This comment letter response contains two parts:

(1) The original submittal from the commenter. (2) A data base printout of EPA’s response to each point raised by the commenter.

Notes about the response letters:

• The response letters were generated by a data base used to track the content of all public

comment submittals and ensure that the Agency responds to each. Each comment letter

was assigned a Letter ID that corresponds to the last four digits of the docket number of the

original comment (as posted on www.regulations.gov).

• Each response letter includes: comment text; an EPA

‐ assigned comment code; and an

individual response. These are described and explained below.

• The data base contains Comment text from the letters submitted by commenters.

Many hard copy letters were scanned into electronic format for inclusion in the data

base. As a result, there may be some typographical errors attributable to optical

character recognition issues. However, all original submittals were reviewed in the

process of drafting responses to ensure that the comment content was understood and

appropriately addressed.

• The content of each comment letter was divided into topic areas and assigned a unique

Comment ID. Additionally, one or more Comment Codes (i.e., unique topic area ID) was assigned to each discrete point raised by a commenter. This information was added to

the data base. To inform final rulemaking decisions, all comments and information

received on a given topic were reviewed by technical experts in each rule area (e.g., on

construction requirements).

• Following decisions on the final rule requirements, Individual responses were drafted

by topic area to ensure completeness and consistency of the responses with the final

rule and other responses to similar comments. Each discrete point made by a

commenter was given a unique response.

• Upon completion of comment responses, all information was entered into the data base.

Each letter response is a compilation of each comment and its individual response, compiled in the order of the original comment letter. As a result of this process, there is

repetition in the response text. The Agency believes this approach ensures completeness

and attention to each comment letter that was submitted.

• All comments in a topic area were reviewed, evaluated, and responded to concurrently.

Responses on each topic area are compiled and are also available in the rulemaking docket.Letter ID: 0188

Commenter: Daniel Plath Organization: NiSource, Inc.

Letter ID: 0188 Comment ID: 25225 Letter Lines: 50 to 55

Comment Code: 1500 1.2.2.2.4 Some other agency should regulate GS

Comment: We believe numerous program areas need to be developed to address the multitude

of issues that are certain arise to make GS a commercially viable option for the CO2 capture and storage. In all likelihood, other regulat ory authorities will be responsible for components of the GS re gulatory framework. Cl ose coordination between all parties will be needed to assure a consiste nt set of standards for

effective GS.

Individual Response: EPA clarifies that the scope of the GS regulation is limited to injection of CO2, and that all requirements in the GS rule are designed for the purpose of protecting USDWs from endangerment. The SDWA does not provide th e UIC Program with the authority to develop regulations for all areas related to GS, such as releases to the atmosphere.

EPA acknowledges that GS falls within the broade r context of CCS and the need for regulatory clarity to ensure that USDWs are protected from endangerment. In develo ping the final GS rule,

the Office of Water coordinated with other Agency program offices and across federal agencies (e.g., with the Department of Energy; United Stat es Geological Survey; Bureau of Ocean Energy Management, Regulation, and Enforcement, formerly the Minerals Management Service; Bureau of Land Management). The Agency continues to eval uate areas of potential applicability of other Federal environmental statutes including, but not limited to: the Clean Air Act; the Resource Conservation and Recovery Act; the Comprehe nsive Environmental Response, Compensation, and Liability Act; and the Marine Protection, Resear ch and Sanctuaries Act to various aspects of GS and CCS. The Agency will continue to coordinate on GS and CCS related issues to minimize redundancy and maximize efficiencies for owners or operators. For additional information, please see the discussion entitle d "How Does This Rulemaking Relate to Other Federal

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

Regarding the need for a CCS agency to coordi nate across agencies, EPA is coordinating with

and will continue to facilitate communication among federal and state agencies during the implementation phase of the GS regulation.

EPA adds that the intent of the GS rule is not to promote GS. Rather , the purpose of the GS regulation is to assure that, where deployed, GS is conducted in a manner that protects USDWs from endangerment.

