operational-phase monitoring results to provide warning of potential USDW endangerment. For this reason owners or operators must perform an analysis of the chemical and physical characteristics of the CO2 stream, as required at §146.82 (a)(7)(iv). In addition, Section §146.90(a) requires owners or operators to perform analysis of the CO2 stream during injection operations with sufficient frequency to yield data representative of its chemical and physical characteristics.

The necessary frequency of injectate analysis will be project-specific and will depend upon the CO2 source and the likelihood of variability in injectate composition. For example, a CO2-capture process from a coal-fired power plant with a consistent coal source and operating parameters islikely to produce a CO2 stream with a fairly consistent composition. A process with a changing composition of coal may have more variability in the purity of the CO2 that is captured. In such a setting, more frequent sampling may be appropriate. The details of the sampling should be describedin the testing and monitoring plan, which will be approved by the Director based on a review of sitespecific information, including information on the source and characteristics of the injectate.

EPA clarifies that, following an initial characterization of the injectate, EPA expects that the permit would stipulate the acceptable composition of the injectate (e.g., as CO2 plus an acceptable range of expected impurities). Any divergence from this would be a permit violation.

EPA notes however, that the final GS rule, which adds new regulations for Class VI wells under the Safe Drinking Water Act (SDWA), is not making any changes to the RCRA regulations. Accordingly, the CO2 stream characterization requirements under the GS rule would not substitute for the obligation of a generator of RCRA solid waste to characterize its waste in accordance with EPA’s RCRA regulations. Injection of a RCRA hazardous waste may only occur in a Class I hazardous waste injection well.

EPA notes that CO2 itself is not listed as a hazardous substance under CERCLA, although the CO2 stream may contain a listed hazardous substance (such as mercury) or may mobilize substances in the subsurface that could react with ground water to produce listed hazardous substances (such as sulfuric acid). Whether such substances may result in CERCLA liability from a sequestration facility depends entirely on the composition of the specific CO2 stream and the environmental media in which it is stored (e.g., soil or ground water). CERCLA exempts from liability, under CERCLA section 107, 42 U.S.C. 9607, certain “federally permitted releases” (FPR) as defined in CERCLA, 42 U.S.C. 9601(10). Class VI permits will need to be carefully structured to ensure that they prevent potential releases from the well which are outside the scope of the Class VI permit.

The commenter’s reference to a Class I liability exemption is unclear and not legally correct. 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.

Commenter Name: Ronald Evans Letter ID: 0215 Commenter Organization: Denbury Resources, Inc. (DRI) Comment ID: 24308 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: G. § 146.90 Testing and monitoring requirements.

1. EPA Proposed §146.90(b) Installation and use, except during well workovers 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;

Consistent with our comment regarding proposed § 146.88(e) in Section 5 above, Denbury is unaware of a methodology to monitor the actual volume of annular fluid in the annulus on a continuous basis, and thus seeks agency clarificationon this portion of the proposed rule.

Response: EPA believes that knowing annulus fluid volume, as required at §146.88(e), is a necessary component of monitoring well mechanical integrity, but believes that monitoring the annulus fluid volume added is sufficient to meet the intent of continuous monitoring of the pressure on the annulus. The final GS rule at §146.90 (b) requires that owners or operators use 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 added.

Commenter Name: Darrick Eugene Letter ID: 0223 Commenter Organization: Texas Carbon Capture and Storage Association Comment ID: 23988

Comment: 8. § 146.90 Testing and monitoring requirements.

EPA Proposed §146.90(b) Installation and use, except during well workovers 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;

Consistent with our comment regarding proposed § 146.88(e) in Section 5 above, TxCCSA is unaware of a methodology to monitor the actual volume of annular fluid in the annulus on a continuous basis, and thus seeks agency clarification on this portion of the proposed rule.

Response: EPA believes that knowing annulus fluid volume, as required at §146.88(e), is a necessary component of monitoring well mechanical integrity, but believes that monitoring the annulus fluid volume added is sufficient to meet the intent of continuous monitoring of the pressure on the annulus. The final GS rule at §146.90 (b)) requires that owners or operators use 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 added.

Commenter Name: Mark Bohrer Letter ID: 0241 Commenter Organization: North Dakota Industrial Commission Comment ID: 23301

Comment: 146.90(b) Is continuous recording of annular fluid volume possible or practical?

Response: EPA believes that knowing annulus fluid volume, as required at §146.88(e), is a necessary component of monitoring well mechanical integrity, but believes that monitoring the annulus fluid volume added is sufficient to meet the intent of continuous monitoring of the pressure on the annulus. The final GS rule at §146.90 (b)) requires that owners or operators use 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 added.

Comment Code: 4630 2.6.3 Corrosion monitoring



### Individual CommentsCommenter Name: Michael H. Cochran Letter ID:

0108 Commenter Organization: Bureau of Water, Division of Environment, Kansas Department of Health & Environment (KDHE) Comment

ID: 21980 Other EPA Comment Codes and Descriptions: 4543 2.5.2.1 MIT procedures and methods for GS (seeking comment)

Comment: 146.89 (c) (3): The casing inspection log (CIL) does not detect fluid movement behind the casing and should not be listed here. This is an excellent log for detecting corrosion problems and the degree of corrosion casing inspection logs conducted periodically is a good method for monitoring corrosion in the well.

Response: EPA agrees that the casing inspection log is not an appropriate test to detect fluid movement behind the casing, but clarifies that it is appropriate for determining the presence or absence of corrosion of the long-string casing, and is required if the Director determines that it is necessary based on site-specific information. EPA has revised the final GS rule to require that the frequency of the casing inspection log be specified in the approved testing and monitoring plan. See §146.89(d). For additional information, please see the discussion of MITs in the final rule preamble.

Commenter Name: Herbert Skolnick, Ph.D. Letter ID: 0110 Commenter Organization: Group Against Smog and Pollution, Inc. (GASP) Comment ID: 22043 Other EPA Comment Codes and Descriptions: 4620 2.6.2 Injectate monitoring; 4660 2.6.6 Geochemical monitoring

Comment: Regardless of what specific form the CO2 sequestration program ultimately takes, at a minimum, the program must ensure that:

2. the sequestered material’s behavior in the chemical, geological, and hydrological environment where it is stored is anticipated and carefully monitored; and

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

Commenter Name: John Stormon Letter ID: 0123 Commenter Organization: Washington State Dept. of Ecology Comment ID: 23007 Other EPA Comment Codes and Descriptions: 4500 2.5 Proposed Mechanical Integrity Testing (MIT) Requirements (40 CFR 146.89)

Comment: Periodic corrosion and well integrity testing is important for all pollution prevention programs. This well testing will help operators to focus maintenance and repair activities on the wells that are degrading. It is far better to prevent leakage from a well breach than to fix the well after discovering that

it has leaked.Response: EPA agrees with the commenter; the final rule requires both internal and external mechanical integrity testing. Mechanical integrity testing is one of the cornerstones of the existing EPA UIC program. The MIT requirements at §146.89, along with the corrosion monitoring required at §146.90(c), ensure protection of USDWs from endangerment and provide an important early warning of potential problems in the injection well. Routine mechanical integrity testing of injection wells provides data that enables the identification and remediation of well integrity problems before they lead to leakage and/or endangerment of USDWs. For additional information, please see the discussion of MITs in the final rule preamble.

EPA also agrees that corrosion monitoring is appropriate given the potentially corrosive nature of the CO2 stream. CO2 in the presence of water becomes acidic, potentially accelerating corrosion of well materials. The CO2 stream for a GS project may also contain small volumes of impurities that could contribute to corrosion. For these reasons, the final rule requires quarterly corrosion monitoring (at §146.90(c)).

Commenter Name: Brianne Metzger Letter ID: 0151 Commenter Organization: Spectra Energy Corp Comment ID: 21837

Comment: For reasons described above, we also believe that the requirement to conduct corrosion monitoring on a quarterly basis is excessive and unnecessary. To require quarterly monitoring could negatively impact the flow rate, thus requiring operators to add more wells. This could limit the overall effectiveness of the project. In addition, quarterly corrosion monitoring would require the operator to remove the bottom hole configuration to perform necessary tests. This is both costly and time consuming and would require operations to be temporarily shutdown.

Response: EPA believes that quarterly corrosion monitoring is reasonable and appropriate given the potentially corrosive nature of the CO2 stream. CO2 in the presence of water becomes acidic, potentially accelerating corrosion of well materials. The CO2 stream for a GS project may also contain small volumes of impurities that could contribute to corrosion. For these reasons, the final rule requires quarterly corrosion monitoring (at §146.90(c)).

Commenter Name: Brianne Metzger Letter ID: 0151 Commenter Organization: Spectra Energy Corp Comment ID: 21840

Comment: EPA’s proposal also calls for the use of "coupons" to monitor for corrosion. 40 C.F.R. § 146.90(c)(1). Based on our experience with the use of coupons, we would recommend against this requirement, as coupons are susceptible to failure and can lodge deep in the injection well, thereby causing problems with flow rate. In addition, coupons do not identify where corrosion may or may not be taking place, due to the differences in temperature and pressure between ambient and downhole conditions. The results from the use of coupons could suggest that an entire casing or tubing string needs to be replaced when, in fact, only a portion of the well casing may need to be replaced. Therefore, coupons do not produce representative results and the data will generally not be helpful. Similarly, the concept of a "constructed loop" at the surface to monitor and test material integrity is also not recommended, as it does not replicate actual downhole conditions. 40 C.F.R. § 146.90(c)(2). We believe that one of the best tests for corrosion monitoring is the casing evaluationlogs, which allow an operator to identify specific zones where corrosion may be occurring.

Response: EPA believes that the use of coupons for corrosion monitoring is feasible and appropriate for GS wells. Corrosion monitoring by various techniques, including the use of coupons, has been performed by operators of Class I hazardous waste injection wells for many years. Use of coupons can help provide early warning of corrosion of well materials that could compromise the well's integrity.

The use of well coupons for testing with CO2 for compatibility is one of three options outlined in §146.90(c). Operators also have the option of routing the CO2 stream through a loop constructed with the material used in the well or using an alternative method approved by 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 logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Kyle Isakower Letter ID: 0170 Commenter Organization: American Petroleum Institute Comment ID: 24189 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90(c)

API Comments: (c) WHERE CONDITIONS WARRANT, corrosion monitoring of the well materials for loss of mass, thickness, cracking, pitting and other signs of corrosion must be performed on aAND RECORDED AT LEAST quarterly basis WHICH MAY BE MODIFIED TO BE LESS FREQUENT AS APPROVED BY THE DIRECTOR

BASED ON
CONSTRUCTION MATERIALS, OPERATING CONDITIONS, AND MONITORING HISTORY

to ensure that the well components meet the minimum standards for material strength and performance set forth in §146.86(b) by:

Rationale: Technical correction. API questions the need for corrosion monitoring of most injected CO2 streams since they will typically be nearly pure and dry thus having no corrosive properties. Industry experience with production, transportation, and injection of dry CO2 strongly illustrates the non-corrosive nature of this type of CO2

stream.

Response: EPA believes that corrosion monitoring is warranted and necessary for all Class VI wells in order to protect USDWs. CO2 in the presence of water (including water with NOx, SOx, and H2S impurities) can be corrosive to well materials and cements. Thus, although a CO2 stream may be dry, the potential for corrosion of well materials down-hole, where the injectate can potentially mixwith water in the target formation, must be considered.

Several laboratory studies and a limited number of field studies have investigated and characterized the effects of carbonic acid on well materials. Laboratory studies (e.g., Kutchko et al., 2007; Kutchko et al., 2008) consistently identify alterations (typically carbonation) of cement as the result

of interactions between cement and CO2-saturated brine.

Currently, there are only a few analyses of cement from wells that have been in prolonged contact with CO2 in actual field (down-hole) conditions. Evaluation of cement from a well at the Scurry Area Canyon Reef Operators Committee (SACROC) site showed alteration, but did not show degradation that compromised the structural integrity of the cement (Carey et al., 2007). In another study, cement samples were collected and analyzed from a CO2 production well in a natural CO2 reservoir in Colorado exposed to a CO2-water down-hole environment for 30 years (Crow et al., 2008). The study found evidence of reaction between the CO2-rich water and the cement.

Oil industry research also addresses the effects of corrosion of steel tubing and pipes. Lopez et al. (2003) noted that 60 percent of oilfield failures are related to the effects of carbonic acid from produced brines on carbon and low alloy steels.

Laboratory investigation of cement alteration/degradation is an ongoing research area. Few fieldbased studies have been completed to date. The laboratory and field studies currently available suggest that corrosion problems can be managed; however, there is not a large enough body of research to rule out potential corrosion problems of steel components of injection wells. The IPCC (2005) report on carbon dioxide capture and storage reviewed oil and gas industry experience with gas injection wells, close industry analogues to CO2 injection wells. The report stated that while the design of CO2 injection wells will be very similar to gas injection wells, most down-hole components of the CO2 injection wells will “need to be upgraded for higher pressure ratings and corrosion resistance.” Given the pressure and corrosion considerations, anticipated long lifespan of a GS well, and the difficulties that would be associated with a corrosion-related well failure, EPA believes that corrosion monitoring in the down-hole environment is justified. For these reasons, the final rule requires quarterly corrosion monitoring (at §146.90(c)).

Commenter Name: Kyle Isakower Letter ID: 0170 Commenter Organization: American Petroleum Institute Comment ID: 24190 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90(c)

API Comments: (1) PlacingANALYZING coupons of the well construction materials PLACED 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 AND INSPECTING THE MATERIALS IN THE LOOP; or (3) Using an alternative method, MATERIALS, OR TIME PERIOD approved by the Director;

Rationale: Clarifying edits.

Response: Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment, EPA has made many revisions to the GS rule. See the final ruleand preamble for further discussion on EPA's final approach.

Commenter Name: Frederick R. Eames Letter ID: 0178 Commenter Organization: CCS Alliance Comment ID: 23868 Other EPA Comment Codes and Descriptions: 4546 2.5.2.2 MIT frequency (seeking comment)

Comment: We do not believe there is any compelling reason to require annual integrity testing or quarterly corrosion monitoring. A five-year testing routine has been sufficient for acid gas wells in Canada. Many known injection wells are reused producer wells that have been in corrosive environments for over 15 years and remain in good condition. Annual testing and quarterly corrosion testing could also result in significant costs from plant shutdowns and downtime. Many companies already conduct periodic plant-wide shutdowns to thoroughly inspect piping and equipment for corrosion and make any necessary equipment upgrades. These shutdowns, which ordinarily occur once every three to five years, are also used to inspect injection wells, including pulling tubing, running cement bond logs, and well casing integrity logs to determine the thickness and integrity of the steel in the boreholes. From these tests, companies are able to assess the cement and casing conditions, which provide the primary "isolation" mechanism from the reservoir fluids. Moreover, companies can and often do run noise logs that can assess for "channeling" behind the casing.

Response: EPA disagrees that a five-year external MIT is appropriate. The final GS regulation retains the requirement that owners or operators of Class VI wells must demonstrate injection well external mechanical integrity at least once annually under §146.89(c). While EPA acknowledges the successful history of the Class II injection program, including injection of sour (acid) gas, the Agency believes that CO2 injection for GS is substantially different from Class II ER operations and believes annual MITs are justifiable for the protection of USDWs from endangerment given the unique nature of CO2 GS relative to other injection operations, including the potential corrosive impact of CO2 in the presence of water and impurities on well materials, the potential geomechanical impacts to well integrity due to CO2 phase changes, the temperature and pressure effects associated with injecting supercritical CO2, and the buoyant nature of the injected CO2. Because of the unknown long-term effects of CO2 GS, EPA chose a more conservative initial approach in the early stages of deployment for GS.

In addition, a comprehensive review conducted by EPA of MIT results from 1993 to 1998 found that Class I wells injecting corrosive fluids fail MITs at rates two to three times higher than those that inject non-corrosive fluids (USEPA 1999). Given the potential for CO2 to be corrosive (e.g., in the presence of water or aqueous formation fluids), there is a potential risk factor for MIT failure and, for this reason, EPA believes that the tailored MIT requirements in the final GS rule are appropriate. Regarding concerns about disruptions of plant operations, EPA believes that, due to the expected size of GS fields, many GS operations will have more than one injection well, and that testing of each well can be timed to avoid complete interruption of the project.

On the topic of corrosion monitoring, EPA disagrees with commenters' assertions that corrosion monitoring is unnecessary or excessive. CO2 in the presence of water (including water with NOx, SOx, and H2S impurities) can be corrosive to well materials and cements. Thus, although a CO2 stream may be dry, the potential for corrosion of well materials down-hole, where the injectate can potentially mix with water in the target formation, must be considered.EPA adds that it is using an adaptive approach to regulating GS. The Agency plans to collect and review data every six years on GS projects, including MIT data, to determine whether the appropriate amount and types of information and appropriate documentation are being collected, and to determine if modifications to the requirements are appropriate or necessary.

Commenter Name: Robert F. Van Voorhees Letter ID: 0190 Commenter Organization: Carbon Sequestration Council Comment ID: 24480 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90(c)

Proposed CCS Group Recommendations: (C) WHERE APPROPRIATE, THE TESTING AND

MONITORING PLAN SHALL ALSO INCLUDE:

(1) CONTINUOUS MONITORING FOR PRESSURE CHANGES IN AN APPROPRIATELY

POROUS AND
PERMEABLE FORMATION OVERLYING THE CONFINING ZONE.;

(2) THE USE OF INDIRECT, GEOPHYSICAL TECHNIQUES TO DETERMINE THE POSITION

OF THE CO2 STREAM FRONT, THE WATER QUALITY IN A DESIGNATED FORMATION, OR TO

PROVIDE
OTHER SITE SPECIFIC DATA;

(3) PERIODIC MONITORING OF WATER QUALITY IN AN APPROPRIATELY POROUS AND

PERMEABLE FORMATION OVERLYING THE INJECTION ZONE;

(4) PERIODIC MONITORING OF WATER QUALITY IN ONE OR MORE USDWS;

c(5) Corrosion monitoring of the well materials for loss of mass, thickness, cracking, pitting and other signs of corrosion performed and recorded

AT LEAST on aquarterly WHICH MAY BE MODIFIED TO BE LESS FREQUENT AS
APPROVED BY THE DIRECTOR BASED ON CONSTRUCTION MATERIALS, OPERATING
CONDITIONS, AND MONITORING HISTORY to ensure that the well components meet the minimum standards for material strength and performance set forth in §146.86(b) by:

(1)(I) PlacingANALYZING coupons of the well construction materials placed in contact with the carbon dioxide stream; or

(2)(II) Routing the carbon dioxide stream through a loop constructed with the material used in the well AND INSPECTING THE MATERIALS IN THE LOOP; or

(3)(III) Using an alternative method, MATERIALS, OR TIME PERIOD approved by the Director;

(6) ANY ADDITIONAL TESTING AND MONITORING NECESSARY TO SUPPORT

MODELING THEEXTENT OF THE CARBON DIOXIDE PLUME AND THE POSITION OF THE PRESSURE
FRONT; AND

(7) ANY ADDITIONAL TESTING AND MONITORING NECESSARY TO DETERMINE

WHETHER FLUID

MOVEMENT IS OCCURRING INTO OR BETWEEN USDWS THAT WOULD ENDANGER A

USDW.

Basis for CCS Group Comments: There should be no need for corrosion monitoring of most injected CO2 streams because those streams will typically overwhelmingly CO2 and dry thus having no corrosive properties. Industry experience with production, transportation, and injection of dry CO2 strongly illustrates the non-corrosive nature of this type of CO2 stream.

This proposal revises the provision to make it a requirement only where appropriate based on the materials of construction and characteristics of the injected CO2 stream and other factors.

The corrosion provisions are included in subsection (c)(5).

Response: EPA believes that quarterly corrosion monitoring of GS wells is necessary. CO2 in the presence of water (including water with NOx, SOx, and H2S impurities) can be corrosive to well materials and cements. Thus, although a CO2 stream may be dry, the potential for corrosion of well materials down-hole, where the injectate can potentially mix with water in the target formation, must

be considered.

Several laboratory studies and a limited number of field studies have investigated and characterized the effects of carbonic acid on well materials. Laboratory studies (e.g., Kutchko et al., 2007; Kutchko et al., 2008) consistently identify alterations (typically carbonation) of cement as the result

of interactions between cement and CO2-saturated brine.

Currently, there are only a few analyses of cement from wells that have been in prolonged contact with CO2 in actual field (down-hole) conditions. Evaluation of cement from a well at the Scurry Area Canyon Reef Operators Committee (SACROC) site showed alteration, but did not show degradation that compromised the structural integrity of the cement (Carey et al., 2007). In another study, cement samples were collected and analyzed from a CO2 production well in a natural CO2 reservoir in Colorado exposed to a CO2-water down-hole environment for 30 years (Crow et al., 2008). The study found evidence of reaction between the CO2-rich water and the cement.

Oil industry research also addresses the effects of corrosion of steel tubing and pipes. Lopez et al. (2003) noted that 60 percent of oilfield failures are related to the effects of carbonic acid from produced brines on carbon and low alloy steels.

Laboratory investigation of cement alteration/degradation is an ongoing research area. Few fieldbased studies have been completed to date. The laboratory and field studies currently available suggest that corrosion problems can be managed; however, there is not a large enough body of research to rule out potential corrosion problems of steel components of injection wells. The IPCC (2005) report on carbon dioxide capture and storage reviewed oil and gas industry experience with gas injection wells, close industry analogues to CO2 injection wells. The report stated that, while the design of CO2 injection wells will be very similar to gas injection wells, most down-holecomponents of the CO2 injection wells will “need to be upgraded for higher pressure ratings and corrosion resistance.” Given the pressure and corrosion considerations, anticipated long lifespan of a GS well and the difficulties that would be associated with a corrosion-related well failure, EPA believes that corrosion monitoring in the down-hole environment is justified. For these reasons, the final rule requires quarterly corrosion monitoring at §146.90(c).

EPA maintains that plume tracking and pressure monitoring are key components of monitoring at GS sites. A rigorous plume tracking and pressure monitoring scheme, such as one that meets the requirements at §146.90(g), is imperative for ensuring that the CO2 plume is contained within the injection zone. Pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume. When combined with information on temperature, pressure data provide an indication of the phase (e.g., gas, supercritical) and distribution of the injected CO2. Monitoring can also identify needed remedial actions, provide inputs for AoR reevaluation modeling, evaluate predictions of plume movement, and target additional geochemical and surface monitoring needs.

EPA also believes that the ground water geochemical monitoring 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. See the final rule and preamble for further discussion on EPA's final approach.

Commenter Name: Craig R. Walters Letter ID: 0200 Commenter Organization: Anadarko Petroleum Corporation Comment ID: 24702 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.86(c)

Anadarko Petroleum Corporation (APC) Comments: (C) WHERE APPROPRIATE, THE

TESTING AND MONITORING PLAN SHALL ALSO INCLUDE:

(1) CONTINUOUS MONITORING FOR PRESSURE CHANGES IN AN APPROPRIATELY

POROUS AND

PERMEABLE FORMATION OVERLYING THE CONFINING ZONE. WHEN A WELL IS

INSTALLED TO
ENABLE SUCH MONITORING, THE OWNER OR OPERATOR SHALL, ON A SPECIFIED FREQUENCY OR
AT SPECIFIED TIMES, SAMPLE THE FORMATION AND ANALYZE FOR CONSTITUENTS

SPECIFIED
IN THE PLAN;

(2) THE USE OF INDIRECT, GEOPHYSICAL TECHNIQUES TO DETERMINE THE POSITION

OF THE CO2 STREAM FRONT, THE WATER QUALITY IN A DESIGNATED FORMATION, OR TO

PROVIDE
OTHER SITE SPECIFIC DATA;

(3) PERIODIC MONITORING OF WATER QUALITY IN AN APPROPRIATELY POROUS AND

PERMEABLE FORMATION OVERLYING THE INJECTION ZONE;(4) PERIODIC MONITORING OF WATER QUALITY IN ONE OR MORE USDWS;

(5) CORROSION MONITORING OF THE WELL MATERIALS FOR LOSS OF MASS,
THICKNESS,
CRACKING, PITTING AND OTHER SIGNS OF CORROSION PERFORMED AND RECORDED

AT LEAST QUARTERLY WHICH MAY BE MODIFIED TO BE LESS FREQUENT AS APPROVED BY

THE DIRECTOR
BASED ON CONSTRUCTION MATERIALS, OPERATING CONDITIONS, AND

MONITORING HISTORY TO

ENSURE THAT THE WELL COMPONENTS MEET THE MINIMUM STANDARDS FOR

MATERIAL STRENGTH AND PERFORMANCE SET FORTH IN §146.86(B) BY: (I) ANALYZING COUPONS OF THE WELL CONSTRUCTION MATERIALS PLACED IN

CONTACT WITH
THE CARBON DIOXIDE STREAM; OR (II) ROUTING THE CARBON DIOXIDE STREAM THROUGH A LOOP CONSTRUCTED

WITH THE MATERIAL USED IN THE WELL AND INSPECTING THE MATERIALS IN THE LOOP; OR (III) USING AN ALTERNATIVE METHOD, MATERIALS, OR TIME PERIOD APPROVED BY

THE DIRECTOR;

(6) ANY ADDITIONAL TESTING AND MONITORING APPROPRIATE TO SUPPORT

MODELING THE

EXTENT OF THE CARBON DIOXIDE PLUME AND THE POSITION OF THE PRESSURE
FRONT; AND

(7) ANY ADDITIONAL TESTING AND MONITORING NECESSARY TO DETERMINE

WHETHER FLUID

MOVEMENT IS OCCURRING INTO OR BETWEEN USDWS THAT WOULD ENDANGER A

USDW.

Rationale: Drilling monitoring wells should be carefully considered since each well introduces a potential pathway for movement. In addition the cost of adding multiple wells could create a barrier to CCS development, while providing

limited information on actual movement of the CO2 stream.

APC questions the need for corrosion monitoring of most injected CO2 streams since they will typically be nearly pure and dry thus having no corrosive properties. Industry experience with production, transportation, and injection of dry CO2 strongly illustrates the non-corrosive nature of this type of CO2

stream.

Response: EPA believes that quarterly corrosion monitoring of GS wells is necessary. CO2 in the presence of water (including water with NOx, SOx, and H2S impurities) can be corrosive to well materials and cements. Thus, although a CO2 stream may be dry, the potential for corrosion of well materials down-hole, where the injectate can potentially mix with water in the target formation, must

be considered.Several laboratory studies and a limited number of field studies have investigated and characterized the effects of carbonic acid on well materials. Laboratory studies (e.g., Kutchko et al., 2007; Kutchko et al., 2008) consistently identify alterations (typically carbonation) of cement as the result

of interactions between cement and CO2-saturated brine.

Currently, there are only a few analyses of cement from wells that have been in prolonged contact with CO2 in actual field (down-hole) conditions. Evaluation of cement from a well at the Scurry Area Canyon Reef Operators Committee (SACROC) site showed alteration, but did not show degradation that compromised the structural integrity of the cement (Carey et al., 2007). In another study, cement samples were collected and analyzed from a CO2 production well in a natural CO2 reservoir in Colorado exposed to a CO2-water down-hole environment for 30 years (Crow et al., 2008). The study found evidence of reaction between the CO2-rich water and the cement.

Oil industry research also addresses the effects of corrosion of steel tubing and pipes. Lopez et al. (2003) noted that 60 percent of oilfield failures are related to the effects of carbonic acid from produced brines on carbon and low alloy steels.

Laboratory investigation of cement alteration/degradation is an ongoing research area. Few fieldbased studies have been completed to date. The laboratory and field studies currently available suggest that corrosion problems can be managed; however, there is not a large enough body of research to rule out potential corrosion problems of steel components of injection wells. The IPCC (2005) report on carbon dioxide capture and storage reviewed oil and gas industry experience with gas injection wells, close industry analogues to CO2 injection wells. The report stated that while the design of CO2 injection wells will be very similar to gas injection wells, most down-hole components of the CO2 injection wells will “need to be upgraded for higher pressure ratings and corrosion resistance.” Given the pressure and corrosion considerations, anticipated long lifespan of a GS well and the difficulties that would be associated with a corrosion-related well failure, EPA believes that corrosion monitoring in the down-hole environment is justified. For these reasons, the final rule requires quarterly corrosion monitoring at §146.90(c).

EPA maintains that plume tracking and pressure monitoring are key components of monitoring at GS sites. A rigorous plume tracking and pressure monitoring scheme, such as one that meets the requirements at §146.90(g), is imperative for ensuring that the CO2 plume is contained within the injection zone. Pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume. When combined with information on temperature, pressure data provide an indication of the phase (e.g., gas, supercritical) and distribution of the injected CO2. Monitoring can also identify needed remedial actions, provide inputs for AoR reevaluation modeling, evaluate predictions of plume movement, and target additional geochemical and surface monitoring needs.

EPA also believes that the ground water geochemical monitoring 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. See the final rule and preamble for further discussion on EPA's final approach.

Commenter Name: Craig R. Walters Letter ID: 0200 Commenter Organization: Anadarko Petroleum Corporation Comment ID: 24703 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rulelanguage

Comment: Rule Provision: 146.90(c)

Anadarko Petroleum Corporation (APC) Comments: (c) Corrosion monitoring of the well materials for loss of mass, thickness, cracking, 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;

Rationale: See 146.90(5)(i-iii)

Response: EPA believes that corrosion monitoring is necessary for all Class VI wells to prevent endangerment of USDWs. CO2 in the presence of water (including water with NOx, SOx, and H2S impurities) can be corrosive to well materials and cements. Thus, although a CO2 stream may be dry, the potential for corrosion of well materials down-hole, where the injectate can potentially mix with water in the target formation, must be considered.

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.

Commenter Name: Ronald Evans Letter ID: 0215 Commenter Organization: Denbury Resources, Inc. (DRI) Comment ID: 24309 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: 2. EPA Proposed §146.90(c) Corrosion monitoring of the well materials for loss of mass, thickness, cracking, 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;

Denbury believes the requirements in EPA proposed §146.90(c) related to corrosion monitoring are inapplicable. In the vast majority of cases, the CO2 will be transported to the injection site through pipelines, will be dehydratedprior to transportation and therefore when injected it will be noncorrosive.[FN44] In those instances, the test methods described in § 146.90(c) (1) and (c)(2) (except of course alternatives approved by the Director) will not provide meaningful information regarding the mechanical integrity of down-holecasing, tubing and other equipment because the CO2 will simply not be corrosive at the surface. Consequently, to have any relevance such requirements should be reserved for situations where water saturated CO2 is being injected.

§146.90(c) Corrosion monitoring of the well materials for loss of mass, thickness, cracking, pitting and other signs of corrosion must be performed on a quarterly basis to ensure that thewell components

THAT CONTACT WATER SATURATED CARBON DIOXIDE STREAMS 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. THE REQUIREMENTS

OF THIS SUBPART ARE WAIVED WHEN THE CARBON DIOXIDE STREAM IS

DEHYDRATED

TO MEET PIPELINE SPECIFICATIONS.

[44] For evidence on CO2 corrosiveness in the absence of free water see Don Duttlinger, "Enhanced Recovery Intertwines Naturally With CO2 Sequestration," Tech Connections Column, American Oil and Gas Reporter (January 2004), available at http://www.pttc.org/aogr_columns_archived/aogrcojan04.htm (From the processing/injection standpoint, CO2 is noncorrosive as long as it is dry. Proving that point, Kinder Morgan has hydro-tested the 32-year-old CRC Pipeline built in 1971 to transport CO2. Only one minor failure occurred. After testing, the line was rated for 2,025 psi maximum operating pressure, which established a 200 psi increase over most recent ratings); see also J. Layne, "Results of the Hydrotest of the 30-year old Canyon Reef Carriers CO2 Pipeline," 2003 CO2 Flooding Conference, University of Texas of the Permian Basin's Center for Energy and Economic Diversification, Midland,Texas (December 11-12, 2003).

Response: EPA disagrees that corrosion monitoring is unnecessary or excessive. CO2 in the presence of water (including water with NOx, SOx, and H2S impurities) can be corrosive to well materials and cements. Thus, although a CO2 stream may be dry, the potential for corrosion of well materials down-hole, where the injectate can potentially mix with water in the target formation, must be considered. EPA believes that the testing methods specified in the rule are appropriate and have been used successfully by Class I hazardous waste injection well owners or operators.

Several laboratory studies and a limited number of field studies have investigated and characterized the effects of carbonic acid on well materials. Laboratory studies (e.g., Kutchko et al., 2007; Kutchko et al., 2008) consistently identify alterations (typically carbonation) of cement as the result

of interactions between cement and CO2-saturated brine.

Currently, there are only a few analyses of cement from wells that have been in prolonged contact with CO2 in actual field (down-hole) conditions. Evaluation of cement from a well at the Scurry Area Canyon Reef Operators Committee (SACROC) site showed alteration, but did not show degradation that compromised the structural integrity of the cement (Carey et al., 2007). In another study, cement samples were collected and analyzed from a CO2 production well in a natural CO2 reservoir in Colorado exposed to a CO2-water down-hole environment for 30 years (Crow et al.,2008). The study found evidence of reaction between the CO2-rich water and the cement.

Oil industry research also addresses the effects of corrosion of steel tubing and pipes. Lopez et al. (2003) noted that 60 percent of oilfield failures are related to the effects of carbonic acid from produced brines on carbon and low alloy steels.

Laboratory investigation of cement alteration/degradation is an ongoing research area. Few fieldbased studies have been completed to date. The laboratory and field studies currently available suggest that corrosion problems can be managed; however, there is not a large enough body of research to rule out potential corrosion problems of steel components of injection wells. The IPCC (2005) report on carbon dioxide capture and storage reviewed oil and gas industry experience with gas injection wells, close industry analogues to CO2 injection wells. The report stated that while the design of CO2 injection wells will be very similar to gas injection wells, most down-hole components of the CO2 injection wells will “need to be upgraded for higher pressure ratings and corrosion resistance.” Given the pressure and corrosion considerations, anticipated long lifespan of a GS well and the difficulties that would be associated with a corrosion-related well failure, EPA believes that corrosion monitoring in the down-hole environment is justified. For these reasons, the final rule requires quarterly corrosion monitoring (at §146.90(c)). See the final rule and preamble for further discussion on EPA's final approach.

