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.Serving Wyoming Since 1933 

### WYOMING STATE GEOLOGICAL SURVEY

P.O. BOX 1347 · LARAMIE, WYOMING 82073

- 1347

307/766

- 2286 · FAX 307/766

- 2605

E

- MA IL : wsgs

- info@uwyo.edu · WEB: www.wsgs.uwyo.edu

STATE GEOLOGIST

– Ronald C. Surdam GEOLOGICAL SURVEY BOARD Ex Officio

Governor Dave Freud enthal

William A. Gern Don J. Likwartz

Ronald C. Surdam

Appointed

R . Terry Leigh Christopher E. Mullen

John P. Simons John E. Trummel

Wallace L. Ulrich



### Date: Novem

ber 19, 2008

RE: Docket ID NO. EPA

- HQ

- OW

- 2008

- 0390

From : Ronald Surdam, Director/State Geologist, Wyo mi ng State Geological Survey

, rsurdam @uwyo.edu , 307

- 766

- 2286 ext. 223

With regard to the recently proposed “Geological Aspects of the Proposed

Environm ental Protection Agency’s Federal Requirements under the Underground Injection Control (UIC) Program for Carbon Dioxide (CO 2 

### ) Geological Sequestration (GS) Wells”, the Wyo mi ng State Geological Survey has the following comments.

The r equirements of injecting CO 2 

### only below the lowermost Underground Source of Drinking Water (USDW) aquifer will make it impossible to inject CO 2 

### into deep saline aquifers in Rock Mountain Laramide Basins (RMLB). The problem is when the deep geological sequ estration CO 2 

### targets in RMLB (i.e., deep saline aquifers) occur near the surface, they contain USDW. For example, at a depth of 10,000 to 15,000 feet, a stratigraphic unit such as, but not lim ited to the Madison Limestone, typically has salinity > 10,000 ppm . However, this sam e unit

at 0

- 3,000 feet depth typically has salinity < 500 ppm. Near the surface, the aquifer is recharged with copious quantities of fresh meteoric water; but, because of geohydrologic characteristics common to Laramide Basins of W yo mi ng, the fresh water does not circulate into the deeper portions of the basin. Instead, it discharges in the form of springs or into streams/rivers near the margin of the basin typically along bounding faults or breached, anticlinal structures. As a

c onsequence, due to a lack of m ixing m eteoric and connate fluids, the fluid in the

sam e unit at a depth of 10,000 feet m aintains salinities m ore near the original depositional environment (i.e., marine waters with salinities > 30,000 ppm). If the

form ation fluid was part of a continuous fluid

- flow system, the whole rock/fluid

system would have been flushed during the Pleistocene when recharge rates were

mu ch higher than today. Observations made in all of Wyoming’s Laramide Basins

dem onstrate that fluid

- flo w systems in the deep saline aquifers are

com partm entalized resulting in an absence of shallow

- formation water mixing with deep basin brines.Serving Wyoming Since 1933



### The ram ifications of declaring a stratigraphic unit in Rocky Mountain Basins a USDW aquifer because it supplies fresh water at shallow depth are immense. The stratigraphic section beneath units such as the Paleozoic Madison Limestone and the Tensleep Sandstone (or stratigraphic equivalent units) is relatively thin in Wyo mi ng. If the intention is to use geologica l CO 2 

### sequestration as an effective

mi tigation tool for global clim ate change, the stratigraphic section between the Tensleep/Madison does not have the storage volume required to accommodate the huge quantities of CO 2 

### that will need to be geologically sequ estered.

The Wyo mi ng State Geological Survey suggests that our Nation will be

mu ch better served if the proposed regulations for geological CO 2 

### sequestration, with respect to injecting CO 2 

### only below the lowest USDW aquifer, be modified as

follows: “Geo logical CO 2 

### sequestration will be allowed in deep saline aquifers in Rocky Mountain Laramide Basins unless it can be demonstrated that the injected

CO 2 

### will have a deleterious effect on USDW.” If this change is not made, the geological sequestration of CO 2 

### will be far

mo re onerous than injecting H 2 

### S into the deep portion of RMLB. For economic and regulatory purposes, the regulations as proposed will make geological sequestration of CO 2 

