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.
California State Water Resources Control Board (SWRCB) Comments to: 

Federal Requirements under the Underground Injection Control (UIC) 

Program for Carbon Dioxide (CO2) Geologic Sequestration (GS) Wells; 

Notice of Data Availability and Request for Comment 

SWRCB Comment #1 on: “2. Basin-Scale Hydrologic Impact of CO2

Storage” 

The Lawrence Berkeley National Laboratory (LBNL) modeled an area, 570 

kilometers (km) by 550 km, with 20 carbon dioxide (CO2) injection points at 5 

million tons of CO2 per year, total 100 mln. tons per year. (Humans breathing 

about 6-million tons of CO2/day, which equates to over 2-billion tons/year). To 

store human CO2 alone would require over 20 these areas. The LBNL simulation 

indicated that the subsurface pressure change induced by injection extends over 

area of 400 km2 after 50 years. Model’s assumption was that there was an 

extensive confining layer over the entire CO2 sequestration area. A specific code 

was used for simulation was developed for modeling of water or solute migration 

in porous media, not for subsurface gas migration. 

 

Findings: 

• Confining layer(s) for fluids (water or oil) may not confine CO2 -type gases. 

• CO2 dissolved in water creates carbonic acid. Carbonic acid is corrosive 

to several types of rocks which will dissolve rock. This will increase 

porosity by enlarging existing rock fractures, which creates a conduit for 

CO2 gases to escape from the repository formation into the atmosphere. 

• Injection of CO2 into exhausted oil and natural gas bearing formations will 

have high potential for CO2 to migrate back to the atmosphere. 

Additionally, the formation has been perforated by thousands of oil and 

natural gas wells (abandoned or not) allowing CO2 to escape to the 

atmosphere. 

• Future tectonic events (earthquakes) will likely cause catastrophic release 

of CO2 into drinking or potentially drinking water aquifers and the 

atmosphere. 

B. SWRCB Comment #2 on: “IV. Injection Depth for GS Projects A. What 

did EPA propose for Class VI well injection depth relative to the location of 

USDWs?”

• Injecting CO2 above or below the water supply aquifer is irrelevant since 

under extreme pressure and high temperature, CO2 gas will migrate 

downward and upward, following porosity, fault zones or man-made 

pathways. Plus, you cannot compare CO2 gas to liquid injection since CO2

gas will expand under pressure in all directions, and has much greater 

mobility than fluids. Gas will penetrate rock with much smaller opening 
pores or fractures than those needed for fluid migration. Fluid 

compressibility and subsequent expansibility is negligible compared to this 

of gases. The LBNL modeling showed injected gas will expand for 

hundreds of miles, for many years after injection stops, and sooner or later 

may reach area(s) where will be able to escape to the surface or drinking 

water aquifer. 

• CO2 is heavier than air and if release to the surface at high concentration 

will be deadly. 

• Example: 

o In 1986, a tremendous explosion of CO2 from the lake Nyos, West 

of Cameroon, killed more than 1700 people and livestock up to 25 

km away. The dissolved CO2 is seeping from springs beneath the 

lake and is trapped in deep water by the high hydrostatic pressure. 

If the CO2 saturation level is reached, bubbles appear and draw a 

rich mixture of gas and water up. An avalanche process is triggered 

which results in an explosive over-turn of the whole lake. 

• CO2 injection (to save earth from an uncertain climate changes) may result 

in water supply contamination (EPA declared CO2 as a pollutant that need 

to be regulated) or even catastrophic release that can kill thousands. 

• After 20 years of investigation and billions dollars spent at Yucca Mountain 

repository, the US EPA and some scientists cannot warrant that that 

Yucca Mt repository is totally safe. After thousands of years radioactive 

elements may leak from the repository and in another thousands of years 

may reach drinking ground water at concentration exceeding maximum 

contaminant level. The reported CO2 modeling by LBNL cited in this 

document is limited to 100-years period. 

