Plan to Study the Potential

Impacts of Hydraulic Fracturing

on Drinking Water Resources

EPA/600/R-11/122/November 2011/www.epa.gov/hydraulicfracturing

United States Environmental Protection Agency

Office of Research and Development
EPA Hydraulic Fracturing Study Plan November 2011

EPA/600/R-11/122

November 2011

Plan to Study the Potential

Impacts of Hydraulic Fracturing

on Drinking Water Resources

Office of Research and Development

US Environmental Protection Agency

Washington, D.C.

November 2011
EPA Hydraulic Fracturing Study Plan November 2011

Mention of trade names or commercial products does not constitute

endorsement or recommendation for use.
EPA Hydraulic Fracturing Study Plan November 2011

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TABLE OF CONTENTS

List of Figures....................................................................................................................................vi

List of Tables.....................................................................................................................................vi

List of Acronyms and Abbreviations..................................................................................................vii

Executive Summary.........................................................................................................................viii

1 Introduction and Purpose of Study..............................................................................................1

2 Process for Study Plan Development...........................................................................................3

2.1 Stakeholder Input............................................................................................................................................3

2.2 Science Advisory Board Involvement..............................................................................................................5

2.3 Research Prioritization ....................................................................................................................................6

2.4 Next Steps .......................................................................................................................................................7

2.5 Interagency Cooperation.................................................................................................................................7

2.6 Quality Assurance............................................................................................................................................8

3 Overview of Unconventional Oil and Natural Gas Production ......................................................9

3.1 Site Selection and Preparation......................................................................................................................12

3.2 Well Construction and Development............................................................................................................13

3.2.1 Types of Wells........................................................................................................................................13

3.2.2 Well Design and Construction................................................................................................................13

3.3 Hydraulic Fracturing ......................................................................................................................................15

3.4 Well Production and Closure.........................................................................................................................16

3.5 Regulatory Framework..................................................................................................................................16

4 The Hydraulic Fracturing Water Lifecycle...................................................................................17

5 Research Approach...................................................................................................................20

5.1 Analysis of Existing Data................................................................................................................................20

5.2 Case Studies ..................................................................................................................................................20

5.3 Scenario Evaluations .....................................................................................................................................21

5.4 Laboratory Studies ........................................................................................................................................21

5.5 Toxicological Studies .....................................................................................................................................21

6 Research Activities Associated with the Hydraulic Fracturing Water Lifecycle.............................22

6.1 Water Acquisition: What are the potential impacts of large volume water withdrawals from ground

and surface waters on drinking water resources? ........................................................................................22

6.1.1 Background ............................................................................................................................................22
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6.1.2 How much water is used in hydraulic fracturing operations, and what are the sources of

this water? .............................................................................................................................................24

6.1.2.1 Research Activities – Source Water ................................................................................................24

6.1.3 How might water withdrawals affect short- and long-term water availability in an area with

hydraulic fracturing activity?..................................................................................................................25

6.1.3.1 Research Activities – Water Availability..........................................................................................25

6.1.4 What are the possible impacts of water withdrawals for hydraulic fracturing operations on

local water quality?................................................................................................................................27

6.1.4.1 Research Activities – Water Quality................................................................................................27

6.2 Chemical Mixing: What are the possible impacts of surface spills on or near well pads of hydraulic 

fracturing fluids on drinking water resources? .............................................................................................28

6.2.1 Background ............................................................................................................................................28

6.2.2 What is currently known about the frequency, severity, and causes of spills of hydraulic

fracturing fluids and additives?..............................................................................................................28

6.2.2.1 Research Activities – Surface Spills of Hydraulic Fracturing Fluids and Additives ..........................29

6.2.3 What are the identities and volumes of chemicals used in hydraulic fracturing fluids, and how

might this composition vary at a given site and across the country? ....................................................30

6.2.3.1 Research Activities – Hydraulic Fracturing Fluid Composition........................................................30

6.2.4 What are the chemical, physical, and toxicological properties of hydraulic fracturing chemical 

additives? ...............................................................................................................................................31

6.2.4.1 Research Activities – Chemical, Physical, and Toxicological Properties..........................................31

6.2.5 If spills occur, how might hydraulic fracturing chemical additives contaminate drinking water 

resources? ..............................................................................................................................................32

6.2.5.1 Research Activities – Contamination Pathways..............................................................................33

6.3 Well Injection: What are the possible impacts of the injection and fracturing process on drinking

water resources?...........................................................................................................................................34

6.3.1 Background ............................................................................................................................................34

6.3.1.1 Naturally Occurring Substances......................................................................................................34

6.3.2 How effective are current well construction practices at containing gases and fluids before,

during, and after fracturing?..................................................................................................................35

6.3.2.1 Research Activities – Well Mechanical Integrity .............................................................................35

6.3.3 Can subsurface migration of fluids or gases to drinking water resources occur, and what local

geologic or man-made features may allow this? ...................................................................................37

6.3.3.1 Research Activities – Local Geologic and Man-Made Features ......................................................38

6.3.4 How might hydraulic fracturing fluids change the fate and transport of substances in the

subsurface through geochemical interactions? .....................................................................................40

6.3.4.1 Research activities – Geochemical Interactions..............................................................................40
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6.3.5 What are the chemical, physical, and toxicological properties of substances in the subsurface

that may be released by hydraulic fracturing operations? ....................................................................41

6.3.5.1 Research Activities – Chemical, Physical, and Toxicological Properties..........................................41

6.4 Flowback and Produced Water: What are the possible impacts of surface spills on or near well pads of 

flowback and produced water on drinking water resources?.......................................................................42

6.4.1 Background ............................................................................................................................................42

6.4.2 What is currently known about the frequency, severity, and causes of spills of flowback and

produced water?....................................................................................................................................43

6.4.2.1 Research Activities – Surface Spills of Flowback and Produced Water...........................................44

6.4.3 What is the composition of hydraulic fracturing wastewaters, and what factors might influence

this composition?...................................................................................................................................44

6.4.3.1 Research Activities – Composition of Flowback and Produced Water ...........................................45

6.4.4 What are the chemical, physical, and toxicological properties of hydraulic fracturing wastewater 

constituents?..........................................................................................................................................45

6.4.4.1 Research Activities – Chemical, Physical, and Toxicological Properties..........................................46

6.4.5 If spills occur, how might hydraulic fracturing wastewaters contaminate drinking

water resources?....................................................................................................................................47

6.4.5.1 Research Activities – Contamination Pathways..............................................................................47

6.5 Wastewater Treatment and Waste Disposal: What are the possible impacts of inadequate treatment

of hydraulic fracturing wastewaters on drinking water resources?..............................................................48

6.5.1 Background ............................................................................................................................................48

6.5.2 What are the common treatment and disposal methods for hydraulic fracturing wastewaters,

and where are these methods practiced? .............................................................................................49

6.5.2.1 Research Activities – Treatment and Disposal Methods.................................................................49

6.5.3 How effective are conventional POTWs and commercial treatment systems in removing organic

and inorganic contaminants of concern in hydraulic fracturing wastewaters?.....................................50

6.5.3.1 Research Activities – Treatment Efficacy ........................................................................................50

6.5.4 What are the potential impacts from surface water disposal of treated hydraulic fracturing 

wastewater on drinking water treatment facilities?..............................................................................51

6.5.4.1 Research Activities – Potential Drinking Water Treatment Impacts...............................................51

7 Environmental Justice Assessment............................................................................................53

7.1.1 Are large volumes of water for hydraulic fracturing being disproportionately withdrawn from

drinking water resources that serve communities with environmental justice concerns? ...................54

7.1.1.1 Research Activities – Water Acquisition Locations.........................................................................54

7.1.2 Are hydraulically fractured oil and gas wells disproportionately located near communities with 

environmental justice concerns? ...........................................................................................................54

7.1.2.1 Research Activities – Well Locations...............................................................................................54
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7.1.3 Is wastewater from hydraulic fracturing operations being disproportionately treated or disposed

of (via POTWs or commercial treatment systems) in or near communities with environmental

justice concerns?....................................................................................................................................55

7.1.3.1 Research Activities – Wastewater Treatment/Disposal Locations .................................................55

8 Analysis of Existing Data...........................................................................................................56

8.1 Data Sources and Collection..........................................................................................................................56

8.1.1 Public Data Sources................................................................................................................................56

8.1.2 Information Requests.............................................................................................................................56

8.2 Assuring Data Quality ....................................................................................................................................58

8.3 Data Analysis.................................................................................................................................................58

9 Case Studies.............................................................................................................................58

9.1 Case Study Selection .....................................................................................................................................58

9.2 Retrospective Case Studies ...........................................................................................................................63

9.3 Prospective Case Studies...............................................................................................................................66

10 Scenario Evaluations and Modeling...........................................................................................67

10.1 Scenario Evaluations .....................................................................................................................................68

10.2 Case Studies ..................................................................................................................................................69

10.3 Modeling Tools..............................................................................................................................................69

10.4 Uncertainty in Model Applications................................................................................................................71

11 Characterization of Toxicity and Human Health Effects..............................................................71

12 Summary .................................................................................................................................73

13 Additional Research Needs.......................................................................................................81

13.1 Use of Drilling Muds in Oil and Gas Drilling...................................................................................................81

13.2 Land Application of Flowback or Produced Waters......................................................................................81

13.3 Impacts from Disposal of Solids from Wastewater Treatment Plants ..........................................................81

13.4 Disposal of Hydraulic Fracturing Wastewaters in Class II Underground Injection Wells ..............................82

13.5 Fracturing or Re-Fracturing Existing Wells....................................................................................................82

13.6 Comprehensive Review of Compromised Waste Containment....................................................................82

13.7 Air Quality......................................................................................................................................................82

13.8 Terrestrial and Aquatic Ecosystem Impacts ..................................................................................................83

13.9 Seismic Risks..................................................................................................................................................83

13.10 Occupational Risks.........................................................................................................................................83

13.11 Public Safety Concerns..................................................................................................................................83

13.12 Economic Impacts .........................................................................................................................................84
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13.13 Sand Mining...................................................................................................................................................84

References.......................................................................................................................................85

Appendix A: Research Summary.......................................................................................................98

Appendix B: Stakeholder Comments...............................................................................................110

Appendix C: Department of Energy’s Efforts on Hydraulic Fracturing...............................................113

Office of Oil and Natural Gas and National Energy Technology Laboratory............... Error! Bookmark not defined.

Argonne National Laboratory ..................................................................................... Error! Bookmark not defined.

Geothermal Technologies Program ............................................................................ Error! Bookmark not defined.

Appendix D: Information Requests.................................................................................................114

Appendix E: Chemicals Identified in Hydraulic Fracturing Fluid and Flowback/Produced Water........119

Appendix F: Stakeholder-Nominated Case Studies..........................................................................151

Appendix G: Assessing Mechanical Integrity ...................................................................................159

Cement Bond Tools................................................................................................................................................159

Temperature Logging.............................................................................................................................................159

Noise Logging .........................................................................................................................................................160

Pressure Testing.....................................................................................................................................................160

Appendix H: Field Sampling and Analytical Methods.......................................................................162

Field Sampling: Sample Types and Analytical Focus..............................................................................................162

Field Sampling Considerations...........................................................................................................................163

Use of Pressure Transducers..................................................................................................................................164

Development and Refinement of Laboratory-Based Analytical Methods.............................................................164

Potential Challenges...............................................................................................................................................165

Matrix Interference ...........................................................................................................................................165

Analysis of Unknown Chemical Compounds .....................................................................................................166

Data Analysis..........................................................................................................................................................166

Evaluation of Potential Indicators of Contamination.............................................................................................167

Glossary.........................................................................................................................................170
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LIST OF FIGURES

Figure 1. Fundamental research questions posed for each identified stage................................................2

Figure 2. Natural gas production in the US...................................................................................................9

Figure 3. Shale gas plays in the contiguous US ...........................................................................................10

Figure 4. Coalbed methane deposits in the contiguous US ........................................................................11

Figure 5. Major tight gas plays in the contiguous US..................................................................................12

Figure 6. Illustration of a horizontal well showing the water lifecycle in hydraulic fracturing ..................13

Figure 7. Differences in depth between gas wells and drinking water wells .............................................13

Figure 8. Well construction.........................................................................................................................14

Figure 9. Water use and potential concerns in hydraulic fracturing operations........................................19

Figure 10a. Summary of research projects proposed for the first three stages of the hydraulic

fracturing water lifecycle......................................................................................................................74

Figure 10b. Summary of research projects proposed for the first three stages of the hydraulic

fracturing water lifecycle...................................................................................................................... 74

Figure 11a. Summary of research projects proposed for the last two stages of the hydraulic

fracturing water lifecycle...................................................................................................................... 74

Figure 11b. Summary of research projects proposed for the first three stages of the hydraulic

fracturing water lifecycle...................................................................................................................... 74

LIST OF TABLES

Table 1. Research questions identified to determine the potential impacts of hydraulic fracturing

on drinking water resources.................................................................................................................17

Table 2. Research activities and objectives ................................................................................................20

Table 3. Comparison of estimated water needs for hydraulic fracturing of horizontal wells in

different shale plays.............................................................................................................................22

Table 4. An example of the volumetric composition of hydraulic fracturing fluid.....................................29

Table 5. Examples of naturally occurring substances that may be found in hydrocarbon-containing 

formations............................................................................................................................................35

Table 6. Public data sources expected to be used as part of this study.....................................................57

Table 7. Decision criteria for selecting hydraulic fracturing sites for case studies.....................................59

Table 8. Retrospective case study locations...............................................................................................60

Table 9. General approach for conducting retrospective case studies ......................................................64

Table 10. Tier 2 initial testing: sample types and testing parameters........................................................64

Table 11. Tier 3 additional testing: sample types and testing parameters ................................................65

Table 12. General approach for conducting prospective case studies.......................................................66

Table 13. Tier 3 field sampling phases........................................................................................................67
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LIST OF ACRONYMS AND ABBREVIATIONS

AOE area of evaluation

API American Petroleum Institute

ATSDR Agency for Toxic Substances and Disease Registry

BLM Bureau of Land Management

CBI confidential business information

CWT commercial wastewater treatment facility

DBP disinfection byproducts

DOE US Department of Energy

EIA US Energy Information Administration

EPA US Environmental Protection Agency

FWS US Fish and Wildlife Service

GIS geographic information systems

GWPC Ground Water Protection Council

mcf/d thousand cubic feet per day

mg/L milligram per liter

mmcf/d million cubic feet per day

NGO non-governmental organization

NIOSH National Institute for Occupational Safety and Health

NYS rdSGEIS New York State Revised Draft Supplemental Generic Environmental Impact Statement

ORD Office of Research and Development

pCi/L picocuries per liter

ppmv parts per million by volume

POTW publicly owned treatment works

PPRTV provisional peer-reviewed toxicity value

QA quality assurance

QAPP quality assurance project plan

QSAR quantitative structure-activity relationship

SAB Science Advisory Board

TDS total dissolved solids

UIC underground injection control

USACE US Army Corps of Engineers

USDW underground source of drinking water

USGS US Geological Survey

VOC volatile organic compound
EPA Hydraulic Fracturing Study Plan November 2011

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EXECUTIVE SUMMARY

Natural gas plays a key role in our nation’s clean energy future. Recent advances in drilling 

technologies—including horizontal drilling and hydraulic fracturing—have made vast reserves of natural 

gas economically recoverable in the US. Responsible development of America’s oil and gas resources 

offers important economic, energy security, and environmental benefits.

Hydraulic fracturing is a well stimulation technique used to maximize production of oil and natural gas in 

unconventional reservoirs, such as shale, coalbeds, and tight sands. During hydraulic fracturing, specially 

engineered fluids containing chemical additives and proppant are pumped under high pressure into the 

well to create and hold open fractures in the formation. These fractures increase the exposed surface 

area of the rock in the formation and, in turn, stimulate the flow of natural gas or oil to the wellbore. As 

the use of hydraulic fracturing has increased, so have concerns about its potential environmental and 

human health impacts. Many concerns about hydraulic fracturing center on potential risks to drinking 

water resources, although other issues have been raised. In response to public concern, the US Congress 

directed the US Environmental Protection Agency (EPA) to conduct scientific research to examine the 

relationship between hydraulic fracturing and drinking water resources. 

This study plan represents an important milestone in responding to the direction from Congress. EPA is 

committed to conducting a study that uses the best available science, independent sources of 

information, and a transparent, peer-reviewed process that will ensure the validity and accuracy of the 

results. The Agency will work in consultation with other federal agencies, state and interstate regulatory 

agencies, industry, non-governmental organizations, and others in the private and public sector in 

carrying out this study. Stakeholder outreach as the study is being conducted will continue to be a 

hallmark of our efforts, just as it was during the development of this study plan.

EPA has already conducted extensive stakeholder outreach during the developing of this study plan. The 

draft version of this study plan was developed in consultation with the stakeholders listed above and 

underwent a peer review process by EPA’s Science Advisory Board (SAB). As part of the review process, 

the SAB assembled an independent panel of experts to review the draft study plan and to consider

comments submitted by stakeholders. The SAB provided EPA with its review of the draft study plan in 

August 2011. EPA has carefully considered the SAB’s recommendations in the development of this final 

study plan. 

The overall purpose of this study is to elucidate the relationship, if any, between hydraulic fracturing and 

drinking water resources. More specifically, the study has been designed to assess the potential impacts 

of hydraulic fracturing on drinking water resources and to identify the driving factors that affect the 

severity and frequency of any impacts. Based on the increasing development of shale gas resources in 

the US, and the comments EPA received from stakeholders, this study emphasizes hydraulic fracturing in 

shale formations. Portions of the research, however, are also intended to provide information on 

hydraulic fracturing in coalbed methane and tight sand reservoirs. The scope of the research includes 

the hydraulic fracturing water use lifecycle, which is a subset of the greater hydrologic cycle. For the 

purposes of this study, the hydraulic fracturing water lifecycle begins with water acquisition from 
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surface or ground water and ends with discharge into surface waters or injection into deep wells.

Specifically, the water lifecycle for hydraulic fracturing consists of water acquisition, chemical mixing, 

well injection, flowback and produced water (collectively referred to as “hydraulic fracturing 

wastewater”), and wastewater treatment and waste disposal. 

The EPA study is designed to provide decision-makers and the public with answers to the five 

fundamental questions associated with the hydraulic fracturing water lifecycle: 

• Water Acquisition: What are the potential impacts of large volume water withdrawals from 

ground and surface waters on drinking water resources?

• Chemical Mixing: What are the possible impacts of surface spills on or near well pads of 

hydraulic fracturing fluids on drinking water resources?

• Well Injection: What are the possible impacts of the injection and fracturing process on drinking 

water resources?

• Flowback and Produced Water: What are the possible impacts of surface spills on or near well 

pads of flowback and produced water on drinking water resources?

• Wastewater Treatment and Waste Disposal: What are the possible impacts of inadequate 

treatment of hydraulic fracturing wastewaters on drinking water resources?

Answering these questions will involve the efforts of scientists and engineers with a broad range of 

expertise, including petroleum engineering, fate and transport modeling, ground water hydrology, and 

toxicology. The study will be conducted by multidisciplinary teams of EPA researchers, in collaboration 

with outside experts from the public and private sector. The Agency will use existing data from hydraulic 

fracturing service companies and oil and gas operators, federal and state agencies, and other sources. 

To supplement this information, EPA will conduct case studies in the field and generalized scenario 

evaluations using computer modeling. Where applicable, laboratory studies will be conducted to 

provide a better understanding of hydraulic fracturing fluid and shale rock interactions, the treatability 

of hydraulic fracturing wastewaters, and the toxicological characteristics of high-priority constituents of 

concern in hydraulic fracturing fluids and wastewater. EPA has also included a screening analysis of 

whether hydraulic fracturing activities may be disproportionately occurring in communities with 

environmental justice concerns.

Existing data will be used answer research questions associated with all stages of the water lifecycle, 

from water acquisition to wastewater treatment and waste disposal. EPA has requested information 

from hydraulic fracturing service companies and oil and gas well operators on the sources of water used 

in hydraulic fracturing fluids, the composition of these fluids, well construction practices, and 

wastewater treatment practices. EPA will use these data, as well as other publically available data, to 

help assess the potential impacts of hydraulic fracturing on drinking water resources. 

Retrospective case studies will focus on investigating reported instances of drinking water resource 

contamination in areas where hydraulic fracturing has already occurred. EPA will conduct retrospective 

case studies at five sites across the US. The sites will be illustrative of the types of problems that have 

been reported to EPA during stakeholder meetings held in 2010 and 2011. A determination will be made 
EPA Hydraulic Fracturing Study Plan November 2011

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on the presence and extent of drinking water resource contamination as well as whether hydraulic 

fracturing contributed to the contamination. The retrospective sites will provide EPA with information 

regarding key factors that may be associated with drinking water contamination. 

Prospective case studies will involve sites where hydraulic fracturing will occur after the research is 

initiated. These case studies allow sampling and characterization of the site before, during, and after

water acquisition, drilling, hydraulic fracturing fluid injection, flowback, and gas production. EPA will 

work with industry and other stakeholders to conduct two prospective case studies in different regions 

of the US. The data collected during prospective case studies will allow EPA to gain an understanding of 

hydraulic fracturing practices, evaluate changes in water quality over time, and assess the fate and 

transport of potential chemical contaminants.

Generalized scenario evaluations will use computer modeling to allow EPA to explore realistic 

hypothetical scenarios related to hydraulic fracturing activities and to identify scenarios under which 

hydraulic fracturing activities may adversely impact drinking water resources.

Laboratory studies will be conducted on a limited, opportunistic basis. These studies will often parallel 

case study investigations. The laboratory work will involve characterization of the chemical and 

mineralogical properties of shale rock and potentially other media as well as the products that may form 

after interaction with hydraulic fracturing fluids. Additionally, laboratory studies will be conducted to 

better understand the treatment of hydraulic fracturing wastewater with respect to fate and transport 

of flowback or produced water constituents. 

Toxicological assessments of chemicals of potential concern will be based primarily on a review of 

available health effects data. The substances to be investigated include chemicals used in hydraulic 

fracturing fluids, their degradates and/or reaction products, and naturally occurring substances that may 

be released or mobilized as a result of hydraulic fracturing. It is not the intent of this study to conduct a 

complete health assessment of these substances. Where data on chemicals of potential concern are 

limited, however, quantitative structure-activity relationships—and other approaches—may be used to 

assess toxicity.

The research projects identified for this study are summarized in Appendix A. EPA is working with other 

federal agencies to collaborate on some aspects of the research described in this study plan. All research 

associated with this study will be conducted in accordance with EPA’s Quality Assurance Program for 

environmental data and meet the Office of Research and Development’s requirements for the highest 

level of quality assurance. Quality Assessment Project Plans will be developed, applied, and updated as 

the research progresses. 

A first report of research results will be completed in 2012. This first report will contain a synthesis of 

EPA’s analysis of existing data, available results from retrospective cases studies, and initial results from 

scenario evaluations, laboratory studies, and toxicological assessments. Certain portions of the work 

described here, including prospective case studies and laboratory studies, are long-term projects that 

are not likely to be finished at that time. An additional report in 2014 will synthesize the results of those 

long-term projects along with the information released in 2012. Figures 10 and 11 summarize the 
EPA Hydraulic Fracturing Study Plan November 2011

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estimated timelines of the research projects outlined in this study plan. EPA is committed to ensuring 

that the results presented in these reports undergo thorough quality assurance and peer review. 

EPA recognizes that the public has raised concerns about hydraulic fracturing that extend beyond the 

potential impacts on drinking water resources. This includes, for example, air impacts, ecological effects, 

seismic risks, public safety, and occupational risks. These topics are currently outside the scope of this

study plan, but should be examined in the future.
EPA Hydraulic Fracturing Study Plan November 2011

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1 INTRODUCTION AND PURPOSE OF STUDY

Hydraulic fracturing is an important means of accessing one of the nation’s most vital energy resources, 

natural gas. Advances in technology, along with economic and energy policy developments, have 

spurred a dramatic growth in the use of hydraulic fracturing across a wide range of geographic regions 

and geologic formations in the US for both oil and gas production. As the use of hydraulic fracturing has 

increased, so have concerns about its potential impact on human health and the environment, especially 

with regard to possible effects on drinking water resources. These concerns have intensified as hydraulic 

fracturing has spread from the southern and western regions of the US to other settings, such as the 

Marcellus Shale, which extends from the southern tier of New York through parts of Pennsylvania, West 

Virginia, eastern Ohio, and western Maryland. Based on the increasing importance of shale gas as a 

source of natural gas in the US, and the comments received by EPA from stakeholders, this study plan 

emphasizes hydraulic fracturing in shale formations containing natural gas. Portions of the research, 

however, may provide information on hydraulic fracturing in other types of oil and gas reservoirs, such 

as coalbeds and tight sands.

In response to escalating public concerns and the anticipated growth in oil and natural gas exploration 

and production, the US Congress directed EPA in fiscal year 2010 to conduct research to examine the 

relationship between hydraulic fracturing and drinking water resources (US House, 2009):

The conferees urge the Agency to carry out a study on the relationship between 

hydraulic fracturing and drinking water, using a credible approach that relies on the best 

available science, as well as independent sources of information. The conferees expect 

the study to be conducted through a transparent, peer-reviewed process that will ensure 

the validity and accuracy of the data. The Agency shall consult with other federal 

agencies as well as appropriate state and interstate regulatory agencies in carrying out 

the study, which should be prepared in accordance with the Agency’s quality assurance 

principles.

This document presents the final study plan for EPA’s research on hydraulic fracturing and drinking 

water resources, responding to both the direction from Congress and concerns expressed by the public. 

For this study, EPA defines “drinking water resources” to be any body of water, ground or surface, that 

could currently, or in the future, serve as a source of drinking water for public or private water supplies. 

The overarching goal of this research is to answer the following questions:

• Can hydraulic fracturing impact drinking water resources?

• If so, what conditions are associated with these potential impacts?

To answer these questions, EPA has identified a set of research activities associated with each stage of 

the hydraulic fracturing water lifecycle (Figure 1), from water acquisition through the mixing of 

chemicals and actual fracturing to post-fracturing production, including the management of hydraulic 

fracturing wastewaters (commonly referred to as “flowback” and “produced water”) and ultimate 
EPA Hydraulic Fracturing Study Plan November 2011

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Water Acquisition

Chemical Mixing

Flowback and

Produced Water

Wastewater Treatment 

and Waste Disposal

Well Injection

What are the potential impacts of large volume water withdrawals from 

ground and surface waters on drinking water resources?

What are the possible impacts of surface spills on or near well pads of 

hydraulic fracturing fluids on drinking water resources?

What are the possible impacts of the injection and fracturing process

on drinking water resources?

What are the possible impacts of surface spills on or near well pads of 

flowback and produced water on drinking water resources?

What are the possible impacts of inadequate treatment of hydraulic 

fracturing wastewaters on drinking water resources?

Water Use in Hydraulic

Fracturing Operations Fundamental Research Question

FIGURE 1. FUNDAMENTAL RESEARCH QUESTIONS POSED FOR EACH IDENTIFIED STAGE
EPA Hydraulic Fracturing Study Plan November 2011

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treatment and disposal. These research activities will identify potential impacts to drinking water 

resources of water withdrawals as well as fate and transport of chemicals associated with hydraulic 

fracturing. Information about the toxicity of contaminants of concern will also be gathered. This 

information can then be used to assess the potential risks to drinking water resources from hydraulic 

fracturing activities. Ultimately, the results of this study will inform the public and provide policymakers 

at all levels with sound scientific knowledge that can be used in decision-making processes.

The study plan is organized as follows:

• Chapter 2 details the process for developing the study plan and the criteria for prioritizing the 

research.

• Chapter 3 provides a brief overview of unconventional oil and natural gas resources and 

production.

• Chapter 4 outlines the hydraulic fracturing water lifecycle and the research questions associated 

with each stage of the lifecycle.

• Chapter 5 briefly describes the research approach.

• Chapter 6 provides background information on each stage of the hydraulic fracturing water 

lifecycle and describes research specific to each stage.

• Chapter 7 provides background information and describes research to assess concerns 

pertaining to environmental justice.

• Chapter 8 describes how EPA is collecting, evaluating, and analyzing existing data. 

• Chapter 9 presents the retrospective and prospective case studies.

• Chapter 10 discusses scenario evaluations and modeling using existing data and new data 

collected from case studies.

• Chapter 11 explains how EPA will characterize toxicity of constituents associated with hydraulic 

fracturing fluids to human health.

• Chapter 12 summarizes how the studies will address the research questions posed for each 

stage of the water lifecycle.

• Chapter 13 notes additional areas of concern relating to hydraulic fracturing that are currently 

outside the scope of this study plan.

Also included at the end of this document are eight appendices and a glossary.

2 PROCESS FOR STUDY PLAN DEVELOPMENT

2.1 STAKEHOLDER INPUT

Stakeholder input played an important role in the development of the hydraulic fracturing study plan. 

Many opportunities were provided for the public to comment on the study scope and case study 

locations. The study plan was informed by information exchanges involving experts from the public and 

private sectors on a wide range of technical issues. EPA will continue to engage stakeholders throughout 

the course of the study and as results become available. 
EPA Hydraulic Fracturing Study Plan November 2011

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EPA has engaged stakeholders in the following ways:

Federal, state, and tribal partner consultations. Webinars were held with state partners in May 2010, 

with federal partners in June 2010, and with Indian tribes in August 2010. The state webinar included 

representatives from 21 states as well as representatives from the Association of State Drinking Water 

Administrators, the Association of State and Interstate Water Pollution Control Administrators, the 

Ground Water Protection Council (GWPC), and the Interstate Oil and Gas Compact Commission. Federal 

partners included the Bureau of Land Management (BLM), the US Geological Survey (USGS), the US Fish 

and Wildlife Service (FWS), the US Forest Service, the US Department of Energy (DOE), the US Army 

Corps of Engineers (USACE), the National Park Service, and the Agency for Toxic Substances and Disease 

Registry (ATSDR). There were 36 registered participants for the tribal webinar, representing 25 tribal 

governments. In addition, a meeting with the Haudenosaunee Environmental Task Force in August 2010 

included 20 representatives from the Onondaga, Mohawk, Tuscarora, Cayuga, and Tonawanda Seneca 

Nations. The purpose of these consultations was to discuss the study scope, data gaps, opportunities for 

sharing data and conducting joint studies, and current policies and practices for protecting drinking 

water resources. 

Sector-specific meetings. Separate webinars were held in June 2010 with representatives from industry 

and non-governmental organizations (NGOs) to discuss the public engagement process, the scope of the 

study, coordination of data sharing, and other key issues. Overall, 176 people representing various 

natural gas production and service companies and industry associations participated in the webinars, as 

well as 64 people representing NGOs. 

Informational public meetings. Public information meetings were held between July and September 

2010 in Fort Worth, Texas; Denver, Colorado; Canonsburg, Pennsylvania; and Binghamton, New York. At 

these meetings, EPA presented information on its reasons for studying hydraulic fracturing, an overview 

of what the study might include, and how stakeholders can be involved. Opportunities to present oral 

and written comments were provided, and EPA specifically asked for input on the following questions:

• What should be EPA’s highest priorities?

• Where are the gaps in current knowledge?

• Are there data and information EPA should know about?

• Where do you recommend EPA conduct case studies?

Total attendance for all of the informational public meetings exceeded 3,500 and more than 700 verbal 

comments were heard. 

Summaries of the stakeholder meetings can be found at http://www.epa.gov/hydraulicfracturing.

Technical Workshops. Technical workshops organized by EPA were in February and March 2011 to 

explore the following focus areas: Chemical and Analytical Methods (February 24-25), Well Construction 

and Operations (March 10-11), Fate and Transport (March 28-29), and Water Resource Management 

(March 29-30). The technical workshops centered around three goals: (1) inform EPA of the current 

technology and practices being used in hydraulic fracturing; (2) identify existing/current research related 
EPA Hydraulic Fracturing Study Plan November 2011

5

to the potential impacts of hydraulic fracturing on drinking water resources; and (3) provide an 

opportunity for EPA scientists to interact with technical experts. EPA invited technical experts from the 

oil and natural gas industry, consulting firms, laboratories, state and federal agencies, and 

environmental organizations to participate in the workshops. The information presented at the 

workshops will inform the research outlined in this study plan.

Other opportunities to comment. In addition to conducting the meetings listed above, EPA provided 

stakeholders with opportunities to submit electronic or written comments on the hydraulic fracturing 

study. EPA received over 5,000 comments, which are summarized in Appendix B. 

2.2 SCIENCE ADVISORY BOARD INVOLVEMENT

The EPA Science Advisory Board (SAB) is a federal advisory committee that provides a balanced, expert 

assessment of scientific matters relevant to EPA. An important function of the SAB is to review EPA’s

technical programs and research plans. Members of the advisory board and ad hoc panels are 

nominated by the public and are selected based on factors such as technical expertise, knowledge, and 

experience. The panel formation process, which is designed to ensure public transparency, also includes 

an assessment of potential conflicts of interest or lack of impartiality. SAB panels are composed of 

individuals with a wide range of expertise to ensure that the technical advice is comprehensive and 

balanced.

EPA’s Office of Research and Development (ORD) has engaged the SAB through the development of this 

study plan. This process is described below. 

Initial SAB review of the study plan scope. During fiscal year 2010, ORD developed a document that 

presented the scope and initial design of the study (USEPA, 2010a). The document was submitted to the 

SAB’s Environmental Engineering Committee for review in March 2010. In its response to EPA in June 

2010 (USEPA, 2010c), the SAB recommended that:

• Initial research should be focused on potential impacts to drinking water resources, with later 

research investigating more general impacts on water resources.

• Engagement with stakeholders should occur throughout the research process.

• Five to ten in-depth case studies at “locations selected to represent the full range of regional 

variability of hydraulic fracturing across the nation” should be part of the research plan. 

EPA concurred with these recommendations and developed the draft study plan accordingly.

The SAB also cautioned EPA against studying all aspects of oil and gas production, stating that the study 

should “emphasize human health and environmental concerns specific to, or significantly influenced by, 

hydraulic fracturing rather than on concerns common to all oil and gas production activities.” Following 

this advice, EPA focused the draft study plan on features of oil and gas production that are particular 

to—or closely associated with—hydraulic fracturing, and their impacts on drinking water resources.

SAB review of the draft study plan. EPA developed a Draft Plan to Study the Potential Impacts of 

Hydraulic Fracturing on Drinking Water Resources (USEPA, 2011a) after receiving the SAB’s review of the 
EPA Hydraulic Fracturing Study Plan November 2011

6

scoping document in June 2010 and presented the draft plan to the SAB for review in February 2011. 

The SAB formed a panel to review the plan,1 which met in March 2011. The panel developed an initial

review of the draft study plan and subsequently held two public teleconference calls in May 2011 to 

discuss this review. The review panel’s report was discussed by the full SAB during a public 

teleconference in July 2011. The public had the opportunity to submit oral and written comments at 

each meeting and teleconference of the SAB. As part of the review process, the public submitted over 

300 comments for consideration.2 The SAB considered the comments submitted by the public as they 

formulated their review of the draft study plan. In their final report to the Agency, the SAB generally 

supported the research approach outlined in the draft study plan and agreed with EPA’s use of the 

water lifecycle as a framework for the study (EPA, 2011b). EPA carefully considered and responded to 

the SAB’s recommendations on September 27, 2011.3

2.3 RESEARCH PRIORITIZATION

In developing this study plan, EPA considered the results of a review of the literature,4 technical 

workshops, comments received from stakeholders, and input from meetings with interested parties, 

including other federal agencies, Indian tribes, state agencies, industry, and NGOs. EPA also considered 

recommendations from the SAB reviews of the study plan scope (USEPA, 2010c) and the draft study plan

(USEPA, 2011b).

In response to the request from Congress, EPA identified fundamental questions (see Figure 1) that 

frame the scientific research to evaluate the potential for hydraulic fracturing to impact drinking water 

resources. Following guidance from the SAB, EPA used a risk-based prioritization approach to identify 

research that addresses the most significant potential risks at each stage of the hydraulic fracturing 

water lifecycle. The risk assessment paradigm (i.e., exposure assessment, hazard identification, doseresponse relationship assessment, and risk characterization) provides a useful framework for asking 

scientific questions and focusing research to accomplish the stated goals of this study, as well as to 

inform full risk assessments in the future. For the current study, emphasis is placed on exposure 

assessment and hazard identification. Exposure assessment will be informed by work on several tasks 

including, but not limited to, modeling (i.e., water acquisition, injection/flowback/production,

wastewater management), case studies, and evaluation of existing data. Analysis of the chemicals used 

in hydraulic fracturing, how they are used, and their fate will provide useful data for hazard 

identification. A definitive evaluation of dose-response relationships and a comprehensive risk 

characterization are beyond the scope of this study.

 1 Biographies on the members of the SAB panel can be found at http://yosemite.epa.gov/sab/sabproduct.nsf/

fedrgstr_activites/HFSP!OpenDocument&TableRow=2.1#2. 2 These comments are available as part of the material from the SAB public meetings, and can be found at 

http://yosemite.epa.gov/sab/SABPRODUCT.NSF/81e39f4c09954fcb85256ead006be86e/

d3483ab445ae61418525775900603e79!OpenDocument&TableRow=2.2#2.

3 See http://yosemite.epa.gov/sab/sabproduct.nsf/2BC3CD632FCC0E99852578E2006DF890/$File/EPA-SAB-11-

012_Response_09-27-2011.pdf and http://water.epa.gov/type/groundwater/uic/class2/hydraulicfracturing/

upload/final_epa_response_to_sab_review_table_091511.pdf. 4 The literature review includes information from more than 120 articles, reports, presentations and other 

materials. Information resulting from this literature review is incorporated throughout this study plan.
EPA Hydraulic Fracturing Study Plan November 2011

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Other criteria considered in prioritizing research activities included:

• Relevance: Only work that may directly inform an assessment of the potential impacts of 

hydraulic fracturing on drinking water resources was considered.

• Precedence: Work that needs to be completed before other work can be initiated received a 

higher priority.

• Uniqueness of the contribution: Relevant work already underway by others received a lower 

priority for investment by EPA.

• Funding: Work that could provide EPA with relevant results given a reasonable amount of 

funding received a higher priority.

• Leverage: Relevant work that EPA could leverage with outside investigators received a higher 

priority.

As the research progresses, EPA may determine that modifying the research approach outlined in this 

study plan or conducting additional research within the overall scope of the plan is prudent in order to 

better answer the research questions. In that case, modifications to the activities that are currently 

planned may be necessary.

2.4 NEXT STEPS

EPA is committed to continuing our extensive outreach efforts to stakeholder as the study progresses. 

This will include:

• Periodic updates will be provided to the public on the progress of the research.

• A peer-reviewed study report providing up-to-date research results will be released to the public 

in 2012.

• A second, peer-reviewed study report will be released to the public in 2014. This report will 

include information from the entire body of research described in this study plan.

2.5 INTERAGENCY COOPERATION

In a series of meetings, EPA consulted with several federal agencies regarding research related to 

hydraulic fracturing. EPA met with representatives from DOE5 and DOE’s National Energy Technology 

Laboratory, USGS, and USACE to learn about research that those agencies are involved in and to identify 

opportunities for collaboration and leverage. As a result of those meetings, EPA has identified work 

being done by others that can inform its own study on hydraulic fracturing. EPA and other agencies are 

collaborating on information gathering and research efforts. In particular, the Agency is coordinating

with DOE and USGS on existing and future research projects relating to hydraulic fracturing. Meetings 

between EPA and DOE have enabled the sharing of each agency’s research on hydraulic fracturing and 

the exchange of information among experts.

 5 DOE’s efforts are briefly summarized in Appendix C.
EPA Hydraulic Fracturing Study Plan November 2011

8

Specifically, DOE, USGS, USACE, and the Pennsylvania Geological Survey have committed to collaborate 

with EPA on this study. All four are working with EPA on one of the prospective case studies 

(Washington County, Pennsylvania). USGS is performing stable isotope analysis of strontium for all 

retrospective and prospective case studies. USGS is also sharing data on their studies in Colorado and 

New Mexico.

Federal agencies also had an opportunity to provide comments on EPA’s Draft Plan to Study the 

Potential Impacts of Hydraulic Fracturing on Drinking Water Resources through an interagency review. 

EPA received comments from the ATSDR, DOE, BLM, USGS, FWS, the Office of Management and Budget, 

the US Energy Information Administration (EIA), the Occupational Safety and Health Administration, and 

the National Institute of Occupational Safety and Health (NIOSH). These comments were reviewed and 

the study plan was appropriately modified.

2.6 QUALITY ASSURANCE

All EPA-funded intramural and extramural research projects that generate or use environmental data to 

make conclusions or recommendations must comply with Agency Quality Assurance (QA) Program 

requirements (USEPA, 2002). EPA recognizes the value of using a graded approach such that QA 

requirements are based on the importance of the work to which the program applies. Given the 

significant national interest in the results of this study, the following rigorous QA approach will be used:

• Research projects will comply with Agency requirements and guidance for quality assurance 

project plans (QAPPs), including the use of systematic planning.

• Technical systems audits, audits of data quality, and data usability (quality) assessments will be 

conducted as described in QAPPs.

• Performance evaluations of analytical systems will be conducted.

• Products6 will undergo QA review.

• Reports will have readily identifiable QA sections.

• Research records will be managed according to EPA’s record schedule 501 for Applied and 

Directed Scientific Research (USEPA, 2009).

All EPA organizations involved with the generation or use of environmental data are supported by QA 

professionals who oversee the implementation of the QA program for their organization. Given the 

cross-organizational nature of the research, EPA has identified a Program QA Manager who will 

coordinate the rigorous QA approach described above and oversee its implementation across all 

participating organizations. The organizational complexity of the hydraulic fracturing research effort also 

demands that a quality management plan be written to define the QA-related policies, procedures, 

roles, responsibilities, and authorities for this research. The plan will document consistent QA 

procedures and practices that may otherwise vary between organizations.

 6 Applicable products may include reports, journal articles, symposium/conference papers, extended abstracts, 

computer products/software/models/databases and scientific data.
EPA Hydraulic Fracturing Study Plan November 2011

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3 OVERVIEW OF UNCONVENTIONAL OIL AND NATURAL GAS PRODUCTION

Hydraulic fracturing is often used to stimulate the production of hydrocarbons from unconventional oil 

and gas reservoirs, which include shales, coalbeds, and tight sands.7 “Unconventional reservoirs” refers

to oil and gas reservoirs whose porosity, permeability, or other characteristics differ from those of 

conventional sandstone and carbonate reservoirs (USEIA, 2011a). Many of these formations have poor 

permeability, so reservoir stimulation techniques such as hydraulic fracturing are needed to make oil 

and gas production cost-effective. In contrast, conventional oil and gas reservoirs have a higher 

permeability and operators generally have not used hydraulic fracturing. However, hydraulic fracturing 

has become increasingly used to increase the gas flow in wells that are considered conventional

reservoirs and make them even more economically viable (Martin and Valkó, 2007).

Unconventional natural gas development has become an increasingly important source of natural gas in 

the US in recent years. It accounted for 28 percent of total natural gas production in 1998 (Arthur et al., 

2008). Figure 2 illustrates that this percentage rose to 50 percent in 2009, and is projected to increase to 

60 percent in 2035 (USEIA, 2010). 

 7 Hydraulic fracturing has also been used for other purposes, such as removing contaminants from soil and ground 

water at waste disposal sites, making geothermal wells more productive, and completing water wells (NematNassar et al., 1983; New Hampshire Department of Environmental Services, 2010).

11%

20% 14%

9%

28%

8%

9%

2%

45%

22%

8%

8%

7%

7%

1%

1%

Natural Gas Production in the US

2009

(~24 trillion cubic feet per year)

Projected for 2035

(~26 trillion cubic feet per year)

Sources of Natural Gas

Net imports Coalbed methane Non-associated onshore

Shale gas Alaska Non-associated offshore

Tight sands Associated with oil

FIGURE 2. NATURAL GAS PRODUCTION IN THE US (DATA FROM USEIA, 2010)
EPA Hydraulic Fracturing Study Plan November 2011

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This rise in hydraulic fracturing activities to produce gas from unconventional reservoirs is also reflected 

in the number of drilling rigs operating in the US. There were 603 horizontal gas rigs in June 2010, an 

increase of 277 from the previous year (Baker Hughes, 2010). Horizontal rigs are commonly used when 

hydraulic fracturing is used to stimulate gas production from shale formations.

Shale gas extraction. Shale rock formations have become an important source of natural gas in the US 

and can be found in many locations across the country, as shown in Figure 3. Depths for shale gas 

formations can range from 500 to 13,500 feet below the earth’s surface (GWPC and ALL Consulting, 

2009). At the end of 2009, the five most productive shale gas fields in the country—the Barnett, 

Haynesville, Fayetteville, Woodford, and Marcellus Shales—were producing 8.3 billion cubic feet of 

natural gas per day (Zoback et al., 2010). According to recent figures from EIA, shale gas constituted 14 

percent of the total US natural gas supply in 2009, and will make up 45 percent of the US gas supply in 

2035 if current trends and policies persist (USEIA, 2010). 

Oil production has similarly increased in oil-bearing shales following the increased use of hydraulic 

fracturing. Proven oil production from shales has been concentrated primarily in the Williston Basin in 

North Dakota, although oil production is increasing in the Eagle Ford Shale in Texas, the Niobrara Shale 

FIGURE 3. SHALE GAS PLAYS IN THE CONTIGUOUS US
EPA Hydraulic Fracturing Study Plan November 2011

11

in Colorado, Nebraska, and Wyoming, and the Utica Shale in Ohio (USEIA, 2010, 2011b; 

OilShaleGas.com, 2010). 

Production of coalbed methane. Coalbed methane is formed as part of the geological process of coal 

generation and is contained in varying quantities within all coal. Depths of coalbed methane formations 

range from 450 feet to greater than 10,000 feet (Rogers et al., 2007; National Research Council, 2010). 

At greater depths, however, the permeability decreases and production is lower. Below 7,000 feet, 

efficient production of coalbed methane can be challenging from a cost-effectiveness perspective

(Rogers et al., 2007). Figure 4 displays coalbed methane reservoirs in the contiguous US. In 1984, there 

were very few coalbed methane wells in the US; by 1990, there were almost 8,000, and in 2000, there 

were almost 14,000 (USEPA, 2004). In 2009, natural gas production from coalbed methane reservoirs 

made up 8 percent of the total US natural gas production; this percentage is expected to remain 

relatively constant over the next 20 years if current trends and policies persist (USEIA, 2010). Production 

of gas from coalbeds almost always requires hydraulic fracturing (USEPA, 2004), and many existing 

coalbed methane wells that have not been fractured are now being considered for hydraulic fracturing. 

Tight sands. Tight sands (gas-bearing, fine-grained sandstones or carbonates with a low permeability) 

accounted for 28 percent of total gas production in the US in 2009 (USEIA, 2010), but may account for as 

much as 35 percent of the nation’s recoverable gas reserves (Oil and Gas Investor, 2005). Figure 5 shows 

the locations of tight gas plays in the US. Typical depths of tight sand formations range from 1,200 to 

20,000 feet across the US (Prouty, 2001). Almost all tight sand reservoirs require hydraulic fracturing to 

release gas unless natural fractures are present.

FIGURE 4. COALBED METHANE DEPOSITS IN THE CONTIGUOUS US
EPA Hydraulic Fracturing Study Plan November 2011

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FIGURE 5. MAJOR TIGHT GAS PLAYS IN THE CONTIGUOUS US

The following sections provide an overview of how site selection and preparation, well construction and 

development, hydraulic fracturing, and natural gas production apply to unconventional natural gas 

production. The current regulatory framework that governs hydraulic fracturing activities is briefly 

described in Section 3.5. 

