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.EPA-HQ-OW-2008-0390-0153

Document ID: EPA-HQ-OW-2008-0390-0153

Last Name: Pirner

First Name: Steven Title: Secretary Organization: South Dakota Department of Environment and Natural Resources City: Pierre

State: SD Zip Code: 57501

Phone Number: 6057733151

Fax Number: 6057736035 Country Code:

Email Address: Current Category Code: 250

Comment:

Docket ID: EPA-HQ-OW-2008-0390

Docket Title: Underground Injection Control (UIC) Program: Federal Requirements for Class VI Injection Wells for the Geologic Sequestration of Carbon Dioxide - Proposed Rule

Listed below are comments from the South Dakota Departmment of Environment and Natural Resources regarding the proposed EPA rules establishing a new class of underground injection wells pertaining to the deep well geologic sequestration of carbon dioxide. Part I are more general comments, while Part II consists of more regulation specific comments.

We appreciate the chance to comment on the rules. In general we believe EPA has done a good job in formulating rules that will be protective of underground sources of drinking water (USDW) without being overly stringent on operators, given the potential size, scope and impact of the sequestration operations. Our main concerns focus on states being given sufficient flexibility to regulate such a program efficiently and effectively.

Sincerely,

Steven M. Pirner Secretary South Dakota Department of Environment and Natural Resources

Part I:

1. South Dakota recommends that more flexibility be given to the type and location of formations where CO2 can be sequestered. At this point EPA is proposing to only allow sequestration in formations below the lowermost USDW (as noted in 144.6 (f), and 146.5 (f)). In South Dakota there are strata that could potentially be used for sequestration that are above the lowermost USDW and have significant confining beds. The eastern portion of the state is generally unsuitable for sequestration as the Precambrian basement rock is less than 3000 feet deep in most places, is used as a USDW in some areas, and an additional USDW directly overlies it in some cases.

2. To allow for additional flexibility, South Dakota recommends that aquifer exemptions be allowed for Class VI wells.

3. We would also recommend that a minimum injection depth for CO2 sequestration not be required, again to allow states more flexibility in determining areas where the process can occur. We believe the initial site evaluation, testing, modeling and so forth required of the owner/operators of a geologic sequestration site along with all operational testing would maintain protection of a USDW without requiring a prescriptive depth limitation.

4. South Dakota recommends that EPA allow states to gain regulatory primacy of Page 1EPA-HQ-OW-2008-0390-0153 UIC Class VI wells without having to also take primacy for the other UIC classes in Section 1422 of the SDWA. Class VI wells actually appear more closely related

to UIC Class II wells in Section 1425 of the SDWA than those in Section 1422.

5. There was no appreciable discussion of funding mechanisms to run the program

at the state level.

Part II:

144.18 Requirements of Class VI wells - owners must get a permit versus ruleauthorization - much more detailed application, and has/allows for public input. We are in agreement with this.

146.81 Applicability (c) - exempts Class I, II, and V wells from having to do cement work-overs if wells protective of USDWs - this is good use of these other wells once their original use is completed

(d) - Definitions - Area of review - as defined, is equivalent of Class II Radii

of Influence - since this is calculated instead of established as a fixed radius as set by a lot of states' regulations, this will relieve a lot of confusion, especially for the use of horizontal wells

- Geologic sequestration - subsurface emplacement of CO2 - good specification in definition as some more local organizations refer to "carbon sequestration" as also putting CO2 in wetlands and/or planting trees in surface. If states have to establish their own regulations, this definition could help differentiate the surficial aspect from subsurface sequestration

146.82 Required Class VI permit information - (e) ".... and any additional information the Director may require:" - this is good part, as we as a state have had numerous occasions when operators do not submit all of the information needed to determine the viability of an application for a well because it is not specifically listed in the state regulations

146.84 Area of review and corrective action - (b) (2) (i) the need to reevaluate the area of review a maximum of every 10 years - great clause, we have potential for problems in our Class II program where operators could potentially over inject, especially if the life of permit expires

146.85 Financial responsibility - (b) need to re-evaluate AOR, CAP, P&A, and post-injection site care and closure plans and the financial resources needed to address them on a frequency set by Director - this prevents the initial determination of bonding from becoming inadequate in future - our Class II regulations set a specific amount that can not be changed over time, and allow for a group of wells to be covered under the same, inadequate statewide bonding

mechanism

146.86 Injection well construction requirements - (a) (2) well must be constructed such to allow appropriate testing devices and work-over tools - this is a good clause also, as our Class II regulations have allowed for a temporarily abandoned well that was worked over in such a way so it will be difficult to MIT it - may have to bring in an expensive R(adio)A(ctive)T(racer log) test rig - we couldn't prevent it under our Class II regulations

