### 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.

### October 15, 2009

Water Docket

United States Environmental Protection Agency

Mail Code: 2822T

1200 Pennsylvania Avenue, NW

Washington, DC 20460

Subject: Federal Requirements Under the Un derground Injection Control (UIC)

Program for Carbon Dioxide (CO 2 

### ) Geologic Sequestration (GS) Wells

Docket ID No. EPA–HQ–OW–2008–0390

Fed. Reg. 43492 (July 25, 2008)

The Electric Power Research Institute (EPRI) is pleased to have the opportunity to

provide comments on the Environmental Protection Agency’s Notice of Data

Availability (NODA) dated August 31, 2009 for the proposed rule titled “Federal

Requirements Under the Underground Inje ction Control (UIC) Program for Carbon

Dioxide (CO 2 

### ) Geologic Sequestration (GS) Wells ” of July 25, 2008, (Docket ID No. EPA–

HQ–OW–2008–0390).

EPRI conducts research on key issues facing th e electric power industr y on behalf of its

members, energy stakeholders, and society. EPRI was established as an independent, nonprofit

center for public interest energy and environmental research. Our utility members represent over

90% of the electricity generated in the Unite d States including substantial support from

international energy companies. EPRI also receives funding from various federal and state

government agencies such as the US Department of Energy.

EPRI supports the development of a clear (una mbiguous), reasonable, and flexible framework

that enables wide deployment of geologic storage of CO 2 

### in a safe, environmentally protective,

and cost-effective manner.

Sincerely,

Michael J. Miller

Director, Environment

Electric Power Research Institute

3420 Hillview Avenue

Palo Alto, CA 94304

### EPRI Comments on EPA’s Notice of Da ta Availability for the Proposed UIC

Regulations for CO 2 

### Injection

The Electric Power Research Institute (EPR I) is pleased to have the opportunity to

provide comments on the Environmental Protection Agency’s Notice of Data Availability

(NODA) dated August 31, 2009 for the proposed rule titled “Federal Requirements

Under the Underground Injec tion Control (UIC) Program for Carbon Dioxide (CO 2 

### )

Geologic Sequestration (GS) Wells” of July 25, 2008, (Docket ID No. EPA–HQ–OW–

2008–0390).

EPRI’s comments are focused on the technical elements of the proposed rule discussed in

this NODA. The comments are intended to assist in the development of a clear

(unambiguous), reasonable, and flexible fr amework that enables wide deployment of

geologic storage (GS) of CO 2 

### in a safe environmentally protective, and cost-effective

manner.

General comment

EPRI COMMENT#1: The NODA provides a wa iver process in which a project

proponent can submit a permit appli cation for the injection of CO 2 

### above the lowermost

Underground Source of Drinking Water (USDW) . EPRI supports the EPA’s decision to

create the waiver process because it provides gr eater flexibility in selecting injection sites

that meet all of the proposed technical requir ements of a Class VI injection permit, except

for depth. EPRI agrees that protection of USDWs can be accomplished regardless of

injection depth by selecting and permitting site s with competent confining units that will

isolate the injected CO 2 

### from the adjacent USDW(s).

EPRI COMMENT#2: The EPA presents a numbe r of research projects in the NODA and

often concludes with a general statement that the research will be used to refine and

inform the site characterization, monitoring, and remediation requirements and guidance,

in the Agency’s final rulemaking. Many of the research methods used by the regional

partnerships and others were performe d purely for furthering our fundamental

understanding and knowledge of GS processes and may never evolve beyond the research

stage. A cross-well seismic survey, which has very limited depth of penetration because

of limited source strength and therefore requ ires closely spaced wells, is a good example

of a research monitoring tool that may never be deployed on a commercial scale. The

EPA does not provide clarity on how the results will be used or the position or direction

the Agency has already taken or will take as a result of i ssues raised by the research.

EPRI urges EPA to provide this clarity to the regulated community before issuing the

final rule.

Specific comments

Specific EPRI comments on the EPA NODA follow. EPA draft rules, interpretations or

requests for comments are shown in bold prin t and are identified by page number where

### they appear in the Federal Register / Vol. 74, No. 167 / Monday, August 31, 2009 /

Proposed Rules. EPRI comments im mediately follow the EPA citation.

Page 44808: “The Agency seeks comment on this research and any additional

studies related to a) mobilization of consti tuents and b) the likelihood or frequency

of such leakage/risks.”