3.1 SITE SELECTION AND PREPARATION

The hydraulic fracturing process begins with exploring possible well sites, followed by selecting and 

preparing an appropriate site. In general, appropriate sites are those that are considered most likely to 

yield substantial quantities of natural gas at minimum cost. Other factors, however, may be considered 

in the selection process. These include proximity to buildings and other infrastructure, geologic 

considerations, and proximity to natural gas pipelines or the feasibility of installing new pipelines 

(Chesapeake Energy, 2009). Laws and regulations may also influence site selection. For example, 

applicants applying for a Marcellus Shale natural gas permit in Pennsylvania must provide information 

about proximity to coal seams and distances from surface waters and water supplies (PADEP, 2010a). 

During site preparation, an area is cleared to provide space to accommodate one or more wellheads; 

tanks and/or pits for holding water, used drilling fluids, and other materials; and space for trucks and 

other equipment. At a typical shale gas production site, a 3- to 5-acre space is needed in addition to 

access roads for transporting materials to and from the well site. If not already present, both the site 

and access roads need to be built or improved to support heavy equipment.
EPA Hydraulic Fracturing Study Plan November 2011

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3.2 WELL CONSTRUCTION AND DEVELOPMENT

3.2.1 TYPES OF WELLS

Current practices in drilling for natural gas include drilling vertical, horizontal, and directional (S-shaped) 

wells. On the following pages, two different well completions are depicted with one in a typical deep 

shale gas-bearing formation like the Marcellus Shale (Figure 6) and one in a shallower environment 

(Figure 7), which is often encountered where coalbed methane or tight sand gas production takes place.

The figures demonstrate a significant difference in the challenges posed for protecting underground 

drinking water resources. The deep shale gas environment typically has several thousand feet of rock 

formation separating underground drinking water resources, while the other shows that gas production 

can take place at shallow depths that also contain underground sources of drinking water (USDWs). The 

water well in Figure 7 illustrates an example of the relative depths of a gas well and a water well. 

FIGURE 6. ILLUSTRATION OF A HORIZONTAL WELL SHOWING THE WATER LIFECYCLE IN HYDRAULIC FRACTURING

Figure 6 depicts a horizontal well, which is composed of both vertical and horizontal legs. The depth and 

length of the well varies with the location and properties of the gas-containing formation. In 

unconventional cases, the well can extend more than a mile below the ground surface (Chesapeake 

Water 

Acquisition

Chemical 

Mixing

Well 

Injection

Flowback and 

Produced Water Storage 

tanks

Wastewater 

Treatment and 

Waste Disposal

Induced Fractures

Pit

Hydrocarbon-bearing

Formation

1,000

2,000

3,000

4,000

5,000

6,000

7,000 feet

Hydraulic fracturing often involves 

the injection of more than a million 

gallons of water, chemicals, and sand 

at high pressure down the well. The 

depth and length of the well varies 

depending on the characteristics of 

the hydrocarbon-bearing formation. 

The pressurized fluid mixture causes 

the formation to crack, allowing 

natural gas or oil to flow up the well. 

Large volumes of water are 

transported for the fracturing process.

Equipment mixes water, chemicals, 

and sand at the well site.

The hydraulic fracturing fluid is 

pumped into the well at high injection rates.

Recovered water 

(called flowback and produced water) is stored 

on-site in open pits or storage tanks.

The 

wastewater is then transported for treatment and/or 

disposal.

Water Acquisition - 

Chemical Mixing - 

Well Injection - 

Flowback and Produced Water - 

Wastewater Treatment and Waste Disposal - 

Aquifer

Water Use in Hydraulic Fracturing Operations
EPA Hydraulic Fracturing Study Plan November 2011

13

Energy, 2010) while the “toe” of the 

horizontal leg can be almost two miles 

from the vertical leg (Zoback et al., 

2010). Horizontal drilling provides more 

exposure to a formation than a vertical 

well does, making gas production more 

economical. It may also have the 

advantage of limiting environmental 

disturbances on the surface because 

fewer wells are needed to access the 

natural gas resources in a particular area 

(GWPC and ALL Consulting, 2009).

The technique of multilateral drilling is 

becoming more prevalent in gas 

production in the Marcellus Shale region 

(Kargbo et al., 2010) and elsewhere. In 

multilateral drilling, two or more 

horizontal production holes are drilled 

from a single surface location (Ruszka, 

2007) to create an arrangement 

resembling an upside-down tree, with 

the vertical portion of the well as the 

“trunk,” and multiple “branches”

extending out from it in different 

directions and at different depths.

3.2.2 WELL DESIGN AND CONSTRUCTION

According to American Petroleum Institute (API, 2009a), the goal of well design is to “ensure the 

environmentally sound, safe production of hydrocarbons by containing them inside the well, protecting 

ground water resources, isolating the production formations from other formations, and by proper 

execution of hydraulic fractures and other stimulation operations.” Proper well construction is essential 

for isolating the production zone from drinking water resources, and includes drilling a hole, installing 

steel pipe (casing), and cementing the pipe in place. These activities are repeated multiple times 

throughout the drilling event until the well is completed. 

Drilling. A drilling string—composed of a drill bit, drill collars, and a drill pipe—is used to drill the well. 

During the drilling process, a drilling fluid such as compressed air or a water- or oil-based liquid (“mud”) 

is circulated down the drilling string. Water-based liquids typically contain a mixture of water, barite, 

clay, and chemical additives (OilGasGlossary.com, 2010). Drilling fluid serves multiple purposes, 

including cooling the drill bit, lubricating the drilling assembly, removing the formation cuttings, 

Induced 

Fractures

The targeted formation is 

fractured by fluids injected with 

a pressure that exceeds the 

parting pressure of the rock.

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

2,200

feet

Drinking Water Resources

Gas and Water Resources

Mostly Gas Resources

Gas Well Water Well

Natural 

gas 

flows from 

fractures 

into well

Well

Mixture of 

water, 

chemicals, 

and 

sand

Sand 

keeps 

fractures 

open

FIGURE 7. DIFFERENCES IN DEPTH BETWEEN GAS WELLS AND 

DRINKING WATER WELLS
EPA Hydraulic Fracturing Study Plan November 2011

14

maintaining the pressure control of the well, and 

stabilizing the hole being drilled. Once removed 

from the wellbore, both drilling liquids and drill 

cuttings must be treated, recycled, and/or 

disposed.

Casing. Casings are steel pipes that line the 

borehole and serve to isolate the geologic 

formation from the materials and equipment in 

the well. The casing also prevents the borehole 

from caving in, confines the injected/produced 

fluid to the wellbore and the intended 

production zone, and provides a method of 

pressure control. Thus, the casing must be 

capable of withstanding the external and internal 

pressures encountered during the installation, 

cementing, fracturing, and operation of the well. 

When fluid is confined within the casing, the 

possibility of contamination of zones adjacent to 

the well is greatly diminished. In situations where 

the geologic formation is considered competent 

and will not collapse upon itself, an operator may 

choose to forego casing in what is called an open 

hole completion.

Figure 8 illustrates the different types of casings 

that may be used in well construction: conductor, 

surface, intermediate (not shown), and 

production. Each casing serves a unique purpose. 

Ideally, the surface casing should extend below 

the base of the deepest USDW and be cemented to the surface. This casing isolates the USDW and 

provides protection from contamination during drilling, completion, and operation of the well. Note that 

the shallow portions of the well may have multiple layers of casing and cement, isolating the production 

area from the surrounding formation. For each casing, a hole is drilled and the casing is installed and 

cemented into place.

Casings should be positioned in the center of the borehole using casing centralizers, which attach to the 

outside of the casing. A centralized casing improves the likelihood that it will be completely surrounded 

by cement during the cementing process, leading to the effective isolation of the well from USDWs. The 

number, depth, and cementing of the casings required varies and is set by the states.

Cementing. Once the casing is inserted in the borehole, it is cemented into place by pumping cement 

slurry down the casing and up the annular space between the formation and the outside of the casing. 

Conductor

casing

Surface

casing

Production

casing

Cement

Production

tubing

Cement

Cement

Bold lines 

are pipes

Surface

Aquifer

Hydrocarbon-bearing 

formation

1,000

2,000

3,000

4,000

5,000

6,000

7,000

feet

Wellhead

FIGURE 8. WELL CONSTRUCTION
EPA Hydraulic Fracturing Study Plan November 2011

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The principal functions of the cement (for vertical wells or the vertical portion of a horizontal well) are to 

act as a barrier to migration of fluids up the wellbore behind the casing and to mechanically support the 

casing. To accomplish these functions, the proper cement must be used for the conditions encountered 

in the borehole. Additionally, placement of the cement and the type of cement used in the well must be 

carefully planned and executed to ensure that the cement functions effectively. 

The presence of the cement sheath around each casing and the effectiveness of the cement in 

preventing fluid movement are the major factors in establishing and maintaining the mechanical 

integrity of the well, although even a correctly constructed well can fail over time due to downhole 

stresses and corrosion (Bellabarba et al., 2008). 

3.3 HYDRAULIC FRACTURING

After the well is constructed, the targeted formation (shale, coalbed, or tight sands) is hydraulically 

fractured to stimulate natural gas production. As noted in Figure 6, the hydraulic fracturing process 

requires large volumes of water that must be withdrawn from the source and transported to the well 

site. Once on site, the water is mixed with chemicals and a propping agent (called a proppant). 

Proppants are solid materials that are used to keep the fractures open after pressure is reduced in the 

well. The most common proppant is sand (Carter et al., 1996), although resin-coated sand, bauxite, and 

ceramics have also been used (Arthur et al., 2008; Palisch et al., 2008). Most, if not all, water-based 

fracturing techniques use proppants. There are, however, some fracturing techniques that do not use 

proppants. For example, nitrogen gas is commonly used to fracture coalbeds and does not require the 

use of proppants (Rowan, 2009).

After the production casing has been perforated by explosive charges introduced into the well, the rock 

formation is fractured when hydraulic fracturing fluid is pumped down the well under high pressure. The 

fluid is also used to carry proppant into the targeted formation and enhance the fractures. As the 

injection pressure is reduced, recoverable fluid is returned to the surface, leaving the proppant behind 

to keep the fractures open. The inset in Figure 7 illustrates how the resulting fractures create pathways 

in otherwise impermeable gas-containing formations, resulting in gas flow to the well for production. 

The fluid that returns to the surface can be referred to as either “flowback” or “produced water,” and 

may contain both hydraulic fracturing fluid and natural formation water. “Flowback” can be considered 

a subset of “produced water.” However, for this study, EPA considers “flowback” to be the fluid 

returned to the surface after hydraulic fracturing has occurred, but before the well is placed into 

production, while “produced water” is the fluid returned to the surface after the well has been placed

into production. In this study plan, flowback and produced water are collectively referred to as 

“hydraulic fracturing wastewaters.” These wastewaters are typically stored on-site in tanks or pits 

before being transported for treatment, disposal, land application, and/or discharge. In some cases, 

flowback and produced waters are treated to enable the recycling of these fluids for use in hydraulic 

fracturing.
EPA Hydraulic Fracturing Study Plan November 2011

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3.4 WELL PRODUCTION AND CLOSURE

Natural gas production rates can vary between basins as well as within a basin, depending on geologic 

factors and completion techniques. For example, the average well production rates for coalbed methane 

formations range from 50 to 500 thousand cubic feet per day (mcf/d) across the US, with maximum 

production rates reaching 20 million cubic feet per day (mmcf/d) in the San Juan Basin and 1 mmcf/d in 

the Raton Basin (Rogers et al., 2007). The New York State Revised Draft Supplemental Generic 

Environmental Impact Statement (NYS rdSGEIS) for the Marcellus Shale cites industry estimates that a 

typical well will initially produce 2.8 mmcf/d; the production rate will decrease to 550 mcf/d after 5 

years and 225 mcf/d after 10 years, after which it will drop approximately 3 percent a year (NYSDEC, 

2011). A study of actual production rates in the Barnett Shale found that the average well produces 

about 800 mmcf during its lifetime, which averages about 7.5 years (Berman, 2009).

Refracturing is possible once an oil or gas well begins to approach the point where it is no longer costeffectively producing hydrocarbons. Zoback et al. (2010) maintain that shale gas wells are rarely 

refractured. Berman (2009), however, claims that wells may be refractured once they are no longer 

profitable. The NYS rdSGEIS estimates that wells may be refractured after roughly five years of service

(NYSDEC, 2011).

Once a well is no longer producing gas economically, it is plugged to prevent possible fluid migration

that could contaminate soils or waters. According to API, primary environmental concerns include

protecting freshwater aquifers and USDWs as well as isolating downhole formations that contain

hydrocarbons (API, 2009a). An improperly closed well may provide a pathway for fluid to flow up the 

well toward ground or surface waters or down the wellbore, leading to contamination of ground water

(API, 2009a). A surface plug is used to prevent surface water from seeping into the wellbore and 

migrating into ground water resources. API recommends setting cement plugs to isolate hydrocarbon 

and injection/disposal intervals, as well as setting a plug at the base of the lowermost USDW present in 

the formation (API, 2009a). 

3.5 REGULATORY FRAMEWORK

Hydraulic fracturing for oil and gas production wells is typically addressed by state oil and gas boards or 

equivalent state natural resource agencies. EPA retains authority to address many issues related to 

hydraulic fracturing under its environmental statutes. The major statutes include the Clean Air Act; the 

Resource Conservation and Recovery Act; the Clean Water Act; the Safe Drinking Water Act; the 

Comprehensive Environmental Response, Compensation and Liability Act; the Toxic Substances Control 

Act; and the National Environmental Policy Act. EPA does not expect to address the efficacy of the 

regulatory framework as part of this investigation.
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4 THE HYDRAULIC FRACTURING WATER LIFECYCLE

The hydraulic fracturing water lifecycle—from water acquisition to wastewater treatment and 

disposal—is illustrated in Figure 9. The figure also shows potential issues for drinking water resources

associated with each phase. Table 1 summarizes the primary and secondary research questions EPA has 

identified for each stage of the hydraulic fracturing water lifecycle. 

The next chapter outlines the research approach and activities needed to answer these questions.

TABLE 1. RESEARCH QUESTIONS IDENTIFIED TO DETERMINE THE POTENTIAL IMPACTS OF HYDRAULIC 

FRACTURING ON DRINKING WATER RESOURCES

Water Lifecycle Stage Fundamental Research Question Secondary Research Questions

Water Acquisition What are the potential impacts of 

large volume water withdrawals 

from ground and surface waters 

on drinking water resources?

• How much water is used in hydraulic 

fracturing operations, and what are the 

sources of this water?

• How might withdrawals affect short- and 

long-term water availability in an area with 

hydraulic fracturing activity?

• What are the possible impacts of water 

withdrawals for hydraulic fracturing 

operations on local water quality?

Chemical Mixing What are the possible impacts of 

surface spills on or near well pads 

of hydraulic fracturing fluids on 

drinking water resources?

• What is currently known about the 

frequency, severity, and causes of spills of 

hydraulic fracturing fluids and additives?

• What are the identities and volumes of 

chemicals used in hydraulic fracturing fluids, 

and how might this composition vary at a 

given site and across the country?

• What are the chemical, physical, and 

toxicological properties of hydraulic 

fracturing chemical additives?

• If spills occur, how might hydraulic 

fracturing chemical additives contaminate 

drinking water resources?

Well Injection What are the possible impacts of 

the injection and fracturing 

process on drinking water 

resources?

• How effective are current well construction 

practices at containing gases and fluids 

before, during, and after fracturing?

• Can subsurface migration of fluids or gases 

to drinking water resources occur and what 

local geologic or man-made features may 

allow this?

• How might hydraulic fracturing fluids 

change the fate and transport of substances 

in the subsurface through geochemical 

interactions?

• What are the chemical, physical, and 

toxicological properties of substances in the 

subsurface that may be released by 

hydraulic fracturing operations?

Table continued on next page
EPA Hydraulic Fracturing Study Plan November 2011

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Table continued from previous page

Water Lifecycle Stage Fundamental Research Question Secondary Research Questions

Flowback and 

Produced Water

What are the possible impacts of 

surface spills on or near well pads 

of flowback and produced water 

on drinking water resources?

• What is currently known about the 

frequency, severity, and causes of spills of 

flowback and produced water?

• What is the composition of hydraulic 

fracturing wastewaters, and what factors 

might influence this composition?

• What are the chemical, physical, and 

toxicological properties of hydraulic 

fracturing wastewater constituents?

• If spills occur, how might hydraulic 

fracturing wastewaters contaminate 

drinking water resources?

Wastewater Treatment 

and Waste Disposal

What are the possible impacts of 

inadequate treatment of 

hydraulic fracturing wastewaters

on drinking water resources?

• What are the common treatment and 

disposal methods for hydraulic fracturing 

wastewaters, and where are these methods 

practiced?

• How effective are conventional POTWs and 

commercial treatment systems in removing 

organic and inorganic contaminants of 

concern in hydraulic fracturing 

wastewaters?

• What are the potential impacts from surface 

water disposal of treated hydraulic 

fracturing wastewater on drinking water 

treatment facilities?
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FIGURE 9. WATER USE AND POTENTIAL CONCERNS IN HYDRAULIC FRACTURING OPERATIONS

Water Acquisition

Chemical Mixing

Flowback and

Produced Water

Wastewater Treatment 

and Waste Disposal

Well Injection

• Water availability

• Impact of water withdrawal on water quality

• Release to surface and ground water

(e.g., on-site spills and/or leaks)

• Chemical transportation accidents

• Accidental release to ground or surface water (e.g., well malfunction)

• Fracturing fluid migration into drinking water aquifers

• Formation fluid displacement into aquifers

• Mobilization of subsurface formation materials into aquifers

• Release to surface and ground water

• Leakage from on-site storage into drinking water resources

• Improper pit construction, maintenance, and/or closure

• Surface and/or subsurface discharge into surface and ground water

• Incomplete treatment of wastewater and solid residuals

• Wastewater transportation accidents

Water Use in Hydraulic

Fracturing Operations Potential Drinking Water Issues
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5 RESEARCH APPROACH

The highly complex nature of the problems to be studied will require a broad range of scientific 

expertise in environmental and petroleum engineering, ground water hydrology, fate and transport 

modeling, and toxicology, as well as many other areas. EPA will take a transdisciplinary research 

approach that integrates various types of expertise from inside and outside EPA. This study uses five 

main research activities to address the questions identified in Table 1. Table 2 summarizes these 

activities and their objectives; each activity is then briefly described below with more detailed 

information available in later chapters. 

TABLE 2. RESEARCH ACTIVITIES AND OBJECTIVES

Activity Objective

Analysis of existing data Gather and summarize existing data from various sources to provide current 

information on hydraulic fracturing activities

Case studies

Retrospective

Prospective

Perform an analysis of sites with reported contamination to understand the 

underlying causes and potential impacts to drinking water resources

Develop understanding of hydraulic fracturing processes and their potential impacts 

on drinking water resources

Scenario evaluations Use computer modeling to assess the potential for hydraulic fracturing to impact 

drinking water resources based on knowledge gained during existing data analysis 

and case studies

Laboratory studies Conduct targeted studies to study the fate and transport of chemical contaminants of 

concern in the subsurface and during wastewater treatment processes

Toxicological studies Summarize available toxicological information and, as necessary, conduct screening 

studies for chemicals associated with hydraulic fracturing operations

5.1 ANALYSIS OF EXISTING DATA

EPA will gather and analyze mapped data on water quality, surface water discharge data, chemical 

identification data, and site data among others. These data are available from a variety of sources, such 

as state regulatory agencies, federal agencies, industry, and public sources. Included among these 

sources are information from the September 2010 letter requesting data from nine hydraulic fracturing 

service companies and the August 2011 letter requesting data from nine randomly chosen oil and gas 

well operators. Appendix D contains detailed information regarding these requests.

5.2 CASE STUDIES

Case studies are widely used to conduct in-depth investigations of complex topics and provide a 

systematic framework for investigating relationships among relevant factors. In addition to reviewing 

available data associated with the study sites, EPA will conduct environmental field sampling, modeling, 

and/or parallel laboratory investigations. In conjunction with other elements of the research program, 

the case studies will help determine whether hydraulic fracturing can impact drinking water resources

and, if so, the extent and possible causes of any impacts. Additionally, case studies may provide 

opportunities to assess the fate and transport of fluids and contaminants in different regions and 

geologic settings. 
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Retrospective case studies are focused on investigating reported instances of drinking water resource 

contamination in areas where hydraulic fracturing events have already occurred. Retrospective case 

studies will use a deductive logic approach to determine whether or not the reported impacts are due to 

hydraulic fracturing activity and if so, evaluate potential driving factors for those impacts.

Prospective case studies involve sites where hydraulic fracturing will be implemented after the research 

begins. These cases allow sampling and characterization of the site prior to, during, and after drilling, 

water extraction, injection of the fracturing fluid, flowback, and production. At each step in the process, 

EPA will collect data to characterize both the pre- and post-fracturing conditions at the site. This 

progressive data collection will allow EPA to evaluate changes in local water availability and quality, as 

well as other factors, over time to gain a better understanding of the potential impacts of hydraulic 

fracturing on drinking water resources. Prospective case studies offer the opportunity to sample and 

analyze flowback and produced water. These studies also provide data to run, evaluate, and improve

models of hydraulic fracturing and associated processes, such as fate and transport of chemical 

contaminants.

5.3 SCENARIO EVALUATIONS

The objective of this approach is to use computer modeling to explore realistic, hypothetical scenarios 

across the hydraulic fracturing water cycle that may involve adverse impacts to drinking water 

resources, based primarily on current knowledge and available data. The scenarios will include a 

reference case involving typical management and engineering practices in representative geologic 

settings. Typical management and engineering practices will be based on what EPA learns from case 

studies as well as the minimum requirements imposed by state regulatory agencies. EPA will model 

surface water in areas to assess impact on water availability and quality where hydraulic fracturing 

operations withdraw water. EPA will also introduce and model potential modes of failure, both in terms 

of engineering controls and geologic characteristics, to represent various states of system vulnerability. 

The scenario evaluations will produce insights into site-specific and regional vulnerabilities. 

5.4 LABORATORY STUDIES

Laboratory studies will be used to conduct targeted research needed to better understand the ultimate 

fate and transport of chemical contaminants of concern. The contaminants of concern may be 

components of hydraulic fracturing fluids or may be naturally occurring substances released from the 

subsurface during hydraulic fracturing. Laboratory studies may also be necessary to modify existing 

analytical methods for case study field monitoring activities. Additionally, laboratory studies will assess 

the potential for treated flowback or produced water to cause an impact to drinking water resources if

released.

5.5 TOXICOLOGICAL STUDIES

Throughout the hydraulic fracturing water lifecycle there are routes through which fracturing fluids 

and/or naturally occurring substances could be introduced into drinking water resources. To support 

future risk assessments, EPA will summarize existing data regarding toxicity and potential human health 
EPA Hydraulic Fracturing Study Plan November 2011

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effects associated with these possible drinking water contaminants. Where necessary, EPA may pursue 

additional toxicological studies to screen and assess the toxicity associated with chemical contaminants 

of concern. 

6 RESEARCH ACTIVITIES ASSOCIATED WITH THE HYDRAULIC FRACTURING

WATER LIFECYCLE

This chapter is organized by the hydraulic fracturing water lifecycle depicted in Figure 9 and the 

associated research questions outlined in Table 1. Each section of this chapter provides relevant 

background information on the water lifecycle stage and identifies a series of more specific questions 

that will be researched to answer the fundamental research question. Research activities and expected

research outcomes are outlined at the end of the discussion of each stage of the water lifecycle. A 

summary of the research outlined in this chapter can be found in Appendix A. 

6.1 WATER ACQUISITION: WHAT ARE THE POTENTIAL IMPACTS OF LARGE VOLUME WATER 

WITHDRAWALS FROM GROUND AND SURFACE WATERS ON DRINKING WATER RESOURCES?

6.1.1 BACKGROUND

The amount of water needed in the hydraulic fracturing process depends on the type of formation 

(coalbed, shale, or tight sands) and the fracturing operations (e.g., well depth and length, fracturing fluid 

properties, and fracture job design). Water requirements for hydraulic fracturing in coalbed methane 

range from 50,000 to 350,000 gallons per well (Holditch, 1993; Jeu et al., 1988; Palmer et al., 1991 and 

1993). The water usage in shale gas plays is significantly larger: 2 to 4 million gallons of water are 

typically needed per horizontal well (API, 2010a; GWPC and ALL Consulting, 2009; Satterfield et al., 

2008). Table 3 shows how the total volume of water used in fracturing varies depending on the depth 

and porosity of the shale gas play. 

TABLE 3. COMPARISON OF ESTIMATED WATER NEEDS FOR HYDRAULIC FRACTURING OF HORIZONTAL WELLS IN 

DIFFERENT SHALE PLAYS

Shale Play Formation 

Depth (ft) Porosity (%) Organic Content (%)

Freshwater 

Depth (ft)

Fracturing Water 

(gallons/well)

Barnett 6,500-8,500 4-5 4.5 1,200 2,300,000

Fayetteville 1,000-7,000 2-8 4-10 500 2,900,000

Haynesville 10,500-13,500 8-9 0.5-4 400 2,700,000

Marcellus 4,000-8,500 10 3-12 850 3,800,000

Data are from GWPC and ALL Consulting, 2009.

It was estimated that 35,000 wells were fractured in 2006 alone across the US (Halliburton, 2008). 

Assuming that the majority of these wells are horizontal wells, the annual national water requirement 

may range from 70 to 140 billion gallons. This is equivalent to the total amount of water withdrawn 

from drinking water resources each year in roughly 40 to 80 cities with a population of 50,000 or about 

one to two cities of 2.5 million people. In the Barnett Shale area, the annual estimates of total water 

used by gas producers ranged from 2.6 to 5.3 billion gallons per year from 2005 through 2007 (Bene et 

al., 2007, as cited in Galusky, 2007). During the projected peak shale gas production in 2010, the total 
EPA Hydraulic Fracturing Study Plan November 2011

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water used for gas production in the Barnett Shale was estimated to be 9.5 billion gallons. This 

represents 1.7 percent of the estimated total freshwater demand by all users within the Barnett Shale 

area (554 billion gallons) (Galusky, 2007). 

To meet these large volume requirements, source water is typically stored in 20,000-gallon portable 

steel (“frac”) tanks located at the well site (GWPC and ALL Consulting, 2009; ICF International, 2009a; 

Veil, 2007). Source water can also be stored in impoundment pits on site or in a centralized location that 

services multiple sites. For example, in the Barnett and Fayetteville Shale plays, source water may be 

stored in large, lined impoundments ranging in capacity from 8 million gallons for 4 to 20 gas wells to 

163 million gallons for 1,200 to 2,000 gas wells (Satterfield et al., 2008). The water used to fill tanks or 

impoundments may come from either ground or surface water, depending on the region in which the 

fracturing takes place. The transportation of source water to the well site depends on site-specific 

conditions. In many areas, trucks generally transport the source water to the well site. In the long term, 

where topography allows, a network of pipelines may be installed to transfer source water between the 

source and the impoundments or tanks. 

Whether the withdrawal of this much water from local surface or ground water sources has a significant 

impact and the types of possible impacts may vary from one part of the country to another and from 

one time of the year to another. In arid North Dakota, the projected need of 5.5 billion gallons of water 

per year to release oil and gas from the Bakken Shale has prompted serious concerns by stakeholders 

(Kellman and Schneider, 2010). In less arid parts of the country, the impact of water withdrawals may be 

different. In the Marcellus Shale area, stakeholder concerns have focused on large volume, high rate 

water withdrawals from small streams in the headwaters of watersheds supplying drinking water 

(Maclin et al., 2009; Myers, 2009).

One way to offset the large water requirements for hydraulic fracturing is to recycle the flowback 

produced in the fracturing process. Estimates for the amount of fracturing fluid that is recovered during 

the first two weeks after a fracture range from 25 to 75 percent of the original fluid injected and 

depends on several variables, including but not limited to the formation and the specific techniques 

used (Pickett, 2009; Veil, 2010; Horn, 2009). This water may be treated and reused by adding additional 

chemicals as well as fresh water to compose a new fracturing solution. There are, however, challenges 

associated with reusing flowback due to the high concentrations of total dissolved solids (TDS) and other 

dissolved constituents found in flowback (Bryant et al., 2010). Constituents such as specific cations (e.g., 

calcium, magnesium, iron, barium, and strontium) and anions (e.g., chloride, bicarbonate, phosphate, 

and sulfate) can interfere with hydraulic fracturing fluid performance by producing scale or by 

interfering with chemical additives in the fluids (Godsey, 2011). Recycled water can also become so 

concentrated with contaminants that it requires either disposal or reuse with considerable dilution. Acid 

mine drainage, which has a lower TDS concentration, has also been suggested as possible source water 

for hydraulic fracturing (Vidic, 2010) as well as non-potable ground water, including brackish water, 

saline, and brine (Godsey, 2011; Hanson, 2011).
EPA Hydraulic Fracturing Study Plan November 2011

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6.1.2 HOW MUCH WATER IS USED IN HYDRAULIC FRACTURING OPERATIONS, AND WHAT ARE THE SOURCES OF 

THIS WATER?

As mentioned in the previous section, source water for hydraulic fracturing operations can come from a 

variety of sources, including ground water, surface water, and recycled flowback. Water acquisition has 

not been well characterized, so EPA intends to gain a better understanding of the amounts and sources 

of water being used for hydraulic fracturing operations. 

6.1.2.1 RESEARCH ACTIVITIES – SOURCE WATER

Analysis of existing data. EPA has asked for information on hydraulic fracturing fluid source water 

resources from nine hydraulic fracturing service companies and nine oil and gas operators (see Appendix 

D). The data received from the service companies will inform EPA’s understanding of the general water 

quantity and quality requirements for hydraulic fracturing. EPA has asked the nine oil and gas operating 

companies for information on the total volume, source, and quality of the base fluid8 needed for 

hydraulic fracturing at 350 hydraulically fractured oil and gas production wells in the continental US. 

These data will provide EPA with a nationwide perspective on the volumes and sources of water used for 

hydraulic fracturing operations, including information on ground and surface water withdrawals as well 

as recycling of flowback. 

EPA will also study water use for hydraulic fracturing operations in two representative regions of the US: 

the Susquehanna River Basin and Garfield County, Colorado. The Susquehanna River Basin is in the heart 

of the Marcellus Shale play and represents a humid climate while Garfield County is located in the 

Piceance Basin and represents a semi-arid climate. EPA will collect existing data from the Susquehanna 

River Basin Commission and the Colorado Oil and Gas Conservation Commission to determine the 

volumes of water used for hydraulic fracturing and, if available, the sources of these waters.

EPA expects the research outlined above to produce the following:

• A list of volume and water quality parameters important for hydraulic fracturing operations.

• Information on source, volume, and quality of water used for hydraulic fracturing operations.

• Location-specific data on water use for hydraulic fracturing.

Prospective case studies. EPA will conduct prospective case studies in DeSoto Parish, Louisiana, and 

Washington County, Pennsylvania. As part of these studies, EPA will monitor the volumes, sources, and 

quality of water needed for hydraulic fracturing operations. These two locations are representative of an 

area where ground water withdrawals have been common (Haynesville Shale in Louisiana), and an area 

where surface water withdrawals and recycling practices have been used (Marcellus Shale in 

Pennsylvania). 

 8 In the case of water-based hydraulic fracturing fluids, water would be the base fluid.
EPA Hydraulic Fracturing Study Plan November 2011

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EPA expects the research outlined above to produce the following:

• Location-specific examples of water acquisition, including data on the source, volume, and 

quality of the water.

6.1.3 HOW MIGHT WATER WITHDRAWALS AFFECT SHORT- AND LONG-TERM WATER AVAILABILITY IN AN AREA 

WITH HYDRAULIC FRACTURING ACTIVITY?

Large volume water withdrawals for hydraulic fracturing are different from withdrawals for other 

purposes in that much of the water used for the fracturing process may not be recovered after injection. 

The impact from large volume water withdrawals varies not only with geographic area, but also with the 

quantity, quality, and sources of the water used. The removal of large volumes of water could stress 

drinking water supplies, especially in drier regions where aquifer or surface water recharge is limited. 

This could lead to lowering of water tables or dewatering of drinking water aquifers, decreased stream 

flows, and reduced volumes of water in surface water reservoirs. These activities could impact the 

availability of water for drinking in areas where hydraulic fracturing is occurring. The lowering of water 

levels in aquifers can necessitate the lowering of pumps or the deepening or replacement of wells, as 

has been reported near Shreveport, Louisiana, in the area of the Haynesville Shale (Louisiana Office of 

Conservation, 2011). 

As the intensity of hydraulic fracturing activities increases within individual watersheds and geologic 

basins, it is important to understand the net impacts on water resources and identify opportunities to 

optimize water management strategies.

6.1.3.1 RESEARCH ACTIVITIES – WATER AVAILABILITY 

Analysis of existing data. In cooperation with USACE, USGS, state environmental agencies, state oil and 

gas associations, river basin commissions, and others, EPA will compile data on water use and the 

hydrology of the Susquehanna River Basin in the Marcellus Shale and Garfield County, Colorado, in the 

Piceance Basin. These data will include ground water levels, surface water flows, and water quality as 

well as data on hydraulic fracturing operations, such as the location of wells and the volume of water 

used during fracturing. These specific study areas represent both arid and humid areas of the country. 

These areas were chosen based on the availability of data from the Susquehanna River Basin 

Commission and the Colorado Oil and Gas Conservation Commission. 

EPA will conduct simple water balance and geographic information system (GIS) analysis using the 

existing data. The data collected will be compiled along with information on hydrological trends over the 

same period of time. EPA will compare control areas with similar baseline water demands and no oil and 

gas development to areas with intense hydraulic fracturing activity, isolating and identifying any impacts 

of hydraulic fracturing on water availability. A critical analysis of trends in water flows and water usage 

patterns will be conducted in areas where hydraulic fracturing activities are occurring to determine 

whether water withdrawals alter ground and surface water flows. Data collection will support the 

assessment of the potential impacts of hydraulic fracturing on water availability at various spatial scales 

(e.g., site, watershed, basin, and play) and temporal scales (e.g., days, months, and years). 
EPA Hydraulic Fracturing Study Plan November 2011

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EPA expects the research outlined above to produce the following:

• Maps of recent hydraulic fracturing activity and water usage in a humid region (Susquehanna 

River Basin) and a semi-arid region (Garfield County, Colorado).

• Information on whether water withdrawals for hydraulic fracturing activities alter ground or 

surface water flows.

• Assessment of impacts of hydraulic fracturing on water availability at various spatial and 

temporal scales

Prospective case studies. The prospective case studies will evaluate potential short-term impacts on 

water availability due to large volume water use for hydraulic fracturing in DeSoto Parish, Louisiana, and 

Washington County, Pennsylvania. The data collected during these case studies will allow EPA to 

compare potential differences in effects on local water availability between an area where ground water 

is typically used (DeSoto Parish) and an area where surface water withdrawals are common (Washington 

County).

EPA expects the research outlined above to produce the following:

• Identification of short-term impacts on water availability from ground and surface water 

withdrawals associated with hydraulic fracturing activities.

Scenario evaluation. Scenario evaluations will assess potential long-term quantity impacts as a result of

cumulative water withdrawals. The evaluations will focus on hydraulic fracturing operations at various 

spatial and temporal scales in the Susquehanna River Basin and Garfield County, Colorado, using the 

existing data described above. The scenarios will include at least two futures: (1) average annual 

conditions in 10 years based on the full exploitation of oil and natural gas resources; and (2) average 

annual conditions in 10 years based on sustainable water use in hydraulic fracturing operations. Both 

scenarios will build on predictions for land use and climate (e.g., drought, average, and wet). EPA will 

take advantage of the future scenario work constructed for the EPA Region 3 Chesapeake Bay Program9

and the EPA ORD Future Midwestern Landscape Program.

10 The spatial scales of analysis will reflect 

both environmental boundaries (e.g., site, watershed, river basin, and geologic play) and political 

boundaries (e.g., city/municipality, county, state, and EPA Region). 

These assessments will consider typical water requirements for hydraulic fracturing activities and will 

also account for estimated demands for water from other human needs (e.g., drinking water, 

agriculture, and energy), adjusted for future populations. The sustainability analysis will reflect 

minimum river flow requirements and aquifer drawdown for drought, average, and wet precipitation 

years, and will allow a determination of the number of typical hydraulic fracturing operations that could 

be sustained for the relevant formation (e.g., Marcellus Shale) and future scenario. Appropriate physicsbased watershed and ground water models will be used for representation of the water balance and 

hydrologic cycle, as discussed in Chapter 10.

 9 http://www.epa.gov/region3/chesapeake/.

10 http://www.epa.gov/asmdnerl/EcoExposure/FML.html.
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EPA expects the research outlined above to produce the following:

• Identification of long-term water quantity impacts on drinking water resources due to 

cumulative water withdrawals for hydraulic fracturing.

6.1.4 WHAT ARE THE POSSIBLE IMPACTS OF WATER WITHDRAWALS FOR HYDRAULIC FRACTURING 

OPERATIONS ON LOCAL WATER QUALITY?

Withdrawals of large volumes of ground water can lower the water levels in aquifers. This can affect the 

aquifer water quality by exposing naturally occurring minerals to an oxygen-rich environment, 

potentially causing chemical changes that affect mineral solubility and mobility, leading to salination of 

the water and other chemical contaminations. Additionally, lowered water tables may stimulate 

bacterial growth, causing taste and odor problems. Depletion of aquifers can also cause an upwelling of 

lower quality water and other substances (e.g., methane from shallow deposits) from deeper within an 

aquifer and could lead to subsidence and/or destabilization of the geology.

Withdrawals of large quantities of water from surface water resources (e.g., streams, lakes, and ponds) 

can significantly affect the hydrology and hydrodynamics of these resources. Such withdrawals from 

streams can alter the flow regime by changing their flow depth, velocity, and temperature (Zorn et al., 

2008). Additionally, removal of significant volumes of water can reduce the dilution effect and increase 

the concentration of contaminants in surface water resources (Pennsylvania State University, 2010). 

Furthermore, it is important to recognize that ground and surface water are hydraulically connected 

(Winter et al., 1998); any changes in the quantity and quality of the surface water can affect ground 

water and vice versa.

6.1.4.1 RESEARCH ACTIVITIES – WATER QUALITY

Analysis of existing data. EPA will use the data described in Section 6.1.3.1 to analyze changes in water 

quality in the Susquehanna River Basin and Garfield County, Colorado, to determine if any changes are 

due to surface or ground water withdrawals for hydraulic fracturing. 

EPA expects the research outlined above to produce the following:

• Maps of hydraulic fracturing activity and water quality for the Susquehanna River Basin and 

Garfield County, Colorado.

• Information on whether water withdrawals for hydraulic fracturing alter local water quality.

Prospective case studies. These case studies will allow EPA to collect data on the quality of ground and 

surface waters that may be used for hydraulic fracturing before and after water is removed for hydraulic 

fracturing purposes. EPA will analyze these data to determine if there are any changes in local water 

quality and if these changes are a result of water withdrawals associated with hydraulic fracturing.

EPA expects the research outlined above to produce the following:

• Identification of impacts on local water quality from withdrawals for hydraulic fracturing.
EPA Hydraulic Fracturing Study Plan November 2011

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6.2 CHEMICAL MIXING: WHAT ARE THE POSSIBLE IMPACTS OF SURFACE SPILLS ON OR NEAR 

WELL PADS OF HYDRAULIC FRACTURING FLUIDS ON DRINKING WATER RESOURCES?

6.2.1 BACKGROUND

Hydraulic fracturing fluids serve two purposes: to create pressure to propagate fractures and to carry 

the proppant into the fracture. Chemical additives and proppants are typically used in the fracturing 

fluid. The types and concentrations of chemical additives and proppants vary depending on the 

conditions of the specific well being fractured, creating a fracturing fluid tailored to the properties of the 

formation and the needs of the project. In some cases, reservoir properties are entered into modeling 

programs that simulate fractures (Castle et al., 2005; Hossain and Rahman, 2008). These simulations

may then be used to reverse engineer the requirements for fluid composition, pump rates, and 

proppant concentrations. 

Table 4 lists the volumetric composition of a fluid used in a fracturing operation in the Fayetteville Shale 

as an example of additive types and concentrations (GWPC and ALL Consulting, 2009; API, 2010b). A list 

of publicly known chemical additives found in hydraulic fracturing fluids is provided in Appendix E.

In the case outlined in Table 4, the total concentration of chemical additives was 0.49 percent. Table 4

also calculates the volume of each additive based on a total fracturing fluid volume of 3 million gallons, 

and shows that the total volume of chemical additives is 14,700 gallons. In general, the overall 

concentration of chemical additives in fracturing fluids used in shale gas plays ranges from 0.5 to 2 

percent by volume, with water and proppant making up the remainder (GWPC and ALL Consulting, 

2009), indicating that 15,000 to 60,000 gallons of the total fracturing fluid consist of chemical additives 

(assuming a total fluid volume of 3 million gallons). 

The chemical additives are typically stored in tanks on site and blended with water and the proppant 

prior to injection. Flow, pressure, density, temperature, and viscosity can be measured before and after 

mixing (Pearson, 1989). High pressure pumps then send the mixture from the blender into the well 

(Arthur et al., 2008). In some cases, special on-site equipment is used to measure the properties of the 

mixed chemicals in situ to ensure proper quality control (Hall and Larkin, 1989).

6.2.2 WHAT IS CURRENTLY KNOWN ABOUT THE FREQUENCY, SEVERITY, AND CAUSES OF SPILLS OF HYDRAULIC 

FRACTURING FLUIDS AND ADDITIVES?

Large hydraulic fracturing operations require extensive quantities of supplies, equipment, water, and 

vehicles, which could create risks of accidental releases, such as spills or leaks. Surface spills or releases 

can occur as a result of tank ruptures, equipment or surface impoundment failures, overfills, vandalism, 

accidents, ground fires, or improper operations. Released fluids might flow into a nearby surface water 

body or infiltrate into the soil and near-surface ground water, potentially reaching drinking water 

aquifers (NYSDEC, 2011).
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TABLE 4. AN EXAMPLE OF THE VOLUMETRIC COMPOSITION OF HYDRAULIC FRACTURING FLUID

Data are from GWPC and ALL Consulting, 2009, and API, 2010b.

a Based on 3 million gallons of fluid used.

Over the past few years there have been numerous media reports of spills of hydraulic fracturing fluids 

(Lustgarten, 2009; M. Lee, 2011; Williams, 2011). While these media reports highlight specific incidences 

of surface spills of hydraulic fracturing fluids, the frequency and typical causes of these spills remain 

unclear. Additionally, these reports tend to highlight severe spills. EPA is interested in learning about the 

range of volumes and reported impacts associated with surface spills of hydraulic fracturing fluids and 

additives. 

6.2.2.1 RESEARCH ACTIVITIES – SURFACE SPILLS OF HYDRAULIC FRACTURING FLUIDS AND ADDITIVES

Analysis of existing data. EPA will compile and evaluate existing information on the frequency, severity, 

and causes of spills of hydraulic fracturing fluids and additives. These data will come from a variety of 

sources, including information provided by nine oil and gas operators. In an August 2011 information 

request sent to these operators, EPA requested spill incident reports for any fluid spilled at 350 different 

randomly selected well sites in 13 states across the US. Other sources of data are expected to include 

Component/

Additive Type Example Compounds Purpose

Percent 

Composition 

(by Volume)

Volume of 

Chemical 

(Gallons)a

Water Deliver proppant 90 2,700,000

Proppant Silica, quartz sand Keep fractures open to allow 

gas flow out 9.51 285,300

Acid Hydrochloric acid Dissolve minerals, initiate 

cracks in the rock 0.123 3,690

Friction reducer Polyacrylamide, 

mineral oil

Minimize friction between 

fluid and the pipe 0.088 2,640

Surfactant Isopropanol Increase the viscosity of the 

fluid 0.085 2,550

Potassium 

chloride

Create a brine carrier fluid 0.06 1,800

Gelling agent Guar gum, 

hydroxyethyl 

cellulose

Thicken the fluid to suspend 

the proppant 0.056 1,680

Scale inhibitor Ethylene glycol Prevent scale deposits in the 

pipe 0.043 1,290

pH adjusting agent Sodium or potassium 

carbonate

Maintain the effectiveness of 

other components

0.011 330

Breaker Ammonium 

persulfate

Allow delayed breakdown of 

the gel 0.01 300

Crosslinker Borate salts Maintain fluid viscosity as 

temperature increases 0.007 210

Iron control Citric acid Prevent precipitation of 

metal oxides 0.004 120

Corrosion inhibitor N,N-dimethyl 

formamide

Prevent pipe corrosion 0.002 60

Biocide Glutaraldehyde Eliminate bacteria 0.001 30
EPA Hydraulic Fracturing Study Plan November 2011

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spills reported to the National Response Center, state departments of environmental protection (e.g., 

Pennsylvania and West Virginia), EPA’s Natural Gas Drilling Tipline, and others.

EPA will assess the data provided by these sources to reflect a national perspective of reported surface 

spills of hydraulic fracturing fluids and additives. The goal of this effort is to provide a representative 

assessment of the frequency, severity, and causes of surface spills associated with hydraulic fracturing 

fluids and additives. 

EPA expects the research outlined above to produce the following:

• Nationwide data on the frequency, severity, and causes of spills of hydraulic fracturing fluids and 

additives.

6.2.3 WHAT ARE THE IDENTITIES AND VOLUMES OF CHEMICALS USED IN HYDRAULIC FRACTURING FLUIDS,

AND HOW MIGHT THIS COMPOSITION VARY AT A GIVEN SITE AND ACROSS THE COUNTRY?

EPA has compiled a list of chemicals that are publicly known to be used in hydraulic fracturing (Table E1

in Appendix E). The chemicals identified in Table E1, however, does not represent the entire set of 

chemicals used in hydraulic fracturing activities. EPA also lacks information regarding the frequency, 

quantity, and concentrations of the chemicals used, which is important when considering the toxic 

effects of hydraulic fracturing fluid additives. Stakeholder meetings and media reports have emphasized 

the public’s concern regarding the identity and toxicity of chemicals used in hydraulic fracturing.

Although there has been a trend in recent years of public disclosure of hydraulic fracturing chemicals, 

inspection of these databases shows that much information is still deemed to be proprietary and is not 

made available to the public.

6.2.3.1 RESEARCH ACTIVITIES – HYDRAULIC FRACTURING FLUID COMPOSITION

Analysis of existing data. In September 2010, EPA issued information requests to nine hydraulic 

fracturing service companies seeking information on the identity and quantity of chemicals used in 

hydraulic fracturing fluid in the past five years (Appendix D). This information will provide EPA with a 

better understanding of the common compositions of hydraulic fracturing fluids (i.e., identity of 

components, concentrations, and frequency of use) and the factors that influence these compositions. 

By asking for data from the past five years, EPA expects to obtain information on chemicals that have 

been used recently. Some of these chemicals, however, may no longer be used in hydraulic fracturing 

operations, but could be present in areas where retrospective case studies will be conducted. Much of 

the data collected from this request have been claimed as confidential business information (CBI). In 

accordance with 40 C.F.R. Part 2 Subpart B, EPA will treat it as such until a determination regarding the 

claims is made. 

