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: 0135

Commenter: Jill D. Jonas Organization: Wisconsin Dept. of Natural Resources (WDNR)

Letter ID: 0135 Comment ID: 21666 Letter Lines: 40 to 61

Comment Code: 4322 2.4.4.1.1 Comments in favor of requiri ng injection below the lowermost

USDW

Comment: Limiting CO2 Injection to Formations below the Lowermost USDW

Protecting the quality of groundwater resour ces that may be used as sources of drinking water must continue to be the highest priority for all regulations promulgated under the authority of the UIC program and the federal Safe Drinking Water Act. WDNR supports limiting CO2 inj ection to geologic formations which lie beneath the lowermost USDW and, more specifi cally, only to those deep formations that have also been determined by means of a detailed geological assessment to pose the least potential for endange ring drinking water supplies.

There may be a number of other suitable geologic formations for GS that are situated above the lowermost USDW (e.g. ba salts, salt domes, shales, coal seams, etc.); however, these formations tend to be more limited in their geographic distribution and the economic and technologica l viability of these formations as GS sites is still in quest ion. Additional study of GS in these settings can be accomplished on a case-by-case basis using th e UIC program's existing authority to approve experimental Cl ass V injection wells.

For the present, limiting large-scale CO2 injections to formations that lie

beneath the lowermost USDW while continui ng to investigate CO2 injection above the lowermost USDW using the existing rules for Class V experimental wells will not delay the deployment of this cl imate change mitigation technology.

Individual Response: EPA agrees that protecting USDWs from endangerment must be a top priority. The Agency believes that there are limited circumstances where injection above the lowermost USDW can be performed in a manner that protects USDWs, as long as appropriate protections are in place. The final GS rule at §146.95 establishes a process by which owners or operators can seek a waiver of the Class VI in jection depth requirement s for injection into nonUSDW formations above and/or between USDWs. The waiver approach requires the submission of extensive, site-specific information (in conj unction with the permit appl ication submission) to demonstrate that injection of CO2 into a non-US DW that is above or between USDWs can be done in a manner that is protective of USDWs. It establishes: 1) requirements specifying information that owners or operators must subm it, and Directors must consider, in consultation with PWSS Directors; 2) procedur es for public notice of a waiver application a nd for DirectorRegional Administrator communicat ion; 3) the waiver issuance process; and, 4) additional requirements that apply to owners or operators of Class VI wells granted a waiver of the

1injection depth requirements to ensure USDW protection above and below the injection zone.

EPA believes that the requirements at §146.95 w ill ensure USDW protection while providing flexibility to UIC Program Dir ectors and owners or operators who undertake CO2 injection for GS. The Agency believes this approach: 1) responds to concerns a bout local and regional geologic storage capacity limitations imposed by the proposed injection depth requirements; 2) allows for a more site-specific assessment of injection depth for GS projects; 3) accommodates injection into different formation types; 4) allo ws for injection of CO2 for GS into non-USDWs above and/or between USDWs when appropriate and where it can be demonstrated that USDWs will be protected; and 5) responds to concerns about the use of aquifer exemptions for GS. Finally, EPA’s approach to addressing injecti on depth variability thr ough a waiver process responds to concerns about future drinking water resource availability and the need to ensure that high quality water remains available in sufficien t quantities to supply dr inking water needs. For additional information on the waiver approach, pleas e see the final rule and preamble, as well as EPA's responses to comments on the Notice of Data Availability and Request for Comment.

Regarding the suggestion to allow experimental GS wells to continue to operate under Class V, EPA anticipates that some owners or operators will apply for Class V experimental technology permits for injection into formations including shallow basalts, coal se ams, salt caverns and shales. These formations may or may not be located above the lowermost USDW or between USDWs. To facilitate experime ntal injection for GS and to increase understanding of injection into these formation types, the Agency is amending the Class V experimental technology guidance. The guidance will be available on EPA's web site, at http://water.epa.gov/type/groundw ater/uic/wells_sequestration.cfm. EPA acknowledges that the Class V experimental technology we ll sub-classification may be a ppropriate for these projects, provided they are experimental in nature. EPA e xpects that, following the final GS rule, a limited number of experimental injection projects tes ting GS technology will continue. EPA anticipates that these projects will be small-scale and i nvolve limited CO2 volumes. However, if these projects become larger scale a nd are no longer experimental, they will need to be permitted as Class VI wells. The construction, operation or ma intenance of any non-experimental Class V GS well is prohibited, at §144.15.

Letter ID: 0135 Comment ID: 21667 Letter Lines: 63 to 74

Comment Code: 2020 1.5.1 Support Class VI designation

Comment: Class VI GS Wells

The Department also supports creation of a sixth well class for managing GS injection. The physical and chemical ch aracteristics of the carbon dioxide stream, long capture times required, volume to be injected, and various geologic settings proposed for injec tion suggest that an adaptiv e regulatory approach is most effective for managing GS wells. Cr eating a separate well classification will enable EPA and other permitting au thorities to enact the necessary

technical criteria for site characteri zation, area of review and corrective action, well construction and operation, compliance monitoring, and post2injection site care with minimal impact on existing regulations for injection practices in the other es tablished well classes.

Individual Response: EPA acknowledges the comment and agrees that tailored requirements for Class VI wells are necessary to address the unique nature of injecting large volumes of CO2 and to ensure that USDWs are protected from e ndangerment. The Class VI requirements are appropriate because of the unique nature and ri sks of CO2 injection for long-term storage (e.g., large injection volumes, long proj ect duration, and reservoir pressure conditions). The GS rule contains tailored requirements for the perm itting, geologic site ch aracterization, AoR and

corrective action, well construc tion, operation, mechanical integr ity testing, monitoring, well plugging, post-injection site care, an d site closure of GS wells that directly address issues unique to the nature of large-scale CO2 injection for GS.