Commenter Name: Darrick Eugene Letter ID: 0223 Commenter Organization: Texas Carbon Capture and Storage Association Comment ID: 23989 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: EPA Proposed §146.90(c) Corrosion monitoring of the well materials for loss of mass, thickness, cracking, 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;

TxCCSA believes the requirements in EPA proposed §146.90(c) related to corrosion monitoring are inapplicable. In the vast majority of cases, the CO2 will be transported to the injection site through pipelines, will be dehydrated prior to transportation and therefore when injected it will be non-corrosive.[FN2] In those instances, the test methods described in § 146.90(c)(1) and (c)(2) (except of course alternatives approved by the Director) will not provide meaningful information regarding the mechanical integrity of down-hole casing, tubing and other equipment because the CO2 will simply not be corrosive at the surface. Consequently, to have any relevance such requirements should be reserved for situations where water saturated CO2 is being injected.

[FN2: For evidence on CO2 corrosivity in the absence of free water see Don Duttlinger, Enhanced Recovery Intertwines Naturally With CO2 Sequestration, Tech Connections Column, January 2004, American Oil and Gas Reporter, available athttp://www.pttc.org/aogr_columns_archived/aogrcojan04.htm (From the processing/injection standpoint, CO2 is noncorrosive as long as it is dry. Proving that point, Kinder Morgan has hydro-tested the 32-year-old CRC Pipeline built in 1971 to transport CO2. Only one minor failure occurred. After testing, the line was rated for 2,025 psi maximum operating pressure, which established a 200 psi increase over most recent ratings); see J. Layne, Results of the Hydrotest of the 30-year old Canyon Reef Carriers CO2 Pipeline, 2003 CO2 Flooding Conference, December 11-12, 2003, Midland,Texas (University of Texas of the Permian Basin’s Center for Energy and Economic Diversification).]

§146.90(c) Corrosion monitoring of the well materials for loss of mass, thickness, cracking, pitting and other signs of corrosion must be performed on a quarterly basis to ensure that thewell components

THAT CONTACT WATER SATURATED CARBON DIOXIDE STREAMS 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. THE REQUIREMENTS

OF THIS SUBPART ARE WAIVED WHEN THE CARBON DIOXIDE STREAM IS

DEHYDRATED

TO MEET PIPELINE SPECIFICATIONS.

Response: Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment EPA has made many revisions to the GS rule. See the final rule and preamble for further discussion on EPA's final approach.

EPA disagrees with commenters' assertions that corrosion monitoring is unnecessary or excessive. CO2 in the presence of water (including water with NOx, SOx, and H2S impurities) can be corrosive to well materials and cements. Thus, although a CO2 stream may be dry, the potential for corrosion of well materials down-hole, where the injectate can potentially mix with water in the target formation, must be considered.

Several laboratory studies and a limited number of field studies have investigated and characterized the effects of carbonic acid on well materials. Laboratory studies (e.g., Kutchko et al., 2007; Kutchko et al., 2008) consistently identify alterations (typically carbonation) of cement as the result of interactions between cement and CO2-saturated brine. EPA believes that the testing methods specified in the rule are appropriate and have been used successfully by Class I hazardous waste injection well owners or operators.

Currently, there are only a few analyses of cement from wells that have been in prolonged contact with CO2 in actual field (down-hole) conditions. Evaluation of cement from a well at the Scurry Area Canyon Reef Operators Committee (SACROC) site showed alteration, but did not show degradation that compromised the structural integrity of the cement (Carey et al., 2007). In another study, cement samples were collected and analyzed from a CO2 production well in a natural CO2 reservoir in Colorado exposed to a CO2-water down-hole environment for 30 years (Crow et al., 2008). The study found evidence of reaction between the CO2-rich water and the cement.Oil industry research also addresses the effects of corrosion of steel tubing and pipes. Lopez et al. (2003) noted that 60 percent of oilfield failures are related to the effects of carbonic acid from produced brines on carbon and low alloy steels.

Laboratory investigation of cement alteration/degradation is an ongoing research area. Few fieldbased studies have been completed to date. The laboratory and field studies currently available suggest that corrosion problems can be managed; however, there is not a large enough body of research to rule out potential corrosion problems of steel components of injection wells. The IPCC (2005) report on carbon dioxide capture and storage reviewed oil and gas industry experience with gas injection wells, close industry analogues to CO2 injection wells. The report stated that while the design of CO2 injection wells will be very similar to gas injection wells, most down-hole components of the CO2 injection wells will “need to be upgraded for higher pressure ratings and corrosion resistance.” Given the pressure and corrosion considerations, anticipated long lifespan of a GS well and the difficulties that would be associated with a corrosion-related well failure, EPA believes that corrosion monitoring in the down-hole environment is justified. For these reasons, the final rule requires quarterly corrosion monitoring (at §146.90(c)).

The Agency plans to, every six years, collect and review data on GS projects to determine whether the appropriate amount and types of information and appropriate documentation are being collected, and to determine if modifications to the requirements are appropriate or necessary.

Commenter Name: Andrew Duguid Letter ID: 0226 Commenter Organization: Schlumberger Carbon Services Comment ID: 24054 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Proposed Rule: (c) Corrosion monitoring of the well materials for loss of mass, thickness, cracking, 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:

Schlumberger Suggested Revision: (c) Corrosion monitoring of the well materials for loss of mass, thickness, cracking, pitting and other signs of corrosion must be performed quarterly and may be modified to be less frequent as approved by the Director based on construction materials, operating conditions, and monitoring history to ensure that the well components meet the minimum standards for material strength and performance set forth in §146.86(b) by:

Schlumberger Rationale: Allows application of performance based approach.

Response: EPA believes that corrosion monitoring is appropriate given the potentially corrosive nature of the CO2 stream. CO2 in the presence of water becomes acidic, potentially accelerating corrosion of well materials. The CO2 stream for a GS project may also contain small volumes of impurities that could contribute to corrosion. For these reasons, the final rule requires quarterly corrosion monitoring at §146.90(c), as proposed.

Commenter Name: Andrew Duguid Letter ID: 0226 Commenter Organization: Schlumberger Carbon Services Comment ID: 24055Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Proposed Rule: (1) Placing coupons of the well construction materials in contact with the carbon dioxide stream; or

Schlumberger Suggested Revision: (1) Analyzing coupons of the well construction materials placed in contact with the carbon dioxide stream; or

Schlumberger Rationale: -

Response: Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment EPA has made many revisions to the GS rule. See the final rule and preamble for further discussion on EPA's final approach.

Commenter Name: Andrew Duguid Letter ID: 0226 Commenter Organization: Schlumberger Carbon Services Comment ID: 24056 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

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

Schlumberger Suggested Revision: (2) Routing the carbon dioxide stream through a loop constructed with the material used in the well and inspecting the materials in the loop; or

Schlumberger Rationale: -

Response: Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment EPA has made many revisions to the GS rule. See the final rule and preamble for further discussion on EPA's final approach.

Commenter Name: Andrew Duguid Letter ID: 0226 Commenter Organization: Schlumberger Carbon Services Comment ID: 24057 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Proposed Rule: (3) Using an alternative method approved by the Director;

Schlumberger Suggested Revision: (3) Using an alternative method, materials, or time period approved by the Director;

Schlumberger Rationale: -

Response: Based on its evaluation of all public comments and input on the proposed rule and NODA and Request for Comment EPA has made many revisions to the GS rule. See the final rule and preamble for further discussion on EPA's final approach.

Commenter Name: Neeraj Gupta Letter ID: 0229 Commenter Organization: Battelle Energy Technology (BET) Comment ID: 21848Comment: Page 88, Corrosion Coupons- We would appreciate more clarity on where corrosion coupons would be necessary (i.e. only within the injection zone or spaced within the tubing). Would it be sufficient to use place coupons above-ground in the CO2 pipeline near the well?

Response: EPA clarifies that the requirement to monitor corrosion by placing the coupons in the well would provide a more accurate analogue of the conditions to which well materials are exposed than would surface testing (i.e., in the pipeline). Please note that the use of coupons is one out three methods that an owner or operator may use to monitor corrosion under §146.90(c). EPA adds that, under SDWA authority, the Agency cannot prescribe any testing methods that involve the pipeline.

Several options are available for monitoring corrosion using coupons. For example, corrosion coupons may be placed in a side stream loop so they are exposed to the injectate. Valves on either end of the side stream loop allow the owner or operator to shut off the injectate flow, extract the coupons, and measure any change in thickness. Another monitoring option is to insert the coupons through a "T" in the flowline and directly lower this into the injection flow. The coupons can then be retracted into the side pipe, extracted, and measured. Finally, spool pieces of the construction material can be installed either in the injectate flow line or in a side stream; flanges and valves allow the spool pieces to be isolated from the injectate so they can be evaluated for corrosion.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Mark Bohrer Letter ID: 0241 Commenter Organization: North Dakota Industrial Commission Comment ID: 23302

Comment: 146.90(c) Quarterly is too onerous. Director should have discretion to require less frequently based upon performance.

Response: EPA believes that quarterly corrosion monitoring is appropriate given the potentially corrosive nature of the CO2 stream. CO2 in the presence of water becomes acidic, potentially accelerating corrosion of well materials. The CO2 stream for a GS project may also contain small volumes of impurities that could contribute to corrosion. For these reasons, the final rule requires quarterly corrosion monitoring, at §146.90(c).

Commenter Name: Michel Paque Letter ID: 0259 Commenter Organization: Ground Water Protection Council Comment ID: 24924 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90

EPA Proposal: (c) Corrosion monitoring of the well materials for loss of mass, thickness, cracking, pitting and other signs of corrosion must be performed on aquarterly basis to ensure that the well components meet the minimum standards for material strength and performance set forth in § 146.86(b) by:

GWPC Recommendations: c) Corrosion monitoring of the well materials for loss of mass, thickness, cracking, pitting and other signs of corrosion must be performed and recorded at least quarterly and may be modified to be less frequent as approved by the Director based on construction materials, operating conditions, and monitoring history to ensure that the well components meet the minimum standards for material strength and performance set forth in §146.86(b) by:

Rationale: Allows application of performance based approach.

Rationale: Allows less frequent monitoring, for example, where corrosion

resistant materials are used.

Response: EPA believes that quarterly corrosion monitoring is appropriate given the potentially corrosive nature of the CO2 stream. CO2 in the presence of water becomes acidic, potentially accelerating corrosion of well materials. The CO2 stream for a GS project may also contain small volumes of impurities that could contribute to corrosion. For these reasons, the final rule requires quarterly corrosion monitoring, at §146.90(c).

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.

Commenter Name: Michel Paque Letter ID: 0259 Commenter Organization: Ground Water Protection Council Comment ID: 24925 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90(c)

EPA Proposal: (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;

GWPC Recommendations: (1) Analyzing coupons of the well construction materials placed 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 and inspecting the materials in the loop; or (3) Using an alternative method, materials, or time period approved by the Director;

Rationale: Clarification edits

Response: As described above, EPA believes that quarterly corrosion monitoring is appropriate given the potentially corrosive nature of the CO2 stream. 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 discussion on EPA's final approach.

Commenter Name: Donn Miller Letter ID: 0270 Commenter Organization: State of Oregon, Water Resources Department Comment ID: 22889

Comment: 146.90 Testing and Monitoring Requirements.

(c) We support extensive corrosion monitoring and control, at least until collectively we know more about how cement will react to long-term contact with

CO2.

Response: EPA agrees that corrosion monitoring is appropriate given the potentially corrosive nature of the CO2 stream. CO2 in the presence of water becomes acidic, potentially accelerating corrosion of well materials. The CO2 stream for a GS project may also contain small volumes of impurities that could contribute to corrosion. For these reasons, the final rule requires quarterly corrosion monitoring at §146.90(c).

Comment Code: 4640 2.6.4 Pressure fall-off testing (seeking comment)



### Individual Comments

Commenter Name: John Hanger Letter ID: 0130 Commenter Organization: Pennsylvania Dept. of Env. Protection Comment ID: 21510

Comment: -Depending on the geology surrounding the containment formation, it is possible that the CO2 could be absorbed/adsorbed by some of the surrounding formations. This could cause a drop in pressure not directly associated with leakage. EPA should determine or allow for a maximum allowable pressure drop, or correction value, dependent on the appropriate surrounding geology.

Response: EPA 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 is necessary every five years at a minimum, and the final GS regulation 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) to ensure safe and effective operations.

EPA is developing guidance on testing and monitoring at GS sites, which will address pressure falloff testing. The guidance also describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.Commenter Name: Christine Reimer Letter ID: 0142 Commenter Organization: National Ground Water Association Comment ID: 22608

Comment: Proposed Rule: 146.90(f)

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.

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 regulation 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) to ensure safe and effective operations.

Commenter Name: Kyle Isakower Letter ID: 0170 Commenter Organization: American Petroleum Institute Comment ID: 24248

Comment: Rule Provisions: 146.90(f) EPA Preamble Question: 31. EPA’s proposal would require that owners or operators perform a pressure fall-off test at least once every five years. EPA seeks comment on the use and frequency of pressure fall-off testing for GS wells. EPA

Notice 43515.

API Response: 31. We recommend that an initial falloff test be conducted upon completion of the well prior to any operational injection and after the first year of operational injection. Following the first year, the frequency should be at the discretion of the Director but the frequency should be aligned with the reevaluation of the AoR.

Response: EPA believes that a frequency of at least once every five years, as specified at §146.90(f), is an appropriate interval for pressure fall-off testing (particularly given the suite of tests operators will perform on the well and the site). EPA clarifies that the Director may require more frequent pressure fall-off tests at a specific project, if necessary based on site-specific circumstances. Pressure fall-off tests may be conducted in conjunction with other well performance tests (i.e., mechanical integrity testing) to ensure safe and effective operations. All monitoring data collected, including information from pressure fall-off tests, will be incorporated in AoR reevaluations conducted at least every five years.

Commenter Name: Thomas Curtis Letter ID: 0181 Commenter Organization: American Water Works Association (AWWA) Comment ID: 23698

Comment: Pressure fall-off testing should definitely be required however the five year length between testing is too long. This should be performed on an annual basis as part of the annual reporting requirementsResponse: EPA believes that a frequency of at least once every five years, as specified at §146.90(f), is an appropriate interval for pressure fall-off testing (particularly given the suite of tests operators will perform on the well and the site). EPA clarifies that the Director may require more frequent pressure fall-off tests at a specific project, if necessary based on site-specific circumstances. Pressure fall-off tests may be conducted in conjunction with other well performance tests (i.e., mechanical integrity testing) to ensure safe and effective operations. All monitoring data collected, including information from pressure fall-off tests, will be incorporated in AoR reevaluations conducted at least every five years.

Commenter Name: Bradley J. Field Letter ID: 0186 Commenter Organization: New York State Dept. of Environmental Conservation

Div. of Mineral Resources Comment ID:

25202

Comment: DD. EPA seeks comment on the use and frequency of pressure fall-off testing for

GS wells.

NYSDEC-DMN Response: NYSDEC-DMN is unclear as to the actual utility of pressure fall-off testing for operational GS wells. Instead of being mandated at least once every five years, the Director should have the discretion to require such testing as deemed appropriate.

Response: EPA 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 regulation 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) to ensure safe and effective operations.

EPA believes that a frequency of at least once every five years, as specified at §146.90(f), is an appropriate interval for pressure fall-off testing (particularly given the suite of tests operators will perform on the well and the site). EPA clarifies that the Director may require more frequent pressure fall-off tests at a specific project, if necessary based on site-specific circumstances. Pressure fall-off tests may be conducted in conjunction with other well performance tests (i.e., mechanical integrity testing) to ensure safe and effective operations. All monitoring data collected, including information from pressure fall-off tests, will be incorporated in AoR reevaluations conducted at least every five

years.

Commenter Name: Daniel Plath Letter ID: 0188 Commenter Organization: NiSource, Inc. Comment ID: 25237

Comment: 4. Pressure Falloff Tests (146.90(f))

The EPA proposes and requests comment on the requirement for operators to conduct a pressure falloff test once every 5 years (Preamble (73 Fed. Reg. at 43515). Notwithstanding our comments below about the Proposed Rule having excessive data collection requirements, one area in which NiSource believes the Proposed Rule is actually too lenient is with respect to only requiring a pressure falloff test at least once every 5 years. NiSource recommends whereappropriate that this be either done at an interval no greater than two years or at a site specific injected volume interval. NiSource notes the duration of shut-in will be reservoir dependent but a range of 1 to 5 days, depending on the reservoir circumstances, is recommended.

The key to this being an invaluable tool with natural gas reservoir storage integrity monitoring isn't that the time period is long enough to actually reach pressure stability as it is that the testing is conducted at consistent time intervals and volume levels over the life of the field. This is primarily done by collecting and studying shut-in data at every well every spring and fall when the field is empty and full of working gas, respectively. Testing at a fairly consistent time/volume interval provides for more relevant comparisons over time, and enhances the usefulness for comparisons over extended periods of time, even when comparing test results over several decades. This in turn permits an efficient understanding of what the gas is doing in the vast reservoir area over the life of the field and the identification of even very slowly growing abnormal trends in the gas plume's pressure-volume behavior. An accurate identification of the fields, if any that are experiencing gas migration issues then allows the operator to focus resources to identify the root cause and to rectify the specific probiem. NiSource believes these testing provisions would be helpful if included in the proposed rule. Therefore, we suggest the rule language be adjusted to accommodate these factors.

While the volume in a GS field will be continually increasing versus cycling as with natural gas storage, the concept of having snap shots of the shut-in reservoir pressure for the entire CO2 plume at consistent time/volume intervals should still lead to a similar understanding of the plume's overall behavior. These observations can then be compared with the reservoir simulation predictions and would help with fine tuning model assumptions. Significant deviations, if any, would be quickly identified and would become the investigative focal point for the operator's resources.

In many instances, we recommend this shut-in pressure test and analysis coupled with simulation be recognized as a viable primary method for CO2 plume monitoring with more extensive methods (e.g. 4D seismic, etc.) only being used to periodically fine tune the model or in instances when questions arise. The appropriate testing basis, time or volume based, will likely be site and operator specific. Therefore, the Final Rule needs to provide for flexibility to utilize this method and allow the use of new testing technology that may become

available in the future.

Response: EPA believes that a frequency of at least once every five years, as specified at §146.90(f), is an appropriate interval for pressure fall-off testing (particularly given the suite of tests operators will perform on the well and the site). EPA clarifies that the Director may require more frequent pressure fall-off tests at a specific project, if necessary based on site-specific circumstances. Pressure fall-off tests may be conducted in conjunction with other well performance tests (i.e., mechanical integrity testing) to ensure safe and effective operations. All monitoring data collected, including information from pressure fall-off tests, will be incorporated in AoR reevaluations conducted at least every five years.EPA adds that the pressure fall-off testing will be performed in concert with other testing, including plume monitoring, pursuant to the approved testing and monitoring plan. If any site-specific information indicates a need for additional or more frequent testing to ensure USDWs are protected, it is within the Director's discretion to require additional testing to ensure protection of USDWs.

Commenter Name: Robert F. Van Voorhees Letter ID: 0190 Commenter Organization: Carbon Sequestration Council Comment ID: 24540

Comment: Rule Provisions or Federal Register Cite: 146.90(f) EPA Preamble Question: 31. EPA’s proposal would require that owners or operators perform a pressure fall-off test at least once every five years. EPA seeks comment on the use and frequency of pressure fall-off testing for GS wells. EPA

Notice 43515.

CSC Response: We recommend that an initial falloff test be conducted upon completion of the well prior to any operational injection and after the first year of operational injection. Following the first year, the frequency should be at the discretion of the Director but the frequency should be aligned with the

reevaluation of the AoR.

Response: EPA believes that a frequency of at least once every five years, as specified at §146.90(f), is an appropriate interval for pressure fall-off testing (particularly given the suite of tests operators will perform on the well and the site). EPA clarifies that the Director may require more frequent pressure fall-off tests at a specific project, if necessary based on site-specific circumstances. Pressure fall-off tests may be conducted in conjunction with other well performance tests (i.e., mechanical integrity testing) to ensure safe and effective operations. All monitoring data collected, including information from pressure fall-off tests, will be incorporated in AoR reevaluations conducted at least every five years.

Commenter Name: Craig R. Walters Letter ID: 0200 Commenter Organization: Anadarko Petroleum Corporation Comment ID: 24601

Comment: Rule Provisions: 146.90(f) EPA Rule Issue: 31. EPA’s proposal would require that owners or operators perform a pressure fall-off test at least once every five years. EPA seeks comment on the use and frequency of pressure fall-off testing for GS wells. EPA

Notice 43515.

Anadarko Petroleum Corporation (APC) Response: We recommend that an initial falloff test be conducted upon completion of the well prior to any operational injection and after the first year of operational injection. Following the first year, the frequency should be at the discretion of the Director but the frequency should be aligned with the reevaluation of the AoR.

Response: EPA believes that a frequency of at least once every five years, as specified at §146.90(f), is an appropriate interval for pressure fall-off testing (particularly given the suite of tests operators will perform on the well and the site). EPA clarifies that the Director may require more frequent pressure fall-off tests at a specific project, if necessary based on site-specific circumstances. Pressure fall-off tests may be conducted in conjunction with other well performance tests (i.e., mechanical integrity testing) to ensure safe and effective operations. All monitoring data collected, includinginformation from pressure fall-off tests, will be incorporated in AoR reevaluations conducted at least every five years.

Commenter Name: Ronald Evans Letter ID: 0215 Commenter Organization: Denbury Resources, Inc. (DRI) Comment ID: 24310

Comment: 3. EPA Proposed §146.90(f) A pressure fall-off test at least once every five years unless more frequent testing is required by the Director based on site specific information;

The scope of this proposed requirement is not clear. Does the EPA proposal require the submittal of the actual data, or merely an analysis of the pressure

fall-off test?

Response: EPA expects that the Director would request an electronic copy of the data in addition to an analysis report completed by the owner or operator. This would afford the Director the opportunity to review the data and verify that the analysis is accurate. EPA also expects that the details of what information must be submitted would be described in the testing and monitoring procedures in the Class VI permit.

Commenter Name: Darrick Eugene Letter ID: 0223 Commenter Organization: Texas Carbon Capture and Storage Association Comment ID: 23990

Comment: EPA Proposed §146.90(f) A pressure fall-off test at least once every five years unless more frequent testing is required by the Director based on site specific information;

The scope of this proposed requirement is not clear. Does the EPA proposal require the submittal of the actual data, or merely an analysis of the pressure

fall-off test?

Response: EPA expects that the Director would request an electronic copy of the data in addition to an analysis report completed by the owner or operator. This would afford the Director the opportunity to review the data and verify that the analysis is accurate. EPA also expects that the details of what information must be submitted would be described in the testing and monitoring procedures in the Class VI permit.

Commenter Name: Andrew Duguid Letter ID: 0226 Commenter Organization: Schlumberger Carbon Services Comment ID: 24062 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Proposed Rule: (f) A pressure fall-off test at least once every five years unless more frequent testing is required by the Director based on site specific information;

Schlumberger Suggested Revision: (f) A pressure fall-off test or other equivalent test that identifies reservoir conditions with respect to flow dynamics at least once every five years unless more frequent testing is required by the Director based on site specific information;Schlumberger Rationale: Allows more flexibility while still providing the needed

information

Response: EPA 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 is conducted at least once every five years and the final GS regulation 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) to ensure safe and effective operations.

Commenter Name: Neeraj Gupta Letter ID: 0229 Commenter Organization: Battelle Energy Technology (BET) Comment ID: 21858

Comment: Page 103, Pressure fall-off tests- In our experience, pressure fall-off tests offer more information in initial injection testing. After longer term injection, we’ve seen basically the same, muted response. In addition, the fall-off response tended to take much longer after sustained injection. A concern may be that you need to monitor pressure fall off for several weeks, months, or years after 5 years of continuous injection to obtain useful data. This would lead to the need for standby wells or emitting CO2 to the atmosphere during fall-off tests. We think these should be part of the initial testing sequence for new injection wells, but they might be a more optional rather than a mandatory part of testing.

Response: EPA believes that a frequency of at least once every five years, as specified at §146.90(f), is an appropriate interval for pressure fall-off testing (particularly given the suite of tests operators will perform on the well and the site). EPA clarifies that the Director may require more frequent pressure fall-off tests at a specific project, if necessary based on site-specific circumstances. Pressure fall-off tests may be conducted in conjunction with other well performance tests (i.e., mechanical integrity testing) to ensure safe and effective operations. All monitoring data collected, including information from pressure fall-off tests, will be incorporated in AoR reevaluations, at least every five years.

Commenter Name: Philip Papadeas Letter ID: 0238 Commenter Organization: Sandia Technologies, LLC Comment ID: 23356

Comment: §146.90 (f) Re: Pressure Falloff testing of at least once every 5 years. This is of concern, since annual pressure tests are required for Class I operators, then why is the EPA diluting this requirement. As a consultant, I believe that for the first 5 years of established operation on the well, it should be installed as an annual requirement for Pressure Falloff testing, and thereafter, the operator can request from the Agency for once per 5-years. The behavior of buoyant carbon dioxide suggests more testing and monitoring and not less than Class I wells which have more safeguards present during operations.

Response: EPA believes that a frequency of at least once every five years, as specified at §146.90(f), is an appropriate interval for pressure fall-off testing (particularly given the suite of tests operatorswill perform on the well and the site). EPA clarifies that the Director may require more frequent pressure fall-off tests at a specific project, if necessary based on site-specific circumstances. Pressure fall-off tests may be conducted in conjunction with other well performance tests (i.e., mechanical integrity testing) to ensure safe and effective operations. All monitoring data collected, including information from pressure fall-off tests, will be incorporated in AoR reevaluations, at least every five years.

Commenter Name: Mark Bohrer Letter ID: 0241 Commenter Organization: North Dakota Industrial Commission Comment ID: 23253

Comment: 31. EPA’s proposal would require that owners or operators perform a pressure fall-off test at least once every five years. EPA seeks comment on the use and frequency of pressure fall-off testing for GS wells. EPA Notice 43515.

An initial pressure fall-off test could be required and subsequent tests required at the time the AOR is reevaluated.

Response: EPA believes that a frequency of at least once every five years, as specified at §146.90(f), is an appropriate interval for pressure fall-off testing (particularly given the suite of tests operators will perform on the well and the site). EPA adds that this frequency is the same as that required for AoR reevaluations. EPA clarifies that the Director may require more frequent pressure fall-off tests at a specific project, if necessary based on site-specific circumstances. Pressure fall-off tests may be conducted in conjunction with other well performance tests (i.e., mechanical integrity testing) to ensure safe and effective operations. All monitoring data collected, including information from pressure fall-off tests, will be incorporated in AoR reevaluations, at least every five years.

Letter ID: 0263 Commenter Organization: Interstate Oil & Gas Compact Commission Comment ID: 22817

Comment: III A. 6 Proposed Plume and Pressure Front Monitoring Requirements

FF. EPA seeks comment on the use and frequency of pressure fall-off testing for GS

wells.

IOGCC Response: The IOGCC does not see the necessity of pressure falloff testing for GS wells. It should be used as necessary but not mandated.

Response: EPA disagrees and believes that pressure fall-off testing is necessary for GS wells to ensure the protection of USDWs. 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 regulation 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) to ensure safe and effective operations.

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

### Individual Comments

Commenter Name: Leslie Savage Letter ID: 0122 Commenter Organization: Railroad Commission of Texas (RRC) Comment ID: 24796 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: (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 and/or down-hole CO2 detection tools);

{If there are changes in the first formation overlying the confining zone, the carbon dioxide stream has not been confined.}

Response: The final rule, at §146.90(g), requires owners or operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are required unless the Director determines, based on site-specific geology that such methods are not appropriate

EPA believes that pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume. When combined with information on temperature, pressure data provide an indication of the phase (e.g., gas, supercritical) and distribution of the injected CO2 (73 FR 43515). Monitoring can also identify needed remedial actions, provide inputs for AoR reevaluation modeling, evaluate predictions of plume movement, and target additional geochemical and surface monitoring needs.

EPA adds that owners or operators may consider (or the Director may require) performing additional pressure monitoring in wells that are above the confining zone (e.g., in the same wells used to perform ground water quality monitoring required at §146.90(d)) to provide additional verification that no pressure changes are occurring above the confining zone due to CO2 leakage. The final rule, at §146.90(d), also requires geochemical monitoring above the confining zone.

Commenter Name: John Stormon Letter ID: 0123 Commenter Organization: Washington State Dept. of Ecology Comment ID: 23005 Other EPA Comment Codes and Descriptions: 4655 2.6.5.1 Plume tracking techniques/geophysical methods (seeking comment)

Comment: Monitoring: Direct monitoring of the formations immediately above the confining layer for a geologic sequestration injection zone is an important requirement for the early detection of unacceptable leakage. Monitoring wells installed into this monitoring zone will be quite expensive but should be required for all projects. Geophysical methods and other indirect monitoring, while useful, should not be allowed to substitute for all direct monitoring above the confining layer.

Response: EPA disagrees that pressure monitoring above the confining zone is appropriate. Instead, EPA believes that pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume. The final rule (at §146.90(g)) requires ownersor operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also required unless the Director determines, based on site-specific geology, that such methods are not appropriate.

EPA believes that pressure monitoring within the injection zone is necessary because any such monitoring above the confining zone would not detect movement of the pressure front unless a breach of the confining zone occurs. EPA believes that monitoring using wells in the injection zone (i.e., that penetrate the confining zone) can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that the benefits of monitoring in the injection formation outweigh the manageable risk of those monitoring wells serving as conduits for fluid movement. EPA adds that owners or operators may consider performing additional pressure monitoring in wells that are above the confining zone (e.g., in the same wells used to perform ground water quality monitoring required at §146.90(d)) to provide additional verification that no pressure changes are occurring above the confining zone due to CO2 leakage and that the Director has the authority to require such monitoring under §146.90(i). Monitoring also identifies needed remedial actions, provides inputs for AoR reevaluation modeling, and targets additional geochemical and surface monitoring needs. Knowledge of the location of the CO2 plume and the associated pressure front will assure the public that GS projects are proceeding according to plan, provide sufficient information to the owner or operator and Director, or allow for appropriate actions to address any indication that USDWs may be endangered.

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

Commenter Name: John Stormon Letter ID: 0123 Commenter Organization: Washington State Dept. of Ecology Comment ID: 23006

Comment: The number of wells drilled through the confining layer into the injection zone should be minimized. Each well represents a risk of establishing a pathway for the migration of CO2 or in-situ fluids into shallower aquifers. Projects may be able to get sufficient monitoring data from injection wells to minimize the need for stand-alone injection zone monitoring wells.

Decisions on the level of direct and indirect monitoring should be made on a site by site basis, based upon the geologic characteristics, but some direct monitoring must be required above the confining layer to confirm that indirect monitoring is accurate.

Response: As described above, EPA believes that direct pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume.

EPA believes that monitoring using wells in the injection zone (i.e., that penetrate the confining zone) can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that the benefits of monitoring in theinjection formation outweigh the manageable risk of those monitoring wells serving as conduits for fluid movement. EPA adds that owners or operators may consider performing additional pressure monitoring in wells that are above the confining zone (e.g., in the same wells used to perform ground water quality monitoring required at §146.90(d)) to provide additional verification that no pressure changes are occurring above the confining zone due to CO2 leakage and that the Director has the authority to require such monitoring at §146.90(i). EPA adds that the final rule also requires geochemical monitoring above the confining zone, at §146.90(d).

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. EPA is also developing guidance, available on the same website, on well construction that will include recommendations for monitoring well construction.

In addition, in January 2009, DOE published a best practices manual entitled "Monitoring,Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL311/081508); this manual is included in the docket for the final GS rule.

Commenter Name: John Hanger Letter ID: 0130 Commenter Organization: Pennsylvania Dept. of Env. Protection Comment ID: 21511

Comment: -EPA should identify specific technologies or processes that will enable operators or owners to verify that the CO2 is moving the way in which the models

indicated.

Response: EPA does not believe that prescribing specific technologies to be used in all cases for GS would be appropriate given the variability in sites. Rather, EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the

docket for the final GS rule.

Commenter Name: Christine Reimer Letter ID: 0142 Commenter Organization: National Ground Water Association Comment ID: 22566

Comment: In the injection zone, monitoring must identify the location of the injected CO2 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 CO2 or CO2-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 well. 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.

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. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also required unless the Director determines, based on site-specific geology, that such methods are not appropriate.

EPA believes that pressure monitoring 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, provide inputs 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 sites 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 logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Christine Reimer Letter ID: 0142 Commenter Organization: National Ground Water Association Comment ID: 22571Other EPA Comment Codes and Descriptions: 3530 2.2.3.1 AoR reevaluation frequency (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 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 CO2 during the experimental phase.

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

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

As described above, EPA does not agree that each GS site should have to be permitted as a Class V experimental technology well before being 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.

EPA clarifies that some monitoring frequencies are specified in §146.90; others will be established in the monitoring and testing plan submitted 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 facility 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 logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Directorfor specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Christine Reimer Letter ID: 0142 Commenter Organization: National Ground Water Association Comment ID: 22572 Other EPA Comment Codes and Descriptions: 5460 2.9.2 Comments on transfer of liability 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 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 should be one of the criteria used 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

Response: EPA clarifies that once injection is complete, the owner or operator must monitor as specified in the post-injection site care and site closure plan for at least 50 years (the 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 injection 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 that flexibility is important in developing and implementing a monitoring plan that is appropriately tailored for a specific GS site. The purpose of the requirement at §146.90 to develop site-specific 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 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, 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 regulatory compliance, an owner or operator may be subject to a §1431 response order even after proper site closure 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 present 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. §§ 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.

Commenter Name: James Dooley Letter ID: 0156 Commenter Organization: Joint Global Change Research Institute, Pacific Northwest National Laboratory Comment ID:

22668

Comment: o What if any are the construction requirements and mechanical integrity requirements for monitoring wells?

Response: Construction specifications for monitoring wells must be described in the testing and monitoring plan submitted with the permit application. 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. EPA is also developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in thedocket for the final GS rule.

Commenter Name: James Childress Letter ID: 0158 Commenter Organization: Gasification Technologies Council (GTC) Comment ID: 23775 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: §146.90 Testing and monitoring requirements. (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 and/or down-hole carbon dioxide detection tools); -

We recommend deletion of this requirement in its entirety and replacing with "Testing and monitoring to track the extent of the carbon dioxide plume." Tracking the precise position of a moving pressure front will require a large number of expensive and deeply located probes. A limited number of pressure monitors that can provide information on pressures affecting the confinement layers are more valuable. The Proposed Rule also requires well owners to monitor periodically groundwater quality and geochemical changes above the confining zone. The requirements for such deep monitor wells could be costly. Requiring both pressure and geochemical monitoring will be costly and provide questionable additional information or warning.