EPRI COMMENT #3: As noted in the NODA, the Lawrence Berkeley National

Laboratory (LBNL) project was a modeling stud y and, therefore, calls for experimental

verification before reaching de finitive conclusions. To this end, EPRI conducted an

initial field study and analysis of the potential impact of CO 2 

### on shallow groundwater, to

be completed by the end of 2009. The field study was performed at the Zero Emission

Research and Technology (ZERT) field site in Bozeman, Montana; ZERT was hosted by

Montana State University and was designed to test instruments used to detect leaks of

CO 2 

### to the surface and not groundwater im pacts. ZERT injected food-grade CO 2 

### into

shallow groundwater in 2008 over a thirty da y period. Under the EPRI study, more than

80 groundwater samples were collected and anal yzed using very low detection levels by

the US Geological Survey, under contract to LBNL and EPRI. We observed increases in

the groundwater concentration of several major cations and trace elements above

background, including arse nic and lead, after CO 2 

### injection began, but none of the

constituents exceeded their respective action levels or maximum contaminant levels.

Only three of the constituents, iron, mangane se and total dissolved solids, exceeded the

standard under which they are regulated, in this case the sec ondary drinking water criteria.

It is our understanding that the EPA secondary drinking water criteria are not federally

enforceable but are intended as guidelines for the states. These regulations control

constituents in drinking water that primarily affect the aesthetic qualities relating to the

public acceptance of drinking water.

However, the ZERT site conditions were not ideal for studyi ng the effects of CO 2 

### on

potable groundwater for several reasons:

1. Shallow (<6 feet) unconfined groundwater aqui fers like that at the ZERT field site

are not typically represen tative of USDWs because they do not have an upper

confining unit that serves to protect the aquifer from surface contamination;

2. Shallow aquifers respond to atmosphe ric conditions includ ing recharge from

precipitation and oxidizing conditions th at influence experiment results;

3. Deeper aquifers, which are representative of USDWs, lie below confining units

that serve as barriers to surface contamination;

4. Reducing conditions are more prevalent in deeper aquifers potentially resulting in

different experimental outcomes than observed at ZERT;

5. Results from 2008 study may underestimate impacts since a similar injection

conducted in 2007 injection may ha ve biased the later results.

Therefore, EPRI and its members, recognizi ng the need for more definitive data, are

about to embark on a three-year field study specifically designed to evaluate the impact

of CO 2 

### on potable groundwater, iden tify key reactive transport mechanisms, calibrate and

### validate flow and reactive transport models, a nd test the ability of existing models to

predict transport behavior. These results provide an opportunity for improving models

for commercial use; such models would be a tool for assessing CO 2 

### GS projects.

Page 44808: “EPA believes that the e xample studied by LBNL illustrates the

importance of basin-scale evaluation of reservoir pressures and far-field pressures

resulting from CO 2 

### injection.”

EPRI COMMENT#4: EPRI agrees that pressure interference from multiple projects in a

basin may have an impact on near and far-field pressures. This suggests that basin-scale

management where multiple projects ar e planned would be beneficial.

The next set of comments apply to requi rements included in the proposed waiver

process.

Page 44811: “(3) An injection zone and co nfining formations free of transmissive

fractures and faults.”

EPRI COMMENT#5: EPRI does not see a need to exclude injection zones containing

transmissive fractures or fau lts from being considered as geologic storage targets as long

as these transmissive features are not present in the overl ying/underlying confining units.

Fractured formations often have excellent pe rmeability promoting hi gh injection rates at

relatively low injection pressures. Lower inje ction pressures will lead to lower risk of

fracturing the adjacent confining unit(s).

Page 44811, “(4) A characterization of regional fracture properties and a

demonstration that such fractures will not in terfere with injection, serve as conduits,

or endanger USDWs.”

ERPI COMMENT#6: EPRI does not understand the need for this requirement given the

EPA’s position that the waiver should only be granted for confining units free of

transmissive faults and fracture as quoted above. Why would a regi onal characterization

of the properties of these features be requi red if transmissive members of the population

can’t be present in the confining un it in order to receive the waiver?

EPRI believes a regional characterization of fr acture properties should not be required for

injection zones too. A regional assessment of fracture properties is somewhat academic

and may not aid the project proponent and regu lator in assessing local project safety.