• What fraction of CO2 generated world-wide (30 billion tons/year) can be 

injected into selected formations in the USA and at what cost? How this 

fraction of stored CO2 will affect earth atmosphere and subsequently 

temperature on earth? 

C. SWRCB Comment #3 on: “D. - Evaluation of concerns about injection 

depth for Class VI wells”: 

• Laterally continuous, impermeable confining units on large scale have not 

been found to exist in nature. 

• Laterally continuous, CO2 injection zones with the required porosity and 

chemistry are very rare in nature. 

• Continuous zone free of fractures and faults have not been found to exist 

in nature. 
• Characterization of fractures and faults deep under ground is not currently 

possible; the proposed Yucca Mountain waste repository site 

characterization process includes access to deep zone through miles of 

tunnels and boreholes. Even with all of this, there are still uncertainties 

about its safety. 

D. SWRCB Closing Comments:

• There are hundreds of thousands of undocumented, abandoned 

wells and boreholes across US that are either not mapped or 

identified. These wells and boreholes are a conduit for CO2 to 

either escape to the atmosphere or to adjacent drinking water 

aquifers. To identify, map and properly destroy theses “artificial 

penetrations” before CO2 injection can take place is such a great 

task it borders on the impossible. 

• No waiver should be issued in any area that has extensive 

groundwater use, high density water or oil wells, seismically 

unstable now or potentially in the future, potential for earthquakes, 

volcanic activities presently or in distant future. 

• Injecting such a small fraction of CO2 is high risk and its cost to 

benefit-effect on climate change is negligible. Also, the State of 

California does not allow for permits to dispose of hazardous 

materials through injection wells. 
Letter ID: 0339  

Commenter: John Borkovich  

Organization: California State Water Resources Control Board (SWRCB)  

Letter ID: 0339 Comment ID: 28009 Letter Lines: 22 to 50  

Comment Code: 2220 2.2.2. Basin‐Scale Hydrologic Impacts of CO2 Storage (seeking comment)  

Comment: SWRCB Comment #1 on: "2. Basin‐Scale Hydrologic Impact of CO2 Storage"  

The Lawrence Berkeley National Laboratory (LBNL) modeled an area, 570 kilometers  

(km) by 550 km, with 20 carbon dioxide (CO2) injection points at 5 million tons  

of CO2 per year, total 100 mln. tons per year. (Humans breathing about 6‐  

million tons of CO2/day, which equates to over 2‐billion tons/year). To store  

human CO2 alone would require over 20 these areas. The LBNL simulation  

indicated that the subsurface pressure change induced by injection extends over  

area of 400 km2 after 50 years. Model's assumption was that there was an  

extensive confining layer over the entire CO2 sequestration area. A specific  

code was used for simulation was developed for modeling of water or solute  

migration in porous media, not for subsurface gas migration.  

Findings:  

Confining layer(s) for fluids (water or oil) may not confine CO2 ‐type gases.  

CO2 dissolved in water creates carbonic acid. Carbonic acid is corrosive to  

several types of rocks which will dissolve rock. This will increase porosity by  

enlarging existing rock fractures, which creates a conduit for CO2 gases to  

escape from the repository formation into the atmosphere.  

Injection of CO2 into exhausted oil and natural gas bearing formations will have  

high potential for CO2 to migrate back to the atmosphere. Additionally, the  

formation has been perforated by thousands of oil and natural gas wells  

(abandoned or not) allowing CO2 to escape to the atmosphere.  

Future tectonic events (earthquakes) will likely cause catastrophic release of  

CO2 into drinking or potentially drinking water aquifers and the atmosphere.  

Individual Response: In response to the commenter’s criticism of the specific code used in the study,
EPA clarifies that the TOUGH2 model used is a general purpose simulation program designed for multi‐

dimensional fluid and heat flows of multiphase and multi‐component fluid mixtures in porous and

fractured media. TOUGH2/ECO2N simulates water and solute transport together with gas migration of

supercritical CO2.  