The list of chemicals from the nine hydraulic fracturing service companies will be compared to the list of 

publicly known hydraulic fracturing chemical additives to determine the accuracy and completeness of 

the list of chemicals given in Table E1 in Appendix E. The combined list will provide EPA with an

inventory of chemicals used in hydraulic fracturing operations.
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EPA expects the research outlined above to produce the following:

• Description of types of hydraulic fracturing fluids and their frequency of use (subject to 40 C.F.R. Part 2 

Subpart B regulations).

• A list of chemicals used in hydraulic fracturing fluids, including concentrations (subject to 40 C.F.R. Part 2 

Subpart B regulations).

• A list of factors that determine and alter the composition of hydraulic fracturing fluids.

Prospective case studies. These case studies will allow EPA to collect information on chemical products 

used in hydraulic fracturing fluids. EPA will use these data to illustrate how hydraulic fracturing fluids are 

used at specific wells in the Haynesville and Marcellus Shale plays.

EPA expects the research outlined above to produce the following:

• Illustrative examples of hydraulic fracturing fluids used in the Haynesville and Marcellus Shale 

plays.

6.2.4 WHAT ARE THE CHEMICAL, PHYSICAL, AND TOXICOLOGICAL PROPERTIES OF HYDRAULIC FRACTURING 

CHEMICAL ADDITIVES?

Chemical and physical properties of hydraulic fracturing chemical additives can help to identify potential 

human health exposure pathways by describing the mobility of the chemical additives and possible 

chemical reactions associated with hydraulic fracturing additives. These properties include, but are not 

limited to: density, melting point, boiling point, flash point, vapor pressure, diffusion coefficients, 

partition and distribution coefficients, and solubility.

Chemical characteristics can be used to assess the toxicity of hydraulic fracturing chemical additives. 

Available information may include structure, water solubility, vapor pressure, partition coefficients, 

toxicological studies, or other factors. There has been considerable public interest regarding the toxicity 

of chemicals used in hydraulic fracturing fluids. In response to these concerns, the US House of 

Representatives Committee on Energy and Commerce launched an investigation to examine the practice 

of hydraulic fracturing in the US. Through this inquiry, the Committee learned that “between 2005 and 

2009, the 14 [leading] oil and gas service companies used more than 2,500 hydraulic fracturing products 

containing 750 chemicals and other components” (Waxman et al., 2011). This included “29 chemicals 

that are: (1) known or possible human carcinogens; (2) regulated under the Safe Drinking Water Act for 

their risks to human health; or (3) listed as hazardous air pollutants under the Clean Air Act” (Waxman et 

al., 2011).

6.2.4.1 RESEARCH ACTIVITIES – CHEMICAL, PHYSICAL, AND TOXICOLOGICAL PROPERTIES

Analysis of existing data. EPA will combine the chemical data collected from the nine hydraulic 

fracturing service companies with the public list of chemicals given in Appendix E and other sources that 

may become available to obtain an inventory of chemicals used in hydraulic fracturing fluids. EPA will 

then search existing databases to obtain known chemical, physical, and toxicological properties for the 

chemicals in the inventory. EPA expects to use this list to identify a short list of 10 to 20 chemical 

indicators to track the fate and transport of hydraulic fracturing fluids through the environment. The 
EPA Hydraulic Fracturing Study Plan November 2011

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criteria for selecting these indicators will include, but are not limited to: (1) the frequency of occurrence 

in fracturing fluids; (2) the toxicity of the chemical; (3) the expected fate and transport of the chemical 

(e.g., mobility in the environment); and (4) the availability of detection methods. EPA will also use this 

chemical list to identify chemicals with little or no toxicological information and may be of high concern 

for human health impacts. These chemicals of concern will undergo further toxicological assessment

EPA expects the research outlined above to produce the following:

• A list of hydraulic fracturing chemicals with known chemical, physical, and toxicological 

properties.

• Identification of 10-20 possible indicators to track the fate and transport of hydraulic fracturing 

fluids based on known chemical, physical, and toxicological properties.

• Identification of hydraulic fracturing chemicals that may be of high concern, but have little or no 

existing toxicological information.

Toxicological analysis/assessment. EPA will identify any hydraulic fracturing chemical currently 

undergoing ToxCast Phase II testing to determine if chemical, physical, and toxicological properties are 

being assessed. In other cases where chemical, physical, and toxicological properties are unknown, EPA 

will estimate these properties using quantitative structure-activity relationships. From this effort, EPA 

will identify up to six chemicals used in hydraulic fracturing fluid and without toxicity values to be 

considered for ToxCast screening and provisional peer-reviewed toxicity value (PPRTV) development.

More detailed information on characterization of the toxicity and human health approach is found in 

Chapter 11.

EPA expects the research outlined above to produce the following:

• Lists of high, low, and unknown priority hydraulic fracturing chemicals based on known or 

predicted toxicity data.

• Toxicological properties for up to six hydraulic fracturing chemicals that have no existing 

toxicological information and are of high concern.

Laboratory studies. The list of chemicals derived from the existing data analysis and toxicological studies 

will inform EPA of high priority chemicals for which existing analytical methods may be inadequate for

detection in hydraulic fracturing fluids and/or in drinking water resources. EPA will modify these 

methods to suit the needs of the research.

EPA expects the research outlined above to produce the following:

• Improved analytical methods for detecting hydraulic fracturing chemicals.

6.2.5 IF SPILLS OCCUR, HOW MIGHT HYDRAULIC FRACTURING CHEMICAL ADDITIVES CONTAMINATE DRINKING 

WATER RESOURCES?

Once released unintentionally into the environment, chemical additives in hydraulic fracturing fluid may 

contaminate ground water or surface water resources. The pathway by which chemical additives may 
EPA Hydraulic Fracturing Study Plan November 2011

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migrate to ground and surface water depends on many factors, including site-, chemical-, or fluidspecific factors. Site-specific factors refer to the physical characteristics of the site and the spill. These 

may include the location of the spill with respect to ground and surface water resources, weather 

conditions at the time of the spill, and the type of surface the spill occurred on (e.g., soil, sand, or plastic 

liner). Chemical- or fluid-specific factors include the chemical and physical properties of the chemical 

additives or fluid (e.g., density, solubility, diffusion, and partition coefficients). These properties govern 

the mobility of the fluid or specific chemical additives through soil and other media. To understand 

exposure pathways related to surface spills of hydraulic fracturing fluids, EPA must understand site-, 

chemical-, or fluid-specific factors that govern surface spills. 

6.2.5.1 RESEARCH ACTIVITIES – CONTAMINATION PATHWAYS

Analysis of existing data. Surface spills of chemicals, in general, are not restricted to hydraulic fracturing 

operations and can occur under a variety of conditions. Because these are common problems, there 

already exists a body of scientific literature that describes how a chemical solution released on the 

ground can be transported into the subsurface and/or run off to a surface water body. Using the list of 

hydraulic fracturing fluid chemical additives generated through the research described in Section 

6.2.3.1, EPA will identify available data on the fate and transport of hydraulic fracturing fluid additives. 

The relevant research will be used to assess known impacts of spills of fracturing fluid components on 

drinking water resources and to identify knowledge gaps related to surface spills of hydraulic fracturing 

fluid chemical additives.

EPA expects the research outlined above to produce the following:

• Summary of existing research that describes the fate and transport of hydraulic fracturing 

chemical additives, similar compounds, or classes of compounds.

• Identification of knowledge gaps for future research, if necessary.

Retrospective case studies. Accidental releases from chemical tanks, supply lines or leaking valves have 

been reported at some of the candidate case study sites (listed in Appendix F) have reported. EPA has 

identified two locations for retrospective case studies to consider surface spills of hydraulic fracturing 

fluids through field investigations and sampling: Dunn County, North Dakota, and Bradford and 

Susquehanna Counties, Pennsylvania. This research will identify any potential impacts on drinking water 

resources from surface spills, and if impacts were observed, what factors may have contributed to the 

contamination. 

EPA expects the research outlined above to produce the following:

• Identification of impacts (if any) to drinking water resources from surface spills of hydraulic 

fracturing fluids.

• Identification of factors that led to impacts (if any) to drinking water resources resulting from 

accidental release of hydraulic fracturing fluids.
EPA Hydraulic Fracturing Study Plan November 2011

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6.3 WELL INJECTION: WHAT ARE THE POSSIBLE IMPACTS OF THE INJECTION AND FRACTURING 

PROCESS ON DRINKING WATER RESOURCES?

6.3.1 BACKGROUND

In a cased well completion, the production casing is perforated prior to the injection of hydraulic 

fracturing fluid. The perforations allow the injected fluid to enter, and thus fracture, the target 

formation. Wells can be fractured in either a single stage or multiple stages, as determined by the total 

length of the injection zone. In a multi-stage fracture, the fracturing operation typically begins with the 

stage furthest from the wellhead until the entire length of the fracture zone has been fractured. 

The actual fracturing process within each stage consists of a series of injections using different volumes 

and compositions of fracturing fluids (GWPC and ALL Consulting, 2009). Sometimes a small amount of 

fluid is pumped into the well before the actual fracturing begins. This “mini-frac” may be used to help 

determine reservoir properties and to enable better fracture design (API, 2009b). In the first stage of the 

fracture job, fracturing fluid (typically without proppant) is pumped down the well at high pressures to 

initiate the fracture. The fracture initiation pressure will depend on the depth and the mechanical 

properties of the formation. A combination of fracturing fluid and proppant is then pumped in, often in 

slugs of varying sizes and concentrations. After the combination is pumped, a water flush is used to 

begin flushing out the fracturing fluid (Arthur et al., 2008). 

API recommends that several parameters be continuously monitored during the actual hydraulic 

fracturing process, including surface injection pressure, slurry rate, proppant concentration, fluid rate, 

and proppant rate (API, 2009b). Monitoring the surface injection pressure is particularly important for 

two reasons: (1) it ensures that the pressure exerted on equipment does not exceed the tolerance of the 

weakest components and (2) unexpected or unusual pressure changes may be indicative of a problem 

that requires prompt attention (API, 2009b). It is not readily apparent how often API’s recommendations

are followed.

Hydraulic fracturing models and stimulation bottomhole pressure versus time curves can be analyzed to 

determine fracture height, average fracture width, and fracture half-length. Models can also be used 

during the fracturing process to make real-time adjustments to the fracture design (Armstrong et al., 

1995). Additionally, microseismic monitors and tiltmeters may be used during fracturing to plot the 

positions of the fractures (Warpinski et al., 1998 and 2001; Cipolla and Wright, 2000), although this is 

done primarily when a new area is being developed or new techniques are being used (API, 2009b). 

Comparison of microseismic data to fracture modeling predictions helps to adjust model inputs and 

increase the accuracy of height, width, and half-length determinations. 

6.3.1.1 NATURALLY OCCURRING SUBSTANCES

Hydraulic fracturing can affect the mobility of naturally occurring substances in the subsurface, 

particularly in the hydrocarbon-containing formation. These substances, described in Table 5, include 

formation fluid, gases, trace elements, naturally occurring radioactive material, and organic material. 

Some of these substances may be liberated from the formation via complex biogeochemical reactions 

with chemical additives found in hydraulic fracturing fluid (Falk et al., 2006; Long and Angino, 1982). 
EPA Hydraulic Fracturing Study Plan November 2011

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TABLE 5. EXAMPLES OF NATURALLY OCCURRING SUBSTANCES THAT MAY BE FOUND IN HYDROCARBONCONTAINING FORMATIONS

Type of Contaminant Example(s)

Formation fluid Brinea (e.g., sodium chloride)

Gases Natural gasb (e.g., methane, ethane), carbon dioxide, 

hydrogen sulfide, nitrogen, helium

Trace elements Mercury, lead, arsenicc

Naturally occurring 

radioactive material

Radium, thorium, uraniumc

Organic material Organic acids, polycyclic aromatic hydrocarbons, 

volatile and semi-volatile organic compounds a Piggot and Elsworth, 1996.

b Zoback et al., 2010.

c Harper, 2008; Leventhal and Hosterman, 1982; Tuttle et al., 2009; 

Vejahati et al., 2010.

The ability of these substances to reach to ground or surface waters as a result of hydraulic fracturing 

activities is a potential concern. For example, if fractures extend beyond the target formation and reach 

aquifers, or if the casing or cement around a wellbore fails under the pressures exerted during hydraulic 

fracturing, contaminants could migrate into drinking water supplies. Additionally, these naturally 

occurring substances may be dissolved into or flushed to the surface with the flowback.

6.3.2 HOW EFFECTIVE ARE CURRENT WELL CONSTRUCTION PRACTICES AT CONTAINING GASES AND FLUIDS

BEFORE, DURING, AND AFTER FRACTURING?

A number of reports have indicated that that improper well construction or improperly sealed wells may 

be able to provide subsurface pathways for ground water pollution by allowing contaminant migration 

to sources of drinking water (PADEP, 2010b; McMahon et al., 2011; State of Colorado Oil and Gas 

Conservation Commission, 2009a, 2009b, and 2009c; USEPA, 2010b). EPA will assess to what extent

proper well construction and mechanical integrity are important factors in preventing contamination of 

drinking water resources from hydraulic fracturing activities. 

In addition to concerns related to improper well construction and well abandonment processes, there is 

a need to understand the potential impacts of the repeated fracturing of a well over its lifetime. 

Hydraulic fracturing can be repeated as necessary to maintain the flow of hydrocarbons to the well. The 

near- and long-term effects of repeated pressure treatments on well construction components (e.g., 

casing and cement) are not well understood. While EPA recognizes that fracturing or re-fracturing 

existing wells should also be considered for potential impacts to drinking water resources, EPA has not 

been able to identify potential partners for a case study; therefore, this practice is not considered in the 

current study. The issues of well age, operation, and maintenance are important and warrant more 

study. 

6.3.2.1 RESEARCH ACTIVITIES – WELL MECHANICAL INTEGRITY

Analysis of existing data. As part of the voluntary request for information sent by EPA to nine hydraulic 

fracturing service companies (see Appendix D), EPA asked for the locations of sites where hydraulic 

fracturing operations have occurred within the past year. From this list of more than 25,000 hydraulic 
EPA Hydraulic Fracturing Study Plan November 2011

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fracturing sites, EPA statistically selected a random sample of sites and requested the complete well files 

for 350 sites. Well files generally contain information regarding all activities conducted at the site, 

including any instances of well failure. EPA will analyze the well files to assess the typical frequency, 

causes, and severity of well failures. 

EPA expects the research outlined above to produce the following:

• Data on the frequency and severity of well failures.

• Identification of contributing factors that may lead to well failures during hydraulic fracturing 

activities.

Retrospective case studies. While conducting retrospective case studies, EPA will assess the mechanical 

integrity of existing and historical production wells near the reported area of drinking water 

contamination. To do this, EPA will review existing well construction and mechanical integrity data 

and/or collect new data using the tools described in Appendix G. EPA will specifically investigate

mechanical integrity issues in Dunn County, North Dakota, and Bradford and Susquehanna Counties, 

Pennsylvania. By investigating well construction and mechanical integrity at sites with reported drinking 

water contamination, EPA will work to determine if well failure was responsible for the reported 

contamination and whether original well integrity tests were effective in identifying problems.

EPA expects the research outlined above to produce the following:

• Identification of impacts (if any) to drinking water resources resulting from well failure or 

improper well construction.

• Data on the role of mechanical integrity in suspected cases of drinking water contamination due 

to hydraulic fracturing.

Prospective case studies. EPA will evaluate well construction and mechanical integrity at prospective 

case study sites by assessing the mechanical integrity of the well pre- and post- fracturing. This 

assessment will be done by comparing results from available logging tools and pressure tests taken 

before and after hydraulic fracturing. EPA will also assess the methods and tools used to protect 

drinking water resources from oil and natural gas resources before and during a hydraulic fracture 

event.

EPA expects the research outlined above to produce the following:

• Data on the changes (if any) in mechanical integrity due to hydraulic fracturing.

• Identification of methods and tools used to isolate drinking water resources from oil and gas 

resources before and during hydraulic fracturing.

Scenario evaluation. EPA will use computer modeling to investigate the role of mechanical integrity in 

creating pathways for contaminant migration to ground and surface water resources. The models will 

include engineering and geological aspects, which will be informed by existing data. Models of the 

engineering systems will include the design and geometry of the vertical and horizontal wells in addition 

to information on the casing and cementing materials. Models of the geology will include the expected 
EPA Hydraulic Fracturing Study Plan November 2011

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geometry of aquifers and aquitards/aquicludes, the permeability of the formations, and the geometry 

and nature of boundary conditions (e.g., closed and open basins, recharge/discharge). 

Once built, the models will be used to explore scenarios in which well integrity is compromised before or

during hydraulic fracturing due to inadequate or inappropriate well design and construction. In these 

cases, the construction of the well is considered inadequate due to improper casing and/or cement or 

improper well construction. It is suspected that breakdowns in the well casing or cement may provide a 

high permeability pathway between the well casing and the borehole wall, which may lead to 

contamination of a drinking water aquifer. It will be informative to assess how different types of well 

construction and testing practices perform during these model scenarios and whether drinking water 

resources could be affected.

EPA expects the research outlined above to produce the following:

• Assessment of well failure scenarios during and after well injection that may lead to drinking 

water contamination.

6.3.3 CAN SUBSURFACE MIGRATION OF FLUIDS OR GASES TO DRINKING WATER RESOURCES OCCUR, AND 

WHAT LOCAL GEOLOGIC OR MAN-MADE FEATURES MAY ALLOW THIS?

Although hydraulic fracture design and control have been researched extensively, predicted and actual 

fracture lengths still differ frequently (Daneshy, 2003; Warpinski et al., 1998). Hence, it is difficult to 

accurately predict and control the location and length of fractures. Due to this uncertainty in fracture 

location, EPA must consider whether hydraulic fracturing may lead to fractures intersecting local 

geologic or man-made features, potentially creating subsurface pathways that allow fluids or gases to 

contaminate drinking water resources. 

Local geologic features are considered to be naturally occurring features, including pre-existing faults or 

fractures that lead to or directly extend into aquifers. If the fractures created during hydraulic fracturing 

were to extend into pre-existing faults or fractures, there may be an opportunity for hydraulic fracturing 

fluids, natural gas, and/or naturally occurring substances (Table 5) to contaminate nearby aquifers. Any 

risk posed to drinking water resources would depend on the distance to those resources and the 

geochemical and transport processes that occur in the intermediate strata. A common assumption in 

shale gas formations is that natural barriers in the rock strata that act as seals for the gas in the target 

formation also act as barriers to the vertical migration of fracturing fluids (GWPC and ALL Consulting, 

2009). Additionally, during production the flow direction is toward the wellbore because of a decreasing 

pressure gradient. It is assumed that due to this gradient, gas would be unlikely to move elsewhere as 

long as the well is in operation and maintains integrity. However, in contrast to shale gas, coalbed 

methane reservoirs are mostly shallow and may also be co-located with drinking water resources. In this 

instance, hydraulic fracturing may be occurring in or near a USDW, raising concerns about the 

contamination of shallow water supplies with hydraulic fracturing fluids (Pashin, 2007). 

In addition to natural faults or fractures, it is important to consider the proximity of man-made

penetrations such as drinking water wells, exploratory wells, production wells, abandoned wells 
EPA Hydraulic Fracturing Study Plan November 2011

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(plugged and unplugged), injection wells, and underground mines. If such penetrations intersect the 

injection zone in the vicinity of a hydraulically fractured well, they may serve as conduits for 

contaminants to reach ground water resources. Several instances of natural gas migrations have been 

noted. A 2004 EPA report on coalbed methane indicated that methane migration in the San Juan Basin 

was mitigated once abandoned and improperly sealed wells were plugged. The same report found that 

in some cases in Colorado, poorly constructed, sealed, or cemented wells used for a variety of purposes 

could provide conduits for methane migration into shallow USDWs (USEPA, 2004). More recently, a 

study in the Marcellus Shale region concluded that methane gas was present in well water in areas near

hydraulic fracturing operations, but did not identify the origin of the gas (Osborne et al., 2011).

Additional studies indicate that methane migration into shallow aquifers is a common natural 

phenomenon in this region and occurs in areas with and without hydraulic fracturing operations 

(NYSDEC, 2011). 

6.3.3.1 RESEARCH ACTIVITIES – LOCAL GEOLOGIC AND MAN-MADE FEATURES

Analysis of existing data. EPA is collecting information from nine oil and gas well operators regarding 

operations at specific well sites. This information will be compiled and analyzed to determine whether 

existing local geologic or man-made features are identified prior to hydraulic fracturing, and if so, what 

types are of concern.

EPA will also review the well files for data relating to fracture location, length, and height. This includes 

data gathered to measure the fracture pressure gradients in the production zone; data resulting from 

fracture modeling, microseismic fracture mapping, and/or tiltmeter analysis; and other relevant data. A 

critical assessment of the available data will allow EPA to determine if fractures created during hydraulic 

fracturing were localized to the stimulated zone or possibly intersected pre-existing local geologic or 

man-made features. EPA expects to be able to provide information on the frequency of migration 

effects and the severity of impacts to drinking water resources posed by these potential contaminant 

migration pathways. 

EPA expects the research outlined above to produce the following:

• Information on the types of local geologic or man-made features identified prior to hydraulic 

fracturing.

• Data on whether or not fractures interact with local geologic or man-made features and the 

frequency of occurrence.

Retrospective case studies. In cases of suspected drinking water contamination, EPA will use geophysical 

testing, field sample analysis, and modeling to investigate the role of local geologic and/or man-made 

features in leading to any identified contamination. EPA will also review existing data to determine if the 

induced fractures were confined to the targeted fracture zone. These investigations will determine the 

role of pre-existing natural or man-made pathways in providing conduits for the migration of fracturing 

fluid, natural gas, and/or naturally occurring substances to drinking water resources. In particular, EPA 

will investigate the reported contamination of a USDW in Las Animas County, Colorado, where hydraulic 

fracturing took place within the USDW. 
EPA Hydraulic Fracturing Study Plan November 2011

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EPA expects the research outlined above to produce the following:

• Identification of impacts (if any) to drinking water resources from hydraulic fracturing within a 

drinking water aquifer.

Prospective case studies. The prospective case studies will give EPA a better understanding of the 

processes and tools used to determine the location of local geologic and/or man-made features prior to 

hydraulic fracturing. EPA will also evaluate the impacts of local geologic and/or man-made features on 

the fate and transport of chemical contaminants to drinking water resources by measuring water quality 

before, during, and after injection. EPA is exploring the possibility of using chemical tracers to track the 

fate and transport of injected fracturing fluids. The tracers may be used to determine if fracturing fluid 

migrates from the targeted formation to an aquifer via existing natural or man-made pathways.

EPA expects the research outlined above to produce the following:

• Identification of methods and tools used to determine existing faults, fractures, and abandoned 

wells.

• Data on the potential for hydraulic fractures to interact with existing natural features.

Scenario evaluation. The modeling tools described above allow for the exploration of scenarios in which

the presence of local geologic and man-made features leads to contamination of ground or surface 

water resources. EPA will explore three different scenarios: 

• Induced fractures reaching compromised abandoned wells that intersect and communicate with 

ground water aquifers. 

• Induced fractures reaching ground or surface water resources or permeable formations that 

communicate with shallower groundwater-bearing strata.

• Sealed or dormant fractures and faults being activated by hydraulic fracturing operations, 

creating pathways for upward migration of fluids and gases.

In these studies, the injection pulses will be distinguished by their near-field, short-term impacts (fate 

and transport of injection fluids) as well as their far-field and long-term impacts (including the 

displacement of native brines or existing gas pockets). These studies will allow the exploration of the 

potential impacts of fracturing on drinking water resources with regard to variations in geology and will 

help to inform the retrospective and prospective case studies.

Data provided by these studies will allow EPA to identify and predict the area of evaluation (AOE) 

around a hydraulic fracturing site. The AOE includes the subsurface zone that may have the potential to 

be impacted by hydraulic fracturing activities and is projected as an area at the land surface. Within this 

area, drinking water resources could be affected by the migration of hydraulic fracturing fluids and 

liberated gases outside the injection zone, as well as the displacement of native brines within the 

subsurface. Maps of the AOEs for multiple injection operations can be overlaid on regional maps to 

evaluate cumulative impacts, and, when compared to regional maps of areas contributing recharge to 
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drinking water wells (source water areas), to evaluate regional vulnerability. The AOE may also be used 

to support contaminant fate and transport hypothesis testing in retrospective case studies.

EPA expects the research outlined above to produce the following:

• Assessment of key conditions that may affect the interaction of hydraulic fractures with existing 

man-made and natural features.

• Identification of the area of evaluation for a hydraulically fractured well.

6.3.4 HOW MIGHT HYDRAULIC FRACTURING FLUIDS CHANGE THE FATE AND TRANSPORT OF SUBSTANCES IN 

THE SUBSURFACE THROUGH GEOCHEMICAL INTERACTIONS?

The injection of hydraulic fracturing fluid chemical additives into targeted geologic formations may alter 

both the injected chemicals and chemicals naturally present in the subsurface. The chemical identity of 

the injected chemicals may change because of chemical reactions in the fluid (e.g., the formation and 

breakdown of gels), reactions with the target formation, or microbe-facilitated transformations. These 

chemical transformation or degradation products could also pose a risk to human health if they migrate 

to drinking water resources.

Reactions between hydraulic fracturing fluid chemical additives and the target formation could increase 

or decrease the mobility of these substances, depending on their properties and the complex 

interactions of the chemical, physical, and biological processes occurring in the subsurface. 

For example, several of the chemicals used in fracturing fluid (e.g., acids and carbonates) are known to 

mobilize naturally occurring substances out of rocks and soils by changing the pH or reduction-oxidation 

(redox) conditions in the subsurface. Conversely, a change in the redox conditions in the subsurface may 

also decrease the mobility of naturally occurring substances (Eby, 2004; Sparks, 1995; Sposito, 1989; 

Stumm and Morgan, 1996; Walther, 2009).

Along with chemical mechanisms, biological processes can change the mobility of fracturing fluid 

additives and naturally occurring substances. Many microbes, for example, are known to produce 

siderophores, which can mobilize metals from the surrounding matrix (Gadd, 2004). Microbes may also 

reduce the mobility of substances by binding to metals or organic substances, leading to the localized 

sequestration of fracturing fluid additives or naturally occurring substances (Gadd, 2004; McLean and 

Beveridge, 2002; Southam, 2000).

6.3.4.1 RESEARCH ACTIVITIES – GEOCHEMICAL INTERACTIONS

Laboratory studies. Using samples obtained from retrospective and prospective case study locations, 

EPA will conduct limited laboratory studies to assess reactions between hydraulic fracturing fluid 

chemical additives and various environmental materials (e.g., shale or aquifer material) collected on site. 

Chemical degradation, biogeochemical reactions, and weathering reactions will be studied by 

pressurizing subsamples of cores, cuttings, or aquifer material in temperature-controlled reaction 

vessels. Data will be collected on the chemical composition and minerology of these materials.

Subsamples will then be exposed to hydraulic fracturing fluids used at the case study locations using 

either a batch or continuous flow system to simulate subsurface reactions. After specific exposure 
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conditions, samples will be drawn for chemical, mineralogical, and microbiological characterization. This 

approach will enable the evaluation of the reaction between hydraulic fracturing fluids and 

environmental media as well as observe chemicals that may be mobilized from the solid phase due to 

biogeochemical reactions. 

EPA expects the research outlined above to produce the following:

• Data on the chemical composition and mineralogy of environmental media.

• Data on the reactions between hydraulic fracturing fluids and environmental media.

• List of chemicals that may be mobilized during hydraulic fracturing activities.

6.3.5 WHAT ARE THE CHEMICAL, PHYSICAL, AND TOXICOLOGICAL PROPERTIES OF SUBSTANCES IN THE 

SUBSURFACE THAT MAY BE RELEASED BY HYDRAULIC FRACTURING OPERATIONS?

As discussed above, multiple pathways may exist that must be considered for the potential to allow 

contaminants to reach drinking water resources. These contaminants may include hydraulic fracturing 

fluid chemical additives and naturally occurring substances, such as those listed in Table 5. Chemical and 

physical properties of naturally occurring substances can help to identify potential exposure pathways 

by describing the mobility of these substances and their possible chemical reactions. 

The toxic effects of naturally occurring substances can be assessed using toxicological properties 

associated with the substances. Table E3 in Appendix E provides examples of naturally occurring 

substances released during hydraulic fracturing operations that may contaminate drinking water 

resources. The toxicity of these substances varies considerably. For example, some naturally occurring 

metals, though they can be essential nutrients, exert various forms of toxicity even at low 

concentrations. Natural gases can also have adverse consequences stemming from their toxicity as well 

as their physical characteristics (e.g., some are very explosive). 

6.3.5.1 RESEARCH ACTIVITIES – CHEMICAL, PHYSICAL, AND TOXICOLOGICAL PROPERTIES

Analysis of existing data. Table E3 in Appendix E lists naturally occurring substances that have been 

found to be mobilized by hydraulic fracturing activities. EPA will also evaluate data from the literature, 

as well as from the laboratory studies described above, on the identity of substances and their 

degradation products released from the subsurface due to hydraulic fracturing. Using this list, EPA will 

then search existing databases to obtain known chemical, physical, and toxicological properties for these

substances. The list will also be used to identify chemicals for further toxicological analysis and analytical 

method development.

EPA expects the research outlined above to produce the following:

• List of naturally occurring substances that are known to be mobilized during hydraulic fracturing 

activities and their associated chemical, physical, and toxicological properties.

• Identification of chemicals that may warrant further toxicological analysis or analytical method 

development.
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Toxicological studies. EPA will identify any potential subsurface chemical currently undergoing ToxCast 

Phase II testing to determine if chemical, physical, and toxicological properties are being assessed. In 

other cases where chemical, physical, and toxicological properties are unknown, EPA will estimate these 

properties using quantitative structure-activity relationships. From this effort, EPA will identify up to six 

chemicals without toxicity values that may be released from the subsurface during hydraulic fracturing 

for ToxCast screening and PPRTV development consideration. More detailed information on 

characterization of the toxicity and human health effects of chemicals of concern is found in Chapter 11.

EPA expects the research outlined above to produce the following:

• Lists of high, low, and unknown priority for naturally occurring substances based on known or 

predicted toxicity data.

• Toxicological properties for up to six naturally occurring substances that have no existing 

toxicological information and are of high concern.

Laboratory studies. The list of chemicals derived from the existing data analysis and toxicological studies 

will inform EPA of high priority chemicals for which existing analytical methods may be inadequate for

detection in drinking water resources. EPA will modify these methods to suit the needs of the research.

EPA expects the research outlined above to produce the following:

• Analytical methods for detecting selected naturally occurring substances released by hydraulic 

fracturing.

6.4 FLOWBACK AND PRODUCED WATER: WHAT ARE THE POSSIBLE IMPACTS OF SURFACE 

SPILLS ON OR NEAR WELL PADS OF FLOWBACK AND PRODUCED WATER ON DRINKING

WATER RESOURCES?

6.4.1 BACKGROUND

After the fracturing event, the pressure is decreased and the direction of fluid flow is reversed, allowing 

fracturing fluid and naturally occurring substances to flow out of the wellbore to the surface before the 

well is placed into production. This mixture of fluids is called “flowback,” which is a subset of produced 

water. The definition of flowback is not considered to be standardized. Generally, the flowback period in 

shale gas reservoirs is several weeks (URS Corporation, 2009), while the flowback period in coalbed 

methane reservoirs appears to be longer (Rogers et al., 2007).

Estimates of the amount of fracturing fluid recovered as flowback in shale gas operations vary from as 

low as 25 percent to high as 70 to 75 percent (Pickett, 2009; Veil, 2010; Horn, 2009). Other estimates 

specifically for the Marcellus Shale project a fracture fluid recovery rate of 10 to 30 percent (Arthur et 

al., 2008). Less information is available for coalbed methane reservoirs. Palmer et al. (1991) estimated a 

61 percent fracturing fluid recovery rate over a 19 day period based on sampling from a single well in 

the Black Warrior Basin. 
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The flow rate at which the flowback exits the well can be relatively high (e.g., >100,000 gallons per day) 

for the first few days. However, this flow diminishes rapidly with time, ultimately dropping to the normal 

rate of produced water flow from a natural gas well (e.g., 50 gallons per day) (Chesapeake Energy, 2010; 

Hayes, 2009b). While there is no clear transition between flowback and produced water, produced 

water is generally considered to be the fluid that exits the well during oil or gas production (API, 2010a; 

Clark and Veil, 2009). Like flowback, produced water also contains fracturing fluid and naturally 

occurring materials, including oil and/or gas. Produced water, however, is generated throughout the 

well’s lifetime. 

The physical and chemical properties of flowback and produced water vary with fracturing fluid 

composition, geographic location, geological formation, and time (Veil et al., 2004). In general, analyses 

of flowback from various reports show that concentrations of TDS can range from approximately 1,500

milligram per liter (mg/L) to more than 300,000 mg/L (Gaudlip and Paugh, 2008; Hayes, 2009a; Horn, 

2009; Keister, 2009; Vidic, 2010; Rowan et al., 2011). The Appalachian Basin tends to produce one of the 

higher TDS concentrations by region in the US, with a mean TDS concentration of 250,000 mg/L (Breit, 

2002). It can take several weeks for the flowback to reach these values.

Along with high TDS values, flowback can have high concentrations of several ions (e.g., barium, 

bromide, calcium, chloride, iron, magnesium, sodium, strontium, bicarbonate), with concentrations of 

calcium and strontium sometimes reported to be as high as thousands of milligrams per liter (Vidic, 

2010). Flowback likely contains radionuclides, with the concentration varying by formation (Zielinski and 

Budahn, 2007; Zoback et al., 2010; Rowan et al., 2011). Flowback from Marcellus Shale formation 

operations has been measured at concentrations up to 18,000 picocuries per liter (pCi/L; Rowan et al., 

2011) and elsewhere in the US above 10,000 pCi/L (USGS, 1999). Volatile organic compounds (VOCs), 

including but not limited to benzene, toluene, xylenes, and acetone, have also been detected (URS 

Corporation, 2009; NYSDEC, 2011). A list of chemicals identified in flowback and produced water is 

presented in Table E2 in Appendix E. Additionally, flowback has been reported to have pH values ranging 

from 5 to 8 (Hayes, 2009a). A limited time series monitoring program of post-fracturing flowback fluids 

in the Marcellus Shale indicated increased concentrations over time of TDS, chloride, barium, and 

calcium; water hardness; and levels of radioactivity (URS Corporation, 2009; Rowen et al., 2011).

Flowback and produced water from hydraulic fracturing operations are held in storage tanks and waste 

impoundment pits prior to or during treatment, recycling, and disposal (GWPC, 2009). Impoundments 

may be temporary (e.g., reserve pits for storage) or long-term (e.g., evaporation pits used for 

treatment). Requirements for impoundments can vary by location. In areas of New York overlying the 

Marcellus Shale, regulators are requiring water-tight tanks to hold flowback water (ICF, 2009b; NYSDEC, 

2011).

6.4.2 WHAT IS CURRENTLY KNOWN ABOUT THE FREQUENCY, SEVERITY, AND CAUSES OF SPILLS OF FLOWBACK 

AND PRODUCED WATER?

Surface spills or releases of flowback and produced water (collectively referred to as “hydraulic 

fracturing wastewaters”) can occur as a result of tank ruptures, equipment or surface impoundment 

failures, overfills, vandalism, accidents, ground fires, or improper operations. Released fluids might flow 
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into a nearby surface water body or infiltrate into the soil and near-surface ground water, potentially 

reaching drinking water aquifers (NYSDEC, 2011). However, it remains unclear how often spills of this 

nature occur, how severe these spills are, and what causes them. To better understand potential 

impacts to drinking water resources from surface spills, EPA is interested in learning about the range of 

volumes and reported impacts associated with surface spills of hydraulic fracturing wastewaters.

6.4.2.1 RESEARCH ACTIVITIES – SURFACE SPILLS OF FLOWBACK AND PRODUCED WATER

Analysis of existing data. EPA will available existing information on the frequency, severity, and causes 

of spills of flowback and produced water. These data will come from a variety of sources, including 

information provided by nine oil and gas operators received in response to EPA’s August 2011 

information request. In this request, EPA asked for spill incident reports for any fluid spilled at 350 

different well sites across the US. Other sources of data are expected to include spills reported to the 

National Response Center, state departments of environmental protection (e.g., Pennsylvania and West 

Virginia), EPA’s Natural Gas Drilling Tipline, and others.

EPA will assess the data provided by these sources to create a national picture of reported surface spills 

of flowback and produced water. The goal of this effort is to provide a representative assessment of the 

frequency, severity, and causes of surface spills associated with flowback and produced water.

EPA expects the research outlined above to produce the following:

• Data on the frequency, severity, and common causes of spills of hydraulic fracturing flowback 

and produced water.

6.4.3 WHAT IS THE COMPOSITION OF HYDRAULIC FRACTURING WASTEWATERS, AND WHAT FACTORS MIGHT 

INFLUENCE THIS COMPOSITION?

Flowback and produced water can be composed of injected fracturing fluid, naturally occurring 

materials already present in the target formation, and any reaction or degradation products formed 

during the hydraulic fracturing process. Much of the existing data on the composition of flowback and 

produced water focuses on the detection of ions in addition to pH and TDS measurements, as described 

above. There has been an increased interest in identifying and quantifying the components of flowback 

and produced water since the composition of these wastewaters affects the treatment and 

recycling/disposal of the waste (Blauch, 2011; Hayes, 2011; J. Lee, 2011a). However, less is known about 

the composition and variability of flowback and produced water with respect to the chemical additives 

found in hydraulic fracturing fluids, reaction and degradation products, or radioactive materials.

The composition of flowback and produced water has also been shown to vary with location and time. 

For example, data from the USGS produced water database indicate that the distribution of major ions, 

pH, and TDS levels is not only variable on a national scale (e.g., between geologic basins), but also on the 

local scale (e.g., within one basin) (USGS, 2002). Studies have also shown that the composition of 

flowback changes dramatically over time (Blauch, 2011; Hayes, 2011). A better understanding of the 

spatial and temporal variability of flowback and produced water could lead to improved predictions of 
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the identity and toxicity of chemical additives and naturally occurring substances in hydraulic fracturing 

wastewaters.

6.4.3.1 RESEARCH ACTIVITIES – COMPOSITION OF FLOWBACK AND PRODUCED WATER

Analysis of existing data. EPA requested data on the composition of flowback and produced water in the 

information request sent to nine hydraulic fracturing service companies and nine oil and gas operators

(Appendix D). EPA will use these data, and any other suitable data it can locate, to better understand 

what chemicals are likely to be found in flowback and produced water, the variation in chemical 

concentrations of those chemicals, and what factors may influence their presence and abundance. In 

this manner, EPA may be able to identify potential chemicals of concern (e.g., fracturing fluid additives, 

metals, and radionuclides) in flowback and produced water based on their chemical, physical, and 

toxicological properties. 

EPA expects the research outlined above to produce the following:

• A list of chemicals found in flowback and produced water.

• Information on distribution (range, mean, median) of chemical concentrations.

• Identification of factors that may influence the composition of flowback and produced water.

• Identification of the constituents of concern present in hydraulic fracturing wastewaters.

Prospective case studies. EPA will draw samples of flowback and produced water as part of the full water 

lifecycle monitoring at prospective case study sites. At these sites, flowback and produced water will be 

sampled periodically following the completion of the injection of hydraulic fracturing fluids into the 

formation. Samples will be analyzed for the presence of fracturing fluid chemicals and naturally 

occurring substances found in formation samples analyzed prior to fracturing. This will allow EPA to 

study the composition and variability of flowback and produced water over a given period of time at two 

different locations in the Marcellus Shale and the Haynesville Shale. 

EPA expects the research outlined above to produce the following:

• Data on composition, variability, and quantity of flowback and produced water as a function

of time.

6.4.4 WHAT ARE THE CHEMICAL, PHYSICAL, AND TOXICOLOGICAL PROPERTIES OF HYDRAULIC FRACTURING

WASTEWATER CONSTITUENTS?

Chemical, physical, and toxicological properties can be used to aid identification of potential exposure 

pathways and chemicals of concern related to hydraulic fracturing wastewaters. For example, chemical 

and physical properties—such as diffusion coefficients, partition, factors and distribution coefficients—

can help EPA understand the mobility of different chemical constituents of flowback and produced 

water in various environmental media (e.g., soil and water). These and other properties will help EPA 

determine which chemicals in hydraulic fracturing wastewaters may be more likely to appear in drinking 

water resources. At the same time, toxicological properties can be used to determine chemical 

constituents that may be harmful to human health. By identifying those chemicals that have a high 
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mobility and substantial toxicity, EPA can identify a set of chemicals of concern associated with flowback 

and produced water.

6.4.4.1 RESEARCH ACTIVITIES – CHEMICAL, PHYSICAL, AND TOXICOLOGICAL PROPERTIES

Analysis of existing data. EPA will use the data compiled as described in Sections 6.2.3 and 6.4.4 to 

create a list of chemicals found in flowback and produced water. As outlined in Section 6.2.4, EPA will 

then search existing databases to obtain known chemical, physical, and toxicological properties for the 

chemicals in the inventory. EPA expects to identify a list of 10 to 20 chemicals of concern found in 

hydraulic fracturing wastewaters. The criteria for selecting these chemicals of concern include, but are 

not limited to: (1) the frequency of occurrence in hydraulic fracturing wastewater; (2) the toxicity of the 

chemical; (3) the fate and transport of the chemical (e.g., mobility in the environment); and (4) the 

availability of detection methods.

EPA expects the research outlined above to produce the following:

• List of flowback and produced water constituents with known chemical, physical, and 

toxicological properties.

• Identification of constituents that may be of high concern, but have no existing toxicological 

information.

Toxicological studies. EPA will determine if any identified chemical present in flowback or produced 

water is currently undergoing ToxCast Phase II testing to determine if chemical, physical, and 

toxicological properties are being assessed. In other cases where chemical, physical, and toxicological 

properties are unknown, EPA will estimate these properties using quantitative structure-activity 

relationships. From this effort, EPA will identify up to six chemicals without toxicity values that may be 

present in hydraulic fracturing wastewaters for ToxCast screening and PPRTV development 

consideration. More detailed information on characterization of the toxicity and human health effects 

of chemicals of concern is found in Chapter 11.

EPA expects the research outlined above to produce the following:

• Lists of high, low, and unknown priority chemicals based on known or predicted toxicity data.

• Toxicological properties for up to six hydraulic fracturing wastewater constituents that have no 

existing toxicological information and are of high concern. 

Laboratory studies. The list of chemicals derived from the existing data analysis and toxicological studies 

will inform EPA of high priority chemicals for which existing analytical methods may be inadequate for

detection in hydraulic fracturing wastewaters. EPA will modify these methods to suit the needs of the 

research.

EPA expects the research outlined above to produce the following:

• Analytical methods for detecting hydraulic fracturing wastewater constituents.
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6.4.5 IF SPILLS OCCUR, HOW MIGHT HYDRAULIC FRACTURING WASTEWATERS CONTAMINATE DRINKING 

WATER RESOURCES?

There may be opportunities for wastewater contamination of drinking water resources both below and 

above ground. If the mechanical integrity of the well has been compromised, there is the potential for 

flowback and produced water traveling up the wellbore to have direct access to local aquifers, leading to 

the contamination of drinking water resources. Once above ground, flowback and produced water are 

stored on-site in storage tanks and waste impoundment pits, and then may be transported off-site for 

treatment and/or disposal. There is a potential for releases, leaks, and/or spills associated with the 

storage and transportation of flowback and produced water, which could lead to contamination of 

shallow drinking water aquifers and surface water bodies. Problems with the design, construction, 

operation, and closure of waste impoundment pits may also provide opportunities for releases, leaks, 

and/or spills. To understand exposure pathways related to surface spills of hydraulic fracturing 

wastewaters, EPA must consider both site-specific factors and chemical- or fluid-specific factors that 

govern surface spills (e.g., chemical and physical properties of the fluid).

6.4.5.1 RESEARCH ACTIVITIES – CONTAMINATION PATHWAYS

Analysis of existing data. This approach used here is similar to that described in Section 6.2.5.1 for 

surface spills associated with the mixing of hydraulic fracturing fluids. Surface spills of chemicals, in 

general, can occur under a variety of conditions. There already exists a body of scientific literature that 

describes how a chemical solution released on the ground can infiltrate the subsurface and/or run off to 

a surface water body. EPA will use the list of chemicals found in hydraulic fracturing wastewaters 

generated through the research described in Section 6.4.3.1 to identify individual chemicals and classes 

of chemicals for review in the existing scientific literature. EPA will then identify relevant research on the 

fate and transport of these chemicals. The research will be summarized to determine the known impacts 

of spills of fracturing fluid wastewaters on drinking water resources, and to identify existing knowledge 

gaps related to surface spills of flowback and produced water.

EPA expects the research outlined above to produce the following:

• Summary of existing research that describes the fate and transport of chemicals in hydraulic 

fracturing wastewaters of similar compounds.

• Identification of knowledge gaps for future research, if necessary.

Retrospective case studies. Accidental releases from wastewater pits and tanks, supply lines, or leaking 

valves have been reported at some of the candidate case study sites (listed in Appendix F). EPA has 

identified three retrospective case study locations to investigate surface spills of hydraulic fracturing 

wastewaters: Wise and Denton Counties, Texas; Bradford and Susquehanna Counties, Pennsylvania; and 

Washington County, Pennsylvania. The studies will provide an opportunity to identify any impacts to 

drinking water resources from surface spills. If impacts are found to have occurred, EPA will determine 

the factors that were responsible for the contamination.
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EPA expects the research outlined above to produce the following:

• Identification of impacts (if any) to drinking water resources from surface spills of hydraulic 

fracturing wastewater.

• Identification of factors that led to impacts (if any) to drinking water resources resulting from 

the accidental release of hydraulic fracturing wastewaters.

6.5 WASTEWATER TREATMENT AND WASTE DISPOSAL: WHAT ARE THE POSSIBLE IMPACTS OF 

INADEQUATE TREATMENT OF HYDRAULIC FRACTURING WASTEWATERS ON DRINKING

WATER RESOURCES?

6.5.1 BACKGROUND

Wastewaters associated with hydraulic fracturing can be managed through disposal or treatment, 

followed by discharge to surface water bodies or reuse. Regulations and practices for management and 

disposal of hydraulic fracturing wastes vary by region and state, and are influenced by local and regional

infrastructure development as well as geology, climate, and formation composition. Underground 

injection is the primary method for disposal in all major gas shale plays, except the Marcellus Shale 

(Horn, 2009; Veil, 2007 and 2010). Underground injection can be an effective way to manage 

wastewaters, although insufficient capacity and the costs of trucking wastewater to an injection site can 

sometimes be problematic (Gaudlip and Paugh, 2008; Veil, 2010). 

In shale gas areas near population centers (e.g., the Marcellus Shale), wastewater treatment at publicly 

owned treatment works (POTWs) or commercial wastewater treatment facilities (CWTs) may be an 

option for some operations. CWTs may be designed to treat the known constituents in flowback or 

produced water while POTWs are generally not able to do so effectively. For example, large quantities of 

sodium and chloride are detrimental to POTW digesters and can result in high TDS concentrations in the 

effluent (Veil, 2010; West Virginia Water Research Institute, 2010). If the TDS becomes too great in the 

effluent, it may harm drinking water treatment facilities downstream from POTWs. Additionally, POTWs 

are not generally equipped to treat fluids that contain radionuclides, which may be released from the 

formation during hydraulic fracturing. Elevated levels of bromide, a constituent of flowback in many 

areas, can also create problems for POTWs. Wastewater plants using chlorination as a treatment 

process will produce more brominated disinfection byproducts (DBPs), which have significant health 

concerns at high exposure levels. Bromides discharged to drinking water sources may also form DBPs

during the treatment process. When POTWs are used, there may be strict limits on the volumes 

permitted. In Pennsylvania, for example, the disposal of production waters at POTWs is limited to less 

than 1 percent of the POTW’s average daily flow (Pennsylvania Environmental Quality Board, 2009). 