Local rock properties and stresses (past and pr esent) control evoluti on of local fracture

patterns and their corresp onding hydraulic properties. Re gional stresses and rock

properties may be significantly different th an local conditions leading to erroneous

conclusions. Therefore, fracture characterization, if required at all, should be limited to

the Area of Review where local features would potentially be present and serve as

conduits.

### Page 44811: “The potential capacity of the geologic formation to sequester CO 2 

### , accounting for the availability of alternative injection sites;”

EPRI COMMENT#7: Presumably the projec t proponent will have screened numerous

sites (if available) before selecting an optimum location that meets the requirements of

the EPA rule as finally prom ulgated (including capacity) and the economic, technical and

non-technical needs of the project. However, nu merous factors enter into the decision to

develop a GS project and submit a permit application, not just “capacity” and

“availability of alternative inje ction sites.” Therefore, the need for this requirement is not

clear.

EPRI’s next comment is based on (a) the following EPA assumption: “The basis of

these requirements is the principle that placing distance between the injection

formation and USDWs decreases risks to USDWs” (Page 44809), and (b) the

statement that “The owner/operator may be required to comply with additional

requirements that apply as a result of receip t of the waiver, designed to ensure the

protection of USDWs both above and below the injection zone.” (Page 44811).

EPRI COMMENT#8: EPA’s technical rationale for wanting to include additional

requirements in the permit waiver beyond those already required for an injection into a

zone located below the lowermost USDW is unclear. EP A’s justification appears to be

based on vertical position of the injection zone relative to the adjacent USDWs and

intervening distance between the two. Injec tion below the lowermost USDW appears to

be viewed by EPA as being less risky than injection above the lowermost USDW, even

though the upper boundary condition could be identical in both cases. For example, one

could propose a GS pr oject with injection immediately below the lowermost USDW with

only one intervening confining unit of given thickness (i.e., distance) between it and the

lowermost USDW above to prevent CO 2 

### migration. Likewise, one could propose a GS

project above the lowermost USDW with the sa me identical upper boundary condition

(i.e. one intervening confining unit with sa me thickness) relative to the next USDW

above. The risk of impact from CO 2 

### migration into the overlyi ng USDW is identical. See

figure below for illustration of this concept.This figure illustrates that injection of CO 2 into the center zone be low identical confining

units having identical properties (including thickness) will result in identical risks to the

overlying USDW regardless whether injection is occurring above or below the lowermost

USDW.



### The EPA draft standard publishe d in July 2008 for injection below the lowermost USDW

appears to be deemed adequately protectiv e of USDWs above by EPA. EPRI sees no

physical reason why the same standards woul d not be equally protective of USDWs if

injection occurs into a zone above the lowermost USDW, when the boundary conditions

and risks are essentially identical. Therefore, EPRI questions the need for additional well

construction, operational or monitoring, as required by the proposed waiver process,

regardless of vertical position; it appears that the Agency has already taken this scenario

into account in the July 2008 draft rule.

One could argue that the lower boundary doubles the risk for a GS project injecting

above the lowermost USDW increases the risk of a project because contamination of this

lower USDW could occur from above (refer to figure). However, it is the transmissivity

and lateral continuity of the uppe r and lower seals that control CO 2 

### migration across the

boundary that defines the ris k, not the number of boundaries. (i.e, one or two) across

which CO 2 

### could migrate to adjacent USDWs. In addition, it is far less likely that free

CO 2 

### will migrate across the lower boundary because CO 2 

### is buoyant. Saline groundwater

(and CO 2 

### dissolved in the same) could potentially be displaced below the lower seal, but

the requirements in the dr aft standards published by EPA in July 2008 already affords

adequate USDW protection against these mech anisms – i.e., EPA’s current draft rule

already accounts for the worst case scenario (displaced water containing dissolved CO 2



### and free CO 2 

### ).

In summary, EPRI believes that the above additional requirements proposed for the

waiver process, as well as those for enhanced construction and operational requirements

and type of monitoring technology to be de ployed, address concerns that are already

### covered by the July 2008 draft rule, with one exception. We agree with EPA’s proposed

requirement for monitoring in the USDW below the injection zone when injecting CO 2



### above the lowermost USDW.Letter ID: 0355

Commenter: Michael J. Miller

Organization: Electric Power Research Institute (EPRI)