Response: EPA maintains that plume tracking and pressure monitoring are key components of monitoring at GS sites. A rigorous plume tracking and pressure monitoring scheme, such as one that meets the requirements at §146.90(g), is imperative for ensuring that the CO2 plume is contained within the injection zone.

The final rule (at §146.90(g)) requires owners or operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also required unless the Director determines, based on site-specific geology, that such methods are not appropriate

Pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume. When combined with information on temperature, pressure data provide an indication of the phase (e.g., gas, supercritical) and distribution of the injected CO2 (73 FR 43515). Monitoring can also identify needed remedial actions, provide inputs for AoR reevaluation modeling, evaluate predictions of plume movement, and target additional geochemical and surface monitoring needs.

EPA recognizes that installation of monitoring wells entails additional resources. However, the Agency believes that such monitoring is necessary to ensure that GS projects are appropriately operated and monitored and to protect USDWs from endangerment. 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, provide inputs 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 associatedpressure front will assure the public that GS projects are proceeding according to plan, provide sufficient information to the owner or operator and Director, or allow for appropriate actions to address any indication that USDWs may be endangered.

The combination of site characterization and predictive modeling will help guide the siting ofmonitoring wells and enable operators to optimize the number and position of wells. The Directorapproved testing and monitoring plan will describe the use and installation of monitoring wells at the

site.

EPA acknowledges the commenters' concern about the cost of pressure monitoring. However, EPA believes that this monitoring is essential for protection of USDWs at GS sites Although a significant cost in absolute terms, monitoring costs are expected to be a small fraction of site operating costs, according to EPA's cost analysis for the GS rulemaking (which is available in the docket).

Commenter Name: Michael Mudd Letter ID: 0167 Commenter Organization: FutureGen Alliance (FGIA) Comment ID: 22472

Comment: A-6 Proposed Plume and pressure Front Monitoring III-A-6 Page 102. Pressure gauges placed in the first formation overlying the confining zone would not be useful for tracking the lateral migration of the CO2 plume or pressure front. Would EPA require monitoring wells that penetrate through the confining zone and into the storage formation for this purpose?

Fiber optic pressure and temperature sensors are likely to be prohibitively expensive.

Response: EPA has revised this requirement in the final rule. Instead, the final GS regulation, at §146.90(g)(1), requires all GS project owners or operators to monitor for pressure changes in the injection zone. EPA believes that pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume.

Pressure monitoring within the injection zone is necessary because any such monitoring above the confining zone would not detect movement of the pressure front unless a breach of the confining zone occurs. EPA believes that monitoring using wells in the injection zone (i.e., that penetrate the confining zone) can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that the benefits of monitoring in the injection formation outweigh the manageable risk of those monitoring wells serving as conduits for fluid movement. EPA adds that owners or operators may consider performing additional pressure monitoring in wells that are above the confining zone (e.g., in the same wells used to perform ground water quality monitoring required at §146.90(d)) to provide additional verification that no pressure changes are occurring above the confining zone due to CO2 leakage. Monitoring also identifies needed remedial actions, provides inputs for AoR reevaluation modeling, and targets additional geochemical and surface monitoring needs. Knowledge of the location of the CO2 plume and the associated pressure front will assure the public that GS projects are proceeding according to plan, provide sufficient information to the owner or operator and Director, or allow for appropriate actions to address any indication that USDWs may be endangered.

EPA acknowledges that, at certain sites, there may be a need for additional or different monitoring schemes (which may include monitoring in the confining zone), and adds that it is important tobalance the need for adequate monitoring that ensures USDW protection from endangerment againsttoo many artificial penetrations which could serve as conduits for fluid migration. EPA expects sitespecific testing and monitoring plans to describe the proposed monitoring regime, which must be approved by the Director.

EPA does not believe that prescribing specific technologies to be used in all cases for GS would be appropriate given the variability in sites. Rather, EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the

docket for the for the final GS rule.

EPA acknowledges the commenters' concern about the cost of monitoring. However, EPA believes that monitoring is essential for protection of USDWs at GS sites. Although a significant cost in absolute terms, monitoring costs are expected to be a small fraction of site operating costs, according to EPA's cost analysis for the GS rulemaking (which is available in the docket).

Commenter Name: Michael J. Miller Letter ID: 0168 Commenter Organization: Electric Power Research Institute (EPRI) Comment ID: 22492 Other EPA Comment Codes and Descriptions: 3300 2.2.1 Delineating the AoR/Modeling CO2

movement
Comment: Preamble, page 43505: "The confining system should be of sufficient regional thickness and lateral extent to contain the entire CO2 plume and associated pressure front under the confining system following the plume’s maximum lateral expansion."

EPRI COMMENT #2: The criteria for defining the leading edge of the plume and associated pressure front are not specified in the rule, nor is the basis for determining if these criteria are met -- physical measurement or numerical computation. In either case, what minimum change in pressure from background will EPA use to define the location of the pressure front? Will the lateral extent of the CO2 plume be defined by the leading edge of the dissolved plume or free-phase portion of the plume? Given the difficulties in defining and measuring the leading edge of the plume and pressure front, EPRI believes that the technical focus should be on demonstrating caprock containment, rather than tracking fronts.

Response: EPA agrees that demonstrating cap rock containment is an important technical focal point for permitting Class VI wells, however the Agency also believes that it is important to know the extent of the CO2 plume and pressure front to ensure cap rock integrity and protection of USDWs.

EPA clarifies that the pressure front (defined at §146.81) is the zone of elevated pressure that iscreated by the injection of CO2 into the subsurface. The pressure front of a CO2 plume refers to a zone where there is a pressure differential sufficient to cause the movement of injected fluids or formation fluids into a USDW. The pressure front includes all areas wherein pressure is great enough to cause fluid movement into a USDW if a conduit were to exist.

The calculation of the threshold pressure that defines the edge of the pressure front is dependent on properties of the injection and confining zones, including permeability, porosity, and compressibility, the distance between the injection zone and the lowermost USDW, and operational conditionsincluding injection pressure and rate. For these reasons, the definition of the pressure front is siteand project-specific, and a single pressure value can not be provided for all sites. EPA is developing guidance on AoR and corrective action at GS Class VI sites to assist owners or operators and Directors in evaluating requirements and proposed AoR and corrective action plans under 146.84. The guidance describes EPA's recommended approaches for the data to be considered in an initial AoR delineation, how to apply computational modeling to delineate the AoR, 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_sequestration.cfm.

EPA is also developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, which will include discussion of identifying the extent of the CO2 plume. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this

manual is included in the docket for the for the final GS rule.

Commenter Name: Theresa Pugh Letter ID: 0169 Commenter Organization: American Public Power Association Comment ID: 23423

Comment: Plume and pressure front monitoring- Because of APPA’s inextricable link to the municipal water utilities, we fully appreciate the importance of accurate monitoring of the plume and pressure front. Id. at 43514. APPA defers to AWWA to comment on monitoring and frequency of monitoring requirements. APPA believes that most early projects will likely monitor far more often than will be unnecessary as more information is gained regarding the accuracy of initial modeling.

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

EPA believes that monitoring data should be used to review model assumptions, verify computational model projections, and, when necessary, provide input for model refinements. As data are collected at an injection site, model parameters can be adjusted to match observations (i.e., for model calibration 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 effectiveAoR reevaluations and leading to improved model predictions and changes to an owner and operators testing and monitoring plan.

Commenter Name: Kyle Isakower Letter ID: 0170 Commenter Organization: American Petroleum Institute Comment ID: 24194 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 149.90(g)

API Comments: (g) Testing and monitoring AS APPROPRIATE TO SUPPORT THE MODEL FOR

totrackING 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 and/or down-hole carbon dioxide detection tools);

Rationale: Monitoring outside of the injection zone provides little information of value for tracking and monitoring the injected plume. Examples of how to test

and monitor could be included in the Preamble but need not be included in the

rule itself.

Response: EPA has revised this requirement in the final rule. The final GS regulation, at §146.90(g)(1), requires all GS project owners or operators to monitor for pressure changes in the injection zone. EPA believes that pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume.

Pressure monitoring within the injection zone is necessary because any such monitoring above the confining zone would not detect movement of the pressure front unless a breach of the confining zone occurs. EPA believes that monitoring using wells in the injection zone (i.e., that penetrate the confining zone) can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that the benefits of monitoring in the injection formation outweigh the manageable risk of those monitoring wells serving as conduits for fluid movement. EPA adds that owners or operators may consider performing additional pressure monitoring in wells that are above the confining zone (e.g., in the same wells used to perform ground water quality monitoring required at §146.90(d)) to provide additional verification that no pressure changes are occurring above the confining zone due to CO2 leakage. Monitoring also identifies needed remedial actions, provides inputs for AoR reevaluation modeling, and targets additional geochemical and surface monitoring needs. Knowledge of the location of the CO2 plume and the associated pressure front will assure the public that GS projects are proceeding according to plan, provide sufficient information to the owner or operator and Director, or allow for appropriate actions to address any indication that USDWs may be endangered.

EPA acknowledges that, at certain sites, there may be a need for more or different monitoring schemes (which may include monitoring in the confining zone), and adds that it is important to balance the need for adequate monitoring that ensures USDW protection from endangerment againsttoo many artificial penetrations which could serve as conduits for fluid migration. EPA expects sitespecific testing and monitoring plans to describe the proposed monitoring regime, which must beapproved by the Director. Flexibility is also provided regarding how to monitor for the specific data required by the final rule. The testing and monitoring plan is developed by the owner or operator in consultation with the Director and is designed to ensure that a detailed, Director-approved document describing how monitoring will be conducted during the lifetime of the project exists.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Kyle Isakower Letter ID: 0170 Commenter Organization: American Petroleum Institute Comment ID: 24247

Comment: Rule Provisions: 146.90 EPA Preamble Question: 30. EPA seeks comment on the requirement for monitoring of GS sites for the purpose of tracking the location of the CO2 plume and associated pressure front over time. EPA Notice 43514

API Response: The frequency of monitoring should be dictated by site-specific operational and geologic conditions combined with the results of monitoring with model predictions. The guiding principle for monitoring is to verify proper confinement of the CO2 and ensure protection of USDWs. EPA should recognize that use of modeling and other monitoring techniques are relatively qualitative processes that can have varying degrees of accuracy that will improve over time in an iterative process.

Response: The GS rule stipulates that the monitoring frequency and spatial distribution of monitoring wells must be based on baseline geochemical data that were collected during the initial site characterization and the area of review evaluation (§146.90(d)(2)). The details of thegeochemical monitoring will be based on site-specific information and described in the Directorapproved testing and monitoring plan.

EPA adds that the iterative process of monitoring, modeling, and AoR reevaluation is appropriate to verify that the CO2 plume and pressure front are moving through the subsurface as predicted, verify the accuracy of the delineation model (or identify needed changes), and refine testing and monitoring activities to ensure that USDWs are protected from endangerment and that there would be adequate warning of potential problems at the site before any endangerment could occur.

Commenter Name: Kyle Isakower Letter ID: 0170 Commenter Organization: American Petroleum Institute Comment ID: 24249 Other EPA Comment Codes and Descriptions: 4655 2.6.5.1 Plume tracking techniques/geophysical methods (seeking comment)

Comment: Rule Provisions: 146.90(g) EPA Preamble Question: 32. Based on information evaluated to date, EPA believesthat tracking the plume and pressure front is an important companion step to address any uncertainties associated with initial AoR modeling and requests comment on this approach and more efficient alternatives that may be used to track the plume and pressure front. EPA Notice 43516.

API Response: Based on experience to date, CO2 plume can be monitored using surface or wellbore seismic and possibly some remote satellite techniques. Monitoring of the pressure front will be more difficult since that requires data from the injection formation that can only be obtained by drilling a well (which introduces additional artificial penetrations into the containment system). Modeling can estimate the movement of a pressure front. Those estimations are limited by the accuracy of the model and its iterative adjustments as previously

mentioned.

EPA should note that plume and pressure front are different concepts and should not be confused. They yield information on two different metrics. One tells you about the remaining capacity of the storage formation and the other describes the direction and movement of the CO2 plume.

Response: EPA believes that direct pressure measurements are appropriate and that direct pressure monitoring will be feasible at all 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. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also required unless the Director determines, based on site-specific geology, that such methods are not appropriate.

EPA believes that pressure monitoring 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, provide inputs 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 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 agrees that geophysical (e.g., seismic) methods are useful for plume tracking at GS sites. Remote sensing methods (e.g., PSInSAR) may also prove to be useful. Such methods may be an important component of plume tracking at some GS sites. For this reason, the final rule (at §146.90(g)) requires the use of indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) unless the Director determines, based on site-specific geology, that such methods are not appropriate.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, which will include discussion of identifying the extent of the CO2 plume and pressure front. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. Inaddition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this

manual is included in the docket for the for the final GS rule.

Commenter Name: Robert J. Finley Letter ID: 0180 Commenter Organization: Illinois State Geological Survey Comment ID: 23640

Comment: 146.90

(g)

Tracking of the pressure front needs to be further considered. What tools are suggested for tracking a pressure front in a saline reservoir other than direct measurement at a wellbore? Should the primary seal over a saline reservoir be further penetrated by wellbores just to obtain these data? What detection limits apply to the leading edge of a pressure gradient that are acceptable for monitoring? None of the indirect geophysical techniques listed are sensitive to in-zone pressure changes in a single phase reservoir.

The monitoring option suggested in this section is a questionable option. If the confining zone is maintaining the desired integrity, then monitoring in the first formation overlying the confining zone should not show any pressure changes and hence will not inform as to the position of the pressure front or the CO2 plume (via sampling). Only if the confining zone fails will this be viable. Further, the "first formation" overlying the confining zone may not be suitable for any monitoring if it has little or no effective porosity and suitable permeability. The implication is that you are proposing monitoring in a suitable (permeable) rock interval above the confining zone, but that may not be in the first stratigraphically defined formation.

Are there stress or tilt sensors that be installed in a wellbore or at the surface that can indirectly detect a pressure front in the receiving reservoir? What is their resolution and how does that apply in a regulatory context? Surface tiltmeters are do not work in all situations, dependent on bedrock rigidity and surface soil conditions/thickness.

Also, what is the definition of the CO2 plume boundary? Is it a given saturation over a given thickness? Is it any detectable amplitude brightening on a reflection seismic image or other geophysical indication?

Response: EPA has revised the pressure monitoring requirement for the final rule. EPA believes that direct pressure measurements are appropriate and that direct pressure monitoring will be feasible at all 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. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also required unless the Director determines, based on site-specific geology, that such methods are not appropriate.

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

EPA believes that geophysical (e.g., seismic) methods are useful for plume tracking at GS sites. Remote sensing methods and tiltmeters may also prove to be useful, but are not specified in the final regulation. Such methods may be an important component of plume tracking at some GS sites. For this reason, the final rule at §146.90(g) requires the use of indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) unless the Director determines, based on site-specific geology that such methods are not appropriate.

In response to comments regarding the pressure front at GS sites, EPA clarifies that the pressure front (defined at §146.81) is the zone of elevated pressure that is created by the injection of CO2 into the subsurface. The pressure front of a CO2 plume refers to a zone where there is a pressure differential sufficient to cause the movement of injected fluids or formation fluids into a USDW. The pressure front includes all areas wherein pressure is great enough to cause fluid movement into a USDW if a conduit were to exist. The calculation of the threshold pressure that defines the edge of the pressure front is dependent on properties of the injection and confining zones, including permeability, porosity, and compressibility, the distance between the injection zone and the lowermost USDW, and operational conditions including injection pressure and rate. For these reasons, the definition of the pressure front is site- and project-specific, and a single pressure value can not be provided for all sites.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, which will include discussion of identifying the extent of the CO2 plume and pressure front and the use of tiltmeters. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the

docket for the for the final GS rule.

Commenter Name: Bradley J. Field Letter ID: 0186 Commenter Organization: New York State Dept. of Environmental Conservation

Div. of Mineral Resources Comment ID:

25201

Comment: CC. EPA seeks comment on the requirement for monitoring of GS sites for the purpose of tracking the location of the CO2 plume and associated pressure front

over time.

NYSDEC-DMN Response: NYSDEC-DMN is in favor of the EPA requiring an operator to conduct ongoing and sufficient monitoring to allow the tracking the CO2 plume and associated pressure front. In addition to any regular reporting frequency,an operator should be required to provide notification whenever actual conditions vary significantly from modeled predictions.

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

EPA notes that the results of monitoring to track the plume and pressure front are to be incorporated into the reevaluation of the AoR, which must be conducted at least once every 5 years under §146.84(e). EPA expects the monitoring results to be used to refine the AoR model.

Commenter Name: Robert F. Van Voorhees Letter ID: 0190 Commenter Organization: Carbon Sequestration Council Comment ID: 24355

Comment: 1. Monitoring CO2 Movement and Reservoir Pressure

The preamble to the proposed rule specifically states that the "[m]onitoring of subsurface geochemistry and the position of the CO2 plume and pressure front are necessary to verify predictions of plume movement, provide inputs for modeling, identify needed corrective actions, and target geochemical and surface monitoring activities." 73 Fed. Reg. at 43514. Again, this is inconsistent with experience with Class I hazardous waste injection, where such monitoring has not been necessary and is not required.

Response: EPA disagrees that plume and pressure front monitoring are not justified for Class VI wells. The Agency recognizes that while there are similarities between injection of wastes for disposal (Class I) and GS (Class VI), there are significant differences as well. Important unique considerations for GS include the buoyancy of CO2, its corrosivity when in contact with water, its low viscosity (i.e., high mobility), and the very large injection volumes that are anticipated. There is also a degree of uncertainty regarding the behavior of large volumes of CO2 in the subsurface after injection. Given these characteristics of anticipated GS projects, EPA believes that plume and pressure front monitoring at §146.90(g) are justified to provide early warning of any unforeseen fluid movement that might endanger USDWs.

The final rule (at §146.90(g)) requires owners or operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also 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, provide inputs 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.Commenter Name: Robert F. Van Voorhees Letter ID: 0190 Commenter Organization: Carbon Sequestration Council Comment ID: 24483 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90(g)

Proposed CCS Group Recommendations: (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 and/or down-hole carbon dioxide detection tools);

Basis for CCS Group Comments: Monitoring outside of the injection zone provides little information of value for tracking and monitoring the injected plume. Examples of how to test and monitor could be included in the Preamble but need

not be included in the rule itself.

Response: EPA has revised this requirement in the final rule. The final GS regulation, at §146.90(g)(1), requires all GS project owners or operators to monitor for pressure changes in the injection zone. EPA believes that pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume.

Pressure monitoring within the injection zone is necessary because any such monitoring above the confining zone would not detect movement of the pressure front unless a breach of the confining zone occurs. EPA believes that monitoring using wells in the injection zone (i.e., that penetrate the confining zone) can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that the benefits of monitoring in the injection formation outweigh the manageable risk of those monitoring wells serving as conduits for fluid movement. EPA adds that owners or operators may consider performing additional pressure monitoring in wells that are above the confining zone (e.g., in the same wells used to perform ground water quality monitoring required at §146.90(d)) to provide additional verification that no pressure changes are occurring above the confining zone due to CO2 leakage. Monitoring also identifies needed remedial actions, provides inputs for AoR reevaluation modeling, and targets additional geochemical and surface monitoring needs. Knowledge of the location of the CO2 plume and the associated pressure front will assure the public that GS projects are proceeding according to plan, provide sufficient information to the owner or operator and Director, or allow for appropriate actions to address any indication that USDWs may be endangered.

EPA acknowledges that, at certain sites, there may be a need for more or different monitoring schemes (which may include monitoring in the confining zone), and adds that it is important to balance the need for adequate monitoring that ensures USDW protection from endangerment against too many artificial penetrations which could serve as conduits for fluid migration. Site-specific testing and monitoring plans should describe the proposed monitoring regime, which must be approved by the Director. Flexibility is also provided regarding how to monitor for the specific data required by the final rule. The testing and monitoring plan is developed by the owner or operator in consultation with the Director and is designed to ensure that a detailed, Director-approved document describing how monitoring will be conducted during the lifetime of the project exists.EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Robert F. Van Voorhees Letter ID: 0190 Commenter Organization: Carbon Sequestration Council Comment ID: 24539

Comment: Rule Provisions or Federal Register Cite: 146.90 EPA Preamble Question: 30. EPA seeks comment on the requirement for monitoring of GS sites for the purpose of tracking the location of the CO2 plume and associated pressure front over time. EPA Notice 43514

CSC Response: The amount of monitoring required to track plumes and pressure fronts is not cost justified in comparison with taking the necessary steps to demonstrate containment. The primary focus should be on making sure that the plume and formation fluid are contained within the injection zone rather than trying to show the exact location of the plume within that containment.

The frequency of monitoring should be dictated by site-specific operational and geologic conditions combined with the results of monitoring. .

Response: EPA clarifies that all of the monitoring requirements in the GS rule are for the purpose of ensuring containment so that USDWs are protected from endangerment. EPA believes that knowing the extent of the CO2 plume and pressure front is necessary to make such a determination. Monitoring can also identify needed remedial actions, provide inputs for AoR reevaluation modeling, evaluate predictions of plume movement, and target additional geochemical and surface monitoring needs. Knowledge of the location of the CO2 plume and the associated pressure front will assure the public that GS projects are proceeding according to plan, provide sufficient information to the owner or operator and Director, or allow for appropriate actions to address any indication that USDWs may be endangered.

Pressure monitoring within the injection zone is necessary because any such monitoring above the confining zone would not detect movement of the pressure front unless a breach of the confining zone occurs. EPA believes that monitoring using wells in the injection zone (i.e., that penetrate the confining zone) can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that the benefits of monitoring in the injection formation outweigh the manageable risk of those monitoring wells serving as conduits for fluid movement. EPA adds that owners or operators may consider performing additional pressure monitoring in wells that are above the confining zone (e.g., in the same wells used to perform ground water quality monitoring required at §146.90(d)) to provide additional verification that no pressure changes are occurring above the confining zone due to CO2 leakage.

EPA adds that all monitoring will be conducted pursuant to the approved testing and monitoringplan, which should be based on site-specific information about the site and planned operations.

Commenter Name: Robert F. Van Voorhees Letter ID: 0190 Commenter Organization: Carbon Sequestration Council Comment ID: 24541 Other EPA Comment Codes and Descriptions: 4655 2.6.5.1 Plume tracking techniques/geophysical methods (seeking comment)

Comment: Rule Provisions or Federal Register Cite: 146.90(g) EPA Preamble Question: 32. Based on information evaluated to date, EPA believes that tracking the plume and pressure front is an important companion step to address any uncertainties associated with initial AoR modeling and requests comment on this approach and more efficient alternatives that may be used to track the plume and pressure front. EPA Notice 43516.

CSC Response: Uncertainties associated with AoR determinations may be addressed through the use of a conservative modeling approach. Requirements to "track" plumes or pressure fronts would be extraordinarily burdensome and are not necessary, as extensive experience with "no migration" exemptions for hazardous waste injection wells has shown.

Response: EPA disagrees that plume and pressure front monitoring are not justified for Class VI wells. The Agency recognizes that while there are similarities between injection of hazardous wastes for disposal (Class I) and GS (Class VI), there are significant differences as well. Important unique considerations for GS include the buoyancy of CO2, its corrosivity when in contact with water, its low viscosity (i.e., high mobility), and the very large injection volumes that are anticipated. There is also a degree of uncertainty regarding the behavior of large volumes of CO2 in the subsurface after injection. Given these characteristics of anticipated GS projects, EPA believes that plume and pressure front monitoring at §146.90(g) are justified to provide early warning of any unforeseen fluid movement that might endanger USDWs.

The final rule (at §146.90(g)) requires owners or operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also 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, provide inputs 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.

Commenter Name: Craig R. Walters Letter ID: 0200 Commenter Organization: Anadarko Petroleum Corporation Comment ID: 24600

Comment: Rule Provisions: 146.90 EPA Rule Issue: 30. EPA seeks comment on the requirement for monitoring of GS sites for the purpose of tracking the location of the CO2 plume and associatedpressure front over time. EPA Notice 43514

Anadarko Petroleum Corporation (APC) Response: The frequency of monitoring should be dictated by site-specific operational and geologic conditions combined with the results of monitoring with model predictions and should be set at the permit approval stage. The guiding principle for monitoring is to verify proper confinement of the CO2 and ensure protection of USDWs. EPA should recognize that use of modeling and other monitoring techniques are relatively qualitative processes that can have varying degrees of accuracy that will improve over time in an iterative process, and EPA should provide regulatory flexibility to

account for this.

Response: EPA clarifies that all of the monitoring requirements in the GS rule are for the purpose of ensuring containment so that USDWs are protected from endangerment. EPA believes that knowing the extent of the CO2 plume and pressure front is necessary to make such a determination. Monitoring can also identify needed remedial actions, provide inputs for AoR reevaluation modeling, evaluate predictions of plume movement, and target additional geochemical and surface monitoring needs. Knowledge of the location of the CO2 plume and the associated pressure front will assure the public that GS projects are proceeding according to plan, provide sufficient information to the owner or operator and Director, or allow for appropriate actions to address any indication that USDWs may be endangered.

Pressure monitoring within the injection zone is necessary because any such monitoring above the confining zone would not detect movement of the pressure front unless a breach of the confining zone occurs. EPA believes that monitoring using wells in the injection zone (i.e., that penetrate the confining zone) can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that the benefits of monitoring in the injection formation outweigh the manageable risk of those monitoring wells serving as conduits for fluid movement. EPA adds that owners or operators may consider performing additional pressure monitoring in wells that are above the confining zone (e.g., in the same wells used to perform ground water quality monitoring required at §146.90(d)) to provide additional verification that no pressure changes are occurring above the confining zone due to CO2 leakage.

EPA adds that all monitoring will be conducted pursuant to the approved testing and monitoring plan, which should be based on site-specific information about the site and planned operations.

Commenter Name: Craig R. Walters Letter ID: 0200 Commenter Organization: Anadarko Petroleum Corporation Comment ID: 24602 Other EPA Comment Codes and Descriptions: 4655 2.6.5.1 Plume tracking techniques/geophysical methods (seeking comment)

Comment: Rule Provisions: 146.90(g) EPA Rule Issue: 32. Based on information evaluated to date, EPA believes that tracking the plume and pressure front is an important companion step to address any uncertainties associated with initial AoR modeling and requests comment on this approach and more efficient alternatives that may be used to track the plume and pressure front. EPA Notice 43516.

Anadarko Petroleum Corporation (APC) Response: Plume and pressure front aredifferent concepts and should not be confused. They yield information on two different metrics. The former tells you about the remaining capacity of the storage formation and the latter describes the direction and movement of the CO2 plume. Based on experience to date, CO2 plume can be monitored using surface or wellbore seismic and possibly some remote satellite techniques. Monitoring of the pressure front will be more difficult since that requires data from the injection formation which can only be obtained by drilling a well. Modeling can estimate the movement of a pressure front. Those estimations are limited by the accuracy of the model and its iterative adjustments as previously mentioned.

Response: EPA acknowledges that monitoring the plume and pressure front are different issues and believes that direct pressure measurements are appropriate and that direct pressure monitoring will be feasible at all 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. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also required unless the Director determines, based on site-specific geology, that such methods are not appropriate.

EPA believes that pressure monitoring 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, provide inputs 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 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.

Commenter Name: Craig R. Walters Letter ID: 0200 Commenter Organization: Anadarko Petroleum Corporation Comment ID: 24707 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90(g)

Anadarko Petroleum Corporation (APC) Comments: (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 and/or down-hole carbon dioxide detection tools);

Rationale: See 146.90(c)(1 thru 4 and 7)

Monitoring outside of the injection zone provides little information of value for tracking and monitoring the injected plume. Examples of how to test and

monitor could be included in the Preamble but need not be included in the rule

itself.

Response: EPA believes that direct pressure measurements are appropriate and the final rule (at §146.90(g)) requires owners or operators to perform monitoring to track the extent of the CO2 plumeand pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also required unless the Director determines, based on site-specific geology, that such methods are not appropriate.

EPA believes that pressure monitoring 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, provide inputs 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 assure the public that GS projects are proceeding according to plan, provide sufficient information to the owner or operator and Director, or allow for appropriate actions to address any indication that USDWs may be endangered.

EPA acknowledges that, at certain sites, there may be a need for more or different monitoring schemes (which may include monitoring in the confining zone), and adds that it is important to balance the need for adequate monitoring that ensures USDW protection from endangerment against too many artificial penetrations which could serve as conduits for fluid migration. Site-specific testing and monitoring plans should describe the proposed monitoring regime, which must be approved by the Director. Flexibility is also provided regarding how to monitor for the specific data required by the final rule. The testing and monitoring plan is developed by the owner or operator in consultation with the Director and is designed to ensure that a detailed, Director-approved document describing how monitoring will be conducted during the lifetime of the project exists.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, which will include discussion of identifying the extent of the CO2 plume and pressure front. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this

manual is included in the docket for the final GS rule.

Commenter Name: Richard Guinn Letter ID: 0210 Commenter Organization: Eastman Chemical Company Comment ID: 22725

Comment: §146.90 Testing and monitoring requirements. (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 and/or down-hole carbon dioxide detection tools);"

We recommend deletion of this requirement in its entirety and replacing with "Testing and monitoring to track the extent of the carbon dioxide plume." Tracking the precise position of a moving pressure front will require a large number of expensive and deeply located probes. A limited number of pressuremonitors that can provide information on pressures affecting the confinement layers are more valuable. The Proposed Rule also requires well owners to monitor periodically groundwater quality and geochemical changes above the confining zone. The requirements for such deep monitor wells could be costly. Requiring both pressure and geochemical monitoring will be costly and provide questionable additional information or warning.

Response: EPA maintains that plume tracking and pressure monitoring are key components of monitoring at GS sites. A rigorous plume tracking and pressure monitoring scheme, such as one that meets the requirements at §146.90(g), is imperative for ensuring that the CO2 plume is contained within the injection zone. Pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume. When combined with information on temperature, pressure data provide an indication of the phase (e.g., gas, supercritical) and distribution of the injected CO2 (73 FR 43515). Monitoring can also identify needed remedial actions, provide inputs for AoR reevaluation modeling, evaluate predictions of plume movement, and target additional geochemical and surface monitoring needs.

EPA recognizes that installation of monitoring wells entails additional resources. However, the Agency believes that such monitoring is necessary to ensure that GS projects are appropriately operated and monitored and to protect USDWs from endangerment. Knowledge of the location of the CO2 plume and the associated pressure front will assure the public that GS projects are proceeding according to plan, provide sufficient information to the owner or operator and Director, or allow for appropriate actions to address any indication that USDWs may be endangered.

Commenter Name: John King Letter ID: 0211 Commenter Organization: Shell Exploration and Production Company (SEPCo) Comment ID:

22778

Comment: 1. Monitoring CO2 Movement and Reservoir Pressure

The preamble to the proposed rule specifically states that the "[m]onitoring of subsurface geochemistry and the position of the CO2 plume and pressure front are necessary to verify predictions of plume movement, provide inputs for modeling, identify needed corrective actions, and target geochemical and surface monitoring activities." 73 Fed. Reg. at 43514. Again, this is an assertion that cannot be reconciled with experience with Class I hazardous waste injection, where such monitoring has never been considered necessary and is not required.

Response: EPA disagrees that plume and pressure front monitoring are not justified for Class VI wells. The Agency recognizes that while there are similarities between injection of wastes for disposal (Class I) and GS (Class VI), there are significant differences as well. Important unique considerations for GS include the buoyancy of CO2, its corrosivity when in contact with water, its low viscosity (i.e., high mobility), and the very large injection volumes that are anticipated. There is also a degree of uncertainty regarding the behavior of large volumes of CO2 in the subsurface after injection. Given these characteristics of anticipated GS projects, EPA believes that plume and pressure front monitoring at §146.90(g) are justified to provide early warning of any unforeseen fluid movement that might endanger USDWs.

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 forpressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also required unless the Director determines, based on site-specific geology, that such methods are not appropriate.

EPA believes that pressure monitoring 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, provide inputs 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.

Commenter Name: Andrew Duguid Letter ID: 0226 Commenter Organization: Schlumberger Carbon Services Comment ID: 23999 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: 4. Schlumberger supports the concept of testing and monitoring to track the CO2 plume and the associated pressure front. We feel that without this monitoring the validation and updating of the models used to predict the size and shape of the AOR cannot be properly conducted and that the use of models to predict the size and shape of the AOR will be ineffective. However we feel that the language in section 146.90(g) is too restrictive. The current language states:

(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 and/or down-hole carbon dioxide detection tools);

We feel that the restrictions placed in this language could adversely impact the efficiency of monitoring and modeling depending on site conditions. Schlumberger proposes the following alternate language:

(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, using geophysical techniques (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole carbon dioxide detection tools), other techniques that are approved by the director or a combination of techniques if multiple techniques are deemed necessary by the director;

Response: EPA has revised this requirement in the final rule. The final GS regulation, at §146.90(g)(1), requires all GS project owners or operators to monitor directly for pressure changes in the injection zone. EPA believes that pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume. In addition, §146.90(g)(2) requires owners or operators to track the position of the CO2 plume using indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools), unless the Director determines based on site-specific geology, that such methods are not appropriate.EPA is affording Director's discretion regarding the use of geophysical techniques at some sites because the Agency recognizes that geophysical methods are not appropriate in all geologic settings. EPA clarifies that this determination will be made by the Director based on the site-specific geologic information submitted by the owner or operator with their permit application.