As noted earlier, recycling of flowback for use in fracturing other wells is becoming increasingly common 

and is facilitated by developments in on-site treatment to prepare the flowback for reuse. Researchers 

at Texas A&M, for example, are developing a mobile treatment system that is being pilot tested in the 

Barnett Shale (Pickett, 2009). In addition to being used for fracturing other wells, hydraulic fracturing 

wastewater may be also treated on-site to meet requirements for use in irrigation or for watering 
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livestock (Horn, 2009). Given the logistical and financial benefits to be gained from treatment of 

flowback water, continued developments in on-site treatment technologies are expected.

6.5.2 WHAT ARE THE COMMON TREATMENT AND DISPOSAL METHODS FOR HYDRAULIC FRACTURING 

WASTEWATERS, AND WHERE ARE THESE METHODS PRACTICED?

As mentioned earlier, common treatment and disposal methods for hydraulic fracturing wastewaters 

include underground injection in Class II underground injection control (UIC) wells, treatment followed 

by surface discharge, and treatment followed by reuse as hydraulic fracturing fluid. Treatment, disposal, 

and reuse of flowback and produced water from hydraulic fracturing activities are important because of 

the contaminants present in these waters and their potential for adverse human health impacts. Recent 

events in West Virginia and Pennsylvania have focused public attention on the treatment and discharge 

of flowback and produced water to surface waters via POTWs (Puko, 2010; Ward Jr., 2010; Hopey, 

2011). The concerns raised by the public have prompted Pennsylvania to request that oil and gas 

operators not send hydraulic fracturing wastewaters to 15 facilities within the state (Hopey and Hamill, 

2011; Legere, 2011). While this issue has received considerable public attention, EPA is aware that many 

oil and gas operators use UIC wells as their primary disposal option. Treatment and recycling of flowback 

and produced water are becoming more common in areas where underground injection is not currently 

feasible. 

6.5.2.1 RESEARCH ACTIVITIES – TREATMENT AND DISPOSAL METHODS

Analysis of existing data. As part of the information request to nine oil and gas well operators, EPA 

asked for information relating to the disposal of wastewater generated at 350 wells across the US. 

Specifically, EPA asked for the volume and final disposition of flowback and produced water, as well as 

information relating to recycling of hydraulic fracturing wastewaters (e.g., recycling procedure, volume 

of fluid recycled, use of recycled fluid, and disposition of any waste generated during recycling). EPA will 

use the information received to obtain a nationwide perspective of recycling, treatment, and disposal 

methods currently being used by nine oil and gas operators.

EPA expects the research outlined above to produce the following:

• Nationwide data on recycling, treatment, and disposal methods for hydraulic fracturing 

wastewaters.

Prospective case studies. While conducting prospective case studies in the Marcellus and Haynesville 

Shales, EPA will collect information on the types of recycling, treatment, and disposal practices used at

the two different locations. These areas are illustrative of a region where UIC wells are a viable disposal 

option (Haynesville Shale) and where recycling is becoming more common (Marcellus Shale). 

EPA expects the research outlined above to produce the following:

• Information on wastewater recycling, treatment, and disposal practices at two specific locations.
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6.5.3 HOW EFFECTIVE ARE CONVENTIONAL POTWS AND COMMERCIAL TREATMENT SYSTEMS IN REMOVING 

ORGANIC AND INORGANIC CONTAMINANTS OF CONCERN IN HYDRAULIC FRACTURING WASTEWATERS?

For toxic constituents that are present in wastewater, their separation and appropriate disposal is the 

most protective approach for reducing potential adverse impacts on drinking water resources. Much is 

unknown, however, about the efficacy of current treatment processes for removing certain flowback 

and produced water constituents, such as fracturing fluid additives and radionuclides. Additionally, the 

chemical composition and concentration of solid residuals created by wastewater treatment plants that 

treat hydraulic fracturing wastewater, and their subsequent disposal, warrants more study.

Recycling and reuse of flowback and produced water may not completely alleviate concerns associated 

with treatment and disposal of hydraulic fracturing wastewaters. While recycling and reuse reduce the 

immediate need for treatment and disposal—and also reduce water acquisition needs—there will likely 

be a need to treat and properly dispose of the final concentrated volumes of wastewater from a given 

area of operation. 

6.5.3.1 RESEARCH ACTIVITIES – TREATMENT EFFICACY

Analysis of existing data. EPA will gather existing data on the treatment efficiency and contaminant fate 

and transport through POTWs and CWTs that have treated hydraulic fracturing wastewaters. Emphasis 

will be placed on inorganic and organic contaminants, the latter being an area that has the least 

historical information, and hence the greatest opportunity for advancement in treatment. This 

information will enable EPA to assess the efficacy of existing treatment options and will also identify 

areas for further research. 

EPA expects the research outlined above to produce the following:

• Collection of analytical data on the efficacy of treatment operations that treat hydraulic 

fracturing wastewaters.

• Identification of areas for further research.

Laboratory studies. Section 6.4.3.1 describes research on the composition and variability of hydraulic 

fracturing wastewaters, and on the identification of chemicals of concern in flowback and produced 

water. This information will be coupled with available data on treatment efficacy to design laboratory 

studies on the treatability, fate, and transport of chemicals of concern, including partitioning in 

treatment residues. Studies will be conducted using a pilot-scale wastewater treatment system

consisting of a primary clarifier, activated sludge basin, and secondary clarifier. Commercial treatment 

technologies will also be assessed in the laboratory using actual or synthetic hydraulic fracturing 

wastewater. 

EPA expects the research outlined above to produce the following:

• Data on the fate and transport of hydraulic fracturing water contaminants through wastewater 

treatment processes, including partitioning in treatment residuals.
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Prospective case studies. To the extent possible, EPA will evaluate the efficacy of treatment practices 

used at the prospective case study locations in Pennsylvania and Louisiana by sampling both pre- and 

post-treatment wastewaters. It is expected that such studies will include on-site treatment, use of 

wastewater treatment plants, recycling, and underground injection control wells. In these cases, EPA 

will identify the fate and transport of hydraulic fracturing wastewater contaminants throughout the 

treatment and will characterize the contaminants in treatment residuals. 

EPA expects the research outlined above to produce the following:

• Data on the efficacy of treatment methods used in two locations.

6.5.4 WHAT ARE THE POTENTIAL IMPACTS FROM SURFACE WATER DISPOSAL OF TREATED HYDRAULIC 

FRACTURING WASTEWATER ON DRINKING WATER TREATMENT FACILITIES?

Drinking water treatment facilities could be negatively impacted by hydraulic fracturing wastewaters 

when treatment is followed by surface discharge. For example, there is concern that POTWs may be 

unable to treat the TDS concentrations potentially found in flowback and produced water, which would

lead to high concentrations of both chloride and bromide in the effluent. High TDS levels (>500 mg/L) 

have been detected in the Monongahela and Youghiogheny Rivers in 2008 and 2010, respectively (J. Lee, 

2011b; Ziemkiewicz, 2011). The source of these high concentrations is unknown, however, and they 

could be due to acid mine drainage treatment plants, active or abandoned coal mines, or shale gas 

operations. Also, it is unclear how these high TDS concentrations may affect drinking water treatment 

facilities. It is believed that increased concentrations of chloride and bromide may lead to higher levels 

of both chlorinated and brominated DBPs at drinking water treatment facilities. The presence of high 

levels of bromide in waters used by drinking water systems that disinfect through chlorination can lead 

to higher concentrations of brominated DBPs, which may be of greater concern from a human health 

perspective than chlorinated DBPs (Plewa and Wagner, 2009). Also, because of their inherent higher 

molecular weight, brominated DBPs will result in higher concentrations (by weight) than their 

chlorinated counterparts (e.g., bromoform versus chloroform). This has the potential to cause a drinking 

water utility to exceed the current DBP regulatory limits.

High chloride and bromide concentrations are not the only factors to be addressed regarding drinking 

water treatment facilities. Other chemicals, such as naturally occurring radioactive material, may also 

present a problem to drinking water treatment facilities that are downstream from POTWs or CWTs that 

ineffectively treat hydraulic fracturing wastewaters. To identify potential impacts to drinking water 

treatment facilities, it is important to be able to determine concentrations of various classes of 

chemicals of concern at drinking water intakes. 

6.5.4.1 RESEARCH ACTIVITIES – POTENTIAL DRINKING WATER TREATMENT IMPACTS

Laboratory studies. EPA will conduct laboratory studies on the formation of DBPs in hydraulic fracturingimpacted waters (e.g., effluent from a wastewater treatment facility during processing of hydraulic 

fracturing wastewater), with an emphasis on the formation of brominated DBPs. These studies will 

explore two sources of brominated DBP formation: hydraulic fracturing chemical additives and high 

levels of bromide in flowback and produced water. In the first scenario, water samples with known 
EPA Hydraulic Fracturing Study Plan November 2011

52

amounts of brominated hydraulic fracturing chemical additives will be equilibrated with chlorine, 

chloramines, and ozone disinfectants. EPA will then analyze these samples for regulated 

trihalomethanes (i.e., chloroform, bromoform, bromodichloromethane, and dibromochloromethane), 

haloacetic acids, and nitrosamines. In the second scenario, EPA will use existing peer-reviewed models 

to identify problematic concentrations of bromide in source waters. 

If actual samples of hydraulic fracturing-impacted source waters can be obtained, EPA will perform 

laboratory studies to establish baseline parameters for the sample (e.g., existing bromide concentration, 

total organic concentrations, and pH). The samples will then be subjected to chlorination, 

chloramination, and ozonation and analyzed for brominated DBPs. 

If possible, EPA will identify POTWs or CWTs that are currently treating and discharging hydraulic 

fracturing wastewaters to surface waters. EPA will then collect discharge and stream samples during 

times when these treatment facilities are and are not processing hydraulic fracturing wastewaters. This 

will improve EPA’s understanding of how contaminants in the treated effluent change when treated 

hydraulic fracturing wastewaters are discharged to surface water. EPA will also assess how other sources 

of contamination (e.g., acid mine drainage) alter contaminant concentrations in the effluent. The goal of 

this effort is to identify when hydraulic fracturing wastewaters are the cause of high levels of TDS or 

other contaminants at drinking water treatment facilities.

EPA expects the research outlined above to produce the following:

• Data on the formation of brominated DBPs from chlorination, chloramination, and ozonation 

treatments of water receiving treated effluent from hydraulic fracturing wastewater treatment.

• Data on the inorganic species in hydraulic fracturing wastewater and other discharge sources 

that contribute similar species.

• Contribution of hydraulic fracturing wastewater to stream/river contamination. 

Scenario evaluations. Scenario evaluations will be used to identify potential impacts to drinking water 

treatment facilities from surface discharge of treated hydraulic fracturing wastewaters. To accomplish 

this, EPA will first construct a simplified model of an idealized river section with generalized wastewater 

treatment discharges and drinking water intakes. To the extent possible, the characteristics of the 

discharges will be generated based on actual representative information. This model will be able to 

generate a general guide to releases of treated hydraulic fracturing wastewaters that allows exploration 

of a range of parameters that may affect drinking water treatment intakes (e.g., discharge rates and 

concentrations, river flow rates, and distances).

In a second step, EPA will create a watershed-specific scenario that will include the location of specific 

wastewater and drinking water treatment facilities. Likely candidates for this more detailed scenario 

include the Monongahela, Allegheny, or Susquehanna River networks. The final choice will be based on 

the availability of data on several parameters, including the geometry of the river network and flows, 

and hydraulic fracturing wastewater discharges. The primary result will be an assessment of the 

potential impacts from disposal practices on specific watersheds. Secondarily, the results of the 

watershed-specific scenario will be compared to the simplified scenario to determine the ability of the 
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simplified model to capture specific watershed characteristics. Taken together, the two parts of this 

work will allow EPA to assess the potential impacts of chemicals of concern in flowback and produced 

water at drinking water treatment intakes.

EPA expects the research outlined above to produce the following:

• Identification of parameters that generate or mitigate drinking water exposure.

• Data on potential impacts in the Monongahela, Allegheny, or Susquehanna River networks.

7 ENVIRONMENTAL JUSTICE ASSESSMENT

Environmental justice is the fair treatment and meaningful involvement of all people regardless of race, 

color, national origin, or income with respect to the development, implementation, and enforcement of 

environmental laws, regulations, and policies. Achieving environmental justice is an Agency-wide 

priority (USEPA, 2010d) and is therefore considered in this study plan.

Stakeholders have raised concerns about the environmental justice implications of gas drilling 

operations. It has been suggested that people with a lower socioeconomic status may be more likely to 

consent to drilling arrangements, due to the greater economic need of these individuals, or their more 

limited ability or willingness to engage with policymakers and agencies. Additionally, since drilling 

agreements are between landowners and well operators, tenants and neighbors may have little or no 

input in the decision-making process.

In response to these concerns, EPA has included in the study plan a screening analysis of whether 

hydraulic fracturing activities may be disproportionately occurring in communities with environmental 

justice concerns. An initial screening assessment will be conducted to answer the following fundamental 

research question:

• Does hydraulic fracturing disproportionately occur in or near communities with environmental 

justice concerns?

Consistent with the framework of the study plan, the environmental justice assessment will focus on the 

spatial locations of the activities associated with the five stages of the water lifecycle (Figure 1). Each 

stage of the water lifecycle can be categorized as either occurring onsite (chemical mixing, well injection, 

and flowback and produced water) or offsite (water acquisition and wastewater treatment/disposal). 

Because water acquisition, onsite activities and wastewater treatment/disposal generally occur in 

different locations, EPA has identified three secondary research questions: 

• Are large volumes of water for hydraulic fracturing being disproportionately withdrawn from 

drinking water resources that serve communities with environmental justice concerns? 

• Are hydraulically fractured oil and gas wells disproportionately located near communities with 

environmental justice concerns?
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• Is wastewater from hydraulic fracturing operations being disproportionately treated or disposed 

of (via POTWs or commercial treatment systems) in or near communities with environmental 

justice concerns?

The following sections outline the research activities associated with each of these secondary research 

questions.

7.1.1 ARE LARGE VOLUMES OF WATER FOR HYDRAULIC FRACTURING BEING DISPROPORTIONATELY 

WITHDRAWN FROM DRINKING WATER RESOURCES THAT SERVE COMMUNITIES WITH ENVIRONMENTAL 

JUSTICE CONCERNS?

7.1.1.1 RESEARCH ACTIVITIES – WATER ACQUISITION LOCATIONS

Analysis of existing data. To the extent data are available, EPA will identify locations where large volume 

water withdrawals are occurring to support hydraulic fracturing activities. These data will be compared

to demographic information from the US Census Bureau on race/ethnicity, income, and age, and then

GIS mapping will be used to obtain a visual representation of the data. This will allow EPA to screen for 

locations where large volume water withdrawals may be disproportionately co-located in or near

communities with environmental justice concerns. Locations for further study may be identified, 

depending on the results of this study.

EPA expects the research outlined above to produce the following:

• Maps showing locations of source water withdrawals for hydraulic fracturing and demographic 

data.

• Identification of areas where there may be a disproportionate co-localization of hydraulic 

fracturing water withdrawals and communities with environmental justice concerns.

Prospective case studies. Using data from the US Census Bureau, EPA will also evaluate the demographic 

profile of communities that may be served by water resources used for hydraulic fracturing of the 

prospective case study sites.

EPA expects the research outlined above to produce the following:

• Information on the demographic characteristics of communities in or near the two case study 

sites where hydraulic fracturing water withdrawals occur.

7.1.2 ARE HYDRAULICALLY FRACTURED OIL AND GAS WELLS DISPROPORTIONATELY LOCATED NEAR COMMUNITIES 

WITH ENVIRONMENTAL JUSTICE CONCERNS?

7.1.2.1 RESEARCH ACTIVITIES – WELL LOCATIONS

Analysis of existing data. As a part of the information request sent by EPA to nine hydraulic fracturing 

companies (see Appendix C), EPA asked for the locations of sites where hydraulic fracturing operations 

occurred between 2009 and 2010. EPA will compare these data to demographic information from the 

US Census Bureau on race/ethnicity, income, and age, and use GIS mapping to visualize the data. An 
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55

assessment of these maps will allow EPA to screen for locations where hydraulic fracturing may be 

disproportionately co-located with communities that have environmental justice concerns. Depending 

upon the outcome of this analysis, locations for further study may be identified.

EPA expects the research outlined above to produce the following:

• Maps showing locations of hydraulically fractured wells (subject to CBI rules) and demographic 

data.

• Identification of areas where there may be a disproportionate co-localization of hydraulic 

fracturing well sites and communities with environmental justice concerns.

Retrospective and prospective case studies. EPA will evaluate the demographic profiles of communities 

near prospective case study sites and communities potentially affected by reported contamination on 

retrospective case study sites. An analysis of these data will provide EPA with information on the specific 

communities located at case study locations.

EPA expects the research outlined above to produce the following:

• Information on the demographic characteristics of the communities where hydraulic fracturing 

case studies were conducted.

7.1.3 IS WASTEWATER FROM HYDRAULIC FRACTURING OPERATIONS BEING DISPROPORTIONATELY TREATED OR

DISPOSED OF (VIA POTWS OR COMMERCIAL TREATMENT SYSTEMS) IN OR NEAR COMMUNITIES WITH 

ENVIRONMENTAL JUSTICE CONCERNS?

7.1.3.1 RESEARCH ACTIVITIES – WASTEWATER TREATMENT/DISPOSAL LOCATIONS

Analysis of existing data. To the extent data are available, EPA will compile a list of wastewater 

treatment plants accepting wastewater from hydraulic fracturing operations. These data will be 

compared to demographic information from the US Census Bureau on race/ethnicity, income, and age, 

and then GIS mapping will be used to visualize the data. This will allow EPA to screen for locations where 

POTWs and commercial treatment works may be disproportionately co-located near communities with 

environmental justice concerns, and may identify locations for further study.

EPA expects the research outlined above to produce the following:

• Maps showing locations of hydraulic fracturing wastewater treatment facilities and 

demographic data.

• Identification of areas where there may be a disproportionate co-localization of hydraulic 

fracturing wastewater treatment facilities and communities with environmental justice 

concerns.

Prospective case studies. Using data available from the US Census Bureau, EPA will evaluate the 

demographic profile of communities near treatment and disposal operations that accept wastewater 

associated with hydraulic fracturing operations. 
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EPA expects the research outlined above to produce the following:

• Information on the demographics of communities where treatment and disposal of wastewater 

from hydraulic fracturing operations at the prospective case study sites has occurred.

8 ANALYSIS OF EXISTING DATA

As outlined in Chapter 6, EPA will evaluate data provided by a variety of stakeholders to answer the 

research questions posed in Table 1. This chapter describes the types of data EPA will be collecting as 

well as the approach used for collecting and analyzing these data.

8.1 DATA SOURCES AND COLLECTION

8.1.1 PUBLIC DATA SOURCES

The data described in Chapter 6 will be obtained from a variety of sources. Table 6 provides a selection 

of public data sources EPA intends to use for the current study. The list in the table is not intended to be 

comprehensive. EPA will also access data from other sources, including peer-reviewed scientific 

literature, state and federal reports, and other data sources shared with EPA. 

8.1.2 INFORMATION REQUESTS

In addition to publicly available data, EPA has requested information from the oil and gas industry 

through two separate information requests.11 The first information request was sent to nine hydraulic 

fracturing service companies in September 2010, asking for the following information: 

• Data on the constituents of hydraulic fracturing fluids—including all chemicals, proppants, and 

water—used in the last five years.

• All data relating to health and environmental impacts of all constituents listed.

• All standard operating procedures and information on how the composition of hydraulic 

fracturing fluids may be modified on site.

• All sites where hydraulic fracturing has occurred or will occur within one year of the request 

date.

The nine companies claimed much of the data they submitted to be CBI. EPA will, in accordance with 40 

C.F.R. Part 2 Subpart B, treat these data as such until EPA determines whether or not they are CBI. 

A second information request was sent to nine oil and gas well operators in August 2011, asking for the 

complete well files for 350 oil and gas production wells. These wells were randomly selected from a list 

of 25,000 oil and gas production wells hydraulically fractured during a one-year period of time. The wells 

were chosen to illustrate their geographic diversity in the continental US. 

 11 The complete text of these information requests can be found in Appendix D.
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TABLE 6. PUBLIC DATA SOURCES EXPECTED TO BE USED AS PART OF THIS STUDY

Source Type of Data Applicable Secondary Research Questions

Susquehanna 

River Basin 

Commission

Water use for hydraulic 

fracturing in the 

Susquehanna River Basin

• How much water is used in hydraulic fracturing operations, and what are the sources of this water?

• What are the possible impacts of water withdrawals for hydraulic fracturing operations on local water 

quality?

Colorado Oil and 

Gas 

Conservation 

Commission

Water use for hydraulic 

fracturing in Garfield 

County, CO

• How much water is used in hydraulic fracturing operations, and what are the sources of this water?

• What are the possible impacts of water withdrawals for hydraulic fracturing operations on local water 

quality?

USGS Water use in US counties 

for 1995, 2000, and 2005

• How might withdrawals affect short- and long-term water availability in an area with hydraulic fracturing 

activity?

State 

departments of 

environmental 

quality or 

departments of 

environmental 

protection

Water quality and 

quantity

Hydraulic fracturing

wastewater composition 

(PA DEP)

• How much water is used in hydraulic fracturing operations, and what are the sources of this water?

• What are the possible impacts of water withdrawals for hydraulic fracturing operations on local water 

quality?

• What is the composition of hydraulic fracturing wastewaters, and what factors might influence this 

composition?

US EPA Toxicity databases (e.g., 

ACToR, DSSTox, HERO,

ExpoCastDB, IRIS, HPVIS, 

ToxCastDB, ToxRefDB)

Chemical and physical 

properties databases 

(e.g., EPI Suite, SPARC)

• What are the chemical, physical, and toxicological properties of hydraulic fracturing chemical additives?

• What are the chemical, physical, and toxicological properties of substances in the subsurface that may be 

released by hydraulic fracturing operations?

• What are the chemical, physical, and toxicological properties of hydraulic fracturing wastewater 

constituents?

National 

Response 

Center

Information on spills 

associated with hydraulic 

fracturing operations

• What is currently known about the frequency, severity, and causes of spills of hydraulic fracturing fluids 

and additives?

• What is currently known about the frequency, severity, and causes of spills of flowback and produced 

water?

US Census 

Bureau

Demographic 

information from the 

2010 Census and the 

2005-2009 American 

Community Survey 5-

Year Estimates

• Are large volumes of water for hydraulic fracturing being disproportionately withdrawn from drinking 

water resources that serve communities with environmental justice concerns? 

• Are hydraulically fractured oil and gas wells disproportionately located near communities with 

environmental justice concerns?

• Is wastewater from hydraulic fracturing operations being disproportionately treated or disposed of (via 

POTWs or commercial treatment systems) in or near communities with environmental justice concerns?
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8.2 ASSURING DATA QUALITY 

As indicated in Section 2.6, each research project must have a QAPP, which outlines the necessary QA 

procedures, quality control activities, and other technical activities that will be implemented for a 

specific project. Projects using existing data are required to develop data assessment and acceptance 

criteria for this secondary data. Secondary data will be assessed to determine the adequacy of the data 

according to acceptance criteria described in the QAPP. All project results will include documentation of 

data sources and the assumptions and uncertainties inherent within those data.

8.3 DATA ANALYSIS

EPA will use the data collected from public sources and information requests to create various outputs, 

including spreadsheets, GIS maps (if possible), and tables. Data determined to be CBI will be 

appropriately managed and reported. These outputs will be used to inform answers to the research 

questions described in Chapter 6 and will also be used to support other research projects, including case 

studies, additional toxicity assessments, and laboratory studies. A complete summary of research 

questions and existing data analysis activities can be found in Appendix A. 

9 CASE STUDIES

This chapter of the study plan describes the rationale for case study selection as well as the approaches 

used in both retrospective and prospective case studies. 

9.1 CASE STUDY SELECTION

EPA invited stakeholders nationwide to nominate potential case studies through informational public

meetings and by submitting comments electronically or by mail. Appendix F contains a list of the 

nominated case study sites. Of the 48 nominations, EPA selected seven sites for inclusion in the study: 

five retrospective sites and two prospective sites. The retrospective case study investigations will focus 

on locations with reported drinking water contamination where hydraulic fracturing operations have 

occurred. At the prospective case study sites, EPA will monitor key aspects of the hydraulic fracturing 

process that cover all five stages of the water cycle. 

The final location and number of case studies were chosen based on the types of information a given 

case study would be able to provide. Table 7 outlines the decision criteria used to identify and prioritize 

retrospective and prospective case study sites. The retrospective and prospective case study sites were 

chosen to represent a wide range of conditions that reflect a spectrum of impacts that may result from

hydraulic fracturing activities. These case studies are intended to provide enough detail to determine 

the extent to which conclusions can be generalized at local, regional, and national scales.
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TABLE 7. DECISION CRITERIA FOR SELECTING HYDRAULIC FRACTURING SITES FOR CASE STUDIES

Selection Step Inputs Needed Decision Criteria

Nomination • Planned, active, or historical

hydraulic fracturing activities

• Local drinking water resources 

• Community at risk

• Site location, description, and 

history

• Site attributes (e.g., physical, 

geology, hydrology)

• Operating and monitoring data, 

including well construction and 

surface management activities

• Proximity of population and drinking water 

supplies

• Magnitude of activity (e.g., density of wells)

• Evidence of impaired water quality

(retrospective only)

• Health and environmental concerns

(retrospective only)

• Knowledge gap that could be filled by a case 

study

Prioritization • Available data on chemical use, 

site operations, health, and 

environmental concerns

• Site access for monitoring wells, 

sampling, and geophysical 

testing

• Potential to collaborate with 

other groups (e.g., federal, 

state, or interstate agencies; 

industry; non-governmental 

organizations, communities; 

and citizens)

• Geographic and geologic diversity

• Diversity of suspected impacts to drinking water 

resources

• Population at risk

• Site status (planned, active, or completed)

• Unique geological or hydrological features

• Characteristics of water resources (e.g., 

proximity to site, ground water levels, surface 

water and ground water interactions, unique 

attributes)

• Multiple nominations from diverse stakeholders

• Land use (e.g., urban, suburban, rural, 

agricultural)

Table 8 lists the retrospective case study locations EPA will investigate as part of this study and 

highlights the areas to be investigated and the potential outcomes expected for each site. The case 

study sites listed in Table 8 are illustrative of the types of situations that may be encountered during 

hydraulic fracturing activities and represent a range of locations. In some of these cases, hydraulic 

fracturing occurred more than a year ago, while in others, the wells were fractured less than a year ago. 

EPA expects to be able to coordinate with other federal and state agencies as well as landowners to 

conduct these studies.
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TABLE 8. RETROSPECTIVE CASE STUDY LOCATIONS

Location Areas to be Investigated Potential Outcomes Applicable Secondary Research Questions

Bakken Shale (oil) –

Killdeer, Dunn Co., ND

• Production well failure 

during hydraulic fracturing

• Suspected drinking water 

aquifer contamination

• Possible soil 

contamination

• Identify sources of well 

failure

• Determine if drinking water 

resources are contaminated 

and to what extent

• If spills occur, how might hydraulic fracturing chemical 

additives contaminate drinking water resources?

• How effective are current well construction practices at 

containing gases and fluids before, during, and after 

fracturing?

• Are hydraulically fractured oil and gas wells 

disproportionately located near communities with 

environmental justice concerns?

Barnett Shale (gas) –

Wise Co., TX

• Spills and runoff leading to 

suspected drinking water 

well contamination

• Determine if private water 

wells and /or drinking water 

resources are contaminated

• Obtain information about 

mechanisms of transport of 

contaminants via spills, leaks, 

and runoff

• If spills occur, how might hydraulic fracturing wastewaters

contaminate drinking water resources?

• Are hydraulically fractured oil and gas wells 

disproportionately located near communities with 

environmental justice concerns?

Marcellus Shale (gas) –

Bradford and 

Susquehanna Cos., PA

• Reported Ground water 

and drinking water well 

contamination 

• Suspected surface water 

contamination from a spill 

of fracturing fluids

• Reported Methane 

contamination of multiple 

drinking water wells

• Determine if drinking water 

wells and or drinking water 

resources are contaminated 

and the source of any 

contamination

• Determine source of methane 

in private wells

• Transferable results due to 

common types of impacts

• If spills occur, how might hydraulic fracturing chemical 

additives contaminate drinking water resources?

• How effective are current well construction practices at 

containing gases and fluids before, during, and after 

fracturing?

• Are hydraulically fractured oil and gas wells 

disproportionately located near communities with 

environmental justice concerns?

Table continued on next page
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Table continued from previous page

Location Areas to be Investigated Potential Outcomes Applicable Secondary Research Questions

Marcellus Shale (gas) –

Washington Co., PA

• Changes in water quality 

in drinking water, 

suspected contamination

• Stray gas in wells

• Leaky surface pits

• Determine if drinking water 

resources are impacted and if 

so, what the sources of any 

impacts or contamination 

may be. Identify 

presence/source of drinking 

water well contamination

• Determine if surface waste 

storage pits are properly 

managed to protect surface 

and ground water

• If spills occur, how might hydraulic fracturing wastewaters

contaminate drinking water resources?

• Are hydraulically fractured oil and gas wells 

disproportionately located near communities with 

environmental justice concerns?

Raton Basin (CBM) –

Las Animas and 

Huerfano Cos., CO

• Potential drinking water 

well contamination 

(methane and other 

contaminants) in an area 

where hydraulic fracturing

is occurring within an 

aquifer

• Determine source of methane

• Determine if drinking water 

resources are impacted and if 

so, what the sources of any 

impacts or contamination 

may be. Identify 

presence/source/

cause of contamination in 

drinking water wells

• Can subsurface migration of fluids or gases to drinking water 

resources occur, and what local geological or man-made 

features may allow this?

• Are hydraulically fractured oil and gas wells 

disproportionately located near communities with 

environmental justice concerns?
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Prospective case studies are made possible by partnerships with federal and state agencies, landowners, 

and industry, as highlighted in Appendix A. EPA will conduct prospective case studies in the following 

areas:

• The Haynesville Shale in DeSoto Parish, Louisiana.

• The Marcellus Shale in Washington County, Pennsylvania.

The prospective case studies will provide information that will help to answer secondary research 

questions related to all five stages of the hydraulic fracturing water cycle, including:

• How might water withdrawals affect short- and long-term water availability in an area with 

hydraulic fracturing activity?

• What are the possible impacts of water withdrawals for hydraulic fracturing options on local 

water quality?

• How effective are current well construction practices at containing gases and fluids before, 

during, and after fracturing?

• What local geologic or man-made factors may contribute to subsurface migration of fluids or 

gases to drinking water resources?

• What is the composition of hydraulic fracturing wastewaters, and what factors might influence 

this composition?

• What are the common treatment and disposal methods for hydraulic fracturing wastewaters, 

and where are these methods practiced?

• Are large volumes of water being disproportionately withdrawn from drinking water resources 

that serve communities with environmental justice concerns?

• Are hydraulically fractured oil and gas wells disproportionately located near communities with 

environmental justice concerns?

• Is wastewater from hydraulic fracturing operations being disproportionately treated or disposed 

of (via POTWs or commercial treatment systems) in or near communities with environmental 

justice concerns?

For each case study (retrospective and prospective), EPA will write and approve a QAPP before starting 

any new data collection, as described in Section 2.6. Upon completion of each case study, a report 

summarizing key findings will be written, peer reviewed, and published. The data will also be presented 

in the 2012 and 2014 reports.

The following sections describe the general approaches to be used during the retrospective and 

prospective case studies. As part of the case studies, EPA will perform extensive sampling of relevant 

environmental media. Appendix H provides details on field sampling, monitoring, and analytical 

methods that may be used during both the retrospective and prospective case studies. General 

information is provided in this study plan, as each case study location is unique.
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9.2 RETROSPECTIVE CASE STUDIES

As described briefly in Section 5.2, retrospective case studies are focused on investigating reported 

instances of drinking water contamination in areas where hydraulic fracturing events have already 

occurred. Table 8 lists the five locations where EPA will conduct retrospective case studies. Each case 

study will address one or more stages of the water lifecycle by providing information that will help to 

answer the research questions posed in Table 1. 

While the research questions addressed by each case study vary, there are two goals for all the

retrospective case studies: (1) to determine whether or not contamination of drinking water resources 

has occurred and to what extent; and (2) to assess whether or not the reported contamination is due to 

hydraulic fracturing activities. These case studies will use available data and may include additional 

environmental field sampling, modeling, and related laboratory investigations. Additional information 

on environmental field sampling can be found in Appendix H. 

Each retrospective case study will begin by determining the sampling area associated with that specific 

location. Bounding the scope, vertical, and areal extent of each retrospective case study site will depend

on site-specific factors, such as the unique geologic, hydrologic, and geographic characteristics of the 

site as well as the extent of reported impacts. Where it is obvious that there is only one potential source 

for a reported impact, the case study site will be fairly contained. Where there are numerous reported 

impacts potentially involving multiple possible sources, the case study site will be more extensive in all 

dimensions, making it more challenging to isolate possible sources of drinking water contamination.

The case studies will then be conducted in a tiered fashion to develop integrated data on site history 

and characteristics, water resources, contaminant migration pathways, and exposure routes. This tiered 

approach is described in Table 9.
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TABLE 9. GENERAL APPROACH FOR CONDUCTING RETROSPECTIVE CASE STUDIES

Tier Goal Critical Path

1 Verify potential issue • Evaluate existing data and information from operators, private citizens, 

and state agencies

• Conduct site visits

• Interview stakeholders and interested parties

2 Determine approach

for detailed 

investigations 

• Conduct initial sampling: sample wells, taps, surface water, and soils

• Identify potential evidence of drinking water contamination

• Develop conceptual site model describing possible sources and pathways 

of the reported contamination

• Develop, calibrate, and test fate and transport model(s)

3 Conduct detailed 

investigations to 

evaluate potential 

sources of 

contamination

• Conduct additional sampling of soils, aquifer, surface water and surface 

wastewater pits/tanks (if present)

• Conduct additional testing: stable isotope analyses, soil gas surveys, 

geophysical testing, well mechanical integrity testing, and further water 

testing with new monitoring points

• Refine conceptual site model and further test exposure scenarios

• Refine fate and transport model(s) based on new information

4 Determine the 

source(s) of any 

impacts to drinking 

water resources

• Develop multiple lines of evidence to determine the source(s) of impacts 

to drinking water resources

• Exclude possible sources and pathways of the reported contamination

• Assess uncertainties associated with conclusions regarding the source(s) of 

impacts

Once the potential issue has been verified in Tier 1, initial sampling activities will be conducted based on 

the characteristics of the complaints and the nature of the sites. Table 10 lists sample types and testing 

parameters for initial sampling activities.

TABLE 10. TIER 2 INITIAL TESTING: SAMPLE TYPES AND TESTING PARAMETERS

Sample Type Testing Parameters

Surface and ground water • General water quality parameters (e.g., pH, redox potential, 

dissolved oxygen, TDS)

• General water chemistry parameters (e.g., cations and anions, 

including barium, strontium, chloride, boron)

• Metals and metalloids (e.g., arsenic, barium, selenium)

• Radionuclides (e.g., radium)

• Volatile and semi-volatile organic compounds

• Polycyclic aromatic hydrocarbons

Soil • General water chemistry parameters

• Metals

• Volatile and semi-volatile organic compounds

• Polycyclic aromatic hydrocarbons

Produced water from waste pits or tanks 

where available

• General water quality parameters

• General water chemistry parameters

• Metals and metalloids

• Radionuclides

• Volatile and semi-volatile organic compounds

• Polycyclic aromatic hydrocarbons

• Fracturing fluid additives/degradates
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Results from Tier 1 and initial sampling activities will be used to inform the development of a conceptual 

site model. The site model will account for the hydrogeology of the location to be studied and be used

to determine likely sources and pathways of the reported contamination. The conceptual site model will 

also be informed by modeling results. These models can help to predict the fate and transport of 

contaminants, identify appropriate sampling locations, determine possible contamination sources, and 

understand field measurement uncertainties. The conceptual site model will be continuously updated 

based on new information, data, and modeling results. 

If initial sampling activities indicate potential impacts to drinking water resources, additional testing will 

be conducted to refine the site conceptual model and further test exposure scenarios (Tier 3). Table 11

describes the additional data to be collected during Tier 3 testing activities.

Results from the tests outlined in Table 11 can be used to further elucidate the sources and pathways of 

impacts to drinking water resources. These data will be used to support multiple lines of evidence, 

which will serve to identify the sources of impacts to drinking water resources. EPA expects that it will 

be necessary to examine multiple lines of evidence in all case studies, since hydraulic fracturing 

chemicals and contaminants can have other sources or could be naturally present contaminants in 

shallow drinking water aquifers. The results from all retrospective case study investigations will include a 

thorough discussion of the uncertainties associated with final conclusions related to the sources and 

pathways of impacts to drinking water resources. 

TABLE 11. TIER 3 ADDITIONAL TESTING: SAMPLE TYPES AND TESTING PARAMETERS

Sample Type / Testing Testing Parameters

Surface and ground water • Stable isotopes (e.g., strontium, radium, carbon, oxygen, hydrogen) 

• Dissolved gases (e.g., methane, ethane, propane, butane)

• Fracturing fluid additives

Soil • Soil gas (e.g., argon, helium, hydrogen, oxygen, nitrogen, carbon dioxide, 

methane, ethane, propane) 

Geophysical testing • Geologic and hydrogeologic conditions (e.g., faults, fractures, abandoned 

wells)

• Soil and rock properties (e.g., porous media, fractured rock)

Mechanical integrity (review 

of existing data or testing)

• Casing integrity

• Cement integrity

Drill cuttings and core 

samples

• Metals

• Radionuclides

• Mineralogical analysis

The data collected during retrospective case studies may be used to assess any risks that may be posed 

to drinking water resources as a result of hydraulic fracturing activities. Because of this possibility, EPA 

will develop information on: (1) the toxicity of chemicals associated with hydraulic fracturing; (2) the 

spatial distribution of chemical concentrations and the locations of drinking water wells; (3) how many 

people are served by the potentially impacted drinking water resources, including aquifers, wells and or 

surface waters; and (4) how the chemical concentrations vary over time.
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9.3 PROSPECTIVE CASE STUDIES

EPA will conduct two prospective case studies: one in the Marcellus Shale and the other in the 

Haynesville Shale. In both cases, EPA will have access to the site throughout the process of building and 

fracturing the well. This access will allow EPA to obtain water quality and other data before pad 

construction, after pad and well construction, and immediately after fracturing. Additionally, monitoring 

will continue during a follow-up period of approximately one year after hydraulic fracturing has been 

completed. Data and methods will be similar to the retrospective case studies, but these studies will 

allow for baseline water quality sampling, collection of flowback and produced water for analysis, and 

evaluation of hydraulic fracturing wastewater disposal methods.

The prospective case studies are made possible by partnering with oil and natural gas companies and 

other stakeholders. Because of the need to enlist the support and collaboration of a wide array of 

stakeholders in these efforts, case studies of this type will likely be completed 16-24 months from the 

start dates. However, some preliminary results may be available for the 2012 report.

As in the case of the retrospective studies, each prospective case study will begin by determining the 

sampling area associated with that specific location. Bounding the scope, vertical, and areal extent of 

each prospective case study site will depend on site-specific factors, such as the unique geologic, 

hydrologic, and geographic characteristics of the site. The data collected at prospective case study 

locations will be placed into a wider regional watershed context. Additionally, the scope of the 

prospective case studies will encompass all stages of the water lifecycle illustrated in Figure 1. 

After the boundaries have been established, the case studies will be conducted in a tiered fashion, as 

outlined in Table 12.

TABLE 12. GENERAL APPROACH FOR CONDUCTING PROSPECTIVE CASE STUDIES

Tier Goal Critical Path

1 Collect existing data • Gather existing data and information from operators, private citizens, 

and state agencies

• Conduct site visits

• Interview stakeholders and interested parties

2 Construct a conceptual 

site model

• Evaluate existing data

• Identify all potential sources and pathways for contamination of drinking 

water resources

• Develop flow system model

3 Conduct field sampling • Conduct sampling to characterize ground and surface water quality and 

soil/sediment quality prior to pad construction, following pad and well 

construction, and immediately after hydraulic fracturing

• Collect and analyze time series samples of flowback and produced water

• Collect field samples for up to one year after hydraulic fracturing

• Calibrate flow system model

4 Determine if there are or 

are likely to be impacts 

to drinking water 

resources

• Analyze data collected during field sampling

• Assess uncertainties associated with conclusions regarding the potential 

for impacts to drinking water resources

• Recalibrate flow system model
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Results from Tier 1 activities will inform the development of a conceptual site model, which will be used 

to assess potential pathways for contamination of drinking water resources. This model will help to 

determine the field sampling activities described in Tier 3. Field sampling will be conducted in a phased 

approach, as described in Table 13.

The data collected during field sampling activities may also be used to test whether geochemical and 

hydrologic flow models accurately simulate changes in composition, concentration and or location of

hydraulic fracturing fluids over time in different environmental media. These data will be evaluated to 

determine if there were any impacts to drinking water resources as a result of hydraulic fracturing 

activities during the limited period of the study. In addition, the data will be evaluated to consider the 

potential for any future impacts on drinking water resources that could arise after the study period. If 

impacts are found, EPA will report on the type, cause, and extent of the impacts. The results from all 

prospective case study investigations will include a discussion of the uncertainties associated with final 

conclusions related to the potential impacts of hydraulic fracturing on drinking water resources. 

TABLE 13. TIER 3 FIELD SAMPLING PHASES

Field Sampling Phases Critical Path

Baseline 

characterization of the 

production well site 

and areas of concern

• Sample all available existing wells, catalogue depth to drinking water aquifers and 

their thickness, gather well logs

• Sample any adjoining surface water bodies

• Sample source water for hydraulic fracturing

• Install and sample new monitoring wells

• Perform geophysical characterization

Production well 

construction

• Test mechanical integrity

• Resample all wells (new and existing), surface water

• Evaluate gas shows from the initiation of surface drilling to the total depth of the 

well

• Assess geophysical logging at the surface portion of the hole

Hydraulic fracturing of 

the production well

• Sample fracturing fluids

• Resample all wells, surface water, and soil gas

• Sample flowback

• Calibrate and test flow and geochemical models

Gas production • Resample all wells, surface water, and soil gas

• Sample produced water

10 SCENARIO EVALUATIONS AND MODELING

In this study, modeling will integrate a variety of factors to enhance EPA’s understanding of potential 

impacts from hydraulic fracturing on drinking water resources. Modeling will be important in both 

scenario evaluations and case studies. Scenario evaluations will use existing data to explore potential 

impacts on drinking water resources in instances where field studies cannot be conducted. In 

retrospective and prospective case studies, modeling will help identify possible contamination pathways 

at site-specific locations. The results of modeling activities will provide insight into site-specific and 

regional vulnerabilities as well as help to identify important factors that affect potential impacts on 

drinking water resources across all stages of the hydraulic fracturing water lifecycle.
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10.1 SCENARIO EVALUATIONS

Scenario evaluations will be a useful approach for analyzing realistic hypothetical scenarios across the 

hydraulic fracturing water lifecycle that may result in adverse impacts to drinking water. Specifically, EPA 

will evaluate scenarios relevant to the water acquisition, well injection, and wastewater treatment and 

disposal stages of the hydraulic fracturing water lifecycle. In all cases, the scenarios will use information 

from case studies and minimum state regulatory requirements to define typical management and 

engineering practices, which will then be used to develop reference cases for the scenarios. 

Water acquisition. EPA will evaluate scenarios for two different locations in the US: the Susquehanna 

River Basin and the Upper Colorado River Basin/Garfield County, Colorado. In these instances, the 

reference case for the scenarios will be developed using data collected from USGS, the Susquehanna 

River Basin Commission, and the Colorado Oil and Gas Conservation Commission. The reference case 

will be associated with the year 2000; this year will be classified as low, median, or high flow based on 

watershed simulations over the period of 1970-2000.

EPA will then project the water use needs for hydraulic fracturing in the Susquehanna River Basin and 

Upper Colorado River Basin based on three futures: (1) current business and technology; (2) full natural 

gas exploitation; and (3) a green technology scenario with sustainable water management practices

(e.g., full recycling of produced water), and low population growth. These futures models are described 

below in more detail. Based on these predictions, EPA will assess the potential impacts of large volume 

water withdrawals needed for hydraulic fracturing for the period of 2020-2040.

Well injection. EPA will investigate possible mechanisms of well failure and stimulation-induced 

overburden failure that could lead to upward migration of hydrocarbons, fracturing fluids, and/or brines 

to ground or surface waters. This will be done through numerical modeling using TOUGH2 with 

geomechanical enhancements. The scenarios also include multiple injection and pumping wells and the 

evaluations of diffuse and focused leakage (through fractures and abandoned unplugged wells) within 

an area of potential influence. The reference cases will be determined from current management and 

engineering practices as well as representative geologic settings. The failure scenarios are described in 

greater detail in Section 6.3.2.1. 

Wastewater treatment and disposal. EPA will use a staged approach to evaluate the potential for 

impacts of releases of treated hydraulic fracturing wastewaters to surface waters. The first approach will 

focus on basic transport processes occurring in rivers and will be based on generalized inputs and 

receptor locations. This work will use scenarios representing various flow conditions, distances between 

source and receptor, and available data on possible discharge concentrations. The chemicals of interest 

are the likely residues in treated wastewater, specifically chloride, bromide and naturally occurring 

radioactive materials. In the second stage, specific watersheds will be evaluated using the best data 

available for evaluations. Similar to the first stage, scenarios will be developed to show how various 

conditions in the actual river networks impact concentrations at drinking water receptors. A comparison 

of both stages will help show the level of detail necessary for specific watersheds and might lead to 

revision of the first, or more generic, approach.
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10.2 CASE STUDIES

Modeling will be used in conjunction with data from case studies to gain a better understanding of the 

potential impacts of hydraulic fracturing on drinking water resources. First, models will be developed to 

simulate the flow and transport of hydraulic fracturing fluids and native fluids in an oil or gas reservoir 

during the hydraulic fracturing process. These models will use data from case studies—including 

injection pressures, flow rates, and lithologic properties—to simulate the development of fractures and 

migration of fracturing fluids in the fracture system induced by the hydraulic fracturing process. The 

results of the modeling may be used to help predict the possibility of rock formation damage and the 

spreading area of fracturing fluid. Expected outputs include information on the possibility that hydraulic 

fracturing-related contaminants will migrate to an aquifer system. 

Models can also be developed to simulate flow and transport of the contaminants once migration to an 

aquifer occurs. This modeling will consider a relatively large-scale ground water aquifer system. The 

modeling will consider the possible sources of fracturing fluids emerging from the oil or gas reservoir 

through a damaged formation, geological faults, or an incomplete cementing zone outside the well 

casing. It will also consider local hydrogeological conditions such as precipitation, water well 

distribution, aquifer boundaries, and hydraulic linkage with other water bodies. The modeling will 

simulate ground water flow and transport in the aquifer system, and is expected to output information 

on contamination occurring near water supply facilities. This modeling may also provide the opportunity 

to answer questions about potential risks associated with hypothetical scenarios, such as conditions 

under which an improperly cemented wellbore might release fracturing fluid or native fluids (including 

native gases).