Letter ID: 0355 Comment ID: 28078 Letter Lines: 34 to 42

Comment Code: 3210 3.2.1. Comments Generally in Support of the Approach

Comment: EPRI COMMENT#1: The NODA provides a waiver process in which a project proponent

can submit a permit application for the injection of CO2 above the lowermost

Underground Source of Drinking Water (USDW). EPRI supports the EPA’s decision to

create the waiver process because it provides greater flexibility in selecting

injection sites that meet all of the proposed technical requirements of a Class

VI injection permit, except for depth. EPRI agrees that protection of USDWs can

be accomplished regardless of injection depth by selecting and permitting sites

with competent confining units that will isolate the injected CO2 from the

adjacent USDW(s).

Individual Response: EPA acknowledges the commenter's support of the waiver approach and site

‐

specific flexibility in regulatory development and permitting as described in the NODA and Request for

Comment. The Agency acknowledges that there are some situations where injection into non

‐ USDW

formations above the lowermost USDW can be performed in a manner that protects USDWs. The final

GS rule at §146.95 establishes a process by which owners and operators can seek a waiver of the Class

VI injection depth requirements. The Agency believes the waiver approach: 1) responds to concerns

about 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) allows 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 injection depth variability through a waiver process responds to

concerns about future drinking water resource availability and the need to ensure that high quality

water remains available in sufficient quantities to supply drinking water needs.

Letter ID: 0355 Comment ID: 28079 Letter Lines: 44 to 57

Comment Code: 2000 2. Comments on Research, Data Analysis, and Findings presented in the NODA

(seeking comment)Comment: EPRI COMMENT#2: The EPA presents a number of research projects in the NODA and

often concludes with a general statement that the research will be used to

refine and inform the site characterization, monitoring, and remediation

requirements and guidance, in the Agency’s final rulemaking. Many of the

research methods used by the regional partnerships and others were performed

purely for furthering our fundamental understanding and knowledge of GS

processes and may never evolve beyond the research stage. A cross

‐ well seismic

survey, which has very limited depth of penetration because of limited source

strength and therefore requires closely spaced wells, is a good example of a

research monitoring tool that may never be deployed on a commercial scale. The

EPA does not provide clarity on how the results will be used or the position or

direction the Agency has already taken or will take as a result of issues raised

by the research. EPRI urges EPA to provide this clarity to the regulated

community before issuing the final rule.

Individual Response: EPA believes that the regional partnerships provide important information on GS,

but recognizes that use of a technology in a RCSP project does not necessarily make the technology valid

for all applications. Each project will be unique and the final rule provides for site

‐ specific approaches to

ensure that appropriate construction, operation, and monitoring is performed at each site. However, by

testing multiple technologies, the pilot sites provide valuable data that demonstrate whether or not

these technologies are viable and informed the final GS rule. Please see the discussion of EPA's final

regulatory approach in the preamble to the final GS rule for additional detail on the final requirements

for GS wells.

Letter ID: 0355 Comment ID: 28080 Letter Lines: 67 to 119

Comment Code: 2400 2.4. Other Research Offered by Commenters (seeking comment)

Comment: Page 44808: "The Agency seeks comment on this research and any additional

studies related to a) mobilization of constituents and b) the likelihood or

frequency of such leakage/risks."

EPRI COMMENT #3: As noted in the NODA, the Lawrence Berkeley National Laboratory

(LBNL) project was a modeling study and, therefore, calls for experimental

verification before reaching definitive conclusions. To this end, EPRI

conducted an initial field study and analysis of the potential impact of CO2 on

shallow groundwater, to be completed by the end of 2009. The field study was

performed at the Zero Emission Research and Technology (ZERT) field site in

Bozeman, Montana; ZERT was hosted by Montana State University and was designed

to test instruments used to detect leaks of CO2 to the surface and notgroundwater impacts. ZERT injected food

‐ grade CO2 into shallow groundwater in

2008 over a thirty day period. Under the EPRI study, more than 80 groundwater

samples were collected and analyzed using very low detection levels by the US

Geological Survey, under contract to LBNL and EPRI. We observed increases in the

groundwater concentration of several major cations and trace elements above

background, including arsenic and lead, after CO2 injection began, but none of

the constituents exceeded their respective action levels or maximum contaminant

levels. Only three of the constituents, iron, manganese and total dissolved

solids, exceeded the standard under which they are regulated, in this case the

secondary drinking water criteria. It is our understanding that the EPA

secondary drinking water criteria are not federally enforceable but are intended

as guidelines for the states. These regulations control constituents in drinking

water that primarily affect the aesthetic qualities relating to the public

acceptance of drinking water.