EPA believes that this approach provides flexibility to develop a site-specific monitoring plan, ensures that direct monitoring is available to track the movement of the CO2 and validate models, and recognizes that indirect techniques are not appropriate in all situations. The owner or operator's approved testing and monitoring plan will include the site-specific details, technologies, testing and monitoring frequencies, and other pertinent information.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Andrew Duguid Letter ID: 0226 Commenter Organization: Schlumberger Carbon Services Comment ID: 24059 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Proposed Rule: (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;

Schlumberger Suggested Revision: (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 relevant factors as warranted by a risk-assessment;

Schlumberger Rationale: The monitoring should be designed to reduce risk

Response: EPA agrees that monitoring plans and methods need to be site-specific and believes that the monitoring requirements for GS sites at §146.90 provide an appropriate level of flexibility in structuring a testing and monitoring plan that protects USDWs from endangerment. EPA retains therequirement regarding placement of monitoring wells, but adds that any additional relevant sitespecific information must be considered in the development of the testing and monitoring plan to ensure USDW protection 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 logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Directorfor specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Andrew Duguid Letter ID: 0226 Commenter Organization: Schlumberger Carbon Services Comment ID: 24063 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Proposed Rule: (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 and/or down-hole carbon dioxide detection tools);

Schlumberger Suggested Revision: (g) Testing and monitoring to track the extent of the carbon dioxide plume and the position of the pressure front.

Schlumberger Rationale:Monitoring outside of the injection zone provides little information of value for tracking and monitoring the injected plume. Examples of

how to test and monitor could be included in the Preamble.

Response: As described above, EPA has revised this requirement in the final rule. The final GS regulation, at §146.90(g)(1), requires all GS project owners or operators to monitor directly for pressure changes in the injection zone. EPA believes that pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume. In addition, §146.90(g)(2) requires owners or operators to track the position of the CO2 plume using indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools), unless the Director determines based on site-specific geology, that such methods are not appropriate.

Commenter Name: Steven B. Corneli Letter ID: 0234 Commenter Organization: NRG Energy, Inc. Comment ID: 23170

Comment: data would be needed to verify the model predictions. In particular, it is impractical and cost prohibitive to measure the exact location of the CO2 plume and pressure front using monitor wells. The monitor wells would be very expensive to install and may create a potential pathway for migration of CO2. In addition, plume or pressure front monitoring have never been necessary or required under the Class I hazardous waste injection well program because experience has shown that it is not necessary to verify the model predictions.

Response: 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, provide inputs 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 believes that monitoring using wells in the injection zone, e.g., for pressure monitoring as required at §146.90(g)(1), can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that properly constructed monitoring wells will be a safe way to obtain the data that is essential to ensure that the injected CO2 remains confined in the injection zone and that pressure changes are not causing movement of formation or other fluids. 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.

To mitigate the risk of fluid movement, EPA requires owners and operators to submit a testing and monitoring plan that describes how the owner or operator plans to site and construct monitoring

wells.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

EPA acknowledges the commenters' concern about the cost of monitoring. However, EPA believes that monitoring is essential for protection of USDWs at GS sites. Although a significant cost in absolute terms, monitoring costs are expected to be a small fraction of site operating costs, according to EPA's cost analysis for the GS rulemaking (which is available in the docket).

Commenter Name: Philip Papadeas Letter ID: 0238 Commenter Organization: Sandia Technologies, LLC Comment ID: 23357

Comment: §146.90 (g) Re: Monitoring saline intervals above the Confining Zone. This monitoring approach may provide risk to USDWs, if monitor wells are drilled and installed, and adds significant burden, cost to the operator and uncertainties to the geologic system. One key question is however, what if no permeable intervals are present to monitor? Does one monitor saline intervals, or shallow fresh water wells? The UIC program has worked well for many years with a stringent continuous cemented wellbore, and no migration of fluid as determined from annual testing, and operational pressure monitoring of the injection interval.

Close monitoring of injection pressure, and annual pressure falloff data will supercede a dedicated monitor well where pressure anomalies may exist due to pressure or some distant fluid injection or withdrawal in the shallow subsurface. In areas of depleted reservoirs or drawn down aquifers the pressure effects monitoring may not indicate anything significant.

Calibrated reservoir and flow and containment models can predict the current and future pressure front as a result of the injectate. As with Class I modeling, aproper formation pressure gradient is required to assess a baseline, which can determine all future storage capacity of the reservoir in the subsurface. By bounding the injectate via conservative assumptions offers the best chance to define the pressure front, and assess how large the potential area of review may be necessary.

The CO2 plume is likely to be highly variable in saturation and depends on the distance, location and depth considerations as well as original salinity and residual hydrocarbon saturation. Seismic and or vertical seismic profiling may offer the best approach to identifying where the highest saturation is present. Pressure remains the better indicator, distance from the wellbore.

Response: EPA agrees that good site selection, modeling, and management are crucial elements of a successful GS project, but disagrees that this is an effective substitute for rigorous site monitoring. EPA disagrees that pressure fall-off tests are an appropriate substitute for monitoring pressure changes in the injection zone. Pressure fall-off tests provide information in the vicinity of the injection well(s) and measure pressure conditions within the injection zone. Direct monitoring of pressure changes in the injection zone can provide advance warning of movement of CO2 or brine that might ultimately endanger a USDW.

The Agency recognizes that while there are similarities between injection of wastes for disposal (Class I) and GS (Class VI), there are significant differences as well. Important unique considerations for GS include the buoyancy of CO2, its corrosivity when in contact with water, its low viscosity (i.e., high mobility), and the very large injection volumes that are anticipated. There is also a degree of uncertainty regarding the behavior of large volumes of CO2 in the subsurface after injection. Given these characteristics of anticipated GS projects, EPA believes that plume and pressure front monitoring at §146.90(g) are justified to provide early warning of any unforeseen fluid movement that might endanger USDWs.

The final rule (at §146.90(g)) requires owners or operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also required unless the Director determines, based on site-specific geology, that such methods are not appropriate.

EPA believes that pressure monitoring is necessary and for this reason, all GS well owners or operators must monitor pressure in the injection zone using direct methods (§146.90(g)(1)) to track the development and movement of the pressure front and CO2 plume. Monitoring can also identify needed remedial actions, provide inputs for AoR reevaluation modeling, evaluate predictions of plume movement, and target additional geochemical and surface monitoring needs.

Commenter Name: Mark Bohrer Letter ID: 0241 Commenter Organization: North Dakota Industrial Commission Comment ID: 23252

Comment: 30. EPA seeks comment on the requirement for monitoring of GS sites for the purpose of tracking the location of the CO2 plume and associated pressure front

over time. EPA Notice 43514.

Monitoring of the carbon dioxide plume is appropriate however caution is advised with respect to requiring monitoring wells since these may provide a conduit forunwanted migration. 4D seismic and predictive models will improve over time due to iterative processes.

Response: To mitigate the risk of fluid movement, EPA requires owners and operators to submit a testing and monitoring plan that describes how the owner or operator plans to site and construct monitoring wells.

EPA believes, however, that monitoring using wells in the injection zone, e.g., for pressure monitoring as required at §146.90(g)(1), can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that properly constructed monitoring wells will be a safe way to obtain the data that is essential to ensure that the injected CO2 remains confined in the injection zone and that pressure changes are not causing movement of formation or other fluids. 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.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Mark Bohrer Letter ID: 0241 Commenter Organization: North Dakota Industrial Commission Comment ID: 23254

Comment: 32. Based on information evaluated to date, EPA believes that tracking the plume and pressure front is an important companion step to address any uncertainties associated with initial AoR modeling and requests comment on this approach and more efficient alternatives that may be used to track the plume and pressure

front. EPA Notice 43516.

Tracking the plume and pressure front will allow for verification of the reservoir model. Pressure transient testing and seismic techniques may be

useful alternatives.

Response: The final rule (at §146.90(g)) requires owners or operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also required unless the Director determines, based on site-specific geology, that such methods are not appropriate. EPA is affording Director's discretion regarding the use of geophysical techniques at some sites because the Agency recognizes that geophysical methods are not appropriate in all geologic settings. EPA clarifies that this determination will be made by the Director based on the site-specific geologic information submitted by the owner or operator with their permit application.

EPA believes that this approach provides flexibility to develop a site-specific monitoring plan,ensures that direct monitoring is available to track the movement of the CO2 and validate models, and recognizes that indirect techniques are not appropriate in all situations. The owner or operator's approved testing and monitoring plan will include the site-specific details, technologies, testing and monitoring frequencies, and other pertinent information.

Commenter Name: Kurt Waltzer Letter ID: 0250 Commenter Organization: Clean Air Task Force Comment ID: 22321

Comment: The "position of the pressure front" is not something that is as straightforward to establish as the extent of the CO2 plume. As we have commented above, there is no distinct "front", or discontinuity, but rather a gradient in pressure that dissipates with distance away from the injection zone. Estimating the total injection footprint therefore will require appropriate thresholds to be defined in order to estimate the area of elevated pressure. Additionally, methods such as seismic surveys do not work in the same way for compressed brine as they do

for CO2rich brine. Tracking the extent of the CO2 plume is generally possible and must be part of a comprehensive and credible monitoring plan and a GS project. The extent of the area of elevated pressure will likely be estimated with a combination of measurements, inferences and modeling, but it is presently essential to have monitoring wells penetrating the confining zone to do this. Where the CO2 plume itself is concerned, rather than the area of elevated pressure, the role of measurements (including indirect measurements such as seismic surveys) will and should be far greater than that of modeling.

Response: EPA agrees with commenter that plume tracking must be part of a comprehensive and credible monitoring plan for GS wells. For this reason, EPA believes that direct pressure measurements are appropriate and that direct pressure monitoring will be feasible at all 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. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also required unless the Director determines, based on site-specific geology, that such methods are not appropriate.

EPA believes that pressure monitoring 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, provide inputs 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 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 is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, which will include discussion of identifying the extent of the CO2 plume and pressure front. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification,and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this

manual is included in the docket for the for the final GS rule.

Commenter Name: Kurt Waltzer Letter ID: 0250 Commenter Organization: Clean Air Task Force Comment ID: 22324

Comment: variability or from baseline data is hard). Current scientific thinking also dictates that the CO2 plume and confinement are best monitored near the injection zone or right above the caprock. This implies far greater depths, and a much larger distance between CO2 and displaced fluids from USDWs. The Director should have the discretion to require such techniques, but we do not believe that they should be made mandatory for all permits nor should the rule be limited to listing specific techniques (which might be superseded or have preferable alternatives).

Response: EPA has changed this requirement in the final rule. The final GS regulation, at §146.90(g)(1), requires all GS project owners or operators to monitor for pressure changes in the injection zone. EPA believes that pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume.

Pressure monitoring within the injection zone is necessary because any such monitoring above the confining zone would not detect movement of the pressure front unless a breach of the confining zone occurs. EPA believes that monitoring using wells in the injection zone (i.e., that penetrate the confining zone) can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that the benefits of monitoring in the injection formation outweigh the manageable risk of those monitoring wells serving as conduits for fluid movement. EPA adds that owners or operators may consider performing additional pressure monitoring in wells that are above the confining zone (e.g., in the same wells used to perform ground water quality monitoring required at §146.90(d)) to provide additional verification that no pressure changes are occurring above the confining zone due to CO2 leakage. Monitoring also identifies needed remedial actions, provides inputs for AoR reevaluation modeling, and targets additional geochemical and surface monitoring needs. Knowledge of the location of the CO2 plume and the associated pressure front will assure the public that GS projects are proceeding according to plan, provide sufficient information to the owner or operator and Director, or allow for appropriate actions to address any indication that USDWs may be endangered.

Flexibility is also provided regarding how to monitor for the specific data required by the final rule. The testing and monitoring plan is developed by the owner or operator in consultation with the Director and is designed to ensure that a detailed, Director-approved document describing how monitoring will be conducted during the lifetime of the project exists. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologiesand recommended approaches for implementing a testing and monitoring plan, including preoperational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.Commenter Name: Kurt Waltzer Letter ID: 0250 Commenter Organization: Clean Air Task Force Comment ID: 22325 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: To capture the points made above and resolve current inaccuracies or limitations in the proposed language, we recommend the following additional changes in §146.90(g):

[In the paragraph below the text in all CAPS denotes added text. See also EPA-HQ-OW-0390-0250.pdf, to see the original formatting.]

"(1) Testing and monitoring to track ESTABLISH the extent of the carbon dioxide plume and the position of the pressure frontWITHIN DEFINED THRESHOLDS, WITH THE ASSISTANCE OF MODELING TOOLS WHERE APPROPRIATE

AND THROUGH DIRECT MEASUREMENTS OR INDIRECT, GEOPHYSICAL OR OTHER TECHNIQUES 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 and/or down-hole carbon dioxide detection tools); (2) TESTING AND MONITORING TO ESTABLISH THE EXTENT OF THE AREA OF

ELEVATED

PRESSURE THROUGH DIRECT MEASUREMENTS AND THE ASSISTANCE OF MODELING

TOOLS."

and in §146.90(h):

[In the paragraph below the text in all CAPS denotes added text. See also EPA-HQ-OW-0390-0250.pdf, to see the original formatting.]

"At the Director’s discretion, surface airmonitoring METHODS and/or soil gas monitoringto detect movement of carbon dioxide that could SIGNAL endangerMENT OF a USDW. (1) The testing and monitoring plan must be based on potential vulnerabilities within the area of review; (2) The monitoring frequency and spatial distribution of surface air monitoring and/or soil gas monitoringmust reflect baseline data and the monitoring plan must include how the proposed monitoring will yield useful information on the area of review delineation and/or compliance with standards

under 40 CFR 144.12"

Response: As described above, EPA believes that direct pressure measurements are appropriate and that direct pressure monitoring will be feasible at all GS sites and retains this provision in the final GS rule, at §146.90(g).

EPA acknowledges that air and soil gas monitoring to ensure USDW protection is not necessary at all GS sites and agrees that the decision to use surface monitoring and the selection of monitoringmethods for the purpose of USDW protection will be site-specific.

The Agency believes that surface air and soil gas monitoring, when coupled with subsurface monitoring, may be appropriate at some GS projects to ensure USDW protection. EPA also acknowledges that surface air and soil gas measurements are subject to variability and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believe that this should entirely preclude their use. 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.

In the final rule, at §146.90(h), the decision to require such monitoring as an additional measure to ensure USDW protection rests with the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c).

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.

Commenter Name: Michel Paque Letter ID: 0259 Commenter Organization: Ground Water Protection Council Comment ID: 24928 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: EPA Proposal: (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 and/or down-hole carbon dioxide detection tools);

GWPC Recommendations: (g) Testing and monitoring to track the extent of the carbon dioxide plume and the position of the pressure front.

Rationale: Monitoring outside of the injection zone provides little information of value for tracking and monitoring the injected plume. Examples of how to

test and monitor could be included in the Preamble but need not be included in

the rule itself.

Response: EPA has revised this requirement in the final rule. The final GS regulation, at §146.90(g)(1), requires all GS project owners or operators to monitor for pressure changes in the injection zone. EPA believes that pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume.

Pressure monitoring within the injection zone is necessary because any such monitoring above the confining zone would not detect movement of the pressure front unless a breach of the confining zone occurs. EPA believes that monitoring using wells in the injection zone (i.e., that penetrate the confining zone) can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that the benefits of monitoring in the injection formation outweigh the manageable risk of those monitoring wellsserving as conduits for fluid movement. EPA adds that owners or operators may consider performing additional pressure monitoring in wells that are above the confining zone (e.g., in the same wells used to perform ground water quality monitoring required at §146.90(d)) to provide additional verification that no pressure changes are occurring above the confining zone due to CO2 leakage. Monitoring also identifies needed remedial actions, provides inputs for AoR reevaluation modeling, and targets additional geochemical and surface monitoring needs. Knowledge of the location of the CO2 plume and the associated pressure front will assure the public that GS projects are proceeding according to plan, provide sufficient information to the owner or operator and Director, or allow for appropriate actions to address any indication that USDWs may be endangered.

EPA acknowledges that, at certain sites, there may be a need for more or different monitoring schemes (which may include monitoring in the confining zone), and adds that it is important to balance the need for adequate monitoring that ensures USDW protection from endangerment against too many artificial penetrations which could serve as conduits for fluid migration. Site-specific testing and monitoring plans should describe the proposed monitoring regime, which must be approved by the Director. Flexibility is also provided regarding how to monitor for the specific data required by the final rule. The testing and monitoring plan is developed by the owner or operator in consultation with the Director and is designed to ensure that a detailed, Director-approved document describing how monitoring will be conducted during the lifetime of the project exists. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologiesand recommended approaches for implementing a testing and monitoring plan, including preoperational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Letter ID: 0263 Commenter Organization: Interstate Oil & Gas Compact Commission Comment ID: 22816

Comment: III A. 6 Proposed Plume and Pressure Front Monitoring Requirements

EE. EPA seeks comment on the requirement for monitoring of GS sites for the purpose of tracking the location of the CO2 plume and associated pressure front over time.

IOGCC Response: The IOGCC suggests that the operator be required to conduct ongoing monitoring. The frequency of reporting to the regulatory agency should be flexible depending upon site characteristics.

Response: The final rule (at §146.90(g)) requires owners or operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are required unless the Director determines, based on site-specific geology that such methods are not appropriate.

EPA clarifies that the specifics of this monitoring must be described in the site-specific testing and monitoring plan, which must be approved by the Director. EPA believes that this approach provides flexibility to develop a site-specific monitoring plan, ensures that direct monitoring is available totrack the movement of the CO2 and validate models, and recognizes that indirect techniques are not appropriate in all situations. The owner or operator's approved testing and monitoring plan will include the site-specific details, technologies, testing and monitoring frequencies, and other pertinent

information.

Letter ID: 0263 Commenter Organization: Interstate Oil & Gas Compact Commission Comment ID: 22818 Other EPA Comment Codes and Descriptions: 4655 2.6.5.1 Plume tracking techniques/geophysical methods (seeking comment)

Comment: III A. 6 Proposed Plume andPressure Front Monitoring Requirements

GG. Based on information evaluated to date, EPA believes that tracking the plume and pressure front is an important companion step to address any uncertainties associated with initial AoR modeling and requests comment on this approach and more efficient alternatives that maybe used to track the plume and pressure

front.

IOGCC Response: Tracking of the CO2 plume and pressure front should be required. The methodology, however, should not be specified but determined on a site specific basis. The IOGCC agrees with the following EPA statement: "As such, allowing flexibility in choosing the plume tracking methods and other monitoring technologies may provide an appropriate balance between the protective nature of indirect monitoring and cost considerations, as well as allowing for the adoption of continuously advancing technology."

Response: EPA agrees with the comment and the final rule (at §146.90(g)) requires owners or operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also required unless the Director determines, based on site-specific geology, that such methods are not appropriate. EPA clarifies that the specifics of this monitoring must be described in the site-specific testing and monitoring plan, which must be approved by the Director.

EPA believes that this approach provides flexibility to develop a site-specific monitoring plan, ensures that direct monitoring is available to track the movement of the CO2 and validate models, and recognizes that indirect techniques are not appropriate in all situations. The owner or operator's approved testing and monitoring plan will include the site-specific details, technologies, testing and monitoring frequencies, and other pertinent information.

Commenter Name: Mark Vickery Letter ID: 0280 Commenter Organization: Texas Commission on Environmental Quality Comment ID: 24103 Other EPA Comment Codes and Descriptions: 6220 3.2.2 Assumptions about the number of monitoring wells (seeking comment)

Comment: (d) Concern exists on the practical implementation of the proposed requirements for monitoring the CO2 plume and pressure front. Noting that the actual monitoring plan would be left to director approval, EPA's cost analysis for a CO2-GS project assumes the presence of three monitor wells. This would not seem to be sufficient for identification/confirmation of the position of the plume orpressure front, and leads to speculation whether under the proposed rules, the cost of the geo sequestration portion of a carbon capture and sequestration project would be a significantly greater part of the overall cost of the project than represented. In this regard, monitor wells in any reasonable numbers could confirm or rule out the presence of CO2 or its pressure effects at the monitor well location, but would not be expected to identify or confirm the full extent of the plume or pressure front. Computer modeling informed by monitoring data should however be able to bound the reasonable extent of the plume and pressure

front.

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.

EPA recognizes that the number of monitoring wells associated with GS projects will be site-specific and vary based on many factors, including the local geologic characteristics, the presence of other injection wells, the size of the AoR, and volumes of CO2 injected. The proposed rule Cost Analysis described the number of monitoring wells as a ratio to the number of injection wells; EPA clarifies that the number of injection wells was based on the size of the AoR and the type of project. Therefore, the number of monitoring wells was indirectly based on the size of the AoR. Because ER project sites have injection wells that are more clustered than those in saline formations, the AoR and the number of monitoring wells were anticipated to be smaller at an ER project site compared to a saline formation project. EPA retained this assumption regarding the density of injection wells for the final rule analysis, but it changed its assumption on the number of monitoring wells at each site. For the final rule, the Agency assumes one monitoring well above the injection zone per two square miles of AoR; for monitoring wells into the injection zone, the Agency assumes one monitoring well per four square miles. EPA assumes monitoring wells into the injection zone will also be used to sample above the injection zone. The number of monitoring wells assumed for each project type is presented in Exhibit 5.2 of the Cost Analysis.

Because the actual number of monitoring wells that will be necessary for a given project site is uncertain, EPA tested the sensitivity of overall cost estimates to the number of monitoring wells by applying a 25 percent decrease and increase in monitoring wells per project type to the original assumptions. This change results in annualized incremental rule costs approximately 16 percent less and 16 percent greater than costs estimated for the primary analysis (as shown in Exhibit 5.26 of the Cost Analysis). For additional information on EPA's final regulatory approach, including testing and monitoring requirements, please see the final rule and preamble.

EPA is developing guidance on monitoring and testing to assist owners/operators and Directors in evaluating requirements under §146.90, including developing determining the appropriate number of monitoring wells for a GS site. This guidance will be available on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

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



### Individual CommentsCommenter Name: Michael H. Cochran Letter ID:

0108 Commenter Organization: Bureau of Water, Division of Environment, Kansas Department of Health & Environment (KDHE) Comment

ID: 21983

Comment: 146.90 (g): We believe there are few, if any indirect methods that will work or that can feasibly be used to monitor the plume location. This is based on our experience with some of these methods on other projects. For example, with micro-gravity the difference in values or readings would most likely be so small that these would probably be less than the measurement error of the equipment. There has to be a significant difference in density to measure the difference in gravity.

Response: EPA has revised the final rule at §146.90(g)(2) to require owners or operators to track the position of the CO2 plume using indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools), unless the Director determines based on site-specific geology, that such methods are not appropriate. EPA is affording Director's discretion regarding the use of geophysical techniques at some sites because the Agency recognizes that geophysical methods are not appropriate in all geologic settings. For example, geophysical methods are difficult to execute in areas that are structurally and topographically complex or where lithologies have limited contrast in density, porosity, permeability, and other physical properties. EPA clarifies that this determination will be made by the Director based on the site-specific geologic information submitted by the owner or operator with the permit application.

EPA believes that this approach provides flexibility to develop a site-specific monitoring plan and recognizes that indirect techniques are not appropriate in all situations. The owner or operator's approved testing and monitoring plan will include the site-specific details, technologies, testing and monitoring frequencies, and other pertinent information.

Commenter Name: Iain Wright Letter ID: 0118 Commenter Organization: BP Alternative Energy Comment ID: 22067 Other EPA Comment Codes and Descriptions: 4600 2.6 Proposed Plume and Pressure Front Monitoring Requirements (40 CFR 146.90)

Comment: MONITORING

Moving on to my second point: Monitoring. Monitoring is important, but there is a common mis-perception that if you want secure storage, you need to do lots of monitoring. Well, the UN says that "the proportion of CO2 retained by appropriately selected and managed sites is likely to exceed 99% over 1,000 years". SO THE KEY TO SECURE STORAGE IS THE APPROPRIATE SELECTION AND

MANAGEMENT OF THE SITE. If that is done properly, the site will be very secure and the need for monitoring can be appropriately reduced. Monitoring is like the speedometer on your car. It does contribute to your safety, but more important is the design of the car, the road and how you drive the car.

Having said that, at In Salah, we are doing a big research project into monitoring, so the program is much more extensive than would be appropriate for a commercial project. We are trying out new technologies (such as satellite imagery, micro-seismic), so that we can see how they perform against conventional oilfield monitoring technologies (such as tracers and conventionalseismic).

But as you can probably hear from my accent, I’m a Scotsman, and Scotsmen don’t like to waste money, so every technology that we use at in Salah has been carefully chosen to represent good value for money. Before we started injection at In Salah, we did a site-specific assessment of leakage risk and then we tailored the monitoring program to address those risks. Mandating any specific monitoring technology could waste a great deal of money and resources without contributing to the protection of USDWs. SO WE WOULD CAUTION AGAINST A UNIVERSAL

MANDATE FOR ANY SPECIFIC MONITORING TECHNOLOGY.

Many of you will have heard of the other two monitored, industrial-scale CO2 injection projects in the world, at Sleipner and Weyburn. If you compare the monitoring activities at these sites, you can see that something which works well in one location, may not work at all in another location. WE ENCOURAGE EPA
TO USE RISK-ASSESSED, PERFORMANCE-BASED CRITERIA TO DETERMINE SITESPECIFIC

MONITORING PROGRAMS.

Response: EPA agrees with commenters and believes that flexibility is important in developing and implementing a monitoring plan that is appropriately tailored for a specific GS site. The purpose of the requirement at §146.90 to develop site-specific testing and monitoring plans is to ensure that the monitoring performed at a site is appropriate for site operational conditions and the geologic setting. EPA believes that this is the best approach for addressing potential risks at GS sites. These flexible provisions in the monitoring requirements for Class VI wells enable the owner or operator to tailor monitoring programs to the specific needs of each project in consultation with the Director.

The final regulation provides for flexibility in: 1) methodologies used to collect these data, 2) the spatial resolution at which the data should be collected, and 3) how often the data should be collected. The number and placement of monitoring wells will be based on site-specific information such as the calculated AoR, injection rate and volume, site geology, baseline data, and the presence of artificial penetrations within the AoR. In some instances, there may be a limited number of options for complying with EPA's minimum requirements. For example, monitoring for geochemical changes will require use of monitoring wells and collection of groundwater samples for chemical analysis. Many options currently exist for complying with other requirements, such as tracking the position of the plume and pressure front within the injection zone.

Flexibility is also provided regarding how to monitor for the specific data required by the final rule. The testing and monitoring plan is developed by the owner or operator in consultation with the Director and is designed to ensure that a detailed, Director-approved document describing how monitoring will be conducted during the lifetime of the project exists.

EPA also agrees that good site selection and management are crucial elements of a successful GS project, but disagrees that this is an effective substitute for rigorous site monitoring.

EPA does not believe that prescribing specific technologies to be used in all cases for GS would be appropriate given the variability in sites. Rather 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-operationalgeophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the

docket for the final GS rule.

Commenter Name: John Stormon Letter ID: 0123 Commenter Organization: Washington State Dept. of Ecology Comment ID: 23005 Other EPA Comment Codes and Descriptions: 4650 2.6.5 CO2 plume and pressure front tracking (seeking comment)

Comment: Monitoring: Direct monitoring of the formations immediately above the confining layer for a geologic sequestration injection zone is an important requirement for the early detection of unacceptable leakage. Monitoring wells installed into this monitoring zone will be quite expensive but should be required for all projects. Geophysical methods and other indirect monitoring, while useful, should not be allowed to substitute for all direct monitoring above the confining layer.

Response: EPA disagrees that pressure monitoring above the confining zone is appropriate. Instead, EPA believes that pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume. The final rule (at §146.90(g)) requires owners or operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also required unless the Director determines, based on site-specific geology, that such methods are not appropriate.

EPA believes that pressure monitoring within the injection zone is necessary because any such monitoring above the confining zone would not detect movement of the pressure front unless a breach of the confining zone occurs. EPA believes that monitoring using wells in the injection zone (i.e., that penetrate the confining zone) can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that the benefits of monitoring in the injection formation outweigh the manageable risk of those monitoring wells serving as conduits for fluid movement. EPA adds that owners or operators may consider performing additional pressure monitoring in wells that are above the confining zone (e.g., in the same wells used to perform ground water quality monitoring required at §146.90(d)) to provide additional verification that no pressure changes are occurring above the confining zone due to CO2 leakage and that the Director has the authority to require such monitoring under §146.90(i). Monitoring also identifies needed remedial actions, provides inputs for AoR reevaluation modeling, and targets additional geochemical and surface monitoring needs. Knowledge of the location of the CO2 plume and the associated pressure front will assure the public that GS projects are proceeding according to plan, provide sufficient information to the owner or operator and Director, or allow for appropriate actions to address any indication that USDWs may be endangered.

EPA also agrees that direct monitoring for ground water quality above the confining zone isimportant, 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.

Commenter Name: Christine Reimer Letter ID: 0142 Commenter Organization: National Ground Water Association Comment ID: 22568

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 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 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

Daley, T.M., Solbau, R.D., Ajo-Franklin, J.B., and Benson, S.M., 2007, "Continuous active-source seismic 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 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

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. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UICDirector for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: James Dooley Letter ID: 0156 Commenter Organization: Joint Global Change Research Institute, Pacific Northwest National Laboratory Comment ID:

22663

Comment: - Page 43515. It strikes this reviewer as odd to cite only one study (Burton et al, 2007) to support the statement that "current monitoring technologies are more than adequate for monitoring pressure in a GS project." It is not clear if by including this in the preamble to the draft rule whether EPA shares this assessment or not. This seems like an awfully broad and sweeping statement. Consider rewording. Consider being explicit as to whether EPA shares this view or if part of any NODA associated with this rule making should try to collect information that goes beyond this one study to confirm or refute this assertion that pressure monitoring technologies which exist today are sufficient to meet any GS need in any kind of formation anywhere and at any time across all regions

of the USA.

Response: EPA clarifies that the GS rule, at §146.90(g), requires owners or operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are required unless the Director determines, based on site-specific geology that such methods are not appropriate. EPA recognizes that monitoring technologies will evolve and improve over time, and for these reasons, the Agency is using an adaptive approach to regulate GS injection. The Agency plans, every six years, to collect and review data on GS projects to determine whether the appropriate amount and types of information and appropriate documentation are being collected, and to determine if modifications to the requirements are appropriate or necessary.

Commenter Name: James Dooley Letter ID: 0156 Commenter Organization: Joint Global Change Research Institute, Pacific Northwest National Laboratory Comment ID:

22664

Comment: - Page 43516. It is not clear if the USEPA is asserting that using "seismic crosswell methods" are "costly and time consuming" or if that is a finding of the GEO-SEQ (2004) report mentioned at the start of this paragraph. If it is the latter then it is important to clearly attribute that statement to the authors of the GEO-SEQ report. Otherwise, it appears that the USEPA is calling into question the cost effectiveness and utility of a technique that has yet to be robustly tested with respect to GS. That would seem to be a premature assumption based only on the results of the GEO-SEQ project, since crosswell seismic could be a preferred option for some sites where alternative options are impractical or economically infeasible. This section contains a number of implicit references to cost/benefit calculations for monitoring technologies. If the USEPA believes that these techniques are needed to discharge its responsibilities under the SDWA, then that should be stated and these techniques should be required. The text could say something about encouraging technological progress in the hopes of coming up with less costly but equally effective monitoring technologies, but it does not seem appropriate to try andjustify some actions by alluding to cost benefit analyses as the basis for decision making.

Response: EPA does not believe that prescribing specific technologies to be used in all cases for GS would be appropriate given the variability in sites. Rather, EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

EPA clarifies that cost-benefit analyses are not required to be done under the SDWA to determine the most appropriate monitoring technologies, location, or frequency. Instead, the Agency believes that the flexibility afforded the owner or operator at §146.90 to develop a testing and monitoring plan tailored to site-specific characteristics is appropriate for GS. EPA estimated the costs of monitoring GS sites as part of the GS rulemaking effort, and estimates that the Class VI requirements will result in additional costs. The cost analysis for the final GS rulemaking (which is available in the docket) shows an approximate increase of 30 percent in comparison to Class I wells.

Commenter Name: James Devine Letter ID: 0166 Commenter Organization: United States Geological Survey (USGS) Comment ID: 21351 Other EPA Comment Codes and Descriptions: 4600 2.6 Proposed Plume and Pressure Front Monitoring Requirements (40 CFR 146.90)

Comment: Section 146.90 (g), Testing and Monitoring Requirements, FR page 43540

This section requires the owneror operator "to track the extent ofthe carbon dioxide plume and the position ofthe pressure front" by direct or indirect monitoring. Indirect, geophysical techniques include, for example, seismic, electrical, gravity, or electromagnetic surveys.. ." It is unclear if surface deformation measurement techniques, such as repeat topographic surveys,satellite-based elevation measurements, and tiltmeters, are included as acceptable indirect monitoring techniques. Surface deformation techniques are in use, for example, at In Salah, Algeria (Onuma et al., 2008, abstract, Detection of surface deformation related with CO2 injection by DInSAR at In Salah, Algeria, Proceedings of 33rd International Geological Congress, Oslo, Norway). It is suggested that the proposed regulations allow for techniques beyond the realm of"traditional" geophysics and techniques not yet developed.

Response: The final rule, at §146.90(g), requires owners or operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are required unless the Director determines, based on site-specific geology that such methods are not appropriate. EPA is affording Director's discretion regarding the use of geophysical techniques at some sites because the Agency recognizes that geophysical methods are not appropriate in all geologic settings. EPA clarifies that this determination will be made by the Director based on the site-specific geologic informationsubmitted by the owner or operator with the permit application.

EPA is not prescribing that deformation measurement techniques be used. However, if the owner or operator believes they would enhance the monitoring regime, they may be proposed in the testing and monitoring plan. Likewise, if the Director had reason to believe such methods are necessary to ensure protection of USDWs, he/she is afforded discretion to require the use of additional monitoring techniques at §146.90(i).

EPA believes that this approach provides flexibility to develop a site-specific monitoring plan, ensures that direct monitoring is available to track the movement of the CO2 and validate models, and recognizes that indirect techniques are not appropriate in all situations. The owner or operator's approved testing and monitoring plan will include the site-specific details, technologies, testing and monitoring frequencies, and other pertinent information.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the

docket for the final GS rule.

Commenter Name: Michael J. Miller Letter ID: 0168 Commenter Organization: Electric Power Research Institute (EPRI) Comment ID: 22507

Comment: Preamble, page 43514 & 43515: "Under today’s proposal, owners or operators would be required to track the subsurface extent of the CO2 plume and pressure front using pressure gauges in the first formation overlying the confining zone or using indirect geophysical techniques (e.g., seismic, electrical, gravity, or electromagnetic surveys) or other down-hole CO2 detection tools, monitor for geochemical changes in subsurface formations, and if directed, monitor at the surface. Today’s proposal would also require owners or operators to monitor ground water quality and geochemical changes above the confining system."