10.3 MODELING TOOLS

EPA expects that a wide range of modeling tools may be used in this study. It is standard practice to 

evaluate and model complex environmental systems as separate components, as can be the case with 

potential impacts to drinking water resources associated with hydraulic fracturing. For example, system 

components can be classified based on media type, such as water body models, ground water models, 

watershed models, and waste unit models. Additionally, models can be chosen based on whether a 

stochastic or deterministic representation is needed, solution types (e.g., analytical, semi-analytical, or 

numerical), spatial resolution (e.g., grid, raster, or vector), or temporal resolution (e.g., steady-state or 

time-variant).

The types of models to be used in this study may include:

Hydraulic fracturing models. EPA is considering using MFrac to calculate the development of fracture 

systems during real-time operations. MFrac is a comprehensive design and evaluation simulator 

containing a variety of options, including three-dimensional fracture geometry and integrated acid 

fracturing solutions. EPA may also use MFrac to assess formation damage subject to various engineering 

operations, lithostratigraphy, and depositional environment of oil and gas deposits.
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Multi-phase and multi-component ground water models. Members of the TOUGH family of models 

developed at Lawrence Berkeley National Laboratory can be used to simulate the flow and transport 

phenomena in fractured zones, where geothermal and geochemical processes are active, where 

permeability changes, and where phase-change behavior is important. These codes have been adapted 

for problems requiring capabilities that will be also needed for hydraulic fracturing simulation:

multiphase and multi-component transport, geothermal reservoir simulation, geologic sequestration of 

carbon, geomechanical modeling of fracture activation and creation, and inverse modeling.

Single-phase and multi-component ground water models. These ground water models include:

• The finite difference solutions, such as the USGS Modular Flow and its associated transport 

codes, including Modular Transport 3D-Multispecies and the related Reactive Transport 3D,

• The finite element solutions, such as the Finite Element Subsurface Flow Model and other semianalytical solutions (e.g., GFLOW and TTim). 

Various chemical and/or biological reactions can be integrated into the advective ground water flow 

models to allow the simulation of reaction flow and transport in the aquifer system. For a suitably 

conceptualized system consisting of single-phase transport of water-soluble chemicals, these models 

can support hydraulic fracturing assessments.

Watershed models. EPA has experience with the well-established watershed management models Soil 

Water Assessment Tool (semi-empirical, vector-based, continuous in time) and Hydrologic Simulation 

Program – FORTRAN (semi-physics-based, vector-based, continuous in time). The watershed models will 

play an important role in modeling water acquisition and in water quantity analysis.

Waterbody models. The well-established EPA model for representing water quality in rivers and 

reservoirs is the Water Quality Analysis Simulation Program. Other, simpler approaches include 

analytical solutions to the transport equation and models such as a river and stream water quality model 

(QUAL2K; see Chapra, 2008). Based on extensive tracer studies, USGS has developed empirical 

relationships for travel time and longitudinal dispersion in rivers and streams (Jobson, 1996). 

Alternative futures models. Alternative futures analysis has three basic components (Baker et al., 2004): 

(1) characterize the current and historical landscapes in a geographic area and the trajectory of the 

landscape to date; (2) develop two or more alternative “visions” or scenarios for the future landscape 

that reflect varying assumptions about land and water use and the range of stakeholder viewpoints; and 

(3) evaluate the likely effects of these landscape changes and alternative futures on things people care 

about (e.g., valued endpoints). EPA has conducted alternative futures analysis for much of the landscape 

of interest for this project. The Agency has created futures for 20 watersheds12 across the country, 

including the Susquehanna River basin, which overlays the Marcellus Shale and the Upper Colorado 

River Basin, which includes Garfield County, Colorado.

 12 http://cfpub.epa.gov/ncea/global/recordisplay.cfm?deid=212763
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10.4 UNCERTAINTY IN MODEL APPLICATIONS

All model parameters are uncertain because of measurement approximation and error, uncharacterized 

point-to-point variability, reliance on estimates and imprecise scale-up from laboratory measurements.

Model outputs are subject to uncertainty, even after model calibration (e.g., Tonkin and Dougherty, 

2008; Doherty, 2011). Thus, environmental models do not possess generic validity (Oreskes et al., 1994), 

and the application is critically dependent on choices of input parameters, which are subject to the 

uncertainties described above. Further, a recent review by one of the founders of the field of subsurface 

transport modeling (Leonard F. Konikow) outlines the difficulties with contaminant transport modeling 

and concludes that “Solute transport models should be viewed more for their value in improving the 

understanding of site-specific processes, hypothesis testing, feasibility assessments, and evaluating 

data-collection needs and priorities; less value should be placed on expectations of predictive reliability”

(Konikow, 2010). Proper application of models requires proper expectations (i.e., Konikow, 2010) and 

acknowledgement of uncertainties, which can lead to best scientific credibility for the results (see 

Oreskes, 2003).

11 CHARACTERIZATION OF TOXICITY AND HUMAN HEALTH EFFECTS

EPA will evaluate all stages of the hydraulic fracturing water lifecycle to assess the potential for 

fracturing fluids and/or naturally occurring substances to be introduced into drinking water resources. 

As highlighted throughout Chapter 6, EPA will assess the toxicity and potential human health effects 

associated with these possible drinking water contaminants. To do this, EPA will first obtain an inventory 

of the chemicals associated with hydraulic fracturing activities (and their estimated concentrations and 

frequency of occurrence). This includes chemicals used in hydraulic fracturing fluids, naturally occurring 

substances that may be released from subsurface formations during the hydraulic fracturing process, 

and chemicals that are present in hydraulic fracturing wastewaters. EPA will also identify the relevant 

reaction and degradation products of these substances—which may have different toxicity and human 

health effects than their parent compounds—in addition to the fate and transport characteristics of the 

chemicals. The aggregation of these data is described in Chapter 6.

Based on the number of chemicals currently known to be used in hydraulic fracturing operations, EPA 

anticipates that there could be several hundred chemicals of potential concern for drinking water

resources. Therefore, EPA will develop a prioritized list of chemicals and, where estimates of toxicity are 

not otherwise available, conduct quantitative health assessments or additional testing for certain highpriority chemicals. In the first phase of this work, EPA will conduct an initial screen for known toxicity 

and human health effects information (including existing toxicity values such as reference doses and 

cancer slope factors) by searching existing databases.13 At this stage, chemicals will be grouped into one 

of three categories: (1) high priority for chemicals that are potentially of concern; (2) low priority for 

 13 These databases include the Integrated Risk Information System (IRIS), the Provisional Peer Reviewed Toxicity 

Value (PPRTV) database, the ATSDR Minimal Risk Levels (MRLs), the California EPA Office of Environmental Health 

Hazard Assessment (OEHHA) Toxicity Criteria Database (TCD). Other Agency databases including the Distributed 

Structure Searchable Toxicity (DSSTox) database, Aggregated Computational Toxicology Resources (ACToR) 

database and the Toxicity Reference Database (ToxRefDB) may be used to facilitate data searching activities.
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chemicals that are likely to be of little concern; and (3) unknown priority for chemicals with an unknown 

level of concern. These groupings will be based on known chemical, physical, and toxicological 

properties; reported occurrence levels; and the potential need for metabolism information.

Chemicals with an unknown level of concern are those for which no toxicity information is available. For 

these chemicals, a quantitative structure-activity relationships (QSAR) analysis may be conducted to 

obtain comparative toxicity information. A QSAR analysis uses mathematical models to predict 

measures of toxicity from physical/chemical characteristics of the structure of the chemicals. This 

approach may provide information to assist EPA in designating these chemicals as either high or low

priority.

The second phase of this work will focus on additional testing and/or assessment of chemicals with an 

unknown level of concern. These chemicals may be subjected to a battery of tests used in the ToxCast 

program, a high-throughput screening tool that can identify toxic responses (Judson et al., 2010a and 

2010b; Reif et al., 2010). The quantitative nature of these in vitro assays provides information on 

concentration-response relationships that, tied to known modes of action, can be useful in assessing the 

level of potential toxicity. EPA will identify a small set of these chemicals with unknown toxicity values 

and develop ToxCast bioactivity profiles and hazard predictions for these chemicals.

EPA will use these ToxCast profiles, in addition to existing information, to develop chemical-specific 

Provisional Peer Reviewed Toxicity Values (PPRTVs) for up to six of the highest-priority chemicals that 

have no existing toxicity values. PPRTVs summarize the available scientific information about the 

adverse effects of a chemical and the quality of the evidence, and ultimately derive toxicity values, such 

as provisional reference doses and cancer slope factors, that can be used in conjunction with exposure 

and other information to develop a risk assessment. Although using ToxCast is suitable for many of the 

chemicals used in hydraulic fracturing, the program has excluded any chemicals that are volatile enough 

to invalidate their assays.

In addition to single chemical assessments, further information may be obtained for mixtures of 

chemicals based on which components occur most frequently together and their relevant proportions as 

identified from exposure information. It may be possible to test actual hydraulic fracturing fluids or 

wastewater samples. EPA will assess the feasibility of this research and pursue testing if possible. 

EPA anticipates that the initial database search and ranking of high, low, and unknown priority chemicals 

will be completed for the 2012 interim report. Additional work using QSAR analysis and high-throughput 

screening tools is expected to be available in the 2014 report. The development of chemical-specific 

PPRTVs for high-priority chemicals is also expected to be available in 2014. 

Information developed from this effort to characterize the toxicity and health effects of chemicals will 

be an important component of future efforts to understand the overall potential risk posed by hydraulic 

fracturing chemicals that may be present in drinking water resources. When combined with exposure 

and other relevant data, this information will help EPA characterize the potential public health impacts 

of hydraulic fracturing on drinking water resources.
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12 SUMMARY

The objective of this study is to assess the potential impacts of hydraulic fracturing on drinking water 

resources and to identify the driving factors that affect the severity and frequency of any impacts. The 

research outlined in this document addresses all stages of the hydraulic fracturing water lifecycle shown 

in Figure 1 and the research questions posed in Table 1. In completing this research, EPA will use 

available data, supplemented with original research (e.g. case studies, generalized scenario evaluations 

and modeling) where needed. As the research progresses, EPA may learn certain information that 

suggests that modifying the initial approach or conducting additional research within the overall scope 

of the study plan is prudent in order to better answer the research questions. In that case, EPA may 

modify the current research plan. Figures 10 and 11 summarize the research activities for the study plan 

and reports anticipated timelines for research results. All data, whether generated by the EPA or not, 

will undergo a comprehensive quality assurance. 
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FIGURE 10A. SUMMARY OF RESEARCH PROJECTS 

PROPOSED FOR THE FIRST THREE STAGES OF THE 

HYDRAULIC FRACTURING WATER LIFECYCLE

Compile and analyze existing data on source 

water volume and quality requirements

Collect data on water use, hydrology, and 

hydraulic fracturing activities in an

arid and humid region 

Identify possible chemical indicators and 

existing analytical methods 

Analyze data obtained from 350 well files

Analysis of Existing Data

Compile data on the composition of

hydraulic fracturing fluids

Document the source, quality, and quantity 

of water used for hydraulic fracturing 

Evaluate impacts on local water quality and 

availability from water withdrawals

Identify methods and tools used to protect 

drinking water from oil and gas resources 

before and after hydraulic fracturing

Assess potential for hydraulic fractures to 

interfere with existing geologic features

Prospective Case Studies

Identify chemical products used in hydraulic 

fracturing fluids at case study locations

Water Acquisition Well Injection

Investigate the role of mechanical integrity, 

well construction, and geologic/man-made 

features in suspected cases of drinking

water contamination

Retrospective Case Studies

Results expected for 2012 report 

Results expected for 2014 report

Chemical Mixing

Investigate the location, cause, and impact of 

surface spills/accidental releases of

hydraulic fracturing fluids

Compile information on the frequency, 

severity, and causes of spills of

hydraulic fracturing fluids 

Identify known chemical, physical, and toxicological properties of chemicals found in hydraulic 

fracturing fluids and naturally occurring chemicals released during hydraulic fracturing

Review existing scientific literature on

surface chemical spills
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FIGURE 10B. SUMMARY OF RESEARCH PROJECTS PROPOSED FOR THE FIRST THREE STAGES OF THE HYDRAULIC FRACTURING WATER LIFECYCLE

Characterization of Toxicity and Human Health Effects

Water Acquisition Well Injection

Scenario Evaluations

Results expected for 2012 report 

Results expected for 2014 report

Chemical Mixing

Assess impacts of cumulative water 

withdrawals in a semi-arid and humid region

Test well failure and 

existing subsurface pathway scenarios 

Laboratory Studies

Identify or modify existing analytical methods for hydraulic fracturing fluid chemical additives and 

naturally occurring chemicals released during hydraulic fracturing

Study geochemical reactions between 

hydraulic fracturing fluids and

target formations

Prioritize chemicals of concern based on known toxicity data

Develop a simple AOE model for

hydraulically fractured wells

Predict toxicity of unknown chemicals and develop PPRTVs for chemicals of concern
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FIGURE 11A. SUMMARY OF RESEARCH PROJECTS PROPOSED FOR THE LAST TWO STAGES OF THE HYDRAULIC FRACTURING WATER LIFECYCLE

Flowback and Produced Water

Retrospective Case Studies

Results expected for 2012 report 

Results expected for 2014 report

Wastewater Treatment and

Waste Disposal

Prospective Case Studies

Analysis of Existing Data

Collect and analyze time series samples of 

flowback and produced water

Evaluate efficacy of recycling, treatment,

and disposal practices

Review existing scientific literature on

surface chemical spills

Compile a list of chemicals found in

flowback and produced water

Compile data on the frequency, severity, and 

causes of spills of hydraulic fracturing 

wastewaters

Gather information on treatment and 

disposal practices from well files

Analyze efficacy of existing treatment 

operations based on existing data

Identify known chemical, physical, and 

toxicological properties of chemicals found in 

hydraulic fracturing wastewater

Investigate the location, cause, and impact of 

surface spills/accidental releases of

hydraulic fracturing wastewaters
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FIGURE 11B. SUMMARY OF RESEARCH PROJECTS PROPOSED FOR THE LAST TWO STAGES OF THE HYDRAULIC FRACTURING WATER LIFECYCLE

Characterization of Toxicity and Human Health Effects

Flowback and Produced Water

Scenario Evaluations

Wastewater Treatment and

Waste Disposal

Laboratory Studies

Identify or modify existing analytical methods 

for chemicals found in hydraulic

fracturing wastewaters

Prioritize chemicals of concern based

on known toxicity data

Results expected for 2012 report 

Results expected for 2014 report

Develop watershed-specific version of the 

simplified model

Create a generalized model of surface water 

discharges of treated hydraulic fracturing 

wastewaters

Conduct studies on the formation of 

brominated DBPs during treatment of 

hydraulic fracturing wastewaters 

Determine the contribution of contamination 

from hydraulic fracturing wastewaters

and other sources

Conduct pilot-scale studies of the treatability 

of hydraulic fracturing wastewaters via POTW 

and commercial technologies

Predict toxicity of unknown chemicals and 

develop PPRTVs for chemicals of concern
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Brief summaries of how the research activities described in Chapter 6 will answer the fundamental 

research questions appear below:

Water Acquisition: What are the potential impacts of large volume water withdrawals from ground and 

surface waters on drinking water resources?

The 2012 report will provide a partial answer to this question based on the analysis of existing data. This 

will include data collected from two information requests and from existing data collection efforts in the 

Susquehanna River Basin and Garfield County, Colorado. The requested data from hydraulic fracturing 

service companies and oil and gas operators will provide EPA with general information on the source, 

quality, and quantity of water used for hydraulic fracturing operations. Data gathered in the 

Susquehanna River Basin and Garfield County, Colorado, will allow EPA to assess the impacts of large 

volume water withdrawals in a semi-arid and humid region by comparing water quality and quantity 

data in areas with no hydraulic fracturing activity to areas with intense hydraulic fracturing activities. 

Additional work will be reported in the 2014 report. EPA expects to provide information on local water 

quality and quantity impacts, if any, that are associated with large volume water withdrawals at the two 

prospective case study locations: Washington County, Pennsylvania, and DeSoto Parish, Louisiana. These 

two locations will provide information on impacts from surface (Washington County) and ground 

(DeSoto Parish) water withdrawals for hydraulic fracturing. The site-specific data can then be compared 

to future scenario modeling of cumulative hydraulic fracturing-related water withdrawals in the 

Susquehanna River Basin and Garfield County, Colorado, which will model the long-term impacts of 

multiple hydraulically fractured oil and gas wells within a single watershed. EPA will use the futures 

scenarios to assess the sustainability of hydraulic fracturing activities in semi-arid and humid 

environments and to determine what factors (e.g., droughts) may affect predicted impacts. 

Chemical Mixing: What are the possible impacts of surface spills on or near well pads of hydraulic 

fracturing fluids on drinking water resources? 

In general, EPA expects to be able to provide information on the composition hydraulic fracturing fluids 

and summarize the frequency, severity, and causes of spills of hydraulic fracturing fluids in the 2012 

report. EPA will use the information gathered from nine hydraulic fracturing service operators to 

summarize the types of hydraulic fracturing fluids, their composition, and a description of the factors 

that may determine which chemicals are used. The 2012 report will also provide a list of chemicals used 

in hydraulic fracturing fluids and their known or predicted chemical, physical, and toxicological 

properties. Based on known or predicted properties, a small fraction of these chemicals will be 

identified as chemicals of concern and will be highlighted for additional toxicological analyses or 

analytical method development, if needed. EPA will use this chemical list to identify available research 

on the fate and transport of hydraulic fracturing fluid chemical additives in environmental media.

The 2014 report will contain results of additional toxicological analyses of hydraulic fracturing fluid 

chemical additives with little or no known toxicological data. PPRTVs may be developed for high priority 

chemicals of concern. EPA will also include the results of the retrospective case study investigations. 

These investigations will provide verification of whether contamination of drinking water resources has 
EPA Hydraulic Fracturing Study Plan November 2011 

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occurred, and if so, if a surface spill of hydraulic fracturing fluids could be responsible for the 

contamination. 

Well Injection: What are the possible impacts of the injection and fracturing process on drinking water 

resources?

In 2012, EPA will primarily report on the results of the well file analysis and scenario evaluations to 

assess the role that the mechanical integrity of the wells and existing geologic/man-made features may 

play in the contamination of drinking water resources due to hydraulic fracturing. The well file analysis 

will provide nationwide background information on the frequency and severity of well failures in 

hydraulically fractured oil and gas wells, and will identify any contributing factors that may have led to 

these failures. Additionally, the well file analysis will provide information on the types of local geologic 

or man-made features that industry seeks to characterize prior to hydraulic fracturing, and whether or 

not these features were found to interact with hydraulic fractures. In a separate effort, EPA will use 

computer modeling to explore various contamination pathway scenarios involving improper well 

construction, mechanical integrity failure, and the presence of local geologic/man-made features. 

Results presented in the 2014 report will focus primarily on retrospective and prospective case studies 

and laboratory studies. The case studies will provide information on the methods and tools used to 

protect and isolate drinking water from oil and gas resources before and during hydraulic fracturing. In 

particular, the retrospective case studies may offer information on the impacts to drinking water 

resources from failures in well construction or mechanical integrity. EPA will use samples of the shale 

formations obtained at prospective case study locations to investigate geochemical reactions between 

hydraulic fracturing fluids and the natural gas-containing formation. These studies will be used to 

identify important biogeochemical reactions between hydraulic fracturing fluids and environmental 

media and whether this interaction may lead to the mobilization of naturally occurring materials. By 

evaluating chemical, physical, and toxicological characteristics of those substances, EPA will be able to 

determine which naturally occurring materials may be of most concern for human health.

Flowback and Produced Water: What are the possible impacts of surface spills on or near well pads

of flowback and produced water on drinking water resources?

EPA will use existing data to summarize the composition of flowback and produced water, as well as 

what is known about the frequency, severity, and causes of spills of hydraulic fracturing wastewater. 

Based on information submitted by the hydraulic fracturing service companies and oil and gas 

operators, EPA will compile a list of chemical constituents found in hydraulic fracturing wastewaters and 

the factors that may influence this composition. EPA will then use existing databases to determine the 

chemical, physical, and toxicological properties of wastewater constituents, and will identify specific 

constituents that may be of particular concern due to their mobility, toxicity, or production volumes. 

Properties of chemicals with little or no existing information will be estimated using QSAR methods, and 

high-priority chemicals with no existing toxicological information may be flagged for further analyses. 

The list of hydraulic fracturing wastewater constituents will also be used as a basis for a review of 
EPA Hydraulic Fracturing Study Plan November 2011 

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existing scientific literature to determine the fate and transport of these chemicals in the environment. 

These results, in combination with the above data analysis, will be presented in the 2012 report.

Results from the retrospective and prospective case studies will be presented in the 2014 report. The 

retrospective case studies will involve investigations of reported drinking water contamination at 

locations near reported spills of hydraulic fracturing wastewaters. EPA will first verify if contamination of 

the drinking water resources has occurred, and if so, then identify the source of this contamination. This 

may or may not be due to spills of hydraulic fracturing wastewaters. These case studies may provide EPA 

with information on the impacts of spills of hydraulic fracturing wastewaters to nearby drinking water 

resources. Prospective case studies will give EPA the opportunity to collect and analyze samples of 

flowback and produced water at different times, leading to a better understanding of the variability in 

the composition of these wastewaters. 

Wastewater Treatment and Waste Disposal: What are the possible impacts of inadequate treatment of 

hydraulic fracturing wastewaters on drinking water resources?

In the 2012 report, EPA will analyze existing data, the results from scenario evaluations and laboratory 

studies to assess the treatment and disposal of hydraulic fracturing wastewaters. Data provided by oil 

and gas operators will be used to better understand common treatment and disposal methods and 

where these methods are practiced. This understanding will inform EPA’s evaluation of the efficacy of 

current treatment processes. In a separate effort, EPA researchers will create a generalized computer 

model of surface water discharges of treated hydraulic fracturing wastewaters. The model will be used 

to determine the potential impacts of these wastewaters on the operation of drinking water treatment 

facilities. 

Research presented in the 2014 report will include the results of laboratory studies of current treatment 

and disposal technologies, building upon the results reported in 2012. These studies will provide 

information on fate and transport processes of hydraulic fracturing wastewater contaminants during 

treatment by a wastewater treatment facility. Additional laboratory studies will be used to determine 

the extent of brominated DBP formation in hydraulic fracturing wastewaters, either from brominated 

chemical additives or high bromide concentrations. If possible, EPA will also collect samples of 

wastewater treatment plant discharges and stream/river samples to determine the contribution of 

treated hydraulic fracturing wastewater discharges to stream/river contamination. The generalized 

computer model described above will be expanded to develop a watershed-specific version that will 

provide additional information on potential impacts to drinking water intakes and what factors may 

influence these impacts. 

The results for each individual research project will be made available to the public after undergoing a 

comprehensive quality assurance review. Figures 10 and 11 show which parts of the research will be 

completed in time for the 2012 report and which components of the study plan are expected to be 

completed for the 2014 report. Both reports will use the results of the research projects to assess the 

impacts, if any, of hydraulic fracturing on drinking water resources. Overall, this study will provide data 

on the key factors in the potential contamination of drinking water resources as well as information 
EPA Hydraulic Fracturing Study Plan November 2011 

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about the toxicity of chemicals associated with hydraulic fracturing. The results may then be used in the 

future to inform a more comprehensive assessment of the potential risks associated with exposure to 

contaminants associated with hydraulic fracturing activities in drinking water.

Conclusion

This study plan represents an important milestone in responding to the direction from the US Congress 

in Fiscal Year 2010 to conduct research to examine the relationship between hydraulic fracturing and 

drinking water resources. EPA is committed to conducting a study that uses the best available science, 

independent sources of information, and a transparent, peer-reviewed process that will ensure the 

validity and accuracy of the results. The Agency will work in consultation with other federal agencies, 

state and interstate regulatory agencies, industry, non-governmental organizations, and others in the 

private and public sector in carrying out the study. Stakeholder outreach as the study is being conducted 

will continue to be a hallmark of our efforts, just as it was during the development of this study plan.

13 ADDITIONAL RESEARCH NEEDS

Although EPA’s current study focuses on potential impacts of hydraulic fracturing on drinking water 

resources, stakeholders have identified additional research areas related to hydraulic fracturing

operations, as discussed below. Integrating the results of future work in these areas with the findings of 

the current study would provide a comprehensive view of the potential impacts of hydraulic fracturing 

on human health and the environment. If opportunities arise to address these concerns, EPA will include 

them in this current study as they apply to potential impacts of hydraulic fracturing on drinking water 

resources. However, the research described in this study plan will take precedence.

13.1 USE OF DRILLING MUDS IN OIL AND GAS DRILLING

Drilling muds are known to contain a wide variety of chemicals that might impact drinking water 

resources. This concern is not unique to hydraulic fracturing and may be important for oil and gas 

drilling in general. The study plan is restricted to specifically examining the hydraulic fracturing process 

and will not evaluate drilling muds.

13.2 LAND APPLICATION OF FLOWBACK OR PRODUCED WATERS

Land application of wastewater is a fairly common practice within the oil and gas industry. EPA plans to 

identify hydraulic fracturing-related chemicals that may be present in treatment residuals. However, due 

to time constraints, land application of hydraulic fracturing wastes and disposal practices associated 

with treatment residuals is outside the scope of the current study.

13.3 IMPACTS FROM DISPOSAL OF SOLIDS FROM WASTEWATER TREATMENT PLANTS

In the process of treating wastewater, the solids are separated from the liquid in the mixture. The 

handling and disposal of these solids can vary greatly before they are deposited in pits or undergo other 

disposal techniques. These differences can greatly affect exposure scenarios and the toxicological 

characteristics of the solids. For this reason, a comprehensive assessment of solids disposal is beyond 
EPA Hydraulic Fracturing Study Plan November 2011 

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the current study’s resources. However, EPA will use laboratory-scale studies to focus on determining 

the fate and transport of hydraulic fracturing water contaminants through wastewater treatment 

processes, including partitioning in treatment residuals.

13.4 DISPOSAL OF HYDRAULIC FRACTURING WASTEWATERS IN CLASS II UNDERGROUND 

INJECTION WELLS

Particularly in the West, millions of gallons of produced water and flowback are transported to Class II 

UIC wells for disposal. This study plan does not propose to evaluate the potential impacts of this 

regulated practice or the associated potential impacts due to the transport and storage leading up to 

ultimate disposal in a UIC well.

13.5 FRACTURING OR RE-FRACTURING EXISTING WELLS

In addition to concerns related to improper well construction and well abandonment processes, there 

are concerns about the repeated fracturing of a well over its lifetime. Hydraulic fracturing can be 

repeated as necessary to maintain the flow of hydrocarbons to the well. The near- and long-term effects 

of repeated pressure treatments on well construction components (e.g., casing and cement) are not well 

understood. While EPA recognizes that fracturing or re-fracturing existing wells should also be 

considered for potential impacts to drinking water resources, EPA has not been able to identify potential 

partners for a case study; therefore, this practice is not considered in the current study. The issues of 

well age, operation, and maintenance are important and warrant more study. 

13.6 COMPREHENSIVE REVIEW OF COMPROMISED WASTE CONTAINMENT

Flowback is deposited in pits or tanks available on site. If these pits or tanks are compromised by leaks, 

overflows, or flooding, flowback can potentially affect surface and ground water. This current study 

partially addresses this issue. EPA will evaluate information on spills collected from incident reports 

submitted by hydraulic fracturing service operators and observations from the case studies. However, a 

thorough review of pit or storage tank containment failures is beyond the scope of this study.

13.7 AIR QUALITY

There are several potential sources of air emissions from hydraulic fracturing operations, including the 

off-gassing of methane from flowback before the well is put into production, emissions from truck traffic

and diesel engines used in drilling equipment, and dust from the use of dirt roads. There have been 

reports of changes in air quality from natural gas drilling that have raised public concerns. Stakeholders 

have also expressed concerned over the potential greenhouse gas impacts of hydraulic fracturing. This

study plan does not propose to address the potential impacts from hydraulic fracturing on air quality or 

greenhouse gases because these issues fall outside the scope of assessing potential impacts on drinking 

water resources.
EPA Hydraulic Fracturing Study Plan November 2011 

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13.8 TERRESTRIAL AND AQUATIC ECOSYSTEM IMPACTS

Stakeholders have expressed concern that hydraulic fracturing may have effects on terrestrial and 

aquatic ecosystems unrelated to its effects on drinking water resources. For example, there is concern 

that contamination from chemicals used in hydraulic fracturing could result either from accidents during 

their use, transport, storage, or disposal; spills of untreated wastewater; or planned releases from 

wastewater treatment plants. Other impacts could result from increases in vehicle traffic associated 

with hydraulic fracturing activities, disturbances due to site preparation and roads, or stormwater runoff 

from the drilling site. This study plan does address terrestrial and aquatic ecosystem impacts from 

hydraulic fracturing because this issue is largely outside the scope of assessing potential impacts on 

drinking water resources.

13.9 SEISMIC RISKS

It has been suggested that drilling and/or hydraulically fracturing shale gas wells might cause lowmagnitude earthquakes. Public concern about this possibility has emerged due to several incidences 

where weak earthquakes have occurred in several locations with recent increases in drilling, although no 

conclusive link between hydraulic fracturing and these earthquakes has been found. The study plan does 

not propose to address seismic risks from hydraulic fracturing, because they are outside the scope of 

assessing potential impacts on drinking water resources.

13.10 OCCUPATIONAL RISKS

Occupational risks are of concern in the oil and gas extraction industry in general. For example, NIOSH

reports that the industry has an annual occupational fatality rate eight times higher than the rate for all 

US workers, and that fatality rates increase when the level of drilling activity increases (NIOSH, 2009). 

Acute and chronic health effects associated with worker exposure to hydraulic fracturing fluid chemicals 

could be of concern. Exposure scenarios could include activities during transport of materials, chemical 

mixing, delivery, and any potential accidents. The nature of this work poses potential risks to workers 

that have not been well characterized. Therefore, the recent increase in gas drilling and hydraulic 

fracturing activities may be a cause for concern with regard to occupational safety. The study plan does 

not propose to address occupational risks from hydraulic fracturing, because this issue is outside the 

scope of assessing potential impacts on drinking water resources.

13.11 PUBLIC SAFETY CONCERNS

Emergency situations such as blowouts, chemical spills from sites with hydraulic fracturing, or spills from 

the transportation of materials associated with hydraulic fracturing (either to or from the well pad) 

could potentially jeopardize public safety. Stakeholders also have raised concerns about the possibility 

of public safety hazards as a result of sabotage and about the need for adequate security at drilling sites. 

This issue is not addressed in the study plan because it is outside the scope of assessing potential 

impacts on drinking water resources.
EPA Hydraulic Fracturing Study Plan November 2011 

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13.12 ECONOMIC IMPACTS

Some stakeholders value the funds they receive for allowing drilling and hydraulic fracturing operations 

on their properties, while others look forward to increased job availability and more prosperous 

businesses. It is unclear, however, what the local economic impacts of increased drilling activities are 

and how long these impacts may last. For example, questions have been raised concerning whether the 

high-paying jobs associated with oil and gas extraction are available to local people, or if they are more 

commonly filled by those from traditional oil and gas states who have specific skills for the drilling and 

fracturing process. It is important to better understand the benefits and costs of hydraulic fracturing 

operations. However, the study plan does not address this issue, because it is outside the scope of 

assessing potential impacts on drinking water resources

13.13 SAND MINING

As hydraulic fracturing operations have become more prevalent, the demand for proppants has also 

risen. This has created concern over increased sand mining and associated environmental effects. Some 

stakeholders are worried that sand mining may lower air quality, adversely affect drinking water 

resources, and disrupt ecosystems (Driver, 2011). The impact of sand mining should be studied in the 

future, but is outside the scope of the current study because it falls outside the hydraulic fracturing 

water lifecycle framework established for this study.
EPA Hydraulic Fracturing Study Plan November 2011 

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APPENDIX A: RESEARCH SUMMARY

TABLE A1. RESEARCH TASKS IDENTIFIED FOR WATER ACQUISITION 

Water Acquisition: What are the potential impacts of large volume water withdrawals from ground and surface waters on drinking water resources?

Secondary Question Research Tasks Potential Product(s) Report

How much water is used in hydraulic 

fracturing operations, and what are 

the sources of this water? 

Analysis of Existing Data 

• Compile and analyze data submitted by nine 

hydraulic fracturing service companies for 

information on source water volume and 

quality requirements

• Compile and analyze data from nine oil and gas 

operators on the acquisition of source water 

for hydraulic fracturing operations

• Compile data on water use and hydraulic 

fracturing activity for the Susquehanna River 

Basin and Garfield County, CO

• List of volume and water quality parameters 

that are important for hydraulic fracturing 

operations

• Information on source, volume, and quality of 

water used for hydraulic fracturing operations

• Location-specific data on water use for 

hydraulic fraction 

2012

2012

2012

Prospective Case Studies 

• Document the source of the water used for 

hydraulic fracturing activities 

• Measure the quantity and quality of the water 

used at each case study location

• Location-specific examples of water 

acquisition, including data on the source, 

volume, and quality of the water

2014

How might water withdrawals affect 

short- and long-term water 

availability in an area with hydraulic 

fracturing activity?

Continued on next page

Analysis of Existing Data 

• Compile data on water use, hydrology, and 

hydraulic fracturing activity for the 

Susquehanna River Basin and Garfield County, 

CO

• Compare control areas to areas with hydraulic 

fracturing activity

• Maps of recent hydraulic fracturing activity and 

water usage in a humid region (Susquehanna 

River Basin) and a semi-arid region (Garfield 

County, CO)

• Information on whether water withdrawals for 

hydraulic fracturing activities alter ground and 

surface water flows

• Assessment of impacts of hydraulic fracturing 

on water availability at various spatial and 

temporal scales

2012

2012

2012

Prospective Case Studies 

• Compile information on water availability 

impacts due to water withdrawals from ground 

(DeSoto Parish, LA) and surface (Washington 

County, PA) waters

• Identification of short-term impacts on water 

availability from ground and surface water 

withdrawals associated with hydraulic 

fracturing activities 

2014
EPA Hydraulic Fracturing Study Plan November 2011

99

Water Acquisition: What are the potential impacts of large volume water withdrawals from ground and surface waters on drinking water resources?

Secondary Question Research Tasks Potential Product(s) Report

Continued from previous page

How might water withdrawals affect 

short- and long-term water 

availability in an area with hydraulic 

fracturing activity?

Scenario Evaluations 

• Conduct future scenario modeling of 

cumulative hydraulic fracturing-related water 

withdrawals in the Susquehanna River Basin 

and Garfield County, CO

• Identification of long-term water quantity 

impacts on drinking water resources due to 

cumulative water withdrawals for hydraulic 

fracturing

2014

What are the possible impacts of 

water withdrawals for hydraulic 

fracturing operations on local water 

quality?

Analysis of Existing Data 

• Compile data on water quality and hydraulic 

fracturing activity for the Susquehanna River 

Basin and Garfield County, CO

• Analyze trends in water quality

• Compare control areas to areas with intense 

hydraulic fracturing activity

• Maps of hydraulic fracturing activity and water 

quality for the Susquehanna River Basin and 

Garfield County, CO

• Information on whether water withdrawals for 

hydraulic fracturing activities alter local water 

quality

2012

2012

Prospective Case Studies 

• Measure local water quality before and after 

water withdrawals for hydraulic fracturing

• Identification of impacts on local water quality 

from water withdrawals for hydraulic 

fracturing

2014
EPA Hydraulic Fracturing Study Plan November 2011

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TABLE A2. RESEARCH TASKS IDENTIFIED FOR CHEMICAL MIXING 

Chemical Mixing: What are the possible impacts of surface spills on or near well pads of hydraulic fracturing fluids on drinking water resources?

Secondary Question Research Tasks Potential Product(s) Report

What is currently known about the 

frequency, severity, and causes of 

spills of hydraulic fracturing fluids 

and additives?

Analysis of Existing Data 

• Compile information regarding surface spills 

obtained from nine oil and gas operators

• Compile information on frequency, severity, 

and causes of spills of hydraulic fracturing 

fluids and additives from existing data sources

• Nationwide data on the frequency, severity, 

and causes of spills of hydraulic fracturing 

fluids and additives

2012

What are the identities and volumes 

of chemicals used in hydraulic 

fracturing fluids, and how might this 

composition vary at a given site and 

across the country?

Analysis of Existing Data 

• Compile information on hydraulic fracturing 

fluids and chemicals from publically available 

data and data provided by nine hydraulic 

fracturing service companies

• Identify factors that may alter hydraulic 

fracturing fluid composition 

• Description of types of hydraulic fracturing 

fluids and their frequency of use (subject to 

CBI rules)

• List of chemicals used in hydraulic fracturing 

fluids, including concentrations (subject to CBI 

rules)

• List of factors that determine and alter the 

composition of hydraulic fracturing fluids

2012

2012

2012

Prospective Case Studies 

• Collect information on the chemical products 

used in the hydraulic fracturing fluids at the 

case study locations

• Illustrative examples of hydraulic fracturing 

fluids used in the Haynesville and Marcellus 

Shale plays

2014

What are the chemical, physical, and 

toxicological properties of hydraulic 

fracturing chemical additives?

Continued on next page

Analysis of Existing Data 

• Search existing databases for chemical, 

physical, and toxicological properties 

• Prioritize list of chemicals based on their 

known properties for (1) further toxicological 

analysis or (2) to identify/modify existing 

analytical methods

• List of hydraulic fracturing chemicals with 

known chemical, physical, and toxicological 

properties

• Identification of 10-20 possible indicators to 

track the fate and transport of hydraulic 

fracturing fluids based on known chemical, 

physical, and toxicological properties

• Identification of hydraulic fracturing chemicals 

that may be of high concern, but have no or 

little existing toxicological information

2012

2012

2012
EPA Hydraulic Fracturing Study Plan November 2011

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Chemical Mixing: What are the possible impacts of surface spills on or near well pads of hydraulic fracturing fluids on drinking water resources?

Secondary Question Research Tasks Potential Product(s) Report

Continued from previous page

What are the chemical, physical, and 

toxicological properties of hydraulic 

fracturing chemical additives?

Toxicological Analysis 

• Identify chemicals currently undergoing 

ToxCast Phase II testing

• Predict chemical, physical, and toxicological 

properties based on chemical structure for 

chemicals with unknown properties

• Identify up to six hydraulic fracturing chemicals 

with unknown toxicity values for ToxCast 

screening and PPRTV development

• Lists of high, low, and unknown priority 

hydraulic fracturing chemicals based on known 

or predicted toxicity data 

• Toxicological properties for up to six hydraulic 

fracturing chemicals that have no existing 

toxicological information and are of high 

concern

2012

2014

Laboratory Studies 

• Identify or modify existing analytical methods 

for selected hydraulic fracturing chemicals

• Analytical methods for detecting hydraulic 

fracturing chemicals

2012/14

If spills occur, how might hydraulic 

fracturing chemical additives 

contaminate drinking water 

resources?

Analysis of Existing Data 

• Review existing scientific literature on surface 

chemical spills with respect to hydraulic 

fracturing chemical additives or similar 

compounds

• Summary of existing research that describes 

the fate and transport of hydraulic fracturing 

chemical additives, similar compounds, or 

classes of compounds

• Identification of knowledge gaps for future 

research, if necessary

2012

2012

Retrospective Case Studies 

• Investigate hydraulic fracturing sites where 

surface spills of hydraulic fracturing fluids have 

occurred (Dunn County, ND; Bradford and 

Susquehanna Counties, PA)

• Identification of impacts (if any) to drinking 

water resources from surface spills of hydraulic 

fracturing fluids

• Identification of factors that led to impacts (if 

any) to drinking water resources resulting from 

the accidental release of hydraulic fracturing 

fluids

2014

2014
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TABLE A3. RESEARCH TASKS IDENTIFIED FOR WELL INJECTION 

Well Injection: What are the possible impacts of the injection and fracturing process on drinking water resources?

Secondary Question Research Tasks Potential Product(s) Report

How effective are current well 

construction practices at containing 

gases and fluids before, during, and 

after hydraulic fracturing?

Analysis of Existing Data 

• Compile and analyze data from nine oil and gas 

operators on well construction practices

• Data on the frequency and severity of well 

failures 

• Identification of contributing factors that may 

lead to well failures during hydraulic fracturing 

activities

2014

2014

Retrospective Case Studies 

• Investigate the cause(s) of reported drinking 

water contamination—including testing well 

mechanical integrity—in Dunn County, ND, and 

Bradford and Susquehanna Counties, PA

• Identification of impacts (if any) to drinking 

water resources resulting from well failure or 

improper well construction

• Data on the role of mechanical integrity in 

suspected cases of drinking water 

contamination due to hydraulic fracturing

2014

2014

Prospective Case Studies 

• Conduct tests to assess well mechanical 

integrity before and after fracturing

• Assess methods and tools used to isolate and 

protect drinking water resources from oil and 

gas resources before and during hydraulic 

fracturing

• Data on changes (if any) in mechanical 

integrity due to hydraulic fracturing

• Identification of methods and tools used to 

isolate and protect drinking water resources 

from oil and gas resources before and during 

hydraulic fracturing

2014

2014

Scenario Evaluations 

• Test scenarios involving hydraulic fracturing of 

inadequately or inappropriately constructed or 

designed wells 

• Assessment of well failure scenarios during 

and after well injection that may lead to 

drinking water contamination

2012

Can subsurface migration of fluids or 

gases to drinking water resources 

occur, and what local geologic or 

man-made features may allow this?

Continued on next page

Analysis of Existing Data 

• Compile and analyze information from nine oil 

and gas operators on data relating to the 

location of local geologic and man-made 

features and the location of hydraulically 

created fractures

• Information on the types of local geologic or 

man-made features that are searched for prior 

to hydraulic fracturing

• Data on whether or not fractures interact with 

local geologic or man-made features and the 

frequency of occurrence 

2012

2012
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Well Injection: What are the possible impacts of the injection and fracturing process on drinking water resources?

Secondary Question Research Tasks Potential Product(s) Report

Continued from previous page

Can subsurface migration of fluids or 

gases to drinking water resources 

occur, and what local geologic or 

man-made features may allow this?

Retrospective Case Studies 

• Investigate the cause(s) of reported drinking 

water contamination in an area where 

hydraulic fracturing is occurring within a USDW 

where the fractures may directly extend into 

an aquifer (Las Animas Co., CO)

• Identification of impacts (if any) to drinking 

water resources from hydraulic fracturing 

within a drinking water aquifer

2014

Prospective Case Studies 

• Gather information on the location of known 

faults, fractures, and abandoned wells

• Identification of methods and tools used to 

determine existing faults, fractures, and 

abandoned wells

• Data on the potential for hydraulic fractures to 

interact with existing natural features

2014

2014

Scenario Evaluations 

• Test scenarios involving hydraulic fractures (1) 

interacting with nearby man-made features 

including abandoned or production wells, (2) 

reaching drinking water resources or 

permeable formations, and (3) interacting with 

existing faults and fractures

• Develop a simple model to determine the area 

of evaluation associated with a hydraulically 

fractured well

• Assessment of key conditions that may affect 

the interaction of hydraulic fractures with 

existing man-made and natural features

• Identification of the area of evaluation for a 

hydraulically fractured well

2012

2012

How might hydraulic fracturing fluids 

change the fate and transport of 

substances in the subsurface 

through geochemical interactions?

Laboratory Studies 

• Identify hydraulic fracturing fluid chemical 

additives to be studied and relevant 

environmental media (e.g., soil, aquifer 

material, gas-bearing formation material)

• Characterize the chemical and mineralogical 

properties of the environmental media

• Determine the products of reactions between 

chosen hydraulic fracturing fluid chemical 

additives and relevant environmental media

• Data on the chemical composition and 

mineralogy of environmental media

• Data on reactions between hydraulic fracturing 

fluids and environmental media 

• List of chemicals that may be mobilized during 

hydraulic fracturing activities

2014

2014

2014
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Well Injection: What are the possible impacts of the injection and fracturing process on drinking water resources?

Secondary Question Research Tasks Potential Product(s) Report

What are the chemical, physical, and 

toxicological properties of 

substances in the subsurface that 

may be released by hydraulic 

fracturing operations?

Analysis of Existing Data 

• Compile information from existing literature 

on the identity of chemicals released from the 

subsurface

• Search existing databases for chemical, 

physical, and toxicological properties 

• List of naturally occurring substances that are 

known to be mobilized during hydraulic 

fracturing activities and their associated

chemical, physical, and toxicological properties

• Identification of chemicals that may warrant 

further toxicological analysis or analytical 

method development

2012

2012

Toxicological Analysis 

• Identify chemicals currently undergoing 

ToxCast Phase II testing

• Predict chemical, physical, and toxicological 

properties based on chemical structure for 

chemicals with unknown properties (if any)

• Identify up to six chemicals with unknown 

toxicity values for ToxCast screening and 

PPRTV development (if any)

• Lists of high, low, and unknown priority for

naturally occurring substances based on 

known or predicted toxicity data 

• Toxicological properties for up to six naturally 

occurring substances that have no existing 

toxicological information and are of high 

concern

2012

2014

Laboratory Studies 

• Identify or modify existing analytical methods 

for selected naturally occurring substances 

released by hydraulic fracturing 

• Analytical methods for detecting selected 

naturally occurring substances released by 

hydraulic fracturing

2012/14
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TABLE A4. RESEARCH TASKS IDENTIFIED FOR FLOWBACK AND PRODUCED WATER 

Flowback and Produced Water:

What are the possible impacts of surface spills on or near well pads of flowback and produced water on drinking water resources?

Secondary Question Research Tasks Potential Product(s) Report

What is currently known about the 

frequency, severity, and causes of 

spills of flowback and produced 

water?

Analysis of Existing Data 

• Compile information on frequency, severity, 

and causes of spills of flowback and produced 

waters from existing data sources

• Data on the frequency, severity, and causes of 

spills of flowback and produced waters

2012

What is the composition of hydraulic 

fracturing wastewaters, and what 

factors might influence this 

composition?

Analysis of Existing Data 

• Compile and analyze data submitted by nine 

hydraulic fracturing service companies for 

information on flowback and produced water

• Compile and analyze data submitted by nine

operators on the characterization of flowback 

and produced waters

• Compile data from other sources, including 

existing literature and state reports 

• List of chemicals found in flowback and 

produced water

• Information on distribution (range, mean, 

median) of chemical concentrations 

• Identification of factors that may influence the 

composition of flowback and produced water

• Identification of constituents of concern 

present in hydraulic fracturing wastewaters

2012

2012

2012

2012

Prospective Case Studies 

• Collect time series samples of flowback and 

produced water at locations in the Haynesville 

and Marcellus shale plays

• Data on composition, variability, and quantity 

of flowback and produced water as a function 

of time

2014

What are the chemical, physical, and 

toxicological properties of hydraulic 

fracturing wastewater constituents?

Continued on next page

Analysis of Existing Data 

• Search existing databases for chemical, 

physical, and toxicological properties of 

chemicals found in flowback and produced 

water

• Prioritize list of chemicals based on their 

known properties for (1) further toxicological 

analysis or (2) to identify/modify existing 

analytical methods

• List of flowback and produced water 

constituents with known chemical, physical, 

and toxicological properties

• Identification of 10-20 possible indicators to 

track the fate and transport of hydraulic 

fracturing wastewaters based on known 

chemical, physical, and toxicological properties

• Identification of constituents that may be of 

high concern, but have no or little existing 

toxicological information

2012

2012

2012
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Flowback and Produced Water:

What are the possible impacts of surface spills on or near well pads of flowback and produced water on drinking water resources?