Letter ID: 0188 Comment ID: 25226 Letter Lines: 57 to 71

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

1Comment Code: 2400 1.8 Comments on EPA's adaptive rulemaking process

Comment: Recognizing that a great deal of this technology is curre ntly in development and will not be commercially deployed for seve ral years, it is vital that the final rule, if necessary, in clude reasonable performance ba sed regulations that can be swiftly adjusted and finetuned as experi ence is gained in large-scale CO2 GS. The promulgation of this rule is only but the first step in the establishment of a regulatory framework to support the implem entation of GS as the technology is scaled up from the current experimental stage to fully operational wells, considerable experience will be gained th at would help further identify areas where adjustments to the rules would be necessary. Therefore, we recommend a two phase regulatory approach. The first phase would be to addres s initial projects where operational experience and familiar ity with carbon injection and storage can be gained. That knowledge, includi ng lessons learned from the both the technical and regulatory perspe ctive, could then be uti lized to develop a second phase rule that would more likely be ab le to provide a better balance between risks with regulatory requirements.

Individual Response: EPA agrees that an adaptive approach to the UIC GS rulemaking is appropriate. The Agency plans to use such an appr oach to ensure that USDWs are protected from endangerment and meet the potentially fast p ace of GS deployment. EPA believes that an adaptive approach will allow regulatory developmen t to proceed in time to meet the current and future demand for Class VI permits while recognizi ng the need to: continue to gather data from pilot projects and other research as it becomes available; and to enhanc e understanding of the technical and administrative asp ects of GS deployment, operati on, and technology developments.

EPA plans, every six years, to collect and review data on GS projects to determine whether the appropriate amount and types of information a nd appropriate documentation are being collected,

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

EPA disagrees that the GS rulemaking needs to be based solely on large-volume projects. While studying the impact of injecting large volumes of CO2 is important, data on other aspects of GS—including the buoyancy and corrosivity of CO2 in the presence of water, the potential presence of impurities in captured CO2, and its mobility within subsurface formations— informed the rulemaking.

Letter ID: 0188 Comment ID: 25227 Letter Lines: 73 to 76

Comment Code: 1000 1. General and Administrative Comments

Comment: NiSource would also like to make the point that we support the comments made on the behalf of natural gas utility members by the American Gas Association (AGA). In particular, we would like to echo the AGA's concerns regarding the protection of geologic natural gas storage.

Individual Response: EPA acknowledges the comment. Pleas e see the remainder of EPA's

2responses to this comment and AGA’s comments for further details. For additional information on EPA's final regulatory approach, please see the final rule and preamble as well as the rulemaking docket.

Letter ID: 0188 Comment ID: 25228 Letter Lines: 112 to 119

Comment Code: 1310 1.1.2.4 Comments on other "out of scope" issues, e.g., pore space ownership

Comment: While NiSource will readily agree that there are many differences between storage of natural gas and geologic sequest ration of CO2, NiSource submits that

there are a number of tec hnical and commercial simila rities in addition to lessons that can be applied from decad es of injection and control of high pressure natural gas. These similarities include technical issues, securing mineral rights, landowner relations, coexis ting with third party development of

the surface and subsurface, and a wide range of regulatory and commercial aspects. The following points summarize four primary lessons learned through

Individual Response: EPA recognizes that the oil and gas industry has decades of experience injecting CO2 and has demonstrated the effectiven ess of many of the technologies that will be employed at GS sites. The Class VI GS rule build s on this expertise with requirements tailored to the unique issues associated with GS thr ough proper permitting, siting, well construction, operation, monitoring, and closure of GS projects. However, EPA clar ifies that pore space issues are outside the scope of the Cla ss VI GS rulemaking. EPA clarifies that these issu es are under the purview of states and any of these issues, as th ey relate to GS, will need to be addressed though state regulations.

Letter ID: 0188 Comment ID: 25229 Letter Lines: 119 to 137

Comment Code: 1610 1.3.1 Risks to USDWs

Comment Code: 3400 2.2.2 Corrective Action

Comment Code: 3800 2.3 Proposed Injection Well Construction Requirements (40 CFR 146.86)

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

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

1. History has shown that the one component in the system that has caused the most safety issues is the wells; specifi cally the operator's wells, plugged and abandoned (P&A) wells and third part y operating wells (e .g. oil and gas production wells). The casing and cement in the storage well is the "first line of defense" in the containment of high pressure gas and a properly designed,

constructed and maintained well is crit ical. Even after se veral decades of

3operations over a four State area, NiSour ce subsidiaries have never experienced loss of containment from cap rock leakage, migration up faults, re-activation of faults, earthquakes, or the other potentia l leakage pathways that EPA discusses in the Proposed Rule. While history will ultimately reveal the root causes of future problems, if any, with GS, NiSource submits that the predominant cause will likely be identified as being relate d to an active well, abandoned well or third party well if not properly addressed in the Final Rule. This is based on the belief that the rigorous site se lection process will preclude the other

sites that would have had other issues, e.g. cap rock leakage, from even being activated in the first place.