(b) (2) extending surface casing through the base of the lower-most USDW - this may be over kill in areas where there are multiple aquifers at numerous different depths. Especially in areas where the upper USDWs easily fulfill the needs of the populace, and the deeper USDWs are of high TDS content, and may take considerable, expensive treatment to bring it to palatable levels. In addition, this would be more overkill if both the tubing and long string injection casings are cemented from bottom to surface.

(b) (3) at least one long string must extend to the injection zone and be Page 2EPA-HQ-OW-2008-0390-0153 cemented to the surface - same as comment for (b) (2) previous - especially if tubing is cemented from top to bottom, and long string is cemented into surface casing.

146.88 Injection well requirements - (c) the annulus pressure needs to exceed the injection pressure - don't know why, as long as there is enough difference so sensors/gauges can indicate when something goes wrong.

Page 3Letter ID: 0153

Commenter: Steven Pirner Organization: South Dakota Department of Environment and Natural Resources

Letter ID: 0153 Comment ID: 22133 Letter Lines: 28 to 31

Comment Code: 1420 1.2.1.1 Support the GS rulemaking

Comment: We appreciate the chance to comment on the rules. In general we believe EPA has done a good job in formulating rules that will be protective of underground sources of drinking water (USDW) without being overly stringe nt on operators, given the potential size, scope and impact of the sequestration operations. Our

Individual Response: 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 fram ework for regulating injection of CO2 for GS and adds that the GS regulati on 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 potenti al presence of impurities in captured CO2, and its mobility within subsurface geologic formations.

Letter ID: 0153 Comment ID: 22134 Letter Lines: 31 to 33

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

Comment Code: 1530 1.2.3.1 State regulatory effort s on GS (seeking comment)

Comment: given the potential size, scope and impact of the sequestration operations. Our main concerns focus on states being give n sufficient flexibility to regulate such a program efficien tly and effectively.

Individual Response: EPA clarifies that SDWA, under sec tion 1422(b)(3)(9)(A), requires that the regulations of the Administrator "permit or provide for varying geologic, hydrological, or

historical conditions in di fferent states and in diffe rent areas within a state. " In the final GS rule, EPA has provided the Director di scretion in applying the GS requi rements, taking into account varying conditions, particularly with regard to the evaluation of site characteristics.

For additional information, please see the discussi on of EPA’s Final Regula tory Approach in the preamble to the final GS rule and the section entitled, “How Does This Action Affect UIC Program Implementation?"

Letter ID: 0153 Comment ID: 22135 Letter Lines: 43 to 44

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

1Comment: 1. South Dakota recommends that more fl exibility be given to the type and

location of formations where CO2 can be sequestered. At this point EPA is

Individual Response: EPA agrees that permitting decisions for GS wells should be based on site-specific factors. The GS ru le requires owners or operators to submit, and Directors to consider, extensive site-specific data, specified at §146.82, to demons trate that a site is suitable for GS. Additionally, many of the permit require ments for GS wells are established through individualized site-specific pl ans for AoR and corrective actio n, testing and monitoring, and injection well plugging and post-injection site care and site closure. EPA adds that the final GS rule includes a balance of speci fic criteria to be met by the owner or operator and areas of

Directorial discretion and consider ations 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 prov iding consistency in permitting across the U.S.

Letter ID: 0153 Comment ID: 22136 Letter Lines: 44 to 51

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

USDW

Comment: location of formations where CO2 can be sequestered. At this point EPA is proposing to only allow sequestration in fo rmations below the lowermost USDW (as noted in 144.6 (f), and 146.5 (f)). In Sout h Dakota there are strata that could potentially be used for sequestration that are above the lowermost USDW and have significant confining beds. The eastern portion of the state is generally unsuitable for sequestration as the Precambrian basement rock is less than 3000 feet deep in most places, is used as a USDW in some areas, and an additional USDW directly overlies it in some cases.

Individual Response: EPA acknowledges that there are lim ited circumstances where injection above the lowermost USDW can be performe d in a manner that protects USDWs from endangerment, as long as appropriate protections are in place. The final GS rule at §146.95 establishes a process by which owne rs or operators can seek a waiv er of the Class VI injection depth requirements for injecti on into non-USDW formations a bove and/or between USDWs.