EPRI COMMENT #13: Refer to EPRI comment #2 for questions regarding how EPA

intends to define each front and the need to demonstrate containment instead. Also, EPRI comments #3B and #14 for representative geochemical sampling and sampling of low-yield formations, respectively.

EPRI is not aware of any remote field measurements, including seismic techniques, that can be used to determine the position of the dissolved CO2 front. Therefore, definition of the CO2 front should be limited to the leading edge of the free-CO2 plume if remote monitoring techniques are used. Remote monitoring techniques may not work in all geologic settings. Very small pressure changes measured in the first formation overlying the confining zone may be masked by other pressure effects. For example, relatively large barometricpressure fluctuations translated down the well to the monitoring zone, changes in fluid pressure caused by nearby pumping wells, or limited transducer resolution, accuracy and electronic noise may interfere with or distort the pressure signal, making it difficult to measure the pressure front. Appropriateness of detection tools will need to be evaluated on a site-by-site basis, and the proposed rule recognizes this need. However, EPRI believes the emphasis should be on demonstrating containment through careful characterization of the storage reservoir and caprock, coupled with predictive CO2 fate and transport models of reservoir and caprock performance, rather than on plume and pressure front tracking, as the latter may not be practical or possible.

Response: In response to comments regarding the pressure front at GS sites, EPA clarifies that the pressure front (defined at §146.81) is the zone of elevated pressure that is created by the injection of CO2 into the subsurface. The pressure front of a CO2 plume refers to a zone where there is a pressure differential sufficient to cause the movement of injected fluids or formation fluids into a USDW. The pressure front includes all areas wherein pressure is great enough to cause fluid movement into a USDW if a conduit were to exist. The calculation of the threshold pressure that defines the edge of the pressure front is dependent on properties of the injection and confining zones, including permeability, porosity, and compressibility, the distance between the injection zone and the lowermost USDW, and operational conditions including injection pressure and rate. For these reasons, the definition of the pressure front is site- and project-specific, and a single pressure value can not be provided for all sites.

EPA has revised the final rule, at §146.90(g), to require owners or operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are required unless the Director determines, based on site-specific geology that such methods are not appropriate.

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, provide inputs 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 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 is affording Director's discretion regarding the use of geophysical techniques at some sites because the Agency recognizes that geophysical methods are not appropriate in all geologic settings. For example, geophysical methods are difficult to execute in areas that are structurally and topographically complex or where lithologies have limited contrast in density, porosity, permeability, and other physical properties. EPA clarifies that this determination will be made by the Director based on the site-specific geologic information submitted by the owner or operator with their permit application.

Commenter Name: Kyle Isakower Letter ID: 0170 Commenter Organization: American Petroleum Institute Comment ID: 24249 Other EPA Comment Codes and Descriptions: 4650 2.6.5 CO2 plume and pressure front tracking (seeking comment)Comment: Rule Provisions: 146.90(g) EPA Preamble Question: 32. Based on information evaluated to date, EPA believes that tracking the plume and pressure front is an important companion step to address any uncertainties associated with initial AoR modeling and requests comment on this approach and more efficient alternatives that may be used to track the plume and pressure front. EPA Notice 43516.

API Response: Based on experience to date, CO2 plume can be monitored using surface or wellbore seismic and possibly some remote satellite techniques. Monitoring of the pressure front will be more difficult since that requires data from the injection formation that can only be obtained by drilling a well (which introduces additional artificial penetrations into the containment system). Modeling can estimate the movement of a pressure front. Those estimations are limited by the accuracy of the model and its iterative adjustments as previously

mentioned.

EPA should note that plume and pressure front are different concepts and should not be confused. They yield information on two different metrics. One tells you about the remaining capacity of the storage formation and the other describes the direction and movement of the CO2 plume.

Response: EPA believes that direct pressure measurements are appropriate and that direct pressure monitoring will be feasible at all 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. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also required unless the Director determines, based on site-specific geology, that such methods are not appropriate.

EPA believes that pressure monitoring 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, provide inputs 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 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 agrees that geophysical (e.g., seismic) methods are useful for plume tracking at GS sites. Remote sensing methods (e.g., PSInSAR) may also prove to be useful. Such methods may be an important component of plume tracking at some GS sites. For this reason, the final rule (at §146.90(g)) requires the use of indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) unless the Director determines, based on site-specific geology, that such methods are not appropriate.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, which will include discussion of identifying the extent of the CO2 plume and pressure front. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface airmonitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this

manual is included in the docket for the for the final GS rule.

Commenter Name: Thomas Curtis Letter ID: 0181 Commenter Organization: American Water Works Association (AWWA) Comment ID: 23744 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Part 146.90(g) AWWA recommends revising this part to read:

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 confining zone, in the first formation overlying the confining zone or using indirect, geophysical techniques (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole carbon dioxide detection tools);

Response: EPA has revised the final GS regulation, at §146.90(g)(1), to require all GS project owners or operators to monitor for pressure changes in the injection zone. EPA believes that pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume. Pressure monitoring within the injection zone is necessary because any such monitoring above the confining zone would not detect movement of the pressure front unless a breach of the confining zone occurs. EPA believes that monitoring using wells in the injection zone (i.e., that penetrate the confining zone) can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that the benefits of monitoring in the injection formation outweigh the manageable risk of those monitoring wells serving as conduits for fluid movement. EPA adds that owners or operators may consider and Directors may require performing additional pressure monitoring in wells that are above the confining zone (e.g., in the same wells used to perform ground water quality monitoring required at §146.90(d)) to provide additional verification that no pressure changes are occurring above the confining zone due to CO2 leakage. Monitoring also identifies needed remedial actions, provides inputs for AoR reevaluation modeling, and targets additional geochemical and surface monitoring needs. Knowledge of the location of the CO2 plume and the associated pressure front will assure the public that GS projects are proceeding according to plan, provide sufficient information to the owner or operator and Director, or allow for appropriate actions to address any indication that USDWs may be endangered.

In addition, §146.90(g)(2) requires owners or operators to track the position of the CO2 plume using indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools), unless the Director determines based on site-specific geology, that such methods are not appropriate.

EPA acknowledges that, at certain sites, there may be a need for more or different monitoring schemes (which may include monitoring in the confining zone), and adds that it is important to balance the need for adequate monitoring that ensures USDW protection from endangerment against too many artificial penetrations which could serve as conduits for fluid migration. Site-specific testing and monitoring plans must describe the proposed monitoring regime, which must beapproved by the Director. Flexibility is also provided regarding how to monitor for the specific data required by the final rule. The testing and monitoring plan is developed by the owner or operator in consultation with the Director and is designed to ensure that a detailed, Director-approved document describing how monitoring will be conducted during the lifetime of the project exists.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Bradley J. Field Letter ID: 0186 Commenter Organization: New York State Dept. of Environmental Conservation

Div. of Mineral Resources Comment ID:

25203

Comment: EE. Based on information evaluated to date, EPA believes that tracking the plume and pressure front is an important companion step to address any uncertainties associated with initial AoR modeling and requests comment on this approach and more efficient alternatives that may be used to track the plume and pressure

front.

NYSDEC-DMN Response: NYSDEC-DMN agrees that tracking of the CO2 plume and pressure front is important and should be required. However, the exact methodology should not be specified but determined on a site-specific basis. NYSDEC-DMN also agrees with EPA’s statement "As such, allowing flexibility in choosing the plume tracking methods and other monitoring technologies may provide an appropriate balance between the protective nature of indirect monitoring and cost considerations, as well as allowing for the adoption of continuously advancing technology."

Response: EPA agrees with commenters that an effective monitoring plan will need to consider sitespecific conditions. The final rule (at §146.90(g)) requires owners or operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are required unless the Director determines, based on site-specific geology that such methods are not appropriate.

EPA believes that this approach provides flexibility to develop a site-specific monitoring plan, ensures that direct monitoring is available to track movement of the CO2 and validate models, and recognizes that indirect techniques are not appropriate in all situations. The owner or operator's approved testing and monitoring plan will include the site-specific details, technologies, testing and monitoring frequencies, and other pertinent information.

EPA believes that pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume, and, for this reason, all GS well owners or operators must use direct methods to monitor for pressure changes in the injection zone, as requiredat §146.90(g)(1).

EPA is affording Director's discretion regarding the use of geophysical techniques at some sites because the Agency recognizes that geophysical methods are not appropriate in all geologic settings. For example, geophysical methods are difficult to execute in areas that are structurally and topographically complex or where lithologies have limited contrast in density, porosity, permeability, and other physical properties. EPA clarifies that this determination will be made by the Director based on the site-specific geologic information submitted by the owner or operator with the permit application.

Commenter Name: Bradley J. Field Letter ID: 0186 Commenter Organization: New York State Dept. of Environmental Conservation

Div. of Mineral Resources Comment ID:

25205 Other EPA Comment Codes and Descriptions: 4760 2.7.6 Proposed reporting frequency (seeking comment)

Comment: GG. Specifically, EPA seeks comment regarding the usefulness of indirect geophysical monitoring and surface air and soil gas monitoring.

NYSDEC-DMN Response: NYSDEC-DMN agrees with EPA’s proposal to require operators to report semi- annually on the characteristics of injection fluids, injection pressure, flow rate, temperature, volume and annular pressure, and on the results of MITs, ground water monitoring, and any required atmospheric/soil gas monitoring. However, the amount and types of monitoring that are required should be site specific. Certain geophysical monitoring techniques that successfully monitor plume migration in the southern states may not have any monitoring capability in northern Paleozoic basins.

Response: EPA agrees with commenters and believes that flexibility is important in developing and implementing a monitoring plan that is appropriately tailored for a specific GS site. The purpose of the requirement at §146.90 to develop site-specific testing and monitoring plans is to ensure that the monitoring performed at a site is appropriate for site operational conditions and the geologic setting. EPA believes that this is the best approach for addressing potential risks at GS sites. These flexible provisions in the monitoring requirements for Class VI wells enable the owner or operator to tailor monitoring programs to the specific needs of each project in consultation with the Director.

EPA clarifies that the final rule, at §146.90(g)(2), requires owners or operators to track the position of the CO2 plume using indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools), unless the Director determines based on site-specific geology, that such methods are not appropriate. EPA is affording Director's discretion regarding the use of geophysical techniques at some sites because the Agency recognizes that geophysical methods are not appropriate in all geologic settings. For example, geophysical methods are difficult to execute in areas that are structurally and topographically complex or where lithologies have limited contrast in density, porosity, permeability, and other physical properties. EPA clarifies that this determination will be made by the Director based on the site-specific geologic information submitted by the owner or operator with their permit application.

EPA believes that this approach provides flexibility to develop a site-specific monitoring plan, ensures that direct monitoring is available to track the movement of the CO2 and validate models, and recognizes that indirect techniques are not appropriate in all situations. The owner or operator'sapproved testing and monitoring plan must include the site-specific details, technologies, testing and monitoring frequencies, and other pertinent information.

As described above EPA is retaining the requirement at §146.91(a) for semi-annual reporting of monitoring and operational data. For additional information, please see the final rule and the preamble for a discussion of EPA's final approach to recordkeeping and reporting.

Commenter Name: Robert F. Van Voorhees Letter ID: 0190 Commenter Organization: Carbon Sequestration Council Comment ID: 24357

Comment: b. Geophysical Methods for Plume Tracking

As an alternative to monitor wells, the proposed rule suggests that it may be possible to use remote geophysical techniques for "plume tracking." 73 Fed. Reg. at 43515. Unfortunately, the technologies available would be very expensive to employ on the scale required. Seeking to achieve greater precision can lead to an expensive and unnecessary quest.

Response: The final rule at §146.90(g) requires owners or operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are required unless the Director determines, based on site-specific geology, that such methods are not appropriate.

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, provide inputs 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 is affording Director's discretion regarding the use of geophysical techniques at some sites because the Agency recognizes that geophysical methods are not appropriate in all geologic settings. For example, geophysical methods are difficult to execute in areas that are structurally and topographically complex or where lithologies have limited contrast in density, porosity, permeability, and other physical properties. EPA clarifies that this determination must be made by the Director based on the site-specific geologic information submitted by the owner or operator with their permit application.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil, gas, and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.Commenter Name: Robert F. Van Voorhees Letter ID: 0190 Commenter Organization: Carbon Sequestration Council Comment ID: 24541 Other EPA Comment Codes and Descriptions: 4650 2.6.5 CO2 plume and pressure front tracking (seeking comment)

Comment: Rule Provisions or Federal Register Cite: 146.90(g) EPA Preamble Question: 32. Based on information evaluated to date, EPA believes that tracking the plume and pressure front is an important companion step to address any uncertainties associated with initial AoR modeling and requests comment on this approach and more efficient alternatives that may be used to track the plume and pressure front. EPA Notice 43516.

CSC Response: Uncertainties associated with AoR determinations may be addressed through the use of a conservative modeling approach. Requirements to "track" plumes or pressure fronts would be extraordinarily burdensome and are not necessary, as extensive experience with "no migration" exemptions for hazardous waste injection wells has shown.

Response: EPA disagrees that plume and pressure front monitoring are not justified for Class VI wells. The Agency recognizes that while there are similarities between injection of hazardous wastes for disposal (Class I) and GS (Class VI), there are significant differences as well. Important unique considerations for GS include the buoyancy of CO2, its corrosivity when in contact with water, its low viscosity (i.e., high mobility), and the very large injection volumes that are anticipated. There is also a degree of uncertainty regarding the behavior of large volumes of CO2 in the subsurface after injection. Given these characteristics of anticipated GS projects, EPA believes that plume and pressure front monitoring at §146.90(g) are justified to provide early warning of any unforeseen fluid movement that might endanger USDWs.

The final rule (at §146.90(g)) requires owners or operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also 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, provide inputs 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.

Commenter Name: Craig R. Walters Letter ID: 0200 Commenter Organization: Anadarko Petroleum Corporation Comment ID: 24602 Other EPA Comment Codes and Descriptions: 4650 2.6.5 CO2 plume and pressure front tracking (seeking comment)

Comment: Rule Provisions: 146.90(g) EPA Rule Issue: 32. Based on information evaluated to date, EPA believes that tracking the plume and pressure front is an important companion step to address any uncertainties associated with initial AoR modeling and requests comment onthis approach and more efficient alternatives that may be used to track the plume and pressure front. EPA Notice 43516.

Anadarko Petroleum Corporation (APC) Response: Plume and pressure front are different concepts and should not be confused. They yield information on two different metrics. The former tells you about the remaining capacity of the storage formation and the latter describes the direction and movement of the CO2 plume. Based on experience to date, CO2 plume can be monitored using surface or wellbore seismic and possibly some remote satellite techniques. Monitoring of the pressure front will be more difficult since that requires data from the injection formation which can only be obtained by drilling a well. Modeling can estimate the movement of a pressure front. Those estimations are limited by the accuracy of the model and its iterative adjustments as previously mentioned.

Response: EPA acknowledges that monitoring the plume and pressure front are different issues and believes that direct pressure measurements are appropriate and that direct pressure monitoring will be feasible at all 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. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also required unless the Director determines, based on site-specific geology, that such methods are not appropriate.

EPA believes that pressure monitoring 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, provide inputs 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 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.

Commenter Name: John King Letter ID: 0211 Commenter Organization: Shell Exploration and Production Company (SEPCo) Comment ID:

22780

Comment: b. Geophysical Methods for Plume Tracking

As an alternative to monitor wells, the proposed rule suggests that it may be possible to use remote geophysical techniques for "plume tracking." 73 Fed. Reg. at 43515. Unfortunately, it is not clear that there are established technologies available that are sufficiently reliable and mature in their development for application in a regulatory context. In general, the technologies available would be very expensive to employ on the scale required, and provide inferential data that is subject to considerable interpretation. Such techniques are unsuitable for required use in a regulatory context.

The problem with interpretive tests is that they are interpretive and therefore inherently subject to uncertainties. The suggestion that such techniques could be used for "plume tracking" to "verify" the results of modeling is optimistic at best, and creates unrealistic expectations for the technologies involved. Infact, the use of such techniques may do more to amplify residual uncertainties and thereby undermine public confidence in GS.

Response: The final rule (at §146.90(g)) requires owners or operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also required unless the Director determines, based on site-specific geology, that such methods are not appropriate.

EPA is affording Director's discretion regarding the use of geophysical techniques at some sites because the Agency recognizes that geophysical methods are not appropriate in all geologic settings. For example, geophysical methods are difficult to execute in areas that are structurally and topographically complex or where lithologies have limited contrast in density, porosity, permeability, and other physical properties. EPA clarifies that this determination must be made by the Director based on the site-specific geologic information submitted by the owner or operator with their permit application.

There may also be interference from urban and residential infrastructure, and sites with loose materials such as glacial deposits may produce poor or inaccurate seismic images. But the laterally continuous, confined formations that make many sites appropriate for GS will also render many of them suitable for seismic surveying. In fact, seismic and other geophysical and remote sensing methods have been used with success at GS pilot projects and are likely to be useful for plume tracking at many GS sites. StatOilHydro has used both time-lapse seismic and gravity methods to track the CO2 plume at the Sleipner site. Seismic surveys have also been used successfully at the Weyburn pilot project site in Saskatchewan. Although resolution on seismic surveys is generally accepted to be the best of the geophysical methods, gravity monitoring at Sleipner has also imaged the plume, and results have agreed with seismic surveys. At InSalah, PSInSAR satellite monitoring has been used in combination with tiltmeter data and was able to detect otherwise imperceptible ground displacement (i.e., at the millimeter scale) that indicates the presence of CO2.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

EPA disagrees that monitoring at GS sites will undermine public confidence in GS and the UIC Program. EPA believes that appropriately designed and implemented monitoring plans will increase public confidence in the safety of GS, helping to assure the public that any problems are detected early and that appropriate measures are taken to protect USDWs from endangerment. Knowledge of the location of the CO2 plume and the associated pressure front will enable EPA to 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.

Commenter Name: Tiffany Rau Letter ID: 0224Commenter Organization: Hydrogen Energy International Comment ID: 21675 Other EPA Comment Codes and Descriptions: 1840 1.4.1.3 Other research

Comment: HEI and its affiliated companies in BP have significant and highly relevant experience around monitoring of the subsurface and the surface. For many decades, BP has been effectively employing a number of monitoring technologies to ensure the safety and integrity of its customary oil and gas operations, including CO2 EOR-related operations since the 1970’s in West Texas and Alaska. Notably, since 2004 BP has been operating the In Salah, Algeria, CO2 storage project where BP (and partners) has been storing around 1 million tones CO2 per year in a deep saline formation close to a producing gas field. The In Salah CO2 Storage project also incorporates a research project to test CO2 storage monitoring technologies with a program that is much more extensive than would be appropriate for a commercial project. At In Salah, BP is testing new technologies (such as satellite imagery and micro-seismic) and conventional oilfield technologies (such as tracers and conventional 3D seismic) to compare and contrast results as the partnership endeavors to design and develop monitoring technologies and methodologies that are reliable and cost-effective, given the expectation of future commercial application.

Before initiating injection at In Salah, BP conducted a thorough assessment of potential leakage paths at the site; BP then tailored the monitoring program toaddress those site-specific risks. There are two other monitored, industrialscale CO2 injection projects in the world (at Sleipner and Weyburn) and the site-specific nature of monitoring requirements is demonstrated by comparing these three CO2 storage projects - monitoring that works well at one location may not work at all in another location.

Response: EPA continues to track ongoing field and laboratory research into all aspects of GS, including subsurface CO2 monitoring. The Agency is tracking the operations and technical developments of more than three dozen small- and large-scale GS injection projects in the US and abroad. Also, since field experience and well construction, injection, and monitoring information relevant to GS comes from operations that inject acid gas or inject CO2 for ER, the Agency hasconducted evaluations regarding these commercial field operations and continues to track GSrelevant developments in these commercial operations.

Additionally, EPA ORD's National Center for Environmental Research (NCER) awarded six Science To Achieve Results (STAR) grants in the Fall of 2009 to recipients from major universities and institutions within the scope of "Integrated Design, Modeling and Monitoring of Geologic Sequestration of Anthropogenic Carbon Dioxide to Safeguard Sources of Drinking Water." In one project, the University of Texas at Austin will assess appropriate monitoring approaches at geologic sequestration sites.

Regarding the development of monitoring and testing plans, EPA believes that testing and monitoring plans should be based on site-specific information, similar to the examples described by the commenter, and believes that flexibility is important in developing and implementing a monitoring plan that is appropriately tailored for a specific GS site. The purpose of the requirement at §146.90 to develop site-specific testing and monitoring plans is to ensure that the monitoring performed at a site is appropriate for site operational conditions and the geologic setting. EPA believes that this is the best approach for addressing potential risks at GS sites. These flexible provisions in the monitoring requirements for Class VI wells enable the owner or operator to tailormonitoring programs to the specific needs of each project in consultation with the Director.

The final regulation provides for flexibility in: 1) methodologies used to collect these data, 2) the spatial resolution at which the data should be collected, and 3) how often the data should be collected. The number and placement of monitoring wells will be based on site-specific information such as the calculated AoR, injection rate and volume, site geology, baseline data, and the presence of artificial penetrations within the AoR. In some instances, there may be a limited number of options for complying with EPA's minimum requirements. For example, monitoring for geochemical changes will require use of monitoring wells and collection of groundwater samples for chemical analysis. Many options currently exist for complying with other requirements, such as tracking the position of the plume and pressure front within the injection zone.

Flexibility is also provided regarding how to monitor for the specific data required by the final rule. The testing and monitoring plan is developed by the owner or operator in consultation with the Director and is designed to ensure that a detailed, Director-approved document describing how monitoring will be conducted during the lifetime of the project exists. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologiesand recommended approaches for implementing a testing and monitoring plan, including preoperational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Brian Williams Letter ID: 0225 Commenter Organization: BP Alternative Energy North America, Inc. (BP) Comment ID: 21720 Other EPA Comment Codes and Descriptions: 1840 1.4.1.3 Other research

Comment: BP has significant and highly relevant experience around monitoring of the subsurface and the surface. For many decades, BP has been effectively employing a number of monitoring technologies to ensure the safety and integrity of its customary oil and gas operations, including CO2 EOR-related operations since the 1970’s in West Texas and Alaska. Notably, since 2004 BP has been operating the In Salah, Algeria, CO2 storage project where BP (and partners) has been storing around 1 million tones CO2 per year in a deep saline formation close to a producing gas field. The In Salah CO2 Storage project also incorporates a research project to test CO2 storage monitoring technologies with a program that is much more extensive than would be appropriate for a commercial project. At InSalah, BP is testing new technologies (such as satellite imagery and microseismic) and conventional oilfield technologies (such as tracers and conventional 3D seismic) to compare and contrast results as the partnership endeavors to design and develop monitoring technologies and methodologies that are reliable and cost-effective, given the expectation of future commercial application.

Before initiating injection at In Salah, BP conducted a thorough assessment of potential leakage paths at the site; BP then tailored the monitoring program toaddress those site-specific risks. There are two other monitored, industrialscale CO2 injection projects in the world (at Sleipner and Weyburn) and thesite-specific nature of monitoring requirements is demonstrated by comparing these three CO2 storage projects - monitoring that works well at one location may not work at all in another location.

Response: EPA continues to track ongoing field and laboratory research into all aspects of GS, including subsurface CO2 monitoring. The Agency is tracking the operations and technical developments of more than three dozen small- and large-scale GS injection projects in the US and abroad. Also, since field experience and well construction, injection, and monitoring information relevant to GS comes from operations that inject acid gas or inject CO2 for ER, the Agency hasconducted evaluations regarding these commercial field operations and continues to track GSrelevant developments in these commercial operations.

Additionally, EPA ORD's National Center for Environmental Research (NCER) awarded six Science To Achieve Results (STAR) grants in the Fall of 2009 to recipients from major universities and institutions within the scope of "Integrated Design, Modeling and Monitoring of Geologic Sequestration of Anthropogenic Carbon Dioxide to Safeguard Sources of Drinking Water." In one project, the University of Texas at Austin will assess appropriate monitoring approaches at geologic sequestration sites.

Regarding the development of monitoring and testing plans, EPA believes that testing and monitoring plans should be based on site-specific information, and believes that flexibility is important in developing and implementing a monitoring plan that is appropriately tailored for a specific GS site. The purpose of the requirement at §146.90 to develop site-specific testing and monitoring plans is to ensure that the monitoring performed at a site is appropriate for site operational conditions and the geologic setting. EPA believes that this is the best approach for addressing potential risks at GS sites. These flexible provisions in the monitoring requirements for Class VI wells enable the owner or operator to tailor monitoring programs to the specific needs of each project in consultation with the Director.

The final regulation provides for flexibility in: 1) methodologies used to collect these data, 2) the spatial resolution at which the data should be collected, and 3) how often the data should be collected. The number and placement of monitoring wells will be based on site-specific information such as the calculated AoR, injection rate and volume, site geology, baseline data, and the presence of artificial penetrations within the AoR. In some instances, there may be a limited number of options for complying with EPA's minimum requirements. For example, monitoring for geochemical changes will require use of monitoring wells and collection of groundwater samples for chemical analysis. Many options currently exist for complying with other requirements, such as tracking the position of the plume and pressure front within the injection zone.

Flexibility is also provided regarding how to monitor for the specific data required by the final rule. The testing and monitoring plan is developed by the owner or operator in consultation with the Director and is designed to ensure that a detailed, Director-approved document describing how monitoring will be conducted during the lifetime of the project exists. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologiesand recommended approaches for implementing a testing and monitoring plan, including preoperational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website athttp://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Neeraj Gupta Letter ID: 0229 Commenter Organization: Battelle Energy Technology (BET) Comment ID: 21860

Comment: Page 108, Seismic Monitoring- Seismic and other indirect geophysical monitoring has been used to evaluate CO2 movement at some sites. However, it is also well known that all of these options (threedimensional, cross well, vertical seismic profile etc) may not work in every settings where rocks are too thin, have unsuitable sonic properties, and/or there is too much surface infrastructure or overburden present. Therefore, these options should be required only based on their feasibility at individual locations. In addition, these technologies may be fairly cost prohibitive on a routine basis. Finally, it must be recognized that none of these technologies can provide a complete mass balance or accounting to CO2 movement in subsurface.

Response: EPA agrees that seismic monitoring may not be applicable or appropriate for all 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. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also required unless the Director determines, based on site-specific geology, that such methods are not appropriate.

EPA is affording Director's discretion regarding the use of geophysical techniques at some sites because the Agency recognizes that geophysical methods are not appropriate in all geologic settings. For example, geophysical methods are difficult to execute in areas that are structurally and topographically complex or where lithologies have limited contrast in density, porosity, permeability, and other physical properties. EPA clarifies that this determination will be made by the Director based on the site-specific geologic information submitted by the owner or operator with their permit application.

There may also be interference from urban and residential infrastructure, and sites with loose materials such as glacial deposits may produce poor or inaccurate seismic images. But the laterally continuous, confined formations that that make many sites appropriate for GS will also render many of them suitable for seismic surveying. In fact, seismic and other geophysical and remote sensing methods have been used with success at GS pilot projects and are likely to be useful for plume tracking at many GS sites. StatOilHydro has used both time-lapse seismic and gravity methods to track the CO2 plume at the Sleipner site. Seismic surveys have also been used successfully at the Weyburn pilot project site in Saskatchewan. Although resolution on seismic surveys is generally accepted to be the best of the geophysical methods, gravity monitoring at Sleipner has also imaged the plume, and results have agreed with seismic surveys. At InSalah, PSInSAR satellite monitoring has been used in combination with tiltmeter data and was able to detect otherwise imperceptible ground displacement (i.e., at the millimeter scale) that indicates the presence of CO2.

EPA acknowledges the commenters' concern about the cost of geophysical techniques. However, EPA believes that tracking of the plume is essential for protection of USDWs from endangerment at GS sites and that geophysical methods are necessary for such tracking.

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 guidancedescribes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Kurt Waltzer Letter ID: 0250 Commenter Organization: Clean Air Task Force Comment ID: 22320

Comment: We also strongly support monitoring to track the CO2 plume. There is no unique method for doing this, and we do not believe that 4D-seismic techniques are appropriate or effective in all geologic settings, or that they should be made mandatory. However, tracking the extent of the CO2 plume is generally possible and must be part of a comprehensive and credible monitoring plan and a GS project. Appropriate limits of accuracy will be needed, as neither tracking individual CO2 molecules, nor to the nearest inch are feasible or desirable. However, the monitoring resolution must be such so as to enable confinement to be established, to give regulators confidence that the CO2 and displaced fluids are not near potential leakage pathways, and to warn in advance of any remedial action that might be needed.

Response: EPA agrees that seismic monitoring may not be applicable or appropriate for all 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. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also required unless the Director determines, based on site-specific geology, that such methods are not appropriate.

EPA is affording Director's discretion regarding the use of geophysical techniques at some sites because the Agency recognizes that geophysical methods are not appropriate in all geologic settings. For example, geophysical methods are difficult to execute in areas that are structurally and topographically complex or where lithologies have limited contrast in density, porosity, permeability, and other physical properties. EPA clarifies that this determination will be made by the Director based on the site-specific geologic information submitted by the owner or operator with their permit application.

There may also be interference from urban and residential infrastructure, and sites with loose materials such as glacial deposits may produce poor or inaccurate seismic images. But the laterally continuous, confined formations that that make many sites appropriate for GS will also render many of them suitable for seismic surveying. In fact, seismic and other geophysical and remote sensing methods have been used with success at GS pilot projects and are likely to be useful for plume tracking at many GS sites. StatOilHydro has used both time-lapse seismic and gravity methods to track the CO2 plume at the Sleipner site. Seismic surveys have also been used successfully at the Weyburn pilot project site in Saskatchewan. Although resolution on seismic surveys is generally accepted to be the best of the geophysical methods, gravity monitoring at Sleipner has also imaged the plume, and results have agreed with seismic surveys. At InSalah, PSInSAR satellite monitoring has been used in combination with tiltmeter data and was able to detect otherwise imperceptible ground displacement (i.e., at the millimeter scale) that indicates the presence of CO2.EPA acknowledges the commenters' concern about the cost of geophysical techniques. However, EPA believes that tracking of the plume is essential for protection of USDWs from endangerment at GS sites and that geophysical methods are necessary for such tracking.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Michel Paque Letter ID: 0259 Commenter Organization: Ground Water Protection Council Comment ID: 24818

Comment: EPA Notice Questions: 73 FR 43517

EPA Rule Issue: 33. EPA seeks comment on the appropriate amount and types of monitoring that should be conducted at a GS site. Specifically, EPA seeks comment regarding the usefulness of indirect geophysical monitoring and surface air and soil gas monitoring. In addition, EPA seeks comment regarding the use of a Director-approved monitoring plan for GS sites. EPA Notice 43517.

GWPC CO2 Committee Response: Although actual monitoring of injection formation might be considered most effective you still have the potential problem of putting holes in the confining formation. Perhaps the use of seismic to place monitoring wells into the injection zone would be an appropriate approach. The number of monitoring wells should not be established in advance. Obviously the UIC program does not have complete control over monitoring well construction or operation or closure. With respect to soil and air monitoring there is a

Response: The final rule (at §146.90(g)) requires owners or operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also required unless the Director determines, based on site-specific geology, that such methods are not appropriate.

Pressure monitoring within the injection zone is necessary because any such monitoring above the confining zone would not detect movement of the pressure front unless a breach of the confining zone occurs. EPA believes that monitoring using wells in the injection zone (i.e., that penetrate the confining zone) can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that the benefits of monitoring in the injection formation outweigh the manageable risk of those monitoring wells serving as conduits for fluid movement. EPA adds that owners or operators may consider performing additional pressure monitoring in wells that are above the confining zone (e.g., in the same wells used to perform ground water quality monitoring required at §146.90(d)) to provide additional verification that no pressure changes are occurring above the confining zone due to CO2 leakage. Monitoring also identifies needed remedial actions, provides inputs for AoR reevaluation modeling,and targets additional geochemical and surface monitoring needs. Knowledge of the location of the CO2 plume and the associated pressure front will assure the public that GS projects are proceeding according to plan, provide sufficient information to the owner or operator and Director, or allow for appropriate actions to address any indication that USDWs may be endangered.

EPA notes that plugging of monitoring wells must be addressed as part of the post-injection site care and site closure plan required under §146.93. 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.

EPA acknowledges that, at certain sites, there may be a need for more or different monitoring schemes (which may include monitoring in the confining zone), and adds that it is important to balance the need for adequate monitoring that ensures USDW protection from endangerment against too many artificial penetrations which could serve as conduits for fluid migration. Site-specific testing and monitoring plans should describe the proposed monitoring regime, including the number and location of monitoring wells, which must be approved by 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 logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the

docket for the final GS rule.

Commenter Name: Claire Olson Letter ID: 0260 Commenter Organization: Basin Electric Power Cooperative Comment ID: 22388

Comment: "3. Tracking the Results of CO2 GS Research Projects"

The EPA states,"4-D seismic monitoring may be a valuable tool for CO2 plume tracking." The emphasis on "may be" reflects the fact that there are a variety of monitoring tools available and also a variety of site-specific geologic conditions thus the tools used to track the location of the CO2 plume should be flexible, and the regulations should reflect this flexibility in choosing methods. "4-D seismic monitoring" has been demonstrated as a research tool but may not be needed as a minimum operating tool. "4-D seismic monitoring" is an extremely expensive option. However, geochemical sampling methods and monitoring

wells can be used to determine the distribution of CO2 within a reservoir and monitor for leakage.

Response: EPA agrees that seismic monitoring is not applicable or appropriate for all 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. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also required unless the Directordetermines, based on site-specific geology, that such methods are not appropriate.

EPA is affording Director's discretion regarding the use of geophysical techniques at some sites because the Agency recognizes that geophysical methods are not appropriate in all geologic settings. For example, geophysical methods are difficult to execute in areas that are structurally and topographically complex or where lithologies have limited contrast in density, porosity, permeability, and other physical properties. EPA clarifies that this determination will be made by the Director based on the site-specific geologic information submitted by the owner or operator with the permit application.

EPA acknowledges the commenters' concern about the cost of geophysical techniques. However, EPA believes that tracking of the plume is essential for protection of USDWs from endangerment at GS sites and that geophysical methods are necessary for such tracking.