Individual Response: EPA agrees that proper site characterization should minimize leakage through faults, breaks in the seal of the conf ining layer, and other geologic pathways. EPA believes that the construction, operating, and monito ring requirements in the GS rule will prevent leakage from occurring through active wells. Appr opriately designed and constructed wells are necessary to prevent endangermen t to USDWs and maintain inte grity of the well throughout the lifetime of a GS project. This is the foundation of the requirem ents for construction and preoperational testing of Cla ss VI wells at §§146.86 and 146.87.

EPA also agrees that the AoR and correctiv e action process should identify both abandoned wells and third party wells that could serve as leakage pathways. The UIC Program's longstanding approach to corrective act ion, tailored to the potential corrosivity of and impurities in

the CO2 stream, can address the potential risk associated with improperly plugged wells in the

AoR.

EPA notes that the final rule, at 40 CFR §124.10(c)(1 )(xi), requires the notif ication of state oil and gas agencies, state mineral exploration agen cies, and state public wa ter supply supervision directors about the availability of the draft permit . EPA expects that such notific ation can help with further identifying wells in the area of review.

Letter ID: 0188 Comment ID: 25230 Letter Lines: 119 to 120 ; 139 to 148

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

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 pe rformed many of the pre-activation and monitoring, measuring and verification ( MMV) activities EPA di scusses. While these technologies are useful, a number ar e primarily applicable to the initial development of a new field or as niche diagnostic tools for specific problems. Applying a large number of MMV technique s is appropriate for pilot projects though it is rarely a best practice for an established commercial application

where the historical risks are well know n and where there are practical limits on staff's time, budgets and other resources. Ultimately, the cost of GS will be

4passed on to electric customers and govern ment regulations need to provide a balanced perspective.

Individual Response: EPA agrees with commenters and believ es 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 performe d at a site is appropria te for site operational conditions and the geologic setting. EPA believes th at 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 co llect these data, 2) the spatial resolution at which the data should be co llected, 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, inject ion 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 exis t for complying with other requirements, such as tracking the positio n of the plume and pressure front within the injection zone.

Flexibility is also provided re garding how to monitor for the sp ecific data required by the final rule. The testing and monitoring plan is develope d by the owner or operato r 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 reco mmended approaches for implem enting a testing and monitoring plan, including pre-operational geophysical logging and testin g of injection wells, MITs, injection well testing during ope ration, groundwater quali ty monitoring, tracking the CO2 plume and pressure front, and soil gas and surface ai r monitoring which may be required by the UIC Director for specific GS projects.

Letter ID: 0188 Comment ID: 25231 Letter Lines: 119 to 120 ; 150 to 159

Comment Code: 1310 1.1.2.4 Comments on other "out of scope" issues, e.g., pore space ownership

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

3. NiSource subsidiaries' experience is that it is impossibl e to obtain 100% agreement from thousands of landowners on the development of their subsurface for virtually any activity even with numerous public meeting, private

5discussions, newsletters, et c. For GS to be utilized beyond the pilot project

scale, this issue must be addressed. While this topic is not directly within the scope of EPA and this Proposed Rule, EPA's requirements can have an impact on the degree and extent to which a potential operator will have to interfere with a landowner. That will directly impact a landowner's willingness to accept GS on their property. Excessive MMV regulations can cause the landowner to have an incorrect perception as to the safe ty of GS under their property.

Individual Response: As described above, pore space issues are outside the scope of the Class VI GS rulemaking. EPA clarifies that these issues are under the purview of states and any of these issues, as they relate to GS, will n eed to be addressed th ough state regulations.

EPA acknowledges that CO2 plumes may cross state or even intern ational boundaries and encourages cooperation and coordination among pe rmitting authorities. The final Class VI GS rule, at §146.82(a)(2), requires the owner or operator to identify a ll State, Tribal, and Territorial

boundaries within the AoR. Based on this info rmation, the Director must provide written

notification to all States, Tribes , and Territories to inform them of the permit application and ensure that they are involved in any necessary processes; this new requirement was added to the final rule at §146.82(b). The Agency encourages transparency in the permitting process and anticipates that State-State/State-Tribal communication on Class VI permitting will facilitate information sharing and encourag e safe, protective projects.