However, the ZERT site conditions were not ideal for studying the effects of CO2

on potable groundwater for several reasons:

1. Shallow (

site are not typically representative of USDWs because they do not have an upper

confining unit that serves to protect the aquifer from surface contamination;

2. Shallow aquifers respond to atmospheric conditions including recharge from

precipitation and oxidizing conditions that influence experiment results;

3. Deeper aquifers, which are representative of USDWs, lie below confining units

that serve as barriers to surface contamination;

4. Reducing conditions are more prevalent in deeper aquifers potentially

resulting in different experimental outcomes than observed at ZERT;

5. Results from 2008 study may underestimate impacts since a similar injection

conducted in 2007 injection may have biased the later results.

Therefore, EPRI and its members, recognizing the need for more definitive data,

are about to embark on a three

‐ year field study specifically designed to

evaluate the impact of CO2 on potable groundwater, identify key reactive

transport mechanisms, calibrate and validate flow and reactive transport models,

and test the ability of existing models to predict transport behavior. These

results provide an opportunity for improving models for commercial use; such

models would be a tool for assessing CO2 GS projects.Individual Response: EPA has reviewed the information on the Zero Emission Research and Technology

(ZERT) field site. EPA acknowledges the submittal and will continue to review studies related to

modeling verification, comparisons with field results of CO2 injection, and the study of the effects of

CO2 on shallow ground water. EPA intends to continue to collect data on GS and to incorporate such

data and information as it implements its adaptive approach to the GS rulemaking to incorporate new

research, data, and information about GS. For more information on the adaptive approach, see the

responses to comments on the proposed rule in the rulemaking docket.

Letter ID: 0355 Comment ID: 28081 Letter Lines: 121 to 128

Comment Code: 2220 2.2.2. Basin

‐ Scale Hydrologic Impacts of CO2 Storage (seeking comment)

Comment: Page 44808: "EPA believes that the example studied by LBNL illustrates the

importance of basin

‐ scale evaluation of reservoir pressures and far

‐ field

pressures resulting from CO2 injection."

EPRI COMMENT#4: EPRI agrees that pressure interference from multiple projects in

a basin may have an impact on near and far

‐ field pressures. This suggests that

basin

‐ scale management where multiple projects are planned would be beneficial.

Individual Response: The final GS rule focuses on permitting of individual GS wells and therefore does

not include requirements for basin

‐ scale evaluations. However, EPA agrees that proactive management

of basin scale concerns to maintain pressures within acceptable ranges is important, and encourages

owners or operators and permitting authorities to communicate planned GS activities to maximize

coordination and minimize pressure interference. If a permit applicant (or the permitting authority) is

aware of pending GS projects near a proposed well, the AoR delineation performed pursuant to §146.84

should account for the impacts of multiple owners and operators injecting within a single basin. EPA

anticipates that, where multiple operators are involved, the Director would not approve modeling that

does not account for changes that may result from all injection operations. The proximity of injection

sites to each other and the relative timing of each injection operation might indicate a possible increase

in risk for the containment of the total CO2 and/or the effects of hydraulic perturbations and brine

displacement.

EPA adds that if any new GS projects are permitted within the AoR of a GS project between AoR

evaluations, the AoR reevaluation would need to address such projects. EPA also expects that the

permitting of the newer GS project would have considered the presence of an existing project. For

additional information regarding EPA’s requirements for AoR delineation for GS projects, see the

responses to comments on the proposed rule in the rulemaking docket.Letter ID: 0355 Comment ID: 28082 Letter Lines: 130 to 141

Comment Code: 3310 3.3.1. Site Characterization

Comment: process.

Page 44811: "(3) An injection zone and confining formations free of transmissible

fractures and faults."

EPRI COMMENT#5: EPRI does not see a need to exclude injection zones containing

transmissible fractures or faults from being considered as geologic storage

targets as long as these transmissible features are not present in the

overlying/underlying confining units. Fractured formations often have excellent

permeability promoting high injection rates at relatively low injection

pressures. Lower injection pressures will lead to lower risk of fracturing the

adjacent confining unit(s).