EPA also agrees that other data may be useful for tracking the CO2 plume. For example, geochemical data collected above the confining layer, as required under §146.90(d), will allow the owner or operator and permitting authority to identify any changes in subsurface geochemistry that may indicate fluid movement when compared to baseline geochemistry data collected during site

characterization.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Letter ID: 0263 Commenter Organization: Interstate Oil & Gas Compact Commission Comment ID: 22818 Other EPA Comment Codes and Descriptions: 4650 2.6.5 CO2 plume and pressure front tracking (seeking comment)

Comment: III A. 6 Proposed Plume andPressure Front Monitoring Requirements

GG. Based on information evaluated to date, EPA believes that tracking the plume and pressure front is an important companion step to address any uncertainties associated with initial AoR modeling and requests comment on this approach and more efficient alternatives that maybe used to track the plume and pressure

front.

IOGCC Response: Tracking of the CO2 plume and pressure front should be required. The methodology, however, should not be specified but determined on a site specific basis. The IOGCC agrees with the following EPA statement: "As such, allowing flexibility in choosing the plume tracking methods and other monitoring technologies may provide an appropriate balance between the protective nature of indirect monitoring and cost considerations, as well as allowing for the adoption of continuously advancing technology."Response: EPA agrees with the comment and the final rule (at §146.90(g)) requires owners or operators to perform monitoring to track the extent of the CO2 plume and pressure front. The owner or operator must use direct methods to monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are also required unless the Director determines, based on site-specific geology, that such methods are not appropriate. EPA clarifies that the specifics of this monitoring must be described in the site-specific testing and monitoring plan, which must be approved by the Director.

EPA believes that this approach provides flexibility to develop a site-specific monitoring plan, ensures that direct monitoring is available to track the movement of the CO2 and validate models, and recognizes that indirect techniques are not appropriate in all situations. The owner or operator's approved testing and monitoring plan will include the site-specific details, technologies, testing and monitoring frequencies, and other pertinent information.

Comment Code: 4660 2.6.6 Geochemical monitoring



### Individual Comments

Commenter Name: Herbert Skolnick, Ph.D. Letter ID: 0110 Commenter Organization: Group Against Smog and Pollution, Inc. (GASP) Comment ID: 22043 Other EPA Comment Codes and Descriptions: 4620 2.6.2 Injectate monitoring; 4630 2.6.3 Corrosion monitoring

Comment: Regardless of what specific form the CO2 sequestration program ultimately takes, at a minimum, the program must ensure that:

2. the sequestered material’s behavior in the chemical, geological, and hydrological environment where it is stored is anticipated and carefully monitored; and

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

Commenter Name: Doug Louis Letter ID: 0121 Commenter Organization: Kansas Corporation Commission Comment ID: 22076

Comment: The rule should be more specific as to what geochemical data needs to collected (i.e. from the injection formation, the confining layer or from the USDW?)

Response: Section §146.90(d) requires periodic monitoring of the ground water quality and geochemical changes above the confining zone(s). Monitoring above the confining layer will provide an indication of upward movement of CO2 that might endanger a USDW. The exact number offormations to be tested will, however, be based on site-specific characteristics and vulnerabilities and described in the Director-approved 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 logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Leslie Savage Letter ID: 0122 Commenter Organization: Railroad Commission of Texas (RRC) Comment ID: 24794 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: (d) Periodic monitoring of the ground water quality and geochemical changes above the confining zone (s)that may be a result of carbon dioxide movement through the confining zone or additional identified zones:

Response: Regarding monitoring locations, section §146.90(d) requires periodic monitoring of the ground water quality and geochemical changes above the confining zone(s). EPA clarifies that this monitoring requirement does not include the confining layer itself. Monitoring above the confining layer will provide an indication of upward movement of CO2 that might endanger a USDW. The exact number of formations to be tested must, however, be based on site-specific characteristics and vulnerabilities and described in the Director-approved testing and monitoring plan.

Commenter Name: Christine Reimer Letter ID: 0142 Commenter Organization: National Ground Water Association Comment ID: 22567

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 the major and minor chemical constituents of the formation and ionic

constituents of the formation-fluid.

Response: While each monitoring plan must be site-specific based on data collected during the initial site characterization and baseline 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 logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website athttp://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Christine Reimer Letter ID: 0142 Commenter Organization: National Ground Water Association Comment ID: 22607

Comment: Proposed Rule: 146.90(d)

Comment: The monitoring should be site specific and include particular analytes at risk to the aquifer from the existing geologic environment.

Response: While each monitoring plan must be site-specific based on data collected during the initial site characterization and baseline 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 logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: James Childress Letter ID: 0158 Commenter Organization: Gasification Technologies Council (GTC) Comment ID: 23774 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language; 4400 2.4.4.3 Allowing injection above or between USDWs (seeking comment)

Comment: §146.90 Testing and monitoring requirements. (d) Periodic monitoring of the ground water quality and geochemical changes above the confining zone(s) that may be a result of carbon dioxide movement through the confining zone or

additional identified zones:

We recommend changing to "Periodic monitoring of the ground water quality and geochemical changes between the confining zone(s) and the USDW that may be a result of carbon dioxide movement through the confining zone or additional identified zones:" This rewording is consistent with allowing for injection

either above or below USDWs

Response: EPA disagrees that the GS rule should specify the zones to be monitored. EPA clarifies that §146.90(d) requires periodic monitoring of the ground water quality and geochemical changes above the confining zone(s). EPA clarifies that this monitoring requirement does not include the confining layer itself. Monitoring above the confining layer will provide an indication of upward movement of CO2 that might endanger a USDW. The exact number of formations to be tested will,however, be based on site-specific characteristics and vulnerabilities and described in the Directorapproved testing and monitoring plan.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors inevaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

In the final GS rule, owners or operators granted injection depth waivers are subject to additional requirements at §146.95(f)(3) to monitor above and below the injection zone in order to ensure protection of USDWs underlying and overlying the injection zone during both well operation and the post-injection site care period.

For additional information on the waiver approach, please see the final rule and preamble, as well as EPA's responses to comments on the Notice of Data Availability and Request for Comment.

Commenter Name: Michael J. Miller Letter ID: 0168 Commenter Organization: Electric Power Research Institute (EPRI) Comment ID: 22493 Other EPA Comment Codes and Descriptions: 3150 2.1.5 Comments on required permit information (40 CFR 146.82)

Comment: Preamble, page 43505, §146.82(g), and § 146.90(d): "Today’s proposal would require owners or operators to submit geochemical data on a) the injection zone, b) the confining zones, c) containment zones above the confining zones in which any potentially migrating CO2 could be trapped, d) all USDWs, and e) any other geologic zone or formation that is important to the proposed monitoring program."

EPRI COMMENT #3A: EPA does not provide the technical justification for collecting geochemical data from all zones, geologic formations and USDWs. We

believe the collection of data should be limited to zones needed to demonstrate system performance defined by the minimum siting criteria specified in §146.83(a)(1) and (a)(2). EPRI believes that system performance with the end goal of protecting USDW can be achieved by collecting geochemical data from a maximum of four zones for the reasons provided below:

1) Injection zone -- during site characterization, check for conditions that could lead to CO2-induced rock dissolution, potentially resulting in formation and injection well collapse (well integrity);

2) Primary confining zone -- during site characterization, check for conditions that could lead to caprock dissolution and degradation, potentially resulting in loss of CO2 containment with subsequent CO2 movement through the primary barrier (caprock integrity);

3) Monitoring zone -- a zone proposed by the applicant and approved by the EPA where performance monitoring is required to take place in accordance with §146.90(d). The monitoring zone would lie between the primary confining zone and the USDW. It would be the only zone sampled on a routine schedule during CO2 injection operations and closure to detect the leakage of CO2 through theprimary confining zone (performance monitoring) as noted ; and

4) USDW zone -- during site characterization, collect optional samples at or near the closest USDW boundary to the injection zone to establish baseline water quality.

EPRI COMMENT #3B: Before promulgating the rule, a comprehensive study of deep well fluid sampling techniques needs to be performed to ensure that the techniques cited by EPA consistently produce samples that are representative of deep reservoir conditions. Otherwise, interpretation of geochemical data derived from methods producing inconsistent or non-representative sample data could result in erroneous conclusions, including unnecessary or inappropriate corrective action. Collecting representative deep well samples from confining zones is especially challenging (see EPRI comment #14).

Response: The GS regulation, at §146.82(a)(6), requires the owner or operator to submit baseline geochemical data on subsurface geologic formations. EPA is not specifying for which formations this information should be submitted to allow flexibility, but examples may include the following formations: a) the injection zone, b) the confining zones, c) containment zones above the confining zones in which any potentially migrating CO2 could be trapped, d) all USDWs, and e) any other geologic zone or formation that is important to the proposed monitoring program. The Director has the authority to request additional geochemical data as well.

EPA believes that the necessary sampling techniques are available, and is developing guidance on site characterization for GS projects to assist owners or operators and Directors in evaluating permit requirements and applications under §146.82. The guidance provides recommendations regarding characterizing the regional geology and hydrogeology of a proposed GS site as well as performing the necessary geochemical, geomechanical, and geophysical analyses of the injection and confining zone. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

On the topic of sampling, EPA recognizes that the collection of representative ground water samples from depth poses challenges and that special methods, such as U-tubes, will be needed to preserve the integrity of such samples. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Regarding the comment about the technical justifications and difficulty of sampling within the confining zone, EPA clarifies that §146.90(d) requires owners and operators to monitor ground water quality and geochemical changes above the confining zone(s), rather than within the confining zone.

Commenter Name: Michael J. Miller Letter ID: 0168 Commenter Organization: Electric Power Research Institute (EPRI) Comment ID: 22508

Comment: Preamble, page 43515: "Monitoring within the confining zone for pressure, pH,salinity, or the presence of dissolved minerals, heavy metals, or organic contaminants requires direct access to the subsurface via monitoring wells."

EPRI COMMENT #14: See EPRI comment #3B. We believe that measuring pressure in a deep confining zone is possible, but collecting representative deep well samples from confining zones for geochemical characterization may not be technically possible (with emphasis on representative). This could lead to erroneous results and conclusions. EPA currently requires that all monitoring wells be purged of "stagnant" groundwater in the well prior to sampling to produce a "fresh" sample from the adjacent formation that is representative of the formation fluid. Low-yield confining units are typically purged dry prior to sampling or pumped at a very slow rate to prevent the formation from being dewatered. In either case, this typically results in significant sample depressurization when sampling deep wells. Important geochemical parameters including pH, alkalinity, and dissolved metals (which are dependent on groundwater pH) will change when depressurization occurs, producing erroneous analytical results. The u-tube sample method described by Friefeld et al (2005) cannot be used to overcome this limitation for low-yield confining zones.

Freifeld B.M., R.C. Trautz, Y.K. Kharaka, T.J. Phelps, L.R. Myer, S.D. Hovorka, D.J. Collins (2005) The U-tube: a novel system for acquiring borehole fluid samples from a deep geologic CO2 sequestration experiment. Journal of Geophysical Research, 110, B10203, doi:10.1029/2005JB003735.

Response: As described above, EPA recognizes that the collection of representative ground water samples from depth poses challenges and that special methods, such as U-tubes, will be needed to preserve the integrity of such samples. 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.

Commenter Name: Kyle Isakower Letter ID: 0170 Commenter Organization: American Petroleum Institute Comment ID: 24191 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 149.90(d)

API Comments: (d) Periodic monitoring of the ground waterFORMATION FLUID quality and geochemical changes aboveIN A PERMEABLE AND POROUS FORMATION AS NEAR AS PRACTICABLE TO the confining zone(s) FOR GEOCHEMICAL CHANGES that may

be

a result of carbon dioxide OR DISPLACED FORMATION FLUID 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 RELEVANT factors AS WARRANTED BY A RISK-ASSESSMENT; (2) The monitoring frequency and spatial distribution of monitoring wells must be based on GEOLOGICAL, geochemical AND GEOPHYSICAL data that has been collected

under § 146.82(a)(6)§146.82(D) and any modeling results in the area ofreview evaluation required by §146.84(b);

Rationale: Drilling monitoring wells should be carefully considered since each well introduces a potential pathway for movement. In addition the cost of adding multiple wells could create a barrier to CCS development, while providing

limited information on actual movement of the CO2 stream.

Response: EPA agrees that monitoring plans and methods need to be site-specific and believes that the monitoring requirements for GS sites at §146.90 provide an appropriate level of flexibility in structuring a testing and monitoring plan that protects USDWs from endangerment, while addressing the needs suggested in the commenter’s proposed edits.

Regarding monitoring locations, section §146.90(d) requires periodic monitoring of the ground water quality and geochemical changes above the confining zone(s). EPA clarifies that this monitoring requirement does not include the confining layer itself. Monitoring above the confining layer will provide an indication of upward movement of CO2 that might endanger a USDW. The exact number of formations to be tested must, however, be based on site-specific characteristics and vulnerabilities and described in the Director-approved testing and monitoring plan.

To mitigate the risk of fluid movement, EPA requires owners and operators to submit a testing and monitoring plan that describes how the owner or operator plans to site and construct monitoring

wells.

EPA believes, however, that monitoring using wells in the injection zone, e.g., for pressure monitoring as required at §146.90(g)(1), can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that properly constructed monitoring wells will be a safe way to obtain the data that is essential to ensure that the injected CO2 remains confined in the injection zone and that pressure changes are not causing movement or formation of other fluids. To mitigate the risk of fluid movement, EPA requires owners and operators to submit a testing and monitoring plan that describes how the owner or operator plans to site and construct monitoring wells. 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.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

EPA acknowledges the commenters' concern about the cost of monitoring. However, EPA believes that monitoring is essential for protection of USDWs at GS sites. Although a significant cost in absolute terms, monitoring costs are expected to be a small fraction of site operating costs, according to EPA's cost analysis for the GS rulemaking (which is available in the docket).Commenter Name: Frederick R. Eames Letter ID: 0178 Commenter Organization: CCS Alliance Comment ID: 23872

Comment: EPA proposes in section 146.90(d) "periodic monitoring of the ground water quality and geochemical changes above the confining zone(s)." It is unclear how many wells would be required, and whether EPA expects that all zones would be monitored. Given the potential size of the CO2 plume and the number of confining zones, this could potentially require many monitoring wells, which could be extremely expensive and may not produce useful data. We strongly recommend that EPA limit monitoring to the zone immediately above the confining zone, and only to the extent that the CO2 plume is within close proximity. There may be regional conditions where ground water is separated by hundreds or thousands of feet of confining strata, and where such monitoring is completely unnecessary. Directors should have discretion to limit or tailor ground water monitoring, as appropriate, based on regional and site specific factors.

Response: Regarding monitoring locations, section §146.90(d) requires periodic monitoring of the ground water quality and geochemical changes above the confining zone(s). EPA clarifies that this monitoring requirement does not include the confining layer itself. Monitoring above the confining layer will provide an indication of upward movement of CO2 that might endanger a USDW. The exact number of formations to be tested will, however, be based on site-specific characteristics and vulnerabilities and described in the Director-approved testing and monitoring plan.

EPA believes that monitoring above the confining layer is an important part of a rigorous monitoring program. 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 agrees that geochemical monitoring in the injection zone may not be warranted in all cases, and that it is important to install an appropriate number of monitoring wells based on site-specific information and the planned monitoring regime. However, the Agency believes that the data gained from monitoring wells in carefully selected locations will be invaluable.

EPA disagrees that such monitoring should be restricted to areas near the plume. Research, both EPA-funded and external, has shown that the zone of elevated pressure may be much larger than the plume (e.g., Birkholzer et al., 2008). This area of elevated pressure may cause migration of native brines from the target formation into overlying formations. Careful placement of monitoring wells within the delineated AoR (which includes areas beyond the extent of the CO2 plume) would allow for detection of changes in water quality related to GS activities. EPA acknowledges that very thick confining zones would reduce the chance that CO2 or other fluids will move from the injection zone; however, to increase protectiveness, a multiple-barrier approach to protecting USDWs from endangerment that includes both proper site characterization and a detailed monitoring regime is

warranted.

Commenter Name: Thomas Curtis Letter ID: 0181 Commenter Organization: American Water Works Association (AWWA) Comment ID: 24332 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Part 146.90(d) AWWA recommends revising this part to read:Periodic monitoring of the ground water quality and geochemical changes within (if wells can be installed without adversely affecting the integrity of the confining zone) and above the confining zone(s) that may be a result of carbon dioxide movement through the confining zone or additional identified zones:

Response: EPA clarifies that §146.90(d) requires geochemical monitoring above the confining zone. To mitigate the risk of fluid movement, EPA requires owners and operators to submit a testing and monitoring plan that describes how the owner or operator plans to site and construct monitoring

wells.

EPA believes that monitoring using wells in the injection zone, e.g., for pressure monitoring as required at §146.90(g)(1), can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that properly constructed monitoring wells will be a safe way to obtain the data that is essential to ensure that the injected CO2 remains confined in the injection zone and that pressure changes are not causing movement of formation or other fluids. To mitigate the risk of fluid movement, EPA requires owners and operators to submit a testing and monitoring plan that describes how the owner or operator plans to site and construct monitoring wells. 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. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Robert F. Van Voorhees Letter ID: 0190 Commenter Organization: Carbon Sequestration Council Comment ID: 24356

Comment: a. Monitor Wells

Monitor wells reaching the deep subsurface are problematic in a variety of respects. They are expensive to install, create potential pathways for vertical fluid migration, and - in the deep subsurface where natural fluid movement may be very slow or effectively non-existent - they have little potential to provide more than an isolated "point measurements." Monitor wells also have built-in confounding factors that include both the potential for well construction to impact fluid quality in the target sampling interval and the fact that sampling may itself cause fluid movement that might not otherwise occur. Because pressure fronts extend much further than injected fluid plume fronts during injection, pressure monitoring is more likely to be useful than fluid sampling, but costs would still be very high and the ability to detect relevant changes would still be difficult. For these reasons, EPA chose not to impose monitor well requirements on other classes of injection wells, though it did allow monitor wells to be used for Class I hazardous waste injection wells at the discretionof the Director to address particular circumstances at the site. See 52 Fed. Reg. 32446 at 32463-64 (August 27, 1987), 53 Fed. Reg. 28118 at 28141, 28144-45 (July 26, 1988). Experience with hazardous waste injection does not commend the use of monitor wells even in that context, and there is no justification to impose a more stringent an approach for the injection of CO2. Accordingly, we recommend that the potential for gaining useful information from monitor wells be carefully considered in developing an appropriate monitoring plan and that such wells be used only as justified by specific circumstances. (See Attachment A, 146.90(a).)

Response: EPA believes that monitoring using wells in the injection zone, e.g., for pressure monitoring as required at §146.90(g)(1), can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that properly constructed monitoring wells will be a safe way to obtain the data that is essential to ensure that the injected CO2 remains confined in the injection zone and that pressure changes are not causing movement of formation or other fluids. To mitigate the risk of fluid movement, EPA requires owners and operators to submit a testing and monitoring plan that describes how the owner or operator plans to site and construct monitoring wells. 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.

While EPA chose not to impose similar monitoring requirements on other classes of injection wells (except for Class I hazardous waste injection wells), the Agency believes that a conservative, protective approach is appropriate, given the large volumes of CO2 being injected.

EPA also acknowledges that complete coverage of the potential plume area or leakage in the subsurface is not possible through the use of monitoring wells. However, data from an appropriate number of monitoring wells sited based on site-specific information will provide direct information that is not otherwise obtainable and, along with other monitoring data, will support a broader understanding of fluid behavior at the site.

EPA adds that the iterative process of monitoring, modeling, and AoR reevaluation is appropriate to verify that the CO2 plume and pressure front are moving through the subsurface as predicted, verify the accuracy of the delineation model (or identify needed changes), and refine testing and monitoring activities to ensure that USDWs are protected from endangerment and that there would be adequate warning of potential problems at the site before any endangerment could occur.

EPA acknowledges the commenters' concern about the cost of monitoring. However, EPA believes that monitoring is essential for protection of USDWs at GS sites. Although a significant cost in absolute terms, monitoring costs are expected to be a small fraction of site operating costs, according to EPA's cost analysis for the GS rulemaking (which is available in the docket).

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil, gas, and surface-air monitoring which may be required by the UIC Directorfor specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Robert F. Van Voorhees Letter ID: 0190 Commenter Organization: Carbon Sequestration Council Comment ID: 24481 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90(d)

Proposed CCS Group Recommendations: (d) Periodic monitoring of the ground water quality and geochemical changes above the confining zone(s) that may be a result of carbon dioxide 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);

Response: EPA did not make the suggested changes, but agrees that monitoring plans and methods need to be site-specific and based on baseline data and data collected throughout operations. EPA believes that the monitoring requirements for GS sites at §146.90 provide an appropriate level of flexibility in structuring a testing and monitoring plan that protects USDWs from endangerment.

The final regulation provides for flexibility in: 1) methodologies used to collect these data, 2) the spatial resolution at which the data should be collected, and 3) how often the data should be collected. The number and placement of monitoring wells will be based on site-specific information such as the calculated AoR, injection rate and volume, site geology, baseline data, and the presence of artificial penetrations within the AoR. In some instances, there may be a limited number of options for complying with EPA's minimum requirements. For example, monitoring for geochemical changes will require use of monitoring wells and collection of groundwater samples for chemical analysis. Many options currently exist for complying with other requirements, such as tracking the position of the plume and pressure front within the injection zone.

Flexibility is also provided regarding how to monitor for the specific data required by the final rule. The testing and monitoring plan is developed by the owner or operator in consultation with the Director and is designed to ensure that a detailed, Director-approved document describing how monitoring will be conducted during the lifetime of the project exists. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologiesand recommended approaches for implementing a testing and monitoring plan, including preoperational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. Theguidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Craig R. Walters Letter ID: 0200 Commenter Organization: Anadarko Petroleum Corporation Comment ID: 24704 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90(d)

Anadarko Petroleum Corporation (APC) Comments: (d) Periodic monitoring of the ground water quality and geochemical changes above the confining zone(s) that may be a result of carbon dioxide 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);

Rationale: See 146.90(c)(1 thru 4 and 7)

Response: EPA did not make the suggested changes, but agrees that monitoring plans and methods need to be site-specific and based on baseline data and data collected throughout operations. EPA believes that the monitoring requirements for GS sites at §146.90 provide an appropriate level of flexibility in structuring a testing and monitoring plan that protects USDWs from endangerment.

The final regulation provides for flexibility in: 1) methodologies used to collect these data, 2) the spatial resolution at which the data should be collected, and 3) how often the data should be collected. The number and placement of monitoring wells will be based on site-specific information such as the calculated AoR, injection rate and volume, site geology, baseline data, and the presence of artificial penetrations within the AoR. In some instances, there may be a limited number of options for complying with EPA's minimum requirements. For example, monitoring for geochemical changes will require use of monitoring wells and collection of groundwater samples for chemical analysis. Many options currently exist for complying with other requirements, such as tracking the position of the plume and pressure front within the injection zone.

Flexibility is also provided regarding how to monitor for the specific data required by the final rule. The testing and monitoring plan is developed by the owner or operator in consultation with the Director and is designed to ensure that a detailed, Director-approved document describing how monitoring will be conducted during the lifetime of the project exists. EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologiesand recommended approaches for implementing a testing and monitoring plan, including preoperational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gasand 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.

Commenter Name: Richard Guinn Letter ID: 0210 Commenter Organization: Eastman Chemical Company Comment ID: 22724

Comment: §146.90 Testing and monitoring requirements. (d) Periodic monitoring of the ground water quality and geochemical changes above the confining zone(s) that may be a result of carbon dioxide movement through the confining zone or

additional identified zones:

We recommend changing to " Periodic monitoring of the ground water quality and geochemical changes between the confining zone(s) and the USDW that may be a result of carbon dioxide movement through the confining zone or additional

identified zones: "

This rewording is consistent with allowing for injection either above or below

USDWs

Response: Regarding monitoring locations, section §146.90(d) requires periodic monitoring of the ground water quality and geochemical changes above the confining zone(s). EPA clarifies that this monitoring requirement does not include the confining layer itself. Monitoring above the confining layer will provide an indication of upward movement of CO2 that might endanger a USDW. The exact number of formations to be tested must, however, be based on site-specific characteristics and vulnerabilities and described in the Director-approved testing and monitoring plan.

Commenter Name: John King Letter ID: 0211 Commenter Organization: Shell Exploration and Production Company (SEPCo) Comment ID:

22777

Comment: Suggestions that it should be necessary to monitor geochemical changes or to study interactions between brine and CO2 in the injection zone are particularly troubling, because detailed information concerning such interactions should rarely if ever be relevant from a regulatory standpoint. In particular, USDWs are generally protected by ensuring that injected fluids will remain isolated from them, and experience with hazardous waste injection " where the injection of highly corrosive waste is not uncommon " has shown that geochemical interactions that could actually compromise containment cannot reasonably be expected in the absence of truly unusual circumstances. Accordingly, any general requirement to monitor geochemical changes in the subsurface would be

unreasonable.

Response: EPA disagrees with the commenter. While contamination is unlikely at properly selected, constructed, and operated sites, EPA believes that robust monitoring is necessary to ensure that USDWs are protected.

EPA also acknowledges that complete coverage of the potential plume area or leakage in the subsurface is not possible through the use of monitoring wells. However, data from an appropriate number of monitoring wells sited based on site-specific information will provide direct informationthat is not otherwise obtainable and, along with other monitoring data, will support a broader understanding of fluid behavior at the site.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

EPA adds that the iterative process of monitoring, modeling, and AoR reevaluation is appropriate to verify that the CO2 plume and pressure front are moving through the subsurface as predicted, verify the accuracy of the delineation model (or identify needed changes), and refine testing and monitoring activities to ensure that USDWs are protected from endangerment and that there would be adequate warning of potential problems at the site before any endangerment could occur.

Commenter Name: Diane VanDe Hei Letter ID: 0213 Commenter Organization: Association of Metropolitan Water Agencies (AMWA) Comment ID:

22937

Comment: o Rock cores and thorough geochemical analysis of geosequestration should happen even before the AoR. Advances in research and subsurface modeling make it possible to analyze the interaction between rock formations and CO2. Performing these analyses early on could potentially prevent unintended consequences.

Response: EPA agrees and believes that the baseline geochemical data required at §146.82(a)(6) will provide information on predicting potential interactions between rocks and CO2 as the commentersuggests, and also expects that this information will inform the development and approval of a sitespecific 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 logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. In addition, in January 2009, DOE published a best practices manual entitled "Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations" (DOE/NETL-311/081508); this manual is included in the

docket for the final GS rule.

Commenter Name: Edward Steadman Letter ID: 0220 Commenter Organization: The Energy and Environmental Research Center at the University of North Dakota Comment ID:

21625 Other EPA Comment Codes and Descriptions: 4610 2.6.1 Testing and monitoring plan requirement (seeking comment)Comment: Page 43515. Regarding monitoring wells in the Area of Review (AoR).

Text in this section implies that monitoring wells in the injection zone within the AoR are desirable, which could be interpreted by some as being required. The first comment with respect to this issue is that it is important to note that monitoring wells that penetrate the plume have potential to serve as a leakage pathway and, therefore, their use should be minimized. Secondly, one of the reasons given for the placing of monitoring wells in the AoR is that studying the interactions between brine and CO2 may allow for the determination of whether precipitation and/or dissolution of minerals is occurring. It is important to note that such interactions are currently not well understood and are the topic of great debate and controversy within the published literature. There is no consensus in the technical community as to how such data evaluated in the context of a single site, as site-specific permitting and monitoring must be, can be applied to ensuring the protection of USDWs at that site. While such data would surely be interesting and possibly useful from a scientific standpoint when taken in the context of many sites, it is not clear how it could be applied to prove or disprove that USDWs at a given location are being protected or are in danger of contamination. This requirement comes across as a regulatory-mandated means of gathering data for researchers, an activity that is outside the scope of USDW protection and should not be forcibly paid for by owners/operators of GS wells.

Response: EPA disagrees that the monitoring requirements in the GS rule do not provide sitespecific benefits for protection of USDWs or that monitoring is for the benefit of scientific research only. EPA believes that geochemical monitoring, when compared to baseline data, can provide direct evidence that USDWs may be endangered.

EPA believes that monitoring using wells in the injection zone (i.e., that penetrate the confining zone) can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that the benefits of monitoring in the injection formation outweigh the manageable risk of those monitoring wells serving as conduits for fluid movement. EPA adds that owners or operators may consider performing additional pressure monitoring in wells that are above the confining zone (e.g., in the same wells used to perform ground water quality monitoring required at §146.90(d)) to provide additional verification that no pressure changes are occurring above the confining zone due to CO2 leakage. Monitoring also identifies needed remedial actions, provides inputs for AoR reevaluation modeling, and targets additional geochemical and surface monitoring needs. Knowledge of the location of the CO2 plume and the associated pressure front will assure the public that GS projects are proceeding according to plan, provide sufficient information to the owner or operator and Director, or allow for appropriate actions to address any indication that USDWs may be endangered.

EPA acknowledges that, at certain sites, there may be a need for more or different monitoring schemes (which may include monitoring in the confining zone), and adds that it is important to balance the need for adequate monitoring that ensures USDW protection from endangerment against too many artificial penetrations which could serve as conduits for fluid migration. Site-specific testing and monitoring plans must describe the proposed monitoring regime, which must be approved by the Director.Commenter Name: Andrew Duguid Letter ID: 0226 Commenter Organization: Schlumberger Carbon Services Comment ID: 24058 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Proposed Rule: (d) Periodic monitoring of the ground water quality and geochemical changes above the confining zone(s) that may be a result of carbon dioxide movement through the confining zone or additional identified zones:

Schlumberger Suggested Revision: (d) Periodic monitoring of the ground water quality for geochemical changes above the confining zone(s) that may be a result of carbon dioxide movement through the confining zone or additional identified

zones:

Schlumberger Rationale: -

Response: EPA did not make the suggested change. 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.

Commenter Name: Andrew Duguid Letter ID: 0226 Commenter Organization: Schlumberger Carbon Services Comment ID: 24060 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Proposed Rule: (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);

Schlumberger Suggested Revision: (2) The monitoring frequency and spatial distribution of monitoring wells must be based on geological and geophysical data that has been collected under §146.82(d) and any modeling results in the area of review evaluation required by §146.84(b);

Schlumberger Rationale:Geochemical data does not seem have a high degree of relevance in selecting monitoring well sites.

Response: EPA believes that baseline characterization of the site, including the geochemical data and initial modeling, will be highly valuable in selection of monitoring well locations and in refining plans for monitoring frequency. The GS rule stipulates that the monitoring frequency and spatial distribution of monitoring wells must be based on baseline geochemical data that were collected during the initial site characterization and the area of review evaluation at §146.90(d)(2). The details of the geochemical monitoring will be based on site-specific information and described in the Director-approved testing and monitoring plan.

Commenter Name: Steven B. Corneli Letter ID: 0234 Commenter Organization: NRG Energy, Inc. Comment ID: 23169 Other EPA Comment Codes and Descriptions: 4600 2.6 Proposed Plume and Pressure Front Monitoring Requirements (40 CFR 146.90)Comment: Monitoring Requirements

The preamble of the proposed rule states that the "monitoring of subsurface geochemistry and the position of the CO2 plume and pressure front are necessary to verify predictions of plume movement, provide inputs for modeling, identify needed corrective actions, and target geochemical and surface monitoring activities." 73 Fed. Reg. at 43514. NRG believes that the proposed monitoring requirements are excessive and unjustified. The use of monitor wells or seismic data would be needed to verify the model predictions. In particular, it is

Response: EPA disagrees that the monitoring requirements in the GS rule are excessive or unjustified. 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 important part of a rigorous monitoring program. Such monitoring can provide an early warning that the plume 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). EPA also believes that geophysical (e.g., seismic) methods are useful for plume tracking at GS sites. For this reason, the final rule at §146.90(g) requires the use of indirect methods (e.g., seismic, electrical, gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) unless the Director determines, based on site-specific geology that such methods are not appropriate

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

EPA also acknowledges that complete coverage of the potential plume area or leakage in the subsurface is not possible through the use of monitoring wells. However, data from an appropriate number of monitoring wells sited based on site-specific information will provide direct information that is not otherwise obtainable and, along with other monitoring data, will support a broader understanding of fluid behavior at the site.

EPA adds that the iterative process of monitoring, modeling, and AoR reevaluation is appropriate to verify that the CO2 plume and pressure front are moving through the subsurface as predicted, verify the accuracy of the delineation model (or identify needed changes), and refine testing and monitoring activities to ensure that USDWs are protected from endangerment and that there would be adequate warning of potential problems at the site before any endangerment could occur.

Commenter Name: Michel Paque Letter ID: 0259 Commenter Organization: Ground Water Protection Council Comment ID: 24926 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90(d)

EPA Proposal: (d) Periodic monitoring of the ground water quality andgeochemical changes above the confining zone(s) that may be a result of carbon dioxide 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);

GWPC Recommendations: (d) Periodic monitoring of reservoir formation fluid quality in a permeable and porous formation as near as practicable to the confining zone(s) for geochemical changes that may be a result of carbon dioxide or displaced formation fluid movement:

(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 relevant factors as warranted by a risk-assessment;

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

Rationale: Drilling monitoring wells should be carefully considered since each well introduces a potential pathway for movement.

[Geochemical data do not have a high degree of relevance in selecting monitoring well sites.]

Response: EPA believes that monitoring using wells in the injection zone, e.g., for pressure monitoring as required at §146.90(g)(1), can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years. EPA believes that properly constructed monitoring wells will be a safe way to obtain the data that is essential to ensure that the injected CO2 remains confined in the injection zone and that pressure changes are not causing movement of formation or other fluids. To mitigate the risk of fluid movement, EPA requires owners and operators to submit a testing and monitoring plan that describes how the owner or operator plans to site and construct monitoring wells. EPA has developed a brief technical paper on construction of monitoring wells that perforate the confining zone; this paper can be found in the rulemaking docket. EPA is also 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. Baseline characterization of the site, including the geochemical data and initial modeling, will be highly valuable in selection of monitoring well locations and in refining plans for monitoring frequency. The GS rule stipulates that the monitoring frequency and spatial distribution of monitoring wells must be based on baseline geochemical data that were collected during the initialsite characterization and the area of review evaluation (§146.90(d)(2)). The details of thegeochemical monitoring must be based on site-specific information and described in the Directorapproved testing and monitoring plan.

Letter ID: 0263 Commenter Organization: Interstate Oil & Gas Compact Commission Comment ID: 22819

Comment: III A. 6 Proposed Plume and Pressure Front Monitoring Requirements

HH. EPA seeks comment on the appropriate amount and types of monitoring that

should be conducted at a GS site.