Letter ID: 0188 Comment ID: 25232 Letter Lines: 161 to 168

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

Comment Code: 1260 1.1.1.5 More certainty/stringency is needed

Comment: 4. For an activity covering such a divers e geographic, geologic, and commercial spectrum as GS, NiSource believes it is essential to incorporate considerable regulatory flexibility. However, some relatively high minimum standards of technical requirements should be established in key areas. While this may sound contradictory, NiSource's observation is th at firmly addressi ng those few real risks will ultimately pay significant dividends by preventing a few "bad" projects from being developed that ultimatel y lead to an avoidable incident that taints the entire industry. These issues are addressed below.

Individual Response: The Agency believes that the Class VI requirements balance site-specific flexibility with USDW protection. Rather than setting performance or technology-based standards for GS projects, EPA is adopting a flex ible approach, where operators of GS projects would develop and implement site-specific plans for delineating the AoR, testing and monitoring the site, performing corrective actio n, and post-injection site care . EPA believes that the plans— which would be reviewed and approved by the Director and periodical ly updated throughout the life of the project—promote an ongoing dialogue between the operato r and the Director that will encourage use of the most appropriate t echnologies for a particular project.

6Letter ID: 0188 Comment ID: 25233 Letter Lines: 179 to 183

Comment Code: 3400 2.2.2 Corrective Action

Comment Code: 3800 2.3 Proposed Injection Well Construction Requirements (40 CFR 146.86)

Comment: The Proposed Rule adequately addresse s the issues of well construction requirements and the review of ex isting plugged and abandoned wells. Specifically, Section 146.86 would have suffi cient number of cemented strings of pipe in the well while Section 146.84 w ould ensure that abandoned wells are properly plugged.

Individual Response: EPA acknowledges the comment and ag rees that the requirement for long-string casing of Class VI wells at §146.86(b) will offer the best protection against fluid movement behind the casing, betwee n formations, and above the injection zone and will ensure competency of Class VI wells and protect US DWs from endangerment. The buoyant nature of CO2 dictates deep well construction procedures that address movement of fluid behind the casing and provide necessary barriers to CO2 leakage outside of the injection zone. In developing the construction requir ements for Class VI wells, EPA reviewed the work cited by Carey et al. (2007) and Crow et al. (2008). EPA believes that they offer important justification for the establishment of tailored requirements.

EPA agrees that corrective action as required at §146.84(d) is an importa nt part of preventing endangerment of USDWs from CO2 or associated fluids. EPA believes th at the UIC Program's long-standing approach to correc tive action, tailored to the potential corros ivity, and impurities in the CO2 stream, can address the potential risk associated with imprope rly plugged wells in the

AoR.

Letter ID: 0188 Comment ID: 25234 Letter Lines: 185 to 202

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

Comment: As discussed above, addressing these two i ssues aggressively as proposed by EPA will significantly ensure the confinement of the CO2. The corollary is that it would not be in the interest of USDW pr otection or GS's accep tance by the public for EPA to grandfather well construction pr actices that are significantly below the standard set forth in the Proposed Rule so as to permit the conversion of a

different UIC Class well to Class VI. Simply put, if the operator can not recondition the wells to substantially meet the rigorous standards as set forth

in the Final Rule for technical, financ ial or other reasons, then the wells

should not be used for GS. While S ection 146.81(c) does no t specifically indicate an automatic grandfathering of Cl ass I, II, or V wells for Class VI, it should be clear that the phras e "...at the Director's di scretion ..." means that the wells will have to substantially or virtually meet the "Injection Well Construction Requirements" in Section 146.86 and not simply meet some limited portion of those requirements.

7While NiSource will be advocating for grea ter flexibility in other sections in

its comments, NiSource recommends caution on the issue of grandfathering well construction practices.

Individual Response: EPA agrees that a cautious approach to grandfathering is appropriate, particularly given that the convert ed well will be used for a substa ntially different process, which involves increased reservoir pre ssures associated with large volumes of stored CO2 and the corrosivity of CO2 in the presence of water. The final GS rule allows provides for the construction of these wells to be grandfathere d (per 146.81(c)). EPA has included a requirement

in the final GS rule that owne rs or operators seeking to conv ert existing wells for long term storage must demonstrate to the Director that the grandfathered wells were engineered and constructed meet the requirements at §146.86(a) and ensure protection of USDWs, in lieu of requirements at §146.86(b) and §146.87(a). EPA clarif ies that only the cons truction requirements are grandfathered and th at all other Class VI requiremen ts (reporting, monitoring, mechnical integrity testing, etc.) must be met following a determination under §146.81(c). EPA disagrees that this requirement "lowers the standard" for GS wells. Conversion of th e well would be at the Director's discretion following an evaluation of all other site-sp ecific information about the well and the project, e.g., modeling, monitoring, and other data. Any wells that ha ve deteriorated due to contact with incompatible injected or form ation fluids may not be approved for conversion.