Individual Response: EPA clarifies that the requirement refers to the confining zone. The final GS rule

requires a demonstration that the confining units are free of transmissive faults and fractures per

§146.95(a)(2). For additional information on site characterization for GS projects, see the preamble to

the final rule and the responses to comments on the proposed GS rule.

Letter ID: 0355 Comment ID: 28083 Letter Lines: 143 to 162

Comment Code: 3310 3.3.1. Site Characterization

Comment: Page 44811, "(4) A characterization of regional fracture properties and a

demonstration that such fractures will not interfere with injection, serve as

conduits, or endanger USDWs."

ERPI COMMENT#6: EPRI does not understand the need for this requirement given the

EPA’s position that the waiver should only be granted for confining units free

of transmissible faults and fracture as quoted above. Why would a regional

characterization of the properties of these features be required if transmissible

members of the population can't be present in the confining unit in order to

receive the waiver?

EPRI believes a regional characterization of fracture properties should not be

required for injection zones too. A regional assessment of fracture propertiesis somewhat academic and may not aid the project proponent and regulator in

assessing local project safety. Local rock properties and stresses (past and

present) control evolution of local fracture patterns and their corresponding

hydraulic properties. Regional stresses and rock properties may be significantly

different than local conditions leading to erroneous conclusions. Therefore,

fracture characterization, if required at all, should be limited to the Area of

Review where local features would potentially be present and serve as conduits.

Individual Response: EPA clarifies that the requirement for regional characterization of fracture

properties applies to the confining zone. The final GS rule requires a demonstration that the confining

units are free of transmissive faults and fractures and requires regional characterization of fracture

properties as specified in §146.95(a)(2) to support a determination that no fractures will interfere with

injection, serve as conduits, or endanger USDWs. This requirement applies to all GS projects as specified

in §146.82(a), and the requirements at §146.95 for owners and operators seeking injection depth

waivers are intended to add to and modify the requirements that all GS well owners or operators must

meet, including those for site

‐ specific geologic characterization of faults and fractures, to ensure that

the proposed site is evaluated in the context of the presence of USDWs above and below the injection

zone. EPA anticipates that issuance of waivers will be limited to circumstances where there are deep

USDWs and/or where the lack of a waiver of injection depth requirements would result in impractical or

technically infeasible well construction, and where USDW protection is demonstrated and maintained

through the life of the GS project. For additional information on site characterization for GS projects, see

the preamble to the final rule and the responses to comments on the proposed GS rule.

Letter ID: 0355 Comment ID: 28084 Letter Lines: 164 to 173

Comment Code: 3310 3.3.1. Site Characterization

Comment: Page 44811: "The potential capacity of the geologic formation to sequester CO2,

accounting for the availability of alternative injection sites;"

EPRI COMMENT#7: Presumably the project proponent will have screened numerous

sites (if available) before selecting an optimum location that meets the

requirements of the EPA rule as finally promulgated (including capacity) and the

economic, technical and non

‐ technical needs of the project. However, numerous

factors enter into the decision to develop a GS project and submit a permit

application, not just "capacity" and "availability of alternative injection

sites." Therefore, the need for this requirement is not clear.

Individual Response: EPA clarifies that the intent of the requirement to consider alternative injection

sites ensures the waiver approach is applied only when needed. EPA anticipates that issuance of waiverswill be limited to circumstances where there are deep USDWs and/or where the lack of a waiver of

injection depth requirements would result in impractical or technically infeasible well construction, and

where USDW protection is demonstrated and maintained through the life of the GS project.

Letter ID: 0355 Comment ID: 28085 Letter Lines: 175 to 223

Comment Code: 3380 3.3.8. Additional Requirements Established by the UIC Director

Comment: EPRI’s next comment is based on (a) the following EPA assumption: "The basis of

these requirements is the principle that placing distance between the injection

formation and USDWs decreases risks to USDWs" (Page 44809), and (b) the

statement that "The owner/operator may be required to comply with additional

requirements that apply as a result of receipt of the waiver, designed to ensure

the protection of USDWs both above and below the injection zone." (Page 44811).