IOGCC Response: The IOGCC agrees that owners and operators should report semiannually on the characteristics of injection fluids, injection pressure, flow rate, temperature, volume and annular pressure, and on the results of MITs, ground water monitoring, and any required atmospheric/soil gas monitoring. The amount and types of monitoring to be required, however, should be site specific.

Response: EPA agrees that monitoring plans and methods need to be site-specific and believes that the monitoring requirements for GS sites at §146.90 provide an appropriate level of flexibility in structuring a testing and monitoring plan that protects USDWs from endangerment. The final regulation provides for flexibility in: 1) methodologies used to collect these data, 2) the spatial resolution at which the data should be collected, and 3) how often the data should be collected. The number and placement of monitoring wells will be based on site-specific information such as the calculated AoR, injection rate and volume, site geology, baseline data, and the presence of artificial penetrations within the AoR.

EPA adds that the final rule, at §146.91(a) requires that owners and operators report semi-annually on operating data and some monitoring data. See the preamble to the final rule for additional

information.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Steven Chester Letter ID: 0264 Commenter Organization: Michigan Department of Environmental Quality (MDEQ) Comment ID:

22844 Other EPA Comment Codes and Descriptions: 4670 2.6.7 Surface air monitoring and/or soil gas monitoring (seeking comment)

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

conducted at GS sites.

- Staff is not certain that the monitoring parameters listed will yield anyinformation that relates to endangerment of USDW by leakage from the sequestration zone with the exception of the determination of the position of the CO2 plume and area of elevated pressure. Staff believes, however, that the surface casing and tubing pressures, injection rates, and volumes should be measured daily and reported on a monthly basis. It is not clear that surface monitoring will provide unambiguous information regarding the position of the injected CO2 plume, particularly in view of the uncertainty associated with the movement of the plume. It is also not clear that wells in the confining zone will be of any value since there may be no fluid movement into any particular well, and there is much uncertainty as to appropriate or optimum placement of confining zone monitoring

wells.

Response: EPA agrees that pressure monitoring in the confining zone may not provide the data needed to evaluate plume movement. Instead, the final GS regulation, at §146.90(g)(1), requires all GS project owners or operators to monitor for pressure changes in the injection zone. EPA believes that pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume which provides valuable information in determining whether there is a potential for USDW endangerment.

Pressure monitoring within the injection zone is necessary because any such monitoring above the confining zone would not detect movement of the pressure front unless a breach of the confining zone occurs. EPA believes that monitoring using wells in the injection zone (i.e., that penetrate the confining zone) can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years.

EPA acknowledges that air and soil gas monitoring are subject to variability and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believe that this should entirely preclude their use. For example, if a leak to the surface is suspected, surface monitoring could provide vital information on its location and magnitude to assist owners and operators in identifying what USDWs may have been impacted by a leak. EPA clarifies that the various air and soil gas monitoring methods (e.g., chambers, eddy covariance, hyperspectral imaging) all have different capabilities that may prove useful in specific GS projects (Miles, et al. 2005; Pickles and Cover, 2005; IPCC, 2005; Menzies, et al. 2001). The final rule at §146.90(h) retains the allowance for surface air and soil gas monitoring at the discretion of the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c). EPA clarifies that the decision to use surface monitoring and the selection of monitoring methods will be site-specific (e.g., may be influenced by geology, injection depth, and operational conditions) and must be based on potential risks to USDWs within the AoR.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.Commenter Name: Scott Anderson Letter ID: 0510 Commenter Organization: Environmental Defense Fund Comment ID: 21222

Comment: And we're pleased that 146.90 requires periodic monitoring both the ground water quality and geo-chemical changes above the confining zone. That is really critical to making sure that there's no leaking of fluids or CO2 through the confining zone.

Response: EPA acknowledges the comment; the final rule retains this approach. EPA believes that the ground water geochemical monitoring 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 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.

Commenter Name: Scott Anderson Letter ID: 0520 Commenter Organization: Environmental Defense Fund Comment ID: 21420 Other EPA Comment Codes and Descriptions: 1420 1.2.1.1 Support the GS rulemaking; 3310 2.2.1.1 Comments in favor of requiring computational models to delineate the AoR (seeking comment)

Comment: We think the rule, the proposed rule has done a very good job of keeping the focus on both CO2 leakage risks and also the risk of problems from displaced brine. The confining zone in the rule is required to contain both CO2 and displaced formation fluids. The zone of elevated pressure as defined in the rule focuses on both CO2 and formation fluids that might be driven out of a US -- into a USDW. The modeling requirements are modeling both of the CO2 plume extent and formation fluid movement. There is the requirement for periodic monitoring of groundwater quality and geochemical changes above the confining zone which would help detail whether either CO2 or brine is leaking and there are adequate response provisions.

Response: EPA acknowledges the commenter’s support and believes that predicting the complex multiphase, buoyant flow of the CO2, co-injectates, and compounds that may be mobilized due to injection requires the sophistication of computational models, as required at §146.84(c)(1). Models can predict CO2 fate and transport, as well as changes in formation pressure, in three dimensions, as a function of time in order to delineate the subsurface storage site and the AoR. Models can account for site-specific and predicted operating conditions as well as geologic heterogeneities and potential migration through faults, fractures, and artificial penetrations.

EPA believes that the creation of a new injection well class (VI) under the existing UIC Program is necessary to enable the use of GS as a climate change mitigation technology in a manner that protects USDWs from endangerment. EPA agrees that the UIC Program, under the authority of the SDWA, provides a strong framework for regulating injection of CO2 for GS and adds that the GS regulation tailors the UIC requirements to address the unique issues associated with large-scale GS including large injection volumes, the relative buoyancy of CO2, its corrosivity in the presence of water, the potential presence of impurities in captured CO2, and its mobility within subsurface geologic formations. For additional information on well construction, siting, and testing and monitoring requirements, please also see the discussion of EPA’s Final Regulatory Approach in the preamble to the final GS rule.Commenter Name: Doug Louis Letter ID: 0530 Commenter Organization: Kansas Corporation Commission Comment ID: 21339

Comment: determined and defined for regulatory certainty. The rules should be more specific as to what geochemical data needs to be collected; that is from the injection formation, the confining layer or from the USDW.

Response: Section §146.90(d) requires periodic monitoring of the ground water quality and geochemical changes above the confining zone(s). Monitoring above the confining layer will provide an indication of upward movement of CO2 that might endanger a USDW. The exact number of formations to be tested must, however, be based on site-specific characteristics and vulnerabilities and described in the Director-approved 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 logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

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



### Individual Comments

Commenter Name: Karl R. Moor Letter ID: 0109 Commenter Organization: Southern Company, on behalf of Edison Electric Institute (EEI) Comment ID:

22000 Other EPA Comment Codes and Descriptions: 4490 2.4.5 Use of tracers and potential impact on human health or ecosystems (seeking comment)

Comment: Similarly, EPA should not require the use of tracers or soil flux to monitor for possible carbon dioxide leaks. Not only are tracers relatively untested when it comes to their ability to monitor such leaks - and, in fact, the best tracer for monitoring carbon dioxide leaks would be CO2 itself - but they also will not transmit information sufficiently early to provide any sort of real protection to underground sources of drinking water. Soil flux monitoring is problematic because it can result in false positives based on natural variability in the earth flux rate. What these requirements would do, however, is signal to the public that carbon capture and storage is unsafe because it might be leaking CO2, despite the fact that this is very unlikely to happen. The United Nations’ Intergovernmental Panel on Climate Change has found that the amount of carbon dioxide retained in appropriately sited storage sites is very likely to exceed 99 percent over 100 years.

Response: EPA acknowledges that air and soil gas monitoring are subject to variability and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believethat this should entirely preclude their use. For example, if a leak to the surface is suspected, surface monitoring could provide vital information on its location and magnitude to assist owners and operators in identifying what USDWs may have been impacted by a leak. EPA clarifies that the various air and soil gas monitoring methods (e.g., chambers, eddy covariance, hyperspectral imaging) all have different capabilities that may prove useful in specific GS projects (Miles et al., 2005; Pickles and Cover, 2005; IPCC, 2005; Menzies et al., 2001). The occurrence of false positives will be reduced by comparing monitoring data to baseline data collected prior to injection or from a nearby area away from the GS project.

The final rule at §146.90(h) retains the allowance for surface air and soil gas monitoring at the discretion of the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c). EPA clarifies that the decision to use surface monitoring and the selection of monitoring methods will be site-specific (e.g., may be influenced by geology, injection depth, and operational conditions) and must be based on potential

risks to USDWs within the AoR.

EPA agrees that the use of tracers should not be required at all GS sites, but should be available as an option. For this reason, EPA does not require the use of tracers at all GS sites; however, the Director has discretion to require their use if he/she determines that the use of tracers could improve monitoring of the site and enhance USDW protection from endangerment. The rule will also allow their use if proposed by the owner or operator and approved by the Director.

EPA agrees that the CO2 itself may serve as a tracer in the form of stable isotopes of carbon. For example, anthropogenic CO2 is depleted in 13C compared to naturally occurring CO2. If tracers are determined to be necessary at a GS site, this may be an appropriate option.

EPA disagrees that the use of tracers, if needed, would signal to the public that GS is unsafe. EPA believes that tracers can be useful tools for monitoring, plume tracking, and verification at GS sites and may help improve public confidence in certain projects. EPA believes that providing the public with important information about the project, including how tracers would be an integral part of the site monitoring plan, will be a key part of improving public acceptance of specific projects and GS technology in general.

Commenter Name: Leslie Savage Letter ID: 0122 Commenter Organization: Railroad Commission of Texas (RRC) Comment ID: 24752

Comment: c. delete references to air and soil gas monitoring, since such monitoring is a case of too little too late - and can result in false positives due to ambient variability; and

Response: EPA acknowledges that air and soil gas monitoring are subject to variability and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believe that this should entirely preclude their use. For example, if a leak to the surface is suspected, surface monitoring could provide vital information on its location and magnitude to assist owners and operators in identifying what USDWs may have been impacted by a leak. EPA clarifies that the various air and soil gas monitoring methods (e.g., chambers, eddy covariance, hyperspectral imaging) all have different capabilities that may prove useful in specific GS projects (Miles et al., 2005; Pickles and Cover, 2005; IPCC, 2005; Menzies et al., 2001). The occurrence of false positives will be reduced by comparing monitoring data to baseline data collected prior to injection or from a nearby area away from the GS project.The final rule at §146.90(h) retains the allowance for surface air and soil gas monitoring at the discretion of the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c). EPA clarifies that the decision to use surface monitoring and the selection of monitoring methods will be site-specific (e.g., may be influenced by geology, injection depth, and operational conditions) and must be based on potential

risks to USDWs within the AoR.

Commenter Name: Leslie Savage Letter ID: 0122 Commenter Organization: Railroad Commission of Texas (RRC) Comment ID: 24797 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: (h) At the Director's discretion, surface air monitoring and/or soil gas monitoring to detect movement of carbon dioxide that could endanger a USDW. (1) The testing and monitoring plan must be based on potential vulnerabilities within the area of review; (2) The monitoring frequency and spatial distribution of surface air monitoring and/or 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 and/or compliance with standards under 40 CFR 144.12;

{Any requirement for surface air monitoring and/or soil gas monitoring is not warranted. If the purpose is to detect "movement of carbon dioxide that could endanger a USDW, it would be too late if carbon dioxide were detected in the air or soil. In addition, levels of ambient carbon dioxide are too variable for this to be useful. RRC suggests eliminating any potential requirement for surface air or soil gas monitoring, because formation monitoring should catch whatever condition might reasonably be expected to be caught by surface or soil gas monitoring. }

Response: EPA acknowledges that air and soil gas monitoring to ensure USDW protection is not necessary at all GS sites and believes that the decision to use surface monitoring and the selection of monitoring methods for the purpose of USDW protection will be site-specific. In the final rule, at §146.90(h), the decision to require such monitoring as an additional measure to ensure USDW protection rests with the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c).

EPA clarifies that subsurface geochemical 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 all GS sites, as described at §146.90(d)). The Agency also believes that surface air and soil gas monitoring, when coupled with subsurface monitoring, may be appropriate at 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 protection. 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.Commenter Name: Christine Reimer Letter ID: 0142 Commenter Organization: National Ground Water Association Comment ID: 22569 Other EPA Comment Codes and Descriptions: 4490 2.4.5 Use of tracers and potential impact on human health or ecosystems (seeking comment)

Comment: 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 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 Capture and Sequestration, May 2-5, 2005, Monitor and Exchange Publications and Forum, Washington, D.C.

Response: EPA clarifies that subsurface geochemical 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 all GS sites, as described at §146.90(d)). The Agency also believes that surface air and soil gas monitoring, when coupled with subsurface monitoring, may be appropriate at 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 protection. 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 CO2 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 isotopes of carbon. For example, 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 identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c).

EPA 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 require their use if he/she determines that the use of tracers could improve monitoring of the site and enhance USDW protection from endangerment.Commenter Name: Brianne Metzger Letter ID: 0151 Commenter Organization: Spectra Energy Corp Comment ID: 21843

Comment: H. The Requirement To Perform Ambient Monitoring Exceeds EPA’s Authority Under

SDWA.

EPA is also proposing that the Director be given discretion to require surface air monitoring and/or soil gas monitoring to detect movement of carbon dioxide that could endanger a USDW. 40 C.F.R. § 146.90(h). We would recommend that this provision be deleted. It is not clear how ambient air or soil gas monitoring is related to or supports the protection of USDWs. Based on our experience, the use of surface air monitoring can frequently result in false positives, which could prompt unnecessary and costly response actions and needlessly alarm the public. We believe that targeted ground water monitoring and other wellhead testing and monitoring requirements are sufficient to detect any movement of CO2 that could endanger a USDW. Given the narrow scope of SDWA authority, we question the Agency’s authority to directly or indirectly require such monitoring where it does not naturally bear on the protection of USDWs. If EPA should decide to retain this provision in the final rule, we would ask the Agency to clarify that any requirement for ambient air or soil gas monitoring would be purely discretionary on the part of the State, would be pursuant only to state law and not the federal UIC program, and thus would not be federally enforceable. Bath Petroleum Storage, Inc. v. Sovas, 309 F.Supp. 2d 357 (N.D. N.Y. 2004) (state law requiring sonar survey for UIC injection not federally enforceable).

Response: The final rule at §146.90(h) retains the allowance for surface air and soil gas monitoring at the discretion of the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c). EPA clarifies that the decision to use surface monitoring and the selection of monitoring methods will be site-specific (e.g., may be influenced by geology, injection depth, and operational conditions) and must be based on potential

risks to USDWs within the AoR.

EPA believes that surface air and soil gas monitoring are within the scope of the SDWA in that they can provide additional data to pinpoint the location and magnitude (or absence) of leaks that could endanger USDWs. Used in conjunction with deep subsurface monitoring, as required at §146.90, and as part of a multi-barrier approach to protecting USDWs from endangerment, surface air and soil gas monitoring are within the scope of SDWA’s general authority (SDWA sections 1421 et al).

The Agency believes that surface air and soil gas monitoring, when coupled with subsurface monitoring, may be appropriate at some GS projects to ensure USDW protection. EPA also acknowledges that surface air and soil gas measurements are subject to variability and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believe that this should entirely preclude their use. 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.

Commenter Name: James Childress Letter ID: 0158 Commenter Organization: Gasification Technologies Council (GTC) Comment ID: 23776Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: §146.90 Testing and monitoring requirements. (71) "At the Director's discretion, surface air monitoring and/or soil gas monitoring to detect movement of carbon dioxide that could endanger a USDW. "

We recommend deletion of this requirement in its entirety. While this requirement may be suitable for determining potential air leakage relevant to monitoring of CO2 in a greenhouse gas policy context, this requirement does not provide any additional protection to migration to USDW as surface breakthrough will only occur well after the deep-surface migration of CO2 to a USDW. Surface monitoring to detect CO2 has high uncertainty and seasonal variability that is likely to result in many false positives and operational distractions. Seismic methods of tracking the CO2 plume are more effective than soil gas monitoring of CO2, which is affected by many other factors and thus is highly variable.

Response: EPA acknowledges that surface air and soil gas measurements are subject to variability and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believe that this should entirely preclude their use. 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. The Agency believes that surface air and soil gas monitoring, when coupled with subsurface monitoring, may be appropriate at some GS projects to ensure USDW protection.

The final rule at §146.90(h) retains the allowance for surface air and soil gas monitoring at the discretion of the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c). EPA clarifies that the decision to use surface monitoring and the selection of monitoring methods will be site-specific (e.g., may be influenced by geology, injection depth, and operational conditions) and must be based on potential

risks to USDWs within the AoR.

Commenter Name: James Childress Letter ID: 0158 Commenter Organization: Gasification Technologies Council (GTC) Comment ID: 23786

Comment: EPA seeks comment on the appropriate amount and types of monitoring that should be conducted at a GS site. Specifically. EPA seeks comment regarding the usefulness of indirect geophysical monitoring and surface air and soil gasmonitoring. In addition, EPA seeks comment regarding the use of a Directorapproved monitoring plan for GS sites. EPA Notice 111

Surface air and soil gas monitoring are not useful. Seismic methods of tracking the CO2 plume are more effective than soil gas monitoring of CO2, which is affected by many other factors and thus is highly variable. Surface breakthrough represents an "after-the-fact" event. While this requirement may be suitable for determining potential air CO2 leakage relevant to monitoring of CO2 in a GHG context, this requirement does not provide any additional protection to migration to USDW as surface CO2 breakthrough will only occur well after the deep-surface migration of CO2 to a USDW. Surface monitoring to detect CO2 hashigh uncertainty and seasonal variability that is likely to result in many false positives, operational distractions and unduly raise public concern.

Response: EPA clarifies that subsurface geochemical 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 all GS sites, as described at §146.90(d)). The Agency also believes that surface air and soil gas monitoring, when coupled with subsurface monitoring, may be appropriate at some GS projects to ensure USDW protection.

EPA clarifies that surface air and soil gas monitoring are not required at all GS sites. However, the GS rule at §146.90(h) gives the Director discretion to require surface air and/or soil gas monitoring as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c). EPA clarifies that the decision to use surface monitoring and the selection of monitoring methods will be site-specific (e.g., may be influenced by geology, injection depth, and operational conditions) and must be based on potential risks to USDWs

within the AoR.

EPA acknowledges that air and soil gas monitoring are subject to variability and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believe that this should entirely preclude their use. 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.

Commenter Name: James Devine Letter ID: 0166 Commenter Organization: United States Geological Survey (USGS) Comment ID: 21352

Comment: Section 146.90 (h), Testing and Monitoring Requirements, FR page 43540

This section requires, at the Director's discretion, "surface air monitoring and/or soil gas monitoring to detect movement of carbon dioxide that could endanger a USDW (underground source ofdrinking water)." In § 146.90 (h)(1) and (h)(2), the proposed regulations qualify the application of gas monitoring to sites with suitable conditions and adequate baseline data, that is, sites amenable to the technique.

Current methods for measurement of carbon dioxide in air or soil gas are adequate for the measurement of carbon dioxide; that is, the analytical methodologies are well-developed. However, the representativeness of the samples

and interference from other natural and man- made sources of carbon dioxide can make for problematic correlation of carbon dioxide in the air or soil to carbon dioxide from deep subsurface storage leaks. The efficacy of such correlation techniques are not well-demonstrated by research to date, as evidenced by the paucity of literature on the subject. Correlation with potential endangerment to an USDWis even less understood. As a result, requiring such monitoring at this point amounts to requiring the owner or operator to conduct research into a technique that is not yet well established. Poorly understood detections of elevated carbon dioxide may cause operational disruptions, such as short or long-term cessation of injection, while the monitoring results are investigated and interpreted.Response: EPA acknowledges that air and soil gas monitoring are subject to site-specific limitations and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believe that this should entirely preclude their use. If surface monitoring were the only monitoring method employed to ensure USDW protection, direct correlation of CO2 at the surface with CO2 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 final rule at §146.90(h) retains the allowance for surface air and soil gas monitoring at the discretion of the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c). 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.

Used in conjunction with deep subsurface monitoring, as required at §146.90, and as part of a multibarrier approach to protecting USDWs from endangerment, surface air and soil gas monitoring will increase USDW protection, enable immediate notification of the UIC Director in the case of potential USDW endangerment, and facilitate remedial action.

Commenter Name: Kyle Isakower Letter ID: 0170 Commenter Organization: American Petroleum Institute Comment ID: 24195 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90(h)

API Comments: (h) At the Director’s discretion BASED ON SITE-SPECIFIC CONDITIONS AND RISK-BASED FACTORS, surface air monitoring and/or soil gas monitoring to detect movement of carbon dioxide that could endanger a USDW.

Rationale: In most situations soil and air monitoring does not provide an effective method of protecting USDWs.

Response: EPA clarifies that subsurface geochemical 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 all GS sites, as described at §146.90(d)). The Agency also believes that surface air and soil gas monitoring, when coupled with subsurface monitoring, may be appropriate at some GS projects to ensure USDW protection.

The final rule at §146.90(h) retains the allowance for surface air and soil gas monitoring at the discretion of the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c).

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 withinthe AoR.

Commenter Name: Kyle Isakower Letter ID: 0170 Commenter Organization: American Petroleum Institute Comment ID: 24250

Comment: EPA Preamble Question: 33. EPA seeks comment on the appropriate amount and types of monitoring that should be conducted at a GS site. Specifically, EPA seeks comment regarding the usefulness of indirect geophysical monitoring and surface air and soil gas monitoring. In addition, EPA seeks comment regarding the use of a Director-approved monitoring plan for GS sites. EPA Notice 43517.

API Response: Monitoring techniques and frequency should be determined on a site-specific basis. Selection of monitoring types and frequency should balance the potential risks posed by the project with the cost of monitoring. Surface and soil gas monitoring does not add value to the protection of USDWs. Many of the surface and soil gas monitoring techniques currently being evaluated lack the track record necessary for use in a regulatory compliance setting. Moreover, the potential for false-positives could undermine public confidence in GS technologies. EPA should defer on using surface and soil gas monitoring technologies until the DOE Regional Partnerships can demonstrate their

effectiveness.

Response: As described above, EPA acknowledges that air and soil gas monitoring to ensure USDW protection is not necessary at all GS sites and agrees that the decision to use surface monitoring and the selection of monitoring methods for the purpose of USDW protection will be site-specific.

EPA acknowledges that air and soil gas monitoring are subject to variability and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believe that this should entirely preclude their use. For example, if a leak to the surface is suspected, surface monitoring could provide vital information on its location and magnitude to assist owners and operators in identifying what USDWs may have been impacted by a leak. EPA clarifies that the various air and soil gas monitoring methods (e.g., chambers, eddy covariance, hyperspectral imaging) all have different capabilities that may prove useful in specific GS projects (Miles et al., 2005; Pickles and Cover, 2005; IPCC, 2005; Menzies et al., 2001). The occurrence of false positives will be reduced by comparing monitoring data to baseline data collected prior to injection or from a nearby area away from the GS project.

Commenter Name: James Rower Letter ID: 0173 Commenter Organization: Utility Solid Waste Activities Group (USWAG) Comment ID: 23490 Other EPA Comment Codes and Descriptions: 1400 1.2 Comments on EPA's Authority to Regulate Injection of CO2

Comment: It also is important to clarify in the Final Rule that well plugging is only necessary and appropriate for those wells that are potential conduits of contamination to USDWs. USWAG raises this point because EPA suggests that the Final Rule may give the Director discretion to require Owners or Operators to conduct surface air monitoring and/or soil gas monitoring in the AoR. Id. at 43516. Such a requirement would be appropriate only to the extent that this monitoring would be done with the goal of identifying potential endangerment ofUSDWs as a result of CO2 injection and sequestration activities. Id. To the extent that such monitoring would be required simply to guard against potential atmospheric releases or to trigger a corrective action requirement to terminate such atmospheric releases, it would be outside of the scope of EPA's authority under this rulemaking. See id. at 43498 ("preventing releases of CO2 to the atmosphere is not within the scope of this proposal").

Response: EPA believes that surface air and soil gas monitoring are within the scope of the SDWA in that they can provide additional data to pinpoint the location and magnitude (or absence) of leaks that could endanger USDWs. Used in conjunction with deep subsurface monitoring, as required at §146.90, and as part of a multi-barrier approach to protecting USDWs from endangerment, surface air and soil gas monitoring are within the scope of SDWA’s general authority (SDWA sections 1421 et al.).

EPA clarifies that use of surface air and soil gas monitoring as specified in the final GS rule at §146.90(h), as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c), is at the Director's discretion.

Regarding corrective action for wells in the AoR, EPA clarifies that the rule, at §146.84(d), requires owners or operators to perform corrective action on all deficient wells in the AoR. This requirement is independent of the testing and monitoring requirements at §146.90.

Commenter Name: James Rower Letter ID: 0173 Commenter Organization: Utility Solid Waste Activities Group (USWAG) Comment ID: 23499

Comment: With respect to the Proposal's suggestion for surface monitoring requirements, USWAG believes that such requirements will come at significant cost with little benefit. While surface monitoring may reveal CO2 migration, these data will be of limited use since, by that point, CO2 has already been released to the surface. Moreover, data from surface air and soil gas monitoring are complicated by a number of factors, including natural and anthropogenic impacts from fires, development, and population growth. Rather than spending significant resources on gathering data that are of limited reliability and of little practical use in preventing surface releases, the Final Rule should direct that these resources will be put towards detection of subsurface CO2 movement. This would prove a far more effective use of monitoring resources as it would enable Owners or Operators to correct any problems before CO2 reaches the surface.

Response: EPA acknowledges that air and soil gas monitoring are subject to variability and may not be suitable in all settings as a method to ensure USDW protection. However, the Agency believes that surface air and soil gas monitoring, when coupled with subsurface monitoring, may be appropriate at some GS projects to ensure USDW protection. However, EPA does not believe that this should entirely preclude their use. For example, if a leak to the surface is suspected, surface monitoring could provide vital information on its location and magnitude to assist owners and operators in identifying what USDWs may have been impacted by a leak. EPA clarifies that the various air and soil gas monitoring methods (e.g., chambers, eddy covariance, hyperspectral imaging) all have different capabilities that may prove useful in specific GS projects (Miles et al., 2005; Pickles and Cover, 2005; IPCC, 2005; Menzies et al., 2001). The occurrence of false positiveswill be reduced by comparing monitoring data to baseline data collected prior to injection or from a nearby area away from the GS project.

Commenter Name: Kenneth Nemeth Letter ID: 0176 Commenter Organization: Southern States Energy Board Comment ID: 23543 Other EPA Comment Codes and Descriptions: 4490 2.4.5 Use of tracers and potential impact on human health or ecosystems (seeking comment)

Comment: pressure front. CO2 monitoring should be fit for purpose. Air and soil gas monitoring is unlikely to be beneficial, and the use of tracers should be at the discretion of the owner/operator.

Response: EPA acknowledges that air and soil gas monitoring to ensure USDW protection is not necessary at all GS sites and agrees that the decision to use surface monitoring and the selection of monitoring methods for the purpose of USDW protection will be site-specific.

The Agency believes that surface air and soil gas monitoring, when coupled with subsurface monitoring, may be appropriate at some GS projects to ensure USDW protection. EPA also acknowledges that surface air and soil gas measurements are subject to variability and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believe that this should entirely preclude their use. 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 CO2 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 isotopes of carbon. For example, anthropogenic CO2 is depleted in 13C compared to naturally occurring CO2.

In the final rule, at §146.90(h), the decision to require such monitoring as an additional measure to ensure USDW protection rests with the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c).

EPA agrees that the use of tracers may not be appropriate for all GS sites, but should be available as an option. For this reason, EPA does not require the use of tracers at all GS sites; however, the Director has discretion to require their use if he/she determines that the use of tracers could improve monitoring of the site and enhance USDW protection from endangerment. The rule will also allow their use if proposed by the owner or operator and approved by the Director.

Commenter Name: Quinlan J. Shea Letter ID: 0177 Commenter Organization: Edison Electric Institute Comment ID: 23553 Other EPA Comment Codes and Descriptions: 4490 2.4.5 Use of tracers and potential impact on human health or ecosystems (seeking comment)

Comment: EEI is also concerned about proposed requirements related to monitoring for potential CO2 movement and the use of tracers. Under the proposed regulations,the UIC program director would have discretion to require the use of tracers or surface air/soil gas monitoring "to detect movement of CO2 that could endanger a USDW." Tracers and surface air/soil gas monitoring should not be required, and may create an overly negative and unwarranted public perception regarding the safety of GS projects or tracers.

Response: EPA believes that monitoring at a GS site is of critical importance to ensuring protection of USDWs from endangerment. Appropriately selected monitoring technologies, including surface air and soil-gas monitoring will also serve to increase public confidence in the safety of GS and to assure the public that GS projects are being appropriately operated and monitored. The information gained through such monitoring will also enable permitting authorities to take appropriate steps to address any indication that USDWs may be endangered.

If surface monitoring were the only monitoring method employed to ensure USDW protection, direct correlation of CO2 at the surface with CO2 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 isotopes of carbon. For example, anthropogenic CO2 is depleted in 13C compared to naturally occurring CO2.

EPA clarifies that surface air and soil gas monitoring are not required at all GS sites. However, the GS rule at §146.90(h) gives the Director discretion to require surface air and/or soil gas monitoring as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c).

Regarding the use of tracers, EPA agrees that tracers may not be appropriate for all GS sites, but should be available as an option. For this reason, EPA does not require the use of tracers at all GS sites; however, the Director has discretion to require their use if he/she determines that the use of tracers could improve monitoring of the site and enhance USDW protection from endangerment. The rule will also allow their use if proposed by the owner or operator and approved by the Director.

Commenter Name: Quinlan J. Shea Letter ID: 0177 Commenter Organization: Edison Electric Institute Comment ID: 23589 Other EPA Comment Codes and Descriptions: 4490 2.4.5 Use of tracers and potential impact on human health or ecosystems (seeking comment)

Comment: D. Monitoring Provisions and Use of Tracers

EEI is also concerned about proposed requirements related to monitoring for potential CO2 movement and the use of tracers. Under the proposed regulations, the UIC program director would have discretion to require the use of tracers or surface air/soil gas monitoring "to detect movement of CO2 that could endanger a USDW." For the reasons set forth below, EEI is opposed to such a requirement, even where, as proposed, it is left to the discretion of the program director.

- Functionality, usefulness and cost: Tracers are relatively untested in terms of workability as a leak-detecting mechanism. Of greater concern, however, is the fact that using tracers or surface air or soil gas monitoring would likelyprovide too little information, too late, in terms of providing protection for USDW, in the sense that USDW would likely be affected by the time the results of such methods revealed any concerns. Moreover, by their very nature, tracers can be detected at ultra-low concentrations. If the tracer is spilled or a small amount leaked, or if a pipe downstream from the tracer injection point leaked, the surface air would become contaminated. Minute amounts of tracer might be detectable for quite a distance, making the likelihood of a false positive for the tracer much greater without any real benefit to the overall protection of USDW. In sum, if employed for purposes of long-term monitoring of underground waters, tracers would be unlikely to yield significant useful data and would prove extremely expensive.

- Safety: Tracers may present their own safety concerns depending on the precise nature of the tracer at issue. Further, the use of tracers may pose independent risks for project operators. There may be potential health effects from some tracers if workers are accidentally exposed.

Response: EPA clarifies that subsurface geochemical 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 all GS sites, as described at §146.90(d)). The Agency also believes that surface air and soil gas monitoring, when coupled with subsurface monitoring, may be appropriate at 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 protection. 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.

The final rule at §146.90(h) retains the allowance for surface air and soil gas monitoring at the discretion of the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c).

As described above, EPA agrees that tracer use is not appropriate in all situations. EPA acknowledges that some tracers may have the potential to cause harm to people or the environment. For this reason, EPA does not require the use of tracers at all GS sites. Nevertheless, there are many different types of tracers and not all are problematic; research is being done to overcome problems with existing tracers. EPA believes that tracers have been used safely and successfully in other applications. Therefore the Director has discretion to require their use if he/she determines that the use of tracers could improve monitoring of the site and enhance USDW protection from endangerment. The rule will also allow their use if proposed by the owner or operator and approved by the Director.

EPA has been following new and ongoing research on the safety and efficacy of tracers, and believes that, in some circumstances, tracers can be an effective part of monitoring GS projects. EPA will continue to track research related to tracer use and plans to, every six years, collect and review data on GS projects to determine whether the appropriate amount and types of information and appropriate documentation are being collected, and to determine if modifications to the requirements are appropriate or necessary.Commenter Name: Quinlan J. Shea Letter ID: 0177 Commenter Organization: Edison Electric Institute Comment ID: 23591 Other EPA Comment Codes and Descriptions: 1400 1.2 Comments on EPA's Authority to Regulate Injection of CO2

Comment: - Potential issues of EPA authority: As noted above, EEI views the development and implementation of legally defensible regulations as a key to commercial deployment of CCS. To that end, EEI encourages the Agency to consider carefully the link between each proposed provision and its authority to regulate under SDWA. Where the link is more tenuous, the proposed provision may be subject to greater risk of legal challenge, posing uncertainty for those who desire to move ahead with projects. While, as the Agency points out, the use of tracers or surface air/soil gas monitoring could indicate that some threat to USDW may be posed, it seems more likely that by the time the results of such methods revealed any concerns, such sources would already be affected. Thus, the nexus between those methods and protection of USDW may be subject to challenge by opponents of the proposed provisions. And the nexus between surface air/soil gas monitoring and protection of USDW may be at greater risk of challenge, as the detection of a CO2 leak to surface air conceivably provides no useful information that would serve to protect USDW. Indeed, while EPA notes in the preamble that detection of leakage to the surface "would indicate potential endangerment" to USDW as a last line of defense, the Agency also acknowledges that regulation of surface or atmospheric releases of CO2 are outside the scope of the proposed rules and the Agency‘s SDWA authority.

While the proposed rules would leave these requirements to the discretion of the UIC program director, again the proposal sets no clear parameters for the exercise of such discretion. EEI does not believe that any provisions related to the use of tracers are required or warranted for the protection of USDW, but should EPA choose to impose a discretionary requirement, any such requirement should be bounded by appropriate parameters for its use.

Response: As described above, subsurface geochemical 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 all GS sites, as described at §146.90(d)).

