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-2008-0390-119

Last Name: McCormic

First Name: Rob

Title: 

Organization: Dallas County Park Cities Municipal Utility District

City: 

State: 

Zip Code: 

Phone Number: 

Fax Number: 

Country Code: 

Email Address: 

Current Category Code: 252

Comment: Concerning the proposed rule allowing Geological Sequestration of Carbon Dioxide, what 

safeguards are there against accidently activating or reactivating seismic (earthquake) faults at or near a 

proposed sequestration site, particularly with injecting "supercritical" liquid CO2?
Letter ID: 0119 

Commenter: Rob McCormic 

Organization: Dallas County Park Cities Municipal Utility District 

Letter ID: 0119 Comment ID: 22069 Letter Lines: 15 to 18 

Comment Code: 1620 1.3.2 Induced seismicity 

Comment: Concerning the proposed rule allowing Geological Sequestration of 

Carbon Dioxide, what safeguards are there against accidently activating or 

reactivating seismic (earthquake) faults at or near a proposed sequestration 

site, particularly with injecting "supercritical" liquid CO2? 

Individual Response: EPA acknowledges that induced seismicity is a risk that may be 

associated with GS but maintains that the risk is low (IPCC, 2005). The GS rule contains several 

requirements to address seismic risk. First, as part of the site characterization process under 

§146.82, owners or operators must submit information about the seismic history of and seismic 

sources near a proposed GS site; data on known or suspected faults in the AoR; and 

geomechanical information on fractures, stress, ductility, rock strength, and in situ fluid 

pressures within the confining zone as specified in §146.82(a)(3). This information is evaluated 

by the Director, who determines the suitability of a potential project site for GS. Any sites with 

the potential for reopening or reactivation of faults or unacceptable seismic risk that could 

otherwise interfere with containment will not be permitted as GS sites. During injection, the 

pressure in the injection zone must not exceed 90 percent of the fracture pressure of the injection 

zone as specified in §146.88(a); this requirement is intended to prevent the opening of fractures 

or faults through over-pressurization of the injection zone. 

To support consistent interpretation and application of the safeguards related to induced 

seismicity in the GS rule, EPA is developing guidance on site characterization for GS projects to 

assist owners or operators and Directors in evaluating permit requirements and applications 

under §146.82. The guidance provides recommendations to owners or operators regarding 

information to support characterizing the regional geology and hydrogeology of a proposed GS 

site as well as how to perform the necessary geochemical, geomechanical, and geophysical 

analyses of the injection and confining zone. EPA expects that this guidance will assist permit 

writers and UIC Directors in making an objective decision about requiring additional confining 

layers. The guidance can be found on EPA’s website at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

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