EPA believes that these requirements will ensure USDW protection while providing flexibility to UIC program Directors and owne rs or operators who undertak e CO2 injection for GS. The Agency believes this approach: 1) responds to co ncerns about local and re gional geologic storage capacity limitations imposed by th e proposed injection depth require ments; 2) allows for a more site-specific assessment of injection depth for GS projects; 3) accommodates injection into different formation types; 4) a llows 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 aqui fer exemptions for GS. Finally, EPA’s approach to addressing injection depth va riability through a waiver process responds to concerns about future drinking wa ter resource availability and the need to ensure that high quality water remains available in sufficient qua ntities to supply drinking water needs. For

2additional 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.

Letter ID: 0153 Comment ID: 22137 Letter Lines: 53 to 54

Comment Code: 4450 2.4.4.4 Use of aquifer exemptions (seeking comment)

Comment: 2. To allow for additional flexibility, South Dakota recommends that aquifer exemptions be allowed for Class VI wells.

Individual Response: EPA acknowledges that there are lim ited circumstances where aquifer exemptions for GS may be warranted. The final rule allows for the expansion of the areal extent of existing aquifer exemptions for Class II EOR/ EGR wells transitioning to Class VI injection for GS pursuant to requirements at §§146.4 and 144.7( d). Class VI owners or operators granted expansions of existing Class II EOR/EGR aquifer exemptions for GS projects must meet all of the tailored requirements for GS wells in the final GS rule.

For additional information on aquifer exemptions for Class VI wells, please see the final rule and preamble, as well as EPA's responses to comments on the Notice of Da ta Availability and Request for Comment.

Letter ID: 0153 Comment ID: 22138 Letter Lines: 56 to 61

Comment Code: 4344 2.4.4.2.2 Comments opposed to setting a minimum injection depth

Comment: 3. We would also recommend that a minimu m injection depth for CO2 sequestration not be required, again to allow states more flexibility in determining areas where the process can occur. We believe the initial site evaluation, testing, modeling and so forth required of th e owner/operators of a geologic sequestration site along with all operati onal testing would ma intain protection

of a USDW without re quiring a prescripti ve depth limitation.

Individual Response: EPA agrees that it is not appropriate to set a mi nimum injection depth for GS projects and the Agency believes that a determ ination of site-suitabili ty for GS (i.e., that

subsurface formations will receiv e and confine injected CO2) s hould be made on a site-specific basis. The GS rule, at §146.82, requires the owne r or operator to provide extensive site- and project-specific information to the Director to demonstrate that the site meets the minimum site criteria at §146.83, that the CO2 will be contai ned within the injection formation, and that USDWs will be protected from endangerment.

EPA acknowledges that there are limited circum stances where injectio n above the lowermost USDW can be performed in a manner that protec ts USDWs, as long as appropriate protections are in place. The final GS rule at §146.95 establis hes a process by which owners or operators can seek a waiver of the Class VI injection de pth requirements for in jection into non-USDW

formations above and/or between USDWs. The waiver approach requires the submission of

3extensive, site-specific information (in conjunc tion 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. Th e requirements are designed to ensure that the owner or operator, the Director, and the Regi onal Administrator consid er, on a site-specific basis, the implications, benefits, and challe nges associated with GS and ensuring water availability and USDW protecti on. For additional information on the waiver approach, please see the final rule and preamble, as well as EPA' s responses to comments on the Notice of Data Availability and Request for Comment.

Letter ID: 0153 Comment ID: 22139 Letter Lines: 63 to 66

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

Comment: 4. South Dakota recommends that EPA allow states to gain regulatory primacy of

UIC Class VI wells without ha ving to also take primacy for the other UIC classes

in Section 1422 of the SDWA. Class VI wells actually appear mo re closely related

to UIC Class II wells in Section 1425 of the SDWA than those in Section 1422.

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 access) 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.

The Agency believes that it is important for stat es to use their unique e fficiencies to promote adoption of this burgeoning and important tec hnology, while assuring that USDWs are protected from endangerment through the UIC regulatory framework. EPA believe s that, due to the importance of implementing an effective, comprehensive, and seamless CCS program, States should be provided the flexibility to obtain primacy for Class VI only.