EPA agrees that the implementation of the GS rule in a manner that ensures protection of USDWs from endangerment is important to establishing a foundation for further advances in the field of CO2 GS. EPA acknowledges the need for regulatory certainty: the final GS requirements provide a level of certainty by setting forth unique requirements for GS. These requirements include: the tailored AoR delineation process under §146.84, the types of monitoring appropriate to GS projects under §146.90, and the post-injection site care process under §146.93.

While EPA agrees with commenters that a stable, predictable, nationally consistent, and workable regulatory framework is important, EPA stresses that the focus of the GS rule is to ensure that, where GS is deployed, it is conducted in a manner that protects USDWs from endangerment.

EPA disagrees with the comment with respect to its authority under the SDWA and believes it within the Agency’s authority to provide the Director with discretion to require surface air monitoring and/or soil gas monitoring in the AoR at §146.90(h). This discretion is limited to potential risks to USDWs within the AoR. EPA believes that monitoring for the injected fluid at thesurface for the purposes of protecting USDWs is within the jurisdiction of the SDWA. If the injected CO2 were to migrate through fractures, abandoned well bore holes or other means, it would be released in a gaseous form at the surface, and therefore must be monitored as such. EPA believes that having this information can be critical to allow the Director to determine whether injected CO2 has migrated from the injection zone and endangered a USDW(s).

EPA is developing guidance for permitting authorities that will include recommendations for how Directors may exercise discretion in implementing the requirements of the GS rule, including the testing and monitoring requirements. This guidance will be available on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

The final rule at §146.90(h) retains the allowance for surface air and soil gas monitoring at the discretion of the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c).

Commenter Name: Frederick R. Eames Letter ID: 0178 Commenter Organization: CCS Alliance Comment ID: 23873

Comment: Proposed section 146.90(h) gives Directors discretion to require surface air monitoring and/or soil gas monitoring to detect movement of CO2 that could endanger a USDW. The Alliance recommends deleting this provision. It is not clear how ambient air or soil gas monitoring is related to or supports the protection of USDWs. Surface air monitoring can result in false positives, which could prompt unnecessary and costly response actions and needlessly alarm the public Any requirement for ambient air or soil gas monitoring would be a matter of state discretion pursuant to state law and not the federal UIC program, and would not be federally enforceable. [FN51]

[FN51] Bath Petroleum Storage , Inc. v. Sows, 309 F.Supp. 2d 357 (N.D.N.Y 2004) (state law requiring sonar survey for UIC injection not federally enforceable).

Response: EPA acknowledges that air and soil gas monitoring are subject to variability and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believe that this should entirely preclude their use. EPA believes that surface air and soil gas monitoring in conjunction with deep subsurface monitoring as required at §146.90, can provide additional data to pinpoint the location and magnitude (or absence) of leaks that could endanger USDWs.

The final rule at §146.90(h) retains the allowance for surface air and soil gas monitoring at the discretion of the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c). EPA clarifies that the decision to use surface monitoring and the selection of monitoring methods will be site-specific (e.g., may be influenced by geology, injection depth, and operational conditions) and must be based on potential

risks to USDWs within the AoR.

EPA clarifies that use of surface air and soil gas monitoring as specified in the final GS rule at §146.90(h), as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c) is at the Director's discretion.Commenter Name: Thomas Curtis Letter ID: 0181 Commenter Organization: American Water Works Association (AWWA) Comment ID: 23699

Comment: Surface air and soil gas monitoring should be required however, baseline soil carbon dioxide levels should be determined prior to the start of monitoring. Testing for other compounds such as tracers that may included as part of the carbon dioxide injectate stream should also be considered in the development of the monitoring plan.

Response: EPA agrees that surface air and soil gas monitoring, when coupled with subsurface monitoring, may be appropriate at some GS projects to ensure USDW protection. In the final rule, at §146.90(h), the decision to require such monitoring rests with the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c). The Agency agrees with the commenter that, if air and soil gas monitoring is performed, baseline soil CO2 levels need to be determined before monitoring. This would be considered and described in the site-specific testing and monitoring plan.

Commenter Name: Robert F. Van Voorhees Letter ID: 0190 Commenter Organization: Carbon Sequestration Council Comment ID: 24358

Comment: 2. Surface Air and Soil Gas Monitoring

The goal of any UIC program regulations for GS should be to ensure that injected CO2 streams remain confined in the subsurface and do not endanger underground sources of drinking water. We are recommending sufficient requirements to ensure that this goal is achieved. As EPA seems to recognize, surface air or soil gas monitoring would impose substantial costs and the results of such monitoring would be subject to a host of confounding factors. Worst of all, such monitoring would be aimed at leakage of CO2 all the way to the surface, which - in the case of any properly-permitted GS project - would by definition be an extraordinarily low probability scenario. Accordingly, such requirements should not be imposed, nor should regulators have discretion to impose them. If there is any serious concern that injected CO2 might actually vent to the surface in a particular location, injection should not be permitted at that site in the first place. The regulations should not suggest otherwise.

Response: EPA acknowledges that air and soil gas monitoring are subject to site-specific limitations and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believe that this should entirely preclude their use. If surface monitoring were the only monitoring method employed to ensure USDW protection, direct correlation of CO2 at the surface with CO2 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 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. The final rule at §146.90(h) retains the allowance forsurface air and soil gas monitoring at the discretion of the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c).

Used in conjunction with deep subsurface monitoring, as required at §146.90, and as part of a multibarrier approach to protecting USDWs from endangerment, surface air and soil gas monitoring will increase USDW protection, enable immediate notification of the UIC Director in the case of potential USDW endangerment, and facilitate remedial action.

Commenter Name: Robert F. Van Voorhees Letter ID: 0190 Commenter Organization: Carbon Sequestration Council Comment ID: 24484 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90(h)

Proposed CCS Group Recommendations: (h) At the Director’s discretion, surface air monitoring and/or soil gas monitoring to detect movement of carbon dioxide that could endanger a USDW.

(1) The testing and monitoring plan must be based on potential vulnerabilities within the area of review;

(2) The monitoring frequency and spatial distribution of surface air monitoring and/or 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 and/or compliance with standards under 40 CFR
144.12;

Basis for CCS Group Comments: In most situations soil and air monitoring does not provide an effective method of protecting USDWs.

Response: EPA acknowledges that air and soil gas monitoring to ensure USDW protection is not necessary at all GS sites and agrees that the decision to use surface monitoring and the selection of monitoring methods for the purpose of USDW protection will be site-specific.

The Agency believes that surface air and soil gas monitoring, when coupled with subsurface monitoring, may be appropriate at some GS projects to ensure USDW protection. EPA also acknowledges that surface air and soil gas measurements are subject to variability and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believe that this should entirely preclude their use. 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.

In the final rule, at §146.90(h), the decision to require such monitoring as an additional measure to ensure USDW protection rests with the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c).Commenter Name: Robert F. Van Voorhees Letter ID: 0190 Commenter Organization: Carbon Sequestration Council Comment ID: 24542

Comment: Rule Provisions or Federal Register Cite: 73 FR 43517 EPA Preamble Question: 33. EPA seeks comment on the appropriate amount and types of monitoring that should be conducted at a GS site. Specifically, EPA seeks comment regarding the usefulness of indirect geophysical monitoring and surface air and soil gas monitoring. In addition, EPA seeks comment regarding the use of a Director-approved monitoring plan for GS sites. EPA Notice 43517.

CSC Response: Monitoring techniques and frequency should be determined on a site-specific basis. Selection of monitoring types and frequency should balance the potential risks posed by the project with the cost and potential utility of monitoring.

Surface and soil gas monitoring does not add value to the protection of USDWs. Many of the surface and soil gas monitoring techniques currently being evaluated lack the track record necessary for use in a regulatory compliance setting. Moreover, the potential for false-positives could undermine public confidence in GS technologies.

Response: EPA acknowledges that air and soil gas monitoring to ensure USDW protection is not necessary at all GS sites and agrees that the decision to use surface monitoring and the selection of monitoring methods for the purpose of USDW protection will be site-specific.

The Agency believes that surface air and soil gas monitoring, when coupled with subsurface monitoring, may be appropriate at some GS projects to ensure USDW protection. EPA also acknowledges that surface air and soil gas measurements are subject to variability and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believe that this should entirely preclude their use. 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.

In the final rule, at §146.90(h), the decision to require such monitoring as an additional measure to ensure USDW protection rests with the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c).

Commenter Name: Craig R. Walters Letter ID: 0200 Commenter Organization: Anadarko Petroleum Corporation Comment ID: 24603

Comment: Rule Provisions: 73 FR 43517 EPA Rule Issue: 33. EPA seeks comment on the appropriate amount and types of monitoring that should be conducted at a GS site. Specifically, EPA seeks comment regarding the usefulness of indirect geophysical monitoring and surface air and soil gas monitoring. In addition, EPA seeks comment regarding the use of a Directorapproved monitoring plan for GS sites. EPA Notice 43517.

Anadarko Petroleum Corporation (APC) Response: Monitoring techniques and frequency should be determined on a site-specific basis. Selection of monitoring types and frequency should balance the potential risks posed by the project withthe cost of monitoring.

Surface and soil gas monitoring does not add value to the protection of USDWs. Many of the surface and soil gas monitoring techniques currently being evaluated lack the track record necessary for use in a regulatory compliance setting. Moreover, the potential for false-positives could undermine public confidence in GS technologies. EPA should defer on using surface and soil gas monitoring technologies until their effectiveness can be demonstrated.

Response: EPA acknowledges that air and soil gas monitoring to ensure USDW protection is not necessary at all GS sites and agrees that the decision to use surface monitoring and the selection of monitoring methods for the purpose of USDW protection will be site-specific.

The Agency believes that surface air and soil gas monitoring, when coupled with subsurface monitoring, may be appropriate at some GS projects to ensure USDW protection. EPA also acknowledges that surface air and soil gas measurements are subject to variability and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believe that this should entirely preclude their use. 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.

In the final rule, at §146.90(h), the decision to require such monitoring as an additional measure to ensure USDW protection rests with the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c).

Commenter Name: Craig R. Walters Letter ID: 0200 Commenter Organization: Anadarko Petroleum Corporation Comment ID: 24708 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90(h)

Anadarko Petroleum Corporation (APC) Comments: (h) At the Director’s discretion, surface air monitoring and/or soil gas monitoring to detect movement of carbon dioxide that could endanger a USDW.

(1) The testing and monitoring plan must be based on potential vulnerabilities within the area of review;

(2) The monitoring frequency and spatial distribution of surface air monitoring and/or 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 and/or compliance with standards under 40 CFR
144.12;

Rationale: In most situations soil and air monitoring does not provide an effective method of protecting USDWs.

Response: As described above, EPA acknowledges that air and soil gas monitoring to ensureUSDW protection is not necessary at all GS sites and agrees that the decision to use surface monitoring and the selection of monitoring methods for the purpose of USDW protection will be site-specific.

In the final rule, at §146.90(h), the decision to require such monitoring as an additional measure to ensure USDW protection rests with the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c).

The Agency agrees with the commenter that, if air and soil gas monitoring is performed, baseline soil CO2 levels need to be determined before monitoring. This would be considered and described in the site-specific testing and monitoring plan.

Commenter Name: Richard Guinn Letter ID: 0210 Commenter Organization: Eastman Chemical Company Comment ID: 22726

Comment: §146.90 Testing and monitoring requirements. (h) "At the Director’s discretion, surface air monitoring and/or soil gas monitoring to detect movement of carbon dioxide that could endanger a USDW."

We recommend deletion of this requirement in its entirety. While this requirement may be suitable for determining potential air leakage relevant to monitoring of CO2 in a greenhouse gas policy context, this requirement does not provide any additional protection to migration to USDW as surface breakthrough will only occur well after the deep-surface migration of CO2 to a USDW. Surface monitoring to detect CO2 has high uncertainty and seasonal variability that is likely to result in many false positives and operational distractions. Seismic methods of tracking the CO2 plume are more effective than soil gas monitoring of CO2, which is affected by many other factors and thus is highly variable.

Response: EPA acknowledges that surface air and soil gas measurements are subject to variability and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believe that this should entirely preclude their use. 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. The Agency believes that surface air and soil gas monitoring, when coupled with subsurface monitoring, may be appropriate at some GS projects to ensure USDW protection.

The final rule at §146.90(h) retains the allowance for surface air and soil gas monitoring at the discretion of the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c). EPA clarifies that the decision to use surface monitoring and the selection of monitoring methods will be site-specific (e.g., may be influenced by geology, injection depth, and operational conditions) and must be based on potential

risks to USDWs within the AoR.

Commenter Name: Richard Guinn Letter ID: 0210 Commenter Organization: Eastman Chemical Company Comment ID: 22736

Comment: EPA seeks comment on the appropriate amount and types of monitoring that shouldbe conducted at a GS site. Specifically, EPA seeks comment regarding the usefulness of indirect geophysical monitoring and surface air and soil gasmonitoring. In addition, EPA seeks comment regarding the use of a Directorapproved monitoring plan for GS sites. EPA Notice 111

Surface air and soil gas monitoring are not useful. Seismic methods of tracking the CO2 plume are more effective than soil gas monitoring of CO2, which is affected by many other factors and thus is highly variable. Surface breakthrough represents an "after-the-fact" event. While this requirement may be suitable for determining potential air CO2 leakage relevant to monitoring of CO2 in a GHG context, this requirement does not provide any additional protection to migration to USDW as surface CO2 breakthrough will only occur well after the deep-surface migration of CO2 to a USDW. Surface monitoring to detect CO2 has high uncertainty and seasonal variability that is likely to result in many false positives, operational distractions and unduly raise public concern.

Response: EPA agrees that subsurface geochemical 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 all GS sites, as described at §146.90(d)). The Agency also believes that surface air and soil gas monitoring, when coupled with subsurface monitoring, may be appropriate at some GS projects to ensure USDW protection.

EPA clarifies that surface air and soil gas monitoring are not required at all GS sites. However, the GS rule at §146.90(h) gives the Director discretion to require surface air and/or soil gas monitoring as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c). EPA clarifies that the decision to use surface monitoring and the selection of monitoring methods will be site-specific (e.g., may be influenced by geology, injection depth, and operational conditions) and must be based on potential risks to USDWs

within the AoR.

Commenter Name: John King Letter ID: 0211 Commenter Organization: Shell Exploration and Production Company (SEPCo) Comment ID:

22781

Comment: 2. Surface Air and Soil Gas Monitoring

The goal of any UIC program regulations for GS should be to ensure that injected CO2 streams remain confined in the subsurface and do not endanger underground sources of drinking water. EPA has proposed elaborate -- and in many cases overly-elaborate -- requirements to ensure that this goal is achieved. Consequently, it is difficult to imagine how requirements for surface air or soil gas monitoring could be justified.

As EPA seems to recognize, surface air or soil gas monitoring would impose substantial costs and the results of such monitoring would be subject to a host of confounding factors. Worst of all, such monitoring would be aimed at leakageof CO2 all the way to the surface, which -- in the case of any properlypermitted GS project -- would by definition be an extraordinarily low probability scenario.Recommendation:

Surface Air and Soil Gas Monitoring should not be imposed, nor should regulators have discretion to impose them. The potential for possible leakage pathways should be demonstrated and managed during the permitting process.

Response: EPA clarifies that subsurface geochemical 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 all GS sites, as described at §146.90(d)).

The Agency also believes that surface air and soil gas monitoring, when coupled with subsurface monitoring, may be appropriate at 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 protection. However, EPA does not believe that this should entirely preclude theiruse. The decision to use surface monitoring and the selection of monitoring methods will be sitespecific (e.g., may be influenced by geology, injection depth, and operational conditions) and must be based on potential risks to USDWs within the AoR.

The final rule at §146.90(h) retains the allowance for surface air and soil gas monitoring at the discretion of the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c).

Commenter Name: Andrew Duguid Letter ID: 0226 Commenter Organization: Schlumberger Carbon Services Comment ID: 24064 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Proposed Rule: (h) At the Director’s discretion, surface air monitoring and/or soil gas monitoring to detect movement of carbon dioxide that could endanger a

USDW.

Schlumberger Suggested Revision: (h) At the Director’s discretion based on sitespecific conditions and risk- based factors, surface air monitoring and/or soil gas monitoring to detect movement of carbon dioxide that could endanger a USDW.

Schlumberger Rationale: In most situations soil and air monitoring does not provide an effective method of protecting USDWs.

Response: EPA acknowledges that air and soil gas monitoring to ensure USDW protection is not necessary at all GS sites and agrees that the decision to use surface monitoring and the selection of monitoring methods for the purpose of USDW protection will be site-specific.

In the final rule, at §146.90(h), the decision to require such monitoring as an additional measure to ensure USDW protection rests with the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c).

The Agency believes that surface air and soil gas monitoring, when coupled with subsurfacemonitoring, may be appropriate at some GS projects to ensure USDW protection. EPA also acknowledges that surface air and soil gas measurements are subject to variability and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believe that this should entirely preclude their use. 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.

Commenter Name: Mark Bohrer Letter ID: 0241 Commenter Organization: North Dakota Industrial Commission Comment ID: 23255

Comment: 33. EPA seeks comment on the appropriate amount and types of monitoring that should be conducted at a GS site. Specifically, EPA seeks comment regarding the usefulness of indirect geophysical monitoring and surface air and soil gasmonitoring. In addition, EPA seeks comment regarding the use of a Directorapproved monitoring plan for GS sites. EPA Notice 43517.

Monitoring techniques should be determined on a site-specific basis and be based upon potential risks posed by the project and the cost versus benefit of monitoring.

Response: EPA agrees that monitoring plans and methods need to be site-specific and believes that the monitoring requirements for GS sites at §146.90 provide an appropriate level of flexibility in structuring a testing and monitoring plan that protects USDWs from endangerment. The final regulation provides for flexibility in: 1) methodologies used to collect these data, 2) the spatial resolution at which the data should be collected, and 3) how often the data should be collected. The number and placement of monitoring wells will be based on site-specific information such as the calculated AoR, injection rate and volume, site geology, baseline data, and the presence of artificial penetrations within the AoR. EPA believes that this is the best approach for addressing potential

risks at GS sites.

EPA recognizes that installation of monitoring wells entails additional resources. However, the Agency believes that such monitoring is necessary to ensure that GS projects are appropriately operated and monitored and to protect USDWs from endangerment.

Although a significant cost in absolute terms, monitoring costs are expected to be a small fraction of site operating costs, according to EPA's cost analysis for the GS rulemaking (which is available in the docket). While the rule requirements will necessitate additional costs, the requirements are guided by the necessity to address the unique challenges posed by CO2 injection (including large injection volumes, the relative buoyancy of CO2, its corrosivity in the presence of water, the potential presence of impurities in captured CO2, and its mobility within subsurface geologic formations) as they protect USDWs from endangerment.

The UIC requirements are designed to ensure that where GS is employed, it is done in a manner that protects USDWs from endangerment, consistent with the UIC Program's authority under SDWA.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume andpressure 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.

Commenter Name: Kurt Waltzer Letter ID: 0250 Commenter Organization: Clean Air Task Force Comment ID: 22322

Comment: Finally, surface air monitoring techniques will not always be necessary for GS projects. As with other monitoring methods, they may work well in particular settings but not in others (for example where distinguishing from natural variability or from baseline data is hard). Current scientific thinking also

Response: EPA acknowledges that air and soil gas monitoring are subject to site-specific limitations and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believe that this should entirely preclude their use. If surface monitoring were the only monitoring method employed to ensure USDW protection, direct correlation of CO2 at the surface with CO2 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 final rule at §146.90(h) retains the allowance for surface air and soil gas monitoring at the discretion of the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c). EPA clarifies that the decision to use surface monitoring and the selection of monitoring methods will be site-specific (e.g., may be influenced by geology, injection depth, and operational conditions) and must be based on potential

risks to USDWs within the AoR.

Commenter Name: Michel Paque Letter ID: 0259 Commenter Organization: Ground Water Protection Council Comment ID: 24819

Comment: operation or closure. With respect to soil and air monitoring there is a question as to the efficacy of these as a means of protecting USDWs.

Response: EPA acknowledges that air and soil gas monitoring are subject to site-specific limitations and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believe that this should entirely preclude their use. If surface monitoring were the only monitoring method employed to ensure USDW protection, direct correlation of CO2 at the surface with CO2 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.

Used in conjunction with deep subsurface monitoring, as required at §146.90, and as part of a multibarrier approach to protecting USDWs from endangerment, surface air and soil gas monitoring will increase USDW protection, enable immediate notification of the UIC Director in the case of potential USDW endangerment, and facilitate remedial action.

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. The final rule at §146.90(h) retains the allowance for surface air and soil gas monitoring at the discretion of the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c).

Commenter Name: Michel Paque Letter ID: 0259 Commenter Organization: Ground Water Protection Council Comment ID: 24929 Other EPA Comment Codes and Descriptions: 1240 1.1.1.3 Suggested changes/edits to rule language

Comment: Rule Provision: 146.90

EPA Proposal: (h) At the Director’s discretion, surface air monitoring and/or soil gas monitoring to detect movement of carbon dioxide that could endanger a

USDW.

GWPC Recommendations: (h) At the Director’s discretion based on site-specific conditions and risk-based factors, surface air monitoring and/or soil gas monitoring to detect movement of carbon dioxide that could endanger a USDW.

Rationale: In most situations soil and air monitoring does not provide an effective method of protecting USDWs.

Response: As described above, EPA acknowledges that air and soil gas monitoring are subject to site-specific limitations and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believe that this should entirely preclude their use. The final rule at §146.90(h) retains the allowance for surface air and soil gas monitoring at the discretion of the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c).

Letter ID: 0263 Commenter Organization: Interstate Oil & Gas Compact Commission Comment ID: 24962

Comment: III A. 6 Proposed Plume and Pressure Front Monitoring Requirements

11. Specifically, EPA seeks comment regarding the usefulness of indirect geophysical monitoring and surface air and soil gas monitoring.

IOGCC Response: The IOGCC agrees that owners and operators should report semiannually on the characteristics of injection fluids, injection pressure, flow rate, temperature, volume and annular pressure, and on the results of MITs, ground water monitoring, and any required atmospheric/soil gas monitoring. The amount and types of monitoring to be required, however, should be site specific.

Response: EPA agrees that monitoring plans and methods need to be site-specific and believes that the monitoring requirements for GS sites at §146.90 provide an appropriate level of flexibility in structuring a testing and monitoring plan that protects USDWs from endangerment. The finalregulation provides for flexibility in: 1) methodologies used to collect these data, 2) the spatial resolution at which the data should be collected, and 3) how often the data should be collected. The number and placement of monitoring wells will be based on site-specific information such as the calculated AoR, injection rate and volume, site geology, baseline data, and the presence of artificial penetrations within the AoR.

EPA adds that the final rule, at §146.91(a) requires that owners and operators report semi-annually on operating data and some monitoring data. See the preamble to the final rule for additional

information.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Steven Chester Letter ID: 0264 Commenter Organization: Michigan Department of Environmental Quality (MDEQ) Comment ID:

22844 Other EPA Comment Codes and Descriptions: 4660 2.6.6 Geochemical monitoring

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

conducted at GS sites.

- Staff is not certain that the monitoring parameters listed will yield any information that relates to endangerment of USDW by leakage from the sequestration zone with the exception of the determination of the position of the CO2 plume and area of elevated pressure. Staff believes, however, that the surface casing and tubing pressures, injection rates, and volumes should be measured daily and reported on a monthly basis. It is not clear that surface monitoring will provide unambiguous information regarding the position of the injected CO2 plume, particularly in view of the uncertainty associated with the movement of the plume. It is also not clear that wells in the confining zone will be of any value since there may be no fluid movement into any particular well, and there is much uncertainty as to appropriate or optimum placement of confining zone monitoring

wells.

Response: EPA agrees that pressure monitoring in the confining zone may not provide the data needed to evaluate plume movement. Instead, the final GS regulation, at §146.90(g)(1), requires all GS project owners or operators to monitor for pressure changes in the injection zone. EPA believes that pressure monitoring in the injection zone is necessary to track the development and movement of the pressure front and CO2 plume which provides valuable information in determining whether there is a potential for USDW endangerment.

Pressure monitoring within the injection zone is necessary because any such monitoring above the confining zone would not detect movement of the pressure front unless a breach of the confining zone occurs. EPA believes that monitoring using wells in the injection zone (i.e., that penetrate theconfining zone) can be safely performed if the wells are constructed to prevent flow between the injection zone and USDWs or other layers above the confining zone. Such construction technologies exist and have been used in the oil and gas industry for years.

EPA acknowledges that air and soil gas monitoring are subject to variability and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believe that this should entirely preclude their use. For example, if a leak to the surface is suspected, surface monitoring could provide vital information on its location and magnitude to assist owners and operators in identifying what USDWs may have been impacted by a leak. EPA clarifies that the various air and soil gas monitoring methods (e.g., chambers, eddy covariance, hyperspectral imaging) all have different capabilities that may prove useful in specific GS projects (Miles, et al. 2005; Pickles and Cover, 2005; IPCC, 2005; Menzies, et al. 2001). The final rule at §146.90(h) retains the allowance for surface air and soil gas monitoring at the discretion of the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c). EPA clarifies that the decision to use surface monitoring and the selection of monitoring methods will be site-specific (e.g., may be influenced by geology, injection depth, and operational conditions) and must be based on potential risks to USDWs within the AoR.

EPA is developing guidance on testing and monitoring to assist owners or operators and Directors in evaluating requirements under §146.90, including proposed monitoring plans. The guidance describes available technologies and recommended approaches for implementing a testing and monitoring plan, including pre-operational geophysical logging and testing of injection wells, MITs, injection well testing during operation, groundwater quality monitoring, tracking the CO2 plume and pressure front, and soil gas and surface air monitoring which may be required by the UIC Director for specific GS projects. The guidance can be found on EPA’s website at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm.

Commenter Name: Michael Moore Letter ID: 0265 Commenter Organization: North American Carbon Capture & Storage Association (NACCSA) Comment ID:

22853 Other EPA Comment Codes and Descriptions: 4490 2.4.5 Use of tracers and potential impact on human health or ecosystems (seeking comment)

Comment: - Monitoring Provisions/Use of Tracers/Use ofDown-Hole Shut-off Valves: NACCSA is opposed to imposition of mandatory requirements to use tracers; conduct surface air/soil gas monitoring.

Response: EPA believes that surface air and soil gas monitoring, when coupled with subsurface monitoring, may be appropriate at 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 protection. However, EPA does not believe that this should entirely preclude theiruse. The decision to use surface monitoring and the selection of monitoring methods will be sitespecific (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 CO2 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 monitoringmay provide valuable data on the magnitude and location of a leak. The CO2 itself may serve as a tracer in the form of stable isotopes of carbon. For example, anthropogenic CO2 is depleted in 13C compared to naturally occurring CO2.

In the final rule, at §146.90(h), the decision to require such monitoring rests with the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c).

EPA 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 require their use if he/she determines that the use of tracers could improve monitoring of the site and enhance USDW protection from endangerment.

Commenter Name: Michael Moore Letter ID: 0265 Commenter Organization: North American Carbon Capture & Storage Association (NACCSA) Comment ID:

22865 Other EPA Comment Codes and Descriptions: 4490 2.4.5 Use of tracers and potential impact on human health or ecosystems (seeking comment)

Comment: 4. Monitoring Provisions/Use ofTracers/Use of Down-Hole Shut-off Valves

The proposed regulations would vest discretion in the program director to require the use of tracers and/or surface air/soil gas monitoring "to detect movement of CO2 that could endanger a USDW." NACCSA is opposed to this proposed requirement for the reasons outlined below.

The proposal raises potential issues regarding the scope ofEPA's authority. The Preamble acknowledges that regulation of surface/atmospheric releases of CO2 is outside the scope of the proposed rule and the Agency's jurisdiction under SDWA. The UIC program is designed to protect USDW`s from endangerment due to subsurface injection. The use of tracers combined with surface or soil monitoring is unlikely to be protective because by the time any tracers or CO2 is detected in these zones it may have passed through all USDWs between the injection zone and

the surface.

NACCSA is also concerned that tracers are relatively untested in terms of leak detection capabilities and transport properties. Because there have been limited tests of tracers it is not clear how they interact with the subsurface and if they are conservatively transported with CO2. Further, tracers may also pose independent safety concerns for project operators, workers, and other potentially

affected individuals and the environment.

Response: EPA clarifies that use of surface air and soil gas monitoring as specified in the final GS rule at §146.90(h), as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c), is at the Director's discretion.

If surface monitoring were the only monitoring method employed to ensure USDW protection, directcorrelation of CO2 at the surface with CO2 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 isotopes of carbon. For example, anthropogenic CO2 is depleted in 13C compared to naturally occurring CO2.

EPA believes that surface air and soil gas monitoring are within the scope of the SDWA in that they can provide additional data to pinpoint the location and magnitude (or absence) of leaks that could endanger USDWs. Used in conjunction with deep subsurface monitoring, as required at §146.90, and as part of a multi-barrier approach to protecting USDWs from endangerment, surface air and soil gas monitoring are within the scope of SDWA’s general authority (SDWA sections 1421 et al).

Regarding the use of tracers, 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 require their use if he/she determines that the use of tracers could improve monitoring of the site and enhance USDW protection from endangerment.

While the intent of the GS regulations is to prevent leaks of CO2 to USDWs, EPA clarifies that all of the protective components of the regulation, including a comprehensive monitoring program per §146.90 (which includes testing of the well, ground water quality monitoring, and tracking of the CO2 plume and pressure front) support a multi-barrier approach to protecting USDWs. Additionally, some studies (e.g., Phelps and Cole, 2008; Hovorka et al., 2004; McCallum et al., 2005) found thattracers can provide useful CO2 monitoring information at injection wells both at depth and at nearsurface locations. At Frio, tracers enabled quantification of CO2 plume behavior and provided a technique for model validity testing (McCallum et al., 2005). EPA will continue to track research related to tracer use. The Agency plans to, every six years, collect and review data on GS projects to determine whether the appropriate amount and types of information and appropriate documentation are being collected, and to determine if modifications to the requirements are appropriate or

necessary.

The provision allowing the Director to require the use of tracers and surface air and soil gas monitoring is within EPA's authority under the SDWA because these methods can provide additional data to pinpoint the location and magnitude (or absence) of leaks that could endanger USDWs. Usedin conjunction with deep subsurface monitoring, as required at §146.90, and as part of a multibarrier approach to protecting USDWs from endangerment, tracers and surface air and soil gas monitoring are within the scope of SDWA's general authority (SDWA sections 1421 et al).

Commenter Name: Karl R. Moor Letter ID: 0501 Commenter Organization: Southern Company Comment ID: 21161

Comment: I'm told that soil flux monitoring is also problematic because it can result in false positives based on natural variability in flux.

What these requirements do is, by way of example, is signal to the public that carbon capture and storage is unsafe because it could lead to a leak in CO2, despite the fact that this is very unlikely to happen. The United Nations Intergovernmental Panel on Climate Change has found that the amount of carbondioxide retained in the appropriately sited storage site was very likely to exceed 99 percent of over one hundred years.

Response: EPA believes that monitoring at a GS site is of critical importance to ensuring protection of USDWs from endangerment. Appropriately selected monitoring technologies, including surface air and soil-gas monitoring will also serve to increase public confidence in the safety of GS and to assure the public that GS projects are being appropriately operated and monitored. The information gained through such monitoring will also enable permitting authorities to take appropriate steps to address any indication that USDWs may be endangered.

EPA clarifies that surface air and soil gas monitoring are not required at all GS sites. However, the GS rule at §146.90(h) gives the Director discretion to require surface air and/or soil gas monitoring as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c).

Commenter Name: Mike Moore Letter ID: 0532 Commenter Organization: North American Carbon Capture and Storage Association (NACCSA) Comment ID:

21368 Other EPA Comment Codes and Descriptions: 4490 2.4.5 Use of tracers and potential impact on human health or ecosystems (seeking comment)

Comment: dioxide. Also the director would have discretion without any guidance to require tracers and/or gas monitoring to detect movement of carbon dioxide that could endanger a USDW. NACSA believes that these methods should not be required because there are too many questions about their efficacy and the potential risk posed by tracers.

Response: EPA acknowledges that air and soil gas monitoring are subject to site-specific limitations and may not be suitable in all settings as a method to ensure USDW protection. However, EPA does not believe that this should entirely preclude their use. If surface monitoring were the only monitoring method employed to ensure USDW protection, direct correlation of CO2 at the surface with CO2 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 isotopes of carbon. For example, anthropogenic CO2 is depleted in 13C compared to naturally occurring

CO2.

Used in conjunction with deep subsurface monitoring, as required at §146.90, and as part of a multibarrier approach to protecting USDWs from endangerment, surface air and soil gas monitoring will increase USDW protection, enable immediate notification of the UIC Director in the case of potential USDW endangerment, and facilitate remedial action.

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. The final rule at §146.90(h) retains the allowance for surface air and soil gas monitoring at the discretion of the Director as a means of identifying leaks that may pose a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC Director in the event of a USDW endangerment, pursuant to requirements at§146.91(c).

EPA agrees that tracer use is not appropriate in all situations. Some tracers may have the potential to cause harm to people or the environment. For this reason, EPA does not require the use of tracers at all GS sites. Nevertheless there are many different types of tracers and not all are problematic; research is being done to overcome problems with existing tracers. EPA believes that tracers have been used safely and successfully in other applications. Therefore the Director has discretion to require their use if he/she determines that the use of tracers could improve monitoring of the site and enhance USDW protection from endangerment. The rule will also allow their use if proposed by the owner or operator and approved by the Director.

EPA continues to follow new and ongoing research on the safety and efficacy of tracers. For example, studies at the Frio Brine Pilot Experiment site (Dayton, TX) used various types of tracers, including perfluorocarbon tracers (PFTs), sulfur hexafluoride, and the noble gases krypton, neon, and xenon. These studies (e.g., Phelps and Cole, 2008; Hovorka et al., 2004; McCallum et al., 2005) found that tracers can provide useful CO2 monitoring information at injection wells at depth and at near-surface locations. At Frio, tracers enabled quantification of CO2 plume behavior and provided a technique for model validity testing (McCallum et al., 2005). EPA will continue to track research related to tracer use. The Agency plans to, every six years, collect and review data on GS projects to determine whether the appropriate amount and types of information and appropriate documentation are being collected, and to determine if modifications to the requirements are appropriate or

necessary.