Secondary Question Research Tasks Potential Product(s) Report

Continued from previous page

What are the chemical, physical, and 

toxicological properties of hydraulic 

fracturing wastewater constituents?

Toxicological Analysis 

• Predict chemical, physical, and toxicological 

properties based on chemical structure for 

chemicals with unknown properties

• Identify up to six hydraulic fracturing 

wastewater constituents with unknown 

toxicity values for ToxCast screening and 

PPRTV development

• Lists of high, low, and unknown-priority 

hydraulic fracturing chemicals based on known 

or predicted toxicity data 

• Toxicological properties for up to six hydraulic 

fracturing wastewater constituents that have 

no existing toxicological information and are of 

high concern

2012

2014

Laboratory Studies 

• Identify or modify existing analytical methods 

for selected hydraulic fracturing wastewater 

constituents

• Analytical methods for detecting hydraulic 

fracturing wastewater constituents

2014

If spills occur, how might hydraulic 

fracturing wastewaters contaminate 

drinking water resources?

Analysis of Existing Data 

• Review existing scientific literature on surface 

chemical spills with respect to chemicals found 

in hydraulic fracturing wastewaters or similar 

compounds

• Summary of existing research that describes 

the fate and transport of chemicals in 

hydraulic fracturing wastewaters or similar 

compounds

• Identification of knowledge gaps for future 

research, if necessary

2012

2012

Retrospective Case Studies 

• Investigate hydraulic fracturing sites where 

surface spills of hydraulic fracturing 

wastewaters have occurred (Wise and Denton 

Counties, TX; Bradford and Susquehanna 

Counties, PA; Washington County, PA)

• Identification of impacts (if any) to drinking 

water resources from surface spills of hydraulic 

fracturing wastewaters

• Identification of factors that led to impacts (if 

any) to drinking water resources resulting from 

the accidental release of hydraulic fracturing 

wastewaters

2014

2014
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TABLE A5. RESEARCH TASKS IDENTIFIED FOR WASTEWATER TREATMENT AND WASTE DISPOSAL 

Wastewater Treatment and Waste Disposal:

What are the possible impacts of inadequate treatment of hydraulic fracturing wastewaters on drinking water resources?

Secondary Question Research Tasks Potential Product(s) Report

What are the common treatment 

and disposal methods for hydraulic 

fracturing wastewaters, and where 

are these methods practiced?

Analysis of Existing Data 

• Gather information from well files requested 

from nine well owners and operators on 

treatment and disposal practices

• Nationwide data on recycling, treatment, and 

disposal methods for hydraulic fracturing 

wastewaters

2012

Prospective Case Studies 

• Gather information on recycling, treatment, and 

disposal practices in two different locations 

(Haynesville and Marcellus Shale)

• Information on wastewater recycling, 

treatment, and disposal practices at two 

specific locations

2014

How effective are conventional 

POTWs and commercial treatment 

systems in removing organic and 

inorganic contaminants of concern in 

hydraulic fracturing wastewaters?

Analysis of Existing Data 

• Gather existing data on the treatment 

efficiency and contaminant fate and transport 

through treatment trains applied to hydraulic 

fracturing wastewaters

• Collection of analytical data on the efficacy of 

existing treatment operations that treat 

hydraulic fracturing wastewaters

• Identification of areas for further research

2014

2014

Laboratory Studies 

• Pilot-scale studies on synthesized and actual 

hydraulic fracturing wastewater treatability via 

conventional POTW technology (e.g. 

settling/activated sludge processes) and 

commercial technologies (e.g. filtration, RO)

• Data on the fate and transport of hydraulic 

fracturing water contaminants through 

wastewater treatment processes, including 

partitioning in treatment residuals

2014

Prospective Case Studies 

• Collect data on the efficacy of any treatment 

methods used in the case study

• Data on the efficacy of treatment methods used 

in two locations 

2014
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Wastewater Treatment and Waste Disposal:

What are the possible impacts of inadequate treatment of hydraulic fracturing wastewaters on drinking water resources?

Secondary Question Research Tasks Potential Product(s) Report

What are the potential impacts from 

surface water disposal of treated 

hydraulic fracturing wastewater on 

drinking water treatment facilities?

Laboratory Studies 

• Conduct studies on the formation of 

brominated DBPs during treatment of hydraulic 

fracturing wastewaters

• Collect discharge and stream/river samples in 

locations potentially impacted by hydraulic 

fracturing wastewater discharge

• Data on the formation of brominated DBPs 

from chlorination, chloramination, and 

ozonation treatments

• Data on the inorganic species in hydraulic 

fracturing wastewater and other discharge 

sources that contribute similar species

• Contribution of hydraulic fracturing wastewater 

to stream/river contamination

2012/14

2014

2014

Scenario Evaluation 

• Develop a simplified generic scenario of an 

idealized river with generalized inputs and 

receptors

• Develop watershed-specific versions of the 

simplified scenario using location-specific data 

and constraints

• Identification of parameters that generate or 

mitigate drinking water exposure

• Data on potential impacts in the Monongahela, 

Allegheny, or Susquehanna River networks

2012

2014
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TABLE A6. RESEARCH TASKS IDENTIFIED FOR ENVIRONMENTAL JUSTICE 

Environmental Justice: Does hydraulic fracturing disproportionately occur in or near communities with environmental justice concerns?

Secondary Question Research Tasks Potential Product(s) Report

Are large volumes of water being 

disproportionately withdrawn from 

drinking water resources that serve 

communities with environmental 

justice concerns?

Analysis of Existing Data 

• Compare data on locations of source water 

withdrawals to demographic information (e.g., 

race/ethnicity, income, and age)

• Maps showing locations of source water 

withdrawals and demographic data

• Identification of areas where there may be a 

disproportionate co-localization of large 

volume water withdrawals for hydraulic 

fracturing and communities with 

environmental justice concerns

2012

2012

Prospective Case Studies 

• Analyze demographic profiles of communities 

located near the case study locations 

• Illustrative information on the types of 

communities where hydraulic fracturing occurs 

2014

Are hydraulically fractured oil and

gas wells disproportionately located 

near communities with 

environmental justice concerns?

Analysis of Existing Data 

• Compare data on locations of hydraulically 

fractured oil and gas wells to demographic 

information (e.g., race/ethnicity, income, and 

age)

• Maps showing locations of hydraulically 

fractured wells (subject to CBI rules) and 

demographic data

• Identification of areas where there may be a 

disproportionate co-localization of hydraulic 

fracturing well sites and communities with 

environmental justice concerns

2012

2012

Retrospective and Prospective Case Studies 

• Analyze demographic profiles of communities 

located near the case study locations 

• Illustrative information on the types of 

communities where hydraulic fracturing occurs 

2014

Is wastewater from hydraulic 

fracturing operations being 

disproportionately treated or 

disposed of (via POTWs or 

commercial treatment systems) in or 

near communities with 

environmental justice concerns?

Analysis of Existing Data 

• Compare data on locations of hydraulic 

fracturing wastewater disposal to demographic 

information (e.g., race/ethnicity, income, and 

age)

• Maps showing locations of wastewater 

disposal and demographic data

• Identification of areas where there may be a 

disproportionate co-localization of wastewater 

disposal and communities with environmental 

justice concerns

2012

2012

Prospective Case Studies 

• Analyze demographic profiles of communities 

located near the case study locations 

• Illustrative information on the types of 

communities where hydraulic fracturing occurs 

2014
EPA Hydraulic Fracturing Study Plan November 2011 

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APPENDIX B: STAKEHOLDER COMMENTS

In total, EPA received 5,521 comments that were submitted electronically to 

hydraulic.fracturing@epa.gov or mailed to EPA. This appendix provides a summary of those comments. 

More than half of the electronic comments received consisted of a form letter written by 

Energycitizens.org14 and sent by citizens. This letter states that “Hydraulic fracturing has been used 

safely and successfully for more than six decades to extract natural gas from shale and coal deposits. In 

this time, there have been no confirmed incidents of groundwater contamination caused by the 

hydraulic fracturing process.” Additionally, the letter states that protecting the environment “should not 

lead to the creation of regulatory burdens or restrictions that have no valid scientific basis.” EPA has

interpreted this letter to mean that the sender supports hydraulic fracturing and does not support the 

need for additional study. 

Table B1 provides an overall summary of the 5,521 comments received15.

TABLE B1. SUMMARY OF STAKEHOLDER COMMENTS 

Stakeholder Comments

Percentage of 

Comments

(w/ Form Letter)

Percentage of 

Comments

(w/o Form Letter)

Position on Study Plan

For 18.2 63.2

Opposed 72.1 3.0

No Position 9.7 33.8

Expand Study 8.8 30.5

Limit Study 0.7 2.5

Position on Hydraulic Fracturing

For 75.7 15.7

Opposed 11.6 40.3

No Position 12.7 44.1

Table B2 further provides the affiliations (i.e., citizens, government, industry) associated with the 

stakeholders, and indicates that the majority of comments EPA received came from citizens. 

 14 Energy Citizens is financially sponsored by API, as noted at http://energycitizens.org/ec/advocacy/contentrail.aspx?ContentPage=About. 

15 Comments may be found at 

http://yosemite.epa.gov/sab/SABPRODUCT.NSF/81e39f4c09954fcb85256ead006be86e/d3483ab445ae614185257

75900603e79!OpenDocument&TableRow=2.2#2
EPA Hydraulic Fracturing Study Plan November 2011 

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TABLE B2. SUMMARY OF COMMENTS ON HYDRAULIC FRACTURING AND RELATED STUDY PLAN

Category

Percentage of 

Comments

(w/ Form Letter)

Percentage of 

Comments

(w/o Form Letter)

Association 0.24 0.82

Business association 0.69 2.39

Citizen 23.47 81.56

Citizen (form letter Energycitizens.org) 71.22 NA

Elected official 0.18 0.63

Environmental 1.10 3.84

Federal government 0.07 0.25

Lobbying organization 0.04 0.13

Local government 0.62 2.14

Oil and gas association 0.09 0.31

Oil and gas company 0.38 1.32

Political group 0.16 0.57

Private company 0.78 2.71

Scientific organization 0.02 0.06

State government 0.13 0.44

University 0.24 0.82

Water utility 0.02 0.06

Unknown 0.56 1.95

Table B3 provides a summary of the frequent research areas requested in the stakeholder comments.

TABLE B3. FREQUENT RESEARCH AREAS REQUESTED IN STAKEHOLDER COMMENTS

Research Area Number of 

Requests*

Ground water 292

Surface water 281

Air pollution 220

Water use (source of water used) 182

Flowback treatment/disposal 170

Public health 165

Ecosystem effects 160

Toxicity and chemical identification 157

Chemical fate and transport 107

Radioactivity issues 74

Seismic issues 36

Noise pollution 26

* Out of 485 total requests to expand the hydraulic fracturing study.
EPA Hydraulic Fracturing Study Plan November 2011 

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In addition to the frequently requested research areas, there were a variety of other comments and 

recommendations related to potential research areas. These comments and recommendations are listed 

below:

• Abandoned and undocumented wells

• Auto-immune diseases related to hydraulic fracturing chemicals

• Bioaccumulation of hydraulic fracturing chemicals in the food chain

• Biodegradable/nontoxic fracturing liquids

• Carbon footprint of entire hydraulic fracturing process

• Comparison of accident rates to coal/oil mining accident rates

• Disposal of drill cuttings

• Effects of aging on well integrity

• Effects of hydraulic fracturing on existing public and private wells

• Effects of truck/tanker traffic 

• Effects on local infrastructure (e.g., roads, water treatment plants)

• Effects on tourism

• Hydraulic fracturing model

• Economic impacts on landowners

• Land farming on fracturing sludge

• Light pollution

• Long-term corrosive effects of brine and microbes on well pipes

• Natural flooding near hydraulic fracturing operations

• Radioactive proppants

• Recovery time and persistence of hydraulic fracturing chemicals in contaminated aquifers

• Recycling of flowback and produced water

• Removal of radium and other radionuclides from flowback and produced water

• Restoration of drill sites

• Review current studies of hydraulic fracturing with microseismic testing

• Sociological effects (e.g., community changes with influx of workers)

• Soil contamination at drill sites

• Volatile organic compound emissions from hydraulic fracturing operations and impoundments

• Wildlife habitat fragmentation

• Worker occupational health
EPA Hydraulic Fracturing Study Plan November 2011 

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APPENDIX C: DEPARTMENT OF ENERGY’S EFFORTS ON HYDRAULIC FRACTURING

DOE has invested in research on safer hydraulic fracturing techniques, including research related to well 

integrity, greener additives, risks from abandoned wells, possible seismic impacts, water treatment and 

recycling, and fugitive methane emissions. 

DOE’s experience includes quantifying and evaluating potential risks resulting from the production and 

development of shale gas resources, including multi-phase flow in wells and reservoirs, well control, 

casing, cementing, drilling fluids, and abandonment operations associated with drilling, completion, 

stimulation, and production operations. DOE also has experience in evaluating seal-integrity and 

wellbore-integrity characteristics in the context of the protection of groundwater.

DOE has developed a wide range of new technologies and processes, including innovations that reduce 

the environmental impact of exploration and production, such as greener chemicals or additives used in 

shale gas development, flowback water treatment processes and water filtration technologies. Data 

from these research activities may assist decision-makers.

DOE has developed and evaluated novel imaging technologies for areal magnetic surveys for the 

detection of unmarked abandoned wells, and for detecting and measuring fugitive methane emissions 

from exploration, production, and transportation facilities. DOE also conducts research in produced 

water characterization, development of shale formation fracture models, development of microseismic 

and isotope-based comprehensive monitoring tools, and development of integrated assessment models 

to predict geologic behavior during the evolution of shale gas plays. DOE's experience in engineered 

underground containment systems for CO2 storage and enhanced geothermal systems also brings 

capabilities that are relevant to the challenges of safe shale gas production.

As part of these efforts, EPA and DOE are working together on a prospective case study located in the 

Marcellus Shale region that leverages DOE’s capabilities in field-based monitoring of environmental 

signals. DOE is conducting soil gas surveys, hydraulic fracturing tracer studies, and electromagnetic 

induction surveys to identify possible migration of natural gas, completion fluids, or production fluids. 

Monitoring activities will continue throughout the development of the well pad, and during hydraulic 

fracturing and production of shale gas at the site. The Marcellus Test Site is undergoing a comprehensive 

monitoring plan, including potential impacts to drinking water resources.

More information can be found on the following websites:

• http://www.fe.doe.gov/programs/oilgas/index.html 

• http://www.netl.doe.gov/technologies/oil-gas/index.html

• http://www.netl.doe.gov/kmd/Forms/Search.aspx

• http://ead.anl.gov/index.cfm

• http://www1.eere.energy.gov/geothermal/
EPA Hydraulic Fracturing Study Plan November 2011 

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APPENDIX D: INFORMATION REQUESTS

Request to hydraulic fracturing service companies. In September 2010, EPA issued information requests 

to nine hydraulic fracturing service companies to collect data that will inform this study. The requests 

were sent to the following companies: BJ Services, Complete Well Services, Halliburton, Key Energy 

Services, Patterson-UTI, RPC, Schlumberger, Superior Well Services, and Weatherford. These companies 

are a subset of those from which the House Committee on Energy and Commerce requested comment. 

Halliburton, Schlumberger, and BJ Services are the three largest companies operating in the US; the 

others are companies of varying size that operate in the major US shale plays. EPA sought information 

on the chemical composition of fluids used in the hydraulic fracturing process, data on the impacts of 

the chemicals on human health and the environment, standard operating procedures at hydraulic 

fracturing sites and the locations of sites where fracturing has been conducted. EPA sent a mandatory 

request to Halliburton on November 9, 2010, to compel Halliburton to provide the requested 

information. All companies have submitted the information.

The questions asked in the voluntary information request are stated below.

QUESTIONS

Your response to the following questions is requested within thirty (30) days of receipt of this 

information request:

1. Provide the name of each hydraulic fracturing fluid formulation/mixture distributed or utilized 

by the Company within the past five years from the date of this letter. For each 

formulation/mixture, provide the following information for each constituent of such product. 

“Constituent” includes each and every component of the product, including chemical 

substances, pesticides, radioactive materials and any other components.

a. Chemical name (e.g., benzene—use IUPAC nomenclature);

b. Chemical formula (e.g., C6H6);

c. Chemical Abstract System number (e.g., 71-43-2);

d. Material Safety Data Sheet;

e. Concentration (e.g., ng/g or ng/L) of each constituent in each hydraulic fracturing fluid 

product. Indicate whether the concentration was calculated or determined analytically. 

This refers to the actual concentration injected during the fracturing process following 

mixing with source water, and the delivered concentration of the constituents to the 

site. Also indicate the analytical method which may be used to determine the 

concentration (e.g., SW-846 Method 8260, in-house SOP), and include the analytical 

preparation method (e.g., SW-846 Method 5035), where applicable; 

f. Identify the persons who manufactured each product and constituent and the persons 
EPA Hydraulic Fracturing Study Plan November 2011 

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who sold them to the Company, including address and telephone numbers for any such 

persons; 

g. Identify the purpose and use of each constituent in each hydraulic fracturing fluid

product (e.g., solvent, gelling agent, carrier);

h. For proppants, identify the proppant, whether or not it was resin coated, and the 

materials used in the resin coating;

i. For the water used, identify the quantity, quality and the specifications of water needed 

to meet site requirements, and the rationale for the requirements; 

j. Total quantities of each constituent used in hydraulic fracturing and the related quantity 

of water in which the chemicals were mixed to create the fracturing fluids to support 

calculated and/or measured composition and properties of the hydraulic fracturing 

fluids; and

k. Chemical and physical properties of all chemicals used, such as Henry’s law coefficients, 

partitioning coefficients (e.g., Kow KOC, Kd), aqueous solubility, degradation products and 

constants and others.

2. Provide all data and studies in the Company’s possession relating to the human health and 

environmental impacts and effects of all products and constituents identified in Question 1.

3. For all hydraulic fracturing operations for natural gas extraction involving any of the products 

and constituents identified in the response to Question 1, describe the process including the 

following:

a. Please provide any policies, practices and procedures you employ, including any 

Standard Operating Procedures (SOPs) concerning hydraulic fracturing sites, for all 

operations including but not limited to: drilling in preparation for hydraulic fracturing 

including calculations or other indications for choice and composition of drilling 

fluids/muds; water quality characteristics needed to prepare fracturing fluid; 

relationships among depth, pressure, temperature, formation geology, geophysics and 

chemistry and fracturing fluid composition and projected volume; determination of 

estimated volumes of flowback and produced waters; procedures for managing 

flowback and produced waters; procedures to address unexpected circumstances such 

as loss of drilling fluid/mud, spills, leaks or any emergency conditions (e.g., blow outs), 

less than fully effective well completion; modeling and actual choice of fracturing 

conditions such as pressures, temperatures, and fracturing material choices; 

determination of exact concentration of constituents in hydraulic fracturing fluid 

formulations/mixtures; determination of dilution ratios for hydraulic fracturing fluids, 

and

b. Describe how fracturing fluid products and constituents are modified at a site during the 
EPA Hydraulic Fracturing Study Plan November 2011 

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fluid injection process.

a. Identify all sites where, and all persons to whom, the Company:

i. provided hydraulic fracturing fluid services that involve the use of hydraulic 

fracturing fluids for the year prior to the date of this letter, and 

ii. plans to provide hydraulic fracturing fluid services that involve the use of 

hydraulic fracturing fluids during one year after the date of this letter.

b. Describe the specific hydraulic fracturing fluid services provided or to be provided for 

each of the sites in Question 4.a.i. and ii., including the identity of any contractor that 

the Company has hired or will hire to provide any portion of such services.

For each site identified in response to Question 4, please provide all information specified in the 

enclosed electronic spreadsheet.

Request to Oil and Gas Operators. On August 11, 2011, EPA sent letters to nine companies that own or 

operate oil and gas wells requesting their voluntary participation in EPA’s hydraulic fracturing study.

Clayton Williams Energy, Conoco Phillips, EQT Production, Hogback Exploration, Laramie Energy II, MDS 

Energy, Noble Energy, Sand Ridge Operating, and Williams Production were randomly selected from a 

list of operators derived from the information gathered from the September 2010 letter to hydraulic 

fracturing service companies. The companies were asked to provide data on well construction, design, 

and well operation practices for 350 oil and gas wells that were hydraulically fractured from 2009 to 

2010. EPA made this request as part of its national study to examine the potential impacts of hydraulic 

fracturing on drinking water resources. As of October 31, 2011, all nine companies have agreed to assist 

EPA and are currently sending or have completed sending their information.

The wells were selected using a stratified random method and reflect diversity in both geography and 

size of the oil and gas operator. To identify the wells for this request, the list of operators was sort in 

order by those with the most wells to those with the fewest wells. EPA defined operators to be “large” if 

their combined number of wells accounted for the top 50 percent of wells on the list, “medium” if their 

combined number of wells accounted for the next 25 percent of wells on the list and “small” if their 

number of wells were among the last 25 percent of wells on the list. To minimize potential burden on 

the smallest operators, all operators with nine wells or less were removed from consideration for 

selection. Then, using a map from the U.S. Energy Information Administration showing all shale gas plays

(Figure 3), EPA classified four different areas of the nation: East, South, Rocky Mountain (including 

California) and Other. To choose the nine companies that received the request, EPA randomly selected 

one “large” operator from each geographic area, for a total of four “large” operators, and then 

randomly, and without geographic consideration, selected two “medium” and three “small” operators. 

Once the nine companies were identified, we used a computer algorithm that balanced geographic 

diversity and random selection within an operator’s list to select 350 wells.
EPA Hydraulic Fracturing Study Plan November 2011 

117

The questions asked in the letters were as follows:

Your response to the following questions is requested within thirty (30) days of receipt of this 

information request: 

For each well listed in Enclosure 5 of this letter, provide any and all of the following information:

Geologic Maps and Cross Sections 

1. Prospect geologic maps of the field or area where the well is located. The map should 

depict, to the extent known, the general field area, including the existing production wells 

within the field, preferably showing surface and bottom-hole locations, names of 

production wells, faults within the area, locations of delineated source water protection 

areas, and geologic structure. 

2. Geologic cross section(s) developed for the field in order to understand the geologic 

conditions present at the wellbore, including the directional orientation of each cross 

section such as north, south, east, and west. 

Drilling and Completion Information 

3. Daily drilling and completion records describing the day-by-day account and detail of drilling 

and completion activities. 

4. Mud logs displaying shows of gas or oil, losses of circulation, drilling breaks, gas kicks, mud 

weights, and chemical additives used. 

5. Caliper, density, resistivity, sonic, spontaneous potential, and gamma logs. 

6. Casing tallies, including the number, grade, and weight of casing joints installed. 

7. Cementing records for each casing string, which are expected to include the type of cement 

used, cement yield, and wait-on-cement times. 

8. Cement bond logs, including the surface pressure during each logging run, and cement 

evaluation logs, radioactive tracer logs or temperature logs, if available. 

9. Pressure testing results of installed casing. 

10. Up-to-date wellbore diagram.

Water Quality, Volume, and Disposition 

11. Results from any baseline water quality sampling and analyses of nearby surface or 

groundwater prior to drilling. 

12. Results from any post-drilling and post-completion water quality sampling and analyses of 

nearby surface or groundwater. 

13. Results from any formation water sampling and analyses, including data on composition, 

depth sampled, and date collected. 

14. Results from chemical, biological, and radiological analyses of “flowback,” including date 

sampled and cumulative volume of “flowback” produced since fracture stimulation. 
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118

15. Results from chemical, biological, and radiological analyses of “produced water,” including 

date sampled and cumulative volume of “produced water” produced since fracture 

stimulation. 

16. Volume and final disposition of “flowback.” 

17. Volume and final disposition of “produced water.” 

18. If any of the produced water or flowback fluids were recycled, provide information, 

including, but not limited to, recycling procedure, volume of fluid recycled, disposition of 

any recycling waste stream generated, and what the recycled fluids were used for. 

Hydraulic Fracturing 

19. Information about the acquisition of the base fluid used for fracture stimulation, including, 

but not limited to, its total volume, source, and quality necessary for successful stimulation. 

If the base fluid is not water, provide the chemical name(s) and CAS number(s) of the base 

fluid.

20. Estimate of fracture growth and propagation prior to hydraulic fracturing. This estimate 

should include modeling inputs (e.g., permeability, Young’s modulus, Poisson’s ratio) and 

outputs (e.g., fracture length, height, and width). 

21. Fracture stimulation pumping schedule or plan, which would include the number, length, 

and location of stages; perforation cluster spacings; and the stimulation fluid to be used, 

including the type and respective amounts of base fluid, chemical additives and proppants 

planned. 

22. Post-fracture stimulation report containing, but not limited to, a chart showing all pressures 

and rates monitored during the stimulation; depths stimulated; number of stages employed 

during stimulation; calculated average width, height, and half-length of fractures; and 

fracture stimulation fluid actually used, including the type and respective amounts of base 

fluid, chemical additives and proppants used. 

23. Micro-seismic monitoring data associated with the well(s) listed in Enclosure 5, or 

conducted in a nearby well and used to set parameters for hydraulic fracturing design. 

Environmental Releases 

24. Spill incident reports for any fluid spill associated with this well, including spills by vendors 

and service companies. This information should include, but not be limited to, the volume 

spilled, volume recovered, disposition of any recovered volume, and the identification of 

any waterways or groundwater that was impacted from the spill and how this is known. 
EPA Hydraulic Fracturing Study Plan November 2011 

119

APPENDIX E: CHEMICALS IDENTIFIED IN HYDRAULIC FRACTURING FLUID AND 

FLOWBACK/PRODUCED WATER

NOTE: In all tables in Appendix E, the chemicals are primarily listed as identified in the cited reference. 

Due to varying naming conventions or errors in reporting, there may be some duplicates or inaccurate 

names. Some effort has been made to eliminate errors, but further evaluation will be conducted as part 

of the study analysis. 

TABLE E1. CHEMICALS FOUND IN HYDRAULIC FRACTURING FLUIDS

Chemical Name Use Ref.

1-(1-naphthylmethyl)quinolinium chloride 12

1-(phenylmethyl)-ethyl pyridinium, methyl derive. Acid corrosion inhibitor 1,6,13

1,1,1-Trifluorotoluene 7

1,1':3',1''-Terphenyl 8

1,1':4',1''-Terphenyl 8

1,1-Dichloroethylene 7

1,2,3-Propanetricarboxylic acid, 2-hydroxy-, trisodium 

salt, dihydrate

12,14

1,2,3-Trimethylbenzene 12, 14

1,2,4-Butanetricarboxylic acid, 2-phosphono- 12,14

1,2,4-Trimethylbenzene Non-ionic surfactant 5,10,12,13,14

1,2-Benzisothiazolin-3-one 7,12,14

1,2-Dibromo-2,4-dicyanobutane 12,14

1,2-Ethanediaminium, N, N'-bis[2-[bis(2-

hydroxyethyl)methylammonio]ethyl]-N,N'bis(2-

hydroxyethyl)-N,N'-dimethyl-,tetrachloride

12

1,2-Propylene glycol 8,12,14

1,2-Propylene oxide 12

1,3,5-Triazine-1,3,5(2H,4H,6H)-triethanol 12,14

1,3,5-Trimethylbenzene 12,14

1,4-Dichlorobutane 7

1,4-Dioxane 7,14

1,6 Hexanediamine Clay control 13

1,6-Hexanediamine 8,12

1,6-Hexanediamine dihydrochloride 12

1-[2-(2-Methoxy-1-methylethoxy)-1-methylethoxy]-2-

propanol

13

1-3-Dimethyladamantane 8

1-Benzylquinolinium chloride Corrosion inhibitor 7,12,14

1-Butanol 7,12,14

1-Decanol 12

1-Eicosene 7,14

1-Hexadecene 7,14

1-Hexanol 12

1-Methoxy-2-propanol 7,12,14

1-Methylnaphthalene 1

Table continued on next page
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120

Chemical Name Use Ref.

1-Octadecanamine, N,N-dimethyl- 12

1-Octadecene 7,14

1-Octanol 12

1-Propanaminium, 3-amino-N-(carboxymethyl)-N,Ndimethyl-, N-coco acyl derivs., chlorides, sodium salts12

1-Propanaminium, 3-amino-N-(carboxymethyl)-N,Ndimethyl-, N-coco acyl derivs., inner salts7,12,14

1-Propanaminium, N-(3-aminopropyl)-2-hydroxy-N,Ndimethyl-3-sulfo-, N-coco acyl derivs., inner salts7,12,14

1-Propanesulfonic acid, 2-methyl-2-[(1-oxo-2-

propenyl)amino]-

7,14

1-Propanol Crosslinker 10,12,14

1-Propene 13

1-Tetradecene 7,14

1-Tridecanol 12

1-Undecanol Surfactant 13

2-(2-Butoxyethoxy)ethanol Foaming agent 1

2-(2-Ethoxyethoxy)ethyl acetate 12,14

2-(Hydroxymethylamino)ethanol 12

2-(Thiocyanomethylthio)benzothiazole Biocide 13

2,2'-(Octadecylimino)diethanol 12

2,2,2-Nitrilotriethanol 8

2,2'-[Ethane-1,2-diylbis(oxy)]diethanamine 12

2,2'-Azobis-{2-(imidazlin-2-yl)propane dihydrochloride 7,14

2,2-Dibromo-3-nitrilopropionamide Biocide 1,6,7,9,10,12,14

2,2-Dibromopropanediamide 7,14

2,4,6-Tribromophenol 7

2,4-Dimethylphenol 4

2,4-Hexadienoic acid, potassium salt, (2E,4E)- 7,14

2,5 Dibromotoluene 7

2-[2-(2-Methoxyethoxy)ethoxy]ethanol 8

2-acrylamido-2-methylpropanesulphonic acid sodium 

salt polymer

12

2-acrylethyl(benzyl)dimethylammonium Chloride 7,14

2-bromo-3-nitrilopropionamide Biocide 1,6

2-Butanone oxime 12

2-Butoxyacetic acid 8

2-Butoxyethanol Foaming agent, breaker 

fluid

1,6,9,12,14

2-Butoxyethanol phosphate 8

2-Di-n-butylaminoethanol 12,14

2-Ethoxyethanol Foaming agent 1,6

2-Ethoxyethyl acetate Foaming agent 1

2-Ethoxynaphthalene 7,14

2-Ethyl-1-hexanol 5,12,14

2-Ethyl-2-hexenal Defoamer 13

2-Ethylhexanol 9

2-Fluorobiphenyl 7

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121

Chemical Name Use Ref.

2-Fluorophenol 7

2-Hydroxyethyl acrylate 12,14

2-Mercaptoethanol 12

2-Methoxyethanol Foaming agent 1

2-Methoxyethyl acetate Foaming agent 1

2-Methyl-1-propanol Fracturing fluid 12,13,14

2-Methyl-2,4-pentanediol 12,14

2-Methyl-3(2H)-isothiazolone Biocide 12,13

2-Methyl-3-butyn-2-ol 7,14

2-Methylnaphthalene 1

2-Methylquinoline hydrochloride 7,14

2-Monobromo-3-nitrilopropionamide Biocide 10,12,14

2-Phosphonobutane-1,2,4-tricarboxylic acid, potassium 

salt

12

2-Propanol, aluminum salt 12

2-Propen-1-aminium, N,N-dimethyl-N-2-propenyl-, 

chloride

7,14

2-Propen-1-aminium, N,N-dimethyl-N-2-propenyl-, 

chloride, homopolymer

7,14

2-Propenoic acid, polymer with sodium phosphinate 7,14

2-Propenoic acid, telomer with sodium hydrogen sulfite 7,14

2-Propoxyethanol Foaming agent 1

2-Substituted aromatic amine salt 12,14

3,5,7-Triazatricyclo(3.3.1.1(superscript 3,7))decane, 1-

(3-chloro-2-propenyl)-, chloride, (Z)-

7,14

3-Bromo-1-propanol Microbiocide 1

4-(1,1-Dimethylethyl)phenol, methyloxirane, 

formaldehyde polymer

7,14

4-Chloro-3-methylphenol 4

4-Dodecylbenzenesulfonic acid 7,12,14

4-Ethyloct-1-yn-3-ol Acid inhibitor 5,12,14

4-Methyl-2-pentanol 12

4-Methyl-2-pentanone 5

4-Nitroquinoline-1-oxide 7

4-Terphenyl-d14 7

(4R)-1-methyl-4-(prop-1-en-2-yl)cyclohexene 5,12,14

5-Chloro-2-methyl-3(2H)-isothiazolone Biocide 12,13,14

6-Methylquinoline 8

Acetaldehyde 12,14

Acetic acid Acid treatment, buffer 5,6,9,10,12,14

Acetic acid, cobalt(2+) salt 12,14

Acetic acid, hydroxy-, reaction products with 

triethanolamine

14

Acetic anhydride 5,9,12,14

Acetone Corrosion Inhibitor 5,6,12,14

Acetonitrile, 2,2',2''-nitrilotris- 12

Acetophenone 12

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122

Chemical Name Use Ref.

Acetylene 9

Acetylenic alcohol 12

Acetyltriethyl citrate 12

Acrolein Biocide 13

Acrylamide 7,12,14

Acrylamide copolymer 12

Acrylamide-sodium acrylate copolymer 7,14

Acrylamide-sodium-2-acrylamido-2-methlypropane 

sulfonate copolymer

Gelling agent 7,12,14

Acrylate copolymer 12

Acrylic acid/2-acrylamido-methylpropylsulfonic acid 

copolymer

12

Acrylic copolymer 12

Acrylic polymers 12,14

Acrylic resin 14

Acyclic hydrocarbon blend 12

Adamantane 8

Adipic acid Linear gel polymer 6,12,14

Alcohol alkoxylate 12

Alcohols 12,14

Alcohols, C11-14-iso-, C13-rich 7,14

Alcohols, C9-C22 12

Alcohols; C12-14-secondary 12,14

Aldehyde Corrosion inhibitor 10,12,14

Aldol 12,14

Alfa-alumina 12,14

Aliphatic acids 7,12,14

Aliphatic alcohol glycol ether 14

Aliphatic alcohol polyglycol ether 12

Aliphatic amine derivative 12

Aliphatic hydrocarbon (naphthalenesulfonic acide, 

sodium salt, isopropylated)

Surfactant 13

Alkaline bromide salts 12

Alkalinity 13

Alkanes, C10-14 12

Alkanes, C1-2 4

Alkanes, C12-14-iso- 14

Alkanes, C13-16-iso- 12

Alkanes, C2-3 4

Alkanes, C3-4 4

Alkanes, C4-5 4

Alkanolamine/aldehyde condensate 12

Alkenes 12

Alkenes, C>10 .alpha.- 7,12,14

Alkenes, C>8 12

Alkoxylated alcohols 12

Alkoxylated amines 12

Alkoxylated phenol formaldehyde resin 12,14

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123

Chemical Name Use Ref.

Alkyaryl sulfonate 12

Alkyl alkoxylate 12,14

Alkyl amine 12

Alkyl amine blend in a metal salt solution 12,14

Alkyl aryl amine sulfonate 12

Alkyl aryl polyethoxy ethanol 7,14

Alkyl esters 12,14

Alkyl hexanol 12,14

Alkyl ortho phosphate ester 12

Alkyl phosphate ester 12

Alkyl quaternary ammonium chlorides 12

Alkyl* dimethyl benzyl ammonium chloride 

*(61% C12, 23% C14, 11% C16, 2.5% C18 2.5% C10 and trace of C8)

Corrosion inhibitor 7

Alkylaryl sulfonate 7,12,14

Alkylaryl sulphonic acid 12

Alkylated quaternary chloride 12,14

Alkylbenzenesulfonate, linear Foaming agent 5,6,12

Alkylbenzenesulfonic acid 9,12,14

Alkylethoammonium sulfates 12

Alkylphenol ethoxylates 12

Almandite and pyrope garnet 12,14

Alpha-C11-15-sec-alkyl-omega-hydroxypoly(oxy-1,2-

ethanediyl)

12

Alpha-Terpineol 8

Alumina Proppant 12,13,14

Aluminium chloride 7,12,14

Aluminum Crosslinker 4,6,12,14

Aluminum oxide 12,14

Aluminum oxide silicate 12

Aluminum silicate Proppant 13,14

Aluminum sulfate 12,14

Amides, coco, N-[3-(dimethylamino)propyl] 12,14

Amides, coco, N-[3-(dimethylamino)propyl], alkylation 

products with chloroacetic acid, sodium salts

12

Amides, coco, N-[3-(dimethylamino)propyl], N-oxides 7,12,14

Amides, tall-oil fatty, N,N-bis(hydroxyethyl) 7,14

Amides, tallow, n-[3-(dimethylamino)propyl],n-oxides 12

Amidoamine 12

Amine 12,14

Amine bisulfite 12

Amine oxides 12

Amine phosphonate 12

Amine salt 12

Amines, C14-18; C16-18-unsaturated, alkyl, ethoxylated 12

Amines, C8-18 and C18-unsatd. alkyl Foaming agent 5

Amines, coco alkyl, acetate 12

Amines, coco alkyl, ethoxylated 14

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Chemical Name Use Ref.

Amines, polyethylenepoly-, ethoxylated, 

phosphonomethylated

12

Amines, tallow alkyl, ethoxylated, acetates (salts) 12,14

Amino compounds 12

Amino methylene phosphonic acid salt 12

Aminotrimethylene phosphonic acid 12

Ammonia 9,11,12,14

Ammonium acetate Buffer 5,10,12,14

Ammonium alcohol ether sulfate 7,12,14

Ammonium bifluoride 9

Ammonium bisulfite Oxygen scavenger 3,9,12,14

Ammonium C6-C10 alcohol ethoxysulfate 12

Ammonium C8-C10 alkyl ether sulfate 12

Ammonium chloride Crosslinker 1,6,10,12,14

Ammonium citrate 7,14

Ammonium fluoride 12,14

Ammonium hydrogen carbonate 12,14

Ammonium hydrogen difluoride 12,14

Ammonium hydrogen phosphonate 14

Ammonium hydroxide 7,12,14

Ammonium nitrate 7,12,14

Ammonium persulfate Breaker fluid 1,6,9

Ammonium salt 12,14

Ammonium salt of ethoxylated alcohol sulfate 12,14

Ammonium sulfate Breaker fluid 5,6,12,14

Amorphous silica 9,12,14

Anionic copolymer 12,14

Anionic polyacrylamide 12,14

Anionic polyacrylamide copolymer Friction reducer 5,6,12

Anionic polymer 12,14

Anionic polymer in solution 12

Anionic surfactants Friction reducer 5,6

Anionic water-soluble polymer 12

Anthracene 4

Antifoulant 12

Antimonate salt 12,14

Antimony 7

Antimony pentoxide 12

Antimony potassium oxide 12,14

Antimony trichloride 12

Aromatic alcohol glycol ether 12

Aromatic aldehyde 12

Aromatic hydrocarbons 13,14

Aromatic ketones 12,14

Aromatic polyglycol ether 12

Aromatics 1

Arsenic 4

Arsenic compounds 14

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Chemical Name Use Ref.

Ashes, residues 14

Atrazine 8

Attapulgite Gelling agent 13

Barium 4

Barium sulfate 5,12,14

Bauxite Proppant 12,13,14

Bentazone 8

Bentone clay 14

Bentonite Fluid additives 5,6,12,14

Bentonite, benzyl(hydrogenated tallow alkyl) 

dimethylammonium stearate complex

14

Benzalkonium chloride 14

Benzene Gelling agent 1,12,14

Benzene, 1,1'-oxybis-, tetrapropylene derivs., 

sulfonated, sodium salts

14

Benzene, C10-16-alkyl derivs. 12

Benzenesulfonic acid, (1-methylethyl)-, ammonium salt 7,14

Benzenesulfonic acid, C10-16-alkyl derivs. 12,14

Benzenesulfonic acid, C10-16-alkyl derivs., potassium 

salts

12,14

Benzo(a)pyrene 4

Benzoic acid 9,12,14

Benzyl chloride 12

Benzyl-dimethyl-(2-prop-2-enoyloxyethyl)ammonium 

chloride

8

Benzylsuccinic acid 8

Beryllium 11

Bicarbonate 7

Bicine 12

Biocide component 12

Bis(1-methylethyl)naphthalenesulfonic acid, 

cyclohexylamine salt

12

Bis(2-methoxyethyl) ether Foaming Agent 1

Bishexamethylenetriamine penta methylene 

phosphonic acid

12

Bisphenol A 8

Bisphenol A/Epichlorohydrin resin 12,14

Bisphenol A/Novolac epoxy resin 12,14

Blast furnace slag Viscosifier 13,14

Borate salts Crosslinker 3,12,14

Borax Crosslinker 1,6,12,14

Boric acid Crosslinker 1,6,9,12,14

Boric acid, potassium salt 12,14

Boric acid, sodium salt 9,12

Boric oxide 7,12,14

Boron 4

Boron sodium oxide 12,14

Boron sodium oxide tetrahydrate 12,14

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Chemical Name Use Ref.

Bromide (-1) 7

Bromodichloromethane 7

Bromoform 7

Bronopol Microbiocide 5,6,12,14

Butane 5

Butanedioic acid, sulfo-, 1,4-bis(1,3-dimethylbutyl) 

ester, sodium salt

12

Butyl glycidyl ether 12,14

Butyl lactate 12,14

C.I. Pigment orange 5 14

C10-C16 ethoxylated alcohol Surfactant 12,13,14

C-11 to C-14 n-alkanes, mixed 12

C12-14-tert-alkyl ethoxylated amines 7,14

Cadmium 4

Cadmium compounds 13,14

Calcium 4

Calcium bromide 14

Calcium carbonate 12,14

Calcium chloride 7,9,12,14

Calcium dichloride dihydrate 12,14

Calcium fluoride 12

Calcium hydroxide pH control 12,13,14

Calcium hypochlorite 12,14

Calcium oxide Proppant 9,12,13,14

Calcium peroxide 12

Calcium sulfate Gellant 13,14

Carbohydrates 5,12,14

Carbon 14

Carbon black Resin 13,14

Carbon dioxide Foaming agent 5,6,12,14

Carbonate alkalinity 7

Carbonic acid calcium salt (1:1) pH control 12,13

Carbonic acid, dipotassium salt 12,14

Carboxymethyl cellulose 8

Carboxymethyl guar gum, sodium salt 12

Carboxymethyl hydroxypropyl guar 9,12,14

Carboxymethylguar Linear gel polymer 6

Carboxymethylhydroxypropylguar Linear gel polymer 6

Cationic polymer Friction reducer 5,6

Caustic soda 13,14

Caustic soda beads 13,14

Cellophane 12,14

Cellulase enzyme 12

Cellulose 7,12,14

Cellulose derivative 12,14

Ceramic 13,14

Cetyl trimethyl ammonium bromide 12

CFR-3 14

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Chemical Name Use Ref.

Chloride 4

Chloride (-1) 14

Chlorine Lubricant 13

Chlorine dioxide 7,12,14

Chlorobenzene 4

Chlorodibromomethane 7

Chloromethane 7

Chlorous ion solution 12

Choline chloride 9,12,14

Chromates 12,14

Chromium Crosslinker 11

Chromium (III) acetate 12

Chromium (III), insoluble salts 6

Chromium (VI) 6

Chromium acetate, basic 13

Cinnamaldehyde (3-phenyl-2-propenal) 9,12,14

Citric acid Iron control 3,9,12,14

Citrus terpenes 7,12,14

Coal, granular 12,14

Cobalt 7

Coco-betaine 7,14

Coconut oil acid/diethanolamine condensate (2:1) 12

Collagen (gelatin) 12,14

Common White 14

Complex alkylaryl polyo-ester 12

Complex aluminum salt 12

Complex organometallic salt 12

Complex polyamine salt 9

Complex substituted keto-amine 12

Complex substituted keto-amine hydrochloride 12

Copolymer of acrylamide and sodium acrylate 12,14

Copper 5,12

Copper compounds Breaker fluid 1,6

Copper sulfate 7,12,14

Copper(I) iodide Breaker fluid 5,6,12,14

Copper(II) chloride 7,12,14

Coric oxide 14

Corn sugar gum Corrosion inhibitor 12,13,14

Corundum 14

Cottonseed flour 13,14

Cremophor(R) EL 7,12,14

Crissanol A-55 7,14

Cristobalite 12,14

Crotonaldehyde 12,14

Crystalline silica, tridymite 12,14

Cumene 7,12,14

Cupric chloride dihydrate 7,9,12

Cuprous chloride 12,14

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Chemical Name Use Ref.

Cured acrylic resin 12,14

Cured resin 9,12,14

Cured silicone rubber-polydimethylsiloxane 12

Cured urethane resin 12,14

Cyanide 11

Cyanide, free 7

Cyclic alkanes 12

Cyclohexane 9,12

Cyclohexanone 12,14

D-(-)-Lactic acid 12,14

Dapsone 12,14

Dazomet Biocide 9,12,13,14

Decyldimethyl amine 7,14

D-Glucitol 7,12,14

D-Gluconic acid 12

D-Glucose 12

D-Limonene 5,7,9

Di(2-ethylhexyl) phthalate 7,12

Diatomaceous earth, calcined 12

Diatomaceus earth Proppant 13,14

Dibromoacetonitrile 7,12,14

Dibutyl phthalate 4

Dicalcium silicate 12,14

Dicarboxylic acid 12

Didecyl dimethyl ammonium chloride Biocide 12,13

Diesel 1,6,12

Diethanolamine Foaming agent 1,6,12,14

Diethylbenzene 7,12,14

Diethylene glycol 5,9,12,14

Diethylene glycol monobutyl ether 8

Diethylene glycol monoethyl ether Foaming agent 1

Diethylene glycol monomethyl ether Foaming agent 1,12,14

Diethylenetriamine Activator 10,12,14

Diisopropylnaphthalene 7,14

Diisopropylnaphthalenesulfonic acid 7,12,14

Dimethyl glutarate 12,14

Dimethyl silicone 12,14

Dinonylphenyl polyoxyethylene 14

Dipotassium monohydrogen phosphate 5

Dipropylene glycol 7,12,14

Di-secondary-butylphenol 12

Disodium 

dodecyl(sulphonatophenoxy)benzenesulphonate

12

Disodium ethylenediaminediacetate 12

Disodium ethylenediaminetetraacetate dihydrate 12

Dispersing agent 12

Distillates, petroleum, catalytic reformer fractionator 

residue, low-boiling

12

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Chemical Name Use Ref.