EPA also believes that allowing states to apply only for Class VI primacy will shorten the primacy approval process for states. EPA's willingness to accept independent primacy applications for Class VI wells represents a shift in its 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

4well 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) provided in the final GS rule. EPA believes that existing programs can adapt their expertise to the new requirements for Class VI wells and will be able to develop a primacy application for Class VI wells under section 1422 of SDWA and en sure that their GS programs integrate into national climate change priori ties and protect USDWs from endangerment.

Letter ID: 0153 Comment ID: 22140 Letter Lines: 68 to 69

Comment Code: 5600 2.11 Comments related to UIC Program primacy for Class VI wells

Comment: 5. There was no appreciable discussion of f unding mechanisms to run the program

at the state level.

Individual Response: EPA acknowledges that there may be technical and administrative challenges including resource concerns , and will work closely with the states to assist them in resolving funding issues or acquiri ng the resources, personnel, and training needed to address the unique technical challenges associated with GS.

EPA will also incorporate Class VI wells into the UIC Program's grant allocation process. The

States/Tribes/Territories must also demonstrate th at they have adequate resources to implement the program through matching resources against those allocated by the UIC Program's grant allocation formula. Currently, primacy programs ar e required to meet a minimum of 25 percent matching requirement.

Letter ID: 0153 Comment ID: 22141 Letter Lines: 73 to 75

Comment Code: 3150 2.1.5 Comments on required permit information (40 CFR 146.82)

Comment: 144.18 Requirements of Class VI wells - owne rs must get a permit versus ruleauthorization - much more detailed application, and ha s/allows for public input. We are in agreement with this.

Individual Response: EPA acknowledges the comment and the final rule retains the requirement as proposed.

Letter ID: 0153 Comment ID: 22142 Letter Lines: 77 to 79

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

Comment: 146.81 Applicability (c) - exempts Class I, II, and V wells from having to do cement work-overs if wells protective of USDWs - this is good use of these other

5wells once their original use is completed

Individual Response: EPA agrees that many Class I, Cl ass II, and Class V experimental technology wells are designed and constructed to withstand exposure to CO2. The final GS rule provides the construction of these wells be gr andfathered per §146.81(c), provided the owner or operator can demonstrate to the Director that the wells were engineered and constructed to meet the requirements at §146.86(a) and ensure prot ection of USDWs, in lieu of requirements at §146.86(b) and §146.87(a). EPA clarifies that only the construction requirements are grandfathered and that all other Class VI requirements (reporting, monitoring, mechnical integrity testing, etc.) must be met fo llowing a determination under §146.81(c). The requirements of the GS rule apply once the project initiates long-term sequestration of CO2.

Letter ID: 0153 Comment ID: 22143 Letter Lines: 81 to 90

Comment Code: 1220 1.1.1.1 Terminology and definitions

Comment: (d) - Definitions - Area of review - as de fined, is equivalent of Class II Radii

of Influence - since this is calculated in stead of established as a fixed radius as set by a lot of states' regulations, this will relieve a lot of confusion, especially for the use of horizontal wells

- Geologic sequestration - subsurface em placement of CO2 - good specification in definition as some more local organizatio ns refer to "carbon sequestration" as also putting CO2 in wetlands and/or planting trees in surface. If states have to establish their own regulations, this de finition could help differentiate the surficial aspect from su bsurface sequestration

Individual Response: EPA believes that the use of co mputational modeling required at §146.84(c)(1), rather than relying on a fixed radi us or simple computation, is necessary to account for the complexity of GS projects. EPA believes that predicting the complex multiphase, buoyant flow of the CO2, co-injectates, and com pounds that may be mobilized due to injection requires the sophistication of computational models. Models can predict CO2 fate and transport, as well as changes in formation pressure, in thr ee 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 heteroge neities and potential migration through faults, fractures, and artificial penetrations.

The Agency has carefully considered all co mments on the AoR defi nition at §146.84(a) and modified it to read as follows: “[T]he region surrounding the geologic sequestration project where USDWs may be endangered by the injection activity. The ar ea of review is delineated using computational modeling that accounts for the physical and chemical properties of all phases of the injected CO2 stream and is base d on available site characterization, monitoring, and operational data.”

The Agency has modified the definition of ge ologic sequestration project at §146.81(d) to read as follows: “[A]n injection well or wells used to emplace a carbon dioxide stream beneath the

6lowermost formation containing a USDW; or, we lls used for geologic sequestration of carbon dioxide that have been granted a waiver of the injection depth requirements pursuant to requirements at § 146.95; or, wells used for geolog ic sequestration of carb on dioxide that have received an aquifer exemption expansion. It incl udes the subsurface three-dimensional extent of the carbon dioxide plume, associated pressure fr ont, and displaced brine, as well as the surface area above that delineated region.”