EPRI COMMENT#8: EPA’s technical rationale for wanting to include additional

requirements in the permit waiver beyond those already required for an injection

into a zone located below the lowermost USDW is unclear. EPA’s justification

appears to be based on vertical position of the injection zone relative to the

adjacent USDWs and intervening distance between the two. Injection below the

lowermost USDW appears to be viewed by EPA as being less risky than injection

above the lowermost USDW, even though the upper boundary condition could be

identical in both cases. For example, one could propose a GS project with

injection immediately below the lowermost USDW with only one intervening

confining unit of given thickness (i.e., distance) between it and the lowermost

USDW above to prevent CO2 migration. Likewise, one could propose a GS project

above the lowermost USDW with the same identical upper boundary condition (i.e.

one intervening confining unit with same thickness) relative to the next USDW

above. The risk of impact from CO2 migration into the overlying USDW is

identical. See figure below for illustration of this concept.

This figure illustrates that injection of CO2 into the center zone below identical

confining units having identical properties (including thickness) will result in identical risks to the

overlying USDW regardless whether injection is occurring above or below the lowermost USDW. [SEE P.

6 of EPA

‐ HQ

‐ OW

‐ 2008

‐ 0390

‐ 0355.PDF FOR FIGURE.]

The EPA draft standard published in July 2008 for injection below the lowermost

USDW appears to be deemed adequately protective of USDWs above by EPA. EPRI

sees no physical reason why the same standards would not be equally protective

of USDWs if injection occurs into a zone above the lowermost USDW, when theboundary conditions and risks are essentially identical. Therefore, EPRI

questions the need for additional well construction, operational or monitoring,

as required by the proposed waiver process, regardless of vertical position; it

appears that the Agency has already taken this scenario into account in the July

2008 draft rule.

One could argue that the lower boundary doubles the risk for a GS project

injecting above the lowermost USDW increases the risk of a project because

contamination of this lower USDW could occur from above (refer to figure).

However, it is the transmissivity and lateral continuity of the upper and lower

seals that control CO2 migration across the boundary that defines the risk, not

the number of boundaries. (i.e., one or two) across which CO2 could migrate to

adjacent USDWs. In addition, it is far less likely that free CO2 will migrate

across the lower boundary because CO2 is buoyant. Saline groundwater (and CO2

dissolved in the same) could potentially be displaced below the lower seal, but

the requirements in the draft standards published by EPA in July 2008 already

affords adequate USDW protection against these mechanisms

‐ i.e., EPA’s current

draft rule already accounts for the worst case scenario (displaced water

containing dissolved CO2 and free CO2).

Individual Response: EPA believes that that injection for the purpose of GS into non

‐ USDW formations

above the lowermost USDW warrants tailored requirements to address the unique challenges and risks

relative to injection below the lowermost USDW. For example, there is a risk of downward migration of

fluids if there is no lower confining layer or inadequate confinement. In addition, there is potential that

wells will be drilled through the injection zone in the future to reach USDWs. EPA believes that the

additional requirements that apply to owners or operators of Class VI wells granted a waiver of the

injection depth requirements at §146.95 will provide additional considerations for the owner or

operator and Director when permitting such wells to ensure protection of all USDWs.

Letter ID: 0355 Comment ID: 28086 Letter Lines: 225 to 230

Comment Code: 3210 3.2.1. Comments Generally in Support of the Approach

Comment: In summary, EPRI believes that the above additional requirements proposed for

the waiver process, as well as those for enhanced construction and operational

requirements and type of monitoring technology to be deployed, address concerns

that are already covered by the July 2008 draft rule, with one exception. We

agree with EPA’s proposed requirement for monitoring in the USDW below the

injection zone when injecting CO2 above the lowermost USDW.Individual Response: EPA agrees that site specific demonstrations of injection zone integrity along with

proper well construction, operation, monitoring, and post

‐ injection site care as required in the GS rule,

are appropriate to ensure USDW protection while allowing GS.

EPA acknowledges the commenter's support of the waiver approach and site

‐ specific flexibility in

regulatory development and permitting as described in the NODA and Request for Comment. The

Agency acknowledges that there are some situations where injection into non

‐ USDW formations above

the lowermost USDW can be performed in a manner that protects USDWs.

The final GS rule at §146.95 establishes a process by which owners and operators can seek a waiver of

the Class VI injection depth requirements and includes additional requirements, such as monitoring

above and below the injection zone, to ensure USDWs are protected from endangerment.