Letter ID: 0188 Comment ID: 25235 Letter Lines: 204 to 224

Comment Code: 3840 2.3.2 Horizontal well drilling techniques (seeking comment)

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

Comment: 2. Horizontal Well Construction and Inj ection Parameter Limitations (73 Fed. Reg. at 43509 and 43510)

The EPA is inclined to permit hydraulic fracturing (frac jobs) and horizontal wells and asks for comments on permitting these technologies. NiSource strongly believes they should be permitted in addi tion to similar new technologies that will be developed sometime in the future.

Columbia has successfully performed thousa nds of fracs and refracs in addition to drilling numerous horizont al and other non-vertical types of wells. One of the keys to ensure gas confinement is to have the fewest number of penetrations of the cap rock. Both frac jobs and horizontal wells permit significantly greater injectability from a single well. Our experience is that this type of work can increase injectability by 2 to 8 times or to phrase it differently, only one- eighth to one-half the number of wells would be required to match the equivalent performance of vertical wells or non-stimulated wells.

Whatever technologies that can be employed, whether exis ting or new, to reduce the number of penetrations are valuable from a surface environmental impact, landowner acceptance, and cost management perspective and should be allowed by

8this regulation.

Individual Response: In the final rule, EPA allows the use of horizontal wells at GS projects. In the proposed rule, EPA sought comment on the appr opriateness of horizontal drilling techniques

for Class VI wells, and commenters representing energy companies, el ectric utilities, the oil and gas industry, CCS associations, states, and the public, unanimously suppo rted the concept and provided many reasons why horizonta l wells could be beneficial at GS sites. Based on an evaluation of these comments and additional research by EPA, the Agency has concluded that horizontal wells that are properly constructed, logged, and tested for mechanical integrity (i.e., to meet the requirements of the GS rule) can ensu re the protection of US DWs from endangerment.

The final rule allows the use of hydraulic fractu ring for purposes of Class VI injection, where approved by the Director. Hydraulic fracturing is one of several st imulation technologies available to improve wellbore and formation injectivity.

EPA clarifies that all stimula tion, including hydraulic fracturing, must be approved by the Director and that §146.88(a) permits injection pr essure to exceed 90 percent of the fracture pressure only during well stimulation. Owners or operators must submit a proposed stimulation program as part of the permit application unde r §146.82(a)(9); the plan mu st demonstrate that any stimulation activities will not compromise the integrity of the confining zone. The Director will evaluate the owner or operator's proposed stimu lation plan in the context of all information about the site, and the owner or operator mu st perform stimulation only as approved.

The final rule at §146.91(d)(2) also requires that the owner or operator notify the Director 30 days before performing stimulation during the operational phase of a GS project; this will provide an additional opportunity for the Director to review the owner or operator's plans for stimulation and add other requirements as neede d. EPA clarifies that UIC regulations prohibit fracturing of the confining zone at any time during injection or stimulation.

Letter ID: 0188 Comment ID: 25236 Letter Lines: 226 to 238

Comment Code: 4490 2.4.5 Use of tracers and potential im pact on human health or ecosystems (seeking comment)

Comment: 3. Proposed Injection Well Operating Requi rements (73 Fed. Reg. at 43512-13)

The Proposed Rule states that tracers are not mandated to be used but are at the

Director's discretion to re quire. Columbia has utili zed tracers in several fields over the years and has found them to be a useful tool for specific applications. It is not, however, a tool that is useful all the time for every field. While it is not overly expensive relative to the rest of the facility cost, it is a very labor and data intensive application and would represent a resource misallocation if mandated by the Final Rule. NiSource believes it would be inappropriate to grant the Director the ability to exercise discretion to require their use. Instead, we believe it would be much more beneficial to simply allow the operator the ability to use tracers at his or her discretion

9when appropriate to addre ss specific situations.