Based on its evaluation of all public comments and input on the proposed rule and the NODA and Request for Comment, EPA has made many revisions to the Cla ss VI GS rule. Please see the final rule and preamble for additional information.

Letter ID: 0153 Comment ID: 22144 Letter Lines: 92 to 96

Comment Code: 3150 2.1.5 Comments on required permit information (40 CFR 146.82)

Comment: 146.82 Required Class VI permit informa tion - (e) ".... and any additional information the Director may require:" - this is good part, as we as a state have had numerous occasions when operators do not submit all of the information needed to determine the viability of an application for a well because it is not specifically listed in the state regulations

Individual Response: The Agency believes that providing th e Director discretion to request additional information will allow consideration of a range of sites for GS, based on site-specific conditions, and ensure USDW protection. EPA believes that requiring appropriate site characterization by the owner or operator (und er §146.82) and providing an appropriate degree of flexibility to the Director to evaluate site -specific geologic data will afford the greatest protection of USDWs from endangerment.

Letter ID: 0153 Comment ID: 22145 Letter Lines: 98 to 101

Comment Code: 3530 2.2.3.1 AoR reevaluation fre quency (seeking comment)

Comment: 146.84 Area of review and co rrective action - (b) (2) (i) the need to reevaluate the area of review a maximum of every 10 years - great clause, we have potential for problems in our Class II pr ogram where operators could potentially over inject, especially if th e life of permit expires

Individual Response: EPA acknowledges the commenters’ suppor t for reevaluation of the AoR. Based on evaluation of the public comments on this topic, EPA has changed the minimum frequency for the AoR reevaluation at §146.84(e) from 10 years to at least every 5 years in the

final GS rule. EPA believes that this revised frequency addresses commenters' concerns about the inherent uncertainties in modeling CO2 m ovement, the emerging nature of GS technology, risk-based targeting of m onitoring activities, and the unique nature of CO2 GS.

In response to the comment that operators could potentially over-inject, EPA clarifies that the

7purpose of the requirement to perform an initial AoR delineation at §46.84(c)(1 ) is to predict, as closely as possible, the ultimate extent of th e CO2 plume and pressure front. The reevaluation should be considered as adjustments to address changes that could not have been anticipated before injection commences.

Letter ID: 0153 Comment ID: 22146 Letter Lines: 103 to 109

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

Comment: 146.85 Financial responsibility - (b) need to re-evalu ate AOR, CAP, P&A, and post-injection site care and closure plans and the financial res ources needed to address them on a frequency set by Dir ector - this prevents the initial determination of bonding from becoming inad equate in future - our Class II regulations set a specific amount that can not be changed over time, and allow for a group of wells to be covered under the same, inadequate statewide bonding

mechanism

Individual Response: EPA agrees and clarifies that th e GS rule, at §146.85, requires the Director to evaluate the financial responsibil ity demonstration annually to confirm that the instrument(s) used remain adequate for purposes of protecting USDWs fr om endangerment. At §146.85(e), it states that if the Dire ctor determines during the annua l evaluation that the original demonstration is no longer adequate to cover the cost of activities for which it is required, the owner or operator must provide an adjustment to the cost estimate within 60 days. EPA also

clarifies that the GS rule, at §146.85(c)(2), requires the owner or operator to provide annual updates to the cost estimate to account for any amendments to the AoR and corrective action plan, the injection well plugging pl an, the PISC and site closur e plan, and the emergency and remedial response plan.

Letter ID: 0153 Comment ID: 22147 Letter Lines: 111 to 116

Comment Code: 3820 2.3.1 Well construction procedures

Comment: 146.86 Injection well constr uction requirements - (a) (2) well must be

constructed such to allow a ppropriate testing devices a nd work-over tools - this is a good clause also, as our Class II regulations have allowed for a temporarily abandoned well that was worked over in such a way so it will be difficult to MIT it - may have to bring in an expensive R(adio)A(ctive)T(racer log) test rig - we couldn't prevent it under our Class II regulations

Individual Response: EPA acknowledges the comment and ag rees that protection of USDWs from endangerment and prevention of fluid m ovement between formations is paramount. Appropriately designed and constructed wells ar e necessary to prevent endangerment to USDWs

8and maintain integrity of the well throughout the lifetime of a GS project . This is the foundation of the requirements for constructi on of Class VI wells at §146.86.