EPA agrees that the factors cited by the commenter are important considerations. The GS rule requires

geologic site characterization to verify the presence of adequate confining layers, help predict

geochemical reactions which can lead to dissolution and/or precipitation of minerals, and identify the

presence of seismic sources and faults or fractures to address these concerns (§146.82).  

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

within the confining zone (§146.82(a)(3)). Owners or operators must also conduct extensive monitoring

to detect possible CO2 movement from the injection zone (§146.90). For additional information

regarding EPA’s requirements for AoR delineation and monitoring of GS projects, see the responses to

comments on the proposed rule in the rulemaking docket.  

Letter ID: 0339 Comment ID: 28010 Letter Lines: 52 to 68  

Comment Code: 3100 3.1. Comments on Concerns About Injection Depth for Class VI Wells  

Comment Code: 3220 3.2.2. Comments in Opposition to the Approach  

Comment: B. SWRCB Comment #2 on: "IV. Injection Depth for GS Projects A. What did EPA  

propose for Class VI well injection depth relative to the location of USDWs?"  

Injecting CO2 above or below the water supply aquifer is irrelevant since under  

extreme pressure and high temperature, CO2 gas will migrate downward and upward,  

following porosity, fault zones or man‐made pathways. Plus, you cannot compare  

CO2 gas to liquid injection since CO2 gas will expand under pressure in all  

directions, and has much greater mobility than fluids. Gas will penetrate rock  

with much smaller opening pores or fractures than those needed for fluid  

migration. Fluid compressibility and subsequent expansibility is negligible  

compared to this of gases. The LBNL modeling showed injected gas will expand for  

hundreds of miles, for many years after injection stops, and sooner or later may  

reach area(s) where will be able to escape to the surface or drinking water  

aquifer.  
CO2 is heavier than air and if release to the surface at high concentration will  

be deadly.  

Individual Response: EPA believes proper siting, well construction, operation, monitoring, and post‐

injection site care will allow CO2 to be sequestered, despite its buoyancy. The GS rule is designed to

ensure that appropriate requirements are in place to protect USDWs from endangerment. EPA

acknowledges that faults and artificial penetrations offer paths for fluid movement. For this reason, the

GS rule contains requirements at §146.82 for characterization of faults and fractures, and §146.84

requires an AoR evaluation and corrective action. For additional information on characterization of

faults and fractures, AoR, and corrective actions, see the preamble to the final rule and the responses to

comments on the proposed GS rule.  

In addition, owners or operators seeking waivers from the injection depth requirements must provide

additional information about the injection zone; identification of confining units above and below the

injection zone; and tailored AoR modeling above and below the injection zone, as required at

§146.95(a).  

Letter ID: 0339 Comment ID: 28011 Letter Lines: 94 to 109  

Comment Code: 3310 3.3.1. Site Characterization  

Comment: C. SWRCB Comment #3 on: "D. ‐ Evaluation of concerns about injection depth for  

Class VI wells":  

Laterally continuous, impermeable confining units on large scale have not been  

found to exist in nature.  

Laterally continuous, CO2 injection zones with the required porosity and  

chemistry are very rare in nature.  

Continuous zone free of fractures and faults have not been found to exist in  

nature.  

Characterization of fractures and faults deep under ground is not currently  

possible; the proposed Yucca Mountain waste repository site characterization  

process includes access to deep zone through miles of tunnels and boreholes.  

Even with all of this, there are still uncertainties about its safety.  