### impossible. To promulgate a geological CO 2 

### sequestration regulation f

or RMLB out of the context of Rocky Mountain Laramide geology will make it extremely difficult to mitigate the effects of greenhouse emissions on

clim ate change in the West. The Wyo mi ng State Geological Survey requests that

the United States Environmental Protection Agency act favorably on the changes

herein described.Letter ID: 0132

Commenter: Ronald Surdam Organization: Wyoming Stat e Geological Survey

Letter ID: 0132 Comment ID: 21542 Letter Lines: 28 to 76

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

USDW

Comment: The requirements of injecting CO2 only below the lowermost Underground Source

of Drinking Water (USDW) aquife r will make it impossible to inject CO2 into deep saline aquifers in Rock Mountain Laramide Basins (RMLB). The problem is when the deep geological sequestration CO2 ta rgets in RMLB (i.e., deep saline aquifers) occur near the surface, they cont ain USDW. For example, at a depth of 10,000 to 15,000 feet, a stratigraphic unit su ch as, but not limited to the Madison Limestone, typically has salinity > 10,000 ppm. However, this same unit at 0-3,000 feet depth typically has salin ity < 500 ppm. Near the surface, the aquifer is recharged with copious quanti ties of fresh meteoric water; but, because of geohydrologic characteristics co mmon to Laramide Basins of Wyoming,

the fresh water does not circulate into the deeper portions of the basin. Instead, it discharges in the form of spri ngs or into streams/rivers near the margin of the basin typically along b ounding faults or breached, anticlinal structures. As a consequence, due to a lack of mixing meteoric and connate fluids, the fluid in the same unit at a depth of 10,000 feet maintains salinities more near the original depositional environment (i.e., marine waters with salinities > 30,000 ppm). If the forma tion fluid was part of a continuous fluid-flow system, the whole rock/fluid system would have been flushed during the Pleistocene when recharge rates were much higher than today. Observations made in all of Wyoming’s Laramide Basins demonstrate that fluid-flow systems in the deep saline aquifers are compartm entalized resulting in an absence of shallow-formation water mixing with deep basin brines.

The ramifications of declaring a stratigr aphic unit in Rocky Mountain Basins a USDW aquifer because it supplies fresh wa ter at shallow depth are immense. The stratigraphic section beneath units such as the Paleozoic Madison Limestone and the Tensleep Sandstone (or stratigraphic e quivalent units) is relatively thin in Wyoming. If the intention is to use geological CO2 sequestration as an effective mitigation tool for global climate change, the stratigraphic section between the Tensleep/Madison does not ha ve the storage volume required to accommodate the huge quantities of CO2 th at will need to be geologically sequestered.

The Wyoming State Geological Survey suggest s that our Nation will be much better served if the proposed regulations fo r geological CO2 sequestration, with

12 respect to injecting CO2 only below the lo west USDW aquifer, be modified as follows: “Geological CO2 sequestration will be allowed in deep saline aquifers in Rocky Mountain Laramide Basins unle ss it can be demonstrated that the injected CO2 will have a deleterious effect on USDW.”

If this change is not made, the geological sequestration of CO2 will be far more onerous than injecting H2S into the d eep portion of RMLB. For economic and regulatory purposes, the regulations as proposed will make geological sequestration of CO2 impossible. To pr omulgate a geological CO2 sequestration regulation for RMLB out of the context of Rocky Mountain Laramide geology will make it extremely difficult to mitigate the effects of greenhouse emissions on climate change in the West. The Wyoming State Geological Survey requests that

the United States Environmental Protecti on Agency act favorably on the changes

herein described.

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 above and/or between USDWs. It establishes: 1) requirements spec ifying information that owners or operators must submit, and Directors must consider, in consultation with PW SS Directors; 2) procedures for public notice of a waiver application and for Director-Regiona l Administrator communicat ion; 3) the waiver issuance process; and, 4) additiona l requirements that apply to owne rs or operators of Class VI wells granted a waiver of the in jection depth requirements to en sure USDW protection above and below the injection zone.

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 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.