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.
Document ID: EPA-HQ-OW-2008-0390-112 

Last Name: Lokey 

First Name: Elizabeth 

Title: 

Organization: Camco International 

City: 

State: 

Zip Code: 

Phone Number: 

Fax Number: 

Country Code: 

Email Address: 

Current Category Code: 257 

Comment: Currently, the proposed rule (EPA-HQ-OW-2008-0390) defines CO2 that can 

be injected under a class VI designation as the following: 

"CO2 that has been captured from an emission source (e.g. power plant), 

plus incidental associated substances derived from the source materials and the 

capture process, and any substances added to the stream to enable or improve the 

injection process. This subpart does not apply to any carbon dioxide stream that 

meets the definition of a hazardous waste under 40 CFR Part 261." 

This definition is vague and needs clarification in terms of the percentage of 

CO2 in a given volume of gas to allow the CO2 to qualify for this injection 

permit. Otherwise, entire stack emissions or chemicals used in the separation 

process could end up being transported and injected. This could have unintended 

consequences on the reservoirs where the CO2 is stored as minerals could be 

dissolved and allow plumes to spread. 
Letter ID: 0112 

Commenter: Elizabeth Lokey 

Organization: Camco International 

Letter ID: 0112 Comment ID: 22046 Letter Lines: 15 to 29 

Comment Code: 1614 1.3.1.2 Impurities in captured CO2; purity standards for CO2 

Comment Code: 1630 1.3.3 RCRA/hazardous waste issues (seeking comment) 

Comment: Currently, the proposed rule (EPA-HQ-OW-2008-0390) defines CO2 that can 

be injected under a class VI designation as the following: 

"CO2 that has been captured from an emission source (e.g. power plant), 

plus incidental associated substances derived from the source materials and the 

capture process, and any substances added to the stream to enable or improve the 

injection process. This subpart does not apply to any carbon dioxide stream that 

meets the definition of a hazardous waste under 40 CFR Part 261." 

This definition is vague and needs clarification in terms of the percentage of 

CO2 in a given volume of gas to allow the CO2 to qualify for this injection 

permit. Otherwise, entire stack emissions or chemicals used in the separation 

process could end up being transported and injected. This could have unintended 

consequences on the reservoirs where the CO2 is stored as minerals could be 

dissolved and allow plumes to spread. 

Individual Response: The GS rule does not set generic purity standards for CO2 injectate 

streams (e.g., a percent CO2). Instead, the GS rule addresses the quality and quantity of 

impurities by requiring owners or operators to submit information on the source of the CO2 and 

its physical and chemical properties. Specifically, the GS rule requires the owner or operator to 

submit data about the site, including an analysis of the chemical and physical characteristics of 

the CO2 stream, as required at §146.82(a)(7)(iv), and information on the compatibility of the 

CO2 stream with fluids in the injection zone and minerals in both the injection and the confining 

zones and the materials used to construct the well, per §146.82(c)(3). This information can help 

the Director determine the potential for geochemical reactions between the injectate (CO2) and 

the host geologic formations, which could result in the plugging of pore spaces or the dissolution 

of formation minerals. 

EPA understands that many CO2 streams may be relatively pure, and research indicates that the 

estimated amounts of impurities in a CO2 stream are likely to be low. However, these estimates 

are based on limited information, and uncertainties remain about the expected concentrations of 

impurities from the various types of CO2 streams. The concentrations of minor and trace 

elements in CO2 streams for GS projects are likely to vary by facility, coal composition, plant 

operating conditions, and pollution removal technologies. EPA clarifies that the GS rule does not 

apply to capture technologies. 

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