Distillates, petroleum, hydrodesulfurized light catalytic 

cracked

12

Distillates, petroleum, hydrodesulfurized middle 12

Distillates, petroleum, hydrotreated heavy naphthenic 5,12,14

Distillates, petroleum, hydrotreated heavy paraffinic 12,14

Distillates, petroleum, hydrotreated light Friction reducer 5,9,10,12,14

Distillates, petroleum, hydrotreated light naphthenic 12

Distillates, petroleum, hydrotreated middle 12

Distillates, petroleum, light catalytic cracked 12

Distillates, petroleum, solvent-dewaxed heavy paraffinic 12,14

Distillates, petroleum, solvent-refined heavy naphthenic 12

Distillates, petroleum, steam-cracked 12

Distillates, petroleum, straight-run middle 12,14

Distillates, petroleum, sweetened middle 12,14

Ditallow alkyl ethoxylated amines 7,14

Docusate sodium 12

Dodecyl alcohol ammonium sulfate 12

Dodecylbenzene 7,14

Dodecylbenzene sulfonic acid salts 12,14

Dodecylbenzenesulfonate isopropanolamine 7,12,14

Dodecylbenzene sulfonic acid, monoethanolamine salt 12

Dodecylbenzene sulphonic acid, morpholine salt 12,14

Econolite Additive 14

Edifas B Fluid additives 5,14

EDTA copper chelate Breaker fluid, activator 5,6,10,12,14

Endo- 1,4-beta-mannanase, or Hemicellulase 14

EO-C7-9-iso; C8 rich alcohols 14

EO-C9-11-iso; C10 rich alcohols 12,14

Epichlorohydrin 12,14

Epoxy resin 12

Erucic amidopropyl dimethyl detaine 7,12,14

Essential oils 12

Ester salt Foaming agent 1

Ethanaminium, N,N,N-trimethyl-2-[(1-oxo-2-

propenyl)oxy]-, chloride

14

Ethanaminium, N,N,N-trimethyl-2-[(1-oxo-2-

propenyl)oxy]-,chloride, polymer with 2-propenamide

12,14

Ethane 5

Ethanol Foaming agent, nonionic surfactant1,6,10,12,14

Ethanol, 2,2'-iminobis-, N-coco alkyl derivs., N-oxides 12

Ethanol, 2,2'-iminobis-, N-tallow alkyl derivs. 12

Ethanol, 2-[2-[2-(tridecyloxy)ethoxy]ethoxy]-, hydrogen 

sulfate, sodium salt

12

Ethanolamine Crosslinker 1,6,12,14

Ethoxylated 4-nonylphenol 13

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Chemical Name Use Ref.

Ethoxylated alcohol/ester mixture 14

Ethoxylated alcohols16 5,9,12,13,14

Ethoxylated alkyl amines 12,14

Ethoxylated amine 12,14

Ethoxylated fatty acid ester 12,14

Ethoxylated fatty acid, coco 14

Ethoxylated fatty acid, coco, reaction product with 

ethanolamine

14

Ethoxylated nonionic surfactant 12

Ethoxylated nonylphenol 8,12,14

Ethoxylated propoxylated C12-14 alcohols 12,14

Ethoxylated sorbitan trioleate 7,14

Ethoxylated sorbitol esters 12,14

Ethoxylated undecyl alcohol 12

Ethoxylated, propoxylated trimethylolpropane 7,14

Ethylacetate 9,12,14

Ethylacetoacetate 12

Ethyllactate 7,14

Ethylbenzene Gelling Agent 1,9,12,14

Ethylcellulose Fluid Additives 13

Ethylene glycol Crosslinker/ Breaker 

Fluids/ Scale Inhibitor

1,6,9,12,14

Ethylene glycol diethyl ether Foaming Agent 1

Ethylene glycol dimethyl ether Foaming Agent 1

Ethylene oxide 7,12,14

Ethylene oxide-nonylphenol polymer 12

Ethylenediaminetetraacetic acid 12,14

Ethylenediaminetetraacetic acid tetrasodium salt 

hydrate

7,12,14

Ethylenediaminetetraacetic acid, diammonium copper 

salt

14

Ethylene-vinyl acetate copolymer 12

Ethylhexanol 14

Fatty acid ester 12

Fatty acid, tall oil, hexa esters with sorbitol, ethoxylated 12,14

Fatty acids 12

Fatty acids, tall oil reaction products w/acetophenone, 

formaldehyde & thiourea

14

Fatty acids, tall-oil 7,12,14

Fatty acids, tall-oil, reaction products with 

diethylenetriamine

12

Fatty acids, tallow, sodium salts 7,14

Fatty alcohol alkoxylate 12,14

Fatty alkyl amine salt 12

Table continued on next page

 16 Multiple categories of ethoxylated alcohols were listed in various references. Due to different naming 

conventions, there is some uncertainty as to whether some are duplicates or some incorrect. Therefore, 

“ethoxylated alcohols” is included here as a single item with further evaluation to follow. 

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Chemical Name Use Ref.

Fatty amine carboxylates 12

Fatty quaternary ammonium chloride 12

FD & C blue no. 1 12

Ferric chloride 7,12,14

Ferric sulfate 12,14

Fluorene 1

Fluoride 7

Fluoroaliphatic polymeric esters 12,14

Formaldehyde polymer 12

Formaldehyde, polymer with 4-(1,1-dimethyl)phenol, 

methyloxirane and oxirane

12

Formaldehyde, polymer with 4-nonylphenol and 

oxirane

12

Formaldehyde, polymer with ammonia and phenol 12

Formaldehyde, polymers with branched 4-nonylphenol, 

ethylene oxide and propylene oxide

14

Formalin 7,12,14

Formamide 7,12,14

Formic acid Acid Treatment 1,6,9,12,14

Formic acid, potassium salt 7,12,14

Fuel oil, no. 2 12,14

Fuller’s earth Gelling agent 13

Fumaric acid Water gelling agent/ 

linear gel polymer

1,6,12,14

Furfural 12,14

Furfuryl alcohol 12,14

Galactomannan Gelling agent 13

Gas oils, petroleum, straight-run 12

Gilsonite Viscosifier 12,14

Glass fiber 7,12,14

Gluconic acid 9

Glutaraldehyde Biocide 3,9,12,14

Glycerin, natural Crosslinker 7,10,12,14

Glycine, N-(carboxymethyl)-N-(2-hydroxyethyl)-, 

disodium salt

12

Glycine, N,N'-1,2-ethanediylbis[N-(carboxymethyl)-, 

disodium salt

7,12,14

Glycine, N,N-bis(carboxymethyl)-, trisodium salt 7,12,14

Glycine, N-[2-[bis(carboxymethyl)amino]ethyl]-N-(2-

hydroxyethyl)-, trisodium salt

12

Glycol ethers 9,12

Glycolic acid 7,12,14

Glycolic acid sodium salt 7,12,14

Glyoxal 12

Glyoxylic acid 12

Graphite Fluid additives 13

Guar gum 9,12,14

Guar gum derivative 12

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Chemical Name Use Ref.

Gypsum 13,14

Haloalkyl heteropolycycle salt 12

Heavy aromatic distillate 12

Heavy aromatic petroleum naphtha 13,14

Hematite 12,14

Hemicellulase 5,12,14

Heptane 5,12

Heptene, hydroformylation products, high-boiling 12

Hexane 5

Hexanes 12

Hydrated aluminum silicate 12,14

Hydrocarbons 12

Hydrocarbons, terpene processing by-products 7,12,14

Hydrochloric acid Acid treatment, solvent 1,6,9,10,12,14

Hydrogen fluoride (Hydrofluoric acid) Acid treatment 12

Hydrogen peroxide 7,12,14

Hydrogen sulfide 7,12

Hydrotreated and hydrocracked base oil 12

Hydrotreated heavy naphthalene 5

Hydrotreated light distillate 14

Hydrotreated light petroleum distillate 14

Hydroxyacetic acid ammonium salt 7,14

Hydroxycellulose Linear gel polymer 6

Hydroxyethylcellulose Gel 3,12,14

Hydroxylamine hydrochloride 7,12,14

Hydroxyproplyguar Linear gel polymer 6

Hydroxypropyl cellulose 8

Hydroxypropyl guar gum Linear gel delivery, 

water gelling agent

1,6,10,12,14

Hydroxysultaine 12

Igepal CO-210 7,12,14

Inner salt of alkyl amines 12,14

Inorganic borate 12,14

Inorganic particulate 12,14

Inorganic salt 12

Instant coffee purchased off the shelf 12

Inulin, carboxymethyl ether, sodium salt 12

Iron Emulsifier/surfactant 13

Iron oxide Proppant 12,13,14

Iron(II) sulfate heptahydrate 7,12,14

Iso-alkanes/n-alkanes 12,14

Isoascorbic acid 7,12,14

Isomeric aromatic ammonium salt 7,12,14

Isooctanol 5,12,14

Isooctyl alcohol 12

Isopentyl alcohol 12

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Chemical Name Use Ref.

Isopropanol Foaming agent/ 

surfactant, acid 

corrosion inhibitor

1,6,9,12,14

Isopropylamine 12

Isoquinoline, reaction products with benzyl chloride and 

quinoline

14

Isotridecanol, ethoxylated 7,12,14

Kerosine, petroleum, hydrodesulfurized 7,12,14

Kyanite Proppant 12,13,14

Lactic acid 12

Lactose 7,14

Latex 2000 13,14

L-Dilactide 12,14

Lead 4,12

Lead compounds 14

Lignite Fluid additives 13

Lime 14

Lithium 7

L-Lactic acid 12

Low toxicity base oils 12

Lubra-Beads coarse 14

Maghemite 12,14

Magnesium 4

Magnesium aluminum silicate Gellant 13

Magnesium carbonate 12

Magnesium chloride Biocide 12,13

Magnesium chloride hexahydrate 14

Magnesium hydroxide 12

Magnesium iron silicate 12,14

Magnesium nitrate Biocide 12,13,14

Magnesium oxide 12,14

Magnesium peroxide 12

Magnesium phosphide 12

Magnesium silicate 12,14

Magnetite 12,14

Manganese 4

Mercury 11

Metal salt 12

Metal salt solution 12

Methanamine, N,N-dimethyl-, hydrochloride 5,12,14

Methane 5

Methanol Acid corrosion inhibitor 1,6,9,10,12,14

Methenamine 12,14

Methyl bromide 7

Methyl ethyl ketone 4

Methyl salicylate 9

Methyl tert-butyl ether Gelling agent 1

Methyl vinyl ketone 12

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Chemical Name Use Ref.

Methylcyclohexane 12

Methylene bis(thiocyanate) Biocide 13

Methyloxirane polymer with oxirane, mono 

(nonylphenol) ether, branched

14

Mica Fluid additives 5,6,12,14

Microbond expanding additive 14

Mineral 12,14

Mineral filler 12

Mineral oil Friction reducer 3,14

Mixed titanium ortho ester complexes 12

Modified lignosulfonate 14

Modified alkane 12,14

Modified cycloaliphatic amine adduct 12,14

Modified lignosulfonate 12

Modified polysaccharide or pregelatinized cornstarch or 

starch

8

Molybdenum 7

Monoethanolamine 14

Monoethanolamine borate 12,14

Morpholine 12,14

Muconic acid 8

Mullite 12,14

N,N,N-Trimethyl-2[1-oxo-2-propenyl]oxy 

ethanaminimum chloride

7,14

N,N,N-Trimethyloctadecan-1-aminium chloride 12

N,N'-Dibutylthiourea 12

N,N-Dimethyl formamide Breaker 3,14

N,N-Dimethyl-1-octadecanamine-HCl 12

N,N-Dimethyldecylamine oxide 7,12,14

N,N-Dimethyldodecylamine-N-oxide 8

N,N-Dimethylformamide 5,12,14

N,N-Dimethyl-methanamine-n-oxide 7,14

N,N-Dimethyl-N-[2-[(1-oxo-2-propenyl)oxy]ethyl]-

benzenemethanaminium chloride

7,14

N,N-Dimethyloctadecylamine hydrochloride 12

N,N'-Methylenebisacrylamide 12,14

n-Alkanes,C10-C18 4

n-Alkanes,C18-C70 4

n-Alkanes,C5-C8 4

n-Butanol 9

Naphtha, petroleum, heavy catalytic reformed 5,12,14

Naphtha, petroleum, hydrotreated heavy 7,12,14

Naphthalene Gelling agent, non-ionic 

surfactant

1,9,10,12,14

Naphthalene derivatives 12

Naphthalenesulphonic acid, bis (1-methylethyl)-methyl 

derivatives

12

Naphthenic acid ethoxylate 14

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Chemical Name Use Ref.

Navy fuels JP-5 7,12,14

Nickel 4

Nickel sulfate Corrosion inhibitor 13

Nickel(II) sulfate hexahydrate 12

Nitrazepam 8

Nitrilotriacetamide scale inhibiter 9,12

Nitrilotriacetic acid 12,14

Nitrilotriacetic acid trisodium monohydrate 12

Nitrobenzene 8

Nitrobenzene-d5 7

Nitrogen, liquid Foaming agent 5,6,12,14

N-Lauryl-2-pyrrolidone 12

N-Methyl-2-pyrrolidone 12,14

N-Methyldiethanolamine 8

N-Oleyl diethanolamide 12

Nonane, all isomers 12

Non-hazardous salt 12

Nonionic surfactant 12

Nonylphenol (mixed) 12

Nonylphenol ethoxylate 8,12,14

Nonylphenol, ethoxylated and sulfated 12

N-Propyl zirconate 12

N-Tallowalkyltrimethylenediamines 12,14

Nuisance particulates 12

Nylon fibers 12,14

Oil and grease 4

Oil of wintergreen 12,14

Oils, pine 12,14

Olefinic sulfonate 12

Olefins 12

Organic acid salt 12,14

Organic acids 12

Organic phosphonate 12

Organic phosphonate salts 12

Organic phosphonic acid salts 12

Organic salt 12,14

Organic sulfur compound 12

Organic surfactants 12

Organic titanate 12,14

Organo-metallic ammonium complex 12

Organophilic clays 7,12,14

O-Terphenyl 7,14

Other inorganic compounds 12

Oxirane, methyl-, polymer with oxirane, mono-C10-16-

alkyl ethers, phosphates

12

Oxiranemethanaminium, N,N,N-trimethyl-, chloride, 

homopolymer

7,14

Oxyalkylated alcohol 12,14

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Chemical Name Use Ref.

Oxyalkylated alkyl alcohol 12

Oxyalkylated alkylphenol 7,12,14

Oxyalkylated fatty acid 12

Oxyalkylated phenol 12

Oxyalkylated polyamine 12

Oxylated alcohol 5,12,14

P/F resin 14

Paraffin waxes and hydrocarbon waxes 12

Paraffinic naphthenic solvent 12

Paraffinic solvent 12,14

Paraffins 12

Pentaerythritol 8

Pentane 5

Perlite 14

Peroxydisulfuric acid, diammonium salt Breaker fluid 1,6,12,14

Petroleum 12

Petroleum distillates 12,14

Petroleum gas oils 12

Petroleum hydrocarbons 7

Phenanthrene Biocide 1,6

Phenol 4,12,14

Phenolic resin Proppant 9,12,13,14

Phosphate ester 12,14

Phosphate esters of alkyl phenyl ethoxylate 12

Phosphine 12,14

Phosphonic acid 12

Phosphonic acid (dimethlamino(methylene)) 12

Phosphonic acid, (1-hydroxyethylidene)bis-, 

tetrasodium salt

12,14

Phosphonic acid, [[(phosphonomethyl)imino]bis[2,1-

ethanediylnitrilobis(methylene)]]tetrakisScale inhibitor 12,13

Phosphonic acid, [[(phosphonomethyl)imino]bis[2,1-

ethanediylnitrilobis(methylene)]]tetrakis-, sodium salt

7,14

Phosphonic acid, [nitrilotris(methylene)]tris-, 

pentasodium salt

12

[[(Phosphonomethyl)imino]bis[2,1-

ethanediylnitrilobis(methylene)]]tetrakis phosphonic 

acid ammonium salt

7,14

Phosphoric acid ammonium salt 12

Phosphoric acid Divosan X-Tend formulation 12

Phosphoric acid, aluminium sodium salt Fluid additives 12,13

Phosphoric acid, diammonium salt Corrosion inhibitor 13

Phosphoric acid, mixed decyl and Et and octyl esters 12

Phosphoric acid, monoammonium salt 14

Phosphorous acid 12

Phosphorus 7

Phthalic anhydride 12

Plasticizer 12

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Chemical Name Use Ref.

Pluronic F-127 12,14

Poly (acrylamide-co-acrylic acid), partial sodium salt 14

Poly(oxy-1,2-ethanediyl), .alpha.-(nonylphenyl)-omegahydroxy-, phosphate12,14

Poly(oxy-1,2-ethanediyl), .alpha.-(octylphenyl)-omegahydroxy-, branched12

Poly(oxy-1,2-ethanediyl), alpha,alpha'-[[(9Z)-9-

octadecenylimino]di-2,1-ethanediyl]bis[.omega.-

hydroxy12,14

Poly(oxy-1,2-ethanediyl), alpha-sulfo-.omega.-hydroxy-, 

C12-14-alkyl ethers, sodium salts

12,14

Poly(oxy-1,2-ethanediyl), alpha-hydro-omega-hydroxy 12

Poly(oxy-1,2-ethanediyl), alpha-sulfo-omega-(hexyloxy)-

ammonium salt

12,14

Poly(oxy-1,2-ethanediyl), alpha-tridecyl-omegahydroxy12,14

Poly-(oxy-1,2-ethanediyl)-alpha-undecyl-omegahydroxy12,14

Poly(oxy-1,2-ethanediyl)-nonylphenyl-hydroxy Acid corrosion 

inhibitor, non-ionic 

surfactant

7,12,13,14

Poly(sodium-p-styrenesulfonate) 12

Poly(vinyl alcohol) 12

Poly[imino(1,6-dioxo-1,6-hexanediyl)imino-1,6-

hexanediyl]

Resin 13

Polyacrylamide Friction reducer 3,6,12,13,14

Polyacrylamides 12

Polyacrylate 12,14

Polyamine 12,14

Polyamine polymer 14

Polyanionic cellulose 12

Polyaromatic hydrocarbons Gelling agent/ 

bactericides

1,6,13

Polycyclic organic matter Gelling agent/ 

bactericides

1,6,13

Polyethene glycol oleate ester 7,14

Polyetheramine 12

Polyethoxylated alkanol 7,14

Polyethylene glycol 5,9,12,14

Polyethylene glycol ester with tall oil fatty acid 12

Polyethylene glycol mono(1,1,3,3-

tetramethylbutyl)phenyl ether

7,12,14

Polyethylene glycol monobutyl ether 12,14

Polyethylene glycol nonylphenyl ether 7,12,14

Polyethylene glycol tridecyl ether phosphate 12

Polyethylene polyammonium salt 12

Polyethyleneimine 14

Polyglycol ether Foaming agent 1,6,13

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Chemical Name Use Ref.

Polyhexamethylene adipamide Resin 13

Polylactide resin 12,14

Polymer 14

Polymeric hydrocarbons 14

Polyoxyalkylenes 9,12

Polyoxylated fatty amine salt 7,12,14

Polyphosphoric acids, esters with triethanolamine, 

sodium salts

12

Polyphosphoric acids, sodium salts 12,14

Polypropylene glycol Lubricant 12,13

Polysaccharide 9,12,14

Polysaccharide blend 14

Polysorbate 60 14

Polysorbate 80 7,14

Polyvinyl alcohol Fluid additives 12,13,14

Polyvinyl alcohol/polyvinylacetate copolymer 12

Portland cement clinker 14

Potassium 7

Potassium acetate 7,12,14

Potassium aluminum silicate 5

Potassium borate 7,14

Potassium carbonate pH control 3,10,13

Potassium chloride Brine carrier fluid 1,6,9,12,13,14

Potassium hydroxide Crosslinker 1,6,12,13,14

Potassium iodide 12,14

Potassium metaborate 5,12,14

Potassium oxide 12

Potassium pentaborate 12

Potassium persulfate Fluid additives 12,13

Propane 5

Propanimidamide, 2,2''-azobis[2-methyl-, 

dihydrochloride

12,14

Propanol, 1(or 2)-(2-methoxymethylethoxy)- 8,12,14

Propargyl alcohol Acid corrosion inhibitor 1,6,9,12,13,14

Propylene carbonate 12

Propylene glycol 14

Propylene pentamer 12

p-Xylene 12,14

Pyridine, alkyl derivs. 12

Pyridinium, 1-(phenylmethyl)-, Et Me derivs., chlorides Acid corrosion 

inhibitor, corrosion 

inhibitor

1,6,12,13,14

Pyrogenic colloidal silica 12,14

Quartz Proppant 5,6,12,13,14

Quartz sand Proppant 3,13

Quaternary amine 8

Quaternary amine compounds 12

Quaternary ammonium compound 8,12

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Chemical Name Use Ref.

Quaternary ammonium compounds, (oxydi-2,1-

ethanediyl)bis[coco alkyldimethyl, dichlorides

7,14

Quaternary ammonium compounds, 

benzylbis(hydrogenated tallow alkyl)methyl, salts with 

bentonite

Fluid additives 5,6,13

Quaternary ammonium compounds, benzyl-C12-16-

alkyldimethyl, chlorides

12

Quaternary ammonium compounds, bis(hydrogenated 

tallow alkyl)dimethyl, salts with bentonite

14

Quaternary ammonium compounds, bis(hydrogenated 

tallow alkyl)dimethyl, salts with hectorite

Viscosifier 13

Quaternary ammonium compounds, dicoco 

alkyldimethyl, chlorides

12

Quaternary ammonium compounds, trimethyltallow 

alkyl, chlorides

12

Quaternary ammonium salts 8,12,14

Quaternary compound 12

Quaternary salt 12,14

Radium (228) 4

Raffinates (petroleum) 5

Raffinates, petroleum, sorption process 12

Residual oils, petroleum, solvent-refined 5

Residues, petroleum, catalytic reformer fractionator 12,14

Resin 14

Rosin 12

Rutile 12

Saline Brine carrier fluid, 

breaker

5,10,12,13,14

Salt 14

Salt of amine-carbonyl condensate 14

Salt of fatty acid/polyamine reaction product 14

Salt of phosphate ester 12

Salt of phosphono-methylated diamine 12

Salts of alkyl amines Foaming agent 1,6,13

Sand 14

Saturated sucrose 7,12,14

Secondary alcohol 12

Selenium 7

Sepiolite 14

Silane, dichlorodimethyl-, reaction products with silica 14

Silica Proppant 3,12,13,14

Silica gel, cryst.-free 14

Silica, amorphous 12

Silica, amorphous precipitated 12,14

Silica, microcrystalline 13

Silica, quartz sand 14

Silicic acid (H4SiO4), tetramethyl ester 12

Silicon dioxide (fused silica) 12,14

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Chemical Name Use Ref.

Silicone emulsion 12

Silicone ester 14

Silver 7

Silwet L77 12

Soda ash 14

Sodium 4

Sodium 1-octanesulfonate 7,14

Sodium 2-mercaptobenzothiolate Corrosion inhibitor 13

Sodium acetate 7,12,14

Sodium alpha-olefin Sulfonate 14

Sodium aluminum oxide 12

Sodium benzoate 7,14

Sodium bicarbonate 5,9,12,14

Sodium bisulfite, mixture of NaHSO3 and Na2S2O5 7,12,14

Sodium bromate Breaker 12,13,14

Sodium bromide 7,9,12,14

Sodium carbonate pH control 3,12,13,14

Sodium chlorate 12,14

Sodium chlorite Breaker 7,10,12,13,14

Sodium chloroacetate 7,14

Sodium cocaminopropionate 12

Sodium decyl sulfate 12

Sodium diacetate 12

Sodium dichloroisocyanurate Biocide 13

Sodium erythorbate 7,12,14

Sodium ethasulfate 12

Sodium formate 14

Sodium hydroxide Gelling agent 1,9,12,13,14

Sodium hypochlorite 7,12,14

Sodium iodide 14

Sodium ligninsulfonate Surfactant 13

Sodium metabisulfite 12

Sodium metaborate 7,12,14

Sodium metaborate tetrahydrate 12

Sodium metasilicate 12,14

Sodium nitrate Fluid additives 13

Sodium nitrite Corrosion inhibitor 12,13,14

Sodium octyl sulfate 12

Sodium oxide (Na2O) 12

Sodium perborate 12

Sodium perborate tetrahydrate Concentrate 7,10,12,13,14

Sodium persulfate 5,9,12,14

Sodium phosphate 12,14

Sodium polyacrylate 7,12,14

Sodium pyrophosphate 5,12,14

Sodium salicylate 12

Sodium silicate 12,14

Sodium sulfate 7,12,14

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Chemical Name Use Ref.

Sodium sulfite 14

Sodium tetraborate decahydrate Crosslinker 1,6,13

Sodium thiocyanate 12

Sodium thiosulfate 7,12,14

Sodium thiosulfate, pentahydrate 12

Sodium trichloroacetate 12

Sodium xylenesulfonate 9,12

Sodium zirconium lactate 12

Sodium α-olefin sulfonate 7

Solvent naphtha, petroleum, heavy aliph. 14

Solvent naphtha, petroleum, heavy arom. Non-ionic surfactant 5,10,12,13,14

Solvent naphtha, petroleum, light arom. Surfactant 12,13,14

Sorbitan, mono-(9Z)-9-octadecenoate 7,12,14

Stannous chloride dihydrate 12,14

Starch Proppant 12,14

Starch blends Fluid additives 6

Steam cracked distillate, cyclodiene dimer, 

dicyclopentadiene polymer

12

Steranes 4

Stoddard solvent 7,12,14

Stoddard solvent IIC 7,12,14

Strontium 7

Strontium (89&90) 13

Styrene Proppant 13

Substituted alcohol 12

Substituted alkene 12

Substituted alkylamine 12

Sugar 14

Sulfamic acid 7,12,14

Sulfate 4,7,12,14

Sulfite 7

Sulfomethylated tannin 5

Sulfonate acids 12

Sulfonate surfactants 12

Sulfonic acid salts 12

Sulfonic acids, C14-16-alkane hydroxy and C14-16-

alkene, sodium salts

7,12,14

Sulfonic acids, petroleum 12

Sulfur compound 12

Sulfuric acid 9,12,14

Surfactant blend 14

Surfactants 9,12

Symclosene 8

Synthetic organic polymer 12,14

Talc Fluid additives 5,6,9,12,13,14

Tall oil, compound with diethanolamine 12

Tallow soap 12,14

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Chemical Name Use Ref.

Tar bases, quinoline derivatives, benzyl chloridequaternized7,12,14

Tebuthiuron 8

Terpenes 12

Terpenes and terpenoids, sweet orange-oil 7,12,14

Terpineol, mixture of isomers 7,12,14

tert-Butyl hydroperoxide (70% solution in water) 12,14

tert-Butyl perbenzoate 12

Tetra-calcium-alumino-ferrite 12,14

Tetrachloroethylene 7

Tetradecyl dimethyl benzyl ammonium chloride 12

Tetraethylene glycol 12

Tetraethylenepentamine 12,14

Tetrakis(hydroxymethyl)phosphonium sulfate 7,9,12,14

Tetramethylammonium chloride 7,9,12,14

Thallium and compounds 7

Thiocyanic acid, ammonium salt 7,14

Thioglycolic acid Iron Control 12,13,14

Thiourea Acid corrosion inhibitor 1,6,12,13,14

Thiourea polymer 12,14

Thorium 2

Tin 1

Tin(II) chloride 12

Titanium Crosslinker 4

Titanium complex 12,14

Titanium dioxide Proppant 12,13,14

Titanium(4+) 2-[bis(2-hydroxyethyl)amino]ethanolate 

propan-2-olate (1:2:2)

12

Titanium, isopropoxy (triethanolaminate) 12

TOC 7

Toluene Gelling agent 1,12,14

trans-Squalene 8

Tributyl phosphate Defoamer 13

Tricalcium phosphate 12

Tricalcium silicate 12,14

Triethanolamine 5,12,14

Triethanolamine hydroxyacetate 7,14

Triethanolamine polyphosphate ester 12

Triethanolamine zirconium chelate 12

Triethyl citrate 12

Triethyl phosphate 12,14

Triethylene glycol 5,12,14

Triisopropanolamine 12,14

Trimethyl ammonium chloride 9,14

Trimethylamine quaternized polyepichlorohydrin 5,12,14

Trimethylbenzene Fracturing fluid 12,13

Tri-n-butyl tetradecyl phosphonium chloride 7,12,14

Triphosphoric acid, pentasodium salt 12,14

Table continued on next page

Table E1 continued from previous page
EPA Hydraulic Fracturing Study Plan November 2011 

143

Chemical Name Use Ref.

Tripropylene glycol monomethyl ether Viscosifier 13

Tris(hydroxymethyl)amine 7

Trisodium citrate 7,14

Trisodium ethylenediaminetetraacetate 12,14

Trisodium ethylenediaminetriacetate 12

Trisodium phosphate 7,12,14

Trisodium phosphate dodecahydrate 12

Triterpanes 4

Triton X-100 7,12,14

Ulexite 12,14

Ulexite, calcined 14

Ultraprop 14

Undecane 7,14

Uranium-238 2

Urea 7,12,14

Vanadium 1

Vanadium compounds 14

Vermiculite Lubricant 13

Versaprop 14

Vinylidene chloride/methylacrylate copolymer 14

Wall material 12

Walnut hulls 12,14

Water Water gelling agent/ 

foaming agent

1,14

White mineral oil, petroleum 12,14

Xylenes Gelling agent 1,12,14

Yttrium 1

Zinc Lubricant 13

Zinc carbonate Corrosion inhibitor 13

Zinc chloride 12

Zinc oxide 12

Zirconium 7

Zirconium complex Crosslinker 5,10,12,14

Zirconium nitrate Crosslinker 1,6

Zirconium oxide sulfate 12

Zirconium oxychloride Crosslinker 12,13

Zirconium sodium hydroxy lactate complex (sodium 

zirconium lactate)

12

Zirconium sulfate Crosslinker 1,6

Zirconium, acetate lactate oxo ammonium complexes 14

Zirconium,tetrakis[2-[bis(2-hydroxyethyl)aminokN]ethanolato-kO]-Crosslinker 10,12,14

α-[3.5-Dimethyl-1-(2-methylpropyl)hexyl]-w-hydroxypoly(oxy-1,2-ethandiyl)7,14

Table E1 continued from previous page
EPA Hydraulic Fracturing Study Plan November 2011 

144

References

1. Sumi, L. (2005). Our drinking water at risk. What EPA and the oil and gas industry don’t want us 

to know about hydraulic fracturing. Durango, CO: Oil and Gas Accountability Project/Earthworks.

Retrieved January 21, 2011, from http://www.earthworksaction.org/pubs/

DrinkingWaterAtRisk.pdf.

2. Sumi, L. (2008). Shale gas: Focus on the Marcellus Shale. Oil and Gas Accountability Project. 

Durango, CO.

3. Ground Water Protection Council & ALL Consulting. (2009). Modern shale gas development in 

the US: A primer. Washington, DC: US Department of Energy, Office of Fossil Energy and 

National Energy Technology Laboratory. Retrieved January 19, 2011, from 

http://www.netl.doe.gov/technologies/oil-gas/publications/

EPreports/Shale_Gas_Primer_2009.pdf.

4. Veil, J. A., Puder, M. G., Elcock, D., & Redweik, R. J. (2004). A white paper describing produced 

water from production of crude oil, natural gas, and coal bed methane. Argonne National 

Laboratory Report for U.S. Department of Energy, National Energy Technology Laboratory.

5. Material Safety Data Sheets; EnCana Oil & Gas (USA), Inc.: Denver, CO. Provided by EnCana upon 

US EPA Region 8 request as part of the Pavillion, WY, ground water investigation.

6. US Environmental Protection Agency. (2004). Evaluation of impacts to underground sources of 

drinking water by hydraulic fracturing of coalbed methane reservoirs. No. EPA/816/R-04/003.

Washington, DC: US Environmental Protection Agency, Office of Water. 

7. New York State Department of Environmental Conservation. (2009, September). Supplemental 

generic environmental impact statement on the oil, gas and solution mining regulatory program 

(draft). Well permit issuance for horizontal drilling and high-volume hydraulic fracturing to 

develop the Marcellus Shale and other low-permeability gas reservoirs. Albany, NY: New York 

State Department of Environmental Conservation. Retrieved January 20, 2010, from 

ftp://ftp.dec.state.ny.us/dmn/download/OGdSGEISFull.pdf.

8. US Environmental Protection Agency.(2010). Region 8 analytical lab analysis.

9. Bureau of Oil and Gas Management. (2010). Chemicals used in the hydraulic fracturing process in 

Pennsylvania. Pennsylvania Department of Environmental Protection. Retrieved September 12, 

2011, from 

http://assets.bizjournals.com/cms_media/pittsburgh/datacenter/DEP_Frac_Chemical_List_6-

30-10.pdf.

10. Material Safety Data Sheets; Halliburton Energy Services, Inc.: Duncan, OK. Provided by 

Halliburton Energy Services during an on-site visit by EPA on May 10, 2010.

11. Alpha Environmental Consultants, Inc., Alpha Geoscience, NTS Consultants, Inc. (2009). Issues 

related to developing the Marcellus Shale and other low-permeability gas reservoirs. Report for 

the New York State Energy Research and Development Authority. NYSERDA Contract No. 11169, 

NYSERDA Contract No. 10666, and NYSERDA Contract No. 11170. Albany, NY.

12. US House of Representatives Committee on Energy and Commerce Minority Staff (2011).

Chemicals used in hydraulic fracturing.
EPA Hydraulic Fracturing Study Plan November 2011 

145

13. US Environmental Protection Agency. (2010). Expanded site investigation analytical report: 

Pavillion Area groundwater investigation. Contract No. EP-W-05-050. Retrieved September 7, 

2011, from 

http://www.epa.gov/region8/superfund/wy/pavillion/PavillionAnalyticalResultsReport.pdf.

14. Submitted non-Confidential Business Information by Halliburton, Patterson and Superior. 

Available on the Federal Docket, EPA-HQ-ORD-2010-0674.
EPA Hydraulic Fracturing Study Plan November 2011 

146

TABLE E2. CHEMICALS IDENTIFIED IN FLOWBACK/PRODUCED WATER

Chemical Ref.

1,1,1-Trifluorotoluene 1

1,2-Bromo-2-nitropropane-1,3-

diol (2-bromo-2-nitro-1,3-

propanediol or bronopol)

3

1,-3-Dimethyladamantane 3

1,4-Dichlorobutane 1

1,6-Hexanediamine 3

1-Methoxy-2-propanol 3

2-(2-Methoxyethoxy)ethanol 3

2-(Thiocyanomethylthio) 

benzothiazole

3

2,2,2-Nitrilotriethanol 3

2,2-Dibromo-3-

nitrilopropionamide

3

2,2-Dibromoacetonitrile 3

2,2-Dibromopropanediamide 3

2,4,6-Tribromophenol 1

2,4-Dimethylphenol 2

2,5-Dibromotoluene 1

2-Butanone 2

2-Butoxyacetic acid 3

2-Butoxyethanol 3

2-Butoxyethanol phosphate 3

2-Ethyl-3-propylacrolein 3

2-Ethylhexanol 3

2-Fluorobiphenyl 1

2-Fluorophenol 1

3,5-Dimethyl-1,3,5-thiadiazinane2-thione3

4-Nitroquinoline-1-oxide 1

4-Terphenyl-d14 1

5-Chloro-2-methyl-4-isothiazolin3-one3

6-Methylquinoline 3

Acetic acid 3

Acetic anhydride 3

Acrolein 3

Acrylamide (2-propenamide) 3

Adamantane 3

Adipic acid 3

Aluminum 2

Ammonia 4

Ammonium nitrate 3

Ammonium persulfate 3

Anthracene 2

Antimony 1

Arsenic 2

Chemical Ref.

Atrazine 3

Barium 2

Bentazon 3

Benzene 2

Benzo(a)pyrene 2

Benzyldimethyl-(2-prop-2-

enoyloxyethyl)ammonium 

chloride

3

Benzylsuccinic acid 3

Beryllium 4

Bicarbonate 1

Bis(2-ethylhexyl)phthalate 1

Bis(2-ethylhexyl)phthalate 4

Bisphenol a 3

Boric acid 3

Boric oxide 3

Boron 1,2

Bromide 1

Bromoform 1

Butanol 3

Cadmium 2

Calcium 2

Carbonate alkalinity 1

Cellulose 3

Chloride 2

Chlorobenzene 2

Chlorodibromomethane 1

Chloromethane 4

Chrome acetate 3

Chromium 4

Chromium hexavalent

Citric acid 3

Cobalt 1

Copper 2

Cyanide 1

Cyanide 4

Decyldimethyl amine 3

Decyldimethyl amine oxide 3

Diammonium phosphate 3

Dichlorobromomethane 1

Didecyl dimethyl ammonium 

chloride

3

Diethylene glycol 3

Diethylene glycol monobutyl 

ether

3

Dimethyl formamide 3

Table continued on next page
EPA Hydraulic Fracturing Study Plan November 2011 

147

Table E2 continued from previous page

Chemical Ref.

Dimethyldiallylammonium 

chloride

3

Di-n-butylphthalate 2

Dipropylene glycol monomethyl

ether

3

Dodecylbenzene sulfonic acid 3

Eo-C7-9-iso-,C8 rich-alcohols 3

Eo-C9-11-iso, C10-rich alcohols 3

Ethoxylated 4-nonylphenol 3

Ethoxylated nonylphenol 3

Ethoxylated nonylphenol 

(branched)

3

Ethoxylated octylphenol 3

Ethyl octynol 3

Ethylbenzene 2

Ethylbenzene 3

Ethylcellulose 3

Ethylene glycol 3

Ethylene glycol monobutyl ether 3

Ethylene oxide 3

Ferrous sulfate heptahydrate 3

Fluoride 1

Formamide 3

Formic acid 3

Fumaric acid 3

Glutaraldehyde 3

Glycerol 3

Hydroxyethylcellulose 3

Hydroxypropylcellulose 3

Iron 2

Isobutyl alcohol (2-methyl-1-

propanol)

3

Isopropanol (propan-2-ol) 3

Lead 2

Limonene 3

Lithium 1

Magnesium 2

Manganese 2

Mercaptoacidic acid 3

Mercury 4

Methanamine,N,N-dimethyl-,Noxide3

Methanol 3

Methyl bromide 1

Methyl chloride 1

Methyl-4-isothiazolin 3

Methylene bis(thiocyanate) 3

Chemical Ref.

Methylene phosphonic acid 

(diethylenetriaminepenta[methyl

enephosphonic] acid)

3

Modified polysaccharide or 

pregelatinized cornstarch or 

starch

3

Molybdenum 1

Monoethanolamine 3

Monopentaerythritol 3

m-Terphenyl 3

Muconic acid 3

N,N,N-trimethyl-2[1-oxo-2-

propenyl]oxy ethanaminium 

chloride

3

n-Alkanes, C10-C18 2

n-Alkanes, C18-C70 2

n-Alkanes, C1-C2 2

n-Alkanes, C2-C3 2

n-Alkanes, C3-C4 2

n-Alkanes, C4-C5 2

n-Alkanes, C5-C8 2

Naphthalene 2

Nickel 2

Nitrazepam 3

Nitrobenzene 3

Nitrobenzene-d5 1

n-Methyldiethanolamine 3

Oil and grease 2

o-Terphenyl 1

o-Terphenyl 3

Oxiranemethanaminium, N,N,Ntrimethyl-, chloride, 

homopolymer

3

p-Chloro-m-cresol 2

Petroleum hydrocarbons 1

Phenol 2

Phosphonium, 

tetrakis(hydroxymethly)-sulfate

3

Phosphorus 1

Polyacrylamide 3

Polyacrylate 3

Polyethylene glycol 3

Polyhexamethylene adipamide 3

Polypropylene glycol 3

Polyvinyl alcohol [alcotex 17f-h] 3

Potassium 1

Propane-1,2-diol 3

Table continued on next page
EPA Hydraulic Fracturing Study Plan November 2011 

148

Table E2 continued from previous page

Chemical Ref.

Propargyl alcohol 3

Pryidinium, 1-(phenylmethyl)-, 

ethyl methyl derivatives, chlorides

3

p-Terphenyl 3

Quaternary amine 3

Quaternary ammonium 

compound

3

Quaternary ammonium salts 3

Radium (226) 2

Radium (228) 2

Selenium 1

Silver 1

Sodium 2

Sodium carboxymethylcellulose 3

Sodium dichloro-s-triazinetrione 3

Sodium mercaptobenzothiazole 3

Squalene 3

Steranes 2

Strontium 1

Sucrose 3

Sulfate 1,2

Sulfide 1

Sulfite 1

Tebuthiuron 3

Terpineol 3

Tetrachloroethene 4

Tetramethyl ammonium chloride 3

Tetrasodium 

ethylenediaminetetraacetate

3

Thallium 1

Thiourea 3

Titanium 2

Toluene 2

Total organic carbon 1

Tributyl phosphate 3

Trichloroisocyanuric acid 3

Trimethylbenzene 3

Tripropylene glycol methyl ether 3

Trisodium nitrilotriacetate 3

Triterpanes 2

Urea 3

Xylene (total) 2

Zinc 2

Zirconium 1
EPA Hydraulic Fracturing Study Plan November 2011 

149

References

1. New York State Department of Environmental Conservation. (2011, September). Supplemental 

generic environmental impact statement on the oil, gas and solution mining regulatory program 

(draft). Well permit issuance for horizontal drilling and high-volume hydraulic fracturing to 

develop the Marcellus Shale and other low-permeability gas reservoirs. Albany, NY: New York 

State Department of Environmental Conservation. Retrieved January 20, 2010, from 

ftp://ftp.dec.state.ny.us/dmn/download/OGdSGEISFull.pdf.

2. Veil, J. A., Puder, M. G., Elcock, D., & Redweik, R. J. (2004). A white paper describing produced 

water from production of crude oil, natural gas, and coal bed methane. Prepared for the US 

Department of Energy, National Energy Technology Laboratory. Argonne, IL: Argonne National 

Laboratory. Retrieved January 20, 2011, from http://www.evs.anl.gov/pub/doc/

ProducedWatersWP0401.pdf.

3. URS Operating Services, Inc. (2010, August 20). Expanded site investigation—Analytical results 

report. Pavillion area groundwater investigation. Prepared for US Environmental Protection 

Agency. Denver, CO: URS Operating Services, Inc. Retrieved January 27, 2011, from 

http://www.epa.gov/region8/superfund/wy/pavillion/

PavillionAnalyticalResultsReport.pdf.

4. Alpha Environmental Consultants, Inc., Alpha Geoscience, & NTS Consultants, Inc. (2009). Issues 

related to developing the Marcellus Shale and other low-permeability gas reservoirs. Albany, NY:

New York State Energy Research and Development Authority. 
EPA Hydraulic Fracturing Study Plan November 2011 

150

TABLE E3. NATURALLY OCCURRING SUBSTANCES MOBILIZED BY FRACTURING ACTIVITIES

Chemical Common 

Valence States Ref.

Aluminum III 1

Antimony V,III,-III 1

Arsenic V, III, 0, -III 1

Barium II 1

Beryllium II 1

Boron III 1

Cadmium II 1

Calcium II 1

Chromium VI, III 1

Cobalt III, II 1

Copper II, I 1

Hydrogen sulfide N/A 2

Iron III, II 1

Lead IV, II 1

Magnesium II 1

Molybdenum VI, III 1

Nickel II 1

Radium (226) II 2

Radium (228) II 2

Selenium VI, IV, II, 0, -II 1

Silver I 1

Sodium I 1

Thallium III, I 1

Thorium IV 2

Tin IV, II, -IV 1

Titanium IV 1

Uranium VI, IV 2

Vanadium V 1

Yttrium III 1

Zinc II 1

References

1. Sumi, L. (2005). Our drinking water at risk: What EPA and the oil and gas industry don’t want us 

to know about hydraulic fracturing. Durango, CO: Oil and Gas Accountability Project/Earthworks.

Retrieved January 21, 2011, from http://www.earthworksaction.org/pubs/

DrinkingWaterAtRisk.pdf.

2. Sumi, L. (2008). Shale gas: Focus on the Marcellus Shale. Durango, CO: Oil and Gas 

Accountability Project/Earthworks. Retrieved January 21, 2011, from 

http://www.earthworksaction.org/pubs/OGAPMarcellusShaleReport-6-12-08.pdf.
EPA Hydraulic Fracturing Study Plan November 2011

151

APPENDIX F: STAKEHOLDER-NOMINATED CASE STUDIES

This appendix lists the stakeholder-nominated case studies. Potential retrospective case study sites can be found in Table F1, while potential 

prospective case study sites are listed in Table F2. 