Individual Response: EPA agrees that tracer use is not ap propriate in all situations. 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 th e use of tracers could improve monitoring of the site and enhance USDW prot ection 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, including their efficiency and cost-effectiveness. The Agency plans to, every six years, collect and review data on GS projects to determin e whether the appropriate amount and types of information and appropriate documentation are being collected, and to determine if modifications to the requirements are appropriate or necessary.

Letter ID: 0188 Comment ID: 25237 Letter Lines: 240 to 287

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

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 ever y 5 years (Preamble (73 Fed. Reg. at 43515). Notwithstanding our comments belo w 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 ev ery 5 years. NiSource recommends where appropriate that this be eith er done at an interval no greater than two years or at a site specific inject ed 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 t ool 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 te sting is conducted at consistent time

intervals and volume levels over the life of the field. Th is 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 ga s, 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 se veral 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 identifi cation 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 experien cing gas migration issues then allows the operator to focus resour ces to identify the root cause and to rectify the specific probiem. NiSource be lieves these testi ng provisions would

10be helpful if included in the proposed ru le. Therefore, we suggest the rule language be adjusted to a ccommodate these factors.

While the volume in a GS field will be c ontinually increasing versus cycling as with natural gas storage, the concept of having snap shots of the shut-in reservoir pressure for the entire CO2 plum e at consistent time/volume intervals

should still lead to a similar understa nding of the plume's overall behavior. These observations can then be compar ed 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-i n 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 vol ume 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.

Individual Response: EPA believes that a frequency of at least once every five years, as specified at §146.90(f), is an appropr iate 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 proj ect, if necessary based on sitespecific circumstances. Pressure fall-off tests ma y be conducted in conjunction with other well performance tests (i.e., mechanical integrity testing) to ensure sa fe 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, pursu ant to the approved testing and monitoring plan. If any sitespecific information indicates a need for additiona l or more frequent testing to ensure USDWs are protected, it is within the Director's discre tion to require additi onal testing to ensure protection of USDWs.

Letter ID: 0188 Comment ID: 25238 Letter Lines: 289 to 303

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

Comment: 5. Data and MMV Requirements (146.82 and 146.90)

The Proposed Rule has potentially very ex tensive data and monitoring, measuring and verification (MMV) requirements, partic ularly once this is an established and proven technology. The required data to prudently develop a GS site and to monitor the gas plume is extremely site specific and industry knowledge base

11dependent. A pilot project will inherently require more frequent and diverse data collection and modeling than the nt h project in the same formation. The Final Rule needs to recognize the clear di fferences in data requirements for first of its kind projects, where the prim ary driver is risk mitigation due to the multitude of unknowns, versus the appl ication of a well developed technology for which cost effectiveness is the primar y consideration because the experience and knowledge exists to effectively identif y and manage the risks. NiSource does not see any recognition of this significan t difference in the Proposed Rule and respectfully submit that EPA in corporate language accordingly.

Individual Response: EPA acknowledges that early pilot proj ects may focus on gathering data to inform GS technology. However, EPA believes that a detailed geological site characterization of every GS site (as required under §146.82) is esse ntial to evaluating the presence and adequacy of the various geologic features necessary to receive and confine inje cted CO2 for GS. The requirements for geologic site characterizati on are based on a long standing UIC regulatory framework developed to address specific risks to USDWs posed by injection. The Class VI GS requirements are tailored so that they are appr opriate for the unique natu re of injecting large volumes of CO2 into a variety of geological forma tions for long-term storage. EPA adds that, if

data on a formation or site collected in connect ion with an earlier proj ect can support a geologic

characterization, the Director has discretion to accept this data, provi ded it is sufficient to demonstrate site suitability.

The mission of the UIC program and the goal of the GS regulation is to protect USDWs from endangerment, and every aspect of the GS rule is designed toward th at end. Therefore, EPA disagrees that any of these pr otective requirements are unnecessa ry, and clarifies that waiving any of the requirements would not be acceptable. The GS regulation allows flexibility where appropriate.

Letter ID: 0188 Comment ID: 25239 Letter Lines: 305 to 320

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

Comment: 6. Automatic Downhole Shut-off Systems (146.88)

The Rule proposes to require automatic downhole shut-off subsurface safety valves. Experience by multiple natural gas storage operators, including Columbia is that subsurface safety valves actua lly increase the safety risks to the public and company personnel. Some operators , including ours, have even realized

that the theoretical benefit does not out weigh the real world risks and have

removed them from most of their wells. The safety valves have been relegated to the role of a niche application where a dditional safety features are necessary, e.g. a very high flow rate well in the midst of suburban housing because the product being stored has a high flammability characteristic.