Letter ID: 0135 Comment ID: 21668 Letter Lines: 76 to 92

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

Comment: Primacy for Class VI Injection Wells

As the state agency which currently regulat es all injection well classes in the State of Wisconsin, WDNR urges EPA to a llow primacy approval for Class VI wells independent of the other well classes. Fi rst, such an approach provides state permitting authorities the flexibility to implement a more comprehensive approach to managing the capture, tran sportation, and sequestration of CO2. Second, some states already have one agen cy responsible for a Class H program and have another agency managing the othe r four existing injection well classes. Independent approval enables each state to determine if it is more suitable and

cost effective to have one of those agencies or an alternative state agency administer the CO2 GS program separately from the UIC programs established for other injection well classes. Third, independent approval of Class VI injection well program primacy more clearly defines the criteria and primacy application process for those states that seek prim ary enforcement authority for GS and makes the administrative review and approva l of state primacy applications for GS more manageable for EPA.

Individual Response: EPA agrees with commenters that states should be allowed to obtain primacy for Class VI wells independently of other well classes, and will allow independent primacy for Class VI wells under §145.1(i) of th e final GS rule. Given the potential for CCS (encompassing capture, transportation, and geologic sequestration) to be an important part of a national priority to address clim ate change, EPA believes that provi ding states the flexibility to obtain primacy for Class VI wells independently of other well cla sses can help foster effective management of CCS. EPA believes that allowing independent Class VI primacy may encourage states to take responsibility for implementation of Class VI regulations and provide for a more comprehensive approach to managing CCS projects by promoting the integrat ion of GS activities

under SDWA into a broader framework for mana ging CCS. Furthermore, GS operations involve ancillary activities (e.g., pipeli ne operations, pore space ownership, land use rights, and surface

3access) for which states can call upon other authorit ies that exist at the state level (but outside UIC authority) to provide a more comp rehensive CCS management approach.

EPA also believes that allowing states to apply only for Class VI primacy will shorten the primacy approval process for states. EPA's willingness to accept independent primacy applications for Class VI wells represents a shift in its longstandi ng policy of discouraging "partial primacy." It is very important to note that this shift in policy allowing for Class VI primacy does not apply to any other well Cl ass under Section 1422. EPA will continue to discourage applications for pa rtial primacy for all other well types under Section 1422.

EPA clarifies that states should be able to obtain primacy for Cla ss VI wells independent of other well classes provided they devel op regulations that are at leas t as stringent as the minimum Federal requirements (e.g., permitting, inspec tion, operation, monitoring, and recordkeeping requirements) in the final GS rule. EPA believes that existing programs can adapt their expertise to the new requirements for Class VI wells and w ill be able to develop a primacy application for

Class VI wells under section 1422 of SDWA and en sure that their GS pr ograms integrate into national climate change priorities an d protect USDWs from endangerment.

EPA also clarifies that primacy is granted to a state, not to any agency within that state, and states are free to choose which agency will im plement the Class VI program—for instance, an environmental quality protection agency (non-Cl ass II) or the state's traditional oil and gas regulatory agency (Class II)—as long as the program meets the minimum federal requirements for Class VI wells as required under section 1422 of SDWA. Some stat es administer their program for all injection well classes through a single agency, whereas other States elect to divide the program between agencies. For example, in most States, the Class II program is run by an oil and gas agency and other well classes are run by a State envir onmental agency (e.g., the Oklahoma Corporation Commission oversees Class II wells in the State, and the Oklahoma Department of Environmental Quality oversees other well classes). Additionally, several States allow their oil and gas agencies to administer their UIC program for specific well classes or subclasses provided they meet all Federal requirements (e.g., the Texas Railroad Commission oversees Class III brine-mining we lls and Class V geothermal well s in Texas). EPA believes that retaining this flexibility for States to identify the appropriate agency to oversee Class VI wells will address commenters’ concerns that States should be afforded the opportunity to determine which agency should oversee Class VI wells, and recognizes the existing e xpertise of both State oil and gas agencies and environmental agencies.

Letter ID: 0135 Comment ID: 21669 Letter Lines: 94 to 106

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

Comment: Tailored Regulatory Requirements

WDNR supports EPA's selecti on of a flexible regulatory approach which recognizes that full-scale projects involving long-term storage of CO2 are unique due to the volume of CO2 that is to be inject ed, the buoyancy and viscosity of the

45 proposed injectate, the corrosive nature of CO2 when mixed with water, and the many geologic formations that can potent ially be used for CO2 storage. By building on the existing regulatory framework for other deep in jection wells and providing flexibility and/or discretion to the permitting authority to address site specific variabilit y, the requirements being proposed by the Agency appropriately balance the need to provi de protection to the nation's underground sources of drinking water w ith the need to provide a degree of regulatory certainty and consistency to owners and operators of GS facilities,

Individual Response: EPA acknowledges the comment, and agrees that permitting decisions for GS wells should be based on site-specific factors. The GS rule requires owners or operators to

submit, and Directors to consider, extensiv e site-specific data, specified at §146.82, to

demonstrate that a site is suita ble for GS. Additionally, many of the permit requirements for GS wells are established through individualized site-specific plans for AoR and corrective action, testing and monitoring, and injec tion well plugging and post-injecti on site care and site closure.

EPA adds that the final GS rule includes a balan ce of specific criteria to be met by the owner or operator and areas of Directorial discretion and considerations for how that discretion would be exercised. The Agency believes this balance allows for GS projects to be designed and permitted to address the unique, site-specific aspects of each project, while providing consistency in permitting across the U.S.