TABLE F1. POTENTIAL RETROSPECTIVE CASE STUDY SITES

Formation Location Key Areas to Be Addressed Key Activities Potential Outcomes Partners

Bakken Shale Killdeer and 

Dunn Co., ND

Production well failure during 

hydraulic fracturing; suspected 

drinking water aquifer 

contamination; surface waters 

nearby; soil contamination; 

more than 2,000 barrels of oil 

and fracturing fluids leaked 

from the well

Monitoring wells to evaluate 

extent of contamination of 

aquifer; soil and surface water 

monitoring

Determine extent of 

contamination of drinking water 

resources; identify sources of 

well failure

NDDMRIndustrial 

Commission, EPA 

Region 8, 

Berthold Indian 

Reservation

Barnett Shale Alvord, TX Benzene in water well RRCTX, 

landowners, 

USGS, EPA 

Region 6

Barnett Shale Azle, TX Skin rash complaints from 

contaminated water

RRCTX, 

landowners, 

USGS, EPA 

Region 6

Barnett Shale Decatur, TX Skin rash complaints from 

drilling mud applications to 

land

RRCTX, 

landowners, 

USGS, EPA 

Region 6

Table continued on next page
EPA Hydraulic Fracturing Study Plan November 2011

152

Table F1 continued from previous page

Formation Location Key Areas to Be Addressed Key Activities Potential Outcomes Partners

Barnett Shale Wise/Denton 

Cos. (including 

Dish), TX

Potential drinking water well 

contamination; surface spills;

waste pond overflow;

documented air contamination

Monitor other wells in area and 

install monitoring wells to 

evaluate source(s)

Determine sources of 

contamination of private well

RRCTX, TCEQ, 

landowners, City 

of Dish, USGS, 

EPA Region 6, 

DFW Regional 

Concerned 

Citizens Group, 

North Central 

Community 

Alliance, Sierra 

Club

Barnett Shale South Parker 

Co. and 

Weatherford, 

TX

Hydrocarbon contamination in 

multiple drinking water wells;

may be from faults/fractures 

from production well beneath 

properties

Monitor other wells in area;

install monitoring wells to 

evaluate source(s)

Determine source of methane 

and other contaminants in 

private water well; information 

on role of fracture/fault 

pathway from hydraulic 

fracturing zone

RRCTX, 

landowners, 

USGS, EPA 

Region 6

Barnett Shale Tarrant Co., TX Drinking water well 

contamination; report of 

leaking pit

Monitoring well Determine if pit leak impacted 

underlying ground water

RRCTX, 

landowners, 

USGS, EPA 

Region 6

Barnett Shale Wise Co. and

Decatur, TX 

Spills; runoff; suspect drinking 

water well contamination; air 

quality impacts

Sample wells, soils Determine sources of 

contamination of private well

RRCTX, 

landowners, 

USGS, EPA 

Region 6, 

Earthworks Oil & 

Gas 

Accountability 

Project

Clinton 

Sandstone

Bainbridge, 

OH

Methane buildup leading to 

home explosion

OHDNR, EPA 

Region 5

Fayetteville 

Shale

Arkana Basin, 

AR

General water quality concerns AROGC, ARDEQ, 

EPA Region 6

Fayetteville 

Shale

Conway Co., 

AR

Gray, smelly water AROGC, ARDEQ, 

EPA Region 6

Table continued on next page
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153

Table F1 continued from previous page

Formation Location Key Areas to Be Addressed Key Activities Potential Outcomes Partners

Fayetteville 

Shale

Van Buren or

Logan Cos., AR

Stray gas (methane) in wells; 

other water quality 

impairments

AROGC, ARDEQ, 

EPA Region 6

Haynesville 

Shale

Caddo Parish, 

LA

Drinking water impacts 

(methane in water)

Monitoring wells to evaluate 

source(s)

Evaluate extent of water well 

contamination and if source is 

from hydraulic fracturing

operations

LGS, USGS, EPA 

Region 6

Haynesville 

Shale

DeSoto Parish, 

LA

Drinking water reductions Monitoring wells to evaluate 

water availability; evaluate 

existing data

Determine source of drinking 

water reductions

LGS, USGS, EPA 

Region 6

Haynesville 

Shale

Harrison Co., 

TX

Stray gas in water wells RRCTX, 

landowners, 

USGS, EPA 

Region 6

Marcellus 

Shale

Bradford Co., 

PA 

Drinking water well 

contamination; surface spill of 

hydraulic fracturing fluids

Soil, ground water, and surface 

water sampling

Determine source of methane in 

private wells

PADEP, 

landowners, EPA 

Region 3, 

Damascus 

Citizens Group, 

Friends of the 

Upper Delaware

Marcellus 

Shale

Clearfield Co., 

PA

Well blowout PADEP, EPA 

Region 3

Marcellus 

Shale

Dimock, 

Susquehanna 

Co., PA

Contamination in multiple 

drinking water wells; surface 

water quality impairment from 

spills

Soil, ground water, and surface 

water sampling

Determine source of methane in 

private wells

PADEP, EPA 

Region 3, 

landowners, 

Damascus 

Citizens Group, 

Friends of the 

Upper Delaware

Marcellus 

Shale

Gibbs Hill, PA On-site spills; impacts to 

drinking water; changes in 

water quality

Evaluate existing data;

determine need for additional 

data

Evaluate extent of large surface 

spill’s impact on soils, surface 

water, and ground water

PADEP, 

landowner, EPA 

Region 3

Table continued on next page
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154

Table F1 continued from previous page

Formation Location Key Areas to Be Addressed Key Activities Potential Outcomes Partners

Marcellus 

Shale

Hamlin 

Township and 

McKean Co., 

PA

Drinking water contamination 

from methane; changes in 

water quality

Soil, ground water, and surface 

water sampling

Determine source of methane in 

community and private wells

PADEP, EPA 

Region 3, 

Schreiner Oil & 

Gas

Marcellus 

Shale

Hickory, PA On-site spill; impacts to 

drinking water; changes in 

water quality; methane in 

wells; contaminants in drinking 

water (acrylonitrile, VOCs)

PADEP, 

landowner, EPA 

Region 3

Marcellus 

Shale

Hopewell 

Township, PA

Surface spill of hydraulic 

fracturing fluids; waste pit 

overflow

Sample pit and underlying soils; 

sample nearby soil, ground 

water, and surface water

Evaluate extent of large surface 

spill’s impact on soils, surface 

water, and ground water

PADEP, 

landowners, EPA 

Region 3

Marcellus 

Shale

Indian Creek 

Watershed, 

WV

Concerns related to wells in 

karst formation

WVOGCC, EPA 

Region 3

Marcellus 

Shale

Lycoming Co., 

PA

Surface spill of hydraulic 

fracturing fluids

PADEP sampled soils, nearby 

surface water, and two nearby 

private wells; evaluate need for 

additional data collection to 

determine source of impact

Evaluate extent of large surface 

spill’s impact on soils, surface 

water, and ground water

Marcellus 

Shale

Monongahela 

River Basin, PA

Surface water impairment 

(high TDS, water availability)

Data exists on water quality 

over time for Monongahela 

River during ramp up of 

hydraulic fracturing activity; 

review existing data

Assess intensity of hydraulic 

fracturing activity 

Marcellus 

Shale

Susquehanna 

River Basin, PA 

and NY

Water availability; water 

quality

Assess water use and water 

quality over time; review 

existing data

Determine if water withdrawals 

for hydraulic fracturing are 

related to changes in water 

quality and availability

Marcellus 

Shale

Tioga Co., NY General water quality concerns

Marcellus 

Shale

Upshur Co., 

WV

General water quality concerns WVOGCC, EPA 

Region 3

Table continued on next page
EPA Hydraulic Fracturing Study Plan November 2011

155

Table F1 continued from previous page

Formation Location Key Areas to Be Addressed Key Activities Potential Outcomes Partners

Marcellus 

Shale

Wetzel Co., 

WV, and 

Washington/

Green Cos., PA

Stray gas; spills; changes in 

water quality; several 

landowners concerned about 

methane in wells

Soil, ground water, and surface 

water sampling

Determine extent of impact 

from spill of hydraulic fracturing

fluids associated with well 

blowout and other potential 

impacts to drinking water 

resources

WVDEP, 

WVOGCC, 

PADEP, EPA 

Region 3, 

landowners, 

Damascus 

Citizens Group

Piceance 

Basin

Battlement 

Mesa, CO

Water quality and quantity 

concerns

COGCC, 

landowners, EPA 

Region 8

Piceance 

Basin (tight 

gas sand)

Garfield Co., 

CO (Mamm 

Creek area)

Drinking water well 

contamination; changes in 

water quality; water levels

Soil, ground water, and surface 

water sampling; review existing 

data

Evaluate source of methane and 

degradation in water quality 

basin-wide 

COGCC,

landowners, EPA 

Region 8, 

Colorado League 

of Women 

Voters 

Piceance 

Basin

Rifle, CO Water quality and quantity 

concerns

COGCC, 

landowners, EPA 

Region 8

Piceance 

Basin

Silt, CO Water quality and quantity 

concerns

COGCC, 

landowners, EPA 

Region 8

Powder River 

Basin (CBM)

Clark, WY Drinking water well 

contamination

Monitoring wells to evaluate 

source(s)

Evaluate extent of water well 

contamination and if source is 

from hydraulic fracturing

operations

WOOGC, EPA 

Region 8, 

landowners

San Juan 

Basin 

(shallow CBM 

and tight 

sand)

LaPlata Co.,

CO

Drinking water well 

contamination, primarily with 

methane (area along the edge 

of the basin has large methane 

seepage)

Large amounts of data have 

been collected through various 

studies of methane seepage; gas 

wells at the margin of the basin 

can be very shallow

Evaluate extent of water well 

contamination and determine if 

hydraulic fracturing operations 

are the source 

COGCC, EPA 

Region 8, BLM, 

San Juan Citizens 

Alliance

Table continued on next page
EPA Hydraulic Fracturing Study Plan November 2011

156

Table F1 continued from previous page

Formation Location Key Areas to Be Addressed Key Activities Potential Outcomes Partners

Raton Basin 

(CBM)

Huerfano Co., 

CO

Drinking water well 

contamination; methane in 

well water; well house 

explosion

Monitoring wells to evaluate 

source of methane and 

degradation in water quality

Evaluate extent of water well 

contamination and determine if 

hydraulic fracturing operations 

are the source

COGCC, EPA 

Region 8

Raton Basin 

(CBM)

Las Animas 

Co., CO

Concerns about methane in 

water wells

COGCC, 

landowners, EPA 

Region 8

Raton Basin 

(CBM)

North Fork 

Ranch, Las 

Animas Co., 

CO

Drinking water well 

contamination; changes in 

water quality and quantity

Monitoring wells to evaluate 

source of methane and 

degradation in water quality

Evaluate extent of water well 

contamination and determine if 

hydraulic fracturing operations 

are the source

COGCC, 

landowners, EPA 

Region 8 

Tight gas 

sand

Garfield Co., 

CO

Drinking water and surface 

water contamination; 

documented benzene 

contamination

Monitoring to assess source of 

contamination

Determine if contamination is 

from hydraulic fracturing

operations in area

COGCC, EPA 

Region 8, 

Battlement 

Mesa Citizens 

Group

Tight gas 

sand

Pavillion, WY Drinking water well 

contamination

Monitoring wells to evaluate 

source(s) (ongoing studies by 

ORD and EPA Region 8)

Determine if contamination is 

from hydraulic fracturing

operations in area 

WOGCC, EPA 

Region 8, 

landowners

Tight gas 

sand

Sublette Co., 

WY (Pinedale 

Anticline)

Drinking water well 

contamination (benzene)

Monitoring wells to evaluate 

source(s)

Evaluate extent of water well 

contamination and determine if 

hydraulic fracturing operations 

are the source

WOGCC, EPA 

Region 8, 

Earthworks
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Within the scope of this study, prospective case studies will focus on key areas such as the full lifecycle and environmental monitoring. To 

address these issues, key research activities will include water and soil monitoring before, during, and after hydraulic fracturing activities.

TABLE F2. PROSPECTIVE CASE STUDIES

Formation Location Potential Outcomes Partners

Bakken Shale Berthold Indian 

Reservation, ND

Baseline water quality data, comprehensive monitoring 

and modeling of water resources during all stages of the 

hydraulic fracturing process

NDDMR-Industrial Commission, University 

of North Dakota, EPA Region 8, Berthold 

Indian Reservation

Barnett Shale Flower Mound/ 

Bartonville, TX

Baseline water quality data, comprehensive monitoring 

and modeling of water resources during all stages of the 

hydraulic fracturing process

NDDMR-Industrial Commission, EPA Region 

8, Mayor of Flower Mound

Marcellus 

Shale

Otsego Co., NY Baseline water quality data, comprehensive monitoring 

and modeling of water resources during all stages of the 

hydraulic fracturing process

NYSDEC; Gastem, USA; others TBD

Marcellus 

Shale

TBD, PA Baseline water quality data, comprehensive monitoring 

and modeling of water resources during all stages of the 

hydraulic fracturing process in a region of the country 

experiencing intensive hydraulic fracturing activity

Chesapeake Energy, PADEP, others TBD

Marcellus 

Shale

Wyoming Co, PA Baseline water quality data, comprehensive monitoring 

and modeling of water resources during all stages of the 

hydraulic fracturing process

DOE, PADEP, University of Pittsburgh, 

Range Resources, USGS, landowners, EPA 

Region 3

Niobrara 

Shale

Laramie Co., WY Baseline water quality data, comprehensive monitoring 

and modeling of water resources during all stages of the 

hydraulic fracturing process, potential epidemiology study 

by Wyoming Health Department

WOGCC, Wyoming Health Department, 

landowners, USGS, EPA Region 8

Woodford 

Shale or 

Barnett Shale

OK or TX Baseline water quality data, comprehensive monitoring 

and modeling of water resources during all stages of the 

hydraulic fracturing process

OKCC, landowners, USGS, EPA Region 6
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Appendix F Acronym List

ARDEQ Arkansas Department of Environmental Quality

AROGC Arkansas Oil and Gas Commission

BLM Bureau of Land Management

CBM coalbed methane

Co. county

COGCC Colorado Oil and Gas Conservation Commission

DFW Dallas-Fort Worth

DOE US Department of Energy

EPA US Environmental Protection Agency

LGS Louisiana Geological Survey

NDDMR North Dakota Department of Mineral Resources

NYSDEC New York Department of Environmental Conservation

OHDNR Ohio Department of Natural Resources

OKCC Oklahoma Corporation Commission

PADEP Pennsylvania Department of Environmental Protection

RRCTX Railroad Commission of Texas

TBD to be determined

TCEQ Texas Commission on Environmental Quality

USACE US Army Corps of Engineers

USGS US Geological Survey

VOC volatile organic compound

WOGCC Wyoming Oil and Gas Conservation Commission

WVDEP West Virginia Department of Environmental Protection

WVOGCC West Virginia Oil and Gas Conservation Commission
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APPENDIX G: ASSESSING MECHANICAL INTEGRITY

In relation to hydrocarbon production, it is useful to distinguish between the internal and external 

mechanical integrity of wells. Internal mechanical integrity is concerned with the containment of fluids 

within the confines of the well. External mechanical integrity is related to the potential movement of 

fluids along the wellbore outside the well casing.

A well’s mechanical integrity can be determined most accurately through a combination of data and 

tests that individually provide information, which can then be compiled and evaluated. This appendix 

provides a brief overview of the tools used to assess mechanical well integrity.

CEMENT BOND TOOLS

The effectiveness of the cementing process is determined using cement bond tools and/or cement 

evaluation tools. Cement bond tools are acoustic devices that produce data (cement bond logs) used to 

evaluate the presence of cement behind the casing. Cement bond logs generally include a gamma-ray 

curve and casing collar locator; transit time, which measures the time it takes for a specific sound wave 

to travel from the transmitter to the receiver; amplitude curve, which measures the strength of the first 

compressional cycle of the returning sound wave; and a graphic representation of the waveform, which 

displays the manner in which the received sound wave varies with time. This latter presentation, the 

variable density log, reflects the material through which the signal is transmitted. To obtain meaningful 

data, the tool must properly calibrated and be centralized in the casing to obtain data that is meaningful 

for proper evaluation of the cement behind the casing.

Other tools available for evaluating cement bonding use ultrasonic transducers arranged in a spiral 

around the tool or in a single rotating hub to survey the circumference of the casing. The transducers 

emit ultrasonic pulses and measure the received ultrasonic waveforms reflected from the internal and 

external casing interfaces. The resulting logs produce circumferential visualizations of the cement bonds 

with the pipe and borehole wall. Cement bonding to the casing can be measured quantitatively, while 

bonding to the formation can only be measured qualitatively. Even though cement bond/evaluation 

tools do not directly measure hydraulic seal, the measured bonding qualities do provide inferences of 

sealing. 

The cement sheath can fail during well construction if the cement fails to adequately encase the well 

casing or becomes contaminated with drilling fluid or formation material. After a well has been 

constructed, cement sheath failure is most often related to temperature- and pressure-induced stresses 

resulting from operation of the well (Ravi et al., 2002). Such stresses can result in the formation of a 

microannulus, which can provide a pathway for the migration of fluids from high-pressure zones.

TEMPERATURE LOGGING

Temperature logging can be used to determine changes that have taken place in and adjacent to 

injection/production wells. The temperature log is a continuous recording of temperature versus depth.
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Under certain conditions the tool can be used to conduct a flow survey, locating points of inflow or 

outflow in a well; locate the top of the cement in wells during the cement curing process (using the heat 

of hydration of the cement); and detect the flow of fluid and gas behind the casing. The temperature 

logging tool is the oldest of the production tools and one of the most versatile, but a highly qualified 

expert must use it and interpret its results.

NOISE LOGGING

The noise logging tool may have application in certain conditions to detect fluid movement within 

channels in cement in the casing/borehole annulus. It came into widespread application as a way to 

detect the movement of gas through liquid. For other flows, for example water through a channel, the 

tool relies on the turbulence created as the water flows through a constriction that creates turbulent 

flow. Two advantages of using the tool are its sensitivity and lateral depth of investigation. It can detect 

sound through multiple casings, and an expert in the interpretation of noise logs can distinguish flow 

behind pipe from flow inside pipe.

PRESSURE TESTING

A number of pressure tests are available to assist in determining the internal mechanical integrity of 

production wells. For example, while the well is being constructed, before the cement plug is drilled out 

for each casing, the casing should be pressure-tested to find any leaks. The principle of such a “standard 

pressure test” is that pressure applied to a fixed-volume enclosed vessel, closed at the bottom and the 

top, should remain constant if there are no leaks. The same concept applies to the “standard annulus 

pressure test,” which is used when tubing and packers are a part of the well completion. 

The “Ada” pressure test is used in some cases where the well is constructed with tubing without a 

packer, in wells with only casing and open perforations, and in dual injection/production wells. 

The tools discussed above are summarized below in Table G1.
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TABLE G1. COMPARISON OF TOOLS USED TO EVALUATE WELL INTEGRITY

Type of Tool Description and Application Types of Data

Acoustic cement 

bond tools

Acoustic devices to evaluate the 

presence of cement behind the 

casing

• Gamma-ray curve

• Casing collar locator: depth control 

• Transit time: time it takes for a specific sound wave 

to travel from the transmitter to the receiver 

• Amplitude curve: strength of the first 

compressional cycle of the returning sound wave 

• Waveform: variation of received sound wave over 

time

• Variable density log: reflects the material through 

which the signal is transmitted

Ultrasonic 

transducers

Transmit ultrasonic pulses and 

measure the received ultrasonic 

waveforms reflected from the 

internal and external casing 

interfaces to survey well casing

• Circumferential visualizations of the cement bonds 

with the pipe and borehole wall 

• Quantitative measures of cement bonding to the 

casing 

• Qualitative measure of bonding to the formation 

• Inferred sealing integrity

Temperature 

logging

Continuous recording of 

temperature versus depth to 

detect changes in and adjacent 

to injection/production wells

• Flow survey

• Points of inflow or outflow in a well 

• Top of cement in wells during the cement curing 

process (using the heat of hydration of the 

cement) 

• Flow of fluid and gas behind casing

Noise logging 

tool

Recording of sound patterns 

that can be correlated to fluid 

movement; sound can be 

detected through multiple 

casings

• Fluid movement within channels in cement in the 

casing/borehole annulus

Pressure tests Check for leaks in casing • Changes in pressure within a fixed-volume 

enclosed vessel, implying that leaks are present

References

Ravi, K., Bosma, M., & Gastebled, O. (2002, April 30-May 2). Safe and economic gas wells through 

cement design for life of the well. No. SPE 75700. Presented at the Society of Petroleum Engineers Gas 

Technology Symposium, Calgary, Alberta, Canada.
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APPENDIX H: FIELD SAMPLING AND ANALYTICAL METHODS

Field samples and monitoring data associated with hydraulic fracturing activities are collected for a 

variety of reasons, including to:

• Develop baseline data prior to fracturing.

• Monitor any changes in drinking water resources during and after hydraulic fracturing.

• Identify and quantify environmental contamination that may be associated with hydraulic 

fracturing.

• Evaluate well mechanical integrity.

• Evaluate the performance of treatment systems.

Field sampling is important for both the prospective and retrospective case studies discussed in Chapter 

9. In retrospective case studies, EPA will take field samples to determine the cause of reported drinking 

water contamination. In prospective case studies, field sampling and monitoring provides for the 

identification of baseline conditions of the site prior to drilling and fracturing. Additionally, data will be 

collected during each step in the oil or natural gas drilling operation, including hydraulic fracturing of the 

formation and oil or gas production, which will allow EPA to monitor changes in drinking water 

resources as a result of hydraulic fracturing.

The case study site investigations will use monitoring wells and other available monitoring points to 

identify (and determine the quantity of) chemical compounds relevant to hydraulic fracturing activities 

in the subsurface environment. These compounds may include the chemical additives found in hydraulic 

fracturing fluid and their reaction/degradation products, as well as naturally occurring materials (e.g., 

formation fluid, gases, trace elements, radionuclides, and organic material) released during fracturing 

events.

This appendix first describes types of samples (and analytes associated with those samples) that may be 

collected throughout the oil and natural gas production process and the development and refinement of 

laboratory-based analytical methods. It then discusses the potential challenges associated with 

analyzing the collected field samples. The appendix ends with a summary of the data analysis process as 

well as a discussion of the evaluation of potential indicators associated with hydraulic fracturing 

activities.

FIELD SAMPLING: SAMPLE TYPES AND ANALYTICAL FOCUS

Table H1 lists monitoring and measurement parameters for both retrospective and prospective case 

studies. Note that samples taken in retrospective case studies will be collected after hydraulic fracturing 

has occurred and will focus on collecting evidence of contamination of drinking water resources.

Samples taken for prospective case studies, however, will be taken during all phases of oil and gas 

production and will focus on improving EPA’s understanding of hydraulic fracturing activities.
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TABLE H1. MONITORING AND MEASUREMENT PARAMETERS AT CASE STUDY SITES

Sample Type Case Study Site Parameters

Surface and ground

water (e.g., existing 

wells, new wells)

Soil/sediments, soil 

gas

Prospective and 

retrospective (collect as 

much historical data as 

available)

• General water quality (e.g., pH, redox, dissolved oxygen) 

and water chemistry parameters (e.g., cations and anions)

• Dissolved gases (e.g., methane)

• Stable isotopes (e.g., Sr, Ra, C, H)

• Metals

• Radionuclides

• Volatile and semi-volatile organic compounds, polycyclic 

aromatic hydrocarbons

• Soil gas sampling in vicinity of proposed/actual hydraulic 

fracturing well location (e.g., Ar, He, H2, O2, N2, CO2, CH4, 

C2H6, C2H4, C3H6, C3H8, iC4H10, nC4H10, iC5H12)

Flowback and 

produced water

Prospective • General water quality (e.g., pH, redox, dissolved oxygen, 

total dissolved solids) and water chemistry parameters 

(e.g., cations and anions)

• Metals

• Radionuclides

• Volatile and semi-volatile organic compounds, polycyclic 

aromatic hydrocarbons

• Sample fracturing fluids (time series sampling)

o Chemical concentrations

o Volumes injected

o Volumes recovered

Drill cuttings, core 

samples

Prospective • Metals

• Radionuclides

• Mineralogic analyses

Table H1 indicates that field sampling will focus primarily on water and soil samples, which will be 

analyzed for naturally occurring materials and chemical additives used in hydraulic fracturing fluid, 

including their reaction products and/or degradates. Drill cuttings and core samples will be used in 

laboratory experiments to analyze the chemical composition of the formation and to explore chemical 

reactions between hydraulic fracturing fluid additives and the hydrocarbon-containing formation.

Data collected during the case studies are not restricted to the collection of field samples. Other data 

include results from mechanical integrity tests and surface geophysical testing. Mechanical well integrity 

can be assessed using a variety of tools, including acoustic cement bond tools, ultrasonic transducers, 

temperature and noise logging tools, and pressure tests. Geophysical testing can assess geologic and 

hydrogeologic conditions, detect and map underground structures, and evaluate soil and rock 

properties.

FIELD SAMPLING CONSIDERATIONS

Samples collected from drinking water taps or treatment systems will reflect the temperature, pressure, 

and redox conditions associated with the sampling site and may not reflect the true conditions in the 

subsurface, particularly in dissolved gas concentrations. In cases where dissolved gases are to be 

analyzed, special sampling precautions are needed. Because the depths of hydraulic fracturing wells can 

exceed 1,000 feet, ground water samples will be collected from settings where the temperature and 
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pressure are significantly higher than at the surface.

When liquid samples are brought to the surface, 

decreasing pressure can lead to off-gassing of dissolved 

gases (such as methane) and to changes in redox 

potential and pH that can lead to changes in the 

speciation and solubility of minerals and metals.

Therefore, the sampling of water from these depths will 

require specialized sampling equipment that maintains 

the pressure of the formation until the sample is 

analyzed. One possible approach for this type of sampling 

is to employ a bomb sampler (shown in Figure G1) with a double-valve configuration that activates a 

series of stainless steel sampling vessels to collect pressurized ground water in one sampling pass. 

USE OF PRESSURE TRANSDUCERS

Pressure transducers are a commonly used tool to measure water pressure changes correlated with 

changes in water levels within wells. The transducers are coupled with data loggers to electronically 

record the water level and time the measurement was obtained. They are generally used as an 

alternative to the frequent manual measurement of water levels. The devices used in this study consist 

of a small, self-contained pressure sensor, temperature sensor, battery, and non-volatile memory. The 

measurement frequency is programmable. Such data are often used to help predict groundwater flow 

directions and to evaluate possible relationships between hydraulic stresses (e.g., pumping, injection, 

natural recharge, etc.) and changes in water levels in wells, if sufficient data regarding the timing of the 

hydraulic stresses are available. These data may aid in evaluations of hydrostratigraphy and hydraulic 

communication within the aquifer.

DEVELOPMENT AND REFINEMENT OF LABORATORY-BASED ANALYTICAL METHODS

The ability to characterize chemical compounds related to hydraulic fracturing activities depends on the 

ability to detect and quantify individual constituents using appropriate analytical methods. As discussed 

in Chapter 6, EPA will identify the chemical additives used in hydraulic fracturing fluids as well as those 

found in flowback and produced water, which may include naturally occurring substances and 

reaction/degradation products of fracturing fluid additives. The resulting list of chemicals will be 

evaluated for existing analytical methods. Where analytical methods exist, detailed information will be 

compiled on detection limits, interferences, accuracy, and precision. In other instances, standardized 

analytical methods may not be readily available for use on the types of samples generated by hydraulic 

fracturing activities. In these situations, a prioritization strategy informed by risk, case studies, and 

experimental and modeling investigations will be used to develop analytical methods for high-priority 

chemicals in relevant environmental matrices (e.g., brines). 

The sampling and analytical chemistry requirements depend on the specific goals of the field 

investigation (e.g., detection, quantification, toxicity, fate and transport). Sample types may include 

formulations of hydraulic fracturing fluid systems, water samples (e.g., ambient water, flowback, and 

FIGURE H1. BOMB SAMPLER
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produced water), drilling fluids, soil, and solid residues. In many cases, samples may reflect the presence 

of multiple phases (gas-liquid-solid) that impact chemical partitioning in the environment. Table H2 

briefly discusses the types of analytical instrumentation that can be applied to samples collected during 

field investigations (both retrospective and prospective case studies).

TABLE H2. OVERVIEW OF ANALYTICAL INSTRUMENTS THAT CAN BE USED TO IDENTIFY AND QUANTIFY 

CONSTITUENTS ASSOCIATED WITH HYDRAULIC FRACTURING ACTIVITIES

Type of Analyte Analytical Instrument(s) MDL Range*

Volatile organics GC/MS: gas chromatograph/mass spectrometer 

GC/MS/MS: gas chromatograph/mass spectrometer/

mass spectrometer

0.25-10 μg/L

Water-soluble organics LC/MS/MS: liquid chromatograph/mass 

spectrometer/mass spectrometer

0.01-0.025 μg/L

Unknown organic compounds LC/TOF: liquid chromatograph/time-of-flight mass 

spectrometer

5 μg/L

Metals, minerals ICP: inductively coupled plasma 1-100 μg/L

GFAA: graphite furnace atomic absorption 0.5-1 μg/L

Transition metals, isotopes ICP/MS: inductively coupled plasma/mass spectrometer 0.5-10 μg/L

Redox-sensitive metal species, 

oxyanion speciation, thioarsenic 

speciation, etc.

LC/ICP/MS: liquid chromatograph/inductively coupled 

plasma/mass spectrometer

0.5-10 μg/L

Ions (charged elements or 

compounds) 

IC: ion chromatograph 0.1-1 mg/L

*The minimum detection limit, which depends on the targeted analyte.

POTENTIAL CHALLENGES

The analysis of field samples collected during case studies is not without challenges. Two anticipated 

challenges are discussed below: matrix interference and the analysis of unknown chemical compounds. 

MATRIX INTERFERENCE

The sample matrix can affect the performance of the analytical methods being used to identify and 

quantify target analytes; typical problems include interference with the detector signal (suppression or 

amplification) and reactions with the target analyte, which can reduce the apparent concentration or 

complicate the extraction process. Some potential matrix interferences are listed in Table H3.
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TABLE H3. EXAMPLES OF MATRIX INTERFERENCES THAT CAN COMPLICATE ANALYTICAL APPROACHES USED TO 

CHARACTERIZE SAMPLES ASSOCIATED WITH HYDRAULIC FRACTURING

Type of Matrix 

Interference Example Interferences Potential Impacts on Chemical Analysis

Chemical • Inorganics: metals, minerals, ions

• Organics: coal, shale, 

hydrocarbons

• Dissolved gases: methane, 

hydrogen sulfide, carbon dioxide

• pH

• Oxidation potential

• Complexation or co-precipitation with analyte, 

impacting extraction efficiency, detection, and 

recovery

• Reaction with analyte changing apparent 

concentration

• Impact on pH, oxidation potential, microbial growth

• Impact on solubility, microbial growth

Biological • Bacterial growth • Biodegradation of organic compounds, which can 

change redox potential, or convert electron acceptors 

(iron, sulfur, nitrogen, metalloids)

Physical • Pressure and temperature

• Dissolved and suspended solids 

• Geologic matrix

• Changes in chemical equilibria, solubility, and 

microbial growth 

• Release of dissolved minerals, sequestration of 

constituents, and mobilization of minerals, metals

Some gases and organic compounds can partition out of the aqueous phase into a non-aqueous phase 

(already present or newly formed), depending on their chemical and physical properties. With the 

numbers and complex nature of additives used in hydraulic fracturing fluids, the chemical composition 

of each phase depends on partitioning relationships and may depend on the overall composition of the 

mixture. The unknown partitioning of chemicals to different phases makes it difficult to accurately 

determine the quantities of target analytes. In order to address this issue, EPA has asked for chemical 

and physical properties of hydraulic fracturing fluid additives in the request for information sent to the 

nine hydraulic fracturing service providers. 

ANALYSIS OF UNKNOWN CHEMICAL COMPOUNDS

Once injected, hydraulic fracturing fluid additives may maintain their chemical structure, partially or 

completely decompose, or participate in reactions with the surrounding strata, fluids, gases, or 

microbes. These reactions may result in the presence of degradates, metabolites, or other 

transformation products, which may be more or less toxic than the parent compound and consequently 

increase or decrease the risks associated with hydraulic fracturing formulations. The identification and 

quantification of these products may be difficult, and can be highly resource intensive and timeconsuming. Therefore, the purpose of each chemical analysis will be clearly articulated to ensure that 

the analyses are planned and performed in a cost-effective manner. 

DATA ANALYSIS

The data collected by EPA during retrospective case studies will be used to determine the source and 

extent of reported drinking water contamination. In these cases, EPA will use different methods to 

investigate the sources of contamination and the extent to which the contamination has occurred. One 

important method to determine the source and migration pathways of natural gas is isotopic 

fingerprinting, which compares both the chemical composition and the isotopic compositions of natural 

gas. Although natural gas is composed primarily of methane, it can also include ethane, propane, 
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butane, and pentane, depending on how it is formed. Table H4 illustrates different types of gas, the 

constituents, and the formation process of the natural gas.

TABLE H4. TYPES OF NATURAL GASES, CONSTITUENTS, AND PROCESS OF FORMATION

Type of Natural Gas Constituents Process of Formation

Thermogenic gas Methane, ethane, propane, 

butane, and pentane

Geologic formation of fossil fuel

Biogenic gas Methane and ethane Methane-producing 

microorganisms chemically break 

down organic material

Thermogenic light hydrocarbons detected in soil gas typically have a well-defined composition indicative 

of reservoir composition. Above natural gas reservoirs, methane dominates the light hydrocarbon 

fraction; above petroleum reservoirs, significant concentrations of ethane, propane, and butane are 

found (Jones et al., 2000). Also, ethane, propane, and butane are not produced by biological processes 

in near-surface sediments; only methane and ethylene are products of biodegradation. Thus, elevated 

levels of methane, ethane, propane, and butane in soil gas indicate thermogenic origin and could serve 

as tracers for natural gas migration from a reservoir.

The isotopic signature of methane can also be used to delineate the source of natural gas migration in 

retrospective case studies because it varies with the formation process. Isotopic fingerprinting uses two 

parameters—δ13C and δD—to identify thermogenic and biogenic methane. These two parameters are 

equal to the ratio of the isotopes 13C/12C and D/H, respectively. Baldassare and Laughrey (1997), Schoell 

(1980 and 1983), Kaplan et al. (1997), Rowe and Muehlenbachs (1999), and others have summarized 

values of δ13C and δD for methane, and their data show that it is often possible to distinguish methane

formed from biogenic and thermogenic processes by plotting δ13C versus δD. Thus, the isotopic 

signature of methane recovered from retrospective case study sites can be compared to the isotopic 

signature of potential sources of methane near the contaminated site. Isotopic fingerprinting of 

methane, therefore, could be particularly useful for determining if the methane is of thermogenic origin 

and in situations where multiple methane sources are present. 

In prospective case studies, EPA will use the data collected from field samples to (1) provide a 

comprehensive picture of drinking water resources during all stages in the hydraulic fracturing water 

lifecycle and (2) inform hydraulic fracturing models, which may then be used to predict impacts of 

hydraulic fracturing on drinking water resources.

EVALUATION OF POTENTIAL INDICATORS OF CONTAMINATION

Natural gas is not the only potential chemical indicator for gas migration due to hydraulic fracturing 

activities: Hydrogen sulfide, hydrogen, and helium may also be used as potential tracers. Hydrogen 

sulfide is produced during the anaerobic decomposition of organic matter by sulfur bacteria, and can be 

found in varying amounts in sulfur deposits, volcanic gases, sulfur springs, and unrefined natural gas and 

petroleum, making it a potential indicator of natural gas migration. Hydrogen gas (H2) and helium (He) 

are widely recognized as good fault and fracture indicators because they are chemically inert, physically 

stable, and highly insoluble in water (Klusman, 1993; Ciotoli et al., 1999 and 2004). For example, H2 and 
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He have been observed in soil gas at values up to 430 and 50 parts per million by volume (ppmv)

respectively over the San Andreas Fault in California (Jones and Pirkle, 1981), and Wakita et al. (1978) 

has observed He at a maximum concentration of 350 ppmv along a nitrogen vent in Japan. The presence 

of He in soil gas is often independent of the oil and gas deposits. However, since He is more soluble in oil 

than water, it is frequently found at elevated concentrations in soil gas above natural gas and petroleum 

reservoirs and hence may serve as a natural tracer for gas migration.

EPA will use the data collected from field samples to identify and evaluate other potential indicators of 

hydraulic fracturing fluid migration into drinking water supplies. For example, flowback and produced 

water have higher ionic strengths (due to large concentrations of potassium and chloride) than surface 

waters and shallow ground water and may also have different isotopic compositions of strontium and 

radium. Although potassium and chloride are often used as indicators of flowback or produced water, 

they are not considered definitive. However, if the isotopic composition of the flowback or produced 

water differs significantly from those of nearby drinking water resources, then isotopic ratios could be 

sensitive indicators of contamination. Recent research by Peterman et al. (2010) lends support for 

incorporating such analyses into this study. Additionally, DOE NETL is working to determine if stable 

isotopes can be used to identify Marcellus flowback and produced water when commingled with surface 

waters or shallow ground water. EPA also plans to use this technique to evaluate contamination 

scenarios in the retrospective case studies and will coordinate with DOE on this aspect of the research.

References

Baldassare, F. J., & Laughrey, C. D. (1997). Identifying the sources of stray methane by using geochemical 

and isotopic fingerprinting. Environmental Geosciences, 4, 85-94.

Ciotoli, G., Etiope, G., Guerra, M., & Lombardi, S. (1999). The detection of concealed faults in the Ofanto 

basin using the correlation between soil-gas fracture surveys. Tectonophysics, 299, 321-332.

Ciotoli, G., Lombardi, S., Morandi, S., & Zarlenga, F. (2004). A multidisciplinary statistical approach to 

study the relationships between helium leakage and neotectonic activity in a gas province: The Vasto 

basin, Abruzzo-Molise (central Italy). The American Association of Petroleum Geologists Bulletin, 88, 355-

372.

Jones, V. T., & Pirkle, R. J. (1981, March 29-April 3). Helium and hydrogen soil gas anomalies associated 

with deep or active faults. Presented at the American Chemical Society Annual Conference, Atlanta, GA. 

Jones, V. T., Matthews, M. D., & Richers, D. M. (2000). Light hydrocarbons for petroleum and gas 

prospecting. In M. Hale (Ed.), Handbook of Exploration Geochemistry (pp. 133-212). Elsevier Science B.V.

Kaplan, I. R., Galperin, Y., Lu, S., & Lee, R. (1997). Forensic environmental geochemistry—Differential of 

fuel-types, their sources, and release time. Organic Geochemistry, 27, 289-317.

Klusman, R. W. (1993). Soil gas and related methods for natural resource exploration. New York, NY:

John Wiley & Sons.
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Peterman, Z. E., Thamke, J., & Futa, K. (2010, May 14). Strontium isotope detection of brine

contamination of surface water and groundwater in the Williston Basin, northeastern Montana.

Presented at the GeoCanada Annual Conference, Calgary, Alberta, Canada.

Rowe, D., & Muehlenbachs, K. (1999). Isotopic fingerprinting of shallow gases in the western Canadian 

sedimentary basin—Tools for remediation of leaking heavy oil wells. Organic Geochemistry, 30, 861-871.

Schoell, M. (1980). The hydrogen and carbon isotopic composition of methane from natural gases of 

various origin. Geochimica et Cosmochimica Acta, 44, 649-661.

Schoell, M. (1983). Genetic characteristics of natural gases. American Association of Petroleum

Geologists Bulletin, 67, 2225-2238.

Wakita, H., Fujii, N., Matsuo, S., Notsu, K., Nagao, K., & Takaoka, N. (1978, April 28). Helium spots:

Caused by diapiric magma from the upper mantle. Science, 200(4340), 430-432.
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GLOSSARY

Abandoned well: A well that is no longer in use, whether dry, inoperable, or no longer productive.1

ACToR: EPA’s online warehouse of all publicly available chemical toxicity data, which can be used to find 

all publicly available data about potential chemical risks to human health and the environment. ACToR 

aggregates data from over 500 public sources on over 500,000 environmental chemicals searchable by 

chemical name, other identifiers, and chemical structure.15

Aerobic: Life or processes that require, or are not destroyed by, the presence of oxygen.2

Anaerobic: A life or process that occurs in, or is not destroyed by, the absence of oxygen.2

Analyte: A substance or chemical constituent being analyzed.3

Aquiclude: An impermeable body of rock that may absorb water slowly, but does not transmit it.4

Aquifer: An underground geological formation, or group of formations, containing water. A source of 

ground water for wells and springs.2

Aquitard: A geological formation that may contain ground water but is not capable of transmitting 

significant quantities of it under normal hydraulic gradients.2

Assay: A test for a specific chemical, microbe, or effect.2

Biocide: Any substance the kills or retards the growth of microorganisms.5

Biodegradation: The chemical breakdown of materials under natural conditions.2

Casing: Pipe cemented in the well to seal off formation fluids and to keep the hole from caving in.1

Coalbed: A geological layer or stratum of coal parallel to the rock stratification.

DSSTox: A public forum for publishing downloadable, structure-searchable, standardized chemical 

structure files associated with toxicity data. 2

ExpoCastDB: A database that consolidates observational human exposure data and links with toxicity 

data, environmental fate data, and chemical manufacture information.13

HERO: Database that includes more than 300,000 scientific articles from the peer-reviewed literature 

used by EPA to develop its Integrated Science Assessments (ISA) that feed into the NAAQS review. It also 

includes references and data from the Integrated Risk Information System (IRIS), a database that 

supports critical agency policymaking for chemical regulation. Risk assessments characterize the nature 

and magnitude of health risks to humans and the ecosystem from pollutants and chemicals in the 

environment.14

HPVIS: Database that provides access to health and environmental effects information obtained through 

the High Production Volume (HPV) Challenge.
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IRIS: A human health assessment program that evaluates risk information on effects that may result 

from exposure to environmental contaminants. 2

Flowback water: After the hydraulic fracturing procedure is completed and pressure is released, the 

direction of fluid flow reverses, and water and excess proppant flow up through the wellbore to the 

surface. The water that returns to the surface is commonly referred to as “flowback.”6

Fluid leakoff: The process by which injected fracturing fluid migrates from the created fractures to other 

areas within the hydrocarbon-containing formation. 

Formation: A geological formation is a body of earth material with distinctive and characteristic 

properties and a degree of homogeneity in its physical properties.2

Ground water: The supply of fresh water found beneath the Earth’s surface, usually in aquifers, which 

supply wells and springs. It provides a major source of drinking water.2

Horizontal drilling: Drilling a portion of a well horizontally to expose more of the formation surface area 

to the wellbore.1

Hydraulic fracturing: The process of using high pressure to pump fluid, often carrying proppants into 

subsurface rock formations in order to improve flow into a wellbore.1

Hydraulic fracturing water lifecycle: The lifecycle of water in the hydraulic fracturing process, 

encompassing the acquisition of water, chemical mixing of the fracturing fluid, injection of the fluid into 

the formation, the production and management of flowback and produced water, and the ultimate 

treatment and disposal of hydraulic fracturing wastewaters.

Impoundment: A body of water or sludge confined by a dam, dike, floodgate, or other barrier.2

Mechanical integrity: An injection well has mechanical integrity if: (1) there is no significant leak in the 

casing, tubing, or packer (internal mechanical integrity) and (2) there is no significant fluid movement 

into an underground source of drinking water through vertical channels adjacent to the injection 

wellbore (external mechanical integrity).7

Natural gas or gas: A naturally occurring mixture of hydrocarbon and non-hydrocarbon gases in porous 

formations beneath the Earth’s surface, often in association with petroleum. The principal constituent is 

methane.1

Naturally occurring radioactive materials: All radioactive elements found in the environment, including 

long-lived radioactive elements such as uranium, thorium, and potassium and any of their decay 

products, such as radium and radon.

Play: A set of oil or gas accumulations sharing similar geologic and geographic properties, such as source 

rock, hydrocarbon type, and migration pathways.1
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Produced water: After the drilling and fracturing of the well are completed, water is produced along 

with the natural gas. Some of this water is returned fracturing fluid and some is natural formation water.

These produced waters move back through the wellhead with the gas.8

Proppant/propping agent: A granular substance (sand grains, aluminum pellets, or other material) that 

is carried in suspension by the fracturing fluid and that serves to keep the cracks open when fracturing 

fluid is withdrawn after a fracture treatment.9

Prospective case study: Sites where hydraulic fracturing will occur after the research is initiated. These 

case studies allow sampling and characterization of the site prior to, and after, water extraction, drilling, 

hydraulic fracturing fluid injection, flowback, and gas production. The data collected during prospective 

case studies will allow EPA to evaluate changes in water quality over time and to assess the fate and 

transport of chemical contaminants.

Public water system: A system for providing the public with water for human consumption (through 

pipes or other constructed conveyances) that has at least 15 service connections or regularly serves at 

least 25 individuals.10

Redox (reduction-oxidation) reaction: A chemical reaction involving transfer or electrons from one 

element to another.3

Residential well: A pumping well that serves one home or is maintained by a private owner.5

Retrospective case study: A study of sites that have had active hydraulic fracturing practices, with a 

focus on sites with reported instances of drinking water resource contamination or other impacts in 

areas where hydraulic fracturing has already occurred. These studies will use existing data and possibly 

field sampling, modeling, and/or parallel laboratory investigations to determine whether reported 

impacts are due to hydraulic fracturing activities.

Shale: A fine-grained sedimentary rock composed mostly of consolidated clay or mud. Shale is the most 

frequently occurring sedimentary rock.9

Source water: Operators may withdraw water from surface or ground water sources themselves or may 

purchase it from suppliers.6

Subsurface: Earth material (as rock) near but not exposed at the surface of the ground.11

Surface water: All water naturally open to the atmosphere (rivers, lakes, reservoirs, ponds, streams, 

impoundments, seas, estuaries, etc.).2

Tight sands: A geological formation consisting of a matrix of typically impermeable, non-porous tight 

sands.

Toe: The far end of the section that is horizontally drilled.

12
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Total dissolved solids (TDS): All material that passes the standard glass river filter; also called total 

filterable residue. Term is used to reflect salinity.2

ToxCastDB: A database that links biological, metabolic, and cellular pathway data to gene and in vitro 

assay data for the chemicals screened in the ToxCast HTS assays. Also included in ToxCastDB are human 

disease and species homology information, which correlate with ToxCast assays that affect specific 

genetic loci. This information is designed to make it possible to infer the types of human disease 

associated with exposure to these chemicals.16

ToxRefDB: A database that collects in vivo animal studies on chemical exposures.17

Turbidity: A cloudy condition in water due to suspended silt or organic matter.2

Underground injection well (UIC): A steel- and concrete-encased shaft into which hazardous waste is 

deposited by force and under pressure.2

Underground source of drinking water (USDW): An aquifers currently being used as a source of drinking 

water or capable of supplying a public water system. USDWs have a TDS content of 10,000 milligrams 

per liter or less, and are not “exempted aquifers.”2

Vadose zone: The zone between land surface and the water table within which the moisture content is 

less than saturation (except in the capillary fringe) and pressure is less than atmospheric. Soil pore space 

also typically contains air or other gases. The capillary fringe is included in the vadose zone.2

Water table: The level of ground water.2

References

1. Oil and Gas Mineral Services. (2010). Oil and gas terminology. Retrieved January 20, 2011, from 

http://www.mineralweb.com/library/oil-and-gas-terms. 

2. US Environmental Protection Agency. (2006). Terms of environment: Glossary, abbreviations and 

acronyms. Retrieved January 20, 2011, from http://www.epa.gov/OCEPAterms/

aterms.html.

3. Harris, D. C. (2003). Quantitative chemical analysis. Sixth edition. New York, NY: W. H. Freeman 

and Company.

4. Geology Dictionary. (2006). Aquiclude. Retrieved January 30, 2011, from http://

www.alcwin.org/Dictionary_Of_Geology_Description-136-A.htm.

5. Webster’s New World College Dictionary. (1999). Fourth edition. Cleveland, OH: Macmillan USA.

6. New York State Department of Environmental Conservation. (2011, September). Supplemental 

generic environmental impact statement on the oil, gas and solution mining regulatory program 

(revised draft). Well permit issuance for horizontal drilling and high-volume hydraulic fracturing 

to develop the Marcellus Shale and other low-permeability gas reservoirs. Albany, NY: New York 

State Department of Environmental Conservation, Division of Mineral Resources, Bureau of Oil 

& Gas Regulation. Retrieved January 20, 2011, from ftp://ftp.dec.state.ny.us/dmn/download/

OGdSGEISFull.pdf.
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7. U. S. Environmental Protection Agency. (2010). Glossary of underground injection control terms.

Retrieved January 19, 2011, from http://www.epa.gov/r5water/uic/glossary.htm#ltds.

8. Ground Water Protection Council & ALL Consulting. (2009, April). Modern shale gas 

development in the US: A primer. Prepared for the US Department of Energy, Office of Fossil 

Energy and National Energy Technology Laboratory. Retrieved January 20, 2011, from 

http://www.netl.doe.gov/technologies/oil-gas/publications/EPreports/

Shale_Gas_Primer_2009.pdf.

9. US Department of the Interior. Bureau of Ocean Energy Management, Regulation and 

Enforcement: Offshore minerals management glossary. Retrieved January 20, 2011, from 

http://www.mms.gov/glossary/d.htm. 

10. U. S. Environmental Protection Agency. (2010.) Definition of a public water system. Retrieved 

January 30, 2011, from http://water.epa.gov/infrastructure/drinkingwater/pws/pwsdef2.cfm.

11. Merriam-Webster’s Dictionary. (2011). Subsurface. Retrieved January 20, 2011, from 

http://www.merriam-webster.com/dictionary/subsurface.

12. Society of Petroleum Engineers. (2011). SPE E&P Glossary. Retrieved September 14, 2011, from 

http://www.spe.org/glossary/wiki/doku.php/welcome#terms_of_use.

13. U.S. Environmental Protection Agency. (2011, September 21). Expocast. Retrieved October 5, 

2011, from http://www.epa.gov/ncct/expocast/.

14. U.S. Environmental Protection Agency. (2011, October 31). The HERO Database. Retrieved 

October 31, 2011, from http://hero.epa.gov/.

15. Judson, R., Richard, A., Dix, D., Houck, K., Elloumi, F., Martin, M., Cathey, T., Transue, T.R., 

Spencer, R., Wolf, M. (2008) ACTOR - Aggregated Computational Toxicology Resource. 

Toxicology and Applied Pharmacology, 233: 7-13.

16. Martin, M.T., Judson, R.S., Reif, D.M., Kavlock, R.J., Dix, D.J. (2009) Profiling Chemicals Based on 

Chronic Toxicity Results from the U.S. EPA ToxRef Database. Environmental Health Perspectives,

117(3):392-9.

17. U.S. Environmental Protection Agency. (2011, October 31). The HERO Database. Retrieved 

October 31, 2011, from http://actor.epa.gov/actor/faces/ToxCastDB/Home.jsp.
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