The Final Rule should not require the appl ication of every safety feature in every instance as much as it should provide regulatory flexibility in

12recognition that the risks pos ed by all wells are not e qual and that the best way is to tailor the design for the specific situation.

Individual Response: After evaluating the risks and benefi ts of down-hole shut-off systems and considering additional research, EPA will not re quire automatic down-hole shut-off devices for onshore Class VI wells since it is not necessary in all cases to ensure protection of USDWs from endangerment. Instead, the final rule, at §146.88(e)(2 ), requires that owne rs or operators of

onshore Class VI wells install automatic surface shut-off devices. The rule affords Director's

discretion to mandate automatic down-hole shut -off devices in onshore situations that may warrant their use. However, the Agency believ es that offshore Class VI wells present unique construction and operational conditi ons, including isolation from shorelines and the need to construct wells through the water column and the subsurface, which may delay response time in

the event of well difficulties. Th e rule requires, at §146.88(e)(3), that owners or operators of

offshore wells within State territorial waters install automatic down-hole shut-off systems. EPA believes that these requirements at §146.88(e) ensure that proper precautions are taken to prevent subsurface fluid movement and ensure protection of USDWs.

Letter ID: 0188 Comment ID: 25240 Letter Lines: 322 to 344

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

Comment: 7. Post Site Care and Site Closure (146.93)

A fixed time period of 50 years of post in jection site monitoring before site closure can occur is highly speculative as noted by EPA in the Preamble. NiSource believes that the appropriate me thod is a performance-based standard which is site specific. While we recogni ze the potential flexibility granted in 146.92(b)(2) for the Director to permit a shorter time period if supported by the data, the reality is that when a potential operator is evaluating development of a site, the 50 year monitori ng period will be use d. This may have the chilling effect of discouraging would- be developers from undertaking a GS project in the first place. On the ot her hand, if while collecting site evaluation data a potential operator has the ability to model the potential closure period based on the expected performa nce of the reservoir, then they are likely to be more willing to undertake the project if the initial data indicates

a more reasonable site closure time fr ame. This would also encourage the development of new technologies to more efficiently manage the closure period.

Based on many of the other discussions taki ng place on the GS topic, such as the Interstate Oil and Gas Compact Commission' s recommendations, this is a topic that may likely have a legi slative solution as opposed to a regulatory solution. The primary outcome of EPA's inclusion of this feature in the Final Rule has the potential of encumbering efforts to devel op GS as a viable means of long-term storage of CO2.

Individual Response: EPA agrees with commenters that th ere will be circumstances where it

1314 can be demonstrated in less than 50 years that the plume and pressure front no longer pose a risk of endangerment to USDWs. For this reason, the GS rule offers owners or operators flexibility regarding the duration of the PISC timeframe by: (1) allowing the Director discretion to shorten or lengthen the PISC timeframe during the pos t-injection period based on site-specific data, pursuant to requirements at §146.93(b) ; or (2) affording the Director discretion to allow a Class VI well owner or operator to demonstrate, during the permitting process based on substantial data, that an alternative PISC timeframe may be appropriate if it ensu res non-endangerment of USDWs pursuant to requirements at §146.93(c).

EPA believes however, that to ensure USDW protection from enda ngerment, a default timeframe for post-injection site care will be necessary in al l but a limited number of cases. This default 50 year post-injection site care ti meframe represents a reasonable and protective monitoring period

based on a review of research studies, industr y reports, and existing environmental programs, and evaluation of public comments.

EPA believes that a default post-injection site car e timeframe of 50 years, with flexibility to adjust the timeframe for a limited number of GS projects during the permitting process where

substantial data exists to demonstrate that an alternative timeframe would be protective of USDWs, or based on data collected during the PISC period, is appropriate to address the range of sites where GS is anticipated to occur, to ac commodate site-specific circumstances and various geologic conditions, and addre sses commenters’ concerns, wh ile ensuring USDW protection. Both approaches will utilize si te-specific data, and be based on pressure monitoring and USDW impacts. EPA adds that the purpose of the GS rule is not to incentivize the use of GS; rather, the purpose

of the GS rule is to ensure that, where GS is deployed, it is conducted in a manner that protects USDWs from endangerment.