Individual Response: EPA disagrees that laterally continuous, impermeable confining zones and laterally

continuous injection zones are rare in nature. Existing geologic structures such as gas and oil fields and
natural CO2 domes have shown the ability to trap and retain gases for millions of years. Many owners or

operators of injection projects have made similar demonstrations to satisfy UIC permitting requirements

(e.g., Class I through V), including evaluating the existence of laterally continuous injection and confining

zones and the absence of transmissive faults and fractures. 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: 0339 Comment ID: 28012 Letter Lines: 111 to 118  

Comment Code: 5000 5. Comments on the Proposed Rule (out of NODA Scope)  

Comment: D. SWRCB Closing Comments:  

There are hundreds of thousands of undocumented, abandoned wells and boreholes  

across US that are either not mapped or identified. These wells and boreholes  

are a conduit for CO2 to either escape to the atmosphere or to adjacent drinking  

water aquifers. To identify, map and properly destroy theses "artificial  

penetrations" before CO2 injection can take place is such a great task it  

borders on the impossible.  

Individual Response: This comment pertains to EPA’s proposed GS rule (73 FR 43492) and is outside the

scope of the Notice of Data Availability. Please see responses to comments on the proposed rule for

EPA’s response to similar comments.  

Letter ID: 0339 Comment ID: 28396 Letter Lines: 70 to 92  

Comment Code: 6000 6. Other Comments that are Out of Scope for the NODA  

Comment: Example:  

In 1986, a tremendous explosion of CO2 from the lake Nyos, West of Cameroon,  

killed more than 1700 people and livestock up to 25 km away. The dissolved CO2  

is seeping from springs beneath the lake and is trapped in deep water by the  

high hydrostatic pressure. If the CO2 saturation level is reached, bubbles  

appear and draw a rich mixture of gas and water up. An avalanche process is  

triggered which results in an explosive over‐turn of the whole lake.  

CO2 injection (to save earth from an uncertain climate changes) may result in  
water supply contamination (EPA declared CO2 as a pollutant that need to be  

regulated) or even catastrophic release that can kill thousands.  

After 20 years of investigation and billions dollars spent at Yucca Mountain  

repository, the US EPA and some scientists cannot warrant that that Yucca Mt  

repository is totally safe. After thousands of years radioactive elements may  

leak from the repository and in another thousands of years may reach drinking  

ground water at concentration exceeding maximum contaminant level. The reported  

CO2 modeling by LBNL cited in this document is limited to 100‐years period.  

What fraction of CO2 generated world‐wide (30 billion tons/year) can be injected  

into selected formations in the USA and at what cost? How this fraction of  

stored CO2 will affect earth atmosphere and subsequently temperature on earth?  

Individual Response: This comment is outside the scope of the Notice of Data Availability and the UIC

Program’s authority under the GS rulemaking.  

Letter ID: 0339 Comment ID: 28579  

Comment: Individual Response:

Letter ID: 0339 Comment ID: 29236 Letter Lines: 120 to 127  

Comment Code: 3220 3.2.2. Comments in Opposition to the Approach  

Comment: No waiver should be issued in any area that has extensive groundwater use, high  

density water or oil wells, seismically unstable now or potentially in the  

future, potential for earthquakes, volcanic activities presently or in distant  

future.  

Injecting such a small fraction of CO2 is high risk and its cost to benefit‐  

effect on climate change is negligible. Also, the State of California does not  

allow for permits to dispose of hazardous materials through injection wells.  

Individual Response: EPA acknowledges the commenter's concerns about USDW protection and clarifies

that the mission of the UIC Program is to protect USDWs from endangerment. Based on an evaluation of

comments on the proposed injection depth requirements and the waiver process discussed in the
NODA, and concerns about USDW protection, EPA believes that there are limited 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 or operators can

seek a waiver of the Class VI injection depth requirements. The waiver approach establishes

requirements for extensive site‐specific information related to injecting above or between USDWs

(including ground water use and water supply needs, as the commenter suggests) that the owner or

operator must submit and the Director must consider, in consultation with PWSS Directors, to ensure

that water supplies in the area and all USDWs are protected.  

EPA clarifies that any decision to grant a waiver (or a Class VI permit) will be based on extensive study of

the proposed area, including the number and condition of wells in the air and seismic history.