Letter ID: 0153 Comment ID: 22148 Letter Lines: 118 to 124

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

Comment: (b) (2) extending surface cas ing through the base of the lower-most USDW - this may be over kill in areas where there are multiple aquifers at numerous different depths. Especially in areas where the upper USDWs easily fulfill the needs of the populace, and the deeper USDW s are of high TDS content, and may take considerable, expensive treatment to bring it to palatable levels. In

addition, this would be more overki ll if both the tubing and long string injection casings are cemented from bottom to surface.

Individual Response: EPA disagrees that protecting deep USDWs underlying multiple, more

shallow USDWs is "overkill." Protection of USDW s, regardless of their depth or stratigraphic location, is the primary mission and mandate of the UIC program—as specified by Congress in the SDWA—and the purpose of all requirements fo r injection wells. Any injection activity must be demonstrated to not endanger USDWs, regardle ss of their depth, and if such a demonstration cannot be made, then the activity will not be allowed under UIC requirements or the SDWA. Water agencies commenting on the proposed rule noted that diminishing water supplies are requiring water utilities to use deeper and more saline sources, and the SDWA mandates EPA to set regulations that protec t USDWs from endangerment.

The final GS rule at §146.86(b)(2) requires that surface casing extend through the base of the

lowermost USDW and be cemented to the surface through the use of a single string or multiple strings of casing and cement. It does not, however, specify how cementing must be accomplished, and it allows the owner or operator to propose alternate methods that provide a

sufficient amount of cement to meet the standard that USDWs are protected from endangerment. EPA notes that there are many potential ways to meet the requirement, such as the use of staged cementing.

EPA recognizes concerns regardi ng construction of Class VI wells where the lowermost USDW is very deep. To further address comments on d eep injection wells, the final GS rule at §146.95 includes requirements for owners or operators that seek a waiver of the injection depth requirements. Owners or operators of wells opera ting under injection depth waivers must comply with additional construction require ments to ensure that wells used to inject above or between USDWs are protective. See the discussion of the wa iver approach in the preamble to the final GS

rule for additional information.

Letter ID: 0153 Comment ID: 22149 Letter Lines: 126 to 129

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

9Comment: (b) (3) at least one long string must ex tend to the injection zone and be cemented to the surface - same as comment for (b) (2) previous - especially if tubing is cemented from top to bottom, and long string is cemented into surface casing.

Individual Response: As described above, EPA believes that protection of US DWs, regardless of their depth or stratigraphic location, is th e primary mission and mandate of the UIC program and the purpose of all require ments for injection wells.

The final GS rule at §146.86(b)(3 ) requires that the long-string casing extend to the injection zone and be cemented by circulating cement to th e surface in one or more stages. It does not, however, specify how cementing would be accomplis hed, and gives flexibility to the owner or operator to propose alternate methods to provide a sufficient amount of cement to meet the standard that USDWs are protected from endanger ment, subject to the appr oval of the Director.

EPA recognizes concerns regardi ng construction of Class VI wells where the lowermost USDW is very deep. To further address comments on d eep injection wells, the final GS rule at §146.95 includes requirements for owners or operators that seek a waiver of the injection depth requirements. Owners or operators of wells opera ting under injection depth waivers must comply with additional construction require ments to ensure that wells used to inject above or between USDWs are protective. See the discussion of the wa iver approach in the preamble to the final GS

rule for additional information.

Letter ID: 0153 Comment ID: 22150 Letter Lines: 131 to 133

Comment Code: 4100 2.4.1 Injection parameters

Comment: 146.88 Injection well requirements - (c) th e annulus pressure needs to exceed the injection pressure - don't know why, as long as there is enough difference so sensors/gauges can indicate when something goes wrong.

Individual Response: EPA believes that maintaining an annulus pressure that is higher than the injection pressure, as required at §146.88(c), will ensure that if there are leaks in the tubing, the annulus fluid will move into the tubing, rather than the injectate moving out of the tubing and potentially along the outside of the well. EPA belie ves this requirement is appropriate for Class VI wells given the potential high volumes and superc ritical nature of the CO2 injectate, potential geomechanical stresses in the wellbore, and the potential for movement of the CO2 in the event of a mechanical integrity loss.

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