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.Letter ID: 0203

Commenter: Brad Castleberry

Organization: Water Environment Association of Texas (WEAT)

Letter ID: 0203 Comment ID: 22178 Letter Lines: 31 to 41

Comment Code: 1600 1.3 Risk Associated with CO2 GS

Comment: These comments are submitted on behalf of the Water Environment Association of

Texas ("WEAT"). Specifically, these comme nts are submitted in response to the

above-referenced rulemaking in an ef fort to urge caution and careful

consideration before adoption of the propos ed regulations. We urge this caution

in the interest of protec ting drinking water sources and groundwater quality.

WEAT is a non-profit techni cal trade organization comp rised of a number of

utilities, industries, and individuals in the State of Texas. WEAT's members

strive to promote sound science, educati on, and environmental stewardship. There

are a number of activities in the propos ed regulations that could impact

groundwater quality as well as public drinking water sources. Careful

Individual Response: EPA believes that injecting large vo lumes of CO2 for GS poses unique

challenges that, if not properly managed, could endanger drinking water s ources or have other

adverse impacts. EPA believes that caution is wa rranted and has, as a result, developed a new

well class with requirements tailored to address the unique challenges posed by GS and potential

risks associated long-t erm injection of CO2.

Letter ID: 0203 Comment ID: 22179 Letter Lines: 41 to 51

Comment Code: 3100 2.1 Proposed Geologic Siting Requirements (40 CFR 146.83)

Comment Code: 4600 2.6 Proposed Plume and Pressure Front Monitoring Requirements (40

CFR 146.90)

Comment: groundwater quality as well as public drinking water sources. Careful

consideration should he given to ensure an adequate assessment is made of each

proposed injection well site. This consid eration should come in the form of

detailed site studies. sophisticated com puter modeling, and other tools used to

predict hydrogeology. Careful consideration shou ld also he given to ensure that

adequate ongoing monitoring and reporting is provided for any site ultimately

permitted pursuant to the proposed rule s. Given the unique circumstances

surrounding this type of pollutant, and th e lack of a significant body of longterm evidence to support the proposed act ivity, we would encourage EPA to

include significant monitori ng and reporting provisions to ensure the long-term

viability of any permitted site with re spect to surrounding groundwater quality.

Individual Response: EPA agrees with the commenter re garding the importance of site

12 characterization, and believes that the extensive requirements for geologic site characterization

(at §146.82), AoR evaluation (§146.84), and testi ng of the well during drilling (§146.87) are

appropriate to ensure that permitting authoritie s have the necessary information to evaluate

whether a specific site will allow safe injection of CO2. EPA adds that submittal and review of

monitoring data (as required at §146.90) and the AoR reevaluation pr ocess (§146.84(e)) will

provide an opportunity for an ongoing review of the site and a dialogue between the Director and

the owner or operator to ensure that the project is being ope rated in a manner that protects

USDWs from endangerment.

EPA believes that monitoring plans and methods need to be site-specific and that the monitoring

requirements for GS sites at §146.90 provide an appropriate level of flexibility in structuring a

testing and monitoring plan that pr otects USDWs from endangerment.

The GS rule, at §146.90, requires injectate mon itoring, mechanical integrity testing, corrosion

monitoring, tracking the CO2 plum e and area of elevated pressure, monitoring geochemical

changes above the confining zone, and, at the discretion of the Director, surface air and soil gas

monitoring for CO2 fluctuations, and any addition al tests necessary to ensure USDW protection

from endangerment.

EPA is developing guidance on testing and mon itoring to assist owne rs or operators and

Directors in evaluating requi rements under §146.90, including pr oposed monitoring plans. The

guidance describes available technologies a nd recommended approaches for implementing a

testing and monitoring plan, including pre-ope rational geophysical l ogging and testing of

injection wells, MITs, injecti on well testing during operation, groundwater quality monitoring,

tracking the CO2 plume and pressure front, a nd soil gas and surface air monitoring which may

be required by the UIC Director for specific GS projects. Th e guidance can be found on EPA’s

website at http://water.epa.gov/type/gr oundwater/uic/wells_se questration.cfm.